In Situ Measurement of 1.8-MeV Proton Radiation Effects on Comb-Drive MEMS Resonators

We report on in situ measurement of proton radiation effects on single-crystal silicon comb-drive resonant microelectromechanical systems (MEMS). The comb-drive resonators are specially designed and can be operated in both linear resonance and large-amplitude contact-impacting (i.e., “tapping”) modes, which offer versatile options for resonant sensing and switching applications. In situ, continuous monitoring of radiation effects induced by impinging 1.8-MeV protons with controlled dosage and exposure time, in both linear and tapping modes of the resonators, have been performed. The resonators exhibit highly sensitive responses in resonance characteristics while maintaining robust operations. For irradiation with a proton flux of
$2.8\times 10^{8}$
cm
$^{-2}\text{s}^{-1}$
, both temporary and permanent radiation effects (i.e., quantified in frequency shift) on the comb-drive MEMS resonators are observed. For irradiation with much higher flux (
$9.1\times 10^{8}$
cm
$^{-2}\text{s}^{-1}$
), the resonance frequency shifts are greater. Based on the transport of ions in matter (TRIM) simulations, we find that the observed radiation effects on resonance frequency could be attributed to a combination of ionizing and displacement damage effects. These in situ observations of radiation effects on comb-drive MEMS resonators show that dynamical MEMS capable of operating in different resonance regimes can be a promising platform for making new types of radiation sensors or radiation-hardened signal processing components.