METHOD FOR MANUFACTURING SiC SUBSTRATE, METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE, SiC SUBSTRATE, AND SEMICONDUCTOR DEVICE

Abstract

To provide a method for manufacturing an SiC substrate that is capable of achieving both a larger diameter and various types of SiC.SOLUTION: The present invention provides a method for manufacturing an SiC substrate 100, the method comprising: a bonding step in which a 3C-SiC layer 1a of a growth substrate 21, which is formed by growing the 3C-SiC layer 1a on a silicon substrate 1, is bonded to a poly SiC substrate, which is a support substrate 3, thereby forming a bonded substrate 10; a removal step in which the silicon substrate 1 is removed from the bonded substrate 10; and a heat treatment step in which the bonded substrate 10 after the removal step is further subjected to heat treatment to cause a phase transition of the 3C-SiC layer 1a, thereby forming the SiC substrate 100 having a SiC layer 1b with a plane orientation that is different from that before the heat treatment.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a SiC substrate, a method for manufacturing a semiconductor device, a SiC substrate, and a semiconductor device. [Background technology]

[0002] SiC is characterized by having many different crystal structures. Depending on this crystal structure, it has a wide band gap of 2.2 to 3.3 eV, which gives it high dielectric breakdown strength. It also has high thermal conductivity, making it a promising semiconductor material for use in a variety of semiconductor devices, such as power devices and high-frequency devices.

[0003] Among the many crystal structures (polytypes), 4H-SiC is grown by methods such as sublimation and gas growth, and is being put to practical use. However, because the crystals are grown by sublimation and gas phase growth, it is difficult to make them larger in diameter. Due to the excellent thermal properties of SiC, it is expected to be used in a wide range of applications, including free wheel diodes in power units, and there is a demand for larger diameters.

[0004] In fact, it has been reported that in devices using SiC, the manufacturing process of the SiC substrate and the subsequent epitaxial process account for half of the cost (Non-Patent Document 1), and therefore reducing the cost of substrates by increasing their diameter is extremely important.

[0005] As a cost reduction measure, H + A method has been proposed in which ion implantation is performed and the substrate is peeled off. For example, Patent Document 1 discloses the use of polycrystalline SiC as the substrate to which the semiconductor device is transferred.

[0006] Furthermore, Patent Document 2 discloses further epitaxial growth of SiC on the single crystal SiC after transfer. Also disclosed is a method of growing the original single crystal SiC on a silicon substrate, growing polycrystalline SiC on the single crystal SiC layer by chemical vapor deposition, and then heating the silicon substrate to 1414°C or higher to melt the silicon substrate, thereby producing a SiC composite substrate (Patent Document 3).

[0007] Patent Document 4 discloses a method of growing 3C-SiC on a silicon substrate, transferring it onto a support substrate, and growing it epitaxially. In particular, 3C-SiC is a material that can be epitaxially grown at low temperatures and can be grown on a silicon substrate.

[0008] However, materials grown on silicon substrates are difficult to adapt to vertical devices, especially those used in power devices, and the fabrication of SiC substrates using the bonding and delamination method is a method that can solve this problem. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2021 / 060518 [Patent Document 2] JP 2014-216555 A [Patent Document 3] JP 2016-063198 A [Patent Document 4] Japanese Patent Application Publication No. 10-223496 [Non-patent literature]

[0010] [Non-Patent Document 1] Iwamuro, "Progress in High Performance and Reliability of SiC MOSFETs," Proceedings of the Wide Bandgap Semiconductor Society Special Open Symposium, Wide Bandgap Semiconductor Society, 2022 [Non-Patent Document 2] H. Biard, W. Schwarzenbach, S. Odoul, I. Radu, A. Potier, M. Ferrato, E. Guajioty, “Tailored polycrystalline substrate for SmartSiCTM substrates enabling high performance power devices”, ICSCRM2022 [Non-Patent Document 3] Suga, "Room-temperature bonding by surface activation and its mechanism," Applied Physics, The Japan Society of Applied Physics, 89(9), 2020, p498. [Non-Patent Document 4] Tokuhei Tagai et al., "SiC Polytype Transitions and Polytype Phenomena," Journal of Mineralogy, Japan Society of Mineralogical Sciences, Vol. 9, No. 6, 1970, p. 475-478 Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, in the bonding and peeling of single crystal SiC and polycrystalline SiC, the diameter of the original single crystal SiC is limited, and it will take some time before single crystal SiC with a diameter of 300 mm is realized. In addition, when growing SiC on a silicon substrate, the polytype is basically limited to 3C-SiC, and there has been no way to achieve both large diameter and various polytypes of SiC.

[0012] Therefore, the present invention has been made to solve the above problems, and has an object to provide a method for manufacturing an inexpensive, high-quality SiC substrate that can achieve both large diameter and various polytypes of SiC. Another object of the present invention is to provide a method for manufacturing a semiconductor device, which is capable of manufacturing a high-quality semiconductor device at low cost.

