PatentDe  


Dokumentenidentifikation EP1158669 18.10.2007
EP-Veröffentlichungsnummer 0001158669
Titel Akustische Oberflächenwellenanordnung
Anmelder Murata Manufacturing Co., Ltd., Nagaokakyo, Kyoto, JP
Erfinder Iwamoto, Takashi, Nagaokakyo-shi, Kyoto-fu 617-8555, JP;
Koshido, Yoshihiro, Nagaokakyo-shi, Kyoto-fu 617-8555, JP
Vertreter Schoppe, Zimmermann, Stöckeler & Zinkler, 82049 Pullach
DE-Aktenzeichen 60130286
Vertragsstaaten DE, FR, GB
Sprache des Dokument EN
EP-Anmeldetag 21.05.2001
EP-Aktenzeichen 014013155
EP-Offenlegungsdatum 28.11.2001
EP date of grant 05.09.2007
Veröffentlichungstag im Patentblatt 18.10.2007
IPC-Hauptklasse H03H 3/08(2006.01)A, F, I, 20051017, B, H, EP
IPC-Nebenklasse H03H 9/145(2006.01)A, L, I, 20051017, B, H, EP   

Beschreibung[en]
Field of the Invention

The present invention relates to a surface acoustic wave device, and more particularly, to a surface acoustic wave device that is especially useful as a band filter or a resonator.

Description of the Related Art

Conventionally, surface acoustic wave devices are widely used as a band filter and a resonator. For surface acoustic wave devices to be used in these fields, it is strongly required to have a good frequency characteristic. In the case in which an interdigital transducer (hereinafter, referred to as IDT), and a reflector are arranged as a film on a surface acoustic wave device, the larger the film thickness is, the longer the film-forming time is, and moreover, it is more difficult to obtain a uniform film thickness. Thus, it is desired that the film thicknesses of the IDT and the reflector are small.

Accordingly, in surface acoustic wave devices using a shear horizontal or SH wave, metals having a high density such as Au, W, Ta, Pt, and so forth are used for the IDTs and the reflectors in many cases. When a metal material having a large density such as Au is used for the IDTs and the reflectors, which have a small film thickness, an SH wave can be easily excited and reflected. Thus, the thicknesses of the IDTs and the reflectors can be reduced.

Moreover, when plural surface acoustic wave devices (especially, surface acoustic wave devices for use as narrow-band filters) are produced, it is desired that dispersions in center frequency between the respective surface acoustic wave devices are as small as possible. Accordingly, regarding surface acoustic wave devices having IDTs and reflectors using metals with a high density such as Au, W, Ta, Pt, dispersions in frequency between the respective surface acoustic wave devices in the same wafer are suppressed by making the film-thicknesses of the IDTs and the reflectors as uniform as possible when the IDTs and the reflectors are film-formed.

However, techniques for making uniform the thicknesses of the IDTs and the reflectors have a limitation. Therefore, when a plurality of surface acoustic wave devices are produced on the same wafer at one time, dispersions in frequency between the respective surface acoustic wave devices become large. Therefore, even if the metal materials having a high density such as Au, W, Ta, Pt, are used, practically it is necessary to adjust the frequencies of the finished surface acoustic wave devices, individually.

Thus, though it is assumed that the metal materials having a high density such as Au, W, Ta, Pt, are desirably used to produce the IDTs and the reflectors of the surface acoustic wave devices using an SH wave, it is necessary to adjust the frequencies individually. Thus, the throughput is reduced, which increases the cost.

As a method of adjusting the frequencies of the surface acoustic wave devices, individually, a method of etching the surfaces of the IDTs and the reflectors by use of ion beams, a method of forming films as insulators between substrates, the IDTs, and the reflectors, a method of etching the substrates, the IDTs, and the reflectors according to RIE (reactive ion etching), and so forth, are generally used. For this reason, when the frequencies are adjusted by use of ion beams or the like, the IDTs, the reflectors, and the substrates suffer damage, which deteriorate the characteristics of the surface acoustic wave devices.

