Magnetoresistive semiconductor pressure sensors and fingerprint identification / verification sensors using same

• US 20050199072A1
• Filed: 05/05/2005
• Published: 09/15/2005
• Est. Priority Date: 07/20/1999
• Status: Active Grant

• Current Assignee: Lenovo PC International Limited (Lenovo Group Ltd.)
• Original Assignee: Fidelica Microsystems, Inc. (Petters Group Worldwide LLC)
• Inventors: Ganapathi, Srinivasan K.
• Granted Patent: US 7,077,010 B2
• Time in Patent Office: Days
• US Class Current: 73/754
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01L 1/125 by using magnetostrictive means magnetostrictive sensors H10N35/101

Abstract

The present invention is directed to a method of sensing pressure in which applied pressure causes a change in the magnetization vector of a magnetoresistive layer within the device and a corresponding change in resistance. The method includes providing a sensing device with a sensor including plurality of layers, the plurality of layers comprising a non magnetic conducting layer disposed between a magnetoresistive layer with non-zero magnetostriction and a ferromagnetic biasing layer. Once provided, the method then includes sensing a resistance in the plurality of layers upon application of pressure to the sensing device, the applied pressure causing the magnetization vector of the magnetoresistive layer to change and thereby result in a change in resistance.

Claims

1. A method of sensing pressure in which applied pressure causes a change in the magnetization vector of a magnetoresistive layer within the device and a corresponding change in resistance comprising the steps of:

providing a sensing device with a sensor including plurality of layers, the plurality of layers comprising a non magnetic conducting layer disposed between a magnetoresistive layer with non-zero magnetostriction and a ferromagnetic biasing layer; and

sensing a resistance in the plurality of layers upon application of pressure to the sensing device, the applied pressure causing the magnetization vector of the magnetoresistive layer to change and thereby result in a change in resistance.

2. A method according to claim 1 wherein the sensing device includes a plurality of sensors that are formed and operate as the one sensor such that each sensor detects the pressure of an area associated with that sensor.

3. A method according to claim 1 further comprising the step of sensing an initial resistance of the device when the pressure to be sensed is not applied to the magnetoresistive layer.

4. A method according to claim 3 further comprising the step of determining the pressure applied to the sensing device, the step of determining using both the initial resistance and the sensed resistance in order to minimize the influence of external conditions on the determined pressure.

5. A method according to claim 4 wherein the sensing device includes a plurality of sensors that are each formed and operate as the one sensor such that each sensor detects the pressure of an area associated with that sensor.

6. A method according to claim 5 wherein the method senses pressure applied during the obtaining of a fingerprint and further includes the step of using the resistance sensed by each sensor to determine the fingerprint.