JPH0758040A - Susceptor for phase growth apparatus - Google Patents

Abstract

PURPOSE:To provide a susceptor for a gas phase growth apparatus capable of reducing deformation of a semiconductor wafer and heating the same uniformly. CONSTITUTION:In a susceptor 20 for a gas phase growth apparatus including a circular counterbore part 21 for supporting a flat portion of a semiconductor wafer 22, there is provided an annular protrusion 30 concentric with the circular counterbore part 21. The center line of the annular protrusion 30 is located in the range of 65-75% of the radius of the counterbore part 21, and recessed cross section portions are formed inside and outside the annular protrusion 30. The depth delta1 of the outer recessed portion 32 is 1.2-2.0 times the depth delta2 of the inner recessed portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a susceptor for a vapor phase growth apparatus which supports a semiconductor wafer.

[0002]

2. Description of the Related Art A vapor phase growth apparatus such as an epitaxial apparatus or a CVD apparatus used for manufacturing a semiconductor device is required to make the temperature of the entire sample substrate uniform in the vapor phase growth due to the demand for high quality of the surface of the sample substrate. Required to do so.

As shown in FIG. 5, in the vapor phase growth apparatus, the sample substrate 12 receives heat from the susceptor 10 heated by the high frequency induction heating method while being placed on the susceptor 10.

When the sample substrate 12 is placed on the flat surface of the susceptor, the sample substrate 12 is warped due to the temperature gradient in the axial (thickness) direction of the sample substrate 12 and its own weight, and the heat received in the radial direction of the sample substrate 12 becomes uneven. There is a problem of becoming. Conventionally, in order to solve this problem, as shown in FIG. 6, a counterbore 11 is processed and provided on the susceptor 10.
The bottom surface 14 of the spot facing portion 11 is processed into a concave surface (spherical surface) instead of a flat surface, and when warpage occurs, the sample substrate 12 is moved to the susceptor 10
I am trying to make a face-to-face contact with.

Further, Japanese Patent Publication No. 5-40457 discloses that
In a vertical type vapor phase growth apparatus that heats a substrate to be vapor-deposited by conduction heat and radiant heat from a heated support table, a counterbore for mounting a substrate on the support is concentric with the counterbore. One circular ridge line is provided, and the inner and outer cavities of the concave bottom whose radial cross section is recessed on an arc are formed inside and outside the ridge line, and the circular ridge line supports the substrate. A support for a vapor phase growth apparatus is described.
Furthermore, the circular ridge supporting the substrate has a substrate radius R of 0.6.
Depth from the substrate supporting surface of the concave bottom of the inner space formed by the circular ridge line that supports the substrate is 25 to 150 μm, and is formed by the circular ridge line that supports the substrate. It is described that the depth of the concave bottom of the formed outer cavity from the substrate supporting surface is 30 to 70 μm.
The support for the vapor phase growth apparatus configured in this manner eliminates the deposition of silicon around the back surface of the vapor phase growth substrate,
Moreover, it is described that the occurrence of slip can be reduced.

[0006]

However, in the susceptor 10 shown in FIGS. 5 and 6 described above, the sample substrate 12 is actually formed due to variations in the flatness of the sample substrate 12 and the processing accuracy of the counterbore bottom surface 23. It does not necessarily come into close contact (face contact) with the counterbore bottom surface 23. 7 (a) and (b)
6A and 6B show a schematic diagram when the sample substrate 12 and the spot facing portion of the susceptor 10 do not come into close contact with each other, and a graph of the temperature distribution of the sample substrate in the radial direction. The sample substrate 12 and the counterbore bottom surface 23 only partially contact each other, and a gap is created between them in the other non-contacting portions. Due to the difference in the heat transfer characteristics of the heat conduction due to the gas in the gap and the heat conduction due to the contact, the temperature on the surface of the ideal substrate has an uneven distribution. The thermal stress due to the in-plane temperature difference of the sample substrate causes the yield behavior of the sample substrate. In addition, the non-uniform temperature distribution in the surface of the sample substrate adversely affects the quality of the thin film deposited by vapor phase growth.

