Acoustic wave device
An acoustic wave device includes a silicon support substrate, a silicon nitride film on the support substrate, a silicon oxide film on the silicon nitride film, a piezoelectric layer on the silicon oxide film and using Y-cut X-SAW propagation lithium tantalate, and an IDT electrode on the piezoelectric layer. A film thickness of the piezoelectric layer is equal to or less than about 1λ, Euler angles of the piezoelectric layer are (0±5°, θ, 0±5°) or (0±5°, θ, 180±5°), θ in the Euler angles of the piezoelectric layer is about 95.5°≤θ<117.5° or about −84.5°≤θ<−62.5°, and a relationship between θ in the Euler angles of the piezoelectric layer and a film thickness of the silicon nitride film is a combination shown in Table 1 or Table 2.
1. An acoustic wave device comprising:
a silicon support substrate;
a silicon nitride film on the support substrate;
a silicon oxide film on the silicon nitride film;
a piezoelectric layer on the silicon oxide film and made of Y-cut X-SAW propagation lithium tantalate; and
an IDT electrode directly or indirectly on the piezoelectric layer and including a plurality of electrode fingers; wherein
when a wavelength defined by an electrode finger pitch of the IDT electrode is λ, a film thickness of the piezoelectric layer is equal to or less than about 1λ;
Euler angles of the piezoelectric layer are (about 0±5°, θ, about 0±5°) or (about 0±5°, θ, about 180±5°), and θ in the Euler angles of the piezoelectric layer is about 95.5°≤θ<117.5° or about −84.5°≤θ<−62.5°; and
a relationship between θ in the Euler angles of the piezoelectric layer and a film thickness of the silicon nitride film is a combination shown in Table 1 or Table 2 below:
TABLE 1
FILM THICKNESS OF SiN FILM
θ
LOWER LIMIT [λ]
UPPER LIMIT [λ]
95.5 ≤ θ < 96.5
0.0005
0.746
96.5 ≤ θ < 97.5
0.0005
0.732
97.5 ≤ θ < 98.5
0.0005
0.736
98.5 ≤ θ < 99.5
0.0005
0.726
99.5 ≤ θ < 100.5
0.0005
0.724
100.5 ≤ θ < 101.5
0.0005
0.718
101.5 ≤ θ < 102.5
0.0005
0.712
102.5 ≤ θ < 103.5
0.0005
0.71
103.5 ≤ θ < 104.5
0.0005
0.704
104.5 ≤ θ < 105.5
0.0005
0.702
105.5 ≤ θ < 106.5
0.0005
0.698
106.5 ≤ θ < 107.5
0.0005
0.695
107.5 ≤ θ < 108.5
0.0005
0.695
108.5 ≤ θ < 109.5
0.0005
0.692
109.5 ≤ θ < 110.5
0.0005
0.689
110.5 ≤ θ < 111.5
0.0005
0.689
111.5 ≤ θ < 112.5
0.0005
0.69
112.5 ≤ θ < 113.5
0.0005
0.686
113.5 ≤ θ < 114.5
0.0005
0.684
114.5 ≤ θ < 115.5
0.0005
0.684
115.5 ≤ θ < 116.5
0.0005
0.682
116.5 ≤ θ < 117.5
0.0005
0.666;
and
TABLE 2
FILM THICKNESS OF SiN FILM
θ
LOWER LIMIT [λ]
UPPER LIMIT [λ]
−84.5 ≤ θ < −83.5
0.0005
0.746
−83.5 ≤ θ < −82.5
0.0005
0.732
−82.5 ≤ θ < −81.5
0.0005
0.736
−81.5 ≤ θ < −80.5
0.0005
0.726
−80.5 ≤ θ < −79.5
0.0005
0.724
−79.5 ≤ θ < −78.5
0.0005
0.718
−78.5 ≤ θ < −77.5
0.0005
0.712
−77.5 ≤ θ < −76.5
0.0005
0.71
−76.5 ≤ θ < −75.5
0.0005
0.704
−75.5 ≤ θ < −74.5
0.0005
0.702
−74.5 ≤ θ < −73.5
0.0005
0.698
−73.5 ≤ θ < −72.5
0.0005
0.695
−72.5 ≤ θ < −71.5
0.0005
0.695
−71.5 ≤ θ < −70.5
0.0005
0.692
−70.5 ≤ θ < −69.5
0.0005
0.689
−69.5 ≤ θ < −68.5
0.0005
0.689
−68.5 ≤ θ < −67.5
0.0005
0.69
−67.5 ≤ θ < −66.5
0.0005
0.686
−66.5 ≤ θ < −65.5
0.0005
0.684
−65.5 ≤ θ < −64.5
0.0005
0.684
−64.5 ≤ θ < −63.5
0.0005
0.682
−63.5 ≤ θ < −62.5
0.0005
0.666.
