Photo-sensor and pixel array with backside illumination and method of forming the photo-sensor
First Claim
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1. An imaging sensor comprising:
- a pixel array, each pixel comprising;
a semiconductor island of a first conduction type,a dielectric layer;
an isolation well of a second conduction type in one surface of said semiconductor layer, said second conduction type being opposite said first conduction with said isolation well forming a photo-sensor on said one surface with said semiconductor layer, the other surface of said semiconductor island being at and adjacent to said dielectric layer,cell wiring to said cell extending from photo-sensor structures in said one surface, anda color filter separated from said semiconductor layer by said dielectric layer;
a trench to said dielectric layer surrounding each said semiconductor island; and
a protective layer on said pixel array at pixel color filters, an optical signal passing through said protective layer, through said dielectric layer and then, through said semiconductor island to said photo-sensor, being filtered by said color filters and causing current flow across said semiconductor island and said isolation well junction selectively sensed by a corresponding said photo-sensor.
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Abstract
An imaging sensor with an array of FET pixels and method of forming the imaging sensor. Each pixel is a semiconductor island, e.g., N-type silicon on a Silicon on insulator (SOI) wafer. FETs are formed in one photodiode electrode, e.g., a P-well cathode. A color filter may be attached to an opposite surface of island. A protective layer (e.g., glass or quartz) or window is fixed to the pixel array at the color filters. The image sensor may be illuminated from the backside with cell wiring above the cell. So, an optical signal passes through the protective layer is filtered by the color filters and selectively sensed by a corresponding photo-sensor.
25 Citations
20 Claims
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1. An imaging sensor comprising:
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a pixel array, each pixel comprising; a semiconductor island of a first conduction type, a dielectric layer; an isolation well of a second conduction type in one surface of said semiconductor layer, said second conduction type being opposite said first conduction with said isolation well forming a photo-sensor on said one surface with said semiconductor layer, the other surface of said semiconductor island being at and adjacent to said dielectric layer, cell wiring to said cell extending from photo-sensor structures in said one surface, and a color filter separated from said semiconductor layer by said dielectric layer; a trench to said dielectric layer surrounding each said semiconductor island; and a protective layer on said pixel array at pixel color filters, an optical signal passing through said protective layer, through said dielectric layer and then, through said semiconductor island to said photo-sensor, being filtered by said color filters and causing current flow across said semiconductor island and said isolation well junction selectively sensed by a corresponding said photo-sensor. - View Dependent Claims (2, 3, 4, 5)
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6. An imaging sensor cell comprising:
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a semiconductor layer of a first conduction type; a dielectric layer; an isolation trench to said dielectric layer surrounding said semiconductor layer; an isolation well of a second conduction type in one surface of said semiconductor layer, said second conduction type being opposite said first conduction type with said isolation well forming a photo-sensor on said one surface with said semiconductor layer, the other surface of said semiconductor layer being at and adjacent to said dielectric layer; a color filter separated from said semiconductor layer by said dielectric layer; and a protective layer on said color filter, light passing through said protective layer, through said dielectric layer and then, through said semiconductor layer, and filtered by said color filter causing current flow across said semiconductor layer and said isolation well junction being selectively sensed by said photo-sensor. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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15. An imaging sensor cell comprising:
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a silicon layer; a photodiode in a first surface of said silicon layer, said photodiode comprising the junction of an isolation well in said silicon layer; a dielectric layer on the other surface of said silicon layer; a photo-sensor on said isolation well and including said photodiode; a color filter separated from said silicon layer by said dielectric layer; and a protective layer on said color filter, light passing through said protective layer, said dielectric layer and said silicon layer filtered color filter photodiode junction current being selectively sensed by said photo-sensor. - View Dependent Claims (16, 17, 18, 19)
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20. An imaging sensor cell comprising:
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a semiconductor layer of a first conduction type; a dielectric layer, wherein said semiconductor layer is an active silicon layer and said dielectric layer is an oxide layer; an isolation trench to said dielectric layer surrounding said semiconductor layer; an isolation well of a second conduction type in one surface of said semiconductor layer, said second conduction type being opposite said first conduction type with said isolation well forming a photo-sensor on said one surface with said semiconductor layer, the other surface of said semiconductor layer being at and adjacent to said dielectric layer, wherein said active silicon layer is doped with an N-type dopant and said isolation well is a P-well in said N-type active silicon layer forming a photodiode, said imaging sensor cell further comprising a plurality of NFETs formed in said P-well, said NFETs connected to selectively sense an optical signal to said photodiode, wherein said plurality of NFETs comprises; a first NFET connected between the cathode of said photodiode and a supply voltage (Vdd), said first NFET being gated by a reset signal, a second NFET connected at the drain to said supply voltage and gated by said cathode, and a third NFET connected between the source of said second NFET and a data output, said third NFET being gated by a pixel select signal, wherein said active silicon layer and said oxide layer are silicon on insulator (SOI) layers in a CMOS SOI chip; a color filter separated from said semiconductor layer by said dielectric layer; and a protective layer on said color filter, light passing through said protective layer, through said dielectric layer and then, through said semiconductor layer, and filtered by said color filter causing current flow across said semiconductor layer and said isolation well junction being selectively sensed by said photo-sensor.
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Specification