Capacitive sensor array for fingerprint recognition

Touch function is merged into the display for the convenient interfaces between man and machine, particularly in mobile phones. In addition, the fingerprint recognition module is also adopted in mobile phones for the security purpose. In this paper, capacitive sensor arrays of oxide thin film transistors (TFTs) were investigated for fingerprint recognition. For the transparent sensor array, oxide TFT was used and also the transparent indium thin oxide (ITO) electrodes was investigated for 450 × 450 pixel arrays. The simulation results of the sensor array of oxide TFT show that ITO can be used in capacitive pixel sensor arrays to achieve its transparency. The electrode area dependence on the sensing signal was investigated for the various glass thicknesses. The rather thick glass gives much reduced sensing signal and the allowed thickness was lower than 8 μm, therefore, for the high sensing signals the coating material with enough hardness is necessary for the replacement of the cover glass.