Double level anodized aluminum CCD

CCD shift registers constructed using double level aluminum metallization are described. The insulation between the two metallization layers is anodized aluminum. The double level metallization relaxes the 2.5 micron tolerance required for single level metallization definition. This fabrication technique provides a simple quick method for forming the double level insulation where the thickness of the Al2O3forms the interelectrode gap. The double level structure seals the interelectrode gap from ambient effects and provides a coplanar high conductivity metallization system on both levels. The technique requires only one additional photomask over those needed for single level metallization. The Al2O3insulation thickness used has ranged from 700 Å to 6000 Å and is both electrically insulating (less than 10 µA/cm²at 40V) and physically hard.