JPH06208949A - Production of soi structure - Google Patents

Abstract

PURPOSE:To completely insulate a silicon carbide seed crystal layer from a silicon substrate by thermally oxidizing a silicon substrate containing a selectively grown silicon carbide seed crystal layer, and growing a silicon carbide film in a horizontal direction until an opening is blocked, to form a field oxidization layer. CONSTITUTION:An opening 35 for seed crystal growth is formed in a silicon oxide film 32 on a silicon substrate 31, and the surface of the substrate 31 is selectively exposed, then a silicon carbide single crystal is epitaxial-grown from the opening 35 to form a silicon carbide seed crystal layer 36. The film 32 is grown in a horizontal direction until the opening is blocked, to form a field oxidization layer 37. Thus, only by thermally oxidizing the substrate 31 containing a selectively grown silicon carbide seed crystal layer 36, the layer 37 can insulate the layer 36 from the substrate 31 thoroughly. Therefore an SOI construction can be obtained by a simplified production method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called SOI (S
EMIconductor On Insulator) structure manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor integrated circuit,
A silicon single crystal epitaxial growth layer was formed on a silicon substrate, and a circuit was formed on this epitaxial growth layer. By the way, in such a structure, the silicon substrate and the epitaxial growth layer of silicon single crystal are made of P.
It is N-junctioned to form a capacitor. The capacitance of the PN junction portion is called a parasitic capacitance and reduces the operating speed of the element. Therefore, the structure in which the silicon single crystal epitaxial growth layer is formed directly on the silicon substrate is not suitable for forming an element that requires high-speed operation.

In recent years, in order to cope with high-speed operation of devices, an insulating film is formed on a silicon substrate, and an epitaxial growth layer of silicon single crystal is further formed on the insulating film.
OI technology is widely used. That is, the SOI technology
By insulating the silicon single crystal epitaxial growth layer from the silicon substrate, P of the semiconductor element formed on the silicon single crystal epitaxial growth layer and the silicon substrate is formed.
It is an attempt to eliminate the N-junction.

FIG. 5 shows an ELO (Epitaxial Lateral Overg
Shows SOI technology by the rowth method (Lateral Epitaxial O
vergrowth of Silicon on SiO ₂ : DDRathmanet, 1982
(October issue, page 2303). First, as shown in FIG. 5A, the silicon oxide film 2 is grown on the silicon substrate 1. Next, the silicon oxide film 2 is etched using a photoresist to form a seed window (hereinafter referred to as “opening”) 3 for seed crystal growth. Further, as shown in FIG. 5B, a silicon single crystal is selectively epitaxially grown in the vertical direction from the opening 3. Following this, a silicon single crystal is laterally epitaxially grown. As a result, a silicon single crystal epitaxial growth layer 4 is formed on the silicon oxide film 2. In this way, the PN junction surface between the silicon single crystal epitaxial growth layer 4 and the silicon substrate 1 can be reduced to the size of the opening 3. Therefore, the PN junction capacitance can be reduced, and the operation speed of the device can be increased.

There is also a method called SENTAXY method (Takahiro Yonehara et al., New SOI-Selective Nucleation E
pitaxy, 1987 (Autumn) Proceedings of the 48th Annual Meeting of the Japan Society of Applied Physics, 19p-Q-15, p. 583). This is a method in which a plurality of silicon nuclei for crystal growth are artificially formed in an insulating layer such as a silicon oxide film and epitaxial growth is performed from each nuclei. As a nucleus, a method of forming and using a silicon nitride film having a small area, a method of forming a nucleus by a FIB (Focused Ion Beam) method, and the like are being studied. According to this method
The epitaxial growth layer of silicon single crystal and the silicon substrate can be insulated by a silicon oxide film or the like.
Therefore, the problem of the PN junction capacitance as described above can be solved.

[0006]

However, the following problems have been pointed out in the conventional SOI technology as described above. In the ELO method shown in FIG. 5, the PN junction between the silicon single crystal epitaxial growth layer and the silicon substrate is small, but the PN junction is not completely eliminated. Therefore, further speeding up of the device has been hindered.

On the other hand, according to the SENTAXY method, it is possible to obtain a structure in which the silicon single crystal epitaxial growth layer and the silicon substrate are completely insulated, and there is no problem as described above. However, according to the SENTAXY method,
The plane orientations of the epitaxial growth layers grown from the respective nuclei provided are different. As described above, when the plane orientation of the epitaxial growth layer of the silicon single crystal is different, the characteristics such as the oxidation rate are different, which causes a problem that elements having desired characteristics cannot be uniformly formed.

