Electric field fingerprint sensor having enhanced features and related methods
DCFirst Claim
1. A fingerprint sensor comprising:
- a substrate;
a plurality of semiconductor devices on said substrate and defining active circuit portions;
a first metal layer on said substrate interconnecting predetermined ones of said plurality of semiconductor devices;
a first dielectric layer on said first metal layer;
a second metal layer on said first dielectric layer defining a ground plane;
a second dielectric layer on said second metal layer; and
a third metal layer on said second dielectric layer and comprising an array of electric field sensing electrodes connected to active circuit portions for generating signals related to a sensed fingerprint.
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Accused Products
Abstract
A fingerprint sensor includes a plurality of semiconductor devices adjacent a substrate and defining active circuit portions, and having only three metal layers. More particularly, the sensor may include a first metal layer interconnecting predetermined ones of the plurality of semiconductor devices; a second metal layer defining a ground plane; and a third metal layer comprising an array of electric field sensing electrodes connected to active circuit portions for generating an output related to a sensed fingerprint. The fingerprint sensor may also include a package surrounding the substrate and having an opening aligned with the sensing electrodes. In addition, a first external electrode may be carried by the package for contact by a finger. The sensor may thus also include an excitation drive circuit connected between the ground plane and the first external electrode for generating electric fields between the electric field sensing electrodes and adjacent finger portions. A power control circuit is for controlling operation of active circuit portions based upon sensing finger contact with the first external electrode so that the active circuit portions are powered upon sensing finger contact with the first external electrode and otherwise grounded. A second external electrode may be connected to a bleed resistor to bleed charge from the finger prior to switching from the grounded to the powered state. An amplifier connected between each electric field sensing electrode and associated shield electrode may be operated at a gain of greater than one for additional noise rejection.
284 Citations
36 Claims
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1. A fingerprint sensor comprising:
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a substrate; a plurality of semiconductor devices on said substrate and defining active circuit portions; a first metal layer on said substrate interconnecting predetermined ones of said plurality of semiconductor devices; a first dielectric layer on said first metal layer; a second metal layer on said first dielectric layer defining a ground plane; a second dielectric layer on said second metal layer; and a third metal layer on said second dielectric layer and comprising an array of electric field sensing electrodes connected to active circuit portions for generating signals related to a sensed fingerprint. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A fingerprint sensor comprising:
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a substrate; a plurality of semiconductor devices adjacent said substrate and defining active circuit portions for generating an output related to a sensed fingerprint; a package surrounding said substrate; a first external electrode carried by said package for contact by a finger; and power control means for controlling operation of active circuit portions based upon sensing finger contact with said first external electrode. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A fingerprint sensor comprising:
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a substrate; a plurality of semiconductor devices adjacent said substrate and defining active circuit portions for generating an output related to a sensed fingerprint; a package surrounding said substrate; finger charge bleed means for bleeding a charge from a finger upon contact therewith to protect the active circuit portions, said finger charge bleed means comprising a second external electrode carried by said package for contact by a finger and a charge bleed resistor connected between said second external electrode and an earth ground. - View Dependent Claims (23, 24, 25)
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26. A fingerprint sensor comprising:
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a substrate; at least one electrically conductive layer adjacent said substrate and comprising portions defining an array of pairs of electric field sensing electrodes and associated shield electrodes; and a respective amplifier connected between each pair of electric field sensing electrodes and associated shield electrodes, each amplifier having an amplification gain greater than about one to thereby increase noise rejection. - View Dependent Claims (27, 28)
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29. A method for making a fingerprint sensor comprising the steps of:
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forming a plurality of semiconductor devices on a substrate and defining active circuit portions; forming a first metal layer on the substrate interconnecting predetermined ones of the plurality of semiconductor devices; forming a first dielectric layer on the first metal layer; forming a second metal layer on the first dielectric layer defining a ground plane; forming a second dielectric layer on the second metal layer; and forming a third metal layer on the second dielectric layer and comprising an array of electric field sensing electrodes connected to active circuit portions for generating signals related to a sensed fingerprint. - View Dependent Claims (30, 31, 32, 33)
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34. A method for controlling operation of a fingerprint sensor of a type comprising a plurality of semiconductor devices on a substrate and defining active circuit portions for generating an output related to a sensed fingerprint, a package surrounding the substrate, a first external electrode carried by the package for contact by a finger, and power control means positioned on the substrate and connected to the active circuit portions, the method comprising the steps of:
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only powering active circuit portions upon sensing finger contact with the first external electrode to thereby conserve power; and grounding active circuit portions upon not sensing finger contact with the first external electrode. - View Dependent Claims (35)
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36. A method of increasing noise rejection in a fingerprint sensor of a type comprising a substrate, and at least one electrically conductive layer adjacent said substrate and comprising portions defining an array of electric field sensing electrodes, the method comprising the steps of:
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forming a shield electrode for each respective electric field sensing electrode; forming a respective amplifier connected between each pair of electric field sensing electrodes and associated shield electrodes; and operating each amplifier at an amplification gain greater than about one to thereby increase noise rejection.
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Specification