FORMATION PROCESS OF HIGHLY RELIABLE ULTRA-THIN GATE OXIDE

A new oxide formation process featuring thermal oxidation in a strongl y reductive ambient, called hydrogen-radical-balanced steam oxidation (H/H2O oxidation), followed by post-oxidation annealing has been deve loped. In this oxidation process, only the strong Si-O bond which is p erfectly resistant even to the strongly reductive ambient survives and a high-integrity oxide him can be grown. From the results of the brea kdown tests under constant current stress (Q(BD)) and gate voltage shi ft (V-g shift) measurement under constant current stress, it has been revealed that the thin oxide film featuring high-integrity in breakdow n and strong resistance to electrical stress is obtained by H/H2O oxi dation with post-oxidation annealing in Ar gas ambient. Furthermore, b y adding O-2 gas to the Ar annealing ambient, the same effect of the p ost-oxidation annealing in Ar gas ambient can be obtained in a very sh ort time. This oxidation method is effective in forming thin oxide for use under a high electric field, such as a tunnel oxide for flush mem ories.