ABSTRACT
This chapter provides the fundamental knowledge required for understanding complementary metal-oxide-semiconductor (CMOS) image sensors. Most photo-detectors used in CMOS image sensors are pn-junction photodiodes (PDs). In a conventional CMOS image sensor, the surface of the silicon is interfaced with SiO2 and has some dangling bonds, which produce surface states or interface states acting as non-recombination centers. In the growth of optical fiber communications and fiber-to-the-home technology, silicon CMOS photo-receivers have been studied and developed. A photo-transistor can be made using the standard CMOS technology for a parasitic transistor. Some photo-conductive detector materials are used as a detector overlaid on the CMOS readout circuitry in a pixel owing to the photo-response with a variety of wavelengths such as X-ray, UV, and infrared. A PD in a CMOS image sensor is usually operated in the accumulation mode. In CMOS image sensors, to address each pixel, a scanner or a decoder is used.
