Lightuning Tech. Inc.

Ligh Tuning Technology Inc.

Wallace Y W Cheng

Bruce C S Chou

Chen-Chih Fan

Ben S B Chang

Ben Chang

A capacitive fingerprint sensor includes a plurality of capacitive sensing members arranged in a 2D array. A charge-sharing principle is utilized to read signals in the capacitive sensing member. Each capacitive sensing member includes an insulating surface layer, a sense electrode, a reference electrode, a reference capacitor, and a signal reading circuit. The sense electrode is below the insulating surface layer. When a finger contacts the insulating surface layer, a sense capacitor is formed therebetween. The reference capacitor is connected between the reference and sense electrodes. The signal reading circuit is connected to the sense and reference electrodes, repeatedly provides control signals to charge the reference capacitor and then enable the reference and sense capacitor to share charges. Finally, the sense voltage of the sense electrode may be read.

Capacitive fingerprint sensor

A chip-type sensor against ESD and stress damages and contamination interference includes a substrate structure and a protection layer covering over the substrate structure. The protection layer includes, from bottom to top, a first layer for providing a first stress against the substrate structure, a second layer for providing a second stress against the substrate structure, and a third layer for providing a third stress against the substrate structure. The first stress and the third stress belong to one of a tensile stress and a compressive stress, and the second stress belongs to the other of the tensile stress and the compressive stress.

Chip-type sensor against ESD and stress damages and contamination interference

A capacitive fingerprint sensor against ESD damage and contamination interference includes a substrate, a plurality of plate electrodes, a metal mesh, a plurality of ESD units, a plurality of bonding pads, and a protection layer. The plate electrodes, bonding pads and metal mesh are positioned on the substrate at the same level, and are composed of the same material. The ESD units are connected to the metal mesh that is conducted to the ground, and are exposed via a plurality of first openings. Thus, electrostatic charges from a finger may be discharged through this path to the ground. The metal mesh is covered by the protection layer and is not exposed. The number of the ESD units is far less than that of the plate electrodes so as to reduce the contamination interference on the captured fingerprint image.

Capacitive fingerprint sensor against ESD damage and contamination interference

The present invention provides a fabrication method of a pressure type fingerprint sensor, which uses the commercial integrated circuit process to form the sensor and the processing circuit together on the same chip. The present invention comprises a plurality of capacitive pressure sensors arranged in a 2-D array and applies the charge sharing principle to each capacitive pressure sensor for signal reading. The main structure of each pressure sensor is a pair of plate electrodes with an air gap between them to form a plate sensor capacitor, wherein the plate electrodes comprise a floating electrode and a fixed electrode. When the finger ridge contacts the floating electrode, the pressure from the finger changes the spacing of the air gap so as to change the capacitance of the plate sensor capacitor. The 2-D sensor array can read the 2-D pressure distribution pressed by the finger ridge to construct the fingerprint pattern.

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Hsinchu, Taiwan

Wallace Y W Cheng