Method of forming CMOS imager with storage capacitor
First Claim
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1. A method of forming a CMOS imager having improved charge storage comprising the steps of:
- providing a semiconductor substrate having a doped layer of a first conductivity type;
forming a first doped region of a second conductivity type in said doped layer, wherein said first doped region is in contact with a charge collection region of a photosensor;
forming a storage capacitor over said substrate for storing charge accumulated by said charge collection region; and
forming a contact between said first doped region and said storage capacitor.
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Abstract
A CMOS imager having an improved signal to noise ratio and improved dynamic range is disclosed. The CMOS imager provides improved charge storage by fabricating a storage capacitor in parallel with the photocollection area of the imager. The storage capacitor may be a flat plate capacitor formed over the pixel, a stacked capacitor or a trench imager formed in the photosensor. The CMOS imager thus exhibits a better signal-to-noise ratio and improved dynamic range. Also disclosed are processes for forming the CMOS imager.
115 Citations
50 Claims
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1. A method of forming a CMOS imager having improved charge storage comprising the steps of:
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providing a semiconductor substrate having a doped layer of a first conductivity type;
forming a first doped region of a second conductivity type in said doped layer, wherein said first doped region is in contact with a charge collection region of a photosensor;
forming a storage capacitor over said substrate for storing charge accumulated by said charge collection region; and
forming a contact between said first doped region and said storage capacitor. - 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, 30, 31, 32)
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33. A method of forming a CMOS imager having improved charge storage comprising the steps of:
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providing a semiconductor substrate having a doped layer of a first conductivity type;
providing a photoconversion device in said semiconductor substrate for accumulating photogenerated charge, said photoconversion device comprising a light sensitive area;
forming a first doped region of a second conductivity type in said doped layer and adjacent said photoconversion device;
forming a trench in said doped layer adjacent to said first doped region;
forming a first conductive layer in said trench;
forming an insulating layer over said first conductive layer in said trench; and
forming a second conductive layer over said insulating layer to form a trench capacitor, wherein said trench capacitor is electrically connected in parallel with said light sensitive area and stores charge accumulated in said photoconversion device. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification