JP5025181B2 - Surface acoustic wave device and communication device - Google Patents

Description

  The present invention relates to a surface acoustic wave device such as a surface acoustic wave filter or a surface acoustic wave resonator used in a mobile communication device such as a mobile phone, and a communication device including the same.

  Conventionally, a surface acoustic wave filter has been widely used as a frequency selection filter used in an RF (radio frequency) stage of a mobile communication device such as a mobile phone or a car phone. In general, characteristics required for a frequency selective filter include various characteristics such as a wide passband, low loss, and high attenuation. In recent years, there has been an increasing demand for lower loss for surface acoustic wave filters in order to improve reception sensitivity and lower power consumption particularly in mobile communication devices. In recent years, in mobile communication devices, the antenna has been shifted from a conventional whip antenna to a built-in antenna using dielectric ceramics for miniaturization. For this reason, it is difficult to obtain a sufficient antenna gain, and there is an increasing demand for further improving the insertion loss of the surface acoustic wave filter.

  In order to realize such a broad band and low loss, for example, three IDT electrodes (Inter Digital Transducer) are provided on a piezoelectric substrate, and a dual mode elastic surface using a longitudinal primary mode and a longitudinal tertiary mode is used. Wave resonator filters have been proposed.

  In particular, by providing a narrow pitch portion of electrode fingers at the ends of adjacent IDT electrodes, the radiation loss of bulk waves between the IDT electrodes is reduced, and the state of the resonance mode is controlled to achieve a wider band and lower loss. (For example, refer to Patent Document 1).

  In recent years, surface acoustic wave devices have been required to be smaller and lighter to reduce the size and weight of mobile communication devices, and the mounting form has been changed from the conventional package mounting using the wire bonding method to the flip chip mounting method. The CSP (Chip Scale Package) type has changed. Therefore, not only the mounting form but also the surface acoustic wave device itself tends to be further miniaturized.

  FIG. 7 is a plan view schematically showing an electrode structure of a conventional surface acoustic wave filter. The surface acoustic wave filters 212 and 213 connected in parallel are arranged on the piezoelectric substrate 201. The surface acoustic wave filters 212 and 213 include three IDT electrodes 202, 203, and 204, and 205, 206, and 207, respectively. The reflector electrodes 208, 209 and 210, 211 are arranged on the surface.

  The surface acoustic wave filters 212 and 213 connected to the unbalanced signal terminal 231 are further connected to the surface acoustic wave filters 216 and 217 via the surface acoustic wave resonators 214 and 215. The IDT electrodes 203 and 206 connected to the unbalanced signal terminal 231 apply an electric field to a pair of mutually opposed comb-like electrodes to excite surface acoustic waves. The excited surface acoustic wave is propagated from the center IDT electrodes 203 and 206 to the IDT electrodes 202, 204, 205 and 207. Further, the phase of the central IDT electrode 203 is opposite in phase by 180 ° with respect to the phase of the central IDT electrode 206, and finally the equilibrium is reached from one of the comb-shaped electrodes of the central IDT electrodes 203 and 206. A signal is transmitted to the output signal terminals 232 and 233 and balanced output is performed. With such a structure, a balanced-unbalanced conversion function is realized. Further, the surface acoustic wave element itself can be miniaturized by adopting a three-dimensional wiring structure through insulators 241 to 248 for a part of the wiring between the surface acoustic wave element and the surface acoustic wave resonator. (For example, see Patent Document 2).

The surface acoustic wave filter 216 includes IDT electrodes 218 to 220 and reflector electrodes 224 and 225, and the surface acoustic wave filter 217 includes IDT electrodes 221 to 223 and reflector electrodes 226 and 227. In FIG. 7, reference numeral 250 denotes a ground terminal.
Japanese Patent Laid-Open No. 2002-9587 JP 2004-282707 A

  When a conventional surface acoustic wave device (surface acoustic wave filter) disclosed in Patent Document 2 as shown in FIG. 7 is used, by adopting a three-dimensional wiring as a part of the wiring between the surface acoustic wave elements, Miniaturization of the surface acoustic wave device can be realized. However, when a three-dimensional wiring structure is used only on one side of the balanced signal wiring or the unbalanced signal wiring, the insertion loss is degraded due to the occurrence of ripples in the passband in the frequency characteristics of the passband of the surface acoustic wave filter. There was a problem to do.

