JPWO2021108281A5

JPWO2021108281A5 - Surface acoustic wave device, its fabrication method, and radio frequency filter

Info

Publication number: JPWO2021108281A5
Application number: JP2022530731A
Authority: JP
Publication date: 2023-11-22

Claims

A surface acoustic wave device,
a crystal substrate,
a piezoelectric film formed from LiTaO ₃ or LiNbO ₃ and disposed on the crystal substrate;
an interdigital transducer electrode formed on the piezoelectric film;
a bonding layer mounted on the piezoelectric film;
a cap layer;
The cap layer is formed on the bonding layer to substantially confine propagating wave energy below the cap layer.

The surface acoustic wave device of claim 1, wherein the bonding layer is formed from _SiO2 .

The surface acoustic wave device of claim 1, wherein the cap layer is formed from Si.

the interdigital transducer electrode is formed directly on the top surface of the piezoelectric film;
The surface acoustic wave device according to claim 1, wherein the lower surface of the cap layer is in direct contact with the upper surface of the bonding layer.

5. The surface acoustic wave device of claim 4, wherein the bonding layer seals the interdigital transducer electrode.

a volume above the interdigital transducer electrode i includes a cavity defined by a top surface of the piezoelectric film and a bottom surface of the cap layer;
5. The surface acoustic wave device of claim 4, wherein the interdigital transducer electrode is exposed in the cavity .

7. The surface acoustic wave device of claim 6, wherein the cavity is further laterally defined by sidewalls.

8. The surface acoustic wave device according to claim 7, wherein the sidewall is formed by a peripheral portion of the bonding layer.

8. The surface acoustic wave device of claim 7, wherein the sidewall is formed by a wall structure at least partially embedded within the bonding layer.

the wall structure includes one or more trenches filled with SiN;
10. The surface acoustic wave device of claim 9, wherein the one or more trenches partially or completely surround the cavity.

2. The surface acoustic wave device of claim 1, further comprising a first contact pad and a second contact pad formed on the piezoelectric film and electrically connected to the interdigital transducer electrode.

12. The surface acoustic wave device of claim 11 , further comprising conductive vias extending from each of the first and second contact pads to a top surface of the cap layer.

2. The surface acoustic wave device of claim 1, further comprising a first reflector and a second reflector mounted on the piezoelectric film and disposed on first and second sides of the interdigital transducer electrode.

A method of producing an acoustic wave device, the method comprising:
forming or providing a piezoelectric layer formed from LiTaO ₃ or LiNbO ₃ ;
forming an interdigital transducer electrode on the piezoelectric layer;
mounting a bonding layer on the piezoelectric layer;
bonding a cap layer to the bonding layer;
thinning the piezoelectric layer to provide a piezoelectric film;
the bonding layer is between the cap layer and the piezoelectric layer,
The method, wherein the cap layer is configured to allow energy confinement of propagating waves in a volume below the cap layer.

15. The method of claim 14 , further comprising attaching a quartz substrate to the piezoelectric film.

15. The method of claim 14 , wherein implementing the bonding layer results in the bonding layer sealing the interdigital transducer electrode.

implementing the bonding layer results in a cavity above the interdigital transducer electrode;
the cavity is defined by a first surface of the piezoelectric film and a lower surface of the cap layer;
15. The method of claim 14 , wherein the interdigital transducer electrodes are exposed in the cavity.

18. The method of claim 17 , further comprising embedding a wall structure at least partially within the bonding layer such that the wall structure forms a sidewall of the cavity.

penetrating the cap layer and the bonding layer to provide electrical connection to each of a first contact pad and a second contact pad associated with the interdigital transducer electrode at a location on or near the top surface of the cap layer; 15. The method of claim 14 , further comprising forming a first conductive via and a second conductive via.

A radio frequency filter,
an input node that receives the signal;
an output node that provides a filtered signal;
a surface acoustic wave device electrically implemented between the input node and the output node to generate the filtered signal;
The surface acoustic wave device includes a quartz crystal substrate, a piezoelectric film formed from LiTaO ₃ or LiNbO ₃ and disposed on the quartz substrate, and an interdigital transducer electrode formed on the piezoelectric film,
The surface acoustic wave device further includes a bonding layer and a cap layer mounted on the piezoelectric film,
The cap layer is formed on the bonding layer to substantially confine propagating wave energy below the cap layer.