High resolution Rutherford Backscattering Spectrometry investigations of ZrO2 layer growth in the initial stage on native silicon oxide and titanium nitride

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 ZrO2-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 (SiO2) or with TiN have been studied. In the first case the interface is sharp, except for a small intermediate ZrSiO4-layer, and no diffusion of Zr-atoms in SiO2 could be detected. A quite different behaviour could be derived from high resolution spectra for the growth of ZrO2 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.

► Rutherford Backscattering has been used to study ultrathin high-k ZrO2-layers.
► Precise knowledge of the surface topography allows an accurate interpretation.
► For ZrO2 on native silicon oxide, Zr showed no diffusion into the substrate.
► At the interface ZrO2/SiO2 a monolayer of ZrSiO4 is formed.
► Deposited on polycrystalline TiN, Zr diffuses into the TiN-layer up to 3 nm deep.