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WO2012114930A1 - Filtre accordable et son procédé de fabrication - Google Patents

Filtre accordable et son procédé de fabrication Download PDF

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Publication number
WO2012114930A1
WO2012114930A1 PCT/JP2012/053342 JP2012053342W WO2012114930A1 WO 2012114930 A1 WO2012114930 A1 WO 2012114930A1 JP 2012053342 W JP2012053342 W JP 2012053342W WO 2012114930 A1 WO2012114930 A1 WO 2012114930A1
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WO
WIPO (PCT)
Prior art keywords
dielectric film
forming
piezoelectric substrate
film
tunable filter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2012/053342
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English (en)
Japanese (ja)
Inventor
門田　道雄
伊保龍 掘露
栄樹 平野
田中　秀治
江刺　正喜
橋本　研也
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tohoku University NUC
Chiba University NUC
Murata Manufacturing Co Ltd
Original Assignee
Tohoku University NUC
Chiba University NUC
Murata Manufacturing Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tohoku University NUC, Chiba University NUC, Murata Manufacturing Co Ltd filed Critical Tohoku University NUC
Priority to JP2013500966A priority Critical patent/JP5548303B2/ja
Publication of WO2012114930A1 publication Critical patent/WO2012114930A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • H03H3/10—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 for obtaining desired frequency or temperature coefficient
    • 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
    • H03H3/02—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 piezoelectric or electrostrictive resonators or networks
    • H03H3/04—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 piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/05—Holders or supports
    • H03H9/0538—Constructional combinations of supports or holders with electromechanical or other electronic elements
    • H03H9/0542—Constructional combinations of supports or holders with electromechanical or other electronic elements consisting of a lateral arrangement
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6403—Programmable filters
    • 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
    • H03H3/02—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 piezoelectric or electrostrictive resonators or networks
    • H03H3/04—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 piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
    • H03H2003/0414—Resonance frequency
    • H03H2003/0464—Resonance frequency operating on an additional circuit element, e.g. a passive circuit element connected to the resonator

Definitions

  • the present invention relates to a tunable filter having a variable capacitor using a dielectric film whose relative dielectric constant changes depending on an applied voltage, and more particularly, an tunable filter in which an acoustic wave resonator and the variable capacitor are formed on a piezoelectric substrate. And a manufacturing method thereof.
  • Patent Document 1 discloses a piezoelectric filter in which a piezoelectric resonator and a variable capacitor are configured on a substrate.
  • FIG. 8 is a circuit diagram showing the piezoelectric filter described in Patent Document 1.
  • the piezoelectric filter 1001 includes a series piezoelectric resonator 1002 and parallel piezoelectric resonators 1003 and 1004.
  • An inductor 1005 is connected between the parallel piezoelectric resonator 1003 and the ground potential.
  • An inductor 1006 is connected between the parallel piezoelectric resonator 1004 and the ground potential.
  • a bypass piezoelectric resonator 1007 is connected between a connection point between the parallel piezoelectric resonator 1003 and the inductor 1005 and a connection point between the parallel piezoelectric resonator 1004 and the inductor 1006.
  • a variable capacitor 1008 is connected in parallel to the bypass piezoelectric resonator 1007.
  • FIG. 9 is a schematic plan view of the piezoelectric filter 1001
  • FIG. 10 is a schematic cross-sectional view of a portion along the line AA in FIG.
  • the piezoelectric filter 1001 is configured using a substrate 1009 made of a silicon or glass substrate.
  • the series piezoelectric resonator 1002 and the parallel piezoelectric resonators 1003 and 1004 are constituted by piezoelectric thin film resonators provided on a substrate 1009.
  • the series piezoelectric resonator 1002 and the bypass piezoelectric resonator 1007 are configured as piezoelectric thin film resonators on cavities 1009 a and 1009 b provided on the substrate 1009.
  • a variable capacitor 1008 for adjusting the filter characteristics is configured by laminating a lower electrode 1011, a ferroelectric layer 1012, and an upper electrode 1013 in this order on an insulator layer 1010 provided on a substrate 1009. Yes.
  • Patent Document 1 shows that the ferroelectric layer 1012 is made of barium strontium titanate (Ba x Sr 1-x TiO 3 ) or the like.
  • the insulator layer 1010 is made of silicon dioxide, silicon nitride, or the like, and the lower electrode 1011 is made of the same material as the lower electrode of the piezoelectric thin film resonator, for example, Mo, Al, Ag, W, or Pt. Has been.
  • a variable capacitor 1008 is formed of a laminated body of a lower electrode 1011, a ferroelectric layer 1012, and an upper electrode 1013. Therefore, it is possible to reduce the size and thickness of the variable capacitance component.
  • a piezoelectric thin film resonator has to be formed on the substrate 1009 by forming a piezoelectric layer.