When plural surface acoustic wave devices are produced using the same wafer, dispersions in center frequency can be reduced by use of metal materials having a high density such as Ni, Al, Cr, Cu, for the IDTs and the reflectors. However, using metal materials such as Ni, Al, it is difficult to excite and reflect an SH wave. Thus, filters and resonators having a good frequency characteristic can be obtained but with great difficulty. The metal materials are not suitable as materials for the IDTs and the reflectors.

JP 62-168410 describes a SAW resonator in which the IDT electrodes are made up of three laminated layers - Al, Au and Al - in order to obtain a good resonator characteristic in a relatively low frequency area of the VHF band.

JP 10-247835 describes a SAW resonator using a Love wave, in which a layer of Ta (or W or Pd) is formed over a layer of Al. The thickness of the Ta layer is set to a desired value to enable production of a Love wave. The Al layer has low resistance. Cost is reduced by using Ta instead of Au.

SUMMARY OF THE INVENTION

In order to solve the problems described above, preferred embodiments of the present invention provide a surface acoustic wave device utilizing an SH wave which minimizes dispersions in center frequency, so that it is not necessary to adjust the frequency after the IDT and the reflector are produced.

The surface acoustic wave device according to the present invention utilizes excitation of an SH wave, and includes an interdigital transducer defined by a laminated body including at least a total of three metal layers having at least two first layers made of a metal with a density of at least about 15 g/cm3 as a major component and at least one second layer made of a metal with a density of up to about 12 g/cm3 on a piezoelectric substrate, the total volume of said first layers being in the range from about 20% to about 95% of the total volume of the interdigital transducer or the reflector. The first and second layers are preferably formed, e.g., by vapor deposition or sputtering.

The surface acoustic wave device according to preferred embodiments of the present invention is preferably used as a filter, a resonator or other electronic component utilizing an SH wave. The second-layer containing a metal with a density of up to about 12 g/cm3 such as Ni, Cr, Cu, Al, Ti, or other suitable material is sandwiched between the first layers containing as a major component a metal with a density of at least about 15 g/cm3 such as Au, W, Ta, Pt, or other suitable material. The second layer is a metal layer having a small effect of reducing the propagation velocity of a surface acoustic wave on the piezoelectric substrate. Since the second layer is sandwiched between the first layers, dispersions in frequency of the IDT or the reflector, caused by dispersions in film thickness thereof, are minimized. Thus, excellent resonator and filter characteristics are achieved.

Accordingly, in the case in which a plurality of surface acoustic wave devices are formed on the same wafer, frequency adjustment of the individual surface acoustic wave devices is unnecessary. The cost of the surface acoustic wave device can be reduced, due to the enhanced throughput. Moreover, the frequency adjustment by ion beam etching or other suitable process is not required. Thus, damage to the piezoelectric substrate, the IDT, and the reflector is prevented, and moreover, the acceptance ratio of the surface acoustic wave devices is greatly improved.

The total volume of the first layers is in the range of from about 20% to 95% of the overall volume of the IDT or the reflector. To decrease the film-thickness of the IDT or the reflector, desirably, the ratio of the first layer is high. For this reason, at least two first-layers are contained in the IDT.

In the surface acoustic wave device of preferred embodiments of the present invention, preferably, in the layers lying in the range of the thickness of up to one-fourth of the total thickness of the interdigital transducer or the reflector measured from the surface of the piezoelectric substrate of the metal layers constituting the interdigital transducer or the reflector, the total volume of the first-layers is at least about 50%. Moreover, preferably, the metal layer disposed directly on the piezoelectric substrate is the first layer, or the second layer which has a small thickness. That is, preferably, of the layers each having a thickness of at least about one-twentieth of the total thickness of the interdigital transducer or the reflector, the layer located nearest to the piezoelectric substrate is the first-layer. Moreover, preferably, the surface of the IDT or the reflector includes the first layer.

In particular, according to another preferred embodiment of the present invention, preferably, the first layer contains Au as a major component and the totality of first layers present in the IDT has a volume of from about 40% to about 80% of the total volume, and the second layer contains Ni as a major component and the totality of second layers present in the IDT has a volume of from about 20% to about 60% of the overall volume.

