Off-chip actuation for angular position control of MEMS mirrors

This paper reports on semi-permanent angular positioning of hinged or compliant, polysilicon plates by using off-chip generated ultrasonic and electrostatic forces. Building upon our previous results of realizing 90deg vertical assembly, we now show how intermediate angles can be realized by built-in stops for the moving plate. By novel lock-in structures and pulsed actuation, the mirrors can be trapped and freed from different rotation angles, such that zero static power is needed to maintain an angular position. Moreover, lack of on-chip actuators and electrical interconnects on the die enable the realization of very high-fill factors.