Wafer holder, chemical vapor deposition apparatus, and method for manufacturing SiC epitaxial wafers

Abstract

To provide a wafer holder, a chemical vapor deposition device, and a manufacturing method of a SiC epitaxial wafer capable of producing a high-quality SiC epitaxial wafer.SOLUTION: A wafer holder according to an embodiment includes a central portion facing a wafer to be placed, and an outer peripheral portion outside the central portion, and the outer peripheral portion includes a first gas discharge path extending outward from the central portion, and a second gas discharge path extending upward in the thickness direction from the first gas discharge path.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wafer holder, a chemical vapor deposition apparatus, and a method for manufacturing a SiC epitaxial wafer. [Background technology]

[0002] Silicon carbide (SiC) has a breakdown field that is one order of magnitude larger than that of silicon (Si), a band gap that is three times larger, and a thermal conductivity that is approximately three times higher. Because of these properties, silicon carbide is expected to be used in power devices, high-frequency devices, high-temperature operating devices, etc. SiC semiconductor devices are fabricated using SiC epitaxial wafers.

[0003] SiC epitaxial wafers are manufactured by growing a SiC epitaxial film, which will become the active region of a SiC semiconductor device, on a SiC substrate. The SiC substrate is obtained by processing a bulk single crystal of SiC produced by a sublimation method or the like, and the SiC epitaxial film is formed by chemical vapor deposition (CVD). In this specification, a SiC epitaxial wafer refers to a wafer after the SiC epitaxial film has been formed, and a SiC substrate refers to a wafer before the SiC epitaxial film has been formed.

[0004] CVD is a technology for growing a high-quality epitaxial film on the surface of a substrate, but the process can sometimes result in roughness on the backside. For example, Patent Documents 1 and 2 describe the formation of an epitaxial film on a Si substrate placed on a susceptor. Film-forming gas and etching gas are supplied to the front side of the Si substrate, and purge gas is supplied to the backside. Supplying purge gas to the backside of the Si substrate prevents some of the gas supplied to the front side from flowing around to the backside, thereby suppressing roughness and cloudiness on the backside of the Si epitaxial wafer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3908112 [Patent Document 2] Special Publication No. 2001-508599 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when using SiC substrates, simply supplying a purge gas to the backside of SiC epitaxial wafers often fails to sufficiently suppress the backside roughness and cloudiness. SiC is more susceptible to backside roughness and cloudiness than Si. This is due to the high deposition temperature for epitaxial film formation, the fact that the H2 carrier gas also functions as an etching gas, the tendency for roughness (step bunching) to occur due to a discrepancy in the ratio of C-based source gas to Si-based source gas (C / Si ratio), and the presence of many thermodynamically stable polytypes that are prone to the formation of mixed crystals. Furthermore, SiC substrates are susceptible to the influence of gas and temperature environments. Therefore, optimizing the growth conditions for SiC epitaxial films is difficult, leading to the problem of abnormal growth.

[0007] Roughness and abnormal growth on the backside of SiC epitaxial wafers can have adverse effects on the inspection process and device fabrication process. For example, backside roughness on SiC epitaxial wafers can be eliminated by backside polishing, but adding a backside polishing step increases the number of production processes, leading to increased costs and reduced throughput.

[0008] One way to prevent roughening of the backside of a SiC substrate is to increase the efficiency of supplying purge gas to the backside of the SiC substrate. However, if the amount of purge gas supplied to the backside of the SiC substrate increases, the blowing of purge gas can cause the SiC substrate to shift from its installed position during the film formation process. Misalignment of the SiC substrate creates a situation in which purge gas is more likely to be supplied to the front side of the SiC substrate, causing deviations from the optimized film formation conditions, promoting abnormal growth, and being one of the causes of reduced quality of the formed epitaxial film.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wafer holder, a chemical vapor deposition apparatus, and a method for manufacturing SiC epitaxial wafers that are capable of producing high-quality SiC epitaxial wafers. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention specifically provides the following means.

[0011] (1) A wafer holder according to a first aspect includes a central portion facing a wafer placed thereon and an outer peripheral portion located outside the central portion, the outer peripheral portion having a first gas exhaust passage extending outward from the central portion and a second gas exhaust passage extending upward in the thickness direction from the first gas exhaust passage.

[0012] (2) In the wafer holder according to the above aspect, a second end of the second gas discharge path opposite to a first end connected to the first gas discharge path may be located outside an inner circumferential end of the outer circumferential portion.

