SiC dummy wafer and method for manufacturing SiC dummy wafer

Abstract

A dummy wafer using SiC produced by a CVD method that can be detected by an optical sensor, and a method for producing a SiC dummy wafer are provided. [Solution] The SiC dummy wafer 1 according to the present disclosure is a SiC dummy wafer fabricated using a chemical vapor deposition method. The SiC dummy wafer 1 comprises a front surface layer 1a constituting a first main surface and including a plurality of SiC columnar crystals, a back surface layer 1b constituting a second main surface opposite the first main surface and including a plurality of SiC columnar crystals, and an intermediate layer 1c formed between the first and second main surfaces. The intermediate layer 1c has at least one non-transparent layer at least in part including a plurality of SiC microcrystals whose grain size is smaller than that of the SiC columnar crystals.

Description

[Technical Field]

[0001] The present disclosure relates to a SiC dummy wafer and a method for manufacturing a SiC dummy wafer. [Background technology]

[0002] In the semiconductor manufacturing process, wafers with the same shape as the silicon wafers used in the final product are used as dummy wafers. However, when silicon wafers are used as dummy wafers, they are almost always disposable, resulting in approximately half of the silicon wafers being wasted in the semiconductor manufacturing process, which is one of the factors driving up the manufacturing costs of semiconductor devices. Furthermore, when demand for semiconductor devices increases, the consumption of silicon wafers and dummy wafers increases, causing the supply of silicon wafers to fall short, resulting in a tight supply of the raw material, polysilicon. Therefore, dummy wafers made of electrically insulating materials other than silicon wafers, such as quartz, glass, and ceramics, are being manufactured (Patent Document 1, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3907400 [Patent Document 2] Patent Publication No. 2021-034465 Summary of the Invention [Problem to be solved by the invention]

[0004] Furthermore, as a dummy wafer that does not use a silicon wafer, a dummy wafer (also referred to as a SiC dummy wafer in this disclosure) is produced using SiC produced by chemical vapor deposition (CVD). SiC dummy wafers have characteristics such as high purity, high oxidation resistance, high corrosion resistance, and a low diffusion coefficient, and can be repeatedly used (long life) while maintaining high purity by performing an acid cleaning process. For example, SiC dummy wafers have excellent corrosion resistance against nitric acid and the like, so deposits can be easily removed by etching, allowing for repeated use.

[0005] Furthermore, the thermal expansion coefficient of the SiC dummy wafer is close to that of the silicon nitride film and polysilicon film, making it difficult for the silicon nitride film and polysilicon film attached to the surface of the SiC dummy wafer to peel off, preventing these films from peeling off during the film formation process and causing a significant increase in particles.In addition, the diffusion coefficient of impurities such as heavy metals at high temperatures is extremely low in the SiC dummy wafer, so there is little concern about furnace contamination due to contained impurities.

[0006] However, SiC dummy wafers contain very little impurities and are semi-transparent plates that are yellow, the color of the SiC material. In the semiconductor manufacturing process, silicon wafers and dummy wafers are detected with optical sensors, but SiC dummy wafers are semi-transparent yellow plates that allow infrared light to pass through, making them undetectable by optical sensors, which has led to the problem of not being able to perform automatic transportation.

[0007] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a SiC dummy wafer using SiC produced by a CVD method that can be detected by an optical sensor, and a method for manufacturing a SiC dummy wafer. [Means for solving the problem]

[0008] A SiC dummy wafer according to an aspect of the present disclosure is a SiC dummy wafer fabricated by chemical vapor deposition. The SiC dummy wafer includes a surface layer that forms a first main surface and includes a plurality of SiC columnar crystals, a back surface layer that forms a second main surface opposite to the first main surface and includes a plurality of SiC columnar crystals, and a bonding layer between the surface layer and the back surface layer. In between and an intermediate layer provided on the substrate, the intermediate layer including a plurality of SiC microcrystals having a grain size smaller than that of the columnar SiC crystals. Multiple Non-transparent layer and a layer including a plurality of SiC columnar crystals, and a plurality of non-transparent layers are stacked symmetrically in the direction of the front layer and the back layer with respect to the center of the cross section of the SiC dummy wafer. .

