Electrostatic frequency tuning of thermal piezoresistive MEMS resonators

This paper presents a new technique for electrostatic tuning of the resonant frequency of in-plane thermal piezoresistive microelectromechanical resonators. The tuning method is based on applying a DC bias voltage between the underlying SOI handle layer and the suspended resonant structure. The DC bias voltage produces an electrostatic force which causes the bending of the resonant structure in the out of plane direction. The resulting stress in the structure causes a shift in its resonant frequency. The experiments were taken place under both atmospheric pressure and partial vacuum. Maximum upward and downward frequency shifts of +580ppm and -430ppm have been demonstrated. As a side product, due to minimized air damping, more than 2X resonator Q improvement was observed while tuning the resonator frequency.