Method for manufacturing an acoustic wave device

Abstract

It has good TCF and can increase the Q and impedance ratio of the resonator. Provide a vice. The present invention relates to a substrate (11) containing 70 mass % or more of silicon dioxide (SiO2), and a substrate (11) on the substrate (11). a piezoelectric thin film 12 made of LiTaO3 crystal or LiNbO3 crystal provided on the piezoelectric thin film; The membrane 12 is provided with an interdigital electrode 13 in contact therewith.

Description

[Technical Field]

[0001] The present invention relates to acoustic wave devices. [Background technology]

[0002] In recent years, with the spread of mobile phones and smartphones, nearly 50 bands have been shifted to 2.4GHz. The bands are concentrated below the centerline, and the spacing between adjacent bands is very narrow, so there is no interference with the adjacent bands. Therefore, there is a strong demand for filters and duplexers with steep frequency characteristics and good temperature characteristics. In addition, in order to realize a filter or diplexer with a steep frequency characteristic, Therefore, a resonator with a large impedance ratio and a high Q is required. Here, Q is the filter In addition to the steepness, the insertion loss of the filter also has an effect. High Q also reduces insertion loss, reducing battery consumption in mobile phones and smartphones. Therefore, filters are required to have good insertion loss, good temperature characteristics, and better steepness. The resonator is required to have a high Q and a large impedance ratio. The value of is proportional to the impedance ratio and inversely proportional to the bandwidth. The impedance ratios are proportional.

[0003] Surface acoustic wave (SAW) filters are designed to operate at frequencies that are within the range of the electromechanical coupling coefficient (coupling) of the piezoelectric substrate used. Therefore, conventionally, the LT (L Piezoelectric substrates made of iTaO3 crystal or LN (LiNbO3 crystal) are widely used. However, the temperature coefficient of frequency (TCF) of these boards ranges from -40 ppm / °C to -120 ppm / °C. pm / ℃, which is not very good. The theoretical formula for temperature coefficient of frequency (TCF) is , which is defined by the following formula:

[0004]

number

[0005] Therefore, in order to obtain the required coupling coefficient and good TCF, a negative TCF is used. By combining LT, LN substrate and SiO2 thin film with positive TCF, SiO2 thin film / high The structure is a high density electrode / LT or LN substrate, and the protrusions on the SiO2 film caused by the electrode are The present inventors have developed a surface acoustic wave filter with a planarized surface by removing the surface (e.g., For example, see Non-Patent Document 1. This structure achieves a relatively good TCF of -10 ppm / °C. Moreover, the same impedance ratio and Q as the characteristics of the LT or LN substrate alone can be obtained. The impedance ratio of this resonator is 60 dB and the Q is about 800.

[0006] Although the quartz substrate has good frequency temperature characteristics, the coupling coefficient that indicates piezoelectricity is small. It is not possible to meet the filter bandwidth required for smartphones and mobile phones. In addition, the bulk wave filter using AlN (aluminum nitride) thin film has a resonator Q of 2. 000, and the filter characteristics are steeper than those of a SAW filter, but the frequency temperature characteristics is -30 ppm / ℃, which is not very good. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] M. Kadota, T. Nakao, K. Nishiyama, N. Taniguchi, and T. Fuyuzume, "A compact surface acoustic wave duplexer with good temperature characteristics," IEICE Transactions on Electrical, Information and Communication Engineers, Vol. J96-A, No. 6, pp. 301-308, 2013. Summary of the Invention [Problem to be solved by the invention]

[0008] The acoustic wave filter described in Non-Patent Document 1 provides a relatively good TCF, but the SiO 2 Because the thin film is a columnar polycrystalline film, the Q and impedance ratio of the resonator are The characteristics are about the same as those of the N substrate alone, and the steepness of the frequency characteristics is still insufficient. There was a problem.

[0009] The present invention has been made in response to these problems, and has been developed to provide a resonator with excellent TCF and low Q. An object of the present invention is to provide an acoustic wave device that can increase the impedance ratio. [Means for solving the problem]

[0010] In order to achieve the above object, an acoustic wave device according to the present invention provides an acoustic wave device that utilizes surface acoustic waves. A dielectric wave device comprising a substrate containing 70 mass % or more of silicon dioxide (SiO2), and a a piezoelectric thin film made of LiTaO3 crystal or LiNbO3 crystal provided on a plate; and an interdigital electrode provided in contact with the thin film. Thin conductive films also include piezoelectric thin plates.

[0011] In the acoustic wave device according to the present invention, the substrate has a shear wave velocity of bulk waves that is equal to the shear wave velocity of LT or LN. The speed of these substrates is preferably between 3,400 m / s and 4,800 m / s, which is close to the speed of the substrate. Most of them are isotropic substrates, meaning there is no anisotropy in the X, Y, or Z directions, but quartz, which is a piezoelectric single crystal, The substrate has anisotropy and therefore has different properties. Therefore, when using a quartz substrate, The quartz crystal substrate has a surface acoustic wave whose sound velocity is equal to that of the surface acoustic wave propagating through the piezoelectric thin film. It is more preferable that the sound velocity is faster than that of the surface wave. Preferably, the velocity is 300 m / s or more, and more preferably 600 m / s or more. In the acoustic wave device according to the invention, the surface acoustic wave is a leaky surface acoustic wave (LSAW). Furthermore, it is preferable that the SH (shear horizontal) component is 50% or more, more preferably 65% ​​or more. % or more. It may be an S wave of 500 m / s or more. It should be noted that the surface acoustic wave used may be a leaky surface acoustic wave. The angle can be theoretically determined from the Euler angles of the substrate.

[0012] Substrates containing 70% or more by mass of silicon dioxide (SiO2) are Therefore, in the acoustic wave device according to the present invention, a negative TCF is obtained. Piezoelectric material consisting of LiTaO3 crystal (LT) or LiNbO3 crystal (LN) with TCF By depositing the thin film on a substrate with a positive TCF, good results close to zero ppm / °C can be achieved. Furthermore, a piezoelectric thin film made of LT or LN can be used as a leaky elastic surface. The Euler angle is set to the wave (LSAW) excitation angle, and the substrate is set to the sound velocity of LSAW of LT or LN. By using Euler angles with a sound velocity that is equal to or faster than that of the piezoelectric thin film, the leakage Therefore, it is possible to use the LSAW mode without leakage components. It is possible to obtain an impedance ratio that is, for example, 15 to 20 dB larger than the characteristics of the body. Also, this impedance ratio corresponds to a 6 to 10 times Q ratio for the same bandwidth. It is possible to obtain very good steepness and insertion loss characteristics. Also, the coupling coefficient is only However, it can be larger than the piezoelectric film itself.

[0013] The acoustic wave device according to the present invention has a grounded short-circuit current between the substrate and the piezoelectric thin film. In this case, for example, an interdigital electrode may be used. / Piezoelectric thin film / Substrate, interdigital electrode / Piezoelectric thin film / Bonding film / Substrate, interdigital electrode / Piezoelectric thin film / Short-circuit electrode / substrate, interdigital electrode / piezoelectric thin film / short-circuit electrode / bonding film / substrate, or interdigital The structure is electrode / piezoelectric thin film / bonding film / short-circuit electrode / substrate. Even with the composite film, the excellent properties are not lost, and the good TCF and high Q and In particular, when there is a short-circuit electrode, the coupling coefficient This can increase the propagation loss of leaky surface acoustic waves. It is preferable that the material is not sound absorbing and is made of a hard material, such as a Si film or SiO2 film. It may consist of:

[0014] In the acoustic wave device according to the present invention, the interdigital transducer has at least one interdigital transducer disposed on the piezoelectric thin film. The lower part is embedded in the piezoelectric thin film and / or at least the upper part is The film may be provided so as to protrude from the film. In this case, either structure provides excellent It has the characteristics of high impedance ratio. When the lower part is embedded in the piezoelectric thin film, the speed of sound increases, which is advantageous for increasing the frequency. In this case, the piezoelectric thin film and the substrate may be electrically short-circuited.

[0015] In the acoustic wave device according to the present invention, the substrate is made of 80 mass % silicon dioxide (SiO2). It is preferable that the content is 99% by mass or more and less than 100% by mass, and more preferable that the content is 99% by mass or more and less than 100% by mass. Preferably, fused quartz containing 100% by mass is more preferable, and further preferably, a quartz substrate which is a piezoelectric single crystal is used. It is more preferable that the substrate is made of a material having a sound velocity of the surface acoustic wave propagating therethrough of 3, The velocity may be 400 to 4,800 m / s. The substrate may be an isotropic substrate other than quartz. The piezoelectric thin film may be a plate, and the thickness may be 0.001 mm or more and less than 0.01 mm. The substrate is made of a quartz crystal substrate, and the acoustic velocity of the propagating surface acoustic wave is 4,500 m / s or more, or 4,800 m / s or more, or 5,000 m / s or more In any of these configurations, the film has excellent properties, good TCF, and high The Q and impedance ratio can be obtained. In the case of a quartz substrate, the substrate is isotropic. Since it has a larger positive TCF, the thickness of the piezoelectric thin film is not important.

[0016] In isotropic substrates other than quartz, there is no dependence on the propagation direction of the elastic wave. Since the crystal has anisotropy, its characteristics change depending on the azimuth angle and propagation direction (Euler angle) of the quartz substrate used. The acoustic wave device according to the present invention is first It is desirable to select Euler angles where the power flow angle (PFA) is approximately zero. When the Euler angles deviate significantly from zero, the acoustic waves propagate in a direction oblique to the interdigital transducer. The Euler angles of the quartz substrate, where the PFA is approximately zero, are (0°±5°). °, 0°~180°, 40°±12°), (10°±5°, 0°~180°, 42°±8 °), (20°±5°, 0°~180°, 50°±8°), (0°±5°, 0°~180° , 0°±5°), (10°±5°, 0°~180°, 0°±5°), (20°±5°, 0 °~180°, 0°±5°), (0°±5°, 0°~180°, 90°±5°), (10° ±5°, 0°~180°, 90°±5°), (20°±5°, 0°~180°, 90°± 5°) and its equivalent azimuth angle.

[0017] In the acoustic wave device according to the present invention, the substrate has an Euler angle of (0°±5°, 0° ~125°, 0°±5°), (0°±5°, 0°~36°, 90°±5°), (0°±5 °, 172°~180°, 90°±5°), (0°±5°, 120°~140°, 30° ~49°), (0°±5°, 25°~105°, 0°±5°), (0°±5°, 0°~4 5°, 15°~35°), (0°±5°, 10°~20°, 60°~70°), (0°± 5°, 90°~180°, 30°~45°), (0°±5°, 0°±5°, 85°~95 °), (90°±5°, 90°±5°, 25°~31°), (0°±5°, 90°±5° The substrate may have an Euler angle of (20°±5°, 1 20°±10°, 115°±10°), (0°±5°, 90°±5°, 0°±10°), (0°±5°, 90°±5°, 75°±10°), (0°±5°, 0°±5°, 0°±1 0°), (0°±5°, 0°±5°, 60°±10°). In these cases, It shows good TCF.

[0018] In addition, to obtain higher Q and impedance ratio characteristics, the following sound velocity and Euler That is, in the acoustic wave device according to the present invention, the substrate is , the sound velocity of the propagating surface acoustic wave is 4,500 m / s or more, and the Euler angle is (0°± 5°, 70°~165°, 0°±5°) or (0°±5°, 95°~155°, 90 Preferably, the substrate has a thickness of 4.8 mm or less, and the thickness of the substrate is 4.8 mm or less. 0 m / s or more, and the Euler angles are (0°±5°, 90°~150°, 0°±5°). or (0°±5°, 103° to 140°, 90°±5°), and Furthermore, the acoustic velocity of the propagating surface acoustic wave is 5,000 m / s or more, and the Euler angle is ( 0°±5°, 100°~140°, 0°±5°) or (0°±5°, 110°~13 5°, 90°±5°).

[0019] In the acoustic wave device according to the present invention, the substrate is preferably a substrate having a TCF for Rayleigh waves or LSAWs. The positive Euler angles are (0°±5°, 0°~132°, 0°±5°), (0°±5° , 0°~18°, 0°±5°), (0°±5°, 42°~65°, 0°±5°), (0° ±5°, 126° to 180°, 0°±5°), and the piezoelectric thin film is a LiTaO3 crystal The Euler angles may be (0°±5°, 82° to 148°, 0°±5°). In this case, the substrate is rotated at Euler angles of (0°±5°, 0°~12°, 0°±5°), (0° ±5°, 44°~63°, 0°±5°), (0°±5°, 135°~180°, 0°±5 It is more preferable that the Euler angles of the piezoelectric thin film are (0°±5°, 90° 140° to 140°, 0±5°) is more preferable. This combination provides a particularly good TCF is obtained.

[0020] In the acoustic wave device according to the present invention, the substrate is preferably a substrate having a TCF for Rayleigh waves or LSAWs. The positive Euler angles are (0°±5°, 0°~42°, 90°±5°), (0°±5° , 170°~190°, 90°±5°), (0°±5°, 0°~45°, 90°±5°) , (0°±5°, 123° to 180°, 90°±5°), and the piezoelectric thin film is LiT It is made of aO3 crystals and has Euler angles of (0°±5°, 80°~148°, 0°±5°). In this case, the substrate may be rotated at an angle of (0°±5°, 0° to 34°, 90°±5°). °), (0°±5°, 126° to 180°, 90°±5°), more preferably. In addition, the piezoelectric thin film has Euler angles of (0°±5°, 90°~140°, 0°±5°). It is more preferable that the angle is (0°±5°, 95° to 143°, 0°±5°). is preferable, and (0°±5°, 103° to 125°, 0°±5°) is even more preferable. preferable.

[0021] In the acoustic wave device according to the present invention, the substrate is made of an Euler material having a high acoustic velocity LSAW. The angle is (1°~39°, 100°~150°, 0°~20° or 70°~120° or 160° to 180°), and the piezoelectric thin film is made of LiTaO3 crystal, and the Euler angle The angle may be (0°±5°, 80° to 148°, 0°±5°). Euler angles (20°±5°) with high sound velocity and fast shear of around 1,000 m / s , 120°±10°, 115°±10°), (0°±5°, 90°±5°, 0°±10° ), (0°±5°, 90°, 75°±10°), (0°±5°, 0°, 0°±10°), (0°±5°, 0°, 60°±10°) is also acceptable.

