An investigation of Si-SiO2 interface charges in thermally oxidated (100), (110), (111), (511) silicon

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, Q(sub f), and interface trap charge, D(sub it), for four silicon orientations: (100), (110), (111), and (511), for oxidation temperatures in the 750 to 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 Q(sub f) and D(sub it) 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.