Resonant Frequency Tuning of Torsional Microscanner by Mechanical Restriction using MEMS Actuator

Abstract

We have demonstrated resonant frequency-tuning of electrostatic torsional microscanners actuated by the staggered vertical comb (SVC) sets. Mechanical restriction unit composed of thermal actuator, scissor mechanism and shaft-holder is used for continuous and reversible resonant frequency tuning. The microscanner and tuning mechanism are fabricated on single crystal silicon of double Silicon-On-Insulator (DSOI) wafer in order to make vertically self-aligned comb sets and electrically insulate the electrostatic microscanner from the thermally actuated tuning unit to prevent charge leakage. The microscanner is actuated at a resonant frequency of 1.698 kHz under driving voltages of 5 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</sub> and 10 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> without frequency tuning. As the stiffness of a torsional spring is modified gradually through the shaft-holding flexure operated by thermal actuator, the resonant frequency of the torsional microscanner is shifted up to 1.880 kHz showing the maximum tuning ratio of 10.7%.