The optimal DRIE parameter for bulk micro-machining process

Deep reactive ion etching (DRIE) process is one of the most popular fabrication techniques due to its flexibility between anisotropic and isotropic etching, and high etching selectivity. The alternating etching cycle flowing only etching gas of SF₆ and then switching to sidewall passivation cycle using only C₄F₈ is used. However, the etching results depend on the process conditions such gas flow rate, electrode power, pressure, temperature and cycling time. The origins of various etching rate together with its effects on the performances of lateral comb-drive sensor, in terms of electrostatic force, mechanical stiffness, stability and displacement, are discussed. The capacitance MEMS sensitivity is decided by comb structure profile, and comb top width and bottom width tolerance are important size. These fabrication tolerances are expected to affect the performances of MEMS devices, this paper using 20% etching ratio to do deep comb structure process and successful to improve the comb structure profile.