Selective lateral germanium growth for local GeOI fabrication

Abstract

High quality local Germanium-on-oxide (GeOI) wafers are fabricated using selective lateral germanium (Ge) growth technique by a single wafer reduced pressure chemical vapor deposition system. Mesa structures of 300 nm thick epitaxial silicon (Si) interposed by SiO2 cap and buried oxide are prepared. HCl vapor phase etching of Si is performed prior to selective Ge growth to remove a part of the epitaxial Si to form cavity under the mesa. By following selective Ge growth, the cavity was filled. Cross section TEM shows dislocations of Ge which are located near Si / Ge interface only. By plan view TEM, it is shown that the dislocations in Ge which direct to SiO2 cap or to buried-oxide (BOX) are located near the interface of Si and Ge. The dislocations which run parallel to BOX are observed only in [110] and [1–10] direction resulting Ge grown toward [010] direction contains no dislocations. This mechanism is similar to aspect-ratio-trapping but here we are using a horizontal approach, which offers the option to remove the defective areas by standard structuring techniques. A root mean square of roughness of ∼0.2 nm is obtained after the SiO2 cap removal. Tensile strain in the Ge layer is observed due to higher thermal expansion coefficient of Ge compared to Si and SiO2.