Epitaxial wafer

Abstract

The present invention is an epitaxial wafer in which an epitaxial film made of a semiconductor material different from silicon is formed on a silicon substrate, and in which the film thickness of the outer peripheral portion of the wafer is less than 1 when the film thickness of the center portion of the wafer is 1. As a result, provided is an epitaxial wafer having a heteroepitaxial film with low defects, independent of the doping concentration, variety, or the like of a silicon wafer.

Description

Technical Field

[0001] The invention relates to an epitaxial wafer, wherein an epitaxial film of a semiconductor material different from silicon is formed on a silicon substrate. Background Art

[0002] Semiconductor materials other than silicon, such as silicon germanium, silicon carbide, and gallium nitride, are also listed as candidates for wafers for cutting-edge devices. However, when heteroepitaxial growth is performed on a silicon wafer, stress is applied due to the difference in lattice constants between silicon and the epitaxial film, and excessive stress causes problems such as stacking defects and threading dislocations.

[0003] In conventional heteroepitaxial growth, a method using a low-resistance silicon wafer containing a high concentration of dopants has been proposed to suppress stress (Patent Document 1). However, this also causes other problems such as self-doping caused by dopants diffusing from the wafer to the outside.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4972330 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epitaxial wafer having a heteroepitaxial film with low defects, which is independent of the doping concentration or type of a silicon substrate.

[0009] (II) Technical solution

[0010] In order to achieve the above object, the present invention provides an epitaxial wafer, which is an epitaxial wafer having an epitaxial film of a semiconductor material different from silicon formed on a silicon substrate, characterized in that:

[0011] In the epitaxial film, when the film thickness at the center of the wafer is set to 1, the film thickness at the outer peripheral portion of the wafer is less than 1.

[0012] Such an epitaxial wafer of the present invention is a low-defect heteroepitaxial wafer that is independent of the doping concentration or type of the silicon substrate and has a low stacking defect density or threading dislocation density.

[0013] At this time, the wafer periphery can be set to a portion ranging from the periphery to 5 mm inside, preferably a portion ranging from the periphery to 10 mm inside, and more preferably a portion ranging from the periphery to 20 mm inside.

[0014] If the wafer periphery is such, it will become a low-defect epitaxial wafer more reliably. In addition, the wider the range of the wafer periphery where the film thickness is less than 1, the lower the defect epitaxial wafer will be.

[0015] In addition, the epitaxial film can be set to have a film thickness of greater than 0.95 and less than 1 at the periphery of the wafer, preferably, it can be set to have a film thickness of greater than 0.9 and less than 1 at the periphery of the wafer, and further preferably, it can be set to have a film thickness of greater than 0.8 and less than 1 at the periphery of the wafer.

[0016] If the wafer periphery is such, it will become a low-defect epitaxial wafer more reliably. Moreover, the thinner the film thickness of the wafer periphery is than the film thickness of the wafer center, the lower the defect of the epitaxial wafer will be.

[0017] Furthermore, the epitaxial film can be any one of a silicon germanium film, a germanium film, a silicon carbide film, and a gallium nitride film.

[0018] The above-mentioned semiconductor materials are suitable for the most advanced devices because they are used.

[0019] Furthermore, the epitaxial wafer can have a diameter of 300 mm or more.

[0020] In recent years, there has been a demand for larger wafers (larger diameters), and epitaxial wafers with a diameter of 300 mm or more can meet such demands.

[0021] (III) Beneficial effects

[0022] According to the epitaxial wafer of the present invention, defects such as stacking defects and threading dislocations caused by stress due to a lattice constant difference in heteroepitaxial growth are extremely reduced and the quality is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an explanatory diagram showing an example of the epitaxial wafer of the present invention.

[0024] Figure 2 It is an explanatory diagram showing an example of an epitaxial growth apparatus.

[0025] Figure 3 This is an explanatory diagram showing an example of the arrangement of the lamp array when viewed from above.

[0026] Figure 4 This is an explanatory diagram showing an example of the epitaxial wafer of the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

[0028] Figure 1is an example of the epitaxial wafer of the present invention. Figure 1 As shown, an epitaxial wafer 1 of the present invention has an epitaxial film 3 formed on a silicon substrate (single crystal substrate) 2 .

[0029] The silicon substrate 2 is not particularly limited, and may be, for example, a silicon substrate obtained by cutting a single crystal silicon ingot produced by the Czochralski method or the floating zone method into a wafer shape and subjecting it to grinding, etching, polishing, and the like.

[0030] In addition, the type and concentration of the dopant, the variety (resistivity, diameter, thickness, oxygen concentration, etc.), etc. are not particularly limited and can be appropriately determined. The present invention is high quality with reduced defect density without relying on controlling the dopant.

[0031] In addition, the diameter of the silicon substrate 2 (the diameter of the epitaxial wafer 1) can be set to, for example, 300 mm or more, and further can be set to 450 mm or more. In order to respond to the demand for large diameters in recent years, the upper limit of the diameter is as large as possible, and there is no particular limitation. In addition, on the contrary, it can also be set to a relatively small diameter size, for example, 200 mm or less.

[0032] The epitaxial film 3 may be made of any semiconductor material other than silicon (heteroepitaxial film). For example, it may be any one of a silicon germanium film, a germanium film, a silicon carbide film, and a gallium nitride film. Such an epitaxial film is suitable as an epitaxial wafer for the most advanced devices.

[0033] Furthermore, the epitaxial film 3 has a film thickness distribution such that when the film thickness (film thickness A) of the wafer center portion (hereinafter also referred to as the center portion) is set to 1, the film thickness (film thickness B) of the wafer periphery portion (hereinafter also referred to as the periphery portion) is less than 1. Thus, since the film thickness of the periphery portion is thinner than that of the center portion, lattice relaxation is less likely to occur in the periphery portion, and the defect density of stacking defects, threading dislocations, etc. in the epitaxial film 3 is small, and the quality is excellent.

[0034] As long as the film thickness distribution of the center and the periphery of the epitaxial film 3 satisfies the above relationship, the film thickness distribution of the inner periphery of the wafer (hereinafter referred to as the inner periphery) between the center and the periphery may be any distribution. Figure 1 As shown, it can be set to the following shape: when viewed from the side, the inner peripheral portion including the central portion has a constant film thickness, the film thickness becomes thinner toward the periphery near the boundary between the inner peripheral portion and the outer peripheral portion, and the thinner film thickness is constant in the outer peripheral portion. Or, as Figure 4 As shown, it is also possible to have a shape in which, when viewed from the side, the film thickness is the thickest in the center and gradually becomes thinner toward the periphery, that is, the film is gently inclined toward the periphery.

[0035] Here, the range of the wafer periphery is not particularly limited, and can be set to, for example, the range from the periphery of the wafer to 5 mm inside. If the periphery, which is thinner than the center, is within this range, a low-defect epitaxial wafer can be more reliably produced.

[0036] Furthermore, the range of the outer periphery is more preferably the range from the outer periphery to the inner side of 10 mm, and further preferably the range from the outer periphery to the inner side of 20 mm. The larger the range of the outer periphery is, the lower the defect density can be.

[0037] The size of the peripheral portion can be appropriately determined according to the diameter of the epitaxial wafer 1, etc. However, if the purpose is to reduce defects caused by stress due to lattice constant differences, it is basically sufficient to set the peripheral portion to a range from the outer periphery to 50 mm inside, for example.

[0038] Furthermore, as described above, when the film thickness at the center is set to 1, the film thickness at the peripheral portion may be less than 1, and in particular may be set to 0.95 or more and less than 1. In this case, a low-defect epitaxial wafer can be more reliably produced.

[0039] Furthermore, the film thickness of the outer peripheral portion is more preferably 0.9 or more and less than 1, and further preferably 0.8 or more and less than 1. The smaller the film thickness of the outer peripheral portion is, the lower the defect density can be.

[0040] In addition, the film thickness of the peripheral portion relative to the film thickness of the central portion can be determined based on the diameter of the epitaxial wafer 1, the absolute value of the film thickness of the epitaxial film 3, etc. (wherein, as mentioned above, it is less than 1). However, if the purpose is to reduce defects caused by stress due to lattice constant differences, then setting it to, for example, greater than 0.6 and less than 1 is basically sufficient.

[0041] Furthermore, it is described that the film thickness of the peripheral portion is less than 1 relative to the film thickness of the central portion, but in order to more reliably achieve low defects, it is preferably 0.99 or less, and more preferably 0.98 or less.

[0042] By the way, in the case of a general epitaxial wafer, the epitaxial film generally seeks uniform film thickness, so the film thickness at the center and the film thickness at the periphery are basically the same value. In addition, abnormal growth of the epitaxial layer is likely to occur at the periphery of the wafer, often resulting in the periphery being thicker than the center.

[0043] Secondly, refer to Figure 2 , an epitaxial growth apparatus (RP-CVD apparatus) that can be used when manufacturing the epitaxial wafer 1 of the present invention is described. Figure 2 The single-wafer epitaxial growth apparatus 11 is an apparatus for vapor-depositing an epitaxial film 3 of a semiconductor material other than silicon on the surface of a silicon substrate 2 .

[0044] The epitaxial growth device 11 includes a chamber 12 made of a transparent quartz member or the like. A susceptor 13 for placing a silicon substrate 2 to be subjected to epitaxial growth is arranged in the chamber 12. The susceptor 13 may be, for example, a susceptor made of SiC or a susceptor in which a SiC coating is applied to a graphite substrate. The susceptor 13 is formed in a disk shape and arranged so that the upper surface and the lower surface are horizontal.

[0045] A concave countersunk hole 14 is formed on the upper surface of the carrier 13, and the silicon substrate 2 is placed inside the countersunk hole 14. In addition, a plurality of through holes 15 are formed on the carrier 13 to penetrate to the back surface. These through holes 15 are, for example, holes into which a pin 16 used to insert and exit the silicon substrate 2 into the countersunk hole 14 is inserted, or for other purposes (for example, holes used to suppress the generation of fog called halo or surface roughness on the back surface of the epitaxial wafer). In addition, the carrier 13 may be in a form without the through holes 15.

[0046] The rear surface of the carrier 13 is supported by a rotating shaft 17. The rotating shaft 17 is provided so that its axis L coincides with the center of the carrier 13. A driver 18 for rotating the carrier 13 around the axis L via the rotating shaft 17 is connected to the rotating shaft 17.

[0047] Lamps 41 and 42 for heating the silicon substrate 2 to an epitaxial reaction temperature (eg, 400 to 1200° C.) during epitaxial growth are arranged above and below the chamber 12 .

[0048] Figure 2 In the example of FIG. 1 , when viewed from above, three rows of light groups arranged in a circle are arranged concentrically. That is, the inner row 41a, the middle row 41b, and the outer row 41c are arranged at the top, and the inner row 42a, the middle row 42b, and the outer row 42c are arranged at the bottom. Here, an example of three rows is shown as described above, but it is not limited to this, and it can also be set to only two rows, or four or more rows.

[0049] For example, it can also be set as: Figure 2 Different, such as Figure 3 As shown in the top view of FIG. 1 , the lamps are arranged in two rows relative to the silicon substrate 2, with 12 lamps in the inner row and 12 lamps in the outer row arranged in a circular shape. In addition, although only the upper lamps are shown in the figure, the lower lamps are arranged in the same manner. Of course, the arrangement positions or numbers of the upper and lower, or inner and outer lamps are not limited to the above. Figure 2 or Figure 3 The pattern can be determined appropriately.

[0050] The power (output) of these lamps can be controlled individually, so that, for example, the power ratio (output ratio) can be changed between the upper and lower parts, and the power ratio between the inner and outer rows can also be changed.

[0051] A gas supply port 19 is provided at one end side of the chamber 12 in the horizontal direction, and a gas exhaust port 20 is provided at a side opposite to the side provided with the gas supply port 19. A processing gas G is introduced from the gas supply port 19, and the processing gas G includes: a raw material gas as a raw material of the epitaxial film 3, a carrier gas (for example, hydrogen), and a dopant gas for adjusting the conductivity type or conductivity of the epitaxial film 2 (for example, a gas containing boron or phosphorus).

[0052] As the raw material gas, when a silicon germanium film is used, SiH 4 or SiH 2 Cl 2 With GeH 4 When it is a germanium film, GeH 4 When it is a silicon carbide film, SiH 4 or SiH 2 Cl 2 With C 3 H 8 When it is a gallium nitride film, GaCl and NH 3 wait.

[0053] The processing gas G supplied from the gas supply port 19 flows along the surface of the silicon substrate 2 which is rotating substantially horizontally in the internal space of the chamber 12. Then, the processing gas G is exhausted from the gas exhaust port 20 to the outside of the chamber 12.

