Relaxation enhancement of SiGe thin layers by ion implantation into Si substrates

Strain-relaxed SiGe buffer layers (SiGe virtual substrates) are of great importance for fabricating such strained SiGe high-speed hetero-devices as strained Si channel MOSFETs. To obtain full relaxation of the SiGe films grown on Si substrates by the conventional graded buffer method, however, the thickness of the SiGe films generally has to be beyond several hundred nm. To overcome this problem, a low temperature (LT) method, where defects in the LT Si buffer layer act as dislocation sources and enhance the relaxation of the overgrown SiGe film, was invented. Here we propose a new method to introduce defects in Si substrates by ion implantation, which enhances the relaxation of SiGe films during growth of the SiGe films on ion implanted Si substrates. This ion implantation method may be superior to the LT method because its controllability of defects is much higher than that of LT method and it is applicable to the CVD method in which the LT growth cannot be performed.