Method for manufacturing composite substrate provided with piezoelectric single crystal film

A method of manufacturing a composite substrate equipped with a piezoelectric single-crystal film, the method comprising:

• performing a first ion implantation treatment into a surface of a piezoelectric single-crystal substrate comprising lithium tantalate or lithium niobate to form a first ion implantation layer in the piezoelectric single-crystal substrate, wherein the first ion implantation treatment is performed with ion species containing at least one of a hydrogen atom ion (H+) and a hydrogen molecule ion (H2+) at an ion implantation dose of 1.0×1016 atoms/cm2 or more and 3.0×1017 atoms/cm2 or less in terms of a hydrogen atom ion (H+);
• performing a second ion implantation treatment into a surface of a temporary bonding substrate to form a second ion implantation layer in the temporary bonding substrate, wherein the temporary bonding substrate is a single-crystal silicon substrate;
• bonding the surface of the piezoelectric single-crystal substrate that has the first ion implantation layer to the surface of the temporary bonding substrate that has the second ion implantation layer;
• separating the piezoelectric single-crystal substrate into the first ion implantation layer and a first remaining portion of the piezoelectric single-crystal substrate and removing the first remaining portion, thereby forming a piezoelectric single-crystal film having a thickness of 2 μm or less on the second ion implantation layer of the temporary bonding substrate;
• bonding a supporting substrate to the piezoelectric single-crystal film;
• and
• separating the temporary bonding substrate into the second ion implantation layer and a second remaining portion of the temporary bonding substrate and removing the second remaining portion, thereby forming a single-crystal silicon film having a thickness of 2 μm or less on the piezoelectric single-crystal film.