Further, the support for a vapor phase growth apparatus described in Japanese Patent Publication No. 5-40457 mentioned above minimizes wafer deformation (deflection, warpage) in a semiconductor wafer heat treatment step (eg, epitaxial step). In addition, it is not sufficient for the technical problem of further improving the soaking property of the wafer.

An object of the present invention is to provide a susceptor for a vapor phase growth apparatus, which can reduce the deformation of a semiconductor wafer and can heat it uniformly.

[0009]

In order to solve the above problems, the present invention provides a susceptor for a vapor phase growth apparatus having a circular counterbore for supporting a flat surface of a semiconductor wafer, wherein the circular counterbore is provided. It has one concentric annular convex portion, and the center line of the circular convex portion is 65 to 7 of the spot facing portion radius.
5% of the area, and concave portions in cross section are formed inside and outside the annular convex portion, and the depth of the outer concave portion is δ ₁
Is 1.2 to 2.0 times the depth δ ₂ of the inner recessed portion, and the susceptor for a vapor phase growth apparatus is a gist.

[0010]

First Embodiment A susceptor for a vapor phase growth apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

On the upper surface of the susceptor 20, twelve circular counterbore portions 21 are provided along the circumference. The spot facing portion 21 is provided with an annular convex portion 30, an inner concave portion 33, and an outer concave portion 34, respectively. Sample substrate 22
Is placed on the annular convex portion 30 of the spot facing portion 21, and vapor phase growth is performed in a conventional manner. The present invention is not limited to the layout (arrangement) and the number of counterbore portions 21 shown in FIG. 1, and those settings may be changed depending on the diameter of the sample substrate, for example. The sample substrate is, for example, a semiconductor wafer.

The susceptor 20 is not in contact with the sample substrate 22 except for the annular projection 30. Annular convex portion 30
Has a contact surface and is in contact with the sample substrate 22 at the contact surface. The annular convex portion 30 has a spot facing portion 21.
Is a ring shape concentric with the spot facing portion 21. The center line of the annular convex portion 30 is located within the range of 65 to 75% of the radius of the spot facing portion 21. The center line of the annular protrusion 30 is the center line of the radial width of the contact surface between the annular protrusion 30 and the semiconductor wafer. The radial width of the annular convex portion 30 is 1% to the diameter of the semiconductor wafer.
10%, preferably 1% to 3%. If it is less than 1%, the contact between the annular convex portion 30 and the semiconductor wafer becomes a substantially linear contact, and the occurrence of slip becomes remarkable due to the concentration of thermal stress. Also,
Manufacturing is also difficult. If it exceeds 10%, the annular convex portion 30
The contact between the semiconductor wafer and the semiconductor wafer becomes a wide surface contact, and the heat conduction to the semiconductor wafer becomes uneven.

The inner side wall and the outer side wall of the annular convex portion 30 are perpendicular to the sample substrate 22, respectively. However, the present invention is not limited to this, and both side walls of the annular convex portion 30 may be slanted so that the contact area between the annular convex portion 30 and the sample substrate 22 becomes small.

The inner concave portion 33 is formed inside the annular convex portion 30 and is a circular concave portion. Outer concave portion 34
Is formed on the outer side of the annular convex portion 30 and is an annular concave portion.

