Measurement of the strain in strained-Si/Si0.79Ge0.21 with HRBS/channeling

The strain in a Si(18 nm)/Si0.79Ge0.21 heterostructure is studied by means of high-resolution RBS/channeling angular scan. The observed channeling dip for the strained-Si layer is found to be shifted from that for the substrate Si0.79Ge0.21. The observed angular shift, however, is only 10-50% of the estimated kink angle of the channeling axis for a coherent interface. This does not necessarily mean that the strain was partly relaxed because the channeled ions could be steered into misaligned channels after crossing the interface. A Monte Carlo simulation of the trajectories of the channeled ions is performed for quantitative evaluation of the tetragonal strain induced in the Si layer. By comparing the result of the simulation with the observed angular shift the tetragonal strain was estimated to be 1.5 +/- 0.1%, which was in agreement with the result of Raman measurement (1.5-1.7%). The present result indicates that high-resolution RBS/channeling in combination with a Monte Carlo simulation is feasible for quantitative strain analysis in the strained-Si/SiGe. (c) 2006 Elsevier B.V. All rights reserved.