[0022] In the acoustic wave device according to the present invention, the substrate has an Euler angle of (0°±5°, 0° ~23°, 0°±5°), (0°±5°, 32°~69°, 0°±5°), (0°±5° , 118°~180°, 0°±5°), (0°±5°, 0°~62°, 90°±5°), (0°±5°, 118°~180°, 90°±5°), (0°±5°, 0°~72°, 3 0° to 60°), (0°±5°, 117° to 180°, 30° to 60°), The thin film is made of LiTaO3 crystal, and the Euler angles are (0°±5°, 80°~148°, In this case, the Euler angles of the substrate may be (0°±5°, 0° to 1 2°, 0°±5°), (0°±5°, 37°~66°, 0°±5°), (0°±5°, 1 32°~180°, 0°±5°), (0°±5°, 0°~50°, 90°±5°), (0 °±5°, 126°~180°, 90°±5°), (0°±5°, 0°~17°, 30° ~60°), (0°±5°, 35°~67°, 30°~60°), (0°±5°, 123 It is more preferable that the angle is between 100° and 180°, or between 30° and 60°).

[0023] In the acoustic wave device according to the present invention, the piezoelectric thin film is made of LiTaO3 crystal, Euler angles are (90°±5°, 90°±5°, 33°~55°), (90°±5°, 90 The piezoelectric thin film may be LiNbO3 It consists of crystals, and the Euler angles are (90°±5°, 90°±5°, 38°~65°), (90 90°±5°, 90°±5°, 118° to 140°).

[0024] In the acoustic wave device according to the present invention, the piezoelectric thin film is made of LiTaO3 crystal, The piezoelectric thin film may have a thickness of 0.001 to 2 times the wavelength of the elastic wave. The thickness of the elastic layer is preferably 0.01 to 0.6 times the wavelength of the elastic wave, and more preferably 0.02 to 0. It is more preferable that the ratio is 0.6, and further more preferable that the ratio is 0.03 to 0.4. Furthermore, it is more preferable that the ratio is 0.03 to 0.3 times.

[0025] In the acoustic wave device according to the present invention, the substrate is preferably a substrate having a TCF for Rayleigh waves or LSAWs. The positive Euler angles are (0°±5°, 0°~132°, 0°±5°), (0°±5° , 0°~18°, 0°±5°), (0°±5°, 42°~65°, 0°±5°), (0° ±5°, 126° to 180°, 0°±5°), and the piezoelectric thin film is a LiNbO3 crystal The Euler angles may be (0°±5°, 75°~165°, 0°±5°). More preferably, it may be (0°±5°, 100° to 160°, 0°±5°). In this case, the Euler angles of the board are (0°±5°, 0°~12°, 0°±5°), (0°±5° , 44°~63°, 0°±5°), (0°±5°, 135°~180°, 0°±5°) In this case, it is more preferable that the piezoelectric thin film has a wavelength of 0.5 μm. It is preferable that the thickness is 0.001 to 2 times, and 0.01 to 0.6 times. is more preferable, and 0.012 to 0.6 times is even more preferable, and 0.02 to 0. It is more preferably 5 times, and even more preferably 0.03 to 0.33 times.

[0026] In the acoustic wave device according to the present invention, the substrate is preferably a substrate having a TCF for Rayleigh waves or LSAWs. The positive Euler angles are (0°±5°, 0°~42°, 90°±5°)(0°±5°, 90°~155°, 90°±5°), (0°±5°, 0°~45°, 90°±5°), ( 0°±5°, 123° to 180°, 90°±5°), and the piezoelectric thin film is LiNbO It consists of three crystals, and the Euler angles are (0°±5°, 70°~170°, 0°±5°). In this case, the Euler angles of the substrate are (0°±5°, 0°~34°, 90°±5°), It is more preferable that the angle is (0°±°, 126° to 180°, 90°±5°). In this case, the piezoelectric thin film has a thickness of 0.001 to 2 times the wavelength of the surface acoustic wave. It is preferable that the thickness is 0.01 to 0.5 times, and it is preferable that the thickness is 0.02 times. It is more preferable that the ratio is 0.06 to 0.3 times, and further more preferable that the ratio is 0.06 to 0.3 times. I wish.

[0027] In the acoustic wave device according to the present invention, the substrate has an Euler angle of (1° to 39°, 1 0°~150°, 0°~20° or 70°~120° or 160°~180°) The piezoelectric thin film is made of LiNbO3 crystal, and the Euler angles are (0°±5°, 95° The substrate may have an Euler angle of (1° to 39°) , 70°~150°, 0°~20° or 70°~120° or 160°~180°) The piezoelectric thin film is made of LiNbO3 crystal, and the Euler angles are (0°±5°, 25°~ 51°, 0°±5°).

[0028] In the acoustic wave device according to the present invention, the substrate has an Euler angle of (0°±5°, 90 80°~178°, 0°±5°), (0°±5°, 80°~160°, 90°±5°) The piezoelectric thin film is made of LiNbO3 crystal, and the Euler angle that excites the Rayleigh wave is (0 °±5°, 35°~70°, 0°±5°), more preferably (0°±5°, 45°~63° 0°, 0°±5°), and more preferably (0°±5°, 48° to 60°, 0°±5°). In this case, the TCF of the substrate is positive for LSAW and Rayleigh waves. The Euler angles are (0°±5°, 90°~178°, 0°±5°), and (0°±5°, 125° to 160°, 90°±5°) is preferable.

[0029] In the acoustic wave device according to the present invention, the substrate has an Euler angle of (0°±5°, 0° ~16°, 0°±5°), (0°±5°, 42°~64°, 0°±5°), (0°±5° , 138°~180°, 0°±5°), (0°±5°, 0°~30°, 90°±5°), (0°±5°, 130°~180°, 90°±5°), (0°±5°, 0°~28°, 3 0°~60°), (0°±5°, 42°~70°, 30°~60°), (0°±5°, 1 32° to 180°, 30° to 60°), and the piezoelectric thin film is made of LiNbO3 crystal. The Euler angles are (0°±5°, 75° to 165°, 0°±5°), and more preferably (0 90° to 160°, 0°±5°). In this case, the Euler The angles are (0°±5°, 43°~61°, 0°±5°), (0°±5°, 147°~180 °, 0°±5°), (0°±5°, 0°~15°, 90°±5°), (0°±5°, 13 4°~180°, 90°±5°), (0°±5°, 0°~23°, 30°~60°), ( 0°±5°, 43°~67°, 30°~60°), (0°±5°, 137°~180°, It is more preferable that the angle is 30° to 60°.

[0030] In the acoustic wave device according to the present invention, the substrate may have an Euler angle of (0°±5°, 32°). °~118°, 0°±5°), (0°±5°, 0°~30°, 90°±5°), (0°± 5°, 173°~180°, 90°±5°), (0°±5°, 0°~142°, 30°~ 60°), and the piezoelectric thin film is made of LiNbO3 crystal, and the Euler angle is (0°±5 °, 35°~70°, 0°±5°), more preferably (0°±5°, 45°~63°, 0 In this case, the Euler angles of the substrate may be (0°±5°, 40° to 1 02°, 0°±5°), (0°±5°, 0°~17°, 90°±5°), (0°±5°, 175°~180°, 90°±5°), (0°±5°, 13°~130°, 30°~60 °) is more preferable.

[0031] In the acoustic wave device according to the present invention, the surface acoustic wave used may be in the fundamental mode. When a high-order mode is used, the piezoelectric thin film has a wavelength of the surface acoustic wave. It is preferable that the thickness of the substrate and the piezoelectric thin film is 0.35 to 9.3 times that of the piezoelectric thin film. When there is a short-circuit electrode between them, the thickness of the piezoelectric thin film is 0.5 to 9 times the wavelength of the surface acoustic wave. In these cases, a high impedance ratio can be obtained. .

[0032] Here, the Euler angles (φ, θ, ψ) are in the right-handed system and are determined by the cross section of the substrate and the piezoelectric thin film and the elastic This expresses the propagation direction of the surface wave. Or, rotate the X axis counterclockwise by φ with the Z axis as the rotation axis for the X, Y, and Z crystal axes of LN, Next, rotate the Z axis counterclockwise by θ using the X axis as the rotation axis to obtain the Z axis. In this case, the Z' axis is the normal line, and the plane including the X' axis is the cut surface of the substrate or the piezoelectric thin film. The direction of rotation of the Z' axis around the X' axis in a counterclockwise direction is called the propagation direction of the surface acoustic wave. The X' and Z' axes are obtained by moving the Y axis due to these rotations. The vertical axis is the Y' axis.

[0033] By defining the Euler angles in this way, for example, the propagation in the X direction on a 40° rotated Y plate is as follows: Expressed in Euler angles as (0°, 130°, 0°), the propagation in the X direction through a 40° rotated Y-plate at 90° is These are expressed in Euler angles as (0°, 130°, 90°).

[0034] In the acoustic wave device according to the present invention, the substrate and the piezoelectric thin film are In this case, it is also possible to use crystallographically equivalent Euler angles. Good TCF and higher Q and impedance ratio characteristics can be obtained In addition, when cutting out the substrate or piezoelectric thin film at the desired Euler angles, As a result, there is a possibility of an error of up to ±0.5°. Regarding the shape of the IDT, There is a possibility of an error of about ±3° in the propagation direction ψ. Regarding the characteristics of elastic waves, Of the Euler angles (φ, θ, ψ), for φ and ψ, there is a difference in characteristics due to a deviation of about ±5°. There are almost none. [Effects of the Invention]

[0035] According to the present invention, the TCF is excellent and the Q and impedance ratio of the resonator can be increased. It is possible to provide an acoustic wave device. [Brief explanation of the drawings]

