JP6493982B2 - Susceptor - Google Patents

Description

  The present invention relates to a susceptor, for example, a susceptor used when forming a film on a semiconductor substrate.

  Conventionally, when forming a film on a semiconductor substrate, a susceptor for mounting the semiconductor substrate is used. As shown in FIG. 7, the susceptor 50 is generally formed of a disk-shaped plate, and a so-called counterbore (recess) 50b for placing a semiconductor substrate on the main surface 50a of the plate-shaped body. Is provided. Although not shown, as a means for placing the semiconductor substrate, there are some provided with a pocket, a plurality of pins, etc. in addition to the spot facing (recessed portion) 50b.

  By the way, as shown in FIG. 7, by forming the spot facing (recessed part) 50b in the susceptor 50, warping occurs so that the side facing (recessed part) 50b becomes a concave curved surface. Moreover, the warpage of the susceptor 50 is further increased by heat generated when the film is formed on the semiconductor substrate, the uniformity of the film thickness formed on the semiconductor substrate is deteriorated, and the number of occurrences of slip of the semiconductor substrate is increased. Is known to have adverse effects.

  In particular, in recent years, semiconductor substrates have a tendency to increase in diameter, and accordingly, susceptors also have a tendency to increase in diameter. Further, the thickness (thickness) of the susceptor tends to be thinner in order to increase the thermal conductivity of the susceptor. As described above, the susceptor has a larger diameter, a thinner thickness, and the susceptor is more likely to warp, resulting in a larger amount of warpage.

  As a susceptor for suppressing this warp, for example, a susceptor shown in Patent Document 1 has been proposed. The susceptor is shown in FIG. 8 and will be described with reference to FIG. As shown in FIG. 8, the susceptor 60 is formed in a disc-like body, and on one main surface 60a (on the upper surface), a substrate placement recess 61 (six in FIG. 8) is placed. Are shown). Further, a back surface depression 62 is provided on the other main surface 60b (lower surface) opposite to the one main surface 60a.

  The substrate mounting recess 61 and the back surface recess 62 have the same shape and dimension, and the substrate mounting recess 61 and the back surface recess 62 are symmetrically formed on the front and back surfaces. Since the susceptor 60 having such a shape is formed symmetrically with the front and back surfaces, it is possible to suppress processing distortion and warpage during manufacturing. Further, although internal stress is generated inside the susceptor 60 due to heat when forming a film on the semiconductor substrate, the internal stress is offset and the occurrence of warpage is suppressed because it is formed symmetrically on the front and back surfaces. .

JP-A-11-16991

  However, in the susceptor shown in Patent Document 1, it is necessary to form, on the back surface side, a back surface recess portion having the same shape and dimensions as the substrate mounting recess portion so as to be symmetrical with the substrate mounting recess portion. In addition, there is a technical problem that not only high-precision processing is required but also the cost is increased.

  In addition, when heated by receiving radiant heat from the back surface of the susceptor, if there are large irregularities on the back surface of the susceptor, the heat uniformity of the susceptor is lowered, so it can be said that it is not particularly suitable for a large-diameter substrate.

  Furthermore, if the front and back shapes are the same and the volume in the thickness direction is the same, the distortion and warpage inherent to the susceptor itself become obvious, and the susceptor is not simply warped, but within the main surface on which the semiconductor substrate is placed. It becomes a highly distorted shape having irregularities, which is not preferable as a susceptor for vapor phase growth.

  In order to solve the above technical problem, the inventors of the present invention mainly processed the main surface side of the susceptor without forming recesses (dents) symmetrically on the front and back surfaces, as described above. We have intensively studied to suppress the warpage when manufacturing the film and to suppress the warpage when forming the film on the semiconductor substrate. As a result, a specific recess is formed on the main surface side of the susceptor, and a ratio between a volume between a predetermined virtual plane and the one main surface and a volume obtained by subtracting the volume from the volume of the entire susceptor is specified. In this range, although the warp when the susceptor is manufactured exists, it is conceived that the warp when the film is formed on the semiconductor substrate can be suppressed, and this finding has been completed.

