Method for processing SiC substrate, method for removing process-modified layer of SiC substrate, and method for reducing surface roughness of SiC substrate

Abstract

Provided is a novel method for processing a SiC substrate. Provided is a method for processing a SiC substrate, the method comprising: an annealing step (S2) for heating a SiC substrate (1) in an inert gas atmosphere; and an etching step (S3) in which the SiC substrate (1) that has been subjected to the annealing step (S2) is etched in an atmosphere containing a gas comprising either or both of Si element and C element.

Description

Technical Field

[0001] This invention relates to a method for processing SiC substrates. Background Technology

[0002] In the manufacturing of SiC semiconductor devices, it is crucial to process the SiC substrate (As-sliced ​​substrate) cut from the ingot to achieve atomic-level surface planarization. Existing SiC substrate processing involves stages such as grinding and lapping to gradually reduce surface roughness.

[0003] However, mechanical damage is known to remain on SiC substrates processed in this way. This damage manifests not only as surface scratches but also as crystalline strain extending from the surface to a certain depth. These damaged layers are called "processing alteration layers" and have a significant adverse impact on the performance of SiC semiconductor devices.

[0004] The inventors have developed a method for reducing surface roughness through non-contact processing, which differs from the stages of conventional processing. Patent Document 1 describes a method in which a SiC substrate is etched by heating it under a vapor pressure environment containing both Si and C elements, thereby reducing macroscopic step clustering on the substrate surface. Furthermore, Patent Document 2 describes a method in which a SiC substrate is etched by heating it under a vapor pressure environment containing both Si and C elements, thereby reducing the processing-induced alteration layer on the substrate.

[0005] Existing technical documents

[0006] Patent documents Patent Document 1: International Publication No. 2020 / 179793 Patent Document 2: International Publication No. 2020 / 179794 Summary of the Invention The problem to be solved by the present invention The later stages of traditional machining can be replaced by the methods described in Patent Documents 1 and 2. However, in the initial stage of machining, due to the very high surface roughness, it is required to substantially reduce the surface roughness. Therefore, it is understood in the art that the initial stage of machining must still be carried out through contact treatments such as grinding and lapping.

[0007] Under these circumstances, the inventors discovered the following problem: In the initial stages of processing, a processing-modified layer forms on the SiC substrate and expands, making it difficult to remove this layer in the later stages of processing. Furthermore, the significant material loss occurring in the initial stages of processing is a major reason for the reduced sustainability of SiC semiconductor device manufacturing.

[0008] Therefore, the problem of this invention is to provide a new processing method for SiC substrates. More specifically, the problem of this invention is to provide a non-contact processing method that can replace the initial stage of existing SiC substrate processing. Furthermore, the problem of this invention is to provide a processing method that can reduce material loss occurring in the initial stage of this processing.

[0009] Solution to the problem One embodiment of the present invention for addressing the above-mentioned problems is a method for processing SiC substrates, which is described in [1] to

[82] .

[0010] Method [1] is a method for processing a SiC substrate, comprising: an annealing process in which the SiC substrate is heated in an inert gas environment; and an etching process in which the SiC substrate after the annealing process is etched in an environment containing one or both of Si and C elements. In Method [1], by strongly promoting both sublimation and recrystallization reactions on the surface of the SiC substrate, atomic exchange can be intensely carried out between the surface layer of the SiC substrate and the environment, that is, the metabolism of atoms constituting the surface layer of the SiC substrate can be strongly promoted. As a result, the processing-modified layer contained in the surface layer can be removed in a short time. Furthermore, during the metabolism process, the surface layer of the SiC substrate is flattened, thereby achieving a SiC substrate with low surface roughness. Subsequently, by etching the SiC substrate, even a SiC substrate with high surface roughness can achieve a SiC substrate with significantly low surface roughness through non-contact processing.

[0011] Method [2] is a method for processing a SiC substrate according to Method [1], wherein the annealing process includes heating the SiC substrate inside a crucible made of SiC, and the interior of the crucible is maintained in the inert gas environment during the annealing process.

[0012] Method [3] is a SiC substrate processing method according to Method [1] or [2], wherein the annealing process includes: etching one surface of the SiC substrate while growing another surface of the SiC substrate.

[0013] Method [4] is a SiC substrate processing method according to Method [3], wherein the annealing process includes: making the etching amount at one surface approximately the same as the growth amount at another surface, so that the substrate thickness of the SiC substrate is approximately the same before and after the annealing process.

[0014] Method [5] is a SiC substrate processing method according to method [3] or [4], wherein the annealing process includes: increasing the substrate thickness of the SiC substrate before and after the annealing process by making the amount of etching at one surface smaller than the amount of growth at another surface.

[0015] Method [6] is a method for processing a SiC substrate according to any one of methods [2] to [5], wherein, in the annealing process, the crucible has a substrate with an opening and a lid, and the interior of the crucible is formed by covering the opening of the substrate with the lid.

[0016] Method [7] is a method for processing a SiC substrate according to any one of methods [2] to [6], wherein, in the annealing process, the SiC substrate is supported by a substrate support.

[0017] Method [8] is a method for processing a SiC substrate according to any one of methods [2] to [7], wherein, in the annealing process, the pressure inside the crucible is 1 kPa or more.

[0018] Method [9] is a method for processing a SiC substrate according to any one of methods [2] to [7], wherein, in the annealing process, the pressure inside the crucible is 5 kPa or more.

[0019] Method

[10] is a method for processing a SiC substrate according to any one of methods [2] to [7], wherein, in the annealing process, the pressure inside the crucible is 10 kPa or more.

[0020] Method

[11] is a method for processing a SiC substrate according to any one of methods [2] to

[10] , wherein, in the annealing process, the temperature inside the crucible is above 1800°C.

[0021] Method

[12] is a method for processing a SiC substrate according to any one of methods [2] to

[10] , wherein, in the annealing process, the temperature inside the crucible is above 2000°C.

[0022] Method

[13] is a method for processing a SiC substrate according to any one of methods [2] to

[10] , wherein, in the annealing process, the temperature inside the crucible is above 2200°C.

[0023] Method

[14] is a method for processing a SiC substrate according to any one of methods [2] to

[13] , wherein, in the annealing process, the combination of pressure and temperature inside the crucible is a combination of 1 kPa or more and 1800°C or more.

[0024] Method

[15] is a method for processing a SiC substrate according to any one of methods [2] to

[13] , wherein, in the annealing process, the combination of pressure and temperature inside the crucible is a combination of 5 kPa or more and 2000°C or more.

[0025] Method

[16] is a method for processing a SiC substrate according to any one of methods [2] to

[13] , wherein, in the annealing process, the combination of pressure and temperature inside the crucible is a combination of 5 kPa or more and 2200°C or more.

[0026] Method

[17] is a method for processing a SiC substrate according to any one of methods [2] to

[13] , wherein, in the annealing process, the combination of pressure and temperature inside the crucible is a combination of 10 kPa or more and 2200°C or more.

[0027] Method

[18] is a method for processing a SiC substrate according to any one of methods [2] to

[17] , wherein, in the annealing process, a temperature gradient is formed inside the crucible in the direction penetrating the SiC substrate.

[0028] Method

[19] is a processing method for a SiC substrate according to method

[18] , wherein, in the annealing process, the temperature gradient is formed in a direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

[0029] Method

[20] is a method for processing a SiC substrate according to any one of methods [2] to

[19] , wherein the annealing process includes a containing process for containing a SiC substrate inside a crucible, wherein the crucible has a substrate having an opening and a lid, and the containing process includes: inserting a SiC substrate from the opening of the substrate and placing the lid on the substrate to cover the opening of the substrate, thereby containing the SiC substrate inside the crucible.

[0030] Method

[21] is a method for processing a SiC substrate according to any one of methods [2] to

[20] , wherein the annealing process includes a receiving process for receiving the SiC substrate inside a crucible, the receiving process including supporting the SiC substrate in the hollow portion inside the crucible using a substrate support member.

[0031] Method

[22] is a method for processing a SiC substrate according to any one of methods [2] to

[21] , wherein the annealing process includes a heating process of heating a crucible, the heating process including: heating the crucible to generate a raw material gas composed of one or two of Si and C elements from the crucible into the interior of the crucible.

[0032] Method

[23] is a method for processing a SiC substrate according to any one of methods [2] to

[22] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible and maintaining the pressure inside the crucible at 1 kPa or higher.

[0033] Method

[24] is a method for processing a SiC substrate according to any one of methods [2] to

[22] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible and maintaining the pressure inside the crucible at or above 5 kPa.

[0034] Method

[25] is a method for processing a SiC substrate according to any one of methods [2] to

[22] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible and maintaining the pressure inside the crucible at or above 10 kPa.

[0035] Method

[26] is a method for processing a SiC substrate according to any one of methods [2] to

[25] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: heating the crucible to maintain the internal temperature of the crucible above 1800°C.

[0036] Method

[27] is a method for processing a SiC substrate according to any one of methods [2] to

[25] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: heating the crucible to maintain the internal temperature of the crucible above 2000°C.

[0037] Method

[28] is a method for processing a SiC substrate according to any one of methods [2] to

[25] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: heating the crucible to maintain the internal temperature of the crucible above 2200°C.

[0038] Method

[29] is a method for processing a SiC substrate according to any one of methods [2] to

[28] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible to maintain the pressure inside the crucible at 1 kPa or higher; and heating the crucible to maintain the temperature inside the crucible at 1800°C or higher.

[0039] Method

[30] is a method for processing a SiC substrate according to any one of methods [2] to

[28] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible to maintain the pressure inside the crucible at 5 kPa or higher; and heating the crucible to maintain the temperature inside the crucible at 2000°C or higher.

[0040] Method

[31] is a method for processing a SiC substrate according to any one of methods [2] to

[28] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible to maintain the pressure inside the crucible at 5 kPa or higher; and heating the crucible to maintain the temperature inside the crucible at 2200°C or higher.

[0041] Method

[32] is a method for processing a SiC substrate according to any one of methods [2] to

[28] , wherein the annealing process includes a heating process for heating a crucible, the heating process including: introducing an inert gas into the interior of the crucible to maintain the pressure inside the crucible at 10 kPa or higher; and heating the crucible to maintain the temperature inside the crucible at 2200°C or higher.

[0042] Method

[33] is a method for processing a SiC substrate according to any one of methods [2] to

[32] , wherein the annealing process includes a heating process of heating a crucible, the heating process including: forming a temperature gradient inside the crucible in a direction penetrating the SiC substrate.

[0043] Method

[34] is a SiC substrate processing method according to method

[33] , wherein the heating process includes: forming a temperature gradient in a direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

[0044] Method

[35] is a method for processing a SiC substrate according to any one of methods [1] to

[34] , wherein a protective film is not formed on the surface of the SiC substrate during the annealing process.

[0045] Method

[36] is a method for processing a SiC substrate according to any one of methods [1] to

[35] , wherein the etching process includes heating the SiC substrate inside a crucible made of SiC, wherein the interior of the crucible is maintained in an environment containing a gas composed of one or both of Si and C elements.

[0046] Method

[37] is a method for processing a SiC substrate according to method

[36] , wherein, during the etching process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment.

[0047] Method

[38] is a method for processing a SiC substrate according to method

[37] , wherein, in the etching process, the temperature inside the crucible is above 1600°C and below 2000°C.

