Highly-reliable electrostatic actuator using filleted electrode made with photoresist solvent reflow

This paper describes a simple 3-mask fabrication process to construct a highly-reliable, large deflection (> 8 μm) and high frequency (> 90 kHz) electrostatic (ES) actuator. The ES actuator consists of a high residual stress dielectric diaphragm and an electroplated nickel electrode separated by an electrostatic air gap defined by sacrificial photoresist (PR). Actuators with filleted electrodes were created using solvent reflow of sacrificial photoresist. The process has moderately high yield of greater than 64%. The filleted electrode enables the actuator to be continuously actuated for more than 43 days without any diaphragm breakage or stiction.