WO2012102131A1 - 弾性波素子およびそれを用いた弾性波装置 - Google Patents
弾性波素子およびそれを用いた弾性波装置 Download PDFInfo
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- WO2012102131A1 WO2012102131A1 PCT/JP2012/050821 JP2012050821W WO2012102131A1 WO 2012102131 A1 WO2012102131 A1 WO 2012102131A1 JP 2012050821 W JP2012050821 W JP 2012050821W WO 2012102131 A1 WO2012102131 A1 WO 2012102131A1
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- mass addition
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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
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/0296—Surface acoustic wave [SAW] devices having both acoustic and non-acoustic properties
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
-
- 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
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
- H03H9/14538—Formation
-
- 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
- H03H9/02937—Means for compensation or elimination of undesirable effects of chemical damage, e.g. corrosion
Definitions
- the present invention relates to an elastic wave element such as a surface acoustic wave (SAW) element and an elastic wave device using the same.
- SAW surface acoustic wave
- An acoustic wave device having a piezoelectric substrate and an IDT (InterDigital Transducer) electrode (excitation electrode) provided on the main surface of the piezoelectric substrate is known (for example, Patent Document 1 or 2).
- the IDT electrode has a plurality of electrode fingers extending in a direction orthogonal to the traveling direction of the elastic wave.
- the elastic wave element converts the electric signal into an elastic wave and converts the elastic wave into an electric signal using the piezoelectric effect.
- Patent Documents 1 and 2 of the techniques the protective layer made of SiO 2 (SiO 2 film) is covered over the IDT electrode on the main surface of the piezoelectric substrate.
- the protective layer contributes to suppression of corrosion of the IDT electrode, compensation for temperature changes in the characteristics of the IDT electrode, and the like.
- Patent Documents 1 and 2 propose forming an adhesion layer between the IDT electrode and the protective layer in order to improve the adhesion (Patent Document 1, paragraph 0011, Patent Document 2). Paragraph 0107).
- the adhesion layer is formed thin so as not to affect the propagation of SAW. Specifically, the adhesion layer is 50 to 100 mm (paragraph 0009 of Patent Document 1) or 1% or less of the SAW wavelength (paragraph 0108 of Patent Document 2).
- a high-band filter can be realized by increasing the electromechanical coupling coefficient.
- An acoustic wave device includes a piezoelectric substrate, an electrode finger disposed on an upper surface of the piezoelectric substrate, and a mass addition film disposed on the upper surface of the electrode finger, and the mass addition film
- the width in the cross section is the smallest on the upper side.
- An elastic wave device includes the elastic wave element described above and a circuit board on which the elastic wave element is attached.
- the electromechanical coupling coefficient can be increased by the smallest value.
- FIG. 1A is a plan view of a SAW element according to an embodiment of the present invention
- FIG. 1B is a cross-sectional view taken along the line Ib-Ib in FIG. 2 (a) to 2 (e) are cross-sectional views corresponding to FIG. 1 (b) for explaining a method of manufacturing a SAW element.
- FIG. 3A and FIG. 3B are cross-sectional views illustrating an example of a method for forming a mass-added film in a trapezoidal shape.
- FIG. 4A and FIG. 4B are cross-sectional views illustrating another example of a method for forming a mass addition film in a trapezoidal shape.
- FIGS. 5C are diagrams for explaining the operation of the SAW element of the comparative example and the embodiment.
- FIGS. 6A and 6B are diagrams for explaining the operation of the SAW element of another comparative example and embodiment.
- FIG. 7A and FIG. 7B are diagrams illustrating calculation result examples for explaining the operation of the SAW element according to the embodiment.
- FIGS. 8A to 8F are cross-sectional views showing modifications of the SAW element.
- FIG. 9A and FIG. 9B are graphs showing the reflection coefficient ⁇ 1 and the electromechanical coupling coefficient K 2 per electrode finger.
- FIGS. 10A and 10B are other graphs showing the reflection coefficient ⁇ 1 and the electromechanical coupling coefficient K 2 per electrode finger. It is another graph which shows the reflection coefficient (GAMMA) 1 per electrode finger.
- FIG. 12A and FIG. 12B are diagrams for explaining how to obtain the lower limit of the preferable range of the thickness of the mass addition film. It is a graph which shows the minimum of the example of the preferable range of the thickness of a mass addition film
- FIG. 1A is a plan view of a SAW element 1 according to an embodiment of the present invention
- FIG. 1B is a cross-sectional view taken along the line Ib-Ib in FIG.
- the SAW element 1 may be either upward or downward, but hereinafter, for convenience, the orthogonal coordinate system xyz is defined and the positive side in the z direction (FIG. 1 (a ) On the front side of the paper surface and the upper side of the paper surface in FIG.
- the SAW element 1 includes a substrate 3, an IDT electrode 5 and a reflector 7 provided on the upper surface 3a of the substrate 3, and a mass addition film 9 provided on the IDT electrode 5 and the reflector 7 (FIG. 1B). And a protective layer 11 (FIG. 1B) that covers the upper surface 3 a from above the mass addition film 9.
- the SAW element 1 may have wiring for inputting / outputting signals to / from the IDT electrode 5.
- the substrate 3 is constituted by a piezoelectric substrate.
- the substrate 3 is composed of a single crystal substrate having piezoelectricity such as a lithium tantalate (LiTaO 3 ) single crystal, a lithium niobate (LiNbO 3 ) single crystal, or the like. More preferably, the substrate 3 is constituted by a 128 ° ⁇ 10 ° YX cut LiNbO 3 substrate.
- the planar shape and various dimensions of the substrate 3 may be set as appropriate.
- the thickness (z direction) of the substrate 3 is 0.2 mm to 0.5 mm.
- the IDT electrode 5 has a pair of comb-like electrodes 13.
- Each comb-like electrode 13 includes a bus bar 13a (FIG. 1A) extending in the SAW propagation direction (x direction) and a plurality of electrode fingers 13b extending from the bus bar 13a in a direction orthogonal to the propagation direction (y direction). And have.
- the two comb-like electrodes 13 are provided so as to mesh with each other (the electrode fingers 13b cross each other).
- FIG. 1A is a schematic diagram, and in practice, a plurality of pairs of comb-like electrodes having a larger number of electrode fingers may be provided.
- a ladder-type SAW filter in which a plurality of IDT electrodes 5 are connected by a system such as a series connection or a parallel connection may be configured, or a dual mode SAW resonance in which a plurality of IDT electrodes 5 are arranged along the X direction.
