CN1745516A

CN1745516A - Elastic boundary wave device

Info

Publication number: CN1745516A
Application number: CN 200380109318
Authority: CN
Inventors: 神藤始
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2003-02-10
Filing date: 2003-12-16
Publication date: 2006-03-08
Anticipated expiration: 2023-12-16
Also published as: CN100586011C

Abstract

An elastic boundary wave device employing an SH type elastic boundary wave having a large electromechanical coupling coefficient, a low propagation loss, a small power flow angle, a temperature coefficient of frequency TCF in an appropriate range, and a simple structure which can be produced through a simple process. A dielectric is deposited on one side of a piezoelectric and an IDT and a reflector are arranged as electrodes on the boundary of the piezoelectric and the dielectric, wherein the thickness of the electrodes is set such that the sound velocity of the SH type elastic boundary wave becomes lower than the sound velocity of a slow transverse wave propagating through the dielectric and the sound velocity of a slow transverse wave propagating through the piezoelectric.

Description

Boundary acoustic wave device

Technical field

The present invention relates to a kind of acoustic boundary wave equipment of the SH of utilization type acoustic boundary wave, particularly, relate to a kind of boundary acoustic wave device: electrode is arranged on boundary between piezoelectric substance and the node substrate with this spline structure.

Background technology

Up to now, various surface acoustic wave devices are used for resonator among the RF of mobile phone and IF filter, the VCO and the VIT filter in the TV.Surface acoustic wave device has used R wave (Rayleigh wave) or first leaky wave of propagating along the surface of medium (firstleaky wave).

Because propagate on the surface along medium, surface acoustic wave is relatively more responsive for the surface condition of medium.Therefore,, surface acoustic wave element has been sealed in the shell with cavity part, so that the surface of above-mentioned explanation is placed wherein in order to protect along the surface of the medium of its propagation surface sound wave.Owing to used the shell that has cavity as mentioned above, improved the cost of surface acoustic wave device inevitably.In addition, because the size of shell becomes much larger than the size of surface acoustic wave element, also increased the size of surface acoustic wave device inevitably.

Except above-mentioned surface acoustic wave, for sound wave, the acoustic boundary wave of propagating along the border between the solid matter has appearred also.

For example, be entitled as " Piezoelectric Acoustic Boundary Waves PropagatingAlong the Interface Between SiO ₂And LiTaO ₃", be published in IEEE Trans.Sonicsand ultrason., VOL.SU-25, No.6 in the paper of 1978 IEEE magazines, discloses a kind of boundary acoustic wave device, wherein IDT is formed on 126 ° of rotation Y to becoming plate X to the LiTaO that propagates ₃On the substrate, and will have the SiO of predetermined thickness ₂Film is formed on IDT and LiTaO ₃On the substrate.In above-mentioned technical papers, disclose a kind of SV+P type acoustic boundary wave (so-called Stoneley ripple) and propagated.In addition, be entitled as " Piezoelectric Acoustic BoundaryWaves Propagating Along the Interface Between SiO ₂And LiTaO ₃", be published in IEEE Trans.Sonics and ultrason, VOL.SU-25, No.6 in the paper of 1978IEEE, also discloses and has worked as above-mentioned SiO ₂Film thickness be made as 1.0 λ when (λ represents the wavelength of acoustic boundary wave), obtained 2% electromechanical coefficient.

When the boundary member of its concentration of energy between solid matter, acoustic boundary wave is propagated.Therefore, because energy does not appear at above-mentioned LiTaO in fact ₃The bottom surface of substrate and SiO ₂The surface of film can not change characteristic owing to the variation of the surface condition of substrate and film.Therefore, do not need the cavity type shell, the result can reduce the size of acoustic wave device.

In addition, be entitled as " Highly Piezoelectric Boundary Acoustic WavePropagating in Si/SiO ₂/ LiNbO ₃Structure " (26 ^ThEM symposium, in May, 1997, the 53rd to 58 page) paper in, disclose a kind of at [001]-Si (110)/SiO ₂/ Y propagates LiNbO to cutting X ₃The SH type acoustic boundary wave of propagating in the structure.This SH type acoustic boundary wave is characterised in that electromechanical coefficient k ²Compare bigger with the coefficient of Stoneley ripple.In addition, still under the situation of SH type acoustic boundary wave, identical with the situation of Stoneley ripple, do not need cavity.In addition,, think and Stoneley phase of wave ratio that the reflection coefficient of the band of formation IDT reflector is bigger because SH type acoustic boundary wave is a kind of SH type ripple.Therefore, for example when forming resonator or resonator filter,, can realize miniaturization, in addition, think to obtain more precipitous characteristic by utilizing SH type acoustic boundary wave.

As a kind of boundary acoustic wave device, need bigger electromechanical coefficient, in addition, also need the temperature coefficient of less propagation loss, power circuit current flow angle and frequency.Follow the propagation of acoustic boundary wave loss to occur, promptly, the degenerated insertion loss of acoustic boundary wave filter of propagation loss, or the impedance ratio of the acoustic boundary wave resonator of having degenerated, impedance ratio are the ratios between the resonance at the resonant resistance at resonance frequency place or impedance and anti-resonance frequency place.Therefore, propagation loss is the smaller the better.

The power circuit current flow angle shows the angle of the direction difference between the group velocity of the phase velocity of acoustic boundary wave and its energy.When the power circuit current flow angle is big, must as one man tilt to place IDT with the power circuit current flow angle.As a result, the design of electrode becomes complicated.In addition, because the deviation of angle is easy to generate loss.

In addition, when temperature change during the frequency of operation of boundary acoustic wave device, under the situation of acoustic boundary wave filter, reduced actual passband and attenuation band zone.Under the situation of resonator, when forming oscillating circuit, the frequency of operation that said temperature causes changes and has caused unusual vibration.Therefore, every degree centigrade frequency change (TCF) is the smaller the better.

For example, be provided with along the direction of propagation when reflector, and be in and be provided with beyond the zone that transmits and receives IDT, the described IDT of transmitting and receiving transmits and receives acoustic boundary wave respectively, so, can form resonance filter with low loss.The bandwidth of this resonance filter depends on the electromechanical coefficient of acoustic boundary wave.As electromechanical coefficient k ²When big, can obtain broadband filter, and when its hour, form narrow band filter.Therefore, consider its application, need be used for the electromechanical coefficient k of the acoustic boundary wave of boundary acoustic wave device ²Has suitable numerical value.When being formed for the RF filter of mobile phone, need electromechanical coefficient k ²Be 5% or bigger.

Yet, be entitled as " Piezoelectric Acoustic Boundary Waves PropagatingAlong the Interface Between SiO ₂And LiTaO ₃", be published in IEEE Trans.Sonicsand ultrason., VOL.SU-25, No.6, in the paper of 1978 IEEE in the disclosed boundary acoustic wave device that utilizes the Stoneley ripple, electromechanical coefficient K ²Less, for example be 2%.

In addition, at paper " Highly Piezoelectric Boundary Acoustic WavePropagating in Si/SiO ₂/ LiNbO ₃Structure " (26 ^ThEM symposium, in May, 1997, the 53rd to 58 page) in disclosed Si/SiO ₂/ LiNbO ₃In the structure,, disclose the shown in Figure 1 of No.10-84247, need to form Si/SiO as the Japanese laid-open patent application for reality excitation acoustic boundary wave ₂/ IDT/LiNbO ₃Complicated four-layer structure.In addition, when reality was arranged on [001]-Si (110) orientation that proposes as optimal conditions with Si, open No.10-84247 was disclosed as the Japanese laid-open patent application, has to use highly difficult joint method.Usually, by joint method, be difficult to engage equably the wafer that is used for raised growth with 3 inches or larger diameter.In addition, when after engaging, wafer being cut into chip, the defective that easy appearance is for example peeled off.

For SH type acoustic boundary wave, as paper " Investigation of Piezoelectric SH TypeBoundary Acoustic Wave ", Technical Report, The Institute ofElectronics, Information and Communication Engineers, Vol.96, No.249 (US96 45-53), the the 21st to 26 page, 1966 is disclosed, in the structure that is made of isotropism substrate and BGSW substrate, when meeting the following conditions, can obtain SH type acoustic boundary wave: during the approximating condition of the velocity of sound of the shear wave of the velocity of sound of the shear wave of isotropic substance and BGSW substrate, density ratio is less, and piezoelectric property is stronger.

Yet,, be difficult to satisfy acoustic boundary wave required above-mentioned various performances and characteristic owing to can satisfy the restriction of the material of above-mentioned condition.For example, at " Highly Piezoelectric " (26 ^ThEMsymposium, in May, 1997, the 53rd to 58 page) disclosed [001]-Si (110)/SiO ₂/ X-LiNbO ₃In the structure, must use highly difficult joint method, be used for producing.

Summary of the invention

Consider the current state of above-mentioned conventional art, the boundary acoustic wave device that the purpose of this invention is to provide a kind of SH of utilization type acoustic boundary wave, boundary acoustic wave device has bigger electromechanical coefficient, frequency-temperature coefficient TCF in less propagation loss, power circuit current flow angle and the proper range, and the simple structure that can make by straightforward procedure.

According to a first aspect of the invention, a kind of boundary acoustic wave device has been proposed, comprise: piezoelectric substance, be laminated to a lip-deep dielectric material of piezoelectric substance and be arranged on piezoelectric substance and dielectric material between the electrode of boundary, wherein boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border.In above-mentioned boundary acoustic wave device, the thickness of electrode is to determine like this, makes to compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, and the velocity of sound of SH type acoustic boundary wave is lower.

According to a second aspect of the invention, a kind of boundary acoustic wave device has been proposed, comprise: piezoelectric substance, be laminated to a lip-deep dielectric material of piezoelectric substance and be arranged on piezoelectric substance and dielectric material between the electrode of boundary, wherein boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border.In above-mentioned boundary acoustic wave device, the band that forms electrode has the duty ratio of determining like this (duty ratio), make and to compare that the velocity of sound of SH type acoustic boundary wave is lower with shear wave of in dielectric material, propagating at a slow speed and the shear wave at a slow speed in piezoelectric substance, propagated.

