JP4420475B2 - Thin film semiconductor manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a thin film semiconductor that can constitute a single semiconductor device made of a semiconductor element such as a thin film transistor, or various semiconductor devices such as a semiconductor integrated circuit (IC), an IC card, and a solar cell made of a plurality of semiconductor elements. Related to the method.
[0002]
[Prior art]
To configure various semiconductor devices such as a single semiconductor device, a semiconductor integrated circuit, an IC card, and a solar cell, the thickness of the device is sufficiently reduced to reduce the size of the device. For example, in a solar cell, It is possible to increase the conversion efficiency or make it flexible by reducing the film thickness, thereby simplifying the assembly of various devices and improving the convenience of use.
[0003]
[Problems to be solved by the invention]
The present invention provides a method of manufacturing a thin film semiconductor that can obtain a thin film semiconductor easily and reliably at low cost from the above-mentioned objects.
[0004]
[Means for Solving the Problems]
  In the method of manufacturing a thin film semiconductor according to the present invention, the surface of the semiconductor substrate isChange the anodizing current density in three steps so as to increase gradually, step by step,A porous surface layer, an intermediate porosity layer formed under the surface layer and having a higher porosity than the surface layer, and the inside of the intermediate porosity layerofA high porosity layer having a larger porosity than the surface layer and the intermediate porosity layer;FormedChanging to a porous layer and then H₂Annealing in atmospheredo itSmoothing the surface of the porous layer, weakening the strength of the interface between the high porosity layer and the intermediate porosity layer, forming the semiconductor film on the porous layer, and passing the semiconductor film through the porous layer It is characterized by having a step of peeling from the semiconductor substrate and a step of removing the porous layer by removing the porous film remaining on the semiconductor substrate of the porous layer by chemical etching.
[0005]
  According to the manufacturing method of the present invention described above, a porous layer is formed on the surface of a semiconductor substrate, a semiconductor film is formed on the porous layer, and the semiconductor film is peeled off from the semiconductor substrate by utilizing a decrease in strength in the porous layer. Then, since the thin film semiconductor is constituted by the peeled semiconductor film, the thickness can be controlled by the thickness of the semiconductor film, so that it can be constituted sufficiently thin, for example, as a flexible thin film semiconductor.
  The porous layer is formed with three layers with different porosities: surface layer, intermediate porosity layer, and high porosity layer, so it can be easily peeled off from the high porosity layer with reduced mechanical strength. Is done. In addition, since an intermediate porosity layer is formed between the surface layer and the high porosity layer, this intermediate porosity layer acts as a buffer layer, and the strain between the surface layer and the high porosity layer is alleviated. A semiconductor film with good crystallinity can be grown.
  H ₂ By annealing in the atmosphere, it has a step of smoothing the porous layer surface and weakening the strength of the interface between the high porosity layer and the intermediate porosity layer, so that a semiconductor film with better crystallinity can be grown. Moreover, it becomes easy to peel in the porous layer.
[0006]
According to the production method of the present invention, the semiconductor thin film is formed on the porous layer formed on the surface of the semiconductor substrate, and this is separated by the porous layer. The semiconductor substrate used for manufacturing the thin film semiconductor by the above-described method is used again as a semiconductor substrate for manufacturing a semiconductor film, and thus a thin film semiconductor, by repeating the same method. That is, the above-described peeling of the semiconductor film is performed in the porous layer, and this peeling is performed at the interface with the semiconductor substrate in the film thickness direction of the porous layer (the interface with the semiconductor substrate is not made porous). In the case where the separation is performed in the porous layer, regardless of the mode of separation in (2), the porous layer is formed on the surface of the semiconductor substrate after the semiconductor film is peeled. However, in this case, in the method of the present invention, the porous film remaining on the semiconductor substrate side is removed by etching. Even in the case of changing the surface of the semiconductor substrate itself into a porous layer, the porous film is removed and the surface of the semiconductor substrate is excellent in clean crystallinity. It can be formed as a porous layer having a predetermined porous property with good actuality, and a semiconductor film formed on the porous layer can be formed with a semiconductor film having a desired characteristic stably with good reproducibility, and thus a thin film semiconductor. can do.
[0007]
Therefore, according to the manufacturing method of the present invention, a thin film semiconductor can be manufactured easily and reliably in mass production, and therefore at low cost.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
In the present invention, the surface of the semiconductor substrate is changed by, for example, anodization to form a porous layer. This porous layer is a porous layer composed of two or more layers having different porosities. Then, a semiconductor film is epitaxially grown on the surface of the porous layer, and a circuit element or an integrated circuit is formed thereon. Thereafter, the epitaxial semiconductor film is peeled off from the semiconductor substrate through the porous layer to produce a target thin film semiconductor device.
[0009]
On the other hand, the remaining semiconductor substrate is repeatedly used for the production of the thin film semiconductor described above. In particular, in the present invention, the porous film remaining on the semiconductor substrate is etched prior to the reuse. A removal process of the porous film to be removed is performed.
[0010]
The step of removing the porous film remaining on the semiconductor substrate can be performed by etching with chemicals and subsequent electrolytic etching by anodization. As a chemical for this etching, a mixed solution of hydrofluoric acid, a mixed solution of hydrofluoric acid and acetic acid, or a mixed solution of hydrofluoric acid and hydrogen peroxide can be used.
[0011]
In addition, the semiconductor substrate that has been repeatedly used to reduce its thickness can be used as a thin film semiconductor.
[0012]
In the step of forming the porous layer, a layer having a low porosity is formed facing the surface, and a layer having a high porosity is formed on the side close to the semiconductor substrate that is not made porous, that is, on the inner side.
[0013]
Further, in the porous layer forming step, for example, a surface layer having a low porosity, an intermediate porosity layer formed between the surface layer and the semiconductor substrate, and having a porosity higher than that of the surface layer, and the intermediate porosity. A high-porosity layer that is formed in the layer or at the lower layer of the intermediate porosity layer, that is, at the interface with the semiconductor substrate that has not been made porous, and has a higher porosity than the intermediate porosity layer can be formed.
[0014]
In the anodization for forming the porous layer, a step of anodizing the surface of the semiconductor substrate at a low current density and a step of anodizing at a high current density are performed thereafter.
[0015]
In the anodization, the step of anodizing the surface of the semiconductor substrate at a low current density, the step of anodizing at an intermediate low current density slightly higher than this low current density, and the anodization at a higher current density than this step. Process.
[0016]
Further, in the anodization, the anodization at the high current density can intermittently energize the high current density.
[0017]
In addition, in the anodization at an intermediate low current density in the anodization for forming the porous layer, the current density can be gradually increased.
[0018]
Anodization can be performed in an electrolytic solution containing hydrogen fluoride and ethanol, or in an electrolytic solution containing hydrogen fluoride and methanol.
