Single layer thin photoresist soft etch mask for MEMS applications

Substrate masking plays an important role in wet chemical etching process, however; coating a cost effective masking material with higher stability in the harsh chemical environment is still a challenge in MEMS technology. The durability of a masking material is determined by its capability in withstanding harsh chemicals, whether the material is a soft mask, hard mask or even a metal mask. Conventional substrate masking over wafers includes metal masks or thick photoresist (PR) masks or even multilayer masking. This paper presents an efficient procedure for substrate masking using an uncommon, less viscous photoresist. The optimization results of this photoresist have been reported in this paper. By optimization, an optimal procedure to withstand the PR in harsh chemicals was formulated. The method is highly reliable and cost effective. This procedure was implemented for different MEMS applications to prove the feasibility of substrate masking.