Strain relaxation in strained-Si layers on SiGe-on-insulator substrates

Abstract

Misfit strain relaxation in tensile-strained Si grown at 600 • C on (0 0 1) SiGe-on-insulator substrates is experimentally studied for a tensile strain range between 0.4 and 1.2%. The critical thickness is found to be rather thinner than Houghton's critical thickness for a compressively-mismatched SiGe/Si(0 0 1) system. The thinner critical thickness in tensile-strained Si is attributed to the fact that the stress-relieving misfit dislocations are 90 • partial dislocations, instead of 60 • misfit dislocations for the compressive SiGe/Si(0 0 1) system. With increasing strained-Si layer thickness thicker than the critical thickness, 60 • misfit dislocation is found to be increasingly formed but the strain relaxation is sluggish. For a supercritical thickness ten times thicker than the critical thickness the tensile strain mostly remains. The initial strain relaxation is discussed in terms of the misfit dislocation morphology.

Variation of Threshold Voltage in Strained Si Metal–Oxide–Semiconductor Field-Effect Transistors Induced by Non-uniform Strain Distribution in Strained-Si Channels on Silicon–Germanium-on-Insulator Substrates

“…16) However, it has also been reported that the introduction of misfit dislocations only has a small impact on the strain relaxation in the Si/SiGe system. 17) The other reason for the variation of strain in the Si channel layers is the variation of the lattice spacing of the template SGOI layers, which is caused by the variation of the Ge content in the SGOI layers or the non-uniform relaxation of the SiGe crystal during the Ge condensation process. In order to estimate the variation of the lattice spacing of the template SGOI layers, the relationship between the Raman shift of the SGOI peak and that of strained Si is evaluated.…”