A CMOS capacitive pressure sensor chip for fingerprint detection

Biometric techniques, such as fingerprint detection, can be applied to identify a specific user for security and safety reasons. We present a capacitive fingerprint sensor that can detect the difference of pressures induced by the ridges and valleys of a finger tip. Post-CMOS fabrication of the 8×32 sensor array is conducted based on wet etch of CMOS metal layers without requiring additional thin-film deposition and patterning. The size of each sensing pixel is 65×65 μm². The measured sensor sensitivity was 0.39 fF/MPa. Part of the fingerprint image was successfully produced by the CMOS sensor chip.