JP2009218272A - Compound semiconductor substrate, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound semiconductor substrate suppressed in warpage, and having a high-quality SiC film formed thereon without degrading crystallinity, and to provide a manufacturing method thereof. <P>SOLUTION: On a surface 10a of an Si substrate 10, a groove part 30 is formed having the width W on the surface 10a and the depth D from the surface 10a both larger than the thickness of the SiC film 20. On the surface 10a of the Si substrate 10, the SiC films 20 are formed as a plurality of SiC island parts 20a respectively divided in island-like forms by the groove part 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a compound semiconductor substrate having a SiC film formed on a Si substrate and a method for manufacturing the same.

SiC has excellent characteristics such as wide band gap, high electron mobility, high heat resistance, etc., and it has abundant resources of constituent elements and has little concern about environmental pollution. It is a material expected to be applied to next-generation electronic devices, electronic devices capable of high-speed and high-temperature operation, solar power generation devices and the like.
In particular, the manufacture of a compound semiconductor substrate on which a SiC film is formed on a Si substrate can inherit the current silicon technology, and therefore, its practical use is required also from the standpoint of industrial technology development cost.

  For the formation of the SiC film, a CVD method, a sputtering method, an MBE method, or the like is used. In these methods, since the bond between Si and C is a covalent bond, chemical bond formation energy and epitaxial crystal growth are required. The diffusion energy of both is large, and for example, high-temperature heating at 600 to 1200 ° C. is required.

  Furthermore, since Si and SiC have a difference of about 20% in lattice constant, there is a large lattice mismatch and a difference in linear thermal expansion coefficient of about 8%. In the cooling process, thermal distortion occurs, and the entire compound semiconductor substrate is warped. This warpage is a factor that causes deterioration of element characteristics and mechanical damage.

  The warpage of the substrate as described above can be slightly suppressed by adjusting the film formation conditions such as the raw material gas ratio and the temperature increase / decrease speed at the time of forming the SiC film. In some cases, it may conflict with the film forming conditions for improving characteristics such as crystallinity of SiC, and it has been difficult to find conditions that simultaneously satisfy the suppression of warpage and the improvement of crystallinity.

Conventionally, as a method of preventing the warp as described above, a method of introducing an intermediate layer for relaxing stress between the Si substrate and the SiC film (see, for example, Patent Document 1), Si on the back surface of the Si substrate. A method of forming a ₃ N ₄ film (see, for example, Patent Document 2) and a method of processing a substrate in a shape that is warped in a direction opposite to the direction in which warpage occurs are known.

  Further, in Patent Document 3, when a nitride compound semiconductor is manufactured, a mask material such as an oxide film is formed on a substrate in a lattice shape, and the substrate surface is separated and exposed. A method for suppressing cracks has been disclosed in which the regions for epitaxial growth are made into independent small regions.

  Further, Patent Document 4 discloses a method of patterning by subdividing almost the entire back surface of the substrate in order to suppress warpage of the substrate due to high-temperature processing heating when forming a contact electrode film on the back surface of the semiconductor substrate. Has been.

JP 2006-253617 A JP 2003-218031 A JP 2002-299252 A JP 2006-165179 A

However, the method described in Patent Document 1 has a limit in reducing warpage because there is a difference in lattice constant and linear thermal expansion coefficient between the Si substrate and the intermediate layer. In addition, due to the increase in the number of film forming steps, the heat treatment time becomes longer, and problems such as impurity contamination also occur.
Similarly, the method as described in Patent Document 2 also increases the number of film forming steps and causes problems such as impurity contamination. In particular, when forming the Si ₃ N ₄ film on the back surface of the substrate, it becomes the device surface. Measures to prevent surface contamination are necessary, which causes a complicated manufacturing process.
In addition, it is not easy to process a substrate having a warp in advance because it is necessary to predict and control the warp during film formation, and strict processing accuracy is required.

  In addition, the method described in Patent Document 3 may cause the mask material to be an impurity, and the nitride compound semiconductor is formed in a step shape in the vicinity of the mask material, so that the crystallinity is low. It has problems such as lowering.

Therefore, the present inventors have repeatedly studied to solve the above technical problem and applied the method of forming the back electrode described in Patent Document 4 to satisfy both the suppression of warpage and the improvement of crystallinity. Thus, the present inventors have found a method capable of forming a SiC film on a Si substrate.
That is, an object of the present invention is to provide a compound semiconductor substrate on which a high-quality SiC film is formed without warping and without reducing crystallinity, and a method for manufacturing the same.