[0036] Unless otherwise specified, the following is a diagram of an interdigital transducer consisting of aluminum electrodes with a thickness of 0.08 wavelengths. The electrode is described as Al-IDT. [Figure 1] 1A is a perspective view showing a conventional acoustic wave device made of an Al-IDT / piezoelectric substrate, FIG. 1B is an acoustic wave device according to an embodiment of the present invention, and FIG. 1C is a perspective view showing a modified example of the acoustic wave device according to the embodiment of the present invention, which has a bonding film. [Figure 2] This is a graph showing the frequency characteristics of impedance (Z) for a conventional acoustic wave resonator: (a) Al-IDT / (0°, 110°, 0°) LT substrate, and (b) Al-IDT / (0°, 132°, 0°) LT substrate. (In the figure, the frequencies where Z is minimum and maximum are the resonant frequency (fr), the anti-resonant frequency (fa), and the impedance is called Zr and Za, respectively. The bandwidth is expressed as (fa-fa) / fr, and the impedance ratio is expressed as 20×LOG(Za / Zr).) [Figure 3] 10 is a graph showing the impedance (Z) frequency characteristics of an elastic wave resonator having the following structure: (a) Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 130°, 90°) quartz substrate; and (b) Al-IDT / (0°, 120°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 130°, 0°) quartz substrate. [Figure 4]10 is a graph showing the impedance (Z) frequency characteristics of an elastic wave resonator having the following structures: (a) Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 130°, 30°) quartz substrate; and (b) Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 130°, 60°) quartz substrate. [Figure 5] 1 is a graph showing the propagation direction ψ dependence of the sound velocity (phase velocity) of Rayleigh waves and LSAWs in a (0°, 130°, ψ) quartz substrate. [Figure 6] 10 is a graph showing the impedance (Z) frequency characteristics of an acoustic wave resonator having a structure of (a) Al-IDT / (0°, 132°, 0°) LT thin film / (110) Si substrate, and (b) Al-IDT / (0°, 132°, 0°) LT thin film / c-sapphire substrate. [Figure 7] 10 is a graph showing the θ dependence of (a) the sound velocity (phase velocity) of Rayleigh waves and LSAW, (b) the TCF of Rayleigh waves and LSAW, and (c) the displacement ratio of the longitudinal wave displacement component U1, SH component U2, and shear vertical (SV) component U3 of LSAW on the substrate surface for a quartz substrate (0°, θ, 0°). [Figure 8] 10A and 10B are graphs showing the θ dependence of (a) the sound velocity (phase velocity) of Rayleigh waves and LSAW, (b) the TCF of Rayleigh waves and LSAW, and (c) the displacement ratio of the longitudinal wave displacement component U1, SH component U2, and SV component U3 of LSAW on the substrate surface for a quartz substrate (0°, θ, 90°). [Figure 9] 1 is a graph showing the ψ dependence of the sound velocity (phase velocity) at various φ and θ in a (φ, θ, ψ) quartz substrate (quartz). [Figure 10](a) The acoustic velocity (phase velocity) of Rayleigh waves and LSAW in an LT substrate (0°, θ, 0°) (in the figure, the solid line (vf) and dashed line (vm) are the acoustic velocity when the LT substrate surface is electrically open and short-circuited, respectively), (b) the electromechanical coupling factor of Rayleigh waves and LSAW, and (c) the TCF of LSAW are graphs showing the θ dependence of these. [Figure 11] 10 is a graph showing the θ dependence of (a) the bandwidth and (b) the impedance ratio of an elastic wave resonator having a structure of Al-IDT / (0°, θ, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 115° to 145°, 0°) quartz substrate (θ in each graph is the θ of the quartz substrate). [Figure 12] This graph shows the θ dependence of the impedance ratio for an acoustic wave resonator with a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, θ, 0°) quartz substrate when (a) the Al thickness is 0.08 wavelength and (b) the Al thickness is 0.2 wavelength (between the resonance and antiresonance frequencies, the solid line shows the characteristics without ripple, and the dashed line shows the characteristics with ripple). [Figure 13] 10 is a graph showing the dependence of (a) the bandwidth and (b) the impedance ratio on the LT film thickness for an elastic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 130°, 0°) quartz crystal substrate when the Al thickness is 0.08 wavelength and 0.2 wavelength. [Figure 14] 10 is a graph showing the θ dependence of (a) the bandwidth and (b) the impedance ratio of an elastic wave resonator having a structure of Al-IDT / (0°, θ, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 100° to 175°, 90°) quartz substrate (θ in each graph is the θ of the quartz substrate). [Figure 15]10 is a graph showing the θ dependence of the impedance ratio of an elastic wave resonator having an Al-IDT / (0°, 110°, 0°) LT thin film / (0°, θ, 90°) quartz substrate structure when (a) the LT thickness is 0.15 wavelengths and the Al thickness is 0.08 wavelengths, (b) the LT thickness is 0.15 wavelengths and the Al thickness is 0.1 wavelengths, and when the LT thickness is 1.25 wavelengths and 2 wavelengths and the Al thickness is 0.2 wavelengths (the solid line shows the characteristics without ripples between the resonance and antiresonance frequencies, and the dashed line shows the characteristics with ripples), and (c) the frequency characteristics of the impedance (Z) of the quartz substrate when θ = 125.25° in (b). [Figure 16] 10 is a graph showing the dependence of (a) the bandwidth and (b) the impedance ratio on the LT film thickness for an acoustic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film / (0°, 128°, 90°) quartz crystal substrate when the Al thickness is 0.08 wavelength and 0.2 wavelength. [Figure 17] 10A shows the frequency characteristics of impedance (Z) of an acoustic wave resonator having an Al-IDT / (0°, 110°, 0°) LT thin film (thickness: 0.15 wavelength) / (0°, 45°, 0°) quartz crystal substrate structure, and (b) shows the dependence of the impedance ratio on the LT film thickness when the Al thickness is 0.12 wavelength and 0.2 wavelength. [Figure 18] 10 is a graph showing the LT film thickness dependence of the impedance ratio of elastic wave resonators having a structure of Al-IDT / (0°, 110°, 0°) LT thin film / (20°, 120°, 115°) quartz crystal substrate and Al-IDT / (0°, 110°, 0°) LT thin film / (0°, 130°, 0°) quartz crystal substrate. [Figure 19]This graph shows the θquartz dependence of TCF for (a) (0°, θLT, 0°) LT thin film (thickness 0.15 wavelength) / (0°, θquartz, 0°) quartz substrate, (b) (0°, θLT, 0°) LT thin film (thickness 0.15 wavelength) / (0°, θquartz, 90°) quartz substrate, and (c) (0°, θLT, 0°) LT thin film (thickness 0.15 wavelength) / (0°, θquartz, 30° to 60°) quartz substrate, when θLT = 80°, 125°, and 148°. [Figure 20] (a) (0°, θ, 0°) Graphs showing the θ dependence of the sound velocity (phase velocity) of Rayleigh waves and LSAW when the surface of the LN substrate is electrically open (Vf) and short-circuited (Vm), (b) the electromechanical coupling coefficient (coupling factor) of Rayleigh waves and LSAW, and (c) the TCF of Rayleigh waves and LSAW. [Figure 21] 1 is a graph showing the frequency characteristics of impedance (Z) of an elastic wave resonator having a structure of Al-IDT / (0°, 131°, 0°) LN thin film (thickness 0.15 wavelength) / (0°, 115°, 90°) quartz substrate. [Figure 22] (a) Graph showing the θ dependence of the impedance ratio for LSAW and Rayleigh waves of an elastic wave resonator having a structure of Al-IDT / (0°, θ, 0°) LN thin film (thickness 0.15 wavelength) / (0°, 130°, 0°) quartz substrate. (b) Graph showing the impedance ratio for LSAW of an elastic wave resonator having a structure of Al-IDT / (0°, 131°, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θ, 0°) quartz substrate when the Al thickness is 0.08 wavelength and 0.2 wavelength, and the impedance ratio for Rayleigh waves of an elastic wave resonator having a structure of Al-IDT / (0°, 55°, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θ, 0°) quartz substrate when the Al thickness is 0.08 wavelength. This is a graph showing the θ dependence of the ratio (between the resonance and anti-resonance frequencies, the solid line shows the characteristics without ripples, and the dashed line shows the characteristics with ripples). [Figure 23]This is a graph showing the dependence of (a) the bandwidth and (b) the impedance ratio on the LN film thickness for an acoustic wave resonator having a structure of Al-IDT / (0°, 131°, 0°) LN thin film / (0°, 130°, 0°) quartz crystal substrate when the Al thickness is 0.08 wavelengths and 0.2 wavelengths. [Figure 24] (a) Graph showing the θ dependence of the impedance ratio to LSAW and Rayleigh waves of an elastic wave resonator having a structure of Al-IDT / (0°, θ, 0°) LN thin film (thickness 0.15 wavelength) / (0°, 130°, 90°) quartz substrate. (b) Graph showing the impedance ratio to LSAW of an elastic wave resonator having a structure of Al-IDT / (0°, 131°, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θ, 90°) quartz substrate when the Al thickness is 0.08 wavelength and 0.2 wavelength, and the impedance ratio to Rayleigh waves of an elastic wave resonator having a structure of Al-IDT / (0°, 38°, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θ, 90°) quartz substrate when the Al thickness is 0.08 wavelength. This is a graph showing the θ dependence of the ratio (between the resonance and anti-resonance frequencies, the solid line shows the characteristics without ripples, and the dashed line shows the characteristics with ripples). [Figure 25] 10 is a graph showing the dependence of (a) the bandwidth and (b) the impedance ratio on the LN film thickness for an acoustic wave resonator having a structure of Al-IDT / (0°, 131°, 0°) LN thin film / (0°, 115°, 90°) quartz crystal substrate when the Al thickness is 0.08 wavelengths and 0.2 wavelengths. [Figure 26] This graph shows the θquartz dependence of TCF for (a) (0°, θLN, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θquartz, 0°) quartz substrate, (b) (0°, θLN, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θquartz, 90°) quartz substrate, and (c) (0°, θLN, 0°) LN thin film (thickness 0.15 wavelength) / (0°, θquartz, 30°-60°) quartz substrate, when θLT = 38°, 85°, and 154°. [Figure 27] 10 is a graph showing the ψ dependence of the impedance ratio of longitudinal-wave leaky surface acoustic wave resonators having a structure of Al-IDT / (90°, 90°, ψ)LT thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz substrate and Al-IDT / (90°, 90°, ψ)LN thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz substrate. [Figure 28] 10 is a graph showing the frequency characteristics of impedance (Z) of an elastic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / fused quartz substrate. [Figure 29] 10 is a graph showing the LT film thickness dependency of the impedance ratio of elastic wave resonators having a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / various substrates. [Figure 30] 10 is a graph showing the SiO film thickness dependence of the LSAW impedance ratio of an acoustic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film / SiO film / high acoustic velocity substrate and an Al-IDT / (0°, 131°, 0°) LN thin film / SiO film / high acoustic velocity substrate. [Figure 31] 10 is a graph showing the dependence of (a) the bandwidth and (b) the impedance ratio of an elastic wave resonator having a structure of various IDTs / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz crystal substrate on the electrode thickness of interdigital transducers made of various materials. [Figure 32] This graph shows the dependence of (a) the bandwidth and (b) the impedance ratio of an acoustic wave resonator having a structure of various IDTs / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz substrate on the metallization ratio of interdigital transducers made of various materials (metallization ratio = 2 × electrode width / wavelength). [Figure 33]These are front views of acoustic wave devices with the following structures: (a) IDT / piezoelectric thin film / substrate structure, (b) IDT / piezoelectric thin film / short-circuit electrode / substrate structure, (c) piezoelectric thin film / IDT / substrate (top: IDT embedded in the substrate side, bottom: IDT embedded in the piezoelectric thin film side), and (d) short-circuit electrode / piezoelectric thin film / IDT / substrate (top: IDT embedded in the substrate side, bottom: IDT embedded in the piezoelectric thin film side). [Figure 34] 33(a) to 33(d) are graphs showing the LT film thickness dependence of (a) the bandwidth and (b) the impedance ratio of the elastic wave resonators of each structure shown in Figures 33(a) to 33(d), which have a (0°, 110°, 0°) LT thin film and a (0°, 132.75°, 90°) quartz crystal substrate. [Figure 35] 1 is a graph showing the LT film thickness dependency of the impedance ratio of an elastic wave resonator having a structure in which a part of or the whole of an Al-IDT is embedded in the LT thin film, and a structure in which the Al-IDT is not embedded in the LT thin film, with a (0°, 110°, 0°) LT thin film and a (0°, 132.75°, 90°) quartz crystal substrate. [Figure 36] 10 is a graph showing the dependence of (a) the phase velocity, (b) the bandwidth, and (c) the impedance ratio on the thickness of the boundary film of an elastic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / bonding film / (0°, 132.75°, 90°) quartz crystal substrate. [Figure 37]Impedance ratios of acoustic wave resonators with the following structures: (a) Al-IDT / (0°, 110°, 0°) LT thin film (0.15 wavelength thickness) / SiO2 / SixNy / (0°, 132.75°, 90°) quartz substrate; (b) Al-IDT / (0°, 110°, 0°) LT thin film (0.15 wavelength thickness) / SixNy / SiO2 / (0°, 132.75°, 90°) quartz substrate; (c) Al-IDT / (0°, 110°, 0°) LT thin film (0.15 wavelength thickness) / ZnO / SiO2 / (0°, 132.75°, 90°) quartz substrate; and (d) Al-IDT / (0°, 110°, 0°) LT thin film (0.15 wavelength thickness) / Ta2O5 / SiO2 / (0°, 132.75°, 90°) quartz substrate. 1 is a graph showing the SiO2 film thickness dependence of the SiO2 film thickness (ratio). [Figure 38] This graph shows the dependence of the impedance ratio on the thickness of the third layer film of the bonding film for elastic wave resonators with the following structures: (a) Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / SiO2 / SixNy / third layer of bonding film / (0°, 132.75°, 90°) quartz substrate; and (b) Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / SixNy / SiO2 / third layer of bonding film / (0°, 132.75°, 90°) quartz substrate, when the third layer of the bonding film is made of various materials. [Figure 39] 1 is a graph showing the frequency characteristics of impedance (Z) of an elastic wave resonator having a structure of Al-IDT / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz crystal substrate. [Figure 40] 10 is a graph showing the dependence of the impedance ratio in higher modes on the electrode thickness of interdigital transducers made of various materials for elastic wave resonators having a structure of various IDTs / (0°, 110°, 0°) LT thin film (thickness 0.15 wavelength) / (0°, 132.75°, 90°) quartz substrates. [Figure 41]10 is a graph showing the LT film thickness dependence of the impedance ratio of elastic wave resonators having a structure of Au-IDT / (0°, 110°, 0°) LT thin film / (0°, 132.75°, 90°) quartz substrate, and Au-IDT / (0°, 110°, 0°) LT thin film / short-circuit electrode / (0°, 132.75°, 90°) quartz substrate. [Figure 42] 10 is a graph showing the θ dependence of the impedance ratio in the higher-order mode (1-th) for various LT film thicknesses of elastic wave resonators having the following structures: (a) Al-IDT / (0°, 110°, 0°) LT thin film / (0°, θ, 0°) quartz substrate; and (b) Al-IDT / (0°, 110°, 0°) LT thin film / (0°, θ, 90°) quartz substrate. [Figure 43] 1A to 1C are side views illustrating a method for manufacturing an acoustic wave device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 43 show acoustic wave devices according to embodiments of the present invention. As shown in FIG. 1(b), an acoustic wave device 10 according to an embodiment of the present invention includes a substrate 11 and A piezoelectric thin film 12 is provided on the substrate 11, and a piezoelectric thin film 13 is provided on the piezoelectric thin film 12. It has an interdigital transducer (IDT) 13.

[0038] The substrate 11 contains 70 mass % or more of SiO2. The substrate 11 is made of, for example, quartz crystal, piezo-electric material, or the like. Rex (registered trademark) glass, fused silica, borosilicate glass, synthetic quartz, quartz glass, etc. The piezoelectric thin film 12 is made of LiTaO3 crystal (LT) or LiNbO3 crystal (L In the case of an elastic wave resonator, the interdigital transducer 13 is sandwiched between two electrodes. It also has a reflector 14 made up of many electrode fingers.

[0039] The interdigital transducer (IDT) 13 is composed of a set of bus bars and a bus bar length and a plurality of electrode fingers 21 connected to the bus bar so as to extend in a direction perpendicular to the direction of the substrate. Each IDT 13 has a plurality of electrode fingers 21 arranged alternately (interdigitated). In each IDT 13, the pitch of the electrode fingers 21 is almost constant. When 1 is m, (m-1) / 2=N is called the number of pairs. The length between adjacent electrode fingers 21 (center) is If the length is l, then 2l = λ is one period, which corresponds to the wavelength of the elastic wave excited by the elastic wave device. Equivalent.

[0040] Each reflector 14 is spaced apart from interdigital transducer 13 along the propagation direction of the surface acoustic wave. Each reflector 14 is provided with a pair of bars, each of which sandwiches an interdigital transducer 13. Each reflector 1 has a busbar and a plurality of electrode fingers extending between the busbars. 4, the pitch of each electrode finger is approximately the same as the pitch of each electrode finger of the interdigital transducer 13, It has become constant.

[0041] For comparison, a conventional acoustic wave device 50 is shown in FIG. 1(a). As shown, the conventional acoustic wave device 50 has a piezoelectric substrate 51 made of LT or LN. The interdigital transducer 52 is formed on the substrate 10. Each of the reflectors 53 has a pair of reflectors 53.

[0042] In the following, the Euler angles (φ, θ, ψ) will be simply expressed as (φ, θ, ψ). The thicknesses of thin conductive film 12, interdigital transducer 13, and interdigital transducer 52 are determined based on the thickness of the acoustic wave device to be used. The wavelength is expressed as a magnification with respect to the wavelength λ. Unless otherwise specified, the substrate 11 is a quartz substrate 1. 1 is used. The Euler angles of the substrate 11 and the piezoelectric thin film 12 shown below are determined by the following crystallographic They may also be equivalent Euler angles.

[0043] [Specific examples of the characteristics of LT, LN, and quartz substrates] 2(a) and (b) show the conventional acoustic wave device 50 shown in FIG. 1(a) at (0°, The piezoelectric substrate 51 is made of an LT substrate with an angle of 110° and 0°, and the piezoelectric substrate 52 is made of an LT substrate with an angle of 0°, 132°, and 0°. On the piezoelectric substrate 51 made of LT, Al interdigital transducers each having a thickness of 0.08 wavelength are placed. The frequency of the obtained impedance (Z) for the SAW resonator fabricated by forming the pole 52 is The numerical properties are shown below.

[0044] As shown in Figure 2(a), for the (0°, 110°, 0°) LT substrate, the resonant frequency fr There is a large ripple between fr and anti-resonance frequency fa, and the bandwidth BW[=( fa-fr) / fr] is 5.2%, and the ratio of resonant impedance to anti-resonant impedance ( The Z ratio was 53 dB. Also, as shown in Figure 2(b), (0°, 132°, 0°) In the case of the LT substrate, the ripple between fr and fa is improved, BW is 3.8%, and the impedance is The ratio of the noise to the noise was 63 dB.

[0045] 3(a) and (b) show the acoustic wave device 10 shown in FIG. 1(b), in which the piezoelectric thin film of LT is used. 12 and a quartz substrate 11 are combined to form a (0°, 110°, 0°) LT thin film 12 (thickness 0 .15 wavelength) / (0°, 130°, 90°) quartz substrate 11, and (0°, 120°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 130°, 0°) on quartz substrate 11 The thickness of each electrode was 0.08 wavelength. The frequency characteristics of the impedance (Z) are shown in Fig.

