Temperature Gradient Method for Alleviating Bonding-Induced Warpage in a High-Precision Capacitive MEMS Accelerometer

Capacitive MEMS accelerometers with area-variable periodic-electrode displacementtransducers found wide applications in disaster monitoring, resource exploration and inertialnavigation. The bonding-induced warpage, due to the difference in the coefficients of thermalexpansion of the bonded slices, has a negative influence on the precise control of the interelectrodespacing that is essential to the sensitivity of accelerometers. In this work, we propose the theory,simulation and experiment of a method that can alleviate both the stress and the warpage byapplying different bonding temperature on the bonded slices. A quasi-zero warpage is achievedexperimentally, proving the feasibility of the method. As a benefit of the flat surface, the spacing ofthe capacitive displacement transducer can be precisely controlled, improving the self-noise of theaccelerometer to 6 ng/√Hz @0.07 Hz, which is about two times lower than that of the accelerometerusing a uniform-temperature bonding process.