Acoustic wave device, radio-frequency front-end circuit, and communication apparatus
An acoustic wave device includes a laminated film on a support substrate and inside a portion of an outer edge of the support substrate in plan view and including a piezoelectric thin film, an IDT electrode on the laminated film, an insulating layer on the support substrate and the laminated film and extending from a region above the support substrate to a region above the laminated film, a connecting electrode on the insulating layer and electrically connected to the IDT electrode, and an external connection terminal electrically connected to the connecting electrode and disposed directly on or above the connecting electrode and outside a region where the laminated film is on the support substrate. A principal surface of the support substrate on the laminated film side includes a recess at an outer edge of the laminated film, and the recess is covered with the insulating layer.
1. An acoustic wave device comprising:
a support substrate;
a laminated film disposed on the support substrate and inside at least a portion of an outer edge of the support substrate in plan view and including a piezoelectric thin film;
an interdigital transducer (IDT) electrode disposed on the laminated film;
an insulating layer disposed on the support substrate and on the laminated film and extending from a region above the support substrate to a region above the laminated film;
a connecting electrode disposed on the insulating layer and electrically connected to the IDT electrode; and
an external connection terminal electrically connected to the connecting electrode and disposed directly on or indirectly above the connecting electrode and in plan view outside a region where the laminated film is disposed on the support substrate; wherein
a principal surface of the support substrate on a side of the laminated film includes a recess at an outer edge of the laminated film in plan view; and
the recess is covered with the insulating layer.
2. The acoustic wave device according to claim 1 , wherein a coefficient of linear expansion of the laminated film and a coefficient of linear expansion of the support substrate differ from each other.
3. The acoustic wave device according to claim 1 , wherein the recess is provided in an entire or substantially an entire region outside the region where the laminated film is disposed on the support substrate in plan view.
4. The acoustic wave device according to claim 1 , wherein the recess surrounds the laminated film.
5. The acoustic wave device according to claim 1 , wherein
the support substrate is made of material in which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of an acoustic wave that propagates in the piezoelectric thin film;
the laminated film includes a low-acoustic-velocity film in which a bulk wave propagates at a lower acoustic velocity than the acoustic velocity of the acoustic wave that propagates in the piezoelectric thin film; and
the piezoelectric thin film is disposed on the low-acoustic-velocity film.
6. The acoustic wave device according to claim 1 , wherein
the laminated film includes a high-acoustic-velocity film in which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of an acoustic wave that propagates in the piezoelectric thin film and a low-acoustic-velocity film in which a bulk wave propagates at a lower acoustic velocity than the acoustic velocity of the acoustic wave that propagates in the piezoelectric thin film;
the low-acoustic-velocity film is disposed on the high-acoustic-velocity film; and
the piezoelectric thin film is disposed on the low-acoustic-velocity film.
7. The acoustic wave device according to claim 1 , wherein
the laminated film includes an acoustic reflective layer that includes a high-acoustic-impedance film having an acoustic impedance that is relatively high and a low-acoustic-impedance film having a lower acoustic impedance than the acoustic impedance of the high-acoustic-impedance film; and
the piezoelectric thin film is disposed on the acoustic reflective layer.
8. The acoustic wave device according to claim 1 , further comprising:
a support including an opening surrounding the IDT electrode and disposed directly on or indirectly above the support substrate and in plan view in a region outside the region where the laminated film is disposed on the support substrate;
a cover disposed on the support so as to cover the opening; and
an under-bump metal layer that penetrates the support and the cover so as to be connected to the connecting electrode; wherein
the external connection terminal is a bump disposed indirectly above the connecting electrode with the under-bump metal layer interposed between the connecting electrode and the external connection terminal; and
the IDT electrode is disposed inside a hollow space enclosed by the support substrate, the support, and the cover.
9. The acoustic wave device according to claim 1 , wherein the external connection terminal is a bump disposed directly on the connecting electrode.
10. A radio-frequency front-end circuit comprising:
the acoustic wave device according to claim 1 ; and
a power amplifier.
11. The radio-frequency front-end circuit according to claim 10 , wherein a coefficient of linear expansion of the laminated film and a coefficient of linear expansion of the support substrate differ from each other.
12. The radio-frequency front-end circuit according to claim 10 , wherein the recess is provided in an entire or substantially an entire region outside the region where the laminated film is disposed on the support substrate in plan view.
13. The radio-frequency front-end circuit according to claim 10 , wherein the recess surrounds the laminated film.
14. The radio-frequency front-end circuit according to claim 10 , wherein
the support substrate is made of material in which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of an acoustic wave that propagates in the piezoelectric thin film;
the laminated film includes a low-acoustic-velocity film in which a bulk wave propagates at a lower acoustic velocity than the acoustic velocity of the acoustic wave that propagates in the piezoelectric thin film; and
the piezoelectric thin film is disposed on the low-acoustic-velocity film.
15. The radio-frequency front-end circuit according to claim 10 , wherein
the laminated film includes a high-acoustic-velocity film in which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of an acoustic wave that propagates in the piezoelectric thin film and a low-acoustic-velocity film in which a bulk wave propagates at a lower acoustic velocity than the acoustic velocity of the acoustic wave that propagates in the piezoelectric thin film;
the low-acoustic-velocity film is disposed on the high-acoustic-velocity film; and
the piezoelectric thin film is disposed on the low-acoustic-velocity film.
16. The radio-frequency front-end circuit according to claim 10 , wherein
the laminated film includes an acoustic reflective layer that includes a high-acoustic-impedance film having an acoustic impedance that is relatively high and a low-acoustic-impedance film having a lower acoustic impedance than the acoustic impedance of the high-acoustic-impedance film; and
the piezoelectric thin film is disposed on the acoustic reflective layer.
17. The radio-frequency front-end circuit according to claim 10 , further comprising:
a support including an opening surrounding the IDT electrode and disposed directly on or indirectly above the support substrate and in plan view in a region outside the region where the laminated film is disposed on the support substrate;
a cover disposed on the support so as to cover the opening; and
an under-bump metal layer that penetrates the support and the cover so as to be connected to the connecting electrode; wherein
the external connection terminal is a bump disposed indirectly above the connecting electrode with the under-bump metal layer interposed between the connecting electrode and the external connection terminal; and
the IDT electrode is disposed inside a hollow space enclosed by the support substrate, the support, and the cover.
18. The radio-frequency front-end circuit according to claim 10 , wherein the external connection terminal is a bump disposed directly on the connecting electrode.
19. A communication apparatus comprising:
the radio-frequency front-end circuit according to claim 10 ; and
a radio-frequency signal processing circuit.