ACTIVE PIXEL SENSOR HAVING TWO WAFERS

• US 20080083939A1
• Filed: 10/04/2007
• Published: 04/10/2008
• Est. Priority Date: 10/05/2006
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Guidash, Robert M.
• Granted Patent: US 8,049,256 B2
• Time in Patent Office: Days
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14641 Electronic components shared by two or more pixel-elements, e.g. one amplifier shared by two pixel elements
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14687 Wafer level processing

Abstract

A vertically-integrated active pixel sensor includes a sensor wafer connected to a support circuit wafer. Inter-wafer connectors or connector wires transfer signals between the sensor wafer and the support circuit wafer. The active pixel sensor can be fabricated by attaching the sensor wafer to a handle wafer using a removable interface layer. Once the sensor wafer is attached to the handle wafer, the sensor wafer is backside thinned to a given thickness. The support circuit wafer is then attached to the sensor wafer and the handle wafer separated from the sensor wafer.

Claims

1. An active pixel sensor comprising:

(a) a sensor wafer comprising;

a first array of pixel regions each pixel region including;

a photodetector for collecting charge in response to incident light;

a transfer gate for transferring charge from the photodetector; and

a charge-to-voltage conversion mechanism for receiving the charge from the photodetector via the transfer gate;

(b) a support circuit wafer connected to the sensor wafer and including;

a second array of pixel regions having support circuitry for each pixel region in the first array, wherein each pixel region in the second array is associated with one or more pixel regions in the first array; and

(c) an inter-wafer connector between each charge-to-voltage conversion mechanism on the sensor wafer and an electrical node in a respective pixel region on the support circuit wafer for transferring charge from the charge-to-voltage conversion mechanism to the support circuit wafer.

2. The active pixel sensor of claim 1, wherein the charge-to-voltage conversion mechanism includes a floating diffusion.

3. The active pixel sensor of claim 1, wherein the support circuit wafer includes an interconnect layer and a Complementary Metal Oxide Semiconductor device layer.

4. The active pixel sensor of claim 3, wherein the Complementary Metal Oxide Semiconductor device layer includes support circuitry for one or more pixel regions in the first array.

5. The active pixel sensor of claim 4, wherein the support circuitry includes at least one transistor.

6. The active pixel sensor of claim 1, wherein the active pixel sensor is disposed in an image capture device.

7. The active pixel sensor of claim 1, wherein the sensor wafer comprises a back-side illuminated sensor wafer.

8. The active pixel sensor of claim 1, wherein the sensor wafer comprises a front-side illuminated sensor wafer.

9. An active pixel sensor comprising:

(a) a sensor wafer including;

an array of active pixel regions, each active pixel region having;

a photodetector for collecting charge in response to light;

readout circuitry for reading charge from the photodetector; and

a first plurality of interconnects connected to the readout circuitry;

(b) a support circuit wafer connected to the sensor wafer, wherein the support circuit wafer includes;

support circuitry for the array of active pixel regions; and

a second plurality of interconnects; and

(c) a plurality of inter-wafer connector wires for transferring one or more signals between the sensor wafer and the support circuit wafer, wherein each inter-wafer connector wire is connected between a first interconnect on the sensor wafer and a corresponding interconnect on the support circuit wafer.

10. The active pixel sensor of claim 9, wherein the sensor wafer comprises a back-side illuminated sensor wafer.

11. The active pixel sensor of claim 9, wherein the sensor wafer comprises a front-side illuminated sensor wafer.

12. The active pixel sensor of claim 9, wherein the active pixel sensor is disposed in an image capture device.

13. A method for fabricating an active pixel sensor comprising a sensor wafer and a support circuit wafer, the method including:

attaching the sensor wafer to a handle wafer using a removable interface layer;

backside thinning the sensor wafer to a given thickness;

attaching the support circuit wafer to the sensor wafer; and

separating the handle wafer from the sensor wafer.

14. The method of claim 13, wherein the interface layer comprises an organic interface layer.

15. The method of claim 13, wherein the interface layer comprises a polymer interface layer.

16. The method of claim 13, further including forming a color filter array and a plurality of microlenses over a surface of the sensor wafer.

17. The method of claim 16, further including applying a protective layer over the plurality of microlenses, the color filter array, and the surface of the sensor wafer prior to attaching the sensor wafer to the handle wafer.

18. The method of claim 17, wherein attaching the sensor wafer to a handle wafer using a removable interface layer includes attaching the protective layer to the handle wafer using a removable interface layer.

19. The method of claim 13, wherein separating the handle wafer from the sensor wafer includes dissolving the interface layer.