SiC polycrystalline substrates and SiC bonded semiconductor substrates

Abstract

The present invention provides a SiC polycrystalline substrate and a SiC bonded semiconductor substrate with small variations in the volume resistivity of the film-forming surface. A SiC polycrystalline substrate for use in SiC bonded semiconductor substrates, characterized in that the coefficient of variation of the volume resistivity of the film-forming surface is 3% or less.

Description

Technical Field

[0001] The present invention relates to a SiC polycrystalline substrate and a bonded SiC semiconductor substrate.

Background Art

[0002] Silicon carbide (SiC) has a wide bandgap and is attracting attention as a material for high-voltage and high-power electronic devices, high-frequency electronic devices, and short-wavelength optical devices due to its excellent physical and chemical properties. However, it is difficult to manufacture high-quality large-diameter SiC single crystals, which has so far hindered the practical application of SiC devices. As a solution, sublimation recrystallization using a SiC single crystal substrate as a seed crystal has been developed, enabling high-quality crystal growth while controlling crystal polymorphism and carrier type concentration. However, the low crystal growth rate and high processing costs are still issues.

[0003] To reduce these manufacturing costs, for example, Patent Document 1 discloses a method for manufacturing a bonded SiC substrate formed by bonding a SiC single crystal substrate and a SiC polycrystalline substrate. In this way, the SiC single crystal substrate functions as a base for growing an epitaxial layer that becomes the active layer of the bonded SiC substrate element, and the lower mechanical support part and heat dissipation part are served by the SiC polycrystalline substrate, enabling the entire SiC substrate to be treated as having the same quality as a substrate composed of a single SiC single crystal. Patent Document 2 discloses a method for manufacturing a SiC polycrystalline substrate used for a bonded SiC substrate using a chemical vapor deposition method (CVD method). Patent Document 3 discloses a film-forming apparatus capable of forming a SiC polycrystalline film on a base substrate by the CVD method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] When the thin film thickness is non-uniform on the deposition surface of a SiC polycrystalline substrate using the CVD method, variations in film thickness directly affect the volume resistivity of the substrate, which has been a problem. In other words, because the electrical properties differ between areas with thick and thin film thickness, it adversely affects the electrical properties of devices formed on the SiC bonded substrate, leading to a decrease in the yield of devices manufactured using SiC bonded substrates. Furthermore, there is a risk of increased heat generation and energy loss in the SiC polycrystalline substrate.

[0006] Therefore, SiC substrates are required to reduce variations in volume resistivity on the film deposition surface.

[0007] This invention addresses these problems and aims to provide a SiC polycrystalline substrate and a SiC bonded semiconductor substrate with small variations in the volume resistivity of the film-forming surface. [Means for solving the problem]

[0008] To solve the above problems, the SiC polycrystalline substrate used in the SiC bonded semiconductor substrate of the present invention is characterized in that the coefficient of variation of the volume resistivity of the film-forming surface is 3% or less.

[0009] The coefficient of variation may be obtained by dividing the standard deviation of the volume resistivity measured at multiple measurement points on the film-forming surface by the mean value.

[0010] The measurement points may be the center point of the film-forming surface, and four or more points arranged at equal intervals or angles in the circumferential direction at a predetermined radial distance from the center point, for a total of five or more points.

[0011] The aforementioned volume resistivity may be 25 mΩcm or less.

[0012] The crystal structure of the SiC polycrystalline substrate may be cubic or hexagonal.

[0013] The diameter of the film-forming surface may be 100 mm or more and 305 mm or less.

