Acoustic wave device with anti-reflection layer

1. An acoustic wave device comprising:

a piezoelectric layer;

an interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a conductive layer;

an anti-reflection layer over the conductive layer, the anti-reflection layer has a thickness and includes a material, wherein the thickness and the material together cause reflectivity of the anti-reflection layer to be less than or equal to 0.2 for light having a wavelength of 365 nanometers, and the material including silicon; and

a temperature compensation layer over the anti-reflection layer.

2. The acoustic wave device of claim 1 wherein the anti-reflection layer is a silicon oxynitride layer.

3. The acoustic wave device of claim 2 wherein the silicon oxynitride layer has a thickness in a range from 100 nanometers to 120 nanometers.

4. The acoustic wave device of claim 1 wherein the anti-reflection layer is an amorphous silicon layer.

5. The acoustic wave device of claim 4 wherein the amorphous silicon layer has a thickness in a range from 5 nanometers to 15 nanometers.

6. The acoustic wave device of claim 1 wherein the conductive layer is an aluminum layer.

7. The acoustic wave device of claim 1 further comprising a substrate layer, the piezoelectric layer being on the substrate layer.

8. The acoustic wave device of claim 1 wherein the conductive layer is in physical contact with the anti-reflection layer.

9. The acoustic wave device of claim 1 further comprising a support substrate, the piezoelectric layer being over the support substrate, and the support substrate having a higher impedance than the piezoelectric layer.

10. An acoustic wave device comprising:

a piezoelectric layer;

a interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a first interdigital transducer electrode finger extending from a first bus bar and a second interdigital transducer electrode finger extending from a second bus bar, the first interdigital transducer electrode finger and the second interdigital transducer electrode finger being spaced apart from each other by a gap; and

an anti-reflection layer over the interdigital transducer electrode, the anti-reflection layer has a thickness and includes a material, wherein the thickness and the material together cause reflectivity of the anti-reflection layer to be less than or equal to 0.2 for light having a wavelength of 365 nanometers, the material including silicon, the anti-reflection layer being free from material of the interdigital transducer electrode, and the piezoelectric layer being free from the anti-reflection layer under the gap.

11. The acoustic wave device of claim 10 wherein the anti-reflection layer is a silicon oxynitride layer having a thickness in a range from 100 nanometers to 120 nanometers.

12. The acoustic wave device of claim 10 wherein the interdigital transducer electrode includes an aluminum layer, and the anti-reflection layer is in physical contact with the aluminum layer.

13. The acoustic wave device of claim 12 wherein the interdigital transducer electrode includes a metal layer positioned between the aluminum layer and the piezoelectric layer.

14. The acoustic wave device of claim 10 further comprising a temperature compensation layer over the anti-reflection layer.

15. The acoustic wave device of claim 10 wherein the anti-reflection layer is an amorphous silicon layer having a thickness in a range from 5 nanometers to 15 nanometers.

16. The acoustic wave device of claim 10 further comprising a support substrate, the piezoelectric layer being over the support substrate, and the support substrate having a higher impedance than the piezoelectric layer.

17. An acoustic wave device comprising:

a piezoelectric layer;

an interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a conductive layer, and a line width distribution of the interdigital transducer electrode is 2% of the line width or less;

an anti-reflection layer over the conductive layer, the anti-reflection layer including silicon; and

a temperature compensation layer over the anti-reflection layer.

18. The acoustic wave device of claim 17 wherein the anti-reflection layer includes a material and has a thickness that together cause reflectivity of the anti-reflection layer to be less than or equal to 0.2 for light having a wavelength of 365 nanometers.

19. The acoustic wave device of claim 17 wherein the anti-reflection layer is either a silicon oxynitride layer or an amorphous silicon layer.

20. An acoustic wave filter comprising:

a first acoustic wave resonator including a piezoelectric layer; a interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a first interdigital transducer electrode finger extending from a first bus bar and a second interdigital transducer electrode finger extending from a second bus bar, the first interdigital transducer electrode finger and the second interdigital transducer electrode finger being spaced apart from each other by a gap; and an anti-reflection layer over the interdigital transducer electrode, the anti-reflection layer has a thickness and includes a material, wherein the thickness and the material together cause reflectivity of the anti-reflection layer to be less than or equal to 0.2 for light having a wavelength of 365 nanometers, the material including silicon, the anti-reflection layer being free from material of the interdigital transducer electrode, and the piezoelectric layer being free from the anti-reflection layer under the gap; and

a plurality of additional acoustic wave resonators, the first acoustic wave resonator and the plurality of additional acoustic wave resonators together arranged to filter a radio frequency signal.