Design and performance of a three phase double level metal 160 × 100 element CCD imager

Our successful experience with four-phase overlapping gate CCD´s using double-level aluminum metallization with anodized aluminum isolation (1) suggested applications of this process to a three-phase design in order to increase circuit density. For example, a three-phase CCD area imager would have 78% more resolution elements than a four-phase imager with the same minimum geometries and overall array size. It should be noted that this trend does not extend simply to two-phase designs: they achieve directionality of transfer by the equivalent of a four-phase layout with pairs of adjacent electrodes clocked together or by additional, typically implanted, geometries whose size and critical placement preclude use of minimum electrode size.