[0019]
In the anodizing step, the composition of the electrolytic solution can be changed when changing the current density.
[0020]
After forming the porous layer, it is preferable to heat in a hydrogen gas atmosphere. Moreover, it is preferable to thermally oxidize a porous layer before the heating process in hydrogen gas atmosphere after forming a porous layer.
[0021]
The semiconductor substrate is formed thereon, that is, depending on the semiconductor film formed on the porous layer on the surface of the semiconductor substrate, for example, a semiconductor substrate made of Si single crystal, polycrystal, SiGe, GaAs, GaP or the like is used. Can be used. For example, in the case of forming a thin film semiconductor using a compound semiconductor, a compound semiconductor substrate is used as the semiconductor substrate. If a compound semiconductor is epitaxially grown on this porous layer, for example, a lattice mismatch can be made smaller than when a compound semiconductor is epitaxially grown on a Si semiconductor substrate, so that a thin film compound semiconductor having good crystallinity can be obtained. Can be formed. In any of the semiconductor substrates such as SiGe, GaAs, and GaP, a porous layer can be formed on the surface by anodizing.
[0022]
Various shapes can be adopted as the shape of the semiconductor substrate. For example, various shapes such as a wafer shape, that is, a disk shape, or a cylindrical ingot formed by pulling a single crystal having a curved substrate surface can be used.
[0023]
The semiconductor substrate can be constituted by a semiconductor substrate doped with n-type or p-type impurities, or a semiconductor substrate not containing impurities. However, in the case of anodizing, a low resistivity semiconductor substrate so-called p-type doped with a high concentration of p-type impurities.⁺It is preferable to use a Si substrate. As this semiconductor substrate, p⁺When using a type Si substrate, p-type impurities such as boron B are about 10¹⁹atoms / cm^ThreeIt is desirable to use a Si substrate that is doped to the extent that the resistance is about 0.01 to 0.02 Ωcm. And this p⁺When the type Si substrate is anodized, fine pores elongated in a direction substantially perpendicular to the substrate surface are formed, and the pores are maintained while maintaining the crystallinity, so that a desirable porous layer is formed.
[0024]
A semiconductor film is epitaxially grown on the porous layer thus made porous while maintaining its crystallinity. This semiconductor film can be composed of a single-layer semiconductor film or a multi-layer semiconductor film having two or more layers.
[0025]
As described above, the semiconductor film epitaxially grown on the semiconductor substrate is peeled off from the semiconductor substrate. Prior to this peeling, for example, a support substrate such as a flexible resin sheet is joined on the semiconductor film, and the support substrate and the epitaxial semiconductor film are bonded. Then, the epitaxial semiconductor film can be peeled from the semiconductor substrate together with the supporting substrate through a porous layer formed on the semiconductor substrate.
[0026]
The support substrate is not limited to a flexible sheet, and can be constituted by a glass substrate, a resin substrate, or a flexible or rigid so-called rigid transparent printed substrate on which a required printed wiring is made, for example.
[0027]
A porous layer composed of two or more layers having different porosities is formed on the surface of the semiconductor substrate. The outermost porous layer is formed as a dense porous layer having a relatively small porosity so that an epitaxial semiconductor film can be satisfactorily grown on the porous layer, and the inner side of the surface layer That is, on the lower layer side, by forming a porous layer having a relatively high porosity along the substrate surface, the mechanical strength is lowered by increasing the porosity of the porous layer itself, or the lattice constant between this porous layer and others is reduced. The layer is weakened by strain based on the difference, and the epitaxial semiconductor film can be easily peeled off, that is, separated in this layer. For example, it is possible to form a porous layer that is weak enough to be separated by application of ultrasonic waves.
[0028]
The layer formed on the inner side of the surface of the porous layer with the increased porosity becomes easier as the porosity increases. However, if the porosity is too high, the above-described epitaxial semiconductor film may be peeled off. In addition, peeling may occur or the porous layer may be damaged. Therefore, the porosity of the layer having a large porosity is set to 40% or more and 70% or less.
[0029]
In addition, when a layer having a high porosity is formed in the porous layer, the strain increases as the porosity increases. When the influence of this strain reaches the surface layer of the porous layer, the surface layer is cracked. There is a risk of generating it. Further, when the influence of strain occurs on the surface of the porous layer in this way, crystal defects are generated in the semiconductor film epitaxially grown thereon. Therefore, the porous layer has a higher porosity than the surface layer as a buffer layer to relieve strain between the layer with high porosity and the surface layer with low porosity. Thus, an intermediate porosity layer having an intermediate porosity with a low porosity is formed. By doing so, the porosity of the high-porosity layer is increased to such an extent that the above-described epitaxial semiconductor film can be reliably peeled off, and an epitaxial semiconductor film having excellent crystallinity can be formed. .
[0030]
The above-mentioned anodization of the surface of the semiconductor substrate is performed by a known method, for example, surface technology Vol. 46, no. 5, pp. 8-13, 1995 [Anodic conversion of porous Si]. That is, for example, it can be performed by the double cell method whose schematic configuration is shown in FIG. In this method, an electrolytic solution tank 1 having a two-tank structure having first and second tanks 1A and 1B is used. Then, a semiconductor substrate 11 on which a porous layer is to be formed is disposed between both tanks 1A and 1B, and each one of a pair of platinum electrodes 3A and 3B connected to a DC power source 2 is disposed in both tanks 1A and 1B. Is done. In the first and second tanks 1A and 1B of the electrolytic solution tank 1, for example, hydrogen fluoride HF and ethanol C are respectively provided.₂H_FiveElectrolytic solution 4 containing OH, or hydrogen fluoride HF and methanol CH_ThreeAn electrolytic solution 4 containing OH is accommodated, the first and second tanks 1A and 1B are disposed so that both surfaces of the semiconductor substrate 11 are in contact with the electrolytic solution 4, and both electrodes 3A and 3B are disposed in the electrolytic solution 4. Soaked in. Then, the DC power source 2 is connected between the electrodes 3A and 3B with the electrode 3A side immersed in the electrolytic solution 4 in the tank 1A on the surface side where the porous layer of the semiconductor substrate 11 is to be formed as the negative electrode side. Energization is performed. In this way, power is supplied with the semiconductor substrate 11 side as the anode side and the electrode 3A as the cathode side, whereby the surface of the semiconductor substrate facing the electrode 3A side is eroded and becomes porous.
[0031]
When this two-cell method is used, it is not necessary to deposit the ohmic electrode on the semiconductor substrate, and the introduction of impurities from the ohmic electrode into the semiconductor substrate is avoided.
[0032]
The structure of the porous layer to be formed changes considerably depending on the selection of conditions in this anodization, and this changes the crystallinity and peelability of the above-described epitaxial semiconductor film formed thereon.
