# US 11,115,003 B2 · Acoustic wave device, multiplexer, high-frequency front end circuit, and communication apparatus

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- Number: US 11,115,003 B2
- Document ID: US11115003B2
- Status: Granted
- Kind: B2
- Application number: 16/920,811
- Filed: 2020-07-06
- Published: 2020-10-22
- Granted: 2021-09-07
- Earliest claimed: 2018-01-12
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Ryo Nakagawa; Hideki Iwamoto; Tsutomu Takai; Yuichi Takamine
- Web page: https://patentgrep.com/patent/US11115003B2

## CPC

- H03H 9/6489: {Compensation of undesirable effects}
- H03H 9/02559: {of lithium niobate or lithium-tantalate substrates}
- H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate}
- H03H 9/145: for networks using surface acoustic waves
- H03H 9/14538: {Formation}
- H03H 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)}
- H03H 9/6483: {Ladder SAW filters}
- H03H 9/72: Networks using surface acoustic waves
- H03H 9/725: {Duplexers}
- H04B 1/006: {using switches for selecting the desired band (H04B1/0057 takes precedence)}
- H04B 1/04: Circuits
- H04B 1/0458: {Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H)}
- H04B 1/18: Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H)
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H04B: TRANSMISSION

## Abstract

In an acoustic wave device, an antenna end resonator electrically closest to a first terminal is a first acoustic wave resonator. In each of the first acoustic wave resonator and a second acoustic wave resonator, a thickness of a piezoelectric layer is equal to or less than about 3.5λ. A cut angle of the piezoelectric layer of the first acoustic wave resonator is within a range of θB±4°. The cut angle of the piezoelectric layer of the second acoustic wave resonator has a larger difference from θB (°) than the cut angle of the piezoelectric layer of the first acoustic wave resonator.

## Claims

### Claim 1

An acoustic wave device that is provided between a first terminal defining an antenna terminal and a second terminal different from the first terminal, the acoustic wave device comprising:
a plurality of acoustic wave resonators; wherein
the plurality of acoustic wave resonators include:
a plurality of series arm resonators provided on a first path connecting the first terminal and the second terminal; and
a plurality of parallel arm resonators provided on a plurality of second paths connecting a plurality of nodes on the first path and ground, respectively;
when an acoustic wave resonator that is electrically closest to the first terminal among the plurality of acoustic wave resonators is an antenna end resonator;
the antenna end resonator is a first acoustic wave resonator; and
at least one acoustic wave resonator other than the antenna end resonator among the plurality of acoustic wave resonators is a second acoustic wave resonator;
each of the first acoustic wave resonator and the second acoustic wave resonator includes:
a piezoelectric layer;
an IDT electrode provided on the piezoelectric layer and including a plurality of electrode fingers;
a high-acoustic-velocity layer located on a side opposite to the IDT electrode with the piezoelectric layer interposed therebetween and in which an acoustic velocity of a bulk wave propagating in the high-acoustic-velocity layer is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric layer; and
a low-acoustic-velocity film provided between the high-acoustic-velocity layer and the piezoelectric layer and in which an acoustic velocity of a bulk wave propagating in the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric layer;
a thickness of the piezoelectric layer is equal to or less than about 3.5λ where a wavelength of an acoustic wave, which is determined by an electrode finger cycle as a cycle of the plurality of electrode fingers of the IDT electrode, is λ;
a cut angle of the piezoelectric layer of the first acoustic wave resonator is within a range of about θB±4° with reference to θB (°) obtained by an equation (1) where the wavelength is λ (μm), a thickness of the IDT electrode is TIDT (μm), a specific gravity of the IDT electrode is ρ (g/cm3), a duty ratio as a value obtained by dividing a width of the electrode fingers by a half value of the electrode finger cycle is Du, a thickness of the piezoelectric layer is TLT (μm), and a thickness of the low-acoustic-velocity film is TVL (μm);
θ
B
=
4
⁢
3
.
0
⁢
9
-
2
⁢
7
.
5
×
(
T
IDT
λ
×
ρ
-
0.1956
)
-
19.2
×
(
D
u
-
0
⁢
.5
)
+
17.4578
×
(
T
LT
λ
-
0
.
3
⁢
5
)
+
5
.
6
⁢
1
⁢
9
×
(
T
V
⁢
L
λ
-
0
⁢
.3
)
+
3
⁢
2
.
6
⁢
6
×
{
(
T
L
⁢
T
λ
-
0
.
3
⁢
5
)
2
-
0
.
0
⁢
1
⁢
25
}
+
2
⁢
4
.
6
⁢
3
×
(
T
L
⁢
T
λ
-
0
.
3
⁢
5
)
×
(
T
VL
λ
-
0.3
)
;
Equation
⁢
⁢
(
1
)
and
a cut angle of the piezoelectric layer of the second acoustic wave resonator has a larger difference from θB (°) than the cut angle of the piezoelectric layer of the first acoustic wave resonator.

