CN112657314A - Method for adjusting FTrPSA (fluorine-doped pressure swing adsorption) by taking SiC-CVD (chemical vapor deposition) process tail gas as reaction circulating gas based on alkane and silane reaction - Google Patents
Method for adjusting FTrPSA (fluorine-doped pressure swing adsorption) by taking SiC-CVD (chemical vapor deposition) process tail gas as reaction circulating gas based on alkane and silane reaction Download PDFInfo
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Abstract
The invention discloses an FTrPSA adjustable method for taking SiC-CVD process tail gas based on alkane and silane reaction as reaction circulating gas, which realizes that SiC-CVD crystal or film epitaxial growth process tail gas based on alkane (methane or propane) and silane reaction is used as the circulating gas of SiC-CVD reaction through a plurality of procedures of pretreatment, medium-temperature pressure swing adsorption, light-cold pressure swing adsorption concentration, adsorption purification, medium-light temperature condensation and medium-light cold rectification, and greatly improves the deposition efficiency and quality of SiC crystal or film by adjusting the concentration and flow of each component in the circulating reaction gas, thereby realizing the comprehensive utilization of the tail gas, reducing the tail gas emission and making up the blank of the SiC-CVD process tail gas treatment technology.
Description
Technical Field
The invention relates to a method for recycling tail gas containing commonly used 'carbon (C) source' -methane (CH 4) or propane (C3H 8) 'silicon (Si) source' -silane (SiH 4) and hydrogen (H2) serving as carrier gas as main components in the CVD (chemical vapor deposition) growth process of third-generation semiconductor material silicon carbide (SiC) crystal and film epitaxy, in particular to a method for adjusting FTrPSA (full-temperature-range pressure swing adsorption) by taking SiC-CVD process tail gas as reaction cycle gas based on the reaction of alkane and silane.
Background
Silicon carbide (SiC) is used as a third-generation semiconductor material, and has excellent characteristics such as wide forbidden band, high temperature and high pressure resistance, high frequency and high power, and radiation resistance, and thus has been widely used in power electronic devices such as power switches, variable frequency transformers, UPSs, etc., in the fields of IT and electronic consumer products, automobiles, photovoltaic photovoltaics, nuclear reactors, and aerospace, military, etc., where the system operating conditions are harsh, and a single crystal or an epitaxial thin film is a key production step in which SiC materials are widely used.
The SiC crystal or film epitaxial process includes high temperature sublimation (PVT), Chemical Vapor Deposition (CVD), liquid phase growth (LPE), molecular beam growth (MBE), electron cyclotron resonance plasma chemical vapor deposition (ECR-MPCVD), etc., while the CVD process having the characteristics of low growth temperature, large production batch, good uniformity of crystal or epitaxial film and easy control of operation is widely adopted in industry, wherein the SiC-CVD growth process of organosilicon compounds without chlorine, chlorine and containing C/Si source can be divided according to the difference of silicon (Si) source and carbon (C) source (called as 'reaction precursor') participating in the reaction, furthermore, the tail gas compositions generated by different growth processes are different, and the treatment methods are different accordingly.
In a chlorine-free SiC-CVD crystal or film epitaxial growth process based on a methane/alkane and silane reaction, CH4 or C3H8 is usually used as a reaction precursor of a "C source", SiH4 is used as a reaction precursor of a "Si source", and the reaction precursor enters a CVD reaction chamber (furnace) under the carrying of hydrogen (H2) or inert argon (Ar) as a carrier gas, and a chemical vapor deposition reaction is performed at a certain temperature and pressure to obtain the growth of an epitaxial film on a SiC crystal or a substrate, wherein the quality of the crystal or film growth depends on the concentration or flow ratio between the reaction precursors, such as the "C/Si" feed ratio of 2-5: 1, the "H2" concentration of 50-90%, and the like, in addition to the process conditions of the purity of the reaction precursor, the reaction temperature, the pressure, the flow rate of the feed gas (precursor), the reaction time, the structure of the reaction chamber, and the like. In practice, the proper ratio of "C/Si/H2" is generally achieved by adjusting the feed amount of CH4 or SiH4 or H2. In addition to the solid crystal or film epitaxial product, the gas phase still contains the reaction products H2 and CH4 which participate in the reaction, a small amount of solid micro-particles such as ethane (C2H 6), Si powder or Si cluster or C powder, unreacted CH4 and SiH4, carrier gas H2 which does not participate in the reaction, and trace or trace amount of other impurities such as carbon monoxide (CO), carbon dioxide (CO 2) and the like,
usually, the gas phase is exhausted after the reaction is finished, and thereby the SiC-CVD process tail gas is formed. Because the tail gas contains toxic, harmful, flammable and explosive components such as H2, SiH4, CH4 and the like, in the process of epitaxial growth of SiC-CVD crystals or thin films, the method for treating the tail gas is generally a dry adsorption and direct combustion method, wherein the dry adsorption method is used for adsorbing SiH4, silicon clusters, ethane, propane and the like by using an adsorbent and then directly discharging the adsorbed components, but the dry adsorption and direct combustion method is suitable for the working condition that the concentration of SiH4, ethane or propane in the tail gas is low, and the direct combustion method is used for introducing air by using all the components in the tail gas to oxidize SiH4, ethane/propane and the like into nontoxic SiO2, CO2, H2O and the like, and the SiO2 slurry is formed after water washing and spraying absorption and is discharged, so that the. The combustion method is relatively commonly adopted in the industry because of the economy, is mostly a miniaturized field treatment device, but need let in the air of several times the tail gas flow, guarantee that the concentration of H2, SiH4 etc. that are very easily exploded in the air is outside explosion limit scope, therefore consume higher and have certain potential safety hazard, simultaneously, the burning produces a large amount of heats and tiny particle and is very easily exploded in the combustion process, need a large amount of water to spray in time, cause secondary pollution to discharge or carry out extra processing. In addition, the large amount of valuable resources such as H2, SiH4, CH4 and C3H8 cannot be effectively utilized, and the emission brings greenhouse effect. In addition, the adsorption method is also used as an auxiliary method for the combustion method, and when the combustion method fails to ignite or is stopped due to potential safety hazard, the tail gas of the SiC-CVD process is automatically switched to the adsorption method device for treatment. Both methods only treat tail gas and then discharge the tail gas after reaching the standard, meet the requirement of environmental protection, but cannot comprehensively utilize the tail gas, especially the important raw material gases of SiC-CVD crystal or film epitaxial growth process, such as H2, SiH4 and CH4/C3H8, cannot be reused, and the production cost of crystal or film epitaxy is high.
The epitaxial growth mechanism of SiC-CVD crystal or film is mainly determined by deposition or substrate surface adsorption control and gas phase reaction control, and the concentration of CH4/SiH4, reaction conversion rate and H2 partial pressure in the gas phase reaction are the key factors influencing the deposition or adsorption control efficiency, thereby having great influence on the deposition efficiency. Thus, the feed gas ratio needs to be continually adjusted to achieve the most efficient deposition. In view of the fact that tail gas of the SiC-CVD process contains a large amount of feed gas components, the invention aims to utilize the effective components in the tail gas, and adjust the concentration and the flow rate of the effective components in the tail gas to the circulating reaction gas which can be returned to the process through proper treatment so as to meet the optimal proportion required by the deposition reaction, thereby saving the consumption of the feed gas and solving the burden of tail gas treatment.