[0054] Furthermore, when epitaxial growth is performed, hydrogen gas is introduced into the chamber 12 from the gas supply port 19 in advance, and then the silicon substrate 2 is introduced into the chamber 12 and placed on the countersunk hole 14 of the carrier 13. Then, the silicon substrate 2 placed on the carrier 13 is heated to a heat treatment temperature (e.g., 1050 to 1200° C.) by the lamps 41a to 41c and 42a to 42c, and vapor phase etching is performed to remove the natural oxide film formed on the surface of the silicon substrate 2 using hydrogen gas.

[0055] Then, the carrier 13 and the silicon substrate 2 placed thereon are rotated by the driving unit 18, and while the power of the lamps 41 and 42 is controlled so that the temperature of the silicon substrate 2 reaches a predetermined reaction temperature (for example, 1050-1180°C), a processing gas G is supplied from the gas supply port 19, thereby causing an epitaxial film 13 of a predetermined film thickness to be vapor deposited to obtain an epitaxial wafer 1.

[0056] In addition, the film thickness distribution in which the film thickness of the peripheral portion is thinner than the film thickness A of the central portion, such as the epitaxial film 3 of the epitaxial wafer 1 of the present invention, is obtained by, for example, adjusting the output of the lamps 41 and 42 of the epitaxial growth device 11. Figure 3 In this way, the lamp rows are described as being arranged in two concentric circles, namely, an inner row and an outer row.

[0057] That is, regarding the output ratio of lamp heating,

[0058] "When the range of the thin peripheral portion is constant and the peripheral portion is to be further reduced within a range less than 1 (the film thickness of the center portion = 1)," is set

[0059] Upper lamp 41: inside>outside, and

[0060] Lower lamp 42: inside < outside, and

[0061] Upper lamp 41: Increase the proportion of the inner side, and

[0062] Lower lights 42: Increase the proportions of the inner side.

[0063] By doing so, the film thickness in the outer peripheral portion can be made thinner.

[0064] "When the film thickness of the outer peripheral portion is constant within a range less than 1 (the film thickness of the central portion = 1) and the range of the outer peripheral portion is to be further widened", it is set to

[0065] Upper lamp 41: inside>outside, and

[0066] Lower lamp 42: inside < outside, and

[0067] Upper lamp 41: Increase the proportion of the inner side, and

[0068] Lower lights 42: Increase the proportions of the inner side.

[0069] By doing so, the range of the outer peripheral portion where the film thickness is thin can be expanded.

[0070] In addition, even if Figure 2 In the case of three rows (inner row: 41a, 42a, middle row: 41b, 42b, outer row: 41c, 42c), for example, only 41a, 42a can be treated as inner lamps, and 41b, 42b, 41c, 42c can be treated as outer lamps. When there are four or more rows, the same appropriate setting can be made.

[0071] By adjusting the magnitude relationship between the outputs of the inner and outer lamps as described above, the film thickness ratio of the peripheral portion relative to the central portion and the range of the peripheral portion can be adjusted, but the specific output ratio will change due to the size of the device 11 or the silicon substrate 2 used. In addition, as can be seen from the above correlation, since the thinness of the film thickness of the peripheral portion and the width of the range of the peripheral portion will change due to the output ratio of the lamp, when actually manufacturing the epitaxial wafer 1 of the present invention, it is sufficient to appropriately set the output ratio of the lamp while referring to the above correlation according to the desired conditions of the epitaxial film.

[0072] As an example, when an epitaxial film 3 (silicon germanium film) is vapor-deposited on a silicon substrate 2 having a diameter of 300 mm at 650° C. using CENTURA (lamps are arranged in two rows, an inner row and an outer row) manufactured by APPLIED MATERIALS, Inc.,

[0073] When the outer periphery is fixed within the range of 10 mm from the outer periphery,

[0074] In order to set the film thickness of the outer peripheral portion to 0.95 to 0.98 when the film thickness of the central portion is 1, it can be set as follows:

[0075] Upper lamp 41: inside (51-60%) > outside (49-40%), and

[0076] Lower lamp 42: inside (26-30%) < outside (75-70%),

[0077] In order to set the film thickness of the outer peripheral portion to 0.90 to 0.98, it can be set as follows:

[0078] Upper lamp 41: inside (61-75%) > outside (39-25%), and

[0079] Lower lamp 42: inside (31-34%) < outside (71-66%),

[0080] In order to set the film thickness of the outer peripheral portion to 0.80 to 0.98, it can be set as follows:

[0081] Upper lamp 41: inside (76-80%) > outside (24-20%), and

[0082] Lower lamp 42: inner side (35-38%) < outer side (65-60%).

