A method for improving the surface life of silicon carbide wafers

Abstract

The present invention relates to the technical field of silicon carbide, and specifically to a method for improving the surface life of a silicon carbide wafer. Based on a PECVD thin film deposition method, a corresponding amorphous silicon thin film is formed on at least one side of the surface of the silicon carbide wafer. During the PECVD annealing process, hydrogen atoms in the amorphous silicon thin film escape to the corresponding surface of the silicon carbide wafer, thereby passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer. Furthermore, since the lattice constant of the amorphous silicon film is close to that of the silicon carbide wafer, the amorphous silicon film can well form bonds with dangling bonds on the surface of the silicon carbide wafer, thereby reducing the number of dangling bonds on the surface of the silicon carbide wafer and eliminating carbon vacancy defects, i.e., passivating the carbon vacancy defects on the surface of the silicon carbide wafer, thereby improving the life of at least one side of the surface of the silicon carbide wafer.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide, and in particular to a method for improving the surface life of a silicon carbide wafer. Background Art

[0002] The equivalent minority carrier lifetime of SiC wafers is an important parameter for measuring the quality of SiC wafers. It can usually be measured in a non-destructive and non-contact manner using microwave technology.

[0003] The equivalent minority carrier lifetime of a SiC wafer consists of two parts: the bulk lifetime of the SiC wafer and the surface lifetime of the SiC wafer. The surface lifetime of the SiC wafer can be significantly improved by passivating carbon vacancy defects on the surface of the SiC wafer, thereby increasing the equivalent minority carrier lifetime of the SiC wafer. A carbon vacancy is a point defect in the crystal lattice where a carbon atom is missing.

[0004] The traditional surface passivation method for SiC wafers is to grow a silicon oxide passivation layer tens of nanometers thick to reduce dangling bonds on the surface of the SiC wafer. However, this traditional method requires growing a relatively thick silicon oxide layer. Growing this silicon oxide layer tens of nanometers thick using thermal oxidation takes at least six hours, and the electricity required for heating is also very expensive. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the traditional surface passivation method of silicon carbide wafer is time-consuming, and provide a method for improving the surface life of silicon carbide wafer.

[0006] In order to achieve the above object, the present invention provides a method for improving the surface life of a silicon carbide wafer, comprising the following steps:

[0007] Provide silicon carbide wafers;

[0008] forming a corresponding amorphous silicon thin film on at least one side of the silicon carbide wafer, wherein the PECVD thin film deposition method includes an annealing process, wherein hydrogen atoms in the amorphous silicon thin film are released to the corresponding surface of the silicon carbide wafer during the annealing process, thereby passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby improving the life of the silicon carbide wafer surface;

[0009] After the amorphous silicon film is formed, the amorphous silicon film forms bonds with dangling bonds on the corresponding surface of the silicon carbide wafer, passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby increasing the surface life of the silicon carbide wafer;

[0010] The amorphous silicon film is removed.

[0011] As an implementation method, the amorphous silicon film is a single-layer film or a double-layer film; when the amorphous silicon film is a double-layer film, the amorphous silicon film includes a first layer of amorphous silicon film located on the surface of the silicon carbide wafer and a second layer of amorphous silicon film located on the surface of the first layer of amorphous silicon film, wherein the density of the first layer of amorphous silicon film is less than the density of the second layer of amorphous silicon film, so that the hydrogen content of the first layer of amorphous silicon film is greater than the hydrogen content of the second layer of amorphous silicon film.

[0012] As an implementation method, the deposition temperature range of the first amorphous silicon film is 150-200°C, and the deposition temperature range of the first amorphous silicon film is 200-250°C.

[0013] As an implementation method, the thickness of the amorphous silicon film is in the range of 50-100 nm.

[0014] As an implementation method, the process of forming a corresponding amorphous silicon thin film on at least one side of the silicon carbide wafer by a PECVD thin film deposition method includes:

[0015] The silicon carbide wafer is placed in a PECVD chamber for reaction, and hydrogen and silane are introduced into the PECVD chamber as reaction gas sources to form an amorphous silicon film on at least one side surface of the silicon carbide wafer.

