JP4272796B2 - Substrate processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention provides a substrate processingMethodAbout.
[0002]
[Prior art]
As a substrate having a single crystal Si layer on an insulating layer, a substrate (SOI substrate) having an SOI (silicon on insulator) structure is known. A device employing this SOI substrate has many advantages that cannot be achieved with a normal Si substrate. As this advantage, the following are mentioned, for example.
(1) Dielectric separation is easy and suitable for high integration.
(2) Excellent radiation resistance.
(3) The stray capacitance is small, and the operation speed of the element can be increased.
(4) No well process is required.
(5) Latch-up can be prevented.
(6) A completely depleted field effect transistor can be formed by thinning.
[0003]
Since the SOI structure has various advantages as described above, research on its formation method has been advanced for several decades.
[0004]
As an SOI technology, an SOS (silicon on sapphire) technology for forming Si on a single crystal sapphire substrate by heteroepitaxial growth using a CVD (chemical vapor deposition) method has been known. Although this SOS technology has been evaluated as the most mature SOI technology, a large amount of crystal defects are generated due to lattice mismatch at the interface between the Si layer and the underlying sapphire substrate, and the aluminum Si that constitutes the sapphire substrate. Practical use has not progressed due to contamination in the layers, the price of the substrate, the delay in increasing the area, and the like.
[0005]
In relatively recent years, attempts have been made to realize an SOI structure without using a sapphire substrate. This attempt is roughly divided into the following two methods.
[0006]
In the first method, after oxidizing the surface of the Si single crystal substrate, the oxide film (SiO₂The Si substrate is partially exposed by forming a window in the layer), and single crystal Si is epitaxially grown in the lateral direction using the portion as a seed, thereby forming SiO.₂This is a method for forming a Si single crystal layer on this (in this method, SiO 2₂A Si layer is deposited on the layer).
[0007]
The second method uses a Si single crystal substrate itself as an active layer, and a SiO 2 layer below it.₂This is a method of forming a layer (this method does not deposit a Si layer).
[0008]
As means for realizing the first method, a method of epitaxially growing single crystal Si laterally from a single crystal Si layer by a CVD method (CVD method), a solid phase by depositing amorphous Si and heat treatment. A method of lateral epitaxial growth (solid phase growth method), an amorphous or polycrystalline Si layer is irradiated with an energy beam such as an electron beam or a laser beam focused and melted and recrystallized to produce SiO.₂A method of growing a single crystal Si layer on the layer (beam annealing method) and a method of scanning a molten region in a strip shape with a rod heater (Zone Melting Recrystallization method) are known.
[0009]
Each of these methods has their merits and demerits, but there are still many problems in controllability, productivity, uniformity and quality, and none of them have been put into practical use yet. For example, the CVD method requires sacrificial oxidation for flattening and thinning, and the solid phase growth method has poor crystallinity. In addition, the beam annealing method has problems in processing time required for scanning the convergent beam, controllability such as beam overlap and focus adjustment. Among them, the Zone Melting Recrystallization method is the most mature and a relatively large scale integrated circuit has been prototyped. However, there are problems that many crystal defects such as subgrain boundaries remain, and a minority carrier device is created. It hasn't been done yet.
[0010]
The following four methods may be mentioned as the second method described above, that is, a method in which the Si substrate is not used as a seed for epitaxial growth.
[0011]
First, an oxide film is formed on a single crystal Si substrate having a V-shaped groove formed on the surface by anisotropic etching, and a polycrystal having a thickness similar to that of the single crystal Si substrate is formed on the oxide film. After depositing the Si layer, the single crystal Si is polished from the back surface of the single crystal Si substrate to form a substrate having a Si single crystal region that is dielectrically separated by being surrounded by a V-groove on the thick polycrystalline Si layer. There is a way to do it. Although this method can form a substrate with good crystallinity, a process of depositing polycrystalline Si as thick as several hundred microns or a single crystal Si substrate is polished from the back surface to leave a separated Si active layer. There is a problem of controllability and productivity regarding the process.
[0012]
Second, there is a SIMOX (Separation by Ion Implanted Oxygen) method. This method uses SiO ions by implanting oxygen ions into a single crystal Si substrate.₂A method of forming a layer. In this method, the SiO inside the substrate₂To form a layer, 10¹⁸(Ions / cm²) The above oxygen ions need to be implanted, and the implantation time is long, so the productivity is low. Moreover, the manufacturing cost is high. Furthermore, since a large number of crystal defects occur, the quality is not sufficient for manufacturing a minority carrier device.
[0013]
Thirdly, there is a method of forming an SOI structure by dielectric separation by oxidation of porous Si. In this method, an N-type Si layer is formed on the surface of a P-type single crystal Si substrate by proton ion implantation (Imai et al., J. Crystal Growth, vol 63, 547 (1983)) or by an epitaxial growth process and a patterning process. The substrate is anodized in an HF solution, and only the P-type Si substrate is made porous so as to surround the N-type Si island. It is a method of separation. In this method, since it is necessary to determine the Si region to be separated before the device process, there is a problem in limiting the degree of freedom in device design.
[0014]
Fourth, there is a method in which an SOI structure is formed by bonding a single crystal Si substrate to another thermally oxidized single crystal Si substrate by heat treatment or an adhesive. In this method, an active layer for forming a device needs to be thinned uniformly. That is, it is necessary to reduce the thickness of a single crystal Si substrate having a thickness of several hundred microns to a micron order or less.
[0015]
As a method for thinning, there are a polishing method and a selective etching method.
[0016]
With the method using polishing, it is difficult to uniformly thin single crystal Si. In particular, when the film thickness is reduced to the submicron order, the variation becomes several tens of percent. As the wafer diameter increases, the difficulty is increasing.
[0017]
The selective etching method is effective in terms of uniform thinning, but the selectivity is 10²There are problems in that it can only be obtained to a certain extent, the surface property after etching is poor, and the crystallinity of the SOI layer is poor.
[0018]
By the way, a light-transmitting substrate typified by glass is important for constituting a contact sensor or a projection type liquid crystal display device which is a light receiving element. In order to further increase the density, resolution, and definition of pixels (picture elements) of sensors and display devices, high-performance drive elements are required. Therefore, there is a need for a technique for forming a single crystal Si layer having excellent crystallinity on a light transmissive substrate.
[0019]
However, when a Si layer is deposited on a light-transmitting substrate typified by glass, the Si layer is only amorphous or polycrystalline. This is because the crystal structure of the light transmissive substrate is amorphous and the Si layer formed thereon reflects the disorder of the crystal structure of the light transmissive substrate.
[0020]
The present applicant has disclosed a new SOI technology in Japanese Patent Laid-Open No. 5-21338. In this technique, a porous layer is formed on a single crystal Si substrate, and a first substrate on which a non-porous layer single crystal layer is formed is bonded to a second substrate through an insulating layer, and then The non-porous single crystal layer is transferred to the second substrate by separating the bonded substrate into two by the porous layer. This technology has excellent film thickness uniformity of the SOI layer, can reduce the crystal defect density of the SOI layer, has good surface flatness of the SOI layer, and does not require expensive special specification manufacturing equipment It is excellent in that an SOI substrate having an SOI film in the range of several hundreds of μm to 10 μm can be manufactured with the same manufacturing apparatus.
[0021]
Furthermore, the present applicant, in JP-A-7-302889, after laminating the first substrate and the second substrate, the first substrate is separated from the second substrate without breaking, and then A technique has been disclosed in which the surface of the separated first substrate is smoothed to form a porous layer again and reused. This technique has the excellent advantage that the first substrate can be used without waste, so that the manufacturing cost can be greatly reduced and the manufacturing process is simple.
[0022]
As a method of separating the bonded substrates into two without destroying both the first and second substrates, for example, the two substrates are mutually connected by applying a force in a direction perpendicular to the bonding surface. A method of pulling in the opposite direction, a method of applying a shear stress parallel to the bonding surface (for example, a method of moving both substrates in directions opposite to each other in a plane parallel to the bonding surface, or a force in the circumferential direction) In this way, both substrates are rotated in opposite directions), a method of applying pressure in a direction perpendicular to the bonding surface, a method of applying wave energy such as ultrasonic waves to the separation region, and bonding to the separation region A method of inserting a peeling member (for example, a sharp blade such as a knife) from the side surface of the substrate in parallel to the bonding surface, and the expansion energy of the substance soaked into the porous layer functioning as a separation region , A method in which a porous layer that functions as a separation region is thermally oxidized from the side surface of a bonded substrate, and the porous layer is expanded by volume, and a porous layer that functions as a separation region is bonded. There is a method of selectively etching and separating from the side surface of the substrate.
[0023]
Porous Si was discovered by Uhlir et al. In 1956 in the research process of electropolishing of semiconductors (A. Uhlir, Bell Syst. Tech. J., vol. 35, 333 (1956)). Porous Si can be formed by anodizing a Si substrate in HF solution.
[0024]
Unagami et al. Studied the dissolution reaction of Si in anodization, and reported that holes were necessary for the anodic reaction of Si in HF solution, and the reaction was as follows (T. Unagami) J. Electrochem. Soc., Vol. 127, 476 (1980)). Si + 2HF + (2-n) e⁺ → SiF₂+ 2H⁺+ ne^-
SiF₂+ 2HF → SiF_Four+ H₂
SiF_Four+ 2HF → H₂SiF₆
Or
Si + 4HF + (4-λ) e + → SiF_Four+ 4H⁺+ λe^-
SiF_Four+ 2HF → H₂SiF₆
Where e⁺And e^-Represents holes and electrons, respectively. Also, n and λ are the number of holes necessary for each Si atom to dissolve, and porous Si is formed when the condition of n> 2 or λ> 4 is satisfied. .
[0025]
From the above, it can be considered that P-type Si having holes is made porous, but N-type Si is not made porous. The selectivity in this porosification has been reported by Nagano et al. And Imai (Nagano, Nakajima, Anno, Onaka, Sugawara, IEICE Technical Report, vol. 79, SSD 79-9549 (1979)), (K Imai, Solid-State Electronics, vol.24,159 (1981)).
[0026]
However, there is a report that a high concentration of N-type Si can be made porous (R. P. Holmstrom and J. Y. Chi, Appl. Phys. Lett., Vol. 42, 386 (1983)). Therefore, it is important to select a substrate that can be made porous regardless of whether it is P-type or N-type.
[0027]
In order to form a porous layer on a Si substrate, a pair of electrodes is supported in a treatment tank filled with an HF solution, and the Si substrate is held between the electrodes, and a current is passed between the electrodes. In this case, the problem is that the Si element is contaminated by the metal element constituting the positive electrode being dissolved into the HF solution.
[0028]
The present applicant discloses an anodizing apparatus for solving this problem in Japanese Patent Application Laid-Open No. 6-275598. In the anodizing apparatus disclosed in Japanese Patent Application Laid-Open No. 6-275598, a conductive partition made of a Si material is disposed between a Si substrate and a positive electrode, and contamination of the Si substrate with a metal element constituting the positive electrode is prevented. Cut off by a conductive electrode.