[0009] A method for manufacturing a SiC dummy wafer according to another aspect of the present disclosure is a method for manufacturing a SiC dummy wafer using a chemical vapor deposition method, which includes the steps of supplying a source gas having a first concentration by volume into a chamber and depositing a first layer including a plurality of columnar SiC crystals around a substrate, and supplying a source gas having a second concentration by volume higher than the first concentration into the chamber and depositing a first layer including a plurality of columnar SiC crystals around a substrate. Layer , containing SiC microcrystals with a grain size smaller than that of the columnar SiC crystals. Multiple Non-transparent layer and a layer including a plurality of columnar SiC crystals. a step of depositing a second layer, a step of supplying a source gas of a first concentration into a chamber and depositing a third layer including columnar crystals of SiC on the first and second layers, and a step of removing the substrate; The second layer is made of a plurality of non-transparent layers stacked symmetrically in the direction of the first and second layers with respect to the center of the cross section of the SiC dummy wafer. . [Effects of the Invention]

[0010] According to the present disclosure, since the intermediate layer has at least one non-transparent layer containing, at least in part, a plurality of SiC microcrystals having a grain size smaller than that of the SiC columnar crystals, it is possible to provide a SiC dummy wafer that can be detected by an optical sensor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a SiC dummy wafer according to an embodiment. [Figure 2] 1 is a graph showing the transmittance of a SiC dummy wafer according to an embodiment. [Figure 3]1 is a schematic diagram of a CVD film-forming apparatus for manufacturing SiC dummy wafers according to an embodiment. [Figure 4] 3A to 3C are cross-sectional views showing a manufacturing process of a SiC dummy wafer according to an embodiment. [Figure 5] 3 is a flowchart showing a manufacturing process of a SiC dummy wafer according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. While multiple embodiments will be described below, it is anticipated from the beginning that the configurations described in each embodiment will be appropriately combined. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0013] [Embodiment 1] (SiC dummy wafer configuration) This disclosure describes a dummy wafer (SiC dummy wafer) made of SiC by chemical vapor deposition (CVD). The SiC dummy wafer according to this disclosure is a wafer of the same shape as a silicon wafer used in a product in a semiconductor manufacturing process, and is a wafer that can be detected by an optical sensor. However, the SiC dummy wafer according to this disclosure is not limited to a wafer of the same shape as a silicon wafer, and the configuration of the SiC dummy wafer according to this disclosure can be applied to any shape of dummy wafer used in a semiconductor manufacturing process. FIG. 1 is a schematic diagram of a SiC dummy wafer 1 according to an embodiment.

[0014] The SiC dummy wafer 1 is a dummy wafer manufactured using a CVD method. The SiC dummy wafer 1 is preferably a high-purity semiconductor substrate containing 0.3 ppm or less of each metal element. The SiC dummy wafer 1 includes a front surface layer 1a constituting the first main surface of the wafer (the upper surface in FIG. 1), a back surface layer 1b constituting the second main surface of the wafer (the lower surface in FIG. 1) opposite the first main surface, and an intermediate layer 1c constituting the space between the first and second main surfaces. For convenience, the front and back surfaces of the SiC dummy wafer 1 are defined as shown in FIG. 1, but they may be reversed.

[0015] The surface layer 1a includes a plurality of SiC columnar crystals that have grown polycrystallinely in a vertical direction from the back surface to the front surface of the SiC dummy wafer 1. The back surface layer 1b includes a plurality of SiC columnar crystals that have grown polycrystallinely in a vertical direction of the SiC dummy wafer 1. In the surface layer 1a and the back surface layer 1b, the grain boundaries between the columnar crystals are aligned along the vertical direction of the SiC dummy wafer 1, as shown in FIG. 1. Therefore, when light is incident in the vertical direction of the SiC dummy wafer 1, the direction of the incident light and the direction of the grain boundaries between the columnar crystals are approximately parallel, and the incident light is therefore less likely to be obstructed by the columnar crystals. As a result, the surface layer 1a and the back surface layer 1b become yellow, translucent transmissive layers that transmit incident light (especially infrared light).