- a filter or the like may be configured.
- weighting by apodization may be performed by making the lengths of the plurality of electrode fingers different.
- the IDT electrode 5 is formed of, for example, a material mainly containing Al (including an Al alloy).
- the Al alloy is, for example, an Al—Cu alloy.
- Al as a main component basically means that Al is used as a material. However, a material mixed with impurities other than Al that can be naturally mixed in the manufacturing process of the SAW device 1 is also possible. Including. Hereinafter, the same meaning is used when the expression “principal component” is used.
- the IDT electrode 5 may be composed of a plurality of metal layers. Various dimensions of the IDT electrode 5 are appropriately set according to electrical characteristics required for the SAW element 1. As an example, the thickness e (FIG. 1B) of the IDT electrode 5 is 100 nm to 300 nm.
- the IDT electrode 5 may be directly disposed on the upper surface 3a of the substrate 3 or may be disposed on the upper surface 3a of the substrate 3 via another member.
- Another member is, for example, Ti, Cr, or an alloy thereof.
- the thickness of the other member has a thickness that does not substantially affect the electrical characteristics of the IDT electrode 5 (for example, Ti In this case, the thickness is set to 5% of the thickness of the IDT electrode 5).
- the plurality of electrode fingers 13b are provided such that the pitch (repetition interval) p (FIG. 1B) is equal to, for example, a half wavelength of the SAW wavelength ⁇ at a frequency to be resonated.
- the wavelength ⁇ (2p) is, for example, 1.5 ⁇ m to 6 ⁇ m.
- the width w1 (FIG. 1B) of each electrode finger 13b is appropriately set according to the electrical characteristics required for the SAW element 1, and is, for example, 0.4p to 0.6p with respect to the pitch p. .
- the reflector 7 is formed in a lattice shape having a pitch substantially equal to the pitch p of the electrode fingers 13 b of the IDT electrode 5.
- the reflector 7 is formed of the same material as the IDT electrode 5 and has a thickness equivalent to that of the IDT electrode 5.
- the mass addition film 9 is for improving the electrical characteristics of the IDT electrode 5 and the reflector 7.
- the mass addition film 9 is provided over the entire upper surfaces of the IDT electrode 5 and the reflector 7.
- the material constituting the mass addition film 9 is, for example, a material whose elastic wave propagation speed is slower than the material constituting the IDT electrode 5 and the reflector 7 (such as Al or Al alloy), or the IDT electrode 5 and the reflection.
- a material whose main component is a material satisfying at least one of the materials (accounting for Al or Al alloy) constituting the container 7 and the material having a different acoustic impedance compared to the material constituting the protective layer 11 (described later) It is constituted by.
- the difference in acoustic impedance is preferably a certain amount or more, for example, 15 MRayl or more, more preferably 20 MRayl or more.
- a suitable material of the mass addition film 9 and a suitable thickness t (FIG. 1B) of the mass addition film 9 will be described later.
- the mass addition film 9 is formed so that the width in the cross section becomes the smallest on the upper side when the cross section in the direction orthogonal to the longitudinal direction (y direction) of the electrode finger 13b is viewed. And the width in this section is larger on the lower side than on the upper side. In other words, the mass addition film 9 is formed so that the upper surface portion is narrower than the lower surface portion when viewed in the y direction.
- the mass addition film 9 has a trapezoidal cross section.
- the length of the lower base of the trapezoid of the mass addition film 9 is, for example, equal to the width w1 of the electrode finger 13b. A preferable range of the length (width w2) of the upper base of the trapezoid will be described later.
- the protective layer 11 is provided over substantially the entire upper surface 3a of the substrate 3, covers the IDT electrode 5 and the reflector 7 on which the mass addition film 9 is provided, and includes the IDT electrode 5 and the reflector 7 on the upper surface 3a. The part exposed from the reflector 7 is covered.
- a thickness T (FIG. 1B) from the upper surface 3a of the protective layer 11 is set to be larger than the thickness e of the IDT electrode 5 and the reflector 7.
- the thickness T is 200 nm to 700 nm, which is 100 nm or more thicker than the thickness e.
- the protective layer 11 is made of a material whose main component is an insulating material.
- the protective layer 11 is formed of a material mainly composed of material such as SiO 2 that when temperature increases the propagation velocity of the acoustic wave becomes faster, thereby suppress the variation in characteristics due to changes in temperature be able to. That is, an acoustic wave device excellent in temperature compensation can be obtained. Note that the propagation speed of an elastic wave of a general material such as a material constituting the substrate 3 becomes slow as the temperature rises.
- the surface of the protective layer 11 be free from large irregularities. Since the propagation speed of the elastic wave propagating on the piezoelectric substrate changes under the influence of the irregularities on the surface of the protective layer 11, if there are large irregularities on the surface of the protective layer 11, the resonance frequency of each manufactured acoustic wave element. A large variation will occur in this case. Therefore, if the surface of the protective layer 11 is made flat, the resonance frequency of each acoustic wave element is stabilized. Specifically, the flatness of the surface of the protective layer 11 is desirably 1% or less of the wavelength of the elastic wave propagating on the piezoelectric substrate.
- FIG. 2 (a) to 2 (e) are cross-sectional views corresponding to FIG. 1 (b) for each manufacturing process for explaining the outline of the method for manufacturing the SAW element 1.
- FIG. The manufacturing process proceeds in order from FIG. 2 (a) to FIG. 2 (e).
- the various layers change in shape and the like with the progress of the process, but common symbols may be used before and after the change.
- a conductive layer 15 to be the IDT electrode 5 and the reflector 7 and an additional layer 17 to be the mass addition film 9 are formed.
- the conductive layer 15 is formed on the upper surface 3a by a thin film forming method such as a sputtering method, a vapor deposition method, or a CVD (Chemical Vapor Deposition) method.
- the additional layer 17 is formed by the same thin film forming method.
- a resist layer 19 is formed as a mask for etching the additional layer 17 and the conductive layer 15 as shown in FIG.
- a negative or positive photosensitive resin thin film is formed by an appropriate thin film forming method, and a part of the thin film is removed at a non-arranged position of the IDT electrode 5 and the reflector 7 by a photolithography method or the like. Is done.
- the additional layer 17 and the conductive layer 15 are etched by an appropriate etching method such as RIE (Reactive Ion Etching). Thereby, the IDT electrode 5 and the reflector 7 provided with the mass addition film 9 are formed. Thereafter, as shown in FIG. 2D, the resist layer 19 is removed by using an appropriate chemical solution.
