Ultrathin silicon dioxide and aluminum oxide on silicon: Fundamental studies of the interface

With aggressive scaling of field effect transistor technology, understanding the dielectric/substrate interface structure has become a topic of paramount importance. Experimental and theoretical analysis of the atomic scale structure of two such interfaces is presented.; The optical phonons of the asymmetric stretch of the O in Si-O-Si bridging bond in amorphous SiO₂ show a red shift with decreasing oxide thickness, primarily due to interface effects like strain and substoichiometric silicon oxides (suboxides). A procedure based on a macroscopic optical model and effective medium approximation enables estimation of the average strain and suboxide concentration in films of different thickness. Analysis of infrared spectra shows that suboxide-rich layers in low temperature dry and wet oxides are confined to a distance of ∼1.5 nm from the interface.; Chemical vapor deposition of aluminum oxide films result in an atomically abrupt interface with the Si substrate. Post-deposition annealing of the as deposited films in an inert ambient induces formation of an interfacial SiO₂ layer. Atomic scale analysis reveals that excess oxygen incorporated into the aluminum oxide film during deposition reacts with the Si substrate during post deposition annealing to form an interfacial SiO₂ layer.