The present invention is a method for cleaning a multilayer substrate, comprising steps of forming a protective film on a surface of the SiGe layer of an outermost
surface layer in the multilayer substrate and then cleaning the protective film with a cleaning liquid capable of
etching the protective film so that the protective film remains, a method for bonding substrates, wherein an outermost
surface layer of the multilayer substrate cleaned by the cleaning method and a surface of another substrate are bonded, and a method for producing a bonded
wafer, comprising steps of, forming a Si1-XGex layer and a protective layer on a surface of a Si
single crystal bond
wafer in order, performing
ion implantation through the protective layer thereby to form an
ion implanted layer, cleaning the bond
wafer, superposing closely a surface of the protective layer and a base wafer, then performing
delamination at the
ion implanted layer, forming a
thermal oxide film on a surface of the delaminated layer transferred to the base wafer side by the
delamination, removing the
thermal oxide film to
expose a condensation SiGe layer, and performing epitaxial growth of a Si
single crystal layer on the surface. Thereby, there is provided a cleaning method and a bonding method for preventing a SiGe layer of an outermost
surface layer in a multilayer substrate from being roughening of the surface, and a method for producing a bonded wafer for preventing bonding defects along with
ion implantation.