[0029]
[Problems to be solved by the invention]
As in the anodizing apparatus according to JP-A-6-275598, when a conductive partition made of Si material is disposed between the Si substrate to be processed and the positive electrode and the Si substrate is subjected to anodizing treatment, the anode Depending on the chemical conversion conditions, not only the surface of the Si substrate to be processed but also the surface of the conductive partition walls may be made porous.
[0030]
In order to perform the production efficiently, it is preferable that the conductive partition wall can withstand many anodizing treatments. However, if the conductive partition wall is used in many anodizing treatments under the condition that the conductive partition wall becomes porous, the surface of the conductive partition wall becomes porous, and finally the conductive partition wall The vicinity of the surface of the material collapses, and Si particles fall off the conductive partition. The particles contaminate the Si substrate and the anodizing tank to be processed.
[0031]
The present invention has been made in view of the above-described background, and an object thereof is to prevent, for example, generation of particles from a conductive partition.
[0032]
[Means for Solving the Problems]
  The substrate processing method according to one aspect of the present invention uses an anodizing apparatus in which a conductive partition wall electrically connected to the positive electrode is disposed between the negative electrode and the positive electrode. A substrate to be processed between the conductive partition and the conductive partition, and forming a porous layer on the substrate by anodization reaction, wherein the negative electrode and the substrate are connected to the first electrode A preparatory step in which the conductive partition and the substrate are in electrical contact with each other through the electrolyte solution, and an electric current is applied between the negative electrode and the positive electrode. An anodizing step of forming a porous layer on the negative electrode side surface of the substrate by flowing, and using the electrolyte solution having the ability to make the substrate porous as the first electrolyte solution, As the second electrolyte solution, substantially the conductive Use electrolyte solution having no ability to porous partition walls,Both the first electrolyte solution and the second electrolyte solution are solutions containing hydrogen fluoride, and the first electrolyte solution has a higher concentration of hydrogen fluoride than the second electrolyte solution,The conductive partition is made of the same material as the substrate.
[0033]
  AboveIn the treatment method, for example, it is preferable to use, as the second electrolyte solution, an electrolyte solution having an ability to electrolytically etch the conductive partition.
[0035]
  AboveIn the processing method, for example, the conductive partition is preferably made of a Si material.
[0039]
  AboveIn the treatment method, for example, the first electrolyte solution preferably has a hydrogen fluoride concentration of 10 to 50%.
[0040]
  AboveIn the treatment method, for example, the second electrolyte solution preferably has a hydrogen fluoride concentration of 10% or less.
[0041]
  AboveIn the treatment method, for example, the second electrolyte solution preferably has a hydrogen fluoride concentration of 2% or less.
[0042]
  AboveIn the processing method, for example, it is preferable that all of the current supplied from the positive electrode to the substrate is supplied through the conductive partition.
[0043]
  AboveIn the treatment method, for example, in the anodizing step, a porous layer having a multilayer structure composed of two or more layers having different porosities is preferably formed on the substrate.
[0044]
  AboveIn the treatment method, for example, in the anodizing step, it is preferable to form a porous layer having a multilayer structure by changing the magnitude of a current flowing between the negative electrode and the positive electrode.
[0045]
  AboveIn the treatment method, for example, in the anodizing step, it is preferable to form a porous layer having a multilayer structure by exchanging the first electrolyte solution with another electrolyte solution.
[0046]
  AboveIn the processing method, for example, the preparation step includes a step of holding a substrate to be processed between the negative electrode and the positive electrode by a substrate holder, and the first electrolyte between the negative electrode and the substrate. It is preferable to include a step of filling the solution and filling the second electrolyte solution between the conductive partition and the substrate.
[0047]
  AboveThe processing method may further include, for example, a step of discharging the first and second electrolyte solutions after a porous layer is formed on the substrate to be processed, and a step of removing the substrate from the substrate holder. preferable.
[0048]
  AboveIn the treatment method, for example, in the anodizing step, the porosity of all or a part of the second and subsequent layers counted from the surface of the substrate is higher than the porosity of the first layer counted from the surface of the substrate. It is preferable to form a porous layer having a multilayer structure.
[0049]
  AboveIn the treatment method, for example, in the anodizing step, the porosity of the first layer may be 30% or less, and the porosity of all or a part of the second and subsequent layers may be 30% or more. preferable.
[0050]
  AboveIn the treatment method, for example, in the anodizing step, the thickness of the second layer is preferably 5 μm or less.
[0051]
  AboveThe processing method preferably further includes, for example, a cleaning step of cleaning the substrate after the porous layer is formed on the substrate to be processed.
[0052]
  AbovePreferably, the processing method further includes, for example, a drying step of drying the substrate cleaned in the cleaning step.
[0053]
  Others described in the specificationThe substrate processing method according to the second aspect of the present invention includes a negative electrode and a positive electrode, and the negative electrode of the anodizing tank is separated into the negative electrode side and the positive electrode side by the substrate to be processed. A substrate is disposed between the anode and the positive electrode, and a porous layer is formed on the substrate by anodizing reaction, wherein the first electrolyte solution is placed on the negative electrode side of the anodizing tank. Filling the second electrolyte solution on the positive electrode side and filling the anode and forming a porous layer on the negative electrode side surface of the substrate by passing a current between the negative electrode and the positive electrode A chemical conversion step, wherein the first electrolyte solution and the second electrolyte solution are electrolyte solutions having different properties in terms of anodization reaction.
[0054]
  AboveIn the substrate processing method according to the second aspect, for example, the anodizing tank preferably includes a conductive partition for isolating the positive electrode and the substrate to be processed.
[0055]
  Other than the invention described in the specificationAn anodizing apparatus according to a third aspect is an anodizing apparatus for forming a porous layer on a substrate by an anodizing reaction, and includes a negative electrode, a positive electrode, and the negative electrode and the positive electrode. A substrate holder that holds the substrate to be processed, a conductive partition that separates the positive electrode and the substrate and is electrically connected to the positive electrode, and a first between the negative electrode and the substrate. First supply means for supplying the electrolyte solution, second supply means for supplying a second electrolyte solution between the conductive partition and the substrate, and the gap between the negative electrode and the substrate. A first discharge means for discharging the first electrolyte solution; a second discharge means for discharging the second electrolyte solution between the conductive partition and the substrate; the first electrolyte solution; The first and second in accordance with a procedure that does not mix with the second electrolyte solution. Further comprising a supply means and control means for controlling said first and second discharge means and said.
[0056]
  Other than the invention described in the specificationAccording to a fourth aspect of the present invention, there is provided a substrate manufacturing method comprising: a first forming step of forming a porous layer on a surface of a substrate according to any one of the substrate processing methods described above; and a non-porous layer on the porous layer. A second forming step to be formed and a substrate obtained by the second forming step as a first substrate, and the first substrate and a separately prepared second substrate are bonded with the non-porous layer interposed therebetween. A bonding step of forming a bonded substrate together, and a removing step of removing a portion from the back surface of the first substrate to the porous layer from the bonded substrate.
[0057]
  Other than the invention described in the specificationThe substrate manufacturing method according to the fifth aspect includes a first forming step of forming a porous layer on the surface of the substrate according to any one of the above-described substrate processing methods, and a non-porous layer on the porous layer. A second forming step to be formed and a substrate obtained by the second forming step as a first substrate, and the first substrate and a separately prepared second substrate are bonded with the non-porous layer interposed therebetween. A bonding step of forming a bonded substrate together, a separation step of separating the bonded substrate at the portion of the porous layer, and a removing step of removing the porous layer remaining on the second substrate after separation It is characterized by including.
[0058]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the separation step, the bonded substrate is preferably separated into two substrates by driving a fluid toward the porous layer.
[0059]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, in the separation step, a force is applied to the bonded substrate in a direction substantially perpendicular to the surface of the bonded substrate. It is preferable to separate the bonded substrate into two substrates.
[0060]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the separation step, the bonded substrate is separated into two substrates by applying shear stress to the bonded substrate in the surface direction. It is preferable.
[0061]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the separation step, the peripheral portion of the porous layer of the bonded substrate is oxidized and volume-expanded so that the bonded substrate is divided into two substrates. It is preferable to separate them.
[0062]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, a liquid is preferably used as the fluid.
[0063]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, a gas is preferably used as the fluid.
[0064]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, it is preferable that the method further includes, for example, a step of removing the porous layer remaining on the surface of the first substrate after separation so that the substrate can be reused.
[0065]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the first forming step, it is preferable to form a porous layer having a multilayer structure having different porosities.
[0066]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the separation step, it is preferable to use an inner layer of the multi-layered porous layer as a separation layer.
[0067]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the first formation step, it is preferable to form a porous layer on the surface of the Si substrate.
[0068]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the non-porous layer preferably includes a semiconductor layer.
[0069]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, the non-porous layer preferably includes a single crystal Si layer.
[0070]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, the non-porous layer preferably includes a single crystal Si layer and an insulating layer in order from the inside.
[0071]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, the insulating layer is made of SiO.₂A layer is preferred.
[0072]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the non-porous layer preferably includes a compound semiconductor layer.
[0073]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the second substrate is preferably a Si substrate.
[0074]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the second substrate is preferably a Si substrate having an oxide film on the surface.
[0075]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the second substrate is preferably a light-transmitting substrate.
[0076]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the second substrate is preferably an insulating substrate.
[0077]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the second substrate is preferably a quartz substrate.
[0078]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, it is preferable to further include a flattening step of flattening the separated second substrate after the removing step.
[0079]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the planarization step preferably includes a heat treatment in an atmosphere containing hydrogen.
[0080]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, in the removing step, a) hydrofluoric acid, b) a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid, c) buffered hydrofluoric acid D) It is preferable that the porous layer is selectively etched using any one of buffered hydrofluoric acid and a mixed liquid obtained by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid as an etchant.
[0081]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, in the removing step, the porous layer may be selectively etched with an etchant that etches the porous layer faster than the compound semiconductor is etched. preferable.
[0082]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, in the removing step, the porous layer is preferably selectively polished using the non-porous layer as a stopper.
[0083]
  Other than the invention described in the specificationIn the substrate manufacturing method according to the fifth aspect, for example, the bonding step is preferably a step of bringing the first substrate on which the non-porous layer is formed into close contact with the second substrate.
[0084]
  Other than the invention described in the specificationIn the method for manufacturing a substrate according to the fifth aspect, for example, the bonding step includes an anode bonding and pressurization after the first substrate on which the non-porous layer is formed is brought into close contact with the second substrate. Or it is preferable that it is the process of performing the process chosen from heat processing or these combination.