  The present invention has been made to solve the above technical problem, and an object of the present invention is to provide a susceptor that can suppress cost and suppress warpage during film formation.

A susceptor according to the present invention made to achieve the above object has a recess for placing a semiconductor substrate on one main surface, and a plate having a rotation axis perpendicular to the one main surface. A susceptor made of a body and used in a film forming apparatus , wherein the minimum thickness is at a position having a minimum thickness dimension between the bottom surface of the recess and the other main surface facing the one main surface. A volume obtained by subtracting the volume Va from the volume of the entire susceptor by setting a virtual plane that passes through the midpoint of the dimension and sets a virtual plane perpendicular to the rotation axis, Va being the volume between the virtual plane and the one main surface Vb, the volume Va is 1.03 times to 1.45 times less than the volume Vb, outside the recess on the one main surface, separately from the recess, A feature is that a shaving portion is formed by shaving off the main surface.

  Thus, when the volume Va is 1.03 times or more and 1.45 times or less of the volume Vb, there is a warp when manufacturing a susceptor, but a warp when forming a film on a semiconductor substrate is It is suppressed. In addition, since it is not necessary to form concave portions (recessed portions) symmetrically on the front and back surfaces as in the prior art, high-precision processing is not required, and a susceptor can be manufactured at low cost.

When the volume Va is less than 1.03 times the volume Vb, the warp due to the volume difference in the thickness direction is almost eliminated, but the inherent strain of the susceptor itself becomes obvious, and the susceptor is simply warped. However, the surface for holding the wafer is convex, and the wafer cannot be stably held on the outer periphery, which is not preferable.
Further, when the volume Va exceeds 1.45 times the volume Vb, warpage occurs at 120 μm or more, which causes a problem in film formation uniformity in the vapor phase growth process, which is not preferable.

In the present invention, the volume Va may be 1.03 times or more and 1.45 times or less of the volume Vb, and by adjusting the depth and diameter of the concave portion of one main surface of the susceptor. The ratio of the volume Va to the volume Vb is adjusted.
Further, the adjustment of the ratio of the volume Va to the volume Vb is performed by forming a scraped portion by scraping one main surface . In this case, the back surface of the susceptor can be designed as a flat surface, and the heat uniformity of the susceptor can be ensured.
Furthermore, it may be performed by forming a shaving portion scraped off in a ring shape around the rotation axis on the other main surface. Even in the case of forming a cut portion on the other main surface, it is not necessary to form a concave portion (dent portion) symmetrically on the front and back surfaces as in the prior art, so that high-precision processing is not required and the susceptor can be manufactured at low cost. Can be produced.

Furthermore, the volume Va is desirably 1.26 times or less of the volume Vb. The warp of the susceptor can be suppressed to about 50 μm, which is preferable.
The susceptor according to the present invention can be suitably used in the vapor phase growth method of the compound semiconductor layer.

  According to the present invention, it is possible to obtain a susceptor that can reduce costs and suppress warping during film formation.

1A and 1B are views showing a susceptor according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line II of FIG. 2A and 2B are diagrams showing a susceptor showing a second embodiment, in which FIG. 2A is a plan view and FIG. 2B is a sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view showing a susceptor showing the third embodiment. 4A and 4B are cross-sectional views showing a susceptor (Comparative Example 1), in which FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a diagram showing the displacement and temperature in the radial direction of the susceptor (Comparative Example 1) shown in FIG. FIG. 6 is a diagram illustrating the relationship between the volume ratio and warpage in Comparative Examples 2 to 12, Examples 1 to 15, and Reference Example 1. FIG. 7 is a cross-sectional view of a conventional susceptor. FIG. 8 is a perspective view of another conventional susceptor.

  Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not accurately illustrated.