[0016] On the other hand, the intermediate layer 1c contains multiple SiC microcrystals with a smaller grain size than the SiC columnar crystals. The SiC microcrystals have a smaller grain size than the SiC columnar crystals and are irregularly arranged as shown in Figure 1. As a result, the grain boundaries between the microcrystals also become irregular, and when light is incident perpendicularly to the SiC dummy wafer 1, the incident light is blocked by the irregularly arranged microcrystals. As a result, the intermediate layer 1c becomes an opaque layer that does not transmit incident light (especially infrared light).

[0017] Layers made of SiC microcrystals with small grain sizes are brittle and easily damaged. On the other hand, layers made of SiC columnar crystals with larger grain sizes than SiC microcrystals are hard and less likely to break. For this reason, SiC dummy wafer 1 uses hard layers made of SiC columnar crystals for the front layer 1a and back layer 1b, and adopts a structure in which a brittle intermediate layer 1c made of SiC microcrystals is sandwiched between them, resulting in a dummy wafer that is hard to damage and opaque to infrared light.

[0018] The non-transmitting intermediate layer 1c preferably has a thickness of approximately 5 μm or more to achieve a transmittance of 5% or less for light in the infrared region. If the thickness of the SiC dummy wafer 1 is at least approximately 100 μm or more, the non-transmitting intermediate layer 1c preferably has a thickness of approximately 1 / 20 or more of the thickness of the SiC dummy wafer 1. The front surface layer 1a and the back surface layer 1b sandwiching the intermediate layer 1c may have any thickness as long as they function as the SiC dummy wafer 1. For example, if the thickness of SiC columnar crystals formed by a typical film formation method is approximately 200 μm to 300 μm, the thickness of the front surface layer 1a and the back surface layer 1b will each be approximately 200 μm, and the thickness of the intermediate layer 1c will be approximately 5 μm, resulting in a thickness of approximately 405 μm for the SiC dummy wafer 1. In this case, the non-transmitting intermediate layer 1c will have a thickness of approximately 1 / 80 or more of the thickness of the SiC dummy wafer 1. Furthermore, when the thickness of the SiC dummy wafer 1 is approximately 800 μm, the thickness of the intermediate layer 1c, which is more than one-twentieth the thickness of the SiC dummy wafer 1, is approximately 40 μm, and the thickness of each of the front surface layer 1a and the back surface layer 1b is approximately 380 μm.

[0019] The transmittance of the SiC dummy wafer 1 having an intermediate layer 1c that is a non-transparent layer will be described. FIG. 2 is a graph showing the transmittance of the SiC dummy wafer 1 according to the embodiment. In FIG. 2, the horizontal axis represents wavelength (unit: nm) and the vertical axis represents transmittance (unit: %). Note that the thickness of the intermediate layer 1c of the SiC dummy wafer 1 is approximately 5 μm or more. Graph A shown in FIG. 2 shows the transmittance of the SiC dummy wafer 1, and the transmittance is approximately 0% for almost all wavelengths. Therefore, as can be seen from graph A in FIG. 2, the SiC dummy wafer 1 has a transmittance of 5% or less for light in the infrared region (for example, approximately 633 nm).

[0020] On the other hand, graph B shows the transmittance of a SiC dummy wafer that does not have a non-transparent layer as a comparison. In graph B, the transmittance increases from light with a wavelength of approximately 500 nm, and is approximately 42% or more for light with a wavelength of approximately 2500 nm. In particular, the comparative SiC dummy wafer has a transmittance of more than 5% for light in the infrared region (for example, approximately 633 nm).

[0021] Generally, optical sensors used in devices such as automatic conveyors in semiconductor manufacturing processes use light in the infrared region (for example, approximately 633 nm), and therefore cannot detect the presence of wafers with high transmittance to that light. SiC dummy wafer 1 with non-transparent intermediate layer 1c has a transmittance of 5% or less to light in the infrared region, so the optical sensor can detect the presence of SiC dummy wafer 1. On the other hand, a comparative SiC dummy wafer has a transmittance of more than 5% to light in the infrared region, so the optical sensor cannot detect its presence.