[0033]
In order to form a porous layer composed of two or more layers having different porosities, a multi-step anodizing method having two or more steps with different current densities is employed in the anodizing treatment. Specifically, in order to produce a relatively dense porous layer having a low porosity on the surface, that is, a fine pore having a small diameter, first, the first anodization is performed at a low current density. Since the film thickness of the porous layer is proportional to time, the anodization is performed in a time period that achieves a desired film thickness. Thereafter, if the second anodization is performed at a considerably high current density, a porous layer having a high porosity and a high porosity is formed below the porous layer having a low porosity formed first. That is, a porous layer having a low porosity layer having a low porosity and a high porosity layer having a high porosity is formed.
[0034]
In this case, a large strain is generated in the vicinity of the interface between the porous layer having a low porosity and the porous layer having a high porosity due to the difference in lattice constant between the two. When this strain exceeds a certain value, the porous layer separates into two. Therefore, if a porous layer is formed under an anodizing condition in the vicinity of the boundary condition of whether or not separation due to this strain or mechanical strength due to porosity will occur, it will be grown on this porous layer. A semiconductor film such as an epitaxial semiconductor film can be easily separated through this porous layer.
[0035]
In this case, the first anodization with a low current density uses, for example, a p-type silicon single crystal substrate of 0.01 to 0.02 Ωcm, and HF: C₂H_FiveWhen OH = 1: 1 (volume ratio of HF in 49% solution and ethanol in 95% solution) (hereinafter the same), 0.5 to 10 mA / cm²It is performed for several minutes to several tens of minutes at a low current density. Further, the second anodization with a high current density is, for example, 40 to 300 mA / cm.²The current density is about 1 to 10 seconds, preferably about 3 seconds.
[0036]
In the first and second two-stage anodization described above, the strain generated in the highly porous layer inside the porous layer becomes considerably large. Therefore, the influence of this strain extends to the surface of the porous layer. As described above, the generation of cracks and the possibility of generating crystal defects in the epitaxial semiconductor film formed thereon are caused. Therefore, the porous layer has a higher porosity than the surface layer as a buffer layer to relieve the distortion generated between the surface layer having a low porosity and the high porosity layer. An intermediate porosity layer having a lower porosity is formed. Specifically, the first anodization with a low current density is first performed, then the second anodization with a slightly higher current density than the first anodization is performed, and then the third anode with a much higher current density than those. Perform formation. The conditions for the first anodization are not particularly limited. For example, a p-type silicon single crystal substrate of 0.01 to 0.02 Ωcm is used, and HF: C is used as the electrolytic solution.₂H_FiveWhen using OH = 1: 1, 0.5 to 3 mA / cm²The current density of the second anodization is, for example, 3 to 20 mA / cm.²The current density of the third anodization is, for example, 40 to 300 mA / cm.²It is preferable to carry out at a degree. For example, 1 mA / cm²When anodization is performed at a current density of about 16%, the porosity is about 7 mA / cm.²When anodizing at a current density of about 26%, the porosity is about 200 mA / cm.²When anodizing is performed at a current density of about 60 to 70%. When epitaxial growth is performed on the anodized porous layer, an epitaxial semiconductor film with good crystallinity can be formed.
[0037]
Further, as described above, when anodizing with three stages of current density is performed, the surface layer with low porosity formed by the first anodizing maintains the low porosity as it is, and the porosity formed by the second anodizing is maintained. A slightly higher intermediate porosity layer, i.e., a buffer layer, is formed inside the surface layer, i.e., at the interface between the surface layer and the non-porous semiconductor substrate. It becomes a two-layer structure with a layer. In addition, the principle of the high porosity layer formed by the above-described third anodization is not known, but the current density is 90 mA / cm.²If it is more than about, it is formed in the intermediate porosity layer formed by the second anodization, that is, in the intermediate portion in the thickness direction of the intermediate porous layer.
[0038]
Further, in the formation of the intermediate porosity layer, the anodic oxidation for forming the intermediate porosity layer is performed in a multi-stage or gradually under, for example, a condition in which the energization current density is changed, so that the low porosity surface layer, the high porosity layer, An intermediate porosity layer is formed in which the porosity is increased stepwise or inclined from the surface layer toward the high porosity layer. In this way, the strain between the surface layer and the high porosity layer is further relaxed, and an epitaxial semiconductor film with good crystallinity can be epitaxially grown more reliably.
[0039]
By the way, the separation surface can be formed by applying a large strain due to the difference in lattice constant at the interface between the release layer having a large porosity performed last and the buffer layer having a low porosity performed immediately before. If the device is devised when anodizing is performed, the separation surface is more easily separated. It is the last anodization with a high current density. For example, it is not energized for a period of 3 seconds, but after an energization for 1 second, the anodization is temporarily stopped and left for about 1 minute after the required time has elapsed. After that, the anodization is stopped by energizing for 1 minute at the same or different high current density, and after leaving the required time, for example, after leaving for about 1 minute, the energization is again performed for 1 second at the same or different high current density. This is a method of intermittently energizing to stop the anodization. When an appropriate anodization condition is selected using this method, a release layer is formed at the interface with the semiconductor substrate, that is, the lowermost surface of the porous layer, and the separation surface is the inside of the intermediate porous layer, that is, the buffer layer as described above. Instead, they are separated at the interface of the porous layer with the semiconductor substrate. The surface of the semiconductor substrate side is electropolished.
[0040]
In this case, the highly porous layer where distortion occurs in the porous layer and the surface are separated as much as possible, and the buffer effect by the intermediate porosity layer is maximized, and the epitaxial semiconductor has good crystallinity. A film can be formed. In addition, since the intermediate porous layer is formed only on the surface side in this way, the entire thickness of the porous layer can be reduced, and the consumption thickness of the semiconductor substrate for forming this porous layer is reduced. Therefore, the number of repeated use of the semiconductor substrate can be increased.
[0041]
As described above, by selecting the anodizing conditions, a large strain can be applied to the separation surface, and the influence of this strain can be prevented from being applied to the epitaxial growth surface of the semiconductor film.
[0042]
Further, in order to perform semiconductor epitaxial growth on the porous layer with good crystallinity, it is desired to reduce the micropores that become seeds for crystal growth on the surface layer of the porous layer. As one of means for reducing the micropores in the surface layer as described above, there is a method of increasing the HF concentration in the electrolytic solution in anodizing. That is, in this case, first, in the low current anodization for forming the surface layer, an electrolytic solution having a high HF concentration is used. Next, an intermediate porosity layer serving as a buffer layer is formed. After that, the HF concentration of the electrolytic solution is lowered, and finally anodization with a high current density is performed. By doing so, the fine pores of the surface layer can be made finer, so that an epitaxial semiconductor film with good crystallinity can be formed thereon, and in the high porosity layer, Since the porosity can be made sufficiently high, the epitaxial semiconductor film can be peeled off satisfactorily.