[0014] Furthermore, in order to solve the above problems, the SiC bonded semiconductor substrate of the present invention is characterized by including the SiC polycrystalline substrate and a SiC single crystal substrate bonded to the film-forming surface.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a SiC polycrystalline substrate and a SiC bonded semiconductor substrate with a small variation in the volume resistivity of the film-forming surface.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective schematic view of the SiC polycrystalline substrate 100. [Figure 2] It is a schematic diagram showing measurement points of the volume resistivity in the SiC polycrystalline substrate 100. [Figure 3] It is a side cross-sectional view schematically showing a support substrate, a SiC polycrystalline film, and a SiC polycrystalline substrate in each step of the method for manufacturing a SiC polycrystalline substrate. [Figure 4] It is a cross-sectional view of the film-forming chamber 1000. [Figure 5] It is a cross-sectional view of the film-forming chamber 1000 as viewed from the direction indicated by arrow B in FIG. 4. [Figure 6] It is a cross-sectional view of the film-forming chamber 1000 as viewed from the direction indicated by arrow D in FIG. 4. [Figure 7] It is a cross-sectional view of the film-forming chamber 2000. [Figure 8] It is a cross-sectional view of the film-forming chamber 2000 as viewed from the direction indicated by arrow B in FIG. 7. [Figure 9] It is a cross-sectional view of the film-forming chamber 2000 as viewed from the direction indicated by arrow D in FIG. 7.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not naturally limited to the following embodiments, and various forms belonging to the technical scope of the present invention can be adopted.

[0018] [SiC polycrystalline substrate] A SiC polycrystalline substrate (polycrystalline SiC substrate) is a substrate (bonded SiC semiconductor substrate polycrystalline base) used for a bonded SiC semiconductor substrate. In a bonded SiC semiconductor substrate, the SiC polycrystalline substrate is a substrate that can reinforce a monocrystalline SiC substrate as a support substrate by directly bonding to the monocrystalline SiC substrate (monocrystalline SiC substrate).

[0019] <Shape> The shape of the SiC polycrystalline substrate may be substantially the same as that of the monocrystalline SiC substrate. For example, it is a substantially disk shape with an orientation flat or a notch, and a substrate with a diameter of 100 mm or more and 305 mm or less can be used. Note that the shape is not limited to a disk shape, and may be, for example, a polygonal shape.

[0020] As an example, FIG. 1 shows a perspective schematic view of a SiC polycrystalline substrate 100. The SiC polycrystalline substrate 100 is a disk-shaped substrate having a first surface 110 and a second surface 120.

[0021] The SiC polycrystalline substrate 100 is formed, for example, in a disk shape with a thickness of about 200 μm to 1000 μm, and the thickness error can be set to ±2.5 μm. The thickness of the bonded SiC semiconductor substrate may be, for example, 350 μm for a diameter of 150 mm and 500 μm for a diameter of 200 mm. Note that the upper limit of the thickness of the SiC polycrystalline substrate is not particularly limited without affecting the solution of the problems of the present invention, and can be set to 1000 μm as described above, for example.

[0022] <Crystal structure> Examples of crystalline structures for SiC polycrystalline substrates include cubic and hexagonal crystals. The SiC polycrystalline substrate may consist of hexagonal 4H-SiC crystals, 6H-SiC crystals, or cubic 3C-SiC crystals, or a mixture thereof. Furthermore, to reduce defects when bonded to a SiC single crystal substrate, a dense SiC polycrystalline substrate is desired, and for example, a cubic 3C-SiC polycrystalline substrate obtained by depositing a layer of SiC polycrystalline material by chemical vapor deposition can be used.

[0023] <Film formation surface> The deposition surface on the SiC polycrystalline substrate 100 is the main surface on which the film is directly deposited when forming a film by chemical vapor deposition (CVD). The deposition surface exposes the crystal grains of the SiC polycrystalline material, and its surface properties and flatness affect the electrical properties of the thin film.

[0024] <Volume resistivity> The volume resistivity of the SiC polycrystalline substrate is preferably 25 mΩcm or less. SiC devices are primarily applied to high-voltage and high-power electronic devices, where minimizing heat loss associated with high current application is crucial. To suppress Joule heat generation due to substrate resistance, low resistance is required for SiC polycrystalline substrates, and this requirement can be met if the volume resistivity is 25 mΩcm or less.