- RIE Reactive Ion Etching
- a thin film to be the protective layer 11 is formed by an appropriate thin film forming method such as a sputtering method or a CVD method. At this time, unevenness is formed on the surface of the thin film to be the protective layer 11 due to the thickness of the IDT electrode 5 and the like. Then, if necessary, the surface is flattened by chemical mechanical polishing or the like, and a protective layer 11 is formed as shown in FIG. Note that a part of the protective layer 11 may be removed by a photolithography method or the like in order to expose a pad 39 (FIG. 15) described later or the like before or after planarization.
- FIGS. 3A and 3B are diagrams for explaining an example of a method for forming the mass addition film 9 in a trapezoidal shape. Specifically, FIG. 3 (a) is an enlarged view of a region IIIa in FIG. 2 (b), and FIG. 3 (b) is an enlarged view of a region IIIb in FIG. 2 (c).
- the resist layer 19 that is a mask is also slightly etched. Therefore, as shown in FIG. 3A, the surface shapes of the resist layer 19 and the additional layer 17 indicated by solid lines are changed from the shape indicated by the dotted line EL1 to the shape indicated by the dotted line EL2 as the etching progresses. Will gradually move to.
- the additional layer 17 located under the outer peripheral portion of the lower surface of the resist layer 19 is exposed, and this portion is exposed.
- the additional layer located below the outer peripheral portion of the lower surface of the slightly etched resist layer 19 is exposed, this part is etched, and the trapezoidal mass-added film 9 is obtained by gradually progressing such etching.
- the etching conditions for example, in the case of etching by RIE, the composition ratio of the etching gas and the applied voltage
- the side surface of the resist layer 19 is more inclined.
- the side surface of the mass addition film 9 also becomes more inclined. That is, the shape of the mass addition film 9 can be controlled by changing the etching conditions.
- FIG. 4 (a) and 4 (b) are diagrams illustrating another example of a method of forming the mass addition film 9 in a trapezoidal shape.
- FIG. 4A is a diagram corresponding to an enlarged view of region IIIa in FIG. 2B during the transition from FIG. 2A to FIG. 2B (exposure process)
- FIG. 4B is an enlarged view of a region IIIa in FIG.
- the resist layer 19 is configured by positive photolithography. Therefore, as shown in FIG. 4A, light is irradiated to the non-arranged position of the IDT electrode 5 and the like through the mask 21. And the part irradiated with light is removed and the resist layer 19 becomes a shape shown in FIG.4 (b).
- the resist layer 19 located under the light shielding portion of the mask 21 is not basically removed because it is not irradiated with light, but the portion located under the outer peripheral portion of the light shielding portion of the mask 21 is not covered with the light shielding portion.
- the light diffracted at the edge is irradiated, and the upper surface side is removed.
- the resist layer 19 has a trapezoidal shape in which the upper surface side portion is smaller than the lower surface side portion.
- the etching direction of the additional layer 17 easily tilts, and the additional layer 17 is etched into a trapezoidal shape as indicated by a dotted line EL3 in FIG. 4B.
- the shape of the mass addition film 9 can be controlled by changing the exposure conditions.
- FIGS. 5 (a) to 5 (c), FIGS. 6 (a) and 6 (b), and FIGS. 7 (a) and 7 (b), the operation of the comparative example will be described.
- the operation of the SAW element 1 of the embodiment will be described.
- FIG. 5A is a cross-sectional view for explaining the operation of the SAW element 101 of the first comparative example.
- the SAW element 101 is in a state where the mass addition film 9 and the protective layer 11 are not provided in the SAW element 1 of the embodiment.
- the SAW element 1 When a voltage is applied to the substrate 3 by the IDT electrode 5, SAW propagating along the upper surface 3a is induced in the vicinity of the upper surface 3a of the substrate 3 as indicated by an arrow y1. Further, the SAW is reflected at the boundary between the electrode finger 13b and the gap portion (non-arrangement region of the electrode finger 13b) as indicated by the arrow y2. And the standing wave which makes the pitch of the electrode finger 13b a half wavelength is formed by SAW shown by arrows y1 and y2. The standing wave is converted into an electric signal having the same frequency as that of the standing wave, and is extracted by the electrode finger 13b. In this way, the SAW element 1 functions as a resonator or a filter.
- the SAW element 101 when the temperature rises, the propagation speed of the elastic wave in the substrate 3 becomes slow and the gap portion becomes large. As a result, the resonance frequency is lowered and the desired characteristics may not be obtained. Further, since the IDT electrode 5 is exposed upward, it is easy to touch moisture and there is a risk of corrosion.
- FIG. 5B is a cross-sectional view for explaining the operation of the SAW element 201 of the second comparative example.
- the SAW element 201 is in a state without the mass addition film 9 in the SAW element 1 of the embodiment.
- the protective layer 11 is added to the SAW element 101 of the first comparative example.
- the protective layer 11 is provided in the SAW element 201, the induced SAW propagates not only in the substrate 3 but also in the protective layer 11, as indicated by the arrow y3.
- the protective layer 11 is formed of a material such as SiO 2 whose propagation speed of elastic waves increases as the temperature rises. Therefore, as a whole SAW propagating through the substrate 3 and the protective layer 11, the speed change due to the temperature rise is suppressed. That is, the protective layer 11 compensates for a change in the characteristics of the substrate 3 due to a temperature rise. In addition, the probability that the IDT electrode 5 is exposed to moisture is reduced by the protective layer 11, and thus the risk of corrosion is reduced.
- the electromechanical coupling coefficient decreases.
- the IDT electrode 5 is made of Al or an Al alloy and the protective layer 11 is made of SiO 2 , the acoustic properties of the IDT electrode 5 and the protective layer 11 are approximated, and the electrode finger 13b and the gap The boundary with the part becomes acoustically ambiguous. In other words, the reflection coefficient at the boundary between the electrode finger 13b and the gap portion decreases.
- FIG. 5B as indicated by the arrow y4 smaller than the arrow y2 in FIG. 5A, the reflected wave of SAW is not sufficiently obtained, and the desired characteristics may not be obtained.