### Claim 2 (depends on 1)

The acoustic wave device according to claim 1, wherein
at least one acoustic wave resonator including the antenna end resonator among the plurality of acoustic wave resonators is the first acoustic wave resonator;
acoustic wave resonators other than the at least one acoustic wave resonator among the plurality of acoustic wave resonators are the second acoustic wave resonators; and
the first acoustic wave resonator is a chip that is different from the second acoustic wave resonators.

### Claim 3 (depends on 1)

The acoustic wave device according to claim 1, wherein
a material of the piezoelectric layer is lithium tantalate or lithium niobate;
a material of the low-acoustic-velocity film is silicon oxide; and
a material of the high-acoustic-velocity layer is silicon.

### Claim 4 (depends on 1)

The acoustic wave device according to claim 1, wherein
each of the first acoustic wave resonator and the second acoustic wave resonator includes a support substrate;
the high-acoustic-velocity layer includes a high-acoustic-velocity film provided on the support substrate and in which an acoustic velocity of a bulk wave propagating in the high-acoustic-velocity film is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric layer; and
the low-acoustic-velocity film is provided on the high-acoustic-velocity film.

### Claim 5 (depends on 4)

The acoustic wave device according to claim 4, wherein
a material of the piezoelectric layer is lithium tantalate or lithium niobate;
a material of the low-acoustic-velocity film is at least one material selected from a group consisting of silicon oxide, glass, silicon oxynitride, tantalum oxide, and a compound obtained by adding fluorine, carbon, or boron to silicon oxide; and
a material of the high-acoustic-velocity film is at least one material selected from a group consisting of diamond-like carbon, aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, and diamond.

### Claim 6 (depends on 1)

The acoustic wave device according to claim 1, wherein
one series arm resonator of the plurality of series arm resonators is electrically closer to the first terminal than the plurality of parallel arm resonators; and
the one series arm resonator is the antenna end resonator.

### Claim 7 (depends on 1)

The acoustic wave device according to claim 1, wherein
one series arm resonator of the plurality of series arm resonators and one parallel arm resonator of the plurality of parallel arm resonators are directly connected to the first terminal; and
at least one of the one series arm resonator and the one parallel arm resonator is the antenna end resonator.

### Claim 8

An acoustic wave device that is provided between a first terminal as an antenna terminal and a second terminal being different from the first terminal, the acoustic wave device comprising:
a plurality of acoustic wave resonators; wherein
the plurality of acoustic wave resonators include:
a plurality of series arm resonators provided on a first path connecting the first terminal and the second terminal; and
a plurality of parallel arm resonators provided on a plurality of second paths connecting a plurality of nodes on the first path and ground, respectively;
when an acoustic wave resonator that is electrically closest to the first terminal among the plurality of acoustic wave resonators is an antenna end resonator,
the antenna end resonator is a first acoustic wave resonator, and
at least one acoustic wave resonator other than the antenna end resonator among the plurality of acoustic wave resonators is a second acoustic wave resonator;
each of the first acoustic wave resonator and the second acoustic wave resonator includes:
a piezoelectric layer;
an IDT electrode provided on the piezoelectric layer and having a plurality of electrode fingers;
a high-acoustic-velocity layer located on a side opposite to the IDT electrode with the piezoelectric layer interposed therebetween and in which an acoustic velocity of a bulk wave propagating in the high-acoustic-velocity layer is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric layer; and
a low-acoustic-velocity film provided between the high-acoustic-velocity layer and the piezoelectric layer and in which an acoustic velocity of a bulk wave propagating in the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric layer;
a thickness of the piezoelectric layer is equal to or less than about 3.5λ where a wavelength of an acoustic wave, which is determined by an electrode finger cycle as a cycle of the plurality of electrode fingers of the IDT electrode, is λ; and
an intensity of a Rayleigh wave response generated in the first acoustic wave resonator is smaller than an intensity of a Rayleigh wave response generated in the second acoustic wave resonator.

