Atomic imaging and modeling of passivation, functionalization, and atomic layer deposition nucleation of the SiGe(001) surface via H_2O_2(g) and trimethylaluminum dosing

摘要

Passivation, functionalization, and atomic layer deposition (ALD) via H_2O_2(g) and trimethylaluminum (TMA) dosing were studied on the clean Si_(0.6)Ge_(0.4)(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 H_2O_2(g) chemisorbates to the substrate. A room temperature saturation dose of H_2O_2(g) covers the surface with a monolayer of - OH and - 0 chemisorbates. XPS and DFT demonstrate that the room temperature H_2O_2/SiGe surface is composed of only Ge- OH and Ge-O 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 Si - OH and Si - O surface is optimal because it can be used to nucleate high-k ALD and Si dangling bonds are readily passivated by forming gas. After H_2O_2(g) functionalization, TMA dosing, and a subsequent 230 ℃ anneal, ordering along the dimer row direction is observed on the surface. STS verifies that the TMA/H_2O_2/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.