[0013] (3) The wafer holder according to the above aspect may have a susceptor and a plurality of cover members that cover the susceptor at the outer periphery, wherein the first gas exhaust path is formed between the susceptor and the plurality of cover members, and the second gas exhaust path is formed between the plurality of cover members.

[0014] (4) In the wafer holder according to the above aspect, the first gas exhaust passage may be inclined with respect to the radial direction so that the outer second end is located rearward of the inner first end in the direction of rotation, and the inclination angle of the first gas exhaust passage with respect to the radial direction may be greater than 0° and less than 90°.

[0015] (5) In the wafer holder according to the above aspect, the first gas exhaust path may extend along a radial direction.

[0016] (6) In the wafer holder according to the above aspect, the second gas exhaust path may be inclined with respect to an in-plane direction in which the central portion extends so that a second end thereof is positioned outward from a first end connected to the first gas exhaust path, and the inclination angle of the second gas exhaust path with respect to the in-plane direction may be greater than 0° and less than 90°.

[0017] (7) In the wafer holder according to the above aspect, the second gas exhaust path may extend in a direction perpendicular to the first gas exhaust path.

[0018] (8) In the wafer holder according to the above aspect, the central portion may have a gas inlet passage for supplying gas to the backside of the wafer.

[0019] (9) A chemical vapor deposition apparatus according to a second aspect includes the wafer holder according to the above aspect.

[0020] (10) A method for producing a SiC epitaxial wafer according to a third aspect uses the wafer holder according to the above aspect. [Effects of the Invention]

[0021] The wafer holder, chemical vapor deposition apparatus, and SiC epitaxial wafer manufacturing method of the present invention can produce high-quality SiC epitaxial wafers. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a characteristic portion of a chemical vapor deposition apparatus according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the wafer holder according to the first embodiment. [Figure 3] FIG. 2 is a plan view of the susceptor according to the first embodiment. [Figure 4] FIG. 2 is a plan view of the cover member according to the first embodiment. [Figure 5] FIG. 3 is a cross-sectional view of a characteristic portion of the wafer holder according to the first embodiment. [Figure 6]3 is a cross-sectional view of a first portion near a slit of the susceptor according to the first embodiment. FIG. [Figure 7] FIG. 4 is a cross-sectional view of a second portion near the slit of the susceptor according to the first embodiment. [Figure 8] FIG. 10 is a cross-sectional view of a wafer holder according to a second embodiment. [Figure 9] FIG. 10 is a plan view of a susceptor according to a second embodiment. [Figure 10] FIG. 10 is a plan view of a cover member according to a second embodiment. [Figure 11] FIG. 10 is a cross-sectional view of a wafer holder according to a third embodiment. [Figure 12] FIG. 10 is a plan view of a wafer holder according to a third embodiment. [Figure 13] FIG. 11 is an enlarged cross-sectional view of the vicinity of a first gas exhaust path of a wafer holder according to a third embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a wafer holder according to a fourth embodiment. [Figure 15] FIG. 10 is a plan view of a wafer holder according to a fourth embodiment. [Figure 16] FIG. 10 is a plan view of a susceptor according to a first modified example. [Figure 17] FIG. 10 is a plan view of a susceptor according to a second modified example. [Figure 18] FIG. 10 is a cross-sectional view of a susceptor according to a third modified example. [Figure 19] FIG. 10 is a plan view of a susceptor according to a fourth modified example. [Figure 20] FIG. 10 is a cross-sectional view of a susceptor according to a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications can be made within the scope of the effects of the present invention.

[0024] First, let's define the directions. The thickness direction of the wafer holder is called the z direction. The direction perpendicular to the z direction is called the in-plane direction, one of the in-plane directions is called the x direction, and the direction perpendicular to the x direction is called the y direction. Furthermore, the direction spreading outward from the center of the wafer holder is called the radial direction, and the direction along the circumference of the wafer holder with the center of the wafer holder as its axis is called the circumferential direction.

[0025] "First embodiment" 1 is a cross-sectional view of a characteristic portion of a chemical vapor deposition apparatus 200 according to the first embodiment. The chemical vapor deposition apparatus 200 has a wafer holder 100, a chamber 110, a support 120, and a heater H.

[0026] The chamber 110 forms a film formation space A1. The chamber 110 has, for example, a gas supply port, a gas exhaust port, a transfer port for transferring the SiC substrate W, and the like. The chamber 110 is made of, for example, carbon, SiC, metal carbide, carbon coated with SiC or metal carbide, stainless steel, or the like. A gas G is supplied to the film formation space A1 from the gas supply port. The gas G is, for example, a film formation gas or an etching gas. The gas G is supplied to the surface of the SiC substrate W placed on the wafer holder 100.

