LOW-TEMPERATURE EPITAXIAL-GROWTH BY MOLECULAR-BEAM EPITAXY ON HYDROGEN-PLASMA-CLEANED SILICON-WAFERS

In a single step, the surfaces of silicon wafers were cleaned in an argon-hydrogen discharge plasma using the Balzers ultrahigh vacuum plasma source. The residual gas ions were monitored during the cleaning procedure to elucidate the process chemistry. Homoepitaxial growth by molecular beam epitaxy (MBE) at low temperatures could be achieved after the cleaning step, indicating a damage-free plasma procedure. Secondary ion mass spectrometry depth profiles of the substrate-epilayer interface show interface contamination levels of approximately 10(-2) monolayers for oxygen and less than 10(-3) monolayers for carbon. In additional experiments, patterned wafers were cleaned in the plasma. Local epitaxial growth by MBE at a temperature of 550-degrees-C avoiding high temperature steps could be achieved on these wafers. Furthermore, the influence of the plasma treatment on the wafer surface was investigated in detail for electron vs. ion bombardment and different bombardment energies using high-resolution X-ray rocking curve diffraction.