- FIG.5 (c) is sectional drawing explaining the effect
- the SAW element 1 has the protective layer 11, a temperature characteristic compensation effect and the like can be obtained in the same manner as the SAW element 201 of the second comparative example. Further, in the case where the mass addition film 9 is formed of a material whose propagation speed of elastic waves is slower than that of the IDT electrode 5, the electrode finger is shown so that the position of the arrow y5 is lower than the position of the arrow y3. In the vicinity of 13b, the SAW is prevented from excessively moving to the protective layer 11, and as a result, the electromechanical coupling coefficient is increased.
- the mass addition film 9 is formed of a material whose acoustic impedance is somewhat different from that of the IDT electrode 5 and the protective layer 11, the reflection coefficient at the boundary position between the electrode finger 13b and the gap portion is high. Become. As a result, it is possible to obtain a sufficient reflected wave of SAW as indicated by the arrow y2.
- FIG. 6A is a cross-sectional view illustrating the operation of the SAW element 301 of the third comparative example.
- the SAW element 301 has a rectangular mass addition film 309 instead of the trapezoidal mass addition film 9 in the embodiment.
- a plurality of points BP indicate an example of the vibration center of SAW.
- SAW is distributed in the vicinity of the surface of the substrate 3 in the non-arrangement region (gap part) of the electrode finger 13b, and is distributed in the mass addition film 309 in the arrangement region of the electrode finger 13b.
- the locus of the vibration center of the SAW is separated from the surface of the substrate 3 in the arrangement region of the electrode finger 13b. As a result, the electromechanical coupling coefficient is reduced.
- FIG. 6B is a cross-sectional view illustrating the operation of the SAW element 1 of the embodiment.
- a plurality of points BP indicate an example of the vibration center of SAW.
- the SAW element 1 since the mass of the mass addition film 9 is reduced at the boundary between the non-arrangement position and the arrangement position of the electrode finger 13b, the substrate 3 at the center of vibration of the SAW as compared with the SAW element 301. The transition from to the mass addition film 9 becomes gentle, and the center of vibration of the SAW passes through the electrode finger 13b as indicated by a point BP1. That is, the vibration center of SAW approaches the substrate 3. As a result, the electromechanical coupling coefficient is increased.
- FIGS. 7 (a) shows changes of the electromechanical coupling coefficient K 2 in the case of changing the shape of the mass adding film 9.
- FIG. 7A is obtained by simulation calculation.
- the calculation conditions are as follows.
- Substrate 3 material 128 ° YX cut LiNbO 3 substrate
- IDT electrode 5 material Al Material of the protective layer 11: SiO 2 Material of mass addition film 9: Ta 2 O 5
- Normalized thickness e / ⁇ of IDT electrode 5 0.08 Normalized thickness T / ⁇ of protective layer 11: 0.33 Normalized thickness of mass addition film 9 t / ⁇ : 0.05 Normalized length w1 / p of the bottom of the mass addition film 9: 0.50
- the normalized length w2 / p of the upper base of the mass addition film 9 was changed in the range of 0.35 to 0.50.
- the horizontal axis represents the normalized length w2 / p of the upper base of the mass adding film 9
- the vertical axis represents the electromechanical coupling coefficient K 2.
- membrane 9 will also reduce as a whole. Therefore, regardless of the shape of the mass adding film, simply may have higher electromechanical coupling coefficient K 2 by volume of the mass adding film is reduced. Therefore, the influence of the decrease in the volume of the mass addition film when the volume of the mass addition film 9 is reduced by changing the thickness t of the mass addition film was examined.
- FIG. 7 (b) shows a change of the electromechanical coupling coefficient K 2 while changing the thickness t of the mass adding film.
- FIG. 7B is obtained by simulation calculation, and the calculation conditions are substantially the same as the calculation conditions of FIG. 7A except for the conditions related to the mass-added film.
- the mass addition film is rectangular (the mass addition film 309 of the third comparative example), and its normalized thickness t / ⁇ is changed in the range of 0.03 to 0.05. It was.
- the horizontal axis represents the normalized thickness t / lambda of the mass adding film 309
- the vertical axis represents the electromechanical coupling coefficient K 2.
- 8 (a) to 8 (f) are cross-sectional views showing modifications of the SAW element.
- the shape of the electrode finger 25 is different from the shape of the electrode finger 13b shown in FIG. Specifically, the side surface along the longitudinal direction of the electrode finger 25 is inclined so as to expand as it approaches the upper surface of the substrate 3. More specifically, the electrode finger 25 is formed so that the cross-sectional shape becomes a trapezoid when the cross section in a direction orthogonal to the longitudinal direction of the electrode finger 25 is viewed.
- the length of the lower base of the mass addition film 9 is equal to the length of the upper base of the electrode finger 25, and the mass addition film 9 and the electrode finger 25 have an inclination angle with respect to the upper surface 3a of these side surfaces. They are identical to each other.
- the SAW element shown in FIGS. 8B and 8C has a trapezoidal electrode finger 25 in the same manner as the SAW element shown in FIG. Is equivalent to the length of the upper base of the electrode finger 25.
- the side surface of the mass addition film 9 is inclined more than the side surface of the electrode finger 25.
- the side surface of the mass addition film 9 is smaller in inclination than the side surface of the electrode finger 25.
- the upper surface portion of the mass addition film 9 is made narrower than the lower surface portion, thereby improving the electromechanical coupling coefficient K 2 as described above. The effect is obtained. Further, in the electrode finger 25, the upper surface side portion is made narrower than the lower surface side portion, so that the transition from the substrate 3 to the mass addition film 9 at the vibration center of the SAW becomes more gradual. it is expected that K 2 is further improved.
- the electrode fingers 25 in FIGS. 8A to 8C are formed into a trapezoidal shape by, for example, relatively shortening the etching time as in the mass addition film 9.
- the inclination angles of the side surfaces of the electrode finger 25 and the mass addition film 9 can be determined by appropriately setting the etching conditions in consideration of the difference between the etching rate of the mass addition film 9 and the etching rate of the electrode finger 25.
- the size is the same or different.
- the inclination angles of the side surfaces of the electrode finger 25 and the mass addition film 9 are the same or different from each other by performing mask formation and etching separately in the electrode finger 25 and the mass addition film 9. .
- the mass addition film in which the upper surface portion is formed narrower than the lower surface portion when viewed in the longitudinal direction of the electrode finger 25. 26, 27 and 28.
- the mass addition films 26, 27, and 28 have a shape different from the trapezoidal shape.
- the mass addition film 26 in FIG. 8D has a shape in which another rectangle having a width smaller than the rectangle is overlapped on one rectangle when viewed in the longitudinal direction of the electrode finger 25. Yes.
