A monolithically integrated 3-axis thermal-convective accelerometer with a pneumatically curved thermopile-cantilever for Z-axis sensing

This paper reports a novel monolithic-integrated three-axis convective accelerometer by using a thermopile-embedded curving cantilever for Z-axis sensing. The cantilever down-curving is caused by pneumatic-effect of mutually stress-mismatched two layers. The convective accelerometer consists of a micro heater and several pairs of sensing thermopiles for 3-D temperature-difference detection. In Z-axis acceleration measurement, two pairs of the thermopiles are serially connected as the sensing element. They are located at the ends of the curving cantilevers which are composed of low-stress (LS) SiN/SiOx bi-layer. The structural layer of SiN/SiOx curves down to detect the heat-convection signal in Z-axis. The other two pairs of thermopiles are utilized as reference temperature sensing element and located in the same plane as the micro-heater. The fabricated sensor is tested. Under the heating power of 10mW, the measured X-axis and Y-axis sensitivities are 0.62μV/g/mW and 0.61μV/g/mW, respectively. Under the same condition, the measured Z-axis sensitivity is 0.16μV/g/mW.