A single-chip fingerprint sensor and identifier

A chip architecture that integrates a fingerprint sensor and an identifier in a single chip is proposed. The fingerprint identifier is formed by an array of pixels, and each pixel contains a sensing element and a processing element. The sensing element senses capacitances formed by a finger surface to capture a fingerprint image. An identification is performed by the pixel-parallel processing of the pixels. The sensing element is built above the processing element in each pixel. The chip architecture realizes a wide-area sensor without a large increase of chip size and ensures high sensor sensitivity while maintaining a high image density. The sensing element is covered with a hard film to prevent physical and chemical degradation and surrounded by a ground wall to shield it. The wall is also exposed on the chip surface to protect against damage by electrostatic discharges from the finger contacting the chip. A 15×15 mm² single-chip fingerprint sensor/identifier LSI was fabricated using 0.5-μm standard CMOS with the sensor process. The sensor area is 10.1×13.5 mm². The sensing and identification time is 102 ms with power consumption of 8.8 mW at 3.3 V. Five hundred tests confirmed a stranger-rejection rate of the chip of more than 99% and a user-rejection rate of less than 1%