2. The acoustic wave device according to claim 1 wherein
the film thickness of the silicon nitride film is equal to or less than about 0.5λ;
a plane orientation of the support substrate is Si (111), a propagation angle of the support substrate is Ψ, and n represents any integer (0, ±1, ±2, . . . );
when the Euler angles of the piezoelectric layer are about (0±5°, θ, about 0±5°), a propagation angle Ψ of the support substrate is within a range of about 60°±50°+120°×n; and
when the Euler angles of the piezoelectric layer are about 0±5°, θ, about 180±5°), the propagation angle Ψ of the support substrate is within a range of about 0°±50°+120°×n.
3. The acoustic wave device according to claim 2 , wherein
when the Euler angles of the piezoelectric layer are (about 0±5°, θ, about 0±5°), the propagation angle Ψ of the support substrate is within a range of about 60°±34°+120°×n; and
when the Euler angles of the piezoelectric layer are within a range of (about 0±5°, θ, about 180±5°), the propagation angle Ψ of the support substrate is within a range of about 0°±34°+120°×n.
4. The acoustic wave device according to claim 1 , wherein
a dielectric layer is between the piezoelectric layer and the IDT electrode; and
an acoustic velocity of a bulk wave propagating through the dielectric layer is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.
5. The acoustic wave device according to claim 4 , wherein
the dielectric layer is a SiN layer; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the SiN layer are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 1 below is equal to or less than about −70°:
Phase of Rayleigh wave=(−81.6949045454545)+(−0.67490613636364)×(θ−110)+(−189.247997265892)×((“SiN film thickness [λ]”)−0.05)+0.111730638111889×((θ−110)×(θ−110)−40)+36.1595358851675×((θ−110)×((“SiN film thickness [λ]”)−0.05))+5258.22469396632×(((“SiN film thickness [λ]”)−0.05)×((“SiN film thickness [λ]”)−0.05)−0.00083125) Equation 1.
6. The acoustic wave device according to claim 4 , wherein
the dielectric layer is an Al 2 O 3 layer; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the Al 2 O 3 layer are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 2 below is equal to or less than about −70°:
Phase of Rayleigh wave=(−80.1333863636364)+(−0.554522499999998)×(θ−110)+(−173.463554340396)×((“Al2O3 film thickness [λ]”)−0.05)+0.149698033216783×((θ−110)×(θ−110)−40)+41.1703301435407×((θ−110)*((“Al2O3 film thickness [λ]”)−0.05))+4990.83763126825×(((“Al2O3 film thickness [λ]”)−0.05)×((“Al2O3 film thickness [λ]”)−0.05)−0.00083125) Equation 2.
7. The acoustic wave device according to claim 4 , wherein
the dielectric layer is an AlN layer; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the AlN layer are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 3 below is equal to or less than about −70°:
Phase of Rayleigh wave=(−87.3504136363636)+(−0.270137500000004)×(θ−110)+(−97.7367464114832)×((“AlN film thickness [λ]”)−0.05)+0.0257423222610727×((θ−110)×(θ−110)−40)+14.0575563909775×((θ−110)×((“AlN β [λ]”)−0.05))+3335.40856272914×(((“AlN film thickness [λ]”)−0.05)×((“AlN film thickness [λ]”)−0.05)−0.00083125) Equation 3.