  Further, in the surface acoustic wave device disclosed in Patent Document 1, when a narrow pitch portion is provided at the end of the IDT electrode, there are portions where the electrode finger pitch is different in a state where the surface acoustic waves are coupled, so that the passband As a result, the filter characteristic ripple becomes large, the shoulder characteristic deteriorates, and a flat characteristic of the pass band cannot be obtained. In addition, only by providing a narrow pitch portion at the end of the IDT electrode, the number of basic resonance modes that can be used for excitation of the surface acoustic wave is limited to two, the longitudinal first-order mode and the longitudinal third-order mode. Since the resonance mode cannot be used, the degree of freedom in design has been reduced. Therefore, it has been insufficient to improve the insertion loss while improving the flatness of the filter characteristics in the passband and increasing the bandwidth.

  Accordingly, the present invention has been proposed in view of the above-described conventional problems, and the object thereof is to reduce the size of the surface acoustic wave device and to reduce the insertion loss in the passband of the surface acoustic wave device. In addition, an object of the present invention is to provide a surface acoustic wave device that can suppress generation of ripples and can function as a high-quality balanced surface acoustic wave filter, and a communication device using the same.

  The surface acoustic wave device according to the present invention includes: 1) three pieces having a plurality of electrode fingers that are long on the piezoelectric substrate in a direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. A surface acoustic wave element having the above-mentioned odd number of IDT electrodes and reflector electrodes each provided on both sides of the odd number of IDT electrodes and provided with a plurality of long electrode fingers in a direction orthogonal to the propagation direction is formed. The surface acoustic wave device is a surface acoustic wave device connected to an unbalanced input terminal and an unbalanced output terminal, wherein the IDT electrode of the surface acoustic wave device is on the unbalanced input terminal side or unbalanced. The ground lead wire connected to the bus bar electrode on the output terminal side, and all the signal lead wires connecting the unbalanced input terminal or unbalanced output terminal and the surface acoustic wave element via the insulator Cross The cross wiring portions are respectively formed, and the cross wiring portions are formed symmetrically with respect to the IDT electrodes arranged in the center in the odd number of IDT electrodes, and The resistance generated by the cross wiring portion is substantially the same.

  In addition, the surface acoustic wave device of the present invention includes 2) a plurality of electrode fingers that are long on the piezoelectric substrate in a direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. First and second having three or more odd-numbered IDT electrodes and reflector electrodes each provided on both sides of the odd-numbered IDT electrodes and provided with a plurality of long electrode fingers in a direction orthogonal to the propagation direction The first and second surface acoustic wave elements are connected to an unbalanced input terminal or an unbalanced output terminal, and the first and second surface acoustic wave elements are connected to each other. A surface acoustic wave device in which each of the elements is a balanced output unit or a balanced input unit, wherein the IDT electrodes of the first and second surface acoustic wave devices are on the unbalanced input terminal side or the unbalanced output terminal side. Ground connected to busbar electrode Cross wiring portions in which lead wires and all signal lead wires connecting the unbalanced input terminal or unbalanced output terminal and the surface acoustic wave element intersect with each other through an insulator are provided. The cross wiring portion is formed symmetrically with respect to the IDT electrode disposed in the center of the odd number of IDT electrodes, and the resistance generated by each of the cross wiring portions is substantially the same. It is characterized by being.

  In the surface acoustic wave device according to the present invention, a surface acoustic wave resonator is provided between the surface acoustic wave element and the unbalanced input terminal or the unbalanced output terminal. Is arranged, and the unbalanced input terminal or the unbalanced output terminal and the surface acoustic wave resonator are connected to each other.

  In the surface acoustic wave device according to the present invention, 4) in the configuration of 2) or 3), the surface acoustic wave resonator and the third and third surface acoustic wave elements are provided in the subsequent stage of the first and second surface acoustic wave elements. At least one of the fourth surface acoustic wave elements is disposed, and the front stage and the rear stage are connected to each other.

