Dry screw vacuum pump in silicon nitride process of application
Thin film deposition in semiconductor production is usually very demanding for vacuum pumps. High failure rate and shutdown are common in this process. Vacuum pumps are specially designed for harsh film process environments. This paper describes the successful application of dry screw vacuum pump in silicon nitride process.
Silicon nitride is very strong, especially hot pressed silicon nitride, is one of the hardest materials in the world. It is extremely high temperature resistant, the strength has been able to maintain to 1200 high temperature without dropping, after being heated will not melt into the melt body, until 1900 will not decompose, and has amazing resistance to chemical corrosion, can withstand almost all inorganic acid and less than 30% of caustic soda solution, also can withstand the corrosion of many organic acids; It is also a kind of high performance electrical insulation material.
Due to process chemicals and their characteristics, film deposition is easy to produce solid dust and compressible steam. The by-products of these processes have great influence on vacuum pumps, especially the deposition or aggregation in vacuum pumps. Serious can cause chip production to stop. Therefore, an effective solution to minimize downtime and maximize stable operation is very important.
The latest dry screw vacuum pumps are specially designed for demanding semiconductor processes. The following three key conclusions are drawn after the study of the technicians: there is no deposition in the vacuum pump; During the experiment, the vacuum pump needs no maintenance. No production downtime.
Dry screw vacuum pump of characteristics
(1) clean vacuum can be obtained without any medium in the working cavity.
(2) the working cavity and the surface of the screw have anti-corrosion coating, which can adapt to bad working conditions.
(3) dry operation of the working chamber is suitable for the extraction of gas containing dust and gas with coagulability.
(4) a single pump can continuously discharge the atmosphere, from atmospheric oil to 5Pa limit full pressure below, the vacuum system can be greatly simplified.
(5) no friction between rotating parts, so long life.
(6) the dry screw vacuum pump can run at high speed and work steadily with small volume after high-precision dynamic balance.
(7) compared with multi-stage claw pump, the structure is simple, compact, less parts, more stable operation, more convenient maintenance.
(8) compared with the oil-sealed and JW vacuum pump, the condensable substance will not be retained in the pump, and there is no oil vapor and oil mist emission. It is the first choice for environmental protection.
(9) compared with the water ring pump, the dry screw vacuum pump only needs the circulating cooling water, and the extracted gas does not contact with the water. The tail gas is easy to be recovered, which saves the sewage treatment link, is more environmentally friendly, and avoids the influence of water temperature on the vacuum.
(10) compared with liquid ring pump, the ultimate pressure is lower, thus saving energy.
Vacuum pumps take advantage of some of the advantages of the old dry pumps, such as improved handling of by-products. Including: improving dust handling capacity (especially important for PECVD); High temperature operation can reduce the deposition of compressible solid materials. Improved nitrogen flushing system; No exhaust muffler, so there is no need for regular muffler maintenance.
The practical application of dry screw vacuum pump in silicon nitride process can reduce the operating cost. Reduce water consumption because vacuum pumps operate at high temperatures; Reduce nitrogen consumption (possibly due to high pump body temperature) without affecting dilution of toxic and flammable gases; Compact structure, small footprint. This is one of the requirements of a modern chip factory because of the limited space in the lower floor.