8. The acoustic wave device according to claim 1 , further comprising:
a protective film on the piezoelectric layer so as to cover the IDT electrode; wherein
the protective film is a SiN protective film made of SiN; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the SiN protective film are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 4 below is equal to or less than about −70° and a phase of a higher-order mode derived by Equation 5 below is equal to or less than about −70°:
Rayleigh wave=(−51.52545)+1.78434436363636×(θ−127.5)+551.57103030303×((“SiN protective film [λ]”)−0.0275)+0.102490363636364×((θ−127.5)×(θ−127.5)−206.25)+60.3989730027549×((θ−127.5)×((“SiN protective film [λ]”)−0.0275)) Equation 4; and
Higher-order mode=(−26.58444)+2.61766496969697×(θ−127.5)+1545.84533333333×((“SiN protective film [λ]”)−0.0275)+(−0.0379121515151515)×((θ−127.5)×(θ−127.5)−206.25)+56.9468179981635×((θ−127.5)×((“SiN protective film [λ]”)−0.0275)) Equation 5.
9. The acoustic wave device according to claim 1 , further comprising:
a protective film on the piezoelectric layer so as to cover the IDT electrode; wherein
the protective film is an Al 2 O 3 protective film made of Al 2 O 3 ; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the Al 2 O 3 protective film are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 6 below is equal to or less than about −70° and a phase of a higher-order mode derived by Equation 7 below is equal to or less than about −70°:
Rayleigh wave=(−40.9578496399338)+2.25601530917004×(θ−127.272727272727)+964.821146439353×((“Al2O3 protective film [λ]”)−0.0274747474747475)+0.100000607678288×((θ−127.272727272727)×(θ−127.272727272727)−203.168044077135)+74.7099873794682×((θ−127.272727272727)×((“Al2O3 protective film [λ]”)−0.0274747474747475)) Equation 6; and
Higher-order mode=(−21.0375184962657)+2.73177575694271×(θ−127.272727272727)+1701.65880601573×((“Al2O3 protective film [λ]”)−0.0274747474747475)+(−0.0499273041403373)×((θ−127.272727272727)×(θ−127.272727272727)−203.168044077135)+53.1637721066764×((θ−127.272727272727)×((“Al 2 O 3 protective film [λ]”)−0.0274747474747475))+(−34811.3628963409)×(((“Al 2 O 3 protective film [λ]”)−0.0274747474747475)×((“Al2O3 protective film [λ]”)−0.0274747474747475)−0.00020826956433017) Equation 7.
10. The acoustic wave device according to claim 1 , further comprising:
a protective film on the piezoelectric layer so as to cover the IDT electrode; wherein
the protective film is an AlN protective film made of AlN; and
θ in the Euler angles of the piezoelectric layer and a film thickness of the AlN protective film are an angle and a film thickness within a range in which a phase of a Rayleigh wave derived by Equation 8 below is equal to or less than about −70° and a phase of a higher-order mode derived by Equation 9 below is equal to or less than about −70°:
Rayleigh wave=(−46.4003800000001)+1.94268775757576×(θ−127.5)+755.618424242424×((“AlN protective film [λ]”)−0.0275)+0.109821151515152×((θ−127.5)×(θ−127.5)−206.25)+69.3031610651975×((θ−127.5)×((“AlN protective film [λ]”)−0.0275)) Equation 8; and
Higher-order mode=(−24.10841)+2.65936036363636×(θ−127.5)+1560.34145454545×((“AlN protective film [λ]”)−0.0275)+(−0.0415194696969697)×((θ−127.5)×(θ−127.5)−206.25)+54.3834578512397×((θ−127.5)×((“AlN protective film [λ]”)−0.0275)) Equation 9.
