WO2020184621A1 - 弾性波装置 - Google Patents
弾性波装置 Download PDFInfo
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- WO2020184621A1 WO2020184621A1 PCT/JP2020/010592 JP2020010592W WO2020184621A1 WO 2020184621 A1 WO2020184621 A1 WO 2020184621A1 JP 2020010592 W JP2020010592 W JP 2020010592W WO 2020184621 A1 WO2020184621 A1 WO 2020184621A1
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- film
- hypersonic
- elastic wave
- sound velocity
- piezoelectric layer
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Images
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02543—Characteristics of substrate, e.g. cutting angles
- H03H9/02574—Characteristics of substrate, e.g. cutting angles of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02543—Characteristics of substrate, e.g. cutting angles
- H03H9/02559—Characteristics of substrate, e.g. cutting angles of lithium niobate or lithium-tantalate substrates
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02637—Details concerning reflective or coupling arrays
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02866—Means for compensation or elimination of undesirable effects of bulk wave excitation and reflections
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
- H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
- H03H9/174—Membranes
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
Definitions
- the present invention relates to an elastic wave device.
- Patent Document 1 discloses an example of an elastic wave device.
- a support substrate, a bonding film, a hypersonic film, a low sound velocity film, and a piezoelectric film are laminated in this order.
- a plurality of IDT electrodes are provided on the piezoelectric film.
- An object of the present invention is to provide an elastic wave device capable of suppressing a response in a higher-order mode.
- a support substrate In a wide aspect of the elastic wave device according to the present invention, a support substrate, a first high-sound velocity film provided on the support substrate, and a low-sound velocity film provided on the first high-sound velocity film.
- a second treble film provided on the bass film, a piezoelectric layer provided on the second treble film, and an IDT electrode provided on the piezoelectric layer.
- the sound velocity of the bulk wave propagating in the low-pitched sound film is lower than the sound velocity of the bulk wave propagating in the piezoelectric layer, and the sound velocity of the bulk wave propagating in the first high-pitched sound film is high.
- the sound velocity of the bulk wave propagating in the second treble film is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer, and is equal to or higher than the sound velocity of the bulk wave propagating in the first treble film.
- a support substrate made of silicon, a first treble velocity film provided on the support substrate and containing silicon nitride, silicon oxynitride, or crystal, and the above-mentioned
- a bass velocity film provided on the first treble velocity film and made of a material mainly composed of silicon oxide, tantalum oxide, or a compound obtained by adding fluorine, carbon, or boron to silicon oxide, and on the bass velocity film.
- a second treble membrane made of a medium containing aluminum oxide, aluminum nitride, titanium nitride, silicon nitride, silicon nitride or DLC as a main component, and a lithium tantalate provided on the second treble membrane.
- a piezoelectric layer made of lithium niobate and an IDT electrode provided on the piezoelectric layer are provided.
- FIG. 1 is a front sectional view showing a part of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a plan view of the elastic wave device according to the first embodiment of the present invention.
- FIG. 3 is a schematic diagram for explaining the crystal orientation Si (111).
- FIG. 4 is a diagram showing the phase characteristics of the elastic wave device of the first embodiment and the comparative example of the present invention.
- FIG. 5 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is an aluminum oxide film. It is a figure which shows the characteristic.
- FIG. 1 is a front sectional view showing a part of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a plan view of the elastic wave device according to the first embodiment of the present invention.
- FIG. 3 is a schematic diagram for explaining the crystal orientation Si (111).
- FIG. 4
- FIG. 6 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is an aluminum nitride film. It is a figure which shows the characteristic.
- FIG. 7 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a silicon nitride film. It is a figure which shows the characteristic.
- FIG. 7 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a silicon nitride film. It is a figure which shows the characteristic.
- FIG. 8 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a titanium nitride film. It is a figure which shows the characteristic.
- FIG. 9 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a silicon carbide film. It is a figure which shows the characteristic.
- FIG. 10 shows the phase characteristics of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second hypersonic film in the elastic wave device is a DLC film. It is a figure which shows.
