Thermal stability of nitrided high-k dielectrics

Abstract

The use of metal oxides and silicate films (high-k) on Si to replace SiO2 and SixNyOz as gate dielectrics in advanced CMOSFET technology presents several challenges, mainly concerning the chemical and structural stability of the high-k during the fabrication steps of microelectronic devices. Recent investigations indicated that incorporation of nitrogen into the high-k films provides substantial improvements on the direction of overcoming such difficulties. We report on the atomic transport and exchange of N, O, Si, Al, and Hf during thermal processing of AlON, HfSiO and HfSiN films on Si. All systems were submitted to rapid thermal annealing in vacuum or in 18O-enriched O2, as well as in combined, sequential thermal processing steps. The areal densities of the chemical species of interest were determined, before and after thermal processing, by nuclear reaction analysis and by Rutherford backscattering spectrometry. The profiles of the light elements were also monitored by narrow nuclear resonant reaction profiling with sub-nanometric depth resolution. In addition, we present some results on x-ray photoelectron spectroscopy and low energy ion spectroscopy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)