A method for preparing a SiC MOS tube with high thermal conductivity and wide operating temperature range

Abstract

A SiC MOS transistor with high thermal conductivity and a wide operating temperature range and a preparation method thereof relate to the technical field of semiconductor devices. The invention comprises the following steps: cleaning and drying a silicon carbide wafer by an RCA standard cleaning method; then depositing an amorphous silicon film on the cleaned and dried silicon carbide surface by a low-pressure chemical vapor deposition method at a temperature below 600°C to obtain a pretreated silicon carbide wafer; oxidizing the amorphous silicon film on the pretreated silicon carbide wafer in a dry oxygen environment at 700-800°C, then performing a primary annealing in a nitrogen atmosphere at 1100-1200°C, then spin-coating a boron diffusion layer on the surface, and performing a secondary annealing treatment at 900-1150°C for 10 minutes; transferring a single layer of hexagonal boron nitride to the wafer surface after the secondary annealing through acrylic organic glass by a mechanical stripping method, then performing a third annealing treatment and then performing an electrode forming treatment; avoiding the occurrence of carbon residue by low-temperature oxidation, and then improving the channel mobility by synergistic passivation with nitrogen and boron elements.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a method for preparing a SiC MOS tube with high thermal conductivity and a wide operating temperature range. Background Art

[0002] SiC MOS tubes, or silicon carbide metal-oxide semiconductor field-effect transistors, are core devices of the third-generation semiconductors. Their performance is limited by SiC / SiO2 interface defects and high-temperature reliability issues. Traditional processes have inherent defects in gate oxide layer formation and interface passivation, and new passivation technologies are urgently needed to break through the bottleneck.

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

[0004] The object of the present invention is to provide a method for preparing a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, so as to at least partially solve the above problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, comprising the following steps:

[0006] The silicon carbide wafer is cleaned and dried by an RCA standard cleaning method; then an amorphous silicon film is deposited on the cleaned and dried silicon carbide surface by a low-pressure chemical vapor deposition method at a temperature of less than 600° C. to obtain a pretreated silicon carbide wafer;

[0007] The amorphous silicon film on the pre-treated silicon carbide wafer is oxidized in a dry oxygen environment at 700-800°C, then annealed in a nitrogen atmosphere at 1100-1200°C, and then a boron diffusion layer is spin-coated on the surface, followed by a secondary annealing treatment at 900-1150°C for 10 minutes;

[0008] The single layer of hexagonal boron nitride is transferred to the surface of the wafer after secondary annealing through acrylic glass by mechanical stripping method, and then electrode forming treatment is performed after three annealing treatments.

[0009] Preferably, the silicon carbide wafer is cleaned and dried by an RCA standard cleaning method and then annealed in a hydrogen atmosphere at 1000° C. for 5 minutes, and then an amorphous silicon film is deposited; the deposition thickness of the amorphous silicon film is 18-22 nm.

[0010] Preferably, the amorphous silicon film on the pretreated silicon carbide wafer is subjected to low temperature oxidation for 28-32 minutes at a temperature of 740-760° C. and a dry oxygen condition with an oxygen concentration greater than 99.999%.

[0011] Preferably, the primary annealing is performed at 1130-1170° C. in a nitrogen atmosphere with a nitrogen concentration greater than 99.999% for 55-65 minutes.

[0012] 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%;

[0013] The secondary annealing treatment is performed in an inert gas atmosphere at 1000-1100° C. for 10 minutes.

[0014] Preferably, the three annealing treatments are performed at 190-210° C. for 55-65 min.

[0015] Preferably, the method further includes an interface bonding process step:

[0016] 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, and the hexagonal boron nitride surface is directionally bombarded, and then three annealing treatments are performed.

[0017] Preferably, the volume ratio of the argon and oxygen mixture is 4:1, the radio frequency power is 45-55W, and the directional bombardment time is 27-33s;

[0018] During the three annealing processes, a pressure of 0.4-0.6 MPa is applied to the surface of the hexagonal boron nitride.

[0019] The present invention also provides a SiC MOS tube with high thermal conductivity and a wide operating temperature range, which is obtained according to the above preparation method.

[0020] The present invention also provides an application of a SiC MOS tube with high thermal conductivity and a wide operating temperature range, and an application of the SiC MOS tube obtained according to the above preparation method in the field of semiconductor device technology.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention avoids the occurrence of carbon residues through low-temperature oxidation, then improves channel mobility through synergistic passivation with nitrogen and boron elements, and then dynamically repairs the integrated two-dimensional passivation layer with hexagonal boron nitride to enhance thermal conductivity and electrical stability, breaking through the interface defect bottleneck of SiC MOS and achieving ultra-low interface state density, wide temperature range coverage and high thermal conductivity network. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] The traditional passivation technology has the problem that when SiC MOSFET is thermally oxidized at high temperature (≥1300℃), the carbon atoms on the SiC surface cannot be completely oxidized, and the 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 , the electron mobility is only 20–40 cm 2 / V·s.