[0022] The transmittance of the non-transmissive layer depends not only on the thickness of the non-transmissive layer but also on the particle size of the SiC microcrystals contained in the non-transmissive layer. Observation of the SiC microcrystals in the intermediate layer 1c using a scanning electron microscope (SEM) revealed that the layer contained many microcrystals with particle sizes of approximately 0.2 μm to approximately 0.5 μm, with the largest containing microcrystals being approximately 5 μm in size. This is a reasonable size range for the SiC microcrystals in the intermediate layer 1c in terms of interference with green to red light, which has a wavelength of approximately 0.5 μm to 0.8 μm. It is believed that a smaller particle size of the SiC microcrystals allows for more irregular arrangement of the SiC microcrystals, thereby blocking incident light and achieving a non-transmissive layer with low transmittance.

[0023] Whether SiC is produced as columnar crystals or microcrystals using the CVD method can be adjusted, for example, by changing the gas concentration of the source gas. Specifically, columnar crystals can be produced by diluting the gas concentration of the source gas to allow slow crystal growth, and conversely, microcrystalline SiC can be produced by increasing the gas concentration of the source gas to allow rapid crystal growth. The particle size of the SiC microcrystals can also be adjusted by the gas concentration of the source gas; for example, increasing the gas concentration of the source gas makes the SiC crystal grains smaller, disrupting crystal growth and resulting in irregularly arranged grain boundaries. If the grain boundaries can be arranged more irregularly, opaque SiC with higher transmittance can be obtained.

[0024] When SiC is produced by the CVD method, the surface layer 1a, back surface layer 1b, and intermediate layer 1c are produced from cubic SiC (3C-SiC). However, the surface layer 1a, back surface layer 1b, and intermediate layer 1c are not limited to being produced from cubic SiC (3C-SiC), and may be produced from hexagonal SiC (4H-SiC), hexagonal SiC (6H-SiC), or trigonal SiC (15R-SiC) as long as SiC can be produced by the CVD method.

[0025] (Semiconductor manufacturing jig manufacturing equipment) FIG. 3 is a schematic diagram of a CVD film-forming apparatus for manufacturing the SiC dummy wafer 1 according to the embodiment.

[0026] The CVD film forming apparatus 4 includes a chamber 41 (pressure-reducing vessel), a high-frequency power supply 42, a vacuum pump 43, a source gas vessel 44, a first valve 451, a second valve 452, and a control device 49.

[0027] The control device 49 includes a CPU (Central Processing Unit) 491, memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 492, an input / output buffer (not shown), and the like. The CPU 491 loads a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM includes a control procedure to be executed by the control device 49 and parameters for producing SiC as columnar crystals or microcrystals. The control device 49 controls various devices in the CVD film formation apparatus 4 in accordance with such programs.

[0028] The control device 49 controls various devices within the chamber 41, such as the high frequency power supply 42, the vacuum pump 43, the first valve 451, and the second valve 452.

[0029] A film formation table 46, a heater 47, and a shower head 48 are provided inside the chamber 41. The heater 47 is provided inside the shower head 48. A substrate 10 of the SiC dummy wafer 1 on which a film is to be formed is held above the film formation table 46. The substrate 10 is made of, for example, graphite. The substrate 10 is held so that a film is formed all around it. Note that the substrate 10 may be made of a material other than graphite.

[0030] The first valve 451 is provided in the gas path between the vacuum pump 43 and the chamber 41. The second valve 452 is provided in the gas path between the source gas container 44 and the chamber 41.

[0031] When forming a film on the substrate 10 in the CVD film forming apparatus 4, the control device 49 controls the second valve 452 to be closed, the first valve 451 to be open, and the vacuum pump 43 to be operated, thereby creating a vacuum state inside the chamber 41.

[0032] Thereafter, the control device 49 controls the second valve 452 to be open while keeping the first valve 451 closed to maintain the inside of the chamber 41 in a vacuum state. As a result, the source gas is supplied from the source gas container 44 into the chamber 41. The control device 49 can adjust the concentration of the source gas supplied into the chamber 41 by adjusting the open state of the second valve 452. When the source gas is supplied into the chamber 41, the control device 49 controls the high-frequency power supply 42 to supply high-frequency power to the electrode of the shower head 48. As a result, the source gas is converted into plasma in the chamber 41 and released from the shower head 48.

