CN117534467A - Preparation method of high-homogeneity special graphite material for epitaxial growth substrate - Google Patents
Preparation method of high-homogeneity special graphite material for epitaxial growth substrate Download PDFInfo
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- 239000007770 graphite material Substances 0.000 title claims abstract description 32
- 239000000758 substrate Substances 0.000 title claims abstract description 24
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 62
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 36
- 239000010439 graphite Substances 0.000 claims abstract description 36
- 229910021383 artificial graphite Inorganic materials 0.000 claims abstract description 29
- 239000002006 petroleum coke Substances 0.000 claims abstract description 29
- 239000006253 pitch coke Substances 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 16
- 239000002245 particle Substances 0.000 claims abstract description 16
- 239000002994 raw material Substances 0.000 claims abstract description 11
- 239000010426 asphalt Substances 0.000 claims description 43
- 238000010438 heat treatment Methods 0.000 claims description 41
- 239000002131 composite material Substances 0.000 claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 13
- 239000004065 semiconductor Substances 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 239000000571 coke Substances 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 10
- 238000005507 spraying Methods 0.000 claims description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 8
- 239000000460 chlorine Substances 0.000 claims description 8
- 229910052801 chlorine Inorganic materials 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- 238000003763 carbonization Methods 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 229920000459 Nitrile rubber Polymers 0.000 claims description 6
- 238000000746 purification Methods 0.000 claims description 6
- 238000010791 quenching Methods 0.000 claims description 6
- 230000000171 quenching effect Effects 0.000 claims description 6
- 230000000087 stabilizing effect Effects 0.000 claims description 6
- 238000000462 isostatic pressing Methods 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- 239000006255 coating slurry Substances 0.000 claims description 4
- 238000005056 compaction Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 claims description 4
- 230000000630 rising effect Effects 0.000 claims description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 230000006837 decompression Effects 0.000 claims description 3
- 238000000265 homogenisation Methods 0.000 claims description 3
- 238000010907 mechanical stirring Methods 0.000 claims description 3
- 239000010453 quartz Substances 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 2
- 239000006185 dispersion Substances 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims description 2
- 238000003754 machining Methods 0.000 claims description 2
- 239000001301 oxygen Substances 0.000 claims description 2
- 229910052760 oxygen Inorganic materials 0.000 claims description 2
- 238000007781 pre-processing Methods 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 238000012216 screening Methods 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract description 4
- 238000000576 coating method Methods 0.000 abstract description 4
- 238000005087 graphitization Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 6
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- 238000012545 processing Methods 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000011049 filling Methods 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
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- 102220043159 rs587780996 Human genes 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
- C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/522—Graphite
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/62605—Treating the starting powders individually or as mixtures
- C04B35/6261—Milling
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/62605—Treating the starting powders individually or as mixtures
- C04B35/62625—Wet mixtures
- C04B35/6264—Mixing media, e.g. organic solvents
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/628—Coating the powders or the macroscopic reinforcing agents
- C04B35/62802—Powder coating materials
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/628—Coating the powders or the macroscopic reinforcing agents
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- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
- C04B35/632—Organic additives
- C04B35/634—Polymers
- C04B35/63496—Bituminous materials, e.g. tar, pitch
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/12—Substrate holders or susceptors
Abstract
The invention belongs to the technical field of preparation of graphite basal discs, in particular to a preparation method of a high-homogeneity special graphite material for an epitaxial growth basal disc, which aims at solving the problems of insufficient homogeneity, unstable thermal expansion coefficient and low thermal conductivity of the existing graphite, and provides the following scheme that the main raw materials are needle petroleum coke, needle pitch coke, modified artificial graphite and modified pitch; the mass ratio of the needle petroleum coke to the needle pitch coke to the modified artificial graphite is 5:4:1-8:1:1; the preparation method can effectively enhance special single indexes while maintaining various indexes of graphite per se, has more uniform coating particles in units forming a block, has stronger binding capacity, can maintain the stability of product preparation, can effectively control the preparation cost, uses low-cost and easily-obtained raw materials, has stable properties, has simple and easily-operated raw material pretreatment process, and can finish the preparation of the high-homogeneity graphite material for the epitaxial growth substrate with excellent performance through traditional equipment.
