Fingerprint detector with improved sensing surface layer

摘要

A fingerprint detector device has: (i) a semiconductor substrate; (ii) an array of capacitive sensor cells formed on the substrate; (iii) a tungsten grid having grid lines (96) surrounding each cell, and a peripheral ground line (98); and (iv) an alumina layer disposed above the cell. The grid is embedded in the alumina layer. The alumina layer and the grid have exposed surface portions for contacting a fingerprint of a finger pressed against the detector device. An independent claim is also included for a method of making a fingerprint detector, comprising: (a) providing a semiconductor substrate (50) with transistor regions; (b) forming conductive layers above the substrate to interconnect the transistors; (c) forming a planarized insulating layer above the conductive layers; (d) defining coplanar capacitor plates (76, 78) on the planarized insulating layer with vias (82) through the planarized insulating layer to portions of the conductive layers below; (e) depositing an alumina layer (108) above and insulated from the capacitor plates; (f) defining openings within the alumina layer; (f) depositing a titanium nitride film on the alumina layer and within the openings; (g) depositing a tungsten layer on the titanium nitride layer; (h) selectively etching back the tungsten layer to remove the tungsten except within the openings; and (i) removing the titanium nitride above a surface of the alumina layer.