WO2009125536A1 - Dispositif à onde acoustique limite et son procédé de fabrication - Google Patents

Dispositif à onde acoustique limite et son procédé de fabrication Download PDF

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Publication number
WO2009125536A1
WO2009125536A1 PCT/JP2009/000891 JP2009000891W WO2009125536A1 WO 2009125536 A1 WO2009125536 A1 WO 2009125536A1 JP 2009000891 W JP2009000891 W JP 2009000891W WO 2009125536 A1 WO2009125536 A1 WO 2009125536A1
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acoustic wave
boundary acoustic
wave device
electrode
groove
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PCT/JP2009/000891
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English (en)
Japanese (ja)
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野竹直弘
稲手謙二
三村昌和
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株式会社村田製作所
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Publication of WO2009125536A1 publication Critical patent/WO2009125536A1/fr

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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
    • H03H9/0222—Details of interface-acoustic, boundary, pseudo-acoustic or Stonely wave devices

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  • the present invention relates to a boundary acoustic wave device and a manufacturing method thereof.
  • a surface acoustic wave device normally requires a package in which the surface acoustic wave element is hermetically sealed and a space is formed on the propagation surface of the surface acoustic wave element.
  • the boundary acoustic wave device In contrast, in the boundary acoustic wave device, the energy of the boundary acoustic wave is substantially confined in the boundary portion between the piezoelectric body and the dielectric body. Therefore, in the boundary acoustic wave device, it is not necessary to provide a package required in the surface acoustic wave device. Therefore, since the boundary acoustic wave device can be further reduced in size, it has been actively studied in recent years.
  • Patent Document 1 discloses a boundary acoustic wave device using an SH type boundary acoustic wave.
  • Patent Document 1 describes that a high resonance frequency of 1370 MHz and a high anti-resonance frequency of 1460 MHz can be obtained by reducing the period of the IDT and the reflector to 2.2 ⁇ m.
  • Patent Document 1 it is possible to realize a high resonance frequency and anti-resonance frequency by reducing the period of the IDT and the reflector.
  • the period of the IDT and the reflector is reduced in order to realize high frequency, there is a problem that the surge withstand voltage is lowered. Therefore, it has been difficult to increase the frequency while maintaining a high surge withstand voltage.
  • An object of the present invention is to increase the frequency while maintaining a high surge withstand voltage.
  • the boundary acoustic wave device includes a piezoelectric body, a dielectric layer laminated on one surface of the piezoelectric body, and an electrode disposed at a boundary between the piezoelectric body and the dielectric body, and an elastic property that propagates through the boundary.
  • the present invention relates to a boundary acoustic wave device using boundary waves.
  • the electrode includes a first comb electrode and a second comb electrode.
  • the first comb electrode has a plurality of electrode fingers.
  • the second comb electrode has a plurality of electrode fingers.
  • the plurality of electrode fingers of the second comb electrode are alternately arranged with the electrode fingers of the first comb electrode in the propagation direction of the boundary acoustic wave.
  • the second comb electrode is connected to a potential different from that of the first comb electrode.
  • a groove extending in the extending direction of the electrode finger is formed on the surface of the piezoelectric body on the dielectric side. The groove is located between the electrode fingers of the adjacent first comb electrode and the electrode fingers of the second comb electrode.
  • a groove located between the electrode finger of the adjacent first comb electrode and the electrode finger of the second comb electrode is formed on the surface of the piezoelectric body on the dielectric side.
  • the dielectric includes a first dielectric layer laminated on one surface of the piezoelectric body, and a first dielectric layer laminated on the first dielectric layer.
  • the resonance frequency and antiresonance frequency can be further increased.
  • the electrode fingers of the adjacent first comb electrodes and the second comb electrodes are formed by forming the groove and the second dielectric layer.
  • the pitch with the electrode fingers can be made relatively long. Therefore, the surge withstand voltage of the boundary acoustic wave device can be further increased.
  • the cross-sectional shape of the groove along the propagation direction of the boundary acoustic wave is rectangular.
  • the distance between the electrode finger of the adjacent first comb electrode and the electrode finger of the second comb electrode is further increased on the surface of the piezoelectric body, and the electrode of the adjacent first comb electrode
  • the dielectric constant of the region between the finger and the electrode finger of the second comb electrode can be further increased. Therefore, the surge withstand voltage of the boundary acoustic wave device can be further increased.
  • the cross-sectional shape of the groove along the propagation direction of the boundary acoustic wave is a trapezoid that becomes narrower in the depth direction.
  • the boundary acoustic wave device can be easily manufactured.
  • the method for manufacturing a boundary acoustic wave device according to the present invention relates to a method for manufacturing the boundary acoustic wave device according to the present invention.
