Boundary acoustic wave device
Regarding a boundary acoustic wave device in which at least a part of an IDT electrode is embedded in a groove disposed in a piezoelectric substrate, the acoustic velocity is increased. A boundary acoustic wave device is provided with a piezoelectric substrate, a first dielectric layer, and an IDT electrode. The surface of the piezoelectric substrate is provided with a groove. The IDT electrode is disposed at the boundary between the piezoelectric substrate and the first dielectric layer in such a way that at least a part thereof is located in the groove. In the inside of the groove, the groove angle γ, which is the size of an angle formed by an upper end portion of the inside surface of the groove with the surface of the piezoelectric substrate, is less than 90 degrees.
1. A boundary acoustic wave device comprising:
a piezoelectric substrate including a surface provided with a groove;
a first dielectric layer disposed on the surface of the piezoelectric substrate; and
an IDT electrode disposed at a boundary between the piezoelectric substrate and the first dielectric layer such that at least a first portion thereof is located in the groove; wherein
inside of the groove, a groove angle, which is defined as an angle between an upper end portion of an inside surface of the groove and the surface of the piezoelectric substrate, is less than 90 degrees;
a second portion of the IDT electrode is located outside of the groove; and
the second portion of the IDT electrode is tapered with decreasing distance away from the piezoelectric substrate.
2. The boundary acoustic wave device according to claim 1 , further comprising a second dielectric layer which is disposed on the first dielectric layer and which has an acoustic velocity larger than that of the first dielectric layer.
3. The boundary acoustic wave device according to claim 2 , wherein each of the first and the second dielectric layers is made of silicon oxide, silicon nitride, or aluminum nitride.
4. The boundary acoustic wave device according to claim 1 , wherein an average density of the first portion of the IDT electrode is higher than an average density of the piezoelectric substrate.
5. The boundary acoustic wave device according to claim 1 , wherein at least a portion of the first portion of the IDT electrode is made of at least one metal selected from the group consisting of Pt, Au, W, Ta, Mo, Ni, and Cu or an alloy containing at least one metal selected from the group consisting of Pt, Au, W, Ta, Mo, Ni, and Cu.
6. The boundary acoustic wave device according to claim 1 , wherein the IDT electrode includes a laminate including a plurality of electrode layers, and a resistivity of at least one layer of the plurality of electrode layers is about 5 μΩcm or less.
7. The boundary acoustic wave device according to claim 6 , wherein the electrode layer having a resistivity of about 5 μΩcm or less is made of at least one metal selected from the group consisting of Al, Cu, Au, and Ag or an alloy containing at least one metal selected from the group consisting of Al, Cu, Au, and Ag.
8. The boundary acoustic wave device according to claim 1 , wherein the IDT electrode includes a laminate including a plurality of electrode layers, and a diffusion preventing film is disposed in at least one of a location between the IDT electrode and a bottom of the groove and a location between adjacent electrode layers of the plurality of electrode layers.
9. The boundary acoustic wave device according to claim 8 , wherein the diffusion preventing film is made of at least one metal selected from the group consisting of Ti, Ni, Cr, and Ta or an alloy containing at least one metal selected from the group consisting of Ti, Ni, Cr, and Ta.
