Pixel structure with improved charge transfer

Abstract

An active pixel is described comprising a semiconductor substrate and a radiation sensitive source of carriers in the substrate, such as for instance, a photodiode. A non-carrier storing, carrier collecting region in the substrate is provided for attracting carriers from the source as they are generated. At least one doped or inverted region of a first conductivity is provided in or on the substrate for storing the carriers before read-out. At least one non-carrier storing, planar current flow, carrier transport pathway is provided from or through the carrier collecting region to the at least one doped or inverted region to transfer the carriers without intermediate storage to the read-out electronics.

Description

BACKGROUND OF THE INVENTION [0001] The present patent application is a continuation-in-part of patent application Ser. No. 09 / 460,630, the entire contents thereof being incorporated herein by reference.TECHNICAL FIELD OF THE INVENTION [0002] The present invention relates to pixel structures such as active or passive pixel sensors and pixel arrays for detecting electromagnetic radiation using, for example, MOS-based processing technology, e.g. CMOS technology. The pixel array may be used in a camera. DESCRIPTION OF RELATED ART [0003] Commonly solid state image devices are implemented in a CCD-technology or in a CMOS or MOS technology. [0004] CCD-technology is the name of a structure of adjacent MOS gates (usually NMOS devices; PMOS CCDs (Charge Coupled Devices) are not common but have been made) that allows both storage and transport of free charge. CCD imaging is performed in a three-step process: exposure of the CCD imaging device comprising an array of pixels, charge transfer, and...

AI Technical Summary

Benefits of technology

"The present invention provides a pixel structure and a pixel array that can capture and use the amount of light that is exposed to it. The pixel structure includes a semiconductor substrate, a photosensitive element, a carrier storing element, a first switch, and a timing circuit for simultaneously opening the first switches of all the pixels in the array. The carrier storing element can be an analog memory element or a parasitic capacitor. The pixel array can be used in a camera and has different sensitivities for different light levels. The technical effects of the invention include improved image quality, reduced noise, and improved performance in low-light conditions."

Problems solved by technology

A disadvantage of CCD technology is that it cannot easily handle the other analog and digital functions that are critical on an imaging system level, such as analog to digital converters, precision amplifiers, memory, arithmetic units, and so on.

Passive pixel sensors usually make serious compromises in image quality.

Disadvantages of the simple passive-pixel CMOS imager architecture are a high noise level.

Active pixel sensors have a better noise performance than their passive pixel CMOS precursors, but typically suffer from a lower fill factor (=photosensitive portion of the pixel), and thus require a larger pixel size.

However, the image quality of pixels with CMOS-technology is still less advanced than image quality of pixels with CCD-technology.

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