Preparation method of SiC MOS tube with high thermal conductivity and wide working temperature range

Abstract

The invention discloses a SiC MOS tube with high thermal conductivity and a wide working temperature range and a preparation method thereof, and relates to the technical field of semiconductor devices. Comprising the following steps: cleaning and drying a silicon carbide wafer through an RCA standard cleaning method; then depositing an amorphous silicon film on the cleaned and dried silicon carbide surface under the condition of less than 600 DEG C through a low-pressure chemical vapor deposition method to obtain a pretreated silicon carbide wafer; oxidizing an amorphous silicon film on the pretreated silicon carbide wafer in a dry oxygen environment of 700-800 DEG C, then performing primary annealing in a nitrogen atmosphere of 1100-1200 DEG C, then spin-coating a boron diffusion layer on the surface, and performing secondary annealing treatment for 10 minutes under the condition of 900-1150 DEG C; single-layer hexagonal boron nitride is transferred to the surface of the wafer subjected to secondary annealing through acrylic organic glass by a mechanical stripping method, and then electrode forming treatment is carried out after tertiary annealing treatment; the condition of carbon residue is avoided through a low-temperature oxidation mode, and then the channel mobility is improved through a nitrogen and boron element synergistic passivation mode.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to a preparation method of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range. Background Art

[0002] The SiC MOS transistor, namely silicon carbide metal-oxide-semiconductor field effect transistor, as the core device of the third-generation semiconductor, its performance is limited by the SiC / SiO2 interface defects and high-temperature reliability problems. The traditional process has inherent defects in the formation of the gate oxide layer and the interface passivation link, and there is an urgent need for a new passivation technology to break through the bottleneck.

[0003] In the prior art, nitric oxide annealing is the mainstream passivation scheme, which reduces the defect-induced traps by forming Si≡N bonds, but there are two major drawbacks: on the one hand, the oxygen atoms in nitric oxide re-oxidize SiC, resulting in new interface defects; on the other hand, nitric oxide is a highly toxic gas and requires supporting safety equipment, increasing the cost by more than 30%. In plasma passivation, the nitrogen-hydrogen mixed plasma can passivate deep / shallow energy level traps synergistically, but its high-temperature treatment above 900°C is likely to damage the oxide layer, and the process window is narrow. A power deviation > 10% will lead to interface deterioration. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range to achieve at least partially solving the above problems.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A preparation method of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, comprising the following steps: Clean and dry the silicon carbide wafer by the RCA standard cleaning method; then deposit an amorphous silicon film on the surface of the cleaned and dried silicon carbide at a temperature of <600°C by low-pressure chemical vapor deposition to obtain a pretreated silicon carbide wafer; Oxidize the amorphous silicon film on the pretreated silicon carbide wafer in a dry oxygen environment at 700 - 800°C, then perform a first annealing in a nitrogen atmosphere at 1100 - 1200°C, then spin-coat a boron diffusion layer on the surface, and perform a second annealing treatment at 900 - 1150°C for 10 min; Transfer the single-layer hexagonal boron nitride to the surface of the wafer after the second annealing by mechanical peeling through acrylic plexiglass, and then perform a third annealing treatment and then electrode forming treatment.

[0006] Preferably, after cleaning and drying the silicon carbide wafer by the RCA standard cleaning method, anneal it in a hydrogen atmosphere at 1000°C for 5 min, and then deposit the amorphous silicon film; the deposition thickness of the amorphous silicon film is 18 - 22 nm.

[0007] Preferably, the amorphous silicon film on the pre-treated silicon carbide wafer is subjected to low-temperature oxidation for 28 - 32 min under dry oxygen conditions with a temperature of 740 - 760 °C and an oxygen concentration > 99.999%.

[0008] Preferably, the first annealing is carried out in a nitrogen atmosphere with a nitrogen concentration > 99.999% at 1130 - 1170 °C for 55 - 65 min.

[0009] Preferably, the boron diffusion layer is borosilicate glass, the thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 - 20 at%; The second annealing treatment is carried out in an inert gas atmosphere at 1000 - 1100 °C for 10 min.

[0010] Preferably, the third annealing treatment is carried out at 190 - 210 °C for 55 - 65 min.

[0011] Preferably, it further includes an interface bonding treatment step: The wafer is placed in a plasma chamber, and then a mixed gas of argon and oxygen is introduced. Radio frequency power is applied to excite the plasma to perform directional bombardment on the surface of hexagonal boron nitride, and then the third annealing treatment is carried out.