According to a third aspect of the invention we, proposed a kind of boundary acoustic wave device, having comprised: mainly by LiNbO ₃The piezoelectric substance that constitutes, be laminated to a lip-deep dielectric material of piezoelectric substance and be arranged on piezoelectric substance and dielectric material between the electrode of boundary, wherein boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border.In above-mentioned boundary acoustic wave device, mainly by LiNbO ₃Piezoelectric substance Euler (Euler) angle that constitutes (φ, θ, φ ψ) in-31 ° to+31 ° scope, wherein θ and ψ be in following by the some A01 in the table 1 in the A13 area surrounded.

Table 1

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	A01	0	116
A02	11	118	A01	0	116
A02	11	118	A03	20	123
A04	25	127	A03	20	123
A04	25	127	A05	33	140
A06	60	140	A05	33	140
A06	60	140	A07	65	132
A08	54	112	A07	65	132
A08	54	112	A09	48	90
A10	43	87	A09	48	90
A10	43	87	A11	24	90
A12	0	91	A11	24	90
A12	0	91	A13	0	116

In the boundary acoustic wave device according to third aspect present invention, the θ of Eulerian angles and ψ are in by the some D01 in the following table 2 in the D07 area surrounded.

Table 2

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	D01	0	126
D02	13	123	D01	0	126
D02	13	123	D03	25	112
D04	30	96	D03	25	112
D04	30	96	D05	29	80
D06	0	80	D05	29	80
D06	0	80	D07	0	126

In the boundary acoustic wave device according to third aspect present invention, the thickness of electrode is to determine like this, makes to compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, and the velocity of sound of SH type acoustic boundary wave is lower.

In boundary acoustic wave device according to third aspect present invention, the band that forms electrode has the duty ratio of determining like this, make and to compare that the velocity of sound of SH type acoustic boundary wave is lower with shear wave of in dielectric material, propagating at a slow speed and the shear wave at a slow speed in piezoelectric substance, propagated.

According to a forth aspect of the invention, proposed a kind of boundary acoustic wave device, having comprised: mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance, described dielectric material is mainly by SiO ₂Constitute; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material.In above-mentioned boundary acoustic wave device, when respectively the density of electrode, the thickness of electrode and the wavelength table of acoustic boundary wave being shown ρ (kg/m ³), when H (λ) and λ, H＞8,261.744 ρ ^-1.376Set up, the Eulerian angles of piezoelectric substance be in (0 °, 90 °, 0 °) to (0 °, 90 °, 38 °), (0 °, 90 °, 142 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 36 °), (90 °, 90 °, 140 °) to (90 °, 90 °, 180 °), (0 °, 55 °, 0 °) to (0 °, 134 °, 0 °), (90 °, 51 °, 0 °) to (90 °, 129 °, 0 °) or the scope of (0 °, 90 °, 0 °) to (180 °, 90 °, 0 °) in.

According to a forth aspect of the invention, the Eulerian angles of piezoelectric substance are equal to the Eulerian angles by following formula (A) expression, have obtained being equal in fact the acoustic boundary wave characteristic of piezoelectric substance at described Eulerian angles place.

F(φ，θ，ψ)＝F(60°-φ，-θ，ψ)

＝F(60°+φ，-θ，180°-ψ)

＝F(φ，180°+θ，180°-ψ)

=F (φ, θ, 180 °+ψ) ... formula (A)

According to a fifth aspect of the invention, proposed a kind of boundary acoustic wave device, having comprised: mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance, described dielectric material is mainly by SiO ₂Constitute; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material, wherein boundary acoustic wave device uses the SH type acoustic boundary wave of propagating along the border.In above-mentioned boundary acoustic wave device, when respectively the density of electrode, the thickness of electrode and the wavelength table of acoustic boundary wave being shown ρ (kg/m ³), when H (λ) and λ, H＞8,261.744 ρ ^-1.376Set up.

In according to the boundary acoustic wave device one of aspect the 3rd to the 5th, preferably, the density p of electrode is greater than 3.745kg/m ³

In according to the boundary acoustic wave device one of aspect the 3rd to the 5th, the thickness H of electrode satisfies following formula (1).

33,000.39050 ρ ^-1.50232＜H＜88,818.90913 ρ ^-1.54998Formula (1)

According to a sixth aspect of the invention, propose a kind of boundary acoustic wave device, comprised the acoustic boundary wave transmission structure that wherein SH type acoustic boundary wave and Stoneley ripple are propagated.In above-mentioned boundary acoustic wave device, compare with the shear wave at a slow speed of the two media that forms the border, the velocity of sound of SH type acoustic boundary wave is lower, and with the shear wave at a slow speed of the two media that forms the border at least a comparing, the velocity of sound of Stoneley ripple is higher.

According to first to the 6th aspect of the present invention, preferably, each electrode mainly comprises the electrode layer that at least a material selected constitutes from the group that comprises following material: Au, Ag, Au, Al, Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, ZnO, ITO and mainly comprise above-mentioned electric conducting material alloy one of at least.

In addition, except electrode layer, each electrode also comprises at least one the second electrode lay, and described the second electrode lay comprises the electric conducting material except that the electric conducting material that forms electrode layer.

Advantage

In boundary acoustic wave device according to first aspect present invention, be provided with piezoelectric substance, be laminated to a lip-deep dielectric material of piezoelectric substance and be arranged on piezoelectric substance and dielectric material between the electrode of boundary, determine the thickness of electrode, so that compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, the velocity of sound of SH type acoustic boundary wave is lower.

In addition, according to a second aspect of the invention, be provided with piezoelectric substance, be laminated to a lip-deep dielectric material of piezoelectric substance and be arranged on piezoelectric substance and dielectric material between the electrode of boundary, determine the duty ratio of the band of formation electrode, so that compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, the velocity of sound of SH type acoustic boundary wave is lower.

According to first and second aspects of the present invention, owing to determine the duty ratio of electrode or band as mentioned above, can provide a kind of SH type boundary acoustic wave device, wherein SH type acoustic boundary wave is propagated in dielectric material and piezoelectric substance.

In boundary acoustic wave device according to a third aspect of the invention we, owing to used mainly by LiNbO ₃The piezoelectric substance that constitutes, LiNbO ₃Eulerian angles (φ, θ, φ ψ) are in-31 ° to+31 ° scope, and wherein θ and ψ are in by the some A01 in the above-mentioned table 1 in the A13 area surrounded, the glitch that causes by the Stonley ripple can be suppressed effectively, and the electromechanical coefficient k of SH type acoustic boundary wave can be improved ²

Particularly, when the θ of Eulerian angles and ψ are in by the some D01 in the table 2 in the D07 area surrounded, can be with the electromechanical coefficient k of SH type acoustic boundary wave ²Improve 10% or more.

In addition, in boundary acoustic wave device according to third aspect present invention, when the thickness of determining electrode, so that compare with shear wave of in dielectric material, propagating at a slow speed and the shear wave at a slow speed in piezoelectric substance, propagated, when the velocity of sound of SH type acoustic boundary wave is low, perhaps determine the duty ratio of the band of formation electrode, so that compare with shear wave of in dielectric material, propagating at a slow speed and the shear wave at a slow speed in piezoelectric substance, propagated, when the velocity of sound of SH type acoustic boundary wave is low, a kind of SH type boundary acoustic wave device can be provided, and wherein SH type acoustic boundary wave can be propagated along the border between dielectric material and the piezoelectric substance reliably.

According to the boundary acoustic wave device of fourth aspect present invention, therein will be mainly by SiO ₂The dielectric material that constitutes is laminated to mainly by LiNbO ₃On the piezoelectric substance that constitutes and electrode is arranged in the structure of the boundary between piezoelectric substance and the dielectric material, because H＞8,261.744 ρ ^-1.376Set up, and the Eulerian angles of piezoelectric substance are in the above-mentioned concrete scope, a kind of boundary acoustic wave device that uses acoustic boundary wave and have big electromechanical coefficient can be provided.

In addition, in the boundary acoustic wave device according to fourth aspect present invention, the Eulerian angles that can replace above-mentioned piezoelectric substance by the Eulerian angles of formula (A) expression equal the acoustic boundary wave characteristic of piezoelectric substance in fact in described Eulerian angles place acoustic boundary wave characteristic.

According to a fifth aspect of the invention, a kind of boundary acoustic wave device has been proposed, owing to be provided with mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance, described dielectric material is mainly by SiO ₂Constitute; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material, and ought respectively the density of electrode, the thickness of electrode and the wavelength table of acoustic boundary wave be shown ρ (kg/m ³), when H (λ) and λ, because H＞8,261.744 ρ ^-1.376Set up, a kind of boundary acoustic wave device can be provided, wherein can propagate SH type acoustic boundary wave, can suppress the glitch that causes by the Stoneley ripple simultaneously effectively.

In addition, the boundary acoustic wave device of the 3rd to the 5th aspect according to the present invention, when density p greater than 3.745kg/m ³The time, can reduce propagation loss and be the thickness of 0 electrode.Therefore, can easily form electrode.

In addition, when thickness of electrode H satisfies above-mentioned formula (1), the frequency-temperature coefficient TCF of SH type acoustic boundary wave can be reduced to ± 20ppm or littler.

Boundary acoustic wave device according to sixth aspect present invention, in having the acoustic boundary wave transmission structure that wherein SH type acoustic boundary wave and Stoneley ripple are propagated, owing to compare with the shear wave at a slow speed of the two media that forms the border, the velocity of sound of SH type acoustic boundary wave is lower, and with the shear wave at a slow speed of the two media that forms the border at least a comparing, the velocity of sound of Stoneley ripple is higher, the Stoneley wave propagation of having degenerated loss, suppressed the glitch that causes by the Stoneley ripple thus, as a result, can improve the frequency characteristic of the boundary acoustic wave device that utilizes SH type acoustic boundary wave.

In the present invention, when each electrode mainly comprises the electrode layer that at least a material selected constitutes from the group that comprises following material: Au, Ag, Cu, Al, Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, ZnO, ITO and when mainly comprising one of at least alloy of above-mentioned metal can provide the boundary acoustic wave device according to the SH of utilization type acoustic boundary wave of the present invention.In addition, when each electrode also comprises at least one the second electrode lay, described the second electrode lay is during by the metal except that the metal that forms electrode layer, by selecting to form the metal material of the second electrode lay, bonding between electrode and dielectric material or the piezoelectric substance can be improved, maybe electrical power resistance can be improved.

