Solid substrate for semiconductor device, method for manufacturing solid substrate, and method for manufacturing solid device

Abstract

To provide a solid substrate that prevents damage at high temperatures to the surface of the substrate made mainly of carbon, such as diamond and silicon carbide, and further makes the thermal radiation from the substrate to be blackbody radiation, a manufacturing method for the same, and a manufacturing method for a solid-state device.SOLUTION: A glassy carbon laminated diamond substrate 101 forms a glassy carbon layer with a thickness of greater than or equal to 100 nm and less than or equal to 100 μm on a first main surface 1a of a solid substrate 1, where a solid consisting mainly of carbon is formed at least on the first main surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid substrate, a method for manufacturing the same, and a method for manufacturing a solid device. [Background technology]

[0002] In recent years, diamond has been expected to be used in quantum devices, and color centers that function as quantum bits have been formed in diamond by ion implantation or electron beam irradiation. In addition, ion implantation of impurities such as boron, which form acceptors or donors in diamond crystals, has also been widely used. Heat treatment is essential after these implantation and irradiation processes, and when introducing point defects into diamond by ion implantation, heat treatment is performed to repair the implantation damage to the diamond crystal. Also, since color centers are pairs of impurities and vacancies, when vacancies are formed by electron beam irradiation, color centers are formed by heat treatment as a post-process.

[0003] Heat treatment at 1000°C or higher has been found to be effective for the above-mentioned purposes. However, at this temperature, the diamond surface is oxidized and etched, deteriorating. If the treatment atmosphere is uncontrolled, such as in air, the diamond surface is significantly oxidized / etched during heat treatment, causing damage to the diamond, such as increased surface roughness and cracks. Ultimately, the entire diamond crystal disappears. Therefore, when heat treating diamonds, atmospheric control, such as ultra-high vacuum or high-purity inert gas, is generally essential to prevent oxidation of the diamond surface. The equipment required for controlling the atmosphere is expensive and large-scale, which has been a problem when heat treating diamonds. Furthermore, the higher the heat treatment temperature, the more precise the degree of vacuum and atmospheric control must be.

[0004] As a method for suppressing surface oxidation, a technique of coating the diamond surface with a carbon layer such as diamond-like carbon (DLC) has been proposed, and is disclosed in Patent Document 1, for example. However, this method requires atmospheric control using an inert gas such as Ar gas, and depositing these carbon layers requires the use of a complex chemical vapor deposition (CVD) device.Furthermore, because the coating film is deposited using a plasma-based CVD method, plasma damage occurs to the diamond surface, which is a problem. Therefore, there was a need for a coating structure that could be formed using a simple method without damage and that would function even in an oxygen-containing atmosphere.

[0005] Furthermore, accurate measurement of the sample temperature after heating is essential to improve the reproducibility of the heat treatment. A non-contact radiation thermometer is generally used for this measurement. Because diamonds are highly transparent, the amount of radiation emitted from diamonds is less than that of ordinary samples. Therefore, when measuring the diamond heating temperature using a radiation thermometer, there is a problem that the diamond temperature is underestimated.

[0006] In addition, silicon carbide (SiC), which is currently attracting attention as a power device material, requires an ion implantation process and high-temperature heat treatment to activate the implanted elements for device fabrication. The activation process requires high temperatures of over 1700°C, and surface degradation during this process has been a problem. As a method for suppressing surface deterioration due to high-temperature treatment, two methods have been proposed: applying resist to the surface and thermally curing it, and forming a film by plasma decomposition of acetylene. However, the former method requires a lot of know-how for application and thermal curing, while the latter requires a special device called a plasma device. These processes are disclosed in Non-Patent Documents 1 and 2 and Patent Document 2. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-9425 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-115875 [Non-patent literature]

[0008] [Non-Patent Document 1] SiC Power Device Production Technology, Technical Journal, ULVAC (June 9, 2016) [Non-patent document 2] Y. Negoro, T. Kimoto, H. Matsunami, F. Schmid and G. Pensl, J. Appl. Phys., Vol. 96, No. 9, pp4916-4922 (2004) [Non-patent document 3] Inayoshi Noda, Materials, Vol. 13, No. 132, pp. 657-663, September 1964 [Non-patent document 4] National Institute of Advanced Industrial Science and Technology (AIST) Safety Data Sheet, NMIJ RM 1102-a, January 31, 2020 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to prevent damage to the surface of a solid substrate, such as diamond or silicon carbide, whose main constituent element is carbon, during high-temperature treatment, and to make the thermal radiation from the solid substrate blackbody radiation. [Means for solving the problem]