According to another preferred embodiment of the present invention, the first layer contains Au as a major component and the totality of first layers present in the IDT has a volume of from about 20% to about 50% of the overall volume, and the second layer contains Al as a major component and the totality of second layers present in the IDT has a volume of from about 50% to about 80% of the overall volume.

According to embodiments of the present invention, at least two of the first layers with a high density having a high effect of decreasing the propagation velocity of a surface acoustic wave on a piezoelectric substrate, and the second layer with a low density having a small effect of decreasing the propagation velocity of the surface acoustic wave on the piezoelectric substrate, that is, being capable of decreasing dispersions in frequency caused by dispersions in film thickness are arranged so as to have a laminated structure. Thereby, excellent resonator and filter characteristics are obtained. Moreover, dispersions in center frequency between plural surface acoustic wave devices produced in the same wafer are minimized.

Accordingly, it becomes unnecessary to carry out the frequency adjustment individually, which has been conventionally needed. Significant improvement in throughput can be realized. Furthermore, cost reduction can be achieved. Moreover, damage and sticking of foreign matters to the piezoelectric substrate caused by frequency adjustment can be eliminated. This is advantageous from the standpoint of characteristics. The acceptance ratio is greatly increased.

Other features, elements, characteristics and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.

For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWINGS

  • Fig. 1 is a schematic plan view of a surface acoustic wave device according to a preferred embodiment of the present invention.
  • Fig. 2 is a cross-sectional view schematically showing the structure of IDT provided in the surface acoustic wave device.
  • Fig. 3 illustrates measurement points on a wafer used to obtain the data of Table 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic plan view of a surface acoustic wave device 1 according to a preferred embodiment of the present invention. In the surface acoustic wave device 1, an IDT 3 is provided on the surface of a piezoelectric substrate 2 such as a quartz substrate or other suitable substrate. The IDT 3 includes a pair of interdigital electrodes 3a and 3b. The electrode portions of both of the interdigital electrodes 3a and 3b are alternately disposed so as to be interdigitated with each other. Moreover, the electrode portions of the IDT 3 are extended in a direction that is substantially perpendicular to the surface acoustic wave propagation direction. In the surface acoustic wave propagation direction of the IDT 3, reflectors 4 and 5 are arranged at the respective sides of the IDT 3. The reflectors 4 and 5 are grating type reflectors, and have the configuration in which the plurality of electrode portions are short-circuited at both of the ends thereof. Moreover, the surface acoustic wave device 1 is a surface acoustic wave resonator utilizing a surface acoustic wave, that is, an SH wave such as a Love wave.

Referring to the above-described surface acoustic wave device 1, when an electric signal is applied across the interdigital electrodes 3a and 3b, the portion of the piezoelectric substrate 2 on which the IDT 3 is provided is excited so that a surface acoustic wave is generated. The surface acoustic wave is propagated on the surface of the piezoelectric substrate 2, which is a uniform propagation medium, to both of the sides of the IDT 3, that is, to reach the respective reflectors 4 and 5. The portion of the substrate 2 where the reflectors 4 and 5 are located has a propagation constant that is different from that of the other portion of the substrate 2. Thus, a portion of the surface acoustic wave, which reaches the reflectors 4 and 5, is reflected therefrom.

In the case in which the surface acoustic wave has a wavelength &lgr; that is substantially equal to about two times the interval &lgr;/2 between the respective electrode portions of the reflectors 4 and 5, reflection waves from the electrode portions of the reflectors 4 and 5 reinforce each other and become strong reflection waves.

The reinforced reflection waves described above are propagated in reciprocation between the reflectors 4 and 5, whereby resonance action can be obtained.

Fig. 2 is a cross sectional view schematically showing the film structure of the IDT 3 (or the interdigital electrodes 3a and 3b). In the IDT 3, a Ti film 6 (second layer) with a film thickness of about 5 nm, for example, is formed on the surface of the piezoelectric substrate 2, an Au film 7 (first layer) with a film thickness of about 150 nm, for example, is film-formed thereon, an Ni film 8 (second film) with a film thickness of about 200 nm, for example, is formed thereon, and an Au film 9 (first layer) with a film thickness of about 50 nm, for example, is formed thereon. Thus, the IDT 3 preferably has a four-layer structure in this example.

