Mechanism of PECVD film formation
May 08, 2024| Mechanism of PECVD film formation
• SiNx insulation film: The mixture of SiH4, N2, and NH3 is used as the reaction gas, and the film is formed on the substrate by glow discharge generating plasma.
• Si:H: SiH4 gas is discharged by glow in the reaction chamber, and after a series of primary and secondary reactions, more complex reaction products such as ions and child active groups are generated, and finally A-Si :H film is produced and deposited on the substrate. Some neutral products, such as SiHn(n:0~3), are directly involved in the film formation growth.
When the film is growing, if the first film-forming process is taken, the defects in the film growth process will continue to grow along the film-forming direction, thus exposing the surface.
At the same time, because the defects of low-speed film formation are less than those of high-speed film formation, to obtain dense A-Si :H film (suppose 2000 A) in the Bottom Gate mechanism, it can be achieved by first growing 300A at low speed and then 1700 A at high speed. Where 300 A is the TFT channel (some of the defects caused by the first step are covered by the second step). The two-step film forming method can also be used for the production of insulating layers.
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