A gap 31 (gap) is formed between the sample substrate 22 and the inner concave portion 33 of the spot facing portion 21 so as to uniformly heat the sample substrate 22 in the area corresponding to the inside of the annular convex portion 30. Has been done. The gap 31 prevents contact between the sample substrate 22 and the inner concave portion 33. Since the surface of the susceptor 20 is coated with SiC (silicon carbide), the inner concave portion 33 has a dimensional tolerance. Therefore, in order to reliably form the above-mentioned gap 31, the depth δ _{2 of the} inner concave portion 33 (the distance between the bottom of the inner concave portion 33 and the sample substrate 22) is set larger than the dimensional tolerance of the inner concave portion 33. Must be set to a value. However, if this depth δ ₂ is too large, there is a problem that the efficiency of heating the sample substrate 22 decreases. Further, there is a problem that the difference between the heat received by the sample substrate 22 in the vicinity of the annular convex portion 30 and the heat received by other portions of the sample substrate 22 becomes large, and it becomes difficult to balance them. Therefore, it is preferable to set the depth δ ₂ to a value larger by the dimensional tolerance of the inner concave portion 33.

Further, the gas in the gap 31 conducts heat from the inner concave portion 33 to the sample substrate 22. In order to perform this heat conduction satisfactorily, it is preferable to make the depth δ ₂ of the inner concave portion 33 uniform over the entire surface.

An outer concave portion 32 is provided in the counterbore portion 21 so that the temperature of the peripheral portion of the sample substrate 22 and the temperature of the central portion thereof substantially match each other. The outer concave portion 32 is formed along the outer side of the annular convex portion 30 and has an annular shape. The cross-sectional shape of the outer concave portion 32 in the radial direction is rectangular. Due to this outer concave portion 32, the above-mentioned gap 3
The same effect as the effect of 1 can be obtained. In consideration of the influence of radiant heat from both side surfaces of the outer concave portion 32 to the sample substrate 22, the depth δ _{1 of the} outer concave portion 32 (the outer concave portion 32
(The distance between the bottom of the sample substrate 22 and the sample substrate 22) is set to 1.2 to 2.0 times the depth δ ₂ of the inner concave portion 33. Thereby, heat conduction by the gas in the outer concave portion 32 is weakened.
Second Embodiment A susceptor for a vapor phase growth apparatus according to a second embodiment of the present invention will be described next.

In the susceptor of the first embodiment described above, the spot facing portion has a diameter of 205 mm, and the depth of the outer concave portion δ ₁
Is 800 μm, and the depth δ ₂ of the inner concave portion is 500 μm
3 susceptors were prepared. The radii of the center lines of the annular projections of these susceptors are made different from each other,
It was set to 7 mm (65% of the radius of the spot facing portion), 72 mm (70% of the radius of the spot facing portion), and 77 mm (75% of the radius of the spot facing portion). The radial width of this annular projection was 4 mm.

An epitaxial process was carried out using each of these susceptors to form a silicon (Si) epitaxial film having a thickness of 50 μm on a silicon wafer having a diameter of 8 inches. A series of steps including this epitaxial step will be described in detail below.

First, a silicon wafer was placed on the susceptor and heated to 1150 ° C. at a temperature rising rate of 35 ° C./min. Next, as a gas purge before the epitaxial step, the silicon wafer was purged with hydrogen (H ₂ ) gas for 5 minutes.

Next, an epitaxial process was performed. That is, with the silicon wafer heated to 1150 ° C.,
Trichlorosilane (SiHCl ₃ ) gas and hydrogen (H ₂ ) gas were supplied to the silicon wafer at a rate of 25 g / min and 200 l / min, respectively, to form an epitaxial film of silicon on the silicon wafer.

Next, as a gas purge after the epitaxial process, the silicon wafer was purged with hydrogen gas for 3 minutes. Then, the silicon wafer was cooled at a temperature decrease rate of 300 ° C./min.

The silicon epitaxial film thus formed was observed with an optical microscope to measure the slip length generated in the epitaxial film (n = 20). When the slip length was 200 μm or more, it was judged as defective and the defective rate was obtained. The results are shown in Table 1.

[0024]

[Table 1] Third Embodiment A susceptor for a vapor phase growth apparatus according to a third embodiment of the present invention will be described next.

