Multiple-Height Microstructure Fabricated by Deep Reactive Ion Etching and Selective Ashing of Resist Layer Combined with Ultraviolet Curing

Abstract

UV-cured photoresist is applied to the delay masking process to realize a multiple-height microstructure for the first time. Although the UV-cured photoresist is a soft mask, its material property becomes stable against resist thinner and UV exposure. A layered resist pattern can be realized by stacking normal photoresist on the UV-cured photoresist. The UV curing increases the glass transition temperature from 120 to 160 C. By controlling the temperature, the normal photoresist can be ashed twice as fast as the UV-cured photoresist. This selectivity can be combined with the deep reactive ion etching of Si, and a microstructure having three different etching depths is realized, thus forming a micromirror. The multipleheight structure is advantageous for reducing the inertia of the mirror plate. For the same rotational spring constant, the micromirror has a higher resonant frequency, which is required for realizing higher-resolution laser displays. #

A microplasma chip for VUV light source

“…Although the mechanism was not clear yet, turbulence of gas flow might have affected the ignition. The step structures were fabricated by embedded mask technique [9]. Film of resist 1 was patterned and UV cure was applied.…”

“…Deep RIE was conducted using the resist 2 mask. The resist 2 mask was selectively removed due to the difference in ashing rates between with and without UV cure [9]. Deep RIE was conducted again.…”

A spatial light modulator fabricated with bionano-crystallized poly-Si film

“…For the optical application, the Si film should be optically flat. Deformation of the film caused by residual stress should be controlled carefully [4]. In order to fulfill those requirements, attentions should be paid for the crystallization structure in a thin Si film.…”