Effects of Surface Functionalization on Titanium Dioxide Atomic Layer Deposition on Ge Surfaces

Abstract

Water contact angle measurements, ellipsometry, transmission infrared spectroscopy, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and density functional theory were employed to study the atomic layer deposition (ALD) of titanium dioxide (TiO2) high-κ dielectric films on brominated, chlorinated, and 1-octadecanethiolate self-assembled monolayer (ODT SAM)-coated Ge(100) and Ge(111) substrates using titanium tetrachloride and water as ALD precursors. A strong dependence on temperature and type of passivation were observed for the TiO2 deposition rate, with deposition at lower temperature occurring to a significant extent only on the Cl-passivated Ge surface. It was found that bromination/thiolation is not compatible with area-selective ALD (ASALD) of TiO2 on Ge, since it would require growth at temperatures above 100 oC where ODT SAMs are not stable under the ALD conditions. On the other hand, the chlorination/thiolation route can be employed for selective deposition of TiO2 on Ge(100).