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CN-122010107-A - Preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth

CN122010107ACN 122010107 ACN122010107 ACN 122010107ACN-122010107-A

Abstract

The invention relates to the technical field of porous graphite preparation, in particular to a preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth, which comprises the following steps of S1, pretreating carbon fibers, selecting high-purity PAN-based fibers or asphalt-based fibers as raw materials, placing the raw materials of long fibers on a high-precision shearing machine, shearing the raw materials into short fiber bundles with the length of 30-50 mm, uniformly putting the sheared short fiber bundles into a fiber scattering machine, preparing a high-speed rotating toothed claw structure by the fiber scattering machine, mechanically scattering the fiber bundles at the rotating speed of 1500-2000 r/min under the driving of a high-power motor, and taking a natural pore structure formed by a carbon fiber bridge frame as a pore-forming mode of the porous graphite without adding pore formers.

Inventors

  • XIAO SHAOYI
  • QIAN HENGLIANG
  • JIA HONGYU
  • Lu Lvyong
  • LIN YUXIANG

Assignees

  • 江苏恒程半导体材料有限公司

Dates

Publication Date
20260512
Application Date
20260206

Claims (8)

  1. 1. The preparation method of the fiber porous graphite for the growth of the semiconductor-grade silicon carbide crystal is characterized by comprising the following steps: s1, pretreating carbon fibers, namely selecting high-purity PAN-based fibers or asphalt-based fibers as raw materials, placing the raw materials of long fibers on a high-precision shearing machine, shearing into short fiber bundles, and uniformly putting the sheared short fiber bundles into a fiber scattering machine; and S2, pulping, namely adding the short fiber and the binder resin in the step S1, adding a dispersing agent, and putting the mixture into a stirrer to obtain porous graphite precursor slurry, and putting the prepared precursor slurry into a sealed high-purity storage tank for standby, wherein the storage environment is controlled to be a clean room, so that the mixing of external pollutants is avoided, and the purity of the slurry is ensured to be stable. S3, hot press forming, namely adopting a high-precision four-column press as forming equipment, adopting a high-purity graphite mould as the mould, quantitatively filling the precursor slurry in the S2 into the mould, applying pressure to the mould by the press, heating the mould at the same time, keeping the pressure stable at the temperature point, pressing the mould to a specified size range, and then preserving the temperature for 0.5-2 h to form a solidified fiber body with compact structure and regular shape; And S4, carrying out high-temperature heat treatment, namely transferring the fiber body obtained in the step S3 after hot press molding into a high-purity heat treatment furnace, introducing high-purity argon into the furnace as protective gas, heating to 2400-2600 ℃ and preserving heat to form a fiber porous graphite structure with uniform pore size distribution, and cooling to room temperature after the heat treatment is finished to obtain the fiber porous material. S5, the fiber porous material in the step S4 is intensively filled into a special purification furnace, high-purity argon is introduced into the furnace in advance to replace air, the heating speed is controlled to be 2000-2400 ℃, organic gas with special halogen elements is introduced into the purification furnace to form volatile gaseous metal halide and nonmetal halide, the gaseous impurities are timely discharged out of the furnace through a high vacuum system matched with the purification furnace, and argon is continuously introduced into the purification process as protective gas, so that 6N-level purification of the fiber porous graphite is finally realized.
  2. 2. The method for preparing porous graphite fiber for growth of semiconductor grade silicon carbide crystal according to claim 1, wherein the length of the short fiber bundle in S1 is 30-50 mm, the fiber breaking machine is provided with a toothed claw structure rotating at high speed, and under the driving of a high-power motor, the toothed claw structure mechanically breaks up the fiber bundle at a rotating speed of 1500-2000 r/min to rapidly disperse the fiber bundle into monofilament microfibers, wherein the diameter of the monofilament is 5-10 μm.
  3. 3. The preparation method of the fiber porous graphite for semiconductor grade silicon carbide crystal growth according to claim 1, wherein in the step S2, the binder resin is selected from one or more of phenolic resin and asphalt resin, the short fiber and the binder resin are proportioned according to the mass ratio of 80% -95%, wherein the dispersing agent is selected from polyethylene glycol or sodium polyacrylate, the adding amount is 0.5% -1.0% of the mass of the fiber, the stirring speed is set to 800-1200 r/min, and the stirring time is set to 30-60 min.
  4. 4. The method for preparing porous graphite fiber for growth of semiconductor grade silicon carbide crystal according to claim 1, wherein the charging density in the mold in S3 is 1.2-1.5 g/cm3, the heating rate is controlled to be 5-8 ℃ per min, the temperature is raised to the hot press forming temperature of 150-200 ℃, and the inert gas in the hot press process is argon.
  5. 5. The method for producing porous graphite for semiconductor grade silicon carbide crystal growth according to claim 4, wherein in S4, the temperature is raised to 2400-2600 ℃ at a slow temperature raising rate of 10-20 ℃ per hour in a heat treatment furnace, and the temperature is kept for 5-13 hours.
  6. 6. The method for preparing porous graphite fiber for growth of semiconductor grade silicon carbide crystal according to claim 1, wherein in S5, the heating rate is 100-200 ℃ per min, the temperature is raised to a purification temperature of 2000-2400 ℃, the total purification treatment time is controlled to be 13-25 h, the organic gas reaction treatment time is 3-5 h, and the heat preservation purification time is 10-20 h.
  7. 7. The method for preparing fibrous porous graphite for semiconductor grade silicon carbide crystal growth according to claim 1, wherein the halogen-containing organic gas is one or a mixture of boron trichloride and carbon tetrachloride.
  8. 8. The method for preparing porous graphite fiber for growth of semiconductor grade silicon carbide crystal according to claim 1, wherein in S5, the organic gas with halogen element is in the purifying furnace, the organic gas can be decomposed rapidly at high temperature to generate high activity halogen element ion, and the high activity halogen element ion reacts with metal impurities in the porous fiber material, including Fe, ni, cu, etc. and non-metal impurities, and finally volatile gaseous metal halide and non-metal halide are formed.