[0010] The configuration of the present invention is shown below. (Configuration 1) A solid substrate having a solid containing carbon as a main constituent element formed on at least a first main surface thereof, and glassy carbon having a thickness of 100 nm or more and 100 μm or less formed on the first main surface of the solid substrate. (Configuration 2) 2. The solid substrate according to claim 1, wherein the solid is one selected from the group consisting of diamond, silicon carbide, boron carbide, and carbon nitride. (Configuration 3) 2. The solid substrate according to claim 1, wherein the solid is diamond. (Configuration 4) 4. The solid substrate according to configuration 3, wherein the surface of the diamond is one plane selected from the group consisting of a (100) plane, a (110) plane, and a (111) plane. (Configuration 5) 5. The solid substrate according to any one of configurations 1 to 4, wherein the glassy carbon has a thickness of 200 nm or more and 50 μm or less. (Configuration 6) preparing a solid substrate having a solid material containing carbon as a main constituent element formed on at least a first main surface thereof; A method for manufacturing a solid substrate, comprising depositing glassy carbon having a thickness of 100 nm or more and 100 μm or less on a first main surface of the solid substrate by one or more methods selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and deposition. (Configuration 7) 7. The method for producing a solid substrate according to claim 6, wherein the solid is one selected from the group consisting of diamond, silicon carbide, boron carbide, and carbon nitride. (Configuration 8) 8. The method for producing a solid substrate according to claim 6 or 7, wherein the glassy carbon has a thickness of 200 nm or more and 50 μm or less. (Configuration 9) 7. The method for producing a solid substrate according to claim 6, wherein after the deposition, the solid substrate is subjected to a heat treatment at 1000° C. or higher under a vacuum of 10 Pa or lower, but below the temperature at which the solid sublimes. (Configuration 10) preparing a solid substrate having a solid material containing carbon as a main constituent element formed on at least a first main surface thereof; depositing glassy carbon to a thickness of 100 nm or more and 100 μm or less on the first main surface of the solid substrate by one or more methods selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and deposition; subjecting the solid substrate to one or more treatments selected from the group consisting of a treatment for forming an NV center and a heat treatment for recovering crystal defects formed in the solid substrate; removing said glassy carbon. (Configuration 11) 11. The method for manufacturing a solid-state device according to claim 10, wherein the solid is one selected from the group consisting of diamond, silicon carbide, boron carbide, and carbon nitride. (Configuration 12) 12. The method for manufacturing a solid-state device according to claim 10, wherein the thickness of the glassy carbon is 200 nm or more and 50 μm or less. (Configuration 13) 11. The method for manufacturing a solid-state device according to claim 10, wherein the glassy carbon is removed by one or more methods selected from the group consisting of wet etching with a mixed acid of sulfuric acid and nitric acid, and dry etching in an oxygen atmosphere. [Effects of the Invention]

[0011] According to the present invention, damage to the surface of a substrate containing carbon as a main constituent element during high-temperature treatment can be suppressed, and further, thermal radiation from the substrate can be made blackbody radiation. Specifically, surface damage during high-temperature heat treatment of diamond can be suppressed. Furthermore, accurate temperature measurement is possible by using blackbody radiation as the thermal radiation from diamond. In this invention, the diamond surface does not deteriorate even when heat treated at 1450°C for 2 hours in a medium vacuum or at 600°C for 2 hours in an oxygen atmosphere. Furthermore, the present invention can suppress surface damage during high-temperature heat treatment of silicon carbide, and by treating the thermal radiation from silicon carbide as blackbody radiation, it becomes possible to accurately evaluate the temperature. The present invention also prevents deterioration of the silicon carbide surface even when heat treated at 1700°C for 2 hours under medium vacuum. Here, the medium vacuum in this application is 10 -3 It refers to a vacuum level of more than 0.1 Pa but less than 0.1 Pa. Incidentally, low vacuum is more than 0.1 Pa but less than 10 Pa, and high vacuum is 10 -5 Pa over 10 -3Pa or less, ultra-high vacuum is 10 -5 Refers to Pa or below. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view illustrating the structure of the solid substrate of the present invention. [Figure 2] 1 is a cross-sectional view illustrating a problem with a conventional solid substrate. [Figure 3] FIG. 1 is a flowchart showing the manufacturing process of a solid substrate of the present invention. [Figure 4] FIG. 2 is a flowchart showing the manufacturing process of the solid-state device of the present invention. [Figure 5] 1A to 1C are process diagrams showing cross-sectional views of essential parts of a manufacturing process for a power device according to the present invention; [Figure 6] 1A to 1C are process diagrams showing cross-sectional views of essential parts of a manufacturing process for a power device according to the present invention; [Figure 7] 1A to 1C are process diagrams showing cross-sectional views of essential parts of a manufacturing process for a power device according to the present invention; [Figure 8] 1A to 1C are process diagrams showing cross-sectional views of essential parts of a manufacturing process for a power device according to the present invention; [Figure 9] 1 is a stereomicroscope photograph showing the state of damage to a diamond substrate before treatment. [Figure 10] This is a stereomicroscope photograph showing the damage state of a diamond substrate after GC treatment and high-temperature (1450°C) medium-vacuum annealing process. [Figure 11] This is a stereomicroscope photograph showing the damage state of a diamond substrate that has undergone GC treatment and oxygen annealing at 600°C. [Figure 12] This is a stereomicroscope photograph showing the damage state of a diamond substrate that has been subjected to a high-temperature (1450°C) medium-vacuum annealing process without GC treatment. [Figure 13] This is a stereomicroscope photograph showing the damage state of a diamond substrate that was subjected to an oxygen annealing process at 600°C without GC treatment. [Figure 14] This is a stereomicroscope photograph showing the damage state of a diamond substrate that has undergone GC treatment and oxygen annealing at 650°C. [Figure 15] 1 is a stereomicroscope photograph showing the state of damage to a SiC substrate before treatment. [Figure 16] This is a stereomicroscope photograph showing the damage state of a SiC substrate that has undergone GC treatment and a high-temperature (1700°C) annealing process. [Figure 17] This is a stereomicroscope photograph showing the damage state of a SiC substrate that has been subjected to a high-temperature (1700°C) annealing process without GC treatment. [Figure 18] FIG. 1 is a characteristic diagram showing the results of Raman spectroscopy measurement of a sample on a diamond substrate that has been subjected to GC processing. [Figure 19] These are stereomicroscope photographs showing the difference in blackening between those with and without GC treatment, and the damage state of the diamond substrate. [Figure 20] These are stereomicroscope photographs showing the difference in blackening between those with and without GC treatment, and the damage state of the diamond substrate. [Figure 21] 10 shows stereomicroscope photographs showing the difference in blackening between those with and without GC treatment, and the state of damage to the SiC substrate. [Figure 22] 10 is a stereomicroscope photograph showing the effect of the thickness of the deposited GC film. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment 1) In the first embodiment, a solid substrate of the present invention will be described.