  • a dielectric layer made of barium strontium titanate (hereinafter abbreviated as BST) described in Patent Document 1 can be satisfactorily formed only on a specific substrate such as sapphire or MgO. Therefore, it has been impossible to form a variable capacitor having a dielectric layer made of BST using an optimum piezoelectric substrate according to the target filter characteristics.
  • BST barium strontium titanate
  • the deposition temperature of the BST film is as high as 800 ° C to 900 ° C. Therefore, when it is formed on a piezoelectric substrate made of a piezoelectric material having a low Curie temperature, the piezoelectric characteristics may be deteriorated. There is also a problem that the piezoelectric substrate is warped or cracked and the BST film is peeled off.
  • a tunable filter in which a variable capacitance element including a surface acoustic wave resonator and a varactor diode is formed on a piezoelectric substrate.
  • the variable capacitance element is a varactor diode and is not a variable capacitor using the ferroelectric layer.
  • An object of the present invention is to configure an acoustic wave resonator and a variable capacitor formed using a dielectric film whose capacitance changes according to an applied voltage on the same piezoelectric substrate.
  • An object of the present invention is to provide a tunable filter and a method for manufacturing the tunable filter.
  • a tunable filter according to the present invention includes a piezoelectric substrate made of a piezoelectric material, an elastic wave resonator formed on the piezoelectric substrate, and a variable capacitor formed on the piezoelectric substrate.
  • the variable capacitor is formed directly or indirectly on the piezoelectric substrate, and a dielectric film whose capacitance changes according to an applied voltage, and a first capacitor provided so that an electric field can be applied to the dielectric film.
  • An electrode and a second electrode is formed directly or indirectly on the piezoelectric substrate, and a dielectric film whose capacitance changes according to an applied voltage, and a first capacitor provided so that an electric field can be applied to the dielectric film.
  • the dielectric film is made of barium strontium titanate, and in this case, a variable capacitor having a large capacitance variable width can be easily configured.
  • the dielectric film is a dielectric film formed by transfer on the piezoelectric substrate. Since the dielectric film is formed by transfer, the dielectric film is formed on a transfer support substrate that is easy to form and transferred, so that the dielectric film can be reliably and directly on the piezoelectric substrate. It can be easily stacked.
  • the acoustic wave resonator is a surface acoustic wave resonator or a piezoelectric thin film resonator.
  • the surface acoustic wave resonator may be a surface acoustic wave resonator or a piezoelectric thin film resonator.
  • the method for manufacturing a tunable filter according to the present invention includes a step of preparing a piezoelectric substrate, a step of forming an elastic wave resonator on the piezoelectric substrate, and a step of forming a variable capacitor on the piezoelectric substrate.
  • the dielectric film is formed by a transfer method.
  • the step of forming the variable capacitor includes the step of forming a dielectric film on the transfer support substrate and the step of forming the transfer capacitor on the transfer support substrate. Transferring the formed dielectric film onto the piezoelectric substrate.
  • the step of forming the variable capacitor forms a removable sacrificial film on the transfer support substrate, and the sacrificial film is formed on the sacrificial film.
  • the step of forming the variable capacitor includes melting or volatilizing by absorbing the laser beam on a transfer support substrate that transmits the laser beam.
  • the step of forming the variable capacitor includes the step of forming the dielectric film on a transfer support substrate that can be removed later,
  • the method includes a step of directly or indirectly bonding a dielectric film on the piezoelectric substrate, and a step of removing the transfer support substrate after bonding.
  • the step of forming the variable capacitor includes a step of forming a peelable strength with respect to the dielectric film on the transfer support substrate with respect to the transfer support substrate.
  • the method further includes a step of forming an alignment film oriented in a specific direction on the piezoelectric substrate, and the dielectric is formed on the alignment film. Films are stacked. In this case, since the dielectric film is laminated on the alignment film oriented in a specific direction, the capacitance variable width can be further increased.
  • the tunable filter according to the present invention since the acoustic wave resonator and the variable capacitor are formed on the same piezoelectric substrate, the size of the tunable filter can be reduced.
  • the variable capacitor is formed using a dielectric film whose capacitance changes with the applied voltage. As a result, it is possible to reduce the size of the variable capacitor itself. Accordingly, it is possible to further reduce the size of the tunable filter.
  • the variable capacitor and the elastic wave resonator can be formed on the same piezoelectric substrate, and the tunable filter can be reduced in size. Can be achieved.
  • the dielectric film is formed by a transfer method, the dielectric film can be easily formed on a transfer support substrate suitable for the formation of the dielectric film whose electrostatic capacity changes depending on the applied voltage. it can. Therefore, the dielectric film can be reliably stacked on the piezoelectric substrate on which it is difficult to directly form the dielectric film. Therefore, the tunable filter of the present invention that can be miniaturized can be provided.
