Retrograde well structure for a CMOS imager
First Claim
1. A method of forming a photosensor for an imaging device, said method comprising:
- forming a retrograde well of a first conductivity type in a substrate;
forming a periphery well of said first or a second conductivity in the substrate;
forming a photosensor within the retrograde well; and
forming output circuitry within the periphery well.
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Accused Products
Abstract
A retrograde and periphery well structure for a CMOS imager is disclosed which improves the quantum efficiency and signal-to-noise ratio of the photosensing portion imager. The retrograde well comprises a doped region with a vertically graded dopant concentration that is lowest at the substrate surface, and highest at the bottom of the well. A single retrograde well may have a single pixel sensor cell, multiple pixel sensor cells, or even an entire array of pixel sensor cells formed therein. The highly concentrated region at the bottom of the retrograde well repels signal carriers from the photosensor so that they are not lost to the substrate, and prevents noise carriers from the substrate from diffusing up into the photosensor. The periphery well contains peripheral logic circuitry for the imager. By providing retrograde and peripheral wells, circuitry in each can be optimized. Also disclosed are methods for forming the retrograde and peripheral well.
45 Citations
54 Claims
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1. A method of forming a photosensor for an imaging device, said method comprising:
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forming a retrograde well of a first conductivity type in a substrate;
forming a periphery well of said first or a second conductivity in the substrate;
forming a photosensor within the retrograde well; and
forming output circuitry within the periphery well. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method of forming a pixel sensor cell for an imaging device, said method comprising:
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forming a retrograde well of a first conductivity type in a substrate;
forming a periphery well of a first conductivity type in said substrate adjacent said retrograde well;
forming a photosensitive region in the retrograde well;
forming a photosensor on an upper surface of the photosensitive region for controlling the collection of charge therein;
forming a floating diffusion region of a second conductivity type in the retrograde well for receiving charges transferred from said photosensitive region; and
forming output circuitry on an upper surface of said periphery well. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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Specification
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- Resources
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Current AssigneeAptina Imaging Corporation (ON Semiconductor Corporation)
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Original AssigneeMicron Technology, Inc.
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InventorsRhodes, Howard E., Durcan, Mark
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Primary Examiner(s)Lee, Eddie
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Assistant Examiner(s)Brock, II, Paul E
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Application NumberUS10/180,088Publication NumberTime in Patent Office586 DaysField of Search438/57, 438/60, 438/63, 438/69, 438/73, 438/75, 438/76, 438/77, 438/78, 438/79, 438/87, 438/116, 250/551US Class Current438/69CPC Class CodesH01L 27/14601 Structural or functional de...H01L 27/14609 Pixel-elements with integra...