[0025] In order to solve the above technical problems, the embodiment of the present invention provides the following technical solution: a method for preparing a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, comprising the following steps:

[0026] The silicon carbide wafers were cleaned and dried using the RCA standard cleaning method: specifically, the silicon carbide wafers were sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a 1:1 volume ratio; a mixture of ammonia, hydrogen peroxide, and water in a 1:1:6 volume ratio; and a mixture of hydrochloric acid, hydrogen peroxide, and water in a 1:1:6 volume ratio to remove organic and metal contaminants on the silicon carbide wafers.

[0027] Then, an amorphous silicon film is deposited on the cleaned and dried silicon carbide surface by low-pressure chemical vapor deposition at <600°C. The film thickness uniformity of the amorphous silicon film is >98%, and no crystallization is performed to avoid stress cracks. The amorphous silicon film serves as a sacrificial layer, and only silicon is subsequently oxidized instead of the SiC substrate to obtain a pretreated silicon carbide wafer.

[0028] The amorphous silicon film on the pre-treated silicon carbide wafer is oxidized in a dry oxygen environment at 700-800°C, then annealed in a nitrogen atmosphere at 1100-1200°C, and then a boron diffusion layer is spin-coated on the surface, followed by a secondary annealing treatment at 900-1150°C for 10 minutes;

[0029] The single layer of hexagonal boron nitride is transferred to the surface of the wafer after secondary annealing through acrylic glass by mechanical stripping method, and then electrode forming treatment is performed after three annealing treatments.

[0030] In a preferred implementation of this embodiment, the silicon carbide wafer is cleaned and dried using the RCA standard cleaning method and then annealed in a hydrogen atmosphere at 1000° C. for 5 minutes, and then an amorphous silicon film is deposited; the deposition thickness of the amorphous silicon film is 18-22 nm.

[0031] In a preferred implementation of this embodiment, the amorphous silicon film on the pre-treated silicon carbide wafer is subjected to low temperature oxidation for 28-32 minutes at a temperature of 740-760° C. and a dry oxygen condition with an oxygen concentration greater than 99.999%.

[0032] In a preferred implementation manner of this embodiment, the primary annealing is performed at 1130-1170° C. in a nitrogen atmosphere with a nitrogen concentration greater than 99.999% for 55-65 minutes.

[0033] In a preferred implementation of this embodiment, 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%;

[0034] The secondary annealing treatment is performed in an inert gas atmosphere at 1000-1100° C. for 10 minutes.

[0035] In a preferred implementation manner of this embodiment, the three annealing treatments are performed at 190-210° C. for 55-65 minutes.

[0036] In a preferred implementation of this embodiment, an interface bonding process step is also included:

[0037] 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, and the hexagonal boron nitride surface is directionally bombarded, and then three annealing treatments are performed.

[0038] In a preferred embodiment of this embodiment, the volume ratio of the argon and oxygen mixture is 4:1, the radio frequency power is 45-55W, and the directional bombardment time is 27-33s;

[0039] During the three annealing processes, a pressure of 0.4-0.6 MPa is applied to the surface of the hexagonal boron nitride.

[0040] It should be noted that a silicon film is deposited on the surface of a silicon carbide wafer and then oxidized at a low temperature of 700-800°C. This is because the oxidation starting temperature of silicon is 700°C, while the oxidation starting temperature of silicon carbide (SiC) is 900°C. Silicon carbide may decompose at temperatures above 800°C. Therefore, in this process, only the silicon film is oxidized without oxidizing the SiC substrate, avoiding carbon residue and producing a high-quality SiO2 layer.

[0041] High-temperature annealing in a nitrogen atmosphere can implant 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 -2 Next, the SiO2 surface is coated with a single layer of hexagonal boron nitride (HBN), which can also be replaced with a single layer of graphene. The high chemical inertness and flexible structure of the two-dimensional material dynamically fills interfacial vacancies under the action of an electric field, suppressing lattice distortion of the SiO2 at high temperatures.