[0013] Another object of the present invention is to provide an inexpensive, high-quality SiC substrate that can accommodate both large diameters and a variety of polytypes of SiC. Another object of the present invention is to provide a semiconductor device which is inexpensive and of high quality. [Means for solving the problem]

[0014] The present invention has been made to achieve the above-mentioned object, and provides a method for manufacturing a SiC substrate, comprising the steps of: a bonding step of bonding a 3C-SiC layer of a growth substrate, in which a 3C-SiC layer is grown on a silicon substrate, to a poly-SiC substrate serving as a support substrate to obtain a bonded substrate; a removal step of removing the silicon substrate from the bonded substrate; and a heat treatment step of further performing a heat treatment on the bonded substrate after the removal step to cause a phase transition of the 3C-SiC layer to obtain a SiC substrate having a SiC layer having a different plane orientation from that before the heat treatment.

[0015] According to this method of manufacturing a SiC substrate, the 3C-SiC layer grown on the silicon substrate is bonded to poly-SiC, the silicon substrate is removed, and then the 3C-SiC layer is heated to cause a phase transition. This makes it possible to provide SiC substrates with various surface orientations at a lower cost, with high quality and large diameter, and to achieve both large diameter and various polytypes of SiC.

[0016] At this time, the surface orientation of the silicon substrate is <111> It can be said that:

[0017] This allows the lattice mismatch between the silicon substrate and the 3C-SiC layer to be smaller than when the silicon substrate has a different plane orientation.

[0018] In this case, the 3C-SiC layer grown on the silicon substrate can have a thickness of 20 nm to 200 nm.

[0019] This makes it possible to reduce the acceleration voltage during hydrogen ion implantation when performing delamination using hydrogen ion implantation in the removal process while ensuring the thickness of the 3C-SiC layer required to form devices, etc. Also, it is possible to suppress warping of the growth substrate.

[0020] In this case, the 3C-SiC layer grown on the silicon substrate can have a thickness of 50 to 100 nm.

[0021] This is advantageous in that it allows the acceleration voltage during hydrogen ion implantation to be reduced when performing delamination using hydrogen ion implantation in the removal process while ensuring the thickness of the 3C-SiC layer required for forming devices, etc. It is also advantageous in that it allows the warping of the growth substrate to be suppressed.

[0022] In this case, the surface roughness Ra of the 3C-SiC layer grown on the silicon substrate can be set to 1 nm or less.

[0023] This enables greater adhesion between the 3C-SiC layer and the poly-SiC substrate during the bonding process.

[0024] In this case, the growth substrate may have an upwardly convex substrate shape.

[0025] This can reduce the number of unjoined portions in the joining process.

[0026] In this case, the removal of the silicon substrate in the removing step can be performed by peeling off the silicon substrate by utilizing the embrittlement effect caused by hydrogen injection into the interface between the silicon substrate and the 3C-SiC layer.

[0027] As a result, compared to the case where etching or grinding / polishing is performed, there is no need for post-processing such as removing the etching solution or abrasive that has adhered to the bonded substrate by etching, grinding / polishing, or the like, by cleaning after the removal process.

[0028] At this time, the silicon substrate can be removed in the removing step by etching or grinding / polishing.

[0029] This makes it possible to omit a pre-process such as hydrogen injection before the removal process, as compared with the case where hydrogen injection is used.

[0030] At this time, a sputtering step of sputtering a silicon thin film onto the surfaces of the 3C-SiC layer and the poly-SiC substrate before the bonding step can be included.

[0031] This makes it possible to more reliably bond the 3C-SiC layer to the poly-SiC substrate without leaving any unbonded areas during the bonding process.

[0032] At this time, an epitaxial step of epitaxially growing 3C-SiC on the surface of the 3C-SiC layer after the removing step can be further included.

[0033] This allows the 3C-SiC layer to be made thicker.

[0034] At this time, in the heat treatment step, the bonded substrate is subjected to a heat treatment in the range of 1900 to 2100° C., so that the 3C—SiC layer can be phase-transformed into a 4H—SiC layer.

[0035] As a result, a 4H-SiC layer can be obtained as the SiC layer.

[0036] At this time, in the heat treatment step, the bonded substrate is subjected to a heat treatment in the range of 2000 to 2050° C., so that the 3C—SiC layer can be phase-transformed into a 4H—SiC layer.

[0037] This makes it possible to more reliably obtain a 4H-SiC layer as the SiC layer.

[0038] At this time, in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2200° C. or more, so that the 3C—SiC layer can be phase-transformed into a 6H—SiC layer.

[0039] As a result, a 6H-SiC layer can be obtained as the SiC layer.

[0040] At this time, in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2300° C. or more, so that the 3C—SiC layer can be phase-transformed into a 6H—SiC layer.

[0041] This makes it possible to more reliably obtain a 6H-SiC layer as the SiC layer.

[0042] The present invention also provides a method for producing a semiconductor device, comprising the step of forming a device on the SiC substrate produced by the above-described production method to obtain a semiconductor device.

[0043] According to such a method for manufacturing a semiconductor device, an inexpensive and high-quality semiconductor device can be manufactured because an inexpensive and high-quality SiC substrate is used.