- FIG. 11 is a schematic view of an elastic wave device according to a second embodiment of the present invention.
- FIG. 1 is a front sectional view showing a part of an elastic wave device according to a first embodiment of the present invention.
- FIG. 2 is a plan view of the elastic wave device according to the first embodiment of the present invention. Note that FIG. 1 shows a portion of the IDT electrode described later near the pair of electrode fingers.
- the elastic wave device 1 has a piezoelectric substrate 2.
- the piezoelectric substrate 2 includes a support substrate 3, a first hypersonic film 4 provided on the support substrate 3, a hypersonic film 5 provided on the first hypersonic film 4, and a low sound velocity. It has a second hypersonic film 6 provided on the film 5 and a piezoelectric layer 7 provided on the second hypersonic film 6.
- the IDT electrode 8 is provided on the piezoelectric layer 7.
- the elastic wave device 1 of the present embodiment uses SH waves as the main mode. As shown in FIG. 2, reflectors 9A and 9B are provided on both sides of the IDT electrode 8 in the elastic wave propagation direction on the piezoelectric substrate 2.
- the elastic wave device 1 of the present embodiment is an elastic wave resonator.
- the elastic wave device according to the present invention is not limited to the elastic wave resonator, and may be a bandpass filter, a duplexer, a multiplexer, or the like having a plurality of elastic wave resonators.
- the piezoelectric layer 7 shown in FIG. 1 is a lithium tantalate layer of 55 ° Y-cut X propagation in this embodiment.
- the thickness of the piezoelectric layer 7 is 1 ⁇ or less.
- the electrode finger pitch refers to the distance between the centers of the electrode fingers.
- the cut angle, material, and thickness of the piezoelectric layer 7 are not limited to the above.
- the material of the piezoelectric layer 7, for example, lithium niobate or the like can be used as the material of the piezoelectric layer 7, for example.
- the support substrate 3 is a silicon substrate in this embodiment. More specifically, the crystal orientation of the silicon constituting the support substrate 3 is Si (111). The propagation angle of the support substrate 3 is 46 °. The propagation angle of the support substrate 3 is an angle formed by the elastic wave propagation direction and the silicon crystal axis [1-10] on the (111) plane.
- Si (111) is a substrate cut on the (111) plane orthogonal to the crystal axis represented by the Miller index [111] in the crystal structure of silicon having a diamond structure, as shown in FIG. Indicates that there is. It also includes other crystallographically equivalent surfaces.
- the crystal orientation, propagation angle, and material of the support substrate 3 are not limited to the above.
- the surface orientation of the surface on the first hypersonic film 4 side is (111). May be good.
- the first hypersonic film 4 is a relatively hypersonic film. More specifically, the sound velocity of the bulk wave propagating in the first hypersonic film 4 is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer 7.
- the first hypersonic film 4 is a silicon nitride film in the present embodiment.
- the material of the first treble speed film 4 is not limited to the above, and for example, aluminum oxide, silicon carbide, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, crystal, alumina, zirconia, and cordierite. , Murite, steatite, forsterite, magnesia, DLC (diamond-like carbon), diamond, and other media containing the above materials as main components can be used.
- the low sound velocity film 5 is a relatively low sound velocity film. More specifically, the sound velocity of the bulk wave propagating in the bass velocity film 5 is lower than the sound velocity of the bulk wave propagating in the piezoelectric layer 7.
- the bass velocity film 5 is a silicon oxide film. Silicon oxide is represented by SiO x . x is any positive number. In the elastic wave device 1, the silicon oxide constituting the bass velocity film 5 is SiO 2 .
- the material of the bass velocity film 5 is not limited to the above, and for example, a material containing glass, silicon nitride, tantalum oxide, or a compound obtained by adding fluorine, carbon, or boron to silicon oxide may be used. it can.