[0012] Preferably, the mixed volume ratio of argon and oxygen is 4:1, the power of the radio frequency is 45 - 55 W, and the directional bombardment time is 27 - 33 s; During the third annealing treatment, a pressure of 0.4 - 0.6 MPa is applied to the surface of hexagonal boron nitride.

[0013] The present invention also provides a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, which is obtained according to the above preparation method.

[0014] The present invention also provides an application of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, which is the application of the SiC MOS transistor obtained according to the above preparation method in the field of semiconductor device technology.

[0015] Compared with the prior art, the beneficial effects of the present invention are: By means of low-temperature oxidation, the present invention avoids the occurrence of carbon residue. Then, through the synergistic passivation of nitrogen and boron elements, the channel mobility is improved. Furthermore, through the dynamic repair of hexagonal boron nitride to integrate the two-dimensional passivation layer, the thermal conductivity and electrical stability are enhanced, breaking through the interface defect bottleneck of SiC MOS, and realizing ultra-low interface state density, wide temperature range coverage, and high thermal conductivity network. Specific embodiments

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0017] In traditional passivation technology solutions, when SiC MOSFET is subjected to high-temperature thermal oxidation (≥1300 °C), carbon atoms on the SiC surface cannot be completely oxidized, and residual carbon forms defect states (such as Si-C dangling bonds) at the SiC / SiO2 interface, resulting in an interface state density (Dit) as high as 10 11 cm -2 , and the electron mobility is only 20–40 cm 2 / V·s.

[0018] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions: A preparation method of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, including the following steps: Clean and dry the silicon carbide wafer by the RCA standard cleaning method: Specifically, the silicon carbide wafer is successively passed through a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide and water with a volume ratio of 1:1:6 for cleaning to remove organic pollutants and metal pollutants on the silicon carbide wafer.

[0019] Then, deposit an amorphous silicon film on the surface of the cleaned and dried silicon carbide at a temperature of <600 °C by low-pressure chemical vapor deposition. The film thickness uniformity of the amorphous silicon film >98%, without crystallization to avoid stress cracks. The amorphous silicon film serves as a sacrificial layer, and only silicon oxide rather than the SiC substrate is oxidized subsequently, obtaining a pretreated silicon carbide wafer.

[0020] Oxidize the amorphous silicon film on the pretreated silicon carbide wafer in a dry oxygen environment at 700-800 °C, then perform a first annealing in a nitrogen atmosphere at 1100-1200 °C, then spin-coat a boron diffusion layer on the surface, and perform a second annealing treatment at 900-1150 °C for 10 min; Transfer monolayer hexagonal boron nitride to the surface of the wafer after the second annealing by mechanical peeling through acrylic plexiglass, and then perform a third annealing treatment and then electrode forming treatment.

[0021] In a preferred implementation manner of this embodiment, after the silicon carbide wafer is cleaned and dried by the RCA standard cleaning method, it is placed in a hydrogen atmosphere at 1000 °C for annealing for 5 min, and then the amorphous silicon film is deposited; the deposition thickness of the amorphous silicon film is 18-22 nm.

[0022] In a preferred embodiment of this example, the amorphous silicon film on the pre-treated silicon carbide wafer is subjected to low-temperature oxidation for 28 - 32 minutes under dry oxygen conditions with a temperature of 740 - 760 °C and an oxygen concentration > 99.999%.

[0023] In a preferred embodiment of this example, the first annealing is carried out for 55 - 65 minutes in a nitrogen atmosphere with a nitrogen concentration > 99.999% at 1130 - 1170 °C.

[0024] In a preferred embodiment of this example, the boron diffusion layer is borosilicate glass, the thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 - 20 at%; The second annealing treatment is carried out for 10 minutes under an inert gas atmosphere at 1000 - 1100 °C.

[0025] In a preferred embodiment of this example, the third annealing treatment is carried out for 55 - 65 minutes at 190 - 210 °C.

[0026] In a preferred embodiment of this example, it further includes an interface bonding treatment step: The wafer is placed in a plasma chamber, and then a mixed gas of argon and oxygen is introduced. Radio frequency power is applied to excite the plasma to perform directional bombardment on the surface of hexagonal boron nitride, and then the third annealing treatment is carried out.

