Preparation method of silicon carbide epitaxial layer on silicon substrate
By injecting carbon ions on the silicon substrate and post-annealing, combined with wet etching and chemical vapor deposition, the lattice mismatch and difference in thermal expansion coefficient of the 3C silicon carbide epitaxial layer on the silicon substrate are solved, and the quality and consistency of the epitaxial layer are improved.
Patent Information
- Application Number
- CN202510570425.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-06
- Publication Date
- 2025-08-08
AI Technical Summary
When the 3C silicon carbide epitaxial layer is grown on a silicon substrate, defects caused by lattice mismatch and thermal expansion coefficient differences are difficult to control, and the traditional silicon carbide buffer layer is insufficient in thickness, which affects device performance and reliability.
By injecting carbon ions onto the silicon substrate and post-annealing, combining wet etching and chemical vapor deposition, a silicon carbide buffer layer with a larger thickness is prepared, and epitaxial growth conditions are optimized to improve crystal quality.
A better matching of lattice constant and thermal expansion coefficient is achieved, avoiding hollows in the buffer layer, and improving the crystal quality and repeatability of the epitaxial layer.
Smart Images
Figure CN120443343A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a method for preparing a silicon carbide epitaxial layer on a silicon substrate. Background Art
[0002] Silicon carbide (SiC) is a typical wide-bandgap semiconductor material, characterized by a wide bandgap, high breakdown electric field, and high thermal conductivity. Compared to traditional silicon-based power devices, SiC power devices offer lower conduction losses and faster switching speeds, making them widely applicable in new energy vehicles, photovoltaic inverters, 5G communication base stations, rail transit, and other fields. Currently, power devices based on 4H SiC have achieved commercialization, but the high cost of single-crystal substrates has limited the competitiveness of 4H SiC.
[0003] Due to its similar crystal structure, 3C silicon carbide can be grown epitaxially on single-crystal silicon substrates, which is expected to further reduce the manufacturing cost of silicon carbide power devices. In addition to the low-cost advantage, 3C silicon carbide also has advantages over 4H silicon carbide in electron mobility and gate oxide reliability. However, due to the lattice mismatch and thermal expansion coefficient difference between 3C silicon carbide and single-crystal silicon, heteroepitaxial single-crystal 3C silicon carbide on silicon substrates requires harsh process conditions and defects in 3C silicon carbide are difficult to effectively control.
[0004] At present, single-crystal 3C silicon carbide on silicon substrates is mainly obtained by chemical vapor deposition. In order to improve the quality of the 3C silicon carbide epitaxial layer, the silicon substrate is usually carbonized by introducing a carbon source before the growth of 3C silicon carbide to generate an extremely thin silicon carbide buffer layer. However, this process still has the following problems: First, the thickness of the silicon carbide buffer layer does not exceed 5nm, which is not enough to alleviate the lattice mismatch between the silicon substrate and the 3C silicon carbide epitaxial layer. Second, the presence of voids in the silicon carbide buffer layer will adversely affect the quality and integrity of the 3C silicon carbide epitaxial layer, resulting in poor performance and reliability of the device. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the present invention provides a method for preparing a silicon carbide epitaxial layer on a silicon substrate, which utilizes carbon ion implantation and chemical vapor deposition to achieve high-quality epitaxial growth of 3C silicon carbide on a silicon substrate.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:
[0007] The invention discloses a method for preparing a silicon carbide epitaxial layer on a silicon substrate. Carbon ions are implanted into the silicon substrate and then annealed. After removing the excess surface layer, 3C silicon carbide is epitaxially grown on the substrate by chemical vapor deposition.
[0008] Preferably, the carbon ion implantation temperature is 200-1000°C, the energy is 50-500keV, and the dose is 1×1016 -1×10 19 / cm 2 , the tilt angle is 0-45° and the rotation angle is 0-360°.
[0009] Preferably, the post-annealing temperature is 1000-1400° C., the time is 1-5 hours, the atmosphere is one or more of oxygen, nitrogen, and argon, and the pressure is 0.1-1 atm.
[0010] Preferably, the excess surface layer is removed by wet etching or wet etching-oxidation-wet etching;
[0011] The solution used in the wet etching is a mixed solution of any of hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride and water, and the molar ratio of the hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride and water is 1:0-10:0-10:0-10:1-50.
[0012] Preferably, the oxidation temperature is 800-1400° C., the time is 0.1-5 h, and the atmosphere is one or more of oxygen, ozone, water vapor, nitrogen, and argon.
[0013] Preferably, the carbon source used in the chemical vapor deposition is one or more of methane, ethylene, ethane, propylene, and propane, the silicon source is one or more of monosilane, dichlorosilane, and trichlorosilane, and the carrier gas is hydrogen;
[0014] The carbon source flow rate is 5-100 mL / min, the silicon source flow rate is 5-100 mL / min, the carrier gas flow rate is 50-150 L / min, the deposition temperature is 1000-1400° C., and the growth time is 0.5-10 h.