In the susceptor of the first embodiment described above, the spot facing portion has a diameter of 205 mm, the center line radius of the annular convex portion is 72 mm, and the radial width of the annular convex portion is 5 m.
m, and three susceptors having a depth δ ₂ of the inner concave portion of 500 μm were prepared. The depths δ ₁ of the outer concave portions of these susceptors are different from each other, and are 600 μm and 8 μm, respectively.
It was set to 0 μm and 1000 μm.

Next, thermocouples were embedded in the center and outer peripheral portion of a silicon wafer having a diameter of 8 inches, and the silicon wafer was placed on the susceptor. 35 ℃ / min
After heating to 1150 ° C at a heating rate of
Hold for minutes. Then, the temperature T ₁ of the outer peripheral portion and the temperature T _{2 of the} central portion of the silicon wafer were measured with a thermocouple, and the difference (T ₁ −T ₂ ) between them was obtained. The results are shown in Table 2.

[0027]

[Table 2] First comparative example The radius of the center line of the annular convex portion is 62 mm and 82 m, respectively.
Two susceptors with m were created. An epitaxial process was carried out in the same manner as in the above-described second embodiment with the other configurations, and the defect rate was obtained. The results are shown in Table 1 above.

As is apparent from comparison with the first embodiment described above, the radius of the center line of the annular convex portion is 6 times the radius of the spot facing portion.
It was found that the occurrence of slip of the silicon wafer was remarkably suppressed by setting it within the range of 5 to 75%.

The second comparative example outside the concave portion 500μm depth [delta] _1, respectively, 1100
Two susceptors having a size of μm were prepared. The difference (T ₁ -T ₂ ) between the temperature T ₁ of the outer peripheral portion of the silicon wafer and the temperature T ₂ of the central portion of the silicon wafer was determined in the same manner as in the third embodiment with the other configurations.

The results are shown in Table 2.

As is clear from comparison with the third embodiment,
The depth δ ₁ of the outer concave portion is 1.2 of the depth δ ₂ of the inner concave portion.
It was found that the heat uniformity during heating of the silicon wafer was remarkably improved by setting the ratio to about 2.0 times.

[0032] With reference to Fourth Embodiment FIG. 3, description will be given of a fourth vapor growth apparatus for a susceptor according to an embodiment of the present invention.

This susceptor 20 has a counterbore portion 21.
The structure is the same as that of the susceptor of the above-described first embodiment except the shape of the inner concave portion 33, and the same reference numerals correspond to each other.

When the sample substrate 22 bends, the counterbore 2
It is preferable that the inner concave portion 33 of No. 1 is formed in a concave portion having the same shape as the curved curved surface of the sample substrate 22.

However, since the flexible curved surface of the sample substrate 22 is approximately spherical, the inner concave portion 33 of the spot facing portion 21 may be a spherical concave portion. In this case, the radius R of this spherical surface is determined by the following equation.

R = (r ² + d ² ) / (2d) where r is the radius of the sample substrate 22 and d is the amount of deflection of the sample substrate 22.

When the deflection amount of the sample substrate 22 is small (for example, ten and several μm), the bottom of the inner concave portion 33 of the counterbore portion 21 is flattened as in the first embodiment (FIG. 2). It can be shaped.

[0038] With reference to the fifth embodiment Figure 4, demonstrates the vapor phase growth apparatus for a susceptor according to a fifth embodiment of the present invention.

The counterbore portion 21 of the susceptor 20 is provided with a further concave portion 34 on the inner side adjacent to the annular convex portion. Other configurations are similar to those of the above-described first embodiment, and the same reference numerals correspond to each other.

This further concave portion 34 is an annular convex portion 3
It is formed in a ring shape along the inside of 0. This further concave portion 34 reduces heat conduction in the vicinity of the annular convex portion 30 to balance the heat reception of the sample substrate 22 in the vicinity of the annular convex portion 30 with the heat reception of other portions of the sample substrate 22. There is.

