Solid state image sensors, also known as imaging devices, have commonly been used in various photo-imaging applications. Current applications of imaging devices include cameras, mobile telephones, scanners, machine vision systems, vehicle navigation systems, video telephones, computer input devices, surveillance systems, auto focus systems, star trackers, motion detector systems, and image stabilization systems among other uses.
Imaging devices, when used with appropriate imaging circuits, capture, process, store, and display images for various purposes. For example, imaging devices are typically formed with an array of pixels containing photosensors, such as photogates, phototransistors, photoconductors, or photodiodes. The photosensors each absorb incident radiation of a particular wavelength (e.g., optical photons or x-rays) and produce a signal corresponding to the intensity of light impinging on that element when an image is focused on the pixel array. The signal is then processed and used for storage, printing, display, or other purposes.
There are a number of different types of semiconductor-based imaging devices, including charge coupled devices (CCDs), photodiode arrays, charge injection devices (CIDs), hybrid focal plane arrays, and complementary metal oxide semiconductor (CMOS) imaging devices. Examples of CMOS imaging devices, processing steps thereof, and detailed descriptions of the functions of various CMOS elements of a CMOS imaging device are described, for example, in U.S. Pat. No. 6,140,630, U.S. Pat. No. 6,376,868, U.S. Pat. No. 6,310,366, U.S. Pat. No. 6,326,652, U.S. Pat. No. 6,204,524, and U.S. Pat. No. 6,333,205, each of which is assigned to Micron Technology, Inc. The disclosures of each of the forgoing patents are hereby incorporated by reference in their entirety.
During operation of imaging devices, photons of incident radiation impinging on the imaging devices may not all reach the photosensors to be converted into electrons. Also, the converted electrons may be lost in the various layers of the device or in adjacent pixel cells, or be mixed with dark current electrons in the various layers. It is thus desirable to provide an imaging device and/or system that mitigates the effects of the above discussed deficiencies.