A sub-fF capacitive fingerprint sensor with neighbor pixel difference sensing

A neighbor pixel difference sensing scheme is proposed for sub-fF detectability in the capacitive fingerprint sensor chip. A proof-of-concept chip with 16 × 16 sensing pixels is designed with 0.18μm 1P6M CMOS process. The output range is 0.61–1.22 V at 1.8 V power supply. A sensitivity of 0.61 mV/af is achieved for capacitance difference ranging from −500 aF to 500 aF.