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

摘要

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℃. 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 multiple-height 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.