The Diffusion Mechanism of Ge During Oxidation of Si/SiGe Nanofins

Abstract

A recently discovered, enhanced Ge diffusion mechanism along the oxidizing interface of Si/SiGe nanostructures has enabled the formation of single-crystal Si nanowires and quantum dots embedded in a defect-free, single-crystal SiGe matrix. Here, we report oxidation studies of Si/SiGe nanofins aimed at gaining a better understanding of this novel diffusion mechanism. A superlattice of alternating Si/Si 0.7 Ge 0.3 layers was grown and patterned into fins. After oxidation of the fins, the rate of Ge diffusion down the Si/SiO 2 interface was measured through the analysis of HAADF-STEM images. The activation energy for the diffusion of Ge down the sidewall was found to be 1.1 eV, which is less than one-quarter of the activation energy previously reported for Ge diffusion in bulk Si. Through a combination of experiments and DFT calculations, we propose that the redistribution of Ge occurs by diffusion along the Si/SiO 2 interface followed by a reintroduction into substitutional positions in the crystalline Si.

A Review of the Gate-All-Around Nanosheet FET Process Opportunities

“…Finally, the initial Si-SiGe stack for nanosheets itself is susceptible to thermal intermixing when going through numerous thermal cycles before the channel release step. There have been several studies examining the extent of this intermixing and the mechanism of such diffusion [33][34][35]. As long as the SiGe channels can etch selective to Si channel sheets, and the Si sheets are not over-etched due to Si-SiGe intermixing, this effect is tolerable.…”