Relaxed graded SiGe donor substrates incorporating hydrogen-gettering and buried etch stop layers for strained silicon layer transfer applications

We report on the use of buried, tensilely strained Si (i.e., epsilon-Si) layers for improving the fabrication of strained silicon-on-insulator (SSOI) substrate via the hydrogen-induced layer exfoliation process. Previous work involving tensile epsilon-Si0.4Ge0.6 layers in relaxed Ge/del(x)(Si1-xGex)/Si demonstrated significant hydrogen gettering via the formation of strain-relieving platelets within the tensile epsilon-Si0.4Ge0.6 layers, leading to an overall increase in layer transfer efficiency for germanium-on-insulator substrate fabrication. The use of buried epsilon-Si layers in relaxed Si1-xGex for SSOI fabrication, however, exhibits more complex exfoliation behavior that is dependent on a combination of both the degree of tensile strain as well the amount of damage present in the adjacent Si1-xGex alloy. It was determined that a tensile strain level of approximately 1.6% in Si (corresponding to a Si0.6Ge0.4-based donor structure) was needed to overcome the intrinsic gettering potential of implantation damage in the adjacent Si0.6Ge0.4 layers to result in enhanced layer exfoliation. The primary mechanism responsible for improving layer exfoliation was found to be the formation of strain-relieving {100}-type platelets in the 1.6% strained-Si epilayer. Lastly, a Si0.6Ge0.4-based donor structure which incorporated epsilon-Si layers as transfer, hydrogen gettering, and etch stop layers was demonstrated. Such a structure may prove useful for the reuse of a significant portion of the original SSOI donor structure. (c) 2007 American Institute of Physics.