Description of drawings

Fig. 1 is the front cross-sectional view of boundary acoustic wave device according to an embodiment of the invention.

Fig. 2 shows when utilizing the electrode material with different densities to be formed on each electrode between piezoelectric substance and the dielectric material, the curve chart of the relation between the velocity of sound V of the electrode that obtains and the thickness H/ λ.

Fig. 3 shows when utilizing the electrode material with different densities to be formed on each electrode between piezoelectric substance and the dielectric material, the curve chart of the relation between the propagation loss α of the electrode that obtains and the thickness H/ λ.

Fig. 4 shows when utilizing the electrode material with different densities to be formed on each electrode between piezoelectric substance and the dielectric material, the electromechanical coefficient k of the electrode that obtains ²And the curve chart of the relation between the thickness H/ λ.

Fig. 5 shows when utilizing the electrode material with different densities to be formed on each electrode between piezoelectric substance and the dielectric material, the curve chart of the relation between the frequency-temperature coefficient TCF of the electrode that obtains and the thickness H/ λ.

Fig. 6 shows when utilizing the electrode material with different densities to be formed on each electrode between piezoelectric substance and the dielectric material, the curve chart of the relation between the power circuit current flow angle PFA of the electrode that obtains and the thickness H/ λ.

Fig. 7 shows the density p of electrode material that propagation loss is 0 place and the curve chart of the relation between the thickness of electrode H (λ).

Fig. 8 show TCF for-20 ,-10,0 ,+10 and+density p of the 20ppm/ ℃ electrode material of locating and the curve chart of the relation between the thickness of electrode H (λ).

Fig. 9 shows the curve chart of frequency characteristic of the acoustic boundary wave resonator of experimental formation in example 2.

Figure 10 shows the Eulerian angles φ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 11 shows Eulerian angles φ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 12 shows the Eulerian angles φ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 13 shows the Eulerian angles φ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 14 shows the Eulerian angles φ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 15 shows the Eulerian angles φ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 16 shows Eulerian angles φ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 17 shows the Eulerian angles φ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 18 shows the Eulerian angles φ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 19 shows the Eulerian angles φ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 0 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 20 shows the Eulerian angles φ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 21 shows Eulerian angles φ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 22 shows the Eulerian angles φ in such structure and the curve chart of the relation between the transmission loss α: the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 23 shows the Eulerian angles φ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 24 shows the Eulerian angles φ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 25 shows the Eulerian angles φ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 26 shows Eulerian angles φ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 27 shows the Eulerian angles φ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 28 shows the Eulerian angles φ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 29 shows the Eulerian angles φ in following structure and the curve chart of the relation between the power circuit current flow angle PFA: the Au electrode is formed on the have Eulerian angles LiNbO of (φ, 90 °, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 30 shows the Eulerian angles θ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 31 shows Eulerian angles θ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 32 shows the Eulerian angles θ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 33 shows the Eulerian angles θ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 34 shows the Eulerian angles θ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 35 shows the Eulerian angles θ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 36 shows Eulerian angles θ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 37 shows the Eulerian angles θ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 38 shows the Eulerian angles θ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 39 shows the Eulerian angles θ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (0 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 40 shows the Eulerian angles θ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 41 shows Eulerian angles θ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 42 shows the Eulerian angles θ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 43 shows the Eulerian angles θ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 44 shows the Eulerian angles θ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 45 shows the Eulerian angles θ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 46 shows Eulerian angles θ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 47 shows the Eulerian angles θ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 48 shows the Eulerian angles θ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 49 shows the Eulerian angles θ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode is formed on the have Eulerian angles LiNbO of (90 °, θ, 90 °) ₃On the substrate, and formed SiO ₂Film.

Figure 50 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode be formed on and have Eulerian angles (0 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 51 shows Eulerian angles ψ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, and the Au electrode be formed on and have Eulerian angles (0 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 52 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode be formed on and have Eulerian angles (0 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 53 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode be formed on and have Eulerian angles (0 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 54 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode be formed on and have Eulerian angles (0 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 55 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode be formed on and have Eulerian angles (0 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 56 shows Eulerian angles ψ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, and the Au electrode be formed on and have Eulerian angles (0 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 57 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode be formed on and have Eulerian angles (0 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 58 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode be formed on and have Eulerian angles (0 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 59 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode be formed on and have Eulerian angles (0 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 60 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode be formed on and have Eulerian angles (90 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 61 shows Eulerian angles ψ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, and the Au electrode be formed on and have Eulerian angles (90 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 62 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode be formed on and have Eulerian angles (90 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 63 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode be formed on and have Eulerian angles (90 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 64 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode be formed on and have Eulerian angles (90 °, 0 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 65 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the velocity of sound V, that is, the Au electrode be formed on and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 66 shows Eulerian angles ψ and the electromechanical coefficient k in such structure ²Between the curve chart of relation, that is, and the Au electrode be formed on and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 67 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the transmission loss α, that is, the Au electrode be formed on and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 68 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the frequency-temperature coefficient TCF, that is, the Au electrode be formed on and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 69 shows the Eulerian angles ψ in such structure and the curve chart of the relation between the power circuit current flow angle PFA, that is, the Au electrode be formed on and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 70 is the example flat figure of the electrode structure of the SH type acoustic boundary wave resonator of preparation in the example 6.

Figure 71 shows in example 6 and to use and have Eulerian angles the LiNbO of (0 °, 90 °, 0 °) ₃Situation under, the curve chart of the impedance operator that obtains.

Figure 72 shows in example 6 and to use and have Eulerian angles the LiNbO of (0 °, 105 °, 0 °) ₃Situation under the curve chart of the impedance operator that obtains.

Figure 73 shows the curve chart of the calculated value of displacement component U1, the U2 of the SH type acoustic boundary wave in the boundary acoustic wave device of example 6 and U3.

Figure 74 comprise the ψ place in 0 ° to the 35 ° scope that shows in example 7 use and to have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃Situation under, the curve chart of the impedance operator that obtains.

Figure 75 show Eulerian angles in the example 7 (90 °, 90 °, the curve chart of the difference between ψ ψ) and resonance frequency and the anti-resonance frequency and the relation of impedance ratio.

Figure 76 shows the figure of the circuit structure of the ladder-type filter that utilizes the formation of SH type acoustic boundary wave resonator in the example 8.

Figure 77 shows the Eulerian angles θ of following structure in example 4 and the electromechanical coefficient k of ψ and SH acoustic boundary wave ²Between the curve chart of relation: the Au electrode that 0.06 λ is thick be formed on and have Eulerian angles (0 °, θ, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 78 shows the Eulerian angles θ of following structure in example 4 and the electromechanical coefficient k of ψ and Stoneley ripple ²Between the curve chart of relation: the Au electrode that 0.06 λ is thick be formed on and have Eulerian angles (0 °, θ, LiNbO ψ) ₃On the substrate, and formed SiO ₂Film.

Figure 79 shows when use the LiNbO with Eulerian angles (φ, 105 °, 0 °) in example 5 ₃The curve chart of the relation between the velocity of sound V of Eulerian angles φ that obtains during substrate and SH acoustic boundary wave and Stoneley ripple.

Figure 80 shows when use the LiNbO with Eulerian angles (φ, 105 °, 0 °) in example 5 ₃The curve chart of the relation between Eulerian angles φ that obtains during substrate and the frequency-temperature coefficient TCF.

Figure 81 shows when use the LiNbO with Eulerian angles (φ, 105 °, 0 °) in example 5 ₃Eulerian angles φ that obtains during substrate and electromechanical coefficient k ²Between the curve chart of relation.

Figure 82 shows when use the LiNbO with Eulerian angles (φ, 105 °, 0 °) in example 5 ₃The curve chart of the relation between Eulerian angles φ that obtains during substrate and the power circuit current flow angle.

Figure 83 shows when using in example 5 has Eulerian angles (φ, 105 °, LiNbO ψ) ₃The curve chart of the relation between the velocity of sound V of Eulerian angles φ that obtains during substrate and SH acoustic boundary wave and Stoneley ripple.

Figure 84 shows when using in example 5 has Eulerian angles (φ, 105 °, LiNbO ψ) ₃The curve chart of the relation between Eulerian angles φ that obtains during substrate and the frequency-temperature coefficient TCF.

Figure 85 shows when using in example 5 has Eulerian angles (φ, 105 °, LiNbO ψ) ₃Eulerian angles φ that obtains during substrate and electromechanical coefficient k ²Between the curve chart of relation.

Figure 86 shows when using in example 5 has Eulerian angles (φ, 105 °, LiNbO ψ) ₃The curve chart of the relation between Eulerian angles φ that obtains during substrate and the power circuit current flow angle.

Figure 87 shows the Eulerian angles θ of following structure in the example 4 and the curve chart of the relation between the velocity of sound: the Au electrode that 0.05 λ is thick is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 88 shows the Eulerian angles θ and the electromechanical coefficient k of following structure in the example 4 ²Between the curve chart of relation: the Au electrode that 0.05 λ is thick is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Figure 89 shows the Eulerian angles θ of following structure in the example 4 and the curve chart of the relation between the frequency-temperature coefficient TCF: the Au electrode that 0.05 λ is thick is formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) ₃On the substrate, and formed SiO ₂Film.

Embodiment

Below, instantiation of the present invention will be described with reference to the accompanying drawings, so that make the present invention more apparent.

When acoustic boundary wave was propagated between two solid layer, must meet the following conditions: the concentration of energy of acoustic boundary wave was between solid layer.In this case, as mentioned above, at " Investigation ofPiezoelectric SH Type Boundary Acoustic Wave ", Technical Report, TheInstitute of Electronics, Information and Communication Engineers, Vol.96, No.249 (US96 45-53), the 21st to 26 page, in 1966, disclose a kind of method, wherein selected material, so that the velocity of sound of the shear wave of the velocity of sound of the shear wave of isotropic substance and BGSW substrate is closer to each other, density between it is less, and piezoelectric property is stronger.