[0044] The present invention further provides a SiC substrate comprising a poly-SiC substrate and a SiC layer bonded to the poly-SiC substrate, wherein the SiC layer is a 4H—SiC layer or a 6H—SiC layer.

[0045] According to such a SiC substrate, it is possible to provide SiC substrates having various plane orientations at lower cost, with high quality and large diameter, and it is possible to achieve both large diameter and various polytypes of SiC.

[0046] The present invention also provides a semiconductor device comprising the SiC substrate described above.

[0047] According to such a semiconductor device, since it has an inexpensive and high-quality SiC substrate, the semiconductor device is also inexpensive and of high quality. Effect of the Invention

[0048] As described above, according to the method for manufacturing a SiC substrate of the present invention, it is possible to achieve both large diameter and various polytypes of SiC, and to manufacture an inexpensive, high-quality SiC substrate. Furthermore, according to the method for manufacturing a semiconductor device of the present invention, a high-quality semiconductor device can be manufactured using an inexpensive and high-quality SiC substrate.

[0049] Furthermore, according to the present invention, it is possible to provide a low-cost, high-quality SiC substrate that can achieve both large diameter and various polytypes of SiC. Furthermore, according to the present invention, it is possible to provide a semiconductor device that is inexpensive and of high quality. [Brief description of the drawings]

[0050] [Figure 1] 1 shows a schematic diagram of a SiC substrate of the present invention. [Diagram 2] 1 shows a flow diagram of a method for manufacturing a SiC substrate according to the present invention. [Diagram 3] 3 shows a flow diagram of another method for manufacturing a SiC substrate according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] The present invention will be described in detail below, but the present invention is not limited thereto.

[0052] As described above, there has been a demand for a manufacturing method for inexpensive, high-quality SiC substrates that can simultaneously achieve large diameters and the production of a variety of SiC polytypes.

[0053] As a result of intensive investigations into the above-mentioned problems, the inventors have found that a method for manufacturing a SiC substrate comprising the steps of: a bonding step of bonding a 3C-SiC layer of a growth substrate, in which a 3C-SiC layer is grown on a silicon substrate, to a poly-SiC substrate serving as a support substrate to obtain a bonded substrate; a removal step of removing the silicon substrate from the bonded substrate; and a heat treatment step of further heat treating the bonded substrate after the removal step to cause a phase transition of the 3C-SiC layer to obtain a SiC substrate having a SiC layer having a different plane orientation from that before the heat treatment, thereby achieving both a large diameter and the production of various polytypes of SiC, and have completed the present invention.

[0054] As described above, there is also a need for a method for manufacturing a semiconductor device that is inexpensive and of high quality.

[0055] As a result of extensive research into the above-mentioned problems, the inventors have discovered that a semiconductor device manufacturing method, which includes a device formation step of forming a semiconductor device on the SiC substrate manufactured by the manufacturing method described above, can achieve both large diameter and various polytypes of SiC, and have completed the present invention.

[0056] As mentioned above, there was a demand for inexpensive, high-quality SiC substrates that could accommodate both large diameters and a variety of SiC polytypes.

[0057] As a result of extensive investigations into the above-mentioned problems, the inventors have discovered that a SiC substrate including a poly-SiC substrate and a SiC layer bonded to the poly-SiC substrate, characterized in that the SiC layer is a 4H—SiC layer or a 6H—SiC layer, can achieve both large diameter and various polytypes of SiC, and can be produced at low cost and with high quality, and have completed the present invention.

[0058] Furthermore, as mentioned above, there is a demand for semiconductor devices that are inexpensive and of high quality.

[0059] As a result of extensive research into the above-mentioned problems, the inventors have discovered that a semiconductor device comprising the above-described SiC substrate can be an inexpensive, high-quality semiconductor device, and have completed the present invention.

[0060] Hereinafter, an embodiment of the present invention will be described. First, the configuration of a SiC substrate according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a SiC substrate 100 according to an embodiment of the present invention includes a support substrate 3 made of poly-SiC (poly-SiC substrate) and a SiC layer 1b bonded to a surface of the support substrate 3.

[0061] The support substrate 3 is a substrate that supports the SiC layer 1b. In addition, a specific example of the support substrate 3 is poly-SiC (a SiC substrate produced by sintering or a polycrystalline SiC substrate) in consideration of cost and the like.

[0062] The SiC layer 1b is a single crystal layer of SiC, and is bonded to the surface of the support substrate 3. For this bonding, the bonding surfaces of the SiC layer 1b and the support substrate 3 may be directly bonded as they are, or a thin silicon film may be grown on the bonding surfaces, and a strong bond may be achieved by bonding via this thin silicon film.

[0063] The SiC layer 1b is a 4H-SiC layer or a 6H-SiC layer. More specifically, this SiC layer 1b is obtained by subjecting the 3C-SiC layer 1a to a phase transition by heat treatment to form 4H-SiC or 6H-SiC. Note that, before this phase transition, epitaxial growth of 3C-SiC may be performed on the 3C-SiC layer 1a, or it may be left as is.