[0027] The support 120 is located below the chamber 110. The support 120 supports the wafer holder 100. The support 120 may rotate the wafer holder 100. The support 120 and the wafer holder 100 surround a purge space A2. A heater H is located within the purge space A2. The heater H is located, for example, below the wafer holder 100. The heater H heats the wafer holder 100. The purge space A2 is filled with an inert gas to protect the heater H. The inert gas is, for example, nitrogen or argon. The inert gas is an example of a purge gas P. The purge gas P is supplied from the purge space A2 to the backside of the SiC substrate W through through-holes (e.g., vertical holes VH and slits SL) of the susceptor 10, which will be described later. The purge gas P supplied to the rear surface of the wafer passes through a first gas discharge path C1 and a second gas discharge path C2, which will be described later, and is released into the film formation space A1.

[0028] 2 is a cross-sectional view of a wafer holder 100 according to the first embodiment. The wafer holder 100 has, for example, a susceptor 10 and a cover member 20. In FIG. 2, a SiC substrate W held by the wafer holder 100 is also shown.

[0029] Wafer holder 100 has a central portion 30 and an outer peripheral portion 31. Central portion 30 is the portion of wafer holder 100 that faces SiC substrate W, and outer peripheral portion 31 is the portion radially outward from central portion 30. In wafer holder 100 shown in FIG. 2, central portion 30 is made up of a portion of susceptor 10, and outer peripheral portion 31 is made up of a portion of susceptor 10 and cover member 20. Cover member 20 is placed on susceptor 10 at outer peripheral portion 31. Outer peripheral portion 31 has a first gas discharge path C1 and a second gas discharge path C2.

[0030] Fig. 3 is a plan view of the susceptor 10 according to the first embodiment. Fig. 4 is a plan view of the cover member 20 according to the first embodiment. Fig. 4 also illustrates the SiC substrate W. The cross section taken along line AA in Figs. 3 and 4 corresponds to Fig. 2.

[0031] The susceptor 10 has a main body portion 15 and a support portion 16. The susceptor 10 rotates, for example, in any direction in the circumferential direction. Hereinafter, the direction in which the susceptor 10 rotates will be referred to as the rotation direction R. The support portion 16 is a portion that protrudes from the main body portion 15 in the z direction and supports the SiC substrate W. For example, the support portion 16 shown in FIG. 3 supports the SiC substrate W at a position that does not interfere with the exhaust port. There are no particular restrictions on the shape or position of the support portion 16 as long as it does not result in a structure that prevents the purge gas P from being exhausted.

[0032] The central portion 30 of the susceptor 10 has, for example, a vertical hole VH and a slit SL. Both the vertical hole VH and the slit SL are holes that penetrate the susceptor 10. A purge gas is supplied to the back surface of the SiC substrate W through the vertical hole VH and the slit SL.

[0033] A groove 17 is formed in the outer peripheral portion 31 of the susceptor 10. The thickness of the susceptor 10 where the groove 17 is formed is preferably 0.3 mm or more. The groove 17 is formed from the central portion 30 toward the outside in the radial direction. The space between the groove 17 and the cover member 20 is a first gas discharge path C1. The first gas discharge path C1 is formed between the susceptor 10 and the cover member 20, and extends from the central portion 30 toward the outside.

[0034] There are, for example, multiple cover members 20. Each of the cover members 20 is, for example, a ring-shaped member that is connected in the circumferential direction. The cover members 20 are, for example, arranged concentrically. There are gaps between the cover members 20. The gaps between the cover members 20 are second gas discharge paths C2. The second gas discharge path C2 extends in the z direction from the first gas discharge path C1.

[0035] The first gas exhaust path C1 and the second gas exhaust path C2 are paths through which the purge gas P supplied to the rear surface of the SiC substrate W is exhausted.

[0036] The first gas discharge channel C1 has a first end e1 and a second end e2. The first end e1 is located radially inward from the second end e2. The first end e1 is located, for example, at the boundary between the central portion 30 and the outer peripheral portion 31. The first end e1 may be located inside the boundary between the central portion 30 and the outer peripheral portion 31. In other words, a portion of the first gas discharge channel C1 may extend to the central portion 30. The second end e2 is located, for example, at the outer peripheral end of the outer peripheral portion 31. The second end e2 of the first gas discharge channel C1 is located rearward from the first end e1 in the rotational direction R.

[0037] The first gas discharge passage C1 is inclined with respect to the radial direction so that the second end e2 is located rearward of the first end e1 in the rotation direction R. The inclination angle θ1 of the first gas discharge passage C1 with respect to the radial direction is, for example, greater than 0° and less than 90°.

