Identification and Elimination of Gate Oxide Defect Origin Produced during Selective Field Oxidation

Abstract

Gate oxide defects induced by selective oxidation processes have been investigated by a copper decoration technique. Gate oxide defects are randomly distributed throughout active device regions and are not locally situated at the edges of isolation oxides. The density of gate oxide film defects has been found to agree with that of masking film defects produced by selective oxidation. Furthermore, by making use of a contrived novel processing, it has been confirmed that each location of gate oxide defects coincides with that of masking film defects induced by selective oxidation. The gate oxide defects are attributed to gate oxide thinning, which results from some Si nitride points formed on the Si substrate through masking defects induced during selective oxidation. Not only an additional sacrifice oxidation, followed by etchback of the resultant oxide, but also a plasma reactive sputter etching procedure prior to gate oxidation have been found to have a remarkable effect on gate oxide defect elimination.