Average power control and positioning of polysilicon thermal actuators

This paper reports on characterizing and modeling the behavior of micromachined polysilicon thermal actuators when driven by DC or pulsed drive signals. Thermal actuators can be controlled and positioned using a pulsed input with a period much less than the thermal time constant of the device as demonstrated by data collected in air and vacuum. Both pulse width and pulse amplitude modulation were successfully employed to position lateral actuators, lateral actuator arrays, and piston micro-mirrors. A SPICE model for polysilicon thermal actuators was developed using relationships between resistance, deflection, and average power. This model incorporates the polysilicon thermal actuator's electrical load, transient response, and deflection characteristics necessary for predicting actuator performance and developing microsystems. The SPICE model exhibits very close agreement with the measured performance of the polysilicon thermal actuators. Published by Elsevier Science S.A.