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 ar ray of pixels, and each pixel contains a sensing element and a processing e lement. 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-are a sensor without a large increase of chip size and ensures high sensor sens itivity while maintaining a high image density. The sensing element is cove red with a hard film to prevent physical and chemical degradation and surro unded by a ground wall to shield it. The wall is also exposed on the chip s urface to protect against damage by electrostatic discharges from the finge r contacting the chip. A 15 x 15 mm(2) single-chip fingerprint sensor/ident ifier LSI was fabricated using 0.5-mu m standard CMOS with the sensor proce ss. The sensor area is 10.1 x 13.5 mm(2). The sensing and identification ti me 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%.