[0043]
The change of the electrolytic solution in the anodization of the porous layer is, for example, as the electrolytic solution in the formation of the surface layer, for example, HF: C₂H_FiveAnodization using an electrolytic solution with OH = 2: 1 is performed, and in forming an intermediate porosity layer as a buffer layer, an electrolytic solution having a slightly lower HF concentration, for example, HF: C₂H_FiveWhen anodization using an electrolytic solution with OH = 1: 1 is performed and a high porosity layer is formed, the electrolytic solution is further reduced in HF concentration, for example, HF: C₂H_FiveAnodization with a high current density is performed using an electrolytic solution of OH = 1: 1 to 1: 2.
[0044]
In the formation of the porous layer described above, when the current density is changed from the formation of the surface layer to the formation of the intermediate porosity layer, the anodization is temporarily stopped and then energization for the next anodization is started. It can also be carried out by changing the current density continuously without stopping anodization, that is, without stopping energization.
[0045]
Moreover, when performing anodization, it is preferable to carry out in the dark place which blocked light. This is because when the light is irradiated, the surface of the porous layer becomes uneven, making it difficult to obtain an epitaxial semiconductor film with good crystallinity.
[0046]
The anodized porous silicon layer can be used as a visible light emitting device. In this case, it is preferable to perform anodization while irradiating light contrary to the above, thereby increasing the light emission efficiency. Further, when oxidized, a blue shift occurs in the wavelength. Further, the semiconductor substrate may be p-type or n-type, but is preferably a high-resistance substrate that does not introduce impurities.
[0047]
Through the above steps, a semiconductor substrate having a porous layer formed on the surface (one side or both sides) can be obtained. The film thickness of the entire porous layer is not particularly limited, but can be 1 to 50 μm, preferably 3 to 15 μm, and usually about 8 μm. The total thickness of the porous layer is preferably as thin as possible so that the semiconductor substrate can be used as repeatedly as possible.
[0048]
Moreover, it is preferable to anneal the porous layer prior to forming the semiconductor film on the porous layer. This annealing can include heat treatment in a hydrogen gas atmosphere, that is, hydrogen annealing. When performing this hydrogen annealing, the natural oxide film formed on the surface of the porous layer can be completely removed, and oxygen atoms in the porous layer can be removed as much as possible, and the surface of the porous layer becomes smooth. An epitaxial semiconductor film having good crystallinity can be formed. At the same time, the pretreatment can further weaken the strength of the interface between the high porosity layer and the intermediate porosity layer, and the epitaxial semiconductor film can be more easily separated from the substrate. In this case, the hydrogen annealing is performed in a temperature range of about 950 ° C. to 1150 ° C., for example.
[0049]
In addition, if the porous layer is oxidized at a low temperature before hydrogen annealing, the inside of the porous layer is oxidized, so that a large structural change occurs in the porous layer even if thermal annealing is performed in a hydrogen gas atmosphere. Absent. That is, it becomes difficult for the strain from the release layer to be transmitted to the surface of the porous layer, and a high-quality crystalline epitaxial semiconductor film can be formed. In this case, the low-temperature oxidation can be performed in a dry oxidation atmosphere at 400 ° C. for about 1 hour, for example.
[0050]
Then, as described above, the semiconductor is epitaxially grown on the porous layer surface. In the epitaxial growth of this semiconductor, since the porous layer formed on the surface of the single crystal semiconductor substrate is porous, it maintains its crystallinity, so that it can be epitaxially grown on this porous layer. The epitaxial growth on the surface of the porous layer can be performed, for example, at a temperature of 700 ° C. to 1100 ° C., for example, by a CVD method.
[0051]
In both of the above-described hydrogen annealing and semiconductor epitaxial growth, a method of heating the semiconductor substrate to a predetermined substrate temperature can be a so-called susceptor heating method, or heating by direct current flow to the semiconductor substrate itself. It is possible to adopt an electric heating method or the like.
[0052]
The semiconductor film grown on the porous layer can be a single-layer semiconductor film or a multilayer semiconductor film formed by stacking a plurality of semiconductor layers. The semiconductor film may be the same material as the semiconductor substrate or a different material. For example, a single-crystal Si semiconductor substrate is used, and a compound layer such as Si or GaAs or a silicon compound such as Si is used for the porous layer formed on the surface thereof._1-yGe_yVarious epitaxial growths can be performed, for example, by epitaxially growing them, or by appropriately combining and laminating them.
[0053]
Further, n-type or p-type impurities can be introduced into the semiconductor film during the growth. Alternatively, after the semiconductor film is formed, impurities can be introduced over the entire surface or selectively by ion implantation, diffusion, or the like. In this case, the conductivity type, impurity concentration, and type are selected according to the purpose of use.
[0054]
Further, the thickness of the semiconductor film can be appropriately selected according to the use of the thin film semiconductor. For example, when the semiconductor integrated circuit is formed on a thin film semiconductor, the operating layer of the semiconductor element has a thickness of about several μm, and thus can be formed to a thickness of about 5 μm, for example.
[0055]
The surface of the epitaxial semiconductor film obtained as described above has a slight unevenness, and an exposure apparatus for exposing the photoresist in a photolithography process, for example, performed in the process of forming a circuit element or an integrated circuit on the semiconductor film. In the case where inconvenience such as a decrease in the accuracy of mask alignment occurs, it is preferable to polish the surface of the semiconductor film. In this case, since the porous layer is fragile and weak, weak polishing is performed so as not to burden the porous layer.
[0056]
Next, in the case of configuring a semiconductor device, a circuit element or an integrated circuit is formed on a semiconductor film. For example, a semiconductor element such as a DRAM (Dynamic Random Access Memory) or a CMOS (Complementary Matal Oxide Semiconductor) or an integrated circuit combining these elements is formed. These circuit elements or integrated circuits can usually be obtained by general semiconductor manufacturing techniques. For example, all circuits that can be formed on a semiconductor substrate using a diffusion furnace, ion implantation apparatus, exposure apparatus, CVD (chemical vapor deposition) apparatus, sputtering apparatus, cleaning apparatus, dry etching apparatus, epitaxial growth apparatus, etc. It can be applied to an element or an integrated circuit. In addition, as a circuit element or an integrated circuit, for example, each semiconductor element such as a diode or a transistor, a digital or analog IC, a flash memory, or the like can be used, for example, a solar cell.
[0057]
As described above, the thin film semiconductor device in which a circuit element or an integrated circuit is formed on a semiconductor film is preferably covered entirely with an insulating layer.