10. The boundary acoustic wave device according to claim 1 , wherein the piezoelectric substrate is made of LiTaO 3 .
11. The boundary acoustic wave device according to claim 10 , wherein
the IDT electrode includes a first electrode layer, which is located in the groove of the piezoelectric substrate and which includes Pt, and a second electrode layer, which is located outside the groove of the piezoelectric substrate and which includes Al, and the first dielectric layer is made of silicon oxide; and
θ of the Euler Angles (φ,θ,φ) and the groove angle γ are within the range specified in Tables 1 to 4 described below and each of φ and φ of the Euler Angles is within the range of 0°±5°, where the Euler Angles of the piezoelectric substrate are specified to be (φ,θ,φ) and the groove angle is specified to be γ
TABLE 1
Thickness of first
θ of Euler Angles
Thickness of first
Thickness of second
dielectric layer h/λ [%]
(φ, θ, φ) [°]
electrode layer h/λ [%]
electrode layer h/λ [%]
Groove angle [°]
10 < h < λ ≦ 30
124 < θ ≦ 128
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
37.1 ≦ γ < 90.0
7.5 < Al ≦ 12.5
39.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
39.5 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
37.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
32.4 ≦ γ < 90.0
12.5 < Al ≦ 17.5
29.9 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
52.1 ≦ γ < 90.0
7.5 < Al ≦ 12.5
57.5 ≦ γ < 90.0
12.5 < Al ≦ 17.5
62.8 ≦ γ < 90.0
128 < θ ≦ 132
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
19.3 ≦ γ < 90.0
7.5 < Al ≦ 12.5
32.1 ≦ γ < 90.0
12.5 < Al ≦ 17.5
34.8 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
38.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
34 ≦ γ < 90.0
12.5 < Al ≦ 17.5
30 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
49.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
50.3 ≦ γ < 90.0
12.5 < Al ≦ 17.5
50.8 ≦ γ < 90.0
132 < θ ≦ 136
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
18.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
27.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
27 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
40 ≦ γ < 90.0
7.5 < Al ≦ 12.5
35 ≦ γ < 90.0
12.5 < Al ≦ 17.5
32.7 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
49.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
39.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
47.4 ≦ γ < 90.0
136 < θ ≦ 140
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
18.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
32.5 ≦ γ < 90.0
12.5 < Al ≦ 17.5
37.3 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
41.3 ≦ γ < 90.0
7.5 < Al ≦ 12.5
38.4 ≦ γ < 90.0
12.5 < Al ≦ 17.5
35 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
49.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
49.8 ≦ γ < 90.0
12.5 < Al ≦ 17.5
49.5 ≦ γ < 90.0
TABLE 2
Thickness of first
θ of Euler Angles
Thickness of first
Thickness of second
dielectric layer h/λ [%]
(φ, θ, φ) [°]
electrode layer h/λ [%]
electrode layer h/λ [%]
Groove angle [°]
10 < h < λ ≦ 30
140 < θ ≦ 144
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
41.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
46.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
46.3 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
46.6 ≦ γ < 90.0
7.5 < Al ≦ 12.5
41.7 ≦ γ < 90.0
12.5 < Al ≦ 17.5
38.1 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
51.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
39.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
41 ≦ γ < 90.0
30 < h < λ ≦ 50
124 < θ ≦ 128
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
18.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
18.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
41.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
34.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
32.6 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
59.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
58.4 ≦ γ < 90.0
12.5 < Al ≦ 17.5
33.0 ≦ γ < 90.0
128 < θ ≦ 132
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
20 ≦ γ < 90.0
7.5 < Al ≦ 12.5
18.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
39.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
36.3 ≦ γ < 90.0
12.5 < Al ≦ 17.5
33.2 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
59.9 ≦ γ < 90.0
7.5 < Al ≦ 12.5
48.6 ≦ γ < 90.0
12.5 < Al ≦ 17.5
41.2 ≦ γ < 90.0
132 < θ ≦ 136
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
20.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
18.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
36.9 ≦ γ < 90.0
7.5 < Al ≦ 12.5
35.8 ≦ γ < 90.0
12.5 < Al ≦ 17.5
33.4 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
38.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
36.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
37.4 ≦ γ < 90.0
TABLE 3
Thickness of first
θ of Euler Angles
Thickness of first
Thickness of second
dielectric layer h/λ [%]
(φ, θ, φ) [°]
electrode layer h/λ [%]
electrode layer h/λ [%]
Groove angle [°]
30 < h < λ ≦ 50
136 < θ ≦ 140
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
22.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
19.3 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
40.5 ≦ γ < 90.0
7.5 < Al ≦ 12.5
30.7 ≦ γ < 90.0
12.5 < Al ≦ 17.5
32.3 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
46 ≦ γ < 90.0
7.5 < Al ≦ 12.5
45 ≦ γ < 90.0