- the second hypersonic film 6 is a film having a higher sound velocity than the first hypersonic film 4. More specifically, the sound velocity of the bulk wave propagating in the second hypersonic film 6 is equal to or higher than the sound velocity of the bulk wave propagating in the first hypersonic film 4.
- the second hypersonic film 6 is an aluminum oxide film in this embodiment.
- the material of the second hypersonic film 6 is not limited to the above, and the above materials such as aluminum nitride (AlN), silicon nitride (SiN), titanium nitride (TiN), silicon carbide (SiC), and DLC can be used. A medium as a main component can be used.
- the material of the second hypersonic film 6 may be the same as the material of the first hypersonic film 4.
- the piezoelectric layer 7 is indirectly provided on the low sound velocity film 5 via the second high sound velocity film 6. Since the elastic wave device 1 has a configuration in which the first hypersonic film 4, the low sound velocity film 5, and the piezoelectric layer 7 are laminated, the energy of the main mode can be effectively confined to the piezoelectric layer 7 side. ..
- the IDT electrode 8 has a first bus bar 16 and a second bus bar 17 facing each other.
- the IDT electrode 8 has a plurality of first electrode fingers 18 each having one end connected to the first bus bar 16.
- the IDT electrode 8 has a plurality of second electrode fingers 19 each having one end connected to the second bus bar 17.
- the plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interleaved with each other.
- the IDT electrode 8 is composed of a laminated metal film in which a Ti layer, an Al layer, and a Ti layer are laminated in this order from the piezoelectric layer 7 side.
- the materials of the reflector 9A and the reflector 9B are the same as those of the IDT electrode 8.
- the materials of the IDT electrode 8, the reflector 9A and the reflector 9B are not limited to the above.
- the IDT electrode 8, the reflector 9A and the reflector 9B may be made of a single-layer metal film.
- the feature of the present embodiment is that the first hypersonic film 4, the low sound velocity film 5, the second hypersonic film 6 and the piezoelectric layer 7 are laminated, and the second high sound velocity film is provided.
- the sound velocity film 6 has a higher sound velocity than the first hypersonic film 4.
- the higher-order mode can be suppressed.
- the higher-order mode is a mode that occurs in the vicinity of twice the resonance frequency of the main mode.
- An elastic wave device having the configuration of the first embodiment and an elastic wave device of a comparative example were prepared.
- the comparative example differs from the first embodiment in that it does not have a second hypersonic film.
- the conditions of the elastic wave device having the configuration of the first embodiment are as follows.
- Support substrate Material: Silicon, Crystal orientation: Si (111), Propagation angle: 46 °
- First hypersonic film Material: Silicon nitride (SiN), Thickness: 300 nm Bass sound film: Material: Silicon oxide (SiO 2 ), Thickness: 300 nm
- Second hypersonic film Material: Aluminum oxide (Al 2 O 3 ), Thickness: 30 nm
- Piezoelectric layer Material: Lithium tantalate (LiTaO 3 ), Cut angle: 55 ° Y cut X propagation
- IDT electrode Material of each layer: Ti / Al / Ti from the piezoelectric layer side, Thickness of each layer: From the piezoelectric layer side 12nm / 100nm / 10nm
- IDT electrode finger pitch 1 ⁇ m
- Electrode finger logarithm 1 pair (calculated as 1 pair because it is based on the periodic boundary condition of the finite element method, but the logarithmic direction is assumed to be an infinite pair)
- the conditions of the elastic wave device of the comparative example are the same as those of the elastic wave device of the first embodiment except that it does not have the second hypersonic film.
- FIG. 4 is a diagram showing the phase characteristics of the elastic wave device of the first embodiment and the comparative example.
- the solid line shows the result of the first embodiment
- the broken line shows the result of the comparative example.
- the higher-order mode can be suppressed for the following reasons.
- the second hypersonic film 6 is provided between the low sound velocity film 5 and the piezoelectric layer 7.
- the second hypersonic film 6 has a higher sound velocity than the first hypersonic film 4.