Description
Technical Field
The invention relates to the technical field of graphite materials, in particular to a preparation method of a high-homogeneity special graphite material for an epitaxial growth substrate.
Background
Graphite for semiconductors is one of the highest-grade special graphite materials. Part of low-end chip products utilize photovoltaic special graphite, so that the preparation yield and quality of the low-end chips are extremely unstable, wherein the most important reasons are insufficient homogeneity of the graphite, unstable thermal expansion coefficient and uneven film components and thickness of wafers epitaxially grown in MOCVD equipment caused by low thermal conductivity, and the chip quality is low.
At present, a graphite substrate of a ceramic coating in widely applied MOCVD equipment is a core material for preparing SBD, MOSFET, HEMT and other devices, the graphite material has high requirements on purity, homogeneity, thermal expansion and heat conduction performance, and although domestic graphite can meet the purity requirement through secondary purification, a comprehensive design and inspection path is required for the structural-thermal performance integration of the graphite material for preparing high-quality chips.
The large-size graphite for the photovoltaic can meet the requirements of the graphite for the semiconductor in terms of size and purity, but the internal structure is solid, the thermal stability is balanced, the thermal expansion is uniform and moderate, and the balance among the three is an important factor for restricting the development of the domestic semiconductor graphite material.
There is a need for a highly homogeneous, thermally stable, semiconductor graphite-based disk material suitable for thermal expansion.
Disclosure of Invention
The invention provides a preparation method of a high-homogeneity special graphite material for an epitaxial growth substrate, and aims to provide a semiconductor graphite substrate material which is high in homogeneity, stable in heat and suitable for thermal expansion and a preparation method thereof so as to meet the requirement of graphite for semiconductors.
The invention provides the following technical scheme:
the application provides a preparation method of a high-homogeneity special graphite material for an epitaxial growth basal disc, wherein the main raw materials of the graphite material are needle petroleum coke, needle pitch coke, high-specific-surface modified artificial graphite and modified pitch; the mass ratio of the needle petroleum coke to the needle pitch coke to the high-ratio surface modified artificial graphite is 5:4:1-8:1:1; the addition amount of the modified asphalt accounts for 22-27% of the total mass of the raw materials, and the preparation method of the graphite material comprises the following steps of,
step one, preprocessing powdery artificial graphite in a low-pressure oxygen-containing atmosphere to obtain high-specific surface modified artificial graphite;
step two, respectively crushing and gradient screening the needle petroleum coke and the needle asphalt coke, and fully mixing the crushed needle petroleum coke and the needle asphalt coke with the high-specific-surface modified artificial graphite to obtain composite coke powder;
step three, mixing the composite coke powder with the dissolved modified asphalt solution to form coating slurry, and sequentially carrying out the steps of negative pressure heating, liquid nitrogen cooling, mechanical depolymerization and uniform mixing on the coating slurry through a spraying device to obtain the composite coke powder of the coated asphalt;
step four, standing the asphalt-coated composite coke powder obtained in the step three, performing sectional isostatic compaction, and demolding to obtain a green body sample;
step five, standing the green body sample obtained in the step four, and carrying out homogenization carbonization treatment;
step six, graphitizing and purifying the sample homogenized and carbonized in the step five to obtain the high-homogeneity special graphite material;
and seventhly, machining the special graphite material with high homogeneity in the step six into a graphite base plate or a base of MOCVD, and performing secondary purification to meet the requirement of the graphite base for the semiconductor.
