Research On RF Plasma Polishing Device And Process

In the field of science and engineering, ultra-precision optics manufacturing technology is becoming the focus of attention. Because of the optical system tending to its limit development request, the optical elements became more and more precision, with the requirements of high surface shape, and by significantly improving the quality of the surface to reduce the microscopic surface scattering loss, and to improve the light energy transmission capability, image transmission quality and the capability of combat laser. Plasma polishing technology is a new ultra-smooth surface processing technology which generated plasma is based on the principles of gas discharge, and the activity of the reaction gas has introduced into the plasma, through chemical reaction to achieve optical surfaces at the atomic level material removal, and avoid the surface and sub-surface damage.This paper focused on RF capacitively coupled plasma polishing technology, analyzed the impact of plasma discharge characteristics when changed working conditions like the working pressure, working gas capacity and power frequency; built a static single probe diagnostic system and completed the original plasma source structure improvement. Then with a fused silica polishing experiments to explore the effects of different process parameters on the surface roughness and removal rate.Experimental results show that:1) Under the given conditions, in the pressure range of 10-2～102Pa, the plasma source can be discharged with Ar gas, within the range of 10-1～102 Pa, it will be stable. Accordingly, with the Ar flow rate increased, the required power is lower, and the discharge is easier; the discharge phenomenon is obvious when He as working gas within 102～105 pa, so it can be achieved at atmospheric;2) Discharge characteristics of plasma source is associated with the RF power frequency, the higher power frequency required larger power to discharge; 3) Under the given conditions, the results of orthogonal experiments show that the primary factor affecting on the removal rate is operating distance and then work pressure, Ar/SF6 flow ratio, effective power in turn, while on the roughness is Ar/SF6 flow ratio and then operating range; After introduced oxygen has obvious influence on the removal rate, when the Ar flow rate is 20ml/min, SF6 and O2 flow rate is 10ml/min, the removal rate is the highest.