- Such a shape is realized, for example, by performing mask formation and etching in two steps.
- the mass-added film 27 in FIG. 8E has a shape in which the corners between the upper surface and the side surface are chamfered by a flat surface or a curved surface (curved surface in FIG. 8E) when viewed in the longitudinal direction of the electrode finger 25. Yes.
- a shape is realized, for example, by appropriately setting etching conditions such as adjustment of etching time, like the trapezoidal mass addition film 9.
- the mass addition film 28 in FIG. 8 (f) has a generally dome shape when viewed in the longitudinal direction of the electrode finger 25. In this case, the upper side in the cross section of the mass addition film 28 is almost close to a point. Such a shape is realized by, for example, the surface tension of the material that is formed by printing the material to be the mass addition film 28 on the electrode finger 25.
- the electrode fingers are trapezoidal electrode fingers 25, but may be rectangular electrode fingers 13b.
- each of the mass adding film like the mass adding film 9, exhibit the effect of the gradual transition from the substrate 3 of the vibration center of the SAW to the mass adding film and thus improve the electromechanical coupling coefficient K 2 is To do.
- Suitable material and thickness of mass-added film a suitable material and thickness t of the mass addition film 9 will be examined.
- the mass addition film is rectangular (the mass addition film 309 of the third comparative example).
- a suitable material and thickness for the mass addition film 309 are also suitable for the mass addition film 9.
- the substrate 3 is a 128 ° YX cut LiNbO 3 substrate
- the IDT electrode 5 is made of Al
- the protective layer 11 is made of SiO 2 .
- FIG. 9A and FIG. 9B are graphs showing the reflection coefficient ⁇ 1 and the electromechanical coupling coefficient K 2 per electrode finger 13b.
- FIG. 9A and FIG. 9B are obtained by simulation calculation.
- the calculation conditions are as follows. Normalized thickness e / ⁇ of IDT electrode 5: 0.08 Normalized thickness T / ⁇ of protective layer 11: 0.25
- the normalized thickness t / ⁇ of the mass addition film 309 was changed in the range of 0.01 to 0.05.
- Material of the mass adding film 309 WC, TiN, TaSi 2 Acoustic impedance of each material (unit: MRayl): SiO 2 : 12.2 Al: 13.5 WC: 102.5 TiN: 56.0 TaSi 2 : 40.6
- the horizontal axis indicates the normalized thickness t / ⁇ of the mass addition film 309.
- the vertical axis represents the reflection coefficient ⁇ 1 per electrode finger 13b.
- the vertical axis in FIG. 9 (b) shows an electromechanical coupling coefficient K 2.
- lines L1, L2, and L3 correspond to the case where the mass addition film 309 is made of WC, TiN, and TaSi 2 , respectively.
- the line LS1 indicates the lower limit of the range are generally preferred reflection coefficient gamma 1.
- line LS2 indicates the lower limit of the range are generally the electromechanical coupling coefficient K 2 preferred.
- the reflection coefficient ⁇ 1 is set to a generally preferred range while the electromechanical coupling coefficient K 2 is kept in a generally preferred range. Is confirmed to be possible.
- the mass addition film 309 is formed of various virtual materials having the same acoustic impedance Z S and different Young's modulus E and density ⁇ (cases No. 1 to No. 7), the reflection coefficient ⁇ 1 and the electric machine the coupling coefficient K 2 was calculated.
- FIG. 10A and FIG. 10B are graphs showing the results calculated based on the above conditions.
- the horizontal axis is No.
- the vertical axis indicates the reflection coefficient ⁇ 1 or the electromechanical coupling coefficient K 2 per electrode finger 13b.
- a line L5 indicates the calculation result.
- the reflection coefficient gamma 1 are identical acoustic impedance Z S, the Young's modulus E is small, it becomes larger as the density ⁇ is greater. No. 1-No.
- the rate of change of the reflection coefficient ⁇ 1 in FIG. 3 to No. 7 is larger than the rate of change of the reflection coefficient ⁇ 1 in FIG. In other words, No. In the vicinity of 3, there is room to find critical significance.
- Such a change in the reflection coefficient ⁇ 1 is considered to be caused by the difference in the propagation speed of the elastic wave of the material constituting the mass addition film 309 as follows.
- the vibration-distributed distribution is more dispersed in the mass-added film 309 having a slower propagation speed of elastic waves where the vibration distribution is concentrated on the mass-added film 309. It is considered that the reflection coefficient is effectively higher than that of the mass addition film 309 in which the propagation speed of the elastic wave is fast.
- the propagation speed of the elastic wave of SiO 2 is 5560 m / s, and the propagation speed of the elastic wave of Al is 5020 m / s. Therefore, no.
- the propagation speed of elastic waves of the mass addition films 309 of 1 and 2 is slower than the propagation speed of elastic waves of the protective layer 11 and the IDT electrode 5.
- the propagation speed of elastic waves of the mass addition films 309 of 3 to 7 is faster than the propagation speed of elastic waves of the protective layer 11 and the IDT electrode 5. Therefore, the above-mentioned No.
- the change in the change rate of the reflection coefficient in the vicinity of 3 can also be explained by the propagation speed of the elastic wave.
- the propagation speed of the elastic wave of SiO 2 and Al when the horizontal axis is regarded as the propagation speed of the elastic wave is indicated by lines LV1 and LV2.
- the electromechanical coupling coefficient K 2 shown in FIG. 10 (b), the Young's modulus E and density ⁇ is also vary, are within the preferred range.
- the mass addition film 309 is a material having an acoustic impedance different from that of the material forming the protective layer 11 and the IDT electrode 5 and having a lower elastic wave propagation speed than the material forming the protective layer 11 and the IDT electrode 5.
- the material having a larger acoustic impedance than the material forming the protective layer 11 and the IDT electrode 5 has a slower propagation speed of the elastic wave than the material forming the protective layer 11 and the IDT electrode 5. It is easy to satisfy the conditions and the selection of materials is easy.
- Examples of such a material include Ta 2 O 5 , TaSi 2 , and W 5 Si 2 .
- These physical properties (acoustic impedance Z S , elastic wave propagation velocity V, Young's modulus E, density ⁇ ) are as follows.
- WC and TiN exemplified in FIG. 9A do not satisfy the condition that the elastic wave propagation speed is slower than the material forming the protective layer 11 and the IDT electrode 5 (WC V: 6504 m / s, TiN V: 10721 m / s).
