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

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, NH₄F, and deionized water of solutions that were used to remove the wet chemical oxide on the substrate surface. In situ bakes between 300 and 800 °C 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)] any in situ hydrogen bake (2 min at 800 °C in 10 Torr) produces an oxygen- and carbon-free surface for silicon and SiGe epitaxy.