[0058]
Thus, after forming a circuit element or an integrated circuit, a support substrate is joined to this semiconductor film, that is, a thin film semiconductor device. The support substrate is not limited in its type such as a resin substrate, a glass substrate, a metal substrate, and a ceramic substrate. For example, the IC card may be configured by being attached to a flexible substrate or a cover sheet that constitutes the IC card. Further, a circuit element or an integrated circuit can also be formed on the support substrate, and can be constituted by a printed circuit board or the like. This support substrate bonding method can be performed by, for example, bonding with an adhesive, solder, adhesive, or the like, and the bonding strength is equal to or higher than the peeling strength through the porous layer performed later, that is, the force required for peeling. Therefore, the bonding strength is such that the bonding does not break, and a bonding agent is used which exhibits an adhesive strength that can be used to integrate the supporting substrate and the semiconductor film and peel the semiconductor film from the semiconductor substrate.
[0059]
Thus, after integrating a support substrate and a semiconductor film, a porous layer is peeled from this by a destruction inside. This peeling is easily separated in the porous layer having the highly porous layer.
[0060]
A porous layer may remain on the peeled surface of the semiconductor film thus peeled from the semiconductor substrate, and this porous layer is removed by polishing, etching or the like, if necessary. To do. Further, it may be left without being removed. Alternatively, a protective film may be attached or a protective substrate such as a resin substrate may be bonded to protect the peeling surface.
[0061]
A thin film semiconductor manufactured as described above or a semiconductor device using the thin film semiconductor has a circuit element or an integrated circuit formed on a thin film semiconductor by an extremely thin epitaxial growth, and is flexible and thin. For example, it can be applied to an electronic device such as an IC card and a portable device, and is adapted to lightness, thinness and smallness in recent years.
[0062]
On the other hand, the separated semiconductor substrate is used again after its surface is polished. For example, since the thickness of the substrate consumed for manufacturing one thin film semiconductor device is about 3 to 20 μm, the thickness consumed even after 10 repeated uses is about 30 to 200 μm. Therefore, since an expensive single crystal semiconductor substrate can be used repeatedly, the method of the present invention can manufacture a thin film semiconductor device with extremely low cost and low energy. If the epitaxial growth for the amount consumed on the surface of the semiconductor substrate is performed, the same semiconductor substrate can be used permanently, and a thin film semiconductor device can be manufactured at low cost and low energy.
[0063]
Next, examples of the present invention will be described. However, the present invention is not limited to this embodiment.
[0064]
[Example 1]
1 and 2 show process diagrams of this embodiment.
First, a wafer-like semiconductor substrate 11 made of single crystal Si doped with boron at a high concentration and having a specific resistance of, for example, 0.01 to 0.02 Ωcm was prepared (FIG. 1A).
.
Then, the surface of the semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this example, anodization was performed using the two-tank structure anodizing apparatus described in FIG. That is, a semiconductor substrate 11 made of single crystal Si is disposed between the first and second tanks 1A and 1B, and both tanks 1A and 1B are both HF: C.₂H_FiveOH = 1: 1 was injected. Then, a current was passed by the DC power source 2 between the Pt electrodes 3A and 3B immersed in the electrolytic solutions 4 of the electrolytic solution tanks 1A and 1B.
[0065]
First, the current density is 1 mA / cm.²This was energized for 8 minutes. As a result, a surface layer 12S constituting a porous layer having fine pores with a small diameter, a dense porosity of 16%, and a thickness of 1.7 μm was formed (FIG. 1B). If the micropores on the surface of the porous layer are small, H to be performed later₂By annealing, the surface of the porous layer becomes flatter and smoother, and there is an effect that the crystallinity of the Si epitaxial semiconductor film epitaxially grown on the surface is further improved.
Thereafter, the energization is temporarily stopped. Next, the current density is 7 mA / cm.²As a result, energization was performed for 8 minutes. Thus, an intermediate porosity layer 12M having a porosity of 26% and a thickness of 6.3 μm was formed under the surface layer 12S (FIG. 1C).
Thereafter, the energization is stopped again. Next, the current density is 200 mA / cm.²And then energized for 3 seconds. In this way, the porosity of about 60% of the porosity higher than that of the surface layer 12S and the intermediate porosity layer 12M so as to be sandwiched from above and below by the intermediate porosity layer 12M. Thus, a high porosity layer 12H having a thickness of about 0.05 μm is formed (FIG. 1D). In this way, the porous layer 12 is formed by the surface layer 12S, the intermediate porosity layer 12M, and the high porosity layer 12H.
[0066]
The porous layer 12 thus formed has a large difference in porosity between the intermediate porosity layer 12M and the high porosity layer 12H, so that a large strain is generated at these interfaces and in the vicinity of the interfaces, and the strength in the vicinity thereof is extremely high. Weakens. However, this strain acts as a buffer due to the presence of the intermediate porosity layer 12M between the high porosity layer 12H and the surface layer 12S, and the surface of the porous layer is greatly affected by this strain. The effect of distortion can be mitigated. Therefore, this strain can effectively avoid the influence of the epitaxial growth performed later on the porous layer on the crystallinity.
[0067]
Thereafter, in a normal pressure Si epitaxial growth apparatus in which epitaxial growth performed later is performed, the semiconductor substrate 11 having the porous layer 12 is made to be H₂Heating at 1100 ° C., that is, annealing treatment was performed in the atmosphere. In this annealing, the temperature was raised from room temperature to 1100 ° C. over about 20 minutes, and annealing was performed at 1100 ° C. for about 30 minutes. This H₂Annealing makes the surface layer of fine holes with a small diameter flat and smooth. At the same time, in the porous layer 12, the separation strength became even weaker in the vicinity of the interface between the intermediate porosity layer 12 </ b> M and the high porosity layer 12 </ b> H.
[0068]
Then H₂ In the annealed atmospheric Si epitaxial growth apparatus, Si was epitaxially grown on the porous layer 12, that is, the surface layer 12S, to form the Si semiconductor film 13 (FIG. 2E). This epitaxial growth is the same as the previous H₂ The annealing temperature in the atmosphere is lowered from 1100 ° C. to 1030 ° C., and SiH_FourSi epitaxial growth using gas was performed for 17 minutes. As a result, a Si epitaxial semiconductor film 13 having excellent crystallinity and a thickness of about 5 μm was formed on the porous layer 12.
[0069]
At this time, if the surface of the Si epitaxial semiconductor film 13 is uneven, this surface is polished. The high-porosity layer 12H has the above-described strain and is made into a frost column shape with a high porosity, so that it is weakened and the separation strength is very weak. Polishing was performed. As a result, the surface of the epitaxial semiconductor film 13 became flatter. By doing in this way, it can perform with higher precision, for example in mask alignment of an exposure apparatus.
[0070]
The semiconductor film 13 is separated from the semiconductor substrate 11. First, a support substrate 61 made of a PET (polyethylene terephthalate) sheet is bonded onto the semiconductor film 13 via an adhesive 60 (FIG. 2F).
[0071]
The adhesive strength of the support substrate 61 at this time is set to a strength stronger than the separation strength from the semiconductor substrate 11 by the porous layer 12, that is, an adhesive strength that does not cause the support substrate 61 to be peeled off during the separation.