[0025] For substrates used in high-performance electronic devices, the volume resistivity of the SiC polycrystalline substrate is preferably 15 mΩcm or less, and more preferably 9 mΩcm or less. The lower limit of the volume resistivity is not particularly limited, and may be the measurement limit; however, if it is 3 mΩcm or higher, it can be used without problems as a substrate for high-performance electronic devices.

[0026] The volume resistivity of a SiC polycrystalline substrate can be measured using a volume resistivity measuring device that employs the eddy current method. Examples of such devices include the NC-80MAP manufactured by Napson Corporation. The volume resistivity distribution of the film-forming surface of a SiC polycrystalline substrate can be evaluated by actually measuring the volume resistivity using the eddy current method or other methods at a total of 37 measurement points on the film-forming surface, either the first surface 110 or the second surface 120, as shown by the points in Figure 2. These points include the center point and 12 points each at first, second, and third distances equally spaced radially from the center point, respectively, with equal circumferential intervals.

[0027] The locations (measurement points) for measuring volume resistivity on the first surface 110 or the second surface 120, which are the film-forming surfaces, can be set as appropriate, in addition to the 37 locations mentioned above. However, if the first surface 110 or the second surface 120, which are the film-forming surfaces of the SiC polycrystalline substrate 100, are circular, it is preferable to set a total of five or more locations: the center point and four or more points arranged at equal intervals or angles in the circumferential direction at a predetermined radial distance from the center point. In particular, when a total of 37 measurement points are set as shown in Figure 2 in this embodiment, the variation in volume resistivity on the film-forming surface can be evaluated more accurately.

[0028] The volume resistivity of the SiC polycrystalline substrate may be 25 mΩcm or less in some areas of the film deposition surface, but it is preferable that it be 25 mΩcm or less in all areas of the film deposition surface, more preferably 15 mΩcm or less as described above, and even more preferably 9 mΩcm or less.

[0029] (Coefficient of variation of volume resistivity) Variations in volume resistivity on the film deposition surface of SiC polycrystalline substrates adversely affect the electrical properties of devices formed on SiC bonded substrates, leading to a decrease in the manufacturing yield of devices using SiC bonded semiconductor substrates. Therefore, to suppress the decrease in manufacturing yield of devices using SiC bonded semiconductor substrates, it is required to reduce variations in volume resistivity on the film deposition surface of SiC polycrystalline substrates.

[0030] Generally, the coefficient of variation (standard deviation / mean), obtained by dividing the standard deviation by the mean, is used as an indicator of variation on the film deposition surface. The coefficient of variation of volume resistivity for commercially available SiC single crystal substrates is 4% or less, and SiC polycrystalline substrates used as support substrates for SiC bonded semiconductor substrates are expected to have a volume resistivity variation equivalent to or less than that of SiC single crystal substrates.

[0031] The coefficient of variation can be calculated by dividing the standard deviation by the mean value, based on the standard deviation and mean value obtained from the measurement results of volume resistivity at multiple measurement points on the film deposition surface, such as the 37 locations mentioned above. To suppress the decrease in manufacturing yield of devices using SiC bonded semiconductor substrates, it is preferable to set the coefficient of variation of the volume resistivity of the SiC polycrystalline substrate to 3% or less. Ideally, the lower limit of the coefficient of variation of volume resistivity should be 0%, but 1% or more can serve as a guideline.

[0032] [SiC bonded semiconductor substrate] The SiC bonded semiconductor substrate of the embodiment comprises the SiC polycrystalline substrate described above and a SiC single-crystal substrate bonded to the film-forming surface.

[0033] A semiconductor substrate is a substrate containing a semiconductor and is used in the manufacturing process of semiconductor devices. In the case of SiC bonded semiconductor substrates, the SiC polycrystalline substrate or SiC single-crystal substrate may be a semiconductor, and an epitaxial growth layer can be formed on the SiC single-crystal substrate, and then an element can be formed. Examples of SiC elements include electronic devices that use SiC bonded semiconductor substrates as the substrate, and these have been commercialized in the form of SiC-MOSFETs, SiC SBDs (Schottky barrier diodes), and SiC power modules equipped with SiC-MOSFETs and SiC SBDs. SiC bonded semiconductor substrates are used as the substrate in these products.

