Noninvasive and Contactless Characterization of Electronic Properties at the Semiconductor/Dielectric Interface Using Optical Second-Harmonic Generation

Optical second-harmonic generation (SHG) is a reliabletechniquefor probing material surface and interface characteristics. Here,we have demonstrated a non-destructive, contactless SHG-based semiconductor/dielectricinterface characterization method to measure the conduction band offsetand quantitatively evaluate charge densities at the interface in oxideand at the oxide surface. This technique extracts the interface-trappedcharge type (donor/acceptor) and qualitatively analyzes the process-inducedvariation in interface states (D (it)), oxide,and oxide surface state density. These qualitative and quantitativeanalyses provide us with a glimpse into the band bending. The metrologymethod is validated through a detailed characterization of the Si/HfO2 interface. An optical setup has been developed to monitorthe time-dependent second-harmonic generation (TDSHG) from the semiconductor/oxideinterface. The temporal characteristics of TDSHG are explained withits relationship to the filling of D (it) and spatio-temporal trapping of photoexcited charge in oxide andat the oxide surface. A numerical solver, based on plausible carrierdynamics, is used to model the experimental data and to extract theelectronic properties at the Si/HfO2 interface.