  In addition, the surface acoustic wave device of the present invention includes 5) a plurality of electrode fingers that are long in the direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate on the piezoelectric substrate. First and second having three or more odd-numbered IDT electrodes and reflector electrodes each provided on both sides of the odd-numbered IDT electrodes and provided with a plurality of long electrode fingers in a direction orthogonal to the propagation direction The first and second surface acoustic wave elements include an IDT electrode and a reflector electrode, and are connected to an unbalanced input terminal or an unbalanced output terminal. The first and second surface acoustic wave elements are each connected as a balanced output section or a balanced input section, and are arranged at the center of each of the first and second surface acoustic wave elements. Equilibrium output to the IDT electrode A surface acoustic wave device to which a terminal or a balanced input terminal is connected, wherein a ground lead wire connected to the IDT electrode at the center of each of the first and second surface acoustic wave elements, and the surface acoustic wave The signal lead wiring connecting the wave resonator and each of the first and second surface acoustic wave elements respectively forms a cross wiring portion disposed so as to cross through an insulator, The cross wiring portion is formed symmetrically around an IDT electrode disposed in the center of the odd number of IDT electrodes, and the resistance generated by each cross wiring portion is substantially the same. It is what.

  The communication device of the present invention is characterized in that it includes 6) at least one of a reception circuit and a transmission circuit having a surface acoustic wave device having any one of the constitutions 1) to 5).

  According to the surface acoustic wave device of the present invention, the piezoelectric substrate has three or more electrode fingers each having a plurality of long electrode fingers in a direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. A surface acoustic wave element having an odd number of IDT electrodes and reflector electrodes each provided on both sides of the odd number of IDT electrodes and provided with a plurality of long electrode fingers in a direction orthogonal to the propagation direction is formed. A surface acoustic wave device in which a surface acoustic wave element is connected to an unbalanced input terminal and an unbalanced output terminal, wherein the IDT electrode of the surface acoustic wave element is connected to the unbalanced input terminal side or the unbalanced output terminal side bus bar electrode. Crossed wiring in which connected grounding lead wires and all signal lead wires connecting unbalanced input terminals or unbalanced output terminals and surface acoustic wave elements intersect via an insulator Shape each part The cross wiring portion is formed symmetrically around the IDT electrode arranged in the center in the odd number of IDT electrodes, and the resistance generated by each cross wiring portion is substantially the same. 9, the resistances R1, R2 and the capacitors C1, C2 in the cross wiring portions 15, 16 in FIG. 1 are substantially the same, so that the currents I1, I2 flowing through the wiring are substantially the same, Ripple in the passband can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band.

  In addition, the resistance generated in the cross wiring portion is caused by a small change in thickness or shape such that, for example, the wiring on the upper side of the cross wiring portion is partially thin, bent up or down, or has a step. Therefore, the resistance is likely to be slightly higher than other wiring portions. With respect to the cross wiring portion showing a different resistance value from the other wiring portions, it is possible to obtain the above-described effects (effects such as improved insertion loss) by making the resistance of each cross wiring portion substantially the same. it can. In addition, in order to make the resistance of each cross wiring portion substantially the same, for example, the formation method thereof, that is, the formation conditions of the wiring portion by sputtering method, the formation of insulators such as CVD method, photolithography method and build-up method This can be achieved by making the conditions the same.

  Further, the surface acoustic wave device of the present invention includes three or more electrode fingers each having a plurality of long electrode fingers in a direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. First and second surface acoustic wave elements each having an odd number of IDT electrodes and reflector electrodes each provided on both sides of the odd number of IDT electrodes and provided with a plurality of long electrode fingers in a direction orthogonal to the propagation direction are provided. The first and second surface acoustic wave elements are connected to an unbalanced input terminal or an unbalanced output terminal, and each of the first and second surface acoustic wave elements is a balanced output unit or A surface acoustic wave device configured as a balanced input unit, wherein the lead wire for grounding is connected to the unbalanced input terminal side or unbalanced output terminal side bus bar electrode of the IDT electrode of the first and second surface acoustic wave elements. And an unbalanced input terminal or All the signal lead wires connecting the unbalanced output terminal and the surface acoustic wave element form cross wiring portions arranged to cross each other through an insulator, and the cross wiring portions are odd numbers. Since each IDT electrode is formed symmetrically around the IDT electrode disposed in the center, and the resistance generated by each cross wiring portion is substantially the same, two cross wirings are the same as described above. Since the resistance and the capacitance in the section and the cross wiring section are substantially the same, the current flowing through the wiring becomes substantially the same, and the ripple in the passband can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band. Further, since the cross wiring portion is formed symmetrically around the IDT electrode disposed in the center in the odd number of IDT electrodes, the resistance and the capacitance introduced on the equivalent circuit of the surface acoustic wave device can be reduced. The first surface acoustic wave element and the second surface acoustic wave element can be finely and precisely adjusted, and the amplitude balance and the phase balance can be improved.