Therefore, in order to deal with the above, the present applicant has filed Japanese Patent Application No. 3-275740 (hereinafter, "Prior Art 1").
And Japanese Patent Application No. 3-279830 (hereinafter, referred to as “Prior Art 2”), it has an epitaxial growth layer of silicon single crystal which is completely insulated from a silicon substrate by an insulating layer and has a uniform plane orientation. , Proposed SOI technology for obtaining SOI structure.

FIG. 6 shows a method of manufacturing an SOI structure according to Prior Art 1. First, as shown in FIGS. 6A to 6D, the silicon oxide film 12 is formed on the silicon substrate 11, and the silicon oxide film 12 is formed using the photoresist 13.
An opening 14 for seed crystal growth is provided in the. And FIG.
As shown in (e), a silicon single crystal is epitaxially grown from the opening 14 to form a silicon seed crystal layer 15. Next, as shown in FIGS. 6F and 6G, a silicon nitride film 16 is formed on the surface of the silicon seed crystal layer 15 except for the portion corresponding to the opening 14. Subsequently, the silicon seed crystal layer 15 is oxidized from the portion where the silicon nitride film 16 is not formed. At this time, the silicon seed crystal layer 15
Is selectively oxidized only on the upper portion of the opening 14, and is completely insulated from the silicon substrate 11 by the field oxide layer 17. Thereafter, as shown in FIGS. 6H and 6I, the silicon nitride film 16 is removed and the silicon seed crystal layer 15 is epitaxially grown to obtain a silicon single crystal epitaxial growth layer 18.

FIG. 7 shows a method of manufacturing an SOI structure according to Prior Art 2. First, as shown in FIGS. 7A to 7D, a silicon oxide film 22 is formed on a silicon substrate 21 and a photoresist 23 is used to form the silicon oxide film 22.
An opening 24 for seed crystal growth is provided in the. And FIG.
As shown in (e), a silicon single crystal is epitaxially grown from the opening 24 to form a silicon seed crystal layer 25. Next, as shown in FIG. 7F, a photoresist 26 is applied on the entire surface. Subsequently, as shown in FIGS. 7G to 7I, while leaving the silicon seed crystal layer 25 necessary for crystal growth, the silicon seed crystal layer 25 inside the opening 24 and above the opening 24 is removed to perform crystal growth. The periphery of the silicon seed crystal layer 25 left for the purpose is oxidized. As a result, the opening 2
The field oxide layer 27 is bonded so as to close 4
The silicon seed crystal layer 25 is insulated from the silicon substrate 21. Then, as shown in FIGS. 7 (j) to (l), SOG (S
Pin on Glass) 28 is filled and flattened until the silicon seed crystal layer 25 is exposed. Subsequently, the silicon seed crystal layer 25 is epitaxially grown to obtain a silicon single crystal epitaxial growth layer 29.

However, in order to obtain the SOI structure,
The prior art 1 requires the step of masking the silicon seed crystal 15 with the silicon nitride film 16 (see FIG. 6F), and the prior art 2 has the silicon seed crystal layer 25. Of removing a part of
(See (g)) is required. Therefore, the manufacturing process is complicated.

In view of the above, the present invention has an SOI, which is insulated from the silicon substrate by an insulating layer and has an epitaxial growth layer of a silicon single crystal having a uniform plane orientation.
It is an object of the present invention to provide a method for manufacturing an SOI structure that allows the structure to be easily obtained.

[0013]

A method of manufacturing an SOI structure according to the present invention comprises a step of growing a silicon oxide film on a silicon substrate by thermal oxidation, and an opening for seed crystal growth at a predetermined position of the silicon oxide film. Forming and selectively exposing the surface of the silicon substrate, the surface of the silicon substrate is carbonized by using the silicon oxide film as a mask, and a silicon carbide seed crystal is selectively epitaxially grown until it protrudes from the opening. Forming a crystal layer,
A field that thermally oxidizes a silicon substrate having a selectively grown silicon carbide seed crystal layer and laterally grows a silicon oxide film until the opening is closed to disconnect the connection between the silicon substrate and the silicon carbide seed crystal layer. A step of forming an oxide layer, a step of removing the silicon oxide film on the silicon carbide seed crystal layer to expose the silicon carbide seed crystal layer, and an epitaxial growth of a silicon single crystal using the silicon carbide seed crystal layer as a nucleus. It includes a step of forming a crystal epitaxial growth layer.

