Zero Loss Transfer Across Gaps in a CCD

In a charge-coupled device,1 charge is transferred from a potential well under one metallization to a deeper potential well under an adjacent metal. Since the metals cannot touch one another, this process involves passing through an interelectrode gap. If the potential pattern is such that there is a potential barrier or a potential well in the space at the end of transfer, then complete charge transfer is impossible. If two layers of metallization are used (which are separated by an insulating layer of 1000 A), no barrier or well can form. This requires a more complex technology, so it would be desirable to make a CCD with one layer of metallization. In this paper the effect of interface charge and substrate doping on potential well and barrier formation will be analyzed. It will be shown that, for any given substrate doping and drive voltages, there is an interface charge for which neither well nor barrier forms. The calculations in this paper will assume an infinitely long gap which will ensure that no yield losses will result from small variations in gap width or surface charge magnitude. 3169