Junction charge-coupled devices

Junction Charge-Coupled Devices, JCCD´s, offer attractive advantages over MOS-CCD´s, such as a high light sensitivity, good antiblooming properties in line sensors, the absence of fatal breakdown and complete compatibility with the fabrication of good bipolar transistors. Overlapping gates are not possible, and previously published potential calculations show that in order to obtain a smooth channel potential, a phosphorus implant under the steering p-type gates must be made with a mask opening slightly larger than the mask opening for the boron deposition. This difference in mask opening was obtained in a self-aligned manner by using the bird´s beaks of the LOCOS process. JCCD´s, containing 54 three-phase cells of 54 µm length each, were fabricated according to the potential calculations. The process consisted of five masking steps. Transfer inefficiencies down to 2 × 10^-5were measured, while the average dark current was 10 nA.cm^-2. The charge handling capability was 3 × 10¹¹el.cm^-2. Further improvement, especially in charge handling capability, seems possible.