On-Display Transparent Half-Diamond Pattern Capacitive Fingerprint Sensor Compatible With AMOLED Display

The need for personal security in portable devices has increased. Among several biometric sensing technologies, fingerprint sensing is the most highlighted method. However, a fingerprint sensor in electronics is stifling the demands for a larger interactive display. In this paper, the bottlenecks of placing the sensor on display is discussed, and an on-display mutual capacitive high-resolution transparent fingerprint sensor with a half-diamond pattern is proposed for adapting to the needs of personal security on a larger screen. To overcome various performance limitations on the on-display fingerprint sensor, a metal mesh is used as an electrode material, and the half-diamond pattern is applied. The proposed pattern is compatible with the diamond-patterned active matrix organic light emitter diode display. The proposed sensor has $72\times72$ channels in a 6 mm $\times6$ mm area. The sensor satisfies the criteria set by the Federal Bureau of Investigation for fingerprint sensing with 322 capacitors per inch, and the measured transmittance in the visible light region is 79.7%. The proposed sensor achieved a capacitance variation 2.3 times larger than that achieved by the conventional sensor. The five-channel fingerprint sensing circuit to examine the feasibility of fingerprint detection is fabricated with the TSMC 0.18- $\mu \text{m}$ process.