[0033] When a film is formed on the substrate 10 in the CVD film forming apparatus 4, the control device 49 supplies power to the heater 47 and controls the heater to heat. As a result, a film of a substance contained in the source gas is formed on the film forming target, such as the substrate 10, while the target is heated. Note that whether SiC is produced as columnar crystals or microcrystals can be changed by adjusting parameters such as the concentration of the source gas, the high-frequency power, and the amount of heating by the heater.

[0034] In such a CVD film-forming apparatus 4, a film of SiC is formed around the substrate 10, thereby forming a film for manufacturing a SiC dummy wafer 1 as shown in FIG.

[0035] The manufacturing equipment for the SiC dummy wafer 1 includes, in addition to the CVD film forming equipment 4, a processing equipment (not shown) for processing the SiC dummy wafer 1, such as cutting.

[0036] (SiC dummy wafer manufacturing method) 4 and 5, which will be described below, show an example in which two SiC dummy wafers 1 are simultaneously manufactured. Fig. 4 is a cross-sectional view showing the manufacturing process of the SiC dummy wafer in the embodiment. Fig. 5 is a flowchart showing the manufacturing process of the SiC dummy wafer in the embodiment.

[0037] The substrate 10 is a circular plate (FIG. 4(a)). First, a source gas is supplied at a first concentration into a chamber 41 (see FIG. 3) around the substrate 10, and a first layer 21 including a plurality of columnar SiC crystals is formed around the substrate 10 (FIG. 4(b), step S1). Specifically, the substrate 10 is held in the chamber 41 of the CVD film-forming apparatus 4 (see FIG. 3). The pressure in the chamber 41 is set to, for example, 1.3 kPa, and a silane-based gas such as SiCH3Cl3, SiHCl3, or SiH4, and a hydrocarbon gas such as CH4, C2H4, or CCl4, which serve as source gases for SiC, are supplied into the chamber 41 together with hydrogen gas or argon gas as a carrier gas at a volume ratio of, for example, about 5 to about 20% (first concentration). The CVD film-forming apparatus 4 forms the first layer 21 including columnar crystals of SiC on the surface of the substrate 10 by heating the substrate 10 to a temperature of 1100 to 1500°C, for example.

[0038] Thereafter, in the CVD film formation apparatus 4, a source gas having a second concentration higher than the first concentration is supplied into the chamber 41 around the first layer 21, and a second layer 22, which is an impermeable layer containing SiC microcrystals having a particle size smaller than that of the columnar SiC crystals, is formed on the first layer 21 (FIG. 4(c), step S2). Specifically, the CVD film formation apparatus 4 supplies the SiC source gas to the surface of the substrate 10 from the middle of the formation of the first layer 21 at a volume ratio of, for example, about 15 to about 30% (second concentration (>first concentration)), thereby forming the second layer 22 (impermeable layer) containing SiC microcrystals on the surface of the first layer 21 to a thickness of about 5 μm to about 20 μm.

[0039] Thereafter, in the CVD film formation apparatus 4, a source gas of a first concentration is supplied into the chamber 41 around the second layer 22, and a third layer 23 including SiC columnar crystals is formed on the second layer 22 (FIG. 4(d), step S3). Specifically, the CVD film formation apparatus 4 returns the SiC source gas to a volume ratio of about 5 to about 20% (first concentration) halfway through the formation of the second layer 22 on the surface of the substrate 10, and forms the third layer 23 including SiC columnar crystals on the surface of the second layer 22. The first layer 21, the second layer 22, and the third layer 23 are successively formed by the CVD film formation apparatus 4 simply by adjusting parameters such as the source gas concentrations.

