WO2010004534A1 - Résonateur à ondes acoustiques de volume utilisant des couches de réflecteur acoustique en tant qu'élément de circuit inductif ou capacitif - Google Patents

Résonateur à ondes acoustiques de volume utilisant des couches de réflecteur acoustique en tant qu'élément de circuit inductif ou capacitif Download PDF

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Publication number
WO2010004534A1
WO2010004534A1 PCT/IB2009/053019 IB2009053019W WO2010004534A1 WO 2010004534 A1 WO2010004534 A1 WO 2010004534A1 IB 2009053019 W IB2009053019 W IB 2009053019W WO 2010004534 A1 WO2010004534 A1 WO 2010004534A1
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WO
WIPO (PCT)
Prior art keywords
resonator
layer
layers
acoustic impedance
inductor
Prior art date
Application number
PCT/IB2009/053019
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English (en)
Inventor
Frederik Willem Maurits Vanhelmont
Alexander Simin
Andreas Bernardus Maria Jansman
Jaap Ruigrok
Roel Daamen
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Nxp B.V.
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Publication of WO2010004534A1 publication Critical patent/WO2010004534A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/582—Multiple crystal filters implemented with thin-film techniques
    • H03H9/586—Means for mounting to a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/589—Acoustic mirrors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
    • H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/175—Acoustic mirrors