[0046] As shown in Figure 3(a), the LT thin film 12 (thickness 0.15 wavelength) is (0°, 110°, 0°). ) / (0°, 130°, 90°) In the case of the quartz substrate 11, the Euler angles of LT are as shown in Figure 2(a) and Although it is the same, the ripple disappears and the BW is about 20% wider at 6.1%. The impedance ratio is 77.5dB, which is 24.5dB larger, a significant improvement. The increase in the impedance ratio corresponds to a factor of 10 or more in Q. Also, as shown in Figure 3(b), (0°, 120°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 130° , 0°) In the case of the quartz substrate 11, the BW is 5.5% and the impedance ratio is 77.0 dB. Compared to Figure 2(b), the BW is wider and the impedance ratio is significantly improved to 15 dB. These increases in impedance ratio correspond to a factor of 10 or more in Q. Therefore, by using the quartz crystal substrate 11, it is possible to obtain a very excellent steepness compared to the case of using only the LT substrate. It can be said that the characteristics of the coupling coefficient and the insertion loss can be obtained. But it can be made larger.

[0047] In addition, the (0°, 130°, 90°) quartz crystal substrate 11 and the (0°, 130°, 0°) quartz crystal substrate 11, LSAW and Rayleigh waves are excited (see Figs. 5, 7 and 8), while Fig. 3 The characteristics shown above are those of LSAW. When Rayleigh waves are used, SAW is either completely or completely different. Only a small response was observed.

[0048] Figure 4(a) and (b) show the LT thin film 12 (thickness 0.15 wave) at (0°, 110°, 0°). Long) / (0°, 130°, 30°) quartz crystal substrate 11, and (0°, 110°, 0°) L A thin film 12 (thickness 0.15 wavelength) / (0°, 130°, 60°) is placed on a quartz substrate 11. The results obtained for the Al interdigital electrodes 13 each having a thickness of 0.08 wavelength were as follows: The frequency characteristics of impedance (Z) are shown in Figure 4(a) and (b). There was a large ripple in the crystal, and good characteristics were not obtained. At angles of 85°, 95°, -5°, and 5°, the same characteristics as those in Figures 3(a) and (b) were obtained. As shown above, large ripples may occur depending on the Al thickness and Euler angle. Therefore, the selection of the Al thickness and Euler angles is important.

[0049] FIG. 5 shows the relationship between the Rayleigh wave and the LSAW in the (0°, 130°, ψ) quartz substrate 11. The dependence of the sound speed on the propagation direction ψ is shown in Figure 5. The LSAW velocity of the crystal substrate 11 is high at about 5,000 m / s, but The LSAW sound velocity at ψ is low, about 3,800 m / s. When the tangent δV / δψ of the sound velocity V is 0, the power flow angle (PFA) is 0. For Rayleigh waves, ψ = 0°, 35°, 90°, and for leaky surface acoustic waves, ψ = 0°, 42°, At around 90°, PFA=0.

[0050] As shown in FIGS. 3 to 5, the LSAW sound velocity of the LT thin film 12 used is 4100 m / s. On the other hand, the LSAW has a low sound velocity of 3,800 m / s (0°, 130°, 30° When the quartz crystal substrate 11 with angles of 0°, 130°, and 60° was used, the Al thickness was 0.0 When there are 8 wavelengths, good characteristics cannot be obtained, and the LSAW sound velocity is about 5,000 m / s. The quartz crystal substrate 11 was used at angles of (0°, 130°, 0°) and (0°, 130°, 90°). In the case of the axial direction, good characteristics are obtained. The (10°, 0°) LT substrate and the (0°, 132°, 0°) LT substrate have a larger Despite the presence of leakage components, the characteristic improvement effect is large. The main reason is that the LSAW is applied to the quartz substrate 11, which has a higher acoustic velocity than the LT thin film 12. It is considered that the leakage component of the LSAW of the LT thin film 12 becomes zero as a result.

[0051] Figure 6(a) and (b) show the (110) and (001) direction propagation directions of the Si substrate and the and c sapphire substrates, respectively (0°, 132°, 0°) LT thin films (thickness 0.15 wave) On top of that, an Al interdigital electrode with a thickness of 0.08 wavelength was formed. The frequency characteristics of the impedance (Z) obtained for the AW resonator are shown in Figure 6. As shown in (a), when a Si substrate is used, the BW is 4.4% and the impedance ratio is 69. As shown in Figure 6(b), when a sapphire substrate was used, the BW was 5 dB. .7% and the impedance ratio was 68dB.

[0052] The characteristics shown in Figures 6(a) and (b) are the same as those of the SAW resonator on the LT substrate alone in Figure 2(b). Compared to the performance, the BW is wider and the impedance ratio is 5 to 6 dB better. The LT thin film 12 / quartz crystal substrate 11 has better characteristics. In addition to Rayleigh waves, LSAWs are excited on piezoelectric substrates such as Si substrates and sapphire. Since the substrate is not piezoelectric, only the Rayleigh wave of the SAW mode is excited. Therefore, the use of a quartz substrate 11 provides better characteristics than the use of a Si substrate or a sapphire substrate. The reason is that the quartz crystal substrate 11 used is made of the same LSAW as the LT thin film 12. On the other hand, the shear wave velocity of bulk waves is larger on Si substrates and sapphire substrates than on LT thin films. This is thought to be because the LT thin film used uses Rayleigh waves that are different from the LSAW. .

[0053] From the above results, for the piezoelectric thin film 12 such as LT or LN used, the sound velocity of the transverse wave of the bulk wave The substrate is made of a material with a high acoustic velocity and a main component of the SH component, which is close to the acoustic velocity of the material. As a result, good characteristics can be obtained. The difference in sound velocity of the LSAW between the piezoelectric thin film 12 and the substrate is large. The higher the speed, the better. For example, 300 m / s or more is preferable, and 600 m / s or more is even better. It is preferable that there is.

[0054] 7(a) and (b) show the Rayleigh wave and LSAW of the (0°, θ, 0°) quartz substrate 11. The θ dependence of the sound velocity and TCF of the LSAW is shown in Fig. 7(c). The ratio of the displacement component U1, SH component U2, and SV component U3 on the substrate surface is shown in Figure 7( As shown in a), the velocity is over 4,500 m / s when θ=70°~165°, and over 4,500 m / s when θ=90°~150°. At θ=100° to 140°, the sound velocity is over 4,800 m / s, and at θ=100° to 140°, the sound velocity is over 5,000 m / s. As shown in Fig. 7(b), the Rayleigh wave TCF becomes positive, and for LSAW, θ = 0°~18°, 43°~66°, 132°~ At 180°, the TCF is positive. At LSAW, the LT and In combination with LN, the Euler wave with a positive TCF for this Rayleigh wave or LSAW A quartz substrate 11 with a corner is preferred, and a good TCF close to zero ppm / °C can be obtained. More preferably, the temperature of the Rayleigh wave is θ=0° to θ=10°C, and the temperature of the Rayleigh wave has a TCF of +5 ppm / °C or more. 130°, LSAW θ=0°~16°, 44°~65°, 135°~180° crystal base By combining with the plate 11, a better TCF can be obtained. As shown in c), when θ = 70° to 165°, where the LSAW sound velocity is large, the SH component (U2 component ) is more than 50%.

[0055] Figure 8(a) and (b) show the Rayleigh wave and LSA of the quartz substrate 11 (0°, θ, 90°). The dependence of W on the sound velocity and TCF is shown in Fig. 8(c). The ratio of the wave displacement component U1, SH component U2, and SV component U3 on the substrate surface is shown in Figure 8. As shown in (a), the velocity is over 4,500 m / s when θ = 90° to 150°, and over 103° to 1 High-pitched sound of over 4,800 m / s at 43° and over 5,000 m / s at θ=110°~135° As shown in Figure 8(b), the Rayleigh wave exhibits a velocity of θ=0° to 42°. , 170°~180°, TCF becomes positive, and for LSAW, θ=0°~41°, 12 The TCF is positive at 3° to 180°. The L with negative TCF at LSAW In combination with T and LN, the Euler wave has a positive TCF for Rayleigh waves and LSAWs. A quartz substrate 11 having a squared angle is preferred, and a good TCF close to zero ppm / °C can be obtained. More preferably, the TCF is +5 ppm / °C or more, and the Rayleigh wave is °~39°, 172°~180°, θ=0°~39°, 126°~180° for LSAW By combining it with the quartz crystal substrate 11, a better TCF can be obtained. As shown in Fig. 8(c), when θ = 85° to 165°, where the LSAW sound velocity is large, the SH component ( It can be seen that the U2 component is more than 65%.

[0056] 9 shows the sound velocity of the quartz substrate 11 at various Euler angles. For plate 11, ψ = 0° to 20°, 70° to 120°, and 160° to 180°, and the A high sound velocity of more than m / s is obtained. °~150°, 0°~20°), (1°~39°, 100°~150°, 70°~120 °), (1°~39°, 100°~150°, 160°~180°), high sound speed LSA W is obtained.

[0057] In acoustic wave devices, the power flow angle is set to zero to prevent LSAW from propagating obliquely. It is preferable to use a substrate with a direction close to the propagation direction of the LSAW (a propagation direction where the tangent to the propagation direction of the LSAW is zero). In the quartz crystal substrate 11 with the Euler angles shown in FIG. are (0°±5°, θ, 35°±8°), (10°±5°, θ, 42°±8°), (20 °±5°, θ, 50°±8°), (0°±5°, θ, 0°±5°), (10°±5°, θ , 0°±5°), (20°±5°, θ, 0°±5°), (0°±5°, θ, 90°±5° ), (10°±5°, θ, 90°±5°), (20°±5°, θ, 90°±5°) It is preferable to use substrates with these Euler angles.

[0058] [Specific example of an acoustic wave device with an LT thin film / quartz substrate structure] Figure 10(a) and (b) show the Rayleigh wave and LSAW on the LT substrate (0°, θ, 0°). The graph shows the θ dependence of the acoustic velocity and the electromechanical coupling factor. Figure 10(c) shows the θ dependence of TCF for LSAW on the LT substrate (0°, θ, 0°). As shown in Figure 10(a) and (b), the leakage component is generally small for the LT substrate. The LSAW with θ=120° to 146°, which has a coupling coefficient of 4% or more, is used. The sound velocity Vm (sound velocity when the board surface is electrically short-circuited) is 4,000 to 4,100 m However, the bandwidth of the filter depends on the coupling coefficient of the substrate used, so It is necessary to select a coupling coefficient that satisfies the above-mentioned band. According to , if a substrate with the same or higher acoustic velocity is used under the LT, the leakage component will be smaller. Therefore, we use θ=65°~148°, which is a large coupling coefficient, and the sound velocity is 3,700~4 By using a quartz substrate 11 with a sound velocity of about 100 m / s or higher, , good characteristics can be obtained.

[0059] In addition, as shown in Fig. 10(c), the TCF of the LSAW on the LT substrate is negative. , -30 to -70 ppm / ℃. θ=120° to 14° when used alone on the LT substrate The TCF of 6°LSAW is about -33 ppm / ℃, but the TCF of Rayleigh wave and LSAW The quartz crystal substrate 11 having the TCF of the glass, that is, the (0°, 0° to 13°) of the Rayleigh wave shown in FIG. 0°, 0°), LSAW (0°, 132°~180°, 0°) quartz crystal substrate 11, or , the Rayleigh wave shown in Figure 8 (0°, 0°~39°, 90°), (0°, 172°~180 °), LSAW (0°, 0°~41°, 90°), (0°, 123°~180°, 90 By combining it with a quartz crystal substrate 11, the TCF can be made to be 1 / 3 or less better than that of a TCF made of a LT substrate alone. A good TCF can be obtained.

[0060] Figure 11(a) and (b) show the (0°, θ, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 115° to 145°, 0°) On the quartz crystal substrate 11, an Al The resonators obtained for the acoustic wave devices 10 each having the interdigital transducer 13 are shown in Fig. The dependence of the bandwidth and impedance ratio on the θ of LT is shown in Fig. 11(a) and (b). ) is the θ of the quartz crystal substrate 11. As shown in FIG. 11(a), θ of LT = A bandwidth of 3.5% is obtained between 82° and 148°. Also, as shown in Figure 11(b), ,LT θ=85°~148°, 70dB or more, LT θ=90°~140°, 73 dB or more, and an impedance ratio of 75 dB or more is obtained at LT θ = 95° to 135°. There are.

[0061] Figure 12(a) shows the results when the Al thickness is 0.08 wavelengths, and Figure 12(b) shows the results when the Al thickness is 0.2 wavelengths. (0°, 110°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, θ, 0°) Regarding an acoustic wave device 10 having an Al interdigital transducer 13 formed on a quartz substrate 11, The impedance ratio of the obtained acoustic wave resonator is shown as a function of the θ angle of the quartz crystal. The solid line shows the characteristics without ripples in the band between fr and fa of the resonator, and the dashed line shows the characteristics with ripples. The characteristics are shown. The quartz crystal (0°, 115°~145°, 0°) has good impedance. The ratio is obtained, but ripples are observed elsewhere. Almost no ripples were observed, and a large impedance was obtained at any azimuth angle. As shown in the figure, the θ dependence of the impedance ratio differs depending on the thickness of the Al electrode. However, when the Al electrode thickness is 0.08 wavelength or more, characteristics close to those of the Al electrode thickness of 0.2 wavelength are obtained. When the Al electrode is 0.08 wavelength, the LSAW of the quartz crystal is positive. Considering the range of TCF, the crystal substrate 11 is (0°, 132° to 145°, 0°). It is preferable that the angle is (0°, 135° to 145°, 0°), and more preferable that the angle is (0°, 135° to 145°, 0°). In this case, the LT thin film 12 has a negative TCF and the quartz substrate has a positive TCF. 11, the TCF of the acoustic wave device 10 can be significantly improved. In particular, when the crystal substrate 11 is at (0°, 135° to 145°, 0°), it is more preferable. A good TCF can be obtained.