[0038] When the tilt angle θ1 is greater than 0°, a flow of purge gas P is formed from the central portion 30 toward the outside, and the purge gas P is efficiently discharged from the back surface side of the SiC substrate W. When the tilt angle θ1 is less than 90°, the gas vector does not deviate significantly from the direction in which the first gas discharge path C1 extends. The gas vector is the flow direction of the purge gas P, and is a direction that spreads radially from the central portion 30 in the radial direction. In other words, when the tilt angle θ1 is within the above range, the purge gas P is efficiently discharged.

[0039] The preferred range of the inclination angle θ1 is determined by the rotation speed of the susceptor 10, the discharge speed of the purge gas P, etc. For example, when the peripheral speed at the first end e1 is V R , the discharge speed of the purge gas P at the first end e1 is V p Then, θ1=sin -1 (V R / V p ) is preferably satisfied.

[0040] FIG. 5 is a cross-sectional view of a characteristic portion of the wafer holder 100 according to the first embodiment. The second gas discharge path C2 has a first end e3 and a second end e4. The first end e3 is an end connected to the first gas discharge path C1. The second end e4 is an end opposite the first end e3. The second end e4 is exposed on the upper surface of the cover member 20. The second end e4 is located outside the first end e3 and outside the inner peripheral end of the outer peripheral portion 31. By separating the second end e4, from which the purge gas P is discharged, from the edge of the SiC substrate W, it is possible to prevent the film formation conditions near the edge of the SiC substrate W from deviating from the optimal conditions.

[0041] The second gas discharge path C2 is, for example, inclined with respect to the in-plane direction. The inclination angle θ2 of the second gas discharge path C2 with respect to the in-plane direction is, for example, preferably greater than 0° and less than 90°. The purge gas P passing through the second gas discharge path C2 acts to press the susceptor 10 downward, thereby preventing the susceptor 10 from shifting out of position. Furthermore, the inclination angle θ2 is preferably greater than or equal to 30° and less than or equal to 60°. The purge gas P passing through the second gas discharge path C2 acts to press the cover member 20 downward, thereby preventing the susceptor 10 from shifting out of position.

[0042] The vertical hole VH and the slit SL are gas inlet paths for supplying a purge gas P to the rear surface side of the SiC substrate W.

[0043] The vertical holes VH penetrate the susceptor 10 in the z direction and extend in the z direction. The vertical holes VH are, for example, located at the center of the susceptor 10 when viewed from above in the z direction. The slits SL penetrate the susceptor 10 at an angle in the circumferential direction with respect to the z direction. The slits SL are, for example, located outside the susceptor 10 relative to the vertical holes VH. The slits SL extend from the center outward.

[0044] As shown in FIG. 3, the slit SL is inclined relative to the radial direction of the susceptor 10. The first inner end of the slit SL is located forward of the second outer end in the rotation direction R. The inclination angle φ1 of the slit SL relative to the radial direction of the susceptor 10 is, for example, greater than 0° and less than 90°. When the inclination angle φ1 is greater than 0°, a flow of purge gas P is easily formed from the center of the susceptor 10 toward the outside. When the inclination angle φ1 is less than 90°, the gas vector and the opening direction of the slit SL do not deviate significantly. The gas vector is the flow direction of the purge gas P passing through the slit SL. The opening direction of the slit SL is from the end on the back side of the slit SL toward the end on the front side.

[0045] 6 and 7 are cross-sectional views of the vicinity of the slit SL of the susceptor 10. Fig. 6 is a cross-section taken along line BB in Fig. 3, and Fig. 7 is a cross-section taken along line CC in Fig. 3. The first portion shown in Fig. 6 is located radially inward of the susceptor 10 relative to the second portion shown in Fig. 7.

[0046] The slits SL are inclined in the circumferential direction with respect to the z direction. The end of the slits SL on the back surface bs side is located forward in the rotation direction R of the end of the slits SL on the front surface fs side. The slits SL are inclined in the opposite direction to the rotation direction R from the end on the back surface bs side.

[0047] The inclination angle φ3 of the slit SL in the second portion with respect to the z direction is larger than the inclination angle φ2 of the slit SL in the first portion with respect to the z direction. The inclination angle of the slit SL with respect to the z direction increases, for example, toward the outside of the susceptor .

