Method for producing composite wafer having oxide single-crystal film

A method of producing a composite wafer having an oxide single-crystal film on a support wafer, comprising steps of:

• implanting hydrogen atom ions or hydrogen molecule ions into an oxide single-crystal wafer through a surface thereof, which wafer is a lithium tantalate or lithium niobate wafer, to form an ion-implanted layer inside the oxide single-crystal wafer;
• subjecting at least one of the surface of the oxide single-crystal wafer and a surface of a support wafer to be laminated with the oxide single-crystal wafer to surface activation treatment;
• after the surface activation treatment, bonding the surface of the oxide single-crystal wafer to the surface of the support wafer to obtain a laminate;
• heat-treating the laminate at a temperature of 90° C. or higher at which cracking is not caused;
• and
• applying ultrasonic vibration to the heat-treated laminate to split the laminate along the ion-implanted layer to obtain an oxide single-crystal film transferred onto the support wafer;
• wherein an implantation dose of the hydrogen atom ions is from 5.0×1016 atom/cm2 to 2.75×1017 atom/cm2 and an implantation dose of the hydrogen molecule ions is from 2.5×1016 atoms/cm2 to 1.37×1017 atoms/cm2.