  • the number of elements used can be greatly reduced, and the parasitic capacitance can also be reduced. Therefore, it is possible to improve communication quality and yield by using a tunable filter.
  • FIGS. 1A and 1B are a plan view of a tunable filter according to an embodiment of the present invention and a partially cutaway enlarged cross-sectional view showing the main part thereof.
  • FIG. 2 is a circuit diagram of a tunable filter according to an embodiment of the present invention.
  • FIGS. 3A to 3F are front sectional views for explaining a method for manufacturing a tunable filter according to an embodiment of the present invention.
  • FIG. 4 is a diagram for explaining the frequency characteristics of the tunable filter according to the embodiment of the present invention.
  • FIGS. 5A to 5F are front sectional views for explaining a method of manufacturing a tunable filter according to the second embodiment of the present invention.
  • FIGS. 6A to 6F are front sectional views for explaining a method of manufacturing a tunable filter according to another embodiment of the present invention.
  • FIGS. 7A to 7F are front sectional views for explaining a method for manufacturing a tunable filter according to still another embodiment of the present invention.
  • FIG. 8 is a circuit diagram of a conventional piezoelectric filter.
  • FIG. 9 is a schematic plan view of the piezoelectric filter shown in FIG.
  • FIG. 10 is a cross-sectional view of a portion along line AA in FIG.
  • FIG. 1A is a schematic plan view of a tunable filter according to the first embodiment of the present invention
  • FIG. 1B is a schematic partial cutaway enlarged cross-sectional view showing a main part thereof.
  • FIG. 2 is a circuit diagram of the tunable filter of this embodiment.
  • the tunable filter 1 has an input terminal 2 and an output terminal 3.
  • the first to third series arm resonators S1 to S3 are connected in series with each other.
  • a first variable capacitor C1 is connected in parallel to the first series arm resonator S1.
  • a second variable capacitor C2 is connected in parallel to the second series arm resonator S2.
  • a third variable capacitor C3 is connected in parallel with the third series arm resonator S3.
  • first parallel arm resonator P1 is connected between the connection point 4 between the first and second series arm resonators S1 and S2 and the ground potential.
  • a fourth variable capacitor C4 is connected in series with the first parallel arm resonator P1.
  • a second parallel arm resonator P2 is connected between the connection point 5 between the second and third series arm resonators S2 and S3 and the ground potential.
  • a fifth variable capacitor C5 is connected in series with the parallel arm resonator P2.
  • the tunable filter 1 has a ladder circuit configuration including the first to third series arm resonators S1 to S3 and the first and second parallel arm resonators P1 and P2.
  • the present embodiment is characterized in that the first to third series arm resonators S1 to S3 and the first and second parallel arm resonators are formed on one piezoelectric substrate 6. Not only P1 and P2, but also first to fifth variable capacitors C1 to C5 are configured.
  • the first series arm resonator S1 includes an IDT electrode 7 and reflectors 8 and 9 disposed on both sides of the IDT electrode 7 in the surface acoustic wave propagation direction. That is, the series arm resonator S1 is a one-port surface acoustic wave resonator.
  • the other resonators that is, the second and third series arm resonators S2 and S3 and the first and second parallel arm resonators P1 and P2 are formed of one-port surface acoustic wave resonators.
  • a plurality of surface acoustic wave resonators and the first to fifth variable capacitors C1 to C5 are integrated on one piezoelectric substrate 6.
  • FIG. 1B is a partially cutaway cross-sectional view showing a portion where the first series arm resonator S1 and the first variable capacitor C1 are formed. That is, FIG. 1B is a cross-sectional view of a portion along the line BB in FIG.
  • a first variable capacitor C1 is formed on the side of the IDT electrode 7.
  • the IDT electrode 7 and the first variable capacitor C1 are electrically connected by a wiring pattern 10 shown in FIG.
  • the first variable capacitor C1 includes a first electrode 11 formed on the piezoelectric substrate 6, a dielectric film 12 formed on the first electrode 11, and a second layer laminated on the dielectric film 12. Electrode 13.
  • the variable capacitor is formed by sandwiching the dielectric film 12 between the first electrode 11 and the second electrode 13, the structure of the variable capacitor is not limited to this. Since it is sufficient that an electric field can be applied to the dielectric film, for example, the first electrode and the second electrode may be formed on the dielectric film.
  • the dielectric film 12 is made of a dielectric material whose capacitance changes according to the magnitude of the applied voltage.
  • BST barium strontium titanate
  • x is a number greater than 0 and less than 1.
  • x is 0.2 ⁇ x ⁇ 0.8 Range.
  • BZN bismuth zinc niobate
  • STO strontium titanate
  • KTaO 3 KTaO 3 or the like
  • a BST film cannot be directly formed on a piezoelectric substrate such as LiTaO 3 or LiNbO 3 . Therefore, a BST film is formed on a substrate made of sapphire or MgO.