11. An acoustic wave device comprising:
a silicon support substrate;
a silicon nitride film on the support substrate;
a silicon oxide film on the silicon nitride film;
a piezoelectric layer on the silicon oxide film and using Y-cut X-SAW propagation lithium tantalate; and
an IDT electrode on the piezoelectric layer and including a plurality of electrode fingers; wherein
when a wavelength defined by an electrode finger pitch of the IDT electrode is λ, a film thickness of the piezoelectric layer is equal to or less than about 1λ;
Euler angles of the piezoelectric layer are (about 0±5°, θ, about 0±5°), and θ in the Euler angles of the piezoelectric layer is about 117.5°≤θ<129.5°; and
a relationship between θ in the Euler angles of the piezoelectric layer and a film thickness of the silicon nitride film is a combination shown in Table 3 below:
TABLE 3
FILM THICKNESS OF SiN FILM
θ
LOWER LIMIT [λ]
UPPER LIMIT [λ]
117.5 ≤ θ < 118.5
0.0005
0.092
117.5 ≤ θ < 118.5
0.166
0.597
118.5 ≤ θ < 119.5
0.0005
0.07
118.5 ≤ θ < 119.5
0.168
0.554
119.5 ≤ θ < 120.5
0.005
0.063
119.5 ≤ θ < 120.5
0.152
0.522
120.5 ≤ θ < 121.5
0.004
0.06
120.5 ≤ θ < 121.5
0.132
0.492
121.5 ≤ θ < 122.5
0.022
0.052
121.5 ≤ θ < 122.5
0.12
0.466
122.5 ≤ θ < 123.5
0.22
0.43
123.5 ≤ θ < 124.5
0.24
0.4
124.5 ≤ θ < 125.5
0.25
0.38
125.5 ≤ θ < 126.5
0.25
0.38
126.5 ≤ θ < 127.5
0.25
0.36
127.5 ≤ θ < 128.5
0.25
0.31
128.5 ≤ θ < 129.5
0.25
0.28.
12. An acoustic wave device comprising:
a silicon support substrate;
a silicon nitride film on the support substrate;
a silicon oxide film on the silicon nitride film;
a piezoelectric layer on the silicon oxide film and using Y-cut X-SAW propagation lithium tantalate; and
an IDT electrode on the piezoelectric layer and including a plurality of electrode fingers; wherein
when a wavelength defined by an electrode finger pitch of the IDT electrode is λ, a film thickness of the piezoelectric layer is equal to or less than about 1λ;
Euler angles of the piezoelectric layer are (about 0±5°, θ, about 0±5°), and θ in the Euler angles of the piezoelectric layer is about 85.5°≤θ<95.5°; and
a relationship between θ in the Euler angles of the piezoelectric layer and a film thickness of the silicon nitride film is a combination shown in Table 4 below:
TABLE 4
FILM THICKNESS OF SiN FILM
θ
LOWER LIMIT [λ]
UPPER LIMIT [λ]
85.5 ≤ θ < 86.5
0.0005
0.03
85.5 ≤ θ < 86.5
0.43
0.46
86.5 ≤ θ < 87.5
0.0005
0.038
86.5 ≤ θ < 87.5
0.42
0.47
87.5 ≤ θ < 88.5
0.0005
0.048
87.5 ≤ θ < 88.5
0.412
0.485
88.5 ≤ θ < 89.5
0.0005
0.058
88.5 ≤ θ < 89.5
0.404
0.506
89.5 ≤ θ < 90.5
0.0005
0.07
89.5 ≤ θ < 90.5
0.388
0.52
90.5 ≤ θ < 91.5
0.0005
0.085
90.5 ≤ θ < 91.5
0.37
0.538
91.5 ≤ θ < 92.5
0.0005
0.102
91.5 ≤ θ < 92.5
0.346
0.56
92.5 ≤ θ < 93.5
0.0005
0.128
92.5 ≤ θ < 93.5
0.315
0.59
93.5 ≤ θ < 94.5
0.0005
0.166
93.5 ≤ θ < 94.5
0.295
0.616
94.5 ≤ θ < 95.5
0.0005
0.226
94.5 ≤ θ < 95.5
0.284
0.66.