[0085]
  Other than the invention described in the specificationA method for manufacturing a semiconductor thin film according to a sixth aspect includes a first forming step of forming a porous layer on a surface of a substrate according to any one of the above-described substrate processing methods, and forming the semiconductor thin film on the porous layer And a separation step of separating the substrate obtained by the second formation step at the portion of the porous layer.
[0086]
  Other than the invention described in the specificationIn the method for manufacturing a semiconductor thin film according to the sixth aspect, for example, in the separation step, the substrate is obtained by attaching a film to the semiconductor thin film of the substrate obtained by the second formation step and peeling the film. Is preferably separated at the porous layer portion.
[0087]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
[0088]
First, the manufacturing process of the semiconductor substrate according to the first embodiment of the present invention will be described. FIG. 1 is a diagram showing a manufacturing process of a semiconductor substrate according to the first embodiment of the present invention.
[0089]
First, in the step shown in FIG. 1A, a single crystal Si substrate 11 is prepared, and one porous layer 12 is formed on the surface side.
[0090]
Next, in the process shown in FIG. 1B, at least one non-porous layer is formed on the porous layer 12, and this is used as the first substrate 10. In the illustrated example, two non-porous layers 13 and 14 are formed. As the lower non-porous layer 13, for example, a single crystal Si layer is suitable. This single crystal Si layer can be used, for example, as an active layer in an SOI substrate. Further, as the non-porous layer 14 on the surface side, for example, SiO₂An (insulating layer) layer is preferred. This SiO₂The layer is suitable for separating the active layer from the bonding interface.
[0091]
As the non-porous layer, in addition to the above, a polycrystalline Si layer, an amorphous Si layer, a metal layer, a compound semiconductor layer, a superconducting layer, and the like are also suitable. Further, an element such as a MOSFET may be formed in the non-porous layer at this time.
[0092]
In the step shown in FIG. 1C, the first substrate 10 and the separately prepared second substrate 20 are brought into close contact with each other with the non-porous layers 13 and 14 interposed therebetween. Then, the 1st board | substrate 10 and the 2nd board | substrate 20 are bonded together by the process which combined anodic bonding, pressurization or heat processing, or these, and the bonded substrate 30 is created.
[0093]
Here, when a single crystal Si layer is formed as the non-porous layer 13, the surface of the single crystal Si layer is SiO 2 by a method such as thermal oxidation as described above.₂It is preferable to bond the first substrate 10 and the second substrate 20 after forming the layer.
[0094]
Further, as the second substrate 20, in addition to the Si substrate, for example, a Si substrate with SiO 2₂A substrate on which a layer is formed, a light-transmitting substrate such as quartz, an insulating substrate, a sapphire substrate, and the like are suitable. However, the material of the second substrate is not limited to these, and other types of substrates can be used as long as the bonding surface is a sufficiently flat substrate. Furthermore, instead of the second substrate 20, for example, a flexible film or the like can be adopted.
[0095]
Note that when the non-porous layer 13 is not composed of Si or when the Si substrate is not used as the second substrate 20, it is not necessary to form the non-porous layer 14 as an insulating layer.
[0096]
Further, at the time of bonding, it is also possible to stack three sheets with a separate insulating thin plate sandwiched between the first substrate 10 and the second substrate 20.
[0097]
In the step shown in FIG. 1D, the bonded substrate stack 30 is separated into two at the porous layer 12 portion. As a separation method, for example, a method of driving a fluid into the porous layer 12, a method of applying a force (for example, pressing force or tensile force) to the bonded substrate 30 in a direction perpendicular to the surface, and bonding A method of applying an external pressure such as a shearing force in a plane direction to the substrate 30, a method of oxidizing the porous Si layer 12 from the peripheral portion to expand it, and generating an internal pressure in the porous Si layer 12, and a bonded substrate 30 A method of applying thermal stress to the porous layer 12 by applying heat that changes in a pulsed manner, a method of softening the porous layer 12, or inserting a wedge between the two substrates constituting the bonded substrate 30 There are other methods, but other methods can also be adopted. Here, in the method of injecting a fluid into the porous layer 12, as the fluid, for example, a liquid such as pure water, a gas such as nitrogen gas, air gas, oxygen gas, hydrogen gas, carbon dioxide gas, or inert gas is preferable. is there.
[0098]
Instead of separating the bonded substrate 30 into two substrates, the portion from the back surface of the first substrate 10 to the porous layer 12 in the bonded substrate 30 may be removed by grinding, polishing, or the like.
[0099]
By this separation process, the bonded substrate 30 is obtained by combining the substrate 10 ′ having the porous layer 12 ′ on the single crystal Si substrate 11, the non-porous layer (for example, the insulating layer) 14, the non-porous layer 14, The substrate is separated into a porous layer (for example, a single crystal Si layer) 13 and a substrate (20 + 10 ″) having a porous layer 12 ″ in this order.
[0100]
In the step shown in FIG. 1E, the porous layer 12 ″ on the second substrate 20 is removed. When the non-porous layer 13 is a single crystal Si layer, for example, for etching Si. Ordinary etching solution, or a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid or hydrofluoric acid, which is an etching solution for selectively etching porous Si, or buffered hydrofluoric acid or Electroless wet chemical etching of only the porous Si layer 12 ″ using at least one kind of etching solution selected from a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide to buffered hydrofluoric acid. Thus, the non-porous layers 14 and 13 can be left on the second substrate 20. Since porous Si has an enormous surface area, as described above, it is possible to selectively etch only porous Si even using a normal Si etchant.
[0101]
There is also a method of selectively removing the porous Si layer 12 ″ by polishing using the non-porous layer 13 as a polishing stopper.
[0102]
When the compound semiconductor layer is formed as the non-porous layer 13, for example, by using an etchant having a faster etching rate of Si than the etching rate of the compound semiconductor, only the porous Si layer 12 ″ is selectively selected. The single crystal compound semiconductor layer (non-porous layer 13) thinned by chemical etching can be left on the second substrate 20. The single crystal compound semiconductor layer (non-porous layer 13) can be used as a polishing stopper. There is also a method of selectively removing the porous Si layer 12 ″ by polishing.
[0103]
FIG. 1E shows the semiconductor substrate manufactured by the above process. According to the above process, a non-porous thin film (for example, a single crystal Si thin film) having a flat and uniform film thickness can be formed over the entire area of the second substrate 20.
[0104]
For example, as the non-porous layer 13 on the surface side, a single-crystal Si layer, and as the non-porous layer 14 inside, SiO₂The semiconductor substrate on which the layer is formed can be used as an SOI substrate. In addition, when an insulating substrate is employed as the second substrate 20, a semiconductor substrate suitable for manufacturing an insulated electronic device can be formed.
[0105]
In the step shown in FIG. 1F, the porous layer 12 'remaining on the single crystal Si substrate 11 is removed. Then, when the surface flatness is unacceptably rough, the surface of the single crystal Si substrate 11 is flattened, whereby the single crystal Si substrate 11 for forming this substrate as the first substrate 10, or It can be used as the second substrate 20.
[0106]
Next, a manufacturing process of the semiconductor substrate according to the second embodiment of the present invention will be described. FIG. 2 is a diagram showing a manufacturing process of a semiconductor substrate according to the second embodiment of the present invention.
[0107]
First, in the step shown in FIG. 2A, a single crystal Si substrate 11 is prepared, and two porous layers 12a and 12b having different porosities are formed on the surface side. Three or more porous layers may be formed.
[0108]
The porous layer 12a as the outermost surface layer preferably has a porosity of 30% or less, for example, in order to form a high quality epitaxial layer thereon. On the other hand, the second porous layer 12b preferably has a porosity of 30% or more, for example, in order to facilitate separation.
[0109]
In the step shown in FIG. 2B, at least one non-porous layer is formed on the outermost porous layer 12 a, and this is used as the first substrate 10. In the illustrated example, two non-porous layers 13 and 14 are formed. As the lower non-porous layer 13, for example, a single crystal Si layer is suitable. This single crystal Si layer can be used, for example, as an active layer in an SOI substrate. Further, as the non-porous layer 14 on the surface side, for example, SiO₂An (insulating layer) layer is preferred. This SiO₂The layer is suitable for separating the active layer from the bonding interface.
[0110]
As the non-porous layer, in addition to the above, a polycrystalline Si layer, an amorphous Si layer, a metal layer, a compound semiconductor layer, a superconducting layer, and the like are also suitable. Further, an element such as a MOSFET may be formed in the non-porous layer at this time.
[0111]
In the step shown in FIG. 2C, the first substrate 10 and the separately prepared second substrate 20 and the non-porous layer are sandwiched at room temperature. Thereafter, the first substrate 10 and the second substrate 20 are bonded to each other by anodic bonding, pressurization, heat treatment, or a combination of these to form a bonded substrate 30.
[0112]
Here, when a single crystal Si layer is formed as the non-porous layer 13, the surface of the single crystal Si is SiO 2 by a method such as thermal oxidation as described above.₂It is preferable to bond the first substrate 10 and the second substrate 20 after forming the layer.
[0113]
Further, as the second substrate 20, in addition to the Si substrate, for example, a Si substrate with SiO 2₂A substrate on which a layer is formed, a light-transmitting substrate such as quartz, an insulating substrate, a sapphire substrate, and the like are suitable. However, the material of the second substrate is not limited to these, and other types of substrates can be used as long as the bonding surface is a sufficiently flat substrate. Furthermore, instead of the second substrate 20, for example, a flexible film or the like can be adopted.
[0114]
Note that when the non-porous layer 13 is not composed of Si or when the Si substrate is not used as the second substrate 20, it is not necessary to form the non-porous layer 14 as an insulating layer.
[0115]
Further, at the time of bonding, it is also possible to stack three sheets with a separate insulating thin plate sandwiched between the first substrate 10 and the second substrate 20.
[0116]
In the step shown in FIG. 2D, the bonded substrate stack 30 is separated into two at the porous layers 12a and 12b, particularly at the lower porous layer 12b. As a separation method, for example, a method of driving a fluid into the porous layers 12a and 12b, a method of applying a force (for example, pressing force, tensile force) to the bonded substrate 30 in a direction perpendicular to the surface thereof, A method of applying an external pressure such as a shearing force to the bonded substrate 30 in a plane direction, and oxidizing and expanding the porous Si layers 12a and 12b from the peripheral portion to generate an internal pressure in the porous Si layers 12a and 12b. A method for applying heat stress to the porous layers 12a and 12b by applying a pulse-like heat to the bonded substrate 30; a method for softening the porous layers 12a and 12b; Although there is a method of inserting a wedge between two substrates, other methods can also be adopted. Here, in the method of driving the fluid into the porous layers 12a and 12b, examples of the fluid include liquids such as pure water, gases such as nitrogen gas, air gas, oxygen gas, hydrogen gas, carbon dioxide gas, and inert gas. Is preferred.
[0117]
Instead of separating the bonded substrate 30 into two substrates, the layers from the back surface of the first substrate 10 to the porous layers 12a and 12b in the bonded substrate 30 may be removed by grinding, polishing, or the like.
