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Two epitaxial layers to reduce crosstalk in an image sensor

an image sensor and crosstalk technology, applied in the field of image sensors, can solve the problems of insufficient effectiveness, difficult to scale to smaller pixels, and structure consumes silicon area, and achieve the effect of reducing crosstalk in the image sensor

Inactive Publication Date: 2008-06-12
EASTMAN KODAK CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008]The present invention has the following advantage of reducing cross talk in an image sensor.

Problems solved by technology

Various approaches have been tried with p / p+ wafers at CMOS foundries, but to date none has been sufficiently effective.
Such a structure consumes silicon area and is difficult to scale to smaller pixels.
This approach is not as effective as the method proposed here and, in fact, part of the subcollector enhances the diffusion of electrons to other pixels.

Method used

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  • Two epitaxial layers to reduce crosstalk in an image sensor
  • Two epitaxial layers to reduce crosstalk in an image sensor
  • Two epitaxial layers to reduce crosstalk in an image sensor

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Embodiment Construction

[0012]Before discussing the present invention in detail, it is instructive to note that the present invention is preferably used in, but not limited to, a CMOS active pixel sensor. Active pixel sensor refers to an active electrical element within the pixel, other than transistors functioning as switches. For example, the amplifier is an active element. CMOS refers to complementary metal oxide silicon type electrical components such as transistors which are associated with the pixel, but typically not in the pixel, and which are formed when the source / drain of a transistor is of one dopant type and its mated transistor is of the opposite dopant type. CMOS devices include some advantages one of which is they consume less power.

[0013]In the preferred embodiment, the invention will be described having n-type and p-type dopings. It is to be understood that the type of doping for the various components could be reversed without departing from the scope of the invention.

[0014]Referring to ...

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Abstract

An image sensor includes a substrate of a first conductivity type having an image area with a plurality of photosensitive sites, wherein a portion of the charge generated in response to light is collected in the pixel; and a subcollector of a second conductivity spanning the image area that collects another portion of the generated charge that would have otherwise diffused to adjacent photosensitive sites.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]Reference is made to and priority claimed from U.S. Provisional Application Ser. No. 60 / 869,431, filed Dec. 11, 2006, entitled TWO EPITAXIAL LAYERS TO REDUCE CROSSTALK IN AN IMAGE SENSOR.FIELD OF THE INVENTION[0002]The invention relates generally to the field of image sensors and, more particularly, to an image sensor having two epitaxial layers to reduce crosstalk.BACKGROUND OF THE INVENTION[0003]Crosstalk results when a photogenerated carrier, say an electron, is generated beyond the depletion region beneath one photodiode or another photosensitive region, and the electron diffuses and / or drifts away and is collected by another photodiode or another photosensitive region. For clarity, photodiodes will be used as examples and the image sensor is assumed to be an array of pixels. Crosstalk by electrons reduces the modulation transfer function and mixes colors. Thus, it is desirable to reduce and / or eliminate such crosstalk.[0004]Many image...

Claims

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Application Information

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IPC IPC(8): H01L21/00
CPCH01L27/14632H01L27/14687H01L27/14654H01L27/146
Inventor LAVINE, JAMES P.STEVENS, ERIC G.
Owner EASTMAN KODAK CO