[0048] Method

[39] is a method for processing a SiC substrate according to method

[38] , wherein, in the etching process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process.

[0049] Method

[40] is a method for processing a SiC substrate according to method

[36] , wherein, during the etching process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

[0050] Method

[41] is a SiC substrate processing method according to method

[40] , wherein, in the etching process, the temperature inside the crucible is above 1800°C and below 2000°C.

[0051] Method

[42] is a SiC substrate processing method according to method

[41] , wherein, in the etching process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process.

[0052] Method

[43] is a method for processing a SiC substrate according to any one of methods

[36] to

[42] , wherein, in the etching process, inside the crucible, a temperature gradient is formed in the direction through the SiC substrate and in the direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

[0053] Method

[44] is a method for processing a SiC substrate according to any one of methods

[36] to

[39] or

[43] , wherein the etching process includes an etching containment process for containing the SiC substrate inside a crucible and an etching heating process for heating the crucible, the etching heating process including maintaining the interior of the crucible in a SiC-C equilibrium vapor pressure environment.

[0054] Method

[45] is a SiC substrate processing method according to Method

[44] , wherein the etching heating process includes: heating the crucible to generate a gas composed of one or two of Si and C elements from the crucible into the interior of the crucible, thereby maintaining the interior of the crucible in a SiC-C equilibrium vapor pressure environment.

[0055] Method

[46] is a SiC substrate processing method according to method

[44] or

[45] , wherein the etching heating process includes: heating the crucible to maintain the internal temperature of the crucible above 1600°C and below 2000°C.

[0056] Method

[47] is a SiC substrate processing method according to method

[46] , wherein the etching heating process includes: heating the crucible to maintain the internal temperature of the crucible below the internal temperature of the crucible in the annealing process.

[0057] Method

[48] is a method for processing a SiC substrate according to any one of methods

[36] or

[40] to

[43] , wherein the etching process includes an etching containment process for containing the SiC substrate inside a crucible and an etching heating process for heating the crucible, the etching heating process including maintaining the interior of the crucible in a SiC-Si equilibrium vapor pressure environment.

[0058] Method

[49] is a method for processing a SiC substrate according to Method

[48] , wherein the etching containment process includes: containing a Si gas source together with the SiC substrate inside the crucible, and the etching heating process includes: heating the crucible together with the Si gas source, so that a gas composed of one or two of Si and C elements is generated from the crucible into the interior of the crucible, while Si gas is generated from the Si gas source into the interior of the crucible, thereby maintaining the interior of the crucible in a SiC-Si equilibrium vapor pressure environment.

[0059] Method

[50] is a SiC substrate processing method according to method

[48] or

[49] , wherein the etching heating process includes: heating the crucible to maintain the internal temperature of the crucible above 1800°C and below 2000°C.

[0060] Method

[51] is a SiC substrate processing method according to Method

[50] , wherein the etching heating process includes: heating the crucible to maintain the internal temperature of the crucible below the internal temperature of the crucible in the annealing process.

[0061] Method

[52] is a method for processing a SiC substrate according to any one of methods

[36] to

[51] , wherein the etching process includes an etching heating process for heating a crucible, the etching heating process including: forming a temperature gradient inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

[0062] Method

[53] is a method for processing a SiC substrate according to any one of methods

[36] to

[52] , wherein the processing method does not include a mechanical processing step of the SiC substrate after the etching step.

[0063] Method

[54] is a method for processing a SiC substrate according to any one of methods

[36] to

[53] , wherein the etching process is performed at least twice, including a first etching process and a second etching process, the first etching process including etching the SiC substrate after the annealing process, the second etching process including etching the SiC substrate after the first etching process, in the first etching process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment, and in the second etching process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

[0064] Method

[55] is a SiC substrate processing method according to Method

[54] , wherein, in the first etching process, the temperature inside the crucible is above 1600°C and below 2000°C, and in the second etching process, the temperature inside the crucible is above 1800°C and below 2000°C.

[0065] Method

[56] is a SiC substrate processing method according to method

[55] , wherein, in the first etching step, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing step, and in the second etching step, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing step and higher than the temperature inside the crucible in the first etching step.

[0066] Method

[57] is a method for processing a SiC substrate according to any one of methods

[54] to

[56] , wherein, in the first etching step, a temperature gradient is formed inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side, and in the second etching step, a temperature gradient is formed inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

[0067] Method

[58] is a method for processing a SiC substrate according to any one of methods

[54] to

[57] , wherein the processing method does not include a mechanical processing step of the SiC substrate after the second etching step.

[0068] Method

[59] is a method for processing a SiC substrate according to any one of methods [1] to

[58] , and further includes a growth process of growing the SiC substrate that has undergone the etching process in an environment containing a gas composed of one or two of Si and C elements.

[0069] Method

[60] is a method for processing a SiC substrate according to method

[59] , wherein the growth process includes heating the SiC substrate inside a crucible made of SiC, wherein the interior of the crucible is maintained in an environment containing a gas composed of one or both of Si and C elements.

[0070] Method

[61] is a method for processing a SiC substrate according to method

[60] , wherein, during the growth process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment.

[0071] Method

[62] is a SiC substrate processing method according to method

[61] , wherein, in the growth process, the internal temperature of the crucible is above 1600°C and below 2000°C.

[0072] Method

[63] is a SiC substrate processing method according to method

[62] , wherein, in the growth process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process.

[0073] Method

[64] is a method for processing a SiC substrate according to method

[60] , wherein, during the growth process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

[0074] Method

[65] is a method for processing a SiC substrate according to method

[64] , wherein, in the growth process, the temperature inside the crucible is above 1800°C and below 2000°C.

[0075] Method

[66] is a SiC substrate processing method according to method

[65] , wherein, in the growth process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process.

[0076] Method

[67] is a method for processing a SiC substrate according to any one of methods

[60] to

[66] , wherein, in the growth process, inside the crucible, a temperature gradient is formed in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the Si surface side of the SiC substrate toward the C surface side.

[0077] Method

[68] is a method for processing a SiC substrate according to any one of methods

[60] to

[63] or

[67] , wherein the growth process includes a growth containment process for containing the SiC substrate inside a crucible and a growth heating process for heating the crucible, the growth heating process including maintaining the interior of the crucible in a SiC-C equilibrium vapor pressure environment.

[0078] Method

[69] is a method for processing a SiC substrate according to method

[68] , wherein the growth heating process includes: heating a crucible to generate a gas composed of one or both of Si and C elements from the crucible into the interior of the crucible, thereby maintaining the interior of the crucible in a SiC-C equilibrium vapor pressure environment.

[0079] Method

[70] is a SiC substrate processing method according to method

[68] or

[69] , wherein the growth heating process includes: heating the crucible to maintain the internal temperature of the crucible above 1600°C and below 2000°C.

[0080] Method

[71] is a SiC substrate processing method according to method

[70] , wherein the growth heating process includes: heating the crucible to maintain the internal temperature of the crucible below the internal temperature of the crucible in the annealing process.

[0081] Method

[72] is a method for processing a SiC substrate according to any one of methods

[60] or

[64] to

[67] , wherein the growth process includes a growth containment process for containing the SiC substrate inside a crucible and a growth heating process for heating the crucible, the growth heating process including maintaining the interior of the crucible in a SiC-Si equilibrium vapor pressure environment.

[0082] Method

[73] is a method for processing a SiC substrate according to Method

[72] , wherein the growth containment process includes: containing a Si gas source together with the SiC substrate inside the crucible, and the growth heating process includes: heating the crucible together with the Si gas source, so that a gas composed of one or two of Si and C elements is generated from the crucible into the interior of the crucible, while Si gas is generated from the Si gas source into the interior of the crucible, thereby maintaining the interior of the crucible in a SiC-Si equilibrium vapor pressure environment.

[0083] Method

[74] is a SiC substrate processing method according to method

[72] or

[73] , wherein the growth heating process includes: heating the crucible to maintain the internal temperature of the crucible above 1800°C and below 2000°C.

[0084] Method

[75] is a SiC substrate processing method according to method

[74] , wherein the growth heating process includes: heating the crucible to maintain the internal temperature of the crucible below the internal temperature of the crucible in the annealing process.

[0085] Method

[76] is a method for processing a SiC substrate according to any one of methods

[60] to

[75] , wherein the growth process includes a growth heating process for heating a crucible, the growth heating process including: forming a temperature gradient inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the Si surface side of the SiC substrate toward the C surface side.

[0086] Method

[77] is a method for processing a SiC substrate according to any one of methods

[60] to

[76] , wherein the processing method does not include a mechanical processing step of the SiC substrate after the growth step.

[0087] Method

[78] is a method for processing a SiC substrate according to any one of methods

[60] to

[77] , wherein the growth process is performed at least twice, including a first growth process and a second growth process, the first growth process including growing a SiC substrate that has undergone the etching process, the second growth process including growing a SiC substrate that has undergone the first growth process, in the first growth process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment, and in the second growth process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

[0088] Method

[79] is a SiC substrate processing method according to Method

[78] , wherein, in the first growth process, the internal temperature of the crucible is above 1600°C and below 2000°C, and in the second growth process, the internal temperature of the crucible is above 1800°C and below 2000°C.

[0089] Method

[80] is a SiC substrate processing method according to method

[79] , wherein, in the first growth process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process, and in the second growth process, the temperature inside the crucible is lower than the temperature inside the crucible in the annealing process and higher than the temperature inside the crucible in the first growth process.

[0090] Method

[81] is a method for processing a SiC substrate according to any one of methods

[78] to

[80] , wherein, in the first growth step, a temperature gradient is formed inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the Si surface side of the SiC substrate toward the C surface side, and in the second growth step, a temperature gradient is formed inside the crucible in a direction penetrating the SiC substrate and in a direction in which the temperature decreases from the Si surface side of the SiC substrate toward the C surface side.

[0091] Method

[82] is a method for processing a SiC substrate according to any one of methods

[78] to

[81] , wherein the processing method does not include a mechanical processing step of the SiC substrate after the second etching step.

[0092] In addition, one of the embodiments of the present invention for achieving the above-mentioned problem is a method for removing the processed modified layer of the SiC substrate, which is the method described below

[83] to

[85] .

[0093] Method

[83] is a method for removing a processing altered layer from a SiC substrate, comprising: performing any one of methods [1] to

[82] on a SiC substrate having a processing altered layer to remove the processing altered layer.

[0094] Method

[84] is a method for removing the processed modified layer of a SiC substrate according to method

[83] , comprising: performing any one of methods [1] to

[82] on a SiC substrate on which the processed modified layer has been formed by mechanical processing.

[0095] Method

[85] is a method for removing the processed modified layer of a SiC substrate according to method

[83] or

[84] , wherein the annealing process includes: performing atomic exchange between the surface layer of the SiC substrate and an inert gas environment to remove the processed modified layer.

[0096] In addition, one embodiment of the present invention for achieving the above-mentioned problem is a method for reducing the surface roughness of a SiC substrate, which is the method described below

[86] to

[88] .

[0097] Method

[86] is a method for reducing the surface roughness of a SiC substrate, comprising: performing any one of methods [1] to

[82] on a SiC substrate with an arithmetic mean roughness Ra of 15 nm or more on the Si surface to reduce the arithmetic mean roughness Ra.