  • the method for manufacturing a boundary acoustic wave device according to the present invention includes an electrode forming step of forming an electrode on a piezoelectric body, a groove forming step of forming a groove on the piezoelectric body, and a step of laminating a dielectric on one surface of the piezoelectric body. Is provided.
  • the groove located between the electrode finger of the adjacent first comb electrode and the electrode finger of the second comb electrode is formed on the dielectric side of the piezoelectric body. Formed on the surface. Therefore, the distance between the electrode fingers of the adjacent first comb electrode and the electrode finger of the second comb electrode is relatively long, and the adjacent first comb electrode The dielectric constant of the region between the electrode finger and the electrode finger of the second comb electrode can be made relatively low. Therefore, it is possible to manufacture a boundary acoustic wave device with a small surge between the electrode fingers of the adjacent first comb electrodes and the electrode fingers of the second comb electrodes and a high surge withstand voltage.
  • the order of performing the electrode forming step and the groove forming step is not particularly limited.
  • the groove forming process may be performed after performing the electrode forming process, or the electrode forming process may be performed after performing the groove forming process.
  • the method for manufacturing the boundary acoustic wave device includes a frequency of the piezoelectric body on which the first and second comb electrodes are formed after the electrode forming step.
  • a step of measuring the characteristics, and the groove forming step includes a frequency characteristic of the boundary acoustic wave device corresponding to the measured frequency characteristics and a predetermined target frequency of the boundary acoustic wave device.
  • the groove is formed so as to have a depth that reduces the difference from the characteristics.
  • the frequency characteristic is adjusted by adjusting the depth of the groove formed in accordance with the frequency characteristic of the piezoelectric body on which the first and second comb electrodes are measured before the groove is formed. Adjustments are made. For this reason, the dispersion
  • the groove depth is substantially the same as the frequency characteristic of the boundary acoustic wave device corresponding to the measured frequency characteristic and the target frequency characteristic of the predetermined boundary acoustic wave device. It is preferable to be a step of forming a groove so as to have a depth. According to this, the dispersion
  • frequency characteristics refers to the overall characteristics related to frequency.
  • the frequency characteristics include, for example, a resonance frequency and an antiresonance frequency when the boundary acoustic wave device is a resonator, and a center frequency when the boundary acoustic wave device is a filter.
  • the method for manufacturing the boundary acoustic wave device includes: a piezoelectric body on which the first and second comb electrodes are formed after the groove forming step; The step of measuring the frequency characteristic and the depth of the groove reduce the difference between the frequency characteristic of the boundary acoustic wave device corresponding to the measured frequency characteristic and the target frequency characteristic of the predetermined boundary acoustic wave device. And a step of deepening the groove formed in the groove forming step so as to obtain a depth to be formed.
  • the frequency characteristic is adjusted by adjusting the depth of the groove in accordance with the frequency characteristic of the piezoelectric body on which the first and second comb electrodes are formed measured after the groove forming step. Is called. For this reason, the dispersion
  • the groove depth is substantially equal to the frequency characteristic of the boundary acoustic wave device corresponding to the measured frequency characteristic and the target frequency characteristic of the predetermined boundary acoustic wave device. It is preferable to deepen the grooves formed in the groove forming step so as to have the same depth. According to this, the dispersion
  • the method for manufacturing the boundary acoustic wave device includes a first dielectric layer on one surface of the piezoelectric body after the electrode forming step and the groove forming step.
  • the thicknesses of the first dielectric layers in the alternately arranged regions are determined based on the frequency characteristics of the boundary acoustic wave device according to the measured frequency characteristics and the target frequency characteristics of the predetermined boundary acoustic wave device.
  • the frequency characteristic is adjusted by adjusting the thickness of the first dielectric layer according to the frequency characteristic of the piezoelectric body on which the first dielectric layer is formed. For this reason, the dispersion
  • the step of increasing or decreasing the thickness of the first dielectric layer is performed in a region where the electrode fingers of the first comb electrode and the electrode fingers of the second comb electrode are alternately arranged in the propagation direction.
  • the thickness of the first dielectric layer is substantially the same as the frequency characteristic of the boundary acoustic wave device according to the measured frequency characteristic and the target frequency characteristic of the predetermined boundary acoustic wave device.
  • a step of increasing or decreasing the thickness is preferable. According to this, the dispersion
  • a groove located between the electrode finger of the adjacent first comb electrode and the electrode finger of the second comb electrode is formed on the surface of the piezoelectric body on the dielectric side.
  • FIG. 1 is a cross-sectional view showing a part of the boundary acoustic wave device according to the first embodiment.
  • FIG. 2 is a plan view of the boundary acoustic wave device.
  • FIG. 3 is a flowchart showing a manufacturing process of the boundary acoustic wave device according to the first embodiment.