[0048] The inclination angles φ2 and φ3 of the slit SL are, for example, tanφ=V R1 / V p1 The relationship between V and V is satisfied. p1 is the vertical component of the relative velocity of the purge gas P with respect to the main body 15 at the position of the slit SL when viewed from the rotating coordinate system of the susceptor 10, and V R1 is the horizontal component of the relative velocity of the purge gas P with respect to the main body portion 15 at the position of the slit SL when viewed from the rotating coordinate system of the susceptor 10.

[0049] The susceptor 10 rotates in a rotation direction R. The peripheral speed (circumferential velocity) at each point on the susceptor 10 is expressed as the product of the distance between the corresponding point and the center and the angular velocity of the susceptor. With the susceptor 10 as the reference, the purge gas flows in the opposite direction to the rotation direction relative to the slit SL at a relative velocity V R1 It moves at a relative velocity V R1 The absolute value of is the same as the absolute value of the peripheral velocity. R1 is referred to as the first vector. The purge gas P flows from below the susceptor 10 in the z direction at a flow velocity V p1 The flow rate is V p1 is called the second vector.

[0050] When each point on the susceptor 10 is considered as a reference, the purge gas P is supplied to each point on the susceptor 10 from the direction of the resultant vector of the first and second vectors. When the inclination angles φ2 and φ3 at each point on the slit SL satisfy the above relationship, the inflow direction of the purge gas into the slit SL coincides with the inclination direction of the slit SL, and the purge gas flows smoothly into the slit SL.

[0051] The wafer holder 100 according to the first embodiment has the first gas exhaust path C1 and the second gas exhaust path C2, and thus can efficiently exhaust the purge gas P from the back surface side of the SiC substrate W. As a result, the purge gas P prevents the SiC substrate W from floating up during the film formation process, and positional deviation of the SiC substrate W can be suppressed. Furthermore, efficient exhaust of the purge gas P from the back surface side of the SiC substrate W can increase the amount of purge gas supplied to the back surface of the SiC substrate W. Increasing the amount of purge gas supplied to the back surface side of the SiC substrate can suppress roughening of the back surface of the SiC substrate.

[0052] Furthermore, by discharging the purge gas P from a position away from the edge of the SiC substrate W by the first gas discharge path C1 and the second gas discharge path C2, it is possible to prevent a decrease in the concentration ratio of the film formation gas near the outer peripheral edge of the SiC substrate W. In other words, it is possible to reduce the variation in film formation conditions near the outer peripheral edge of the SiC substrate W and to suppress abnormal growth.

[0053] Furthermore, the purge gas P discharged from the second end e4 of the second gas discharge path C2 flows over the top surface of the wafer holder 100, thereby pressing down the entire wafer holder 100 and preventing the wafer holder 100 from shifting position. Furthermore, the purge gas P flows over the top and bottom surfaces of the cover member 20, preventing a temperature difference from occurring between the top and bottom surfaces of the cover member 20. The temperature difference between the top and bottom surfaces of the cover member 20 can cause cracks in the cover member 20 and the susceptor 10.

[0054] "Second embodiment" FIG. 8 is a cross-sectional view of a wafer holder 101 according to the second embodiment. The wafer holder 101 has, for example, a susceptor 40 and a cover member 21. FIG. 8 also illustrates a SiC substrate W held by the wafer holder 101. FIG. 9 is a plan view of the susceptor 40 according to the second embodiment. FIG. 10 is a plan view of the cover member 21 according to the second embodiment. FIG. 10 also illustrates the SiC substrate W. The cross sections along line AA in FIGS. 9 and 10 correspond to FIG. 8.

[0055] The susceptor 40 has a main body portion 45 and a support portion 46. The susceptor 40 differs from the susceptor 10 shown in Fig. 2 in that the groove 17 is not formed in the outer peripheral portion 31. A description of the same configuration as in Fig. 2 will be omitted.

[0056] There are, for example, a plurality of cover members 21. Each of the cover members 21 is, for example, a ring-shaped member connected in the circumferential direction. The cover members 21 are, for example, arranged concentrically. A groove 25 is formed on the lower surface of the cover member 21. The space sandwiched between the groove 25 of the cover member 21 and the main body portion 45 of the susceptor 40 is the first gas discharge path C3. The specific configuration of the first gas discharge path C3 is the same as the first gas discharge path C1 shown in FIG. 1. Furthermore, the gap between the plurality of cover members 21 is the second gas discharge path C2.

[0057] The wafer holder 101 according to the second embodiment has the same effect as the wafer holder 100 according to the first embodiment, except that the relationship between the groove and the lid that form the first gas exhaust path C3 is opposite to that of the first gas exhaust path C1 according to the first embodiment.

