Temperature compensation of silicon micromechanical resonators via degenerate doping

We report on the degenerate doping of a silicon resonator as a new method for reducing its temperature coefficient of frequency (TCF). This is the first TCF reduction technique reported till date that takes advantage of free charge carrier effects on the elastic constants of silicon. The TCF of silicon bulk acoustic resonators (SiBAR) are reduced from -29 ppm/°C to -1.5 ppm/°C on 5 ¿m thick devices using degenerate boron doping and to -2.72 ppm/°C on 20 ¿m thick devices using boron-assisted aluminum doping while maintaining a high quality factor (Q) of 28000 in vacuum.