Pixel with spatially varying metal route positions

• US 7,408,140 B2
• Filed: 05/14/2007
• Issued: 08/05/2008
• Est. Priority Date: 05/06/2005
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Gazeley, William G.
• Primary Examiner(s): Epps; Georgia Y.
• Assistant Examiner(s): WILLIAMS, DON J
• Application Number:
  US11/678,986
• Publication Number:
  US 20070205356A1
• Time in Patent Office: 449 Days
• Field of Search: 250/208.1, 250/214.1, 250/216, 250/226, 250/214.R, 257290-293, 257/203, 257/433, 257/431, 257/443, 348/272, 348/294, 348/298
• US Class Current: 250/208.1
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14689 MOS based technologies

Abstract

A method for configuring an image sensor including an array of pixels having an optical center, each pixel of the array including a metal segment disposed in a second metal layer and an interlayer connect element coupled between the metal segment and a first metal layer. The method includes modeling a base pixel configuration for each pixel of the array, the base pixel configuration including the metal segment at a first position in the second metal layer, and the first interlayer connect element at a second position which is coincident with the first position. The method further includes, for each pixel of the array, determining a shift distance for the pixel based on a distance of the pixel from the optical center, determining a direction of the pixel from the optical center, shifting the metal segment from the first position toward the optical center by the shift distance, shifting the interlayer connect element from the second position toward the optical center by the shift distance if the pixel is in a first direction from the optical center, and maintaining the via at the second position and providing a span element to couple the metal segment at the shifted location to the interlayer connect element if the pixel is on a second direction from the optical center.

Claims

1. A method of configuring an image sensor including an array of pixels having an optical center, each pixel of the array including a transistor region, a first metal segment disposed in a first metal layer on one side of the transistor region, a second metal segment disposed in the first metal layer and coupled to the transistor region, a third metal segment disposed in a second metal layer and an interlayer connect element coupled between the third metal segment and the first metal segment, the method comprising:

modeling a base pixel configuration for each pixel of the array, the base pixel configuration including;

the third metal segment at a first position in the second metal layer; and

the interlayer connect element at a second position which is coincident with the first position; and

for each pixel of the array;

determining a shift distance for the pixel based on a distance of the pixel from the optical center;

shifting the third metal segment from the first position toward the optical center by the shift distance to a shifted location;

determining whether the first metal segment obstructs coupling between the third metal segment at

the shifted location and the second metal segment;

shifting the interlayer connect element from the second position toward the optical center by the shift distance if the first metal segment does not obstruct coupling between the third metal segment at the shifted location and the second metal segment; and

maintaining the interlayer connect element at the second position and using a span element to couple the third metal segment at the shifted location to the interlayer connect element if the first metal segment obstructs the coupling between the third metal segment at the shifted location and the second metal segment.

2. The method of claim 1, wherein the determining of the shift distance includes determining an angle of incidence of a principal ray angle of a bundle of light rays incident upon the pixel.

3. The method of claim 1, wherein the coupling of the span element includes extending the span element by at least the shift distance to the interlayer connect element.

4. A method of configuring an image sensor having an array of pixels arranged into rows and columns, the array having an optical center plane substantially parallel to the columns, and each pixel including a photodetector, a transistor region, first and second metal segments positioned in a first metal layer, a further metal segment positioned in a second metal layer, and an interconnect element coupled between the further metal segment and the second metal segment, the second metal segment coupled to the transistor region, the method comprising:

determining a base pixel configuration wherein the further metal segment is positioned a segment distance and the interconnect element is positioned an interconnect distance from an edge of the pixel proximate to the photodetector, the segment distance being substantially equal to the interconnect distance; and

for each pixel of the array;

determining a shift distance of the pixel based on a distance of the pixel from the optical center plane;

decreasing the segment distance and the interconnect distance by the shift distance if the photodetector is positioned between the transistor region and the optical center plane to shift the further metal segment to a shifted location, and

increasing the segment distance by the shift distance if the transistor region is positioned between the photodetector and the optical center plane to shift the further metal segment to the shifted location;

determining if the first metal segment obstructs a path in the first metal layer between the second metal segment and an area of the first metal layer coincident with the shifted location of the further metal segment; and

if the first metal segment obstructs the oath between the second metal segment and the area of the first metal layer coincident with the shifted location of the further metal segment, coupling a span in the second metal layer between the further metal segment and the interconnect element.