  In addition, the above configuration eliminates the need to provide a grounding pad electrode between the unbalanced input terminal or unbalanced output terminal and the longitudinally coupled resonator type surface acoustic wave filter. A surface acoustic wave device can be laid out outside the space between the surface acoustic wave element and the unbalanced input (out) force terminal, and the surface area of the device can be reduced by reducing the device area as much as possible.

  In the surface acoustic wave device according to the present invention, preferably, a surface acoustic wave resonator is disposed between the surface acoustic wave element and the unbalanced input terminal or the unbalanced output terminal. By connecting the terminal or the unbalanced output terminal and the surface acoustic wave resonator, as shown in FIG. 9, the resistors R1 and R2 and the capacitor C1 in the cross wiring portions 15 and 16 of FIG. , C2 are substantially the same, the currents I1, I2 flowing through the wiring are substantially the same, and the ripple in the passband can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band. Further, the crossing width of the IDT electrodes of the surface acoustic wave element can be reduced to half that of the conventional surface acoustic wave element, and the resistance loss can be reduced as compared with the conventional surface acoustic wave device. The insertion loss of the device can be improved.

  Further, since the first and second surface acoustic wave elements are connected in parallel to the unbalanced signal terminal via the surface acoustic wave resonator, the resistance loss can be reduced as compared with the conventional surface acoustic wave device. Therefore, the insertion loss of the surface acoustic wave device can be improved.

  In the surface acoustic wave device according to the present invention, preferably, the surface acoustic wave resonator and the third and fourth surface acoustic waves are provided in the subsequent stage of the first and second surface acoustic wave elements as the preceding stage. Since at least one of the elements is arranged and the former stage and the latter stage are connected, the attenuation outside the passband can be greatly reduced. Further, in this case, the intersection width of the surface acoustic wave resonator and the surface acoustic wave element can be reduced to half of the conventional one, and the first and second surface acoustic wave elements are connected in parallel. The resistance loss can be reduced as compared with the conventional surface acoustic wave device, and the insertion loss of the surface acoustic wave device can be improved.

  Further, on the piezoelectric substrate, three or more odd IDT electrodes each having a plurality of long electrode fingers in the direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate, and the odd number 1st and 2nd surface acoustic wave elements having reflector electrodes each having a plurality of long electrode fingers in the direction orthogonal to the propagation direction are formed on both sides of the IDT electrode, respectively. The surface acoustic wave elements 2 are connected in parallel via a surface acoustic wave resonator that includes an IDT electrode and a reflector electrode and is connected to an unbalanced input terminal or an unbalanced output terminal. Each of the surface acoustic wave elements is a balanced output section or a balanced input section, and the balanced output terminal or the balanced input terminal is connected to the center IDT electrode of each of the first and second surface acoustic wave elements. Device A signal connecting the grounding lead wire connected to the IDT electrode at the center of each of the first and second surface acoustic wave elements, and the surface acoustic wave resonator and each of the first and second surface acoustic wave elements. The lead-out wiring for use forms an intersecting wiring portion arranged so as to intersect with an insulator, and the intersecting wiring portion is centered on an IDT electrode disposed in the center of an odd number of IDT electrodes. Since the resistance generated by each cross wiring portion is substantially the same as well as the above, the resistance and capacitance in the two cross wiring portions and the cross wiring portion are substantially the same as described above. The current flowing through the wiring becomes substantially the same, and the ripple in the pass band can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band. Further, since the cross wiring portion is formed symmetrically around the IDT electrode disposed in the center in the odd number of IDT electrodes, the resistance and the capacitance introduced on the equivalent circuit of the surface acoustic wave device can be reduced. In the first surface acoustic wave element and the second surface acoustic wave element, it is possible to finely adjust with high accuracy, and the amplitude balance and the phase balance can be improved.

