An Investigation of Si-SiO2 Interface Charges in Thermally Oxidized (100), (110), (111), (511) Silicon
NORTH CAROLINA UNIV AT CHAPEL HILL DEPT OF CHEMISTRY
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Trends in the electronic properties of the Si-SiO2 interface with various processing have been frequently reported. The present study focuses on silicon substrate orientation dependent trends in fixed oxide charge, Qf, and interface trap charge, Dit, for four silicon orientations 100, 110, 111 , and 511, for oxidation temperatures in the 750-1100 C range, with and without hydrogen-containing post-metal anneals, and for processing within and without a cleanroom. It is found that the presence of mobile ionic charge in non-cleanroom processing and the lack of post-metal annealing can either obscure or enhance some trends. Both Qf and Dit increase for decreasing oxidation temperature for all silicon orientations. The orientational ordering of the charges varies with oxidation temperature and is dominated by the silicon atom areal density at the lowest temperatures with 110 Si having the highest charge, but a change to the 111 orientation is observed at higher oxidation temperatures. This orientational charge parallels the orientational oxidation rate ordering but not the intrinsic stress. A model is proposed that considers the orientationally dominated oxidation rate, viscous relaxation, and strain accommodation across the interface as crucial processes.
- Physical Chemistry