Methods to reduce the loading effect in selective and non-selective epitaxial growth of sigec layers

Abstract

Various methods to reduce both global and local loading effect during non-selective and selective epitaxial growth of Si1−x−yGexCy (0.09≤x≤0.28 and 0≤y≤0.01) layers have been proposed. Evaluation of the proposed solutions for issues such as defect generation and the possibility for integration in device structures have been performed. The key point in these methods is based on reduction of surface diffusion of the adsorbed species on the oxide. In non-selective epitaxy, this was achieved by introducing a thin silicon polycrystalline seed layer on the oxide prior to Si1−x−yGexCy deposition. The thickness of this seed layer had a crucial role on both the global and local loading effect, and also on the epitaxial quality. Higher carbon content (y≥0.006) in Si1−x−yGexCy layers had no noticeable influence on the loading effect, however, the defect density was clearly increased in these layers. In selective epitaxy case, introducing square polycrystalline Si stripes around the oxide openings acting as diffusion barriers have reduced the loading effect effectively. Meanwhile, using Si nitride stripes showed no visible effect on Si1−x−yGexCy layer profile. Further decrease in loading effect can be performed by increasing the HCl partial pressure during epitaxy. Chemical–mechanical polishing (CMP) was performed to remove the polycrystalline stripe on the oxide.