Search

CN-116288716-B - Preparation method of silicon carbide single crystal

CN116288716BCN 116288716 BCN116288716 BCN 116288716BCN-116288716-B

Abstract

The invention provides a preparation method of silicon carbide single crystals, and belongs to the technical field of semiconductor material preparation. The silicon carbide single crystal is obtained by placing silicon carbide raw materials for growing crystals into a graphite loading crucible, then assembling a first graphite supporting ring, placing coated seed crystals on the first graphite supporting ring, enabling silicon surfaces of the coated seed crystals to face upwards, then assembling a second graphite supporting ring on the first graphite supporting ring, placing a porous graphite plate on the second supporting ring, enabling a space to be reserved between the porous graphite plate and the coated seed crystals, paving a silicon carbide powder layer on the surface of the porous graphite plate, then covering a graphite cover, and heating for growing crystals. According to the invention, the carbonization coating is arranged on the back of the seed crystal, so that volatilization of silicon vapor on the back of the seed crystal can be effectively prevented, and further back corrosion of the seed crystal is prevented, and meanwhile, through the optimal design of the seed crystal supporting structure, back corrosion of the seed crystal can be further prevented, and finally, high-quality silicon carbide single crystal is obtained.

Inventors

  • ZHAO XINTIAN
  • Luo Yedong
  • HAO HAN
  • YANG MIJUN
  • ZHANG XUAN
  • CHEN JINGYING

Assignees

  • 宁波合盛新材料有限公司

Dates

Publication Date
20260512
Application Date
20221109

Claims (9)

  1. 1. A method for producing a silicon carbide single crystal, comprising the steps of: the preparation method of the seed crystal with the coating comprises the steps of mixing phenolic resin with propylene glycol methyl ether acetate to obtain a phenolic resin solution, mixing graphite emulsion, ethanol and phenolic resin to obtain a graphite emulsion diluent, coating the phenolic resin solution on the surface of the silicon surface of the seed crystal, drying to form a first phenolic resin bonding layer on the surface of the silicon surface, coating the graphite emulsion diluent on the surface of the first phenolic resin bonding layer, drying to form a graphite emulsion coating on the surface of the first phenolic resin bonding layer, coating the phenolic resin solution on the surface of the graphite emulsion coating, drying to form a second phenolic resin bonding layer on the surface of the graphite emulsion coating, coating graphite powder on the surface of the second phenolic resin bonding layer, forming a graphite powder coating on the surface of the second phenolic resin bonding layer, and sintering and solidifying to obtain the seed crystal coating; Providing a crystal growth crucible, wherein the crystal growth crucible sequentially comprises a graphite loading crucible, a first graphite supporting ring, a second graphite supporting ring, a porous graphite plate and a graphite cover from bottom to top; Placing a silicon carbide raw material for growing crystals into a graphite crucible for loading, assembling a first graphite support ring on the graphite crucible for loading the silicon carbide raw material for growing crystals, placing a coated seed crystal on the first graphite support ring with the silicon surface of the coated seed crystal facing upwards, then assembling a second graphite support ring on the first graphite support ring, placing a porous graphite plate on the second graphite support ring with a space reserved between the porous graphite plate and the coated seed crystal, paving a silicon carbide powder layer on the surface of the porous graphite plate, covering the graphite cover, and heating for growing crystals to obtain the silicon carbide single crystal.
  2. 2. The method according to claim 1, wherein the carbonized coating has a thickness of 150 to 200 μm.
  3. 3. The preparation method of the graphite emulsion according to claim 1, wherein the D50 of graphite in the graphite emulsion is less than 400nm, and the thickness of the graphite emulsion coating is 60-80 μm.
  4. 4. The preparation method of claim 1, wherein the coating mode of the graphite emulsion diluent is spraying, the spraying distance is 30-40 cm, and the pressure of compressed air is 0.2-0.4 MPa.
  5. 5. The preparation method of the graphite powder according to claim 1, wherein the D50 of the graphite powder is 1-5 μm, and the thickness of the graphite powder coating is 70-130 μm.
  6. 6. The preparation method of claim 1, wherein the graphite powder is coated by spraying, the spraying distance is 30-50 cm, and the pressure of compressed air is 0.2-0.4 MPa.
  7. 7. The preparation method of the phenolic resin adhesive layer according to claim 1, wherein the phenolic resin content in the phenolic resin solution used for preparing the first phenolic resin adhesive layer and the second phenolic resin adhesive layer is independently 15-35 wt%, and the thickness of the first phenolic resin adhesive layer and the second phenolic resin adhesive layer is independently 2-4 μm.
  8. 8. The preparation method of claim 1, wherein the porous graphite plate has a thickness of 5-10 mm, a porosity of 40-60% and a pore diameter of 8-30 μm.
  9. 9. The preparation method of the silicon carbide powder according to claim 1, wherein the thickness of the silicon carbide powder layer is 20-30 mm, and the granularity of silicon carbide powder adopted for paving the silicon carbide powder layer is 40-60 meshes.

