Dimensional dependence of the radiation damage in microelectromechanical system resonators

The effect of 10 keV x-ray and 255 nm UV radiation on MEMS resonators of different sizes were tested. The change in resonance frequency of the resonator during and after radiation was tracked, and a dimensional dependent resonance frequency reduction was observed for both x-ray and UV irradiation. The dimensional dependence of the resonance frequency shift indicates that surface effects are an important factor in both types of radiation damage. We propose two theoretical models that successfully explain the dimensional dependencies of x-ray and UV radiation damage. The x-ray model is based on hydrogen diffusion in silicon and the UV model is based on radiation induced charging of the native oxide. The models show that larger surface-to-volume ratio devices are more susceptible to radiation and need to be considered when scaling MEMS devices.