Analysis of low fixed pattern noise cell structures for photoconversion layer overlaid CCD or CMOS image sensors

A new low fixed pattern noise (FPN) cell structure, which can be used for photoconversion layer overlaid CCD or CMOS image sensors, was proposed and analyzed with a two-dimensional (2-D) device simulator. One of the most serious problems for this type of image sensor is the mixing of signal charges of neighboring cells during signal charge readout. The magnitude of signal mixing was as much as 20% for the conventional 2/3-in 2-million pixel STACK-CCD cell structure. FPN was very visible as a result of this signal mixing. This time, a new cell structure was proposed and analyzed to reduce signal mixing and FPN. It was possible to reduce signal mixing to a low value of 0.7% of the signal level using the new cell structure.