High resolution Rutherford Backscattering Spectrometry investigations of ZrO_2 layer growth in the initial stage on native silicon oxide and titanium nitride

摘要

High Resolution Rutherford Backscattering Spectrometry (HR-RBS) with a depth resolution of about 0.3 nm near the surface was used to analyse the interface between ultrathin high-k ZrO_2-layers and the substrate. In order to improve the quality of the analysis, a method was developed that takes local thickness variations, obtained by atomic force microscopy, into account during simulation of the HR-RBS spectra. The initial stages of atomic layer deposition (ALD) growth processes on Si(100) covered with native silicon oxide (SiO_2) or with TiN have been studied. In the first case the interface is sharp, except for a small intermediate ZrSiO_4-layer, and no diffusion of Zr-atoms in SiO_2 could be detected. A quite different behaviour could be derived from high resolution spectra for the growth of ZrO_2 on TiN. In addition, measurements of the surface topography of the TiN-layer revealed non-negligible surface roughness. Diffusion of Zr into polycrystalline TiN was demonstrated after correction for surface roughness. This observation indicates that already during the first ALD reaction cycle a small proportion of the deposited Zr-atoms diffuses - probably along grain boundaries -into the TiN-layer up to a depth of 3 nm.