[0034] [Manufacturing method for SiC polycrystalline substrates] Next, we will describe an example of a method for manufacturing a SiC polycrystalline substrate.

[0035] <SiC polycrystalline film formation process> The SiC polycrystalline film formation process is a process (Figure 3(B)) in which a SiC polycrystalline film 20 is formed on the surface of a substrate 10 (Figure 3(A)) by the CVD method.

[0036] (SiC polycrystalline film) The SiC polycrystalline film 20 is a thin film formed on the surface of the substrate 10 by fixing the substrate 10 in the reaction furnace of a film deposition apparatus, raising the temperature inside the reaction furnace to the growth temperature (for example, 1400°C) while flowing a gas such as hydrogen or nitrogen, and then flowing a raw material gas and a carrier gas once the growth temperature is reached.

[0037] As the base material 10, a disc-shaped base material made of isotropic graphite, which is commonly used, can be used.

[0038] (Chemical vapor deposition) As for the raw material gas, there are no particular limitations as long as it can form a SiC polycrystalline film 20, and commonly used Si-based and C-based raw material gases can be used.

[0039] For example, as silicon (Si)-based raw material gases, silane (SiH4) can be used, as well as chlorine-based Si raw material-containing gases (chloride-based raw materials) that have etching properties, such as monochlorosilane (SiH3Cl), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), and tetrachlorosilane (SiCl4).

[0040] As carbon (C)-based raw material gases, hydrocarbons such as methane (CH4), ethane (C2H6), propane (C3H8), and acetylene (C2H2) can be used.

[0041] In addition to the above, gases containing both Si and C, such as tetramethylsilane [(CH3)4Si], trichloromethylsilane (CH3Cl3Si), trichlorophenylsilane (C6H5Cl3Si), dichloromethylsilane (CH4Cl2Si), dichlorodimethylsilane [(CH3)2SiCl2], and chlorotrimethylsilane [(CH3)3SiCl], can also be used as raw material gases.

[0042] As the carrier gas, any commonly used carrier gas can be used as long as it can be released onto the substrate 10 without hindering the formation of the SiC polycrystalline film 20. For example, hydrogen (H2), which has excellent thermal conductivity and etching properties for SiC, can be used.

[0043] Furthermore, in order to apply SiC polycrystalline substrates to high-voltage and high-power electronic device applications, impurities such as nitrogen or phosphorus (dopant gases) are introduced into the SiC polycrystalline film 20. The introduced concentration of nitrogen or phosphorus is, for example, 1 × 10⁻¹⁶ 19 / cm 3 That's all.

[0044] <Underlying base material exposure process> The substrate exposure step is a step in which, after the SiC polycrystalline film formation step, the outer peripheral edge 21 of the SiC polycrystalline film 20 formed on the surface of the substrate 10 is removed, thereby exposing the outer peripheral edge 11 of the substrate 10.

[0045] As shown in Figure 3(B), the SiC polycrystalline film 20 is formed on the outer periphery of the substrate 10 by the SiC polycrystalline film formation process described above. This can then be placed in an end-face processing device, for example, and the formed SiC polycrystalline film 20 can be ground inward from the outer edge 21 to a depth of approximately 0.01 mm to 0.5 mm to expose the outer edge 11 of the substrate 10.

[0046] <SiC polycrystalline membrane separation process> The SiC polycrystalline film separation process involves burning the substrate 10, with its outer peripheral edge exposed as shown in Figure 3(C), in an oxygen atmosphere to separate the SiC polycrystalline film 20 from the substrate 10, as shown in Figure 3(D). By heating the substrate 10, with its outer peripheral edge 11 exposed and a SiC polycrystalline film 20 deposited on its surface, in an oxygen-containing atmosphere (oxygen atmosphere) at, for example, 1000°C, the substrate 10 is burned, and a self-supporting SiC polycrystalline substrate 30 can be obtained.

