Atomic imaging and modeling of passivation, functionalization, and atomic layer deposition nucleation of the SiGe(001) surface via H2O2(g) and trimethylaluminum dosing

Abstract

Passivation, functionalization, and atomic layer deposition (ALD) via H2O2(g) and trimethylaluminum (TMA) dosing were studied on the clean Si0.6Ge0.4(001) surface at the atomic level using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Chemical analysis of the surface was performed with in-situ X-ray photoelectron spectroscopy (XPS) while density functional theory (DFT) was employed to model the bonding of H2O2(g) chemisorbates to the substrate. A room temperature saturation dose of H2O2(g) covers the surface with a monolayer of OH and O chemisorbates. XPS and DFT demonstrate that the room temperature H2O2/SiGe surface is composed of only GeOH and GeO bonds while annealing induces an atomic layer exchange bringing Si to the surface to bond with OH or O while pushing Ge subsurface. The resulting SiOH and SiO surface is optimal because it can be used to nucleate high-k ALD and Si dangling bonds are readily passivated by forming gas. After H2O2(g) functionalization, TMA dosing, and a subsequent 230°C anneal, ordering along the dimer row direction is observed on the surface. STS verifies that the TMA/H2O2/SiGe surface has an unpinned Fermi level with no states in the band gap demonstrating the ability to serve as an ideal template for further high-k deposition.