[0118]
By this separation process, the bonded substrate 30 is obtained by combining the substrate 10 ′ having the porous layer 12 b ′ on the single crystal Si substrate 11, the non-porous layer (for example, insulating layer) 14 on the second substrate 20, The substrate is separated into a porous layer (for example, a single crystal Si layer) 13, a porous layer 12a, and a substrate (20 + 10 ″) having a porous layer 12b ″ in this order.
[0119]
2E, the porous layers 12a and 12b ″ on the second substrate 20 are removed. When the nonporous layer 13 is a single crystal Si layer, for example, Si is etched. Or a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid or hydrofluoric acid, which is an etching solution for selectively etching porous Si, or buffered fluorine. Only the porous Si layers 12a and 12b "are electrolessly wetted using at least one etching solution selected from a mixed solution obtained by adding at least one of alcohol and hydrogen peroxide to acid or buffered hydrofluoric acid. By performing chemical etching, the nonporous layers 14 and 13 can be left on the second substrate 20. Since porous Si has an enormous surface area, as described above, it is possible to selectively etch only porous Si even using a normal Si etchant.
[0120]
There is also a method of selectively removing the porous Si layers 12a and 12b ″ by polishing using the non-porous layer 13 as a polishing stopper.
[0121]
When the compound semiconductor layer is formed as the non-porous layer 13, for example, only the porous Si layers 12a and 12b ″ are selected by using an etchant that etches Si faster than the compound semiconductor is etched. The single crystal compound semiconductor layer (non-porous layer 13) thinned on the second substrate 20 by chemical etching can be left, and the single crystal compound semiconductor layer (non-porous layer 13) is polished. There is also a method of selectively removing the porous Si layers 12a and 12b ″ as a stopper by polishing.
[0122]
FIG. 2E shows the semiconductor substrate manufactured by the above process. According to the above process, a non-porous thin film (for example, a single crystal Si thin film) having a flat and uniform film thickness can be formed over the entire area of the second substrate 20.
[0123]
For example, as the non-porous layer 13 on the surface side, a single-crystal Si layer, and as the non-porous layer 14 inside, SiO₂The semiconductor substrate on which the layer is formed can be used as an SOI substrate. In addition, when an insulating substrate is employed as the second substrate 20, a semiconductor substrate suitable for manufacturing an insulated electronic device can be formed.
[0124]
In the step shown in FIG. 2F, the porous layer 12b 'remaining on the single crystal Si substrate 11 is removed. Then, when the surface flatness is unacceptably rough, the surface of the single crystal Si substrate 11 is flattened, whereby the single crystal Si substrate 11 for forming this substrate as the first substrate 10, or It can be used as the second substrate 20.
[0125]
Hereinafter, the step shown in FIG. 1A or FIG. 2A, that is, an anodizing apparatus according to a preferred embodiment of the present invention for forming a porous Si layer on the surface of a single crystal Si substrate will be described. To do. .
[0126]
FIG. 3 is a diagram showing a schematic configuration of an anodizing apparatus according to a preferred embodiment of the present invention.
[0127]
The anodizing apparatus 100 has a conductive partition wall 108 between the negative electrode 104 and the positive electrode 106 for preventing contamination of the Si substrate 101 to be processed by the positive electrode 106 and the electrolyte solution. The conductive partition 108 is preferably composed of, for example, a Si substrate, particularly a Si substrate having a specific resistance comparable to that of the Si substrate 101 to be processed. As described above, the conductive partition 108 is made of the same material as the Si substrate 101 to be processed, so that the Si substrate 101 to be processed can be prevented from being contaminated.
[0128]
The conductive partition 108 is preferably detachable. In the example shown in FIG. 3, for example, it is preferable to provide a vacuum suction mechanism on the surface of the positive electrode 106 or the positive electrode holder 107 as a mechanism for attaching and detaching the conductive partition wall 108. Note that the conductive partition wall 108 and the positive electrode 106 need to be electrically connected. Therefore, when there is a gap between the conductive partition wall 108 and the positive electrode 106, it is necessary to fill the gap with a conductive solution, a conductive material, or the like.
[0129]
The negative electrode 104 is held by a negative electrode holder 105.
[0130]
In this anodizing apparatus 100, the anodizing tank 102 is separated into two tanks, a tank on the negative electrode 104 side and a tank on the conductive partition wall 108 (positive electrode 106) side, by the Si substrate 101 to be processed. Therefore, the first electrolyte solution 131 supplied to the front surface side of the Si substrate 101 to be processed and the second electrolyte solution 141 supplied to the back surface side of the Si substrate 101 are made into electrolyte solutions having different properties. Can do.
[0131]
Here, the electrolyte solutions having different properties refer to, for example, electrolyte solutions having different types of ions contained therein, electrolyte solutions having different concentrations of ions contained therein, and the like.
[0132]
In this anodizing apparatus 100, the negative electrode 104 side of the anodizing tank 102, that is, between the negative electrode 104 and the surface side of the Si substrate 101 to be processed (surface on which the porous Si layer is to be formed) As an electrolyte solution 131, an electrolyte solution having an ability to make the Si substrate 101 porous is filled.
[0133]
On the other hand, between the positive electrode 106 side of the anodizing tank 102, that is, between the conductive partition wall 108 and the back side of the Si substrate 101 to be processed (the surface on which the porous Si layer is not formed), the second electrolyte solution 141. For example, it is preferable to fill an electrolyte solution that does not substantially have the ability to make the conductive partition wall 108 porous. Here, the electrolyte solution that does not substantially have the ability to be porous with the conductive partition 108 has a low ability to make the conductive partition 108 porous, and practically the ability to make the conductive partition 108 porous. Also included are electrolyte solutions that can be regarded as lacking.
[0134]
As an example of such a second electrolyte solution 141, for example, an electrolyte solution capable of electrolytic etching (or electrolytic polishing) of the conductive partition wall 108 can be given. When an electrolyte solution that can electrolytically etch the conductive partition 108 is used, the surface of the conductive partition 108 is entirely etched without making the surface porous. Another example of the second electrolyte solution 141 is an electrolyte solution containing only ions that do not react with the constituent material of the conductive partition wall 108, for example.
[0135]
Specifically, as the first electrolyte solution 131, for example, an HF solution having a concentration of 10 to 50% is suitable. Further, as the second electrolyte solution 141, for example, an HF solution having a concentration of 10% or less is preferable, and an HF solution having a concentration of 2% or less is more preferable.
[0136]
As described above, between the conductive partition wall 108 and the Si substrate 101, the second electrolyte solution 141 is filled with an electrolyte solution that does not substantially have the ability to make the conductive partition wall 108 porous. When the Si substrate 101 is made porous (anodized), the conductive partition 108 can be prevented from being made porous, and the possibility of particles being generated from the conductive partition 108 can be reduced.
[0137]
On the other hand, as in the prior art, the space between the negative electrode (104) and the Si substrate (101) is filled between the conductive partition (108) made of Si material and the Si substrate (101) to be processed. If the electrolyte solution is the same as the electrolyte solution or the electrolyte partition that fills the electrolyte solution that can be made porous like the Si substrate (101) to be treated, the conductive partition (108) is naturally provided. It is made porous from its surface. Therefore, when one conductive partition wall (108) is attached to the anodizing tank (102) and the anodizing process is performed on a large number of Si substrates (101), a thick porous layer becomes conductive according to the number of processed sheets. It is formed on the partition wall.
[0138]
If the conductive partition wall in which the thick porous layer is formed is continuously used, finally, the porous layer is physically collapsed, and particles composed of the constituent material of the conductive partition wall or the reaction product thereof are generated. The particles contaminate the Si substrate and the anodizing tank to be treated and the electrolyte solution.
[0139]
Under the condition that the conductive partition wall (108) is made porous, particularly when a porous layer having a multilayer structure with different porosities is formed on the Si substrate (101) to be processed, the collapse of the conductive partition wall ( Particle generation) occurs remarkably. The cause is considered to be the following two points.
[0140]
1) Since porous layers having different porosities are formed in layers on the conductive partition walls, the pore walls cannot withstand stress.
[0141]
2) When a porous layer having a high porosity is formed under a porous layer having a low porosity, the porosity of the porous layer having a high porosity is determined by the depth from the surface of the conductive partition wall to the layer. The depth of the thickness (the total thickness of the porous layer) increases as the depth increases. Therefore, when the number of processed Si substrates increases, the porosity of the porous layer formed at the deepest portion of the conductive partition reaches the limit value, and the pore wall collapses.
[0142]
Hereinafter, a preferred procedure for forming a porous Si layer on a Si substrate using the anodizing apparatus 100 according to a preferred embodiment of the present invention will be described.
[0143]
First, in a state where the electrolyte solution in the anodizing tank 102 is empty, the Si substrate 101 to be processed is brought into contact with a suction portion (for example, a suction pad) of the substrate holder 103 by a transfer robot or the like and sucked by the substrate holder 103. Let The substrate holder 103 has a vacuum suction mechanism as a suction portion for holding the Si substrate 101.
[0144]
Next, the first electrolyte solution 131 is pumped from the first tank 114 by the pump 112 and supplied between the negative electrode 104 of the anodizing tank 102 and the Si substrate 101 through the filter 111. In parallel with this, the second electrolyte solution 141 is pumped from the second tank 124 by the pump 122 and supplied between the conductive partition wall 108 of the anodizing tank 102 and the Si substrate 101 through the filter 121.
[0145]
As described above, the first electrolyte solution 131 is an electrolyte solution having the ability to make the surface of the Si substrate 101 to be processed porous, and the second electrolyte solution 141 is substantially a conductive partition wall. It is an electrolyte solution that does not have the ability to make 108 porous.
[0146]
When the first electrolyte solution 131 and the second electrolyte solution 141 are filled on the negative electrode 104 side and the positive electrode 106 side of the anodizing tank 102, respectively, a predetermined size is provided between the negative electrode 104 and the positive electrode 106. A current is passed to form a porous layer having a predetermined porosity on the surface of the Si substrate 101 to be processed. At this time, the entire surface of the conductive partition wall 108 is electrolytically etched without being made porous.
[0147]
Next, the first electrolyte solution 131 is extracted from the lower part of the anodizing tank 102 on the negative electrode 104 side by the pump 113 and discharged to the first tank 114. In parallel with this, the pump 123 extracts the second electrolyte solution 141 from the lower part of the anodizing tank 101 on the positive electrode 106 side and discharges it to the second tank 124.
[0148]
Next, the processed Si substrate 101 is removed from the substrate holder 103 by a transfer robot or the like and transferred to a predetermined position (for example, a carrier).
[0149]
The above process is a process of forming one porous layer 12 on the surface of the Si substrate 11 (101) as shown in FIG.
[0150]
Next, as shown in FIG. 2, as a method for forming two porous layers 12a and 12b on the Si substrate 11 (101) or a method for forming three or more porous layers, There are two methods.
