Selective epitaxial growth properties and strain characterization of Si_1−xGe_x in SiO₂ trench arrays

In this study, we investigated the formation of a Si_1−xGe_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 Si_1−xGe_x fin structures with different Ge concentrations (x = 0.2, 0.3 and 0.45) were examined. In addition, the strain evolution of a Si_1−xGe_x fin structure was analyzed by using reciprocal space mapping (RSM). An (111) facet was formed from the Si_1−xGe_x epi-layer and SiO₂ trench wall interface to minimize the interface and the surface energy. The Si_1−xGe_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 Si_0.8Ge_0.2 and Si_0.7Ge_0.3, and a Si_0.55Ge_0.45 strain-relaxed buffer. We further confirmed that the strain on the Si_1−xGe_x fin structures remained stable after oxide removal and H₂/N₂ post-annealing.