As shown in FIG. 1, the susceptor 1 of the first embodiment is formed in a disc-like body having one main surface 2 and another main surface 3 opposite to the one main surface 2. On the surface 2, a single recess 4 is formed for mounting the semiconductor substrate.
The concave portion 4 is formed in a circular shape in plan view, and its center is located on the rotation axis L. That is, the susceptor 1 has a rotation axis L at the center, and the rotational symmetry of the susceptor 1 by the rotation axis L is formed in a circular symmetry.

  As the material of the susceptor 1, a commonly used material can be used. For example, a carbon (C) base coated with silicon carbide (SiC) can be used.

  A volume between the specific plane (virtual plane) F of the susceptor 1 and the one main surface 2, that is, a volume above the specific plane (virtual plane) F is Va. A volume obtained by subtracting the volume Va from the volume of the entire susceptor, that is, a volume below a specific plane (virtual plane) F is defined as Vb. At this time, in the susceptor 1, the volume Va is configured to be 1.03 times or more and 1.45 times or less of the volume Vb.

The specific plane (virtual plane) F is the minimum between the bottom surface of the recess 4 on which the semiconductor substrate is placed on one main surface 2 and the other main surface 3 facing the one main surface 2. At a position P having a thickness dimension, it means an imaginary plane perpendicular to the rotation axis L, passing through an intermediate point M of the minimum thickness dimension (position P on the bottom surface and the other main surface 3).
When a through hole penetrating from one main surface 2 to the other main surface 3 is formed in the susceptor 1, a position P having a minimum thickness dimension is assumed assuming that the through hole is embedded. Is identified.

  Thus, in the susceptor 1 in which the recess 4 for mounting the semiconductor substrate is formed on the main surface 2 of the susceptor 1, the volume Va is configured to be 1.03 times or more and 1.45 times or less of the volume Vb. If it is, the warp of the susceptor 1 can be made 120 μm or less.

Further, in order to make the volume Va of the susceptor 1 to be 1.03 times or more and 1.45 times or less of the volume Vb, the susceptor 1 is formed by scraping the one main surface 2 on the outer peripheral portion of the recess 4. The ring-shaped shaving part 5 formed in plan view is formed. The shaving portion 5 is formed on the main surface on the concave portion 4 side where the semiconductor substrate is placed, and the depth t1 and the width t2 are within a range where the volume Va is 1.03 times or more and 1.45 times or less of the volume Vb. It is adjusted to become.
The concave portion 4 and the shaving portion 5 can be formed by processing the surface of the susceptor 1, and the back surface of the susceptor 1 can be designed to be a flat surface (other main surfaces can be flat surfaces). It is also possible to ensure heat uniformity.

  Here, when the volume Va is less than 1.03 times the volume Vb, the warp of the susceptor is not stable, and the surface holding the wafer becomes convex (so-called upward convex), and the wafer is stably held on the outer periphery. Since it becomes impossible, it is not preferable. In order to hold the semiconductor substrate, it is desirable that the susceptor has a downwardly convex shape. When the susceptor is upwardly convex, the central portion of the semiconductor substrate is likely to come into contact with the susceptor, and the film formation surface of the semiconductor substrate is not stable and uniform film formation Cannot be obtained. Further, when contact is made as described above, scratches such as LPD (Light Point Defects) may occur on the back surface of the semiconductor substrate, which may affect the flatness in a subsequent process. Note that in a vertically symmetrical structure in which the volume Va is one time the volume Vb, the susceptor warpage itself is reduced, but the susceptor swells, which is also not preferable. Further, when the volume Va exceeds 1.45 times the volume Vb, warpage occurs at 120 μm or more, which causes a problem in film formation uniformity in the vapor phase growth process, which is not preferable. In particular, when the volume Va is 1.26 times or less of the volume Vb, the warpage is about 50 μm, which is more preferable.

