Special gas is a general concept, which is different from general gas. It is produced and used in strict accordance with certain specifications in terms of purity, variety and performance. It is generally believed that the special gas is composed of electronic gas, high-purity petrochemical gas and standard mixed gas. In addition, in the semiconductor manufacturing industry, gas can also be divided into bulk gas and electronic gas. Bulk gas refers to the gas that is centrally supplied and used in a large amount, such as N2, H2, O2, AR, he, etc. Electronic gas is mainly used in every process of semiconductor manufacturing, such as high-purity SiH4 (silane), PH3 (phosphine), AsH3 (hydrogen arsenide), B2H6 (ethylborane), N2O (laughing gas), etc., which can also be called electronic special gas. According to different application ways in integrated circuits, it can be divided into gas for doping, gas for extension, gas for ion implantation, gas for light emitting diodes, gas for etching, chemical vapor deposition gas and equilibrium gas. There are more than 110 kinds of unit special gases applied in the semiconductor industry, of which more than 30 are commonly used.

The quality of electronic gas mainly depends on its purity and purity. Generally speaking, the purity of electronic special gas is required to reach 5n-6n (n refers to the number of 9 in the purity percentage, for example, 5.7n represents 99.9997%, 6N represents 99.9999%). Each increase in purity by one n, and each decrease in the content and concentration of particles and metal impurities by one order of magnitude will lead to a significant increase in process complexity and difficulty. The more precise the device is, the higher the requirements of the electronic special gas used. Once the purity or purity of the electronic special gas is not up to the standard, the quality of the downstream products will not pass the standard, or the whole product line will be polluted and the products will be scrapped.

There are many factors affecting the purity improvement of electronic special gas, and it is difficult. There are many factors affecting the purity improvement of electronic special gas, mainly including three aspects:

1) Gas separation and purification.

In principle, the separation and purification methods of electronic special gas can be divided into three categories: distillation separation, molecular sieve adsorption separation and membrane separation. In the actual purification and separation process, in order to achieve better separation efficiency, many separation methods are often used to combine, and the process is more complicated.

2) Gas impurity detection and monitoring.

With the increasing purity of electronic special gas, higher requirements are put forward for analysis and detection methods and instruments. The detection limit has developed from the earliest ppm level to PPT level. At present, the analysis of electronic gas abroad has gone through several stages, such as off-line analysis, on-line analysis and in-situ analysis. For the analysis of high-purity electronic gas, foreign countries have developed systematic and complete analysis and test methods and field analysis instruments. However, the electronic special gas industry in China has always emphasized production rather than detection, so the analytical methods and instruments are relatively backward compared with foreign manufacturers.

3) Transportation and storage of gas.

It is not easy to get high-purity electronic special gas. During storage and transportation, high-quality gas packaging, storage and transportation containers, as well as corresponding gas transmission pipelines, valves and interfaces are required to avoid secondary pollution. However, China's processing technology as a whole is backward and does not conform to international standards, and the market is mainly occupied by foreign companies. The purity of domestic electronic special gas still needs to be improved. At present, the purity of electronic special gas abroad is generally 6 "9" (i.e. 99.9999%), while in China, it is mostly between 4 and 5 "9", and a few can reach 6 "9".

Application of electronic special gases

Electronic special gas (electronic special gas) is a high-tech and high value-added product, which is widely used in the semiconductor and microelectronic industries. In semiconductor chip manufacturing, silicon chips account for 37%, followed by electronic gases, accounting for 13%.

Electronic special gas mainly includes hydride, fluoride, metal organic compounds, etc. it is an indispensable and important material for the production of electronic industry such as VLSI, flat panel display devices, compound semiconductor devices, solar cells, optical fibers, etc. it is widely used in the processes of film manufacturing, etching, doping, vapor deposition, diffusion, etc. in the production of integrated circuits and display panels



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