Elastic wave device and manufacturing method thereof
In an elastic wave device, a multilayer film including a piezoelectric thin film is provided on a support substrate, an interdigital transducer electrode is provided on one surface of the piezoelectric thin film, a wiring electrode is connected to the interdigital transducer electrode, the wiring electrode includes a lead electrode portion and a pad electrode portion, an external connection terminal is located above the pad electrode portion, the external connection terminal is electrically connected to the pad electrode portion, and the external connection terminal is bonded onto the pad electrode portion on the support substrate so that at least the piezoelectric thin film of the multilayer film is not present below the pad electrode portion.
1. An elastic wave device comprising:
a support substrate;
a multilayer film located on the support substrate and including a piezoelectric thin film;
an interdigital transducer electrode provided on a surface of the piezoelectric thin film;
a wiring electrode including a lead electrode portion that is located on the multilayer film and is electrically connected to the interdigital transducer electrode, and a pad electrode portion that is continuous with the lead electrode portion;
a support frame that encloses a region where the interdigital transducer electrode is provided;
a cover located on the support frame;
an under-bump metal layer that is connected to the pad electrode portion and passes through the support frame and the cover; and
an external connection terminal connected to the under-bump metal layer; wherein
at least the piezoelectric thin film of the multilayer film is not present below the pad electrode portion and the support frame.
2. The elastic wave device according to claim 1 , wherein the multilayer film is substantially not provided between the pad electrode portion and the support substrate below the pad electrode portion.
3. The elastic wave device according to claim 2 , wherein the pad electrode portion is provided on the support substrate so that a lower surface of the pad electrode portion is located within a recess provided in an upper surface of the support substrate.
4. The elastic wave device according to claim 1 , wherein the piezoelectric thin film is a piezoelectric single-crystal thin film.
5. The elastic wave device according to claim 4 , wherein Fe is included in the piezoelectric thin film.
6. The elastic wave device according to claim 1 , wherein the multilayer film includes a low acoustic velocity film that contacts with a lower surface of the piezoelectric thin film and that has a lower acoustic velocity of a bulk wave propagating therein than the acoustic velocity of a bulk wave propagating in the piezoelectric thin film, and a high acoustic velocity film that is laminated to a lower surface of the low acoustic velocity film and that has a higher acoustic velocity of a bulk wave propagating therein than the acoustic velocity of an elastic wave propagating in the piezoelectric thin film.
7. The elastic wave device according to claim 6 , wherein at least a portion of a layer in a multilayer body including the high acoustic velocity film and the low acoustic velocity film is provided between the pad electrode portion and the support substrate.
8. The elastic wave device according to claim 1 , further comprising:
a low acoustic velocity film that contacts with a lower surface of the piezoelectric thin film and that has a lower acoustic velocity of a bulk wave propagating therein than the acoustic velocity of a bulk wave propagating in the piezoelectric thin film; wherein
the support substrate is a high acoustic velocity support substrate that is laminated to a lower surface of the low acoustic velocity film and that has a higher acoustic velocity of a bulk wave propagating therein than the acoustic velocity of an elastic wave propagating in the piezoelectric thin film.
9. The elastic wave device according to claim 1 , wherein the external connection terminal includes a metal bump.
10. The elastic wave device according to claim 1 , wherein the lead electrode portion of the wiring electrode is continuous with the pad electrode portion, spanning from an upper surface of the multilayer film and along a side surface of the multilayer film, and the side surface of the multilayer film where the lead electrode portion is located is slanted relative to the upper surface of the support substrate so as to be located closer to the interdigital transducer electrode as the side surface progresses upward.
11. The elastic wave device according to claim 10 , wherein a step portion is provided in the side surface of the multilayer film where the lead electrode portion is provided.
12. The elastic wave device according to claim 1 , wherein a plurality of interdigital transducer electrodes are provided as the interdigital transducer electrode, adjacent ones of the plurality of interdigital transducer electrodes are electrically connected, and the elastic wave device further comprises a connecting wire provided on at least a portion of a layer of the multilayer film.
13. The elastic wave device according to claim 12 , wherein the connecting wire is provided so that at least the piezoelectric thin film of the multilayer film is not present below the connecting wire.
14. The elastic wave device according to claim 12 , wherein a structure between the pad electrode portion and the support substrate is different from a structure between the connecting wire and the support substrate.
15. The elastic wave device according to claim 1 , wherein
the support frame is laminated directly or indirectly onto the support substrate and includes an opening that opens upward;
the cover closes the opening in the support frame;
the under-bump metal layer is bonded to an upper surface of the pad electrode portion; and
the external connection terminal includes a metal bump that is bonded onto the under-bump metal layer.
16. The elastic wave device according to claim 15 , wherein the multilayer film is not present below the support frame.
17. The elastic wave device according to claim 15 , further comprising a partition wall that contacts with at least a portion of a layer in the multilayer film and the cover.
18. An elastic wave device, wherein the elastic wave device according to claim 1 is an upper surface-side elastic wave device provided on an upper surface side of the support substrate;
a lower surface-side elastic wave device is provided on a lower surface side of the support substrate; and
a connecting electrode that electrically connects the upper surface-side elastic wave device and the lower surface-side elastic wave device is provided in the support substrate.
19. The elastic wave device according to claim 18 , wherein the connecting electrode is a via hole electrode that passes through the support substrate.
20. A method of manufacturing the elastic wave device according to claim 1 , the method comprising:
forming the multilayer film including the piezoelectric thin film on the support substrate;
forming the interdigital transducer electrode on the surface of the piezoelectric thin film;
forming the wiring electrode including the lead electrode portion electrically connected to the interdigital transducer electrode and the pad electrode portion; and
forming the external connection terminal so as to be electrically connected to the under-bump metal layer; wherein
in the step of forming the multilayer film, in the formation of the piezoelectric thin film, the piezoelectric thin film is patterned after the piezoelectric thin film is formed.
21. The method according to claim 20 , wherein the piezoelectric thin film is patterned through etching.