- the speed of sound in the higher-order mode near twice the resonance frequency can be effectively increased, and the speed of sound in the higher-order mode is higher than the speed of sound of the bulk wave of the support substrate 3, so that the higher-order mode is supported by the support substrate. It can be leaked to the 3 side. Thereby, the higher-order mode can be suppressed.
- FIG. 4 it can be seen that the phase angle of the main mode in the first embodiment is almost the same as that of the comparative example without the second hypersonic film 6. Therefore, it can be seen that the strength of the main mode has not deteriorated.
- the elastic wave device 1 of the first embodiment for example, a higher-order mode located in the 5 GHz band can be suppressed. Therefore, the elastic wave device 1 can suppress the influence on the filter characteristics of the filter device when the pass band is commonly connected to the filter device located in the 5 GHz band and the antenna or the like.
- the elastic wave device 1 of the first embodiment it is possible to suppress the higher-order mode located in the middle band. Therefore, the elastic wave device 1 can suppress the influence on the filter characteristics of the filter device when the pass band is commonly connected to the filter device located in the middle band and the antenna or the like.
- the material of the second hypersonic film 6 is not limited to aluminum oxide.
- Table 1 below shows the preferred material and thickness combinations of the second hypersonic film 6.
- the higher-order mode is suppressed without increasing the response of the higher-order mode located in the middle band. Can be done. The details will be described below.
- the material and thickness of the second hypersonic film 6 when the material and thickness of the second hypersonic film 6 are changed, the high-order mode generated in the frequency range near twice the frequency of the main mode and the high located in the middle band.
- the phase characteristics of the next mode are shown.
- the elastic wave device exhibiting the phase characteristics below has the same configuration as that of the first embodiment except for the material of the second hypersonic film 6.
- the thickness (unit: ⁇ m) of the second hypersonic film of FIGS. 5 to 10 can be read as a wavelength ⁇ . For example, when the thickness of the Al 2 O 3 film of FIG. 5 is 0.2 ⁇ m, it is 0.1 ⁇ .
- FIG. 5 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is an aluminum oxide film. It is a figure which shows the characteristic. Note that FIG. 5 shows the relationship between the thickness of the second hypersonic film and the phase of each of the above modes.
- the white plot in FIG. 5 shows the phase of the higher-order mode occurring in the frequency range near twice the frequency of the main mode.
- the black plot shows the phase of the higher mode located in the middle band. The same applies to FIGS. 6 to 10 below.
- the phase of the higher-order mode is about 66.3 °.
- the phase of the higher-order mode is about 65.4 °.
- the phase angle of the higher-order mode is substantially constant. It can be seen that the phase angle of the higher-order mode located in the middle band is suppressed to less than 0 °.
- FIG. 6 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is an aluminum nitride film. It is a figure which shows the characteristic.
- the phase angle of the higher-order mode that occurs in the frequency range near twice that of the above is less than 60 °, which is smaller than that in the case where the second hypersonic film 6 is not provided.
- the thickness of the second hypersonic film 6 is very thin, it can be seen that there is an effect of suppressing the higher-order mode that occurs in the frequency range near twice the frequency of the main mode.
- the phase angle of the higher-order mode is substantially constant. It can be seen that the phase angle of the higher-order mode located in the middle band is suppressed to less than -40 °.
- FIG. 7 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a silicon nitride film. It is a figure which shows the characteristic.
- the frequency of the main mode is less than 60 °, which is smaller than that in the case where the second hypersonic film 6 is not provided.
- the thickness of the second hypersonic film 6 is very thin, it can be seen that there is an effect of suppressing the higher-order mode that occurs in the frequency range near twice the frequency of the main mode.
- the phase angle of the higher-order mode is substantially constant. It can be seen that the phase angle of the higher-order mode located in the middle band is suppressed to less than ⁇ 39 °.
- FIG. 8 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a titanium nitride film. It is a figure which shows the characteristic.
- the frequency of the main mode is about 65.4 °, which is smaller than the case where the second hypersonic film 6 is not provided.