[0014] As mentioned in the background section, conventional heat treatment of diamonds has been associated with the problem of etching the diamond surface. This situation can be explained using Figure 2. A chip 3 forms on the surface of a solid substrate 102 (diamond substrate 1), resulting in diamond-based debris 4, which causes significant surface irregularities. The debris 4 acts as a foreign substance, reducing the yield of devices fabricated using the solid substrate 102. Furthermore, unintentional surface irregularities degrade the quality of the solid substrate 102. For example, in a semiconductor device that uses the solid substrate 102 as a semiconductor layer made of diamond, the irregularities formed at the semiconductor layer interface become nests for dangling bonds, generating interface states and reducing mobility due to scattering.

[0015] This occurs when residual oxygen in the processing system reacts with the carbon that makes up the diamond at high temperatures. Therefore, in order to prevent oxygen from reaching the diamond surface, heat treatment of diamonds has had to be carried out using an ultra-high vacuum exhaust system or a system with an inert gas atmosphere.

[0016] This problem is not limited to diamond substrates, but is common to solids whose main component is carbon. Here, a solid whose main component is carbon refers to a solid in which the ratio of carbon to the total constituent elements is 10% to 100% in terms of atomic ratio. Specific examples include diamond, silicon carbide (SiC), boron carbide, and carbon nitride.

[0017] In this first embodiment, the above problem is solved by using a substrate 1 whose main component is carbon, for example, a solid substrate 101 in which a glassy carbon layer (GC layer) 2 is formed on the substrate surface (first main surface) 1a of a diamond substrate 1, as shown in Figure 1. By bonding the GC film 2, which has excellent high-temperature resistance, low gas permeability, and excellent mechanical strength, to the diamond to coat the diamond surface, etching of the diamond surface is significantly suppressed even when heat treatment is performed under medium vacuum or in an oxygen atmosphere. Here, heat treatment under medium vacuum refers to a process in which the GC film 2 is 1x10 -3 Pa over 1 × 10-1 Heat treatment in an oxygen atmosphere is performed at a temperature of 1000°C or higher under an oxygen partial pressure of 1×10 Pa or less. -1 This refers to a temperature of 600°C or higher at a pressure of 21 kPa or higher and 21 kPa or lower. As long as the oxygen partial pressure is within this range, the absolute pressure during the heat treatment may be either reduced or elevated. There is no particular upper limit to the temperature, as long as it is below 3652°C at which the GC layer sublimes and is lower than the temperature at which the solid (substrate) being used sublimes. GC is disclosed in, for example, Non-Patent Document 3, and its sublimation temperature is disclosed in Non-Patent Document 4.

[0018] The material of the solid substrate 101 may be the above-mentioned diamond, silicon carbide, boron carbide, and carbon nitride. Among these, diamond and silicon carbide are particularly susceptible to damage during the heat treatment, and among these, the effect of forming the GC layer 2 is particularly great for diamond. Furthermore, since the characteristics of devices and elements using solid substrates 101 made of diamond with the (100), (110) and (111) faces are susceptible to surface damage to the solid substrate 101, the effect of forming the GC layer 2 on one face selected from the group consisting of the (100), (110) and (111) faces of the diamond is particularly great.

[0019] Here, the thickness of the GC layer 2 is preferably 100 nm or more and 100 μm or less. By making the thickness 100 nm or more, the occurrence of chips 3 on the substrate surface and the resulting separated material 4 shown in FIG. 2 is prevented, the substrate surface becomes a smooth surface with few irregularities, and it is possible to provide a solid substrate 101 with little damage to the surface. There is no particular upper limit on the thickness, but at 100 μm or more, the protective effect on the substrate surface, i.e., the effect of preventing surface damage such as chips 3, separated material 4, and surface irregularities, saturates.

[0020] A method for manufacturing the substrate (solid substrate) 1 of the first embodiment will be described with reference to FIG. First, a solid substrate is prepared, in which a solid containing carbon as the main constituent element is formed on at least the first main surface (step S11 in FIG. 3). The solid can be one selected from the group consisting of diamond, silicon carbide, boron carbide, and carbon nitride. Among them, diamond and silicon carbide, especially diamond, are preferred because they can best demonstrate the effects of the present invention. As the crystal plane of diamond, the (100), (110), and (111) planes are preferred.

[0021] Next, glassy carbon having a thickness of 100 nm or more and 100 μm or less is formed (deposited) on the first main surface 1a of the solid substrate 101 (step S12). The deposition method can be one or more selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and welding. For example, in the thermal evaporation method, a glassy carbon rod is prepared and heated in a vacuum to sublimate the glassy carbon. As seen in this thermal evaporation method, the deposition of the GC layer does not require sophisticated equipment like DLC, and can be achieved with inexpensive and simple equipment. Through the above steps, the solid substrate 101 is obtained (step S14).

[0022] Here, after depositing the GC layer (after step S12), if a heat treatment is performed at 1000°C or higher but below the temperature at which the solid sublimes (step S13), the quality of the GC layer will be improved, resulting in a solid substrate with excellent heat resistance and oxidation resistance. The pressure at this time should be 10 Pa or less. This is because the vacuum level of 1×10 required to prevent surface damage without the GC layer 2 is 1×10 -5 The pressure condition is much milder than that of 1 Pa. This method makes it possible to manufacture the solid substrate 101 cheaply and easily.

[0023] The effect of the GC layer 2 is not limited to suppressing damage to the substrate surface that occurs during heat treatment. If the thickness of the GC layer 2 is 200 nm or more, it will be sufficiently blackened (blackened), and the accuracy of temperature measurement using blackbody radiation can be dramatically improved. For example, the accuracy of temperature control in the subsequent annealing process will be improved.

[0024] In addition, by uniformly blackening the diamond surface in this manner, it becomes possible to increase the infrared absorptivity and at the same time increase the in-plane uniformity of the absorptivity, thereby improving the reproducibility of solid substrate heat treatment.

[0025] The above-mentioned effect can be obtained with a solid substrate having a solid containing carbon as a main constituent element formed on at least the first main surface, but is particularly effective with diamond substrates and silicon carbide substrates. By covering the silicon carbide surface with the GC layer 2, etching of the silicon carbide surface can be significantly suppressed even when high-temperature heat treatment is performed under high vacuum.