The reflectors 4 and 5 have the same film structure as described above, which is not shown. Thereby, the IDT 3 and the reflectors 4 and 5 can be produced at the same time. Thus, a process for producing the IDT 3 and the reflectors 4 and 5 can be simplified.

The IDT 3, and the reflectors 4 and 5 having the above-described film-structure are produced in an EB (electron beam) vapor deposition method and a liftoff process. In particular, a photosensitive resin (photoresist) is applied to the surface of a piezoelectric substrate 2 (wafer). Thereafter, the photosensitive resin is patterned, so that openings corresponding to the IDT 3 and the reflectors 4 and 5 are formed. Then, films of Ti, Au, Ni, and Au are sequentially formed on the photosensitive resin in an EB vapor deposition method to form a Ti layer 6, an Au layer 7, a Ni layer 8, and an Au layer 9. Thereafter, the photosensitive resin is released, and simultaneously, the four layer metal films in the unnecessary areas are removed, so that the IDT 3 and the reflectors 4 and 5 are patterned. It is to be understood that a layered structure according to the present invention can be produced using techniques other than those used in this specific example.

The following Table 1 shows the measurement results obtained when the plurality of surface acoustic wave devices 1 having the above-described electrode structure are formed on a common wafer 10, and the insertion losses and the center frequencies of the respective surface acoustic wave devices 1 are measured at respective points P1 to P9 inside of the wafer 10 as shown in Fig. 3. Moreover, Table 1 shows the maximum value (MAX), the minimum value (MIN), and the average (AVE) of the insertion losses, and the deviation (&sgr;) of the center frequency.

Moreover, Table 1 shows the measurement results obtained when a plurality of conventional surface acoustic wave devices were formed on the same wafer by use of the same wafer and the same film-forming apparatus, and the insertion losses and the center frequencies of the conventional surface acoustic wave devices were measured at the same points P1 to P9 inside of the wafer. In the conventional surface acoustic wave devices, the IDTs and the reflectors each having a two-layer structure (Au/Ti) including a Ti film as an adhesion layer on the surface of the piezoelectric substrate and an Au film as a main component of the electrodes are provided. <u>TABLE 1</u> CONVENTIONAL EXAMPLE PRESENT INVENTION MEASUREMENT POINT Au/Ti/SUBSTRATE Au/Ti/Au/Ti SUBSTRATE INSERTION LOSS (dB) CENTRAL FREQUENCY (MHz) INSERTION LOSS (dB) CENTER FREQUENCY (MHz) P1 -3.51 200.74 -3.23 200.43 P2 -3.61 200.49 -3.18 200.19 P3 -3.48 199.63 -3.2 199.91 P4 -3.55 200.01 -3.48 200.03 P5 -3.34 200.64 -3.09 200.29 P6 -3.41 200.79 -3.35 200.3 7 P7 -3.72 200.48 -3.31 200.15 P8 -3.82 199.81 -3.28 200.14 P9 -3.54 200.93 -3.28 200.37 TOTAL MAX -3.82 3&sgr; 0.4627 MAX -3.48 3&sgr; 0.1722 MIN -3.41 MIN -3.09 AVE -3.55 AVE -3.27

While preferred embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.


