CMOS imager having a nitride dielectric
First Claim
Patent Images
1. An imaging device comprising:
- a substrate;
a photosensitive area within said substrate for accumulating photo-generated charge in said area;
a photogate for controlling the accumulation of photo-generated charge in said photosensitive area;
a first and a second gate stack;
a first insulating layer in contact with said substrate and beneath each of said first and second gate stacks; and
a nitrogen containing second insulating layer distinct from said first insulating layer such that none of said second insulating layer is located beneath either of said first or second gate stacks, said second insulating layer being in contact with said substrate and being located only in an area beneath said photogate.
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Abstract
An imaging device formed as a CMOS semiconductor integrated circuit includes a nitrogen containing insulating material beneath a photogate. The nitrogen containing insulating material, preferably be one of a silicon nitride layer, an ONO layer, a nitrode/oxide layer and an oxide/nitrode layer. The nitrogen containing insulating layer provides an increased capacitance in the photogate region, higher breakdown voltage, a wider dynamic range and an improved signal to noise ratio. The invention also provides a method for fabricating a CMOS imager containing the nitrogen containing insulating layer.
23 Citations
87 Claims
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1. An imaging device comprising:
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a substrate; a photosensitive area within said substrate for accumulating photo-generated charge in said area; a photogate for controlling the accumulation of photo-generated charge in said photosensitive area; a first and a second gate stack; a first insulating layer in contact with said substrate and beneath each of said first and second gate stacks; and a nitrogen containing second insulating layer distinct from said first insulating layer such that none of said second insulating layer is located beneath either of said first or second gate stacks, said second insulating layer being in contact with said substrate and being located only in an area beneath said photogate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An imaging device including a semiconductor integrated circuit substrate, said imaging device comprising:
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a photosensitive device, including a photogate overlying said substrate, for accumulating photo-generated charge in a photosensitive area of said substrate; a readout circuit comprising at least an output transistor formed in said substrate for reading out charge from a node which stores said photogenerated charge; a reset transistor for periodically resetting said charge storage node to a predetermined voltage; and a nitrogen containing insulating material in contact with said substrate and located only in the area beneath said photogate. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. An imaging system comprising:
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a plurality of active pixel sensors arranged in an array of rows and columns, each active pixel sensor being operable to generate a voltage at a diffusion node corresponding to detected light intensity by the sensor; a photogate formed over a charge collection area in a substrate in said pixel sensor, wherein a nitrogen containing insulating layer is in contact with said substrate and located only in an area beneath said photogate; a reset device to periodically reset the voltage of said diffusion node; a row decoder having a plurality of control lines connected to the sensor array, each control line being connected to activate the sensors in a respective row; and a plurality of output circuits, each output circuit being connected to the respective sensors in a column, operable to store voltage signals received from the sensors and to provide a sensor output signal. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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51. An imaging system comprising:
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a plurality of active pixel sensors arranged in an array of rows and columns, each active pixel sensor being operable to generate a voltage at a floating diffusion node corresponding to detected light intensity by the sensor; a photogate formed over a charge collection area in a substrate in said pixel sensor, wherein a nitrogen containing insulating layer is in contact with said substrate and located only in an area beneath said photogate; a reset device to periodically reset the voltage of said diffusion node; a row decoder having a plurality of control lines connected to the sensor array, each control line being connected to activate the sensors in a respective row; and a plurality of output circuits, each output circuit being connected to the respective sensors in a column, operable to store voltage signals received from the sensors and to provide a sensor output signal. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69)
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70. A system comprising:
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(i) a processor for processing image data; and (ii) a CMOS imaging device for providing image data to said processor and including; a substrate; a photosensitive area within said substrate for accumulating photo-generated charge in said area; a photogate for controlling the accumulation of photo-generated charge in said photosensitive area; and a nitrogen containing insulating layer in contact with said substrate and located in an area only beneath said photogate. - View Dependent Claims (71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87)
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Specification