[0083] [Example]

[0084] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0085] (Example 1)

[0086] On a silicon substrate with a diameter of 300 mm, an epitaxial growth device (RP-CVD device: CENTURA manufactured by APPLIED MATERIALS INC.) (lamps are arranged in two rows, an inner row and an outer row) was used to deposit an epitaxial layer containing SiH 2 Cl 2 With GeH 4In a mixed gas atmosphere as a raw material gas, a silicon germanium epitaxial film was formed so that the film thickness of the central portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to the inner side of 10 mm) was 28.5-29.5 nm (the ratio of the film thickness of the peripheral portion to the film thickness of the central portion: 0.95-0.98). As a result, the defect density was 0.06 / cm 2 .

[0087] The film thickness of the epitaxial film was measured using a spectroscopic ellipsometer (M2000 manufactured by JA Woolam).

[0088] In addition, the defect density was measured using Surfscan SP3 manufactured by KLA-Tencor Corporation.

[0089] (Example 2)

[0090] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to 10 mm inside) was 27.0-29.5 nm (film thickness ratio: 0.90-0.98). As a result, the defect density was 0.06 / cm 2 .

[0091] (Example 3)

[0092] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to 10 mm inside) was 24.0-29.5 nm (film thickness ratio: 0.80-0.98). As a result, the defect density was 0.04 / cm 2 .

[0093] (Example 4)

[0094] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to 20 mm inside) was 28.5-29.5 nm (film thickness ratio: 0.95-0.98). As a result, the defect density was 0.05 / cm 2 .

[0095] (Example 5)

[0096] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (range from the periphery to 5 mm inside) was 28.5-29.5 nm (film thickness ratio: 0.95-0.98). As a result, the defect density was 0.12 / cm 2 .

[0097] (Comparative Example 1)

[0098] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (range from the periphery to 5 mm inside) was 30.0-31.5 nm (film thickness ratio: 1-1.05). As a result, the defect density was 2.52 / cm 2 .

[0099] (Comparative Example 2)

[0100] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to 10 mm inside) was 30.0-31.5 nm (film thickness ratio: 1-1.05). As a result, the defect density was 5.32 / cm 2 .

[0101] (Comparative Example 3)

[0102] The epitaxial wafer evaluated was formed under the same conditions as in Example 1 except that the film thickness of the center portion of the epitaxial film was 30 nm and the film thickness of the peripheral portion (the range from the periphery to the inside of 20 mm) was 30.0-31.5 nm (film thickness ratio: 1-1.05). As a result, the defect density was 7.37 / cm 2 .

[0103] The film forming conditions and measurement results of each example are shown in Table 1. That is, the following contents are shown for each example:

[0104] (1) Output ratio of inner power and outer power of the top side

[0105] (2) Output ratio of inner and outer lights on the bottom side

[0106] (3) Ratio of the film thickness at the periphery to the film thickness at the center (peripheral film thickness / center film thickness)

[0107] (4) Peripheral area

[0108] (5) Defect density.

[0109] In addition, the description is repeated in Example 1. In addition, regarding (1) and (2), an equal sign or an unequal sign is described so that the magnitude relationship between the inner lamp and the outer lamp can be easily understood.

[0110] In addition, (3) to (5) are shown in Table 2 in another arrangement. Regarding (3), the film thickness value of the outer peripheral portion is also shown. The value of the position surrounded by a bold frame is the defect density of (5).

[0111] [Table 1]

[0112]

[0113] [Table 2]

[0114]

[0115] Regarding the film thickness ratio, the range of the outer peripheral portion, and the defect density, the following relationship can be confirmed from Tables 1 and 2 in particular.

[0116] First, each Example is compared with each Comparative Example.

[0117] Regarding the magnitude relationship of the output ratio of the inner lamp and the outer lamp, in the lower lamp, each embodiment and each comparative example is set to "inside < outside", while in the upper lamp, each embodiment is set to "inside > outside", while in comparative example 1 it is set to "inside = outside", and in comparative examples 2 and 3 it is set to "inside < outside". Then, the defect density in each embodiment is 0.04 to 0.12 / cm 2 , while in each comparative example it is 2.52 to 7.37 / cm 2 , compared with each comparative example, each embodiment has a different number of low defects. It can be seen that the adjustment of the output ratio of the inner lamp and the outer lamp can effectively reduce the defect density.

[0118] Furthermore, the various embodiments are compared with one another.