Disclosure of Invention
The invention provides an adjustable method for FTrPSA (Full Temperature Swing Adsorption) taking SiC-CVD process tail gas as reaction circulating gas based on alkane and silane reaction, wherein the Full Temperature Swing Adsorption (Full name: Full Temperature Swing-Pressure Swing Adsorption, short for FTrPSA) is a method which is based on Pressure Swing Adsorption (PSA) and can be coupled with various separation technologies, and the method adopts the differences of Adsorption/condensation/rectification separation coefficients and physicochemical properties of different material components (H2, CH4 and SiH 4) in the tail gas generated in the SiC-CVD crystal or film epitaxial growth process under different pressures and temperatures to separate and purify each effective component proportion by adopting the cycle operation of easy matching and balancing of Adsorption and desorption in the concentration process of Pressure Swing Adsorption, Pressure Swing Adsorption and medium-shallow condensation rectification, therefore, the tail gas of the process is directly returned to the SiC-CVD crystal or film epitaxy growth process as the circulating reaction gas for recycling, more raw material gas is not required to be consumed, or all effective components are completely and clearly separated from the tail gas and then returned to the process for using, so that the problem of high cost is solved, the effective comprehensive utilization of the tail gas of the SiC-CVD process and the reduction of the exhaust gas emission are realized, and the deposition efficiency and quality of the SiC crystal or film epitaxy are effectively increased:
an adjustable method for taking SiC-CVD process tail gas as reaction circulating gas FTrPSA based on alkane and silane reaction comprises the following steps:
(1) raw material gas, which is tail gas in a chlorine-free process for preparing silicon carbide (SiC) crystals or epitaxial growth on a substrate by Chemical Vapor Deposition (CVD) by taking methane (CH 4) or propane (C3H 8) as a main carbon (C) source and silane (SiH 4) as a silicon (Si) source, mainly comprises hydrogen (H2), methane (CH 4), silane (SiH 4), a small amount of carbon dioxide and alkane (C2 +) with the components above the carbon dioxide, trace carbon monoxide (CO), carbon dioxide (CO 2), high-silicon alkane, silicon dioxide (SiO 2) and carbon (C) fine particles, the pressure is normal pressure or low pressure, and the temperature is normal temperature.
(2) And (2) pretreating, namely pressurizing the feed gas, feeding the feed gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher, sequentially removing dust, particles, oil mist, part of high alkane and high silane impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, carrying out cold-heat exchange on the formed purified feed gas to 30-80 ℃, pressurizing to 0.6-1.0 MPa, and then entering the next process, namely a medium-temperature pressure swing adsorption process.
(3) And (2) medium-temperature pressure swing adsorption, wherein purified feed gas from a pretreatment process enters a multi-tower pressure swing adsorption process consisting of at least 4 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 30-80 ℃, at least one adsorption tower is in an adsorption step, non-adsorption phase gas flowing out of the tops of the adsorption towers in the adsorption step is intermediate gas, the intermediate gas is subjected to heat exchange to 5-20 ℃ and then enters the next process, namely shallow-cooling pressure swing adsorption concentration, and carbon-rich secondary gas flowing out of the bottoms of the adsorption towers in a desorption step mainly comprises CO2, C2+ and a small amount of H2/CH4/SiH4, and the pressurized purified feed gas enters the subsequent medium-temperature and shallow-temperature condensation process.
(4) The method comprises the steps of light cold pressure swing adsorption concentration, wherein intermediate gas from a medium temperature pressure swing adsorption process at 5-20 ℃ and 0.6-1.0 MPa enters a multi-tower pressure swing adsorption concentration process at least consisting of 4 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 5-20 ℃, at least one adsorption tower is in an adsorption step, the other adsorption towers are in a desorption regeneration step, non-adsorption phase gas flowing out of the top of the adsorption tower in the adsorption step is methane hydrogen gas, the next process, namely adsorption purification, enters a next process, adsorption purification, adsorption phase gas formed at the bottom of the adsorption tower in the desorption step is concentrated gas, the concentrated gas and purified methane hydrogen gas from the subsequent adsorption purification are mixed according to a ratio and are used as a cyclic reaction gas of a SiC-CVD crystal or a film epitaxial growth process based on alkane and silane reaction, wherein an adsorbent of the light cold pressure swing adsorption concentration process adopts active alumina, One or a combination of silica gel, active carbon and molecular sieve, replacement and vacuumizing regeneration are adopted during desorption, replacement gas comes from crude silane gas of a subsequent medium-shallow cold rectification process to adjust the C/Si ratio in reaction circulating gas, and the requirements of the SiC-CVD process are met.
(5) And (2) performing adsorption purification, namely performing precise filtration on the methane hydrogen gas from the shallow cold pressure swing adsorption concentration process, then performing adsorption purification in an adsorption purification process consisting of 2 or 3 adsorption towers at an operating temperature of 5-20 ℃ and an operating pressure of less than 1.0MPa, further purifying and removing trace CO in the methane hydrogen gas to form purified methane hydrogen gas, mixing one part of the purified methane hydrogen gas with the concentrated gas from the shallow cold pressure swing adsorption concentration process according to a proper proportion, returning the mixed gas as reaction cycle gas to the SiC-CVD crystal or film epitaxial growth process for recycling, and using the other part of the reaction cycle gas as fuel gas for heating.
(6) And (2) medium and shallow temperature condensation, namely performing fine filtration to remove fine particles of the carbon-rich gas from the medium-temperature pressure swing adsorption process, performing heat exchange to the temperature of minus 35 to minus 10 ℃, pressurizing to 1.0 to 2.5MPa, entering a medium and shallow condenser with the operating temperature of minus 35 to minus 10 ℃, allowing non-condensable gas to escape from the condenser, passing through a heat exchanger to the temperature of 5 to 20 ℃, directly returning to the shallow pressure swing adsorption concentration process or heating as fuel gas, and allowing the condensed fluid which is rich in SiH4/C3H8 and trace easily-condensable impurity components including carbon dioxide (CO 2) and flows out of the condenser to directly enter the next process, namely medium and shallow cooling rectification.
(7) Medium and shallow cold rectification, wherein a condensed fluid generated in a medium and shallow temperature condensation process enters a medium and shallow cold rectification tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, a small amount of non-condensable gas of light components flows out from the top of the rectification tower-1, or returns to the feed of a shallow cold pressure swing adsorption concentration process after passing through a cold-heat exchanger to reach the temperature of 5 to 20 ℃ and reducing the pressure to be less than 1MPa, or is used as fuel gas for heating, a heavy component fluid flows out from the bottom of the rectification tower-1 and then enters a medium and shallow cold rectification tower-2 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, a top gas of a crude SiH4 containing methane and hydrogen flows out from the top of the tower to be used as a replacement gas of the shallow cold pressure swing adsorption concentration process to adjust the C/Si ratio in a reaction circulation gas so as to meet the requirements of SiC-CVD process, heavy components enriched in C3H8 flow out of the tower bottom, are subjected to decarburization (CO 2) to serve as reaction circulating gas, are mixed with concentrated gas from a shallow cold pressure swing adsorption concentration process, purified methane hydrogen gas from an adsorption purification process and crude silane gas from the tower top of the process for replacing gas in the shallow cold pressure swing adsorption concentration process in proportion, and serve as reaction circulating gas to be returned to the SiC-CVD process for recycling.