Usually, when presenting high-speed region and low-speed region, ripple concentrates on the lower location of the velocity of sound, and propagates therein.Therefore, the present inventor finds, when by will be for example metal material with greater density and low velocity of sound such as Au increase thickness of electrode as being arranged on two electrode materials between the solid layer, thereby during the velocity of sound of the acoustic boundary wave that reduces to propagate between the solid layer, can satisfy the condition of concentration of energy between solid layer, as a result, realized the present invention.

Before, known three types the bulk wave of in solid matter, propagating, that is, and compressional wave, fast shear wave and shear wave at a slow speed, and respectively it is referred to as P ripple, SH ripple and SV ripple.Determine by the anisotropic properties of base material whether SH ripple and SV ripple become shear wave at a slow speed.In above-mentioned three types bulk wave, the bulk wave with minimum velocity of sound is a shear wave at a slow speed.When solid matter is SiO for example ₂Isotropic substance the time, can only propagate one type shear wave therein, this shear wave is a shear wave at a slow speed.

In addition, in the acoustic boundary wave of in the anisotropy base material of for example Piezoelectric Substrates, propagating, in most cases, be coupled in the time of the propagation of three displacement components of P ripple, SH ripple and SV ripple, determine the type of acoustic boundary wave by fundamental component.For example, the Stoneley ripple is the acoustic boundary wave that mainly is made of P ripple and SV ripple, and SH type acoustic boundary wave is the acoustic boundary wave that mainly is made of the SH component.In addition, depend on condition, under the situation about not being coupled between it, SH wave component and P ripple or SV wave component can propagated in some cases.

In acoustic boundary wave, because above-mentioned three kinds of displacement components are coupled, in the acoustic boundary wave that has faster than the velocity of sound of SH ripple, leak SH component and SV component when propagating, and in the acoustic boundary wave that has faster than the velocity of sound of SV ripple, leak the SV component.This leaky wave causes the propagation loss of acoustic boundary wave.

Therefore, when with two kinds of two kinds of solid layer at a slow speed shear wave compare, reduce the velocity of sound of SH type acoustic boundary wave, when making it low, the concentration of energy of SH type acoustic boundary wave can be arranged at around two electrodes between the solid layer, and can propagate and have big electromechanical coefficient k ²SH type acoustic boundary wave; Therefore, the result can access propagation loss and be 0 condition.Realize the present invention based on above-mentioned consideration.

In addition, when forming at least one solid layer by piezoelectric substance, and when forming other solid layer, encourage SH type acoustic boundary wave by the electrode that is arranged between the solid layer by the dielectric material that comprises piezoelectric substance.Knowledge according to the present inventor, when piezoelectric substance is used as dielectric material, and when the inexpensive films formation method by for example sputter or CVD formed the film of piezoelectric substance, the piezoelectric constant of piezoelectric substance became instability, and can produce unnecessary signal imitation; Therefore, preferably, the material that will have non-piezoelectric property is as dielectric material.

Fig. 1 is the front cross-sectional view of boundary acoustic wave device according to an embodiment of the invention.In boundary acoustic wave device 1, on the upper surface of piezoelectric substance that with the plate is form, be provided with dielectric material 3.Boundary between piezoelectric substance 2 and dielectric material 3 is provided with IDT 4 and

reflector

5,6, as electrode.The direction of propagation of sound wave surfacewise is arranged on the both sides of IDT 4 with

reflector

5 and 6, is provided with by this, has formed the acoustic boundary wave resonator in the present embodiment.

The boundary acoustic wave device 1 of present embodiment is characterised in that, increases the thickness of IDT 4 and

reflector

5 and 6, so that compare with the shear wave at a slow speed of shear wave of propagating in dielectric material 3 at a slow speed and propagation in piezoelectric substance 2, the velocity of sound of SH type acoustic boundary wave is lower.

In the present embodiment, owing to increased the thickness of electrode, reduced the velocity of sound of SH type acoustic boundary wave thus, make its velocity of sound that is lower than the shear wave of in piezoelectric substance 2 and dielectric material 3, propagating respectively at a slow speed, with the boundary of concentration of energy between piezoelectric substance 2 and dielectric material 3 of SH type acoustic boundary wave.Therefore, can propagate with less propagation loss and have big electromechanical coefficient k ²SH type acoustic boundary wave.

Except propagate SH type acoustic boundary wave by the thickness that increases electrode, according to the present invention, as described below, form the duty ratio of the band of electrode by control, can reduce the velocity of sound of SH type acoustic boundary wave, make its velocity of sound that is lower than the shear wave of in piezoelectric substance 2 and dielectric material 3, propagating respectively at a slow speed, SH type acoustic boundary wave can be concentrated on boundary and propagation therein thus.

Below, the example with reference to concrete illustrates in greater detail the present invention.

[example 1]

As piezoelectric substance 2, prepared and had Eulerian angles the LiNbO of (0 °, 90 °, 0 °) ₃Substrate, that is, Y is to becoming plate X to propagating LiNbO ₃Substrate.By utilizing LiNbO ₃Substrate can access excellent piezoelectric property.In addition, the material as being used to form node material 3 has used SiO ₂Can be easily by forming SiO ₂Form film, be offset LiNbO owing to have ₃The positive frequency temperature coefficient TCF of negative TCF, SiO ₂Can improve temperature characterisitic.

Have the various electrode materials of different densities by utilization, electrode is formed between piezoelectric substance 2 and the dielectric material 3, and has measured thickness of electrode and velocity of sound V, electromechanical coefficient k ², the relation between propagation loss α, frequency-temperature coefficient TCF and the power circuit current flow angle PFA.Fig. 2 to 6 shows the result.

By based at " A method for estimating optimal cuts and propagationdirections for excitation and propagation directions for excitation ofpiezoelectric surface waves " (J.J.Campbell, with W.R Jones, IEEETrans.Sonics and Ultrason., Vol.SU-15 (1968), the the 209th to 217 page) in the calculating of disclosed method, obtained the result shown in Fig. 2 to 6.

Under the situation of free boundary (free boundary), think at SiO ₂And between the Au and Au and LiNbO ₃Between each boundary displacement, electromotive force, dielectric (flux) density and upwards be continuous with the stress of downward direction, think SiO ₂And LiNbO ₃Thickness be unlimited, and think that the relative dielectric constant of Au is 1, can access the velocity of sound and propagation loss thus.In addition, under the situation on short circuit border, think SiO ₂And between the Au and Au and LiNbO ₃Between the electromotive force of each boundary be 0.In addition, obtain electromechanical coefficient k by following formula (2) ²

k ²=2 * | Vf-V|/Vf ... formula (2)

In above-mentioned formula, Vf represents the velocity of sound of free boundary.

By following formula (3), obtain frequency-temperature coefficient TCF from the phase velocity of 20 ℃, 25 ℃ and 30 ℃.

TCF=V ^-1(25 ℃) * [V (30 ℃)-V (20 ℃)/10 ℃]-α s ... formula (3)

In above-mentioned formula, α s is the LiNbO along the acoustic boundary wave direction of propagation ₃The thermal coefficient of expansion of substrate.

In addition, by following formula (4), obtain being positioned at any Eulerian angles (φ, θ, the power circuit current flow angle PFA that ψ) locates from ψ-0.5 °, the phase velocity of ψ, ψ+0.5 ° angle.

PFA=tan ^-1[V ^-1(ψ) * [V (ψ+0.5 °)-V (ψ-0.5 °)] ... formula (4)

At Y to becoming plate X to propagating LiNbO ₃In the substrate, compressional wave, fast shear wave and at a slow speed the velocity of sound of shear wave be respectively 6,547,4,752 and 4,031m/ second.In addition, SiO ₂Compressional wave and at a slow speed the velocity of sound of shear wave be respectively 5,960 and 3,757m/ second.

Shown in Fig. 2 and 3, be appreciated that electrode material by any type, the velocity of sound of SH type acoustic boundary wave become as compressional wave, fast shear wave and at a slow speed the minimum speed in the shear wave 3,757m/ second or littler thickness place, the propagation loss α of SH type acoustic boundary wave becomes 0.

The propagation loss that Fig. 7 shows SH type acoustic boundary wave is the density p of electrode material at 0 place and the curve chart of the relation between the thickness of electrode H.As shown in Figure 7, be appreciated that when following formula (5) is set up, can access that to have propagation loss α be 0 SH type acoustic boundary wave.

H＞8,261.744 ρ ^-1.376Formula (5)

In addition, when making the boundary acoustic wave device of the type, the photoetching method by comprising demoulding (lift-off), dry etching etc. etc. are formed on the electrode of for example IDT by LiNbO ₃On the Piezoelectric Substrates that constitutes, and on the electrode that forms thus,, form SiO by the deposition process of for example sputter, evaporation or CVD ₂Dielectric film etc.Therefore, because the scrambling that the thickness of IDT causes, under certain conditions, dielectric film is grown obliquely, or its quality disunity that becomes, result, the characteristic of the boundary acoustic wave device of having degenerated under certain conditions.For fear of the degeneration of above-mentioned characteristic, preferably, reduce the thickness of electrode as small as possible.

According to the research of being undertaken by the present inventor, when the film thickness H of the electrode material that is used for IDT etc. is 0.1 λ or when bigger, because its scrambling, become and be difficult to form dielectric film with excellent quality, therefore, preferably, thickness of electrode is reduced to 0.1 λ or littler.Therefore, as shown in Figure 7, be appreciated that when use has density p be 3.745kg/m ³Electrode material the time, the thickness of electrode H that propagation loss can be become 0 place is reduced to 0.1 λ.

In addition, as shown in Figure 4, be appreciated that the thickness of electrode place that sets up at above-mentioned formula (5), electromechanical coefficient k ²Bigger, for example 10% to 38%, therefore, can access boundary acoustic wave device with big bandwidth and low loss.

In addition, as shown in Figure 5, be appreciated that, in most of the cases, frequency-temperature coefficient TCF is in-40 to+40ppm/ ℃ the scope, by adjusting thickness of electrode, TCF can be reduced to ± 20ppm/ ℃ or littler, or ± 10ppm/ ℃ or littler, and can further be reduced to ± 0ppm/ ℃ or littler.

