CVD Si 1-x Ge x epitaxial growth and its applications to MOS devices

Abstract

By ultraclean low-pressure CVD using SiH 4 and GeH 4 gases, high quality Si 1-x Ge x epitaxial growth on Si(100) is achieved. In order to prevent island growth and generation of misfit dislocations in the heterostructure, relatively low deposition temperatures and optimization of the layer thickness are inevitable for the high Ge fractions. Atomically flat surfaces and interfaces for the Si/Si 1-x Ge x /Si heterostructures containing Si 0.8 Ge 0.2 , Si 0.5 Ge 0.5 and Si 0.3 Ge 0.7 layers are obtained by deposition at 550, 500 and 450 degrees C, respectively. It is also found that the Si 0.5 Ge 0.5 -channel pMOSFET has the highest peak field- effect mobility. The deposition rate, the Ge fraction and the in-situ doping characteristics with the B 2 H 6 and PH 3 addition are expressed based on the modified Langmuir-type adsorption and reaction scheme, assuming that the reactant gas adsorption/reaction depends on the surface materials. Ultrasmall MOSFETs have been also realized by selective epitaxy of impurity-doped Si 1-x Ge x on the source/drain regions.