[0042] The silicon carbide surface and the single-layer hexagonal boron nitride surface can produce a synergistic effect. The thermal conductivity of the single-layer hexagonal boron nitride surface is about 400 W / m·K, which matches the thermal conductivity of the silicon carbide surface of about 490 W / m·K, enhancing lateral heat dissipation. It also has wide temperature range stability. In the high temperature range, the hexagonal boron nitride layer enhances high-temperature oxidation resistance and stabilizes it to 1000°C to protect the inner layer of silicon carbide. In the low temperature range, the reduction of interface traps in this scheme can effectively suppress the carrier freezing effect, ensuring stability at -220°C.

[0043] An embodiment of the present invention further provides a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, which is obtained according to the above-mentioned preparation method.

[0044] The embodiment of the present invention further provides an application of a SiC MOS transistor with high thermal conductivity and a wide operating temperature range, and an application of the SiC MOS transistor obtained according to the above preparation method in the field of semiconductor device technology. Example

[0045] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0046] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 700°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0047] The first annealing was performed at 1100°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0048] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0049] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0050] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0051] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580℃ by introducing monosilane. The amorphous silicon film was low-temperature oxidized for 30 minutes at 740℃ under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0052] The first annealing was performed at 1100°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0053] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0054] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0055] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0056] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 750°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0057] The first annealing was performed at 1100°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0058] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0059] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0060] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0061] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580℃ by introducing monosilane. The amorphous silicon film was low-temperature oxidized for 30 minutes at 760℃ under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0062] The first annealing was performed at 1100°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0063] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0064] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0065] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0066] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 800°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0067] The first annealing was performed at 1100°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0068] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0069] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0070] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0071] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 750°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0072] The first annealing was performed at 1130°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes; after annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0073] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0074] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0075] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0076] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 750°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0077] The first annealing was performed at 1150°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes. After annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0078] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0079] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0080] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0081] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 750°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0082] The first annealing was performed at 1170°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes. After annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0083] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0084] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature. Example

[0085] The silicon carbide wafer was sequentially cleaned with a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 1:1; a mixture of ammonia, hydrogen peroxide and water in a volume ratio of 1:1:6; and a mixture of hydrochloric acid, hydrogen peroxide and water in a volume ratio of 1:1:6 to remove organic and metal contaminants on the silicon carbide wafer, and then dried.

[0086] A 20nm amorphous silicon film was deposited by low-pressure chemical vapor deposition at 580°C by introducing monosilane. The amorphous silicon film was then low-temperature oxidized for 30 minutes at 750°C under dry oxygen conditions with an oxygen concentration of >99.999%. The thickness of the oxide film was 45nm.

[0087] The first annealing was performed at 1200°C in a nitrogen atmosphere with a nitrogen concentration of >99.999% for 60 minutes. After annealing, a borosilicate glass diffusion layer was spin-coated on the surface. The thickness of the boron diffusion layer was 100 nm, and the proportion of boron atoms in the boron diffusion layer was 5 at%. Then, a second annealing treatment was performed at 1000°C in an inert gas atmosphere for 10 minutes.

[0088] A single layer of hexagonal boron nitride was transferred to the surface of the secondary annealed wafer through acrylic glass by mechanical stripping. The wafer was then placed in a plasma chamber, and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. A 50W radio frequency power was applied to excite the plasma, and the hexagonal boron nitride surface was directionally bombarded for 30 seconds. The hexagonal boron nitride surface was subjected to three annealing treatments for 60 minutes at 200°C and a pressure of 0.5MPa.

[0089] The source and drain regions are formed on the wafer in sequence by coating, photolithography, etching, debonding, and ion implantation. The wafer is then annealed at 1500°C for 20 minutes under Ar or N2 atmosphere. Electrodes are made by thermal evaporation or sputtering of metal Al, Ti, or TiC using a metal mask. The wafer is then heated to 430°C under nitrogen protection, annealed for 20 minutes, and cooled to room temperature.

[0090] The interface state density, channel mobility, operating temperature range and thermal conductivity of the SiC MOSFET tubes prepared in Examples 1 to 9 were tested respectively.

[0091] Among them, the detection method of interface state density adopts the pulse current response method, which specifically applies a high-frequency pulse voltage to the gate, with a high level greater than V th , the low level is less than the flat band voltage V fb The charge trapped in the interface trap is neutralized with the channel carriers during pulse switching. The drain current convergence time is positively correlated with the interface state density D. The pulse voltage applied is: V gh = V th +1V, V gl = V fb -0.5V, frequency ≤ 1MHz, record the drain current I d The time required for the current to converge to 90% of the steady state is extracted from the time decay curve, and D is calculated by calibration curve.