[0062] Figure 13(a) and (b) show the LT thin film 12 (0°, 110°, 0°) and the LT thin film 13 (0°, 13 0°, 0°) On the quartz substrate 11, Al blinds with thicknesses of 0.08 wavelength and 0.2 wavelength are For the acoustic wave device 10 on which the shaped electrode 13 is formed, the band of the obtained acoustic wave resonator is As shown in Fig. 13(a), the thickness dependence of the L When the film thickness of T is between 0.02 wavelengths and 2 wavelengths, a bandwidth of 3% or more is obtained. ), when the Al thickness is 0.08 wavelength, the LT film thickness is 0.01 wavelength to 0.6 wavelength. 70dB or more at 0.02 wavelength to 0.4 wavelength, 73dB or more at 0.03 wavelength to 0.3 wavelength On the other hand, when the Al thickness is 0.2 wavelength, the impedance ratio is 75 dB. Impedance ratio of 70dB for thickness of 2 wavelengths or less, and 73dB for thickness of 0.02 wavelengths to 0.043 wavelengths dB or more, and an impedance ratio of 75 dB is obtained from 0.03 wavelength to 0.33 wavelength. When the Al thickness is 0.1 wavelength to 0.3 wavelength, the values ​​are almost the same as when the Al thickness is 2 wavelengths. show.

[0063] Figure 14(a) and (b) show the (0°, θ, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 100° to 175°, 90°) A The acoustic waves obtained from the acoustic wave device 10 having the interdigital transducer 13 of 1 are shown in FIG. The figure shows the dependence of the bandwidth and impedance ratio of the resonator on the θ of LT. The θ in the graphs (a) and (b) is the θ of the quartz crystal substrate 11. Except for θ=165° and 175° of the crystal substrate 11, LT has a θ=75° to 155° of 3.5%. As shown in FIG. 14(b), the LT θ is 80° to 152°. 70dB or more at θ=90°~140°, 73dB or more at θ=95°~135°, 75dB or more at θ=95°~135° B or more, and an impedance ratio of approximately 77 dB or more is obtained at LT θ = 103° to 125°. It is being done.

[0064] Figure 15(a) shows the (0°, 120°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0 On a quartz crystal substrate 11 (°, θ, 90°), an Al interdigital transducer 13 having a thickness of 0.08 wavelengths is formed. The impedance ratio of the resulting acoustic wave resonator of the formed acoustic wave device 10 was compared. The graph shows the θ dependence of the crystal substrate 11. In the graph, the solid line indicates the characteristics without ripples within the resonator band. On the other hand, in Fig. 15(b), the line shows the ripple characteristics when the LT thickness is 0.15 wavelengths. When the Al thickness is 0.1 wavelength, and when the LT thickness is 1.25 wavelength and 2 wavelength, The relationship between the impedance ratio and the Euler angle θ is shown for a thickness of 0.2 wavelengths.

[0065] In Figure 15(a) for the Al thickness of 0.08 wavelength, the quartz crystal (0°, 100°-165°, 90 From Fig. 8(b), a good impedance ratio is obtained at 0.08 wave of Al thickness. In the vicinity of the long distance, the Rayleigh wave and LSAW of the quartz crystal become positive TCF. The angle is preferably (0°, 123° to 165°, 90°±5°), and +5 ppm Euler angles of quartz crystals with TCF of 0°, 126°-165°, 90°±5° is more preferable, and the TCF is +7 ppm / ℃ or more (0°, 127° to 165°, 90 In this case, the LT thin film having a negative TCF is By combining the quartz substrate 11 with the TCF 12, an elastic wave device In particular, the TCF of the device 10 can be improved significantly. A better TCF is obtained when the angle is between 90° and 165°, 90° ± 5°.

[0066] Figure 15(c) shows the results of the LT thin film (1) at (0°, 120°, 0°) when the Al thickness is 0.1 wavelength. 2 (thickness 0.15 wavelength) / (0°, 125.25°, 90°) Frequency characteristics of the quartz substrate 11 At this azimuth angle of the crystal, ripples occur within the band at a specific Al thickness. Therefore, the impedance ratio in Figure 15(b) is smaller than that at other azimuth angles. (°, 126°, 0°) Large ripples tend to occur when combined with LT thin film 12. Therefore, (0°, 126°, 0°) LT thin film 12 and (0°, 125.25°, 90°) water It is desirable to avoid combining it with the crystalline substrate 11.

[0067] Figure 16(a) and (b) show the (0°, 110°, 0°) LT thin film 12 / (0°, 12 On a quartz crystal substrate 11, Al sheets having a thickness of 0.08 wavelength and 0.2 wavelength are formed. For the acoustic wave device 10 on which the groove-shaped electrode 13 is formed, The dependence of the bandwidth and impedance ratio on the thickness of LT is shown in Figure 16(a). The characteristics are almost the same as those in Fig. 13(a). The LT film thickness is 0.04 wavelengths or more and 2 wavelengths or less, and the % or more. Also, as shown in Fig. 16(b), the bandwidth is almost the same as that in Fig. 13(b). The same characteristics were obtained, and when the Al thickness was 0.08 wavelengths, the LT film thickness was 0.01 wavelengths to 0.6 wavelengths. 70dB or more at 0.02 wavelength to 0.4 wavelength, 73dB or more at 0.03 wavelength to 0.3 wavelength On the other hand, when the Al thickness is 0.2 wavelength, the impedance ratio is 75 dB. The impedance ratio is 70 dB for thicknesses of 2 wavelengths or less, and 70 dB for thicknesses of 0.02 wavelengths to 0.043 wavelengths. 3dB or more, and an impedance ratio of 75dB or more is obtained from 0.03 wavelength to 0.33 wavelength. When the Al thickness is 0.1 wavelength or less, the value is similar to that of 0.08 wavelength. When the wavelength is 0.1 to 0.3, the value is almost the same as when the Al thickness is 0.2 wavelength.

[0068] Figure 17(a) and (b) show the LT thin film 12 (0°, 110°, 0°) / (0°, 45°) On the quartz crystal substrate 11, Al interdigital plates with thicknesses of 0.12 wavelength and 0.2 wavelength are For the acoustic wave device 10 on which the electrode 13 is formed, the thickness of the LT thin film 12 is 0. Frequency characteristics of impedance (Z) at 15 wavelengths and LT of impedance ratio The film thickness dependence is shown. The quartz substrate 11 used here (0°, 45°, 0°) The TCF of the wave is positive 25 ppm / ℃, the sound speed of the Rayleigh wave is 3270 m / s, and the The speed of sound is 3950 m / s. As shown in Figure 17(a), the frequency is low at 3 GHz, but A good impedance ratio of 75 dB is obtained. Also, as shown in Figure 17(b), When the LT film thickness is 0.43 wavelengths or less, an impedance ratio of 70 dB or more is obtained. As shown in the figure, by making the Al electrode a little thicker, good characteristics can be achieved even on substrates with slow LSAW sound velocity. is obtained.

[0069] Figure 18 shows the LT thin film 12 (0°, 110°, 0°) / (20°, 120°, 115°) Quartz crystal substrate 11 and (0°, 110°, 0°) LT thin film 12 / (0°, 130°, 0 1) An elastic plate having an Al interdigital transducer 13 with a thickness of 0.08 wavelength formed on a quartz substrate 11. The dependence of the impedance ratio on the film thickness of LT for the wave device 10 is shown. The quartz crystal substrate 11 is oriented at an angle of 20°, 120°, or 115°, and is exposed to high sound velocity of about 5000 m / s. It has an azimuth angle that excites S waves (fast shear waves), and is made of a quartz substrate (0°, 130°, 0°). 11 has an azimuth angle that excites a high sonic velocity LSAW. (0°, 130°, 0°) The quartz substrate 11 has an impedance ratio of 70 dB or more. This can be obtained only when the LT thickness is 0.8 wavelength or less, whereas the (2 0°, 120°, 115°) In the case of a quartz substrate, even if the LT thickness is 10 wavelengths, Although not shown, the impedance ratio is 70 dB even when the LT thickness is 20 wavelengths. The Euler angles of such high-speed S waves include (20°±5°, 120°±10°, 115°±10°), (0°±5°, 90°±5°, 0°±10°), (0°±5°, 9 0°, 75°±10°), (0°±5°, 0°, 0°±10°), (0°±5°, 0°, 60°±10°).

[0070] Figure 19(a) to (c) show the (0°, θ LT , 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, θ quartz , 0°) Crystal substrate 11, (0°, θ LT ,0°)LT thin film 12( Thickness 0.15 wavelength) / (0°, θ quartz , 90°) crystal substrate 11, (0°, θ LT , 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, θ quartz , 30°~60°) Crystal substrate 11 θ of TCF in quartz The dependence of the quartz substrate 11 in FIG. The angle θ of the quartz substrate 11 changes the propagation direction of PFA=0. However, the propagation direction of PFA=0 is in the range of 30° to 60°. is the optimum azimuth angle (0°, 80° to 148°, 0°) of the TCF shown in Figure 10(c). Indicates the maximum absolute value (0°, 125°, 0°), indicates the minimum absolute value (0°, 80°, 0°). 19(a) to (c) are shown for (0°, 148°, 0°) and (0°, 148°, 0°). In addition, the water vapor can achieve practical -20 to +20 ppm / ℃ with half the TCF of LT thin film 12. The azimuth angles of the crystal substrate 11 are (0°±5°, 0° to 23°, 0°±5°), (0°±5°, 3 2°~69°, 0°±5°), (0°±5°, 118°~180°, 0°±5°), (0 °±5°, 0°~62°, 90°±5°), (0°±5°, 118°~180°, 90° ±5°), (0°±5°, 0°~72°, 30°~60°), (0°±5°, 117°~ 180°, 30°~60°). Achieves better -10~+10ppm / ℃ The azimuth angles of the quartz crystal substrate 11 are (0°±5°, 0° to 12°, 0°±5°), (0°±5°, 37°~66°, 0°±5°), (0°±5°, 132°~180°, 0°±5°), ( 0°±5°, 0°~50°, 90°±5°), (0°±5°, 126°~180°, 90 °±5°), (0°±5°, 0°~17°, 30°~60°), (0°±5°, 35°~ 67°, 30°~60°), (0°±5°, 123°~180°, 30°~60°) do.

[0071] [Specific examples of acoustic wave devices with an LN thin film / quartz substrate structure] Figures 20(a) and (b) show the Rayleigh wave and LSAW on the (0°, θ, 0°) LN substrate. , the θ dependence of the acoustic velocity and the electromechanical coupling coefficient. 20(a) and 20(b) show the θ dependence of the TCF of the Rayleigh wave and LSAW on the LN substrate. As shown in (a) and (b), the LN substrate generally has a small leakage component and a large coupling coefficient, θ LSAW with θ = 131° to 154°, LSAW with a large coupling coefficient near θ = 90°, Love waves, which use electrodes with slow sound speeds on the surface of the substrate to eliminate leakage components, are used. The sound velocity Vm of the LSAW used is 4,150 to 4,450 m / s.

[0072] Moreover, as shown in Figure 20(c), the TCF of the LSAW on the LN substrate is negative. LSA is used for θ=131°~154° and θ=90°. The TCF of W is not good at -73 to -93 ppm / ℃.

[0073] Figure 21 shows the LN thin film 12 at (0°, 131°, 0°) with an LSAW sound velocity of 4,250 m / s. (Thickness 0.15 wavelength) and LSAW sound velocity 5,040 m / s (0°, 115°, 90° ) a quartz crystal substrate 11 (see FIG. 8(a)), and a 0.0 mm thick film was formed on the LN thin film 12. The impedance obtained for the elastic wave resonator with the Al interdigital transducer 13 of 8 wavelengths is As shown in Figure 21, the impedance ratio is 79.3dB. B, which is 19 dB higher than the conventional SAW characteristics of the LN substrate alone. Even when LN is used, good characteristics can be obtained, similar to the case of LT. A thin LN film 12 with a large thickness was used, and the sound velocity was the same as or higher than the LSAW sound velocity. By using a certain quartz crystal substrate 11, good characteristics can be obtained.

[0074] In Figure 22(a), (0°, θ, 0°) LN thin film 12 (thickness 0.15 wavelength) / (0°, 1 On a quartz crystal substrate 11, Al sheets having thicknesses of 0.08 wavelength and 0.2 wavelength are formed. The acoustic wave device 10 having the groove-shaped electrode 13 was tested for LSAW and Rayleigh waves. The impedance ratio of the elastic wave resonator obtained by this experiment is shown as a function of the θ of the LN. As shown in the figure, in the case of LSAW, the impedance of the resonator when the Al thickness is 0.08 wavelength and 0.2 wavelength is The solid line with an impedance ratio of 70 dB or more spreads out in the center and shows the ripple-free The dashed lines on both sides below 70 dB show good characteristics, while the broken lines on both sides show ripple characteristics. When the LN θ is 100° to 160° and the Al thickness is 0.2 wavelengths, A large impedance ratio is obtained when θ of N is between 70° and 165°. When the wavelength is 6 to 0.09, the impedance ratio is the same as when the Al thickness is 0.08. When the Al thickness is from 0.09 wavelength to 0.22 wavelength, the impedance is the same as when it is 0.2 wavelength. On the other hand, in the case of Rayleigh waves, the resonator when the Al thickness is 0.08 wavelength The impedance ratio of LN is over 70dB at θ=35°~70°, and A large impedance ratio of over 75 dB is obtained at 3°.

[0075] In Fig. 22(b), (0°, 131°, 0°) LN thin film 12 (thickness 0.15 wavelength) / (0 On a quartz crystal substrate 11, Al layers having thicknesses of 0.08 wavelength and 0.2 wavelength are formed. For the acoustic wave device 10 having the groove-shaped electrode 13, the acoustic wave obtained in response to LSAW The impedance ratio of the resonator and the (0°, 55°, 0°) LN thin film 12 (thickness 0. 15 wavelength) / (0°, θ, 0°) quartz crystal substrate 11, on which an Al sheet having a thickness of 0.08 wavelength is placed. For the acoustic wave device 10 having the groove-shaped electrode 13, the acoustic wave obtained for the Rayleigh wave was 1 shows the θ dependence of the impedance ratio of the wave resonator on the quartz substrate 11. The impedance ratio of 75dB or less indicates that there is a ripple in the band. , the impedance ratio shows a value of 75dB or more, which is a good characteristic with no ripple. As shown in FIG. 22(b), the (0°, 131°, 0°) LN thin film 12 has a thickness of Al. Even with a wavelength of 0.08, a large impedance ratio can be obtained with quartz crystal at θ = 120° to 145°. However, when the Al thickness is 0.2 wavelength, a large impedance ratio is obtained at all azimuth angles. When the Al thickness is between 0.06 wavelength and 0.09 wavelength, the Al thickness is 0.08 wavelength. When the Al thickness is between 0.09 wavelength and 0.22 wavelength, The same impedance ratio as when the Al thickness is 0.2 wavelength is obtained. When the Al thickness is 0.08 wavelength, ,From FIG. 7(b), the Euler angle at which the TCF of the LSAW of the quartz substrate 11 becomes positive is (0 °, 132°~180°, 0°±5°) and a TCF of +5 ppm / °C. The angle is (0°, 135°~180°, 0°±5°). In this case, the TCF is negative. By combining the LN thin film 12 having the TCF and the quartz crystal substrate 11 having the TCF, As a result, the TCF of the acoustic wave device 10 can be significantly improved. From the results of 22(b), when the TCF and impedance ratio are taken into consideration, the oil content of the quartz substrate 11 is The angle is preferably (0°, 132° to 145°, 0°±5°), and 35° to 145°, 0°±5°) is more preferable. As shown in the solid line, the (0°, 55°, 0°) LN thin film 12 is 1 Euler angle (0°, 90°~178°, 0°±5°) and impedance of 70dB The broken line indicates that there is a lip, and the impedance ratio is 70 dB or less. At this azimuth angle of the quartz substrate 11, either LSAW or Rayleigh wave is observed. Either one indicates TCF positive.

