Design and Characterization of a CMOS Capacitive Sensor Array for Fast Normal Stress Analysis

This letter presents a dense 32 × 32 sensor array integrated in a complementary metal oxide semiconductor process for fast and sensitive detection of contact forces with fine spatial resolution. The sensing membranes made of metal and oxide thin films with a total thickness of 1.9
μ
m are released by wet etch of metal layers. Each sensing pixel is 140 × 140
μ
m
²
in size, leading to an array size of 4.8 × 2.4 mm
²
. The simulated sensing and parasitic capacitance of 63 and 231 fF, respectively, are very close to the measured data. The array exhibited a capacitive sensitivity of 5.8 fF/kPa and an output change of 19.2 mV/kPa based on an integration time of 0.125
μ
s. This letter successfully demonstrated dynamic stress measurements with a maximum frame rate up to 1.8 kHz.