  • FIG. 4 is a flowchart showing a manufacturing process of the boundary acoustic wave device according to the second embodiment.
  • FIG. 5 is a flowchart showing a manufacturing process of the boundary acoustic wave device according to the third embodiment.
  • FIG. 6 is a cross-sectional view illustrating a part of the boundary acoustic wave device according to the fourth embodiment.
  • FIG. 1 is a cross-sectional view showing a part of the boundary acoustic wave device according to the first embodiment.
  • FIG. 2 is a plan view of the boundary acoustic wave device.
  • FIG. 3 is a flowchart showing a manufacturing process of the
  • FIG. 7 is a cross-sectional view illustrating a part of the boundary acoustic wave device according to the fifth embodiment.
  • FIG. 8 is a cross-sectional view showing a part of the boundary acoustic wave device according to the sixth embodiment.
  • FIG. 9 is a flowchart illustrating an example of a manufacturing process of the boundary acoustic wave device according to the sixth embodiment.
  • FIG. 10 is an evaluation circuit diagram of a surge breakdown voltage in the first embodiment.
  • FIG. 11 is a graph showing the correlation between the surge breakdown voltage ratio and the depth of the groove 11 in Example 1.
  • FIG. 12 is a cross-sectional view of a boundary acoustic wave device having an FEM calculation model in the second embodiment.
  • FIG. 13 is a graph showing the results of TCF simulation in Example 2.
  • FIG. 10 is an evaluation circuit diagram of a surge breakdown voltage in the first embodiment.
  • FIG. 11 is a graph showing the correlation between the surge breakdown voltage ratio and the depth of the groove 11 in Example 1.
  • FIG. 14 is a graph showing the result of simulation of the electromechanical coupling coefficient in Example 2.
  • FIG. 15 is a graph showing the result of simulation of the sound velocity (V) in the second embodiment.
  • FIG. 16 is a graph showing TCF measurement results in Example 3.
  • FIG. 17 is a graph showing the measurement result of the resonance frequency in Example 3.
  • FIG. 18 is a graph showing the measurement result of the bandwidth ratio in Example 3.
  • FIG. 1 is a sectional view showing a part of a boundary acoustic wave device 1 according to the first embodiment.
  • FIG. 2 is a plan view of the boundary acoustic wave device 1.
  • the drawing of the dielectric 20 is omitted in FIG.
  • the boundary acoustic wave device is a resonator.
  • the boundary acoustic wave device is not limited to a resonator.
  • the boundary acoustic wave device may be, for example, a filter using a boundary acoustic wave.
  • Specific examples of the filter include a longitudinally coupled resonator type filter and a ladder type filter.
  • boundary acoustic wave is not particularly limited.
  • the boundary acoustic wave may be, for example, an SH type boundary acoustic wave or a Stoneley wave.
  • the boundary acoustic wave device 1 includes a piezoelectric body 10.
  • a dielectric 20 is stacked on one surface of the piezoelectric body 10.
  • An electrode 30 is disposed at the boundary between the piezoelectric body 10 and the dielectric body 20.
  • the piezoelectric body 10 and the dielectric body 20 are not particularly limited as long as the piezoelectric body 10 and the dielectric body 20 are a combination that generates a boundary acoustic wave at the boundary between the piezoelectric body 10 and the dielectric body 20.
  • the dielectric 20 is, SiO 2, SiON, or may be formed of SiN or the like.
  • the piezoelectric body 10 may be made of, for example, LiNbO 3 or LiTaO 3 . More specifically, the piezoelectric body 10 may be, for example, 15 ° Y-cut X-propagation LiNbO 3 .
  • the material of the electrode 30 is not particularly limited.
  • the electrode 30 can be formed of, for example, any one of Pt, Au, Cu, Ag, Al, and W, or an alloy obtained by adding other elements to Pt, Au, Cu, Ag, Al, and W.
  • the electrode 30 may be composed of a plurality of conductive layers made of different materials.
  • the electrode 30 may be configured by a metal layer or alloy layer having strong adhesion to the piezoelectric body 10 and the dielectric 20 and the metal layer or alloy layer. Examples of the metal or alloy having strong adhesion to the piezoelectric body 10 and the dielectric body 20 include NiCr, Ti, and Cr.
  • the electrode 30 includes an IDT 37 and grating reflectors 33 and 34.
  • the grating reflectors 33 and 34 are disposed on both sides of the IDT 37 in the propagation direction d of the boundary acoustic wave.
  • the IDT 37 includes a first comb electrode 31 and a second comb electrode 32.
  • the first comb electrode 31 is connected to the first terminal 35.
  • the second comb electrode 32 is connected to the second terminal 36.
  • the first terminal 35 and the second terminal 36 are connected to different potentials.
