Surface carrier concentration effect on elastic modulus of piezoelectric MEMS silicon cantilevers

This paper provides experimental observation of the variation of the silicon elastic modulus with changing near surface carrier concentration. A piezoresistive MEMS cantilever is used that can simultaneously detect resistance and resonant frequency to probe the correlation between the electrical and mechanical properties of silicon under UV irradiation. Since both resistance and resonant frequency are sensitive to UV's thermal power, an identically processed reference device is used to separate optical effects from thermal effects and other environmental changes. Theory shows that charge carrier generation near the Si surface modifies the elastic modulus in agreement with our observed data.