Formation of Ultrathin Stacked Dielectrics Prepared by In-Situ Multi-Step RTP-CVD

Abstract

ABSTRACTUltrathin stacked SiO2/Si3N4/SiO2 films have been fabricated successfully using in-situ multi-step rapid thermal processing chemical vapor deposition (RTP-CVD). Stacked Si3N4/SiO2 (NO) layers were deposited first by RTP-CVD. Some samples were further rapid-thermal oxidized after stacked layer deposition to form oxide/nitride/oxide (ONO) stacked layers. Ellipsometry, Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) were performed to characterize the films. Results show that well defined stacked Si3N4/SiO2 layers were fabricated and for wafers subjected to rapid-thermal oxidation an oxygen-rich SixNyOz layer was formed on the top of the dielectric stack. Nitrogen pile-up at the dielectric/substrate interface was observed for all wafers indicating that nitrogen diffuses into the bottom oxide during nitride deposition even though the deposition temperature is well below those used in thermal nitridation of thermal oxides.