[0072]
Next, an external force is applied between the semiconductor substrate 11 and the support substrate 61 in a direction to separate them. Thus, as described above, separation occurs at or near the high-porosity layer 12H of the porous layer 12 having weak strength, and the semiconductor film 13 in which an integrated circuit is formed from the semiconductor substrate 11 together with the support substrate 61 is formed. It is peeled off (FIG. 2G).
[0073]
In this way, the flexible semiconductor film 13 having a thickness of, for example, 5 μm and formed on the flexible substrate 61 is formed.
[0074]
In this case, the separation surface of the semiconductor substrate 11 from the semiconductor film 13 has the above-described H₂ There is a porous film 22 having a thickness of 5 μm due to the remaining porous layer 12 recrystallized by annealing in the atmosphere.
[0075]
The porous film 22 remaining on the semiconductor substrate 11 is removed by etching. The porous film 22 is etched by chemicals, in this example, hydrofluoric acid, that is, hydrofluoric acid HF and nitric acid HNO._ThreeAnd water H₂ The semiconductor substrate 11 is immersed in an etching solution using a mixed solution with O. In this way, the porous film 22 is removed by etching (FIG. 2H).
[0076]
Further, this semiconductor substrate 11 is subjected to electropolishing using the anodizing apparatus shown in FIG. In this case, both tanks 1A and 1B have both HF: C₂ H_FiveAn electrolytic solution with OH = 1: 2 is injected. And, 200 mA / cm between the Pt electrodes 3A and 3B²For 15 seconds. At this time, the surface of the semiconductor substrate 11 was electrolytically polished, and a surface with good crystallinity was exposed on the substrate surface.
[0077]
In this manner, the semiconductor substrate 11 having a surface with good crystallinity is reused, and the steps described with reference to FIGS. 1 and 2 described above are repeated, whereby a plurality of thin film semiconductors can be obtained.
[0078]
[Example 2]
Also in this example, the process described in FIGS. 1A to 1D is performed in the same manner as in Example 1, and the surface layer 12S and the intermediate porosity layer 12M are formed on the surface of the semiconductor substrate 11 with a high porosity. The porous layer 12 formed with the rate layer 12H is formed.
[0079]
In this example, after the porous layer 12 was formed, annealing was performed at 400 ° C. for 1 hour in an oxygen atmosphere using a diffusion furnace. By this treatment, the inside of the porous layer 12 is oxidized, and the H which is performed thereafter₂ It is possible to prevent a large structural change from occurring in the porous layer even by annealing in the atmosphere, and to more effectively avoid the influence of the strain generated near the interface of the high porosity layer 12H on the surface layer 12S. Can do.
[0080]
After that, as in Example 1, the atmospheric pressure Si epitaxial growth apparatus was used to produce H₂ Annealing was performed in an atmosphere, and then a semiconductor film 13 having excellent crystallinity with a thickness of 5 μm was formed by Si epitaxial growth as in Example 1 (FIG. 2E).
[0081]
Even in this case, if the surface of the Si epitaxial semiconductor film 13 is uneven, this surface is polished. The high-porosity layer 12H has the above-described strain and is made into a frost column shape with a high porosity, so that it is weakened and the separation strength is very weak. Polishing was performed. As a result, the surface of the epitaxial semiconductor film 13 became flatter. By doing in this way, it can perform with higher precision, for example in mask alignment of an exposure apparatus.
[0082]
The semiconductor film 13 is separated from the semiconductor substrate 11 by the same method as in the first embodiment. (FIG. 2F, FIG. 2G).
[0083]
In this manner, the flexible semiconductor film 13 having a thickness of, for example, 5 μm and formed on the flexible substrate 61 is formed as in the first embodiment.
[0084]
Also in this case, the separation surface of the semiconductor substrate 11 from the semiconductor film 13 is not limited to the H described above.₂ There is a porous film 22 having a thickness of 5 μm due to the remaining porous layer 12 recrystallized by annealing in the atmosphere.
[0085]
Thereafter, in this embodiment, the porous film 22 remaining on the semiconductor substrate 11 is replaced with hydrofluoric acid and hydrogen peroxide H.₂ O₂ And water H₂ Etching is removed by immersing the semiconductor substrate 11 in an etching solution of a mixed solution with O (FIG. 2H).
[0086]
Further, this semiconductor substrate 11 is subjected to electropolishing using the anodizing apparatus shown in FIG. In this case, both tanks 1A and 1B have both HF: C₂ H_FiveAn electrolytic solution with OH = 1: 2 is injected. And, 200 mA / cm between the Pt electrodes 3A and 3B²For 15 seconds. At this time, the surface of the semiconductor substrate 11 was electrolytically polished, and a surface with good crystallinity was exposed on the substrate surface.
[0087]
In this manner, a plurality of thin film semiconductors can be obtained by reusing the semiconductor substrate 11 having a surface with good crystallinity and repeating the same process.
[0088]
Next, an embodiment of manufacturing the solar cell according to the present invention will be described.
[0089]
Example 3
3 to 4, in this embodiment, the surface layer is formed by anodizing the surface of the semiconductor substrate 11 by performing the steps shown in FIGS. The porous layer 12 is formed by 12S, the intermediate porosity layer 12M, and the high porosity layer 12H formed therein. And the same H as explained in Example 1₂ Annealing was performed in the atmosphere, and then the semiconductor film 13 was epitaxially grown (FIG. 3A). The semiconductor film 13 in this embodiment is p⁺-P^--N⁺With a three-layer structure.
[0090]
The epitaxial growth of the semiconductor film 13 is H₂ In the atmospheric pressure Si epitaxial growth apparatus that has been annealed in the atmosphere, SiH_FourGas and B₂H₆Epitaxial growth using gas is performed for 3 minutes, and boron B is 10¹⁹atoms / cm^ThreeP doped in⁺A first semiconductor layer 131 made of Si is formed, and then B₂H₆By changing the gas flow rate, Si epitaxial growth is performed for 10 minutes, and boron B is 10¹⁶atoms / cm^ThreeP doped at low concentration^-A second semiconductor layer 132 made of Si is formed, and B₂ H₆PH instead of gas_ThreeGas is supplied and epitaxial growth is performed for 4 minutes.^-On the epitaxial semiconductor layer 132, phosphorus P is 10¹⁹atoms / cm^ThreeHighly doped n⁺A third semiconductor layer 133 made of Si is formed, and p made of the first to third epitaxial semiconductor layers 131 to 133 is formed.⁺-P^--N⁺A semiconductor film 13 having a structure was formed.
