Method of making a multilayer piezoelectric substrate for acoustic wave device
A method of manufacturing a surface acoustic wave resonator includes forming or providing a support substrate layer, forming or providing piezoelectric layer of lithium niobate over the support substrate layer, and forming or providing an interdigital transducer electrode including a plurality of fingers over the piezoelectric layer. The piezoelectric layer formed or provided having a cut angle (e.g., the piezoelectric angle is cut so as to have a crystal orientation) that allows the surface acoustic wave device to operate as a longitudinally leaky surface acoustic wave device that confines the acoustic wave energy within the piezoelectric substrate and that has less propagation attenuation and a higher electromechanical coupling coefficient k 2 .
1 . A method of manufacturing a surface acoustic wave resonator, the method comprising:
forming a support substrate layer;
cutting a piezoelectric layer of lithium niobate, to form a cut angle defined by first, second and third Euler angles (φ 1 , θ 1 , ψ 1 ) so that the second Euler angle θ 1 has a value of about 76<θ 1 <86 degrees, and forming the piezoelectric layer over the support substrate layer to have a height H 1 with a value of about 0.3L<H 1 <0.9L, where L is a pitch between a plurality of fingers of an interdigital transducer electrode; and
forming the interdigital transducer electrode including the plurality of fingers over the piezoelectric layer.
2 . The method of claim 1 wherein forming the support substrate layer includes using a material chosen from the group consisting of quartz, silicon and diamond.
3 . The method of claim 2 further comprising cutting an angle on the support substrate layer to form a cut angle defined by first, second and third Euler angles (φ 2 , θ 2 , ψ 2 ) so that the second Euler angle θ 2 has a value of about 25<θ 2 <70 degrees.
4 . The method of claim 3 wherein the first Euler angle φ 1 of the support substrate layer is 0 degrees and the third Euler angle ψ 2 of the support substrate layer is 90 degrees.
5 . The method of claim 1 wherein the first Euler angle φ 1 of the piezoelectric layer is 0 degrees and the third Euler angle ψ 1 of the piezoelectric layer is 90 degrees.
6 . The method of claim 1 wherein the height H 1 has a value of about 0.5L<H 1 <0.9L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
7 . The method of claim 1 further including forming a functional layer between the piezoelectric layer and the support substrate layer.
8 . The method of claim 7 wherein forming the functional layer comprises forming a silicon dioxide layer with a thickness H 2 with a value of about 0.3L<H 2 <0.7L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
9 . The method of claim 8 wherein the height H 1 has a value of about 0.3L<H 1 <0.7L, where L is the pitch between the plurality of fingers of the interdigital transducer electrode.
10 . A method of manufacturing a surface acoustic wave resonator, the method comprising:
cutting a support substrate layer to form a first cut angle defined by first, second and third Euler angles (φ 2 , θ 2 , ψ 2 ) so that the second Euler angle θ 2 has a value of about 25<θ 2 <70 degrees;
cutting a piezoelectric layer of lithium niobate to form a second cut angle defined by first, second and third Euler angles (φ 1 , θ 1 , ψ 1 ) so that the second Euler angle θ 1 has a value of about 76<θ 1 <86 degrees, and forming the piezoelectric layer over the support substrate layer to have a height H 1 with a value of about 0.3L<H 1 <0.9L, where L is a pitch between a plurality of fingers of an interdigital transducer electrode; and
forming the interdigital transducer electrode including the plurality of fingers over the piezoelectric layer.
11 . The method of claim 10 wherein forming the support substrate layer includes using a material chosen from the group consisting of quartz, silicon and diamond.
12 . The method of claim 10 wherein the first Euler angle φ 1 of the piezoelectric layer is 0 degrees and the third Euler angle ψ 1 of the piezoelectric layer is 90 degrees.
13 . The method of claim 10 wherein the height H 1 has a value of about 0.5L<H 1 <0.9L, where L is a pitch between the fingers of the interdigital transducer electrode.
14 . The method of claim 10 wherein the first Euler angle φ 1 of the support substrate layer is 0 degrees and the third Euler angle ψ 2 of the support substrate layer is 90 degrees.
15 . The method of claim 10 further including forming a functional layer between the piezoelectric layer and the support substrate layer.
16 . The method of claim 15 wherein the functional layer is a silicon dioxide layer having a thickness H 2 with a value of about 0.3L<H 2 <0.7L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
17 . The method of claim 16 wherein the piezoelectric layer has a thickness H 1 with a value of about 0.3L<H 1 <0.7L, where L is the pitch between the plurality of fingers of the interdigital transducer electrode.