- TaSi for 2 more difference of about 20MRayl acoustic impedance between the Al and SiO 2 more (difference of about 20MRayl acoustic impedance between the Al and SiO 2)
- Ta 2 O 5 is close to the acoustic impedance of the acoustic impedance protective layer 11 and the IDT electrode 5 than (line L3 in to FIG. 9 (a))
- the reflection coefficient was calculated and the knowledge about the above materials was confirmed.
- the calculation conditions are as follows. Normalized thickness e / ⁇ of IDT electrode 5: 0.08 Normalized thickness T / ⁇ of protective layer 11: 0.27, 0.30 or 0.33 The normalized thickness t / ⁇ of the mass addition film 309 was changed in the range of 0.01 to 0.09.
- FIG. 11 is a graph showing the results calculated based on the above conditions.
- the horizontal and vertical axes are the same as the vertical and horizontal axes in FIG.
- the lines L7, L8, and L9 correspond to the cases where the normalized thickness T / ⁇ of the protective layer 11 is 0.27, 0.30, and 0.33, respectively (the lines L7, L8, and L9 are substantially the same). overlapping).
- Ta 2 O 5 has a lower acoustic wave propagation speed than TiN (line L2 in FIG. 9A), although the acoustic impedance is close to the acoustic impedance of the protective layer 11. Therefore, the reflection coefficient is high.
- the normalized thickness T / ⁇ of the protective layer 11 generally does not affect the reflection coefficient.
- a preferable range of the thickness t of the mass addition film 309 will be examined.
- a lower limit value of a preferable range of the thickness t of the mass addition film 309 (hereinafter, “preferable range” may be omitted and simply referred to as a “lower limit value”) is examined.
- FIG. 12A is a graph schematically showing the reflection coefficient ⁇ all of the IDT electrode 5 (all electrode fingers 13b).
- the horizontal axis indicates the frequency f
- the vertical axis indicates the reflection coefficient ⁇ all .
- the frequency band (f 1 to f 2 ) in which the reflection coefficient ⁇ all is approximately 1 (100%) is called a stop band.
- the reflection coefficient ⁇ all in the stop band need not be completely 1, and for example, a frequency band in which the reflection coefficient ⁇ all is 0.99 or more may be specified as the stop band.
- the interval between these changes may be specified as the stop band.
- the reflection coefficient ⁇ all of the IDT electrode 5 is determined by the reflection coefficient ⁇ 1 per electrode finger 13b, the number of electrode fingers 13b, and the like. It is generally known that when the reflection coefficient ⁇ 1 becomes small, the width SB of the stop band becomes small.
- FIG. 12B is a graph schematically showing the electrical impedance Ze of the IDT electrode 5.
- the horizontal axis indicates the frequency f
- the vertical axis indicates the absolute value
- takes a minimum value at the resonance frequency f 3 and takes a maximum value at the anti-resonance frequency f 4 .
- the upper end f 2 of the stop band and the antiresonance frequency f 4 change in a state where the lower end f 1 of the stop band and the resonance frequency f 3 coincide. Rate of change of this time, towards the stop band of the upper end f 2 is greater than the anti-resonance frequency f 4.
- the resonance frequency f 3 spurious in the frequency band (width Delta] f) between the anti-resonance frequency f 4 is generated.
- a desired filter characteristic or the like may not be obtained.
- the upper end f2 of the stop band indicated by a line L12 assuming that the frequency higher than the antiresonance frequency f 4, as shown in phantom in the region Sp2 (two-dot chain line), spurious, antiresonance frequency It occurs at a higher frequency than f 4. In this case, the influence of spurious on the filter characteristics and the like is suppressed.
- the upper end f 2 of the stop band is preferably higher frequency than the anti-resonance frequency f 4.
- the reflection coefficient of the IDT electrode 5 may be adjusted so that the upper end f 2 of the stop band is higher than the antiresonance frequency f 4 . Since the reflection coefficient of the IDT electrode 5 increases linearly as the normalized thickness t / ⁇ of the mass addition film 309 increases as shown in FIGS. 9 and 11, the normalized thickness t / of the mass addition film 309 increases.
- the upper end f 2 of the stop band can be set to a frequency higher than the antiresonance frequency f 4 .
- the normalized thickness t / lambda of the mass adding film 309 upper f 2 of the stop band by a higher becomes thicker than the anti-resonance frequency f 4, between the resonance frequency f 3 and the anti-resonance frequency f 4 Spurious generation is suppressed in the frequency band (width ⁇ f).
- the reflection coefficient ⁇ 1 is affected by the normalized thickness T / ⁇ of the protective layer 11.
- the width ⁇ f is affected by the normalized thickness T / ⁇ of the protective layer 11. Therefore, the normalized thickness t / ⁇ of the mass addition film 309 is preferably determined according to the normalized thickness T / ⁇ of the protective layer 11.
- the normalized thickness t / ⁇ at which the upper end f 2 of the stop band is equivalent to the antiresonance frequency f 4 is calculated by changing the normalized thickness T / ⁇ of the protective layer 11, and the normalized thickness t / ⁇ is calculated based on the calculation result.
- the lower limit value of the normalized thickness t / ⁇ was defined by the normalized thickness T / ⁇ .
- FIG. 13 is a graph for explaining the normalized thickness t / ⁇ in which the upper end f 2 of the stop band is higher than the antiresonance frequency f 4 , and a case where the material of the mass addition film 309 is Ta 2 O 5 is taken as an example. Yes.
- the horizontal axis represents the normalized thickness T / ⁇ of the protective layer 11
- the vertical axis represents the normalized thickness t / ⁇ of the mass addition film 309.
- the solid line LN1 is to the upper end f 2 of the stop band showed the calculation result of the normalization thickness t / lambda made equal to the antiresonance frequency f 4.
- the normalized thickness e / ⁇ of the IDT electrode 5 was set to 0.08 ⁇ .
- the upper end f 2 of the stop band is normalized thickness t / lambda made equal to the antiresonance frequency f 4, it was possible to derive a suitably approximated curve by a quadratic curve.
- the minimum value of the normalized thickness t / ⁇ is larger than the maximum value (0.01) of the normalized thickness of the adhesion layer shown in Patent Document 2.
- an upper limit value of a preferable range of the thickness t of the mass addition film 309 (hereinafter, “preferable range” may be omitted and simply referred to as an “upper limit value”) is examined.