[0014]

In the method of manufacturing an SOI structure described above, since silicon carbide is used as a seed crystal, when the connection between the silicon carbide seed crystal layer and the silicon substrate is cut off, a selectively grown silicon carbide seed crystal layer is provided. Only by thermally oxidizing the silicon substrate, the field oxide layer can completely insulate the silicon carbide seed crystal layer from the silicon substrate. Therefore, the SOI structure can be obtained by a simple manufacturing method.

Since the silicon carbide seed crystal layer and the silicon substrate are insulated and separated by the field oxide layer, the epitaxial growth layer of silicon single crystal is also insulated from the silicon substrate. Further, each silicon carbide seed crystal layer has the same plane orientation by carbonizing the surface of the silicon substrate using the silicon oxide film as a mask and epitaxially growing the silicon carbide single crystal until it protrudes from the seed crystal growth opening. become. For this reason, the plane orientation of the epitaxial growth layer of silicon single crystal epitaxially grown with each silicon carbide seed crystal layer as a nucleus also becomes uniform.

[0016]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1A to 1I are schematic cross-sectional views showing a method of manufacturing an SOI structure according to an embodiment of the present invention in the order of steps. A method of manufacturing an SOI structure according to this embodiment will be described with reference to FIGS.

First, a silicon oxide film is formed on a silicon substrate. That is, as shown in FIG. 1A, a silicon substrate 31 having a plane orientation (100) is placed in an oxygen stream to a high temperature to oxidize the surface. As a result, the silicon substrate 31
A silicon oxide (SiO ₂ ) film 32 grows on the upper surface of the. The thickness of the silicon oxide film 32 is about 30 to 300.
It is preferable to form it as thin as about nm. This is because the interface with the silicon oxide film 32 is reduced during the epitaxial growth of the seed crystal, which will be described later, and a high quality seed crystal layer can be formed.

After the step of forming the silicon oxide film is completed, an opening for growing a seed crystal is formed. That is, as shown in FIG. 1B, the photoresist 3 is formed on the silicon oxide film 32.
Apply 3. Subsequently, a mask is placed on the photoresist 33, exposed to ultraviolet rays, and then developed to form an etching window 34 for forming an opening for seed crystal growth described later, as shown in FIG. In this state, the silicon oxide film 32 is formed using the photoresist 33 as a mask.
Isotropic etching is performed. At this point, since the photoresist 33 has been used up, the photoresist 33 is ashed with a mixed solution of sulfuric acid and hydrogen peroxide. As a result, as shown in FIG. 1D, an opening 35 for seed crystal growth is formed in the silicon oxide film 32, and the surface of the silicon substrate 21 is selectively exposed.

When the step of forming the seed crystal growth opening is completed, a silicon carbide seed crystal layer is formed. That is, FIG.
In the state of (d), using the silicon oxide film 32 as a mask,
The surface of silicon substrate 31 exposed in opening 35 is carbonized. This is to reduce the lattice mismatch between the silicon substrate 31 and the silicon carbide seed crystal layer (3C-SiC) when the silicon carbide single crystal is epitaxially grown next. That is, the surface of the silicon substrate 31 is carbonized to form a buffer film. Next, FIG.
As shown in (e), a silicon carbide single crystal is selectively epitaxially grown until it protrudes from the opening 35 to form a silicon carbide seed crystal layer 36. At this time, the epitaxial growth is controlled so as to suppress the lateral growth of the silicon carbide single crystal. For example, 1 in the vertical direction
The growth is performed up to 4 μm, and the growth is 1 μm or less in the lateral direction.

By the way, when epitaxially growing a silicon carbide single crystal, a stacking fault may occur at the interface of the silicon oxide film 32. In order to deal with this, in the step shown in FIG. 1A, the silicon oxide film 32 is formed thin to reduce the interface area, so that stacking faults can be prevented. Further, it is preferable that the epitaxial growth is performed at a temperature as low as possible. For example, about 1100-12
A temperature of about 00 ° C is appropriate. In this way, stacking faults can be suppressed by performing epitaxial growth at a low temperature.
Further, on the (100) silicon substrate 31, the (100)
If the silicon oxide film 32 is formed in a rectangular pattern in the direction, stacking faults are suppressed. Further, crystal defects can be further suppressed by attaching a thin polysilicon or silicon nitride film to the side wall of the opening 35 of the silicon oxide film 32 before growth to improve lattice matching. The silicon carbide seed crystal layers 36 formed as described above have the same plane orientation.