If it demonstrates concretely, the diameter D1 of the susceptor 1 will be set to 300 mm or more and 1500 mm or less, for example. The reason why the diameter D1 (the maximum diameter of one main surface) of the susceptor 1 is set to 300 mm or more and 1500 mm or less corresponds to the dimensions of the semiconductor substrate.
For example, the diameter D1 of the susceptor 1 is 340 mm, the dimension (thickness) T1 between the one main surface 2 and the other main surface 3 is 2.4 mm, and the diameter D2 of the recess 4 is 202.5 mm. The depth t3 of the recess 4 (the depth on the rotation axis L, which is shifted from the rotation axis L for clarity in FIG. 1) is 0.84 mm, and the depth t1 of the shaving portion 5 is 0. When 84 mm and width t2 are set to 115 mm, the virtual plane F is at a position 1.62 mm from the one main surface 2 and the volume Va is 1.26 times the volume Vb.

Next, a 2nd form is demonstrated based on FIG.
In the first embodiment, the susceptor in which one recess 4 for mounting the semiconductor substrate is formed on the main surface 2 is shown. However, in the second embodiment, the semiconductor substrate is mounted on the main surface 2. It is characterized in that three recesses 13 are formed.

As shown in FIG. 2, on the main surface 11 of the susceptor 10 of the second embodiment, as described above, three recesses 13 are formed for placing three semiconductor substrates. The concave portion 13 corresponds to the concave portion 4 of the first embodiment.
Further, on the main surface 11 of the susceptor 10, three arc-shaped shaving portions 14 are formed between the concave portions 13 and the outer edge portion of the susceptor 10 in plan view. The shaving portion 14 corresponds to the shaving portion 5 of the first embodiment.

  The susceptor 10 has a rotation axis L at its center, and the rotational symmetry of the susceptor 10 by the rotation axis L is three-fold symmetry. That is, the concave portion 13 and the shaving portion 14 are formed with an interval of 120 degrees with respect to the rotation axis L (the center of the susceptor 10).

In the second embodiment, the specific plane (virtual plane) F includes a bottom surface of three recesses 13 on which a semiconductor substrate is placed on one main surface 11 and another surface facing the one main surface 11. At a position P having a minimum thickness dimension with respect to the main surface 12, it passes through an intermediate point M of the minimum thickness dimension (position P on the bottom surface and the other main surface 3) and is perpendicular to the rotation axis L. A virtual plane.
In addition, when the recessed part depth (bottom surface position) of the three recessed parts 13 differs, between the deepest recessed part bottom face and the other main surface 12 becomes the minimum thickness dimension among the three recessed parts 13, the said bottom face Position P exists above.

  Even in the second embodiment, the volume between the specific plane (virtual plane) F of the susceptor 10 and the one main surface 11 is Va, and the volume Va is subtracted from the volume of the entire susceptor. Assuming that the volume is Vb, in the susceptor 10, the volume Va is configured to be not less than 1.03 times and not more than 1.45 times the volume Vb.

Since the volume Va is configured to be not less than 1.03 times and not more than 1.45 times the volume Vb, the warp of the susceptor is stable, the wafer can be stably held on the outer periphery, and the warp is suppressed to 120 μm or less. Can do.
In particular, when the volume Va is configured to be 1.26 times or less of the volume Vb, warpage can be suppressed to 50 μm or less, which is more preferable.

In order to make the volume Va of the susceptor 10 not less than 1.03 times and not more than 1.45 times the volume Vb, in the susceptor 10 of the second embodiment, a shaved part 14 is formed on the outer peripheral part of the recess 13.
The shaving portion 14 is formed on the main surface on the concave portion 13 side on which the semiconductor substrate is placed, and the diameter r and depth t5 are within a range where the volume Va is 1.03 times or more and 1.45 times or less of the volume Vb. It is adjusted to become.
The ratio of the volume Va to the volume Vb may be adjusted by adjusting the depth of the recess 13.
In addition, since the said recessed part 13 and the cutting part 14 can be formed by processing the surface of the susceptor 10, the back surface of the susceptor 10 can be designed in a flat surface (other main surfaces can be made into a flat surface). In addition, it is possible to ensure the thermal uniformity of the susceptor.