[0016] As an implementation method, the conditions for growing an amorphous silicon film are as follows: the deposition temperature is set at 200°C, the pressure is 0.5 mbar, the hydrogen flow rate is 150 sccm, the silane flow rate is 15 sccm, and the deposition time is 40 minutes to obtain an amorphous silicon film of the desired thickness.

[0017] As an implementation method, the step of removing the amorphous silicon film includes: immersing the silicon carbide wafer on which the amorphous silicon film is formed into a sodium hydroxide solution, thereby removing the amorphous silicon film on the silicon carbide wafer.

[0018] As an implementation method, the specific steps of providing a silicon carbide wafer include:

[0019] The silicon carbide ingot is generated by the PVT method, and then the silicon carbide ingot is cut into wafers;

[0020] The contaminants on the wafer surface are removed by using the RCA standard cleaning method, followed by rinsing and drying to obtain a silicon carbide wafer.

[0021] Beneficial effects of the present invention: The present invention provides a method for improving the surface life of a silicon carbide wafer, by forming a corresponding amorphous silicon film on at least one side of the surface of the silicon carbide wafer, and utilizing the lattice constant of the amorphous silicon film to be relatively close to the lattice constant of the silicon carbide wafer, which can well form bonds with dangling bonds on the surface of the silicon carbide wafer, reduce the number of dangling bonds on the surface of the silicon carbide wafer, eliminate carbon vacancy defects, that is, passivate the surface defects of silicon carbide, thereby improving the surface life of the silicon carbide wafer.

[0022] The present invention utilizes the high temperature during the PECVD deposition process to allow hydrogen atoms in the amorphous silicon film to escape to the corresponding surface of the silicon carbide wafer, passivating the carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby increasing the life of the silicon carbide wafer surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the method steps for improving the surface life of silicon carbide wafers according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] See also Figure 1 This embodiment provides a technical solution: a method for improving the surface life of a silicon carbide wafer, comprising the following steps:

[0026] Step S100: providing a silicon carbide wafer;

[0027] Step S200: forming a corresponding amorphous silicon thin film on at least one side of the silicon carbide wafer using a PECVD thin film deposition method, wherein the PECVD thin film deposition method includes an annealing process, wherein hydrogen atoms in the amorphous silicon thin film are released to the corresponding surface of the silicon carbide wafer during the annealing process, thereby passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby improving the life of the silicon carbide wafer surface;

[0028] Step S300: After the amorphous silicon film is formed, the amorphous silicon film forms bonds with dangling bonds on the corresponding surface of the silicon carbide wafer, passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby increasing the surface life of the silicon carbide wafer;

[0029] Step S400: removing the amorphous silicon thin film.

[0030] The specific steps of performing step S100 and providing a silicon carbide wafer include:

[0031] The silicon carbide ingot is generated by the PVT method, and then the silicon carbide ingot is cut into wafers;

[0032] The contaminants on the wafer surface are removed by using the RCA standard cleaning method, followed by rinsing and drying to obtain a silicon carbide wafer.

[0033] Specifically, the technology for cutting the silicon carbide ingot into wafers is a slurry slicing technology, and the method for rinsing and then drying is to repeatedly rinse with deionized water and then blow dry with nitrogen.

[0034] Execute step S200. In this embodiment, the method for forming the corresponding amorphous silicon thin film on at least one side surface of the silicon carbide wafer is a PECVD thin film deposition method. The amorphous silicon formed by the PECVD thin film deposition method has a high hydrogen content and a faster deposition speed.

[0035] The process of forming a corresponding amorphous silicon thin film on at least one side surface of the silicon carbide wafer based on the PECVD thin film deposition method includes annealing. This embodiment uses the annealing process to release hydrogen atoms in the amorphous silicon thin film to the corresponding surface of the silicon carbide wafer, passivate the carbon vacancy defects on the corresponding surface of the silicon carbide wafer, and thus improve the life of the silicon carbide wafer surface.

