Dwelling time calculation for film uniformity correction by ion beam sputtering process on larger optical materials

Abstract

It is difficult to obtain film with uniform thickness and constant performance for optical components with larger diameter. It is a critical technology to improve the film uniformity during the deposition process. The ion beam sputtering system was used to prepare the film on the surface of large-aperture optical elements. The performance of film including thickness and roughness were measured by step profiler and optical profilometer instrument. The film thickness correction model was proposed in this paper. The optimized dwell time ratio was obtained by the film thickness data obtained from former experiments, and the dwell time distribution was calculated, after several iteration with the model, uniform film can be achieved on optical elements over 300mm in diameter. Taking the Si film on the surface of fused silica as an example. The research results show that, different film thickness between 100nm and 400nm can be obtained, when the film thickness is more than 200 nm, the film uniformity from more than 13% to less than 0.5%. The surface roughness variation of optical material before and after film deposition were studied, which provide stable process for obtaining high performance film on larger optical components.