If it demonstrates concretely, the diameter D3 of the susceptor 10 will be set to 300 mm or more and 1500 mm or less, for example.
For example, the diameter D3 of the susceptor 10 is 340 mm, the dimension (thickness) T2 between the one main surface 11 and the other main surface 12 is 2.4 mm, and the diameter D4 of the recess 13 is 151.3 mm. When the depth t4 of the recess 13 is 0.725 mm, the diameter r of the shaving portion 14 is 70 mm, and the depth t5 is 0.725 mm, the virtual plane F is 1. At the position of 5625 mm, the volume Va is 1.16 times the volume Vb.

Next, a 3rd form is demonstrated based on FIG.
In the first embodiment, the case where one shaving portion 5 is formed on the main surface 2 has been shown, but this third embodiment is also applied to the other main surface opposite to the main surface of the susceptor. It is characterized by the formation of a shaved part.

  As shown in FIG. 3, on the main surface 21 of the susceptor 20, a single recess 25 for mounting a semiconductor substrate is formed. The recess 25 corresponds to the recess 4 of the first form. Further, on the main surface 21 of the susceptor 20, a ring-shaped first cut portion 23 is formed on the outer peripheral portion of the concave portion 25 by cutting the one main surface 21 in plan view. The The first shaving portion 23 corresponds to the shaving portion 5 of the first form.

Further, on the other main surface 22 facing the main surface 21, a ring in plan view formed by scraping the other main surface 22 from the corresponding position of the concave portion 25 to the outside region. A second shaving portion 24 is formed.
The susceptor 10 has a rotation axis L at the center, and the rotational symmetry of the susceptor 10 by the rotation axis L is circular symmetry.

  Also in this third embodiment, the minimum thickness dimension between the one main surface 21 and the other main surface 22 facing the one main surface 21 is the concave portion as shown in FIG. 25 and the other main surface 22, and the virtual plane F is intermediate between the minimum thickness dimension (the position P on the bottom surface and the other main surface 22) at the position P having the minimum thickness dimension. A plane passing through the point M and perpendicular to the rotation axis L.

  Further, in the case of the third embodiment, Va is a volume between a specific plane (virtual plane) F of the susceptor 20 and the one main surface 21, and the volume Va is subtracted from the volume of the entire susceptor. Assuming that the volume is Vb, also in the susceptor 20, the volume Va is configured to be 1.03 times or more and 1.45 times or less of the volume Vb.

Since the volume Va is configured to be not less than 1.03 times and not more than 1.45 times the volume Vb, the warp of the susceptor is stable, the wafer can be stably held on the outer periphery, and the warp is suppressed to 120 μm or less. Can do.
In particular, when the volume Va is configured to be 1.26 times or less of the volume Vb, warpage can be suppressed to 50 μm or less, which is more preferable.

  If it demonstrates concretely, the diameter D5 of the susceptor 20 will be set to 300 mm or more and 1500 mm or less, for example. The reason why the diameter D5 (maximum diameter of one main surface) of the susceptor 20 is set to 300 mm or more and 1500 mm or less corresponds to the dimensions of the semiconductor substrate.

  For example, the diameter D5 of the susceptor 20 is 340 mm, the dimension (thickness) T3 between the one main surface 21 and the other main surface 22 is 2.4 mm, and the diameter D6 of the recess 25 is 202.5 mm. The depth t10 of the concave portion 25 (shown by shifting from the rotation axis L for clarity in FIG. 3) is 0.84 mm, the width t6 of the first shaving portion 23 is 58.75 mm, and the depth t7 is When the width t8 of the second shaving portion 24 is 10 mm and the depth t9 is 0.5 mm, the imaginary plane F is at a position 1.62 mm from the one main surface 21. The volume Va is 1.33 times the volume Vb.

  The susceptors 1, 10, and 20 according to the present invention are particularly effective in a process for vapor-phase growth of a compound semiconductor layer on a base substrate. As an example, there is a susceptor for vapor phase growth of a nitride semiconductor substrate in which several types of gallium nitride semiconductor layers are formed on one main surface of a silicon wafer.