As a further improvement to the above-described solution,
preferably, in the first step, artificial graphite with the range of 8-20 μm is placed into a quartz crucible and stirred; placing the crucible in an environment with the temperature of 260-450 ℃ and the pressure of 0.02-0.08 mpa for reaction for 1-8 h; and cooling and taking out from the crucible to obtain the high-specific-surface-area modified artificial graphite.
Preferably, in the second step, the needle petroleum coke and the needle pitch coke are respectively crushed, and the granularity interval is 8-50 mu m; respectively passing the crushed needle petroleum coke and the pulverized coke powder of the needle asphalt coke through an ultrasonic annular shaking screen with the granularity of 30 meshes to 500 meshes in sequence; and finally, carrying out VC mixing on the screened needle petroleum coke and needle asphalt coke and the high-ratio modified artificial graphite in a ratio of 5:4:1-8:1:1 to obtain the composite coke powder.
Preferably, in the third step, the modified asphalt is placed in a THF solvent, the mass ratio of the modified asphalt to the THF solvent is 1:8, the modified asphalt and the THF solvent are uniformly mixed, then the modified asphalt and the THF solvent are placed in a spraying device with the temperature of room temperature to 70 ℃ for dispersion, and then the modified asphalt and the THF solvent are sent into a negative pressure heating bin with gradient heating under the pressure of 0.5 to 2mpa, wherein the temperature range is 100 ℃ to 240 ℃; after passing through the buffer area, entering a liquid nitrogen quenching bin for liquid nitrogen heat preservation, wherein the temperature is between minus 10 ℃ and minus 50 ℃; and then the mixture is sent into a mechanical depolymerization bin and uniformly stirred by a mechanical stirring device, and finally VC is mixed, so that the composite coke powder coated with asphalt is obtained.
In the fourth step, the composite coke powder coated with asphalt is loaded into a nitrile rubber mold and then subjected to twice isostatic compaction, the mixture is loaded into the nitrile rubber mold, compacted and vacuumized, and then is fed into an isostatic press, the mixture is firstly risen to 10-30 MPa at a rate of 1-5 MPa/min, is stabilized for 5-7 min, and is decompressed to 1-5 MPa at a decompression rate of 5-10 MPa/min, and is stabilized for 2-4 min; then reducing the pressure to the room pressure, and standing for 2-10 h; standing, vacuumizing again, carrying out secondary isostatic pressing, rising to 120MPa at the rate of 7-10 MPa/min, stabilizing the pressure for 5-7 min, and then decompressing to 50-70 MPa at the decompression rate of 12-15 MPa/min, and stabilizing the pressure for 2-4 min; then pressure is released to 20-40 MPa at a pressure release rate of 8-10 MPa/min, and the pressure is stabilized for 5-6 min; and finally, pressure is released to the room pressure at a pressure release rate of 8-10 MPa/min.
Preferably, in the fifth step, the temperature is raised to 220-280 ℃ at a heating rate of 4-9 ℃/h; then heating to 400-500 ℃ at a heating rate of 2-5 ℃/h; then heating to 650-720 ℃ at a heating rate of 1-3 ℃/h; then heating to 750-880 ℃ at a heating rate of 2-3 ℃/h; then heating to 1008-1100 ℃ at a heating rate of 5-6 ℃/h; finally, the temperature is reduced to 60-80 ℃ at the temperature reduction rate of 7 ℃/h, and the furnace is discharged and naturally cooled.
Preferably, in the sixth step, the carbonized sample is heated to 1350-1850 ℃ uniformly, kept for 2-8 h, then heated to 2580-2920 ℃ uniformly, chlorine-containing purified gas is introduced in the process of 1700-2500 ℃ with the weight of 0.5-1 ton, finally cooled to 90 ℃ at the cooling rate of 0.2-0.6 ℃/h, and discharged from the furnace, and naturally cooled to obtain the high-homogeneity special graphite.