[0026] A thickness of 100 nm or more of the GC layer 2 is effective in preventing damage near the surface of the solid substrate 1, and a thickness of 200 nm or more provides sufficient blackening, improving the accuracy of temperature measurement and enabling increased in-plane uniformity during heat treatment. On the other hand, there is no particular upper limit to the thickness of the GC layer 2, but a thickness of 100 μm or less is preferable in order to achieve a saturation point in the protective effect on the substrate surface, i.e., the effect of preventing surface damage such as chips 3, separated particles 4, and surface irregularities, and a thickness of 50 μm or less has the effect of improving the surface flatness and adhesion of the GC layer.

[0027] (Embodiment 2) In the second embodiment, a method for manufacturing a solid-state device will be described with reference to FIG. First, a solid substrate 1 is prepared, in which a solid containing carbon as a main constituent element is formed on at least the first main surface (step S21 in FIG. 4). As in the first embodiment, the solid can be one selected from the group consisting of diamond, silicon carbide, boron carbide, and carbon nitride. Among them, diamond and silicon carbide, especially diamond, can best exhibit the effects of the present invention and are therefore preferably used. As the crystal planes of diamond, the (100), (110), and (111) planes are preferably used.

[0028] Next, glassy carbon (GC layer 2) having a thickness of 100 nm or more and 100 μm or less is formed (deposited) on the first main surface 1a of the solid substrate 1 (step S22). As in the first embodiment, the deposition method can be one or more selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and welding. For example, in the thermal evaporation method, a glassy carbon rod is prepared and heated in a vacuum by passing an electric current through it to sublimate the glassy carbon. As can be seen from this thermal evaporation method, the deposition of the GC layer 2 does not require sophisticated equipment like that required for DLC, and can be achieved with inexpensive and simple equipment.

[0029] Thereafter, a heat treatment for forming NV centers (nitrogen-vacancy centers) and / or a heat treatment for recovering crystal defects formed in the solid substrate (these heat treatments are also referred to as first heat treatments) is performed (step S23). For example, when diamond is used as the solid substrate 1, the heat treatment temperature for forming NV centers can be 700°C or higher and 1900°C or lower, and the heat treatment temperature for recovering crystal defects can be 800°C or higher and 2300°C or lower. Furthermore, when silicon carbide is used as the solid substrate 1, the heat treatment temperature for recovering crystal defects can be 1300°C or higher and 2000°C or lower. The heat treatment environment can be a vacuum, a rare gas atmosphere, a hydrogen atmosphere, or a mixed atmosphere of rare gas and hydrogen.

[0030] Thereafter, the GC layer 2 is removed (step S24). Methods for removing the GC layer 2 include one or more methods selected from the group consisting of wet etching, heat treatment in an oxygen atmosphere (temperature, for example, 400°C to 600°C), and dry etching using oxygen such as oxygen plasma, oxygen ions, activated oxygen, or ozone. Among these, wet etching, particularly wet etching using a mixed acid of sulfuric acid and nitric acid, is preferred because it is less likely to damage the substrate 1. In wet etching using a mixed acid, it is preferable to set the processing temperature to 150°C to 300°C, as this increases the etching rate. Then, a solid-state device is fabricated using the substrate 1 from which the GC layer 2 has been removed (step S25).

[0031] This method allows the desired NV centers to be formed in the solid substrate 1 and / or the crystal defects formed in the solid substrate 1 to be repaired while suppressing damage to the substrate surface that occurs during the first heat treatment, resulting in solid-state devices with excellent electrical characteristics.

[0032] Here, the effect of the GC layer 2 is not limited to suppressing damage to the substrate surface that occurs during the first heat treatment. If the thickness of the GC layer 2 is 200 nm or more, it will be sufficiently blackened (blackened), making it possible to dramatically improve the accuracy of temperature measurement using blackbody radiation, and increasing the accuracy of temperature control in the first heat treatment. In addition, by uniformly blackening the surface of the solid substrate in this manner, it becomes possible to increase the infrared absorptivity and at the same time increase the in-plane uniformity of the absorptivity, thereby improving the reproducibility of the first heat treatment.

[0033] If the thickness of the GC layer 2 is less than 800 nm, it will adhere sufficiently to the solid substrate 1 and will not easily peel off from the solid substrate 1. The adhesion to the solid substrate 1 strongly depends on the surface condition of the solid substrate 1 and the deposition conditions of the GC layer 2, particularly the stress generated during deposition. By using a solid substrate material that has high adhesion to the GC layer 2, such as a transition metal such as titanium, by increasing the cleanliness of the surface of the solid substrate 1 through a cleaning process, or by using deposition conditions that suppress or mitigate the generation of stress in the GC layer 2, peeling of the GC layer 2 can be prevented even if the thickness exceeds 800 nm, and depending on the conditions, peeling of the GC layer 2 can be suppressed even if the thickness is 100 μm. There is no particular upper limit to the thickness of the GC layer 2, but at 100 μm or more, the effect of protecting the substrate surface, that is, the effect of preventing surface damage such as chips 3, separated particles 4 and surface irregularities, becomes saturated. Here, if the thickness of the GC layer 2 is set to 50 μm or less, the surface flatness and adhesiveness of the GC layer are improved.

[0034] (Embodiment 3) In the third embodiment, a method for manufacturing a semiconductor device (MOSFET) 201 suitable for power applications using a vertical structure will be described with reference to FIGS.

[0035] First, n + Semiconductor layer 51,n - A semiconductor substrate is prepared in which a drift layer 52a and a p-type semiconductor layer 53a are sequentially stacked (FIG. 5(a)). + The semiconductor layer 51 is disposed for the purpose of making an ohmic contact that reduces the contact resistance with the drain electrode 65 that will be formed later. Note that the drift layer 52a can be made of phosphorus-doped diamond or nitrogen-doped silicon carbide (SiC), and the p-semiconductor layer 53a can be made of boron-doped diamond or aluminum-doped SiC.