Anspruch[de]
Ein Oberflächenwellenbauelement, das eine Shear-Horizontal-Welle verwendet und folgende Merkmale aufweist: ein piezoelektrisches Substrat (2); und einen Interdigitalwandler (3), der auf dem piezoelektrischen Substrat vorgesehen ist, wobei der Interdigitalwandler zumindest drei Metallschichten umfasst; dadurch gekennzeichnet, dass der Interdigitalwandler zumindest zwei erste Schichten (7, 9), die aus einem Metall mit einer Dichte von etwa 15 g/cm3 oder mehr als Hauptkomponente hergestellt sind, und zumindest eine zweite Schicht (6, 8), die aus einem Metall mit einer Dichte von etwa 12 g/cm3 oder weniger als Hauptkomponente hergestellt ist, umfasst, wobei das Gesamtvolumen der ersten Schichten zwischen etwa 20 % und etwa 95 % des Gesamtvolumens des Interdigitalwandlers beträgt. Ein Oberflächenwelienbauelement gemäß Anspruch 1, bei dem das Metall mit einer Dichte von zumindest etwa 15 g/cm3, das eine Hauptkomponente der zumindest zwei ersten Schichten (7, 9) darstellt, aus der Gruppe Au, W, Ta und Pt ausgewählt ist, wobei die Auswahl nicht unbedingt dieselbe für jede erste Schicht ist. Ein Oberflächenwellenbauelement gemäß Anspruch 1 oder 2, bei dem das Metall mit einer Dichte von zumindest etwa 12 g/cm3, das eine Hauptkomponente der zumindest einen zweiten Schicht (6, 8) darstellt, aus der Gruppe Ni, Cr, Cu, Al und Ti ausgewählt ist, wobei die Auswahl nicht unbedingt dieselbe für jede zweite Schicht ist. Ein Oberflächenwellenbauelement gemäß Anspruch 1, 2 oder 3, bei dem jede der Metallschichten, die den Interdigitalwandler darstellt, eine Dicke von bis zu etwa einem Viertel der Gesamtdicke des Interdigitalwandlers (3), von der Oberfläche des piezoelektrischen Substrats (2) gemessen, aufweist, und die Gesamtheit der ersten Schichten ein Volumen von zumindest 50 % des Gesamtvolumens aufweist . Ein Oberflächenwellenbauelement gemäß Anspruch 1, bei dem jede der Metallschichten, die den Interdigitalwandler darstellen, eine Dicke von zumindest etwa einem Zwanzigstel der Gesamtdicke des Interdigitalwandlers aufweist und die am nächsten an dem piezoelektrischen Substrat befindliche Schicht eine erste Schicht (7, 9) ist. Ein Oberflächenwellenbauelement gemäß einem der vorhergehenden Ansprüche, bei dem eine erste Schicht (7, 9) an der Oberfläche des Interdigitalwandlers angeordnet ist. Ein Oberflächenwellenbauelement gemäß einem der vorhergehenden Ansprüche, bei dem bei dem Interdigitalwandler (3) die zumindest zwei ersten Schichten (7, 9) Au als Hauptkomponente enthalten und ein Volumen von etwa 40 % bis etwa 80 % des Gesamtvolumens aufweisen, und die zumindest eine zweite Schicht (6, 8) Ni als Hauptkomponente enthält und ein Volumen von etwa 20 % bis etwa 60 % des Gesamtvolumens aufweist. Ein Oberflächenwellenbauelement gemäß einem der Ansprüche 1 bis 6, bei dem bei dem Interdigitalwandler die zumindest zwei ersten Schichten (7, 9) Au als Hauptkomponente aufweisen und ein Volumen von etwa 20 % bis etwa 50 % des Gesamtvolumens aufweisen und die zumindest eine zweite Schicht 6, 8) Al als Hauptkomponente enthält und ein Volumen von etwa 50 % bis etwa 80 % des Gesamtvolumens aufweist. Ein Oberflächenwellenbauelement gemäß einem der vorhergehenden Ansprüche, das ferner Reflektoren (4, 5) aufweist, die zu beiden Seiten des IDT (3) angeordnet sind. Ein Oberflächenwellenbauelement gemäß Anspruch 9, bei dem die Reflektoren Reflektoren vom Gittertyp (4, 5) sind und die Konfiguration aufweisen, bei der die Mehrzahl von Elektrodenabschnitten an beiden Enden derselben kurzgeschlossen werden. Ein Oberflächenwellenbauelement gemäß Anspruch 9 oder 10, bei dem Abschnitte des Substrats (2), an denen sich die Reflektoren (4, 5) befinden, eine Ausbreitungskonstante aufweisen, die sich von der des restlichen Abschnitts des Substrats (2) unterscheidet. Ein Oberflächenwellenbauelement gemäß Anspruch 9, bei dem jeder der Reflektoren zumindest eine zweite Schicht (6, 8), die einen Ti-Film umfasst, und zumindest zwei erste Schichten (7, 9), die einen Au-Film umfassen, aufweist. Ein Oberflächenwellenbauelement gemäß Anspruch 9, bei dem jeder der Reflektoren (4, 5) eine Vierschicht-Struktur aufweist. Ein Oberflächenwellenbauelement gemäß Anspruch 13, bei dem die Vierschicht-Struktur der Reflektoren (4, 5) Filme aus Ti, Au, Ni und Au umfasst.
Anspruch[en]
A surface acoustic wave device utilizing a Shear Horizontal wave, comprising: a piezoelectric substrate (2); and an interdigital transducer (3) provided on the piezoelectric substrate, the interdigital transducer including at least three metal layers; characterized in that the interdigital transducer includes at least two first layers (7,9) made of a metal with a density of about 15 g/cm3 or more as a major component and at least one second layer (6,8) made of a metal with a density of about 12 g/cm3 or less as a major component, the total volume of said first layers being in the range from about 20% to about 95% of the total volume of the interdigital transducer. A surface acoustic wave device according to Claim 1, wherein the metal with a density of at least about 15 g/cm3 constituting a major component of the at least two first layers (7,9) is selected from the group of Au, W, Ta, and Pt, the selection not necessarily being the same for each first layer. A surface acoustic wave device according to Claim 1 or 2, wherein the metal with a density of up to about 12 g/cm3 constituting a major component of the at least one second layer (6,8) is selected from the group of Ni, Cr, Cu, Al, and Ti, the selection not necessarily being the same for each second layer. A surface acoustic wave device according to Claim 1, 2 or 3, wherein each of the metal layers constituting the interdigital transducer has a thickness of up to approximately one-fourth of the total thickness of the interdigital transducer (3) measured from the surface of the piezoelectric substrate (2), and the totality of the first layers has a volume of at least 50% of the total volume. A surface acoustic wave device according to Claim 1, wherein each of the metal layers constituting the interdigital transducer has a thickness of at least about one-twentieth of the total thickness of the interdigital transducer, and the layer located nearest to the piezoelectric substrate is a first layer (7,9). A surface acoustic wave device according to any previous Claim, wherein a first layer (7,9) is arranged at the surface of the interdigital transducer. A surface acoustic wave device according to any previous Claim, wherein in the interdigital transducer (3), the at least two first layers (7,9) contain Au as a major component and have a volume of from about 40% to about 80 % of the overall volume, and the at least one second layer (6,8) contains Ni as a major component and has a volume of from about 20% to about 60% of the overall volume. A surface acoustic wave device according to any one of claims 1 to 6, wherein in the interdigital transducer, the at least two first layers (7,9) contain Au as a major component and have a volume of from about 20% to about 50% of the overall volume, and the at least one second layer (6,8) contains Al as a major component and has a volume of from about 50% to about 80% of the overall volume. A surface acoustic wave device according to any previous claim, further comprising reflectors (4,5) arranged on both of the sides of the IDT (3). A surface acoustic wave device according to claim 9, wherein the reflectors are grating type reflectors (4,5), and have the configuration in which the plurality of electrode portions are short-circuited at both of the ends thereof. A surface acoustic wave device according to claim 9 or 10, wherein portions of the substrate (2) where the reflectors (4,5) are located have a propagation constant that is different from that of the remaining portion of the substrate (2). A surface acoustic wave device according to claim 9, wherein each of the reflectors comprises at least one second layer (6,8) including a Ti film and at least two first layers (7,9) including an Au film. A surface acoustic wave device according to claim 9, wherein each of the reflectors (4,5) has a four layer structure. A surface acoustic wave device according to claim 13, wherein the four layer structure of the reflectors (4,5) includes films of Ti, Au, Ni, and Au.
Anspruch[fr]