[0064] In this way, the SiC substrate 100 has the SiC layer 1b of 4H-SiC or 6H-SiC bonded to the support substrate 3 made of inexpensive poly-SiC, making it possible to achieve both large diameter and various polytypes of SiC at low cost. In addition, since the SiC layer 1b is a 4H-SiC layer or a 6H-SiC layer, it is of high quality and high reliability.

[0065] The thickness of the SiC layer 1b is preferably about 50 nm to about 100 nm, which is easy to maintain the shape of the layer. The maximum thickness of 100 nm is preferable when considering the use of a high-current ion implantation device in consideration of productivity when transferring the 3C-SiC layer 1a from the silicon substrate 1 to the support substrate 3 by peeling using hydrogen ion implantation. Furthermore, if the thickness is within this range, the 3C-SiC layer 1a suppresses warping of the SiC substrate 100, and bonding defects are unlikely to occur when transferring the 3C-SiC layer 1a.

[0066] Next, the configuration of the semiconductor device will be described with reference to FIG. The semiconductor device includes a SiC substrate 100 shown in FIG. A specific example of the semiconductor device is a SiC substrate 100, particularly a SiC layer 1b obtained by phase-transitioning a 3C-SiC layer 1a to 4H-SiC or 6H-SiC, on which a desired semiconductor device is formed. Of course, the semiconductor device can also be made into chips by dicing.

[0067] By providing a semiconductor device with SiC substrate 100 that is inexpensive, high quality, and highly reliable, and that is capable of both large diameter and various polytypes of SiC, the semiconductor device also becomes inexpensive, high quality, and reliable.

[0068] Next, an outline of a method for manufacturing SiC substrate 100 according to the present invention will be described with reference to FIG. First, a growth substrate 21 is prepared, in which a 3C-SiC layer 1a is grown on a silicon substrate. Specifically, first, a single crystal silicon substrate 1 is prepared as shown in FIG. 2(a). In this case, a diameter of 300 mm or more is preferable since there is no large-diameter SiC substrate. In addition, considering that the atomic density (atomic distance) of the surface is closer to that of SiC, the surface orientation is set to 100 mm. <111> It is preferable to set the above.

[0069] On this silicon substrate 1, epitaxial growth is performed to grow a 3C-SiC layer 1a as shown in FIG. 2(b), thereby obtaining a growth substrate 21.

[0070] The thickness of the 3C-SiC layer 1a grown on the silicon substrate 1 is preferably 20 nm to 200 nm. This ensures a thickness of the 3C-SiC layer 1a necessary for forming devices, etc., while allowing the acceleration voltage during hydrogen ion implantation to be reduced when delamination is performed using hydrogen ion implantation in the subsequent removal step. Also, warping of the growth substrate 21 can be suppressed.

[0071] It is more preferable that the thickness of the 3C-SiC layer 1a is 50 to 100 nm. This is advantageous in that the acceleration voltage during hydrogen ion implantation can be reduced when performing delamination using hydrogen ion implantation in the removal step while ensuring the thickness of the 3C-SiC layer 1a required for forming devices, etc. It is also advantageous in that warping of the growth substrate 21 can be suppressed.

[0072] Furthermore, if the surface roughness Ra of the 3C-SiC layer 1a grown on the silicon substrate is 1 nm or less, the adhesion between the 3C-SiC layer 1a and the support substrate 3 can be further improved when the 3C-SiC layer 1a and the support substrate 3 are bonded in a later process.

[0073] Furthermore, by forming the growth substrate 21 into a convex shape on the 3C-SiC layer 1a side, it is possible to reduce the unbonded portion in the subsequent bonding process. Note that the convex shape here refers to a shape with a BOW of 10 μm or more, for example.

[0074] 2(c), hydrogen ions are implanted into the interface between the 3C-SiC layer 1a and the silicon substrate 1 to form a hydrogen embrittlement layer 2. By adjusting the acceleration voltage of the ion implantation, the hydrogen embrittlement layer 2 can be formed to a specified depth even if the thickness of the 3C-SiC layer 1a changes.

[0075] More specifically, hydrogen ions are implanted from the 3C-SiC layer 1a side into a growth substrate 21 having a 3C-SiC layer 1a grown on a silicon substrate 1. At this time, if the 3C-SiC layer 1a is thin, about 100 nm, a large current ion implanter can be used to implant the hydrogen ions required for delamination in a short time.

[0076] In this case, the hydrogen embrittlement layer 2 is formed at the interface between the 3C-SiC layer 1a and the silicon substrate 1, and more specifically, it is desirably formed on the silicon substrate 1 directly below the 3C-SiC layer 1a. In this way, the process of removing the excess silicon layer becomes unnecessary in the next removal process. In the following explanation, unless otherwise specified, the case where the hydrogen embrittlement layer 2 is formed on the silicon substrate 1 directly below the 3C-SiC layer 1a will be explained as an example.