5. The method of claim 4, wherein the base pixel configuration is suitable for pixels receiving a bundle of incident light rays having a principal ray angle substantially perpendicular to the photodetector.

6. The method of claim 4, wherein the base pixel configuration is suitable for pixels wherein the optical center plane passes through the photodetector.

7. The method of claim 4, wherein the determining of the shift distance includes determining an angle of incidence of a principal ray of a bundle of light rays incident upon the pixel.

8. The method of claim 7, wherein the image sensor includes a lens, and wherein the determining of the angle of incidence includes modeling optical characteristics of the lens.

9. The method of claim 4, wherein for pixels in a given row of the array, the shift distance increases with increasing distance of the pixels from the optical center plane.

10. The method of claim 4, wherein the shift distance is the same for each pixel in a given column of pixels.

11. The method of claim 4, wherein the shift distance increases non-linearly with distance of the pixel from the optical center plane.

12. The method of claim 4, wherein the coupling of the span includes providing the span element with a length at least equal to the shift distance.

13. An image sensor comprising:

an array of pixels arranged into rows and columns, the array having an optical center plane substantially parallel to the columns, and each pixel including a photodetector, a transistor region, first and second metal segments positioned in a first metal layer, at least one further metal segment positioned in a second metal layer, an interconnect element coupled between the at least one further metal segment and the second metal segment, and having a first pixel edge proximate to the photodetector;

wherein each pixel of at least one column of the array proximate to the optical center plane has a center configuration wherein the at least one further metal segment is positioned a segment distance from the first pixel edge and the interconnect element is positioned an interconnect distance from the first pixel edge;

wherein for each pixel of the remaining columns of the array to one side of the at least one column, the at least one further metal segment is positioned at the segment distance minus a shift distance and the interconnect element is positioned at the interconnect distance minus the shift distance from the corresponding first pixel edge;

wherein for each pixel of the remaining columns of the array to the other side of the at least one column, the at least one further metal segment is positioned at the segment distance plus the shift distance and the interconnect element is positioned at the interconnect distance from the corresponding first pixel edge, and

wherein, for each pixel having a path in the first metal layer between the second metal segment and an area in the first metal layer coincident with the at least one further metal segment obstructed by the first metal segment, a span element is positioned in the second metal layer that extends between the at least one further metal segment and the interconnect element; and

wherein the shift distance is based on a distance of the pixel from the optical center plane.

14. The image sensor of claim 13, wherein the pixels in the remaining columns to the one side of the at least one column are positioned such that the photodetector is positioned between the transistor region and the optical center plane, and the pixels in the remaining columns to the other side of the at least one column are positioned such the transistor region is positioned between the photodetector and the optical center plane.

15. The image sensor of claim 13, wherein a magnitude of the shift distance increases non-linearly with increasing distance of the pixel from the at least one column of pixels.

16. The image sensor of claim 13, wherein the shift distance is based on an angle of incidence of a principle ray of a bundle of light rays incident upon the pixel.

17. The image sensor of claim 13, wherein the span element has a length at least equal to the shift distance of the corresponding pixel.

18. The image sensor of claim 13, wherein the image sensor comprises a complimentary metal-oxide semiconductor imaging sensor and each pixel of the array comprises a buried-gate photodiode type pixel.

19. The image sensor of claim 13, wherein the at least one further metal segment comprises a portion of a signal bus extending across the array.