[0098] Method

[87] is a method for reducing the surface roughness of a SiC substrate according to method

[86] , comprising: performing any one of methods [1] to

[82] on a mechanically treated SiC substrate.

[0099] Method

[88] is a method for reducing the surface roughness of a SiC substrate according to method

[86] or

[87] , wherein the annealing process includes: performing atomic exchange between the surface layer of the SiC substrate and an inert gas environment to make the surface layer smooth.

[0100] Effects of the present invention According to the present invention, a novel processing method for SiC substrates can be provided. Specifically, a non-contact processing method can be provided to replace the initial stage of existing SiC substrate processing. Furthermore, a processing method that reduces material loss occurring in the initial stage of this processing can be provided. Attached Figure Description

[0101] Figure 1 This is an explanatory diagram illustrating the concept of the processing method according to an embodiment of the present invention.

[0102] Figure 2 This is an explanatory diagram illustrating the concept of the processing method according to an embodiment of the present invention.

[0103] Figure 3 This is an explanatory diagram illustrating the concept of the processing method according to an embodiment of the present invention.

[0104] Figure 4 This is an explanatory diagram illustrating the concept of the processing method according to an embodiment of the present invention.

[0105] Figure 5 This is an explanatory diagram illustrating the concept of the processing method according to an embodiment of the present invention.

[0106] Figure 6 This is an explanatory diagram of a first preferred embodiment of the present invention.

[0107] Figure 7 This is an explanatory diagram of a modification of the first preferred embodiment of the present invention.

[0108] Figure 8 This is an explanatory diagram of a first preferred embodiment of the present invention.

[0109] Figure 9 This is an explanatory diagram of a second preferred embodiment of the present invention.

[0110] Figure 10 This is an explanatory diagram of a second preferred embodiment of the present invention.

[0111] Figure 11 This is an explanatory diagram of a third preferred embodiment of the present invention.

[0112] Figure 12 This is an explanatory diagram of the fourth preferred embodiment of the present invention.

[0113] Figure 13 This is an explanatory diagram of the fifth preferred embodiment of the present invention.

[0114] Figure 14 This is an explanatory diagram showing the results of an embodiment of the present invention.

[0115] Figure 15 This is an explanatory diagram showing the results of an embodiment of the present invention.

[0116] Figure 16 This is an explanatory diagram showing the results of an embodiment of the present invention.

[0117] Figure 17 This is an explanatory diagram showing the results of an embodiment of the present invention. Detailed Implementation

[0118] One embodiment of the present invention is a method for processing a SiC substrate. This method includes an annealing step of heating the SiC substrate inside a crucible made of SiC.

[0119] In the annealing process of this method, the interior of the crucible is maintained in an inert gas environment. The term "inert gas environment" refers to an environment containing an inert gas. Examples of inert gases include Ar gas and N2 gas. The inert gas environment of this method contains Ar gas. Here, it is preferable that the majority of the inert gas is Ar gas, and it is also preferable that the substantially entire inert gas is Ar gas. Alternatively, a portion of the inert gas may also be N2 gas. That is, the annealing process of this method can be a process of annealing a SiC substrate in an inert gas environment.

[0120] The following is for reference Figures 1 to 5 The concept of this processing method will be explained in detail. Figures 1 to 5 The diagram shows a SiC substrate 1, the surfaces 11 of the SiC substrate (Si surface 111 and C surface 112), a processing-modified layer 12 on the SiC substrate, a crucible 2 made of SiC, a substrate 21 of the crucible 2, and a cover 22. The term "processing-modified layer" refers to a layer that contains damage caused by mechanical processing and is highly likely to adversely affect the performance of the SiC semiconductor device. An example of a processing-modified layer is a mechanically processed surface layer on the Si surface 111 side, which will later form the device. The term "mechanical processing" refers to a process that physically disrupts the atomic arrangement of the substrate. Examples of mechanical processing include ingot cutting (e.g., multi-wire sawing, laser cutting, electrical discharge cutting), grinding, and polishing (e.g., mechanical polishing, chemical mechanical polishing).

[0121] As an example, heating the SiC substrate 1 causes reactions represented by chemical formulas 1 to 3 to occur. That is, heating the SiC substrate 1 causes the raw material gas to sublimate from the SiC substrate 1 and recrystallize onto the SiC substrate 1. The term "raw material gas" refers to a gas composed of one or both of the elements Si and C. Examples of raw material gases include Si gas, SiC2 gas, Si2C gas, and mixtures thereof.

[0122] [Chemical Formula 1]

[0123] [Chemical Formula 2]

[0124] [Chemical Formula 3]

[0125] The reaction of chemical formula 1 is equivalent to a thermal decomposition reaction. In the thermal decomposition reaction, Si gas escapes from the SiC substrate 1, while C remains on the SiC substrate 1. When the thermal decomposition reaction is dominant, the SiC substrate 1 carbonizes.

[0126] The reaction of chemical formula 2 is equivalent to a sublimation reaction. In the sublimation reaction, C from the SiC substrate 1 sublimates as a raw material gas. When the sublimation reaction dominates, the SiC substrate 1 is etched.

[0127] The reaction in chemical formula 3 is equivalent to a recrystallization reaction. In the recrystallization reaction, the raw material gas recrystallizes on the SiC substrate 1. When the recrystallization reaction dominates, the SiC substrate 1 grows.

[0128] This processing method is based on the idea that by strongly promoting both sublimation and recrystallization reactions, intense atomic exchange occurs between the surface layer of the SiC substrate 1 and the annealing environment, that is, the metabolism of atoms constituting the surface layer of the SiC substrate 1 is strongly promoted. The term "surface layer" refers to the layer from the surface to a predetermined depth.

[0129] like Figure 1 As shown, this processing method includes inducing metabolism of atoms constituting the surface layer from the surface 11 to a depth d. The depth d depends on the intensity of the sublimation and recrystallization reactions. Therefore, the processed modified layer 12 contained in the range from the surface 11 to the depth d can be removed in a short time. Furthermore, during the metabolism process, the surface layer of the SiC substrate 1 is smoothed, thereby achieving a SiC substrate 1 with low surface roughness. That is, this processing method can be used as a method for removing the processed modified layer 12 of the SiC substrate 1, and also as a method for reducing the roughness of the surface 11 of the SiC substrate 1.

[0130] When the sublimation reaction dominates over the recrystallization reaction, the number of atoms on the surface layer constituting the SiC substrate 1 decreases macroscopically, and the surface 11 is etched. Here, in the etching process of this method, the balance between the reduction and increase of microscopic atoms is biased towards reduction, resulting in a macroscopic reduction in atoms. In contrast, in conventional etching, the macroscopic reduction in atoms occurs due to the repeated reduction of microscopic atoms.

[0131] When recrystallization is more dominant than sublimation, the number of atoms on the surface of the SiC substrate 1 increases macroscopically, resulting in the growth of surface 11. Here, in the growth process of this method, the balance between the decrease and increase of microscopic atoms tends to favor the increase, leading to an increase in macroscopic atoms. In contrast, in conventional growth processes, the repeated increase in microscopic atoms results in an increase in macroscopic atoms.

[0132] In the etching and growth processes of this method, the processing-modified layer 12, encompassing the area from surface 11 to depth d, can be consistently removed. Therefore, in the etching process of this method, the processing-modified layer 12 can be removed over a wider area than the etching range. Furthermore, in the growth process of this method, a growth layer free from the influence of the processing-modified layer 12 can be formed using a single step. In contrast, conventional etching methods cannot remove processing-modified layers not included in the etching range, and conventional growth methods cannot remove all processing-modified layers. That is, in conventional methods, to eliminate the adverse effects of the processing-modified layer on the device, the entire surface layer encompassing the processing-modified layer needs to be etched before forming the growth layer.

[0133] This processing method includes controlling the etching and growth of surface 11 by controlling the macroscopic flow of the feed gas. Examples of methods for controlling the macroscopic flow of the feed gas include controlling the temperature gradient and controlling the feed gas concentration gradient.

[0134] like Figure 2 As shown, when a temperature gradient is formed such that the temperature decreases with increasing distance from surface 11, the macroscopic flow of the feed gas moves away from surface 11. At this time, sublimation predominates over recrystallization, and surface 11 is etched. On the other hand, as... Figure 3 As shown, when a temperature gradient is formed in such a way that the temperature decreases as it approaches the surface 11, the macroscopic flow of the feed gas becomes directed towards the surface 11. At this point, the recrystallization reaction dominates over the sublimation reaction, and the surface 11 grows.

[0135] This processing method includes: inducing the atoms constituting the surface layer of the SiC substrate 1 to undergo metabolism on both the Si surface 111 and the C surface 112, that is, simultaneously processing both the Si surface 111 and the C surface 112. For example... Figure 4As shown, when a temperature gradient is formed in the direction where the temperature decreases from the C-plane 112 side towards the Si-plane 111 side, the macroscopic flow of the feed gas becomes a direction away from the Si-plane 111 and closer to the C-plane 112. At this time, the C-plane 112 is grown simultaneously with the etching of the Si-plane 111. On the other hand, as... Figure 5 As shown, when a temperature gradient is formed along the direction from the Si surface 111 side towards the C surface 112 side, the macroscopic flow of the feed gas becomes a direction approaching the Si surface 111 and away from the C surface 112. At this time, the C surface 112 is etched while the Si surface 111 is growing.

[0136] This processing method includes maintaining the substrate thickness of the SiC substrate 1 while simultaneously processing both the Si surface 111 and the C surface 112. The etching rate or growth rate at surface 11 typically depends on the temperature gradient near surface 11. Here, the temperature gradient itself varies over time, but by making the Si surface 111 and the C surface 112 very close in space (e.g., around 400 μm), the temperature gradients of the Si surface 111 and the C surface 112 are always approximately the same. As a result, the etching rate on one surface 11 is always approximately the same as the growth rate on the other surface 11. That is, regardless of the magnitude, direction, or temporal variation of the temperature gradient, the amount of etching on one surface 11 is approximately the same as the amount of growth on the other surface 11, and the substrate thickness of the SiC substrate 1 is maintained. Therefore, the material loss accompanying the processing of the SiC substrate 1 can be made substantially zero in the substrate.

[0137] <Processing Method X> Reference Figures 6 to 8 The first preferred method of this processing method will be described in detail. Figures 6 to 8 Use the same symbol to represent and Figures 1 to 5 The structure shown is the same. Hereinafter, the first preferred embodiment of this processing method will be designated as processing method X.

[0138] <Preparation Process S1> Processing method X includes a preparation step S1 for preparing a SiC substrate 1. Alternatively, preparation step S1 may also include preparing multiple SiC substrates 1.

[0139] The preparation step S1 may also include preparing a substrate with a process-modified layer as a SiC substrate 1. This substrate may be a substrate with a process-modified layer formed by mechanical processing (e.g., ingot cutting, grinding, mechanical polishing, chemical mechanical polishing) (e.g., an as-sliced ​​substrate). That is, processing method X can be used as a method to remove the process-modified layer 12 of the SiC substrate 1.