- the reflection coefficient increases as the normalized thickness t / ⁇ of the mass addition film 309 increases. Therefore, the upper limit value of the normalized thickness t / ⁇ is a range in which the mass addition film 309 is not exposed from the protective layer 11.
- the thickness e / ⁇ of the IDT electrode 5 is set to the thickness of a general SAW element. In light of e / ⁇ , it is estimated to be less than 0.1 and can be defined as the following equation.
- Upper limit value: t / ⁇ T / ⁇ 0.1
- FIG. 14 A preferable range of the normalized thickness t / ⁇ derived from the above study is shown in FIG. 14 using Ta 2 O 5 as an example.
- the horizontal and vertical axes indicate the normalized thickness T / ⁇ of the protective layer 11 and the normalized thickness t / ⁇ of the mass addition film 309, as in FIG.
- a line LL1 indicates a lower limit value (corresponding to the line LN1 in FIG. 13), and a line LH1 indicates an upper limit value.
- a hatched region between these lines is a preferable range of the normalized thickness t / ⁇ of the mass addition film 309.
- the line LH5 indicates the upper limit (0.01) of the normalized thickness of the adhesion layer shown in Patent Document 2.
- FIG. 15 is a cross-sectional view showing the SAW device 51 according to the present embodiment.
- the SAW device 51 constitutes, for example, a filter or a duplexer.
- the SAW device 51 includes a SAW element 31 and a circuit board 53 on which the SAW element 31 is mounted.
- the SAW element 31 is configured as, for example, a so-called wafer level package SAW element.
- the SAW element 31 includes the above-described SAW element 1, a cover 33 that covers the SAW element 1 side of the substrate 3, a terminal 35 that penetrates the cover 33, and a back surface portion 37 that covers the opposite side of the substrate 3 from the SAW element 1. have.
- the cover 33 is made of resin or the like, and a vibration space 33a for facilitating SAW propagation is formed above the IDT electrode 5 and the reflector 7 (on the positive side in the z direction).
- a wiring 38 connected to the IDT electrode 5 and a pad 39 connected to the wiring 38 are formed on the upper surface 3 a of the substrate 3.
- the terminal 35 is formed on the pad 39 and is electrically connected to the IDT electrode 5.
- the back surface portion 37 includes a back electrode for discharging a charge charged on the surface of the substrate 3 due to a temperature change or the like, and an insulating layer covering the back electrode.
- the circuit board 53 is constituted by, for example, a so-called rigid printed wiring board.
- a mounting pad 55 is formed on the mounting surface 53 a of the circuit board 53.
- the SAW element 31 is arranged with the cover 33 side facing the mounting surface 53a.
- the terminals 35 and the mounting pads 55 are bonded by solder 57. Thereafter, the SAW element 31 is sealed with a sealing resin 59.
- the substrate 3 is an example of a piezoelectric substrate
- the protective layer 11 is an example of an insulating layer.
- the present invention is not limited to the above embodiment, and may be implemented in various modes.
- the acoustic wave element is not limited to a SAW element (in the narrow sense).
- it may be a so-called boundary acoustic wave element (however, included in a broad sense SAW element) in which the thickness of the insulating layer (11) is relatively large (for example, 0.5 ⁇ to 2 ⁇ ).
- the boundary acoustic wave element it is not necessary to form the vibration space (33a), and thus the cover 33 and the like are also unnecessary.
- the insulating layer (11) is not an essential requirement, and the insulating layer is provided only for the purpose of preventing corrosion and may be thinner than the thickness of the electrode finger.
- the mass-added film can be made of, for example, a material whose propagation speed of elastic waves is slower than that of the electrode finger material, so that the reflection coefficient can be increased and the SAW reflection efficiency is improved. Therefore, the confinement effect in the SAW resonator is improved. Thereby, for example, there is an effect that loss can be reduced.
- the additional layer is formed such that the upper surface side portion is narrower than the lower surface side portion, so that the vibration center of the SAW rapidly changes to the surface of the electrode finger. It is suppressed, and the effect of improving the electromechanical coupling coefficient is achieved.
- the acoustic wave element is not limited to a wafer level package.
- the SAW element does not have the cover 33 and the terminal 35, and the pad 39 on the upper surface 3 a of the substrate 3 and the mounting pad 55 of the circuit board 53 may be directly bonded by the solder 57.
- a vibration space may be formed by a gap between the SAW element 1 (protective layer 11) and the mounting surface 53a of the circuit board 53.
- the mass addition film is preferably provided over the entire surface of the electrode.
- the mass addition film may be provided only on a part of the electrode, such as provided only on the electrode finger. Further, the mass addition film may be provided only on a part of the center side in the longitudinal direction of the electrode finger. Further, the mass addition film may be provided not only on the upper surface of the electrode but also on the side surface.
- the material of the mass addition film may be a conductive material or an insulating material. Specifically, conductive materials such as tungsten, iridium, tantalum, and copper, and insulating materials such as Ba x Sr 1-x O 3 , Pb x Zn 1-x O 3 , and ZnO 3 are listed as materials for the mass addition film. Can do. Further, WC or the like that is not a preferable material in FIG. 9A may also be a material for the mass addition film.
- the mass addition film By forming the mass addition film with an insulating material, it is possible to suppress corrosion of the electrode and stabilize the electrical characteristics of the acoustic wave device, compared to the case where the mass addition film is formed of a metal material. This is because a pinhole may be formed in the insulating layer made of SiO 2 , and when this pinhole is formed, moisture penetrates into the electrode portion, but the electrode is formed on the electrode. This is because if a metal film made of a material different from the material is disposed, corrosion due to the battery effect between different metals may occur due to the infiltrated moisture. Therefore, if the mass-added film is formed of an insulating material such as Ta 2 O 5 , the battery effect hardly occurs between the electrode and the mass-added film. Therefore, a highly reliable elastic wave element in which corrosion of the electrode is suppressed. It can be.
- the upper surface of the insulating layer (11) may have irregularities so as to be convex at the position of the electrode fingers. In this case, the reflection coefficient can be further increased. As described with reference to FIG. 2 (e), the unevenness may be formed due to the thickness of the electrode finger during the formation of the insulating layer, or the surface of the insulating layer may be formed on the electrode finger. It may be formed by etching in the region between.
- the material of the electrode is not limited to Al and alloys containing Al as a main component.
- the material of the insulating layer is not limited to SiO 2, and may be silicon oxide other than SiO 2 , for example.
