Selective epitaxial growth properties and strain characterization of Si 1− x Ge x in SiO 2 trench arrays

In this study, we investigated the formation of a Si1−x Ge x fin structure in SiO2 trench arrays via an ultra-high-vacuum chemical-vapor deposition (UHV-CVD) selective epitaxial growth (SEG) process. Defect generation and microstructures of Si1−x Ge x fin structures with different Ge concentrations (x = 0.2, 0.3 and 0.45) were examined. In addition, the strain evolution of a Si1−x Ge x fin structure was analyzed by using reciprocal space mapping (RSM). An (111) facet was formed from the Si1−x Ge x epi-layer and SiO2 trench wall interface to minimize the interface and the surface energy. The Si1−x Ge x fin structures were fully relaxed along the direction perpendicular to the trenches regardless of the Ge concentration. On the other hand, the fin structures were fully or partially strained along the direction parallel to the trenches depending on the Ge concentration: fully strained Si0.8Ge0.2 and Si0.7Ge0.3, and a Si0.55Ge0.45 strain-relaxed buffer. We further confirmed that the strain on the Si1−x Ge x fin structures remained stable after oxide removal and H2/N2 post-annealing.