Patent ID: 6165918
Filing Date: 2000-12-26
Classification: H01L,Y10S

Abstract:
A method for forming gate oxides of different thicknesses, comprising:growing a first gate oxidation sub-layer precursor on a silicon substrate having a first gate region separated from a second gate region by a local oxidation of silicon field;depositing a first layer of poly-silicon on said first gate oxidation sub-layer precursor;masking a first portion of said first layer of poly-silicon that overlies both i) a first portion of said first gate oxidation sub-layer precursor and ii) said first gate region;removing a) a second portion of said first layer of poly-silicon that overlies both a second portion of said first gate oxidation sub-layer precursor and said second gate region so as to form a first poly-silicon sub-layer and b) at least a fraction of a thickness of said second portion of said first gate oxidation sub-layer precursor that overlies said second gate region so as to form a first gate oxidation sub-layer;growing a second gate oxidation sub-layer precursor on both I) said first poly-silicon sub-layer and ii) a portion of said first gate oxidation sub-layer that overlies said second gate region;depositing a second layer of poly-silicon on said second gate oxidation sub-layer precursor;masking a first portion of said second layer of poly-silicon that overlies said second gate region;removing a second portion of said second layer of poly-silicon that overlies said first gate region so as to form a second poly-silicon sub-layer having a gap, said first poly-silicon sub-layer and said second poly-silicon sub-layer together composing a poly-silicon layer;filling the gap in said second layer of poly-silicon with an oxide; andremoving a portion of said second gate oxidation sub-layer precursor that overlies said first gate region by etching back so as to form a second gate oxidation sub-layer, said first gate oxidation sub-layer and said second gate oxidation sub-layer together composing a gate oxidation layer having gate oxides of different thicknesses.