  Compared to the case where silicon is vapor-phase grown on a silicon wafer, in the case of the nitride semiconductor described above, the warpage of the substrate greatly varies during the vapor-phase growth process. In addition, the in-plane uniformity of the vapor-deposited layer thickness requires more precise temperature control when the thickness of each nitride semiconductor layer is thin, but when both the substrate warpage and the susceptor warpage are large, This temperature controllability is significantly impaired.

  In this respect, the susceptors 1, 10 and 20 according to the present invention have the warp of the susceptor itself within an appropriate range, and it is necessary to form an unnecessarily complicated recess on the back surface of the susceptors 1, 10 and 20. Therefore, the in-plane uniformity of the radiant heat from the back surfaces of the susceptors 1, 10, and 20 is maintained well, and as a result, it can be said that the in-plane uniformity of the susceptor surface temperature does not decrease.

Further, it is desirable that the minimum thickness dimension is 1/1000 or more and 23/1000 or less of the maximum diameter of the one main surface, and the maximum diameter of the one main surface is 300 mm or more and 1500 mm or less.
The reason that the maximum diameter of the one main surface is set to 300 mm or more and 1500 mm or less corresponds to the size of the semiconductor substrate as described above, and the minimum thickness dimension is 1/1000 of the maximum diameter of the one main surface. By being in the range of 23/1000 or less, the thermal conductivity of the susceptor can be improved, and the temperature uniformity within the surface of the susceptor can be improved.
Therefore, for example, it can be suitably used as a susceptor used when forming a high-purity epitaxial film by a vapor phase growth method that requires strict temperature control on a semiconductor substrate.

As shown in FIG. 4, a susceptor 30 in which the shaving portion 5 in FIG. 1 was not formed was prepared (Comparative Example 1). The material of the susceptor 1 was a carbon (C) substrate coated with silicon carbide (SiC).
The diameter of the susceptor 30 is 340 mm, the dimension (thickness) between the one main surface 31 and the other main surface 32 is 2.4 mm, the diameter of the recess 33 is 194.5 mm, and the depth of the recess 33 is 0. .84 mm, the imaginary plane F is at a position 1.62 mm from the one main surface 31, and the volume Va is 1.8 times the volume Vb.

The warpage of the susceptor when the susceptor 30 was heated to 1090 ° C. was measured. The result is shown in FIG. As can be seen from FIG. 5, the outer periphery of the susceptor 30 was warped by approximately 0.180 mm, and the surface temperature was found to be approximately 20 ° C. different from the central portion and the outer periphery.
5 represents the radius from the center of the susceptor 30, the right vertical axis represents the amount of warpage, and the left vertical axis represents the susceptor surface temperature. In the figure, the line segment represents the susceptor surface temperature, and the circle represents the amount of warpage.

Next, in each susceptor having the form shown in FIGS. 1, 2, and 3, susceptors were manufactured by changing the volume ratio of the volume Va and the volume Vb. The material of each susceptor was a carbon (C) substrate coated with silicon carbide (SiC).
The diameter D1 of the susceptor 1 shown in FIG. 1 is 340 mm, the dimension (thickness) T1 between the one main surface 2 and the other main surface 3 is 2.4 mm, and the diameter D2 of the recess 4 is 194.5 mm. The depth t3 of the recess 4 (depth on the rotation axis L) is 0.84 mm, the width t2 of the shaving portion 5 is 115 mm, the depth of the shaving portion 5 is changed, and the volume ratio is as shown in Table 1. (Comparative Examples 2-5, Examples 1-5).

  Further, the diameter D3 of the susceptor 10 shown in FIG. 2 is 340 mm, the dimension (thickness) T2 between the one main surface 11 and the other main surface 12 is 2.4 mm, and the diameter D4 of the recess 13 is 151.3 mm. The depth t4 of the recess 13 was 0.725 mm, the diameter r of the shaved portion 14 was 70 mm, the depth t5 of the shaved portion 14 was changed, and the volume ratio was changed as shown in Table 2 (Comparative Examples 6 to 6). 9, Examples 6-10).

