A deep-depletion CCD imager for soft X-ray, visible, and near-infrared sensing

The design, fabrication and performance of a high-resolution 512 96 element buried-channel charge-coupled (CCD) imager on 1-5 kiloohm cm p-type 100-line uncompensated float-zone silicon substrates for soft X-ray (1-10 keV) and near-infrared (0.75-1 micron) sensing, are described. The greater-than-50-micron depletion layer width minimizes modulation transfer function degradation due to lateral minority-carrier diffusion effects, and both high- and low-resistivity regions are integrated on the same chip for deep-depletion CCDs and MOS transistor periphery circuitry. The low-resistivity region prevents transistor punchthrough caused by the very low substrate doping. The present process eliminates many of the high-resistivity silicon processing problems such as wafer breakage, and typical dark signal current levels of 4 nA/sq cm, and a 25 C imager transfer efficiency of 0.99997 are obtained.