Design and simulation of Tri-morph based MEMS thermal sensor for harsh environment

Abstract

Cantilever beam is an important basic structure of micro-electro-mechanical system thermal devices. Tri-morph cantilever beam is a combination of three metals or composites bonded in stack. This paper describes the design, model and simulation of high temperature Tri-morph with piezoelectric sensing technique which works as thermal sensor. Three proposed composite layers namely Titanium Nitride (TiN), Beryllium Oxide (BeO) and Silicon Carbide(SiC) are arranged in order of their thermal expansion coefficients. The Tri-morph cantilever beam is embedded with piezoelectric material Barium Titanate (BaTiO ₃ ) in middle layer. To enhance the temperature range thermal insulation of ceramic Al ₂ O ₃ -SiO ₂ composition is sputtered all-around piezoelectric material BaTiO ₃ . The structure is grown over substrate Alumina which is also thermally insulated. Bernoulli-Euler beam equation has been used for deflection and strain analysis at the point of piezoelectric sensor location. The charge conversion from strain induced using basic piezoelectric equation has been studied. The stress, deflection and piezoelectric voltage output with varying temperature have been analyzed. Verification has been performed by comparing analytic results with simulation results. With material properties and simulation results it is concluded that sensor should perform well upto temperature range of 2100K.