GasIndustrial terms,semiconductorIndustrial gases are collectively referred to as electronic gases.According to its category, it can be divided into three categories: pure gas, high purity gas and semiconductor special material gas.Special material gases are mainly used for epitaxy, doping and etching processes;High purity gas is mainly used as dilution gas and carrier gas.Electronic gas is an important branch of special gases.Electronic gas can be divided into electronic grade and LSI according to purity grade and application occasion（large-scale integrated circuit）Class, VLSI (Very Large Scale Integrated Circuit) class and ULSI (Very Large Scale Integrated Circuit) class.
Electronic gas is an indispensable basic supporting source material in the process of developing integrated circuits, optoelectronics, microelectronics, especially VLSI, LCD devices, semiconductor light-emitting devices and semiconductor materials manufacturing. It is called the "blood" and "grain" of the electronic industry. Its purity and cleanliness directly affect the quality of optoelectronic and microelectronic componentsIntegration, specific technical indicators and yield, and fundamentally restrict the accuracy and accuracy of circuits and devices[1]。
In recent years, with the development of China's super large scale data research centerIntegrated circuitWith the rapid development of flat panel display, photovoltaic power generation and other industries, the demand of electronic gas market has increased significantly, and the localization of electronic special gases has become a general trend.It is understood that China has made gratifying progress in localization: domestic high-purity ammonia has changed the monopoly pattern of foreign gas companies in the market, the era of high-purity carbon tetrafluoride "with price but without stock" has also ended, and high-purity hydrogen chloride has successfully opened the domestic market.
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Increasingly strict requirements for electronic gas pollution control
With the upgrading of consumer electronics, the manufacturing size of products is becoming larger and larger, and the product yield and defect control are becoming more and more strict. The entire electronic industry has increasingly stringent requirements on the purity of electronic gas source and the elimination of secondary pollution in the transportation system.Basically, the technical indicators proposed by the industry for electronic gas gas impurity and particle size pollution are directly related to the lowest detection limit (LDL) brought by the technical progress of analytical instruments.For example, the traditional laser particle tester can measure 0.1 μ m, while the nuclear coagulation technology (CNC) can reach 0.01 μ m.
At present, the line width of 12 inch VLSI manufacturing has developed to 45 nm. The purity of bulk gas is required to be at the ppt level, and the particle size control directly refers to the lower limit of CNC analytical instruments.The laboratory's ultra-high brightness light-emitting diode (LED) technical indicators have reached more than 200Lm/w (lumens/watt), and the purity control requirements for hydrogen and ammonia are both less than 1 ppb (one billionth). Ammonia is produced by multi-stage distillation, and the technical indicators reach 7N (seven nines) of "white ammonia", and 5N of hydrogen needs to be purified to 9N by advanced palladium membrane purifier.
The timely application of bulk special gas system (BSGS) is conducive to improving pollution control.First, the large packaging container ensures the continuity of gas quality and reduces the risk of multiple filling pollution.In addition, the reduction of bottle changing frequency also reduces the probability of pollution.BSGS mostly adopts deep purging, which significantly improves the purging effect.
316L stainless steel electropolishing (EP) pipes, high-purity pressure regulating valves, diaphragm valves, high-precision filters (<0.003 μ m), VCR connectors, etc. are generally used in the transmission pipeline system. The surface roughness of pipeline components contacting gas can be controlled at 5 uin, and zero dead zone design is adopted.Full automatic track welding is adopted for construction technology, and strict ultrahigh purity construction and QA/QC assurance procedures are formulated and implemented.
After the completion of the gas transmission system, it must undergo strict pressure maintaining, helium leak detection, particle size and moisture, oxygen and other gaseous impurities tests.
Large flow, uninterrupted and stable transmission
How to meet the requirements of large-scale mass production plants for large flow, uninterrupted and stable transmission of electronic gas is a challenge.
Electronic gas tends to be supplied in a centralized manner, and special gas is placed in the gas room in a centralized manner.The number of conveying systems is reasonably configured according to the flow demand of the machine.Special gas transmission equipment must adopt fully automatic switching gas supply, and more standby equipment is designed.For low steam pressure gas (WF6, DCS, BCl3, C5F8, ClF3, etc.), cylinder heating, gas panel heating, pipe tracing, etc. need to be considered.In order to control the flow accurately, high-precision pressure transmitter, electronic scale, temperature controller, etc. will be generally considered at the air source end.The gas consumption points of the machine are also equipped with mass flow meters.