Fig. 8 show TCF be .20 ,-10,0 ,+10 and+density p of the 20ppm/ ℃ electrode material of locating to obtain and the curve chart of the relation between the thickness of electrode H, by the point and curve of approximation represent described relation.As shown in Figure 8, when following formula (6) is set up, had-20 the thickness of electrode H of preferred TCF in the+20ppm/ ℃ scope, when following formula (7) is set up, had-10 the thickness of electrode H of more preferably TCF in the+10ppm/ ℃ scope, and when following formula (8) is set up, obtain having the thickness of electrode H of 0ppm/ ℃ most preferably TCF.

33,000.39050 ρ ^-1.50232＜H＜88,818.90913 ρ ^-1.54998Formula (6)

49,889.90887 ρ ^-1.53872＜H＜112,510.78359 ρ ^-1.60019Formula (7)

H=96,984.47020 ρ ^-1.59706Formula (8)

In addition, as shown in Figure 6, be appreciated that advantageously that power circuit current flow angle PFA is 0 at any film thickness H place.

[example 2]

Based on the result who obtains in the above-mentioned example 1, formed acoustic boundary wave resonator shown in Figure 1 and that have the structure shown in the following table 3 experimentally.The frequency characteristic of the acoustic boundary wave resonator that forms thus has been shown among Fig. 9.

Table 3

Project	Details
Project	Details	Structure	SiO ₂/Au/LiNbO ₃
SiO ₂Thickness	7.5λ	Structure	SiO ₂/Au/LiNbO ₃
SiO ₂Thickness	7.5λ	Au thickness	0.035λ
IDT, reflector periods λ	3.2μm	Au thickness	0.035λ
IDT, reflector periods λ	3.2μm	The IDT configuration	The single band of plain edition, 50, opening length 25 λ
Reflector arrangement	The single band of plain edition, 40, opening length 25 λ	The IDT configuration	The single band of plain edition, 50, opening length 25 λ

In above-mentioned acoustic boundary wave resonator, impedance ratio, i.e. the impedance at antiresonance point place is 45.6dB with the ratio of the impedance at resonance point place, and the difference between resonance frequency and the anti-resonance frequency is 8.1%; Therefore, obtained preferred result.In addition, the frequency-temperature coefficient TCF of resonator is 45ppm/ ℃.

Therefore, owing to the band that utilizes than peanut, for example the electrode combs of 52 couples of IDT refers to and the band of 40 reflectors, can access preferred resonance characteristic, believes that the reflection coefficient of IDT and reflector is higher.

Yet, as shown in Figure 9, around anti-resonance frequency, observe the less signal imitation of representing by arrow A.In the application of the propagation characteristic around using resonance frequency, for example, jump in sunken (trap) circuit at acoustic boundary wave, above-mentioned phenomenon may not can cause any problem; Yet for the trapezoidal border acoustic wave filter or the longitudinal coupling resonator type acoustic boundary wave filter that utilize anti-resonance frequency propagation characteristic on every side, under certain conditions, above-mentioned phenomenon may cause problem.Therefore, in order to increase the range of application of SH type boundary acoustic wave device, and further improve its characteristic, preferably, suppress above-mentioned signal imitation.

[example 3]

Identical with the situation of SH type acoustic boundary wave, because the increase of thickness of electrode, the above-mentioned signal imitation that produces around the anti-resonance frequency in example 2 is to be limited to be arranged at SiO ₂And LiNbO ₃Between the electrode of boundary around the response of Stoneley ripple.Because under many situations, the velocity of sound of Stoneley ripple is lower than the velocity of sound of SH type acoustic boundary wave, even when comparing with the situation of SH type acoustic boundary wave, thickness of electrode hour, the Stoneley ripple also is expressed as acoustic boundary wave.

For example, when propagating (by Eulerian angles (0 °, 90 °, 0 °) expression) LiNbO to cutting X at Y ₃Form on the substrate and have enough SiO of big thickness ₂Film so that do not encourage the surface acoustic wave of the R wave for example or first leaky wave, and is arranged on LiNbO with the Au electrode ₃Substrate and SiO ₂In the time of between the film, SH type acoustic boundary wave has than high attenuation, and can not propagate, unless the thickness of Au electrode is 0.0105 λ or bigger; Yet even when the thickness of Au electrode is 0, although its decay is not 0, the Stoneley ripple still can be propagated.

Therefore, for the glitch that suppresses to cause,, measured LiNbO respectively by utilizing the computational methods of example 1 by the Stoneley ripple ₃The velocity of sound V of the Eulerian angles of substrate and Stoneley ripple and SH type acoustic boundary wave, electromechanical coefficient k ², the relation between propagation loss α, frequency-temperature coefficient TCF and the power circuit current flow angle PFA.

As the structure that is used for this measurement, at LiNbO ₃On the substrate, form the Au electrode, and formed SiO ₂Film.The thickness of Au electrode is made as 0.07 λ, and Eulerian angles be set to (0 °, 0 °, ψ), (0 °, 90 °, ψ), (90 °, 0 °, ψ), (90 °, 90 °, ψ), (0 °, θ, 0 °), (0 °, θ, 90 °), (90 °, θ, 0 °), (90 °, θ, 90 °), (φ, 0 °, 0 °), (φ, 0 °, 90 °), (φ, 90 °, 0 °) and (φ, 90 °, 90 °), wherein each ψ, θ and φ are in 0 ° to 180 ° the scope.

In Figure 10 to 69, show the result.

In Figure 10 to 69, the numerical value that is equipped with the numeric representation of subscript m to calculate in the short circuit border wherein is arranged on SiO with metal film ₂Film and LiNbO ₃Between the substrate, and the numerical value that is equipped with the numeric representation of subscript f to calculate in virtual free boundary (virtual free boundary), wherein the relative dielectric constant by the hypothesis metal film is 1 to obtain described virtual free boundary.Be equipped with the calculated value of the numeric representation SH type acoustic boundary wave of prefix U2, and be equipped with the calculated value of the numeric representation Stoneley ripple of prefix U3.

Electromechanical coefficient k when the Stoneley ripple ²Be 2% or more hour, since less based on the degeneration of the characteristic of the glitch that has the Stoneley ripple to cause, can will utilize the boundary acoustic wave device of SH type acoustic boundary wave to be used for limited relatively application.More preferably, electromechanical coefficient k ²Be 1% or littler, in this case, can manyly use boundary acoustic wave device widely.In addition, the electromechanical coefficient k of Stoneley ripple ²Or even 0.1% or littler, in this case, owing to can ignore the influence of the glitch of Stoneley ripple in fact, boundary acoustic wave device can be used for to have filter, or wherein can not accept the pinpoint accuracy resonator of trickle glitch resonance response than high attenuation.

In Figure 10 to 69, the electromechanical coefficient k of Stoneley ripple wherein ²Be 2% or littler Eulerian angles be in (0 °, 90 °, 0 °) to (0 °, 90 °, 50 °), (0 °, 90 °, 130 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 60 °), (90 °, 90 °, 143 °) to (90 °, 90 °, 180 °), (0 °, 84 °, 0 °) to (0 °, 120 °, 0 °), (90 °, 68 °, 90 °) to (90 °, 112 °, 90 °) and (0 °, 90 °, 0 °) in the scope of (180 °, 90 °, 0 °); The electromechanical coefficient k of Stoneley ripple wherein ²Be 1% or littler Eulerian angles be in (90 °, 90 °, 0 °) to (90 °, 90 °, 52 °), (90 °, 90 °, 164 °) to (90 °, 90 °, 180 °), (0 °, 91 °, 0 °) to (0 °, 114 °, 0 °), (90 °, 78 °, 90 °) to (90 °, 102 °, 90 °), (7 °, 90 °, 0 °) to (53 °, 90 °, 0 °), (67 °, 90 °, 0 °) to (113 °, 90 °, 0 °) and (127 °, 90 °, 0 °) in the scope of (173 °, 90 °, 0 °); And the electromechanical coefficient k of Stoneley ripple wherein ²Be 0.1% or littler Eulerian angles be in the scope of (90 °, 90 °, 20 °) to (90 °, 90 °, 40 °) and (0 °, 100 °, 0 °) to (0 °, 106 °, 0 °).

Has the LiNbO that is in the Eulerian angles in one of above-mentioned scope by utilization ₃Substrate can also provide a kind of boundary acoustic wave device of the SH of utilization type acoustic boundary wave, and wherein signal imitation is less or can not produce signal imitation.

Under all conditions of the result of calculation of Figure 10 to 69, the propagation loss U2-am and the U2-af of SH type acoustic boundary wave are 0, have obtained excellent propagation characteristic.

In addition, be appreciated that in most cases that the velocity of sound U2-Vm of SH type acoustic boundary wave is in the scope of approximate 3000 to 3400m/ seconds, and the variation that is caused by the angle of cut is less.

Therefore, by above-mentioned formula (5),, also can access propagation loss and be 0 thickness of electrode H even be appreciated that when changing the angle of cut.

In addition, be appreciated that in most cases that the frequency-temperature coefficient U2-TCFm of SH acoustic boundary wave is in-30 to-39ppm/ ℃ the scope, and the variation that is caused by the angle of cut is not obvious.Therefore, even be appreciated that when the angle of cut changes to (8) according to above-mentioned formula (6), also can determine thickness of electrode H, so that reduce frequency-temperature coefficient TCF.