When the step of forming the silicon carbide seed crystal layer is completed, the connection between the silicon carbide seed crystal layer and the silicon substrate is cut off. That is, the silicon substrate 31 having the selectively grown silicon carbide seed crystal layer 36 is thermally oxidized. Then, as shown in FIG. 1F, the silicon oxide film 32 and the silicon substrate 31 are oxidized to form a field oxide layer 37. At this time, since the silicon oxide grows not only in the vertical direction but also in the horizontal direction, the bird's beaks of the field oxide layer 37 are connected to each other in the opening 35. As a result, field oxide layer 37 completely disconnects silicon carbide seed crystal layer 36 from silicon substrate 31. Note that the oxidation rate of silicon carbide is sufficiently slower than that of the silicon oxide film 32 and the silicon substrate 31,
In other words, the oxide film growth rate on silicon carbide is
It is about 10. Therefore, the silicon carbide seed crystal layer 36
A thin silicon oxide film 38 is only formed on the surface of the silicon oxide film, but most of it remains as silicon carbide.

When the step of disconnecting the connection between the silicon carbide seed crystal layer and the silicon substrate is completed, an epitaxial growth layer of silicon single crystal is formed. That is, as shown in FIG. 1G, etching is performed with weak hydrogen fluoride (Buffered HF) or the like to remove the silicon oxide film 38 grown on the surface of the silicon carbide seed crystal layer 36. Then, Figure 1
As shown in (h), a silicon single crystal is epitaxially grown using the silicon carbide seed crystal layer 36 selectively present on the field oxide layer 37 as a nucleus to form an epitaxial growth layer 39 of a silicon single crystal in an island shape. When the epitaxial growth is further continued, as shown in FIG. 1I, the silicon single crystal epitaxial growth layers 39 grown from the nuclear silicon carbide seed crystal layer 36 are connected to each other. The silicon single crystal epitaxial growth layer 39 thus obtained is used as a base silicon carbide seed crystal 3
Since the plane orientation of 6 is uniform, the epitaxial growth layer 3
The plane orientation of 9 is also uniform. Depending on the circuit configuration, the epitaxial growth 39 of silicon single crystal may be different from that shown in FIG.
You may stop at the stage of (h).

As described above, according to the manufacturing method of this embodiment, since silicon carbide is used as the seed crystal, when the connection between the silicon carbide seed crystal layer 36 and the silicon substrate 31 is cut off, it is shown in FIG. It is not necessary to mask the seed crystal layer with a silicon nitride film as in Prior Art 1 or to remove a part of the seed crystal layer by etching as in Prior Art 2 shown in FIG. That is, the silicon oxide seed crystal layer 36 and the silicon substrate 31 can be completely insulated by the field oxide layer 37 only by thermally oxidizing the silicon substrate 31 having the selectively grown silicon carbide seed crystal layer 36. (See FIG. 1 (f)). Therefore, the SOI structure can be obtained by a simple manufacturing method.

Since the silicon carbide seed crystal layer 36 and the silicon substrate 31 are insulated and separated by the field oxide layer 37, the silicon single crystal epitaxial growth layer 3 is formed.
9 is also insulated from the silicon substrate 31. Therefore, no PN junction capacitance is generated between the silicon single crystal epitaxial growth layer 39 and the silicon substrate 31. That is, the epitaxial growth layer 39
If elements such as a transistor and a FET (Feild Effect Transistor) are formed in the
A high speed device can be obtained. Further, since there is no capacitance due to the PN junction, the high frequency characteristic is good and the latch-up characteristic can be improved.

Further, by using the silicon oxide film 32 as a mask, the surface of the silicon substrate 31 is carbonized, and a silicon carbide single crystal is epitaxially grown until it protrudes from the opening 35 for seed crystal growth (see FIG. 1E). , The silicon carbide seed crystal layers 36 have the same plane orientation. Therefore, the plane orientation of the epitaxial growth layer 39 of silicon single crystal epitaxially grown with each silicon carbide seed crystal layer 36 as a nucleus is also uniform. Therefore,
As the oxidation rate becomes uniform, the epitaxial growth layer 39
It becomes easy to control the characteristics of the element when the element is formed.

