Effect of Proton Radiation on Mechanical Structure of Silicon MEMS Inertial Devices

Abstract

This article investigates the effect of proton radiation on the mechanical structure of microelectromechanical systems (MEMS) inertial devices, including gyroscopes and accelerometers. To distinguish the effect of radiation on MEMS element and the circuit, the mechanical part and electronics are shielded by an aluminum barrier separately in the experiments where 7-Mev protons with a dose rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> p/(cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}\cdot s$ </tex-math></inline-formula> ) are utilized. The results show that proton radiation on the MEMS mechanical structure may not cause device function failure or output drift but increase the white noise. The angle random walk and bias stability of the MEMS gyroscopes exhibit a linear relationship with the proton dose rate. Based on these observations, we propose a particle collision model to describe this effect for the first time. The radiation noise can dominate the output noise when the dose rate is more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.1\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> p/(cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}\cdot s$ </tex-math></inline-formula> ) for the custom-designed gyroscopes. However, this phenomenon is not found in the accelerometers since the radiation noise did not exceed the inherent device noise level. Finally, in order to evaluate the effects of proton radiation caused by the application-specific integrated circuit (ASIC), the ASIC is exposed alone to protons, which makes the device’s output abnormal such as spikes, drift, and even failure. These findings discriminate the different effects of MEMS structure and circuit on device performance under irradiation and also give guidance to determine the radiation failure mechanism of MEMS inertial devices.