ABSTRACT
With the invention of the charge-coupled device (CCD) in 1970 byWillard S. Boyle and George E. Smith, which has been rewarded with a Nobel Prize in 2009, the first step towards image sensors based on integrated circuits (IC) being fabricated in semiconductor processes was taken [BS70]. Since then the total demand for image sensors has been continuously growing until now [Fro08]. Since the 1990s, research has began to focus on image sensors based on complementary metal-oxide-semiconductor (CMOS) processes that were capable of competing against the well established CCD solutions [Fos97], which are especially designed to serve the needs of high performance imaging and have virtues in parameters such as linearity, spectral responsivity, fill factor, possibilities of miniaturization, noise performance and dynamic range. Major drawbacks, however, are the need for nearly perfect charge transfer [Fos93], a lack of flexibility and the relatively high cost due to the need of an additional IC, which provides the readout circuitry. The flexibility of CMOS processes allows for on-chip signal conditioning circuitry or in-pixel intelligence. CMOS solutions are thus first of all often cost-efficient due to the possible camera on-a-chip approach [Fos93], which allows for instance in-pixel signal amplification, e.g. with common-drain/source follower amplifiers.