[0151]
In the first method, the first layer (upper layer) porous layer 12 a is formed by flowing a current having a first current value between the negative electrode 105 and the positive electrode 106, and then the negative electrode 105 and the positive electrode 106. The second layer (lower layer) porous layer 12b is formed by passing a current having a second current value therebetween. When three or more porous layers are formed, the process may be repeated by further changing the magnitude of the current flowing between the negative electrode 105 and the positive electrode 106.
[0152]
In the second method, after the first (upper) porous layer 12a is formed on the Si substrate 101, the first electrolyte solution 131 on the negative electrode 104 side is replaced with a third electrolyte solution, and the third electrolyte solution is replaced. The second layer (lower layer) porous layer 12b is formed on the Si substrate 101 with the electrolyte solution. When three or more porous layers are formed, the third electrolyte solution may be changed to another electrolyte solution and the treatment repeated.
[0153]
FIG. 4 is a diagram showing a schematic configuration of an anodizing apparatus according to a modification of the anodizing apparatus 100 shown in FIG. In addition, the same code | symbol is attached | subjected to the component substantially the same as the anodizing apparatus 100 shown in FIG.
[0154]
The anodizing tank 201 of the anodizing apparatus 200 is provided with a conductive partition holder 103a which is a dedicated holder for fixing the conductive partition 108. This anodizing tank 201 is used in a state where a conductive solution 151 is filled between the conductive partition wall 108 and the positive electrode 106. The conductive solution 151 is used simply to electrically connect the conductive partition wall 108 and the positive electrode 106.
[0155]
The processing of the Si substrate 101 by the anodizing apparatus 200 is the same as the processing by the anodizing apparatus 100 shown in FIG.
[0156]
FIG. 5 is a diagram showing a schematic configuration of an anodizing apparatus according to a modification of the anodizing apparatus 100 shown in FIG. This anodizing apparatus 300 has the ability to process a large number of Si substrates at once. Specifically, in this anodizing apparatus 300, a large number of substrate holders 103 are attached to the anodizing tank 301.
[0157]
The processing of the Si substrate 101 by the anodizing apparatus 300 is the same as the processing by the anodizing apparatus 100 shown in FIG.
[0158]
Furthermore, a modified example in which the anodizing apparatus shown in FIG. 3 is modified so that a large number of substrates can be collectively processed by including a large number of substrate holders 103 is also suitable.
[0159]
FIG. 6 is a diagram showing a schematic configuration of an automatic processing line in which the anodizing apparatus 100 shown in FIG. 3 is incorporated. In FIG. 6, the first tank 131, the second tank 141, and the like, which are components outside the anodized layer 102, are omitted.
[0160]
Instead of the anodizing apparatus 100 shown in FIG. 3, the anodizing apparatus 200 shown in FIG. 4 or the anodizing apparatus 300 shown in FIG. 5 may be adopted.
[0161]
Hereinafter, a processing procedure in the automatic manufacturing line 700 will be described. The automatic manufacturing line 700 is controlled by a computer 750 having an input unit such as an operation panel.
[0162]
In this automatic production line 700, a wafer carrier 702 containing a Si substrate 101 to be processed is placed on a loader 701, and an instruction to start processing is given from the operator via the operation panel of the computer 750. The following series of processes is started. In the state before the start of the treatment, the anodizing tank 102 is not filled with the electrolyte solution.
[0163]
First, under the control of the computer 750, the first transfer robot 721 sucks and takes out the back surface of the Si substrate 101 in the wafer carrier 702 by the suction unit and moves it to the negative electrode 104 side in the anodizing tank 102. . Then, under the control of the computer 750, the second transfer robot 722 causes the suction portion to contact the back surface of the Si substrate 101 through the opening of the substrate holder 103, and sucks the Si substrate 101 by the suction portion to perform the first transfer. Receiving from the robot 721, the Si substrate 101 is moved to a position where the Si substrate 101 contacts the suction part of the substrate holder 103. In this state, under the control of the computer 750, the vacuum adsorption mechanism of the substrate holder 103 attracts the Si substrate 102 to the adsorption portion.
[0164]
Next, under the control of the computer 750, the first electrolyte solution 131 is filled between the negative electrode 104 of the anodizing tank 102 and the Si substrate 101, and the second electrode is interposed between the conductive partition wall 108 and the Si substrate 101. The electrolyte solution 141 is filled.
[0165]
Next, under the control of the computer 750, a current having a predetermined magnitude is passed between the negative electrode 104 and the positive electrode 106 of the anodizing apparatus 100 to form a porous layer on the surface of the Si substrate 101. Here, as described above, a porous layer having a multilayer structure may be formed on the surface of the Si substrate 101.
[0166]
Next, under the control of the computer 750, the first electrolyte solution 131 between the negative electrode 104 and the Si substrate 101 is discharged, and the second electrolyte solution 141 between the conductive partition wall 108 and the Si substrate 101 is discharged. Discharged.
[0167]
Next, under the control of the computer 750, the second transfer robot 722 sucks the back surface of the Si substrate 101 in the anodizing tank 102, and after the vacuum suction by the substrate holder 103 is released, the second transfer robot 722 moves to the substrate holder. The Si substrate 101 is pulled away from 103. Then, the second transfer robot 722 delivers the Si substrate 101 to the first transfer robot 721 under the control of the computer 750.
[0168]
Next, under the control of the computer 750, the first transfer robot 721 accommodates the Si substrate 101 in a wafer carrier 702 that is pre-immersed in the water washing tank 703.
[0169]
By repeating the above processing, all the Si substrates 101 in the wafer carrier 702 on the loader 701 are processed and accommodated in the wafer carrier 702 in the water washing tank 703. Under the control of the computer 750, the Si substrate 101 Is washed.
[0170]
Next, under the control of the computer 750, the third transfer robot 731 takes out the Si substrate 101 in the washing tank 703 while being accommodated in the wafer carrier 702 and transfers it to the spin dryer 704. Then, the Si substrate 101 is dried by the spin dryer 704 under the control of the computer 750.
[0171]
Then. Under the control of the computer 750, the third transport robot 731 transports the Si substrate onto the unloader 705 while being accommodated in the wafer carrier 702.
[0172]
Next, examples of anodizing treatment by the anodizing apparatus described above will be given.
[0173]
[Example 1]
A single-crystal Si substrate was set in any one of the above anodizing apparatuses to form one porous Si layer. The anodizing conditions at this time are as follows. Note that the current density is the current density of the current flowing between the negative electrode 104 and the positive electrode 106, and the first electrolyte solution is an electrolyte solution 131 filled between the negative electrode 104 and the single crystal Si substrate to be processed, The second electrolyte solution means an electrolyte solution 141 filled between the conductive partition wall 108 and the single crystal Si substrate to be processed (the same applies to other examples).
[0174]
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 145 μm by electrolytic etching.
[0175]
[Example 2]
A single-crystal Si substrate was set in any of the anodizing apparatuses described above, and a porous layer having a three-layer structure was formed by changing the current density. The anodizing conditions for forming the first to third porous layers are as follows.
[0176]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 20 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
<Anodizing conditions for the formation of the third porous layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 1 (min)
Porous Si thickness (target): 1.1μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 271 μm by electrolytic etching.
[0177]
In addition, the above results show that even when the porous layers of the first layer to the third layer are continuously formed on each Si substrate and the porous layer is formed on 100 Si substrates, In the case where the first porous layer is formed, the second porous layer is formed on the 100 Si substrates, and then the third porous layer is formed on the Si substrate. Was the same.
[0178]
[Example 3]
A single-crystal Si substrate was set in any of the above anodizing apparatuses, and a porous layer having a two-layer structure was formed by changing the current density. The anodizing conditions for forming the first and second porous layers are as follows.
[0179]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 30 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 110 (sec)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 169 μm by electrolytic etching.
[0180]
In addition, the above results show that even when the porous layer is formed on 100 Si substrates while the first and second porous layers are continuously formed on each Si substrate, 100 Si substrates are formed. The same applies to the case where the first porous layer was formed on the first Si layer and the second porous layer was then formed on the 100 Si substrates.
[0181]
[Example 4]
A single-crystal Si substrate was set in any one of the above anodizing apparatuses, and the porous layers 12a and 12b having a two-layer structure were formed by changing the current density (FIG. 2 (a)). The anodizing conditions for forming the first and second porous layers are as follows.
[0182]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 20 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 145 μm by electrolytic etching.
[0183]
In addition, the above results show that even when the porous layer is formed on 100 Si substrates while the first and second porous layers are continuously formed on each Si substrate, 100 Si substrates are formed. The same applies to the case where the first porous layer was formed on the first Si layer and the second porous layer was then formed on the 100 Si substrates.
[0184]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the pores of the porous Si layers 12a and 12b were covered with a thermal oxide film.
[0185]
Next, a single crystal Si layer 13 having a thickness of 0.3 μm was epitaxially grown on the porous Si layer by a CVD (Chemical Vapor Deposition) method (FIG. 2B). The growth conditions are as follows. In the previous stage of epitaxial growth, H₂Since the surface of the porous Si layer is exposed inside, the pores on the surface are filled and the surface becomes flat.
[0186]
<Epitaxial growth conditions>
Source gas: SiH₂Cl₂/ H₂
Gas flow rate: 0.5 / 180 (l / min)
Gas pressure: 80 (Torr)
Temperature: 950 (℃)
Growth rate: 0.3 (μm / min)
Next, 200 nm thick SiO2 is formed on the surface of the epitaxially grown single crystal Si layer 13 by thermal oxidation.₂Layer 14 was formed (FIG. 2B).
[0187]
Then this SiO₂After the surface of the layer and the surface of a separately prepared Si substrate (second substrate) 20 were brought into close contact with each other, heat treatment was performed at 1000 ° C. for 1 hour to form a bonded substrate 30 (FIG. 2 ( c)). This heat treatment is N₂Alternatively, it may be performed in an inert gas, in an oxidizing atmosphere, or a combination thereof.
[0188]
Next, the bonded substrate 30 was removed by grinding, polishing, or etching until the porous Si layer 12b was exposed from the back surface side of the first substrate 10 (FIG. 2D).
[0189]
Next, the porous Si layers 12a and 12b ″ remaining on the bonded substrate 30 were etched with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide, and water (FIG. 2 (e)). The crystalline Si layer 13 functions as an etch stop, and the porous Si layer is selectively etched.
[0190]
Since the etching rate of non-porous single-crystal Si by the etching solution is extremely low, the etching selectivity between porous single-crystal Si and non-porous single-crystal Si is 10⁵As a result, the etching amount in the non-porous layer (about several tens of angstroms) can be ignored in practice.
[0191]
Through the above steps, an SOI substrate (FIG. 2E) having the single crystal Si layer 13 having a thickness of 0.2 μm on the Si oxide film 14 is obtained. When the film thickness of the single crystal Si layer of this SOI substrate was measured at 100 points over the entire surface, the uniformity of the film thickness was 201 nm ± 4 nm.