Particularly, when Eulerian angles are in following scope, can access the excellent power circuit current flow angle U2-PFAm of SH type acoustic boundary wave, for example 1 ° absolute value or littler: (0 °, 0 °, 0 °) to (0 °, 0 °, 180 °), (0 °, 90 °, 0 °) to (0 °, 90 °, 10 °), (0 °, 90 °, 74 °) to (0 °, 90 °, 106 °), (0 °, 90 °, 170 °) to (0 °, 90 °, 180 °), (90 °, 0 °, 0 °) to (90 °, 0 °, 180 °), (90 °, 90 °, 12 °) to (90 °, 90 °, 31 °), (90 °, 90 °, 106 °) to (90 °, 90 °, 117 °), (0 °, 0 °, 0 °) to (0 °, 180 °, 0 °), (0 °, 0 °, 90 °) to (0 °, 180 °, 90 °), (90 °, 0 °, 0 °) to (90 °, 22 °, 0 °), (90 °, 158 °, 0 °) to (90 °, 180 °, 0 °), (90 °, 68 °, 90 °) to (90 °, 112 °, 90 °), (0 °, 0 °, 0 °) to (180 °, 0 °, 0 °), (0 °, 0 °, 90 °) to (180 °, 0 °, 90 °), (0 °, 90 °, 0 °) to (8 °, 90 °, 0 °), (52 °, 90 °, 0 °) to (68 °, 90 °, 0 °), (112 °, 90 °, 0 °) to (128 °, 90 °, 0 °), (172 °, 90 °, 0 °) to (180 °, 90 °, 0 °), (0 °, 90 °, 90 °) to (16 °, 90 °, 90 °), (44 °, 90 °, 90 °) to (76 °, 90 °, 90 °), (104 °, 90 °, 90 °) to (136 °, 90 °, 90 °) and (164 °, 90 °, 90 °) to (180 °, 90 °, 90 °).

In addition, be in (0 °, 90 °, 0 °) to (0 ° when Eulerian angles, 90 °, 38 °), (0 °, 90 °, 142 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 36 °), (90 °, 90 °, 140 °) to (90 °, 90 °, 180 °), (0 °, 55 °, 0 °) to (0 °, 134 °, 0 °), (90 °, 51 °, 0 °) to (90 °, 129 °, 0 °) and (0 °, 90 °, 0 °) to (180 °, 90 °, 0 °) scope in the time, the electromechanical coefficient k of SH type acoustic boundary wave ²Be 5% or bigger, even as big as forming the RF filter; When Eulerian angles are in (0 °, 90 °, 0 °) to (0 °, 90 °, 25 °), (0 °, 90 °, 155 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 23 °), (90 °, 90 °, 151 °) to (90 °, 90 °, 180 °), (0 °, 67 °, 0 °) to (0 °, 121 °, 0 °), (90 °, 63 °, 0 °) to (90 °, 117 °, 0 °) and (0 °, 90 °, 0 °) to (180 °, 90 °, 0 °) scope in the time, with the electromechanical coefficient k of SH type acoustic boundary wave ²More preferably increase to 10% or bigger; When Eulerian angles are in (0 °, 90 °, 0 °) to (0 °, 90 °, 13 °), (0 °, 90 °, 167 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 11 °), (90 °, 90 °, 162 °) to (90 °, 90 °, 180 °), (0 °, 80 °, 0 °) to (0 °, 110 °, 0 °), (90 °, 75 °, 0 °) to (90 °, 105 °, 0 °) and (0 °, 90 °, 0 °) to (180 °, 90 °, 0 °) scope in the time, with the electromechanical coefficient k of SH type acoustic boundary wave ²More preferably increase to 15% or bigger.

According to the present inventor's knowledge, for the k that has reduced the Stoneley ripple at this place ²Excellent Eulerian angles, U2-TCFm becomes at this place-Eulerian angles of 35ppm/ ℃ and become 1% or littler Eulerian angles at the power circuit current flow angle U2-PFAm of this place, even, still can access to be equal to above-mentioned excellent specific property when φ, θ and ψ all depart from about 5 ° of described scope.In addition, when the thickness of Au electrode is 0.07 λ, obtained evaluation, under the situation of other electrode material, also can access and the above-mentioned result who is equal to.

[example 4]

By being formed on the have Eulerian angles LiNbO of (0 °, θ, 0 °) by the electrode that the Au with thickness 0.05 λ makes ₃On the substrate, form SiO then ₂Film so that cover the Au electrode, has formed boundary acoustic wave device.In this boundary acoustic wave device, measure LiNbO ₃The velocity of sound V of Eulerian angles θ on the substrate and SH type acoustic boundary wave and Stoneley ripple, electromechanical coefficient k ²Relation with frequency-temperature coefficient TCF.Figure 87 to 89 shows the result.

By θ=0 ° in the whole zone of 180 ° of expressions, propagation loss a is that 0dB/ λ and power circuit current flow angle PFA are 0.

Shown in Figure 88, when θ=106 °, under the situation of using SH type acoustic boundary wave, be appreciated that the electromechanical coefficient k of the Stoneley ripple that causes signal imitation ²Be similar to and become 0.

Next, have Eulerian angles by being formed on by the electrode that the Au with thickness 0.06 λ makes (0 °, θ, LiNbO ψ) ₃On the substrate, on the electrode that AU makes, form SiO then ₂Film.In this boundary acoustic wave device, measure LiNbO ₃The velocity of sound V of Eulerian angles θ on the substrate and ψ and SH type acoustic boundary wave and Stoneley ripple, electromechanical coefficient k ², propagation loss α and frequency-temperature coefficient TCF relation.Figure 77 shows the result of SH type acoustic boundary wave, and Figure 78 shows the result of Stoneley ripple.

In the whole zone shown in Figure 77 and 78, propagation loss α is 0dB/ λ.In addition, for velocity of sound V and frequency-temperature coefficient TCF, the condition with respect to φ shown in Figure 87 to 89 is 0 does not observe tangible change.Therefore, in Figure 77 and 78, only show electromechanical coefficient k ²Result (%).

Shown in Figure 78, by the some A01 shown in the following table 4 in the A13 area surrounded, as the electromechanical coefficient k of the response of Stoneley ripple ²Less, for example 1.5% or littler.In addition, by the some B01 shown in the following table 5 in the B12 area surrounded, preferably, with electromechanical coefficient k ²Be reduced to 1.0% or littler, and by the some C01 shown in the following table 6 in the C08 area surrounded, preferably, with k ²Be reduced to 0.5% or littler.In addition, locate electromechanical coefficient k in Eulerian angles (0 °, 106 °, 0 °) ², promptly the response of Stoneley ripple is approximately 0%.

Table 4

Table 5

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	B01	0	114
B02	11	115	B01	0	114
B02	11	115	B03	24	120
B04	37	132	B03	24	120
B04	37	132	B05	42	137
B06	48	137	B05	42	137
B06	48	137	B07	52	135
B08	55	129	B07	52	135
B08	55	129	B09	46	99
B10	40	93	B09	46	99
B10	40	93	B11	0	94
B12	0	114	B11	0	94

Table 6

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	C01	0	112
C02	11	112	C01	0	112
C02	11	112	C03	36	116
C04	40	110	C03	36	116
C04	40	110	C05	36	103
C06	20	99	C05	36	103
C06	20	99	C07	0	98
C08	0	112	C07	0	98

Shown in Figure 77, by the some F01 shown in the following table 9 in the F06 area surrounded, the electromechanical coefficient k of SH type acoustic boundary wave ²Bigger, for example be 2% or bigger; By the some E01 shown in the following table 8 in the E07 area surrounded, preferably, with electromechanical coefficient k ²Increase to 5% or bigger; And by the some D01 shown in the following table 7 in the D07 area surrounded, more preferably, with electromechanical coefficient k ²Increase to 10% or bigger, and locate to become maximum in Eulerian angles (0 °, 97 °, 0 °).

Table 7

Table 8

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	E01	0	133
E02	16	129	E01	0	133
E02	16	129	E03	27	120
E04	37	98	E03	27	120
E04	37	98	E05	38	80
E06	0	80	E05	38	80
E06	0	80	E07		0

Table 9

The point	ψ(°)	θ(°)
The point	ψ(°)	θ(°)	F01	20	140
F02	34	125	F01	20	140
F02	34	125	F03	44	106
F04	55	80	F03	44	106
F04	55	80	F05	0	80
F06	20	140	F05	0	80

In addition, under the condition shown in the table 9, can confirm, even when Ag, Cu, Al, Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, ZnO or ITO are replaced Au as electrode material, also can access aforesaid excellent specific property at table 4.

In addition, Figure 77 and 78 and table 4 to 9 in, can confirm that when utilization-ψ replaces ψ, or when utilizing θ+180 ° to replace θ, for example, only the positive sign of backward power angle of flow or negative sign also can access aforesaid excellent specific property.

[example 5]

By will be respectively formed at by the electrode that the Au with thickness 0.06 λ makes have Eulerian angles (φ, 105 °, 0 °) and (0 °, 105 °, LiNbO ψ) ₃On the substrate, form SiO then ₂Film so that cover the Au electrode, has formed boundary acoustic wave device.In these cases, measure LiNbO ₃The velocity of sound V of the Eulerian angles φ of substrate and ψ and SH type acoustic boundary wave and Stoneley ripple, electromechanical coefficient k ², propagation loss α and frequency-temperature coefficient TCF relation.Figure 79 to 82 shows the LiNbO that has Eulerian angles (φ, 105 °, 0 °) when using ₃The result who obtains during substrate, Figure 83 to 86 show when using and have Eulerian angles (0 °, 105 °, LiNbO ψ) ₃The result who obtains during substrate.By θ=0 ° in the whole zone of 90 ° of expressions, propagation loss α is 0dB/ λ.

Shown in Figure 79 to 82, by φ=0 ° in the zone of 31 ° of expressions, the electromechanical coefficient k of Stoneley ripple ²Less, for example 1.5% or littler; By φ=0 ° in the zone of 26 ° of expressions, the k of Stoneley ripple ²Further be reduced to 1.0% or littler; And by φ=0 ° in the zone of 19 ° of expressions, the k of Stoneley ripple ²Be reduced to 0.5% or littler.In addition, be appreciated that when set up φ=0 ° the electromechanical coefficient k of Stoneley ripple ²Become and be approximately 0%, therefore, reduced the signal imitation that causes by the Stoneley ripple.In addition, by φ=0 ° in the zone of 90 ° of expressions, preferably, the TCF of SH acoustic boundary wave is in-37 to-35ppm/ ℃ the scope.

In addition, can confirm, be under two kinds of situations of (φ, 105 °, 0 °) and (φ, 105 °, 0 °) in Eulerian angles, obtained mutually the same result.

