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

Photoluminescenee (PL) from commensurately strained Sice layers grown direc tly on silicon substrates and secondary ion mass spectroscopy (SIMS) of bur ied Si/SiGe interfaces are used to evaluate different low-temperature clean ing methods of substrate surfaces) for silicon and SiGe epitaxy in a nonult rahigh vacuum system. Both the sources of contamination as well as effectiv e cleaning methods were investigated. The dominant sourer of contamination came from the wafer being outside the reactor, not in the load lock or depo sition chamber itself. The optimum surface preparation depends on the ratio s of HF . NH4F and deionized water uf solutions that were used to remove th e wet chemical oxide on the substrate surface. In situ bakes between 300 an d 800 degreesC in 0.25-250 Torr of hydrogen were examined after the ex situ clean using PL and SIMS measurements. An optimized ex situ clean 11:1000 H F(49%):deionized water (DI)] and in situ hydrogen bake (2 min at 800 degree sC in 10 Torr) produces an oxygen- and carbon-free surface for silicon and SiGe epitaxy. (C) 2000 The Electrochemical Society. S0013-4651(00)03-083-4. All rights reserved.