  • the first comb electrode 31 includes a first bus bar 31a and a plurality of first electrode fingers 31b connected to the first bus bar 31a.
  • the plurality of first electrode fingers 31b are arranged substantially parallel to each other.
  • the second comb electrode 32 includes a second bus bar 32a and a plurality of second electrode fingers 32b connected to the second bus bar 32a.
  • the plurality of second electrode fingers 32b are arranged in parallel to each other.
  • the plurality of second electrode fingers 32b are alternately arranged with the first electrode fingers 31b in the propagation direction d of the boundary acoustic wave.
  • the pitch (electrode finger center interval) between the first electrode finger 31b and the second electrode finger 32b is not particularly limited.
  • the pitch between the first electrode finger 31b and the second electrode finger 32b can be appropriately set according to the desired frequency characteristics.
  • the pitch between the first electrode finger 31b and the second electrode finger 32b is generally set to about 0.5 ⁇ m to 3 ⁇ m.
  • the pitch (distance between electrode finger centers) between the first electrode finger 31b and the second electrode 32b is represented by ⁇ / 2.
  • ⁇ is the period of the IDT 37.
  • a plurality of grooves 11 are formed on the surface 10a of the piezoelectric body 10 on the dielectric 20 side.
  • the groove 11 extends in the extending direction of the electrode fingers 31b and 32b between the adjacent first electrode finger 31b and the second electrode finger 32b.
  • channel 11 is formed in all between the adjacent 1st electrode finger 31b and the 2nd electrode finger 32b.
  • the groove 11 does not necessarily have to be formed at all between the adjacent first electrode finger 31b and the second electrode finger 32b.
  • channel 11 may be formed in the whole between the adjacent 1st electrode finger 31b and the 2nd electrode finger 32b in planar view, and the adjacent 1st electrode finger 31b and 2nd You may form only in a part between electrode fingers 32b.
  • the first electrode finger 31b and the second electrode finger 32b adjacent to each other are formed on the entire surface. This is because the surge withstand voltage of the boundary acoustic wave device 1 can be increased and the frequency temperature coefficient (TCF) can be reduced.
  • TCF frequency temperature coefficient
  • the cross-sectional shape of the groove 11 along the propagation direction D is a rectangle.
  • the depth of the groove 11 is not particularly limited.
  • the depth of the groove 11 can be appropriately set according to a desired surge withstand voltage, frequency temperature coefficient (TCF), or the like.
  • the depth of the groove 11 can typically be set to about 0 to 500 nm.
  • the surge withstand voltage of the boundary acoustic wave device tends to decrease as the distance between the first electrode finger and the second electrode finger becomes shorter. For this reason, if the distance between the first electrode finger and the second electrode finger is shortened to increase the resonance frequency and anti-resonance frequency of the boundary acoustic wave device, the surge withstand voltage of the boundary acoustic wave device decreases. Become. That is, it is usually difficult to increase the resonance frequency and antiresonance frequency while maintaining the surge withstand voltage.
  • the groove 11 is formed between the first electrode finger 31b and the second electrode finger 32b.
  • the distance on the surface 10a of the piezoelectric body 10 between the 1st electrode finger 31b and the 2nd electrode finger 32b can be made comparatively large.
  • the substantial dielectric constant of the region between the adjacent first electrode finger 31b and the second electrode finger 32b can be made relatively small. Therefore, according to the present embodiment, the surge withstand voltage can be increased as compared with the case where the groove 11 is not formed between the first electrode finger 31b and the second electrode finger 32b. That is, according to the present embodiment, the surge withstand voltage can be increased even when the distance between the first electrode finger 31b and the second electrode finger 32b is short. Therefore, it is possible to increase the frequency of the boundary acoustic wave device 1 while maintaining the surge withstand voltage of the boundary acoustic wave device 1 high.
  • the frequency temperature coefficient can be adjusted by changing the depth of the groove 11. Therefore, the absolute value of the frequency temperature coefficient can be further reduced by adjusting the depth of the groove 11. Specifically, for example, when the piezoelectric body 10 has a negative temperature characteristic and the dielectric body 20 has a positive temperature characteristic, the frequency temperature coefficient can be shifted to the positive side by deepening the groove 11. it can. Usually, in the boundary acoustic wave device in which the groove 11 is not formed, when the piezoelectric body 10 has a negative temperature characteristic and the dielectric body 20 has a positive temperature characteristic, the frequency temperature coefficient is negative. For this reason, the frequency temperature coefficient can be shifted to the positive side by forming the groove 11. Therefore, the absolute value of the frequency temperature coefficient of the boundary acoustic wave device can be reduced.
  • the piezoelectric body 10 is formed of LiNbO 3 and the dielectric body 20 is formed of SiO 2 , a relatively large electromechanical coupling coefficient K 2 can be obtained.
