Modeling and characterization of a CMOS sensor with surface trenches for high-pressure applications

This paper reports on the systematic characterization and modeling of a CMOS-based sensor for high-pressure applications. The sensor consists of an anodically bonded silicon-glass stack comprising an n-type Wheatstone bridge as the piezoresistive stress-sensing element. Surface trenches introduced into the silicon close to the Wheatstone bridge significantly increase the pressure sensitivity of the device. Pyrex (PX) and SD2 glass substrates are compared in this study with respect to the sensor performance. The sensors were characterized for the first time at temperatures between -40°C and 125°C and hydrostatic pressures up to 600 bar. Experimental results are compared with a theoretical sensor model based on finite element (FE) simulations. The extracted sensitivities at 25°C are 20.7 μV/V/bar and 9.68 μV/V/bar for sensors built on PX and SD2 substrates, respectively. Long-term measurements reveal an insignificant signal drift.