[0077] 2(d), a substrate other than the silicon substrate 1 on which 3C-SiC is grown is prepared as a support substrate 3. Taking into consideration costs, etc., this support substrate 3 is made of sintered SiC or polycrystalline SiC, etc., and is called a poly-SiC substrate.

[0078] In this way, by using a poly-SiC substrate as the support substrate 3, it is possible to obtain a large diameter of 300 mm or more, which is not possible to obtain by the sublimation method, and it is possible to significantly reduce costs. It has also been reported that using a poly-SiC substrate as the support substrate 3 is effective in terms of reducing the substrate resistance (Non-Patent Document 2), and is extremely effective when considering a vertical device in addition to the cost.

[0079] Next, as shown in FIG. 2(e), the hydrogen ion implanted surface of the growth substrate 21 in which the 3C-SiC layer 1a has been grown on the silicon substrate 1, i.e., the 3C-SiC layer 1a, is bonded to a support substrate 3 to obtain a bonded substrate 10 (bonding process).

[0080] During bonding, the 3C-SiC layer 1a and the support substrate 3 may be directly bonded at room temperature, or a thin silicon film may be formed by sputtering on the surfaces of the 3C-SiC layer 1a and the support substrate 3 before the bonding process (sputtering process), and then these may be bonded by room temperature bonding or the like to obtain the bonded substrate 10. In other words, by sputtering silicon on the bonding surfaces and bonding via this, it is possible to bond the SiC substrates together without leaving any unbonded portions.

[0081] A specific sputtering method is to use silicon as a target and irradiate Ar ions onto the target to form a film. This method is effective because it does not require high-temperature heating of the substrate and does not damage the SiC surface at the bonding surface. It is known that the roughness of the bonding surface during bonding is preferably 1 nm or less (Non-Patent Document 3).

[0082] Next, as shown in FIG. 2(f), the bonded substrate 10 is heat-treated to perform peeling at the hydrogen embrittlement layer 2 into which hydrogen ions have been implanted, thereby removing the silicon substrate 1 from the bonded substrate 10 (removal step). Alternatively, a method of inserting a thin metal object from the side to peel it off may also be used.

[0083] The heat treatment temperature at this time is sufficient at about 400 to 600° C. because the hydrogen embrittlement layer 2 is formed in the silicon layer. As described above, as a method other than heating to separate the hydrogen embrittlement layer 2, it is also possible to simply insert a thin metal blade into the hydrogen embrittlement layer 2.

[0084] By peeling in this manner, the 3C-SiC layer 1a on the surface of the silicon substrate 1 on which the 3C-SiC layer 1a is grown is transferred onto the support substrate 3, and the silicon substrate 1 becomes the peeled substrate 11, which is the substrate after the surface 3C-SiC layer 1a has been peeled off, and is removed from the bonded substrate 10.

[0085] In this way, by removing the silicon substrate 1 in the removal step by utilizing the embrittlement effect caused by hydrogen injection into the interface between the silicon substrate 1 and the 3C-SiC layer 1a, post-treatment such as removing the etching solution or abrasive adhering to the bonded substrate 10 during the etching or grinding / polishing by cleaning or the like is not required, as compared to removing the silicon substrate 1 from the bonded substrate 10 by etching or grinding / polishing. However, the removal step can also be performed by etching or grinding / polishing as described below.

[0086] Note that an epitaxial step of epitaxially growing 3C-SiC may be further performed on the surface of the 3C-SiC layer 1a after the removing step, in which case the 3C-SiC layer 1a can be made thicker.

[0087] The bonded substrate 10 from which the silicon substrate 1 has been removed is then heat-treated at high temperature, causing the 3C-SiC layer 1a transferred onto the support substrate 3 to undergo a phase transition to 4H-SiC or 6H-SiC, forming a SiC layer 1b as shown in Figure 2(g), ultimately obtaining a SiC substrate 100 having a SiC layer 1b with a different plane orientation than before the heat treatment (heat treatment process).

[0088] 3C-SiC is stable at low temperatures, and changes to 4H-SiC and then 6H-SiC as the heating temperature is increased (Non-Patent Document 4). Thus, it can be seen that there is an advantage to using 3C-SiC as the starting material not only because it can be grown on the silicon substrate 1, but also because it can be subjected to a phase transition to 4H-SiC and 6H-SiC.

[0089] In this case, in order to cause a phase transition of the SiC layer 1b to a 4H-SiC layer, the heating temperature is preferably in the range of 1900 to 2100°C, and more preferably in the range of 2000 to 2050°C.

[0090] For the heating temperature, see Non-Patent Document 4. When the SiC layer 1b is to undergo a phase transition to a 6H-SiC layer, the temperature is preferably 2200° C. or higher, and more preferably 2300° C. or higher.

[0091] Incidentally, even when an epitaxial process for epitaxially growing 3C-SiC is further performed on the surface of the 3C-SiC layer 1a after the removal process, it is possible to perform a heat treatment to cause a phase transition of the 3C-SiC layer 1a to 4H-SiC or 6H-SiC, and finally obtain the SiC substrate 100. In this case, the 3C-SiC layer 1a can be made thicker, and therefore the SiC layer 1b can also be made thicker.