[0058] "Third embodiment" FIG. 11 is a cross-sectional view of a wafer holder 102 according to the third embodiment. The wafer holder 102 is made of, for example, a susceptor 50. The wafer holder 102 differs from the first and second embodiments in that it does not have a cover member. FIG. 11 also shows the SiC substrates W held by the wafer holder 102. FIG. 12 is a plan view of the wafer holder 102 according to the third embodiment. The cross section taken along line AA in FIG. 12 corresponds to FIG. 11.

[0059] The susceptor 50 has a main body portion 55, a support portion 56, and a sidewall 57. The sidewall 57 is located on the side of the SiC substrate W and prevents the SiC substrate W from protruding in the radial direction. The susceptor 50 differs from the susceptor 10 shown in Fig. 2 in that the outer peripheral portion 31 is made up of a part of the main body portion 55 and the sidewall 57. A description of the same configuration as in Fig. 2 will be omitted.

[0060] A hole 58 is formed in the main body portion 55. The hole 58 is formed from the central portion 30 toward the outside. The hole 58 may be formed by hollowing out a part of the main body portion 55 as shown in FIG. 13(a), or may be formed by a recess 55A and a lid 55B covering the recess 55A as shown in FIG. 13(b). The lid 55B may be provided with a protrusion 55C to prevent misalignment. The inside of the hole 58 becomes a first gas discharge path C4.

[0061] A hole 59 is formed in the side wall 57. The hole 59 is connected to the hole 58 and extends in the z direction. The inside of the hole 59 serves as a second gas discharge path C5.

[0062] The wafer holder 102 according to the third embodiment has a first gas exhaust path C4 and a second gas exhaust path C5, and provides the same effects as the wafer holder 100 according to the first embodiment.

[0063] "Fourth embodiment" Fig. 14 is a cross-sectional view of a wafer holder 103 according to the fourth embodiment. The wafer holder 103 has, for example, a susceptor 60 and a cover member 22. Fig. 14 also shows a SiC substrate W held by the wafer holder 103. Fig. 15 is a plan view of the wafer holder 103 according to the fourth embodiment. The cross section taken along line AA in Fig. 15 corresponds to Fig. 14.

[0064] The susceptor 60 has a main body portion 65, a support portion 66, and a sidewall 67. The sidewall 67 is located on the side of the SiC substrate W. The susceptor 60 differs from the susceptor 10 shown in Fig. 2 in that it has the sidewall 67 and the groove 68 does not extend all the way to the outer periphery. A description of the same configuration as in Fig. 2 will be omitted.

[0065] A groove 68 is formed in the main body portion 65 at the outer circumferential portion 31. The groove 68 is formed from the central portion 30 toward the outside. The groove 68 does not reach the outer circumferential edge but extends to the side wall 67. The space between the groove 68 and the cover member 22 is the first gas discharge path C6.

[0066] The cover member 22 is located between the SiC substrate W and the side wall 67. The cover member 22 is, for example, a ring-shaped member. There is a gap between the cover member 22 and the side wall 67. The gap between the cover member 22 and the side wall 67 is a second gas discharge path C7. The second gas discharge path C7 extends in the z direction from the first gas discharge path C6.

[0067] The wafer holder 103 according to the fourth embodiment has a first gas exhaust path C6 and a second gas exhaust path C7, and provides the same effects as the wafer holder 100 according to the first embodiment.

[0068] As described above, specific examples of the wafer holder have been described in detail in the first to fourth embodiments, but the wafer holder can be modified and changed in various ways within the scope of the gist of the present invention.

[0069] For example, in the first to fourth embodiments, examples have been shown in which the gas inlet passage is composed of the vertical hole VH and the slit SL, but the shape, position, etc. of the gas inlet passage are not important. For example, as shown in FIG. 16, the gas inlet passage may be composed of only the vertical hole VH.

[0070] For example, in the first to fourth embodiments, examples have been shown in which the first gas inlet channels C1, C3, and C4 are inclined relative to the radial direction. However, as shown in FIG. 17, the first gas inlet channel C1' may extend in the radial direction. That is, the inclination angle θ1 of the first gas inlet channel C1' relative to the radial direction may be 0°. While FIG. 17 illustrates a modified example of the first embodiment (FIG. 3), the same applies to the second to fourth embodiments. If the inclination angle θ1 is 0°, the flow of the purge gas P from the central portion 30 toward the outside is not impeded, and the purge gas P is efficiently discharged from the back surface side of the SiC substrate W.