[0140] The preparation step S1 may also include preparing a substrate with an arithmetic mean roughness Ra of 15 nm or more as a SiC substrate 1. This arithmetic mean roughness Ra can be 30 nm or more (or more than 30 nm), or 100 nm or more (or more than 100 nm). There is no particular upper limit to this arithmetic mean roughness Ra, but it is preferably 500 nm or less (or less than 500 nm). Furthermore, the "arithmetic mean roughness Ra" is calculated as the average of the absolute differences between the contour lines and their mean lines in the AFM image (10 μm × 10 μm) of the substrate surface (excluding the ends). This SiC substrate may be a SiC substrate that has undergone mechanical processing (e.g., ingot cutting, grinding). That is, processing method X can be used as a method to reduce the surface roughness 11 of the SiC substrate 1.

[0141] The preparation process S1 includes preparing a substrate without a protective film on its surface as a SiC substrate 1. This allows for the simultaneous processing of both the Si surface 111 and the C surface 112.

[0142] Annealing process S2 like Figure 6 As shown, the processing method X includes an annealing process S2 in which the SiC substrate 1 is heated inside the crucible 2.

[0143] The inner wall of crucible 2 is made of SiC (e.g., polycrystalline SiC, monocrystalline SiC). It is also preferable that the crucible 2 is substantially entirely made of SiC. Polycrystalline SiC is preferred.

[0144] The crucible 2 includes a substrate 21 with an opening and a lid 22. The interior of the crucible 2 is formed by covering the opening of the substrate 21 with the lid 22. The SiC substrate 1 is disposed inside the crucible 2 with the opening of the substrate 21 facing upward, the lid 22 placed on the substrate 21 and the opening of the substrate 21 covered.

[0145] The SiC substrate 1 is supported by a substrate support 3. The substrate support 3 is integrally formed with the substrate 21 or the cover 22. Here, the substrate support 3 can be provided from the inner wall of the substrate 21 or from the inner wall of the cover 22. Alternatively, the substrate support 3 can be formed separately from the substrate 21 or the cover 22. Here, the substrate support 3 is preferably placed on the inner bottom of the substrate 21.

[0146] The substrate support 3 is preferably made of SiC (e.g., polycrystalline SiC, monocrystalline SiC).

[0147] With the SiC substrate 1 facing upwards and the C-surface 112 facing downwards, it is supported by the substrate support 3 from below the C-surface 112. Alternatively, with the Si-surface 111 facing downwards and the C-surface 112 facing upwards, it can also be supported by the substrate support 3 from below the Si-surface 111.

[0148] The SiC substrate 1 is supported by the substrate support 3 via a small contact area, resulting in it being supported within the hollow portion of the crucible 2. The SiC substrate 1 can be supported by three or more points, or by circular or other linear supports. The SiC substrate 1 is preferably positioned inside the crucible 2 such that, through the hollow portion supported within the crucible 2, one surface 11 directly faces the inner wall of the crucible 2, and another surface 11 directly faces the inner wall of the crucible 2. The term "directly facing" means that the two components are facing each other without being obstructed by other components. The SiC substrate 1 is preferably supported as a hollow portion and positioned approximately at the center of the interior of the crucible 2.

[0149] The interior of crucible 2 is maintained in an inert gas environment. The pressure inside crucible 2 is 1 kPa or more. This pressure can be 5 kPa or more, 10 kPa or more, or 100 kPa or more. There is no particular upper limit to this pressure, but it is preferably 300 kPa or less. The temperature inside crucible 2 is 1800°C or more. This temperature is preferably 1900°C or more, preferably 2000°C or more, preferably 2100°C or more, and preferably 2200°C or more. There is no particular upper limit to this temperature, but it is preferably 2300°C or less. The preferred combination of pressure and temperature inside crucible 2 is 1 kPa or more and 1800°C or more. This combination is preferably 1 kPa or more and 1900°C or more, and more preferably 1 kPa or more and 2000°C or more. This combination is also preferably 10 kPa or more and 1800°C or more, more preferably 10 kPa or more and 1900°C or more, and more preferably 10 kPa or more and 2000°C or more.

[0150] A particularly preferred combination of pressure and temperature inside the crucible 2 is 5 kPa or more and 2000°C or more. This combination is preferably 5 kPa or more and 2200°C or more, more preferably 10 kPa or more and 2000°C or more, and even more preferably 10 kPa or more and 2200°C or more.

[0151] A temperature gradient is formed inside the crucible 2. Additionally, a temperature difference is formed between the substrate 21 and the cover 22. The magnitude of this temperature gradient is not particularly limited. This temperature gradient is formed in a direction penetrating the SiC substrate 1. The temperature gradient is formed in a direction in which the temperature decreases from the C-surface 112 side towards the Si-surface 111 side. Alternatively, the temperature gradient may also be formed in a direction in which the temperature decreases from the Si-surface 111 towards the C-surface 112.

[0152] In processing method X, by annealing the SiC substrate 1 in the crucible 2, the Si surface 111 can be etched while maintaining the substrate thickness of the SiC substrate 1, and the C surface 112 can be grown simultaneously. As a result, the processing-modified layer 12 contained in the surface layer on the Si surface 111 side can be sufficiently removed, and the roughness of both the Si surface 111 and the C surface 112 can be reduced. Furthermore, if the temperature gradient is opposite, the Si surface 111 can be grown while maintaining the substrate thickness of the SiC substrate 1, and the C surface 112 can be etched simultaneously. As a result, a growth layer can be formed on the Si surface 111 while removing the processing-modified layer 12 contained in the surface layer on the Si surface 111 side.

[0153] In processing method X, by supporting the SiC substrate 1 inside the crucible 2 in the manner described above, the surface 11 can be etched or grown under suitable conditions.

[0154] By constructing the crucible 2 and substrate support 3 with SiC, raw material gas is generated from the crucible 2 and substrate support 3 into the interior of the crucible 2, maintaining a sufficient amount of raw material gas inside the crucible 2. As a result, both sublimation and recrystallization reactions are strongly promoted. Here, in the crucible 2, similarly to the SiC substrate 1, carbonization of the crucible 2 can be suppressed by strongly promoting both sublimation and recrystallization reactions. In addition, the gas that has not recrystallized on the SiC substrate 1 can be recrystallized on the crucible 2 and substrate support 3 and recovered, resulting in virtually zero raw material loss in the crucible 2 and its entire interior. Furthermore, since the crucible 2 is made of polycrystalline SiC, more raw material gas is generated per unit area from the crucible 2 than per unit area from the SiC substrate 1, which is monocrystalline SiC, thereby slightly reducing the etching amount of the Si surface 111 and slightly increasing the growth amount of the C surface 112. As a result, the substrate thickness of the SiC substrate 1 can be slightly increased before and after heating.

[0155] The interior of the crucible 2 is formed by placing a lid 22 on the substrate 21. The interior of the crucible 2 is a closed environment, and gas (e.g., inert gas) can flow between the inside and outside of the crucible 2 through a small gap between the substrate 21 and the lid 22. That is, the gas inside the crucible 2 can be adjusted without opening the crucible 2.

[0156] By supporting the SiC substrate 1 with the substrate support device 3 as described above, macroscopic flow of raw material gas is formed from the inner wall of the crucible 2 to the C-surface 112 and from the Si-surface 111 to the inner wall of the crucible 2. This allows for a stable exchange of raw material gas between the SiC substrate 1 and the inner wall of the crucible 2 via an inert gas environment, maintaining a balanced annealing environment throughout the crucible 2 and its interior. Furthermore, since the macroscopic flow of raw material gas from the inner wall of the crucible 2 to the C-surface is approximately the same as the macroscopic flow of raw material gas from the Si-surface 111 to the inner wall of the crucible 2, the etching amount at the Si-surface 111 can be approximately the same as the growth amount at the C-surface 112, and the substrate thickness of the SiC substrate 1 can be approximately the same before and after heating.

[0157] In processing method X, by keeping the interior of crucible 2 in an inert gas environment as described above, etching or growth of surface 11 can be performed under suitable conditions.

[0158] By maintaining the interior of crucible 2 in an inert gas environment as described above, the diffusion of the raw material gas sublimating from the SiC substrate 1 is suppressed, the concentration of the raw material gas near the SiC substrate 1 increases, and the thermal motion of the raw material gas becomes more intense. As a result, both the sublimation reaction and the recrystallization reaction are strongly promoted on the surface 11 of the SiC substrate 1.

[0159] In addition, such as Figure 7 As shown, crucible 2 can also be placed inside large crucible 4.

[0160] The inner wall of the large crucible 4 is constructed with a carbon-containing absorbing material. The term "carbon-containing absorbing material" refers to a material that stores carbon during heating. Examples of carbon-containing absorbing materials include Ta and TaC. Preferably, the large crucible 4 is constructed substantially entirely with a carbon-containing absorbing material.

[0161] The inner wall of the large crucible 4 is preferably constructed containing a Si gas-generating material. The term "Si gas-generating material" refers to a material that generates Si gas upon heating. Examples of Si gas-generating materials include Si and tantalum silicide. The large crucible 4 may also be constructed generally as a Si gas-generating material.

[0162] A Si gas source can also be configured inside the large crucible 4 and outside the crucible 2. The term "Si gas source" refers to a component that generates Si gas upon heating. As an example of a Si gas source, Si (e.g., a Si wafer) can be cited.

[0163] The large crucible 4 includes a large base 41 with an opening and a large lid 42. The interior of the large crucible 4 is formed by covering the opening of the large base 41 with the large lid 42. The crucible 2 is arranged inside the large crucible 4 with the opening of the large base 41 facing upward, the large lid 42 placed on the large base 41, and the opening of the large base 41 covered.

[0164] In processing method X, by arranging crucible 2 inside large crucible 4 as described above, etching or growth of surface 11 can be performed under suitable conditions.

[0165] By constructing the inner wall of the large crucible 4 with a carbon-containing absorbent material, carbon is removed from the raw material gas generated from the crucible 2, creating a Si-dominated environment outside the crucible 2. As a result, carbonization of the crucible 2 can be suppressed.

[0166] The crucible 4 is constructed by containing a Si gas-generating material on its inner wall, or by having a Si gas source located inside the crucible 4 and outside the crucible 2, creating a Si-dominated environment outside the crucible 2. As a result, carbonization of the crucible 2 can be suppressed.

[0167] The following is a detailed description of the processes involved in the annealing process S2.

[0168] <Accommodation process S21> The annealing process S2 includes a containment process S21 in which the SiC substrate 1 is contained inside the crucible 2.

[0169] The containment process S21 includes: inserting the SiC substrate 1 through the opening of the substrate 21, placing the cover 22 on the substrate 21 and covering the opening of the substrate 21, thereby containing the SiC substrate 1 inside the crucible 2.

[0170] The containment process S21 includes: supporting the SiC substrate 1 in the hollow portion inside the crucible 2 using a substrate support 3, such that one surface 11 is directly opposite the inner wall of the crucible 2, and the other surface 11 is also directly opposite the inner wall of the crucible 2. The containment process S21 includes: supporting the SiC substrate 1 with the Si surface 111 facing upwards and the C surface 112 facing downwards using the substrate support 3 from below the C surface 112. Here, the containment process S21 includes: supporting the SiC substrate 1 with the substrate support 3 via a small contact area. Preferably, the containment process S21 includes: supporting the SiC substrate 1 in the hollow portion inside the crucible 2 and positioning the SiC substrate 1 approximately at the center inside the crucible 2, so that the macroscopic flow of the raw material gas from the inner wall of the crucible 2 to the C surface is approximately the same as the macroscopic flow of the raw material gas from the Si surface 111 to the inner wall of the crucible 2.

