Apparatus and method for forming optical black pixels with uniformly low dark current
First Claim
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1. An optical black pixel comprising:
- a photodiode;
a single metal layer overlaying the photodiode; and
a single Ti/TiN layer overlaying the single metal layer to increase opacity of the optical black pixel;
wherein the single metal layer comprises a metal stub formed in a top inter-level metal layer to increase opacity of the optical black pixel, and wherein the metal stub is smaller than a full pixel area.
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Abstract
An apparatus and method for forming optical black pixels having uniformly low dark current. Optical Black opacity is increased without having to increase Ti/TiN layer thickness. A hybrid approach is utilized combining a Ti/TiN OB layer in conjunction with in-pixel metal stubs that further occlude the focal radius of each pixel'"'"'s incoming light beam. Additional metal layers can be used to increase the opacity into the infrared region.
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Citations
7 Claims
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1. An optical black pixel comprising:
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a photodiode; a single metal layer overlaying the photodiode; and a single Ti/TiN layer overlaying the single metal layer to increase opacity of the optical black pixel; wherein the single metal layer comprises a metal stub formed in a top inter-level metal layer to increase opacity of the optical black pixel, and wherein the metal stub is smaller than a full pixel area. - View Dependent Claims (2, 3, 4)
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5. A method of increasing the opacity in an optical black pixel, the method comprising:
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forming a metal stub in a single inter-level metal layer, the metal stub covering an area of a photodiode in the pixel; and forming a single Ti/TiN layer above the metal stub; wherein the metal stub and the single Ti/TiN layer increase the opacity of an optical black pixel.
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6. An image sensor comprising an array of clear pixels, and a plurality of optical black pixels, the optical black pixels comprising:
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a metal stub formed in a single inter-level metal layer, the metal stub covering an area of a photodiode in the pixel; and a single Ti/TiN layer formed above the metal stub; wherein the metal stub and the single Ti/TiN layer increase the opacity of an optical black pixel. - View Dependent Claims (7)
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Specification