Methods and assemblies related to fabrication of acoustic wave devices
Methods and assemblies related to fabrication of acoustic wave devices. In some embodiments, a method for fabricating an acoustic wave device can include attaching a first surface of a piezoelectric layer, such as a LiTaO 3 or LiNbO 3 layer, to a handling substrate, and performing a thinning operation on the piezoelectric layer to expose a second surface of a reduced-thickness piezoelectric layer attached to the handling substrate. The method can further include bonding the second surface of the reduced-thickness piezoelectric layer to a first surface of a permanent substrate, and removing the handling substrate from the reduced-thickness piezoelectric layer. The handling substrate can be, for example, a silicon substrate, and the permanent substrate can be, for example, a quartz substrate.
1. A method for fabricating an acoustic wave device, the method comprising:
forming or providing a piezoelectric layer having a surface on a first side and a surface on a second side opposite from the first side;
attaching the first side of the piezoelectric layer to a handling substrate;
performing a thinning operation on the second side of the piezoelectric layer to form a reduced-thickness piezoelectric layer having a new surface on the second side;
bonding the second side of the reduced-thickness piezoelectric layer to a permanent substrate; and
removing the handling substrate from the second side of the reduced-thickness piezoelectric layer.
2. The method of claim 1 wherein the removing of the handling substrate from the reduced-thickness piezoelectric layer exposes the surface of the first side of the reduced-thickness piezoelectric layer, the surface of the first side of the reduced-thickness piezoelectric layer configured to support a surface acoustic wave.
3. The method of claim 2 further comprising forming an interdigital transducer electrode on the surface of the first side of the reduced-thickness piezoelectric layer to provide transducer functionality associated with the surface acoustic wave.
4. The method of claim 3 wherein an assembly of the acoustic wave device and the respective interdigital transducer electrode is one of an array of similar assemblies implemented as a wafer.
5. The method of claim 4 further comprising singulating the wafer to provide a plurality of acoustic wave devices.
6. The method of claim 1 wherein the handling substrate includes a silicon substrate.
7. The method of claim 1 wherein the permanent substrate includes a quartz substrate.
8. The method of claim 1 wherein the piezoelectric layer is formed from LiTaO 3 or LiNbO 3 with a crystal structure orientation such that the new surface of the second side of the reduced-thickness piezoelectric layer is a minus surface.
9. The method of claim 8 wherein the crystal structure orientation of the piezoelectric plate includes Euler angles (0°, 90°<θ<270°, 0°).
10. The method of claim 9 wherein the permanent substrate includes a surface bonded to the second side of the reduced-thickness piezoelectric layer, the bonded surface of the permanent substrate being a plus surface, a minus surface or an unpolarized surface resulting from crystal structure orientation of the permanent substrate.
11. The method of claim 10 wherein the bonded surface of the permanent substrate is a plus surface, and the permanent substrate includes Euler angles (φ, 90°<θ<270°, ψ), the angle φ having a value in a range of 0°≤φ<180°, the angle w having a value in a range of 0°≤ψ<180°.
12. The method of claim 10 wherein the bonded surface of the permanent substrate is a minus surface, and the permanent substrate includes Euler angles (φ, −90°<θ<90°, ψ), the angle φ having a value in a range of 0°≤φ<180°, the angle ψ having a value in a range of 0°≤ψ<180°.
13. The method of claim 10 wherein the bonded surface of the permanent substrate is an unpolarized surface, and the permanent substrate includes Euler angles (φ, 90°, ψ) or (φ, −90°, ψ), the angle φ having a value in a range of 0°≤φ<180°, the angle ψ having a value in a range of 0°≤ψ<180°.