Furthermore, the method for adjusting FTrPSA (fluorine-doped silica gel PSA) by taking tail gas of the SiC-CVD process based on the reaction of alkane and silane as the reaction circulating gas is characterized in that when the C source of the raw material gas is only a methane working condition, the number of the rectifying towers in the medium and light cold rectifying process is 1, the rectifying tower-1 is omitted, and the rectifying tower-2 is omitted, namely, condensed fluid generated in the medium and light temperature condensing process enters the medium and light cold rectifying tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, crude SiH4 gas containing methane hydrogen flows out of the top of the rectifying tower-1 and is used as replacement gas in the light cold pressure swing adsorption and concentration process to adjust the C/Si ratio in the reaction circulating gas, so as to meet the requirements of the SiC-CVD process, and a small amount of heavy components enriched in CO2 flows out of the bottom of the rectifying tower and is directly discharged.
Furthermore, the method for adjusting FTrPSA (fluorine-doped PSA) by using tail gas of SiC-CVD (silicon carbide chemical vapor deposition) process based on alkane and silane reaction as reaction cycle gas is characterized in that the raw material gas C source is only methane, and under the condition that the content of CO2 in the purified raw material is less than 10ppm, a part of desorbed gas of carbon-rich two flowing out from the medium-temperature pressure swing adsorption process is used as replacement gas of a shallow-cold pressure swing adsorption concentration process to form a reaction cycle gas for cycle use after adsorption decarburization (CO 2), and a part of desorbed gas is used as fuel gas after water vapor washing and oxidation, and intermediate gas flowing out from the shallow-cold pressure swing adsorption concentration process enters the shallow-cold pressure swing adsorption concentration process, so that the middle and shallow-temperature condensation and middle and shallow-cold rectification processes are omitted.
Furthermore, the method for adjusting FTrPSA (fluorine-doped pressure swing adsorption) by using tail gas of SiC-CVD (silicon carbide chemical vapor deposition) process based on alkane and silane reaction as reaction circulating gas is characterized in that the raw material gas C source is only methane, and under the working condition that the content of CO2 in the purified raw material gas is more than 0.1%, the purified raw material gas from the pretreatment process is firstly subjected to decarburization in a decarburization process, an adsorption method loaded with a disposable adsorbent is adopted to remove CO2 in the purified raw material gas, the purified raw material gas subjected to CO2 removal is subjected to heat exchange to 5-20 ℃ and is pressurized to 0.6-1.0 MPa, and then the purified raw material gas directly enters a shallow-cooling pressure swing adsorption concentration process, and concentrated gas flowing out from the bottom of an adsorption tower in a desorption step and subsequently purified methane-hydrogen gas from a purified methane-hydrogen gas after adsorption purification are mixed according to a ratio and are used as circulating reaction gas of SiC-CVD crystal based on methane and silane reaction or a thin, thus, the procedures of medium-temperature pressure swing adsorption, medium-and shallow-temperature condensation and medium-and shallow-cold rectification are omitted.
Furthermore, the method for adjusting FTrPSA (carbon fluoride pressure swing adsorption) by using tail gas of SiC-CVD (silicon carbide chemical vapor deposition) process based on alkane and silane reaction as reaction circulating gas is characterized in that under the working condition that the purified raw material gas contains C2+ with higher concentration, the purified raw material gas from the pretreatment process enters a medium-temperature pressure swing adsorption process consisting of two sections of PSA (pressure swing adsorption) after being subjected to heat exchange and pressurization, wherein the purified raw material gas enters from the bottom of a first PSA adsorption tower (1 section of PSA) for medium-temperature pressure swing adsorption, the intermediate gas of a non-adsorption phase flowing out from the top of the 1 section of PSA in the adsorption stage enters a shallow-cold pressure swing adsorption concentration process, the desorption gas flowing out from the 1 section of PSA adsorption tower in the desorption step enters from the bottom of a second PSA adsorption tower (2 sections of PSA) after being subjected to pressurization, and the desorption gas flowing out from the bottom of the 2 section of PSA adsorption tower in the desorption step enters a medium, the non-adsorption phase gas flowing out of the top of the 2-stage PSA adsorption tower in the adsorption step is mixed with the purified feed gas as a feed gas and returned to the 1-stage PSA adsorption tower.
Furthermore, the method for adjusting FTrPSA (fluorine-modified pressure swing adsorption) by using tail gas of SiC-CVD (silicon carbide-chemical vapor deposition) process based on alkane and silane reaction as reaction circulating gas is characterized in that the purified raw material gas contains C2+ with very high concentration under the working condition that the ratio of C2+/Si exceeds 5:1, the purified raw material gas from the pretreatment process is subjected to heat exchange to-35 to-15 ℃ and is compressed to 2.5 to 3.5MPa, a shallow cold oil absorption process is adopted to replace a medium-temperature pressure swing adsorption process, namely, the shallow cold oil absorption process consists of an absorption tower and an desorption tower, propane (C3) is adopted as an absorbent, the absorption temperature is-35 to-15 ℃, the absorption pressure is 2.5 to 3.5MPa, the desorption temperature is normal temperature, the desorption pressure is normal pressure or micro positive pressure, the purified raw material gas enters from the bottom of the absorption tower and is subjected to reverse mass transfer with a C3 absorbent sprayed from the top of the absorption tower, the noncondensable intermediate gas escaping from the top of the absorption tower enters the subsequent shallow cold pressure swing adsorption concentration, the C2+ rich liquid flowing out from the bottom of the absorption tower enters the desorption tower, the C2+ rich gas flowing out from the top of the desorption tower directly enters the subsequent medium and shallow temperature condensation process, the absorbent C3 flows out from the bottom of the desorption tower, and the absorbent is circulated and pressurized and then returns to the top of the absorption tower for spray absorption.
