Researches of a novel 2D CMOS thermal based accelerometer

Conventionally the accelerometer behaves like a spring - mass system and its structures involve solid proof mass, which is allowed to move under acceleration conditions. In this paper, we design and fabrication a novel thermal-bubble-based micromachined accelerometer with advantages of minimum solid thermal conductance and high sensitivity successfully. The proposed accelerometer based on thermal convection creates a tiny heated air bubble hermetically sealed inside the sensor package cavity. Four thermopiles around the center heater serve as the temperature sensors to detect two-dimension motion of the chip and also are adequately applied to the technology of inclinometers, anemometers and flow meters. A new micro-link structure is also proposed to enhance the construction of accelerometer with the micro heater and two pairs of thermopiles floating over an etched cavity. The heater and the thermopiles are connected by network-like structure of micro-links, which enhance the structure and greatly reduce the solid heat flow from the heater to the hot junctions of thermopiles. The samples are fabricated by TSMC 0.35μm 2P4M CMOS process which is provided by CIC with outstanding strong structures and uniform quality. Our design is proved to be adequate for commercial batch production. We measure the output signal by inclining the sensor to evaluate the performance of this accelerometer.