[0027] In a preferred embodiment of this example, the mixed volume ratio of argon and oxygen is 4:1, the power of the radio frequency is 45 - 55 W, and the directional bombardment time is 27 - 33 s; A pressure of 0.4 - 0.6 MPa is applied to the surface of hexagonal boron nitride during the third annealing treatment.

[0028] It should be noted that: A silicon film is deposited on the surface of the silicon carbide wafer, and then the silicon oxide film is oxidized in a low-temperature environment of 700 - 800 °C. Since the oxidation starting temperature of silicon is 700 °C and the oxidation starting temperature of silicon carbide SiC is 900 °C, and silicon carbide may decompose at temperatures above 800 °C. Therefore, only the silicon oxide film is oxidized and the SiC substrate is not oxidized during this process, avoiding carbon residue and generating a high-quality SiO2 layer.

[0029] High-temperature annealing in a nitrogen atmosphere is used to inject nitrogen atoms into the interface to form Si≡N bonds to replace unstable Si - C bonds, which can reduce the defect-induced traps to 1.2×10 10 cm -2Next; then, a single layer of hexagonal boron nitride is covered on the SiO2 surface, and the hexagonal boron nitride can also be replaced by a single layer of graphene. The high chemical inertness and flexible structure of the two-dimensional material can dynamically fill the interface vacancies under the action of an electric field, inhibiting the lattice distortion of SiO2 in a high-temperature environment.

[0030] The silicon carbide surface and the single-layer hexagonal boron nitride surface can produce a synergistic effect. The in-plane thermal conductivity of the single-layer hexagonal boron nitride surface is about 400 W / m·K, which matches the thermal conductivity of about 490 W / m·K of the silicon carbide surface, enhancing the lateral heat dissipation; and it has wide-temperature-range stability. In the high-temperature section, the hexagonal boron nitride layer enhances the high-temperature oxidation resistance and stabilizes up to 1000 °C to protect the inner-layer silicon carbide, while in the low-temperature section, the interface traps of this solution are reduced, which can effectively inhibit the carrier freeze-out effect and ensure stability even at -220 °C.

[0031] The embodiment of the present invention also provides a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, which is obtained according to the above preparation method.

[0032] The embodiment of the present invention also provides an application of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, which is the application of the SiC MOS transistor obtained according to the above preparation method in the field of semiconductor device technology.

[0033] Example 1

[0034] The silicon carbide wafer is successively cleaned with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dried.

[0035] By low-pressure chemical vapor deposition, silane is introduced at 580 °C to deposit a 20-nm amorphous silicon film, and the amorphous silicon film is subjected to low-temperature oxidation for 30 min under dry oxygen conditions at 700 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0036] One-time annealing is carried out for 60 min in a nitrogen atmosphere at 1100 °C with a nitrogen concentration > 99.999%; after annealing, a borosilicate glass diffusion layer is spin-coated on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, secondary annealing treatment is carried out for 10 min in an inert gas atmosphere at 1000 °C.

[0037] Transfer the monolayer hexagonal boron nitride to the surface of the wafer after secondary annealing through an acrylic organic glass by the mechanical exfoliation method. Then place the wafer in a plasma chamber, and then introduce a mixed gas of argon and oxygen with a volume ratio of 4:1. Apply a radio frequency power of 50 W to excite the plasma, and conduct a directional bombardment on the surface of the hexagonal boron nitride for 30 s. Perform three annealing treatments for 60 min under the conditions of 200 °C and applying a pressure of 0.5 MPa to the surface of the hexagonal boron nitride.

[0038] Coat photoresist, perform photolithography, etching, resist stripping, and ion implantation on the wafer in sequence to form the source region and the drain region, and conduct a high-temperature annealing at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Use a metal mask to fabricate electrodes by thermal evaporation or sputtering of metals Al, Ti, and TiC. Heat up to 430 °C under nitrogen protection, anneal for 20 min, and then cool to room temperature.

[0039] Example 2

[0040] Clean the silicon carbide wafer successively with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide, and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide, and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dry it.

[0041] Deposit a 20-nm-thick amorphous silicon film by introducing silane through low-pressure chemical vapor deposition at 580 °C, and perform low-temperature oxidation on the amorphous silicon film for 30 min under dry oxygen conditions at 740 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0042] Conduct a primary annealing for 60 min in a nitrogen atmosphere at 1100 °C with a nitrogen concentration > 99.999%; spin-coat a boron-silicate glass diffusion layer on the surface after annealing, with the thickness of the boron diffusion layer being 100 nm and the proportion of boron atoms in the boron diffusion layer being 5 at%, and then conduct a secondary annealing treatment for 10 min under an inert gas atmosphere condition at 1000 °C.