- the thickness of the second hypersonic film 6 is very thin, it can be seen that there is an effect of suppressing the higher-order mode that occurs in the frequency range near twice the frequency of the main mode.
- FIG. 9 shows the phases of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second high-sound velocity film in the elastic wave device is a silicon carbide film. It is a figure which shows the characteristic.
- the frequency of the main mode is about 65.6 °, which is smaller than that in the case where the second hypersonic film 6 is not provided.
- the thickness of the second hypersonic film 6 is very thin, it can be seen that there is an effect of suppressing the higher-order mode that occurs in the frequency range near twice the frequency of the main mode.
- FIG. 10 shows the phase characteristics of the high-order mode generated in the frequency range near twice the frequency of the main mode and the high-order mode located in the middle band when the second hypersonic film in the elastic wave device is a DLC film. It is a figure which shows.
- the frequency of the main mode is less than 51 °, which is smaller than that in the case where the second hypersonic film 6 is not provided.
- the phase angle of the higher-order mode sharply decreases from the case where the thickness of the second hypersonic film 6 is 0.001 ⁇ m to the case where the thickness is 0.02 ⁇ m.
- the phase angle becomes larger as the second hypersonic film 6 becomes thicker, but when the thickness of the second hypersonic film 6 is 0.2 ⁇ m or less, It can be seen that it is suppressed to less than 56 °.
- a Rayleigh wave may be generated as an unnecessary wave.
- the Rayleigh wave phase derived from the second Euler angles ⁇ of the piezoelectric layer 7, the thickness of the piezoelectric layer 7, and the thickness of the second hypersonic film 6 may be ⁇ 70 [deg] or less. preferable.
- the second Euler angles are ⁇ in Euler angles ( ⁇ , ⁇ , ⁇ ).
- the relational expression between the phase of the Rayleigh wave and the second Euler angles ⁇ of the piezoelectric layer 7, the thickness of the piezoelectric layer 7, and the thickness of the second hypersonic film 6 was derived.
- the material of the second hypersonic film 6 is aluminum oxide, aluminum nitride, silicon nitride, titanium nitride, silicon carbide or DLC, the above relational expressions are shown.
- the thickness of the piezoelectric layer 7 is described as the LT film thickness.
- the Rayleigh wave phase derived by Equation 1 is preferably ⁇ 70 [deg] or less.
- the Rayleigh wave phase derived by Equation 2 is preferably ⁇ 70 [deg] or less.
- the Rayleigh wave phase derived by Equation 3 is preferably ⁇ 70 [deg] or less.
- the Rayleigh wave phase derived by Equation 4 is preferably ⁇ 70 [deg] or less.
- the Rayleigh wave phase derived by Equation 5 is preferably ⁇ 70 [deg] or less.
- the Rayleigh wave phase derived by Equation 6 is preferably ⁇ 70 [deg] or less.
- FIG. 11 is a schematic view of the elastic wave device according to the second embodiment.
- the elastic wave device 20 is a multiplexer having a first filter device 21A, a second filter device 21B, and a third filter device 21C.
- the first filter device 21A is a filter device including an elastic wave resonator having the same configuration as the elastic wave device 1 according to the first embodiment.
- the second filter device 21B has a pass band in the 5 GHz band.
- the third filter device 21C has a pass band in the middle band.
- the elastic wave device 20 has a common connection terminal 22.
- the first filter device 21A, the second filter device 21B, and the third filter device 21C are commonly connected to the common connection terminal 22.
- the common connection terminal 22 may be, for example, an antenna terminal connected to the antenna.
- the number of filter devices included in the elastic wave device 20 is not particularly limited.
- the elastic wave device 20 also has a filter device other than the first filter device 21A, the second filter device 21B, and the third filter device 21C connected to the common connection terminal 22.
- the first filter device 21A includes an elastic wave resonator having the same configuration as that of the first embodiment, it is possible to suppress a higher-order mode generated in a frequency range near twice the frequency of the main mode. Moreover, the response of the high-order mode of the middle band is small. Therefore, deterioration of the filter characteristics of the second filter device 21B and the third filter device 21C in the elastic wave device 20 can be suppressed.