[0076] Figure 23(a) and (b) show the LN thin film 12 (0°, 131°, 0°) and the LN thin film 13 (0°, 13 0°, 0°) On the quartz substrate 11, Al blinds with thicknesses of 0.08 wavelength and 0.2 wavelength are For the acoustic wave device 10 on which the shaped electrode 13 is formed, the band of the obtained acoustic wave resonator is As shown in Fig. 23(a), the LN film thickness dependence of the area and impedance ratio is A bandwidth of 7% or more is obtained when the N film thickness is between 0.03 wavelengths and 2 wavelengths. ), when the Al thickness is 0.08 wavelengths, the LN film thickness is 0.012 wavelengths to 0.6 wavelengths. 70dB or more at 0.02 wavelength to 0.5 wavelength, 73dB or more at 0.03 wavelength to 0.33 wavelength An impedance ratio of 75 dB is obtained for the Al thickness of 0.2 wavelength. 70dB or more for film thicknesses of 0.012 wavelength to 2 wavelength, and 73dB or more for film thicknesses of 0.02 wavelength to 0.7 wavelength Above all, an impedance ratio of 75 dB or more is obtained at 0.03 wavelength to 0.4 wavelength.

[0077] In Figure 24(a), (0°, θ, 0°) LN thin film 12 (thickness 0.15 wavelength) / (0°, 1 On the quartz crystal substrate 11, Al layers with thicknesses of 0.08 wavelength and 0.2 wavelength are The acoustic wave device 10 having the delta electrodes 13 formed thereon was subjected to LSAW and Rayleigh wave The impedance ratio of the acoustic wave resonator obtained by the above experiment is shown as a function of the θ of the LN. As shown in Fig. 1, in the case of LSAW, the impedance of the resonator when the Al thickness is 0.08 wavelength and 0.2 wavelength is The solid line in the middle indicates the impedance ratio of 70 dB or more, and the ripple is within the band. The broken lines on both sides below 70 dB show the characteristics with ripples. When the Al thickness is 0.2 wavelength, the LN θ is 7°, and the θ is 95° to 155°. A large impedance ratio is obtained between 0° and 170°. When the distance from the longest point is 0.09 wavelength, the impedance ratio is the same as when the Al thickness is 0.08 wavelength. When the Al thickness is from 0.09 wavelength to 0.22 wavelength, the impedance is the same as when it is 0.2 wavelength. On the other hand, in the case of Rayleigh waves, the impedance ratio of the resonator when the Al thickness is 0.08 wavelength is The impedance ratio is shown as follows: LN: 70dB or more at θ=25°~51°, and θ=29°~47° An impedance ratio of 75 dB or more is obtained.

[0078] In Fig. 24(b), (0°, 131°, 0°) LN thin film 12 (thickness 0.15 wavelength) / (0 On the quartz crystal substrate 11, a layer of Al having a thickness of 0.08 wavelength and 0.2 wavelength is formed. The elasticity obtained for LSAW in the acoustic wave device 10 having the interdigital electrode 13 was The impedance ratio of the wave resonator and the LN thin film 12 (thickness 0°, 38°, 0°) 0.15 wavelength) / (0°, θ, 90°) quartz crystal substrate 11 is provided with an Al film with a thickness of 0.08 wavelength. For the acoustic wave device 10 having the interdigital transducer 13, the The impedance ratio of the acoustic wave resonator depends on the angle θ of the quartz substrate 11. As shown in the figure, in the case of LSAW, the central solid line with an impedance ratio of 70 dB or more indicates that there is a ripple within the band. The dashed lines below 70 dB on both sides show the characteristics with ripple. When the thickness is 0.08 wavelength, the quartz crystal θ is 90° to 155°, and the Al thickness is 0.2 wavelength. A large impedance ratio is obtained at all azimuth angles. At 0.09 wavelength, the impedance ratio is the same as that at 0.08 wavelength. When the wavelength is 0.09 to 0.22, the impedance ratio is the same as when the wavelength is 0.2. On the other hand, as can be seen from FIG. 8(b), the quartz substrate 11 has a positive TCF of LSAW. Euler angles are (0°, 123°~180°, 90°±5°) and +5ppm / ℃ The Euler angles that result in TCF are (0°, 126°~180°, 90°±5°). In this case, the LN thin film 12 has a negative TCF and the quartz substrate 11 has a positive TCF. By combining these, the TCF of the acoustic wave device 10 can be significantly improved. From the results of Fig. 8(b) and Fig. 24(b), it is possible to consider the TCF and the impedance ratio. The Euler angles of the quartz crystal substrate 11 are (0°, 123° to 155°, 90°±5°). It is preferable that the angle is (0°, 126° to 155°, 90°±5°), and it is more preferable that the angle is (0°, 126° to 155°, 90°±5°). More preferably, the TCF of the LSAW crystal is +7 ppm / °C or higher (0°, 127°C). On the other hand, in the case of Rayleigh waves, the Euler angle of the quartz substrate 11 is - Angle (0°, 80°~160°, 90°±5°) 70dB, (0°, 115°~1 An impedance ratio of 75 dB is obtained at angles of 45° and 90° ± 5°. Taking into account the azimuth angle at which the Lee wave exhibits positive TCF, the Euler angles of the quartz substrate 11 are ( 0°, 125°~160°, 90°±5°) are preferable.

[0079] Figure 25(a) and (b) show the LN thin film 12 (0°, 131°, 0°) and the LN thin film 11 (0°, 11°). On a quartz crystal substrate 11, Al sheets having a thickness of 0.08 wavelength and 0.2 wavelength are formed. For the acoustic wave device 10 on which the groove-shaped electrode 13 is formed, The dependence of the bandwidth and impedance ratio on the LN film thickness is shown in Figure 25(a). A bandwidth of 5% or more is obtained when the LN film thickness is between 0.012 wavelengths and 2 wavelengths. As shown in (b), when the Al thickness is 0.08 wavelength, the LN film thickness is 0.01 wavelength to 0.5 wavelength. More than 70dB for wavelengths, more than 73dB for wavelengths from 0.02 wavelengths to 0.33 wavelengths, and more than 73dB for wavelengths from 0.06 wavelengths to 0. An impedance ratio of 75 dB is obtained for 3 wavelengths. On the other hand, when the Al thickness is 0.2 wavelengths, , 70dB or more for LN film thicknesses of 0.01 wavelength to 2 wavelengths, and 70dB or more for LN film thicknesses of 0.02 wavelength to 0.43 wavelengths. 3dB or more, and an impedance ratio of 75dB or more is obtained from 0.06 wavelength to 0.36 wavelength. There are.

[0080] Figure 26(a) to (c) show the (0°, θ LN , 0°) LN thin film 12 (thickness 0.15 wavelength) / (0°, θ quartz , 0°) Crystal substrate 11, (0°, θ LN , 0°) LN thin film 12( Thickness 0.15 wavelength) / (0°, θ quartz , 90°) crystal substrate 11, (0°, θ LN , 0°) LN thin film 12 (thickness 0.15 wavelength) / (0°, θ quartz , 30°~60°) Crystal substrate 11 θ of TCF in quartz The dependence of the quartz substrate 11 in FIG. The angle θ of the quartz substrate 11 changes the propagation direction of PFA=0. However, the propagation direction of PFA=0 is in the range of 30° to 60°. The optimum azimuth angle (0°±5°, 75-165°, 0°±5°) is shown in Figure 20(c). The minimum absolute value of the TCF of the LSAW is shown (0°, 154°, 0°), and the maximum absolute value is shown ( 0°, 85°, 0°), and the optimal orientation of Rayleigh waves (0°, 38°, 0°). As shown in Figure 26(a) to (c), the practical range of TCF is -20 to +20 ppm / The azimuth angle of the quartz crystal substrate 11 that can achieve this is (0°±5°, 0° to 16°, 0°±5°), (0°±5°, 42°~64°, 0°±5°), (0°±5°, 138° ~180°, 0°±5°), (0°±5°, 0°~30°, 90°±5°), (0°±5 °, 130°~180°, 90°±5°), (0°±5°, 0°~28°, 30°~60 °), (0°±5°, 42°~70°, 30°~60°), (0°±5°, 132°~1 80°, 30°~60°). For Rayleigh waves, (0°±5°, 32°~118°, 0°±5°), (0°±5°, 0°~30°, 90°±5°), (0°±5°, 173° ~180°, 90°±5°), (0°±5°, 0°~142°, 30~60°). The azimuth angle of the quartz substrate 11 that can achieve a better -10 to +10 ppm / °C is (0°±5°, 43°~61°, 0°±5°), (0°±5°, 147°~180° , 0°±5°), (0°±5°, 0°~15°, 90°±5°), (0°±5°, 134 °~180°, 90°±5°), (0°±5°, 0°~23°, 30°~60°), (0 °±5°, 43°~67°, 30°~60°), (0°±5°, 137°~180°, 3 0°~60°). For Rayleigh waves, (0°±5°, 40°~102°, 0°±5° ), (0°±5°, 0°~17°, 90°±5°), (0°±5°, 175°~180° , 90°±5°), (0°±5°, 13°~130°, 30~60°).

[0081] Figure 27 shows the (90°, 90°, ψ) LT thin film 12 (thickness 0.15 wavelength) / (0°, 13 2.75°, 90°) quartz crystal substrate 11 and (90°, 90°, ψ) LN thin film 12 (thickness 0.15 wavelength) / (0°, 132.75°, 90°) A quartz substrate 11 with a thickness of 0. Elastic waves of a longitudinal-wave leaky surface acoustic wave resonator with an Al interdigital transducer 13 of 0.8 wavelength. For device 10, the ψ dependence of the impedance ratio on L is shown in Figure 27. For the LT thin film 12, when ψ=33°~55° and 125°~155°, the LN thin film For film 12, when ψ=38°~65° and 118°~140°, the gain is 70dB or more. The impedance ratio is obtained.

[0082] [Consideration of substrates other than quartz] Materials other than quartz were examined for the substrate 11. Using a fused silica substrate, (0°, 110°, 0°) LT thin film 12 (thickness 0.15 wavelength) / fused An acoustic wave device was formed on a quartz substrate with an Al interdigital transducer 13 having a thickness of 0.08 wavelength. The frequency characteristics of impedance (Z) for the sensor 10 are shown in Table 7. The constants of various materials used for the thin film of the substrate 11 are shown in Table 7. Fused silica is 100% SiO2 by mass, and the sound velocity of the bulk shear wave is approximately 3,757 m / s. As shown in Figure 28, a good impedance ratio of 76 dB is obtained with a fused silica substrate. As shown in Table 7, the SiO2 film has the same constant as fused silica, and is composed of SiO The film containing the component is a film such as SiOF or SiON, and when the component other than SiO is Z, SiO x Z y In the chemical formula, x represents a film in which x + y is 30% or more. This film has the same properties as an SiO2 film.

[0083] [Table 7]

[0084] In FIG. 29, the substrate 11 may be made of Pyrex glass, borosilicate glass, synthetic quartz, or fused silica. , and quartz glass substrates were used, and LT thin film 12 (thickness 0. 15 wavelength) / An aluminum interdigital electrode 13 with a thickness of 0.08 wavelength was formed on each of the various substrates. The dependence of the impedance ratio on the film thickness of LT for the acoustic wave device 10 is shown in FIG. As shown above, fused silica, synthetic silica, and quartz glass substrates with high SiO2 content have a high LT Pyrex glass with a film thickness of 0.52 wavelengths or less and an SiO2 content of approximately 70 to 80 mass% For borosilicate glass substrates, the LT film thickness is 0.34 wavelengths or less, and the good performance is 70 dB or more. In addition, when an LN thin film is used instead of an LT thin film, It has also been confirmed that similar characteristics can be obtained.

[0085] Figure 30 shows the (0°, 110°, 0°) LT thin film 12 / SiO2 film / high acoustic velocity substrate, and , (0°, 131°, 0°) LN thin film 12 / SiO2 film / high acoustic velocity substrate with a thickness of 0. The acoustic wave device 10 having the Al interdigital transducer 13 with a wavelength of 0.8 was The impedance ratio depends on the thickness of the SiO2 film. Al2O3), SiC, etc., on a high acoustic velocity substrate with a shear wave acoustic velocity of 5,900 m / s or more. As shown in Fig. 6(b), the thickness of the sapphire substrate is 70d. However, as shown in Figure 30, the impedance ratio can be reduced by 1 / 2 or less. By forming a 0.15 wavelength SiO2 film at the boundary between the LT thin film and the thin film, B. A large impedance ratio of 78 dB can be obtained with the LN thin film. When the wavelength is 0.3 or more, the LT thin film has a large impedance of 75 dB and the LN thin film has a large impedance of 79 dB. Since a substrate with a thick SiO2 film will warp, Therefore, the thickness of the SiO2 film should be less than one wavelength, preferably Preferably, it should be 0.5 wavelength or less.

[0086] [Study on interdigital electrodes] The optimum thickness and metallization ratio of the interdigital transducer 13 were investigated. (a) and (b) show (0°, 110°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 132.75°, 90°) On the quartz substrate 11, interdigital electrodes 13 made of various materials are For the acoustic wave devices 10 in which the respective resonators were formed, the band and inductance of the respective resonators were measured. The figure shows the dependence of the impedance ratio on the thickness of the interdigital transducer 13. The metallization of the interdigital electrode 13 was made of Cu, Mo, and Pt. The ion ratio was set to 0.5.