[0043] Transfer the monolayer hexagonal boron nitride to the surface of the wafer after secondary annealing through an acrylic organic glass by the mechanical exfoliation method. Then place the wafer in a plasma chamber, and then introduce a mixed gas of argon and oxygen with a volume ratio of 4:1. Apply a radio frequency power of 50 W to excite the plasma, and conduct a directional bombardment on the surface of the hexagonal boron nitride for 30 s. Perform three annealing treatments for 60 min under the conditions of 200 °C and applying a pressure of 0.5 MPa to the surface of the hexagonal boron nitride.

[0044] Coat photoresist, perform photolithography, etching, photoresist stripping, and ion implantation on the wafer in sequence to form the source region and the drain region, and perform high-temperature annealing at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Use a metal mask to fabricate electrodes by thermal evaporation or sputtering of metals Al, Ti, and TiC. Heat up to 430 °C under the protection of nitrogen, anneal for 20 min, and then cool to room temperature.

[0045] Example 3

[0046] Clean the silicon carbide wafer in sequence with a mixture of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide, and water with a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide, and water with a volume ratio of 1:1:6 to remove organic contaminants and metal contaminants on the silicon carbide wafer, and then dry it.

[0047] Deposit a 20-nm-thick amorphous silicon film by low-pressure chemical vapor deposition at 580 °C by introducing silane, and perform low-temperature oxidation on the amorphous silicon film for 30 min under dry oxygen conditions at 750 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0048] Perform a first annealing for 60 min in a nitrogen atmosphere at 1100 °C with a nitrogen concentration > 99.999%; spin-coat a boron-silicate glass diffusion layer on the surface after annealing, the thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%, and then perform a second annealing treatment for 10 min in an inert gas atmosphere at 1000 °C.

[0049] Transfer monolayer hexagonal boron nitride to the surface of the wafer after the second annealing by mechanical exfoliation through acrylic organic glass, then place the wafer in a plasma chamber, and then introduce a mixed gas with a volume ratio of argon to oxygen of 4:1, apply a radio frequency power of 50 W to excite the plasma, and perform directional bombardment on the surface of hexagonal boron nitride for 30 s. Perform a third annealing treatment for 60 min at 200 °C and apply a pressure of 0.5 MPa to the surface of hexagonal boron nitride.

[0050] Coat photoresist, perform photolithography, etching, photoresist stripping, and ion implantation on the wafer in sequence to form the source region and the drain region, and perform high-temperature annealing at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Use a metal mask to fabricate electrodes by thermal evaporation or sputtering of metals Al, Ti, and TiC. Heat up to 430 °C under the protection of nitrogen, anneal for 20 min, and then cool to room temperature.

[0051] Example 4

[0052] The silicon carbide wafer is successively cleaned with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dried.

[0053] A 20-nm amorphous silicon film is deposited by low-pressure chemical vapor deposition at 580 °C by introducing silane. The amorphous silicon film is subjected to low-temperature oxidation for 30 min under dry oxygen conditions at 760 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0054] A first annealing is performed for 60 min in a nitrogen atmosphere at 1100 °C with a nitrogen concentration > 99.999%. After annealing, a borosilicate glass diffusion layer is spin-coated on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, a second annealing treatment is performed for 10 min in an inert gas atmosphere at 1000 °C.

[0055] Monolayer hexagonal boron nitride is transferred to the surface of the wafer after the second annealing by mechanical peeling through acrylic plexiglass. Then, the wafer is placed in a plasma chamber, and a mixed gas with a volume ratio of argon to oxygen of 4:1 is introduced. A radio frequency power of 50 W is applied to excite the plasma, and the surface of the hexagonal boron nitride is directionally bombarded for 30 s. A third annealing treatment is performed for 60 min at 200 °C and under a pressure of 0.5 MPa applied to the surface of the hexagonal boron nitride.

[0056] Photoresist coating, photolithography, etching, photoresist stripping, and ion implantation are successively performed on the wafer to form source and drain regions. Then, a high-temperature annealing is performed at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Electrodes are fabricated by thermal evaporation or sputtering of metals Al, Ti, and TiC using a metal mask. The temperature is raised to 430 °C under nitrogen protection, annealed for 20 min, and then cooled to room temperature.

