Image sensors with underlying and lateral insulator structures

• US 6,737,626 B1
• Filed: 08/06/2001
• Issued: 05/18/2004
• Est. Priority Date: 08/06/2001
• Status: Active Grant

• Current Assignee: Pixim, Inc. (Sony Group Corp.)
• Original Assignee: Pixim, Inc. (Sony Group Corp.)
• Inventors: Bidermann, William R., Motta, Ricardo J.
• Primary Examiner(s): Luu, Thanh X.
• Application Number:
  US09/923,274
• Time in Patent Office: 1,016 Days
• Field of Search: 250/208.1, 250/214.1, 250/214.R, 257/290, 257/292, 257/294, 257/297, 257/305, 348/294, 348/308
• US Class Current: 250/208.1
• 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 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/1463 Pixel isolation structures

Abstract

An integrated image sensor having a conditioned top silicon oxide layer and/or one or more additional insulating layers/structures to reduce optical and/or electrical noise. The image sensor has an array of one or more pixels, each pixel having a photoelement formed on a substrate and configured to generate an electrical signal in response to incident light, and associated circuitry formed on the substrate and configured to process the electrical signal generated in the photoelement. In one embodiment, a portion of a top insulating layer in the integrated image sensor corresponding to each photoelement has a thickness different from the thickness of a portion of the top insulating layer corresponding to its associated circuitry to inhibit the flow of light between the associated circuitry and the photoelement and/or between the pixel and an adjacent pixel in the array. In another embodiment, the image sensor has one or more insulating structures formed on the substrate and configured to inhibit the flow of electricity between a photoelement and its associated circuitry and/or the pixel and an adjacent pixel in the array. The present invention can reduce optical and/or electrical noise and crosstalk to improve image quality and diminish artifacts in the image sensor'"'"'s output.

Claims

1. An integrated circuit having an image sensor, wherein the image sensor has an array of one or more pixels, wherein at least one pixel in the array comprises:

(a) a photoelement formed on a substrate and configured to generate an electrical signal in response to incident light;

(b) associated circuitry formed on the substrate and configured to process the electrical signal generated in the photoelement; and

(c) two or more insulator structures formed on the substrate and configured to inhibit flow of electricity between at least one of (1) the photoelement and the associated circuitry and (2) the pixel and an adjacent pixel in the array, wherein the two or more insulator structures comprise;

(i) an insulator layer between the substrate and at least one of (1) the photoelement and (2) the associated circuitry; and

(ii) at least one lateral insulator structure between at least one of (1) the photoelement and the associated circuitry and (2) the pixel and the adjacent pixel, wherein the at least one lateral insulator structure is in direct physical contact with the insulator layer to form a contiguous electrical isolation barrier, wherein;

at least part of the photoelement and at least part of the associated circuitry are formed within a common insulator layer formed on the substrate, wherein a portion of the common insulator layer corresponding to the photoelement has a thickness different from a thickness of a portion of the common insulator layer corresponding to the associated circuitry.

2. The invention of claim 1, wherein:

the at least one lateral insulator structure is between the photoelement and the associated circuitry; and

the contiguous electrical isolation barrier inhibits the flow of electricity between the photoelement and the associated circuitry.

3. The invention of claim 2, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

4. The invention of claim 1, wherein:

the at least one lateral insulator structure is between the pixel and the adjacent pixel; and

the contiguous electrical isolation barrier inhibits the flow of electricity between the pixel and the adjacent pixel.

5. The invention of claim 4, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

6. The invention of claim 4, wherein the one or more insulator structures further comprises a second lateral insulator structure between the photoelement and the associated circuitry and in direct physical contact with the insulator layer, wherein the contiguous electrical isolation barrier further inhibits the flow of electricity between the photoelement and the associated circuitry.

7. The invention of claim 6, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

8. The invention of claim 7, wherein:

the pixel further comprises a mask layer formed on top of at least some of the associated circuitry, wherein the mask layer inhibits light incident at the associated circuitry from contributing to the electrical signal at the photoelement; and

the portion of the common insulator layer corresponding to the associated circuitry is thicker than the portion of the common insulator layer corresponding to the photoelement.

9. The invention of claim 8, wherein:

the image sensor is a CMOS image sensor;

the one or more insulator structures comprise an oxide of silicon;

the pixel further comprises a microlens positioned over the photoelement; and

the photoelement is a photodiode, a phototransistor, a photogate, photo-conductor, a charge-coupled device, a charge-transfer device, or a charge-injection device.

