Hafnium based oxides, grown by atomic layer deposition, are the most prominent candidates for future high-k dielectrics in next generation DRAM technology. In order to temperature stabilize these materials and to achieve the crystalline phases with the desired high dielectric constant k in the range of 25 - 30, doping, e.g. by Al or Si has drawn considerable interest over the last years.

Although much work was done in examination of the initial growth of HfO₂-films from hafnium tetrachloride and water, there is a lack of information regarding the usage of metal-organic precursors and ozone, especially in the case of ternary films like Hf_xSi_(1-x)O₂. Therefore we have in our work examined the initial growth of Hf_xSi_(1-x)O₂-films using tetrakis(ethylmethylamino)hafnium, tetrakis(dimethylamino)silane and ozone in dependence of process parameters (deposition temperature and chamber pressure) as well as substrate materials (SiO₂, Si₃N₄, Al₂O₃, TiN). Most measurements were done by angle resolved X-ray photoelectron spectroscopy and interpreted with a model proposed by Mack et al [1]. With the model it is possible to determine the coverage and/or thickness of submonolayers/layers of Hf_xSi_(1-x)O₂ in dependence of process conditions.

In general the film growth is inhibited during the first 5 - 10 cycles, but nevertheless is 2-dimensional. It also does not show significant difference depending on the substrate material except for TiN. In this case the growth rate is nearly constant from the first cycle on, which is attributed to TiN-substrate roughness. It will be shown, that with increased deposition temperature and chamber pressure there is an increase in the growth per cycle value together with a change in Si/Hf-ratio to higher values. This can be explained by decomposition of the precursors at higher deposition temperatures along with lower impurity content.

[1] Mack et al, Applied Surfaces Science, Volume 252, Issue 23, 2006, Pages 8270-8276

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1. Thermal Stability of thin ALD ZrO₂ Layers as Dielectrics in Deep Trench DRAM Devices Annealed in N₂ and NH₃