[0087] As shown in FIG. 31(a), regardless of the material of the interdigital transducer 13, the thickness of the electrode A bandwidth of 4% or more is obtained in the wavelength range of 0.005 to 0.2. As shown, the interdigital electrode 13 has a density of 2,699 kg / m 3 When the electrode thickness is 70dB or more for 0.005 to 0.32 wavelengths, 73dB or more for 0.005 to 0.28 wavelengths, An impedance ratio of 75 dB or more is obtained at wavelengths of 0.005 to 0.25. The density of the electrode 13 is 8,930 kg / m 3 When the electrode thickness is 0.005 mm, the 70dB or more at wavelengths up to 0.20, 73dB or more at wavelengths from 0.005 to 0.19, 0.005 An impedance ratio of 75 dB or more is obtained at ~0.18 wavelength.

[0088] The interdigital electrode 13 has a density of 10,219 kg / m 3 When made of Mo, the electrode thickness is 70dB or more for wavelengths of 0.005 to 0.28, and 73dB or more for wavelengths of 0.005 to 0.27. Furthermore, an impedance ratio of 75 dB or more is obtained at wavelengths of 0.005 to 0.20. , the density of the interdigital electrode 13 is 21,400 kg / m 3 When made of Pt, the electrode thickness is 0. 70dB or more for wavelengths from 0.005 to 0.20, 73dB or more for wavelengths from 0.005 to 0.13, and 0. An impedance ratio of 75 dB or more is obtained at wavelengths from 0.05 to 0.11.

[0089] Thus, the optimum thickness varies depending on the type of electrode, and the lower the density of the electrode, the larger the intrinsic The optimum thickness range for obtaining a good impedance ratio is wide. The relationship between the optimum thickness range and the electrode density is shown in Table 8. "A" is the condition for obtaining an impedance ratio of 70dB or more, and "B" is the condition for obtaining an impedance ratio of 73dB or more. "A" is the condition where an impedance ratio of 75 dB or more is obtained. When using alloys or multilayer electrode films, the average value is calculated from the electrode thickness and theoretical electrode density. The uniform density can be calculated, and the optimum electrode thickness can be calculated from Table 8 based on the average density. It has been confirmed that the relationship in Table 8 is applicable even when the piezoelectric thin film 12 is made of LN.

[0090] [Table 8]

[0091] Figure 32(a) and (b) show the LT thin film 12 (thickness 0.15 mm) at (0°, 110°, 0°). Wavelength) / (0°, 132.75°, 90°) On the quartz substrate 11, interdigital electrodes of each material are For the acoustic wave device 10 in which the 13 is formed, the band and The dependence of the metallization ratio of the electrodes on the impedance ratio is shown. are the optimum film thicknesses obtained from FIG. When l, the electrode thickness is 0.08 wavelength, when Cu it is 0.045 wavelength, when Mo it is 0.05 wavelength For Pt, the wavelength was 0.03.

[0092] As shown in FIG. 32(a), regardless of the material of the interdigital transducer 13, the metallized The widest bandwidth is obtained when the polarization ratio is smaller than 0.5. As shown in b), the metallization with higher impedance ratio depending on the type of electrode. The optimum metallization ratio is different. The relationship between the impedance ratio and the density of the electrode is shown in Table 9. "A" in Table 9 indicates a high impedance ratio (approximately 75 "B" indicates a higher impedance ratio (approximately 76.5dB) "C" is the condition where the highest impedance ratio (approximately 77.5 dB or more) is obtained. When using alloys or multilayer electrode films, the theoretical electric potential and the electrode thickness are The average density is calculated from the pole density, and the optimum metallization is selected from Table 9 based on the average density. The relationship in Table 9 can also be applied when the piezoelectric thin film 12 is made of LN. We have confirmed that this is possible.

[0093] [Table 9]

[0094] [Variations of the arrangement of the quartz substrate, piezoelectric thin film, interdigital electrode, and short-circuit electrode] FIG. 1(b) shows an acoustic wave device 10 including an IDT (interdigital transducer) 13 and a piezoelectric thin film. 12 / The structure of the quartz crystal substrate 11 is shown, including the short-circuit electrode 31, as shown in FIGS. 33(a) to 33(d). ) is also possible. In FIG. 33, the piezoelectric thin film 12 is made of LiTaO3 crystal. (LT) and the substrate 11 is a quartz substrate. The structure is composed of T13 / piezoelectric thin film 12 (LT) / substrate 11, and is the same as that shown in Figure 1(b). FIG. 33(b) shows a structure of an IDT 13 / piezoelectric thin film 12 (LT) / short-circuit electrode 31 / substrate 11. FIG. 33(c) shows a structure of the piezoelectric thin film 12 (LT) / IDT 13 / substrate 11, and the IDT 1 3 is embedded on the side of the substrate 11 (top view), and on the side of the piezoelectric thin film 12 (bottom view). Figure 33(d) shows a structure of short-circuit electrode 31 / piezoelectric thin film 12 (LT) / ID. T13 / substrate 11, with IDT 13 embedded in the side of substrate 11 (see above). Some are embedded on the side of the piezoelectric thin film 12 (see the lower diagram).

[0095] Figures 34(a) and (b) show the acoustic wave devices with the four structures shown in Figures 33(a) to (d). 10, the band and impedance ratio of the obtained elastic wave resonators, LT Here, the piezoelectric thin film 12 is a (0°, 110°, 0°) LT thin film. The quartz substrate 11 is a (0°, 132.75°, 90°) quartz substrate, and the IDT 13 is The short-circuit electrode 31 is an Al electrode with a thickness of 0.08 wavelength. 1 and the piezoelectric thin film 12, and all of the electrode surfaces are electrically shorted. The short-circuit electrode 31 is a floating electrode that is not connected to the IDT 13. .

[0096] As shown in FIG. 34(a), regardless of the LT film thickness, the The IDT / LT / quartz structure provides the widest bandwidth. As shown in Fig. 33(a), the IDT / LT / crystal and the ID shown in Fig. 33(b) The T / LT / short-circuit electrode / quartz crystal structure provides a large impedance ratio. The required bandwidth varies depending on the application, but the impedance ratio has a significant effect on the mechanical Q. Therefore, even with the structure shown in FIG. 33(b), It is believed that similar effects can be obtained under the same conditions as the structure shown in a).

[0097] As shown in FIG. 35, in the acoustic wave device 10, the entire IDT 13 is formed on the piezoelectric thin film 12. The lower part may be embedded in the piezoelectric thin film 12 and the upper part may be embedded in the piezoelectric thin film 12. The two structures and the structure shown in FIG. For the acoustic wave device 10 having the structure of Here, the piezoelectric thin film 12 is a (0°, 110°, 0°) LT thin film. The crystal substrate 11 is a (0°, 132.75°, 90°) crystal substrate, and the IDT 13 As shown in Figure 35, the LT film thickness is 0.5 wavelengths. Below this length, both structures have similar impedance ratios. As shown in FIG. 1, the structure in which the IDT 13 is embedded in the piezoelectric thin film 12 is different from the structure in which the IDT 13 is not embedded. Compared to the conventional method, the speed of sound is faster and it is thought to be advantageous for higher frequencies.

[0098] [Modification with bonding film] As shown in FIG. 1(c), the acoustic wave device 10 has a quartz substrate 11 and a piezoelectric thin film 12. The insulating bonding film 32 may be formed on the surface of the substrate 30. The bonding film 32 is made of a hard material with low sound absorption. It is preferable that the material is made of, for example, tantalum pentoxide (Ta2O5), zinc oxide (Z nO), silicon dioxide (SiO2), polycrystalline Si, silicon nitride (Si x N y :x,y is an integer), etc.

[0099] Figure 36(a) to (c) shows the LT thin film 12 (thickness 0.15 wavelength) at (0°, 110°, 0°). ) / bonding film 32 / (0°, 132.75°, 90°) on the quartz substrate 11, The results obtained for the acoustic wave device 10 having the Al interdigital transducer 13 of eight wavelengths were as follows. The thickness of the bonding film 32 is shown to be dependent on the acoustic velocity, bandwidth, and impedance ratio of the elastic wave resonator. The bonding film 32 is made of tantalum pentoxide (Ta2O5), zinc oxide (ZnO), and Silicon (SiO2), polycrystalline Si, and silicon nitride (Si x N y :x,y are integers) The material constants of the bonding film 32 used are shown in Table 7. Although not shown, the material constants of materials that can be used as the bonding film 32 are also shown.

[0100] As shown in FIGS. 36(a) to 36(c), the bonding film 32 has a bulk shear wave acoustic velocity [(C 44 E / Dense degrees) 1 / 2 ] is made of Ta2O5 or ZnO, which has a sound velocity significantly slower than that of quartz, As the thickness of 32 increases, the sound velocity of the SAW decreases rapidly and the bandwidth also narrows rapidly. In addition, the bonding film 32 is made of Si, which has a high shear wave velocity. x N y In this case, the acoustic velocity of the SAW increases as the thickness of the bonding film 32 increases. The band becomes slightly narrower and the impedance becomes slightly smaller. In the case of polycrystalline Si or SiO2, the shear wave acoustic velocity of which is close to that of quartz, the thickness of the bonding film 32 is As the impedance increases, the sound velocity of the SAW changes slightly and the bandwidth narrows slightly. The impedance ratio does not show any significant fluctuations up to three wavelengths of the thickness of the bonding film 32. In the case of the SiO2 film, it has a positive TCF, so it is effective in improving the TCF. TCF is plus 5 ppm / °C or more for wavelengths of 0.1 or more, plus 10 ppm / °C for wavelengths of 0.2 or more The TCF is improved by more than m / ℃. In addition, the same TCF can be obtained even if the azimuth angle θ of the crystal is shifted by about ±10°. Moreover, as shown in FIG. 36(c), when the SiO2 film is 1.2 wavelengths or less, the impedance As shown in Figure 36(b), the SiO2 film has a wavelength of 0.3 or more. Below this, there is no reduction in the bandwidth, and 94% of the bandwidth can be secured even with 0.5 wavelengths. SiO with iO as the main component x Z y The film has the same properties as SiO2.

[0101] From Table 7 and FIG. 36, the relationship between the bonding film 32 and its optimum thickness depends on the bulk shear wave velocity. The characteristics of the acoustic wave device 10 when the bonding film 32 is used are shown in FIG. As shown in (c), when the thickness of the bonding film 32 is 0.34 wavelength or less, the bulk shear wave velocity is almost Regardless of thickness, a large impedance ratio can be obtained. The optimum thickness of the bonding film 32 depends greatly on the bulk shear wave acoustic velocity of the bonding film 32. When the thickness of the bonding film 32 is 0.13 wavelength or less, a larger impedance ratio is obtained. An even larger impedance ratio can be obtained when the thickness of 32 is 0.04 wavelength or less.

[0102] Table 10 shows the relationship between the shear wave acoustic velocity of the bonding film 32 and the optimum film thickness of the bonding film 32. "A" in the middle indicates the condition for obtaining a high impedance ratio (generally 70dB or more), and "B" indicates the condition for obtaining a higher impedance ratio (generally 70dB or more). The condition for obtaining a high impedance ratio (generally 73dB or more), "C" is the highest impedance. The relationship in Table 10 shows the conditions under which a good impedance ratio (approximately 75 dB or more) can be obtained. It has been confirmed that this method is also applicable to cases where the conductive thin film 12 is made of LN.

[0103] [Table 10]

[0104] [Modification example in case of multiple bonding films] The case where the bonding layer 32 has two layers was examined. (0°, 110°, 0°) LT thin film 1 2 (thickness 0.15 wavelength) / 1st layer of bonding film 32 / 2nd layer of bonding film 32 / (0°, 132. On a quartz substrate 11 (75°, 90°), an Al interdigital transducer 13 having a thickness of 0.08 wavelength is formed. For the formed acoustic wave device 10, the impedance ratio of the resonator is The thickness dependence of the first and second layers was calculated. The materials are designated as Vs1, Vs2, Vs3, and Vs4, and two of these are used as the bonding film 3. We calculated the results for various combinations of the first and second layers of 2. Ta2O5, Vs2 to ZnO, Vs3 to SiO2, Vs4 to Si x N y It was considered as follows.

[0105] As a result of the investigation, the first and second layers of the bonding film 32 were designated as Vs3 film and Vs4 film, respectively. Vs4 membrane and Vs3 membrane, Vs2 membrane and Vs3 membrane, Vs1 membrane and Vs3 membrane The results of the film thickness dependence of the Vs3 (SiO2) film are shown in Figures 37(a) to (d). The numerical values ​​in the figure indicate the thickness (wavelength) of the film of the bonding film 32 that is different from Vs3. Table 11 shows the results of these investigations on the first and second layers of the bonding film 32. The relationship between the combination of these and the optimum total film thickness is shown. "A" in Table 11 indicates a high impedance ratio ( "B" indicates a higher impedance ratio (generally 73dB or more). "C" is the condition where the highest impedance ratio (approximately 75 dB or more) is obtained. The conditions for a good impedance ratio are as shown in Table 1 for the first layer of the bonding film 32. The total thickness of the first and second layers must satisfy the conditions in Table 11. As shown in 37(a)-(d), when the second layer is an SiO2 film, the type and thickness of the first layer By selecting this, the SiO2 film can achieve an impedance ratio of 75 dB or more within 1.5 wavelengths. can be obtained.

[0106] [Table 11]

[0107] Next, we investigated the case where the bonding layer 32 has three layers. (0°, 110°, 0°)LT Thin film 12 (thickness 0.15 wavelength) / first layer of bonding film 32 / second layer of bonding film 32 / bonding film 32 The third layer (0°, 132.75°, 90°) of the quartz crystal substrate 11 is For the acoustic wave device 10 having the Al interdigital transducer 13, the impedance of the resonator The dependence of the shear wave acoustic velocity on the thickness of the third layer of the bonding film 32 was calculated. The four materials with different values ​​are designated as Vs1, Vs2, Vs3, and Vs4, respectively. Various combinations of these three as the first, second and third layers of the bonding film 32 Vs1 was Ta2O5, Vs2 was ZnO, Vs3 was SiO2, and Vs4 was Si x N y It was considered as follows.

[0108] From the results of the investigation, the first layer of the bonding film 32 was Vs3 (thickness 0.1 wavelength), and the second layer was Vs4 ( The results are as follows: the thickness is 0.1 wavelength, and the third layer is Vs1, Vs2, Vs3, or Vs4. The results are shown in Figure 38(a). As shown in Figure 38(a), the third layer is Vs1 (Ta2O5) In the case of Vs2 (ZnO) film, an impedance ratio of 70 dB or more can be obtained with a film thickness of one wavelength or less. The third layer is a Vs3 (SiO2) film or a Vs4 (Si x N y ) When the film is used, the film thickness is 5 wavelengths or less An impedance ratio of about 75 dB is obtained.

