Deep reactive ion etching (DRIE) process is specially invented for bulk micromachining fabrication with the objective of realizing high aspect ratio microstructures. However, various tolerances, such as slanted etched profile, uneven deep beams and undercut, cannot be avoided during the fabrication process. In this paper, the slanted etched profile fabrication tolerance with its effect on the performances of lateral comb-driving resonator, in terms of electrostatic force, mechanical stiffness, and resonance frequency, are discussed. It shows that comb finger with positive slope generates larger electrostatic force. The mechanical stiffness along lateral direction increases when the suspended beam slants negatively. The resonance frequency is 1.116 times larger if the comb finger and beam are tapered to -20and + 20, respectively. These analytical results can be used to compensate the fabrication tolerances at design stage and allow the resonator to provide more predictable performance.
Characterization of Capacitive Comb-finger MEMS Accelerometers