Use of SU-8 photoresist for very high aspect ratio x-ray lithography

摘要

This paper describes the process of deep x-ray lithography using epoxy negative photoresist SU-8. Coating, softabake, exposure, post exposure bake, and developmnet of the resist is characterized. Influence of x-ray source spectrum on the lithographic image contrast is calculated and optimal c-ray mask layers compositions for the spectrum in use are proposed. Method for resist film thickness control during casting step is reported. Temperature limit of the post exposure bake was found to ensure safe post bake to obtain maximum resistssensitivity. Optimized development and rinsing process is presented. Resist structures with aspect ratio as high as 100:1 (height: width) are demonstrated.