Deep infrared photodiode for a CMOS imager
First Claim
Patent Images
1. A photosensor for use in an imaging device, said photosensor comprising:
- a doped layer formed in a substrate;
an insulating layer formed over the doped layer;
a trench formed in said insulating layer over at least a portion of said doped layer;
an infrared sensitive silicide layer formed of a conductive material in said trench on at least a portion of the doped layer, said infrared sensitive silicide layer permitting image radiation to pass therethrough; and
a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer.
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Abstract
A photodiode photosensor for use in a CMOS imager exhibiting improved infrared response. The photosensor is a diode with an infrared sensitive silicide layer, such as an iridium silicide, formed on a doped substrate. The infrared sensitive silicide is highly sensitive to infrared radiation, especially in the deep infrared spectral range. A reflective layer may be used on the infrared sensitive silicide layer so that infrared radiation entering the diode from the bottom is reflected back to the photodiode. Also disclosed are processes for forming the photodiode.
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Citations
145 Claims
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1. A photosensor for use in an imaging device, said photosensor comprising:
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a doped layer formed in a substrate;
an insulating layer formed over the doped layer;
a trench formed in said insulating layer over at least a portion of said doped layer;
an infrared sensitive silicide layer formed of a conductive material in said trench on at least a portion of the doped layer, said infrared sensitive silicide layer permitting image radiation to pass therethrough; and
a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A photosensor for use in an imaging device, said photosensor comprising:
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a doped layer formed in a substrate;
an insulating layer formed over said doped layer;
a trench formed in said insulating layer over at least a portion of said doped layer;
an infrared sensitive silicide layer formed of a conductive material in said trench on at least a portion of the doped layer;
a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer;
a doped region formed in said substrate spaced apart from said infrared sensitive silicide layer for receiving image charge transferred from said doped layer; and
a transfer gate formed in said substrate for gating image charge accumulated in said doped layer to said doped region. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A pixel sensor cell for use with an imaging device, said cell comprising:
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a doped layer formed in a substrate;
an insulating layer formed over said doped layer;
a trench formed in said insulating layer over at least a portion of said doped layer;
an infrared sensitive silicide layer formed of a conductive material in said trench on at least a portion of the doped layer;
a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer;
a doped region formed in said substrate spaced apart from said infrared sensitive silicide layer for receiving image charge transferred from said doped layer;
a transfer gate formed in said substrate for gating image charge accumulated in said doped layer to said doped region;
a reset transistor for periodically resetting said doped layer to a predetermined potential; and
an output transistor having a gate electrically connected to said doped layer for providing a signal representing image charge stored in said doped layer. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. A CMOS imager comprising:
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a doped layer formed in a substrate;
an insulating layer formed over said doped layer;
a trench formed in said insulating layer over at least a portion of said doped layer;
an array of pixel sensor cells formed in said doped layer, wherein each pixel sensor cell has a photodiode, said photodiode comprising an infrared sensitive silicide layer formed of a conductive material in said trench on at least a portion of the doped layer, and a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer, each of said cells having a respective doped region for receiving and outputting image charge received from said doped layer; and
signal processing circuitry formed in said substrate and electrically connected to the array for receiving and processing signals representing image charge outputted by the array. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62)
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63. An integrated circuit imager comprising:
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an array of pixel sensor cells formed in a substrate, wherein each pixel sensor cell has a photodiode, said photodiode comprising an iridium silicide layer on said substrate and a conductive iridium layer formed on the sidewalls of a trench formed in an insulating layer over said substrate;
signal processing circuitry formed in said substrate and electrically connected to the array for receiving and processing signals representing an image output by the array and for providing output data representing said image; and
a processor for receiving and processing data representing said image.
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64. An integrated circuit imager comprising:
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a CMOS imager, said CMOS imager comprising an array of pixel sensor cells formed in a doped layer on a substrate, wherein each pixel sensor cell has a photodiode, said photodiode comprising an infrared sensitive silicide layer formed of a conductive material in a trench formed in an insulating layer formed on said doped layer, said trench being formed over at least a portion of said doped layer; and
a conductive layer formed on the sidewalls of said trench, said conductive layer being formed of the same conductive material used to form said infrared sensitive silicide layer, each of said cells having a respective doped region for receiving and outputting image charge received from said doped layer, and signal processing circuitry formed in said substrate and electrically connected to the array for receiving and processing signals representing an image output by the array and for providing output data representing said image; and
a processor for receiving and processing data representing said image. - View Dependent Claims (65, 66, 67, 68, 69, 70, 71)
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72. A method of forming a photodiode for use in an imaging device, said method comprising the steps of:
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forming a doped layer in a substrate;
forming an insulating layer over said doped layer;
forming an opening in said insulating layer to expose at least a portion of said doped layer;
forming a metal layer on said portion of said doped layer and also on sidewalls of said opening;
forming an infrared sensitive silicide layer from said metal layer; and
removing the unreacted metal by chemical mechanical polishing. - View Dependent Claims (73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90)
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91. A method of forming a photodiode for use in an imaging device, said method comprising the steps of:
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forming a doped layer in a substrate having devices formed thereon and a protective layer over the devices;
removing at least a portion of the protective layer to expose a portion of the doped layer;
forming a metal layer on the exposed portion of the doped layer and also on sidewalls of a trench formed in said protective layer;
forming an infrared sensitive silicide layer from said metal layer; and
removing the unreacted metal by chemical-mechanical-polishing. - View Dependent Claims (92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112)
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113. A method of forming a photodiode for use in an imaging device, said method comprising the steps of:
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forming a doped layer in a substrate having devices formed thereon and a protective layer over the devices;
forming a trench in the protective layer, wherein the trench bottom exposes said doped layer;
forming a blocking layer on the sides of the trench;
forming a metal layer on the bottom and sides of the trench;
forming an infrared sensitive silicide layer from said metal layer; and
removing the unreacted metal by chemical-mechanical-polishing. - View Dependent Claims (114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130)
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131. A method of forming a photodiode for use in an imaging device, said method comprising the steps of:
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forming a doped layer in a substrate;
forming an insulating layer on said substrate;
forming a trench in said insulating layer to said doped layer;
forming a conductive layer on sidewalls and on the bottom of said trench;
forming an infrared sensitive silicide layer with said conductive layer on at least a portion of said doped layer in said trench; and
removing the conductive layer from an upper surface of said insulating layer. - View Dependent Claims (132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145)
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Specification