The compound semiconductor substrate according to the present invention is a compound semiconductor substrate in which a SiC film is formed on the surface of a Si substrate, and the SiC film is separated into islands by grooves formed on the surface of the Si substrate. It is characterized by.
As described above, the SiC film is divided and formed by the groove formed on the surface of the Si substrate without being continuous over the entire surface, thereby suppressing the warpage of the compound semiconductor substrate and reducing the crystallinity. Therefore, a high quality SiC film can be formed.

The groove preferably has a width on the surface of the Si substrate and a depth from the surface of the Si substrate larger than the thickness of the SiC film.
By using the groove having such a width and depth, the SiC film can be efficiently separated into islands without being continuously formed.

Moreover, it is preferable that the angle which the Si substrate surface and the side surface of the said groove part make is 90 degrees or less.
By forming the groove having such an inclination angle, the SiC film is more efficiently separated, and the warpage of the entire compound semiconductor substrate can be suppressed.

The method for manufacturing a compound semiconductor substrate according to the present invention includes a step of forming a groove on the surface of the Si substrate and a step of forming an SiC film separated in an island shape by the groove on the surface of the Si substrate. It is characterized by that.
According to such a manufacturing method, only by forming a predetermined groove on the surface of the Si substrate in advance, there is no fear of impurities and the like, warpage is suppressed, and crystallinity is not lowered. A compound semiconductor substrate provided with a high-quality SiC film is obtained.

In the manufacturing method, it is preferable that the width of the groove portion on the surface of the Si substrate and the depth from the surface of the Si substrate are larger than the thickness of the SiC film.
Further, it is preferable that the groove is formed such that an inclination angle of an inner surface in the depth direction of the groove from the Si substrate surface is 90 ° or less.

According to the present invention, a compound semiconductor substrate on which a high-quality SiC film is formed can be obtained without warping and without reducing crystallinity.
Therefore, the compound semiconductor substrate according to the present invention can be used as a high-power electronic device or the like, and is also suitably used as a crystal growth substrate for hexagonal compound semiconductors such as 4H—SiC, 6H—SiC, and GaN. be able to.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 shows an example of a compound semiconductor substrate according to the present invention. 2 shows an enlarged view of the AA cross section of the compound semiconductor substrate shown in FIG.
In the compound semiconductor substrate 1 shown in FIGS. 1 and 2, the surface 10 a of the Si substrate 10 is formed in a lattice shape by the groove portions 30. On the Si substrate 10, SiC films 20 are formed as a plurality of SiC island portions 20 a separated into island shapes by the groove portions 30.
That is, the SiC film 20 is not formed on the entire surface of the Si substrate 10, but is formed by being divided by the groove portions 30 formed on the surface 10 a of the Si substrate 10.
For this reason, generation | occurrence | production of curvature is also parted and the curvature of the compound semiconductor substrate 1 whole can be suppressed.

The groove 30 preferably has a width W on the surface 10 a of the Si substrate 10 larger than the thickness T of the SiC film 20. Further, the depth D from the surface 10 a of the Si substrate 10 is also preferably larger than the thickness D of the SiC film 20.
By forming the groove portion 30 having such a width W and depth D on the surface of the Si substrate 10, the SiC film 20 is not formed continuously on the surface 10a of the Si substrate 10 and the groove portion 30, thereby improving efficiency. Can be separated into islands.

On the other hand, as shown in FIG. 3, even when the width W of the groove 30 is large and the depth D of the groove 30 is small, the SiC film 20 is grown in the lateral direction so that the surface 10a of the Si substrate 10 and the groove 30 It will be formed continuously.
When the SiC film 20 is formed in this way, a large warp occurs in the entire compound semiconductor substrate 1 as in the case where the SiC film 20 is formed on the entire surface of the flat Si substrate 10 on which the groove 30 is not formed. To do.
The width W of the groove 30 is more preferably about 2 to 5 mm larger than the thickness T of the SiC film 20. The depth D of the groove 30 is more preferably about 2 to 4 times the thickness T of the SiC film 20.
For example, when the thickness T of the SiC film 20 is 10 μm, the groove 30 is preferably formed with a width W of about 12 to 15 mm and a depth D of 20 to 40 μm.

Furthermore, it is preferable that the groove portion 30 is formed up to the peripheral edge portion 10b of the Si substrate 10. That is, it is preferable that all SiC island portions 20a are completely separated on surface 10a of Si substrate 10 as shown in FIG.
If the groove 30 does not reach the peripheral edge 10b of the Si substrate 10 and the SiC island 20a is not completely separated in the vicinity of the peripheral edge 10b of the Si substrate 10, the SiC film 20 In the vicinity of the portion 10b, the state is the same as that formed on the entire surface of the flat Si substrate, and the compound semiconductor substrate is warped.