Description

Preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth Technical Field The invention relates to the technical field of porous graphite preparation, in particular to a preparation method of fibrous porous graphite for semiconductor-grade silicon carbide crystal growth. Background At present, porous graphite is needed to be used as a filter screen for SiC gas in the growth process of the semiconductor grade silicon carbide crystal, on one hand, floating carbon particles are screened out, the metering proportion of Si and C is controlled, on the other hand, the high-temperature sublimated SiC gas can be homogenized, and the two points are prepared for growing the high-quality semiconductor grade SiC crystal. The traditional porous graphite technical scheme generally adopts coke or graphite as aggregate, asphalt and resin as binder, and a pore-forming agent as pore-forming technology of porous graphite. The existing porous graphite preparation method has the problems that fiber dispersion is uneven, a pore channel structure is difficult to accurately control, purity is insufficient, the preparation process is complex and the like, and the core requirement of semiconductor-grade application cannot be met. Secondly, the existing method does not optimize technological parameters aiming at the silicon carbide crystal growth scene, and the prepared porous graphite has poor adaptability to the crystal growth requirement, so that the mass production requirement of semiconductor-grade products is difficult to meet; Thirdly, the structural stability is poor, and structural deformation and cracking are easy to occur under the high temperature (1800-2400 ℃) and inert atmosphere environment required by the growth of silicon carbide crystals, so that the carrier is invalid, and the continuity and consistency of the crystal growth are affected. Disclosure of Invention Aiming at the defects existing in the prior art, the invention provides a preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth, which can effectively solve the problems of insufficient purity, uncontrollable pore channel structure, poor high-temperature stability, low scene suitability and the like of the conventional fiber porous graphite in the application of semiconductor-grade silicon carbide crystal growth in the prior art, and provides a preparation method with controllable flow and performance adaptation, so as to obtain the fiber porous graphite with the purity of 6N grade, uniform pore channel and stable high-temperature structure, meet the core requirement of silicon carbide crystal growth on carrier materials, and ensure the crystal growth quality and mass production stability. The invention provides a preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth, which comprises the following steps: s1, pretreating carbon fibers, namely selecting high-purity PAN-based fibers or asphalt-based fibers as raw materials, placing the raw materials of long fibers on a high-precision shearing machine, shearing into short fiber bundles, and uniformly putting the sheared short fiber bundles into a fiber scattering machine; and S2, pulping, namely adding the short fiber and the binder resin in the step S1, adding a dispersing agent, and putting the mixture into a stirrer to obtain porous graphite precursor slurry, and putting the prepared precursor slurry into a sealed high-purity storage tank for standby, wherein the storage environment is controlled to be a clean room, so that the mixing of external pollutants is avoided, and the purity of the slurry is ensured to be stable. S3, hot press forming, namely adopting a high-precision four-column press as forming equipment, adopting a high-purity graphite mould as the mould, quantitatively filling the precursor slurry in the S2 into the mould, applying pressure to the mould by the press, heating the mould at the same time, keeping the pressure stable at the temperature point, pressing the mould to a specified size range, and then preserving the temperature for 0.5-2 h to form a solidified fiber body with compact structure and regular shape; And S4, carrying out high-temperature heat treatment, namely transferring the fiber body obtained in the step S3 after hot press molding into a high-purity heat treatment furnace, introducing high-purity argon into the furnace as protective gas, heating to 2400-2600 ℃ and preserving heat to form a fiber porous graphite structure with uniform pore size distribution, and cooling to room temperature after the heat treatment is finished to obtain the fiber porous material. S5, the fiber porous material in the step S4 is intensively filled into a special purification furnace, high-purity argon is introduced into the furnace in advance to replace air, the heating speed is controlled to be 2000-2400 ℃, organic gas with special halogen elements is introduced i