A Novel Two-Axis CMOS Accelerometer Based on Thermal Convection

Accelerometers based on thermal convection use a tiny bubble of heated air and pairs of temperature sensors hermetically sealed inside the sensor package cavity. In this paper, we successfully design and fabricate a novel thermal-bubble-based micromachined accelerometer with the advantages of minimized solid thermal conductance and higher sensitivity. The proposed accelerometer consists of a microheater and two pairs of thermopiles floating over an etched cavity and is constructed by our proposed microlink structure. Two-dimensional acceleration detection is easily realized using the microlink structure, and it can be applied to the technology of inclinometers, anemometers, and flowmeters. The heater and thermopiles are connected by netlike microlink structures, which enhance the structure and greatly reduce the solid heat flow from the heater to the hot junctions of the thermopiles. The samples are fabricated by the TSMC 0.35-mum 2P4M CMOS process, which has been provided by the national chip implementation center (CIC). Our design has proved to be applicable for commercial batch production with outstanding strong structures and uniform quality. We measure the output signal by inclining the sensor to evaluate the performance of this accelerometer. The best sensitivity of 22 muV/g was obtained from acceleration versus output voltage under several experimental conditions.