The depth δ ₃ of the further concave portion 34 is 1.2 to 2.0 times the depth δ ₂ of the inner concave portion 33 and is the same as the depth δ ₁ of the outer concave portion 32, or It is preferably less than that. The radial width of the further concave portion 34 is preferably approximately the same as the radial width of the annular convex portion.

The present invention is not limited to the above-mentioned first to fifth embodiments. For example, the radial cross-sectional shape of the annular convex portion is not limited to the above-mentioned shape, and may be another shape.

Further, the radial cross-sectional shapes of the outer concave portion and the further concave portion do not have to be rectangular. For example, the shape may be a curve.

Further, the susceptor according to the present invention can be manufactured by manufacturing the susceptor by using the conventional material and manufacturing method of the susceptor and processing the spot facing portion of the susceptor.

[0045]

As described above, according to the present invention, since the center line of the annular convex portion is located within the range of 65 to 75% of the radius of the spot facing portion, it is possible to prevent the slip phenomenon from occurring in the semiconductor wafer. It can be prevented.

Moreover, since the depth of the outer concave portion is 1.2 to 2.0 times the depth of the inner concave portion, the influence of radiation and contact heat transfer by the annular convex portion on the semiconductor wafer can be suppressed. You can Therefore, the semiconductor wafer can be uniformly heated by heat conduction through the gas in the outer concave portion and the inner concave portion.

[Brief description of drawings]

FIG. 1 is a plan view showing a susceptor according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the susceptor shown in FIG. 1 taken along line FF.

FIG. 3 is a partial sectional view of a susceptor according to a fourth embodiment of the present invention.

FIG. 4 is a partial sectional view of a susceptor according to a fifth embodiment of the present invention.

[Explanation of symbols]

 20 susceptor 21 counterbore 22 sample substrate 30 annular convex 32 outer concave 33 inner concave 34 further concave

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[Procedure amendment]

[Submission date] June 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a plan view showing a susceptor according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the susceptor shown in FIG. 1 taken along line FF.

FIG. 3 is a partial sectional view of a susceptor according to a fourth embodiment of the present invention.

FIG. 4 is a partial sectional view of a susceptor according to a fifth embodiment of the present invention.

FIG. 5 is a plan view showing a conventional susceptor.

6 is a partial cross-sectional view of the susceptor shown in FIG. 5, taken along line 2-2.

FIG. 7 is a schematic diagram for explaining a state in which the sample substrate does not adhere to the susceptor shown in FIG. 6 and a graph showing a temperature distribution of the sample substrate in that state.

[Explanation of Codes] 10 susceptor 11 counterbore 12 sample base 14 bottom 20 susceptor 21 counterbore 22 sample substrate 30 annular convex 32 outer concave 33 inner concave 34 further concave

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenro Hayashi, No. 30 Soya, Hadano City, Kanagawa Prefecture, Research & Development Laboratory, Toshiba Ceramics Co., Ltd. Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A susceptor for a vapor phase growth apparatus having a circular counterbore for supporting a flat surface of a semiconductor wafer, the susceptor having one circular annular concentric portion concentric with the circular counterbore. The center line of the is 65 to 75 of the counterbore radius.
%, And a concave section in cross section is formed inside and outside the annular convex section, and the depth δ ₁ of the outer concave section is 1.2 to ₂ of the depth δ ₂ of the inner concave section. A susceptor for a vapor phase growth apparatus characterized by being 0 times. 2. A concave portion further formed than the inner concave portion is formed on the inner side adjacent to the annular convex portion, and the depth δ ₃ of the further concave portion is equal to or smaller than the depth δ ₁ of the outer concave portion. And the depth δ ₂ of the inner concave portion is 1.
Claim 1 to 2 to 2.0 times
A susceptor for a vapor phase growth apparatus according to the item.