  • LiNbO 3 has negative temperature characteristics, while SiO 2 has positive temperature characteristics.
  • the frequency temperature coefficient can be made relatively small by forming the piezoelectric body 10 from LiNbO 3 and forming the dielectric body 20 from SiO 2 .
  • the negative temperature characteristic of LiNbO 3 is larger than the positive temperature characteristic of SiO 2 , it is difficult to sufficiently reduce the absolute value of the frequency temperature coefficient.
  • the frequency temperature coefficient is shifted to the positive side by forming the groove 11. Therefore, the piezoelectric body 10 is formed of SiO 2 , the dielectric body 20 is formed of LiNbO 3 , and the groove 11 is formed, whereby an elastic boundary where the electromechanical coupling coefficient K 2 is large and the absolute value of the frequency temperature coefficient is small. A wave device can be realized.
  • the depth and the electromechanical coupling coefficient K 2 of the groove 11 has a correlation. Therefore, by adjusting the depth of the groove 11, it is possible to adjust the electromechanical coefficient K 2.
  • the depth of the groove 11 and the frequency characteristic of the boundary acoustic wave device 1 have a correlation as can be seen from the following examples. For this reason, the frequency characteristic of the boundary acoustic wave device 1 can be adjusted by adjusting the depth of the groove 11.
  • the depth of the groove 11 can be adjusted frequency temperature coefficient, the frequency characteristics of the electro-mechanical coupling coefficient K 2 and the boundary acoustic wave device 1. That is, by providing the groove 11, the temperature coefficient of frequency, the frequency characteristics of the electro-mechanical coupling coefficient K 2 and the boundary acoustic wave device 1 can be adjusted.
  • the cross-sectional shape of the groove 11 is preferably rectangular.
  • the distance on the surface 10a of the piezoelectric body 10 between the first electrode finger 31b and the second electrode finger 32b can be further increased. Therefore, the surge withstand voltage of the boundary acoustic wave device 1 can be further increased.
  • the frequency temperature coefficient of the boundary acoustic wave device can be effectively shifted to the temperature characteristic side of the dielectric 20. Therefore, the frequency temperature coefficient of the boundary acoustic wave device can be effectively reduced.
  • the manufacturing method of the boundary acoustic wave device 1 shown below is merely an example.
  • the manufacturing method of the boundary acoustic wave device according to the present invention is not limited to the following method.
  • step S1 the piezoelectric body 10 is prepared.
  • an electrode forming process for forming the electrode 30 on the piezoelectric body 10 is performed.
  • the electrode 30 can be formed, for example, by forming a metal film or an alloy film by a known thin film forming method and then patterning by a known patterning method.
  • the thin film forming method include an electron beam evaporation method and a sputtering method.
  • the patterning method include a photolithography method.
  • a groove forming step for forming the grooves 11 is performed.
  • the groove 11 can be formed by, for example, a known etching method.
  • Specific examples of the etching method include dry etching such as reactive ion etching, wet etching using an etchant, and the like.
  • Examples of ions used in the reactive ion etching method include fluorine ions.
  • An etchant used for wet etching includes, for example, hydrofluoric acid.
  • the groove 11 may be formed by milling using Ar ions, for example.
  • the electrode 30 may be used as a mask for patterning, and a separately formed oxide film such as SiO 2 or a nitride film such as Si 3 N 4 may be used as a mask for patterning. It may be used as
  • the boundary acoustic wave device 1 is completed by forming the dielectric 20 in step S4.
  • the method for forming the dielectric 20 is not particularly limited.
  • the dielectric 20 can be formed by, for example, a known film forming method.
  • the dielectric 20 can be formed by, for example, a sputtering method such as RF magnetron sputtering.
  • FIGS. 1 and 2 are referred to in common with the first embodiment.
  • members having substantially the same functions as those of the first embodiment are referred to by common reference numerals, and description thereof is omitted.
  • step S1 and step S2 are performed as shown in FIG.
  • step S5 is performed subsequent to step S2.
  • step S5 the frequency characteristic of the piezoelectric body 10 on which the electrode 30 is formed is measured.
  • the boundary acoustic wave device to be manufactured as in this embodiment is a resonator
  • step S5 for example, at least one of a resonance frequency and an anti-resonance frequency is measured.
  • the boundary acoustic wave device to be manufactured is a filter
  • step S5 for example, the center frequency is measured.
  • step S6 the depth of the groove 11 is determined. Specifically, the difference between the frequency characteristic of the boundary acoustic wave device 1 estimated according to the frequency characteristic measured in step S5 and the target frequency characteristic of the boundary acoustic wave device 1 determined in advance is reduced. As described above, the depth of the groove 11 is determined.
