Inherent substrate-dependent growth initiation and selective-area atomic layer deposition of TiO2 using "water-free" metal-halide/metal alkoxide reactants

Titanium dioxide atomic layer deposition (ALD) is shown to proceed selectively on oxidized surfaces with minimal deposition on hydrogen-terminated silicon using titanium tetrachloride (TiCl4) and titanium tetra-isopropoxide [Ti(OCH(CH3)(2))(4), TTIP] precursors. Ex situ x-ray photoelectron spectroscopy shows a more rapid ALD nucleation rate on both Si-OH and Si-H surfaces when water is the oxygen source. Eliminating water delays the oxidation of the hydrogen-terminated silicon, thereby impeding TiO2 film growth. For deposition at 170 degrees C, the authors achieve similar to 2 nm of TiO2 on SiO2 before substantial growth takes place on Si-H. On both Si-H and Si-OH, the surface reactions proceed during the first few TiCl4/TTIP ALD exposure steps where the resulting products act to impede subsequent growth, especially on Si-H surfaces. Insight from this work helps expand understanding of "inherent" substrate selective ALD, where native differences in substrate surface reaction chemistry are used to promote desired selective-area growth. (C) 2015 American Vacuum Society.