Method for preparing germanium-on-insulator (GeOI) substrate

The invention discloses a method for preparing a germanium-on-insulator (GeOI) substrate. In the method, a back interface is passivated in the process of preparing the GeOI substrate; and the method comprises the following steps of: providing a semiconductor germanium substrate and a silicon substrate respectively, cleaning the germanium substrate and the silicon substrate, and removing natural oxide layers on the surfaces of the germanium substrate and the silicon substrate; growing a layer of SiO2 on the silicon substrate; depositing a layer of SixNy on the SiO2; depositing SiO2 for bonding on the SixNy, and depositing fluoridized SiO2 (FSG) for bonding on the germanium substrate; performing surface activation treatment on the SiO2 on the SixNy and the fluoridized SiO2 (FSG) on the germanium substrate, and performing alignment bonding along activated surfaces; annealing; and thinning. By the method, the quality of the back interface of the GeOI substrate can be improved.