[0047] <Polishing process> In the polishing process, the thickness of the SiC polycrystalline substrate 30 is adjusted and the surface is smoothed for use in SiC bonded semiconductor substrates. First, high-precision grinding is performed, then high-precision mechanical polishing is performed, and finally CMP polishing is performed to obtain a SiC polycrystalline substrate 100 with a smooth surface.

[0048] [Film forming equipment] Next, we will describe an example of a film deposition apparatus that can be used in the SiC polycrystalline film deposition process when manufacturing SiC polycrystalline substrates.

[0049] An example of a film deposition apparatus capable of depositing a SiC polycrystalline film 20 on a substrate 10 by the CVD method is the film deposition apparatus described in Patent Document 3. This film deposition apparatus comprises a housing that serves as the exterior of the film deposition apparatus, a film deposition chamber for depositing the SiC polycrystalline film 20 on the substrate 10, an exhaust gas introduction chamber for introducing raw material gas and carrier gas discharged from the film deposition chamber to a gas outlet, a box covering the exhaust gas introduction chamber, a carbon heater for heating the film deposition chamber from outside the box, a gas inlet and gas outlet located at the bottom of the film deposition chamber for introducing raw material gas and carrier gas into the film deposition chamber, and a substrate holder for holding the substrate 10. The film deposition chamber 1000 of a typical film deposition apparatus will be described in more detail below.

[0050] <Deposition chamber 1000> Figure 4 is a cross-sectional view of the deposition chamber 1000, Figure 5 is a cross-sectional view of the deposition chamber 1000 viewed from the direction indicated by arrow B in Figure 4, and Figure 6 is a cross-sectional view of the deposition chamber 1000 viewed from the direction indicated by arrow D in Figure 4. The deposition chamber 1000 is shown vertically in Figures 4 and 6 and is covered by a box-shaped wall 1010 shown as a rectangle in Figure 5. The inside of the wall 1010 is the interior 1020 of the deposition chamber 1000, and the outside is the exterior of the deposition chamber 1000. Inside the interior 1020, a substrate holder 1030, which has a substrate holding portion 1031 and a holder side surface 1032, holds multiple substrates 10.

[0051] Furthermore, a shaft 1040 is provided on the side of the substrate holder 1030, and the shaft 1040 rotates around its central axis and a corresponding rotation axis A, causing the substrate 10 to rotate together with the substrate holder 1030. The raw material gas and carrier gas pass through the rotating substrate 10 with arrow B upstream and arrow C downstream, thereby forming a SiC polycrystalline film 20 on the substrate 10.

[0052] However, in the deposition chamber 1000, the resulting SiC polycrystalline substrate has a large coefficient of variation in volume resistivity on the deposition surface of the substrate. The reason for this is that, inside the interior 1020 covered by the box-shaped walls 1010 of the deposition chamber 1000, the SiC polycrystalline film 20 tends to be deposited more easily on the outer periphery of the rotating substrate 10. As a result, the SiC polycrystalline film 20 is deposited thickly on the outer periphery of the substrate 10 and thinly in the center, causing variations in volume resistivity on the deposition surface.

[0053] Therefore, in order to obtain a SiC polycrystalline substrate 30 with a coefficient of variation of volume resistivity of 3% or less on the film deposition surface, it is important to use the film deposition chamber 2000 described below.

[0054] 〈Film formation room 2000〉 Figure 7 is a cross-sectional view of the deposition chamber 2000, Figure 8 is a cross-sectional view of the deposition chamber 2000 viewed from the direction indicated by arrow B in Figure 7, and Figure 9 is a cross-sectional view of the deposition chamber 2000 viewed from the direction indicated by arrow D in Figure 7. The deposition chamber 2000 is shown vertically in Figures 7 and 9 and is covered by a box-shaped wall 2010 shown as a rectangle in Figure 8. The inside of the wall 2010 is the interior 2020 of the deposition chamber 2000, and the outside is the exterior of the deposition chamber 2000. Inside the interior 2020, a substrate holder 1030, which has a substrate holding portion 1031 and a holder side surface 1032, holds multiple substrates 10.