Preferably, in the seventh step, the processed graphite substrate is placed in a purification furnace, vacuumized to 0.005Mpa, introduced with Ar atmosphere to 0.08Mpa, heated to 2000-2500 ℃, introduced with chlorine at a flow rate of 0.1-0.8L/min for 3-10 h, finally stopped to supply chlorine, kept for 2-5 h, and finally cooled to room temperature at 5-10 ℃ to obtain the graphite substrate for the semiconductor.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
In the invention, needle petroleum coke and needle asphalt coke are used as main materials, high-specific-surface modified artificial graphite is used as auxiliary materials, modified asphalt is used as a binder, and aggregate types and proportions are reasonably matched, so that the graphite product is more outstanding in heat conduction, strength and performance of a proper thermal expansion coefficient; compared with the existing photovoltaic graphite, the thermal conductivity of the photovoltaic graphite is improved from 80W/(m.K) to 120W (m.K), the thermal conductivity is increased by more than 50%, the expansion coefficient is reduced from 6.5 x 10 < -6 >/DEG C to 4.6 x 10 < -6 >/DEG C, the compressive strength is increased from 90Mpa to 102Mpa, the thermal conductivity is increased by more than 13%, and the special single index can be effectively enhanced while the indexes of the graphite are maintained.
The invention forms coated particles by using a coating mode of high-pressure spraying, rapid vacuum hot melting and quenching setting, and is characterized in that the binding agent is tightly combined with aggregate, the binding agent in a molten state is adsorbed into the pores of the particles by vacuum hot melting, compared with the traditional kneading coating, the coated particles are more uniform, the coated particles are free from flowing or missing of the binding agent on the outer wall of the particles caused by gravity or friction force by quenching setting, and the coated particles are more uniform in units forming a block material and have stronger binding capability.
According to the preparation method, through reasonable scientific proportion and reasonable roasting carbonization and graphitization curve control, the qualification rate of the graphite product in roasting and graphitization can reach 85%, the stability of product preparation is maintained, and the preparation cost can be effectively controlled.
In the invention, the raw materials used are low in price and easy to obtain, the property is stable, the raw material pretreatment process is simple and easy to operate, and the preparation can be completed by traditional equipment.
Detailed Description
Example 1:
the invention comprises a preparation method of a high-homogeneity special graphite material for an epitaxial growth basal disc, which mainly comprises needle petroleum coke, needle pitch coke, modified artificial graphite and modified pitch, wherein the softening point of the modified pitch is 115 ℃, and the mass ratio of the needle petroleum coke, the needle pitch coke and the high-ratio modified artificial graphite is 5:4:1; the addition amount of the modified asphalt is 30% of the total weight of the modified asphalt composite coke powder, the processes of raw material grading, molding, roasting, graphitization and the like are optimized in the whole process, and through the optimized proportioning of the raw materials and the two heat treatment processes at the service rear end, the modified asphalt can be prepared by only using traditional roasting and graphitization equipment, so that the difficulty of the heat treatment process is reduced, and the qualification rate of graphite finished products is improved.