[0036] Thereafter, a resist pattern 54 is formed by lithography and ions are implanted to implant n ions in predetermined locations near the surface of the p semiconductor layer 53a. +A layer 55a is formed (FIG. 5(b)), and the resist pattern 54 is removed by ashing or using a stripping solution. Here, examples of ion implantation species include phosphorus and nitrogen. Thereafter, a resist pattern 56 is formed by lithography and ions are implanted to form p ions in predetermined locations near the surface of the p semiconductor layer 53a. + A layer 57a is formed (FIG. 5(c)), and the resist pattern 56 is removed by ashing or using a stripping solution. Here, examples of the ion implantation species include boron and aluminum.

[0037] Next, a glassy carbon layer (GC layer) 58 is formed on the first main surface of the sample by the method described in the first embodiment (FIG. 5(d)). The thickness of the GC layer 58 can be 100 nm or more and 100 μm or less. By making the GC layer 58 100 nm or more, damage to the substrate during subsequent annealing, i.e., the occurrence of chips 3 and separated particles 4 on the substrate surface as described in FIG. 2, can be suppressed. By making the GC layer 58 200 nm or more, the GC layer 58 is sufficiently blackened, dramatically improving the accuracy of temperature measurement using blackbody radiation. This, for example, increases the accuracy of temperature control during subsequent annealing, thereby improving the characteristics of the manufactured semiconductor device 201, reducing lot-to-lot variations, and improving quality control accuracy. Furthermore, by making the GC layer 58 less than 800 nm, the GC layer 58 is less likely to peel, contributing to an improvement in the manufacturing yield of the semiconductor device 201. While there is no particular upper limit to the thickness of the GC layer 58, the surface damage suppression effect saturates at a thickness of 100 μm.

[0038] Annealing is then performed (not shown) at a temperature of 800°C to 2300°C in a vacuum environment when diamond is used as the semiconductor substrate, or at a temperature of 1300°C to 2000°C in an argon atmosphere when SiC is used. Thereafter, the GC layer 58 is removed (FIG. 6(a)). The GC layer 58 can be removed, for example, by a hot mixed acid treatment in a mixed solution of sulfuric acid and nitric acid at 220°C.

[0039] Next, a hard mask 59a for etching is formed on the first main surface of the sample (FIG. 6(b)), and subsequently a resist pattern 60 for gate formation is formed by lithography (FIG. 6(c)). Here, an oxide film such as SiO2 can be preferably used as the hard mask, and the film formation method can include CVD and sputtering.

[0040] Then, n + through the layer 55a and the p semiconductor layer 53a, - An opening reaching a part of the semiconductor layer 52a is opened by etching (FIG. 6(d)). In FIG. 6(d), the resist pattern 60 and the hard mask pattern 59b are used as an etching mask. + layer 55a, p semiconductor layer 53a and n - The example shows a case where a part of the semiconductor layer 52a is etched. The resist pattern 60 is used as an etching mask to process the hard mask 59a to form a hard mask pattern 59b. The resist pattern 60 is then removed, and the hard mask pattern 59b is used as an etching mask to perform etching. + layer 55a, p semiconductor layer 53a and n - Alternatively, the semiconductor layer 52a may be partially etched without forming the hard mask 59a, and the resist pattern 60 may be used as an etching mask. + layer 55a, p semiconductor layer 53a and n - A portion of the semiconductor layer 52a may be etched. Thereafter, the resist pattern 60 is removed by ashing and using a remover (FIG. 7(a)).

[0041] Thereafter, an insulating film 61a is deposited (FIG. 7(b)). The insulating film 61a may be made of SiO2, SiON, Si3N4, Al2O3, HfO2, or HfSiO xExamples of gate insulating film materials include oxide films such as AlON, oxynitride films, and nitride films. These films may be used as single-layer films, or multiple types of films may be used as laminated films. Examples of film formation methods include ALD, PE-ALD, sputtering, and CVD. It is preferable that the insulating film 61a be conformally deposited.

[0042] Thereafter, a conductive film 62a, which is an electrode material for forming a gate electrode, is deposited on the gate insulating film 61a (FIG. 7(c)), and processed to form the gate electrode 62. During this process, a part of the insulating film 61a is removed to become the gate insulating film 61 (FIG. 7(d)). Examples of electrode materials include at least one selected from the group consisting of Al, Ti, W, Pt, Au, Ag, Ru, Rh, Pd, Ni, Sn, Zn, and poly-Si, alloys containing at least one selected from these groups, and compounds such as nitrides, carbides, and carbonitrides containing at least one selected from these groups. Methods for applying this electrode material include vapor deposition, sputtering, and CVD. Examples of this processing method include a method using lithography and etching, a polishing method such as CMP (Chemical Mechanical Polishing), and an etch-back method.

[0043] Thereafter, the hard mask 59c remaining after processing is removed by etching or the like, and an insulating film 63a is deposited (FIG. 8(a)). Examples of the insulating film 63a include SiO2, SiON, Si3O4, and SOG (Spin on Glass). Examples of the method for forming the insulating film 63a include CVD, sputtering, and coating. Note that if the remaining hard mask 59c does not adversely affect the operation of the semiconductor device 201, it is not necessary to remove the hard mask 59c.

[0044] Thereafter, the insulating film 63a is +An opening for electrical contact with the layer is made in the insulating film 63 (FIG. 8(b)).