### Claim 9 (depends on 8)

The acoustic wave device according to claim 8, wherein
at least one acoustic wave resonator including the antenna end resonator among the plurality of acoustic wave resonators is the first acoustic wave resonator;
acoustic wave resonators other than the at least one acoustic wave resonator among the plurality of acoustic wave resonators are the second acoustic wave resonators; and
the first acoustic wave resonator is a chip that is different from the second acoustic wave resonators.

### Claim 10 (depends on 8)

The acoustic wave device according to claim 8, wherein
a material of the piezoelectric layer is lithium tantalate or lithium niobate;
a material of the low-acoustic-velocity film is silicon oxide; and
a material of the high-acoustic-velocity layer is silicon.

### Claim 11 (depends on 1)

A multiplexer comprising:
a first filter including the acoustic wave device according to claim 1; and
a second filter provided between the first terminal and a third terminal that is different from the first terminal; and
a pass band of the first filter is in a higher frequency range than a pass band of the second filter.

### Claim 12 (depends on 11)

The multiplexer according to claim 11, further comprising:
a plurality of resonator groups each defined by the plurality of acoustic wave resonators; wherein
in the plurality of resonator groups, the first terminal is a common terminal and the second terminal is an individual terminal; and
the antenna end resonators of the plurality of resonator groups are integrated in one chip.

### Claim 13 (depends on 11)

The multiplexer according to claim 11, wherein a minimum frequency of the pass band of the first filter is higher than a maximum frequency of the pass band of the second filter.

### Claim 14 (depends on 8)

A multiplexer comprising:
a first filter including the acoustic wave device according to claim 8; and
a second filter provided between the first terminal and a third terminal that is different from the first terminal; and
a pass band of the first filter is in a higher frequency range than a pass band of the second filter.

### Claim 15 (depends on 14)

The multiplexer according to claim 14, further comprising:
a plurality of resonator groups each defined by the plurality of acoustic wave resonators; wherein
in the plurality of resonator groups, the first terminal is a common terminal and the second terminal is an individual terminal; and
the antenna end resonators of the plurality of resonator groups are integrated in one chip.

### Claim 16 (depends on 14)

The multiplexer according to claim 14, wherein a minimum frequency of the pass band of the first filter is higher than a maximum frequency of the pass band of the second filter.

### Claim 17 (depends on 11)

A high-frequency front end circuit comprising:
the multiplexer according to claim 11; and
an amplifier circuit connected to the multiplexer.

### Claim 18 (depends on 14)

A high-frequency front end circuit comprising:
the multiplexer according to claim 14; and
an amplifier circuit connected to the multiplexer.

### Claim 19 (depends on 17)

A communication apparatus comprising:
the high-frequency front end circuit according to claim 17; and
a signal processing circuit that processes a high-frequency signal received by an antenna; wherein
the high-frequency front end circuit transmits the high-frequency signal between the antenna and the signal processing circuit.

### Claim 20 (depends on 18)

A communication apparatus comprising:
the high-frequency front end circuit according to claim 18; and
a signal processing circuit that processes a high-frequency signal received by an antenna; wherein
the high-frequency front end circuit transmits the high-frequency signal between the antenna and the signal processing circuit.