MOS Isolation processing
Patent 4551910 Issued on November 12, 1985. Estimated Expiration Date: 
November 27, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 27, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3751722 3752711 3906541 Double field oxidation process Patent #: 4352236 InventorApplicationNo. 06/675128 filed on 11/27/1984US Classes:438/452, Plural oxidation steps to form recessed oxide257/640, At least one layer of silicon nitride257/E21.258, Using masks (EPO)257/E21.293, Of silicon nitride (EPO)257/E21.559With plurality of successive local oxidation steps (EPO)ExaminersPrimary: Hearn, Brian E.Assistant: Hey, David A. Attorney, Agent or FirmInternational ClassesH01L 21/02 (20060101)H01L 21/762 (20060101) H01L 21/32 (20060101) H01L 21/70 (20060101) H01L 21/318 (20060101) AbstractA process for growing field oxide regions in an MOS circuit. An initial thermally grown layer of silicon nitride seals the substrate surface and reduces lateral oxidation, or bird's beak formation along the substrate-nitride interface. Field oxidation takes place in two steps, with the first step being a dry oxidation in HCL and the second taking place in steam.Other References
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