[0036] Specifically, amorphous silicon thin films are in a thermodynamically metastable state, typically containing weak hydrogen bonds. Depositing an amorphous silicon film on a silicon carbide wafer and then heating the film can break the hydrogen bonds within the film, allowing some hydrogen atoms to escape during rapid annealing and enter the silicon carbide wafer surface, passivating surface defects and increasing minority carrier lifetime, thereby enhancing the surface passivation of the silicon carbide wafer. Silicon oxide and other materials do not have this effect.

[0037] At the same time, the amorphous silicon film grown by PECVD undergoes a high-temperature processing process, and the stability of the passivation effect it produces is comparable to that of the silicon oxide film grown by thermal oxidation. This is because annealing not only increases the degree of crystallization of the amorphous silicon film, but also improves the quality of the film, changes the hydrogen bonding mode, and enhances the passivation effect.

[0038] The thickness of the grown amorphous silicon film can be in the range of 50-100 nm, so that there is enough hydrogen in the amorphous silicon film to passivate the surface of the silicon carbide wafer. Since the growth rate of amorphous silicon is much faster than the growth rate of silicon oxide, it does not take too much time and is conducive to industrial growth.

[0039] Furthermore, the amorphous silicon film is a single-layer film or a double-layer film; when the amorphous silicon film is a double-layer film, the amorphous silicon film includes a first layer of amorphous silicon film located on the surface of the silicon carbide wafer and a second layer of amorphous silicon film located on the surface of the first layer of amorphous silicon film, wherein the density of the first layer of amorphous silicon film is less than the density of the second layer of amorphous silicon film, so that the hydrogen content of the first layer of amorphous silicon film is greater than the hydrogen content of the second layer of amorphous silicon film; wherein the high hydrogen content of the first layer of amorphous silicon film enables the first layer of amorphous silicon film to better passivate the surface of the silicon carbide wafer; the high density of the second layer of amorphous silicon film can prevent the overflow of hydrogen in the first layer of amorphous silicon film, thereby achieving a better passivation effect on the surface of the silicon carbide wafer.

[0040] The deposition temperature of the first layer of amorphous silicon thin film is in the range of 150-200° C., the deposition temperature of the second layer of amorphous silicon thin film is in the range of 200-250° C., and other conditions may be the same.

[0041] The process of forming a corresponding amorphous silicon thin film on at least one side of the silicon carbide wafer by a PECVD thin film deposition method includes:

[0042] The silicon carbide wafer is placed in a PECVD chamber for reaction, and hydrogen and silane are introduced into the PECVD chamber as reaction gas sources to form an amorphous silicon film on at least one side surface of the silicon carbide wafer.

[0043] Among them, the conditions for growing an amorphous silicon film in a PECVD chamber are: the deposition temperature is set at 200°C, and the deposition time is corresponding to a predetermined reaction chamber pressure and gas flow rate to obtain an amorphous silicon film of the desired thickness; specifically, the deposition temperature is set at 200°C, the pressure is 0.5mbar, the hydrogen flow rate is 150sccm, the silane flow rate is 15sccm, and the deposition time is 40min to obtain an amorphous silicon film of the desired thickness.

[0044] Execute step S300. An embodiment of the present invention proposes a new method for passivating the surface of a silicon carbide wafer by growing an amorphous silicon film on at least one side of the surface of the silicon carbide wafer. Since the lattice constant of the amorphous silicon film is relatively close to the lattice constant of the silicon carbide wafer, it can form a good bond with the dangling bonds on the surface of the silicon carbide wafer, thereby eliminating carbon vacancy defects, i.e., passivating the carbon vacancy defects on the surface of the silicon carbide wafer.

[0045] Executing step S400, the step of removing the amorphous silicon thin film includes: immersing the silicon carbide wafer on which the amorphous silicon thin film is formed into a sodium hydroxide solution, thereby removing the amorphous silicon thin film on the silicon carbide wafer.

