Low Temperature Epitaxy on H-Passivated Si(100) by Sputter Deposition

Abstract

ABSTRACTConventional preparation of Si for epitaxy involves high-temperature heating to remove surface oxide or to remove H passivation left by HF cleaning. Attempted MBE on H-passivated Si(100) has resulted in amorphous films below 640 K. We show that the use of ion beam sputtered Si allows the growth of thick (300 nm) epitaxial layers on H-passivated Si(100) at high rate (0.65 nm/s) and at 483 K, well below the H desorption temperature. This is because the sputtered Si has translational kinetic energy of tens of eV, well above the Si-H bond strength of a few eV, so that the passivating H does not block the epitaxial bonding sites as it does in MBE. The ability to grow epitaxially on H-passivated Si not only reduces the maximum Si processing temperature required, but also keeps the substrate passivated against contamination until the onset of deposition.During deposition, the LEED pattern changes gradually from the 1 × 1 of the H-passivated Si to the 2 × 1 reconstruction of bare or partially hydrogenated Si(1 00), yet SIMS shows that little of the disappearing H accumulates at the substrate interface or in the bulk of the film. Thermal desorption spectra show that its bonding remains similar to that on the substrate surface. Thus, it appears to float to the surface of the depositing film and become gradually knocked off of the surface over the course of a few hundred nm of deposition. Cross-sectional TEM lattice imaging shows near-perfect ordering of the epilayer and a barely distinguishable substrate interface.