Furthermore, the method for adjusting FTrPSA (fluorine-doped pressure swing adsorption) by using tail gas of SiC-CVD (silicon carbide-chemical vapor deposition) process based on reaction of alkane and silane as reaction cycle gas is characterized in that under the working condition that the concentration of silane in the purified raw material gas is high, the purified raw material gas is directly subjected to heat exchange to 5-20 ℃ and pressurization to 0.6-1.0 MPa, and then directly enters a shallow cold pressure swing adsorption concentration process consisting of two sections of PSA (pressure swing adsorption) processes, wherein the purified raw material gas enters from the bottom of a first PSA adsorption tower (1 section PSA) in the shallow cold pressure swing adsorption concentration process, intermediate gas of a non-adsorption phase flowing out from the top of the 1 section PSA tower in an adsorption stage enters a second PSA adsorption tower (2 section PSA), concentrated gas flowing out from the bottom of the 2 section PSA adsorption towers in a desorption step and purified methane hydrogen gas from a subsequent adsorption purification process after adsorption and purification are mixed according to be used as cycle reaction gas of SiC-CVD crystal based on reaction of methane and silane or a, and (2) replacing and vacuumizing for regeneration during desorption of the PSA, wherein the replacement gas is crude silane gas from a subsequent medium-and-light-cooling rectification process to adjust the C/Si ratio in the reaction circulating gas and meet the requirements of the SiC-CVD process, the intermediate gas flowing out from the top of the PSA adsorption tower of the section 2 in the adsorption step enters a subsequent adsorption purification process, and the desorption gas flowing out from the bottom of the PSA adsorption tower of the section 1 in the desorption step is used as carbon-rich secondary gas and enters a medium-and-light-temperature condensation process.
Furthermore, the FTrPSA adjustable method is characterized in that the PSA adsorption tower in the desorption step in the medium-temperature pressure swing adsorption or shallow-cold pressure swing adsorption concentration process comprises 1-section PSA and 2-section PSA, the desorption steps comprise pressure equalization, sequential release, vacuumizing, pressure equalization and final charging, wherein the desorption step for forming the concentrated gas in the medium-temperature or shallow-cold pressure swing adsorption process comprises displacement, pressure equalization, sequential release, vacuumizing, pressure equalization and final charging, the displaced gas comes from crude silane gas in the subsequent process, and the final charging gas adopts the feeding gas of the respective front-end process.
Furthermore, the method for adjusting FTrPSA (fluorine-doped silica gel PSA) by taking tail gas of SiC-CVD (silicon carbide-chemical vapor deposition) process as reaction circulating gas based on alkane and silane reaction is characterized in that the concentration of CH4, C2+, H2 in the concentrated gas is adjusted by adjusting the operation time of adsorption and desorption steps in the processes of medium-temperature pressure swing adsorption and light-cooling pressure swing adsorption concentration, one or more combined adsorbents comprising aluminum oxide, silica gel, activated carbon and molecular sieves and the quantity thereof filled in adsorption towers, and the opening and closing degree of program control valves or other valves loaded on pipelines connected among the adsorption towers, so that mixed gas is formed by proportionally mixing the raw silane gas from the subsequent process and enters a SiC-CVD reactor (cavity) for continuous reaction as circulating reaction gas of SiC-CVD crystal and film growth process, wherein medium-temperature pressure swing adsorption, When the operating pressure of the shallow cold pressure swing adsorption concentration or adsorption purification process is greater than 0.6MPa, the pressure change in the adsorption and desorption cycle operation process realizes the slow and uniform control through the program control valve and the regulating valve on the pipeline connected between the adsorption towers, and prevents the air flow caused by the overlarge pressure change of the system from scouring the bed layers of the adsorption towers and the generation of adsorbent pulverization, so that the operation of the system in the process is stable and safe.
The invention has the beneficial effects that:
(1) by adopting the method, the tail gas of the SiC-CVD crystal or film epitaxial growth process based on the reaction of methane and silane can be used as the circulating gas of the CVD reaction, and the deposition efficiency and quality of the SiC crystal or film can be greatly improved by adjusting the concentration and the flow of each component in the circulating reaction gas, so that the comprehensive utilization of the tail gas is realized, the tail gas emission is reduced, and the blank of the tail gas treatment technology of the SiC-CVD process is made up;
(2) the invention utilizes the physical chemistry and relative separation coefficient characteristics of H2, CH4/C2+ and SiH4 components in tail gas in the range of medium temperature of 30-80 ℃, shallow cooling of 5-20 ℃ and medium and shallow cooling of-35 to-10 ℃, selectively separating H2/CH4 from C2+/SiH4 by medium-temperature pressure swing adsorption, light-cold pressure swing adsorption concentration and coupling of medium-light temperature condensation and medium-light cold rectification, utilizing the concentrated gas of the light-cold pressure swing adsorption concentration procedure and silane or C2+ obtained by medium-light cold rectification and methane hydrogen gas obtained by adsorption purification procedure, the catalyst can be adjusted and mixed according to the required proportion and then used as reaction circulating gas of the SiC-CVD process based on the reaction of methane and silane for recycling, thereby solving the technical bottleneck that the traditional adsorption separation process is difficult to use tail gas as the reaction circulating gas and filling the technical blank of tail gas comprehensive utilization;
(3) the invention can realize the comprehensive utilization of the process tail gas as the reaction circulating gas by adopting the combination of two-stage PSA (pressure swing adsorption) or combination of middle-temperature pressure swing adsorption or shallow-cold pressure swing adsorption concentration, combination of shallow-cold oil absorption instead of middle-temperature pressure swing adsorption, adjustment of the adsorption and desorption circulating operation time of the adsorption tower, the types and the quantity of adsorbents, and adjustment measures of replacement and the like arranged in the desorption step of the shallow-cold pressure swing adsorption concentration process according to the concentration of CH4/C2+, H2, Si and the like in the tail gas and according to the proportion of the required circulating reaction gas;
(4) the invention does not need to completely and clearly separate the effective components in the tail gas of the SiC-CVD crystal or film epitaxial growth process based on the reaction of alkane and silane, saves the cost of comprehensive utilization of the tail gas, also saves the consumption of raw material gas required by the process, further reduces the cost of the SiC crystal or epitaxial wafer obtained by the SiC-CVD process, and further improves the deposition efficiency and the product quality.
Drawings
FIG. 1 is a schematic flow chart of example 1 of the present invention.
Fig. 2 is a schematic flow chart of embodiment 2 of the present invention.
Fig. 3 is a schematic flow chart of embodiment 3 of the present invention.
Fig. 4 is a schematic flow chart of embodiment 4 of the present invention.
FIG. 5 is a schematic flow chart of embodiment 5 of the present invention.
Fig. 6 is a schematic flow chart of embodiment 6 of the present invention.
FIG. 7 is a flowchart illustrating an embodiment 7 of the present invention.
Detailed Description
In order to make those skilled in the art better understand the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention.
Example 1
As shown in FIG. 1, an adjustable method for using SiC-CVD process tail gas as reaction recycle gas FTrPSA based on alkane and silane reaction comprises the following steps,
(1) raw material gas, which is used for preparing silicon carbide (SiC) crystals or tail gas in a chlorine-free process for epitaxial growth on a substrate by Chemical Vapor Deposition (CVD) by taking propane (C3H 8) as a main carbon (C) source and taking silane (SiH 4) as a silicon (Si) source, mainly comprises hydrogen (H2), methane (CH 4), silane (SiH 4), a small amount of carbon dioxide and alkane (C2 +) with more than two components, trace carbon monoxide (CO), carbon dioxide (CO 2), high-silicon alkane, silicon dioxide (SiO 2) and carbon (C) fine particles, and is normal pressure and temperature.
