MEASUREMENTS OF INTERFACE STATE DENSITY BY X-RAY PHOTOELECTRON-SPECTROSCOPY

A novel technique has been developed for measuring interface state density at a dielectric-semiconductor interface in conjunction with X-ray photoelectron spectroscopy. In this technique, a thin dielectric film with a thickness up to 15 nm, is deposited on a semiconductor substrate. Surface potentials of the semiconductor and dielectric are then measured using X-ray photoelectron spectroscopy, the latter of which can be varied by charging the dielectric with low energy electrons. The interface state density at the dielectric-semiconductor interface is extracted from the relationship between the surface potentials of the semiconductor and the dielectric with a simple space-charge calculation similar to the conventional capacitance-voltage technique. As an example for the application of the proposed technique, interface state densities were measured on two different samples: (a) 2 nm SiO2 on n-Si(100) grown by dry oxidation at 600-degrees-C; (b) 3 nm SiO2 on n-Si(100) grown by dry oxidation at 900-degrees-C. The results obtained show that the proposed technique is useful in measuring interface state distributions across the bandgap.