Composite substrate and method of manufacturing composite substrate

A method of manufacturing a composite substrate including a piezoelectric layer and a support substrate, the method comprising:

• performing ion implantation into a piezoelectric substrate;
• bonding the piezoelectric substrate and the support substrate;
• and separating the bonded substrate, at an ion-implanted portion of the piezoelectric substrate, into the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate after the bonding the piezoelectric substrate and the support substrate, wherein the piezoelectric substrate is lithium tantalate, has a portion in which Li concentration is 48.5±0.5% and a portion in which the Li concentration is 50.0±0.5%, and has a range in which the Li concentration becomes higher on a substrate surface side in a thickness direction.

A method of manufacturing a composite substrate including a piezoelectric layer and a support substrate, the method comprising:

• performing ion implantation into a piezoelectric substrate;
• bonding the piezoelectric substrate and the support substrate;
• and a step of separating the bonded substrate, at an ion-implanted portion of the piezoelectric substrate, into the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate after the bonding the piezoelectric substrate and the support substrate, wherein the piezoelectric substrate is lithium tantalate or lithium niobate, and Li concentration at a depth position of the piezoelectric substrate implanted with ions is greater than 50.0%.

A method of manufacturing a composite substrate including a piezoelectric layer and a support substrate, the method comprising:

• performing ion implantation into a piezoelectric substrate;
• bonding the piezoelectric substrate and the support substrate;
• and separating the bonded substrate, at an ion-implanted portion of the piezoelectric substrate, into the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate after the bonding the piezoelectric substrate and the support substrate, wherein the piezoelectric substrate is lithium tantalate, has a portion in which Li concentration is 48.5±0.5% and a portion in which the Li concentration is 50.0±0.5%, has a range in which the Li concentration becomes higher on a substrate surface side in a thickness direction, and the Li concentration at a depth position of the piezoelectric substrate implanted with ions is greater than 50.0%.

A composite substrate comprising:

• a piezoelectric layer and a support substrate, wherein the piezoelectric layer is lithium tantalate or lithium niobate, Li concentration of a surface of the piezoelectric layer is greater than 49.9%, a thickness of the piezoelectric layer is equal to or lower than 1.0 μm, and a maximum height Rz value of surface roughness of the piezoelectric layer is equal to or lower than 10% of the thickness of the piezoelectric layer.