(2) And (2) pretreating, namely pressurizing the feed gas, feeding the feed gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher, sequentially removing dust, particles, oil mist, part of high alkane and high silane impurities under the operating conditions of pressure of 0.2-0.3 MPa and normal temperature, carrying out cold-heat exchange on the formed purified feed gas to 30-80 ℃, pressurizing to 0.6-1.0 MPa, and then entering a medium-temperature pressure swing adsorption process.
(3) And (2) medium-temperature pressure swing adsorption, wherein purified feed gas from the pretreatment process enters a multi-tower pressure swing adsorption process consisting of 5 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 30-80 ℃, one adsorption tower is in the adsorption step, non-adsorption phase gas flowing out of the tops of the adsorption towers in the adsorption step is intermediate gas, the intermediate gas is subjected to heat exchange to 5-20 ℃, then enters shallow-cold pressure swing adsorption and concentration, and carbon-rich secondary gas flows out of the bottoms of the adsorption towers in the desorption step mainly comprises CO2, C2+ and a small amount of H2/CH4/SiH4, and enters the medium-temperature and shallow-temperature condensation process after being pressurized.
(4) Performing light cold pressure swing adsorption concentration, wherein intermediate gas from a medium temperature pressure swing adsorption process at 5-20 ℃ and 0.6-1.0 MPa enters a multi-tower pressure swing adsorption concentration process consisting of 4 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 5-20 ℃, one adsorption tower is in an adsorption step, the other adsorption towers are in a desorption regeneration step, non-adsorption phase gas flowing out of the top of the adsorption tower in the adsorption step is methane hydrogen gas and enters an adsorption purification process, adsorption phase gas formed at the bottom of the adsorption tower in the desorption step is concentrated gas, and the concentrated gas and the purified methane hydrogen gas from the subsequent adsorption purification are mixed according to a ratio and are recycled as cyclic reaction gas of SiC-CVD crystal based on alkane and silane reaction or a thin film epitaxial growth process, wherein an adsorbent of the light cold pressure swing adsorption concentration process adopts active aluminum oxide, The combination of silica gel, active carbon and molecular sieve adopts replacement and vacuum-pumping regeneration during desorption, and replacement gas comes from crude silane gas of a subsequent medium-shallow cold rectification process to adjust the C/Si ratio in reaction circulating gas and meet the requirements of a SiC-CVD process.
(5) And (2) performing adsorption purification, namely performing precise filtration on the methane hydrogen gas from the shallow cooling pressure swing adsorption concentration process, then performing adsorption purification in an adsorption purification process consisting of 2 adsorption towers, performing adsorption at the operating temperature of 5-20 ℃ and the operating pressure of less than 1.0MPa, further purifying and removing trace CO in the methane hydrogen gas to form purified methane hydrogen gas, mixing one part of the purified methane hydrogen gas with the concentrated gas from the shallow cooling pressure swing adsorption concentration process according to a proper proportion, returning the mixed gas as reaction cycle gas to the SiC-CVD crystal or film epitaxial growth process for recycling, and using one part of the reaction cycle gas as fuel gas for heating.
(6) And (2) medium and light temperature condensation, namely performing fine filtration to remove fine particles of the carbon-rich gas from the medium temperature pressure swing adsorption process, performing heat exchange to minus 35 to minus 20 ℃, pressurizing to 2.0 to 2.5MPa, entering a medium and light condenser with the operating temperature of minus 35 to minus 20 ℃, allowing non-condensable gas to escape from the condenser, passing through a heat exchanger to reach the temperature of 5 to 20 ℃, decompressing to less than 1.0MPa, returning to the light temperature pressure swing adsorption concentration process, and directly entering a condensed fluid which is rich in SiH4/C3H8 and trace easily condensable impurity components including carbon dioxide (CO 2) and flows out of the condenser into medium and light temperature pressure swing rectification.
(7) Medium and shallow cold rectification, wherein a condensed fluid generated in a medium and shallow temperature condensation process enters a medium and shallow cold rectification tower-1 with the operating temperature of minus 35 to minus 2 ℃ and the operating pressure of 2.0 to 2.5MPa, a small amount of non-condensable gas of light components flows out from the top of the rectification tower-1, the gas passes through a cold-heat exchanger to reach the temperature of 5 to 20 ℃ and is decompressed to be less than 1MPa, the gas returns to the shallow pressure swing adsorption concentration process for feeding, a heavy component fluid flows out from the bottom of the rectification tower-1, then the heavy component fluid enters a medium and shallow cold rectification tower-2 with the operating temperature of minus 25 to minus 10 ℃ and the operating pressure of 1.5 to 2.5MPa, a top gas of a crude SiH4 containing methane and hydrogen flows out from the top of the tower to be used as a replacement gas in the shallow pressure swing adsorption concentration process to adjust the C/Si ratio in a reaction circulating gas so as to meet the requirements of a SiC-CVD process, and a heavy component enriched in C3H8 flows out from, after decarbonization (CO 2), the reaction cycle gas is mixed with the concentrated gas from the shallow cooling pressure swing adsorption concentration process, the purified methane hydrogen gas from the adsorption purification process and the crude silane gas from the tower top of the process used for the replacement gas of the shallow cooling pressure swing adsorption concentration process according to the proportion, and the reaction cycle gas is returned to the SiC-CVD process for recycling.
Example 2
As shown in fig. 2, based on example 1, when the raw material gas "C source" is only methane, the number of the rectifying towers in the medium and light cooling rectifying process is 1, and the rectifying tower-1 omits the rectifying tower-2, that is, the condensed fluid generated from the medium and light temperature condensing process enters the medium and light cooling rectifying tower-1 with the operating temperature of-35 to-20 ℃ and the operating pressure of 2.0 to 2.5MPa, crude SiH4 gas containing methane and hydrogen flows out from the top of the rectifying tower-1 as the replacement gas for the light cooling pressure swing adsorption concentrating process to adjust the C/Si ratio in the reaction cycle gas, so as to meet the requirements of the SiC-CVD process, and a small amount of heavy components enriched in CO2 flows out from the bottom of the tower and is directly discharged.
Example 3
As shown in fig. 3, in examples 1 and 2, under the condition that the raw material gas "C source" is only methane and the content of CO2 in the purified raw material is less than 10ppm, the desorbed gas rich in carbon two flowing out from the medium temperature pressure swing adsorption step is subjected to adsorption purification to remove CO2, a part of the desorbed gas is used as a replacement gas in the shallow cold pressure swing adsorption concentration step to form a reaction cycle gas for recycling, and a part of the desorbed gas is subjected to steam scrubbing oxidation and then used as a fuel gas, thereby omitting the medium and shallow temperature condensation and medium and shallow cold rectification steps.