[0045] Next, an electrode material (conductive material) is deposited, and the source electrode 64 is formed by performing lithography and dry etching. Then, the electrode material (conductive material) is applied to the back surface (n + A drain electrode 65 is formed by applying lithography and dry etching to provide the semiconductor device 201 (FIG. 8(c)). Examples of the electrode material include at least one selected from the group consisting of Al, Ti, W, Pt, Au, Ag, Ru, Rh, Pd, Ni, Sn, Zn, and poly-Si, alloys containing at least one selected from these groups, and compounds such as nitrides, carbides, and carbonitrides containing at least one selected from these groups. Methods for applying the electrode material include vapor deposition, sputtering, and CVD.

[0046] The semiconductor device 201 provided by the manufacturing method of the third embodiment has high electrical withstand voltage and stable electrical operation because the surface of the semiconductor substrate made of diamond, SiC, etc. is less damaged. Furthermore, there is little manufacturing variation between lots of the semiconductor device 201, making it possible to provide a stable, high-quality semiconductor device 201. Furthermore, as described above, since the sample surface is sufficiently blackened during annealing, temperature measurement using the blackbody radiation principle can be performed with extremely high measurement accuracy. This makes it possible to significantly improve annealing temperature control, and to provide semiconductor devices 201 that operate stably with little variation and with a high yield.

[0047] When the semiconductor device 201 is made of a semiconductor material with a wide band gap and high dielectric strength, such as diamond or SiC, it becomes a power device with excellent power characteristics that utilizes the high dielectric breakdown field strength in combination with the vertical MOS structure. In conventional methods, damage to the semiconductor substrate surface during annealing prevents the material from fully utilizing its inherent performance, such as dielectric strength. However, this method minimizes damage to the semiconductor substrate surface, allowing the material's inherent performance to be fully utilized, and the element structure, which is suitable for power transistors, makes it possible to provide power devices with excellent electrical characteristics. [Example]

[0048] Example 1 In Example 1, the surface condition of the diamond substrate was observed and measured using a stereomicroscope and a laser microscope to evaluate surface damage. Here, the stereomicroscope used was an SZ61 (manufactured by Olympus Corporation), and the surface was observed at a magnification of 1.5 with an auxiliary objective. The laser microscope VK-9700 (manufactured by Keyence Corporation) used a wavelength of 408 nm, and was used to evaluate the roughness of the diamond substrate surface.

[0049] The sample to be evaluated, a glassy carbon laminated diamond substrate (hereinafter referred to as GC laminated substrate) 101, is shown in Figure 1. The GC laminated substrate 101 has a diamond substrate 1 and a GC layer 2 integrally formed on the substrate surface 1a of the diamond substrate 1. Here, the substrate surface 1a of the diamond substrate 1 is a (100) plane, and the thickness of the GC layer 2 is 200 nm.

[0050] To confirm the GC layering effect, we first observed the state of the diamond substrate 1 before heat treatment. Figure 9 shows a stereomicroscope image of the surface, and no surface damage was observed. Furthermore, as shown in Table 1, the surface roughness Rz was 77 nm, indicating high flatness.

[0051] Next, a GC layer 2 was thermally evaporated onto the diamond surface to produce a GC laminate substrate 101 . The GC deposition conditions were as follows: a glassy carbon rod was heated in a low vacuum by passing an electric current through it, causing it to sublimate, and the GC was deposited on the surface of the diamond substrate 1, 1 cm away from the glassy carbon rod. The current during the electric heating deposition was 70 A, the current time was 0.3 seconds, and the current was passed 10 times in total. The pressure was 4 Pa, and the substrate temperature was room temperature (24°C). The purity of the GC layer 2 of the GC laminated substrate 101 was increased by low-vacuum heat treatment at temperatures above 1000°C after deposition.

[0052] Thereafter, the GC laminated substrate 101 was placed in a vacuum (1.1×10 -3 The heat treatment was carried out at 1450°C for 120 minutes at a temperature of 1000 Pa. Thereafter, the diamond substrate 1 was treated with a hot mixed acid (a mixture of sulfuric acid and nitric acid at a temperature of 220° C.) to remove the GC layer 2 and surface deposits. After undergoing the series of steps of depositing the GC layer 2, heat treatment, and removing the GC layer 2, the surface stereomicroscope image and surface roughness of the diamond substrate 1 were evaluated in the same manner as above. The results are shown in FIG. 10 and Table 1. This sample was heat-treated at 1450°C for 120 minutes. However, because the heat treatment was carried out while covered with the GC layer 2, no surface damage was observed in the stereomicroscope image of the surface of the diamond substrate 1, and the surface roughness Rz was 82 nm, indicating high flatness.

[0053] [Table 1]

[0054] (Comparative Example 1) The diamond substrate 1 without the GC layer 2 was heat-treated at 1450°C for 120 minutes in the same medium vacuum as in Example 1, and then treated with hot mixed acid (a mixture of sulfuric acid and nitric acid, at a temperature of 220°C) to remove surface deposits, yielding a diamond substrate 1. Then, as in Example 1, surface damage of the diamond substrate 1 was evaluated using a stereomicroscope and a laser microscope. Figure 12 shows a stereomicroscope image of the surface of the diamond substrate 1 after heat treatment. Multiple surface damages are observed on the surface. The surface roughness of the surface of the diamond substrate 1 after the heat treatment is shown in Table 1. Reflecting the surface damage, the surface roughness Rz was 885 nm, an order of magnitude larger than the 77 nm before the heat treatment, resulting in a rough surface with large irregularities. For reference, an image of the surface damage is shown in FIG. 2 as surface damage 3 on the solid substrate 102 and separated matter 4 due to cracks.

[0055] Example 2 In Example 2, the heat treatment conditions were an oxygen atmosphere (2×10 4 The surface damage of the diamond substrate 1 was evaluated when the diamond substrate 1 was heated at 600°C for 120 minutes under a temperature of 1000 Pa. Here, the diamond substrate 1 to be used as the evaluation sample was obtained in accordance with Example 1 except for the heat treatment conditions. FIG. 11 shows the surface of the diamond substrate 1 after the heat treatment under a stereomicroscope, and no surface damage was observed. The surface roughness of the diamond substrate 1 after heat treatment is shown in Table 1. The surface roughness Rz was 67 nm, indicating high flatness.