[0057] Example 5

[0058] The silicon carbide wafer is successively cleaned with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dried.

[0059] A 20-nm amorphous silicon film is deposited by low-pressure chemical vapor deposition at 580 °C by introducing silane. The amorphous silicon film is subjected to low-temperature oxidation for 30 min under dry oxygen conditions at 800 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0060] Perform a one-time annealing for 60 min in a nitrogen atmosphere at 1100 °C with a nitrogen concentration > 99.999%; after annealing, spin-coat a borosilicate glass diffusion layer on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, perform a secondary annealing treatment for 10 min in an inert gas atmosphere at 1000 °C.

[0061] Transfer monolayer hexagonal boron nitride to the surface of the wafer after secondary annealing through an acrylic organic glass by the mechanical exfoliation method. Then, place the wafer in a plasma chamber, and then introduce a mixed gas with a volume ratio of argon to oxygen of 4:1. Apply a radio frequency power of 50 W to excite the plasma, and perform a directional bombardment on the surface of hexagonal boron nitride for 30 s. Perform a tertiary annealing treatment for 60 min at 200 °C and apply a pressure of 0.5 MPa to the surface of hexagonal boron nitride.

[0062] Coat photoresist, perform photolithography, etching, resist stripping, and ion implantation on the wafer to form source and drain regions in sequence, and perform a high-temperature annealing at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Use a metal mask to fabricate electrodes by thermal evaporation or sputtering of metals Al, Ti, TiC. Heat up to 430 °C under nitrogen protection, anneal for 20 min, and then cool to room temperature.

[0063] Example 6

[0064] Clean the silicon carbide wafer successively with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide, and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide, and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dry it.

[0065] Deposit a 20-nm amorphous silicon film by low-pressure chemical vapor deposition at 580 °C by introducing silane. Perform a low-temperature oxidation of the amorphous silicon film for 30 min under dry oxygen conditions at 750 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0066] Perform a one-time annealing for 60 min in a nitrogen atmosphere at 1130 °C with a nitrogen concentration > 99.999%; after annealing, spin-coat a borosilicate glass diffusion layer on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, perform a secondary annealing treatment for 10 min in an inert gas atmosphere at 1000 °C.

[0067] Transfer the monolayer hexagonal boron nitride to the surface of the wafer after secondary annealing through acrylic organic glass by mechanical exfoliation method. Then place the wafer in a plasma chamber, and then introduce a mixed gas with a volume ratio of argon to oxygen of 4:1. Apply a radio frequency power of 50 W to excite the plasma, and conduct a directional bombardment on the surface of hexagonal boron nitride for 30 s. Perform three annealing treatments for 60 min at 200 °C and under a pressure of 0.5 MPa applied to the surface of hexagonal boron nitride.

[0068] Apply photoresist, lithography, etching, resist stripping, and ion implantation on the wafer in sequence to form the source region and the drain region. Then perform a high-temperature annealing at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Use a metal mask to fabricate electrodes by thermal evaporation or sputtering of metals Al, Ti, and TiC. Heat up to 430 °C under nitrogen protection, anneal for 20 min, and then cool to room temperature.

[0069] Example 7

[0070] Clean the silicon carbide wafer successively with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide, and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide, and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dry it.

[0071] Deposit a 20-nm-thick amorphous silicon film by low-pressure chemical vapor deposition method by introducing silane at 580 °C. Perform low-temperature oxidation on the amorphous silicon film for 30 min under dry oxygen conditions at 750 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0072] Perform a primary annealing for 60 min in a nitrogen atmosphere at 1150 °C with a nitrogen concentration > 99.999%. After annealing, spin-coat a boron-silicate glass diffusion layer on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then perform a secondary annealing treatment for 10 min in an inert gas atmosphere at 1000 °C.

[0073] Transfer the monolayer hexagonal boron nitride to the surface of the wafer after secondary annealing through acrylic organic glass by mechanical exfoliation method. Then place the wafer in a plasma chamber, and then introduce a mixed gas with a volume ratio of argon to oxygen of 4:1. Apply a radio frequency power of 50 W to excite the plasma, and conduct a directional bombardment on the surface of hexagonal boron nitride for 30 s. Perform three annealing treatments for 60 min at 200 °C and under a pressure of 0.5 MPa applied to the surface of hexagonal boron nitride.

