Efficient large-area polishing of fused silica surfaces based on inductively coupled plasma

Abstract

Components with excellent surface quality have important applications in high-energy lasers, optics, and semiconductors. The atmospheric pressure plasma polishing (APPP) technique can obtain the desired surface roughness with high efficiency. This study analyzed in detail the radial and temporal evolution of the microscopic morphology of the surface during the polishing process which utilizes inductively coupled plasma (ICP). Experimental results demonstrated that after a two-minute exposure to plasma polishing, the optical transmittance of fused silica (FS) was significantly enhanced, increasing from 85.1% to 93.3%. The effects of radio frequency (RF) power and polishing distance on the surface morphology and optical property of FS were also evaluated. By utilizing molecular dynamics (MD) simulations and finite element (FE) analysis to investigate the influence mechanisms of the process parameters, it was observed that the RF power contributes to the elevation of temperature, facilitating the desorption of protruding surface atoms. Concurrently, the plasma density was found to enhance the in-plane diffusion of these atoms, leading to improved surface smoothness. Moreover, we propose to use a single crystal silicon substrate as the support structure to circumvent the deformation in shape precision, which reduced the PV value from 210.7μm to 5.2μm in a polishing experiment. Finally, it was demonstrated that parallel line scanning facilitates efficient, high-quality polishing of large-area specimens. The PV value within a circular area of 26 mm radius reached 11.063μm by adopting the proposed approach.