  Further, the diameter D5 of the susceptor 20 shown in FIG. 3 is 340 mm, the dimension (thickness) T3 between the one main surface 21 and the other main surface 22 is 2.4 mm, and the diameter D6 of the recess 25 is 202. 5 mm, the depth t10 of the recess 25 is 0.84 mm, the width t8 of the second shaving portion 24 is 10 mm, the depth t9 is 0.5 mm, and the width t6 of the first shaving portion 23 is 58.75 mm, depth. The length t7 was changed, and the volume ratio was changed as shown in Table 3 (Comparative Examples 10-12, Examples 11-15, Reference Example 1).

  And the curvature of the susceptor when each susceptor which changed volume ratio was heated to 1090 degreeC was measured. The results are shown in Table 1, Table 2, Table 3, and FIG. In FIG. 6, the susceptor 1 shown in FIG. 1 is indicated by S1, the susceptor 10 shown in FIG. 2 is indicated by S10, and the susceptor 20 shown in FIG. 3 is indicated by S20.

  Further, the surface temperature of each susceptor was measured, and the temperature difference between the central portion and the outer peripheral portion of each susceptor was 20 ° C. or less.

As is apparent from the results, when the volume Va is 1.45 times or less of the volume Vb, the warpage amount is 120 μm or less, and it was confirmed that the warpage amount was suppressed.
In addition, as seen in Reference Example 1, even when the volume Va is 1.61 of the volume Vb, the warpage amount is 102 μm and can be 120 μm or less. Since the warpage is reduced by thinning the back side, the heat capacity of the thinned portion decreases, the temperature difference between the spot facing portion and other places increases, making it difficult to control the temperature of the susceptor. Is concerned. Further, on the back surface side of the susceptor, there are a supporting rotating jig, a thermocouple, and the like peculiar to the vapor phase growth apparatus, and it is difficult to adopt the same structure as the countersink surface. Such a structure is not preferable.

  In particular, when the volume Va is 1.26 times or less of the volume Vb, it was confirmed that the warpage amount was further suppressed to 68 μm. Furthermore, when the volume Va was 1.2 times or less of the volume Vb, it was confirmed that the warpage amount was extremely suppressed at 50 μm.

DESCRIPTION OF SYMBOLS 1 Susceptor 2 One main surface 3 Other main surface 4 Recessed part 5 Cutting part 10 Susceptor 11 One main surface 12 Other main surface 13 Recessed part 14 Cutting part 20 Susceptor 21 One main surface 22 Other main surface 23 1st Cutting part 24 Second cutting part 25 Concave F Virtual plane P Position M having minimum thickness dimension Intermediate point Va of minimum thickness dimension Volume Vb between virtual plane and one main surface From volume of entire susceptor to volume Va Minus the volume

Claims (4)

A susceptor used in a film forming apparatus, comprising a plate-like body having a recess for placing a semiconductor substrate on one main surface and having a rotation axis perpendicular to the one main surface,
At a position having a minimum thickness dimension between the bottom surface of the recess and the other main surface opposite to the one main surface, an imaginary plane perpendicular to the rotation axis passes through an intermediate point of the minimum thickness dimension. Set, when the volume between the virtual plane and the one main surface is Va, and the volume obtained by subtracting the volume Va from the volume of the entire susceptor is Vb,
The volume Va is 1.03 times or more and 1.45 times or less of the volume Vb,
A susceptor characterized in that, on the outer side of the concave portion on the one main surface, a shaving portion obtained by scraping the one main surface is formed separately from the concave portion.   2. The susceptor according to claim 1, wherein a shaving portion is formed on the other main surface by scraping in a ring shape with the rotation axis as a center.   The susceptor according to claim 1, wherein the volume Va is equal to or less than 1.26 times the volume Vb.   The susceptor according to claim 1, wherein the susceptor is used in a vapor phase growth method of a compound semiconductor layer.

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