Dispositif à ondes acoustiques de surface utilisant une onde de cisaillement horizontale, comprenant : un substrat piézoélectrique (2) ; et un transducteur interdigital (3) prévu sur le substrat piézoélectrique, le transducteur interdigital comprenant au moins trois couches métalliques ; caractérisé en ce que le transducteur interdigital comprend au moins deux premières couches (7, 9) constituées d'un métal ayant une densité d'environ 15 g/cm3 ou plus en tant que composant majeur et au moins une seconde couche (6, 8) constituée d'un métal ayant une densité d'environ 12 g/cm3 ou moins en tant que composant majeur, le volume total desdites premières couches étant de l'ordre d'environ 20% à environ 95% du volume total du transducteur interdigital. Dispositif à ondes acoustiques de surface selon la revendication 1, dans lequel le métal ayant une densité d'environ 15 g/cm3 constituant un composant majeur desdites au moins deux premières couches (7, 9) est choisi parmi le groupe de Au, W, Ta et Pt, le choix n'étant pas nécessairement le même pour chaque première couche. Dispositif à ondes acoustiques de surface selon la revendication 1 ou 2, dans lequel le métal ayant une densité allant jusqu'à environ 12 g/cm3 constituant un composant majeur de ladite au moins une seconde couche (6, 8) est choisi parmi le groupe de Ni, Cr, Cu, Al et Ti, le choix n'étant pas nécessairement le même pour chaque seconde couche. Dispositif à ondes acoustiques de surface selon la revendication 1, 2 ou 3, dans lequel chacune des couches de métal constituant le transducteur interdigital possède une épaisseur allant jusqu'à environ un quart de l'épaisseur totale du transducteur interdigital (3) mesurée à partir de la surface du substrat piézoélectrique (2), et la totalité des premières couches possède un volume d'au moins 50% du volume total. Dispositif à ondes acoustiques de surface selon la revendication 1, dans lequel chacune des couches de métal constituant le transducteur interdigital possède une épaisseur d'au moins un vingtième de l'épaisseur totale du transducteur interdigital, et la couche située le plus près du substrat piézoélectrique est une première couche (7, 9). Dispositif à ondes acoustiques de surface selon l'une quelconque des revendications précédentes, dans lequel une première couche (7, 9) est agencée au niveau de la surface du transducteur interdigital. Dispositif à ondes acoustiques de surface selon l'une quelconque des revendications précédentes, dans lequel, dans le transducteur interdigital (3), lesdites au moins deux premières couches (7, 9) contiennent du Au en tant que composant majeur et possèdent un volume d'environ 40% à environ 80% du volume global, et ladite au moins une seconde couche (6, 8) contient du Ni en tant que composant majeur et possède un volume d'environ 20% à environ 60% du volume global. Dispositif à ondes acoustiques de surface selon l'une quelconque des revendications 1 à 6, dans lequel, dans le transducteur interdigital, lesdites au moins deux premières couches (7, 9) contiennent du Au en tant que composant majeur et possèdent un volume d'environ 20% à environ 50% du volume global, et ladite au moins une seconde couche (6, 8) contient du AI en tant que composant majeur et possède un volume d'environ 50% à environ 80% du volume global. Dispositif à ondes acoustiques de surface selon l'une quelconque des revendications précédentes, comprenant en outre des réflecteurs (4, 5) agencés des deux côtés de l'IDT (3). Dispositif à ondes acoustiques de surface selon la revendication 9, dans lequel les réflecteurs sont des réflecteurs à réseau (4, 5), et possèdent la configuration dans laquelle la pluralité de parties d'électrodes est court-circuitée aux deux extrémités de celles-ci. Dispositif à ondes acoustiques de surface selon la revendication 9 ou 10, dans lequel les parties du substrat (2) dans lesquelles les réflecteurs (4, 5) sont situés possèdent une constante de propagation qui est différente de celle de la partie restante du substrat (2). Dispositif à ondes acoustiques de surface selon la revendication 9, dans lequel chacun des réflecteurs comprend au moins une seconde couche (6, 8) comprenant un film de Ti et au moins deux premières couches (7, 9) comprenant un film de Au. Dispositif à ondes acoustiques de surface selon la revendication 9, dans lequel chacun des réflecteurs (4, 5) possède une structure à quatre couches. Dispositif à ondes acoustiques de surface selon la revendication 13, dans lequel la structure à quatre couches des réflecteurs (4, 5) comprend des films de Ti, Au, Ni et Au.






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