[0046] The method of growing amorphous silicon by PECVD thin film deposition in the embodiment of the present invention can grow an amorphous silicon film of tens of nanometers in more than ten minutes. Therefore, its growth rate far exceeds the silicon oxide film grown by thermal oxidation in the prior art, and is suitable for industrial production needs.

[0047] This patent proposes a method for passivating the surface of a silicon carbide wafer using amorphous silicon thin films grown by PECVD. This method allows for the growth of a thin layer of amorphous silicon to passivate the surface of a silicon carbide wafer in just over ten minutes. Furthermore, because the lattice constant of amorphous silicon is closer to that of silicon carbide, it is possible to achieve better surface passivation of silicon carbide.

[0048] Although the present invention has been disclosed above in terms of preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for improving the surface life of a silicon carbide wafer, characterized in that: The following steps are involved: Provide silicon carbide wafers; A corresponding amorphous silicon thin film is formed on at least one side of the silicon carbide wafer based on a PECVD thin film deposition method, wherein the PECVD thin film deposition method includes an annealing process, wherein hydrogen atoms in the amorphous silicon thin film are released to the corresponding surface of the silicon carbide wafer during the annealing process, thereby passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby improving the life of the silicon carbide wafer surface; After the amorphous silicon film is formed, the amorphous silicon film forms bonds with dangling bonds on the corresponding surface of the silicon carbide wafer, passivating carbon vacancy defects on the corresponding surface of the silicon carbide wafer, thereby increasing the surface life of the silicon carbide wafer; The amorphous silicon film is removed.

2. The method for improving the surface life of a silicon carbide wafer according to claim 1, characterized in that: The amorphous silicon film is a single-layer film or a double-layer film; when the amorphous silicon film is a double-layer film, the amorphous silicon film includes a first layer of amorphous silicon film located on the surface of the silicon carbide wafer and a second layer of amorphous silicon film located on the surface of the first layer of amorphous silicon film, wherein the density of the first layer of amorphous silicon film is less than the density of the second layer of amorphous silicon film, so that the hydrogen content of the first layer of amorphous silicon film is greater than the hydrogen content of the second layer of amorphous silicon film.

3. The method for improving the surface life of a silicon carbide wafer according to claim 1, wherein: The deposition temperature of the first layer of amorphous silicon thin film ranges from 150 to 200°C, and the deposition temperature of the second layer of amorphous silicon thin film ranges from 200 to 250°C.

4. The method for improving the surface life of a silicon carbide wafer according to claim 1, wherein: The thickness of the amorphous silicon film is in the range of 50-100 nm.

5. The method for improving the surface life of a silicon carbide wafer according to claim 1, wherein: The process of forming a corresponding amorphous silicon thin film on at least one side of the silicon carbide wafer by a PECVD thin film deposition method includes: The silicon carbide wafer is placed in a PECVD chamber for reaction, and hydrogen and silane are introduced into the PECVD chamber as reaction gas sources to form an amorphous silicon film on at least one side surface of the silicon carbide wafer.

6. The method for improving the surface life of a silicon carbide wafer according to claim 5, characterized in that: The conditions for growing an amorphous silicon film are as follows: the deposition temperature is set at 200°C, the pressure is 0.5 mbar, the hydrogen flow rate is 150 sccm, the silane flow rate is 15 sccm, and the deposition time is 40 min to obtain an amorphous silicon film of the desired thickness.

7. The method for improving the surface life of a silicon carbide wafer according to claim 1, wherein: The step of removing the amorphous silicon film includes: immersing the silicon carbide wafer on which the amorphous silicon film is formed into a sodium hydroxide solution, thereby removing the amorphous silicon film on the silicon carbide wafer.

8. The method for improving the surface life of a silicon carbide wafer according to claim 1, wherein: The specific steps for providing silicon carbide wafers include: The silicon carbide ingot is generated by the PVT method, and then the silicon carbide ingot is cut into wafers; The contaminants on the wafer surface are removed by using the RCA standard cleaning method, followed by rinsing and drying to obtain a silicon carbide wafer.

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