[0074] On the wafer, spin coating, photolithography, etching, stripping, and ion implantation are sequentially performed to form the source and drain regions, and then high-temperature annealing is carried out at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Electrodes are fabricated by thermally evaporating or sputtering metals Al, Ti, and TiC using a metal mask. The temperature is raised to 430 °C under nitrogen protection, annealed for 20 min, and then cooled to room temperature.

[0075] Example 8

[0076] The silicon carbide wafer is sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide, and water with a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide, and water with a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0077] A 20-nm-thick amorphous silicon film is deposited by low-pressure chemical vapor deposition at 580 °C by introducing silane. The amorphous silicon film is subjected to low-temperature oxidation for 30 min at 750 °C under dry oxygen conditions with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0078] Primary annealing is carried out for 60 min at 1170 °C in a nitrogen atmosphere with a nitrogen concentration > 99.999%. After annealing, a borosilicate glass diffusion layer is spin-coated on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, secondary annealing treatment is carried out for 10 min in an inert gas atmosphere at 1000 °C.

[0079] Single-layer hexagonal boron nitride is transferred to the surface of the wafer after secondary annealing by mechanical exfoliation through acrylic organic glass. Then, the wafer is placed in a plasma chamber, and a mixed gas with a volume ratio of argon to oxygen of 4:1 is introduced. A radio frequency power of 50 W is applied to excite the plasma, and the surface of hexagonal boron nitride is directionally bombarded for 30 s. Tertiary annealing treatment is carried out for 60 min at 200 °C and under a pressure of 0.5 MPa on the surface of hexagonal boron nitride.

[0080] On the wafer, spin coating, photolithography, etching, stripping, and ion implantation are sequentially performed to form the source and drain regions, and then high-temperature annealing is carried out at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Electrodes are fabricated by thermally evaporating or sputtering metals Al, Ti, and TiC using a metal mask. The temperature is raised to 430 °C under nitrogen protection, annealed for 20 min, and then cooled to room temperature.

[0081] Example 9

[0082] The silicon carbide wafer is successively cleaned with a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a volume ratio of 1:1; a mixed solution of ammonia water, hydrogen peroxide and water with a volume ratio of 1:1:6; and a mixed solution of hydrochloric acid, hydrogen peroxide and water with a volume ratio of 1:1:6 to remove organic pollutants and metal pollutants on the silicon carbide wafer, and then dried.

[0083] A 20-nm-thick amorphous silicon film is deposited by low-pressure chemical vapor deposition by introducing silane at 580 °C. The amorphous silicon film is subjected to low-temperature oxidation for 30 min under dry oxygen conditions at 750 °C with an oxygen concentration > 99.999%. The thickness of the oxide film is 45 nm.

[0084] One-time annealing is carried out for 60 min in a nitrogen atmosphere at 1200 °C with a nitrogen concentration > 99.999%. After annealing, a borosilicate glass diffusion layer is spin-coated on the surface. The thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 at%. Then, secondary annealing treatment is carried out for 10 min in an inert gas atmosphere at 1000 °C.

[0085] The monolayer hexagonal boron nitride is transferred to the surface of the wafer after secondary annealing through acrylic organic glass by mechanical exfoliation method. Then, the wafer is placed in a plasma chamber, and a mixed gas with a volume ratio of argon to oxygen of 4:1 is introduced. A radio frequency power of 50 W is applied to excite the plasma, and the surface of the hexagonal boron nitride is directionally bombarded for 30 s. Tertiary annealing treatment is carried out for 60 min at 200 °C and under a pressure of 0.5 MPa applied to the surface of the hexagonal boron nitride.

[0086] Coating, photolithography, etching, stripping, and ion implantation are successively carried out on the wafer to form source and drain regions, and high-temperature annealing is carried out at 1500 °C for 20 min under the protection of an Ar or N2 atmosphere. Electrodes are fabricated by thermal evaporation or sputtering of metals Al, Ti, TiC using a metal mask. The temperature is raised to 430 °C under nitrogen protection, annealed for 20 min, and then cooled to room temperature.

[0087] The interface state density, channel mobility, operating temperature range, and thermal conductivity of the SiC MOSFET tubes prepared in Examples 1 - 9 are respectively detected.

