Quasi-3D microstructure fabrication technique utilizing hard X-ray lithography of synchrotron radiation

Quasi-three-dimensional (3D) microstructure fabrication technique utilizing hard X-ray lithography (HXL) has been developed. In this technique, as the intensity distribution of the X-rays is controlled by a newly developed bending mirror, the exposure residual depth of polymethyl methacrylate (PMMA) resist is controlled over the exposed area. The maximum difference of depths was approximately 50 mum over the large area more than 60 mm (horizontal) x 5 mm (vertical). We also investigated the effects of controlling the beam intensity distribution for exposure changing X-ray mask absorber shapes and angle on the obtained quasi-3D resist pattern shapes. As the results, Quasi-3D PMMA patterns with inclined shape sidewall and graded depths were successfully fabricated. We believe this technique greatly expands applications of LIGA process.