Inductively Coupled Plasma Jet Processing For Silicon-based Materials

In the space-ground based observation, Inertial Confinement Fusion, extremeultraviolet lithography and some challenging international cutting-edge scientificprograms, the demand for the large ultra-precision silicon-based optical surfaces isincreasing, and the requirements for the optical surfaces quality are becomingharsher. The programs need thousands of optical elements, requiring them to reachseveral meters or tens of meters in diameter, and hoping them to have a high surfaceprecision. Currently, the processing cycle, sub-surface damage, processing costs andother issues continue to plague the development and deployment of these projects.Atmospheric plasma processing method provides a unique solution to solve theabove problem. Inductively Coupled Plasma （ICP） jet machining technology is oneof the atmospheric pressure plasma processing technologies. ICP jet processing isbased on ICP torch, forming a nearly Gaussian stable etching footprint for chemicaletching at atmospheric pressure, combining the advantages of a high materialremoval rate and a non-contact processing.This paper is the first case for the research of the atmospheric pressure ICP jetmachining technology in China. The establishment and adjustment of the firstprototype of the atmospheric pressure ICP jet machining system is completed.Through the combination of the preliminary theoretical and experimental analysishow various experimental parameters affect the removal rate can be researched,surface temperature and surface quality during the silicon-based material removalprocess, establish a stable, fast, high-quality silicon-based materials’ machiningprocess, and lay a foundation of the uniform removal of the large-scaleultra-precision optical elements.First, basic theoretical knowledge and related properties of ICP jet processingare introduced; the various components and their functions are analyzed, and thecomponents are chosen according to the principles; the first prototype of ICP jetprocessing system in China is established and adjusted.Then, studies on the ICP jet prosessing silicon-based materials such as siliconcarbide（SiC） and fused silica（SiO₂） are conducted based on the new InductivelyCoupled Plasma（ICP） jet processing system, aiming at the material removal rate.Appropriate diagnostic instruments are selected to analyze the characteristics of ICPjet processing; processing experiments are conducted to explore how variousexperimental parameters affect the material removal rate and surface temperatureduring the process of ICP jet machining, and technological parameters are seeked toincrease the material removal rate; uniform and rapid removal of the silicon-based materials surface is realized based on the stable processing parameters obtained.Finally, research on the surface roughness of silicon-based materials such assilicon carbide（SiC） and fused silica（SiO₂） during the ICP jet machining isconducted. The surface quality of SiC and SiO₂after the ICP jet processing isdetected, how the ICP jet processing affect the surface roughness of SiC and SiO₂isanalyzed, and the evolution of the surface roughness is assessed.