[0040] Next, the substrate 10 is removed from the CVD deposition apparatus 4, and the outer periphery of the laminated body, in which the SiC film is formed on the substrate 10, is cut in a processing device to expose the side surfaces of the substrate 10 (FIG. 4(e), step S4). By cutting the outer periphery of the laminated body, SiC dummy wafers are formed on each of the two surfaces of the substrate 10. Furthermore, the laminated body with the outer periphery cut is heated in an oxygen atmosphere at approximately 900 to approximately 1400°C to burn and remove the substrate 10 (FIG. 4(f), step S5). This allows two SiC dummy wafers deposited by chemical vapor deposition (CVD) to be produced. Note that by polishing the surfaces of the first layer 21 and the third layer 23, the cross-sectional shape of the SiC dummy wafer 1 shown in FIG. 1 can be obtained. Note that the first layer 21 corresponds to the front surface layer 1a or the back surface layer 1b, the third layer 23 corresponds to the back surface layer 1b or the front surface layer 1a, and the second layer 22 corresponds to the intermediate layer 1c.

[0041] As described above, the SiC dummy wafer 1 according to the embodiment is a SiC dummy wafer 1 manufactured using a chemical vapor deposition method. The SiC dummy wafer 1 includes a front surface layer 1a that forms a first main surface and includes a plurality of SiC columnar crystals, a back surface layer 1b that forms a second main surface opposite the first main surface and includes a plurality of SiC columnar crystals, and an intermediate layer 1c that forms between the first and second main surfaces. The SiC dummy wafer 1 is a dummy wafer using SiC manufactured by a CVD method that can be detected by an optical sensor because the intermediate layer 1c is an opaque layer that includes a plurality of SiC microcrystals whose grain size is smaller than that of the SiC columnar crystals.

[0042] [Variations] In the SiC dummy wafer 1 according to the embodiment, as shown in FIG. 1, the intermediate layer 1c is described as an opaque layer containing a plurality of SiC microcrystals having a grain size smaller than that of the SiC columnar crystals. However, the intermediate layer 1c is not limited to being composed of only one opaque layer containing a plurality of SiC microcrystals, and may include at least one opaque layer containing a plurality of SiC microcrystals. For example, the SiC dummy wafer 1 may include two or more opaque layers containing a plurality of SiC microcrystals, or may include a layer containing a plurality of SiC columnar crystals between the two opaque layers. By including two or more opaque layers containing a plurality of SiC microcrystals in the intermediate layer, the SiC dummy wafer 1 can further reduce transmittance, enabling more reliable detection by an optical sensor.

[0043] When the intermediate layer is composed of two or more non-transmissive layers containing a plurality of SiC microcrystals, it is preferable to stack the non-transmissive layers so that they are vertically symmetrical with respect to the center of the cross section of the SiC dummy wafer 1. This is because the in-plane stress differs between the layer containing a plurality of SiC columnar crystals and the non-transmissive layer containing a plurality of SiC microcrystals, and stacking the non-transmissive layers asymmetrically with respect to the center of the cross section may cause warping of the SiC dummy wafer 1. Therefore, when the intermediate layer has two non-transmissive layers, it is preferable to provide a layer containing a plurality of SiC columnar crystals between the two non-transmissive layers and stack the non-transmissive layers so that they are vertically symmetrical with respect to the center of the cross section.

[0044] In the SiC dummy wafer 1 according to the embodiment, a non-transparent layer containing a plurality of SiC microcrystals is provided on the entire surface of the intermediate layer 1c as shown in Fig. 1. However, since the SiC dummy wafer 1 only needs to be detected by an optical sensor, it is sufficient that the non-transparent layer is provided at least in a position corresponding to the optical sensor. In other words, it is sufficient that the intermediate layer 1c has a non-transparent layer containing a plurality of SiC microcrystals in at least a portion thereof.

[0045] [Aspect] (Item 1) The SiC dummy wafer according to the present disclosure is A SiC dummy wafer fabricated using a chemical vapor deposition method, a surface layer that forms the first main surface and includes a plurality of SiC columnar crystals; a back surface layer that forms a second main surface opposite to the first main surface and includes a plurality of SiC columnar crystals; an intermediate layer formed between the first main surface and the second main surface, The intermediate layer has at least one non-transparent layer at least partly including a plurality of SiC microcrystals having a grain size smaller than that of the columnar SiC crystals.

