Electronic gas, an important raw material for semiconductor industry
Introduction to electronic gas
Electronic special gas is an important branch of special gas. It is an indispensable raw material for integrated circuit (IC), flat panel display (LCD, led, OLED), solar cell and other electronic industry production.
Generally, in semiconductor industry, gases are divided into common gases and special gases. Among them, the commonly used gases refer to the gases which are supplied in a centralized way and use a lot of them, such as N2, H2, O2, AR, he, etc. Special gases refer to some chemical gases used in semiconductor production, such as extension, ion implantation, mixing, washing and mask formation, i.e. electronic gases in gas categories, such as high-purity SiH4, PH3, AsH3, B2H6, N2O, NH3, SF6, NF3, CF4, BCl3, BF3, HCl, Cl2, etc., in IC In the production process, there are almost 100 kinds of electronic gases used, and about 30 kinds are common in the core section. It is these gases that make silicon wafers have semiconductor properties through different processes, which in turn determines the performance, integration and yield of integrated circuits. Even if a certain specific impurity exceeds the standard, it will lead to serious quality defects. In serious cases, due to the diffusion of unqualified gas, the whole production line will be polluted, and even the production will be completely paralyzed. Therefore, electronic gas is the key basic material of electronic manufacturing process, which is worthy of the name of "blood" of electronic industry.
The raw materials of electronic gas are mainly air separation gas, low purity feed gas produced in petrochemical and coal chemical production process, waste gas and other basic chemical raw materials. The main raw materials come from a wide range of sources and the market supply is sufficient, which is easy to obtain from relevant raw material suppliers. China's large-scale steel-making enterprises and chemical fertilizer enterprises are basically equipped with air separation equipment, and the air separation gas supply is large and the price is stable. The consumption of electronic special gas to raw gas accounts for a small proportion of the output of petrochemical and coal chemical feedstock gas. Stable petrochemical and basic chemical industry can provide sufficient raw materials for the electronic special gas industry. The 13th five year plan further clarifies the goals of environmental protection and industrial waste gas emission, and the supply of upstream industries will be more adequate. Due to the long-term use of gas containers, the cost of electronic gas is relatively low, and the price fluctuation has little impact on the industry.
Classification and application of electronic gases
There are many kinds of electronic gases, which are widely used in the manufacturing process of electronic products. At present, there are more than 60 kinds of pure gas and more than 80 kinds of mixture gas. Electron gas can be divided into three categories: pure gas, high purity gas and semiconductor special material gas. Special material gases are mainly used in epitaxy, doping and etching processes; high purity gases are mainly used as diluents and carrier gases.
Electronic gas is mainly used in semiconductor, flat panel display, solar cell and other fields, with a domestic market demand of 8 billion yuan. According to the statistics of China Industrial Gas Industry Association, in 2019, the domestic demand for special electronic gases will reach 8 billion yuan, including 3.5 billion yuan for integrated circuits, 2.2 billion yuan for plane display and 800 million yuan for solar cells.
Many kinds of electronic gases are needed in the manufacture of IC chips, such as silanes, doping gases such as PH3, etching gases such as CF4, metal vapor deposition gases such as wf6, and other reaction gases and cleaning gases. In the preparation process of electronic grade silicon, the electronic gases involved include SiHCl3, SiCl4, etc. In the process of chemical vapor deposition (CVD) on silicon wafer surface, SiH4, SiCl4 and wf6 are mainly involved. In the process of wafer fabrication, some processes involve the application of gas etching process, also known as dry etching. The electronic gases involved include CF4, NF3, HBr, etc. the amount of such etching gas is relatively small. In the process of etching, it is necessary to work together with related inert gases such as ar and N2 to achieve uniform etching process. The doping process is to change the electrical properties of semiconductors by doping impurities into specific semiconductor regions. The electronic gases involved include trivalent gases such as B2H6 and BF3, and pentavalent gases such as PH3 and AsH3.
The main kinds of electronic gases used in the flat panel display industry include silanes, doped gases such as PH3 and etching gases such as SF6. In the film process, SiO2 and SiNx films are deposited on the glass substrate by chemical vapor deposition. The special gases used include SiH4, PH3, NH3, NF3, etc. In dry etching process, substrate is selectively corroded in plasma gas atmosphere. SF6, HCl, Cl2 and other gases are usually used.
Solar cells can be divided into crystalline silicon solar cells and thin film solar cells. In the production of crystalline silicon cells, POCl3 and O2 are used in diffusion process, SiH4 and NH3 are used in PECVD process, and CF4 is used in etching process. In thin film solar cells, diethylzinc (DEZn) and B2H6 are used in the process of transparent conductive film deposition, and silane is used in the amorphous / microcrystalline silicon deposition process.