  • a BST film is formed on a piezoelectric substrate directly or indirectly by a transfer method described later, or after a buffer layer is formed on the piezoelectric substrate. It has been found that a variable capacitor using a BST film can be integrally formed on a piezoelectric substrate.
  • a process of forming a dielectric film by this transfer method and a process of directly forming a BST film on a piezoelectric substrate will be described in detail in this embodiment and second to fifth embodiments described later.
  • the variable capacitors C1 to C5 are formed using the dielectric film 12 whose electrostatic capacitance changes according to the applied voltage. Therefore, as described above, since a plurality of acoustic wave resonators and a plurality of variable capacitors are integrated on one piezoelectric substrate 6, the tunable filter 1 can be reduced in size.
  • the surface acoustic wave resonator is used as the acoustic wave resonator.
  • the acoustic wave resonator may be configured using a boundary acoustic wave resonator or a piezoelectric thin film resonator. That is, the acoustic wave resonator formed on the piezoelectric substrate 6 is not limited to the surface acoustic wave resonator.
  • the piezoelectric substrate 6 is a 15 ° YX LiNbO 3 substrate.
  • the frequency variable width in the tunable filter having a variable capacitor cannot exceed the passband of the surface acoustic wave resonator itself. Therefore, in order to widen the variable frequency range, it is desirable to widen the pass band of the surface acoustic wave resonator. Therefore, in this embodiment, a 15 ° YX LiNbO 3 substrate having a large Love-wave electromechanical coupling coefficient k 2 is used as the piezoelectric substrate 6.
  • the material constituting the piezoelectric substrate may be LiNbO 3 having another cut angle, or may be formed of another piezoelectric single crystal such as LiTaO 3 .
  • the elastic wave to be used is not limited to the love wave.
  • the electrodes of the respective surface acoustic wave resonators including the IDT electrode 7 and the reflectors 8 and 9 are made of Au.
  • the manufacturing method will be described as a representative of the portion where the IDT electrode 7 and the first variable capacitor C1 of the first series arm resonator S1 are formed. To do.
  • a transfer support substrate 21 made of (100) silicon single crystal having a thickness of 625 ⁇ m was prepared.
  • the transfer support substrate 21 has a thermal oxide film 21a having a thickness of 300 nm on the upper surface.
  • a Ge film having a thickness of 300 nm was laminated as a sacrificial layer 22 by a sputtering method.
  • a Pt film 13 ⁇ / b> A was stacked on the sacrificial layer 22. That is, a Pt film 13A having a thickness of 100 nm was formed by sputtering.
  • a dielectric film 12A made of BST having a thickness of 120 nm was formed by sputtering at a substrate temperature of 700 ° C.
  • the dielectric film 12A from BST thus obtained was analyzed by X-ray diffraction, and it was confirmed that it had (111) orientation with excellent varactor characteristics.
  • the dielectric film 12A and the Pt film 13A were patterned by a reactive ion etching method. Thereby, as shown in FIG. 3B, the second electrode 13 and the dielectric film 12 were formed.
  • a first electrode 11 made of Au having a thickness of 100 nm was formed on the dielectric film 12 by a sputtering method by a lift-off method.
  • FIG. 3C a plurality of surface acoustic wave resonators shown in FIG. 1A including an IDT electrode 7 separately on a piezoelectric substrate 6 made of LiNbO 3 of 15 ° YX.
  • the wiring pattern 10 connected to the surface acoustic wave resonator was formed of Au.
  • the transfer support substrate 21 shown in FIG. 3B and the piezoelectric substrate 6 shown in FIG. 3C are heated in an argon plasma for 1 minute, as shown in FIG.
  • the transfer support substrate 21 was turned upside down and laminated.
  • the first electrode 11 was brought into contact with the wiring pattern 10 and thermocompression bonded under conditions of 100 ° C. and 10000 Pa in a nitrogen atmosphere to join the two.
  • the surface of the bonding surface made of Au was removed, and the surface was activated.
  • the bonding temperature is as low as 100 ° C. Therefore, there was no crack caused by the difference in thermal expansion coefficient between the transfer support substrate 21 made of silicon and the piezoelectric substrate 6 made of LiNbO 3 .
  • the laminated structure was immersed in 30% by weight hydrogen peroxide solution, and the sacrificial layer 22 was etched as shown in FIG.
  • the second electrode 13 and the thermal oxide film 21a of the transfer support substrate 21 were separated, and the dielectric film 12 was transferred to the piezoelectric substrate 6 side. That is, the variable capacitor component was transferred to the piezoelectric substrate 6 side.
  • the periphery of the variable capacitor component was sealed with an insulating layer 24 made of photosensitive polyimide. Further, the wiring pattern 10A connected to the second electrode 13 of the variable capacitor C1 was formed of Cu.
