Massachusetts Institute of Technology

United States of America as Represented by the Secretary of the Air Force

Eugene D Savoye

Barry E Burke

Bernard B Kosicki

Robert K Reich

James A Gregory

Andrew H Loomis

James E Carrick

Allen M Waxman

David A Fay

Alan N Gove

John Tonry

William H McGonagle

Robert W Mountain

Provided is a method of fabrication of a blooming control structure for an imager. The structure is produced in a semiconductor substrate in which is configured an electrical charge collection region. The electrical charge collection region is configured to accumulate electrical charge that is photogenerated in the substrate, up to a characteristic charge collection capacity. A blooming drain region is configured in the substrate laterally spaced from the charge collection region. The blooming drain region includes an extended path of a conductivity type and level that are selected for conducting charge in excess of the characteristic charge collection capacity away from the charge collection region. A blooming barrier region is configured in the substrate to be adjacent to and laterally spacing the charge collection and blooming drain regions by a blooming barrier width. This barrier width corresponds to an acute blooming barrier impurity implantation angle with the substrate. The blooming barrier region is of a conductivity type and level that is selected based on the blooming barrier width to produce a corresponding electrical potential barrier between the charge collection and blooming drain regions. The blooming barrier regions of the structure are very precisely defined by the selected acute blooming barrier impurity implantation angle, and optionally in addition by a rotation of the blooming barrier impurity implantation, as well as a non-vertical sidewall profile of the an impurity implantation masking layer.

Fabrication of a high-precision blooming control structure for an image sensor

A CCD imaging system is provided, including a short focal length lens for accepting light from the scene to be imaged and a charge storage medium having a charge storage substrate that is curved in a selected nonplanar focal surface profile and located a selected distance from the lens with the focal surface facing the lens, the focal surface profile and the lens-to-substrate distance selected such that the light accepted by the lens is in focus at the position of the substrate. There is provided a support substrate on which the nonplanar charge storage substrate is supported to maintain the selected surface profile of the charge storage substrate. An array of pixels defined in the charge storage substrate by pixel interconnections is supported on the front side of the substrate, such that exposure of the substrate to light from the scene through the lens produces charge packets in the pixels, with the pixel interconnection providing selective electronic temporal control of transfer of charge packets from one pixel to another in the substrate. The invention provides a technique for suppressing dark current charge packet generation in the substrate pixels. An output circuit converts the charge packets in the pixels to an electrical pixel signal of output pixel values based on the light from the scene. A plurality of pixel values together form an image frame, the output pixel values being produced at a rate corresponding to the image frame rate, R.

Large field of view CCD imaging system

Provided is a blooming control structure for an imager and a corresponding fabrication method. The structure is produced in a semiconductor substrate in which is configured an electrical charge collection region. The electrical charge collection region is configured to accumulate electrical charge that is photogenerated in the substrate, up to a characteristic charge collection capacity. A blooming drain region is configured in the substrate laterally spaced from the charge collection region. The blooming drain region includes an extended path of a conductivity type and level that are selected for conducting charge in excess of the characteristic charge collection capacity away from the charge collection region. A blooming barrier region is configured in the substrate to be adjacent to and laterally spacing the charge collection and blooming drain regions by a blooming barrier width. This barrier width corresponds to an acute blooming barrier impurity implantation angle with the substrate. The blooming barrier region is of a conductivity type and level that is selected based on the blooming barrier width to produce a corresponding electrical potential barrier between the charge collection and blooming drain regions. This blooming control structure, and particularly the blooming barrier regions of the structure, are very precisely defined by the selected acute blooming barrier impurity implantation angle, and optionally in addition by a rotation of the blooming barrier impurity implantation, as well as a non-vertical sidewall profile of the an impurity implantation masking layer.

High-precision blooming control structure formation for an image sensor

The wafer thickness of a CCD front illuminated silicon wafer is reduced to about ten to twenty microns, the Al substrate is removed and a 5-35 nanometer silicon oxide layer is produced on the thinned back of the silicon wafer followed by implanting boron ions within the back surface to a depth up to about ten nanometers. Furnace annealing the wafer is now carried out, and the Al substrate is redeposited to enable the formation of gate contacts.

Fabrication of UV-sensitive back illuminated CCD image sensors

An imaging system is provided for imaging a scene to produce a sequence of image frames of the scene at a frame rate, R, of at least about 25 image frames per second. The system includes an optical input port, a charge-coupled imaging device, an analog signal processor, and an analog-to-digital processor (A/D). The A/D digitizes the amplified pixel signal to produce a digital image signal formatted as a sequence of image frames each of a plurality of digital pixel values and having a dynamic range of digital pixel values represented by a number of digital bits, B, where B is greater than 8. A digital image processor is provided for processing digital pixel values in the sequence of image frames to produce an output image frame sequence at the frame rate, R, representative of the imaged scene, with a latency of no more than about 1/R and a dynamic range of image frame pixel values represented by a number of digital bits, D, where D is less than B. The output image frame sequence is characterized by noise-limited resolution of at least a minimum number, N.sub.M, of line pairs per millimeter, referred to the charge-coupled imaging device pixel array, in an imaged scene as a function of illuminance of the input light impinging the charge-coupled imaging device pixels.

Low-light-level imaging and image processing

A multidirectional charge transfer device configured in a charge storage medium. The device includes an array of charge storage regions. Each of said charge storage regions includes a plurality of first gates, each of which is arranged in a first portion of each charge storage region, a plurality of second gates, each of which is arranged in a second portion of each charge storage region, a plurality of third gates, each of which is arranged in a third portion of each charge storage region, and a plurality of fourth gates, each of which is arranged in a fourth portion of each charge storage region. The plurality of gates and charge storage regions are configured to define at least three bidirectional charge transfer paths which are noncollinear with respect to each other. The plurality of gates are sequentially biased to establish charge transfer along one of said bidirectional charge transfer paths and forming blocking potentials to charge transfer in the remaining charge transfer paths.

Multidirectional transfer charge-coupled device

A charge modulation device having a semiconductor region of a first conductivity type. An epitaxial layer of second conductivity type is provided on a portion of the semiconductor region so as to define an FET channel region. A first epitaxial region of the second conductivity type is provided adjacent to and in contact with the epitaxial layer so as to define an FET drain region, the first epitaxial region being electrically isolated from the semiconductor region. A second epitaxial region of the second conductivity type is provided adjacent to and in contact with the epitaxial layer so as to define an FET source region, the second epitaxial region being electrically isolated from the semiconductor region. A third epitaxial region of the first conductivity type or a metal oxide semiconductor is provided to the channel region between the source and drain regions.

Charge modulation device

A charge-coupled device having an array of pixel elements formed in a substrate, which device is operable in a first state to expand the depletion well regions of each pixel element into the substrate for storing incoming photoelectrons therein and in a second state to contract the expanded depletion well regions to prevent storage of photoelectrons in the contracted depletion well regions.

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Concord, MA, United States of America

Eugene D Savoye