[0092] The atmosphere in the heating step is, for example, a hydrogen atmosphere or an Ar (argon) atmosphere. The heating time may be the time required for the phase transition, for example, about 1 hour. The upper limit of the heating time is, for example, 20 hours. The pressure in the heating step is, for example, atmospheric pressure.

[0093] A device formation process is performed on the SiC substrate 100 manufactured by the above process to form a semiconductor device, thereby manufacturing the semiconductor device.

[0094] Next, as another example of a manufacturing flow of the method for manufacturing SiC substrate 100 of the present invention, a manufacturing method that does not involve peeling at hydrogen embrittlement layer 2 due to hydrogen ion implantation will be described with reference to Fig. 3. First, a growth substrate 21 in which a 3C-SiC layer 1a is grown on a silicon substrate 1 is prepared.

[0095] Specifically, first, a silicon substrate 1 is prepared as shown in FIG. 3(a). In this case, a diameter of 300 mm or more is preferable since no large-diameter SiC exists. In addition, considering that the atomic density (atomic distance) of the surface is closer to that of SiC, the surface orientation of the silicon substrate 1 is <111> It is preferable to set the above.

[0096] Next, as shown in FIG. 3(b), a 3C-SiC layer 1a is grown on the silicon substrate 1 by epitaxial growth, thereby obtaining a growth substrate 21.

[0097] 3(c), a substrate other than the silicon substrate 1 on which 3C-SiC is grown is prepared as the support substrate 3. Taking into consideration costs, etc., this support substrate 3 is a poly-SiC substrate made of sintered SiC or polycrystalline SiC, for example.

[0098] 3(d), the surface of the 3C-SiC layer 1a of the silicon substrate 1 on which 3C-SiC has been grown is bonded to a support substrate 3 (bonding step). In this case, the surface of the 3C-SiC layer 1a may be directly bonded to the support substrate 3, or a silicon thin film may be formed on the surface of the 3C-SiC layer 1a and the support substrate 3, and then these may be bonded to obtain a bonded substrate 10.

[0099] An example of the bonding method is room temperature bonding. The silicon thin film before bonding can be formed by sputtering, which uses silicon as a target and irradiates Ar ions onto the target to form a film, which is effective because it does not require high-temperature heating of the substrate and does not damage the SiC surface of the bonding surface.

[0100] 3(e), the silicon substrate 1 of the bonded substrate 10 is removed by grinding and polishing, etching, etc. By removing the silicon substrate 1 in this manner, the 3C-SiC layer 1a on the surface of the silicon substrate 1 on which the 3C-SiC is grown is transferred onto the support substrate 3, and the bonded substrate 10 from which the silicon substrate 1 has been removed can be obtained.

[0101] By subjecting the bonded substrate 10 from which the silicon substrate 1 has been removed in this manner to a high-temperature heat treatment, the 3C-SiC layer 1a transferred onto the support substrate 3 undergoes a phase transition to 4H-SiC or 6H-SiC, forming a SiC layer 1b as shown in Figure 3(f), and finally, the SiC substrate 100 is obtained.

[0102] At this time, it is also possible to first epitaxially grow 3C-SiC on the 3C-SiC layer 1a, and then perform a heat treatment to cause a phase transition to 4H-SiC or 6H-SiC, thereby finally obtaining the SiC substrate 100.

[0103] In this way, in the present invention, a 3C-SiC layer 1a grown on a large-diameter silicon substrate 1 having a diameter of 300 mm or more is bonded to a poly-SiC substrate, which is a support substrate 3, and the silicon substrate 1 is removed to produce a substrate made only of SiC. By further performing heat treatment and causing a phase transition of the 3C-SiC layer 1a, it is possible to provide SiC substrates 100 with various surface orientations at a lower cost, in a higher quality, and in a larger diameter.

[0104] Furthermore, by transferring the 3C-SiC layer 1a grown on a silicon substrate to a poly-SiC substrate and then undergoing a phase transition, not only can a large-diameter SiC substrate 100 be provided, but it also becomes possible to manufacture vertical devices that were not possible with 3C-SiC on Si. EXAMPLES

[0105] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[0106] Example 1 First, the silicon substrate 1 has a main surface with a plane orientation of <111> A single crystal substrate with a diameter of 300 mm, a thickness of 775 μm, a p-type, and a resistivity of 10 Ω·cm was prepared, and a 3C-SiC layer 1a was grown to 100 nm on the substrate in a low-pressure CVD furnace at 1080°C / 5 Torr (666.612 Pa) using trimethylsilane as the source gas. In addition, hydrogen ions were injected at an acceleration energy of 10 keV into the interface between the silicon substrate 1 and the 3C-SiC layer 1a at a thickness of 1.0×10 17 atoms / cm 2 Injected.