[0088] Among them, the detection method of the interface state density adopts the pulsed current response method. Specifically, a high-frequency pulsed voltage is applied to the gate, the high level is greater than V th , and the low level is less than the flat-band voltage V fb . The charge trapped by the interface traps is neutralized with the channel carriers when the pulse switches. The drain current convergence time is positively correlated with the interface state density D. The applied pulsed voltage: V gh = V th +1V, V gl fb = V fb-0.5V, frequency ≤ 1MHz, record the drain current I d The decay curve of the current over time is obtained, and the time required for the current to converge to 90% of the steady state is extracted. D is calculated through the calibration curve.

[0089] The working temperature range is tested through the electrical parameters across the entire temperature range. Specifically, it is obtained by combining a cryogenic probe station, liquid nitrogen cooling, a high-temperature stage at -196°C and 1000°C, and a semiconductor parameter analyzer. The experimental test results are shown in Table 1 below.

[0090] Table 1

[0091] From the above experimental data, it can be seen that the SiC MOSFET prepared by the technical solution of the present invention has greatly improved performance in terms of interface state density, channel mobility, working temperature range, and thermal conductivity compared to the traditional SiC MOSFET. It can meet the wide working temperature range of -200~1000°C and has high thermal conductivity.

[0092] By comparing Examples 1 - 5, it can be seen that the effect of low-temperature oxidation is better under the condition of 740 - 760°C, and the best effect is achieved at 750°C. By comparing Example 3 and Examples 6 - 9, it can be seen that the annealing effect is better when the primary annealing temperature is 1130 - 1170°C, and the best effect can be achieved at 1150°C.

[0093] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A preparation method of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, characterized in that, It includes the following steps: Clean and dry the silicon carbide wafer by the RCA standard cleaning method; Then deposit an amorphous silicon film on the surface of the cleaned and dried silicon carbide at a temperature of <600°C by low-pressure chemical vapor deposition to obtain a pretreated silicon carbide wafer; Oxidize the amorphous silicon film on the pretreated silicon carbide wafer in a dry oxygen environment at 700 - 800°C, then perform a first annealing in a nitrogen atmosphere at 1100 - 1200°C, then spin-coat a boron diffusion layer on the surface, and perform a second annealing treatment at 900 - 1150°C for 10 min; Transfer monolayer hexagonal boron nitride to the surface of the wafer after the second annealing by mechanical peeling through acrylic plexiglass, and then perform a third annealing treatment and then electrode forming treatment.

2. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: Clean and dry the silicon carbide wafer by the RCA standard cleaning method and then anneal it in a hydrogen atmosphere at 1000°C for 5 min, and then deposit an amorphous silicon film; the deposition thickness of the amorphous silicon film is 18 - 22 nm.

3. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, wherein: Perform low-temperature oxidation of the amorphous silicon film on the pretreated silicon carbide wafer for 28 - 32 min under dry oxygen conditions at a temperature of 740 - 760°C and an oxygen concentration >99.999%.

4. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The first annealing is performed in a nitrogen atmosphere at 1130 - 1170°C and a nitrogen concentration >99.999% for 55 - 65 min.

5. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, wherein: The boron diffusion layer is borosilicate glass, the thickness of the boron diffusion layer is 100 nm, and the proportion of boron atoms in the boron diffusion layer is 5 - 20 at%; The second annealing treatment is performed in an inert gas atmosphere at 1000 - 1100°C for 10 min.

6. The preparation method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The third annealing treatment is performed at 190 - 210°C for 55 - 65 min.

7. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: It also includes an interface bonding treatment step: Place the wafer in a plasma chamber, then introduce a mixed gas of argon and oxygen, apply radio frequency power to excite the plasma, perform directional bombardment on the surface of hexagonal boron nitride, and then perform a third annealing treatment.

8. The manufacturing method of the SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 7, characterized in that: The volume ratio of the mixed argon and oxygen is 4:1, the power of the radio frequency is 45 - 55 W, and the directional bombardment time is 27 - 33 s; A pressure of 0.4 - 0.6 MPa is applied to the surface of hexagonal boron nitride during the third annealing treatment.

9. A SiC MOS transistor with high thermal conductivity and a wide operating temperature range, characterized in that, The SiC MOS transistor obtained by the preparation method according to any one of claims 1 - 8.

10. Application of a SiC MOS transistor with high thermal conductivity and wide operating temperature range, characterized in that, The application of the SiC MOS transistor obtained by the preparation method according to any one of claims 1 - 8 in the field of semiconductor device technology.

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