Phosphorus doping and sharp profiles in silicon and silicon-germanium epitaxy by rapid thermal chemical vapor deposition

In situ phosphorus doping of silicon epitaxy from 700 to 1000 °C by low pressure rapid thermal chemical vapor deposition in a cold wall system, using dichlorosilane as the silicon source, has been investigated. At a high phosphine flow rate, the growth rate of silicon decreases dramatically (by approximately 60%) and the phosphorus incorporation level saturates. A significant persistence effect of phosphorus after turning off phosphine is observed. However, a sharper transition and higher doping level are observed in Si_1-xGe_x layers grown at 625 °C. Improvement of the phosphorus profile in silicon to approximately 13 nm/decade is demonstrated by reactor cleaning and ex situ etching of the wafer surface during a growth interruption after phosphorus-doped epitaxy. Despite the growth interruption, an in situ 800 °C bake at 10 Torr in hydrogen before regrowth can give an oxygen- and carbon-free interface without excessive dopant diffusion.