  • the dielectric film 12 made of the BST film is laminated on the piezoelectric substrate 6 by the transfer method. That is, a variable capacitor having the dielectric film 12 made of a BST film on the piezoelectric substrate 6 can be integrally formed with the piezoelectric substrate 6.
  • FIG. 4 is a diagram for explaining the frequency characteristics of the tunable filter 1 of the present embodiment.
  • the center frequency was 1.71 GHz when no voltage was applied to the variable capacitors C1 to C5.
  • the center frequency Changed to 1.64 GHz.
  • the attenuation pole on the high band side of the filter pass band changed from 1.85 GHz to 1.76 GHz.
  • Ge is used as the material for the sacrificial layer.
  • An appropriate material such as Ti, Ru, or W can be used.
  • an etchant for removing the sacrificial layer an appropriate etchant that does not damage the BST film can be used. Further, wet etching or dry etching may be used.
  • a combination of a ruthenium sacrificial layer and an etching gas made of ozone gas a combination of a sacrificial layer made of TiW and hydrogen peroxide solution, or the like is used. Can do.
  • the second transfer substrate having a thermal expansion coefficient between the two thermal expansion coefficients is used. After preparing a support substrate and transferring the dielectric film to the second transfer support substrate, the dielectric film may be transferred from the second transfer support substrate side to the piezoelectric substrate side.
  • a tunable filter according to the second embodiment A method for manufacturing a tunable filter according to the second embodiment will be described with reference to FIGS.
  • a tunable filter having a structure substantially similar to that of the first embodiment is manufactured. However, as described below, it differs in the method of forming a variable capacitor having a dielectric film.
  • a transfer support substrate 31 made of a sapphire single crystal having a thickness of 500 ⁇ m was prepared.
  • a Ru film having a thickness of 20 nm was formed by sputtering to form a release layer 32.
  • a Pt film 13A having a thickness of 100 nm was formed on the release layer 32 as a buffer layer.
  • a dielectric film 12A made of a bismuth zinc niobate (BZN) film having a thickness of 150 nm was formed by sputtering at a substrate temperature of 650 ° C.
  • the dielectric film 12A and the Pt film 13A as the buffer layer were processed by a reactive ion etching method so as to have a final planar shape of the variable capacitor.
  • the second electrode 13 made of the Pt film 13A and the dielectric film 12 for the variable capacitor were formed.
  • a 100 nm-thick Sn film was formed on the BZN layer by a lift-off method to form the first electrode 11.
  • the IDT electrode 7 and the wiring pattern 10 are separately made of Au on the piezoelectric substrate 6 made of LiNbO 3 of 15 ° YX as in the first embodiment. Formed.
  • the transfer support substrate 31 and the piezoelectric substrate 6 processed as described above were eutectic bonded as shown in FIG. 5D under a nitrogen atmosphere at a temperature of 250 ° C. and 10,000 Pa. That is, the structure shown in FIG. 5B was turned upside down on the piezoelectric substrate 6 and bonded under the above conditions. As a result, the first electrode 11 was eutectic bonded to the wiring pattern 10.
  • the insulating layer 24 and the wiring pattern 10A were formed to obtain a tunable filter.
  • the center frequency was 1.71 GHz when no voltage was applied to any of the first to fifth variable capacitors C1 to C5.
  • a voltage of +4 V was applied only to the first to third variable capacitors C1 to C3 connected in parallel to the series arm resonators S1 to S3, the center frequency was changed to 1.68 GHz.
  • a voltage of +4 V was applied only to the fourth and fifth variable capacitors C4 and C5 connected to the parallel arm resonators P1 and P2
  • the center frequency changed to 1.73 GHz. Therefore, it can be seen that the center frequency can be arbitrarily adjusted in the range of 1.68 GHz to 1.73 GHz by appropriately changing the voltage applied to the variable capacitors C1 to C5.
  • the material constituting the isolation layer that is isolated by laser light irradiation is not limited to Ru. Any material can be used as long as it is stable at the film formation temperature of the dielectric film, is a material that rapidly decomposes at a heating temperature by a laser beam, for example, 1000 ° C. to generate gas, and does not disturb the orientation of the dielectric film Materials can be used.
  • An example of such a material is GaN. In GaN, nitrogen gas is generated when pyrolyzed, and at the same time, the remaining Ga melts and facilitates peeling.
  • a transfer support substrate 41 made of a silicon single crystal (111) substrate having a thickness of 625 ⁇ m is used.
  • the transfer support substrate 41 has a thermal oxide film 41a having a thickness of 300 nm on the surface.
  • a rhodium film (Rh film) 42A having a thickness of 10 nm was formed as a separation promoting layer on the upper surface of the transfer support substrate 41 on which the thermal oxide film 41a was formed by a sputtering method.
  • a Pt film 13A having a thickness of 100 nm was stacked as a buffer layer by a sputtering method. Furthermore, a dielectric film 12A made of a BST film having a thickness of 120 nm was formed by sputtering under the condition of a substrate temperature of 700 ° C.
  • the dielectric film 12A and the Pt film 13A were patterned by a reactive ion etching method so as to have a planar shape in the finally formed variable capacitor.
  • the dielectric film 12 and the second electrode 13 were formed.
  • the Rh film 42A located below is also patterned to form the Rh film 42.
  • a first electrode 11 made of Au having a thickness of 100 nm was formed on the dielectric film 12 by a sputtering method by a lift-off method.
  • the surface acoustic wave resonator including the IDT electrode 7 and the wiring pattern 10 are formed of Au on the piezoelectric substrate 6.
  • FIGS. 6 (b) and 6 (c) is treated for 1 minute in an argon plasma, and then shown in FIG. 6 (d) under conditions of 100 ° C. and 10,000 Pa in a nitrogen atmosphere.
  • both structures were laminated. That is, the structure shown in FIG. 6B was turned upside down, and the first electrode 11 was implanted on the wiring pattern 10 of the piezoelectric substrate 6 and joined by thermocompression bonding.
  • the bonding temperature is as low as 100 ° C. Therefore, there was no crack caused by the difference in thermal expansion coefficient between the transfer support substrate 41 made of silicon and the piezoelectric substrate 6 made of LiNbO 3 .
  • the film was peeled off at the interface between the dielectric film 12 and the Rh film 42.
  • the variable capacitor constituent portion including the first and second electrodes 11 and 13 and the dielectric film 12 was transferred to the piezoelectric substrate 6 side.
  • the insulating layer 24 and the wiring pattern 10A were formed to obtain a tunable filter.
  • the center frequency was 1.71 GHz when no voltage was applied to any of the first to fifth variable capacitors C1 to C5.
  • a voltage of + 4V was applied only to the first to third variable capacitors C1 to C3 connected in parallel to the series arm resonators S1 to S3, the center frequency changed to 1.64 GHz.
  • a voltage of +4 V was applied only to the fourth and fifth variable capacitors C4 and C5 connected to the parallel arm resonators P1 and P2
  • the center frequency changed to 1.75 GHz. Therefore, it can be seen that the center frequency can be arbitrarily adjusted in the range of 1.64 GHz to 1.75 GHz by appropriately changing the voltage applied to the variable capacitors C1 to C5.
  • the buffer layer is not necessarily provided.
  • the dielectric film is transferred to the piezoelectric substrate side by dissolving the substrate on which the dielectric film is grown.
  • a transfer support substrate 51 made of a silicon single crystal (100) having a thickness of 625 ⁇ m and having a thermal oxide film 51a having a thickness of 300 nm on the upper surface was prepared.
  • a Pt film 13A functioning as a buffer layer was formed on the transfer support substrate 51.
  • the Pt film 13A was formed by sputtering and the thickness was 100 nm.
  • a dielectric film 12A made of a BST film having a thickness of 120 nm was formed on the Pt film 13A at a substrate temperature of 700 ° C.
  • the formed dielectric film 12A was analyzed by the X-ray diffraction method, it was confirmed that it had a (111) orientation excellent in varactor characteristics.
  • the dielectric film 12A and the Pt film 13A were processed by a reactive ion etching method so as to become the dielectric film 12 and the second electrode 13 of the variable capacitor to be finally formed.
  • a 100 nm-thick Au film was formed on the dielectric film 12 by a sputtering method by a lift-off method to form a first electrode 11.
  • the IDT electrode 7 and the wiring pattern 10 were separately formed on the piezoelectric substrate 6 in the same manner as in the first embodiment.
  • thermocompression bonding is performed on the wiring pattern 10 on the piezoelectric substrate 6 so that the first electrode 11 shown in FIG. Even in this case, the pasting temperature is as low as 100 ° C. Therefore, there was no crack caused by the difference in thermal expansion coefficient between the transfer support substrate 51 made of silicon and the piezoelectric substrate 6 made of LiNbO 3 .
  • the transfer support substrate 51 is polished from the surface opposite to the piezoelectric substrate 6 to reduce the thickness to 150 ⁇ m, and then immersed in a TMAH aqueous solution having a temperature of 60 ° C. and a concentration of 25% by weight to transfer the substrate.
  • the supporting substrate 51 was removed, and the thermal oxide film 51a was exposed as shown in FIG.
  • the thermal oxide film 51a was removed with buffered hydrofluoric acid. In this way, the second electrode 13 was exposed as shown in FIG.
  • the first and second electrodes 11 and 13 and the dielectric film 12 constituting the variable capacitor could be transferred to the piezoelectric substrate 6 side. Thereafter, as in the first embodiment, as shown in FIG. 7F, the insulating layer 24 and the wiring pattern 10A were formed to obtain a tunable filter.
  • the center frequency was 1.71 GHz when no voltage was applied to any of the first to fifth variable capacitors C1 to C5.
  • a voltage of + 4V was applied only to the first to third variable capacitors C1 to C3 connected in parallel to the series arm resonators S1 to S3, the center frequency changed to 1.64 GHz.
  • a voltage of +4 V was applied only to the fourth and fifth variable capacitors C4 and C5 connected to the parallel arm resonators P1 and P2
  • the center frequency changed to 1.75 GHz. Therefore, it can be seen that the center frequency can be arbitrarily adjusted in the range of 1.64 GHz to 1.75 GHz by appropriately changing the voltage applied to the variable capacitors C1 to C5.
  • the transfer support substrate 51 may be made of a material other than silicon. That is, an appropriate material that can withstand the growth temperature of the dielectric film, does not hinder the orientation growth of the dielectric film, and can be easily removed as described above can be used.
  • An example of such a material is MgO. In the case of a substrate made of MgO, it can be removed with hydrochloric acid.
  • the dielectric film 12 is directly formed on the piezoelectric substrate.
  • the structure of the produced tunable filter is the same as that of the first embodiment, but the materials used and the thicknesses of the respective films are different as follows.
  • an electrode of a surface acoustic wave resonator including an IDT electrode 7 is formed by a lift-off method with a Pt film having a thickness of 0.02 ⁇ , the wiring pattern 10 and the variable.
  • the capacitor first electrode 11 was formed.
  • the wavelength determined by the IDT electrode 7 in the surface acoustic wave resonator, that is, ⁇ was 2 ⁇ m.
  • the cross width of the IDT electrode was 15 ⁇ , the number of electrode fingers was 100, and the number of pole fingers in the reflector was 20.
  • a dielectric film made of BST of 0.6 ⁇ m was directly formed on the first electrode 11 by RF magnetron sputtering at a temperature of 700 ° C.
  • a rectangular Pt film having a thickness of 0.02 ⁇ and 20 ⁇ 20 ⁇ m was formed on the dielectric film 12 obtained as described above, thereby forming the second electrode 13.
  • a surface acoustic wave resonator and a variable capacitor were formed on the piezoelectric substrate 6 to obtain a tunable filter.
  • the capacitance changed in the range of 4 pF to 1 pF. Therefore, also in the tunable filter of this embodiment, it can be seen that the frequency can be changed greatly by applying a voltage to the variable capacitors C1 to C5, as in the first to fourth embodiments.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

L'invention concerne un filtre accordable qui peut être de plus petite taille et dont la fabrication est simplifiée, en utilisant un condensateur variable doté d'un film diélectrique dont la capacité varie avec la tension appliquée. Le filtre accordable (1) comprend un substrat piézoélectrique (6) fait d'un matériau piézoélectrique, des résonateurs à ondes élastiques (S1 à S3, P1, P2) formés sur le substrat piézoélectrique (6) et des condensateurs variables (C1 à C5) formés sur le substrat piézoélectrique (6). Les condensateurs variables (C1 à C5) comprennent : un film diélectrique (12) formé directement ou indirectement sur le substrat piézoélectrique (6), la capacité du film diélectrique variant en fonction de la tension appliquée ; et une première électrode (11) et une seconde électrode (13) conçues pour permettre d'appliquer un champ électrique au film diélectrique (12).
PCT/JP2012/053342 2011-02-25 2012-02-14 Filtre accordable et son procédé de fabrication Ceased WO2012114930A1 (fr)

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WO2015025651A1 (fr) * 2013-08-21 2015-02-26 株式会社村田製作所 Filtre accordable
WO2015119177A1 (fr) * 2014-02-10 2015-08-13 株式会社村田製作所 Circuit de filtre variable et dispositif de communication sans fil
WO2015119178A1 (fr) * 2014-02-10 2015-08-13 株式会社村田製作所 Circuit de filtrage variable, et dispositif de communication sans fil