10. The invention of claim 1, wherein:

the image sensor is a CMOS image sensor;

the one or more insulator structures comprise an oxide of silicon;

the pixel further comprises a microlens positioned over the photoelement; and

the photoelement is a photodiode, a phototransistor, a photogate, photo-conductor, a charge-coupled device, a charge-transfer device, or a charge-injection device.

11. The invention of claim 1, wherein the pixel further comprises a mask layer formed on top of at least some of the associated circuitry, wherein the mask layer inhibits light incident at the associated circuitry from contributing to the electrical signal at the photoelement.

12. The invention of claim 1, wherein the portion of the common insulator layer corresponding to the associated circuitry is thicker than the portion of the common insulator layer corresponding to the photoelement.

13. A method for fabricating an integrated circuit having an image sensor, wherein the image sensor has an array of one or more pixels, the method comprises, for at least one pixel in the array, the steps of:

(a) forming a photoelement formed on a substrate and configured to generate an electrical signal in response to incident light;

(b) forming associated circuitry formed on the substrate and configured to process the electrical signal generated in the photoelement; and

(c) forming two or more insulator structures formed on the substrate and configured to inhibit flow of electricity between at least one of (1) the photoelement and the associated circuitry and (2) the pixel and an adjacent pixel in the array, wherein the two or more insulator structures comprise;

(i) an insulator layer between the substrate and at least one of (1) the photoelement and (2) the associated circuitry; and

(ii) at least one lateral insulator structure between at least one of (1) the photoelement and the associated circuitry and (2) the pixel and the adjacent pixel, wherein the at least one lateral insulator structure is in direct physical contact with the insulator layer to form a contiguous electrical isolation barrier, wherein;

at least part of the photoelement and at least part of the associated circuitry are formed within a common insulator layer formed on the substrate, wherein a portion of the common insulator layer corresponding to the photoelement has a thickness different from a thickness of a portion of the common insulator layer corresponding to the associated circuitry.

14. The invention of claim 13, wherein:

the at least one lateral insulator structure is between the photoelement and the associated circuitry; and

the contiguous electrical isolation barrier inhibits the flow of electricity between the photoelement and the associated circuitry.

15. The invention of claim 14, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

16. The invention of claim 13, wherein:

the at least one lateral insulator structure is between the pixel and the adjacent pixel; and

the contiguous electrical isolation barrier inhibits the flow of electricity between the pixel and the adjacent pixel.

17. The invention of claim 16, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

18. The invention of claim 16, wherein the one or more insulator structures further comprises a second lateral insulator structure between the photoelement and the associated circuitry and in direct physical contact with the insulator layer, wherein the contiguous electrical isolation barrier further inhibits the flow of electricity between the photoelement and the associated circuitry.

19. The invention of claim 18, wherein the insulator layer is between the substrate and both the photoelement and the associated circuitry.

20. The invention of claim 19, wherein:

the pixel further comprises a mask layer formed on top of at least some of the associated circuitry, wherein the mask layer inhibits light incident at the associated circuitry from contributing to the electrical signal at the photoelement; and

the portion of the common insulator layer corresponding to the associated circuitry is thicker than the portion of the common insulator layer corresponding to the photoelement.

21. The invention of claim 20, wherein:

the image sensor is a CMOS image sensor;

the one or more insulator structures comprise an oxide of silicon;

the pixel further comprises a microlens positioned over the photoelement; and

the photoelement is a photodiode, a phototransistor, a photogate, photo-conductor, a charge-coupled device, a charge-transfer device, or a charge-injection device.

22. The invention of claim 13, wherein:

the image sensor is a CMOS image sensor;

the one or more insulator structures comprise an oxide of silicon;

the pixel further comprises a microlens positioned over the photoelement; and

the photoelement is a photodiode, a phototransistor, a photogate, photo-conductor, a charge-coupled device, a charge-transfer device, or a charge-injection device.

23. The invention of claim 13, wherein the pixel further comprises a mask layer formed on top of at least some of the associated circuitry, wherein the mask layer inhibits light incident at the associated circuitry from contributing to the electrical signal at the photoelement.

24. The invention of claim 13, wherein the portion of the common insulator layer corresponding to the associated circuitry is thicker than the portion of the common insulator layer corresponding to the photoelement.