The preparation method of the high-homogeneity special graphite material for the epitaxial growth substrate comprises the following steps:
firstly, crushing artificial graphite with graphitization degree of 78-80 to 15 μm by adopting a hammer machine, placing the crushed artificial graphite into a quartz crucible, slowly stirring, and placing the crucible into an environment of 380 ℃ and 0.05Mpa for reaction for 5 hours; cooling and discharging from the crucible to obtain high-specific-surface-area modified artificial graphite, wherein the high-specific-surface-area modified artificial graphite powder enhances the structural strength of the graphite blocks, and the dispersion-type distribution enhances the homogenization of the blocks;
respectively crushing the needle petroleum coke and the needle asphalt coke to the granularity D50=15 mu m by a high-speed hammer machine, and mixing the needle petroleum coke, the needle asphalt coke and the high-ratio surface modified artificial graphite according to the mass ratio of 5:4:1 to prepare composite coke powder; meanwhile, the needle petroleum coke and the needle pitch coke are very rare in the field of special carbon materials, and because the anisotropy of the needle petroleum coke and the needle pitch coke is obvious, the needle petroleum coke and the needle pitch coke are unfavorable for constructing products with high isotropy requirements, on particle pretreatment, the high-ratio modified artificial graphite is introduced to balance the sharp orientation caused by the needle petroleum coke and the needle pitch coke, and the needle petroleum coke and the needle pitch coke can better stabilize the thermal expansion coefficient interval, so that the thermal expansion coefficient is lower and stable, the strength of a block is favorably enhanced through the regulation and control of the particle size, the higher particle strength and purity are obtained, the treatment temperature of the needle petroleum coke and the needle pitch coke is higher, the density, the strength and the purity are higher, the modified pitch is placed in a THF solvent, the mass ratio of the modified pitch to the THF solvent is 1:8, and the modified pitch and the THF solvent are uniformly mixed to form a mixed solution; 45Kg of composite coke powder and 115.8Kg of mixed solution are put into a sealing stirrer at 60 ℃ for stirring for 0.5h, then the mixed solution is poured into a storage bin of a spraying device and then pressurized to 1.8Mpa for spraying and dispersing, dispersed slurry drops pass through a negative pressure heating bin, the temperature in the negative pressure heating bin is kept at 240 ℃, slurry retention time is 30s, the slurry drops enter a liquid nitrogen quenching bin, the temperature is reduced to-20 ℃ and retained for 5min, the slurry drops enter a mechanical depolymerization bin for uniform stirring by a mechanical stirring device, finally VC mixing is carried out to obtain high-homogeneity coated coke powder, the high-homogeneity coated coke powder is prepared by adopting modes of high-pressure spraying, vacuum hot melting, quenching and the like, compared with the traditional mixed kneading coated coke powder, the high-homogeneity coated coke powder has three advantages of improving sphericity and uniformity of particles and coated asphalt, ensuring uniform liquid drops through constant nozzles in a constant pressure spraying mode, improving asphalt coating strength, vacuum hot melting asphalt penetrating into pores, improving integrity of coated asphalt on aggregate, avoiding rapid solidification of asphalt on an outer layer of aggregate, and improving wear resistance of the mixed abrasion.
And thirdly, putting the coated coke powder obtained in the second step into a V-shaped mixer for preliminary mixing for 30min, wherein the rotating speed of the mixer is 80r/min.
And fourthly, standing for 5 hours after blanking in the third step, wherein the mass of volatile matters in the mixture accounts for 11 weight percent of the total mass of the mixture.
Step five, slowly putting the mixture in the step four into a 400 mm-280 mm-150 mm nitrile rubber mold, compacting, sealing, vacuumizing for 20min, rising to 25MPa at the rate of 4-5 MPa/min, stabilizing the pressure for 6-7 min, releasing the pressure to 5MPa at the pressure release rate of 6-7MPa/min, maintaining for 2-3min, and releasing the pressure to the room pressure; vacuumizing and sealing the nitrile rubber mold again, boosting the pressure to 120MPa at the speed of 9-10 MPa/min, and stabilizing the pressure for 6min; and then the pressure is released to 65MPa at the speed of 15MPa/min, the pressure is released to 20MPa at the pressure release speed of 9-10 MPa/min after the pressure is maintained for 4min, the pressure is stabilized for 5min, finally the pressure is released to the room pressure at the speed of 8MPa/min, then the demoulding is carried out, a regular square green body sample is obtained after demoulding, the square green body sample is placed in a room temperature environment for standing for 24h, and the homogeneity of the block material formed by powder, the low-density green body and the high-density green body is improved by a secondary isostatic pressing technology. Because the isotropy is low by adopting the traditional pre-pressing and isostatic pressing processes, and the traditional one-time isostatic pressing molding is easy to cause the rising of the pressure and friction between the air of the blank body and particles in the process from low density to high density, internal hole defects can be generated to influence the blank structure.
