Gamma Irradiation Effects on Surface-Micromachined Polysilicon Resonators

The effects of gamma irradiation on the resonant frequency of a surface-micromachined polysilicon doubly clamped resonator are examined by a laser Doppler vibrometer. The resonant frequency of the resonator decreases by 2.1% for the 500-μm-long beam and 2.7% for the 300- μm-long beam after 32-krad (Si) gamma irradiation. The residual strains of the surface-micromachined polysilicon beams, which are estimated through the change of the resonant frequency, decrease by 2.7% and 5.4% for the 500- and 300-μm-long beams, respectively. Radiation effects of the polysilicon beams have been explained in terms of injection annealing.