  • the frequency characteristic of the boundary acoustic wave device 1 estimated according to the frequency characteristic measured in step S5 is substantially the same as the target frequency characteristic of the predetermined boundary acoustic wave device 1. As described above, the depth of the groove 11 is determined.
  • step S7 the groove 11 is formed.
  • step S7 the groove 11 having the depth calculated in step S6 is formed.
  • the boundary acoustic wave device 1 is completed by forming the dielectric 20 in step S4.
  • the frequency characteristics of the produced boundary acoustic wave device may vary.
  • the frequency characteristic of the piezoelectric body 10 on which the electrode 30 is formed is measured, and the groove 11 having a depth determined based on the measurement result is formed.
  • the frequency characteristics of the boundary acoustic wave device can be finely adjusted. Therefore, variation in frequency characteristics of the produced boundary acoustic wave device 1 can be reduced.
  • the boundary acoustic wave device is a resonator, it is possible to suppress variation in at least one of the resonance frequency and the antiresonance frequency.
  • the boundary acoustic wave device is a filter, it is possible to suppress variations in the center frequency.
  • step S3 after the groove 11 having a predetermined depth is formed in step S3, the frequency characteristic may be measured in step S8.
  • step S8 the frequency characteristic of the piezoelectric body 10 in which the electrode 30 and the groove 11 are formed is measured.
  • step S9 the adjustment amount of the depth of the groove 11 is determined. Specifically, the difference between the frequency characteristic of the boundary acoustic wave device 1 estimated according to the frequency characteristic measured in step S8 and the target frequency characteristic of the boundary acoustic wave device 1 determined in advance is reduced. The depth of the groove 11 is calculated. Preferably, the frequency characteristic of the boundary acoustic wave device 1 estimated according to the frequency characteristic measured in step S8 is substantially the same as the target frequency characteristic of the predetermined boundary acoustic wave device 1. The depth of the groove 11 is calculated. An adjustment amount of the depth of the groove 11 is determined from the calculated preferable depth of the groove 11 and the current depth of the groove 11.
  • step S10 the depth of the groove 11 is adjusted. Specifically, the groove 11 is deepened so that the depth of the groove 11 becomes the depth calculated in step S9.
  • a method for deepening the groove 11 a known etching method, milling method, or the like can be used.
  • step S4 the boundary acoustic wave device 1 is completed by forming the dielectric 20.
  • the depth of the groove 11 is adjusted based on the measurement result of the frequency characteristic, similarly to the second embodiment, variation in the frequency characteristic of the boundary acoustic wave device 1 to be manufactured is reduced. be able to.
  • the cross-sectional shape of the groove 11 is rectangular.
  • the cross-sectional shape of the groove 11 is not limited to a rectangle.
  • the cross-sectional shape of the groove 11 may be, for example, a trapezoid that becomes narrower in the depth direction.
  • channel 11 may be a triangle which becomes narrow toward a depth direction, for example.
  • the dielectric 20 In the first embodiment, the example in which the dielectric 20 is configured by one dielectric layer has been described. However, the dielectric 20 may be formed of a plurality of dielectric layers as shown in FIG.
  • the dielectric 20 includes a first dielectric layer 21 and a second dielectric layer 22.
  • the first dielectric layer 21 is formed so as to cover the piezoelectric body 10 and the electrode 30.
  • the second dielectric layer 22 is formed on the first dielectric layer 21.
  • the sound speed of the second dielectric layer 22 is faster than the sound speed of the first dielectric layer 21.
  • the frequency characteristics of the boundary acoustic wave can be increased. Therefore, the distance between the first electrode finger 31b and the second electrode finger 32b adjacent to each other can be made relatively wide as compared with the case where the dielectric layer 20 is formed only by the first dielectric material 21. Therefore, the surge withstand voltage of the boundary acoustic wave device can be further increased.
  • the frequency characteristic of the boundary acoustic wave device obtained by adjusting the thickness of the first dielectric layer 21 can be adjusted. Therefore, it is possible to reduce variation in frequency characteristics of the manufactured boundary acoustic wave device 1.
  • FIG. 9 is a flowchart showing an example of a manufacturing process of the boundary acoustic wave device according to the sixth embodiment. As shown in FIG. 9, in this embodiment as well, in the same manner as in the first embodiment, the preparation of the piezoelectric body 10 in step S1, the formation of the electrode 30 in step S2, and the formation of the groove 11 in step S3 are sequentially performed. .
  • step S11 is performed following step S3.
  • step S11 the first dielectric layer 21 having a predetermined thickness is formed.
  • step S12 the frequency characteristics of the piezoelectric body 10 on which the first dielectric layer 21 is formed are measured.