[0109] In addition, the first layer of the bonding film 32 was Vs4 (thickness 0.01 wavelength), and the second layer Vs3 (thickness 0.1 wavelength), and the third layer was Vs1, Vs2, Vs3, or Vs4. The results are shown in Figure 38(b). As shown in Figure 38(b), the third layer is Vs1 (Ta 2O5) film or Vs2 (ZnO) film, the impedance is 70 dB or more when the film thickness is less than one wavelength. The third layer is a Vs3 (SiO2) film or a Vs4 (Si x N y ) film, film thickness 5 An impedance ratio of approximately 73 dB is obtained below the wavelength.

[0110] Table 12 shows the combinations of the first to third layers of the bonding film 32 obtained from the results of these studies. The relationship between the thickness and the optimum total film thickness is shown. 0dB or higher), "B" indicates a higher impedance ratio (generally 73dB or higher) The condition for obtaining a good impedance ratio is as follows: The first layer should meet the conditions in Table 10, and the total thickness of the first to third layers should meet the conditions in Table 12. Even if the bonding film 32 has four or more layers, the first layer must satisfy Table 10. The material constants used to calculate the sound velocity and other properties are publicly available. When the thin film is a mixture of two or more films, the arithmetic mean of the individual films may be used. As shown in Figures 38(a) and 38(b), when the first or second layer is an SiO2 film, In this case, by selecting the type and thickness of layers other than the SiO2 film, the SiO2 film can be , an impedance ratio of 75 dB or more can be obtained.

[0111] [Table 12]

[0112] [Study on the use of higher modes of surface acoustic waves] The acoustic wave device 10 was investigated using a higher mode of a surface acoustic wave. In Figure 39, (0°, 110°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 1 32.75°, 90°) on a quartz substrate 11, an aluminum interdigital transducer 11 having a thickness of 0.6 wavelengths is 1 shows the frequency characteristics of impedance (Z) for an acoustic wave device 10 in which the semiconductor device 3 is formed. As shown in Figure 39, the fundamental mode (0-th) is at 1.25 GHz and its higher modes are at 3.6 GHz. Mode (1-th) was confirmed.

[0113] FIG. 40 shows the results of the acoustic wave propagation in higher modes for interdigital transducers 13 made of various materials. The relationship between the impedance ratio and the electrode thickness of the device 10 is shown. As 0, (0°, 110°, 0°) LT thin film 12 (thickness 0.15 wavelength) / (0°, 13 2.75°, 90°) on a quartz substrate 11, various interdigital transducers 13 with a thickness of 0.6 wavelengths are As shown in Figure 40, the optimum thickness varies depending on the type of electrode. The lower the density of the electrode, the wider the range of the optimum thickness at which a large impedance ratio can be obtained. The relationship between the optimum thickness range and the electrode density is shown in Table 13. Table 13 shows the results when the metallization ratio of the interdigital transducer 13 is 0.5.

[0114] [Table 13]

[0115] When an alloy or multilayer electrode film is used as the interdigital electrode 13, the electrode thickness and the theoretical electrode Calculate the average density from the density, and based on that average density, find the optimum electrode thickness from Table 13. In addition, since the metallization ratio in Table 13 is 0.5, Considering the metallization ratio, for example, if the metallization ratio is 0.25, the electrode thickness is , 0.5 / 0.25=2, so we need to consider a thickness twice that of Table 13.

[0116] The thickness of the piezoelectric thin film 12 was examined when using a higher mode of surface acoustic waves. FIG. 41 shows the structure of the IDT 13 / piezoelectric thin film 12 / quartz crystal substrate 11 shown in FIG. 33(a), and 33(b) shows the structure of IDT 13 / piezoelectric thin film 12 / short-circuit electrode 31 / quartz crystal substrate 11. For the acoustic wave device 10, the film of the piezoelectric thin film 12 having the impedance ratio obtained is Here, the piezoelectric thin film 12 is a (0°, 110°, 0°) LT thin film, The quartz crystal substrate 11 is a (0°, 132.75°, 90°) quartz crystal substrate, and the IDT 13 is 41, the Au electrode has a width of 0.2 wavelength. In the structure of (a), when the LT film thickness is 0.35 to 9.3 wavelengths, the structure having the short-circuit electrode 31 In the structure of 33(b), when the LT film thickness is 0.5 to 9 wavelengths, the impedance is 70 dB or more. In addition, when an LN thin film is used instead of an LT thin film, similar characteristics are obtained. It has also been confirmed that sexual activity can be obtained.

[0117] Figure 42(a) and (b) show the LT thin film 12 / (0°) at (0°, 110°, 0°), respectively. °, θ, 0°) quartz crystal substrate 11, and (0°, 110°, 0°) LT thin film 12 / (0°, θ, 90°) on a quartz substrate 11, an Au interdigital transducer 13 is formed. 0, the impedance ratio of the higher mode (1-th) of the obtained elastic wave resonator, The θ dependence of the plate 11 is shown. Here, the thickness of LT is set to 0.5 wavelengths (λ), 1 wavelength, 2 wavelengths, The thickness of interdigital transducer 13 was set to 0.2 wavelengths.

[0118] As shown in Figures 42(a) and (b), when the LT film thickness is 0.5 to 4 wavelengths, almost all In the entire θ range, an impedance ratio of approximately 70 dB or more is obtained. As in the case of the electrode, even if the LT film thickness is thick, the thickness of the Au of the interdigital transducer 13 is 0.2 wave. This is thought to be because of its length and relatively thick structure.

[0119] [Method for manufacturing an acoustic wave device according to an embodiment of the present invention] As shown in FIG. 43, the acoustic wave device 10 is manufactured as follows. A piezoelectric substrate 12a made of T or LN is prepared (see FIG. 43(a)). The piezoelectric substrate 12a is bonded to the piezoelectric substrate 12a (see the left diagram of FIG. 43(b)). When a short-circuit electrode 31 or a bonding film 32 is formed between the crystal substrate 11 and the crystal substrate 11, After bonding the short-circuit electrode 31 and the bonding film 32 on top of the piezoelectric substrate 12a (see FIG. (See the right figure of 43(b)). Each substrate and film may be bonded using adhesive, but the bonding surface should be They may also be bonded by so-called direct bonding, in which they are bonded after being activated by plasma or the like.

[0120] After bonding, the piezoelectric substrate 12a is polished to form a thin film (piezoelectric thin film 12) (see FIG. 43(c)). An electrode film made of Al or the like is formed on the surface of the piezoelectric thin film 12, and a resist is applied thereon. After coating, patterning (exposure and development) is performed, followed by etching, and then the resist is removed. This forms the interdigital transducer 13 and the reflector 14 (see FIG. 43(d)). By separating the unnecessary portions, the acoustic wave device 10 can be manufactured (FIG. 4 3(e)). Figures 43(c) to (e) show the case of the left diagram of Figure 43(b). However, in the case of the right diagram of FIG. 43(b), a short circuit occurs between the quartz substrate 11 and the piezoelectric thin film 12. An acoustic wave device 10 having a pole 31 and a bonding film 32 can be manufactured. [Explanation of symbols]

[0121] 10 Acoustic Wave Devices 11 Substrate (quartz substrate) 12 Piezoelectric thin film (LT thin film, LN thin film) 12a Piezoelectric substrate 13 Interdigital transducer (IDT) 21 Electrode finger 14 Reflector 31 Short-circuit electrode 32 Bonding film 50 Conventional Acoustic Wave Devices 51 Piezoelectric substrate 52 Interdigital transducer (IDT) 53 Reflector

Claims

1. A method for manufacturing an acoustic wave device that utilizes surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, The method is configured such that the substrate is formed from a material having a bulk wave transverse wave acoustic velocity constant of 3,400 to 4,800 m / s, and the acoustic velocity of the surface acoustic wave propagating through the substrate is faster than the acoustic velocity of the surface acoustic wave propagating through the piezoelectric thin film by adjusting the Euler angles of the piezoelectric thin film.

2. A method for manufacturing an acoustic wave device that utilizes surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, a method in which the Euler angles of the substrate are (0°±5°, 70° to 165°, 0°±5°), (0°±5°, 95° to 155°, 90°±5°), or crystallographically equivalent Euler angles, and the Euler angles of the piezoelectric thin film are adjusted so that the sound velocity of the surface acoustic wave propagating through the substrate is faster than the sound velocity of the surface acoustic wave propagating through the piezoelectric thin film.

3. A method for manufacturing an acoustic wave device utilizing surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, The Euler angles of the substrate are (0°±5°, 0° to 125°, 0°±5°), (0°±5°, 0° to 36°, 90°±5°), (0°±5°, 172° to 180°, 90°±5°), (0°±5°, 120° to 140°, 30° to 49°), (0°±5°, 25° to 105°, 0°±5°), (0°±5°, 0 to 45°, 15° to 35°), (0°±5°, 10° to 20°, 60° to 70°), (0°±5°, 90° to 18 and a piezoelectric thin film having a thickness of 1000 nm or less, the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less, the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less, and the thickness of the piezoelectric thin film being 1000 nm or less,

4. A method for manufacturing an acoustic wave device utilizing surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, a piezoelectric thin film having a piezoelectric effect, the piezoelectric effect being such that the sound velocity of the surface acoustic wave propagating through the substrate is greater than the sound velocity of the surface acoustic wave propagating through the piezoelectric thin film by adjusting the Euler angles of the substrate to be (20°±5°, 120°±10°, 115°±10°), (0°±5°, 90°±5°, 0°±10°), (0°±5°, 90°±5°, 75°±10°), (0°±5°, 0°±5°, 0°±10°), (0°±5°, 0°±5°, 60°±10°), or crystallographically equivalent Euler angles thereto, and the Euler angles of the piezoelectric thin film are adjusted.

5. A method for manufacturing an acoustic wave device utilizing surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, The piezoelectric thin film is LiTaO ３ a piezoelectric thin film including a crystal, the Euler angles of which are (90°±5°, 90°±5°, 33° to 55°), (90°±5°, 90°±5°, 125° to 155°) or crystallographically equivalent thereto, and the Euler angles of the substrate are adjusted so that the sound velocity of the surface acoustic wave propagating through the substrate is faster than the sound velocity of the surface acoustic wave propagating through the piezoelectric thin film.

6. A method for manufacturing an acoustic wave device utilizing surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital electrode in contact with the piezoelectric thin film; Including, The piezoelectric thin film is LiNbO ３ a piezoelectric thin film including a crystal, the Euler angles of which are (90°±5°, 90°±5°, 38° to 65°), (90°±5°, 90°±5°, 118° to 140°), or crystallographically equivalent Euler angles thereof, and the Euler angles of the substrate are adjusted so that the sound velocity of the surface acoustic wave propagating through the substrate is faster than the sound velocity of the surface acoustic wave propagating through the piezoelectric thin film.

7. A method for manufacturing an acoustic wave device utilizing surface acoustic waves, comprising: providing or forming a substrate containing 70% by mass or more of silicon dioxide (SiO 2 ) so as to exhibit a positive frequency-temperature characteristic; bonding a piezoelectric substrate comprising a LiTaO 3 crystal or a LiNbO 3 crystal onto the substrate; polishing the piezoelectric substrate to form a piezoelectric thin film; forming an interdigital transducer in contact with the piezoelectric thin film; mounting a Si-containing film between the substrate and the piezoelectric thin film; Including, The Si-containing film is SiO ２ or containing 30% or more of SiO, the substrate is formed from a material having a bulk wave transverse wave acoustic velocity of 5,900 m / s or more as a constant, so that the acoustic velocity of the surface acoustic wave propagating through the substrate is faster than the acoustic velocity of the surface acoustic wave propagating through the piezoelectric thin film; The method, wherein the Si-containing film has a thickness of 0.15 to 1 times the wavelength of the surface acoustic wave.

8. The method of claim 7, wherein the Si-containing film has a thickness of 0.3 to 0.5 times the wavelength of the surface acoustic wave.

9. 8. The method of claim 1, wherein the interdigital transducer has a thickness as shown in Table 1 depending on its density. 【Table 1】

10. The method of any one of claims 1 to 7, wherein the interdigital transducers have metallization ratios as shown in Table 2 according to their densities. 【Table 2】

11. an insulating bonding film is provided between the substrate and the piezoelectric thin film; The method according to any one of claims 1 to 7, wherein the bonding film has a thickness of 0.34 wavelengths or less.

12. an insulating bonding film is provided between the substrate and the piezoelectric thin film; The method according to any one of claims 1 to 7, wherein the bonding film has one or more layers, and the layer closest to the piezoelectric thin film has a thickness shown in Table 3 according to its bulk shear wave velocity. 【Table 3】

13. the surface acoustic wave has a higher mode; 8. The method of claim 1, wherein the interdigital transducer has a thickness as shown in Table 4 depending on its density. 【Table 4】

14. the surface acoustic wave has a higher mode; The method according to any one of claims 1 to 7, wherein the piezoelectric thin film has a thickness of 0.35 to 9.3 times the wavelength of the surface acoustic wave.

15. The method according to any one of claims 1 to 7, wherein the surface acoustic waves include one or both of leaky surface acoustic waves and longitudinal leaky surface acoustic waves.

16. The piezoelectric thin film is LiNbO ３ Contains crystals, The method according to any one of claims 1 to 7, wherein the surface acoustic wave is a Rayleigh wave.

17. The method of any one of claims 1 to 7, further comprising mounting a shorting electrode and / or an insulating bonding film between the substrate and the piezoelectric thin film.

18. 8. The method of claim 1, wherein the interdigital transducers are mounted such that at least a lower portion of the interdigital transducers is embedded in the piezoelectric thin film and / or at least an upper portion of the interdigital transducers protrudes from the piezoelectric thin film.

19. The method of any one of claims 1 to 6, wherein providing or forming the substrate comprises providing or forming a quartz substrate.

20. the substrate comprises an isotropic substrate; The method according to any one of claims 1 to 7, wherein the piezoelectric thin film has a thickness of 0.001 mm or more and less than 0.01 mm.

21. the substrate includes a quartz substrate; 7. The method of claim 1, wherein Euler angles of the substrate are adjusted so that the sound velocity of the surface acoustic wave propagating through the substrate is 4,500 m / s or more, 4,800 m / s or more, or 5,000 m / s or more.

22. the substrate includes a quartz substrate; 7. The method according to claim 1, wherein the Euler angles of the substrate are adjusted so that the surface acoustic waves propagating through the substrate include leaky acoustic waves mainly composed of SH components or S waves having a sound velocity of 4,500 m / s or more.

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