Description

Preparation method of silicon carbide single crystal Technical Field The invention relates to the technical field of semiconductor material preparation, in particular to a preparation method of silicon carbide single crystals. Background Semiconductor chip structures include substrates, epitaxy, and device structures. The substrate usually plays a supporting role, and epitaxy is a specific film required by a device, and the device structure is a topological structure with a certain circuit pattern processed by using procedures such as photoetching and the like. The third generation semiconductor material mainly comprises silicon carbide (SiC) and gallium nitride (GaN), and has higher forbidden band width, breakdown voltage, electric conductivity and thermal conductivity compared with the first and second generation semiconductor materials, and the third generation semiconductor material can replace the first two generation semiconductor materials in the fields of high temperature, high voltage, high power and high frequency. Among them, gallium nitride lacks large-sized single crystal, so silicon carbide is widely used, for example, the main forms of third generation semiconductor materials are silicon carbide-based silicon carbide epitaxial devices and silicon carbide-based gallium nitride epitaxial devices. And the thermal conductivity of silicon carbide is about 3 times of that of gallium nitride, so that the silicon carbide has stronger heat conduction capability, longer service life of devices, higher reliability and smaller heat dissipation system required by the system. Through many years of research, the technology of growing SiC single crystals by a physical vapor transport method (PVT method) is becoming mature. At present, a graphite crucible is generally used for growing SiC single crystals, specifically, siC raw materials are placed at the lower part of a growth chamber, a seed crystal is adhered and fixed on a graphite cover at the top of the growth chamber, the SiC raw materials are sublimated from the lower part of the growth chamber by controlling the temperature and pressure conditions of the growth chamber, and then the SiC raw materials rise to the seed crystal to be piled up and grown, so that the SiC single crystals are finally obtained. However, the thermal expansion coefficient of graphite is 6×10 -6K-1 under the condition of 2000-2200 ℃, and the thermal expansion coefficients of 4H-SiC single crystal are 5.2×10 -6K-1 and 4.6×10 -6K-1 respectively in the axial direction and the radial direction under the same temperature, and the difference of the expansion coefficients can lead to larger thermal stress, further cause mechanical stress, lead to oversized stress of the final substrate product, excessive dislocation defects and even lead to proliferation of microtubes. In order to overcome the problems, the prior method is to increase the buffer of the graphite paper between the seed crystal and the graphite cover, namely, bond and fix the seed crystal and one surface of the graphite paper, and bond and fix the other surface of the graphite paper and the graphite cover, so as to reduce the stress. But the bonding difficulty of seed crystal and graphite paper and graphite lid is big, and bonding time is long, and leads to the uneven problem of seed crystal back heat dissipation easily, the easy corrosion situation that appears in higher department of temperature. In addition, the graphite paper has lower strength, is not compact enough and cannot resist the corrosion of silicon vapor, once corrosion holes in a local area appear, the area can accelerate the corrosion speed, so that polycrystal growth occurs, and the polycrystal growth speed is higher than that of the monocrystal, and the monocrystal can be extruded to cause stress, cracking or polytype defects. Disclosure of Invention The invention aims to provide a preparation method of silicon carbide single crystals, which can avoid the problem of uneven heat dissipation caused by bonding and fixing of seed crystals, graphite paper and graphite covers in the existing method, and can effectively prevent back corrosion of the seed crystals, so that high-quality silicon carbide single crystals can be obtained. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of silicon carbide single crystal, which comprises the following steps: Providing a seed crystal with a coating, wherein the seed crystal with the coating comprises a seed crystal and a carbonized coating arranged on the surface of a silicon surface of the seed crystal; Providing a crystal growth crucible, wherein the crystal growth crucible sequentially comprises a graphite loading crucible, a first graphite supporting ring, a second supporting ring, a porous graphite plate and a graphite cover from bottom to top; Placing a silicon carbide raw material for growing crystals into a graph