In FIG. 4, the preferable aspect of the cross-sectional shape of the said groove | channel 30 is shown. As shown in FIG. 4A, the angle θ formed by the Si substrate surface 10a and the side surface 30b of the groove is preferably 90 ° or less than 90 ° as shown in FIG. 4B.
By forming the groove 30 having such an inclination angle, the SiC film 20 can be more efficiently separated by the groove 30, and the warpage of the entire compound semiconductor substrate 1 can be suppressed.
On the other hand, as shown in FIG. 5, when the angle θ exceeds 90 °, the source gas easily flows into the groove portion 30 when the SiC film 20 is formed, so that the SiC film is also formed on the bottom surface 30 a and the side surface 30 b of the groove 30. 20 is formed, and it is difficult to separate the SiC film 20 by the groove 30, which is not preferable.
From the viewpoint of suppressing the flow of the raw material gas into the groove 30, as shown in FIG. 4B, it is more preferable that the angle θ is less than 90 °.

Further, the arrangement of the groove 30 on the Si substrate 10 is used when dicing a plurality of circuits into chips so that a circuit configuration region can be efficiently secured in a subsequent device manufacturing process. It is preferable to design in accordance with the position of the cutting margin. At this time, it is preferable that the width W of the groove portion 30 is equal to or less than the cutting allowance.
The SiC film 20b formed in the groove 30 is more crystalline than the SiC film 20a formed on the surface 10a of the Si substrate 10 due to the flow of the source gas on the Si substrate 10 during the film formation. There is a tendency to be slightly inferior. Also from this, it is preferable to arrange | position the groove part 30 so that it may become a cutting allowance in the case of dicing.

Hereinafter, the manufacturing method of the compound semiconductor substrate according to the present invention as described above will be described.
In FIG. 6, the outline | summary of the process of the manufacturing method of the compound semiconductor substrate of the 1st aspect which concerns on this invention is shown.
First, the Si substrate 10 is prepared. The Si substrate 10 is not limited to those manufactured by the CZ (Czochralski) method, but is manufactured by the FZ (floating zone) method, or alternatively, these Si single crystal substrates can be obtained by vapor phase growth. A crystal film epitaxially grown (Si epi substrate) or the like may be used.
The Si substrate 10 is preferably cleaned by removing the natural oxide film by etching or heat treatment at 1000 to 1350 ° C. in a hydrogen atmosphere.

Next, after forming a resist film on the Si substrate 10 by sputtering or the like, patterning is performed by photolithography to form a protective film 40 in a region where the groove 30 is not formed on the Si substrate 10 (FIG. 6). (A)).
Then, after forming the groove 30 by etching using a chemical solution or the like (FIG. 6B), the protective film 40 made of a resist film is removed using the chemical solution or the like (FIG. 6C).
The compound semiconductor substrate according to the present invention is obtained by forming the SiC film 20 on the Si substrate 10 in which the groove 30 is formed by a known CVD method or the like (FIG. 6D).

FIG. 7 shows an outline of the steps of the compound semiconductor substrate manufacturing method according to the second aspect of the present invention. The manufacturing process as shown in FIG. 7 is performed when a compound semiconductor substrate having a groove 30 having an angle θ of less than 90 ° formed by the Si substrate surface 10a and the side surface 30b of the groove as shown in FIG. It is suitable for.
First, after forming a resist film on the Si substrate 10 by sputtering or the like, patterning is performed by photolithography to form a trapezoidal protective film 40 in a region where the groove 30 is to be formed (FIG. 7A). )).
Then, after forming the Si film 50 so that the upper surface of the protective film 40 is exposed by a well-known CVD method or the like (FIG. 7B), the protective film 40 made of a resist film is removed with a chemical solution or the like. (FIG. 7C).
A compound semiconductor substrate according to the present invention is obtained by forming the SiC film 20 on the Si substrate 10 with the groove 30 formed by a well-known CVD method or the like (FIG. 7D).