  • step S13 the adjustment amount of the thickness of the first dielectric layer 21 is determined. Specifically, the difference between the frequency characteristic of the boundary acoustic wave device 1 estimated according to the frequency characteristic measured in step S12 and the target frequency characteristic of the boundary acoustic wave device 1 determined in advance is reduced. The thickness of the first dielectric layer 21 is calculated. Preferably, the frequency characteristics of the boundary acoustic wave device 1 estimated according to the frequency characteristics measured in step S12 are substantially the same as the target frequency characteristics of the predetermined boundary acoustic wave device 1. The thickness of the first dielectric layer 21 is calculated.
  • step S14 the thickness of the first dielectric layer 21 is adjusted. Specifically, the thickness of the first dielectric layer 21 is adjusted so that the thickness of the first dielectric layer 21 becomes the thickness determined in step S13.
  • step S15 the second dielectric layer 22 is formed, and the boundary acoustic wave device is completed.
  • the thickness of the first dielectric layer 21 is adjusted based on the measured frequency characteristics, variations in the frequency characteristics of the manufactured boundary acoustic wave device 1 can be reduced. .
  • the depth of the groove 11 may be adjusted by measuring the frequency characteristics before or after the formation of the groove 11.
  • Example 1 A one-port resonator 1 shown in FIGS. 1 and 2 was produced. Specifically, a 15 ° Y-cut LiNbO 3 single crystal substrate was used as the piezoelectric body 10. An electrode 30 having a total film thickness of 315 nm was formed on the piezoelectric body 10 by forming a film by electron beam evaporation and then patterning by photolithography. The structure of the electrode 30 is NiCr film (film thickness: 30 nm) / AlCu film (film thickness: 150 nm) / Ti film (film thickness: 10 nm) / Pt film (film thickness: 105 nm) / NiCr film (film) from the piezoelectric body side. (Thickness: 10 nm).
  • the groove 11 was formed by etching the piezoelectric body 10 by reactive ion etching using a fluorine-based gas using the NiCr film located on the uppermost layer of the electrode 30 as a mask. Thereafter, a dielectric 20 was formed by forming a SiO 2 film having a thickness of 5000 nm by RF magnetron sputtering, and the resonator 1 was obtained.
  • a machine model evaluation circuit shown in FIG. 10 was formed using the obtained resonator 1, and the surge breakdown voltage of the resonator 1 was measured based on the EIA / JESD22-A115-A standard. Specifically, first, the resonator 1 and the capacitor C having a capacitance of 200 pF were connected in parallel to the high voltage pulse power supply G. Then, a voltage was applied to the capacitor C by the high voltage pulse power source G with the switch SW connected to the high voltage pulse power source G side. Thereafter, the switch SW was switched to connect the capacitor C and the resonator 1, thereby applying a surge voltage to the resonator 1. Thereafter, whether or not the resonator 1 was broken was observed with a microscope, and impedance characteristics were measured. Repeat this inspection while increasing the voltage of the high-voltage pulse power supply in increments of 2 to 3 V. Surge breakdown voltage.
  • the surge breakdown voltage is increased by forming the groove 11. That is, it can be seen that the surge withstand voltage of the resonator can be increased by forming the groove 11. It can also be seen that the surge breakdown voltage can be further increased by deepening the groove 11.
  • Example 2 Next, using the boundary acoustic wave device shown in FIG. 12 as a calculation model, the depth of the groove 11, the specific bandwidth, the electromechanical coupling coefficient K 2 , the frequency temperature coefficient (TCF), and the speed of sound are each determined by a finite element method (FEM). The relationship was simulated. The simulation conditions are shown in Table 2 below. The simulation results are shown in Table 3 and FIGS.
  • FEM finite element method
  • the specific bandwidth is defined by the following formula (1).
  • TCF frequency temperature coefficient
  • TCF V ⁇ 1 (25 ° C.) ⁇ ⁇ (V (30 ° C.) ⁇ V (20 ° C.) ⁇ / 10 (° C.) ⁇ ⁇ S (2)
  • V (25 ° C.) speed of sound at 25 ° C.
  • V (30 ° C.) speed of sound at 30 ° C.
  • V (20 ° C.) speed of sound at 20 ° C.
  • ⁇ S linear expansion coefficient
  • the value of the frequency temperature coefficient (TCF) can be increased by deepening the groove 11. It can be seen that the absolute value of the frequency temperature coefficient can be reduced by forming the groove 11 as compared to the case where the groove 11 is not formed. From the results shown in Table 3 and FIG. 13, the depth of the groove 11 is preferably 0.05 ⁇ or more, and more preferably 0.1 ⁇ or more and 0.15 ⁇ or less. This is because the absolute value of the frequency temperature coefficient can be particularly reduced by doing so.