Step six, loading the green body sample into a high-temperature stainless steel crucible, filling quartz sand with granularity less than 1mm, jolt ramming, and enabling the distance between the sample and the crucible wall to be more than 100mm and the distance between the sample and the crucible top to be more than 300mm.
And (3) starting the roasting and carbonizing process:
(a) Heating to 220-280 ℃ at a heating rate of 6-9 ℃/h;
(b) Then heating to 400-420 ℃ at a heating rate of 2-3 ℃/h;
(c) Then heating to 650-680 ℃ at a heating rate of 1-2 ℃/h;
(d) Then heating to 750-800 ℃ at a heating rate of 2-3 ℃/h;
(e) Then heating to 1008-1012 ℃ at a heating rate of 5-6 ℃/h;
(f) Finally, cooling to 60-80 ℃ at a cooling rate of 7 ℃/h, discharging, and naturally cooling; the percent of pass of the first carbonization is 88-95%.
And seventhly, filling the primary carbonized product into an asphalt dipping tank, vacuumizing to below 20pa, maintaining for 30min, then introducing molten asphalt, maintaining for 20min, pressurizing to 0.2Mpa, maintaining for 10min, and marking as the primary dipped product after being taken out.
And step eight, carrying out secondary carbonization on the impregnated product in the step seven, wherein a carbonization curve is as in the step six, and the secondary carbonization qualification rate is 98%, so as to obtain a secondary carbonized product.
And step nine, loading the secondary carbonized sample into an Acheson graphitization furnace, uniformly heating to 1750-1800 ℃, preserving heat for 5 hours, uniformly heating to 2750-2800 ℃, introducing chlorine at 2000 ℃, reducing the flow rate to 90 ℃ at a speed of 0.2-0.6 ℃/h, discharging from the furnace, and naturally cooling to obtain the graphite material for the semiconductor, wherein the graphitization qualification rate is more than 90%.
And step ten, processing the graphite material for the semiconductor into a graphite substrate, then placing the graphite substrate in a secondary purification high-temperature furnace, heating to 1800 ℃ at 20 ℃/min, introducing chlorine at a flow rate of 0.3L/min, keeping for 1h, then heating to 2200 ℃ and keeping for 3h, and slowly cooling to room temperature at 10-20 ℃/min to obtain the graphite substrate for the semiconductor.
The graphite substrate of this example was tested to have an average particle size of 15 μm and a bulk density of 1.84g/cm 3 The compressive strength is 92.2MPa, the flexural strength is 45.7MPa, the resistivity is 13.1 mu omega. M, the porosity is 12%, and the thermal expansion coefficient is 4.6 x 10 -6 The heat conductivity is 128W (m.K), the isotropy coefficient is 1.03, the qualification rate of finished products is more than 88%, and the production period of the whole product is 7 months.
Example 2:
the process of this example was the same as that of example 1, except that in step one, the mass ratio of needle petroleum coke, needle pitch coke and high-ratio modified artificial graphite was 7:2:1, the volatile content in the mix was 11.5wt% of the total mass of the mix, and the final yield was 88%.
The graphite substrate of this example was tested to have an average particle size of 15 μm; bulk density of 1.83g/cm 3 The compressive strength is 95.8Mpa, the flexural strength is 46.9Mpa, the resistivity is 13.6 mu omega-m, the porosity is 13%, and the thermal expansion coefficient is 4.8 x 10 -6 The thermal conductivity was 113W (m.K), the isotropy coefficient was 1.02, and the sample processing period of this example was 7 months.
Example 3:
the process of this example was identical to that of example 1, except that in step one, the mass ratio of needle petroleum coke, needle pitch coke and high specific surface modified artificial graphite was 6:3:1, the volatile content in the mix was 11.9wt% of the total mass of the mix, and the final yield was 87%.