According to the manufacturing method as described above, an intermediate layer made of a different material is provided between the Si substrate 10 and the SiC film 20, or a mask material made of an oxide film or the like is provided on the surface of the Si substrate 10. Since it is not necessary, impurities resulting from these do not enter the compound semiconductor substrate, and problems such as deterioration of crystallinity near the mask material due to decomposition of the mask material do not occur.
That is, according to the above manufacturing method, there is no fear of mixing impurities and the like, and warpage is suppressed and crystallinity is not lowered only by forming a predetermined groove portion on the Si substrate surface in advance. A compound semiconductor substrate provided with a high-quality SiC film can be easily obtained.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
A cross section as shown in FIG. 4A, in which a Si substrate surface having a diameter of 3 inches (oxide film thickness: 0.5 μm), a width of 4 mm, a depth of 10 μm, and an angle formed by the Si substrate surface and the side surface of the groove is 90 °. Shaped groove portions were formed by etching in a lattice shape with an interval of 16 mm.
The Si substrate surface was heated at 1000 ° C. or higher in a hydrogen atmosphere to remove the natural oxide film.
Thereafter, the temperature of the Si substrate is decreased to 300 ° C., 7.2 sccm of C ₃ H ₈ is supplied to the carrier gas 18 slm under a reduced pressure of 50 Torr, and the substrate temperature is increased to 1150 ° C. at a temperature increase rate of 20 ° C./min. Raised and held for 5 minutes to form a char layer.
Next, the supply gas was switched to C ₃ H ₈ : 0.9 sccm and SiH ₄ : 1.8 scm and held for 300 minutes, and a 3C—SiC single crystal film having a thickness of about 5 μm was formed by vapor phase growth.

As a result of X-ray diffraction analysis, the SiC single crystal film was found to have a very sharp peak of 3C—SiC (111).
Further, the SiC single crystal film was completely separated by the groove, and the warp of the obtained compound semiconductor substrate was 34 μm.

[Example 2]
The groove has a cross-sectional shape as shown in FIG. 4B in which the angle formed between the surface of the Si substrate and the side surface of the groove is 75 °, and otherwise the SiC single crystal film is formed in the same manner as in Example 1. Formed.
As a result of X-ray diffraction analysis, the SiC single crystal film was found to have a very sharp peak of 3C—SiC (111).
The SiC single crystal film was completely separated by the groove, and the warpage of the compound semiconductor substrate was 28 μm.

[Comparative Example 1]
A SiC single crystal film was formed on the surface of the Si substrate in the same manner as in Example 1 while maintaining the flat mirror surface without forming the groove.
The warpage of the obtained compound semiconductor substrate was 89 μm.

[Comparative Example 2]
The groove has a cross-sectional shape as shown in FIG. 5B in which the angle formed between the Si substrate surface and the side surface of the groove is 135 °, and otherwise, the SiC single crystal film is formed in the same manner as in Example 1. Formed.
The SiC film was not separated even in the groove 30 and was formed continuously over the entire surface of the Si substrate.
The warpage of the obtained compound semiconductor substrate was 93 μm.

1 is a top view of a compound semiconductor substrate according to the present invention. It is AA sectional drawing in FIG. It is sectional drawing for demonstrating the groove part of the Si substrate surface. The cross-sectional shape of the groove portion on the surface of the Si substrate is shown. (A) shows an angle θ formed by the Si substrate surface and the side surface of the groove portion is 90 °, and (b) shows the surface of the Si substrate and the side surface of the groove portion. This is a case where the angle θ is less than 90 °. This shows the cross-sectional shape of the groove on the surface of the Si substrate, where the angle θ formed by the Si substrate surface and the side surface of the groove exceeds 90 °. It is sectional drawing for demonstrating the outline | summary of the process of the manufacturing method of the compound semiconductor substrate which concerns on this invention. It is sectional drawing for demonstrating the outline | summary of the process of the manufacturing method of the compound semiconductor substrate of the other aspect which concerns on this invention.

Explanation of symbols

1 Compound Semiconductor Substrate 10 Si Substrate 20 SiC Film 30 Groove 40 Protective Film 50 Si Film

Claims (6)

  A compound semiconductor substrate having a SiC film formed on a surface of a Si substrate, wherein the SiC film is separated in an island shape by a groove formed on the surface of the Si substrate.   2. The compound semiconductor substrate according to claim 1, wherein a width of the groove portion on the surface of the Si substrate and a depth from the surface of the Si substrate are larger than a thickness of the SiC film.   3. The compound semiconductor substrate according to claim 1, wherein an angle formed between the surface of the Si substrate and a side surface of the groove is 90 ° or less. 4.   A method for producing a compound semiconductor substrate, comprising: forming a groove portion on a Si substrate surface; and forming a SiC film separated in an island shape by the groove portion on the Si substrate surface.   5. The method of manufacturing a compound semiconductor substrate according to claim 4, wherein the width of the groove portion on the surface of the Si substrate and the depth from the surface of the Si substrate are made larger than the thickness of the SiC film.   6. The method of manufacturing a compound semiconductor substrate according to claim 4, wherein the groove is formed so that an angle formed between the surface of the Si substrate and a side surface of the groove is 90 [deg.] Or less.

Images