For BSGS with large flow rate, not only the influence of pipeline pressure drop and evaporation heat absorption of liquefied steel cylinder on the flow rate, but also the Joule Thompson effect of gas after pressure reduction through pressure regulating valve should be considered.Generally speaking, the temperature will decrease or even liquefy after the gas is decompressed.This will result in unstable delivery pressure and damage to the pipeline system.Therefore, it is necessary to consider preheating the gas before decompression.The gas monitoring system (GMS) realizes real-time monitoring of the gas transmission system through the computer network to ensure the stability of the system.
in the light ofLiquefied gasThe BSGS (such as ammonia gas) has been developed and molded, and will soon be popularized in the application of BSGS.
Increasingly strict security
The electronic gas may be suffocating, corrosive, toxic, flammable and explosive, and its harmfulness has been classified in detail by different countries, regions and industrial organizations.For an electronic factory with mass production, the amount of electronic gas used and stored in the factory can be regarded as having a "mass destruction" arsenal without exaggeration.Any potential safety hazard in design, construction and daily operation will bring huge disaster to the plant, personnel and environment.
Many international standards and specifications, such as SEMI, NFPA, CGA and FM, have detailed provisions on how to ensure the safe storage, use and operation of electronic gases, and the intrinsic safety design of the system process and products. At present, China is also drafting national standards and specifications for electronic special gases.Generally speaking, the gas room will be divided into combustible gas room, corrosive gas room, inert gas room, silane gas room, chlorine trifluoride gas room, etc. according to the gas properties and compatibility.The gas room planning needs to consider the building's fire prevention, explosion relief, fire and explosion prevention spacing, total amount control of hazardous materials, etc.For silane conveying system, especially BSGS system, due to the large amount, isolated buildings should be used.Automatic sprinkler system shall be adopted for gas room and gas holder.The reaction of chlorine trifluoride with water requires the use of carbon dioxide fire extinguishing system.
The factory exhaust system using electronic gas is also divided into general exhaust system (GEX), acid exhaust system (SEX), solvent exhaust system (VEX) and ammonia exhaust system (AEX) according to the nature of dangerous goods.It is also recommended that the purge tail gas during cylinder replacement be discharged into the tail gas processor.
The seamless SS316L EP pipe is generally used as the transmission pipeline.Automatic track welding is adopted for construction, which has passed pressure maintaining, helium leak detection and purity test.For highly toxic, highly reactive and spontaneous combustion gases, double casing pipes shall be used for transportation.Some highly toxic gases, such as phosphine and arsenic, are being widely used in the safe transportation system (SDS).The negative pressure absorption method is adopted in the cylinder, and the vacuum method is used for transportation, which fundamentally avoids the leakage of gas.
Gas detection system (GDS) is an important part of plant life safety system (LSS).In addition to high precision and rapid response, the detector shall also have self inspection function.
Construction costs are decreasing
Because the scale of investment in the electronic industry is becoming larger and larger, it is more and more important to shorten the construction period and reduce the construction cost.For the electronic gas transmission system, it is also a challenge to try to reduce the construction and operation costs without reducing the system pollution control level and sacrificing the safety configuration.
The initial investment cost can be significantly reduced by reasonably configuring the system and selecting materials.This requires the electronic gas transmission system contractor to have strong system design capability.The same purging nitrogen system is used for gases with matching properties, which can significantly save the investment of gas cylinder cabinet.For VMB, mobile purging nitrogen disk can be used.For the construction of small pipelines (≤ 1/2 "), the elbow method is directly adopted, which not only saves the cost of elbow, but also greatly improves the construction efficiency.Strict implementation of high purity pipeline construction specifications can greatly reduce the test gas and test time.These are effective cost control measures.Using the gas source of large packaging containers can greatly reduce the operating costs of logistics and human operation.Therefore, BSGS is more and more popular with customers.
To sum up, the electronic gas transmission system is facing the challenges of high purity, large flow, strict safety measures and vigorously reducing construction costs, which are also the future development direction.
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Electronic gases are very large scale integrated circuits, flat panel display devices, compoundssemiconductorDevices,solar energyBattery,Optical fiberThey are widely used in film, etching, doping, vapor deposition, diffusion and other processes.For example, in the wafer manufacturing process of the ultra large scale integrated circuit factory with relatively advanced technology, the total process steps exceed 450, of which about 50 different kinds of electronic gases are used.The electronic gas transmission system refers to the stable transmission of electronic gas from the gas source end to the gas consumption point of the process production equipment without secondary pollution, controlling the flow and pressure and other parameters required by the process, in order to meet the needs of the process process and fully ensure the safe use of the process and products.According to different gas properties and supply packages, general electronic gases can be divided into bulk ordinary gases, special gases and bulk special gases.
