Characterization techniques for contaminated gate oxide

The effect of homogeneous contamination on the oxide integrity is studied by electrical measurements. The contamination is introduced in the Buffered Oxide Etchant (BOE) used for the pre-oxidation clean. The DC parametric test of forcing 1 nA and measuring voltage across the oxide is used to relate contamination to the leakage current and also to the number of failures. The factors affecting the measured voltage such as temperature, light and noise are eliminated so that contamination dominates the change in the measured voltage. The current-transport mechanism through the oxide was found to obey the Fowler-Nordheim equation at high fields. The barrier height at both interfaces was lowered in some devices. A technique for measuring the low-field breakdown which is caused by defects in the oxide is developed