Example 4
As shown in fig. 4, based on the embodiments 1 and 2, under the condition that the raw material gas "C source" is only methane and the content of CO2 in the purified raw material gas is greater than 0.1%, the purified raw material gas from the pretreatment step is first subjected to a decarburization step to be decarbonized, an adsorption method loaded with a disposable adsorbent is adopted to remove CO2 therein, the purified raw material gas from which CO2 is removed is subjected to heat exchange to 5 to 20 ℃ and pressurization to 0.6 to 1.0MPa, directly entering a shallow cold pressure swing adsorption concentration process, and concentrating gas flowing out from the bottom of the adsorption tower in the desorption step, and the purified methane hydrogen gas from the subsequent adsorption purification is mixed according to the proportion and is used as the circulating reaction gas of the SiC-CVD crystal or the film epitaxial growth process based on the reaction of methane and silane for circulating use, thereby omitting the working procedures of medium temperature pressure swing adsorption, medium and light temperature condensation and medium and light cold rectification.
Example 5
As shown in fig. 5, under the working condition that the purified raw material gas contains C2+ with higher concentration based on example 1, wherein C2+ components mainly comprise 15% C3H8 and a small amount of ethane (C2H 6), the purified raw material gas enters the medium-temperature pressure swing adsorption process consisting of two-stage PSA after being subjected to heat and pressure exchange, the purified raw material gas enters the bottom of the first PSA adsorption tower (1-stage PSA) in medium-temperature pressure swing adsorption, the intermediate gas of the non-adsorption phase flowing out from the top of the 1-stage PSA tower in the adsorption stage enters the shallow-temperature pressure swing adsorption concentration process, the desorbed gas flowing out from the 1-stage PSA adsorption tower in the desorption step enters the bottom of the second PSA adsorption tower (2-stage PSA) after being subjected to pressure increase, the desorbed gas flowing out from the bottom of the 2-stage PSA adsorption tower in the desorption step enters the medium-shallow-temperature condensation process as the carbon-rich secondary gas, and the non-adsorption phase gas flowing out from the top of the 2-stage PSA adsorption, mixed with purified feed gas as feed gas and returned to the 1-stage PSA adsorption tower.
Example 6
As shown in fig. 6, based on example 1, under the condition that the purified feed gas contains very high concentration of C2+, for example, the C2+/Si ratio exceeds 5:1, the purified feed gas is subjected to heat exchange to-35 to-15 ℃ and compressed to 2.5 to 3.5MPa, a shallow cold oil absorption process is used to replace the medium temperature pressure swing adsorption process, that is, the shallow cold oil absorption process is composed of an absorption tower and a desorption tower, propane (C3) is used as an absorbent, the absorption temperature is-35 to-15 ℃, the absorption pressure is 2.5 to 3.5MPa, the desorption temperature is normal temperature, the desorption pressure is normal pressure, the purified feed gas enters from the bottom of the absorption tower and performs reverse mass transfer with a C3 absorbent sprayed from the top of the absorption tower, the intermediate gas which is not condensed from the top of the absorption tower enters into a shallow cold pressure swing adsorption and concentration, the C2+ rich liquid flowing out from the bottom of the absorption tower enters into the desorption tower, the C2+ rich gas flows out from the top, directly enters a subsequent medium-and-light-temperature condensation process, flows out of the absorbent C3 from the bottom of the desorption tower, is circularly pressurized and then returns to the top of the absorption tower as the absorbent to be sprayed and absorbed.
Example 7
As shown in fig. 7, based on example 1, under the condition of high concentration of silane in the purified raw material gas, the purified raw material gas is subjected to heat exchange to 5 to 20 ℃, pressurized to 0.6 to 1.0MPa, and then directly enters a shallow cold pressure swing adsorption concentration process consisting of two-stage PSA, wherein the purified raw material gas enters from the bottom of a first PSA adsorption tower (1-stage PSA) in the shallow cold pressure swing adsorption concentration process, an intermediate gas 1 of a non-adsorption phase flowing out from the top of the 1-stage PSA tower in an adsorption stage enters a second PSA adsorption tower (2-stage PSA), a concentrated gas flowing out from the bottom of the 2-stage PSA adsorption tower in a desorption step and a purified methane-hydrogen gas from a subsequent adsorption purification process are mixed in proportion and recycled as a cyclic reaction gas of SiC-CVD crystal or a thin film epitaxial growth process based on the reaction of alkane and silane, and replacement and vacuum pumping regeneration are adopted in the 2-stage PSA desorption, the replacement gas comes from the crude silane gas of the subsequent medium and light cold rectification process to adjust the C/Si ratio in the reaction circulating gas, so as to meet the requirements of the SiC-CVD process, the intermediate gas 2 flowing out from the top of the 2-section PSA adsorption tower in the adsorption step enters the subsequent adsorption purification process, and the desorption gas flowing out from the bottom of the 1-section PSA adsorption tower in the desorption step is used as carbon-rich secondary gas and enters the medium and light temperature condensation process.
It should be apparent that the above-described embodiments are only some, but not all, of the embodiments of the present invention. All other embodiments and structural changes that can be made by those skilled in the art without inventive effort based on the embodiments described in the present invention or based on the teaching of the present invention, all technical solutions that are the same or similar to the present invention, are within the scope of the present invention.
Claims (15)
1. An adjustable method for using SiC-CVD process tail gas as reaction circulating gas FTrPSA based on alkane and silane reaction is characterized by comprising the following steps:
raw material gas, which is tail gas in a chlorine-free process for preparing silicon carbide (SiC) crystals or epitaxial growth on a substrate by Chemical Vapor Deposition (CVD) by taking methane (CH 4) or propane (C3H 8) as a main carbon (C) source and silane (SiH 4) as a silicon (Si) source, mainly comprises hydrogen (H2), methane (CH 4), silane (SiH 4), a small amount of carbon dioxide and alkane (C2 +) with the components above the carbon dioxide, trace carbon monoxide (CO), carbon dioxide (CO 2), high-silicon alkane, silicon dioxide (SiO 2) and carbon (C) fine particles, the pressure is normal pressure or low pressure, and the temperature is normal temperature.
2. And (2) pretreating, namely pressurizing the feed gas, feeding the feed gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher, sequentially removing dust, particles, oil mist, part of high alkane and high silane impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, carrying out cold-heat exchange on the formed purified feed gas to 30-80 ℃, pressurizing to 0.6-1.0 MPa, and then entering the next process, namely a medium-temperature pressure swing adsorption process.
3. And (2) medium-temperature pressure swing adsorption, wherein purified feed gas from a pretreatment process enters a multi-tower pressure swing adsorption process consisting of at least 4 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 30-80 ℃, at least one adsorption tower is in an adsorption step, non-adsorption phase gas flowing out of the tops of the adsorption towers in the adsorption step is intermediate gas, the intermediate gas is subjected to heat exchange to 5-20 ℃ and then enters the next process, namely shallow-cooling pressure swing adsorption concentration, and carbon-rich secondary gas flowing out of the bottoms of the adsorption towers in a desorption step mainly comprises CO2, C2+ and a small amount of H2/CH4/SiH4, and the pressurized purified feed gas enters the subsequent medium-temperature and shallow-temperature condensation process.
