SENSITIVITY CAPACITIVE SENSOR

• US 20080157787A1
• Filed: 01/03/2007
• Published: 07/03/2008
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Cufer Asset Ltd LLC (Intellectual Ventures LLC)
• Original Assignee: Cubic Wafer, Inc.
• Inventors: Trezza, John, Misra, Abhay
• Granted Patent: US 7,705,613 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49144 by metal fusion

Abstract

A method of creating an improved sensitivity capacitive fingerprint sensor involves forming vias from a first side of a sensor chip having an array of capacitive sensors, making the vias electrically conductive, and attaching a cover plate over the first side of the sensor chip spaced from the sensor chip by a distance of less than 25 μm. An improved sensitivity capacitive fingerprint sensor has a capacitive sensor array including multiple sensor cells and electrically conductive, through-chip vias extending from connection points for sensor cell circuitry to a back side of the capacitive sensor array, a chip including active detection circuitry and electrical connection points, the electrical connection points being respectively connected to corresponding ones of the sensor cell circuitry connection points, and a cover plate, disposed above the sensor cells at a spacing of less than 25 μm.

Claims

1. A method of creating an improved sensitivity capacitive fingerprint sensor comprising:

forming vias from a first side of a sensor chip, the sensor chip having an array of capacitive sensors useful for fingerprint detection, the vias extending from the first side to a side opposite the first side;

making the vias electrically conductive in order to form complete electrical connections extending from contacts on the first side through the vias to the side opposite the first side; and

attaching a cover plate over the first side of the sensor chip and spaced from the sensor chip by a distance of less than 25 μ

m.

2. The method of claim 1, further comprising:

attaching the sensor chip to electronic detection circuitry that, when operating, will receive values from the capacitive sensors indicative of the presence of ridges and valleys when a finger is brought into contact with the cover plate.

3. The method of claim 1, wherein the sensor chip is one of multiple sensor chips formed on a wafer, and wherein the method comprises:

after the attaching the cover plate, dicing the wafer so at to separate the sensor chip from others of the multiple sensor chips.

4. The method of claim 1, wherein the attaching the cover plate occurs before the attaching the sensor chip to electronic detection circuitry.

5. The method of claim 1, wherein the attaching the cover plate occurs before the attaching the sensor chip to the electronic detection circuitry.

6. The method of claim 1, wherein, prior to attaching the cover plate, the method comprises:

attaching a standoff configured to separate the cover plate from the array of capacitive sensors by a distance.

7. The method of claim 1, wherein the distance that the cover plate is spaced from the sensor chip is less than 10 μ

m.

8. The method of claim 1, wherein the distance that the cover plate is spaced from the sensor chip is as minimum as allowed by a topography of the sensor chip.

9. An improved sensitivity capacitive fingerprint sensor comprising:

a capacitive sensor array including multiple sensor cells and having electrically conductive, through-chip vias extending from connection points for sensor cell circuitry to a back side of the capacitive sensor array;

a chip including active detection circuitry and electrical connection points, the electrical connection points being respectively connected to corresponding ones of the sensor cell circuitry connection points so as to form an electrical path therebetween; and

a cover plate, disposed above the sensor cells at a spacing from a bottom side of the cover plate to the sensor cells of less than 25 μ

m.

10. The improved sensitivity capacitive fingerprint sensor of claim 9 further comprising:

a interposer located between the capacitive sensor array chip and the chip including the active detection circuitry.

11. The improved sensitivity capacitive fingerprint sensor of claim 10 further comprising:

a spacer located between the cover plate and the interposer.

12. The improved sensitivity capacitive fingerprint sensor of claim 9, wherein the electrically conductive, through-chip vias comprise:

at least one of an annular via, a backside via, coaxial via or a triaxial via.

13. The improved sensitivity capacitive fingerprint sensor of claim 9, wherein at least some of the electrically conductive, through-chip vias are located near a peripheral edge of the sensor chip.

14. The improved sensitivity capacitive fingerprint sensor of claim 9, wherein at least some of the electrically conductive, through-chip vias are located somewhere other than near a peripheral edge of the sensor chip.