A reduced-temperature process for preparing atomically clean Si(100) and SiGe(100) surfaces with vapor HF

TL;DR

This paper introduces a vapor HF cleaning process that effectively prepares atomically clean Si(100) and SiGe(100) surfaces at lower temperatures, facilitating advanced manufacturing and epitaxial growth.

Contribution

The study demonstrates that vapor HF cleaning reduces surface contamination and enables atomic-scale surface reconstruction at significantly lower temperatures than traditional methods.

Findings

VHF cleaning reduces carbon contamination on Si surfaces.

Lower temperature (600°C for Si, 580°C for SiGe) reconstruction achieved.

STM hydrogen desorption lithography demonstrated on VHF-treated surfaces.

Abstract

Silicon processing techniques such as atomic precision advanced manufacturing (APAM) and epitaxial growth require surface preparations that activate oxide desorption (typically >1000 $^{\circ}$C) and promote surface reconstruction toward atomically-clean, flat, and ordered Si(100)-2$\times$1. We compare aqueous and vapor phase cleaning of Si and Si/SiGe surfaces to prepare APAM-ready and epitaxy-ready surfaces at lower temperatures. Angle resolved X-ray photoelectron spectroscopy (ARXPS) and Fourier transform infrared (FTIR) spectroscopy indicate that vapor hydrogen fluoride (VHF) cleans dramatically reduce carbon surface contamination and allow the chemically prepared surface to reconstruct at lower temperatures, 600 $^{\circ}$C for Si and 580 $^{\circ}$C for a Si/Si$_{0.7}$Ge$_{0.3}$ heterostructures, into an ordered atomic terrace structure indicated by scanning tunneling microscopy (STM). After thermal treatment and vacuum hydrogen termination, we demonstrate STM hydrogen desorption lithography (HDL) on VHF-treated Si samples, creating reactive zones that enable area-selective chemistry using a thermal budget similar to CMOS process flows. We anticipate these results will establish new pathways to integrate APAM with Si foundry processing.