[0107] Next, a poly-SiC substrate with the same diameter as the silicon substrate 1 was prepared as the support substrate 3. This substrate and the surface on which the 3C-SiC layer 1a had been grown were irradiated with Ar ions using silicon as a target to form a silicon film on both surfaces by sputtering. The silicon thin film had a thickness of 20 nm. Then, room temperature bonding was performed to obtain a bonded substrate 10. Next, a heat treatment was performed at 650° C. to peel off and remove the silicon substrate 1 from the bonded substrate 10.

[0108] As an epitaxial process, a low-pressure CVD apparatus was used to epitaxially grow 3C-SiC on this bonded substrate 10 using trimethylsilane as the raw material gas, and then annealing was performed in a hydrogen atmosphere at 2000°C for 1 hour, thereby obtaining a SiC substrate 100 having a SiC layer 1b in which the 3C-SiC layer 1a had undergone a phase transition to 4H-SiC.

[0109] Example 2 First, the silicon substrate 1 has a main surface with a plane orientation of <111> A single crystal substrate with a diameter of 300 mm, a thickness of 775 μm, p-type and a resistivity of 10 Ω·cm was prepared, and a 3C-SiC layer 1a of 100 nm was grown on it in a low-pressure CVD furnace under conditions of 1080°C / 5 Torr (666.612 Pa) using trimethylsilane as the source gas.

[0110] Next, a poly-SiC substrate with the same diameter as the silicon substrate 1 was prepared as the support substrate 3. This substrate and the surface on which the 3C-SiC had been grown were irradiated with Ar ions using silicon as a target to form a silicon film by sputtering on both. The silicon thin film at this time was 20 nm.

[0111] Thereafter, the silicon thin films formed on both substrates were bonded at room temperature to obtain a bonded substrate 10. Next, the silicon substrate 1 of the bonded substrate 10 was etched and removed in a spin etching device using hydrofluoric and nitric acid as an etching solution.

[0112] On the bonded substrate 10 from which the silicon substrate 1 had been removed, a low-pressure CVD apparatus was used as an epitaxial process to perform epitaxial growth of 3C-SiC using trimethylsilane as the raw material gas, and then annealing was performed in a hydrogen atmosphere at 2000°C for 1 hour, thereby obtaining a SiC substrate 100 having a SiC layer 1b in which the 3C-SiC layer 1a had undergone a phase transition to 4H-SiC.

[0113] As described above, according to an embodiment of the present invention, a 3C-SiC layer 1a grown on a silicon substrate was transferred to a poly-SiC substrate, and the 3C-SiC layer 1a was then heated to cause a phase transition, thereby producing a large-diameter SiC substrate 100 having a 4H-SiC layer.

[0114] The present specification includes the following aspects. [1]: A method for manufacturing a SiC substrate, comprising the steps of: a bonding step of bonding a 3C-SiC layer of a growth substrate, in which a 3C-SiC layer is grown on a silicon substrate, to a poly-SiC substrate serving as a support substrate to obtain a bonded substrate; a removal step of removing the silicon substrate from the bonded substrate; and a heat treatment step of further performing a heat treatment on the bonded substrate after the removal step to cause a phase transition of the 3C-SiC layer to obtain a SiC substrate having a SiC layer having a different plane orientation from that before the heat treatment. [2]: The surface orientation of the silicon substrate is <111> The method for producing a SiC substrate according to [1] above, [3]: The method for producing a SiC substrate according to [1] or [2] above, wherein the thickness of the 3C-SiC layer grown on the silicon substrate is 20 nm to 200 nm. [4]: The method for producing a SiC substrate according to any one of [1] to [3] above, characterized in that the 3C-SiC layer grown on the silicon substrate has a thickness of 50 to 100 nm. [5]: The method for producing a SiC substrate according to any one of [1] to [4] above, characterized in that the 3C-SiC layer grown on the silicon substrate has a surface roughness Ra of 1 nm or less. [6]: The method for producing a SiC substrate according to any one of [1] to [5] above, wherein the growth substrate has an upwardly convex substrate shape. [7]: The method for manufacturing a SiC substrate according to any one of [1] to [6] above, characterized in that the removal of the silicon substrate in the removal step is performed by peeling off the silicon substrate by utilizing the embrittlement effect caused by hydrogen injection into the interface between the silicon substrate and the 3C-SiC layer. [8]: The method for producing a SiC substrate according to any one of [1] to [6] above, wherein the removal of the silicon substrate in the removing step is performed by etching or grinding / polishing. [9]: The method for manufacturing a SiC substrate according to any one of [1] to [8] above, characterized in that it includes a sputtering step of sputtering a silicon thin film onto the surfaces of the 3C-SiC layer and the poly-SiC substrate before performing the bonding step.

[10] : The method for manufacturing a SiC substrate according to any one of [1] to [9] above, further comprising an epitaxial step of epitaxially growing 3C-SiC on the surface of the 3C-SiC layer after the removal step.

[11] : The method for manufacturing a SiC substrate according to any one of [1] to

[10] above, characterized in that in the heat treatment step, the bonded substrate is heat-treated at a temperature in the range of 1900 to 2100°C to cause a phase transition of the 3C-SiC layer to a 4H-SiC layer.