4. The method comprises the steps of light cold pressure swing adsorption concentration, wherein intermediate gas from a medium temperature pressure swing adsorption process at 5-20 ℃ and 0.6-1.0 MPa enters a multi-tower pressure swing adsorption concentration process at least consisting of 4 towers, the operating pressure of the adsorption towers is 0.6-1.0 MPa, the operating temperature is 5-20 ℃, at least one adsorption tower is in an adsorption step, the other adsorption towers are in a desorption regeneration step, non-adsorption phase gas flowing out of the top of the adsorption tower in the adsorption step is methane hydrogen gas, the next process, namely adsorption purification, enters a next process, adsorption purification, adsorption phase gas formed at the bottom of the adsorption tower in the desorption step is concentrated gas, the concentrated gas and purified methane hydrogen gas from the subsequent adsorption purification are mixed according to a ratio and are used as a cyclic reaction gas of a SiC-CVD crystal or a film epitaxial growth process based on alkane and silane reaction, wherein an adsorbent of the light cold pressure swing adsorption concentration process adopts active alumina, One or a combination of silica gel, active carbon and molecular sieve, replacement and vacuumizing regeneration are adopted during desorption, replacement gas comes from crude silane gas of a subsequent medium-shallow cold rectification process to adjust the C/Si ratio in reaction circulating gas, and the requirements of the SiC-CVD process are met.
5. And (2) performing adsorption purification, namely performing precise filtration on the methane hydrogen gas from the shallow cold pressure swing adsorption concentration process, then performing adsorption purification in an adsorption purification process consisting of 2 or 3 adsorption towers at an operating temperature of 5-20 ℃ and an operating pressure of less than 1.0MPa, further purifying and removing trace CO in the methane hydrogen gas to form purified methane hydrogen gas, mixing one part of the purified methane hydrogen gas with the concentrated gas from the shallow cold pressure swing adsorption concentration process according to a proper proportion, returning the mixed gas as reaction cycle gas to the SiC-CVD crystal or film epitaxial growth process for recycling, and using the other part of the reaction cycle gas as fuel gas for heating.
6. And (2) medium and shallow temperature condensation, namely performing fine filtration to remove fine particles of the carbon-rich gas from the medium-temperature pressure swing adsorption process, performing heat exchange to the temperature of minus 35 to minus 10 ℃, pressurizing to 1.0 to 2.5MPa, entering a medium and shallow condenser with the operating temperature of minus 35 to minus 10 ℃, allowing non-condensable gas to escape from the condenser, passing through a heat exchanger to the temperature of 5 to 20 ℃, directly returning to the shallow pressure swing adsorption concentration process or heating as fuel gas, and allowing the condensed fluid which is rich in SiH4/C3H8 and trace easily-condensable impurity components including carbon dioxide (CO 2) and flows out of the condenser to directly enter the next process, namely medium and shallow cooling rectification.
7. Medium and shallow cold rectification, wherein a condensed fluid generated in a medium and shallow temperature condensation process enters a medium and shallow cold rectification tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, a small amount of non-condensable gas of light components flows out from the top of the rectification tower-1, or returns to the feed of a shallow cold pressure swing adsorption concentration process after passing through a cold-heat exchanger to reach the temperature of 5 to 20 ℃ and reducing the pressure to be less than 1MPa, or is used as fuel gas for heating, a heavy component fluid flows out from the bottom of the rectification tower-1 and then enters a medium and shallow cold rectification tower-2 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, a top gas of a crude SiH4 containing methane and hydrogen flows out from the top of the tower to be used as a replacement gas of the shallow cold pressure swing adsorption concentration process to adjust the C/Si ratio in a reaction circulation gas so as to meet the requirements of SiC-CVD process, heavy components enriched in C3H8 flow out of the tower bottom, are subjected to decarburization (CO 2) to serve as reaction circulating gas, are mixed with concentrated gas from a shallow cold pressure swing adsorption concentration process, purified methane hydrogen gas from an adsorption purification process and crude silane gas from the tower top of the process for replacing gas in the shallow cold pressure swing adsorption concentration process in proportion, and serve as reaction circulating gas to be returned to the SiC-CVD process for recycling.
8. The method as claimed in claim 1, wherein when the raw material gas "C source" is only methane, the number of the rectifying towers in the medium and light cooling rectifying process is 1, and the rectifying tower-1 is omitted, namely, the condensed fluid generated in the medium and light temperature condensing process enters the medium and light cooling rectifying tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.5MPa, the crude SiH4 gas containing methane hydrogen flows out of the top of the rectifying tower-1, and is used as the replacement gas in the light cooling pressure swing adsorption concentrating process to adjust the C/Si ratio in the reaction cycle gas, so as to meet the requirements of the SiC-CVD process, and a small amount of heavy components enriched in CO2 flows out of the bottom of the rectifying tower and is directly discharged.
9. The method for adjusting FTrPSA (fluorine-modified PSA) as a reaction cycle gas based on tail gas of SiC-CVD (silicon carbide chemical vapor deposition) process of alkane and silane reaction as claimed in claims 1 and 2, wherein the raw material gas C source is only methane and the purified raw material gas has a CO2 content of less than 10ppm, a part of desorbed gas rich in carbon two flowing out from the medium-temperature pressure swing adsorption process is used as a replacement gas of the shallow-cooling pressure swing adsorption concentration process after adsorption decarburization (CO 2), a part of desorbed gas is used as a fuel gas after washing and oxidation by water vapor, and the intermediate gas flowing out from the shallow-cooling pressure swing adsorption concentration process, thereby omitting the medium and shallow-temperature condensation and medium and shallow-cooling rectification processes.
10. The method as claimed in claims 1 and 2, wherein the raw material gas "C source" is only methane, and the purified raw material gas from the pretreatment step is subjected to decarburization in the working condition that the content of CO2 in the purified raw material gas is greater than 0.1%, an adsorption method loaded with a disposable adsorbent is adopted to remove CO2, the purified raw material gas from which CO2 is removed is subjected to cold-heat exchange to 5-20 ℃, pressurized to 0.6-1.0 MPa, and then directly subjected to a shallow-cooling pressure swing adsorption concentration step, and concentrated gas flowing out from the bottom of the adsorption tower in the desorption step is mixed with purified methane hydrogen gas from the subsequent adsorption purification step according to a ratio to be recycled as the recycled reaction gas of the SiC-crystal or thin film epitaxial growth CVD process based on the reaction of methane and silane, thus, the procedures of medium-temperature pressure swing adsorption, medium-and shallow-temperature condensation and medium-and shallow-cold rectification are omitted.
11. The method for adjusting FTrPSA based on the reaction cycle gas of SiC-CVD process tail gas of alkane and silane as claimed in claim 1, wherein the purified raw material gas contains C2+ with higher concentration, the purified raw material gas from the pretreatment process enters the medium temperature pressure swing adsorption process consisting of two-stage PSA after being subjected to heat exchange and pressurization, wherein the purified raw material gas enters from the bottom of the first PSA adsorption tower (1-stage PSA) for medium temperature pressure swing adsorption, the intermediate gas of the non-adsorption phase flowing out from the top of the 1-stage PSA in the adsorption stage enters the shallow cold pressure swing adsorption concentration process, the desorbed gas flowing out from the 1-stage PSA adsorption tower in the desorption step enters from the bottom of the second PSA adsorption tower (2-stage PSA) after being pressurized, the desorbed gas flowing out from the bottom of the 2-stage PSA adsorption tower in the desorption step enters the medium shallow temperature condensation process as the carbon-rich secondary gas, the non-adsorption phase gas flowing out of the top of the 2-stage PSA adsorption tower in the adsorption step is mixed with the purified feed gas as a feed gas and returned to the 1-stage PSA adsorption tower.
