Active pixel sensor pixel having a photodetector whose output is coupled to an output transistor gate
DCFirst Claim
1. An imaging device, comprising:
- a monolithic semiconductor integrated circuit substrate;
a focal plane array of pixel cells, each one of said pixel cells comprising;
a photodetector having a photodetector portion formed in said substrate and a photodetector electrode overlying said photodetector portion, said photodetector operable to accumulate photo-generated charge in said photodetector portion in response to incident radiation, and a charge coupled device section formed on said substrate adjacent said photodetector and having an output transistor whose gate is connected to said photodetector electrode to form a floating gate and at least one charge coupled device stage, said charge coupled device section configured and operable to transfer charge through said charge coupled device stage from said photodetector portion of said substrate to a drain of said output transistor during a reset operation and to produce an electrical signal indicative of said photo-generated charge.
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Abstract
An imaging device formed as a monolithic complementary metal oxide semiconductor integrated circuit in an industry standard complementary metal oxide semiconductor process, the integrated circuit including a focal plane array of pixel cells, each one of the cells including a photogate overlying the substrate for accumulating photo-generated charge in an underlying portion of the substrate and a charge coupled device section formed on the substrate adjacent the photogate having a sensing node and at least one charge coupled device stage for transferring charge from the underlying portion of the substrate to the sensing node. There is also a readout circuit, part of which can be disposed at the bottom of each column of cells and be common to all the cells in the column. A Simple Floating Gate (SFG) pixel structure could also be employed in the imager to provide a non-destructive readout and smaller pixel sizes.
71 Citations
33 Claims
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1. An imaging device, comprising:
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a monolithic semiconductor integrated circuit substrate;
a focal plane array of pixel cells, each one of said pixel cells comprising;
a photodetector having a photodetector portion formed in said substrate and a photodetector electrode overlying said photodetector portion, said photodetector operable to accumulate photo-generated charge in said photodetector portion in response to incident radiation, and a charge coupled device section formed on said substrate adjacent said photodetector and having an output transistor whose gate is connected to said photodetector electrode to form a floating gate and at least one charge coupled device stage, said charge coupled device section configured and operable to transfer charge through said charge coupled device stage from said photodetector portion of said substrate to a drain of said output transistor during a reset operation and to produce an electrical signal indicative of said photo-generated charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An imaging device, comprising:
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a monolithic semiconductor integrated circuit substrate;
a focal plane array of pixel cells formed on said substrate by an integrated circuit process that is compatible with a complementary metal oxide semiconductor (CMOS) process, each one of said pixel cells comprising;
a photodetector electrode overlying said substrate and operable to accumulate photo-generated charge in an underlying photodetector portion of said substrate, a barrier gate formed on said substrate adjacent said photodetector portion, and a pixel transistor formed on said substrate and configured to have a first diffusion region adjacent said barrier gate, a gate and a second diffusion region, said gate connected to said photodetector electrode to form a floating gate, wherein said barrier gate is operable to transfer said photo-generated charge from said underlying photodetector portion of said substrate to said first diffusion region of said pixel transistor, and wherein said gate of said pixel transistor produces an electrical signal comprising a signal component indicative of said photo-generated charge and a noise component indicative of noise associated with said pixel; and
MOS image signal processing electronics integrated on said substrate and connected to communicate with said focal plane array and to provide on-chip signal processing of electrical signals from said pixel cells. - View Dependent Claims (22, 23, 24, 25, 26)
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27. An imaging device, comprising:
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a monolithic semiconductor integrated circuit substrate;
a focal plane array of pixel cells formed on said substrate by an integrated circuit process that is compatible with complementary metal oxide semiconductor (CMOS) process, each one of said pixel cells comprising, a photodetector electrode overlying said substrate and operable to accumulate photo-generated charge in an underlying portion of said substrate, a barrier gate formed on said substrate adjacent said underlying portion, and a pixel transistor formed on said substrate and configured to have a drain adjacent said barrier gate, a gate and a source, a capacitor having a terminal connected to both said photodetector electrode and said gate of said pixel transistor to make said gate of said pixel transistor a floating gate, wherein said barrier gate is operable to transfer said photo-generated charge from said underlying portion of said substrate under said photodetector electrode to said drain of said pixel transistor which produces an electrical signal having a signal component indicative of said photo-generated charge. - View Dependent Claims (28, 29)
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30. A method, comprising:
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producing charge in a portion of a semiconductor substrate under a photodetector electrode in response to incident photons incident to said portion;
using a transfer gate formed in said substrate next to said portion under said photodetector electrode to output said charge;
using a drain of an output transistor formed in said substrate next to said transfer gate to receive said charge from said portion; and
connecting a gate of said output transistor to said photodetector electrode to form a floating gate so as to convert said charge into an electrical signal. - View Dependent Claims (31, 32, 33)
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Specification