Ultra-small high‐temperature pressure sensor chips fabricated in single‐layer (111) SOI wafers
Peng Li, Wei Li, Changnan Chen, Ke Sun, Min Liu, Zao Ni, Jiachou Wang, Xinxin Li
Abstract
Abstract This paper presents a 0.5 mm × 0.5 mm tiny-sized high-temperature piezoresistive pressure sensor fabricated with a thin-film under bulk single-sided micromachining process from the front-side of single-layer (111) silicon on insulator (SOI) wafer. The (111)-device layer of the SOI wafer is specifically selected to optimize the piezoresistor performance where the SiO 2 buried layer isolates the piezoresistors from the handle substrate. And the (111)-handle layer is employed to subtly construct a single-crystalline-silicon beam-island combining with a very thin but uniform poly-silicon diaphragm for realization of both low nonlinearity and high sensitivity. Without double-sided micromachining process and wafer bonding used, a tiny sensor-chip size of 0.5 mm × 0.5 mm is achieved, which is required in wind-tunnel systems for measuring pressure distribution at high temperature. The testing results of the fabricated sensor show high sensitivity of 0.15 mV V −1 kPa −1 for 150 kPa measure range and satisfactory linearity of ±0.11% FS (full scale) at ambient temperature. At 350 °C, the overall accuracy is 0.17% FS and the thermal hysteresis is 0.22% FS. The temperature coefficient of zero-point offset of the sensor is tested as low as 0.01% °C −1 FS and the temperature coefficient of sensitivity is −0.07% °C −1 FS within the whole temperature range from −55 °C to 350 °C. Featuring the advantages of high accuracy and high-yield low-cost fabrication, the tiny-sized high-temperature pressure sensors exhibit promising perspectives in the field of aerospace industry including wind-tunnel applications.