Further, an SOI structure in which a silicon carbide seed crystal layer 36 having a good thermal conductivity of 5.0 W / cm ° C. is interposed between the silicon substrate 31 and the silicon single crystal epitaxial growth layer 39 ( By adopting FIG. 1 (h) (i)), it is suitable for a large power element that generates a large amount of heat, a so-called power element. The present invention is not limited to the above embodiment, and many modifications and changes can be made within the scope of the present invention.

For example, when the width of the seed crystal growth opening 35 cannot be made sufficiently large, as shown in FIG. 2, the mouth wall of the opening 35 is formed to be inclined inward, that is, the opening 35. It is good to attach a slope to. This is because, as shown by the arrow in FIG. 2, the growth of the silicon carbide single crystal in the lateral direction is promoted, and stacking faults are less likely to occur in the silicon carbide seed crystal layer 36.

Further, the shape of the opening 35 for seed crystal growth is
Necessary silicon single crystal epitaxial growth layer 39
It may be appropriately selected according to For example, it may be a circular hole as shown in FIG. 3, or may be a lattice-shaped one as shown in FIG. However, if the patterning direction of the silicon oxide film 32 is (100), the occurrence of defects can be suppressed, and this point should be taken into consideration.

[0029]

As is apparent from the above description, according to the method for manufacturing an SOI structure of the present invention, the silicon substrate having the selectively grown silicon carbide seed crystal layer is merely thermally oxidized to form the field oxide layer. It is possible to completely insulate the silicon carbide seed crystal layer and the silicon substrate. Therefore, the SOI structure can be obtained by a simple manufacturing method.

Since the silicon carbide seed crystal layer and the silicon substrate are insulated and separated by the field oxide layer, the epitaxial growth layer of silicon single crystal is also insulated from the silicon substrate. Therefore, between the silicon single crystal epitaxial growth layer and the silicon substrate,
No capacitance is generated by the PN junction. Further, each silicon carbide seed crystal layer has the same plane orientation by carbonizing the surface of the silicon substrate using the silicon oxide film as a mask and epitaxially growing the silicon carbide single crystal until it protrudes from the seed crystal growth opening. become.
For this reason, the plane orientation of the epitaxial growth layer of silicon single crystal epitaxially grown with each silicon carbide seed crystal layer as a nucleus also becomes uniform.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a method of manufacturing an SOI structure according to an embodiment of the present invention in the order of steps.

FIG. 2 is a diagram showing a state in which an opening for seed crystal growth is provided with a slope.

FIG. 3 is a diagram showing a state in which a seed crystal growth opening has a circular hole shape.

FIG. 4 is a diagram showing a state in which the seed crystal growth openings have a lattice shape.

FIG. 5 is a diagram showing a conventional SOI technique by an ELO method.

FIG. 6 is a schematic cross-sectional view showing a method of manufacturing an SOI structure according to Prior Art 1 in the order of steps.

FIG. 7 is a schematic cross-sectional view showing a method of manufacturing an SOI structure according to Prior Art 2 in the order of steps.

[Explanation of symbols]

 31 Silicon Substrate 32, 38 Silicon Oxide Film 35 Opening for Seed Crystal Growth 36 Silicon Carbide Seed Crystal Layer 37 Field Oxide Layer 39 Silicon Single Crystal Epitaxial Growth Layer

Claims (1)

[Claims] 1. A step of growing a silicon oxide film on a silicon substrate by thermal oxidation, a step of forming an opening for seed crystal growth at a predetermined position of the silicon oxide film, and selectively exposing the surface of the silicon substrate. , A step of carbonizing the surface of the silicon substrate by using the silicon oxide film as a mask and selectively epitaxially growing a silicon carbide seed crystal until the silicon carbide seed crystal protrudes from the opening to form a silicon carbide seed crystal layer, the selectively grown silicon carbide A step of thermally oxidizing a silicon substrate having a seed crystal layer, laterally growing a silicon oxide film until the opening is closed, and forming a field oxide layer that disconnects the silicon substrate and the silicon carbide seed crystal layer; A step of removing the silicon oxide film on the silicon carbide seed crystal layer to expose the silicon carbide seed crystal layer, and the silicon carbide seed crystal layer And a step of epitaxially growing a silicon single crystal by using as a nucleus to form an epitaxial growth layer of the silicon single crystal.