12. The method of claim 1, wherein the purified feed gas contains C2+ with a high concentration, such as a C2+/Si ratio of more than 5:1, the purified feed gas from the pretreatment step is subjected to heat exchange to-35 to-15 ℃ and compressed to 2.5 to 3.5MPa, a shallow cold oil absorption step is used to replace the medium temperature pressure swing adsorption step, i.e., the shallow cold oil absorption step comprises an absorption tower and a desorption tower, propane (C3) is used as an absorbent, the absorption temperature is-35 to-15 ℃, the absorption pressure is 2.5 to 3.5MPa, the desorption temperature is normal temperature, the desorption pressure is normal pressure or slight positive pressure, the purified feed gas enters from the bottom of the absorption tower and is subjected to reverse mass transfer with a C3 absorbent sprayed from the top of the absorption tower, the noncondensable intermediate gas escaping from the top of the absorption tower enters the subsequent shallow cold pressure swing adsorption concentration, the C2+ rich liquid flowing out from the bottom of the absorption tower enters the desorption tower, the C2+ rich gas flowing out from the top of the desorption tower directly enters the subsequent medium and shallow temperature condensation process, the absorbent C3 flows out from the bottom of the desorption tower, and the absorbent is circulated and pressurized and then returns to the top of the absorption tower for spray absorption.
13. The method of claim 1, wherein under the condition of high silane concentration in the purified raw material gas, the purified raw material gas enters a shallow cold pressure swing adsorption concentration process consisting of two stages of PSA directly after being subjected to heat and heat exchange to 5-20 ℃ and pressurized to 0.6-1.0 MPa, wherein the purified raw material gas enters from the bottom of a first PSA adsorption tower (1-stage PSA) in the shallow cold pressure swing adsorption concentration process, an intermediate gas 1 of a non-adsorption phase flowing out from the top of the 1-stage PSA in an adsorption stage enters a second PSA adsorption tower (2-stage PSA), a concentrated gas flowing out from the bottom of the 2-stage PSA adsorption tower in a desorption step and a purified methane gas from a subsequent adsorption purification process are mixed in proportion to be recycled as a cyclic reaction gas in a SiC-CVD crystal or a thin film epitaxial growth process based on the reaction of methane and silane, and (2) replacement and vacuumizing regeneration are adopted during desorption of the PSA, replacement gas is crude silane gas from a subsequent medium-and-light-cooling rectification process to adjust the C/Si ratio in reaction cycle gas and meet the requirements of a SiC-CVD process, intermediate gas 2 flowing out of the top of the PSA adsorption tower in the section 2 in the adsorption step enters a subsequent adsorption purification process, and desorbed gas flowing out of the bottom of the PSA adsorption tower in the section 1 in the desorption step is used as carbon-rich secondary gas and enters a medium-and-light-temperature condensation process.
14. The method for adjusting FTrPSA as reactive recycle gas based on tail gas of SiC-CVD process of alkane and silane reaction as claimed in claim 1, wherein the PSA adsorption tower in desorption step in the medium temperature pressure swing adsorption or shallow cold pressure swing adsorption concentration process comprises 1-stage PSA and 2-stage PSA, and the desorption steps are pressure drop, concurrent release, vacuum pumping, pressure rise and final charge, wherein the desorption step of the concentrated gas formed in the medium temperature or shallow cold pressure swing adsorption process comprises displacement, pressure drop, concurrent release, vacuum pumping, pressure rise and final charge, while the displacement gas comes from crude silane gas of the subsequent process, and the final charge gas adopts the feed gas of the respective front-end process.
15. The method for adjusting FTrPSA as a reaction cycle gas based on the tail gas of SiC-CVD process of alkane and silane reaction as claimed in claims 1, 5 and 7, wherein the concentration of CH4, C2+ and H2 in the concentrated gas is adjusted by adjusting the operation time of adsorption and desorption steps in the medium temperature pressure swing adsorption and light cold pressure swing adsorption concentration process, the amount of one or more combined adsorbents comprising alumina, silica gel, activated carbon and molecular sieve filled in the adsorption towers, and the opening and closing degree of program control valves or other valves loaded on the pipelines connecting the adsorption towers, so as to form a mixed gas proportionally with the crude silane gas from the subsequent process, and the mixed gas is used as the cycle reaction gas of SiC-CVD crystal and film growth process to enter the SiC-CVD reactor (cavity) for continuous reaction, wherein, when the operating pressure of the medium-temperature pressure swing adsorption, the shallow-cold pressure swing adsorption concentration or the adsorption purification process is more than 0.6MPa, the pressure change in the adsorption and desorption cycle operation process is realized, and the slow and uniform control is realized through the program control valves and the regulating valves on the pipelines connected among the adsorption towers, so that the condition that the bed layers of the adsorption towers are flushed by air flow and the adsorbent is pulverized due to overlarge system pressure change is prevented, and the operation of the system in the process is stable and safe.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105749699A (en) * | 2016-03-31 | 2016-07-13 | 四川天采科技有限责任公司 | Full-temperature-range pressure swing adsorption gas separation, refinement and purification method |
| CN107433107A (en) * | 2017-08-29 | 2017-12-05 | 四川天采科技有限责任公司 | C2+ two sections of points of concentration PSA methods are reclaimed from oil refinery dry gas |
| CN108658042A (en) * | 2018-05-29 | 2018-10-16 | 四川天采科技有限责任公司 | A kind of LED-MOCVD processing procedures tail gas warm journey pressure-variable adsorption full constituent recycling method entirely |
| CN108715436A (en) * | 2018-05-29 | 2018-10-30 | 四川天采科技有限责任公司 | The useless hydrogen of the manufacture of semiconductor normal pressure method that warm journey Pressure Swing Adsorption recycles entirely |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105749699A (en) * | 2016-03-31 | 2016-07-13 | 四川天采科技有限责任公司 | Full-temperature-range pressure swing adsorption gas separation, refinement and purification method |
| CN107433107A (en) * | 2017-08-29 | 2017-12-05 | 四川天采科技有限责任公司 | C2+ two sections of points of concentration PSA methods are reclaimed from oil refinery dry gas |
| CN108658042A (en) * | 2018-05-29 | 2018-10-16 | 四川天采科技有限责任公司 | A kind of LED-MOCVD processing procedures tail gas warm journey pressure-variable adsorption full constituent recycling method entirely |
| CN108715436A (en) * | 2018-05-29 | 2018-10-30 | 四川天采科技有限责任公司 | The useless hydrogen of the manufacture of semiconductor normal pressure method that warm journey Pressure Swing Adsorption recycles entirely |
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