[0015] The present invention has the following beneficial effects:
[0016] 1. The silicon carbide buffer layer introduced by the present invention through high-dose carbon ion implantation has a thickness of more than 50nm, which is much thicker than the traditional carbonization method. It can better buffer the mismatch between the lattice constant and thermal expansion coefficient between silicon and 3C silicon carbide.
[0017] 2. The method disclosed in the present invention avoids the problem of voids in the buffer layer in traditional carbonization methods, improves the crystal quality of epitaxial silicon carbide on silicon substrates, and improves repeatability and consistency. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION
[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0020] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.
[0021] refer to Figure 1 As shown, the present invention discloses a method for preparing a silicon carbide epitaxial layer on a silicon substrate, comprising the following steps:
[0022] S1. Select a silicon substrate and perform RCA standard cleaning;
[0023] S2, implanting a large dose of carbon ions into the silicon substrate and then annealing; the carbon ion implantation temperature is 200-1000 ° C, the energy is 50-500 keV, and the dose is 1×10 16 -1×10 19 / cm 2 The tilt angle is 0-45°, the rotation angle is 0-360°, the post-annealing temperature is 1000-1400°C, the time is 1-5 hours, the atmosphere is one or more of oxygen, nitrogen, and argon, and the pressure is 0.1-1 atm.
[0024] S3. Remove the excess surface layer by wet etching or wet etching-oxidation-wet etching; the solution used for the wet etching is a mixed solution of any of hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride, and water, and the molar ratio of the hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride, and water is 1:0-10:0-10:0-10:1-50.
[0025] The oxidation temperature is 800-1400° C., the time is 0.1-5 hours, and the atmosphere is one or more of oxygen, ozone, water vapor, nitrogen, and argon.
[0026] S4. Epitaxially grow 3C silicon carbide on the substrate by chemical vapor deposition. The carbon source used in the chemical vapor deposition is one or more of methane, ethylene, ethane, propylene, and propane, the silicon source is one or more of monosilane, dichlorosilane, and trichlorosilane, and the carrier gas is hydrogen. The carbon source flow rate is 5-100 mL / min, the silicon source flow rate is 5-100 mL / min, the carrier gas flow rate is 50-150 L / min, the deposition temperature is 1000-1400°C, and the growth time is 0.5-10 hours.
[0027] The present invention will be further described below with reference to specific embodiments.
[0028] Example 1
[0029] A method for preparing a silicon carbide epitaxial layer on a silicon substrate comprises the following steps:
[0030] S1: Select a commercially available six-inch silicon {111} substrate and perform RCA standard cleaning.
[0031] S2: A high-dose carbon ion implantation is performed on the silicon substrate and then annealed to obtain an 80nm thick single-crystal silicon carbide buffer layer and a surface excess layer (including polycrystalline silicon carbide and silicon layer on the upper side of the single-crystal silicon carbide). The carbon ion implantation temperature is 400℃, the energy is 180keV, and the dose is 8.5×10 17 / cm 2 , the tilt angle is 0°, the rotation angle is 0°. The post-annealing temperature is 1200°C, the time is 2h, the atmosphere is oxygen, and the pressure is 1atm.
[0032] S3, wet etching-oxidation-wet etching to remove excess surface layers;
[0033] The wet etch-oxidation-wet etch process includes the following steps:
[0034] S31. Soak the wafer in a mixed solution of hydrofluoric acid, nitric acid, acetic acid, and water (49% hydrofluoric acid, 69% nitric acid, and acetic acid in a volume ratio of 3:1:8) for 15 minutes to remove the silicon layer on the surface of the wafer. After taking out the wafer, rinse it repeatedly with deionized water and finally dry it with a nitrogen gun.
[0035] S32. Place the sample in an oxidation furnace for oxidation to convert the polycrystalline silicon carbide layer on the surface of the wafer into a silicon oxide layer. The oxidation temperature is 1100°C, the time is 1 hour, and the atmosphere is oxygen.
[0036] S33. Soak the wafer in 49% hydrofluoric acid for 20 minutes to remove the silicon oxide layer on the surface of the wafer. After taking out the wafer, rinse it repeatedly with deionized water and finally dry it with a nitrogen gun.
[0037] S4. 3C silicon carbide was epitaxially grown on the substrate by chemical vapor deposition. The carbon source was ethylene, the silicon source was monosilane, the carrier gas was hydrogen, the carbon source flow rate was 2.5 mL / min, the silicon source flow rate was 5 mL / min, the carrier gas flow rate was 100 L / min, the deposition temperature was 1350°C, and the growth time was 1 h.
[0038] Example 2
[0039] A method for preparing a silicon carbide epitaxial layer on a silicon substrate comprises the following steps:
[0040] S1: Select a commercially available six-inch silicon {111} substrate and perform RCA standard cleaning.
[0041] S2: A large dose of carbon ions is implanted into the silicon substrate and then annealed to obtain a 150nm thick single-crystal silicon carbide buffer layer and a surface excess layer (the silicon layer on the upper side of the single-crystal silicon carbide). The carbon ion implantation temperature is 600℃, the energy is 180keV, and the dose is 8.5×10 17 / cm 2 The tilt angle is 0°, the rotation angle is 0°, the post-annealing temperature is 1300°C, the time is 5h, the atmosphere is nitrogen, and the pressure is 1atm.