- Elastic wave device 2 ... Piezoelectric substrate 3 ... Support substrate 4 ... First high-sound velocity film 5 . Low-sound velocity film 6 ... Second high-sound velocity film 7 ... Piezoelectric layer 8 ... IDT electrodes 9A, 9B ... Reflector 16, 17 ... 1st and 2nd bus bars 18, 19 ... 1st and 2nd electrode fingers 20 ... Elastic wave devices 21A to 21C ... 1st to 3rd filter devices 22 ... Common connection terminals
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Abstract
Description
第1の高音速膜:材料…窒化ケイ素(SiN)、厚み…300nm
低音速膜:材料…酸化ケイ素(SiO2)、厚み…300nm
第2の高音速膜:材料…酸化アルミニウム(Al2O3)、厚み…30nm
圧電体層:材料…タンタル酸リチウム(LiTaO3)、カット角…55°YカットX伝搬
IDT電極:各層の材料…圧電体層側からTi/Al/Ti、各層の厚み…圧電体層側から12nm/100nm/10nm
IDT電極の電極指ピッチ:1μm
電極指対数:1対(有限要素法の周期境界条件に基づくため1対で計算しているが、対数方向は無限対と仮定している。)
2…圧電性基板
3…支持基板
4…第1の高音速膜
5…低音速膜
6…第2の高音速膜
7…圧電体層
8…IDT電極
9A,9B…反射器
16,17…第1,第2のバスバー
18,19…第1,第2の電極指
20…弾性波装置
21A~21C…第1~第3のフィルタ装置
22…共通接続端子
Claims (7)
- 支持基板と、
前記支持基板上に設けられている第1の高音速膜と、
前記第1の高音速膜上に設けられている低音速膜と、
前記低音速膜上に設けられている第2の高音速膜と、
前記第2の高音速膜上に設けられている圧電体層と、
前記圧電体層上に設けられているIDT電極と、
を備え、
前記低音速膜を伝搬するバルク波の音速が、前記圧電体層を伝搬するバルク波の音速よりも低く、
前記第1の高音速膜を伝搬するバルク波の音速が、前記圧電体層を伝搬する弾性波の音速よりも高く、
前記第2の高音速膜を伝搬するバルク波の音速が、前記第1の高音速膜を伝搬するバルク波の音速以上である、弾性波装置。 - 前記第2の高音速膜の材料が、酸化アルミニウム、窒化アルミニウム、窒化ケイ素、窒化チタン、炭化ケイ素またはダイヤモンドライクカーボンである、請求項1に記載の弾性波装置。
- 前記支持基板がシリコン基板である、請求項1~3のいずれか1項に記載の弾性波装置。
- 前記支持基板の前記第1の高音速膜側の面の面方位が(111)である、請求項4に記載の弾性波装置。
- 前記圧電体層の第2オイラー角θと、前記圧電体層の厚みと、前記第2の高音速膜の厚みから導出されるレイリー波位相が-70[deg]以下となる、請求項1~5のいずれか1項に記載の弾性波装置。
- シリコンからなる支持基板と、
前記支持基板上に設けられ、窒化ケイ素、酸窒化ケイ素、または、水晶を含む第1の高音速膜と、
前記第1の高音速膜上に設けられ、酸化ケイ素、酸化タンタル、または、酸化ケイ素にフッ素、炭素やホウ素を加えた化合物を主成分とする材料からなる低音速膜と、
前記低音速膜上に設けられ、酸化アルミニウム、窒化アルミニウム、窒化チタン、炭化ケイ素、窒化ケイ素、またはDLCを主成分とする媒質からなる第2の高音速膜と、
前記第2の高音速膜上に設けられ、タンタル酸リチウムまたはニオブ酸リチウムからなる圧電体層と、
前記圧電体層上に設けられているIDT電極と、
を備える弾性波装置。
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