Ultra-Thin SiO2/Si Interface Quality In-Line Monitoring Using Multiwavelength Room Temperature Photoluminescence and Raman Spectroscopy

Abstract

Multiwavelength room temperature photoluminescence (RTPL) and Raman spectroscopy were proposed as in-line monitoring techniques for characterizing the dielectric/Si interface. As an application example, ∼7.0 nm thick ultra-thin SiO2 films on 300 mm Si wafers, prepared by various oxidation techniques and conditions, were characterized using multiwavelength RTPL and Raman spectroscopy. Specifically, overall quality of the ultra-thin SiO2/Si interface (including passivation characteristics) and Si lattice stress beneath SiO2 films are investigated. The overall SiO2/Si interface quality was seen to be very dependent on oxidation technique and process conditions. Within wafer and wafer-to-wafer variations of SiO2/Si interface quality were successfully characterized by RTPL and Raman spectra measurements. For electrical analysis of SiO2/Si-based structures, non-contact corona charge-based, in-line (capacitance-voltage (C-V) and stress induced leakage current (SILC)) measurements were performed and compared with RTPL and Raman characterization results. Surprisingly, significant variations in RTPL intensity at and near the corona charge-based measurement sites, indicated that the corona-based electrical measurement technique, though non-contact, was indeed invasive. The effect of corona-charge based electrical measurements on SiO2/Si interface was permanent and even clearly visible from the back side of the wafer. RTPL intensity variations at and near the measurement sites remained, even after a forming gas anneal.