High crystal quality strained Si0.5Ge0.5 layer with a thickness of up to 50 nm grown on the three-layer SiGe strain relaxed buffer

Abstract

In this work, a novel stacking structure of three-layer SiGe strain relaxed buffer/strained Si0.5Ge0.5 layer for shallow trench isolation last scheme is successfully developed. Firstly, a three-layer SiGe epitaxy with Ge concentration increased from bottom to top by roughly 10% combining with each layer post growth in-situ annealing is employed to effectively constrain the threading dislocation defect in the bottom and middle strain relaxed buffer layer and the top layer of strain relaxed buffer with thickness of ∼1 μm has no obviously defect impact. Before Si0.5Ge0.5 layer epitaxy on the top of this strain relaxed buffer layer, a chemical-mechanical planarization step is employed to improve surface roughness of strain relaxed buffer layer from 6.09 nm to 0.23 nm and final Si0.5Ge0.5 layer surface roughness from 6.73 nm to 0.76 nm. Finally, on the post CMP three-layer SiGe strain relaxed buffer, a smooth and high crystal quality strained Si0.5Ge0.5 layer with a thickness of 50 nm, which is larger than its critical thickness of ∼20 nm, is successfully prepared by utilizing our new developed technique.