[0192]
Further, heat treatment was performed at 1100 ° C. in hydrogen for 1 hour. When the surface roughness was evaluated with an atomic force microscope, the mean square roughness in a 50 μm square region was about 0.2 nm, which was equivalent to a commercially available Si wafer.
[0193]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the Si layer and that good crystallinity was maintained.
[0194]
Similar results were obtained when no oxide film was formed on the surface of the epitaxially grown single crystal Si layer.
[0195]
[Example 5]
This embodiment is a modification of the above-described fourth embodiment. Specifically, the production conditions in Example 4 were changed as follows.
1) Epitaxial Si layer thickness: 2μm
2) The thickness of the thermal oxide film on the surface of the epitaxial Si layer: 0.1 μm
3) Second substrate: 1.9μm SiO₂Si substrate with layers
4) Bonding step: After the surfaces of the first and second substrates are exposed to nitrogen plasma, the substrates are brought into close contact with each other and annealed at 400 ° C. for 10 hours.
[0196]
[Example 6]
This embodiment is a modification of the above-described fourth embodiment. Specifically, the production conditions in Example 4 were changed as follows.
1) Second substrate: quartz substrate
2) Bonding step: After the surfaces of the first and second substrates are exposed to nitrogen plasma, both substrates are brought into close contact and annealed at 200 ° C. for 24 hours.
3) Heat treatment in hydrogen: Further heat treatment in hydrogen at 970 ° C. for 2 hours (Evaluation of surface roughness with an atomic force microscope reveals that the mean square roughness in a 50 μm square region is approximately 0.2 nm. It was equivalent to a commercially available Si wafer).
[0197]
[Example 6]
The single crystal Si substrate 11 was set in any one of the anodizing apparatuses described above to form a single porous layer 12 (FIG. 1 (a)). The anodizing conditions at this time are as follows.
[0198]
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the conductive partition 108 was reduced by about 66 μm by electrolytic etching.
[0199]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the pores of the porous Si layer 12 were covered with a thermal oxide film.
[0200]
Next, a single crystal GaAs layer 13 having a thickness of 1 μm was epitaxially grown on the porous Si layer 12 by MOCVD (Metal Organic Chemical Vapor Deposition) method (FIG. 1B). The growth conditions are as follows.
[0201]
<Epitaxial growth conditions>
Source gas: TMG / AsH_Three/ H₂
Gas pressure: 80 (Torr)
Temperature: 700 (℃)
Next, the surface of the GaAs layer 13 and the surface of a separately prepared Si substrate (second substrate) 20 were brought into close contact with each other to form a bonded substrate 30 (FIG. 1C).
[0202]
Next, the bonded substrate 30 was removed by grinding, polishing, or etching until the porous Si layer 12 was exposed from the back surface side of the first substrate 10 (FIG. 1D).
[0203]
Next, the porous Si layer 12 ″ remaining on the bonded substrate 30 was etched at 110 ° C. with a mixed solution (etching solution) of ethylenediamine / pyrocatechol / water (ratio of 17 ml: 3 g: 8 ml). Single crystal GaAs layer 13 functioned as an etch stop, and porous Si was selectively etched.
[0204]
The etching rate of the GaAs single crystal by the etching solution is extremely low, and the etching amount (about several tens of angstroms) in the GaAs single crystal can be ignored in practice.
[0205]
Through the above steps, a substrate having the single crystal GaAs layer 13 having a thickness of 1 μm on the single crystal Si substrate 20 is obtained. When the film thickness of the single crystal GaAs layer of this substrate was measured at 100 points over the entire surface, the film thickness uniformity was 1 μm ± 29.8 nm.
[0206]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the GaAs layer and that good crystallinity was maintained.
[0207]
By using a Si substrate with an oxide film as a support substrate, it was possible to form a substrate having a GaAs layer on an insulating film.
[0208]
[Example 8]
A single-crystal Si substrate was set in any one of the above anodizing apparatuses to form one porous layer 12 (FIG. 1A). The anodizing conditions at this time are as follows.
[0209]
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the conductive partition 108 was reduced by about 145 μm by electrolytic etching.
[0210]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the pores of the porous Si layer 12 were covered with a thermal oxide film.
[0211]
Next, a single crystal InP layer 13 having a thickness of 1 μm was epitaxially grown on the porous Si layer 12 by MOCVD (Metal Organic Chemical Vapor Deposition) method (FIG. 1B).
[0212]
Next, the surface of this InP layer 13 and the surface of a separately prepared quartz substrate (second substrate) 20 are exposed to nitrogen plasma and then brought into close contact with each other and annealed at 200 ° C. for 10 hours to form a bonded substrate 30. (FIG. 1 (c)).
[0213]
Next, a 0.2 mm diameter water jet was sprayed toward the gap in the beveling of the bonded substrate 30 to separate the bonded substrate 30 into two at the porous Si layer 12 (FIG. 1D). ).
[0214]
Next, the porous Si layer 12 ″ remaining on the second substrate side was selectively etched while stirring with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide and water (FIG. 1 (e)). At this time, the single crystal InP layer 13 functions as an etch stop, and the porous Si layer 12 ″ is selectively etched.
[0215]
The etching rate of the InP single crystal by the etching solution is extremely low, and the etching amount (about several tens of angstroms) in the single crystal InP layer 13 can be ignored in practice.
[0216]
Through the above steps, a substrate (FIG. 1E) having the single crystal InP layer 13 having a thickness of 1 μm on the quartz substrate 20 is obtained. When the film thickness of the single crystal InP layer of this substrate was measured at 100 points over the entire surface, the film thickness uniformity was 1 μm ± 29.0 nm.
[0217]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the InP layer, and good crystallinity was maintained.
[0218]
[Example 9]
In this embodiment, the processes described in the respective embodiments are performed on both surfaces of the single crystal Si substrate constituting the first substrate in the fourth to eighth embodiments.
[0219]
[Example 10]
The single crystal Si substrate 11 was set in any one of the above anodizing apparatuses, and the porous layers 12a and 12b having a two-layer structure were formed by changing the current density (FIG. 2A). The anodizing conditions for forming the porous layers of the first layer and the second layer are as follows.
[0220]
<Anodizing conditions for forming the first porous layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 20 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 258 μm by electrolytic etching.
[0221]
In addition, the above results show that even when the porous layer is formed on 100 Si substrates while the first and second porous layers are continuously formed on each Si substrate, 100 Si substrates are formed. The same applies to the case where the first porous layer was formed on the first Si layer and the second porous layer was then formed on the 100 Si substrates.
[0222]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the pores of the porous Si layers 12a and 12b were covered with a thermal oxide film.
[0223]
Next, a single crystal Si layer 13 having a thickness of 0.3 μm was epitaxially grown on the porous Si layer 12a by a CVD (Chemical Vapor Deposition) method (FIG. 2B). The growth conditions are as follows. In the previous stage of epitaxial growth, H₂Since the surface of the porous Si layer is exposed inside, the pores on the surface are filled and the surface becomes flat.
[0224]
<Epitaxial growth conditions>
Source gas: SiH₂Cl₂/ H₂
Gas flow rate: 0.5 / 180 (l / min)
Gas pressure: 80 (Torr)
Temperature: 950 (℃)
Growth rate: 0.3 (μm / min)
Next, 200 nm thick SiO2 is formed on the surface of the epitaxially grown single crystal Si layer 13 by thermal oxidation.₂Layer 14 was formed (FIG. 2 (b)).
[0225]
Then this SiO₂After the surface of the layer 14 and the surface of a separately prepared Si substrate (second substrate) 20 were brought into close contact with each other, heat treatment was performed at 1000 ° C. for 1 hour to form a bonded substrate 30 (FIG. 2). (C)).
[0226]
Next, a 0.2 mm diameter water jet is sprayed toward the gap between the beveling of the bonded substrate 30 to separate the bonded substrate 30 into two substrates at the porous Si layer 12b of the second layer. (FIG. 2D).
[0227]
Next, the porous Si layers 12a and 12b ″ remaining on the second substrate side were etched with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide water, and water (FIG. 2 (e)). The single crystal Si layer 13 functions as an etch stop, and the porous Si layers 12a and 12b ″ are selectively etched.
[0228]
Since the etching rate of non-porous single-crystal Si by the etching solution is extremely low, the etching selectivity between porous single-crystal Si and non-porous single-crystal Si is 10⁵As a result, the etching amount in the non-porous layer (about several tens of angstroms) can be ignored in practice.
[0229]
Through the above steps, an SOI substrate (FIG. 2E) having the single crystal Si layer 13 having a thickness of 0.2 μm on the Si oxide film 14 is obtained. When the film thickness of the single crystal Si layer of this SOI substrate was measured at 100 points over the entire surface, the uniformity of the film thickness was 201 nm ± 4 nm.
[0230]
Further, heat treatment was performed at 1100 ° C. in hydrogen for 1 hour. When the surface roughness was evaluated with an atomic force microscope, the mean square roughness in a 50 μm square region was about 0.2 nm, which was equivalent to a commercially available Si wafer.
[0231]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the Si layer and that good crystallinity was maintained.
[0232]
Similar results were obtained when no oxide film was formed on the surface of the epitaxially grown single crystal Si layer.
[0233]
Further, the porous Si remaining on the first substrate side was also selectively etched with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide, and water. At this time, the single crystal Si functions as an etch stop, and the porous Si is selectively etched. This substrate can be again input to the anodizing step as a substrate for forming the first substrate, or can be input to the bonding step as the second substrate.
[0234]
Before reusing the substrate for forming the first substrate, heat treatment may be performed in hydrogen at 1100 ° C. for 1 hour to recover the surface roughness (microroughness) caused by the micropores. However, when the above substrate is reused for forming the first substrate, the surface flattening is performed simultaneously with the sealing of the pores on the surface of the porous Si layer during the pre-baking in hydrogen before the epitaxial growth process. Therefore, it is not always necessary to flatten the microroughness.
[0235]
Here, instead of the heat treatment in hydrogen, the microroughness caused by the micropores may be flattened by the surface touch polish.
[0236]
[Example 11]
This embodiment is a modification of the tenth embodiment. Specifically, the anodizing conditions for forming the porous layers of the first layer and the second layer were changed as follows.
[0237]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 30 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 169 μm by electrolytic etching.
[0238]
[Example 12]
This embodiment is a modification of the tenth embodiment. Specifically, the production conditions in Example 4 were changed as follows.
1) Epitaxial Si layer thickness: 2μm
2) The thickness of the thermal oxide film on the surface of the epitaxial Si layer: 0.1 μm
3) Second substrate: 1.9μm SiO₂Si substrate with layers
4) Bonding step: After the surfaces of the first and second substrates are exposed to nitrogen plasma, the substrates are brought into close contact with each other and annealed at 400 ° C. for 10 hours.