[0056] (Comparative Example 2) Comparative Example 2 is the result of preparing a sample in the same manner as in Example 2, except that the GC layer 2 was not laminated, and evaluating the sample in the same manner as in Example 2. Therefore, Comparative Example 2 does not include the GC layer 2, and the heat treatment conditions are an oxygen atmosphere (2×10 4 The diamond substrate 1 was heated at 600°C for 120 minutes under a temperature of 100 Pa. Figure 13 shows a stereomicroscope image of the diamond substrate surface after heat treatment. Multiple surface damages are observed on the surface. The surface roughness of the diamond substrate surface after heat treatment is shown in Table 1. The surface roughness Rz was 472 nm, indicating a deterioration in flatness.

[0057] (Comparative Example 3) The heat treatment conditions were oxygen atmosphere (2 × 10 4A diamond substrate was obtained in the same manner as in Example 2, except that the heating was carried out at 650°C for 120 minutes at a temperature of 1000 kJ / cm2 (Pa). Surface damage to the diamond substrate was evaluated using a stereomicroscope and a laser microscope. Figure 14 shows a stereomicroscope image of the diamond substrate surface after heat treatment. Multiple surface damages were formed on the surface. The surface damage is considered to be the state shown as surface damage 3 in Figure 2. The surface roughness of the diamond substrate surface after heat treatment is shown in Table 1. The surface roughness Rz was 770 nm, indicating a deterioration in flatness.

[0058] Example 3 In FIG. 1, the substrate 1 is a silicon carbide (SiC) substrate, and the heat treatment conditions are medium vacuum (3×10 -4 A SiC substrate was obtained in the same manner as in Example 1, except that the heating was performed at 1700°C for 120 minutes at a temperature of 1000 Pa. Also, in the same manner as in Example 1, surface damage of the diamond substrate was evaluated using a stereomicroscope and a laser microscope. Fig. 15 shows a stereomicroscope image of the SiC substrate surface before heat treatment, and Fig. 16 shows that after heat treatment and after removing the GC layer 2. No surface damage was observed in either case. The surface roughness of the SiC substrate surface after heat treatment is shown in Table 2. The surface roughness Rz was 56 nm, almost the same as the 60 nm before heat treatment, demonstrating high flatness.

[0059] [Table 2]

[0060] Comparative Example 4 Except for not depositing the GC layer 2, an SiC substrate was obtained in the same manner as in Example 3. Then, surface damage of the SiC substrate was evaluated using a stereomicroscope and a laser microscope. Figure 17 shows a stereomicroscope image of the SiC substrate surface after heat treatment. Multiple surface damages were observed on the surface. The surface roughness of the SiC substrate surface after heat treatment is shown in Table 1. The surface roughness Rz was 214 nm, indicating a deterioration in flatness.

[0061] Example 4 In Example 4, the heat treatment was carried out in a medium vacuum (1.1 × 10 -3 A GC laminate substrate 1 was prepared using a diamond substrate 1 in the same manner as in Example 1, except that the temperature was 1000°C under 1 Pa, and Raman spectroscopy was performed on the sample. The Raman spectroscopy measurement device used was an α-300R (manufactured by WITec). As a result, as shown in Figure 18, it was confirmed that the deposited GC layer 2 was glassy carbon, and it was also shown that the quality of the glassy carbon improved when the heat treatment was performed in a low vacuum (10 Pa). Similarly, when the temperature rise rate in the heat treatment process is slow, the quality of the GC improves during the heat treatment process, resulting in a solid substrate with excellent heat resistance and oxidation resistance.

[0062] Example 5 In Example 5, a sample was prepared according to Example 1, and before the treatment, after the deposition of the CG layer 2 (composite formation), a medium vacuum (1.1 × 10 -3 The change in blackness was measured by taking photographs at each stage after annealing at 1450°C under 100 Pa and acid (hot mixed acid) treatment (GC / diamond composite). For comparative evaluation, measurements were also taken on a sample that underwent the same process without depositing the CG layer 2. The results are shown in Figure 19. In the GC / diamond composite state in which the GC layer 2 is formed on the diamond substrate 1, sufficient blackening of the sample is observed only at the time when the GC layer 2 is formed. This blackening enabled accurate temperature measurement of the surface of the GC / diamond composite sample using blackbody radiation.When the CG layer 2 was not deposited, the formation of segregated matter was confirmed after annealing at 1450°C under medium vacuum and acid treatment.

[0063] Example 6 In Example 6, a sample was prepared according to Example 2, and before the treatment, after the deposition of the CG layer 2 (composite formation), the sample was placed in an oxygen gas atmosphere (2 × 10 4Photographs were taken at each stage after annealing at 600°C under (Pa) and acid (hot mixed acid) treatment to measure the change in blackness. For comparative evaluation, measurements were also taken on a sample that underwent the same process without depositing the CG layer 2. The results are shown in Figure 20. As in Example 5, in the GC / diamond composite state in which the GC layer 2 is formed on the diamond substrate 1, sufficient blackening of the sample is observed only at the time when the GC layer 2 is formed. This blackening enabled accurate temperature measurement of the sample surface made of GC / diamond composite by utilizing blackbody radiation.

[0064] Example 7 In Example 7, a sample using a SiC substrate was prepared according to Example 3, and before the treatment, after the deposition of the CG layer 2, the sample was placed in a high vacuum (3×10 -4 Photographs were taken at each stage to measure the change in blackness after annealing at 1700°C under (Pa) and after acid (hot mixed acid) treatment. For comparative evaluation, measurements were also taken on a sample that underwent the same process without depositing the CG layer 2. The results are shown in Figure 21. In the GC / SiC composite state where GC layer 2 is formed on SiC substrate 1, blackening of the sample is observed when GC layer 2 is formed and when heat treatment is performed. After heat treatment, blackening is also observed in the case of only the SiC substrate without GC layer 2, but as can be seen from the grid placed underneath the substrate, the blackening is more severe in the GC / SiC composite where GC layer 2 is formed. Furthermore, the blackening in the case of only the SiC substrate is due to surface damage, and the degree of blackening is poorly reproducible. This blackening enabled accurate temperature measurement of the sample surface made of GC / SiC composite by utilizing blackbody radiation.