At present, there are a wide range of consumer electronics products and their upgrading is increasingly frequent, and production plants and scientific research institutions with different manufacturing scales and levels coexist for similar products.Based on the different actual requirements of investment scale and product grade, the industry basically has the following three types of demands for electronic gas transmission system:
Large scale gas supply system
The large-scale gas supply system is mainly aimed at large-scale mass production of 8-12 inch (1 inch=25.4mm) large-scale integrated circuit plants, solar cell production lines of more than 100MW, LED epitaxial process lines, LCD plants of more than 5 generations, optical fiber, silicon material epitaxial production lines and other industries.They have a huge investment scale, adopt the most advanced process equipment, have a large demand for gas, and put forward the most stringent requirements for stable and uninterrupted supply, purity control and safe production.
The bulk common gas of the above plants is mostly supplied through on-site gas production or pipeline in the industrial park. The demand for high-purity nitrogen of an 8-inch VLSI plant with an annual output of 50000 pieces exceeds 5000Nm3/h, and the demand for hydrogen of the LED epitaxial process line and silicon epitaxial production line exceeds 100Nm3/h.
In addition to the special gases packed in ordinary steel cylinders (50L and below), there are many kinds of special gases that generally use large packaging containers, so they are called bulk special gases, including Y-steel cylinders (450L), T-steel cylinders (980L), cylinder racks (940L), ISO tanks (22500L), torpedo cars (13400L), etc.
The bulk special gas supply system (BSGS) adopts fully automatic PLC controller and color touch screen;The gas panel adopts pneumatic valve and pressure sensor, which can realize automatic switching, automatic nitrogen purging, and automatic vacuum assisted venting;Multiple safety protection measures, leakage detection, remote emergency cut-off;Origin of dedicated nitrogen purging, etc.Independent gas source is used for special gas, VMB or VMP branch supply is used for multi-purpose points, and branch pneumatic valve, nitrogen purging, vacuum assisted evacuation, etc. are used for VMB or VMP.Due to the large amount of BSGS gas sources, independent gas rooms and independent exhaust systems are often used.
Conventional gas supply system
The conventional gas supply system is mainly used in 4-6 inch large-scale integrated circuit plants, solar cell production lines below 50MW, LED chip process lines and other electronic industries with medium gas consumption.Their investment scale is medium, the production line may be second-hand equipment, the requirements for gas purity control are not strict, and the system configuration is as simple as possible to save investment on the premise of safety.
Most of the large amount of ordinary gas in the conventional gas supply system will be supplied by on-site liquid storage tanks (LIN, LOX, LAR) or container grids.The gas is delivered to the plant by the pipeline system, and is directly delivered to the gas consumption point by opening a tee.
Special gas is supplied by ordinary steel cylinder (<50L).Special gas transmission system adopts gas cylinder cabinet.Equipped with full-automatic PLC controller and color touch screen;The gas panel adopts pneumatic valve and pressure sensor, which can realize automatic switching, automatic nitrogen purging, and automatic vacuum assisted venting;Multiple safety protection measures, leakage detection, remote emergency cut-off;Origin of dedicated nitrogen purging, etc.VMB adopts branch pneumatic valve, nitrogen purging and vacuum assisted evacuation.Inert gas is mostly semi-automatic cylinder rack, controlled by relay, automatically switched, manually purged and manually vented;VMB main pipe pneumatic valve, nitrogen purging;Branch pneumatic valve, nitrogen purging, vacuum assisted evacuation.Gas rooms and exhaust systems are classified according to the nature of the gas.
Simple gas supply system
The simple gas supply system is mainly aimed at semiconductor chip factories and semiconductor material research institutions with the size of 4 inches and below.Their manufacturing process is simple, they usually do not need continuous gas supply, their investment budget for the gas supply system is low, and production and management personnel lack safety awareness.
Due to the small gas flow, ordinary steel cylinders (<50L) are mostly used as special gas sources.The conveying system mostly adopts semi-automatic cylinder cabinet or cylinder rack, equipped with relay control, automatic switching, manual purging, manual venting, and emergency shut-off valve for harmful gases.Inert gas bottle rack adopts full manual system, and some even use single bottle system.The gas room is shared, and even there is no gas room. The special gas cylinder and conveying system are sometimes placed in the return air duct, or directly next to the process manufacturing equipment.Share one exhaust system.The system usually has potential safety hazards.
Current major electronic gases
At present, it mainly includes silane, ammonia, carbon tetrafluoride, sulfur hexafluoride, hydrogen chloride, octafluorocyclobutane, methane, nitrous oxide, boron trichloride, hydrogen bromide, carbon monoxide, neon, krypton, etc.