[0171] The containment process S21 preferably includes containing the crucible 2 inside the heating furnace. Here, the heating furnace preferably has a line for introducing inert gas and a line for evacuating a vacuum.

[0172] Preferably, no components containing materials other than SiC are placed inside the crucible 2. Specifically, it is preferable that no components other than the SiC substrate 1 are placed inside the crucible 2. When the substrate support 3 is formed separately from the substrate 21 or the cover 22, it is preferable that no components other than the SiC substrate 1 and the SiC substrate support 3 are placed inside the crucible 2. This allows for the proper maintenance of the internal environment of the crucible 2 during heating.

[0173] For example, it is preferable not to place a heat source inside the crucible 2. This prevents impurities from the heat source from entering the internal environment of the crucible 2. In addition, it prevents the abnormality of the closed environment inside the crucible 2 due to the circulation of the heat source.

[0174] The containing process S21 may also include containing the crucible 2 inside the large crucible 4. Here, the containing process S21 includes: inserting the crucible 2 through the opening of the large substrate 41, placing the large cover 42 on the large substrate 41 and covering the opening of the large substrate 41, thereby containing the crucible 2 inside the large crucible 4.

[0175] <Heating process S22> The annealing process S2 includes a heating process S22 after the containment process S21, which heats the crucible 2. The heating process S22 includes heating the SiC substrate 1 contained inside the crucible 2 by heating the crucible 2.

[0176] The heating process S22 includes heating the crucible 2 to generate the raw material gas from the crucible 2 into the interior of the crucible 2.

[0177] The heating step S22 includes: introducing an inert gas into the interior of the crucible 2 to maintain the pressure inside the crucible 2 at 1 kPa or more (or exceeding 1 kPa). This pressure can be 5 kPa or more (or exceeding 5 kPa), 10 kPa or more (or exceeding 10 kPa), or 100 kPa or more (or exceeding 100 kPa). There is no particular upper limit to this pressure, but it is preferably 300 kPa or less (or less than 300 kPa). Here, the heating step S22 includes: introducing an inert gas into the interior of the crucible 2, which is housed inside the heating furnace, by introducing an inert gas into the interior of the heating furnace.

[0178] The heating step S22 includes heating the crucible 2 to maintain the internal temperature of the crucible 2 at or above 1800°C. This temperature is preferably 1900°C or above, more preferably 2000°C or above, more preferably 2100°C or above, and more preferably 2200°C or above. There is no particular upper limit to this temperature, but it is preferably below 2300°C.

[0179] The heating step S22 includes maintaining the combination of pressure and temperature inside the crucible 2 at 1 kPa or more and 1800°C or more. This combination is preferably a combination of 1 kPa or more and 1900°C or more, and more preferably a combination of 1 kPa or more and 2000°C or more. This combination is also preferably a combination of 10 kPa or more and 1800°C or more, more preferably a combination of 10 kPa or more and 1900°C or more, and more preferably a combination of 10 kPa or more and 2000°C or more.

[0180] In the heating step S22, a particularly preferred combination of pressure and temperature inside the crucible 2 is a combination of 5 kPa or more (or more than 5 kPa) and 2000°C or more (or more than 2000°C). This combination is preferably a combination of 5 kPa or more (or more than 5 kPa) and 2200°C or more (or more than 2200°C), more preferably a combination of 10 kPa or more (or more than 10 kPa) and 2000°C or more (or more than 2200°C), and even more preferably a combination of 10 kPa or more (or more than 10 kPa) and 2200°C or more (or more than 2200°C).

[0181] In heating step S22, the heating time of crucible 2 is 10 minutes or more. This heating time is preferably 30 minutes or more, and more than 1 hour. There is no particular upper limit to this time, but it is preferably 3 hours or less, and more preferably 2 hours or less.

[0182] The heating process S22 includes: forming a temperature gradient inside the crucible 2 in a direction penetrating the SiC substrate 1, thereby creating a macroscopic flow of raw material gas inside the crucible 2. Here, the heating process S22 preferably includes forming a temperature gradient inside the crucible 2 by creating a temperature difference between the substrate 21 and the cover 22. Furthermore, although SiC is a material with high thermal conductivity, the contact portion between the substrate 21 and the cover 22 becomes a thermal resistance, thus enabling a temperature difference between the substrate 21 and the cover 22. This temperature difference is formed such that the substrate 21 is at a high temperature and the cover 22 is at a low temperature. Therefore, as a temperature gradient is formed in a direction where the temperature decreases from the C-surface 112 side towards the Si-surface 111 side, it is possible to etch the Si-surface 111 while simultaneously growing the C-surface 112. Alternatively, this temperature difference can also be formed such that the substrate 21 is at a low temperature and the cover 22 is at a high temperature. As a result, a temperature gradient is formed in the direction where the temperature decreases from the Si surface 111 side to the C surface 112 side, which makes it possible to grow the Si surface 111 while etching the C surface 112.

[0183] The heating process S22 includes heating the crucible 2 using a heating furnace as a heat source. This allows heating of the interior of the crucible 2 from the outside. Furthermore, by creating a difference in heating output above and below the heating furnace, a desired temperature gradient can be formed inside the crucible 2.

[0184] The process of processing method X is as follows: Figure 8As shown. Processing method X includes: performing a preparation step S1, followed by an annealing step S2. Annealing step S2 includes: performing a receiving step S21, followed by a heating step S22. Alternatively, processing method X may include any processing step after annealing step S2. Here, processing method X preferably does not include a mechanical processing step after annealing step S2.

[0185] <Processing Method Y> Reference Figures 9 to 10 The second preferred method of this processing method will be described in detail. Figures 9 to 10 Use the same symbol to represent and Figures 1 to 8 The structure shown is the same. Hereinafter, the second preferred embodiment of this processing method will be described as processing method Y.

[0186] <Preparation Process S1> Processing method Y includes a preparation step S1 for preparing the SiC substrate 1. Preparation step S1 is the same as preparation step S1 in processing method X, therefore its description is omitted.

[0187] Annealing process S2 Processing method Y includes an annealing step S2 in which the SiC substrate 1 is annealed inside a crucible 2 made of SiC. Annealing step S2 is the same as annealing step S2 in processing method X, therefore its description is omitted.

[0188] <Etching process S3> Processing method Y includes an etching process S3, which involves etching the SiC substrate 1 that has undergone annealing process S2.

[0189] Similar to conventional etching, the etching in etching process S3 reduces macroscopic atoms through repeated reduction of microscopic atoms. That is, it differs from the etching in annealing process S2. At this time, the surface 11 of the SiC substrate 1 is finely etched, resulting in a SiC substrate 1 with significantly low surface roughness.

[0190] The component configuration method is roughly the same as that of annealing process S2, but as... Figure 7 As shown, it is preferable to use a large crucible 4 in addition to using a SiC substrate 1, a crucible 2 and a substrate support 3.

[0191] The interior of crucible 2 is maintained in a raw material vapor phase equilibrium environment. The term "raw material vapor phase equilibrium environment" refers to an environment where the raw material gas pressure causes the SiC substrate and the raw material gas to be essentially in equilibrium. Examples of raw material vapor phase equilibrium environments include a C-dominant SiC-C equilibrium vapor pressure environment and a Si-dominant SiC-Si equilibrium vapor pressure environment. That is, the etching process of this method can be a process of etching the SiC substrate in a raw material vapor phase equilibrium environment.

[0192] The internal temperature of crucible 2, maintained in a SiC-C equilibrium vapor pressure environment, is preferably 1600°C or higher, more preferably 1700°C or higher. This temperature is preferably 2000°C or lower, more preferably 1900°C or lower. This temperature is preferably lower than the internal temperature of crucible 2 during the annealing process S2.

[0193] The temperature inside the crucible 2, maintained in a SiC-Si equilibrium vapor pressure environment, is preferably 1800°C or higher (or more than 1800°C), more preferably 1900°C or higher (or more than 1900°C). This temperature is preferably 2000°C or lower (or below 2000°C). This temperature is preferably lower than the temperature inside the crucible 2 during the annealing process S2.

[0194] like Figure 9 As shown, when a Si gas source 5 (e.g., a Si wafer) is arranged inside the crucible 2, a SiC-Si equilibrium vapor pressure environment is formed inside the crucible 2. On the other hand, as... Figure 7 As shown, without the Si gas source 5 inside the crucible 2, a SiC-C equilibrium vapor pressure environment is formed inside the crucible 2.

[0195] A temperature gradient is formed inside the crucible 2. The magnitude of this temperature gradient is greater than or equal to 0.1 mm / K and less than or equal to 5 mm / K. This temperature gradient is formed in a direction penetrating the SiC substrate 1. This temperature gradient is formed in a direction in which the temperature decreases from the C surface 112 toward the Si surface 111.

[0196] In processing method Y, since the interior of crucible 2 is maintained in the raw material gas phase equilibrium environment as described above, the etching of the Si surface 111 can be performed under suitable conditions.

[0197] Because the interior of crucible 2 is maintained in a raw material gas phase equilibrium environment as described above, the sublimation and recrystallization reactions are smoothly and evenly balanced, with a slight bias towards the sublimation reaction, and the raw material gas gradually sublimates from the Si surface 111. As a result, the Si surface 111 can be finely etched, significantly reducing the surface roughness of the Si surface 111.

[0198] The following details the steps included in etching step S3.

[0199] <Etching and Accommodation Process S31> Etching step S3 includes an etching containment step S31 in which the SiC substrate 1 is contained inside the crucible 2. The etching containment step S31 is largely the same as the containment step S21 of processing method X, but when etching is performed under SiC-C equilibrium vapor pressure conditions, such as... Figure 7As shown, this includes cases where the Si gas source 5 is not placed inside the crucible 2, and where etching of the SiC substrate is performed under SiC-Si equilibrium vapor pressure conditions. Figure 9 As shown, this includes the case where the Si gas source 5 is arranged inside the crucible 2. Furthermore, in the etching and containing process S31, the crucible 2 can be the same crucible used in the containing process S21, or it can be a different crucible. Here, the etching and containing process S31 may include: preparing the crucible 2 after the annealing process S2 while the SiC substrate 1 is contained, rather than containing the SiC substrate 1 in the crucible 2.

[0200] <Etching heating process S32> The etching process S3 includes an etching heating process S32 after the etching containment process S31, which involves heating the crucible 2. The etching heating process S32 includes heating the SiC substrate 1 contained inside the crucible 2 by heating the crucible 2.

[0201] The etching heating process S32 preferably includes maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment. Here, the etching heating process S32 preferably involves evacuating the interior of the crucible 2 while heating the crucible 2, generating raw material gas from the crucible 2 into the interior of the crucible 2, thereby maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment.

[0202] While maintaining the interior of crucible 2 in a SiC-C equilibrium vapor pressure environment, the etching heating step S32 includes heating crucible 2 and maintaining the internal temperature of crucible 2 at or above 1600°C. This temperature is preferably above 1700°C. Alternatively, it can be below 2000°C. More preferably, it can be below 1900°C. This temperature is preferably lower than the internal temperature of crucible 2 in the heating step S22.