  • the specific bandwidth can be changed by changing the depth of the groove 11. Specifically, it can be seen that the specific bandwidth can be narrowed by deepening the groove 11.
  • the electromechanical coupling coefficient K 2 can be changed by changing the depth of the groove 11. Specifically, it can be seen that the electromechanical coupling coefficient K 2 can be reduced by deepening the groove 11.
  • the sound velocity (V) can be changed by changing the depth of the groove 11. Specifically, it can be seen that the sound velocity (V) can be increased by deepening the groove 11.
  • Example 3 A 1-port resonator similar to that in Example 1 was fabricated in the same procedure as in Example 1. For the obtained resonator, the frequency temperature coefficient, the resonance frequency, and the ratio band were measured. Specifically, the impedance temperature was measured, the frequency at each temperature was measured, and the frequency temperature coefficient (TCF), resonance frequency, and ratio band were obtained by applying the measurement results to the following formulas (3) and (4). .
  • Ratio band ⁇ (fa (25 ° C.) ⁇ Fr (25 ° C.)) / Fr (25 ° C.) ⁇ ⁇ 100 (4)
  • the frequency temperature coefficient is improved by deepening the groove 11 in the measurement results of this example as well as the simulation results.
  • channel 11 and each of a resonant frequency and a specific band have a correlation.
  • the resonance frequency is shifted to the lower frequency side by deepening the groove 11.
  • the ratio band is reduced by deepening the groove 11. From the above, it can be seen that each of the resonance frequency and the ratio band can be adjusted by adjusting the depth of the groove 11.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

La présente invention permet d’augmenter la fréquence d’ondes acoustiques tout en maintenant une pression de résistance à une surtension élevée. Un dispositif à onde acoustique limite (1) comporte un corps piézo-électrique (10), un corps diélectrique (20) et une électrode (30) disposée à la limite entre le corps piézo-électrique (10) et le corps diélectrique (20), et utilise des ondes acoustiques limites se propageant à travers la limite. L'électrode (30) comprend une première électrode (31) en dents de peigne comprenant une pluralité d'électrodes en forme de doigt (31b), et une seconde électrode en dents de peigne (32) comprenant une pluralité d'électrodes en forme de doigt (32b). Les électrodes en forme de doigt (32b) sont agencées en alternance avec les électrodes en forme de doigt (31b) dans la direction de propagation des ondes acoustiques limites. La seconde électrode en dents de peigne (32) est connectée à un potentiel différent de celui de la première électrode en dents de peigne (31). Dans la surface (10a) du corps piézo-électrique (10) placé sur le côté du corps diélectrique (20), des rainures (11) sont formées dans la direction dans laquelle les électrodes en forme de doigt. Les rainures (11) sont positionnées respectivement entre les électrodes en forme de doigt (31b) et les électrodes en forme de doigt (32b) respectivement adjacentes les unes aux autres.
PCT/JP2009/000891 2008-04-10 2009-02-27 Dispositif à onde acoustique limite et son procédé de fabrication WO2009125536A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011135469A (ja) * 2009-12-25 2011-07-07 Murata Mfg Co Ltd 弾性波装置
WO2012102131A1 (fr) * 2011-01-27 2012-08-02 京セラ株式会社 Élément à ondes élastiques et appareil à ondes élastiques faisant appel à celui-ci

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04199906A (ja) * 1990-11-29 1992-07-21 Kokusai Electric Co Ltd 弾性表面波共振子
WO2005093949A1 (fr) * 2004-03-29 2005-10-06 Murata Manufacturing Co., Ltd. Procédé de fabrication de dispositif à onde acoustique limite et dispositif à onde acoustique limite
WO2006114930A1 (fr) * 2005-04-25 2006-11-02 Murata Manufacturing Co., Ltd. Dispositif a ondes acoustiques de bord

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04199906A (ja) * 1990-11-29 1992-07-21 Kokusai Electric Co Ltd 弾性表面波共振子
WO2005093949A1 (fr) * 2004-03-29 2005-10-06 Murata Manufacturing Co., Ltd. Procédé de fabrication de dispositif à onde acoustique limite et dispositif à onde acoustique limite
WO2006114930A1 (fr) * 2005-04-25 2006-11-02 Murata Manufacturing Co., Ltd. Dispositif a ondes acoustiques de bord

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011135469A (ja) * 2009-12-25 2011-07-07 Murata Mfg Co Ltd 弾性波装置
WO2012102131A1 (fr) * 2011-01-27 2012-08-02 京セラ株式会社 Élément à ondes élastiques et appareil à ondes élastiques faisant appel à celui-ci
JPWO2012102131A1 (ja) * 2011-01-27 2014-06-30 京セラ株式会社 弾性波素子およびそれを用いた弾性波装置

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