[0065] Example 8 In Example 8, the applicable range of film thickness of the GC layer 2 was evaluated. A diamond substrate 1 similar to that in Example 1 was prepared, and a GC layer 2 was deposited by a process conforming to Example 1. Here, the film thickness of the GC layer 2 was set to five levels: 40 nm, 120 nm, 200 nm, 400 nm, and 800 nm. The results are shown in Figure 22. The thicker the GC layer 2, the greater the degree of blackening, but it can be seen that when the thickness is 200 nm or more, it becomes difficult to distinguish the grid placed below the diamond substrate 2. On the other hand, when the film thickness is 800 nm, peeling of the GC layer 2 occurred in some areas after film formation. Note that the photograph showing film peeling in the lower right of Figure 22 was taken under different exposure conditions. Peeling was observed in some areas immediately after film formation. From the above results, it was confirmed that a sufficient blackening can be obtained when the film thickness of the GC layer 2 is 200 nm or more, but that film peeling can occur when the film thickness is 800 nm. [Industrial Applicability]

[0066] As described above, the present invention makes it possible to suppress surface damage during high-temperature heat treatment of diamond, and also makes it possible to accurately evaluate the temperature by treating the thermal radiation from diamond as blackbody radiation. Furthermore, the present invention can suppress surface damage during high-temperature heat treatment of silicon carbide, and by treating the thermal radiation from silicon carbide as blackbody radiation, it also becomes possible to accurately evaluate the temperature. Diamond and silicon carbide are semiconductors that are at the core of power semiconductors, which are expected to be one of the engines of a smart society. Reducing damage to these semiconductors and managing their heat treatment temperatures are essential to improving the performance of products that use these semiconductors. Therefore, it is believed that the present invention will have a great impact on society and will also have a great influence on industry. [Explanation of symbols]

[0067] 1 Diamond substrate, substrate, solid substrate 1a 1st main surface (substrate surface) 2. Glassy carbon layer (GC layer) 3. Chip (surface damage) 4 Separate 51n + Semiconductor layer 52 Drift layer (n - semiconductor layer) 52a n- Semiconductor layer 53 Base layer (p semiconductor layer) 53a p-semiconductor layer 54 Resist Pattern 55n + layer 55a n + layer 56 Resist Pattern 57 pages + layer 57a p + layer 58 Glassy carbon layer (GC layer) 59a Hard Mask 59b Hard mask pattern 59c Hard Mask Pattern 60 Resist Pattern 61 Gate insulating film 61a Insulating film 62 gate electrode 62a Conductive film 63 Insulating layer 63a Insulating film 64 Source electrode 65 Drain electrode 101 Glassy carbon laminated diamond substrate (GC laminated substrate), solid substrate 102 Solid substrate 201 Semiconductor devices (power devices, MOSFETs)

Claims

1. a solid substrate having a solid containing carbon as a main constituent element formed on at least a first main surface thereof, and blackened glassy carbon having a thickness of 200 nm or more but less than 800 nm formed on the first main surface thereof; A solid substrate for a semiconductor device, wherein the solid is diamond or silicon carbide.

2. 2. The solid substrate for a semiconductor device according to claim 1, wherein said solid is diamond.

3. 3. A solid substrate for a semiconductor device according to claim 2, wherein the surface of said diamond is one plane selected from the group consisting of a (100) plane, a (110) plane and a (111) plane.

4. The solid substrate for a semiconductor device according to claim 1, wherein the solid is silicon carbide.

5. A solid substrate for a semiconductor device described in any one of claims 1 to 4, wherein the blackened glassy carbon is a blackbody radiator.

6. preparing a solid substrate having a solid material containing carbon as a main constituent element formed on at least a first main surface thereof; A method for manufacturing a solid substrate, comprising depositing glassy carbon having a thickness of 100 nm or more and 100 μm or less on a first main surface of the solid substrate by one or more methods selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and welding.

7. 7. The method for producing a solid substrate according to claim 6, wherein the solid is one selected from the group consisting of diamond, silicon carbide, boron carbide and carbon nitride.

8. 8. The method for producing a solid substrate according to claim 6, wherein the thickness of the glassy carbon is 200 nm or more and 50 [mu]m or less.

9. The method for producing a solid substrate according to claim 6, wherein after the deposition, the solid substrate is subjected to a heat treatment in a low vacuum of 10 Pa or less at a temperature of 1000°C or more but below the temperature at which the solid sublimes.

10. preparing a solid substrate having a solid material containing carbon as a main constituent element formed on at least a first main surface thereof; depositing glassy carbon to a thickness of 100 nm to 100 μm on the first main surface of the solid substrate by one or more methods selected from the group consisting of thermal evaporation, electron beam evaporation, sputtering, and deposition; subjecting the solid substrate to one or more treatments selected from the group consisting of a treatment for forming an NV center and a heat treatment for recovering crystal defects formed in the solid substrate; removing said glassy carbon.

11. 11. The method for manufacturing a solid-state device according to claim 10, wherein the solid is one selected from the group consisting of diamond, silicon carbide, boron carbide and carbon nitride.

12. 12. The method for manufacturing a solid-state device according to claim 10, wherein the thickness of the glassy carbon is 200 nm or more and 50 [mu]m or less.

13. 11. The method for manufacturing a solid-state device according to claim 10, wherein the glassy carbon is removed by at least one method selected from the group consisting of wet etching with a mixed acid of sulfuric acid and nitric acid, and dry etching in an oxygen atmosphere.

Images