In addition, shown in Figure 83 to 86, by ψ=0 ° in the zone of 53 ° of expressions, the electromechanical coefficient k of Stoneley ripple ²Less, for example 1.5% or littler; By ψ=0 ° in the zone of 47 ° of expressions, the k of Stoneley ripple ²Further be reduced to 1.0% or littler; And by ψ=0 ° in the zone of 38 ° of expressions, the k of Stoneley ripple ²Be reduced to 0.5% or littler.When set up ψ=0 °, the electromechanical coefficient k of Stoneley ripple ²Become and be approximately 0%, therefore, be appreciated that to have reduced the signal imitation that causes by the Stoneley ripple.In addition, ° in 90 ° zone, can access the TCF of excellent SH acoustic boundary wave in ψ=0 with-37 to-35ppm/ ℃.

In addition, can confirm, when Eulerian angles be (0 °, 105 °, ψ) and (0 °, 105 ° ,-ψ) time, for example, only the positive sign of backward power angle of flow or negative sign can access the characteristic that is equal to each other.

[example 6]

Under the condition shown in the following table 10, form SH type acoustic boundary wave resonator.Figure 70 shows the schematic plan view of electrode structure of the SH type acoustic boundary wave resonator of present embodiment.In this structure,, be provided with

reflector

22 and 23 in the both sides of IDT21.Figure 71 shows when using and has Eulerian angles the LiNbO of (0 °, 90 °, 0 °) ₃The time impedance operator that obtains.Impedance ratio (ratio between the minimum and maximum absolute value of the impedance of resonator) is 56.8dB, and poor (numerical value that obtains divided by resonance frequency by the absolute value with the difference between resonance frequency and the anti-resonance frequency) between resonance frequency and the antiresonance frequently is 6.9%.

Figure 72 shows when using and has Eulerian angles the LiNbO of (0 °, 105 °, 0 °) ₃The time impedance operator that obtains.Impedance ratio is 59.4dB, and the difference between resonance frequency and the antiresonance frequently is 6.8%, and TCF is 31ppm/ ℃.

The LiNbO that has following Eulerian angles when use ₃The time: be in Eulerian angles in the scope of the electromechanical coefficient that has increased SH type acoustic boundary wave, be in Eulerian angles in the scope of the electromechanical coefficient that has reduced the Stoneley ripple, be in Eulerian angles in the scope of the frequency-temperature coefficient that has increased SH type acoustic boundary wave, be in the Eulerian angles in the scope that has reduced Stoneley wave frequency temperature coefficient and be in Eulerian angles in the scope of the power circuit current flow angle that has reduced SH type acoustic boundary wave, can form and wherein not produce the SH type acoustic boundary wave resonator Stoneley ripple, that have excellent resonance characteristic.

Figure 73 shows location components U1, the U2 of this SH type acoustic boundary wave and the calculated value of U3.As shown in the figure, displacement concentrates on around the Au as the boundary layer, distributes described displacement, infiltrates SiO simultaneously ₂And LiNbO ₃Therefore, when electrode as mentioned above hour, the SH acoustic boundary wave is subjected to each SiO with high velocity of sound ₂And LiNbO ₃Influence, the result can not reduce the velocity of sound of SH type acoustic boundary wave, makes it be lower than SiO ₂The velocity of sound of shear wave at a slow speed.On the other hand, when thickness of electrode increases according to the condition of formula (5) expression, can reduce the velocity of sound of SH type acoustic boundary wave, make it be lower than SiO ₂The velocity of sound of shear wave at a slow speed.

Table 10

Project	Details
Project	Details	Structure	SiO ₂/Au/LiNbO ₃
SiO ₂Thickness	3λ	Structure	SiO ₂/Au/LiNbO ₃
SiO ₂Thickness	3λ	Au thickness	0.055λ
IDT, reflector periods λ	2.2μm	Au thickness	0.055λ
IDT, reflector periods λ	2.2μm	The IDT configuration	The single band of plain edition, 50 pairs, opening length 31 λ, cross-sectional width 30 λ
Reflector arrangement	The single band of plain edition, 51, opening length 31 λ	The IDT configuration

[example 7]

When poor between the resonance frequency of the bandwidth that can regulate longitudinal coupling resonator filter or ladder-type filter arbitrarily and resonator and the anti-resonance frequency, can expect the application's market development.Direct and the electromechanical coefficient k of difference between the bandwidth of longitudinal coupling resonator filter or ladder-type filter and the resonance frequency of resonator and the anti-resonance frequency ²Proportional.Shown in the curve of Figure 66, (90 °, 90 °, 0 °) to (90 °, 90 °, 60 °) and (90 °, 90 °, 143 °) to (90 °, 90 °, 180 °) the interior Eulerian angles place of scope, be appreciated that electromechanical coefficient k as the SH type acoustic boundary wave of main response ²Be 0.8% to 17.8%, and as the electromechanical coefficient k of the Stoneley ripple of signal imitation ²Less, for example 2%.Therefore, in order to adjust the electromechanical coefficient k of SH type acoustic boundary wave ², formed a kind of SH type acoustic boundary wave resonator with the structure shown in the following table 11.Figure 74 shows when in 0 ° to 35 ° scope, use and have Eulerian angles (90 °, 90 °, LiNbO ψ) ₃The time impedance operator that obtains curve chart.Shown in Figure 66 and since when ψ when 0 ° changes to 35 °, electromechanical coefficient k ²Change to 5.3% from 17.6%, reduced poor between the resonance of resonator and the anti-resonance frequency.Figure 75 show Eulerian angles (90 °, 90 °, the curve chart of the difference between ψ ψ) and resonance frequency and the anti-resonance frequency and the relation of impedance ratio.Be appreciated that along with k shown in Figure 66 ²Variation, when ψ when 0 ° changes to 60 °, the difference between resonance and the anti-resonance frequency reduces.In addition, can confirm, when ψ is in 0 ° to 50 ° the scope, can access excellent resonance characteristic with 30dB or bigger impedance ratio.When forming ladder-type filter or 2IDT or 3IDT longitudinal coupling resonator type filter under the same terms as mentioned above, as everyone knows, the bandwidth of filter is two times of difference between resonance and the anti-resonance frequency.Therefore, can form various devices from broadband resonator and filter to arrowband resonator and filter.

Table 11

When the thickness of electrode hour, compare with SH type acoustic boundary wave, the Stoneley ripple is slower; Yet when increasing thickness of electrode, SH type acoustic boundary wave becomes with the Stoneley phase of wave fuller.Reason is to be sure of and Stoneley phase of wave ratio that at the place, boundary layer with slow velocity of sound, the energy concentration of SH type acoustic boundary wave is apparent in view.

Depend on LiNbO ₃The Eulerian angles of substrate change the become thickness of the electrode that is higher or lower than SH type acoustic boundary wave of velocity of sound at its Stoneley of place ripple; Yet, at the thickness of electrode place of 0.01 λ in the 0.03 λ scope, above-mentioned relationship change between it has appearred.In example 2,4 and 5, the reason that produces the signal imitation that is caused by the Stonley ripple in the frequency side of the response that is higher than SH type acoustic boundary wave is exactly this phenomenon.

As mentioned above, in the time will being arranged on the frequency side that is higher than as the response of the SH type acoustic boundary wave of main response as the response of the Stoneley ripple of signal imitation, the velocity of sound of Stoneley ripple becomes and is higher than the velocity of sound of SH type acoustic boundary wave.In this case, when the velocity of sound that reduces SH type acoustic boundary wave, when making the velocity of sound of its shear wave at a slow speed that is lower than the two media that forms the border, and the velocity of sound that increases the Stoneley ripple, make its shear wave at a slow speed that is higher than the two media that forms the border the velocity of sound at least one of them the time, increase Stoneley wave propagation loss, therefore, can suppress signal imitation.When utilizing IDT to form boundary acoustic wave device, response frequency by doubling acoustic boundary wave and the band cycle λ I of IDT can access the velocity of sound of the acoustic boundary wave of propagating in the IDT part.

In addition, except Au, Ag, Cu or Al, for example, can utilize the conducting film that constitutes by Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, ZnO or ITO to form electrode.In addition, in order to improve bonding and the electrical power impedance, at least one the second electrode lay of being made by the different metal material of for example Ti, Cr or NiCr alloy can be laminated on the electrode layer of being made by Au, Ag, Cu, Al or its alloy.In this case, the second electrode lay can be arranged between first electrode layer and the piezoelectric substance, or between first electrode layer and the dielectric material, perhaps, the second electrode lay can be arranged on above-mentioned two positions.

In addition, in boundary acoustic wave device of the present invention, in order to improve the intensity of boundary acoustic wave device, or prevent to enter etchant gas, can form protective layer in the laminate outside that constitutes by dielectric material, electrode and piezoelectric substance along laminating direction.Under certain conditions, can be in the enclosure with boundary acoustic wave device encapsulation of the present invention.

Above-mentioned protective layer can be formed by following material: for example the insulating material of titanium oxide, aluminium nitride or aluminium oxide forms; The metal film of Au, Al or W for example; Or the resin of polyurethane, epoxy resin or silicones for example.

In addition, in the present invention, above-mentioned piezoelectric substance can be formed in the piezoelectric film on the dielectric material.

In the present invention, in the time of around the energy with acoustic boundary wave is limited to as the electrode on border, need not to be unlimited, enough get final product greatly with the model different dielectric material that is used as the calculating basis and the thickness of piezoelectric substance.That is, for example, thickness can be 1 λ or bigger.

[example 8]

In addition; for example; when the outside in the acoustic boundary wave structure that is made of dielectric material, electrode and piezoelectric substance forms above-mentioned protective layer; so that when forming the structure that constitutes by protective layer, dielectric material, electrode, piezoelectric substance and protective layer; and when infiltrating the protective layer part slightly, can reduce the thickness of dielectric material and piezoelectric substance when also allowing to vibrate.For example, has epoxy resin/SiO by utilization ₂/ Au-IDT/LiNbO ₃In the SH type acoustic boundary wave resonator of the structure ladder-type filter 24 that form, that have the circuit structure shown in Figure 76, work as SiO ₂Thickness when being 1 λ, the insertion of propagation characteristic loss is 1.5dB, and when thickness was 0.71 λ, loss was 1.8dB; Therefore, can confirm, although along with SiO ₂The reducing of thickness, loss worsens, but loss is still in practice in the acceptable scope.In boundary acoustic wave device of the present invention owing to utilize heavy metal to form IDT, as mentioned above, with the concentration of energy of SH acoustic boundary wave and be distributed in around the Au-IDT as the boundary layer, from having the SiO of less acoustic damping ₂The quantity of energy that penetrates into the epoxy resin with big acoustic damping is less.Therefore, even when reducing SiO ₂Thickness the time, the deterioration of loss is also less.