Definitions

  • This invention relates to bulk acoustic wave resonators.
  • a Bulk Acoustic Wave (BAW) resonator is essentially an acoustic cavity comprising a piezoelectric layer sandwiched between metal electrode layers. When an alternating electric signal is applied across these electrodes, the0 electric energy is converted to mechanical form and a standing acoustic wave can be excited.
  • the principle mode of vibration in practical thin-film resonators is the fundamental thickness-extensional (TE1 ) acoustic mode, i.e. vibration is normal to the layers, at a frequency for which half a wavelength of this mode is approximately equal to the total thickness of the cavity. 5
  • TE1 fundamental thickness-extensional
  • a thin membrane forms the acoustic cavity with a thickness of about one micrometer.
  • SBAR solidly-mounted BAW resonator
  • a set layers is used with alternating high and low acoustic impedance beneath the bottom electrode. These layers reflect the acoustic wave. This concept is analogous to the0 Bragg reflector in optics.
  • the reflector layers are deposited on a solid substrate, typically glass or silicon (Si), so this structure is physically more robust than the FBAR.
  • BAW resonators For mobile communication applications with high demands on RF filter selectivity, thin-film BAW filters are becoming more and more the technology5 of choice.
  • BAW resonators In order to get high-performance BAW filters, their building blocks, BAW resonators, need to have high quality factors and a minimal ripple on the electrical characteristics. The former is achieved by trapping the acoustic energy in the resonator. Unfortunately, energy trapping often leads to the occurrence of extra acoustic standing waves, resulting in unwanted peaks in0 the impedance curve of a BAW resonator.
  • the response of a BAW resonator is shown in Figure 1 , as the BAW resonator impedance vs. frequency. It shows a low impedance value (the minimum) at the resonance frequency and a high impedance value (the maximum) at the anti-resonance frequency.
  • Figure 2 shows the circuit and circuit frequency response when capacitors with different capacitance values are placed in series with the BAW resonator. The resonance frequency shifts and the antiresonance frequency is not affected.
  • Figure 3 shows the circuit and circuit frequency response when capacitors with different capacitance values are placed in parallel with the BAW resonator. The antiresonance frequency decreases and the resonance frequency is not affected.
  • Figure 4 shows the circuit and circuit frequency response when inductors with different inductance values are placed in series with the BAW resonator. The resonance frequency decreases and the antiresonance frequency is not affected.
  • Figure 5 shows the circuit and circuit frequency response when inductors with different inductance values are placed in parallel with the BAW resonator. The antiresonance frequency shifts and the resonance frequency is not affected.
  • a BAW ladder filter consists of resonators operating at two different frequencies: the series resonators at one frequency and the shunt resonators at a slightly lower frequency. This is realised by massloading the shunt resonator so that its antiresonance frequency (almost) coincides with the resonance frequency of the series resonators.
  • the performance of the filter can be significantly influenced by the addition of the passive components and tuning of the operating frequencies as described above.
  • the bandwidth can be decreased by adding capacitors to make a channel filter, for example.
  • the bandwidth can be increased by adding inductors in series to the shunt resonators and in parallel to the series resonators. The addition of the inductors in series to the shunt resonators is very often done.
  • shunt resonators are connected by one terminal to the ground.
  • the ground is implemented directly on the BAW die, and then connected to a common ground of the whole module, but more often there is no shared ground of the BAW. Instead, every shunt resonator is individually connected to the common ground on the laminate (or any other substrate).
  • series inductors can thus be realized by the bond wires from the shunt resonators to the ground on the laminate onto which the BAW die is flip-chipped or bond wired.
  • the inductance of the interconnect i.e. the bond wire
  • an extra coil can be placed on the laminate, that electrically will behave as an inductor connected in series with the shunt resonator.
  • Placing inductors parallel to the series resonators is much more difficult and cannot be performed with the bond wires.
  • Series BAW resonators do not have any interconnect with external circuitry and therefore it is not possible to use any components outside the BAW die to make inductors.
  • Figure 6 shows the addition of inductors L ex ti to L ex tN to the shunt resonators to widen the stopband bandwidth and to improve the matching in the passband.
  • the three notches at the low frequency side of the band pass region are the result of the additional inductors.
  • a filter has an odd number of resonators (so that the number of series resonators is one more or less than the number of shunt resonators), the filter can easily be matched to the required input/output impedance.
  • Filters with an even number of resonators do not provide 50 Ohm to 50 Ohm matching because of the asymmetric distribution of impedance levels over the resonators. External matching has to be used in this case.
  • BAW filters are often manually fine-tuned and sometimes additional components at the input or output can significantly improve performance, especially matching conditions.
  • an impedance transformer can be added to the end of the circuit.
  • the transformer can be implemented as lumped-element network with two series components with the output from the junction. This requires extra capacitors or inductors (depending on filter specifications LL, LC, CL or CC networks can be used).
  • Figu re 7 Two possible config urations are shown in Figu re 7, for filter configurations incorporating the same number of series and shunt resonators.
  • Cinv an extra series capacitor
  • Linv an extra shunt inductor
  • impedance transformers are placed in the middle of the filter structure and realized by series capacitors or shunt inductors, as shown in Figure 8.
  • an extra series capacitor Cinv is provided in the middle of the circuit
  • an extra shunt inductor Linv is provided with the middle resonator split into two components.
  • capacitors and inductors are very useful if they are located close to the resonator. Typical required values are a few pF and around 0.5 nH.
  • the invention relates to the provision of these additional circuit elements, and particularly in a way which avoids the need for separate passive elements on a laminate onto which the BAW die is flip-chipped or wire bonded.
  • Other applications in which capacitors and/or inductors are needed together with BAW resonators include baluns, or oscillators based on a BAW resonator.
  • a resonator comprising: a bottom electrode layer; a top electrode layer; a piezoelectric layer sandwiched between the top and bottom electrode layers; and a multi-layer acoustic reflector beneath the bottom electrode layer which comprises a stack of alternating layers of relatively high and relatively low acoustic impedance, wherein the external electrical circuit connections to the resonator comprise a first electrical connection to the top or bottom electrode layer and a second electrical connection to a first one of the acoustic impedance layers which is spaced from the bottom electrode layer by at least a second one of the acoustic impedance layers.
  • This arrangement uses the layers of the acoustic reflector to function as control electrodes.
  • external connections are made to the acoustic impedance layers deep in the stack, i.e. spaced from the bottom electrode.
  • This spacing means that the high acoustic impedance layer to which the connection is made is not electrically connected to the bottom electrode by its physical position.
  • the acoustic reflector layers are used to form part of the resonator circuit, with external connections made to a layer or layers within the acoustic reflector.
  • the multi-layer acoustic reflector layers can define at least one circuit element in the form of a capacitor or inductor which forms part of the resonator circuit.
  • series and/or parallel circuit elements can be defined from the layers of the acoustic reflector.
  • the circuit element can comprise an inductor.
  • the inductor can be in series with the resonator (with the bottom electrode connected to one portion of the inductor layer and another portion of the inductor layer comprising the second electrical connection; alternatively, the top electrode can be connected to one portion of the inductor layer and another portion of the inductor layer comprises the second electrical connection) or it can be in parallel with the resonator (with the bottom electrode connected to one portion of the inductor layer and the top electrode connected to another portion of the inductor layer).
  • the circuit element can comprise a capacitor.
  • the capacitor can be in series with the resonator (with the bottom or top electrode connected to one of the capacitor electrodes and the other capacitor electrode comprising the second electrical connection), or it can be in parallel with the resonator (with the bottom electrode connected to one of the capacitor electrodes and the top electrode connected to the other of the capacitor electrodes).
  • the multilayer acoustic reflector comprises a stack of alternating layers of relatively high and relatively low acoustic impedance.
  • the second electrical connection can then be to one of the relatively high acoustic impedance layers.
  • the relatively high acoustic impedance layers can comprise metal layers, which are therefore suitable for electrical connections.
  • the relatively high acoustic impedance materials can comprise W or Pt.
  • the relatively low acoustic impedance layers can for example comprise SiO2
  • One of the relatively high acoustic impedance layers is preferably used to define the inductor, the electrodes of the capacitor or a new bottom electrode.
  • two of the relatively high acoustic impedance layers can define capacitor electrodes and a relatively low acoustic layer therebetween defines a capacitor dielectric. This provides a capacitor defined by the acoustic reflector layers.
  • the original bottom electrode is electrically floating and one of the relatively high acoustic impedance layers is used as bottom electrode of the BAW resonator.
  • the layer stack is not altered.
  • This provides a BAW resonator with altered resonance and antiresonance frequencies. In this way, the frequency of the resonator can be made dependent on the vertical spacing between the first and second electrical connections
  • the invention also provides a resonator device comprising at least first and second resonators, wherein: the first resonator has electrical connections to top and bottom electrodes between which a piezoelectric layer is sandwiched, with the resonant frequency defined by the spacing between the top and bottom electrodes; and the second resonator is a resonator of the invention.
  • the first and second resonators can share the same piezoelectric layer and multi-layer acoustic reflector layers, and have different resonant frequencies.
  • Figure 1 shows the response of a typical BAW resonator
  • Figure 2 shows the circuit and circuit frequency response when capacitors with different capacitance values are placed in series with the resonator;
  • Figure 3 shows the circuit and circuit frequency response when capacitors with different capacitance values are placed in parallel with the resonator
  • Figure 4 shows the circuit and circuit frequency response when inductors with different inductance values are placed in series with the resonator
  • Figure 5 shows the circuit and circuit frequency response when inductors with different inductance values are placed in parallel with the resonator
  • Figure 6 shows a ladder filter design in which extra inductors are placed in series with the shunt resonators and the corresponding frequency response;
  • Figure 7 shows two ladder filter designs with the same number of series and shunt resonators incorporating impedance transformers;
  • Figure 8 shows the use of impedance transformers in the middle of the filter structure for even order-filters;
  • Figure 9 shows a conventional BAW device in cross section
  • Figure 10 shows three examples of providing capacitors into the resonator circuit which can be employed in combination with the approach of invention
  • Figure 11 shows three examples of providing inductors into the resonator circuit which can be employed in combination with the approach of the invention; and Figure 12 shows an example of how with the same layer stack a resonator can be made with a different resonance frequency.
  • the invention provides a piezoelectric resonator in which isolated metal layers that are present in the acoustic reflector underneath the resonator are used as part of the resonator circuit, for example being used to make inductors or capacitors.
  • Figure 9 shows a conventional BAW device in cross section consisting of a piezoelectric layer 10, a bottom electrode 12 and a top electrode 14, and a Bragg reflector 16 consisting of high acoustic impedance materials 16a and low acoustic impedance materials 16b.
  • the low acoustic impedance material is typically SiO2
  • the high acoustic impedance materials are typically W or Pt.
  • the connection of the RF signal is shown, between the top and bottom electrodes.
  • Figure 10 shows how an underlying capacitor can be placed in series with the bottom electrode of the BAW resonator (Figure 10a), in parallel to the resonator ( Figure 10b), and in series with the top electrode of the BAW resonator ( Figure 10c)
  • the capacitor has the high acoustic impedance material layers as its two electrodes, and one layer of the low impedance material as the dielectric.
  • a metal layer within the reflector can also be used as an inductor in accordance with the invention, in series or in parallel to the resonator as shown in Figure 11.
  • an inductor is defined by one of the layers of high acoustic impedance material.
  • the inductor is in series with the bottom electrode of the resonator, and in Figure 11 b, it is in parallel.
  • Figure 11 a the inductor is in series with the bottom electrode of the resonator, and in Figure 11 b, it is in parallel.
  • the inductor is in series with the top electrode of the resonator.
  • Connections to the layer are made at different portions of the layer, for example at opposite end faces, so that the conduction path is across the layer; the layer is functioning as a transmission line.
  • Figure 11 shows two layers of high acoustic impedance material in the stack, and with the use of the top layer as the inductor. It is of course also possible to connect to the lowest-lying high acoustic impedance layer as the inductor. It is also possible to replace the dielectric low acoustic impedance layer (in between the two metallic high acoustic impedance layers) with a metallic low acoustic impedance layer (e.g. Al). Such a design gives comparable results (the acoustic impedance of Al and Si ⁇ 2 are comparable) but with a lower series resistance.
  • a metallic low acoustic impedance layer e.g. Al
  • one or two extra mask steps are needed in comparison to the normal processing. These steps are needed to contact the underlying metal layers.
  • Deeper lying layers in the Bragg reflector can also be used as long as they are electrically conductive in nature. In this way, several inductors or capacitors can be arranged in series so as to obtain the required electrical characteristics.
  • the inductor and optional capacitor is positioned underneath the resonator, thereby saving silicon area.
  • the capacitance value is limited to the value determined by the area of the resonator. However, it is not desirable to make the area of the capacitor much larger than the area of the resonator, otherwise the resonator will suffer from stray capacitance, reducing its coupling coefficient.
  • a resonator is typically 200 x 200 microns. With a thickness of SiO2 as the low acoustic impedance material of 762 nm (quarter wavelength for a resonator with resonance frequency at 1.88 GHz (USPCS frequency)), a capacitance of 2.05 pF results. SiO2 is only one example of possible low acoustic impedance material.
  • lead zirconium titanate or barium strontium titanate can instead be used .
  • These materials also have the advantage of being tunable dielectrics.
  • a tuneable capacitor can be placed in series or parallel to the BAW resonator thereby enabling the shift in frequency to be adjustable.
  • the metal layer(s) underneath the resonator are used as an inductor. Taking the rule of thumb that 1 nH of self- inductance results per mm wiring, a 200 micrometer line (corresponding to the size of the resonator) results in 0.2 nH.
  • the inductance value is again determined by the size of the resonator. The advantage is again that less Si area is consumed. However, the area to the side of the resonator can additionally be used. In this way, the desired inductance value can be obtained.
  • Figure 12 shows an example in which one of the high acoustic impedance metal layers in the reflector stack is used as the new bottom electrode, and this results in a BAW resonator operating at a lower frequency.
  • the original bottom electrode is electrically floating in this case.
  • Line 30 shows how a standing wave of half a wavelength can be established in this resonator... A substantial part of the acoustic wave is in this case standing in non-piezoelectric layers and therefore it can be expected that at these new frequencies, the coupling coefficient (and therefore also the bandwidth) of the devices will decrease substantially.
  • narrow band filters are often also needed for example a GPS filter or a channel filter.
  • the reflector stack that is present underneath this new BAW resonator is of course not intended for this new frequency and will give a poor performance. To circumvent this, extra layers can be introduced (forming a new reflector stack at the new frequency) underneath the original reflector stack.
  • the new combined reflector stack will then reflect the acoustic waves at the original frequency in the top layers and the acoustic waves at the new frequency in the lower layers.
  • the new resulting frequency is not necessarily the frequency for which half a wavelength is present between the bottom and top electrical contacts. This can also be a complete wavelength (line 32). In that case, about half a wavelength is present in the oxide and half a wavelength in the piezoelectric layer. This still gives acceptable BAW performance. In this way, a third frequency (this time higher than the original frequency) can be created in the same device. It is also possible to make in this way devices operating at different frequencies on the same die, dependent on the electrical connections made to the structure.
  • the invention enables different combinations of circuit elements to be provided in a simple way and using existing layers of the structure.
  • the circuit elements (capacitors and inductors) can be stand alone passive devices for use in circuits. Thus, the same layers can be used for resonators with no other circuit elements, for resonators with associated circuit elements, or for circuit elements not associated with the overlying resonator structure.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

L'invention porte sur un résonateur qui comprend une couche d'électrode inférieure (12), une couche d'électrode supérieure (14) et une couche piézoélectrique (10) prise en sandwich entre les couches d'électrode supérieure et inférieure. Un réflecteur acoustique multicouche (16) est installé au-dessous de la couche d'électrode inférieure. Les connexions électriques externes du résonateur comprennent une première connexion électrique à la couche d'électrode supérieure ou inférieure et une seconde connexion électrique à l'une des couches du réflecteur acoustique (16). Les couches du réflecteur acoustique multicouche peuvent définir au moins un élément de circuit sous la forme d'un condensateur ou d'une bobine d'inductance qui fait partie du circuit résonateur. Selon une variante, les connexions électriques peuvent être utilisées pour définir un résonateur fonctionnant à une fréquence différente. Cet agencement utilise les couches du réflecteur pour remplir des fonctions de circuit supplémentaires, incluant une bobine d'inductance et/ou un condensateur, ou pour changer les caractéristiques de fréquence. Cela permet de définir des éléments de circuit supplémentaires d'une façon intégrée et sans utiliser une surface de substrat supplémentaire.
PCT/IB2009/053019 2008-07-11 2009-07-10 Résonateur à ondes acoustiques de volume utilisant des couches de réflecteur acoustique en tant qu'élément de circuit inductif ou capacitif WO2010004534A1 (fr)

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EP08104716.9 2008-07-11
EP08104716 2008-07-11

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010122024A1 (fr) * 2009-04-24 2010-10-28 Epcos Ag Electrode de masse pour résonateur à ondes acoustiques de volume (baw)
US20140184358A1 (en) * 2011-05-04 2014-07-03 Epcos Ag Baw-filter operating using bulk acoustic waves
WO2018125516A1 (fr) * 2016-12-29 2018-07-05 Snaptrack, Inc. Résonateur baw et agencement de résonateur
FR3076126A1 (fr) * 2017-12-26 2019-06-28 Commissariat A L'energie Atomique Et Aux Energies Alternatives Procede de realisation d'un resonateur acoustique a ondes de volume a capacite parasite reduite
WO2020048737A1 (fr) * 2018-09-05 2020-03-12 RF360 Europe GmbH Résonateur baw à bobine intégrée dans une couche d'impédance élevée d'un miroir de bragg ou dans une couche métallique à haute impédance supplémentaire au-dessous du résonateur
CN117310669A (zh) * 2023-11-07 2023-12-29 海底鹰深海科技股份有限公司 一种水声换能器的匹配层的制作方法

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EP0829957A2 (fr) * 1996-09-12 1998-03-18 Murata Manufacturing Co., Ltd. Résonateur piézoélectrique et composant électronique en faisant usage
US6107721A (en) * 1999-07-27 2000-08-22 Tfr Technologies, Inc. Piezoelectric resonators on a differentially offset reflector
EP1120910A2 (fr) * 2000-01-18 2001-08-01 Texas Instruments Incorporated Ensemble réflecteur acoustique à fréquences multiples, couvercle monolithique pour résonateurs et méthode
US20010030490A1 (en) * 1999-12-20 2001-10-18 Murata Manufacturing Co., Ltd. Piezoelectric resonator and piezoelectric oscillator
US20030227357A1 (en) * 2002-06-06 2003-12-11 Thomas Metzger Component working with acoustic waves and having a matching network
US20040095042A1 (en) * 1998-12-01 2004-05-20 Murata Manufacturing Co., Ltd. Multilayer piezoelectric component
US20050134147A1 (en) * 2003-11-18 2005-06-23 Matsushita Electric Industrial Co., Ltd. Acoustic resonator device, filter device, manufacturing method for acoustic resonator device, and communication apparatus
US20050231072A1 (en) * 2004-03-22 2005-10-20 Tdk Corporation Piezoelectric resonator and electronic component provided therewith
US20080048802A1 (en) * 2001-09-25 2008-02-28 Robert Aigner Piezoelectric Component and Method for Producing It

Patent Citations (9)

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Publication number Priority date Publication date Assignee Title
EP0829957A2 (fr) * 1996-09-12 1998-03-18 Murata Manufacturing Co., Ltd. Résonateur piézoélectrique et composant électronique en faisant usage
US20040095042A1 (en) * 1998-12-01 2004-05-20 Murata Manufacturing Co., Ltd. Multilayer piezoelectric component
US6107721A (en) * 1999-07-27 2000-08-22 Tfr Technologies, Inc. Piezoelectric resonators on a differentially offset reflector
US20010030490A1 (en) * 1999-12-20 2001-10-18 Murata Manufacturing Co., Ltd. Piezoelectric resonator and piezoelectric oscillator
EP1120910A2 (fr) * 2000-01-18 2001-08-01 Texas Instruments Incorporated Ensemble réflecteur acoustique à fréquences multiples, couvercle monolithique pour résonateurs et méthode
US20080048802A1 (en) * 2001-09-25 2008-02-28 Robert Aigner Piezoelectric Component and Method for Producing It
US20030227357A1 (en) * 2002-06-06 2003-12-11 Thomas Metzger Component working with acoustic waves and having a matching network
US20050134147A1 (en) * 2003-11-18 2005-06-23 Matsushita Electric Industrial Co., Ltd. Acoustic resonator device, filter device, manufacturing method for acoustic resonator device, and communication apparatus
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010122024A1 (fr) * 2009-04-24 2010-10-28 Epcos Ag Electrode de masse pour résonateur à ondes acoustiques de volume (baw)
DE102009018879B4 (de) * 2009-04-24 2016-03-17 Epcos Ag Bodenelektrode für Bulk Acoustic Wave (BAW) Resonator
US20140184358A1 (en) * 2011-05-04 2014-07-03 Epcos Ag Baw-filter operating using bulk acoustic waves
US9859868B2 (en) * 2011-05-04 2018-01-02 Snaptrack, Inc. BAW-filter operating using bulk acoustic waves and passive components forming a balun
WO2018125516A1 (fr) * 2016-12-29 2018-07-05 Snaptrack, Inc. Résonateur baw et agencement de résonateur
US11012053B2 (en) 2016-12-29 2021-05-18 Snaptrack, Inc. BAW resonator and resonator arrangement
FR3076126A1 (fr) * 2017-12-26 2019-06-28 Commissariat A L'energie Atomique Et Aux Energies Alternatives Procede de realisation d'un resonateur acoustique a ondes de volume a capacite parasite reduite
US11601107B2 (en) 2017-12-26 2023-03-07 Commissariat a l'energie atomique etaux energies alternatives Method for the production of a bulk acoustic wave resonator with a reduced parasitic capacitance
WO2020048737A1 (fr) * 2018-09-05 2020-03-12 RF360 Europe GmbH Résonateur baw à bobine intégrée dans une couche d'impédance élevée d'un miroir de bragg ou dans une couche métallique à haute impédance supplémentaire au-dessous du résonateur
CN117310669A (zh) * 2023-11-07 2023-12-29 海底鹰深海科技股份有限公司 一种水声换能器的匹配层的制作方法

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