[0203] The etching heating process S32 preferably also includes maintaining the interior of the crucible 2 in a SiC-Si equilibrium vapor pressure environment. Here, the etching heating process S32 preferably involves heating the crucible 2 while evacuating the interior of the crucible 2, generating raw material gas from the crucible 2 into the interior of the crucible 2, and generating Si gas from the Si gas source 5 into the interior of the crucible 2, thereby maintaining the interior of the crucible 2 in a SiC-Si equilibrium vapor pressure environment.

[0204] While maintaining the interior of crucible 2 in a SiC-Si equilibrium vapor pressure environment, the etching heating step S32 includes: heating crucible 2 and maintaining the internal temperature of crucible 2 at or above 1800°C. This temperature is preferably above 1900°C. Alternatively, it can be below 2000°C. This temperature is preferably lower than the internal temperature of crucible 2 in heating step S22.

[0205] The etching heating process S32 includes: forming a temperature gradient inside the crucible 2 in the direction penetrating the SiC substrate 1, thereby creating a macroscopic flow of raw material gas inside the crucible 2. Here, the etching heating process S32 includes: forming a temperature difference such that the substrate 21 is at a high temperature and the cover 22 is at a low temperature. As a result, a temperature gradient is formed in the direction that decreases in temperature from the C-surface 112 side to the Si-surface 111 side, which results in the ability to perform fine etching on the Si-surface 111.

[0206] The etching heating process S32 includes heating the crucible 2 using a heating furnace as a heat source. This allows heating of the interior of the crucible 2 from the outside. Furthermore, by creating a difference in heating output above and below the heating furnace, a desired temperature gradient can be formed inside the crucible 2.

[0207] The process of processing method Y is as follows: Figure 10 As shown. Processing method Y includes: a preparation step S1, followed by an annealing step S2, and then an etching step S3. Annealing step S2 includes: a receiving step S21, followed by a heating step S22. Etching step S3 includes: an etching receiving step S31, followed by an etching heating step S32. Alternatively, processing method Y may include any processing step after etching step S3. Here, processing method Y preferably does not include a mechanical processing step after etching step S3.

[0208] <Processing Method Z> Reference Figure 11 The third preferred method of this processing method will be described in detail. Figure 11 In, with Figures 1 to 10 Structures with the same structure shown are represented by the same symbol. Hereinafter, the third preferred embodiment of this processing method will be designated as processing method Z.

[0209] <Preparation Process S1> Processing method Z includes a preparation step S1 for preparing the SiC substrate 1. Preparation step S1 is the same as preparation step S1 in processing method Y, therefore its description is omitted.

[0210] Annealing process S2 Processing method Z includes an annealing step S2 in which the SiC substrate 1 is annealed inside a crucible 2 made of SiC. Annealing step S2 is the same as annealing step S2 in processing method Y, therefore its description is omitted.

[0211] <First Etching Process S4> Processing method Z includes a first etching step S4 that etches the SiC substrate 1 after annealing step S2. The first etching step S4 is largely the same as the etching step S3 of processing method Y, but the interior of the crucible 2 is maintained in a SiC-C equilibrium vapor pressure environment.

[0212] <First Etching Accommodation Process S41> The first etching step S4 includes a first etching containment step S41 in which the SiC substrate 1 is contained inside the crucible 2. The first etching containment step S41 is substantially the same as the etching containment step S31 of processing method Y, but... Figure 7 As shown, this includes the Si gas source 5 not being placed inside the crucible 2.

[0213] <First Etching Heating Process S42> The first etching step S4 includes a first etching heating step S42 after the first etching containment step S41, which heats the crucible 2. The first etching heating step S42 is substantially the same as the etching heating step S32 of processing method Y, but includes maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment.

[0214] <Second Etching Process S5> Processing method Z includes a second etching step S5 that further etches the SiC substrate 1 after the first etching step S4. The second etching step S5 is substantially the same as the etching step S3 of processing method Y, but the interior of the crucible 2 is maintained in a SiC-Si equilibrium vapor pressure environment.

[0215] <Second Etching Accommodation Process S51> The second etching process S5 includes a second etching containment process S51 in which the SiC substrate 1 is contained inside the crucible 2. The second etching containment process S51 is substantially the same as the etching containment process S31 of processing method Y, but... Figure 9 As shown, a Si gas source 5 is arranged inside the crucible 2.

[0216] <Second Etching Heating Process S52> The second etching step S5, following the second etching containment step S51, includes a second etching heating step S52, which heats the crucible 2. The second etching heating step S52 is substantially the same as the etching heating step S32 of processing method Y, but includes maintaining the interior of the crucible 2 in a SiC-Si equilibrium vapor pressure environment.

[0217] In processing method Z, as described above, the SiC substrate 1 is etched in a SiC-C equilibrium vapor pressure environment in the first etching step S4, and then the SiC substrate 1 is etched in a SiC-Si equilibrium vapor pressure environment in the second etching step S5. This allows for more precise etching of the Si surface 111 and a more significant reduction in the surface roughness of the Si surface (in particular, it allows for the decomposition of macroscopic step clusters on the Si surface).

[0218] The process of processing method Z is as follows: Figure 11 As shown. Processing method Z includes a preparation step S1, followed by an annealing step S2, a first etching step S4, and a second etching step S5. Annealing step S2 includes a receiving step S21 followed by a heating step S22. First etching step S4 includes a first etching receiving step S41 followed by a first etching heating step S42. Second etching step S5 includes a second etching receiving step S51 followed by a second etching heating step S52. Furthermore, processing method Z may also include any processing steps performed after the second etching step S5. Here, processing method Z preferably does not include mechanical processing steps after the second etching step S5.

[0219] <Processing Method V> Reference Figure 12 The fourth preferred method of this processing method will be described in detail. Figure 12 Use the same symbol to represent and Figures 1 to 11 The structure shown is the same. Hereinafter, the fourth preferred method of this processing method will be designated as processing method V.

[0220] <Preparation Process S1> Processing method V includes a preparation step S1 for preparing the SiC substrate 1. Preparation step S1 is the same as preparation step S1 in processing method Z, therefore its description is omitted.

[0221] Annealing process S2 Processing method V includes an annealing step S2 in which the SiC substrate 1 is annealed inside a crucible 2 made of SiC. Annealing step S2 is the same as annealing step S2 in processing method Z, therefore its description is omitted.

[0222] <Etching process S3> Processing method V includes an etching step S3 that etches the SiC substrate 1 after the annealing step S2. Etching step S3 is the same as etching step S3 in processing method Y, so its description is omitted.

[0223] Processing method V preferably includes a first etching step S4 and a second etching step S5 as etching step S3. The first etching step S4 and the second etching step S5 are the same as the first etching step S4 and the second etching step S5 in processing method Z, so the description is omitted.

[0224] <Growth Process S6> The processing method V includes a growth process S6 in which the SiC substrate 1, which has undergone etching process S3, is grown.

[0225] In the growth process S6, similar to conventional growth, the microscopic atoms are repeatedly increased, leading to a macroscopic increase in atoms. That is, it differs from the growth in the annealing process S2. At this point, the surface 11 of the SiC substrate 1 is precisely grown, and a SiC substrate 1 with significantly small surface roughness is achieved.

[0226] The component configuration method is the same as that of etching process S3.

[0227] The interior of crucible 2 is maintained in a raw material gas-phase equilibrium environment. That is, the growth process of this method can be a process of growing SiC substrate in a raw material gas-phase equilibrium environment.

[0228] The internal temperature of crucible 2, maintained in a SiC-C equilibrium vapor pressure environment, is preferably 1600°C or higher, more preferably 1700°C or higher. This temperature is preferably 2000°C or lower, more preferably 1900°C or lower. This temperature is preferably lower than the internal temperature of crucible 2 during the annealing process S2.

[0229] The temperature inside the crucible 2, maintained in a SiC-Si equilibrium vapor pressure environment, is preferably 1800°C or higher (or more than 1800°C), more preferably 1900°C or higher (or more than 1900°C). This temperature is preferably 2000°C or lower (or below 2000°C). This temperature is preferably lower than the temperature inside the crucible 2 during the annealing process S2.

[0230] A temperature gradient is formed inside the crucible 2. The magnitude of this temperature gradient is greater than or equal to 0.1 mm / K and less than or equal to 5 mm / K. This temperature gradient is formed in a direction penetrating the SiC substrate 1. This temperature gradient is formed in a direction in which the temperature decreases from the Si surface 111 towards the C surface 112.

[0231] In processing method V, since the interior of crucible 2 is maintained in a raw material gas phase equilibrium environment as described above, the growth of Si surface 111 can be carried out under suitable conditions.

[0232] By maintaining the interior of crucible 2 in a balanced environment of the raw material gas phase as described above, the sublimation and recrystallization reactions are stably balanced, with a slight bias towards recrystallization, and the raw material gas gradually recrystallizes on the Si surface 111. As a result, the Si surface 111 can be grown finely, and the increase in the surface roughness of the Si surface 111 is significantly suppressed.

[0233] The following details the steps included in growth step S6.

[0234] <Growth and Accommodation Process S61> The growth process S6 includes a growth containment process S61 in which the SiC substrate 1 is contained inside the crucible 2. The growth containment process S61 is the same as the etching containment process S31 of processing method Y. Furthermore, in the growth containment process S61, the crucible 2 can be the crucible used in the containment process S21, the crucible used in the etching containment process S31, or a different crucible. Here, the growth containment process S61 may include preparing the crucible 2 after the etching process S3 while the SiC substrate 1 is contained, rather than containing the SiC substrate 1 inside the crucible 2.

[0235] <Growth heating process S62> The growth process S6 includes a growth heating process S62 after the growth containment process S61, which involves heating the crucible 2. The growth heating process S62 includes a process of heating the SiC substrate 1 contained inside the crucible 2 by heating the crucible 2.

[0236] The preferred growth heating step S62 includes maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment. Here, the growth heating step S62 preferably involves heating the crucible 2 while evacuating its interior, generating raw material gas from the crucible 2 into its interior, thereby maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment.

[0237] While maintaining the interior of crucible 2 in a SiC-C equilibrium vapor pressure environment, the growth heating step S62 includes heating crucible 2 and maintaining the internal temperature of crucible 2 at or above 1600°C. This temperature is preferably above 1700°C. Alternatively, it can be below 2000°C. More preferably, it can be below 1900°C. This temperature is preferably lower than the internal temperature of crucible 2 in heating step S22.

[0238] The growth heating process S62 preferably also includes maintaining the interior of the crucible 2 as a SiC-Si equilibrium vapor pressure environment. Here, the growth heating process S62 preferably involves heating the crucible 2 while evacuating the interior of the crucible 2, generating raw material gas from the crucible 2 into the interior of the crucible 2, and generating Si gas from the Si gas source 5 into the interior of the crucible 2, thereby maintaining the interior of the crucible 2 as a SiC-Si equilibrium vapor pressure environment.

[0239] While maintaining the interior of crucible 2 in a SiC-Si equilibrium vapor pressure environment, the growth heating step S62 includes heating crucible 2 and maintaining the internal temperature of crucible 2 at or above 1800°C. This temperature is preferably above 1900°C. Alternatively, it can be below 2000°C. This temperature is preferably lower than the internal temperature of crucible 2 in heating step S22.