12.5 < Al ≦ 17.5
36.3 ≦ γ < 90.0
140 < θ ≦ 144
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
19 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
26.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
22.7 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.1 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
41.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
39.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
40.7 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
46.9 ≦ γ < 90.0
7.5 < Al ≦ 12.5
46.1 ≦ γ < 90.0
12.5 < Al ≦ 17.5
45.7 ≦ γ < 90.0
50 < h < λ ≦ 70
124 < θ ≦ 128
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
56.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
46.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
36.5 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
33.8 ≦ γ < 90.0
7.5 < Al ≦ 12.5
29.4 ≦ γ < 90.0
12.5 < Al ≦ 17.5
26.1 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
57.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
51.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
39.9 ≦ γ < 90.0
128 < θ ≦ 132
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
54.1 ≦ γ < 90.0
7.5 < Al ≦ 12.5
40.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
35.8 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
48.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
40.6 ≦ γ < 90.0
12.5 < Al ≦ 17.5
53.7 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
51.6 ≦ γ < 90.0
7.5 < Al ≦ 12.5
50.6 ≦ γ < 90.0
12.5 < Al ≦ 17.5
46 ≦ γ < 90.0
TABLE 4
Thickness of first
θ of Euler Angles
Thickness of first
Thickness of second
dielectric layer h/λ [%]
(φ, θ, φ) [°]
electrode layer h/λ [%]
electrode layer h/λ [%]
Groove angle [°]
50 < h < λ ≦ 70
132 < θ ≦ 136
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
18.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
42.6 ≦ γ < 90.0
12.5 < Al ≦ 17.5
27.6 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
34.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
32.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
43 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
44.6 ≦ γ < 90.0
7.5 < Al ≦ 12.5
49.9 ≦ γ < 90.0
12.5 < Al ≦ 17.5
45.2 ≦ γ < 90.0
136 < θ ≦ 140
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
19.7 ≦ γ < 90.0
7.5 < Al ≦ 12.5
18.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
34.4 ≦ γ < 90.0
7.5 < Al ≦ 12.5
33 ≦ γ < 90.0
12.5 < Al ≦ 17.5
30.1 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
41.2 ≦ γ < 90.0
7.5 < Al ≦ 12.5
48 ≦ γ < 90.0
12.5 < Al ≦ 17.5
44 ≦ γ < 90.0
140 < θ ≦ 144
1 < Pt ≦ 3
2.5 < Al ≦ 7.5
10.0 ≦ γ < 90.0
7.5 < Al ≦ 12.5
10.0 ≦ γ < 90.0
12.5 < Al ≦ 17.5
10.0 ≦ γ < 90.0
3 < Pt ≦ 5
2.5 < Al ≦ 7.5
26.3 ≦ γ < 90.0
7.5 < Al ≦ 12.5
19.4 ≦ γ < 90.0
12.5 < Al ≦ 17.5
18.0 ≦ γ < 90.0
5 < Pt ≦ 7
2.5 < Al ≦ 7.5
45 ≦ γ < 90.0
7.5 < Al ≦ 12.5
43.2 ≦ γ < 90.0
12.5 < Al ≦ 17.5
39.5 ≦ γ < 90.0
7 < Pt ≦ 9
2.5 < Al ≦ 7.5
48.9 ≦ γ < 90.0
7.5 < Al ≦ 12.5
48.1 ≦ γ < 90.0
12.5 < Al ≦ 17.5
48 ≦ γ < 90.0.
12. The boundary acoustic wave device according to claim 1 , wherein the piezoelectric substrate is made of LiNbO 3 .
13. A boundary acoustic wave device comprising:
a piezoelectric substrate including a surface provided with a groove;
a first dielectric layer disposed on the surface of the piezoelectric substrate; and
an IDT electrode disposed at a boundary between the piezoelectric substrate and the first dielectric layer such that at least a first portion thereof is located in the groove; wherein
inside of the groove, a groove angle, which is defined as an angle between an upper end portion of an inside surface of the groove and the surface of the piezoelectric substrate, is less than 90 degrees;
the piezoelectric substrate is made of LiNbO 3 ; and
−5°≦φ≦+5°, +80°≦θ≦+130°, −10°≦φ≦+10°, and 10°≦γ<90° are satisfied, where the Euler Angles of the piezoelectric substrate are specified to be (φ,θ,φ) and the groove angle is specified to be γ.
14. A boundary acoustic wave device comprising:
a piezoelectric substrate including a surface provided with a groove;
a first dielectric layer disposed on the surface of the piezoelectric substrate; and
an IDT electrode disposed at a boundary between the piezoelectric substrate and the first dielectric layer such that at least a first portion thereof is located in the groove; wherein
inside of the groove, a groove angle, which is defined as an angle between an upper end portion of an inside surface of the groove and the surface of the piezoelectric substrate, is less than 90 degrees;
the piezoelectric substrate is made of LiNbO 3 ; and
−5°≦φ≦+5°, +200°≦θ≦+250°, −10°≦φ≦+10°, and 10°≦γ<90° are satisfied, where the Euler Angles of the piezoelectric substrate are specified to be (φ,θ,φ) and the groove angle is specified to be γ.
15. A boundary acoustic wave device comprising:
a piezoelectric substrate including a surface provided with a groove;
a first dielectric layer disposed on the surface of the piezoelectric substrate; and
an IDT electrode disposed at a boundary between the piezoelectric substrate and the first dielectric layer such that at least a first portion thereof is located in the groove; wherein
in an inside of the groove, a groove angle, which is defined as an angle between an upper end portion of an inside surface of the groove with the surface of the piezoelectric substrate, is in a range of about 10° to about 80°.