[0055] Furthermore, a shaft 1040 is provided on the side of the substrate holder 1030, and the shaft 1040 rotates around its central axis and a corresponding rotation axis A, causing the substrate 10 to rotate together with the substrate holder 1030. The raw material gas and carrier gas pass through the rotating substrate 10 with arrow B upstream and arrow C downstream, thereby forming a SiC polycrystalline film 20 on the substrate 10.

[0056] The key difference between the deposition chamber 2000 and the deposition chamber 1000 is that the deposition chamber 2000 has a tapered inner wall 2011 that narrows from upstream of the source gas and carrier gas toward the rotation axis A, and a tapered inner wall 2012 that widens from the rotation axis A toward the downstream of the source gas and carrier gas, whereas the deposition chamber 1000 does not have such an inner wall.

[0057] When the deposition chamber 2000 is equipped with tapered inner walls 2011 and 2012, the flow velocity of the raw material gas is fastest at the rotation axis A. As a result, an environment is created in which the SiC polycrystalline film 20 can be easily deposited not only on the outer periphery of the substrate 10 but also in the central part where the flow velocity of the raw material gas is high. Compared to when the deposition chamber 1000 is used, a SiC polycrystalline film 20 of uniform thickness is deposited on the substrate 10. If a SiC polycrystalline film 20 of uniform thickness is deposited by chemical vapor deposition, the variation in volume resistivity on the deposition surface of the film will also be reduced, making it possible to realize the SiC polycrystalline substrate 30 of the present invention, in which the coefficient of variation of volume resistivity on the deposition surface is 3% or less. [Examples]

[0058] The present invention will be described in detail below with reference to examples and comparative examples.

[0059] [Example 1] A disc-shaped substrate 10 made of isotropic graphite with a diameter of 23 cm and a thickness of 0.5 cm was prepared, and eight substrates 10 were placed in the deposition chamber 2000 of the aforementioned deposition apparatus using a substrate holder 1030. Then, while rotating the substrates 10 by rotating the shaft 1040, a SiC polycrystalline film 20 was deposited on the substrates 10 by chemical vapor deposition for 10 hours (SiC polycrystalline film deposition process).

[0060] The film deposition conditions were as follows: a pressure of 98 kPa in the deposition chamber 2000, a deposition temperature of 1350°C, and a rotation speed of 10 revolutions / minute for the substrate 10. Dichlorosilane (SiH2Cl2) gas and acetylene (C2H2) gas were introduced into the deposition chamber 2000 at flow rates of 1000 sccm and 350 sccm, respectively. Nitrogen gas was dopant at 5000 sccm, and hydrogen gas was used as a carrier gas at a flow rate of 10000 sccm. Inside the deposition chamber 2020, the ratio of the length of the short side E on the rotation axis A in the direction parallel to the rotation axis A to the length of the long side F upstream or downstream of the substrate holder 1030 was set to E:F = 1:1.25. The length of the sides in the direction perpendicular to the rotation axis A inside the deposition chamber 2020 was kept constant without any taper or other variations.

[0061] Next, a disc-shaped base material 10, on which a SiC polycrystalline film 20 is deposited on both sides, is placed into an end-face processing device, and the outer periphery of the base material 10 is ground to a thickness of 0.05 mm to expose the outer edge 11 of the base material 10 (base material exposure process).

[0062] Then, in an atmospheric environment at 1000°C, the substrate 10 with its outer peripheral edge 11 exposed was heated and burned for 24 hours to separate the SiC polycrystalline film 20 from the substrate 10 (SiC polycrystalline film separation step). Subsequently, the front and back surfaces of the SiC polycrystalline substrate 30 were flattened by grinding them to a thickness of 0.5 mm each (polishing step) to produce a cubic SiC polycrystalline substrate 100.