[0240] The growth heating process S62 includes forming a temperature gradient inside the crucible 2 in a direction penetrating the SiC substrate 1, thereby creating a macroscopic flow of raw material gas inside the crucible 2. The growth heating process S62 includes creating a temperature difference such that the substrate 21 has a low temperature while the cap 22 has a high temperature. As a result, a temperature gradient is formed in a direction where the temperature decreases from the Si surface 111 side towards the C surface 112 side, which enables fine growth of the Si surface 111.

[0241] The growth heating process S62 includes heating the crucible 2 using a heating furnace as a heat source. This allows heating of the interior of the crucible 2 from the outside. Furthermore, by creating a difference in heating output above and below the heating furnace, a desired temperature gradient can be formed inside the crucible 2.

[0242] The process of processing method V is as follows: Figure 12 As shown. Processing method V includes: a preparation step S1, followed by an annealing step S2, followed by an etching step S3, followed by a growth step S6. Annealing step S2 includes: a containment step S21, followed by a heating step S22. Etching step S3 includes: an etching containment step S31, followed by an etching heating step S32. Growth step S6 includes: a growth containment step S61, followed by a growth heating step S62. Alternatively, processing method V may include any processing step after growth step S6. Here, processing method V preferably does not include a mechanical processing step after growth step S6.

[0243] <Processing Method W> Reference Figure 13 The fifth preferred method of this processing method will be described in detail. Figure 13 Use the same symbol to represent and Figures 1 to 12 The structure shown is the same. Hereinafter, the fifth preferred embodiment of this processing method will be designated as processing method W.

[0244] <Preparation Process S1> Processing method W includes a preparation step S1 for preparing the SiC substrate 1. Preparation step S1 is the same as preparation step S1 in processing method V, so its description is omitted.

[0245] Annealing process S2 Processing method W includes an annealing step S2 in which the SiC substrate 1 is annealed inside a crucible 2 made of SiC. Annealing step S2 is the same as annealing step S2 in processing method V, so its description is omitted.

[0246] <First Etching Process S4> Processing method W includes a first etching step S4 that etches the SiC substrate 1 after annealing step S2. The first etching step S4 is the same as the first etching step S4 of processing method Z, so its description is omitted.

[0247] <Second Etching Process S5> Processing method W includes a second etching step S5 that further etches the SiC substrate 1 after the first etching step S4. The second etching step S5 is the same as the second etching step S5 of processing method Z, so its description is omitted.

[0248] <First growth process S7> Processing method W includes a first growth step S7 that grows on the SiC substrate 1 after the second etching step S5. The first growth step S7 is substantially the same as the growth step S6 of processing method V, but the interior of the crucible 2 is maintained in a SiC-C equilibrium vapor pressure environment.

[0249] <First growth and containment process S71> The first growth process S7 includes a first growth containment process S71 in which the SiC substrate 1 is contained inside the crucible 2. The first growth containment process S71 is substantially the same as the growth containment process S61 of processing method V, but... Figure 7 As shown, this includes the case where the Si gas source 5 is not placed inside the crucible 2.

[0250] <First growth heating process S72> The first growth step S7 includes a first growth heating step S72 after the first growth containment step S71, which heats the crucible 2. The first growth heating step S72 is substantially the same as the growth heating step S62 of processing method V, but includes maintaining the interior of the crucible 2 in a SiC-C equilibrium vapor pressure environment.

[0251] <Second growth process S8> Processing method W includes a second growth step S8 that further grows the SiC substrate 1 that has undergone the first growth step S7. The second growth step S8 is substantially the same as the growth step S6 of processing method V, but the interior of the crucible 2 is maintained in a SiC-Si equilibrium vapor pressure environment.

[0252] <Second growth and containment process S81> The second growth process S8 includes a second growth containment process S81 in which the SiC substrate 1 is contained inside the crucible 2. The second growth containment process S81 is substantially the same as the growth containment process S61 of processing method V, but... Figure 9 As shown, the process includes arranging a Si gas source 5 inside the crucible 2.

[0253] <Second growth heating process S82> The second growth step S8, following the second growth containment step S81, includes a second growth heating step S82, which heats the crucible 2. The second growth heating step S82 is substantially the same as the growth heating step S62 of processing method V, but includes maintaining the interior of the crucible 2 in a SiC-Si equilibrium vapor pressure environment.

[0254] In the processing method W, the SiC substrate 1 is etched in the SiC-Si equilibrium vapor pressure environment in the second etching step S5 as described above, and then the SiC substrate 1 is grown in the SiC-C equilibrium vapor pressure environment in the first growth step S7. As a result, the propagation of substrate surface dislocations (BPDs) to the growth layer can be significantly suppressed.

[0255] Furthermore, in the processing method W, the SiC substrate 1 is grown in the SiC-C equilibrium vapor pressure environment in the first growth step S7, and then the SiC substrate 1 is grown in the SiC-Si equilibrium vapor pressure environment in the second growth step S8, which can significantly reduce the surface roughness of the Si surface (in particular, can decompose the macroscopic step clusters of the Si surface).

[0256] In summary, in processing method W, SiC substrates in any state can be processed into SiC substrates suitable for manufacturing SiC semiconductor devices, in which surface roughness is significantly suppressed, BPD is significantly suppressed, and the processing-modified layer that causes in-grown stacking faults (IGSF) is significantly removed.

[0257] The process of processing method W is as follows: Figure 13As shown. Processing method Z includes: a preparation step S1, followed by an annealing step S2, followed by a first etching step S4, followed by a second etching step S5, followed by a first growth step S7, followed by a second growth step S8. Annealing step S2 includes: a receiving step S21, followed by a heating step S22. First etching step S4 includes: a first etching receiving step S41, followed by a first etching heating step S42. Second etching step S5 includes: a second etching receiving step S51, followed by a second etching heating step S52. First growth step S7 includes: a first growth receiving step S71, followed by a first growth heating step S72. Second growth step S8 includes: a second growth receiving step S81, followed by a second growth heating step S82. Alternatively, processing method W may include any processing step after the second growth step S8. Here, processing method W preferably does not include a mechanical processing step after the second growth step S8.

[0258] Example 1 Processing method X according to the following procedure.

[0259] <Preparation Process S1> A substrate with the following properties is prepared as SiC substrate 1. In addition, in order to eliminate the influence of measuring SiC substrate 1 on surface 11, SiC substrate 1 is cleaned with a chemical solution.

[0260] Material: 4H-SiC Deviation angle: 4° Deviation from direction: [11-20] direction Size: 6 inches The arithmetic mean roughness Ra of the Si 111 surface is 46.2 nm. Substrate thickness: 400.0 μm Annealing process S2 The SiC substrate 1 is annealed according to the following process.

[0261] <Accommodation process S21> like Figure 6 As shown, the SiC substrate 1 is housed inside the crucible 2, which is made of polycrystalline SiC.

[0262] <Heating process S22> Heat the SiC substrate 1 under the following conditions.

[0263] Imported gas: Ar gas Pressure: Above 1 kPa and below 300 kPa Temperature: Above 1800℃ and below 2300℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour Figure 14 The outline is shown based on an AFM image (10μm × 10μm). In Figure 12 In the diagram, (a) is the SiC substrate 1 prepared in preparation process S1, and (b) is the SiC substrate 1 after annealing process S2. By comparing the shapes of the contour lines, it can be seen that the surface roughness of the Si surface 111 is reduced.

[0264] Figure 15 The relationship between the arithmetic mean roughness Ra of the Si surface 111 and the substrate thickness is shown. The arithmetic mean roughness Ra of the Si surface 111 is reduced from 46.2 nm to 13.7 nm by the annealing process S2. Furthermore, the substrate thickness of the SiC substrate 1 is increased from 400.0 μm to 409.8 μm by the annealing process S2. Thus, it can be seen that the surface roughness of the Si surface 111 is reduced while the substrate thickness of the SiC substrate 1 is almost maintained. Based on the temperature difference conditions, it can be assumed that the Si surface 111 is etched while the C surface 112 is grown. Furthermore, the amount of etching on the Si surface 111 is considered to be approximately the same as or less than the amount of growth on the C surface 112.

[0265] Example 2 Processing method X according to the following procedure.

[0266] <Preparation Process S1> A substrate with the following properties is prepared as SiC substrate 1. To eliminate the influence of measuring SiC substrate 1 on surface 11, SiC substrate 1 is cleaned with a chemical solution.

[0267] Material: 4H-SiC Deviation angle: 4° Deviation from direction: [11-20] direction Size: 6 inches The arithmetic mean roughness Ra of the Si 111 surface is 46.2 nm. Substrate thickness: 400.0 μm Annealing process S2 The SiC substrate 1 is annealed according to the following process.

[0268] <Accommodation process S21> like Figure 6 As shown, the SiC substrate 1 is housed inside the crucible 2, which is made of polycrystalline SiC.

[0269] <Heating process S22> Heat the SiC substrate 1 under the following conditions.

[0270] Imported gas: Ar gas Pressure: Any of vacuum (~10⁻⁴ kPa), 5 kPa, or 10 kPa Temperature: any one of 1800℃, 2000℃, or 2200℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour Figure 16 Laser micrographs of the Si surface 111 of a SiC substrate processed under various conditions are shown. Compared to the pressure under vacuum, it is evident that the surface roughness scale decreases at pressures above 5 kPa. Furthermore, it is shown that at temperatures above 2200°C, a step-plateau structure is exhibited on the surface, indicating a cleaner surface shape.

[0271] The arithmetic mean height Sa is 70 nm at 1800℃ under vacuum and 153 nm at 10 kPa; 174 nm at 2000℃ under vacuum and 71 nm at 5 kPa and 86 nm at 10 kPa; and 242 nm at 2200℃ under vacuum and 56 nm at 5 kPa and 54 nm at 10 kPa. The comparison of the arithmetic mean height Sa shows that the surface roughness of Si 111 decreases significantly at pressures above 5 kPa. Furthermore, it is evident that the surface roughness of Si 111 decreases significantly at temperatures above 2000℃, and further significantly at temperatures above 2200℃.

[0272] Example 3 Following Example 1, processing method Y is performed according to the following steps. Furthermore, in order to eliminate the influence of the measured SiC substrate 1 on the surface 11, the SiC substrate 1 is cleaned with a chemical solution.

[0273] <Etching process S3> The SiC substrate 1 is etched according to the following steps.

[0274] <Etching and Accommodation Process S31> like Figure 7 As shown, the SiC substrate 1 is housed inside the crucible 2.

[0275] <Etching heating process S32> The SiC substrate 1 is heated under the following conditions. At this time, the interior of the crucible 2 is a SiC-C equilibrium vapor pressure environment.

[0276] Gas introduced: None Pressure: Vacuum (pressure of the raw material gas) Temperature: Above 1600℃ and below 2000℃ (lower than the temperature in heating process S22) Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour exist Figure 14 In the image, (c) shows the SiC substrate 1 after etching process S3. As can be seen from the comparison of the contour shapes, the surface roughness of the Si surface 111 is further reduced.

[0277] The arithmetic mean roughness Ra of the Si surface 111 is reduced from 13.7 nm to 6.1 nm through the etching process S3. Furthermore, the substrate thickness of the SiC substrate 1 is increased from 409.8 μm to 414.0 μm through the etching process S3. Thus, it can be seen that the surface roughness of the Si surface 111 is reduced while maintaining almost the same substrate thickness. Based on the temperature difference condition, it can be assumed that the Si surface 111 is etched while the C surface 112 is grown. Furthermore, the amount of etching on the Si surface 111 is considered to be approximately the same as or less than the amount of growth on the C surface 112.