The graphite substrate of this example was tested to have an average particle size of 15 μm; bulk density of 1.82g/cm 3 The compressive strength is 96.8Mpa, the flexural strength is 46.5Mpa, the resistivity is 13.7 mu omega-m, the porosity is 13%, and the thermal expansion coefficient is 5.1 x 10 -6 The thermal conductivity was 107W (m.K), the isotropy coefficient was 1.03, and the sample processing period of this example was 7 months.
The present invention is not limited to the above embodiments, and any person skilled in the art can easily think about the changes or substitutions within the technical scope of the present invention, and the changes or substitutions are intended to be covered by the scope of the present invention; embodiments of the invention and features of the embodiments may be combined with each other without conflict. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (8)
1. A preparation method of a high-homogeneity special graphite material for an epitaxial growth basal disc is characterized in that the main raw materials of the graphite material are needle petroleum coke, needle pitch coke, high-specific-surface modified artificial graphite and modified pitch; the mass ratio of the needle petroleum coke to the needle pitch coke to the high-ratio surface modified artificial graphite is 5:4:1-8:1:1; the addition amount of the modified asphalt accounts for 22-27% of the total mass of the raw materials, and the preparation method of the graphite material comprises the following steps of,
step one, preprocessing powdery artificial graphite in a low-pressure oxygen-containing atmosphere to obtain high-specific surface modified artificial graphite;
step two, respectively crushing and gradient screening the needle petroleum coke and the needle asphalt coke, and fully mixing the crushed needle petroleum coke and the needle asphalt coke with the high-specific-surface modified artificial graphite to obtain composite coke powder;
step three, mixing the composite coke powder with the dissolved modified asphalt solution to form coating slurry, and sequentially carrying out the steps of negative pressure heating, liquid nitrogen cooling, mechanical depolymerization and uniform mixing on the coating slurry through a spraying device to obtain the composite coke powder of the coated asphalt;
step four, standing the mixture obtained in the step three, performing segmented isostatic compaction, and demolding to obtain a green body sample;
step five, standing the green body sample obtained in the step four, and carrying out homogenization carbonization treatment;
step six, graphitizing and purifying the sample homogenized and carbonized in the step five to obtain the high-homogeneity special graphite material;
and seventhly, machining the high-homogeneity special graphite material in the step six into a graphite base plate or a base of MOCVD, and performing secondary purification to meet the requirement of the graphite base for the semiconductor.
2. The method for producing a high-homogeneity special graphite material for an epitaxial growth substrate according to claim 1, wherein in the first step, artificial graphite in the range of 8 to 20 μm is put into a quartz crucible and stirred; placing the crucible in an environment with the temperature of 260-450 ℃ and the pressure of 0.02-0.08 mpa for reaction for 1-8 h; and cooling and taking out from the crucible to obtain the high-specific-surface-area modified artificial graphite.
3. The method for producing a high-homogeneity special graphite material for an epitaxial growth substrate according to claim 2, characterized in that in the second step, needle petroleum coke and needle pitch coke are pulverized, respectively, with a particle size interval of 8 to 50 μm; respectively passing the crushed needle petroleum coke and the pulverized coke powder of the needle asphalt coke through an ultrasonic annular shaking screen with the granularity of 30 meshes to 500 meshes in sequence; and finally, carrying out VC mixing on the sieved needle petroleum coke and the coke powder of the needle asphalt coke and the high-ratio modified artificial graphite at a ratio of 5:4:1-8:1:1 to obtain the composite coke powder.
4. The method for preparing the high-homogeneity special graphite material for the epitaxial growth substrate, as claimed in claim 3, characterized in that in the third step, modified asphalt is placed in a THF solvent, the mass ratio of the modified asphalt to the THF solvent is 1:8, after being uniformly mixed, the modified asphalt is placed in a spraying device with the temperature of room temperature to 70 ℃ for dispersion, and then the dispersed modified asphalt is sent into a negative pressure heating bin with the temperature of gradient heating under the pressure of 0.5 to 2mpa, wherein the temperature range is 100 ℃ to 240 ℃; after passing through the buffer area, entering a liquid nitrogen quenching bin for liquid nitrogen heat preservation, wherein the temperature is between minus 10 ℃ and minus 50 ℃; and then the mixture is sent into a mechanical depolymerization bin and uniformly stirred by a mechanical stirring device, and finally VC is mixed, so that the composite coke powder coated with asphalt is obtained.
