Formation Process of Highly Reliable Ultra-Thin Gate Oxide

A new oxide formation process featuring thermal oxidation in a strongly reductive ambient, called hydrogen-radical-balanced steam oxidation (H*/H 2 O oxidation), followed by post-oxidation annealing has been developed. In this oxidation process, only the strong Si-O bond which is perfectly resistant even to the strongly reductive ambient survives and a high-integrity oxide film can be grown. From the results of the breakdown tests under constant current stress (Q BD ) and gate voltage shift (V g shift) measurement under constant current stress, it has been revealed that the thin oxide film featuring high-integrity in breakdown and strong resistance to electrical stress is obtained by H*/H 2 O oxidation with post-oxidation annealing in Ar gas ambient. Furthermore, by adding O 2 gas to the Ar annealing ambient, the same effect of the post-oxidation annealing in Ar gas ambient can be obtained in a very short time. This oxidation method is effective in forming thin oxide for use under a high electric field, such as a tunnel oxide for flush memories.