Low-Temperature Preparation of Oxygen- and Carbon-Free Silicon and Silicon-Germanium Surfaces for Silicon and Silicon-Germanium Epitaxial Growth by Rapid Thermal Chemical Vapor Deposition

Abstract

Photoluminescence (PL) from commensurately strained SiGe layers grown directly on silicon substrates and secondary ion mass spectroscopy (SIMS) of buried Si/SiGe interfaces are used to evaluate different low-temperature cleaning methods of substrate surfaces for silicon and SiGe epitaxy in a nonultrahigh vacuum system. Both the sources of contamination as well as effective cleaning methods were investigated. The dominant source of contamination came from the wafer being outside the reactor, not in the load lock or deposition chamber itself. The optimum surface preparation depends on the ratios of HF, NH 4 F, and deionized water of solutions that were used to remove the wet chemical oxide on the substrate surface. In situ bakes between 300 and 800ЊC in 0.25-250 Torr of hydrogen were examined after the ex situ clean using PL and SIMS measurements. An optimized ex situ clean [1:1000 HF(49%):deionized water (DI)] and in situ hydrogen bake (2 min at 800ЊC in 10 Torr) produces an oxygen-and carbonfree surface for silicon and SiGe epitaxy.

Low temperature Si homo-epitaxy by reduced pressure chemical vapor deposition using dichlorosilane, silane and trisilane

“…As explained before, any defect (either dislocation or point defects) in the Si seed layer or at the SiGe/Si interface will enhance non-radiative recombination of excited carriers in SiGe and will decrease photoluminescence of the SiGe layer [15]. Fig.…”

Strain relaxation of SiGe islands on compliant oxide

“…A short low temperature ͑800°C͒ hydrogen bake was able to remove the native oxide before growth without contributing to relaxation or buckling. 19 The growth temperature was 625°C, low enough to avoid any glass flow during the growth. Relaxation is negligible at temperature lower than 700°C.…”

Laser Activated Radical Generation in Rapid Thermal Processing

“…For silicon the main contaminants are carbon and oxygen, which forms SiO2. One cleaning method is the well known hydrogen bake [6,7]. Therefore the removal of carbon and SiO2 using hydrogen radicals or molecules was investigated by experiments [2,3].…”