Designing radiation-resistant multilayer MEMS covers taking into account thermomechanical limitations

A new approach to radiation protection of MEMS devices in conditions of strict size requirements is proposed. This article solves the problem of the occurrence of thermal stresses caused by ionizing radiation from outer space. The thermomechanical behavior of a multilayer cover for protecting MEMS devices under high thermal loads has been numerically and analytically investigated. COMSOL Multiphysics modeling method has studied structures based on thin films of W, Mo, Ti, Si₃n₄, sio₂ on Si and SiC substrates. It is established that the main source of stress is the incompatibility of thermal deformations of the layers. The maximum stresses are localized in the upper metal layers and increase linearly with temperature. System parametric optimization has shown that the Young's modulus of the substrate affects the stresses more strongly than its KTLR. The introduction of an intermediate Mo layer and the optimization of the thicknesses of metal films (increasing the thickness of W and Mo, reducing the thickness of Ti) provided a twofold increase in the safety margin. The reliability of the structure can be increased by matching the properties of the substrate and the thicknesses of the layers without complicating the architecture. An analytical model with separation into membrane and flexural components is proposed for estimating thermoelastic stresses in multilayer MEMS structures in the temperature range of 300-500 K.