Fabrication of ultra thick, ultra high aspect ratio microcomponents by deep and ultra deep X-ray lithography

Two advanced processes have been developed for fabricating ultra thick and ultra high aspect ratio (HAR) microstructures. One is the SU-8 based deep X-ray lithography (SU-8 based DXRL) process which uses the normal deep X-ray beam to expose the negative SU-8 resist. Another one is wave length shifter(WLS) based Ultra deep X-ray lithography (WLS-UDXRL) process which uses special ultra deep X-ray beam from wave length shifter to expose the positive PMMA resist. For SU-8 based DXRL process, the typical exposure time of a layer of SU-8 is about 1% of that of PMMA. Even for a few millimeters thick resists the exposure time are just a few minutes. In WLS-UDXRL process, the X-ray beam is strengthened by a wave length shifter(WLS) so the required exposure time for ultra thick PMMA is reduced greatly. In the paper, the characteristic of the these two processes are discussed and the examples of the ultra thick and ultra HAR microstructures fabricated by these processes are presented (ultra thick up to 3600 μm and HAR up to 360).