[0278] Example 4 Next, in Example 3, processing method Z is performed according to the following steps. However, the first etching step S4 of processing method Z is the same as the etching step S3 in Example 2. In addition, in order to eliminate the influence of the SiC substrate 1 on the surface 11, the SiC substrate 1 is cleaned with a chemical solution.

[0279] <Second Etching Process S5> The SiC substrate 1 is etched according to the following steps.

[0280] <Second Etching Accommodation Process S51> like Figure 9 As shown, the SiC substrate 1 and the Si gas source 5 are housed together inside the crucible 2.

[0281] <Second Etching Heating Process S52> The SiC substrate 1 is heated under the following conditions. At this time, the interior of the crucible 2 is a SiC-Si equilibrium vapor pressure environment.

[0282] Gas introduced: None Pressure: Vacuum (pressure of the raw material gas) Temperature: 1800℃ to 2000℃ (lower than the temperature in heating process S22 and higher than the temperature in the first etching heating process S42) Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour exist Figure 14In the image, (d) is the SiC substrate 1 after the second etching process S5. As can be seen from the comparison of the shape of the contour lines, the surface roughness of the Si surface 111 is further reduced.

[0283] The arithmetic mean roughness Ra of the Si surface 111 is reduced from 6.1 nm to 0.7 nm through the second etching process S5. Furthermore, the substrate thickness of the SiC substrate 1 is increased from 414.0 μm to 426.1 μm through the second etching process S5. Thus, it can be seen that the surface roughness of the Si surface 111 is reduced while maintaining almost the same substrate thickness as the SiC substrate 1. Based on the temperature difference condition, it can be assumed that the Si surface 111 is etched while the C surface 112 is grown. Additionally, the amount of etching on the Si surface 111 is considered to be approximately the same as or less than the amount of growth on the C surface 112.

[0284] Example 5 Processing method V is carried out according to the following procedures.

[0285] <Preparation Process S1> A substrate with the following properties is prepared as SiC substrate 1. In addition, in order to eliminate the influence of measuring SiC substrate 1 on surface 11, SiC substrate 1 is cleaned with a chemical solution.

[0286] Material: 4H-SiC Deviation angle: 4° Deviation from direction: [11-20] direction Size: 3 inches The arithmetic mean roughness Ra of Si 111 surface is above 60 nm. Photoluminescence image of Si surface 111: Figure 17 Left Annealing process S2 The SiC substrate 1 is annealed according to the following process.

[0287] <Accommodation process S21> like Figure 6 As shown, the SiC substrate 1 is housed inside the crucible 2, which is made of polycrystalline SiC.

[0288] <Heating process S22> Heat the SiC substrate 1 under the following conditions.

[0289] Imported gas: Ar gas Pressure: 10 kPa Temperature: 2200℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour <First Etching Process S4> The SiC substrate 1 is etched according to the following steps.

[0290] <First Etching Accommodation Process S41> like Figure 7 As shown, the SiC substrate 1 is housed inside the crucible 2.

[0291] <First Etching Heating Process S42> The SiC substrate 1 is heated under the following conditions. At this time, the interior of the crucible 2 is a SiC-C equilibrium vapor pressure environment.

[0292] Gas introduced: None Pressure: Vacuum (pressure of the raw material gas) Temperature: 1800℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour <Second Etching Process S5> The SiC substrate 1 is etched according to the following steps.

[0293] <Second Etching Accommodation Process S51> like Figure 9 As shown, the SiC substrate 1 is housed inside the crucible 2.

[0294] <Second Etching Heating Process S52> The SiC substrate 1 is heated under the following conditions. At this time, the interior of the crucible 2 is a SiC-Si equilibrium vapor pressure environment.

[0295] Gas introduced: None Pressure: Vacuum (pressure of the raw material gas) Temperature: 1800℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 1 hour <Growth Process S6> The SiC substrate 1 is grown according to the following process.

[0296] <Growth and Accommodation Process S61> like Figure 7 As shown, the SiC substrate 1 is housed inside the crucible 2.

[0297] <Growth heating process S62> The SiC substrate 1 is heated under the following conditions. At this time, the interior of the crucible 2 is a SiC-C equilibrium vapor pressure environment.

[0298] Gas introduced: None Pressure: Vacuum (pressure of the raw material gas) Temperature: 1800℃ Temperature difference: The substrate 21 is at a high temperature, while the cover 22 is at a low temperature. Time: 2 hours The arithmetic mean roughness Ra of the Si surface 111 is less than 5 nm. Furthermore, the photoluminescence pattern of the Si surface 111 becomes... Figure 17 As shown on the right. Additionally, there are 3 BPDs (number density of 0.07 cm⁻¹) across the entire surface of SiC substrate 1. -2 ), IGSF has 12 (number density is 0.27 cm⁻¹). -2 That is, it can be seen that the surface roughness of Si surface 111 is reduced, and BPD and IGSF are almost completely removed.

[0299] Symbol Explanation X: Processing method S2: Annealing process S21: Accommodation process S22: Heating process 1: SiC substrate 11: Surface 111: Si surface 112: Side C 12: Processing the metamorphic layer 2: Crucible 21: Matrix 22: Cover 3: Substrate support d: Depth.

Claims

1. A method for processing a SiC substrate, the method comprising: Annealing process of heating SiC substrate in an inert gas environment; as well as An etching process in which the SiC substrate that has undergone the annealing process is etched in an environment containing a gas composed of one or both of Si and C elements.

2. The method for processing a SiC substrate according to claim 1, wherein, The annealing process includes heating the SiC substrate inside a crucible made of SiC. During the annealing process, the interior of the crucible is maintained in the inert gas environment.

3. The method for processing a SiC substrate according to claim 1 or 2, wherein, The annealing process includes etching one surface of the SiC substrate while simultaneously growing another surface of the SiC substrate.

4. The method for processing a SiC substrate according to claim 3, wherein, The annealing process includes making the amount of etching at one surface approximately the same as the amount of growth at the other surface, so that the substrate thickness of the SiC substrate is approximately the same before and after the annealing process.

5. The method for processing a SiC substrate according to claim 3 or 4, wherein, The annealing process includes increasing the substrate thickness of the SiC substrate before and after the annealing process by making the amount of etching at one surface smaller than the amount of growth at the other surface.

6. The method for processing a SiC substrate according to any one of claims 2 to 5, wherein, During the annealing process, the pressure inside the crucible is above 5 kPa.

7. The method for processing a SiC substrate according to any one of claims 2 to 5, wherein, During the annealing process, the pressure inside the crucible is above 10 kPa.

8. The method for processing a SiC substrate according to any one of claims 2 to 7, wherein, During the annealing process, the internal temperature of the crucible is above 2000°C.

9. The method for processing a SiC substrate according to any one of claims 2 to 7, wherein, During the annealing process, the internal temperature of the crucible is above 2200°C.

10. The method for processing a SiC substrate according to any one of claims 2 to 9, wherein, In the annealing process, the combination of pressure and temperature inside the crucible is a combination of 5 kPa or more and 2000°C or more.

11. The method for processing a SiC substrate according to any one of claims 2 to 9, wherein, In the annealing process, the combination of pressure and temperature inside the crucible is a combination of 5 kPa or more and 2200°C or more.

12. The method for processing a SiC substrate according to any one of claims 1 to 11, wherein, During the annealing process, no protective film is formed on the surface of the SiC substrate.

13. The method for processing a SiC substrate according to any one of claims 1 to 12, wherein, The etching process includes heating the SiC substrate inside a crucible made of SiC. During the etching process, the interior of the crucible is maintained in an environment containing a gas composed of one or both of the elements Si and C.

14. The method for processing a SiC substrate according to claim 13, wherein, During the etching process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment.

15. The method for processing a SiC substrate according to claim 13, wherein, During the etching process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

16. The method for processing a SiC substrate according to any one of claims 13 to 15, wherein, In the etching process, inside the crucible, a temperature gradient is formed in the direction penetrating the SiC substrate and in the direction in which the temperature decreases from the C-side of the SiC substrate toward the Si-side.

17. The method for processing a SiC substrate according to any one of claims 13 to 16, wherein, The processing method does not include a mechanical treatment of the SiC substrate after the etching process.

18. The method for processing a SiC substrate according to any one of claims 13 to 17, wherein, The etching process is performed at least twice, including a first etching process and a second etching process. The first etching process includes etching the SiC substrate that has undergone the annealing process. The second etching process includes etching the SiC substrate that has undergone the first etching process. In the first etching process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment. In the second etching process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

19. The method for processing a SiC substrate according to any one of claims 1 to 18, the method further comprising: A growth process in which the SiC substrate, after the etching process, is grown in an environment containing a gas composed of one or both of Si and C elements.

20. The method for processing a SiC substrate according to any one of claims 1 to 19, wherein, The growth process includes heating the SiC substrate inside a crucible made of SiC. During the growth process, the interior of the crucible is maintained in an environment containing a gas composed of one or both of the elements Si and C.

21. The method for processing a SiC substrate according to claim 20, wherein, During the growth process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment.

22. The method for processing a SiC substrate according to claim 20, wherein, During the growth process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

23. The method for processing a SiC substrate according to any one of claims 20 to 22, wherein, In the growth process, inside the crucible, a temperature gradient is formed in the direction penetrating the SiC substrate and in the direction in which the temperature decreases from the Si surface side of the SiC substrate toward the C surface side.

24. The method for processing a SiC substrate according to any one of claims 20 to 23, wherein, The growth process is performed at least twice, including a first growth process and a second growth process. The first growth process includes growing a SiC substrate that has undergone the etching process. The second growth process includes growing the SiC substrate that has undergone the first growth process. In the first growth process, the interior of the crucible is maintained in a SiC-C equilibrium vapor pressure environment. In the second growth process, the interior of the crucible is maintained in a SiC-Si equilibrium vapor pressure environment.

25. A method for removing a processed modified layer from a SiC substrate, the method comprising: A SiC substrate having a processing altered layer is subjected to a processing method according to any one of claims 1 to 24 to remove the processing altered layer.

26. The method for removing the processed modified layer of a SiC substrate according to claim 25, the method comprising: The processing method is applied to the SiC substrate on which the modified processing layer has been formed by mechanical processing.

27. The method for removing the processed modified layer from a SiC substrate according to claim 25 or 26, wherein, The annealing process includes performing atomic exchange between the surface layer of the SiC substrate and the inert gas environment to remove the processed and altered layer.

28. A method for reducing the surface roughness of a SiC substrate, the method comprising: A SiC substrate with an arithmetic mean roughness Ra of 15 nm or more on the Si surface is subjected to a SiC substrate processing method according to any one of claims 1 to 24 to reduce the arithmetic mean roughness Ra.

29. The method for reducing the surface roughness of a SiC substrate according to claim 28, the method comprising: The processing method is applied to the SiC substrate that has undergone mechanical processing.

30. The method for reducing the surface roughness of a SiC substrate according to claim 28 or 29, wherein, The annealing process includes performing atomic exchange between the surface layer of the SiC substrate and the inert gas environment to make the surface layer smooth.

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