Non-destructive Characterization of Dielectric - Semiconductor Interfaces by Second Harmonic Generation

Here we present the characterization of dielectric - semiconductor interfaces using optical second harmonic generation (SHG). The technique is contactless, which makes it useful for non-destructive monitoring of ultra-thin dielectrics. The generated second harmonic is sensitive to material parameters and charges near interfaces. The signal exhibits time dependence due to charging of traps with carriers generated by the incident laser during the measurement. Quantitative models are applied to the time dependent SHG signals in the Al2O3 stacks, which provide trapping kinetics information, and thus Al2O3 film quality. Al2O3 films are commonly used for passivating Si in photovoltaic stacks. To further demonstrate that time dependent behavior is due to changes in the electric field across the semiconductor/dielectric interface, additional systems are presented for comparison: SiNx on silicon, passivated and non-passivated silicon-on-insulator substrates. Results confirm the value of SHG as a quality control method for multiple thin film dielectrics.