A New Technique for Hardening CCD Imagers by Suppression of Interface State Generation

A new technique has recently been developed to suppress dark current generation by interface states in buried channel CCD imagers by a change in the operating biases of the CCD during the integration cycle. In this work, this technique is successfully applied to suppressing interface state generated dark current in two irradiated CCDs. A dark current of only 1.3 nA/cm2 at 1 Mrad dose has been obtained on a CCD fabricated with radiation hardened oxides using this technique, compared to 360 nA/cm2 in the normal mode of operation. Experimental data on the irradiated CCDs show an excellent correlation between dark current generated by interface states in the normal mode of operation and the density of interface states measured using the periodic pulse technique.