  Also, with the above configuration, it is not necessary to provide a grounding pad electrode or the like between the surface acoustic wave resonator and the first and second surface acoustic wave elements. The surface acoustic wave device can be downsized by reducing the device area as much as possible.

  The communication device of the present invention includes at least one of the reception circuit and the transmission circuit having any one of the above-described surface acoustic wave devices of the present invention, so that generation of ripples in the passband can be suppressed. A communication device that can satisfy the more severe insertion loss that has been demanded can be obtained, power consumption can be reduced, and sensitivity can be realized.

  Embodiments of a surface acoustic wave device according to the present invention will be described below in detail with reference to the drawings. The surface acoustic wave device of the present invention will be described taking a resonator type surface acoustic wave filter as an example. In the drawings described below, parts having the same configuration are denoted by the same reference numerals. In addition, the number of electrodes, the distance between electrodes, and the like, such as the size of each electrode and the distance between the electrodes, are schematically illustrated for explanation.

  FIG. 1 shows a plan view of an electrode structure of a surface acoustic wave device according to the present invention. As shown in FIG. 1, a surface acoustic wave device according to the present invention has an electrode finger that is long on a piezoelectric substrate 1 in a direction perpendicular to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate 1. Reflector electrodes each having three or more odd IDT electrodes 2 to 4 and a plurality of electrode fingers that are arranged on both sides of the odd number of IDT electrodes 2 to 4 and that are long in the direction perpendicular to the propagation direction The surface acoustic wave element 31 having 8 and 9 is formed, the surface acoustic wave element 31 is connected to the unbalanced input terminal 12 and the unbalanced output terminal 12, and the IDT electrode 2 of the surface acoustic wave element 31 is formed. To 4 connected to the bus bar electrode on the unbalanced input terminal 12 side or the unbalanced output terminal 12 side, and the unbalanced input terminal 11 or the unbalanced output terminal 11 and the surface acoustic wave element 31 are connected. All signal drawers The wirings 19 and 20 form cross wiring parts 23 and 24, respectively, which are arranged so as to cross each other via the insulators 15 and 16, and the cross wiring parts 23 and 24 are formed by odd-numbered IDT electrodes 2 to 2. 4 are formed symmetrically around the IDT electrode 3 disposed in the center, and the resistances generated by the cross wiring portions 23 and 24 are substantially the same.

  Thereby, since the resistance and the capacitance in the cross wiring portions 23 and 24 are substantially the same, the currents flowing through the signal lead wires 19 and 20 are substantially the same, and the ripple in the passband is greatly reduced. Can do. Therefore, it is possible to improve the insertion loss in the pass band.

  Further, with the above configuration, it is not necessary to provide a grounding pad electrode or the like between the unbalanced input terminal 12 or the unbalanced output terminal 12 and the surface acoustic wave element 31, and the pattern of the grounding pad electrode or the like is elastic. The surface acoustic wave device 31 and the unbalanced input / output force terminal 12 can be laid out outside, and the surface area of the device can be reduced by reducing the device area as much as possible.

  In the present invention, the resistance generated by the cross wiring portions 23 and 24 is about 1.5Ω or less, and if it exceeds 1.5Ω, the loss of the signal increases due to the increase in resistance. Further, the resistances generated by the cross wiring portions 23 and 24 are substantially the same, but the difference between the resistance of the cross wiring portion 23 and the resistance of the cross wiring portion 24 may be 10% or less. If it exceeds 10%, the difference in amplitude between the two balanced output (input) force signals becomes large, and the degree of amplitude balance tends to deteriorate.

  Further, electrical capacitance is also generated in the cross wiring portions 23 and 24, and the value thereof is about 0.1 pF or less, and the respective capacitances generated by the cross wiring portions 23 and 24 are substantially the same. The difference between the capacity of the cross wiring portion 23 and the capacity of the cross wiring portion 24 may be 10% or less. If it exceeds 10%, the difference between the two balanced output (input) force signals from a predetermined phase difference (phase difference 180 °) becomes large, and the phase balance tends to deteriorate.

  The cross wiring portions 23 and 24 are formed symmetrically around the IDT electrode 3 disposed in the center of the odd number of IDT electrodes 2 to 4. It is formed symmetrically about a central axis parallel to the direction orthogonal to the propagation direction, in other words, a central axis parallel to the longitudinal direction of the electrode fingers.