[0091]
Next, in this embodiment, SiO 2 is formed on the semiconductor film 13 by surface thermal oxidation.₂A film, that is, a transparent insulating film 16 is formed, and pattern etching by photolithography is performed to form an opening 16W that makes contact with an electrode or wiring (FIG. 3B). The openings 16W can be formed in parallel with a stripe shape extending in a direction orthogonal to the paper surface in the drawing while maintaining a required interval. SiO formed in this way₂The film can minimize the generation of carriers and recombination at the interface.
[0092]
Then, a metal film is deposited on the entire surface, and pattern etching by photolithography is performed to form electrodes or wirings 17 on the light receiving surface side along the stripe-shaped openings 16W (FIG. 4C). The metal film forming this electrode or wiring 17 is a multilayer formed by, for example, sequentially depositing a Ti film with a thickness of 30 nm, Pd with a thickness of 50 nm, and Ag with a thickness of 100 nm, and further performing Ag plating thereon. It may be constituted by a structural film. Thereafter, annealing was performed at 400 ° C. for 20 to 30 minutes.
[0093]
Next, in this embodiment, a conductive wire 41, a metal wire in this embodiment is joined to the striped electrodes or wirings 17 along these, respectively, and a transparent adhesive 21 is used on the conductive wire 41. The substrate 42 is bonded (FIG. 4D). Bonding of the conductive member 41 to the electrode or the wiring 17 can be performed by soldering. These conductive wires 41 are led out outward by making one end or the other end longer than the electrode or wiring 17.
[0094]
Thereafter, an external force is applied to the semiconductor substrate 11 and the transparent substrate 42 to separate them from each other. In this way, the semiconductor substrate 11 and the epitaxial semiconductor film 13 are separated at or near the fragile high porosity layer 12H of the porous layer 12, and the thin film in which the epitaxial semiconductor film 13 is bonded on the transparent substrate 42. A semiconductor 23 is obtained (FIG. 5E).
[0095]
In this case, although the porous layer 12 remains on the back surface of the thin film semiconductor 23, a silver paste is applied on the porous layer 12, and a metal plate is further bonded to form the other back electrode 24. In this way, p is applied to the transparent substrate 42.⁺-P^--N⁺A solar cell in which a thin film semiconductor 23 having a structure is formed is formed (FIG. 5F). The metal electrode 24 also functions as an element layer protective film on the back surface of the solar cell.
[0096]
In the solar cell thus formed, the light receiving side electrode or the wiring 17 is covered with the transparent substrate 42, but the electrical external derivation from this is performed by the conductive wire 41. Can be easily connected. Further, for example, as in the above-described embodiment, the conductive line 41 is led out from each of the plurality of electrodes or wirings 17 that are in contact with the epitaxial semiconductor film 13, that is, the active part of the solar cell. Thus, the series resistance of the solar cell can be made sufficiently small.
[0097]
Then, the same etching and electrolytic etching as in Example 1 are performed on the solar cell, that is, the semiconductor substrate 11 from which the semiconductor film 13 has been peeled off.
That is, the porous film 22 is removed by etching with hydrofluoric acid, and the semiconductor substrate 11 is electropolished using the anodizing apparatus shown in FIG. In this case, both tanks 1A and 1B have both HF: C₂ H_FiveAn electrolytic solution with OH = 1: 2 is injected. And, 200 mA / cm between the Pt electrodes 3A and 3B²For 15 seconds. At this time, the surface of the semiconductor substrate 11 was electrolytically polished, and a surface with good crystallinity was exposed on the surface of the substrate (FIG. 6).
[0098]
In this way, a plurality of solar cells can be obtained by repeating the process of forming the semiconductor film 13 similar to that described above on the semiconductor substrate 11 having a surface with good crystallinity exposed.
[0099]
In each of the above-described examples, the epitaxial semiconductor film is peeled off from the semiconductor substrate 11 by applying an external force that separates the epitaxial semiconductor films from each other. However, in some cases, the epitaxial semiconductor film can be peeled off by ultrasonic vibration.
[0100]
In each of the examples described above, when the current density is large in the anodization or when the semiconductor, for example, Si is peeled off due to a long-time energization, the silicon waste is generated and adhered to the electrolytic solution tank, etc. in the apparatus. Then, after removing the semiconductor substrate 11, unnecessary Si deposits can be dissolved and removed by injecting a hydrofluoric acid solution into the tank.
The apparatus for performing anodization is not limited to the example of FIG. 7, and an apparatus for immersing a semiconductor substrate in a single tank structure can be used.
[0101]
In addition, the above-described thin film solar cell is repeatedly manufactured by epitaxially growing a semiconductor having a thickness corresponding to the reduced thickness on a semiconductor substrate whose thickness is reduced by manufacturing the thin film semiconductor and the solar cell. By doing so, since the same semiconductor substrate can be used permanently, a solar cell can be manufactured at lower cost and lower energy.
[0102]
According to the manufacturing method of the present invention described above, the semiconductor substrate is formed with a porous layer on the surface, the semiconductor is epitaxially grown on the semiconductor layer, and the semiconductor substrate is peeled off. However, since the surface of the semiconductor substrate is removed by etching and electrolytic etching after the formation and peeling of the epitaxial semiconductor film described above, the target thin film semiconductor is repeatedly used again. That is, since a plurality of various thin-film semiconductor devices, for example, flexible semiconductor devices, can be manufactured, it can be manufactured at low cost.
[0103]
Further, although the semiconductor substrate 11 is thinned by forming the porous layer, the thickness of the semiconductor substrate 11 is compensated by epitaxially growing a semiconductor having a thickness corresponding to the thickness reduction. You can also. Further, when the thickness is not compensated when the thickness is not compensated, the semiconductor substrate itself can be used as a thin film semiconductor, and for example, a solar cell can be manufactured. Therefore, the semiconductor substrate can be used almost without waste without finally becoming ineffective, and this can also reduce the cost.
[0104]
In the production method of the present invention, when electrolytic etching is finally performed, the next porous layer 12 forming step can be performed continuously thereafter.
[0105]
Further, according to the above-described manufacturing method, after the support substrate 42 is bonded onto the semiconductor film 13 to integrate the substrate and the epitaxial semiconductor film, the substrate is peeled off from the semiconductor substrate together with the epitaxial semiconductor film. Therefore, there are no restrictions on the type of this substrate, and flexible printed circuit boards, rigid printed circuit boards, metal plates, ceramics, glass, resins, etc., which have never been considered by conventional common sense in semiconductor technology A thin film single crystal semiconductor can be formed thereon, or a solar cell can be formed.