[0046] (Item 2) The SiC dummy wafer according to item 1, The non-transmitting layer has a thickness that is at least about 1 / 20 of the thickness of the SiC dummy wafer.

[0047] (Item 3) The SiC dummy wafer according to item 1 or 2, The non-transparent layer has a thickness of about 5 μm or greater.

[0048] (Item 4) The SiC dummy wafer according to any one of items 1 to 3, The non-transmitting layer has a transmittance of 5% or less for light in the infrared region.

[0049] (Item 5) The SiC dummy wafer according to any one of items 1 to 4, The grain size of the SiC microcrystals is about 0.2 μm to about 5 μm.

[0050] (Item 6) The SiC dummy wafer according to any one of items 1 to 5, When the intermediate layer has two non-transparent layers, a layer containing a plurality of columnar SiC crystals is provided between the two non-transparent layers.

[0051] (Item 7) A method for manufacturing a SiC dummy wafer according to the present disclosure includes: A method for manufacturing a SiC dummy wafer by using a chemical vapor deposition method, supplying a source gas at a first concentration into a reduced pressure vessel to form a first layer including a plurality of columnar crystals of SiC around a substrate; supplying a source gas having a second concentration higher than the first concentration into a reduced pressure vessel and depositing a second non-transmitting layer containing SiC microcrystals having a grain size smaller than that of the columnar SiC crystals on the first layer; supplying a source gas having a first concentration into a reduced pressure vessel and depositing a third layer including columnar crystals of SiC on the second layer; and removing the substrate.

[0052] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0053] 1 SiC dummy wafer, 1a front surface layer, 1b back surface layer, 1c intermediate layer, 4 CVD film formation apparatus, 10 substrate, 21 first layer, 22 second layer, 23 third layer, 41 chamber, 42 high frequency power supply, 43 vacuum pump, 44 raw material gas container, 46 film formation table, 47 heater, 48 shower head, 49 control device, 451 first valve, 452 second valve.

Claims

1. A SiC dummy wafer fabricated using a chemical vapor deposition method, a surface layer that forms the first main surface and includes a plurality of SiC columnar crystals; a back surface layer that forms a second main surface opposite to the first main surface and includes a plurality of SiC columnar crystals; an intermediate layer provided between the front surface layer and the back surface layer, The intermediate layer has a plurality of non-transparent layers containing a plurality of SiC microcrystals having a grain size smaller than that of the columnar crystals of SiC, and a layer containing a plurality of SiC columnar crystals, and the plurality of non-transparent layers are stacked symmetrically in the directions of the front surface layer and the back surface layer with respect to the center of the cross section of the SiC dummy wafer.

2. The SiC dummy wafer according to claim 1 , wherein the non-transmissive layer has a thickness that is at least about 1 / 20 of the thickness of the SiC dummy wafer.

3. The SiC dummy wafer of claim 1 , wherein the non-transparent layer has a thickness of about 5 μm or more.

4. The SiC dummy wafer according to claim 1 , wherein the non-transmissive layer has a transmittance of 5% or less for light in the infrared region.

5. The SiC dummy wafer according to any one of claims 1 to 4, wherein the grain size of the SiC microcrystals is about 0.2 µm to about 5 µm.

6. 5. The SiC dummy wafer according to claim 1, wherein, when the intermediate layer has two non-transparent layers, a layer containing a plurality of SiC columnar crystals is provided between the two non-transparent layers.

7. A method for manufacturing a SiC dummy wafer by using a chemical vapor deposition method, comprising: supplying a source gas having a first concentration by volume into a chamber to form a first layer including a plurality of columnar crystals of SiC around a substrate; supplying the source gas having a second concentration higher in volume ratio than the first concentration into the chamber, and depositing a second layer on the first layer, the second layer including a plurality of non-transmitting layers including SiC microcrystals having a grain size smaller than that of the SiC columnar crystals, and a layer including a plurality of SiC columnar crystals; supplying the source gas having the first concentration into the chamber to form a third layer including columnar crystals of SiC on the first layer and the second layer; removing the substrate; a second layer formed by stacking the plurality of non-transparent layers symmetrically in the direction of the first layer and the second layer with respect to a center of a cross section of the SiC dummy wafer;

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