[0239]
[Example 13]
This embodiment is a modification of the tenth embodiment. Specifically, the production conditions in Example 4 were changed as follows.
1) Second substrate: quartz substrate
2) Bonding step: After the surfaces of the first and second substrates are exposed to nitrogen plasma, both substrates are brought into close contact and annealed at 200 ° C. for 24 hours.
3) Heat treatment in hydrogen: Further heat treatment in hydrogen at 970 ° C. for 2 hours (Evaluation of surface roughness with an atomic force microscope reveals that the mean square roughness in a 50 μm square region is approximately 0.2 nm. It was equivalent to a commercially available Si wafer).
4) Reuse: The first substrate side after separation is put into the anodizing process for forming the first substrate.
[0240]
[Example 14]
The single crystal Si substrate 11 was set in any one of the anodizing apparatuses described above, and the porous layers 12a and 12b having a two-layer structure were formed by changing the current density. The anodizing conditions for forming the porous layers of the first layer and the second layer are as follows.
[0241]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 30 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 110 (sec)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 169 μm by electrolytic etching.
[0242]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the porous Si holes were covered with a thermal oxide film.
[0243]
Next, a single crystal GaAs layer 13 having a thickness of 1 μm was epitaxially grown on the porous Si layer 12a by MOCVD (Metal Organic Chemical Vapor Deposition) method (FIG. 2B). The growth conditions are as follows.
[0244]
<Epitaxial growth conditions>
Source gas: TMG / AsH_Three/ H₂
Gas pressure: 80 (Torr)
Temperature: 700 (℃)
Subsequently, the surface of the GaAs layer 13 and the surface of a separately prepared Si substrate (second substrate) 20 were adhered to form a bonded substrate 30 (FIG. 2C).
[0245]
Next, a 0.2 mm diameter water jet is sprayed toward the beveling gap of the bonded substrate 30, thereby separating the bonded substrate 20 into two at the portion of the second porous layer 12 b (FIG. 2). (D)).
[0246]
Next, the porous Si layer 12b ″ remaining on the second substrate side was etched at 110 ° C. with a mixed solution (etching solution) of ethylenediamine / pyrocatechol / water (ratio of 17 ml: 3 g: 8 ml). Single crystal GaAs Layer 13 served as an etch stop, and porous Si layers 12a and 12b ″ were selectively etched.
[0247]
The etching rate of the GaAs single crystal by the etching solution is extremely low, and the etching amount (about several tens of angstroms) in the GaAs single crystal 13 can be ignored in practice.
[0248]
Through the above steps, a substrate having the single crystal GaAs layer 13 having a thickness of 1 μm on the single crystal Si substrate 20 is obtained. When the film thickness of the single crystal GaAs layer of this substrate was measured at 100 points over the entire surface, the film thickness uniformity was 1 μm ± 29.8 nm.
[0249]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the GaAs layer and that good crystallinity was maintained.
[0250]
By using a Si substrate with an oxide film as the support substrate 20, it was possible to form a substrate having a GaAs layer on the insulating film.
[0251]
Furthermore, the porous Si remaining on the first substrate side was also selectively etched while stirring with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide water, and water. At this time, the single crystal Si functions as an etch stop, and the porous Si is selectively etched. This substrate can be again input to the anodizing step as a substrate for forming the first substrate, or can be input to the bonding step as the second substrate.
[0252]
Before reusing the substrate for forming the first substrate, heat treatment may be performed in hydrogen at 1100 ° C. for 1 hour to recover the surface roughness (microroughness) caused by the micropores. However, when the above substrate is reused for forming the first substrate, the surface flattening is performed simultaneously with the sealing of the pores on the surface of the porous Si layer during the pre-baking in hydrogen before the epitaxial growth process. Therefore, it is not always necessary to flatten the microroughness.
[0253]
Here, instead of the heat treatment in hydrogen, the microroughness caused by the micropores may be flattened by the surface touch polish.
[0254]
[Example 15]
The single crystal Si substrate 11 was set in any one of the above anodizing apparatuses, and the porous layers 12a and 12b having a two-layer structure were formed by changing the current density (FIG. 2A). The anodizing conditions for forming the porous layers of the first layer and the second layer are as follows.
[0255]
<Anodizing conditions for forming the first porous layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 11 (min)
Porous Si thickness (target): 12 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 20 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the thickness of the conductive partition wall 108 was reduced by about 258 μm by electrolytic etching.
[0256]
In addition, the above results show that even when the porous layer is formed on 100 Si substrates while the first and second porous layers are continuously formed on each Si substrate, 100 Si substrates are formed. The same applies to the case where the first porous layer was formed on the first Si layer and the second porous layer was then formed on the 100 Si substrates.
[0257]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. By this oxidation, the inner walls of the pores of the porous Si layer were covered with a thermal oxide film.
[0258]
Next, a single crystal InP layer 13 having a thickness of 1 μm was epitaxially grown on the porous Si layer by MOCVD (Metal Organic Chemical Vapor Deposition) method (FIG. 2B).
[0259]
Next, the surface of this InP layer 13 and the surface of a separately prepared quartz substrate (second substrate) 20 are exposed to nitrogen plasma and then brought into close contact with each other and annealed at 200 ° C. for 10 hours to produce a bonded substrate 30. (FIG. 2 (c)).
[0260]
Next, a 0.2 mm diameter water jet is sprayed toward the beveling gap of the bonded substrate 30, thereby separating the bonded substrate 20 into two at the portion of the second porous layer 12 b (FIG. 2). (D)).
[0261]
Next, the porous Si layer remaining on the second substrate side was selectively etched while stirring with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide and water (FIG. 2E). At this time, the single crystal InP layer 13 functions as an etch stop, and the porous Si layers 12a and 12b ″ are selectively etched.
[0262]
The etching rate of single crystal InP by the etching solution is extremely low, and the etching amount (about several tens of angstroms) in the single crystal InP layer 13 can be ignored in practice.
[0263]
Through the above steps, a substrate having the single crystal InP layer 13 having a thickness of 1 μm on the quartz substrate 20 is obtained. When the film thickness of the single crystal InP layer of this substrate was measured at 100 points over the entire surface, the film thickness uniformity was 1 μm ± 29.0 nm.
[0264]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the InP layer, and good crystallinity was maintained.
[0265]
Furthermore, the porous Si remaining on the first substrate side was also selectively etched while stirring with a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide water, and water. At this time, the single crystal Si functions as an etch stop, and the porous Si is selectively etched. This substrate can be put into the anodizing step again as a substrate for forming the first substrate.
[0266]
Before reusing the substrate for forming the first substrate, heat treatment may be performed in hydrogen at 1100 ° C. for 1 hour to recover the surface roughness (microroughness) caused by the micropores. However, when the above substrate is reused for forming the first substrate, the surface flattening is performed simultaneously with the sealing of the pores on the surface of the porous Si layer during the pre-baking in hydrogen before the epitaxial growth process. Therefore, it is not always necessary to flatten the microroughness.
[0267]
Here, instead of the heat treatment in hydrogen, the microroughness caused by the micropores may be flattened by the surface touch polish.
[0268]
[Example 16]
In this embodiment, the method for separating the bonded substrates in Embodiments 10 to 15 is changed. Specifically, in this embodiment, instead of using the water jet method, a thin wedge of resin is inserted into the gap of the beveling of the bonded substrate, so that the bonded substrate 30 is made into a second layer (lower layer) porous. It separates into two by the quality Si layer 12b.
[0269]
[Example 17]
In this embodiment, the processes described in the respective embodiments are performed on both surfaces of the single crystal Si substrate constituting the first substrate in the embodiments 10 to 15.
[0270]
[Example 18]
A single-crystal Si substrate was set in any one of the above anodizing apparatuses, and a porous layer having a four-layer structure was formed by changing the first electrolyte solution and the current density. The anodizing conditions for forming the first to fourth porous layers are as follows.
[0271]
<Anodizing conditions for forming porous layer of first layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 10 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 2: 2
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 3 (min)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si
<Anodizing conditions for the formation of the third porous layer>
Current density: 7 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 1
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si
<Anodizing conditions for the formation of the fourth porous layer>
Current density: 20 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 2: 2
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 80 (sec)
Porous Si thickness (target): 1 (μm)
Conductive partition material: Si
Under this anodizing condition, 100 Si substrates were processed without replacing the conductive partition 108. A porous layer was not formed on the conductive partition wall 108, and the surface was subjected to electrolytic etching (electropolishing). Therefore, no particles were generated from the conductive partition. By processing 100 Si substrates, the conductive partition 108 was reduced by about 208 μm by electrolytic etching.
[0272]
In addition, the above results show that even when the porous layer is formed on 100 Si substrates while the first to fourth porous layers are continuously formed on each Si substrate, 100 Si substrates are formed. Forming a first porous layer, then forming a second porous layer on the 100 Si substrates, then forming a third porous layer on the Si substrate, The same was true when the fourth porous layer was formed on the Si substrate.
[0273]
As a method of forming a porous layer having a multilayer structure on a single crystal Si substrate while changing the first electrolyte solution 131, for example, a single anodizing device is used, and the negative electrode 104, the single crystal Si to be processed, There are a method of exchanging the first electrolyte solution 131 filled between the two as necessary, a method of using a plurality of anodizing apparatuses, and transferring a Si substrate to be processed to a corresponding anodizing tank.
[0274]
[Example 19]
A single-crystal Si substrate was set in any one of the anodizing apparatuses described above, and a porous layer having a four-layer structure was formed by performing three-step anodizing treatment while changing the current density. The anodizing conditions for forming the porous layers in the first stage to the third stage are as follows.
[0275]
<First stage anodization conditions, etc.>
Current density: 1 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 2
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 8 (min)
Porous Si thickness (target): 10 (μm)
Conductive partition material: Si
<Second stage anodization conditions, etc.>
Current density: 7 (mA · cm^-2)
First anodizing solution: HF: H₂O: C₂H_FiveOH = 1: 1: 2
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 8 (min)
Porous Si thickness (target): 10 (μm)
Conductive partition material: Si
<Third stage anodization conditions, etc.>
Current density: 100 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 1: 1: 2
Second electrolyte solution: HF: H₂O: C₂H_FiveOH = 0.5: 67: 33
Processing time: 4 (sec)
Conductive partition material: Si
According to the above treatment, a porous layer having a two-layer structure consisting of a first layer (upper layer) and a second layer (lower layer) both having a thickness of about 10 μm is formed by the first and second stage anodizing treatments. A new layer having a thickness of 1 μm or less is formed in the second layer by the three-step anodizing treatment, and a porous layer having a total of four layers is formed on the single crystal Si substrate.
[Example 20]
A single crystal Si substrate was set in any one of the above anodizing apparatuses, and the porous layers 12a and 12b having a two-layer structure were formed by changing the current density (FIG. 2A). The anodizing conditions for forming the first and second porous layers are as follows.