[0119] In Examples 5, 1, and 4, where the film thickness ratios were the same (0.95 to 0.98) and the outer periphery ranges were 5 mm, 10 mm, and 20 mm, the defect density was 0.12 / cm 2 , 0.06 / cm 2 , 0.05 / cm 2 , the following tendency was observed: the wider the range of the peripheral part, the lower the defect density.

[0120] In Examples 5, 1, and 4, the output ratio of the upper lamp was "inside>outside" and that of the lower lamp was "inside<outside", and the following tendency was observed: the higher the output ratio of the upper or lower inner lamp, the wider the range of the outer periphery.

[0121] In Examples 1, 2, and 3, where the outer peripheral area was the same (10 mm) and the film thickness ratio was 0.95 to 0.98, 0.90 to 0.98, and 0.80 to 0.98, the defect density was 0.06 / cm 2 , 0.06 / cm 2 , 0.04 / cm 2 , the following tendency was observed: the smaller the film thickness ratio, that is, the thinner the film thickness of the peripheral portion was compared to the film thickness of the central portion, the lower the defect density was.

[0122] In Examples 1, 2, and 3, the output ratio was "inside>outside" for the upper lamp and "inside<outside" for the lower lamp. As a result, the following tendency was observed: the higher the output ratio of the upper or lower inner lamp, the lower the film thickness ratio.

[0123] This specification contains the following protocols.

[0124] [1]: An epitaxial wafer having an epitaxial film of a semiconductor material different from silicon formed on a silicon substrate, wherein:

[0125] In the epitaxial film, when the film thickness at the center of the wafer is set to 1, the film thickness at the outer peripheral portion of the wafer is less than 1.

[0126] [2]: The epitaxial wafer according to [1] above, wherein the wafer outer peripheral portion is a portion ranging from the outer periphery to within 5 mm.

[0127] [3]: The epitaxial wafer according to [1] above, wherein the wafer outer peripheral portion is a portion ranging from the outer periphery to within 10 mm.

[0128] [4]: The epitaxial wafer according to [1] above, wherein the wafer outer peripheral portion is a portion ranging from the outer periphery to within 20 mm.

[0129] [5]: The epitaxial wafer as described in any one of [1] to [4] above, wherein the film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.95 and less than 1.

[0130] [6]: The epitaxial wafer as described in any one of [1] to [4] above, wherein the film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.9 and less than 1.

[0131] [7]: The epitaxial wafer as described in any one of [1] to [4] above, wherein the film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.8 and less than 1.

[0132] [8]: An epitaxial wafer as described in any one of [1] to [7] above, wherein the epitaxial film is any one of a silicon germanium film, a germanium film, a silicon carbide film, and a gallium nitride film.

[0133] [9]: The epitaxial wafer as described in any one of [1] to [8] above, wherein the diameter of the epitaxial wafer is greater than 300 mm.

[0134] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely illustrative, and any configuration having substantially the same configuration and producing the same effects as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. An epitaxial wafer, wherein an epitaxial film of a semiconductor material different from silicon is formed on a silicon substrate, characterized in that: In the epitaxial film, when the film thickness at the center of the wafer is set to 1, the film thickness at the outer peripheral portion of the wafer is less than 1.

2. The epitaxial wafer according to claim 1, characterized in that: The wafer outer periphery is a portion ranging from the outer periphery to 5 mm inside.

3. The epitaxial wafer according to claim 1, characterized in that: The wafer outer periphery is a portion ranging from the outer periphery to 10 mm inside.

4. The epitaxial wafer according to claim 1, characterized in that: The wafer outer periphery is a portion ranging from the outer periphery to 20 mm inside.

5. The epitaxial wafer according to any one of claims 1 to 4, characterized in that: The film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.95 and less than 1.

6. The epitaxial wafer according to any one of claims 1 to 4, characterized in that: The film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.9 and less than 1.

7. The epitaxial wafer according to any one of claims 1 to 4, characterized in that: The film thickness of the epitaxial film at the wafer periphery is greater than or equal to 0.8 and less than 1.

8. The epitaxial wafer according to any one of claims 1 to 4, characterized in that: The epitaxial film is any one of a silicon germanium film, a germanium film, a silicon carbide film, and a gallium nitride film.

9. The epitaxial wafer according to any one of claims 1 to 4, characterized in that: The diameter of the epitaxial wafer is greater than 300 mm.

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