[0092] The operating temperature range is determined through full-temperature electrical parameter testing using a cryogenic probe station, liquid nitrogen refrigeration, high-temperature stations at -196°C and 1000°C, and a semiconductor parameter analyzer. The experimental test results are shown in Table 1 below.

[0093] Table 1

[0094] <![CDATA[Interface state density (cm -2 ).]]> <![CDATA[Channel mobility (cm 2 / V·s)]]> Operating temperature range Thermal conductivity (W / m·K) Example 1 <![CDATA[2.92×10 10 ]]> 102 -200~1000℃ 406 Example 2 <![CDATA[2.29×10 10 ]]> 110 -200~1000℃ 421 Example 3 <![CDATA[1.96×10 10 ]]> 113 -200~1000℃ 426 Example 4 <![CDATA[2.32×10 10 ]]> 111 -200~1000℃ 419 Example 5 <![CDATA[2.89×10 10 ]]> 103 -200~1000℃ 409 Example 6 <![CDATA[1.38×10 10 ]]> 118 -200~1000℃ 457 Example 7 <![CDATA[1.03×10 10 ]]> 139 -200~1000℃ 461 Example 8 <![CDATA[1.26×10 10 ]]> 124 -200~1000℃ 453 Example 9 <![CDATA[1.93×10 10 ]]> 109 -200~1000℃ 426

[0095] From the above experimental data, it can be seen that the SiC MOSFET tube prepared by the technical solution of the present invention has greatly improved performance in terms of interface state density, channel mobility, operating temperature range and thermal conductivity compared with traditional SiC MOSFET tubes. It can meet the wide operating temperature range of -200~1000℃ and has high thermal conductivity.

[0096] By comparing Examples 1 to 5, it can be seen that the effect of low-temperature oxidation is better at 740-760°C, and the best effect is achieved at 750°C. By comparing Examples 3 and 6 to 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.

[0097] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range, characterized in that: The following steps are involved: The silicon carbide wafer was cleaned and dried using the RCA standard cleaning method; Then, an amorphous silicon film is deposited on the cleaned and dried silicon carbide surface by low pressure chemical vapor deposition at a temperature of less than 600° C. to obtain a pretreated silicon carbide wafer; The amorphous silicon film on the pre-treated silicon carbide wafer is oxidized in a dry oxygen environment at 700-800°C, then annealed in a nitrogen atmosphere at 1100-1200°C, and then a boron diffusion layer is spin-coated on the surface, followed by a secondary annealing treatment at 900-1150°C for 10 minutes; The single layer of hexagonal boron nitride was transferred to the surface of the wafer after secondary annealing through acrylic glass by mechanical peeling, and then the electrode was formed after the third annealing treatment; Also includes interface bonding processing steps: The wafer is placed in a plasma chamber, and then a mixture of argon and oxygen is introduced. Radio frequency power is applied to excite the plasma, which directionally bombards the hexagonal boron nitride surface, and then three annealing treatments are performed; 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 secondary annealing treatment is performed in an inert gas atmosphere at 1000-1100° C. for 10 minutes.

2. The method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The silicon carbide wafer was cleaned and dried using an RCA standard cleaning method, and then annealed in a hydrogen atmosphere at 1000° C. for 5 minutes, and then an amorphous silicon film was deposited; the deposition thickness of the amorphous silicon film was 18-22 nm.

3. The method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The amorphous silicon film on the pre-treated silicon carbide wafer is subjected to low temperature oxidation for 28-32 minutes at a temperature of 740-760° C. and an oxygen concentration of >99.999% in dry oxygen.

4. The method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, wherein: The primary annealing is performed at 1130-1170° C. in a nitrogen atmosphere with a nitrogen concentration greater than 99.999% for 55-65 minutes.

5. The method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The three annealing treatments are performed at 190-210° C. for 55-65 minutes.

6. The method for preparing a SiC MOS transistor with high thermal conductivity and wide operating temperature range according to claim 1, characterized in that: The volume ratio of the argon and oxygen mixture is 4:1, the radio frequency power is 45-55W, and the directional bombardment time is 27-33s; During the three annealing processes, a pressure of 0.4-0.6 MPa is applied to the surface of the hexagonal boron nitride.

7. A SiC MOS transistor with high thermal conductivity and wide operating temperature range, characterized in that: A SiC MOS transistor obtained according to the preparation method according to any one of claims 1 to 6.

8. Application of a SiC MOS tube with high thermal conductivity and wide operating temperature range, characterized in that: Application of the SiC MOS transistor obtained by the preparation method according to any one of claims 1 to 6 in the field of semiconductor device technology.