[0071] Furthermore, for example, in the first to fourth embodiments, examples have been shown in which the second gas inlet channels C2, C5, and C7 are inclined with respect to the in-plane direction, but the second gas inlet channel C2' may extend in a direction perpendicular to the first gas inlet channel C1, as shown in Fig. 18. Even in this case, a portion of the purge gas P discharged from the second end e4 of the second gas inlet channel C2' flows over the upper surface of the cover member 20, thereby pressing down the entire wafer holder 100.

[0072] Furthermore, for example, in the first to fourth embodiments, examples have been shown in which the support portions 16, 46, 56, 66 do not overlap with the first gas inlet channel C1 in the radial direction, but the support portions 76 may be provided at positions that overlap with the first gas inlet channel C1 in the radial direction over the entire circumferential direction, as shown in Fig. 19. In this case, as shown in Fig. 20, by forming a groove that extends radially below the support portion 76, the central portion 30 and the first gas inlet channel C1 are connected.

[0073] Furthermore, for example, in the first to fourth embodiments, the arrangement of the first and second gas exhaust paths does not have to be regular. When there is symmetry as in the first to fourth embodiments, it is preferable to arrange the gas exhaust paths regularly so as to have N-fold symmetry, where N=3 or more, with the center of the wafer holder 100 as the center of rotation. For example, the flow velocity of the purge gas P at the second end e4 is V c2 Then, at the narrow outlet of the second end e4, V c2 The speed of the cover member 20 increases, and the force that moves the cover member 20 inward becomes relatively strong. That is, the cover member 20 receives a vector force that moves toward the center of the wafer holder 100. As a result, the position of the cover member 20 changes from V c2 The thickness of the first gas discharge channel and the thickness of the second gas discharge channel may be stabilized at a position where the thickness of the first gas discharge channel and the second gas discharge channel are the same, making it easier to design optimal film formation conditions and suppressing abnormal growth. [Example]

[0074] Example 1 A susceptor 10 having the configuration shown in FIG. 3 was prepared. The susceptor 10 had grooves 17 in its outer peripheral portion 31. The area of ​​the grooves 17 occupying the outer peripheral portion 31 was set to 50%. The depth of the grooves 17 was set to 1 mm. Three concentrically arranged ring-shaped members were placed on the outer peripheral portion 31 of the susceptor 10 as cover members 20. The area surrounded by the grooves 17 and the cover members 20 functions as a first gas discharge path C1. The spaces between the multiple cover members 20 function as second gas discharge paths C2. The inclination angle θ1 of the first gas discharge path C1 with respect to the radial direction was set to 45°. The inclination angle θ2 of the second gas discharge path C2 with respect to the in-plane direction was set to 45°.

[0075] A SiC substrate having a diameter of 150 mm was placed on the susceptor 10, and film formation was performed. During film formation, the susceptor 10 was rotated at a rotation speed of 100 rpm. Purge gas was supplied to the rear surface of the SiC substrate W at a supply rate of 25 sccm. The surface roughness (Rq: root mean square height) of the rear surface after film formation was measured. In Example 1, the area of ​​the region having a surface roughness (Rq) of 10 μm or more was 3.7% of the total area.

[0076] Example 2 Example 2 differs from Example 1 in that the amount of purge gas supplied to the back surface side of the SiC substrate W was 100 sccm. The surface roughness (Rq) was measured under the same conditions as in Example 1. In Example 2, the area of ​​the region where the surface roughness (Rq) was 10 μm or more was 0.5% of the total area.

[0077] (Comparative Example 1) Comparative Example 1 differs from Example 1 in that no grooves 17 were formed. That is, the susceptor of Comparative Example 1 does not have the first gas discharge channel C1. The surface roughness (Rq) was measured under the same conditions as in Example 1. In Comparative Example 1, the area of ​​the region where the surface roughness (Rq) was 10 μm or more was 29.8% of the total area.

[0078] (Comparative Example 2) Comparative Example 2 differs from Example 2 in that no grooves 17 were formed. That is, the susceptor of Comparative Example 2 does not have the first gas discharge channel C1. The surface roughness (Rq) was measured under the same conditions as in Example 2. In Comparative Example 2, the area of ​​the region where the surface roughness (Rq) was 10 μm or more was 25.4% of the total area.

