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Significance Statement
Micro pore optics (MPO) has been used as an X-ray imaging system in space exploration. The dominating commercial products are made of glass through drawing and stacking process, though much effort has been made to fabricate MPO using other techniques which are still in the stage of research. X-ray lithography is employed to fabricate MPO in our study. Basically, it may provide square pores with more accurate position leading to an improvement in telescope resolution. The sidewall surface roughness of MPO plates should be paid more attention since these surfaces are used as mirrors to reflect X-ray. A root mean square (RMS) roughness below 10 nm of the MPO plate sidewalls can be obtained directly from the conventional process because the sidewall roughness of the PMMA columns used as a mold for subsequent electroplating is in the same level. Post polishing of the sidewalls is supposed to be necessary since the requirement for the roughness is around 1 nm for application. X-ray lithography is believed to be a promising technique for the fabrication of MPO and other similar metal structures with high aspect ratio.
Microsystem Technologies, 2014, Volume 20, Issue 10-11, pp 2005-2010.
Tianchong Zhang, Futing Yi, Bo Wang, Jing Liu, Marina Ashmkhan, Xinshuai Zhang.
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
Abstract
Micro pore optics (MPO) as an X-ray imaging system is perfectly suited for the applications in space telescopes due to its light-weight and high-resolution properties. We report the fabrication of MPO samples by LIGA process focusing on its sidewall surface used as mirrors for X-ray reflection. An intermediate mask is fabricated and used to obtain the working mask in order to avoid the UV exposure to a very thick photo resist layer. Around 400 um-thick nickel MPO plate is obtained with the aspect ratio of the square pore and sidewall of 8 and 32, respectively. The root mean square roughness of the sidewall surface is below 10 nm in a 5 × 5 um2 region. Some striations are found on the sidewall surface originating from the jagged edge of the chromium coating on the UV mask.