[12] : The method for manufacturing a SiC substrate according to any one of [1] to

[10] above, characterized in that in the heat treatment step, the bonded substrate is heat-treated at a temperature in the range of 2000 to 2050°C to cause a phase transition of the 3C-SiC layer to a 4H-SiC layer.

[13] : The method for manufacturing a SiC substrate according to any one of [1] to

[10] above, characterized in that in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2200°C or higher to cause a phase transition of the 3C-SiC layer to a 6H-SiC layer.

[14] : The method for manufacturing a SiC substrate according to any one of [1] to

[10] above, characterized in that in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2300°C or higher to cause a phase transition of the 3C-SiC layer to a 6H-SiC layer.

[15] : A method for producing a semiconductor device, comprising: a device formation step of forming a semiconductor device on the SiC substrate produced by any one of the production methods described above in [1] to

[14] to obtain a semiconductor device.

[16] : A SiC substrate comprising a poly-SiC substrate and a SiC layer bonded to the poly-SiC substrate, wherein the SiC layer is a 4H-SiC layer or a 6H-SiC layer.

[17] : A semiconductor device comprising the SiC substrate described in

[16] above.

[0115] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0116] 1...silicon substrate, 1a...3C-SiC layer, 1b...SiC layer, 2...hydrogen embrittlement layer, 3...support substrate, 10...bonded substrate, 11...peeled substrate, 21...growth substrate, 100...SiC substrate.

Claims

1. A method for manufacturing a SiC substrate, comprising the steps of: a bonding step of bonding a 3C-SiC layer of a growth substrate, in which a 3C-SiC layer is grown on a silicon substrate, to a poly-SiC substrate serving as a support substrate to obtain a bonded substrate; a removing step of removing the silicon substrate from the bonded substrate; a heat treatment step of further performing a heat treatment on the bonded substrate after the removing step, thereby causing a phase transition of the 3C-SiC layer to obtain a SiC substrate having a SiC layer having a plane orientation different from that before the heat treatment; A method for manufacturing a SiC substrate, comprising:

2. 2. The method for producing a SiC substrate according to claim 1, wherein the surface orientation of the silicon substrate is <111>.

3. 2. The method for producing a SiC substrate according to claim 1, wherein the 3C-SiC layer grown on the silicon substrate has a thickness of 20 nm to 200 nm.

4. 2. The method for producing a SiC substrate according to claim 1, wherein the 3C-SiC layer grown on the silicon substrate has a thickness of 50 to 100 nm.

5. 2. The method for producing a SiC substrate according to claim 1, wherein the 3C-SiC layer grown on the silicon substrate has a surface roughness Ra of 1 nm or less.

6. 2. The method for producing a SiC substrate according to claim 1, wherein the growth substrate has an upwardly convex substrate shape.

7. 2. The method for manufacturing a SiC substrate according to claim 1, wherein the removal of the silicon substrate in the removal step comprises peeling off the silicon substrate by utilizing an embrittlement effect caused by hydrogen injection into an interface between the silicon substrate and the 3C-SiC layer.

8. 2. The method for manufacturing a SiC substrate according to claim 1, wherein the silicon substrate is removed in the removing step by etching or grinding / polishing.

9. 2. The method for manufacturing a SiC substrate according to claim 1, further comprising a sputtering step of sputtering a silicon thin film on surfaces of the 3C-SiC layer and the poly-SiC substrate before the bonding step.

10. 2. The method for producing a SiC substrate according to claim 1, further comprising an epitaxial step of epitaxially growing 3C-SiC on the surface of the 3C-SiC layer after the removal step.

11. 11. The method for manufacturing a SiC substrate according to claim 1, wherein in the heat treatment step, the bonded substrate is heat-treated at a temperature in the range of 1900 to 2100° C. to cause a phase transition of the 3C-SiC layer to a 4H-SiC layer.

12. 11. The method for manufacturing a SiC substrate according to claim 1 or 10, wherein in the heat treatment step, the bonded substrate is heat treated at a temperature in the range of 2000 to 2050° C. to cause a phase transition of the 3C-SiC layer to a 4H-SiC layer.

13. 11. The method for manufacturing a SiC substrate according to claim 1 or 10, wherein in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2200° C. or higher to cause a phase transition of the 3C-SiC layer to a 6H-SiC layer.

14. 11. The method for manufacturing a SiC substrate according to claim 1 or 10, wherein in the heat treatment step, the bonded substrate is subjected to a heat treatment at 2300° C. or higher to cause a phase transition of the 3C-SiC layer to a 6H-SiC layer.

15. 2. A method for producing a semiconductor device, comprising the step of forming a semiconductor device on the SiC substrate produced by the method according to claim 1 to obtain a semiconductor device.

16. A SiC substrate including a poly-SiC substrate and a SiC layer bonded to the poly-SiC substrate, The SiC substrate, wherein the SiC layer is a 4H-SiC layer or a 6H-SiC layer.

17. A semiconductor device comprising the SiC substrate according to claim 16.

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