In this case, the thickness of epoxy resin is 3 λ, and the thickness of Au is 0.054 λ, and the thickness of LN is 146 λ, and LiNbO ₃Eulerian angles be (0 °, 105 °, 0 °) in addition, be used for the SH type acoustic boundary wave resonator of ladder-type filter, IDT has opening length 30 λ and has 50 pairs of bands of the single ribbon structure of plain edition, and reflector has 50 single slice result of plain edition, as the distance between the center of adjacent ribbons, distance between IDT and the reflector is 0.5 λ, and the cycle of IDT be 2.4 μ m, equal the cycle of reflector.

In addition, in the present invention, electrode can comprise the plate electrode film that forms waveguide or bus (bus bar), the IDT of excitation acoustic boundary wave or the reflector of comb-type electrode and reflecting boundary sound wave.

In addition, in this manual, Eulerian angles as the direction of propagation of the cutting surface of expression substrate and acoustic boundary wave, used and (edited by Acoustic Wave Device Technology 150th Committee of the JapanSociety for the Promotion of Science at " Acoustic Wave Device Technology Handbook ", November 30 calendar year 2001 the first impression/front page, 549 pages) in disclosed right hand Eulerian angles system.That is, crystallographic axis X, Y and Z with respect to LN rotate φ by X-axis in the counterclockwise direction with respect to the Z axle, obtain the Xa axle.Next, rotate θ in the counterclockwise direction with respect to the Xa axle, obtain Z ' axle by the Z axle.To comprise the Xa axle and have Z ' axle is made as substrate as the plane of normal cutting planes.Subsequently, will be made as the direction of propagation of acoustic boundary wave by the direction that the Xa axle rotates the X ' axle that ψ obtains in the counterclockwise direction with respect to Z '.

In addition, for the LiNbO of the initial value that is expressed as Eulerian angles ₃Crystallographic axis X, Y and Z, the Z axle is set, make it be parallel to the c axle, X-axis is set, make it be parallel to three any one that are equal in a axle, and Y-axis be set along three different directions, make it be parallel to the normal on the plane that comprises X-axis and Z axle.

Except LiNbO of the present invention ₃Eulerian angles (φ, θ ψ) in addition, can also use the Eulerian angles that are equal to from the angle of crystallization.For example, according to technical literature 7 (Journal of the AcousticalSociety of Japan, Vol.36, No.3,1980, the 140 to 145 pages), because LiNbO ₃Be the trigonal crystal of a kind of 3m of belonging to some family, following formula (A) is set up.

F(φ，θ，ψ)＝F(60°-φ，-9，ψ)

＝F(60°+φ，-θ，180°-ψ)

＝F(φ，180°+θ，180°-ψ)

=F (φ, θ, 180 °+ψ) ... formula (A)

In above-mentioned formula, F is any acoustic boundary wave characteristic, for example electromechanical coefficient k ², propagation loss, TCF, PFA or intrinsic unidirectional characteristic.For PFA and intrinsic unidirectional characteristic, for example, when the backpropagation direction, although changed the positive sign or the negative sign of direction indication, the absolute value of characteristic does not change, and therefore, can be interpreted as it and be equal in fact each other.In addition, although technical literature 7 relates to surface acoustic wave, even when acoustic boundary wave is discussed, as disclosed in the technical literature 7, symmetry of crystals is also set up according to identical mode.For example, Eulerian angles (30 °, θ, the propagation characteristic of the acoustic boundary wave of ψ) locating be equal to Eulerian angles (90 °, 180 °-θ, 180 °-ψ) locate.In addition, the propagation characteristic of the acoustic boundary wave of locating in Eulerian angles (30 °, 90 °, 45 °) is equal to the propagation characteristic at the Eulerian angles place shown in the following table 12.

In addition, the material constant that is used to the electrode that calculates in the present invention is the numerical value of polycrystalline material; Yet, even in the crystalline solid of for example epitaxial film, owing to compare with film self, the grain arrangement that depends on substrate mainly influences the acoustic boundary wave characteristic, under the situation that is equal to Eulerian angles, can access the propagation characteristic that is equal to that can not cause any practical problem by formula (A) expression.

Claims

1. a boundary acoustic wave device comprises: piezoelectric substance; Be laminated to a lip-deep dielectric material of piezoelectric substance; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material, described boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border,

Wherein, in above-mentioned boundary acoustic wave device, the thickness of electrode is to determine like this, makes to compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, and the velocity of sound of SH type acoustic boundary wave is lower.

2. a boundary acoustic wave device comprises: piezoelectric substance; Be laminated to a lip-deep dielectric material of piezoelectric substance; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material, described boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border,

Wherein, form electrode band have a duty ratio of determining like this, make and compare that the velocity of sound of SH type acoustic boundary wave is lower with shear wave of in dielectric material, propagating at a slow speed and the shear wave at a slow speed in piezoelectric substance, propagated.

3. a boundary acoustic wave device comprises: mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance; And

Be arranged on the electrode of the boundary between piezoelectric substance and the dielectric material, described boundary acoustic wave device has used the SH type acoustic boundary wave of propagating along the border,

Wherein, mainly by LiMbO ₃The piezoelectric substance Eulerian angles that constitute (φ, θ, φ ψ) in-31 ° to+31 ° scope, wherein θ and ψ be in following by the some A01 in the table 1 in the A13 area surrounded,

Table 1 The point ψ(°) θ(°) A01 0 116 A02 11 118 A03 20 123 A04 25 127 A05 33 140 A06 60 140 A07 65 132 A08 54 112 A09 48 90 A10 43 87 A11 24 90 A12 0 91 A13 0 116

4. boundary acoustic wave device according to claim 3 is characterized in that, the θ of Eulerian angles and ψ are in by the some D01 in the following table 2 in the D07 area surrounded,

Table 2 The point ψ(°) θ(°) D01 0 126 D02 13 123 D03 25 112 D04 30 96 D05 29 80 D06 0 80 D07 0 126

5. according to claim 3 or 4 described boundary acoustic wave devices, it is characterized in that, the thickness of electrode is to determine like this, makes to compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, and the velocity of sound of SH type acoustic boundary wave is lower.

6. according to claim 3 or 4 described boundary acoustic wave devices, it is characterized in that, the band that forms electrode has the duty ratio of determining like this, makes to compare with shear wave of propagating in dielectric material at a slow speed and the shear wave at a slow speed propagated in piezoelectric substance, and the velocity of sound of SH type acoustic boundary wave is lower.

7. a boundary acoustic wave device comprises: mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance, described dielectric material is mainly by SiO ₂Constitute; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material,

Wherein, when respectively the density of electrode, the thickness of electrode and the wavelength table of acoustic boundary wave being shown ρ (kg/m ³), when H (λ) and λ, H＞8,261.744 ρ ^-1.376Set up, the Eulerian angles of piezoelectric substance be in (0 °, 90 °, 0 °) to (0 °, 90 °, 38 °), (0 °, 90 °, 142 °) to (0 °, 90 °, 180 °), (90 °, 90 °, 0 °) to (90 °, 90 °, 36 °), (90 °, 90 °, 140 °) to (90 °, 90 °, 180 °), (0 °, 55 °, 0 °) to (0 °, 134 °, 0 °), (90 °, 51 °, 0 °) to (90 °, 129 °, 0 °) or the scope of (0 °, 90 °, 0 °) to (180 °, 90 °, 0 °) in.

8. boundary acoustic wave device according to claim 7 is characterized in that, the Eulerian angles of piezoelectric substance are equal to the Eulerian angles by following formula (A) expression, has obtained being equal in fact the acoustic boundary wave characteristic of piezoelectric substance at described Eulerian angles place.

F(φ，θ，ψ)＝F(60°-φ，-θ，ψ)

＝F(60°+φ，-θ，180°-ψ)

＝F(φ，180°+θ，180°-ψ)

=F (φ, θ, 180 °+ψ) ... formula (A)

9. a boundary acoustic wave device comprises: mainly by LiNbO ₃The piezoelectric substance that constitutes; Be laminated to a lip-deep dielectric material of piezoelectric substance, described dielectric material is mainly by SiO ₂Constitute; And the electrode that is arranged on the boundary between piezoelectric substance and the dielectric material, described boundary acoustic wave device uses the SH type acoustic boundary wave of propagating along the border,

Wherein, when respectively the density of electrode, the thickness of electrode and the wavelength table of acoustic boundary wave being shown ρ (kg/m ³), when H (λ) and λ, H＞8,261.744 ρ ^-1.376Set up.

10. according to any described boundary acoustic wave device among the claim 3 to 9, it is characterized in that the density p of electrode is greater than 3.745kg/m ³

11., it is characterized in that the thickness H of electrode satisfies following formula (1) according to any described boundary acoustic wave device among the claim 3 to 9.

33,000.39050 ρ ^-1.50232＜H＜88,818.90913 ρ ^-1.54998... formula (1)

12. boundary acoustic wave device, comprise the acoustic boundary wave transmission structure that wherein SH type acoustic boundary wave and Stoneley ripple are propagated, wherein compare with the shear wave at a slow speed of the two media that forms the border, the velocity of sound of SH type acoustic boundary wave is lower, and with the shear wave at a slow speed of the two media that forms the border at least a comparing, the velocity of sound of Stoneley ripple is higher.

13. according to any described boundary acoustic wave device among the claim 1 to 12, it is characterized in that, each electrode mainly comprises the electrode layer that at least a material selected constitutes from the group that comprises following material: Au, Ag, Au, Al, Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, ZnO, ITO, and mainly comprise above-mentioned electric conducting material alloy one of at least.

14. boundary acoustic wave device according to claim 13 is characterized in that, except electrode layer, each electrode also comprises at least one the second electrode lay, and described the second electrode lay comprises the electric conducting material except that the electric conducting material that forms electrode layer.