[0042] S3. Wet etching removes excess surface layers. The process involves soaking the wafer in a mixture of hydrofluoric acid, nitric acid, acetic acid, and water (49% hydrofluoric acid, 69% nitric acid, and acetic acid in a volume ratio of 3:1:8) for 15 minutes to remove the silicon layer from the wafer surface. After removing the wafer, rinse it repeatedly with deionized water and finally dry it with a nitrogen gun.
[0043] S4. 3C silicon carbide was epitaxially grown on the substrate by chemical vapor deposition. The carbon source was ethylene, the silicon source was monosilane, the carrier gas was hydrogen, the carbon source flow rate was 2.5 mL / min, the silicon source flow rate was 5 mL / min, the carrier gas flow rate was 100 L / min, the deposition temperature was 1350°C, and the growth time was 1 hour.
[0044] Example 3
[0045] A method for preparing a silicon carbide epitaxial layer on a silicon substrate comprises the following steps:
[0046] S1: Select a commercially available six-inch silicon {111} substrate and perform RCA standard cleaning.
[0047] S2: A high-dose carbon ion implantation is performed on the silicon substrate and then annealed to obtain an 80nm thick single-crystal silicon carbide buffer layer and a surface excess layer (including polycrystalline silicon carbide and silicon layer on the upper side of the single-crystal silicon carbide). The carbon ion implantation temperature is 400℃, the energy is 180keV, and the dose is 8.5×10 17 / cm 2 , the tilt angle is 0°, the rotation angle is 0°. The post-annealing temperature is 1200°C, the time is 2h, the atmosphere is oxygen, and the pressure is 1atm.
[0048] S3, wet etching-oxidation-wet etching to remove excess surface layers;
[0049] The wet etch-oxidation-wet etch process includes the following steps:
[0050] S31. Soak the wafer in a mixed solution of hydrofluoric acid, nitric acid, acetic acid, and water (49% hydrofluoric acid, 69% nitric acid, and acetic acid in a volume ratio of 3:1:8) for 15 minutes to remove the silicon layer on the surface of the wafer. After taking out the wafer, rinse it repeatedly with deionized water and finally dry it with a nitrogen gun.
[0051] S32. Place the sample in an oxidation furnace for oxidation to convert the polycrystalline silicon carbide layer on the surface of the wafer into a silicon oxide layer. The oxidation temperature is 1100° C., the time is 1 hour, and the atmosphere is oxygen.
[0052] S33. Soak the wafer in 49% hydrofluoric acid for 20 minutes to remove the silicon oxide layer on the surface of the wafer. After taking out the wafer, rinse it repeatedly with deionized water and finally dry it with a nitrogen gun.
[0053] S4. 3C silicon carbide was epitaxially grown on the substrate by chemical vapor deposition. The carbon source was propane, the silicon source was monosilane, the carrier gas was hydrogen, the carbon source flow rate was 5 mL / min, the silicon source flow rate was 15 mL / min, the carrier gas flow rate was 100 L / min, the deposition temperature was 1350°C, and the growth time was 5 h.
[0054] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.
Claims
1. A method for preparing a silicon carbide epitaxial layer on a silicon substrate, characterized in that: Carbon ions are implanted into the silicon substrate and then annealed to remove the excess surface layer. 3C silicon carbide is then epitaxially grown on the substrate by chemical vapor deposition.
2. The preparation method according to claim 1, wherein: The carbon ion implantation temperature is 200-1000°C, the energy is 50-500keV, and the dose is 1×10 16 -1×10 19 / cm 2 , the tilt angle is 0-45° and the rotation angle is 0-360°.
3. The preparation method according to claim 1 or 2, characterized in that: The post-annealing temperature is 1000-1400° C., the time is 1-5 hours, the atmosphere is one or more of oxygen, nitrogen, and argon, and the pressure is 0.1-1 atm.
4. The preparation method according to claim 1, wherein: Removing excess surface layers by wet etching or wet etching-oxidation-wet etching; The solution used in the wet etching is a mixed solution of any of hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride and water, and the molar ratio of the hydrofluoric acid, nitric acid, acetic acid, ammonium fluoride and water is 1:0-10:0-10:0-10:1-50.
5. The preparation method according to claim 4, characterized in that: The oxidation temperature is 800-1400° C., the time is 0.1-5 hours, and the atmosphere is one or more of oxygen, ozone, water vapor, nitrogen, and argon.
6. The preparation method according to claim 1, wherein: The carbon source used in the chemical vapor deposition is one or more of methane, ethylene, ethane, propylene, and propane, the silicon source is one or more of monosilane, dichlorosilane, and trichlorosilane, and the carrier gas is hydrogen; The carbon source flow rate is 5-100 mL / min, the silicon source flow rate is 5-100 mL / min, the carrier gas flow rate is 50-150 L / min, the deposition temperature is 1000-1400° C., and the growth time is 0.5-10 h.