[0106]
In addition, when a method of epitaxially growing a semiconductor layer on a porous layer having a single porosity is used, in order to improve the crystallinity of the semiconductor film, the porosity of the porous layer serving as the nucleus of crystal growth Since it is necessary to reduce the rate, it is necessary to reduce the current density and increase the HF mixing ratio of the electrolytic solution after anodization. However, when the porosity is lowered as described above, the porous layer becomes hard and separation of the epitaxial semiconductor film becomes difficult. Therefore, in order to increase the porosity in order to weaken the separation strength, for example, if the current density is increased and the HF mixing ratio of the electrolytic solution is reduced in the anodizing conditions, separation is facilitated in this case. The crystallinity of the epitaxial semiconductor film is extremely deteriorated. However, when the above-described method is used, the porosity of the surface portion of the porous layer is reduced to form a porous layer having a two-sided property that the porosity inside the porous layer is large. The epitaxial semiconductor film can be satisfactorily formed thereon, and the epitaxial semiconductor film can be easily separated. For example, it is possible to form a porous layer that is weak enough to be easily separated by ultrasonic waves.
[0107]
In addition, the higher the porosity layer formed in the porous layer, the easier the peeling is as the porosity is increased, but the greater the strain, the greater the influence on the surface layer of the porous layer. For this reason, a crack may arise in a surface layer. In addition, when performing epitaxial growth, it causes a defect in the epitaxial semiconductor film. However, in the above-described method, an intermediate porosity having a slightly higher porosity than the surface layer is used as a buffer layer that relieves strain generated from these layers between the layer having a very high porosity and the surface layer having a low porosity. By forming the rate layer, it is possible to form a high-quality epitaxial semiconductor film that is easy to peel off.
[0108]
Further, in the anodization at a high current density in the above method, when the current is intermittently passed, a high porosity layer can be formed in the porous substrate side interface or in the vicinity thereof, In this case, the surface and the highly porous layer serving as the peeling layer can be separated as much as possible, so that the buffer layer can be thinned, and accordingly the thickness of the porous layer is reduced, and the thickness of the semiconductor substrate is reduced. Consumption can be reduced, and the cost can be further reduced.
[0109]
In addition, when anodizing at a low current density, by gradually increasing the current, the porosity of the buffer layer between the surface layer and the release layer of the porous layer is gradually increased toward the inside. Can further improve the function of the buffer layer.
[0110]
Moreover, a porous layer can be easily formed by performing anodization in the electrolytic solution containing hydrogen fluoride and ethanol, or the liquid mixture of hydrogen fluoride and methanol. In this case, when changing the current density of the anodization, the range of adjusting the porosity is further increased by changing the composition of the electrolytic solution.
[0111]
Further, if the irradiation of light during anodization is avoided, the generation of irregularities on the surface of the porous layer can be reduced or avoided, and an epitaxial semiconductor film having good crystallinity can be formed.
[0112]
Further, by forming the porous layer and then heating in a hydrogen gas atmosphere, the surface of the surface layer of the porous layer became smooth, and an epitaxial semiconductor film having good crystallinity could be formed.
In addition, after the porous layer is formed and before the heating step in the hydrogen gas atmosphere, the porous layer is thermally oxidized to oxidize the inside of the porous layer. Even if applied, it is difficult for a large structural change to occur in the porous layer, and strain from the inside is hardly transmitted to the surface of the porous layer, so that an epitaxial semiconductor film with good crystallinity can be formed.
[0113]
【The invention's effect】
According to the above-described manufacturing method of the present invention, a porous layer is formed on the surface of a semiconductor substrate, a semiconductor film is grown on the porous layer, and the thin film having excellent crystallinity is peeled off from the semiconductor substrate in the porous layer. Semiconductors can be manufactured easily, reliably and inexpensively. However, in the present invention, the remaining semiconductor substrate can be reused by removing the porous layer. It is used and can be configured at a lower cost.
[Brief description of the drawings]
FIG. 1 is a process diagram (part 1) of an embodiment of the method of the present invention;
A to D are sectional views of the respective steps.
FIG. 2 is a process diagram (part 2) of an embodiment of the method of the present invention;
EH is sectional drawing of each process.
FIG. 3 is a process chart (part 1) of another embodiment of the method of the present invention;
A and B are sectional views of the respective steps.
FIG. 4 is a process diagram (2) of another embodiment of the method of the present invention;
C and D are sectional views of the respective steps.
FIG. 5 is a process diagram (3) of another embodiment of the method of the present invention;
EF is sectional drawing of each process.
FIG. 6 is a process diagram (part 4) of another embodiment of the method of the present invention;
FIG. 7 is a configuration diagram of an example of an anodizing apparatus for carrying out the method of the present invention.
[Explanation of symbols]
11 Semiconductor substrate, 12 Porous layer, 12M Intermediate porosity layer, 12H High porosity layer, 13 Semiconductor film, 131 First semiconductor film, 132 Second semiconductor film, 133 Third semiconductor film, 41 Conductive line, 42 Transparent substrate

Claims (9)

The surface of the semiconductor substrate is changed in three stages so that the anodization current density is increased in order, and the porosity is increased in a stepwise manner compared to the porous surface layer and the surface layer formed under the surface layer. Changing to a porous layer formed with an intermediate porosity layer, and the surface layer inside the intermediate porosity layer and a high porosity layer having a higher porosity than the intermediate porosity layer;
Thereafter, the then annealed in an H ₂ atmosphere, to smooth the surface of the porous layer, weakening the strength of the interface between the high porosity layer and the intermediate porosity layer step,
Forming a semiconductor film on the porous layer;
Peeling the semiconductor film from the semiconductor substrate through the porous layer;
And a step of removing the porous layer of the porous layer remaining on the semiconductor substrate by etching with chemicals. The method for producing a thin film semiconductor according to claim 1, wherein electrolytic etching by anodization is performed after the step of removing the porous film remaining on the semiconductor substrate by etching. 2. The method of manufacturing a thin film semiconductor according to claim 1, wherein the chemical is a mixed solution of hydrofluoric acid, a mixed solution of hydrofluoric nitric acid and acetic acid, or a mixed solution of hydrofluoric nitric acid and hydrogen peroxide. . The method for producing a thin film semiconductor according to claim 1, wherein the semiconductor film formed on the porous layer is an epitaxial semiconductor film. 2. The method of manufacturing a thin film semiconductor according to claim 1, wherein after forming a circuit element or an integrated circuit on the semiconductor film, a step of peeling the semiconductor film from the semiconductor substrate through the porous layer is performed. . The method of manufacturing a thin film semiconductor according to claim 1, wherein the semiconductor substrate is made of any one of Si, SiGe, GaAs, and GaP. The method for producing a thin film semiconductor according to claim 1, wherein after the step of forming a semiconductor film on the porous layer, a step of flat polishing the surface of the semiconductor film is performed. After the step of forming the semiconductor film on the porous layer, the step of bonding a support substrate onto the semiconductor film via an adhesive, and then peeling the semiconductor film from the semiconductor substrate via the porous layer The method for manufacturing a thin film semiconductor according to claim 1, wherein the step of: The method for manufacturing a thin film semiconductor according to claim 8, wherein the support substrate is made of a polyethylene terephthalate sheet.

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