WO2015128003A1 (fr) 2014-02-28 2015-09-03 Epcos Ag Filtre hf accordable électroacoustique à propriétés électriques améliorées et procédé de fonctionnement d'un tel filtre
JP2015228638A (ja) * 2013-12-28 2015-12-17 株式会社弾性波デバイスラボ 可変周波数弾性波変換器とこれを用いた電子装置
JPWO2015119176A1 (ja) * 2014-02-10 2017-03-23 株式会社村田製作所 フィルタ回路および無線通信装置
CN107005215A (zh) * 2014-12-10 2017-08-01 株式会社村田制作所 可变滤波电路
JP2017135568A (ja) * 2016-01-27 2017-08-03 太陽誘電株式会社 共振回路、フィルタ回路および弾性波共振器
US20180123549A1 (en) * 2015-07-06 2018-05-03 Murata Manufacturing Co., Ltd. Radio-frequency module
KR20180053381A (ko) 2015-10-19 2018-05-21 가부시키가이샤 무라타 세이사쿠쇼 주파수 가변 필터, rf 프론트엔드 회로, 통신 장치
WO2020080018A1 (fr) * 2018-10-16 2020-04-23 株式会社村田製作所 Module haute fréquence
JP2021164053A (ja) * 2020-03-31 2021-10-11 太陽誘電株式会社 通信装置、制御装置および制御方法
JP2021533579A (ja) * 2018-08-01 2021-12-02 ドレクセル ユニバーシティ エンジニアリング誘電体メタマテリアル

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US9882547B2 (en) 2013-08-21 2018-01-30 Murata Manufacturing Co., Ltd. Tunable filter
CN105474541B (zh) * 2013-08-21 2018-01-12 株式会社村田制作所 可调谐滤波器
WO2015025651A1 (fr) * 2013-08-21 2015-02-26 株式会社村田製作所 Filtre accordable
JPWO2015025651A1 (ja) * 2013-08-21 2017-03-02 株式会社村田製作所 チューナブルフィルタ
JP2015228638A (ja) * 2013-12-28 2015-12-17 株式会社弾性波デバイスラボ 可変周波数弾性波変換器とこれを用いた電子装置
US9787277B2 (en) 2014-02-10 2017-10-10 Murata Manufacturing Co., Ltd. Variable filter circuit and wireless communication apparatus
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JPWO2015119178A1 (ja) * 2014-02-10 2017-03-23 株式会社村田製作所 可変フィルタ回路および無線通信装置
JPWO2015119177A1 (ja) * 2014-02-10 2017-03-23 株式会社村田製作所 可変フィルタ回路および無線通信装置
JPWO2015119176A1 (ja) * 2014-02-10 2017-03-23 株式会社村田製作所 フィルタ回路および無線通信装置
US9985605B2 (en) 2014-02-10 2018-05-29 Murata Manufacturing Co., Ltd. Filter circuit and wireless communication apparatus
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US9780760B2 (en) 2014-02-10 2017-10-03 Murata Manufacturing Co., Ltd. Variable filter circuit and wireless communication apparatus
WO2015119177A1 (fr) * 2014-02-10 2015-08-13 株式会社村田製作所 Circuit de filtre variable et dispositif de communication sans fil
WO2015119178A1 (fr) * 2014-02-10 2015-08-13 株式会社村田製作所 Circuit de filtrage variable, et dispositif de communication sans fil
WO2015128003A1 (fr) 2014-02-28 2015-09-03 Epcos Ag Filtre hf accordable électroacoustique à propriétés électriques améliorées et procédé de fonctionnement d'un tel filtre
US10326428B2 (en) 2014-02-28 2019-06-18 Snaptrack, Inc. Tunable electroacoustic RF filter with improved electric properties and method for operating such a filter
DE102014102707A1 (de) 2014-02-28 2015-09-03 Epcos Ag Abstimmbares elektroakustisches HF-Filter mit verbesserten elektrischen Eigenschaften und Verfahren zum Betrieb eines solchen Filters
CN107005215A (zh) * 2014-12-10 2017-08-01 株式会社村田制作所 可变滤波电路
CN107005215B (zh) * 2014-12-10 2020-05-29 株式会社村田制作所 可变滤波电路
US20180123549A1 (en) * 2015-07-06 2018-05-03 Murata Manufacturing Co., Ltd. Radio-frequency module
US10396749B2 (en) * 2015-07-06 2019-08-27 Murata Manufacturing Co., Ltd. Radio-frequency module
KR20180053381A (ko) 2015-10-19 2018-05-21 가부시키가이샤 무라타 세이사쿠쇼 주파수 가변 필터, rf 프론트엔드 회로, 통신 장치
US10659007B2 (en) 2015-10-19 2020-05-19 Murata Manufacturing Co., Ltd. Tunable filter, radio frequency front-end circuit, and communication apparatus
US10256791B2 (en) 2016-01-27 2019-04-09 Taiyo Yuden Co., Ltd. Resonant circuit, filter circuit, and acoustic wave resonator
JP2017135568A (ja) * 2016-01-27 2017-08-03 太陽誘電株式会社 共振回路、フィルタ回路および弾性波共振器
JP2021533579A (ja) * 2018-08-01 2021-12-02 ドレクセル ユニバーシティ エンジニアリング誘電体メタマテリアル
JP7245402B2 (ja) 2018-08-01 2023-03-27 ドレクセル ユニバーシティ エンジニアリング誘電体メタマテリアル
WO2020080018A1 (fr) * 2018-10-16 2020-04-23 株式会社村田製作所 Module haute fréquence
US11799450B2 (en) 2018-10-16 2023-10-24 Murata Manufacturing Co., Ltd. Radio frequency module
JP2021164053A (ja) * 2020-03-31 2021-10-11 太陽誘電株式会社 通信装置、制御装置および制御方法

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