[0063] [Comparative Example 1] A SiC polycrystalline substrate was manufactured in the same manner as in Example 1, except that a film deposition apparatus equipped with a film deposition chamber 1000 was used.

[0064] <Measurement of film thickness> A non-contact film thickness gauge was used to measure the film thickness at points 0 mm and 100 mm from the outer edge of the SiC polycrystalline substrates of Example 1 and Comparative Example 1.

[0065] <Measurement of volume resistivity> The volume resistivity of the same film-deposited surface of the SiC polycrystalline substrates in Example 1 and Comparative Example 1 was measured using a Napson NC-80MAP eddy current volume resistivity measuring instrument. 37 measurement points were taken within the same surface per SiC polycrystalline substrate (Figure 2).

[0066] Table 1 shows the results of measuring the film thickness and volume resistivity of the SiC polycrystalline substrates 100 of Example 1 and Comparative Example 1, and the coefficient of variation calculated based on the volume resistivity. The film thickness and volume resistivity are the average values ​​of a total of 16 SiC polycrystalline substrates 100 deposited in the same batch.

[0067] [Table 1]

[0068] As shown in Example 1, by using the deposition chamber 2000, a SiC polycrystalline substrate with a coefficient of variation of volume resistivity of 3% or less on the deposition surface was realized, and the volume resistivity was 25 mΩcm or less (Table 1).

[0069] On the other hand, Comparative Example 1 was obtained using a film deposition apparatus equipped with a conventional film deposition chamber 1000. Compared to Example 1, the variation in film thickness was larger, and the volume resistivity was 25 mΩcm or less, but a SiC polycrystalline substrate with large variation in volume resistivity on the film deposition surface was obtained.

[0070] The present invention makes it possible to realize a SiC polycrystalline substrate with low volume resistivity and low variation in volume resistivity across the film deposition surface. By providing such a SiC polycrystalline substrate and a SiC bonded semiconductor substrate, it is possible to suppress a decrease in the manufacturing yield of devices using the SiC bonded semiconductor substrate. [Explanation of symbols]

[0071] 10: Substrate, 11: Outer edge, 20: SiC polycrystalline film, 21: Outer edge, 30: SiC polycrystalline substrate, 100: SiC polycrystalline substrate, 110: First surface, 120: Second surface, 1000: Film deposition chamber, 1010: Wall, 1020: Interior, 1030: Substrate holder, 1031: Substrate holding part, 1032: Holder side, 1040: Shaft, 2000: Film deposition chamber, 2010: Wall, 2011: Inner wall, 2012: Inner wall, 2020: Interior

Claims

1. A SiC polycrystalline substrate for use in SiC bonded semiconductor substrates, characterized in that the coefficient of variation of the volume resistivity of the film-forming surface is 3% or less.

2. The SiC polycrystalline substrate used in a SiC bonded semiconductor substrate according to claim 1, characterized in that the coefficient of variation is obtained by dividing the standard deviation of the volume resistivity measured at a plurality of measurement points on the film-forming surface by the mean value.

3. The SiC polycrystalline substrate used in the SiC bonded semiconductor substrate according to claim 2, characterized in that the measurement points are the center point of the film-forming surface and a total of five or more points, four or more points arranged at equal intervals or angles in the circumferential direction at a predetermined radial distance from the center point.

4. A SiC polycrystalline substrate for use in a SiC bonded semiconductor substrate according to claim 1, characterized in that the volume resistivity is 25 mΩcm or less.

5. A SiC polycrystalline substrate for use in a SiC bonded semiconductor substrate according to claim 1 or 2, characterized in that its crystal structure is cubic or hexagonal.

6. A SiC polycrystalline substrate for use in a SiC bonded semiconductor substrate according to claim 1 or 2, wherein the diameter of the film-forming surface is 100 mm or more and 305 mm or less.

7. A SiC bonded semiconductor substrate comprising a SiC polycrystalline substrate according to claim 1 and a SiC single crystal substrate bonded to the film-forming surface.

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