[0079] In Examples 1 and 2 in which the susceptor had the first gas exhaust passage C1, the back surface of the SiC substrate was prevented from becoming rough, as compared with Comparative Examples 1 and 2 in which the susceptor did not have the first gas exhaust passage C1. [Explanation of symbols]

[0080] 10,40,50,60... susceptor, 15,45,55,65... main body portion, 16,46,56,66... ​​support portion, 17,25,68... groove, 20,21,22... cover member, 30... central portion, 31... outer peripheral portion, 55A... recess, 55B... lid, 55C... protrusion, 57,67... side wall, 58,59... hole, 100,101,102,103... wafer holder, 11 0...chamber, 120...support, 200...chemical vapor deposition apparatus, A1...film formation space, A2...purge space, C1, C3, C4, C6...first gas discharge path, C2, C5, C7...second gas discharge path, e1, e3...first end, e2, e4...second end, G...gas, P...purge gas, R...rotation direction, VH...vertical hole, SL...slit, W...SiC substrate, fs...front surface, bs...back surface

Claims

1. The wafer support includes a central portion facing the wafer to be placed thereon, and an outer peripheral portion located outside the central portion, the central portion has a gas inlet passage for supplying a purge gas to the backside of the wafer; the central portion has a support portion, and by supporting the wafer with the support portion, the center of the wafer is spaced apart from the central portion, and a space into which a purge gas is supplied is formed between the central portion and the wafer; the outer peripheral portion has a first gas discharge path extending outward from the central portion and a second gas discharge path extending upward in a thickness direction from the first gas discharge path, the first gas discharge path is connected to the space, a second end of the second gas discharge path opposite to a first end connected to the first gas discharge path is positioned outside the outer peripheral edge of the wafer, and the second end is located at the same position as the first end or outside the first end in the radial direction.

2. A wafer support device comprising: a central portion facing a wafer to be placed thereon; and a peripheral portion located outside the central portion; the central portion has a gas inlet passage for supplying a purge gas to the backside of the wafer; a space to which a purge gas is supplied is provided between the central portion and the wafer; the outer peripheral portion has a first gas discharge path extending outward from the central portion and a second gas discharge path extending upward in a thickness direction from the first gas discharge path, the first gas discharge path is connected to the space, a second end of the second gas discharge path opposite to a first end connected to the first gas discharge path is disposed outside an outer peripheral edge of the wafer, and the second end is located at the same position as the first end or outside the first end in a radial direction; the second end of the second gas exhaust path is located outside an inner peripheral end of the outer circumferential portion.

3. A wafer support device comprising: a central portion facing a wafer to be placed thereon; and a peripheral portion located outside the central portion; the central portion has a gas inlet passage for supplying a purge gas to the backside of the wafer; a space to which a purge gas is supplied is provided between the central portion and the wafer; the outer peripheral portion has a first gas discharge path extending outward from the central portion and a second gas discharge path extending upward in a thickness direction from the first gas discharge path, the first gas discharge path is connected to the space, a second end of the second gas discharge path opposite to a first end connected to the first gas discharge path is disposed outside an outer peripheral edge of the wafer, and the second end is located at the same position as the first end or outside the first end in a radial direction; a susceptor; and a plurality of cover members that cover the susceptor at the outer periphery, the first gas discharge path is formed between the susceptor and the plurality of cover members, The second gas exhaust path is formed between the plurality of cover members.

4. the first gas discharge passage is inclined with respect to the radial direction so that an outer second end is located rearward of an inner first end in the rotation direction; 4. The wafer holder of claim 1, wherein an inclination angle of the first gas discharge path with respect to the radial direction is greater than 0° and less than 90°.

5. 4. The wafer holder of claim 1, wherein the first gas exhaust path extends along a radial direction.

6. A wafer support device comprising: a central portion facing a wafer to be placed thereon; and a peripheral portion located outside the central portion; the central portion has a gas inlet passage for supplying a purge gas to the backside of the wafer; a space to which a purge gas is supplied is provided between the central portion and the wafer; the outer peripheral portion has a first gas discharge path extending outward from the central portion and a second gas discharge path extending upward in a thickness direction from the first gas discharge path, the first gas discharge path is connected to the space, a second end of the second gas discharge path opposite to a first end connected to the first gas discharge path is disposed outside an outer peripheral edge of the wafer, and the second end is located at the same position as the first end or outside the first end in a radial direction; the second gas discharge path is inclined with respect to an in-plane direction in which the central portion extends so that a second end thereof is positioned outward from a first end thereof connected to the first gas discharge path; a tilt angle of the second gas exhaust path with respect to the in-plane direction being greater than 0° and less than 90°;

7. 6. The wafer holder according to claim 1, wherein the second gas exhaust path extends in a direction perpendicular to the first gas exhaust path.

8. A chemical vapor deposition apparatus comprising the wafer holder according to any one of claims 1 to 7.

9. A method for manufacturing a SiC epitaxial wafer using the wafer holder according to any one of claims 1 to 7.

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