438/773, In atmosphere containing water vapor (i.e., wet oxidation)438/774, In atmosphere containing halogen438/762, At least one layer formed by reaction with substrate438/297, Recessed oxide formed by localized oxidation (i.e., LOCOS)438/287, Gate insulator structure constructed of diverse dielectrics (e.g., MNOS, etc.) or of nonsilicon compound438/452, Plural oxidation steps to form recessed oxide257/E21.193, On single crystalline silicon (EPO)257/E21.285Of silicon (EPO)
A novel process for forming a robust, sub-100 Å oxide is disclosed. Native oxide growth is tightly controlled by flowing pure nitrogen during wafer push and nitrogen with a small amount of oxygen during temperature ramp and stabilization. First, a dry oxidation is performed in oxygen and 13% trichloroethane. Next, a wet oxidation in pyrogenic steam is performed to produce a total oxide thickness of approximately 80 Å. The oxide layer formed is ideally suited for use as a high integrity gate oxide below 100 Å. The invention is particularly useful in devices with advanced, recessed field isolation where sharp silicon edges are difficult to oxidize. For an oxide layer of more than 100 Å, a composite oxide stack is used which comprises 40-90 Å of pad oxide formed using the above novel process, and 60-200 Å of deposited oxide.
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