[0276]
<Anodizing conditions for forming porous layer of first layer>
Current density: 8.15 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 17: 21: 13
(HF = 35.6wt%, C₂H_Five(OH = 18.6wt%)
Second electrolyte solution: HF (1 wt%, 1.5 wt% or 2.0 wt%)
Processing time: 5 (min)
Porous Si thickness (target): 6 (μm)
Conductive partition material: Si (specific resistance = 0.01Ω to 0.02Ω)
<Anodizing conditions for forming the porous layer of the second layer>
Current density: 30.6 (mA · cm^-2)
First electrolyte solution: HF: H₂O: C₂H_FiveOH = 17: 21: 13
(HF = 35.6wt%, C₂H_Five(OH = 18.6wt%)
Second electrolyte solution: HF (1 wt%, 1.5 wt% or 2.0 wt%)
Processing time: 80 (sec)
Porous Si thickness (target): 3 (μm)
Conductive partition material: Si (specific resistance = 0.01Ω to 0.02Ω)
Under these three anodizing conditions (HF = 1 wt%, 1.5 wt%, or 2.0 wt%), the Si substrate was processed without replacing the conductive partition wall 108.
[0277]
When the HF concentration of the second electrolyte solution is 1 wt% and 1.5 wt%, no porous layer is formed on the conductive partition wall 108, and the surface is subjected to electrolytic etching (electropolishing). This was confirmed by observation with a microscope. Therefore, no particles were generated from the conductive partition. By processing five Si substrates, the thickness of the conductive partition wall 108 was reduced by about 1 μm by electrolytic etching. By employing these anodizing conditions, the throughput can be improved by reducing the processing time while preventing the conductive partition wall 108 from collapsing.
[0278]
On the other hand, when the HF concentration of the second electrolyte solution is 2 wt%, the porous layer is formed on the conductive partition wall 108 when the first porous layer is formed on the Si substrate, and the first substrate is formed on the Si substrate. It was observed that the conductive partition wall 108 collapsed when the two porous layers were formed.
[0279]
Note that the above results show that even when the porous layers are formed on the five Si substrates while the porous layers of the first layer and the second layer are continuously formed on each Si substrate, The same applies to the case where the first porous layer is formed on the first Si layer and then the second porous layer is formed on the five Si substrates.
[0280]
Next, the substrate thus made porous was oxidized in an oxygen atmosphere at 400 ° C. for 1 hour. Due to this oxidation, the inner walls of the pores of the porous Si layers 12a and 12b were covered with a thermal oxide film.
[0281]
Next, a single crystal Si layer 13 having a thickness of 0.3 μm was epitaxially grown on the porous Si layer by a CVD (Chemical Vapor Deposition) method (FIG. 2B). The growth conditions are as follows. In the previous stage of epitaxial growth, H₂Since the surface of the porous Si layer is exposed inside, the pores on the surface are filled and the surface becomes flat.
[0282]
<Epitaxial growth conditions>
Source gas: SiH₂Cl₂/ H₂
Gas flow rate: 0.5 / 180 (l / min)
Gas pressure: 80 (Torr)
Temperature: 950 (℃)
Growth rate: 0.3 (μm / min)
Next, 200 nm thick SiO2 is formed on the surface of the epitaxially grown single crystal Si layer 13 by thermal oxidation.₂Layer 14 was formed (FIG. 2B).
[0283]
Then this SiO₂After the surface of the layer and the surface of the Si substrate (second substrate) 20 prepared separately were adhered, heat treatment was performed at 1100 ° C. for 1 hour to bond them together to create a bonded substrate 30 (FIG. 2C). . This heat treatment is N₂Alternatively, it may be performed in an inert gas, in an oxidizing atmosphere, or a combination thereof.
[0284]
Next, the bonded substrate 30 was removed by grinding, polishing, or etching until the porous Si layer 12b was exposed from the back surface side of the first substrate 10 (FIG. 2D).
[0285]
Next, the porous Si layers 12a and 12b ″ remaining on the bonded substrate 30 were etched with a mixture of 49% hydrofluoric acid, 30% hydrogen peroxide, and water (FIG. 2E). The Si layer 13 functions as an etch stop, and the porous Si layer is selectively etched.
[0286]
Since the etching rate of non-porous single-crystal Si by the etching solution is extremely low, the etching selectivity between porous single-crystal Si and non-porous single-crystal Si is 10⁵As a result, the etching amount in the non-porous layer (about several tens of angstroms) can be ignored in practice.
[0287]
Through the above steps, an SOI substrate (FIG. 2E) having the single crystal Si layer 13 having a thickness of 0.2 μm on the Si oxide film 14 is obtained. When the film thickness of the single crystal Si layer of this SOI substrate was measured at 100 points over the entire surface, the uniformity of the film thickness was 201 nm ± 4 nm.
[0288]
Further, heat treatment was performed at 1100 ° C. in hydrogen for 1 hour. When the surface roughness was evaluated with an atomic force microscope, the mean square roughness in a 50 μm square region was about 0.2 nm, which was equivalent to a commercially available Si wafer.
[0289]
As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that no new crystal defects were introduced into the Si layer and that good crystallinity was maintained.
[0290]
Similar results were obtained when no oxide film was formed on the surface of the epitaxially grown single crystal Si layer.
[0291]
[Others]
In the above embodiment, in the step of epitaxially growing a non-porous layer such as a single crystal Si layer on the porous Si layer, in addition to the CVD method, for example, an MBE method, a sputtering method, a liquid phase growth method, etc. may be adopted. You can also.
[0292]
The etching solution for selectively etching the porous Si layer is not limited to a mixed solution of 49% hydrofluoric acid, 30% hydrogen peroxide water, and water, for example,
1) liquid mixture of hydrofluoric acid and water,
2) A mixed solution obtained by adding at least one of alcohol or hydrogen peroxide to a mixed solution of hydrofluoric acid and water,
3) Buffered hydrofluoric acid,
4) A mixed solution obtained by adding at least one of alcohol or hydrogen peroxide to buffered hydrofluoric acid,
5) A mixture of hydrofluoric acid, nitric acid and acetic acid,
Etc. can be adopted. Since porous Si has a huge surface area, it can be selectively etched with various etching solutions as described above.
[0293]
In addition to the separation method using a fluid to which the water jet method is applied, various methods can be adopted for the separation process of the bonded substrate. For example, a method of applying a force (for example, pressing force or tensile force) to the bonded substrate in a direction perpendicular to the surface of the bonded substrate, an external pressure such as a shearing force is applied to the bonded substrate in the surface direction. A method in which the porous Si layer is oxidized and expanded from the peripheral portion to generate an internal pressure in the porous Si layer, and heat applied in a pulsed manner is applied to the bonded substrate to apply thermal stress to the porous layer. There are a method of adding, a method of softening the porous layer, a method of inserting a wedge between two substrates constituting the bonded substrate, etc., but other methods can also be adopted.
[0294]
In addition, the first electrolyte solution filled between the negative electrode 104 and the substrate to be processed is not limited to the above-described embodiments, and other electrolyte solutions containing different ions or different concentrations may be employed. it can. Further, as the second electrolyte solution 141 filled between the conductive partition wall 108 and the substrate to be processed, in each of the above embodiments, HF, H₂O, C₂H₅An electrolyte solution in which OH is mixed at a ratio of 0.5: 67: 33 is used. For example, this ratio is 1:67:33, 0.3: 67: 33, 1: 100: 0, 0. .5: 50: 50 or the like. In addition, as the second electrolyte solution 141, for example, a KOH solution is also suitable.
[0295]
The other steps are not limited to the above-described embodiments, and various methods can be adopted.
[0296]
The idea as described above, that is, the idea of using electrolyte solutions having different properties from the viewpoint of anodizing reaction as the first electrolyte solution and the second electrolyte solution, is an anodizing apparatus that does not have a conductive partition. It can also be applied when using. For example, an electrolyte solution capable of making the surface of the substrate to be processed porous is used as the first solution, and no particles are generated from the electrolyte solution or positive electrode that does not elute contaminants from the positive electrode as the second electrolyte solution. An electrolyte solution or the like can be used.
[0297]
【The invention's effect】
According to the present invention, for example, generation of particles from the conductive partition can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing process of a semiconductor substrate according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a manufacturing process of a semiconductor substrate according to a second embodiment of the present invention.
FIG. 3 is a diagram showing a schematic configuration of an anodizing apparatus according to a preferred embodiment of the present invention.
4 is a diagram showing a schematic configuration of an anodizing apparatus according to a modification of the anodizing apparatus shown in FIG.
5 is a diagram showing a schematic configuration of an anodizing apparatus according to another modification of the anodizing apparatus shown in FIG.
6 is a diagram showing a schematic configuration of an automatic processing line in which the anodizing apparatus 100 shown in FIG. 3 is incorporated.
[Explanation of symbols]
10 First substrate
11 Single crystal Si substrate
12, 12a, 12b porous layer
14,15 Non-porous layer
20 Second substrate
30 bonded substrates
100, 200, 300 Anodizing equipment
101 Si substrate
102 Anodizing tank
103 Substrate holder
103a Conductive partition wall holder
104 Negative electrode
105 Negative electrode holder
106 positive electrode
107 Positive electrode holder
108 conductive barrier
111,121 filters
112,122 pump
113,123 pump
114 First tank
124 Second tank
131 First electrolyte solution
141 Second electrolyte solution
201,301 Anodizing tank
701 Loader
702 Wafer carrier
703 Flush tank
704 Spin dryer
705 Unloader
710 Drive shaft
721 First transfer robot
722 Second transfer robot
731 Third transfer robot

Claims (3)

Using an anodizing device in which a conductive partition electrically connected to the positive electrode is disposed between the negative electrode and the positive electrode, a substrate to be processed is disposed between the negative electrode and the conductive partition. A processing method for disposing and forming a porous layer on the substrate by anodization reaction,
A preparatory step in which the negative electrode and the substrate are brought into electrical contact with each other through a first electrolyte solution and the conductive partition and the substrate are brought into electrical contact with each other through a second electrolyte solution;
An anodizing step of forming a porous layer on the surface of the negative electrode side of the substrate by passing a current between the negative electrode and the positive electrode,
As the first electrolyte solution, an electrolyte solution having an ability to make the substrate porous is used, and as the second electrolyte solution, an electrolyte solution having substantially no ability to make the conductive partition porous. The first electrolyte solution and the second electrolyte solution are both solutions containing hydrogen fluoride, and the first electrolyte solution has a hydrogen fluoride concentration higher than that of the second electrolyte solution. high,
The conductive partition is made of the same material as the substrate,
A processing method characterized by the above.   The processing method according to claim 1, wherein the conductive partition is made of a Si material. The anodization step, the substrate processing method according to claim 1 or 2, characterized in that to form a porous layer of a multilayer structure composed of two or more layers porosity are different from each other.

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