5. The method for preparing the high-homogeneity special graphite material for the epitaxial growth basal disc, which is characterized in that in the fourth step, the composite coke powder coated with asphalt is put into a nitrile rubber mold and then subjected to twice isostatic compaction, the composite coke powder coated with asphalt is put into the nitrile rubber mold, compacted and vacuumized, then sent into an isostatic press, firstly, the pressure is increased to 10-30 MPa at a rate of 1-5 MPa/min, the pressure is stabilized for 5-7 min, then the pressure is relieved to 1-5 MPa at a pressure relief rate of 5-10 MPa/min, and the pressure is stabilized for 2-4 min; then reducing the pressure to the room pressure, and standing for 2-10 h; standing, vacuumizing again, carrying out secondary isostatic pressing, rising to 120MPa at the rate of 7-10 MPa/min, stabilizing the pressure for 5-7 min, and then decompressing to 50-70 MPa at the decompression rate of 12-15 MPa/min, and stabilizing the pressure for 2-4 min; then pressure is released to 20-40 MPa at a pressure release rate of 8-10 MPa/min, and the pressure is stabilized for 5-6 min; and finally, pressure is released to the room pressure at a pressure release rate of 8-10 MPa/min.
6. The method for producing a high-homogeneity special graphite material for an epitaxial growth substrate according to claim 5, wherein in step five, the temperature is raised to 220 to 280 ℃ at a temperature-raising rate of 4 to 9 ℃/h; then heating to 400-500 ℃ at a heating rate of 2-5 ℃/h; then heating to 650-720 ℃ at a heating rate of 1-3 ℃/h; then heating to 750-880 ℃ at a heating rate of 2-3 ℃/h; then heating to 1008-1100 ℃ at a heating rate of 5-6 ℃/h; finally, the temperature is reduced to 60-80 ℃ at the temperature reduction rate of 7 ℃/h, and the furnace is discharged and naturally cooled.
7. The method for preparing a high-homogeneity special graphite material for an epitaxial growth substrate according to claim 6, wherein in the sixth step, the carbonized sample is heated to 1350-1850 ℃ uniformly, kept at the temperature for 2-8 h, heated to 2580-2920 ℃ uniformly, chlorine-containing purified gas is introduced during the temperature of 1700-2500 ℃, the weight is 0.5-1 ton, and finally cooled to 90 ℃ at a cooling rate of 0.2-0.6 ℃/h, and discharged from the furnace for natural cooling, thus obtaining the high-homogeneity special graphite.
8. The method for preparing a high-homogeneity special graphite material for an epitaxial growth substrate according to claim 7, wherein in the seventh step, the processed graphite substrate is placed in a purification furnace, vacuumized to 0.005Mpa, introduced with Ar atmosphere to 0.08Mpa, heated to 2000 ℃ to 2500 ℃, introduced with chlorine at a flow rate of 0.1L/min to 0.8L/min for 3 to 10 hours, finally stopped to supply chlorine, kept for 2 to 5 hours, finally cooled to room temperature at 5 ℃ to 10 ℃ to obtain the semiconductor graphite substrate.
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| CN116082041A (en) * | 2023-02-20 | 2023-05-09 | 平顶山东方碳素股份有限公司 | Graphite material with low thermal expansion coefficient and production method thereof |
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| CN105586022A (en) * | 2014-10-22 | 2016-05-18 | 中国石油化工股份有限公司 | Water-in-oil based drilling fluid with high temperature resistance and preparation method thereof |
| US20180194631A1 (en) * | 2015-11-13 | 2018-07-12 | Showa Denko Carbon Holding GmbH | Method for producing graphite bodies |
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