- SAW element elastic wave element
- Substrate piezoelectric substrate
- 3a Upper surface
- IDT electrode electrode
- membrane membrane
- Protective layer insulating layer
Abstract
Description
図1(a)は本発明の実施形態に係るSAW素子1の平面図、図1(b)は図1(a)のIb-Ib線における断面図である。なお、SAW素子1は、いずれの方向が上方または下方とされてもよいものであるが、以下では、便宜的に、直交座標系xyzを定義するとともに、z方向の正側(図1(a)の紙面手前側、図1(b)の紙面上方)を上方として、上面、下面等の用語を用いるものとする。
計算条件は、以下のとおりである。
基板3の材料:128°Y-XカットのLiNbO3基板
IDT電極5の材料:Al
保護層11の材料:SiO2
質量付加膜9の材料:Ta2O5
IDT電極5の正規化厚みe/λ:0.08
保護層11の正規化厚みT/λ:0.33
質量付加膜9の正規化厚みt/λ:0.05
質量付加膜9の下底の正規化長さw1/p:0.50
質量付加膜9の上底の正規化長さw2/p:0.35~0.50の範囲で変化させた。
図7(b)の計算においては、質量付加膜は矩形(第3の比較例の質量付加膜309)とされ、その正規化厚みt/λを0.03~0.05の範囲で変化させた。
図7(b)において、横軸は、質量付加膜309の正規化厚みt/λを示し、縦軸は、電気機械結合係数K2を示している。
以下、質量付加膜9の好適な材料および厚みtについて検討する。ただし、以下の検討におけるシミュレーション計算においては、質量付加膜は矩形(第3の比較例の質量付加膜309)とされている。しかし、質量付加膜9は、質量付加膜309を改良したものであるから、質量付加膜309における好適な材料および厚みは、質量付加膜9においても好適な材料および厚みである。
IDT電極5の正規化厚みe/λ:0.08
保護層11の正規化厚みT/λ:0.25
質量付加膜309の正規化厚みt/λ:0.01~0.05の範囲で変化させた。
質量付加膜309の材料:WC、TiN、TaSi2
各材料の音響インピーダンス(単位はMRayl):
SiO2:12.2 Al:13.5
WC:102.5 TiN:56.0 TaSi2:40.6
IDT電極5の正規化厚みe/λ:0.08
保護層11の正規化厚みT/λ:0.30
質量付加膜309の正規化厚みt/λ:0.03
質量付加膜309の物性値:
ZS E ρ
(MRayl)(GPa)(103kg/m3)
No.1: 50 100 25.0
No.2: 50 200 12.5
No.3: 50 300 8.33
No.4: 50 400 6.25
No.5: 50 500 5.00
No.6: 50 600 4.17
No.7: 50 700 3.57
なお、ZS=√(ρE)である。
No.1: 2000 No.2: 4000 No.3: 6000
No.3: 8000 No.4:10000 No.6:12000
No.7:14000
ZS V E ρ
(MRayl)(m/s)(GPa)(103kg/m3)
Ta2O5 :33.8 4352 147 7.76
TaSi2 :40.6 4438 180 9.14
W5Si2 :67.4 4465 301 15.1
IDT電極5の正規化厚みe/λ:0.08
保護層11の正規化厚みT/λ:0.27、0.30または0.33
質量付加膜309の正規化厚みt/λ:0.01~0.09の範囲で変化させた。
Ta2O5:
t/λ=0.5706(T/λ)2-0.3867(T/λ)+0.0913
TaSi2:
t/λ=0.3995(T/λ)2-0.2675(T/λ)+0.0657
W5Si2:
t/λ=0.2978(T/λ)2-0.1966(T/λ)+0.0433
上限値:t/λ=T/λ-0.1
図14において、横軸および縦軸は、図13と同様に、保護層11の正規化厚みT/λおよび質量付加膜309の正規化厚みt/λを示している。線LL1は下限値を示し(図13の線LN1に対応)、線LH1は上限値を示している。これらの線の間のハッチングされた領域が質量付加膜309の正規化厚みt/λの好ましい範囲である。なお、線LH5は、特許文献2において示された密着層の正規化厚みの上限値(0.01)を示している。
図15は、本実施形態に係るSAW装置51を示す断面図である。
Claims (9)
- 圧電基板と、
該圧電基板の上面に配置された電極指と、
該電極指の上面に配置された質量付加膜と、を備え、
該質量付加膜は、前記電極指が伸びている方向に直交する断面を見たときに、該断面における幅が上辺で最も小さい、弾性波素子。 - 前記質量付加膜が配置された前記電極指と、前記圧電基板の上面のうち前記電極指から露出する部分とを覆い、前記圧電基板の上面からの厚みが前記電極指および前記質量付加膜の合計の厚みよりも大きい絶縁層をさらに備える、請求項1に記載の弾性波素子。
- 前記絶縁層は酸化珪素を主成分とする、請求項2に記載の弾性波素子。
- 前記質量付加膜は、前記電極指の材料および前記絶縁層の材料よりも音響インピーダンスが大きく、かつ前記電極指の材料および前記絶縁層の材料よりも弾性波の伝搬速度が遅い材料を主成分とする、請求項2または3に記載の弾性波素子。
- 前記質量付加膜は絶縁材料を主成分とする、請求項1~4のいずれか1項に記載の弾性波素子。
- 前記質量付加膜は、前記断面における形状が台形である、請求項1~5のいずれか1項に記載の弾性波素子。
- 前記台形の下底に対する前記台形の上底の長さの比が0.7以上1.0未満である、請求項6に記載の弾性波素子。
- 前記電極指は、該電極指の長手方向に沿った側面が、前記圧電基板の上面に近づくにつれて広がるように傾斜している、請求項1~7のいずれか1項に記載の弾性波素子。
- 請求項1~8のいずれか1項に記載の弾性波素子と、
該弾性波素子が取り付けられた回路基板と、を備える弾性波装置。
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JPWO2018116680A1 (ja) * | 2016-12-20 | 2019-06-27 | 株式会社村田製作所 | 弾性波装置、高周波フロントエンド回路及び通信装置 |
US11336255B2 (en) | 2017-02-16 | 2022-05-17 | Acoustic Wave Device Labo., Ltd. | Acoustic wave element and method for manufacturing same |
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WO2021060523A1 (ja) * | 2019-09-27 | 2021-04-01 | 株式会社村田製作所 | 弾性波装置及びフィルタ装置 |
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JPWO2012102131A1 (ja) | 2014-06-30 |
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