Improvement in sidewall roughness of MEMS X-ray optics

Low-cost and high-resolution X-ray optics based on MEMS technologies is proposed and being developed by our group. We have succeeded in soft X-ray imaging using sample optics. However, roughness of the side walls etched through a thin silicon wafer, which are used as X-ray mirrors, limited the image resolution. In this paper, a new process condition is tested in the dry etching process to achieve better resolution. By simply changing the etching mask from aluminum to thick photoresist plus aluminum, the side wall roughness is improved by a factor of ~3 to about 38 nm at 200 um scale.