Segmented channel stop grid for crosstalk mitigation in visible imaging arrays

• US 10,672,826 B2
• Filed: 04/18/2018
• Issued: 06/02/2020
• Est. Priority Date: 04/18/2018
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Kilcoyne, Sean P., Vampola, John L., Paloczi, George
• Primary Examiner(s): Epps, Georgia Y
• Assistant Examiner(s): Williams, Don J
• Application Number:
  US15/955,820
• Publication Number:
  US 20190326346A1
• Time in Patent Office: 776 Days
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/1463 Pixel isolation structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof

Abstract

An imaging system includes a focal plane array comprising a first row of photodetectors, a second row of photodetectors adjacent to the first row of photodetectors, and a segmented isolation grid including portions disposed between photodetectors in the first row of photodetectors and photodetectors in the second row of photodetectors.

Claims

1. An imaging system including a focal plane array comprising:

a first row of photodetectors including photodiodes;

a second row of photodetectors including photodiodes, the second row of photodetectors disposed adjacent to the first row of photodetectors; and

a segmented isolation grid disposed between photodetectors in the first row of photodetectors and photodetectors in the second row of photodetectors, the segmented isolation grid including individual grid elements surrounding each individual photodiode in the first and second rows of photodetectors, a region of intrinsic semiconductor disposed between each individual photodiode and a corresponding segmented isolation grid element, each individual grid element including a plurality of electrically isolated regions that prevent flow of current between grid elements surrounding the photodiodes in the first and second rows of photodetectors.

2. The imaging system of claim 1, wherein the photodetectors in each of the first row of photodetectors and the second row of photodetectors comprise P-I-N diodes, each of the P-I-N diodes including a region of P-type semiconductor, a region of N-type semiconductor, and a region of intrinsic semiconductor disposed between the region of P-type semiconductor and the region of N-type semiconductor.

3. The imaging system of claim 2, wherein the photodetectors in each of the first row of photodetectors and the second row of photodetectors comprise silicon P-I-N diodes.

4. The imaging system of claim 1, wherein the segmented isolation grid includes doped wall segments formed surrounding P-type regions of the photodetectors in each of the first row of photodetectors and the second row of photodetectors.

5. The imaging system of claim 4, further comprising regions of intrinsic semiconductor disposed between the P-type regions and N-type regions of the photodetectors in each of the first row of photodetectors and the second row of photodetectors and the segmented isolation grid.

6. The imaging system of claim 4, wherein the segmented isolation grid includes a contiguous wall extending across one of the first row of photodetectors and the second row of photodetectors.

7. The imaging system of claim 4, wherein the segmented isolation grid includes discontinuous grid elements surrounding the photodetectors in each of the first row of photodetectors and the second row of photodetectors.

8. The imaging system of claim 5, wherein the segmented isolation grid has a doping concentration less than that of the P-type regions of the photodetectors and less than that of the N-type regions of the photodetectors.

9. The imaging system of claim 1, wherein the segmented isolation grid reduces a level of electrical crosstalk between photodetectors in the first row of photodetectors and photodetectors in the second row of photodetectors as compared to a substantially similar imaging system including a non-segmented isolation grid by deflecting free carriers generated in one photodetector from another photodetector.

10. The imaging system of claim 1, wherein the segmented isolation grid is electrically floating.

11. A method of operating a focal plane array, the method comprising:

applying a reverse bias to photodetectors in a first row of photodetectors of the focal plane array;

integrating photocurrent produced in the photodetectors in the first row of photodetectors; and

applying a reverse bias to photodetectors in a second row of photodetectors of the focal plane array while continuing to integrate the photocurrent produced in the photodetectors in the first row of photodetectors, application of the reverse bias to the photodetectors in the second row of photodetectors inducing a voltage potential in portions of a segmented isolation grid associated with the second row of photodetectors, the voltage potential being prevented from propagating to portions of the segmented isolation grid associated with the first row of photodetectors by breaks in the segmented isolation grid between the portions of the segmented isolation grid associated with the first row of photodetectors and the portions of the segmented isolation grid associated with the second row of photodetectors.

12. The method of claim 11, comprising operating the focal plane array in a rolling shutter mode.

13. An imaging system including a focal plane array comprising:

an array of photodetectors including P-I-N photodiodes arranged in a plurality of rows and a plurality of columns; and

an electrically floating segmented isolation grid comprising a wall of doped semiconductor having a doping level less than that of P-type regions of the P-I-N photodiodes and N-type regions of the P-I-N photodiodes, the segmented isolation grid including individual grid elements surrounding each individual P-I-N photodiode in the array of photodetectors, a region of intrinsic semiconductor disposed between each individual P-I-N photodiode and a corresponding segmented isolation grid element, each individual grid element including a plurality of electrically isolated regions that prevent flow of current between grid elements surrounding P-I-N photodiodes in adjacent rows.