Preparation of Germanium-on-insulator (GOI) wafers by means of layer transfer tehnique

In this work, transfer of the Ge layer on to a SiO2 layer to realize a Ge-on-Insulator (GOI) wafer is performed based on a wafer-level bonding process. The process flow starts with the preparation of the target (Si wafer with SiO2) and the donor (Si wafer with Ge) wafers. The target and the donor wafers are bonded using oxide-oxide fusion bonding technique. The silicon substrate of the donor wafer is removed afterwards with wafer grinding and chemical-mechanical-polishing (CMP). Finally, Ge CMP is applied to finish the Ge surface and remove dislocations and GeSi intermixing formed during initial growth on the Si substrate of the donor wafer. The entire layer transfer process is done on 8-inch wafer level. Analysis after finalizing the process shows that a very smooth Ge surface with a RMS (Rq) roughness of 0.1 nm is achieved. The developed layer transfer process allows to achieve Ge layer on isolator; thus GOI wafers; which is considered as a key substrate for electro-optical applications [1].