  As the insulators 15 and 16 of the present invention, silicon oxide, polyimide resin, acrylic resist, or the like is preferably used. As a result, it is possible to maintain good insulation between the grounding lead wire 27 and the signal lead wires 19 and 20.

  The thickness of the insulators 15 and 16 is preferably about 1.0 μm to 10.0 μm. If the thickness is less than 1.0 μm, it is difficult to ensure insulation between the wirings, and if the thickness exceeds 10.0 μm, disconnection of the wiring occurs. Is difficult to suppress, and the reliability of the surface acoustic wave device is likely to decrease.

  The insulators 15 and 16 are formed by a method such as a build-up method. When the insulators 15 and 16 are formed, a plurality of insulating layers may be stacked.

  Insulators 15 and 16 are mixed with insulator particles made of alumina ceramics or metal particles made of silver or the like, or the insulators 15 and 16 are made porous with a large number of bubbles formed. Thus, the dielectric constant of the insulators 15 and 16 can be adjusted to a desired one.

The cross wiring portions 23 and 24 are formed as follows, for example. First, on the main surface of the piezoelectric substrate 1, a metal layer to be the IDT electrodes 2 to 4 and the reflector electrodes 8 and 9 is formed. A sputtering apparatus is used for forming the metal layer, and an Al (99 mass%)-Cu (1 mass%) alloy or the like is used as a material for the metal layer. Next, a photoresist is spin-coated on the metal layer to a thickness of about 0.5 μm, and is patterned into a desired shape by a reduction projection exposure apparatus (stepper). And dissolve to reveal the desired pattern. Thereafter, the metal layer is etched by the RIE apparatus, the patterning is finished, and each electrode pattern constituting the surface acoustic wave device is obtained. Thereafter, a protective film and insulators 15 and 16 are formed on a predetermined region of the electrode. That is, a CVD (Chemical Vapor Deposition) apparatus is used to form a SiO ₂ film to be a protective film and insulators 15 and 16 with a thickness of about 1.0 μm on each electrode pattern and the piezoelectric substrate 1. Further, patterning is performed by photolithography, and the SiO ₂ film at portions other than the insulators 15 and 16 is etched by an RIE apparatus or the like to adjust the film thickness to about 0.2 μm. Thereafter, the signal extraction electrodes 19 and 20 are formed of an Al—Cu alloy using a sputtering apparatus. Thereby, a surface acoustic wave device having the cross wiring portions 23 and 24 is manufactured.

When a resin such as polyimide resin is used as the insulators 15 and 16, for example, a SiO ₂ film serving as a protective film is formed on each electrode pattern and the piezoelectric substrate 1 with a thickness of about 0.01 μm, and the SiO ₂ A resin layer to be the insulators 15 and 16 is spin-coated on the film to a thickness of about 2 to 3 μm, patterned by photolithography, and a resin layer other than the insulators 15 and 16 is removed by an RIE apparatus or the like. The insulators 15 and 16 are formed by laminating the SiO ₂ film and the resin layer.

  FIG. 2 shows a plan view of another embodiment of the surface acoustic wave device of the present invention. As shown in FIG. 2, the surface acoustic wave device of the present invention has a long electrode finger on the piezoelectric substrate 1 along the direction of propagation of the surface acoustic wave propagating on the piezoelectric substrate 1 in a direction orthogonal to the propagation direction. 3 or more odd-numbered IDT electrodes 2 to 4, 5 to 7 and a plurality of odd-numbered IDT electrodes 2 to 4, 5 to 7 are arranged on both sides, and are long electrode fingers in a direction perpendicular to the propagation direction. The first and second surface acoustic wave elements 31 and 32 having the reflector electrodes 8 to 11 including a plurality of the first and second surface acoustic wave elements 31 and 32 are formed. A surface acoustic wave device to which a terminal 12 or an unbalanced output terminal 12 is connected and each of the first and second surface acoustic wave elements 31 and 32 is a balanced output unit or a balanced input unit, Of the IDT electrodes of the first and second surface acoustic wave elements 31 and 32 The ground lead wires 27 and 28 connected to the bus bar electrode on the input terminal 12 side or the unbalanced output terminal 12 side, and the unbalanced input terminal 12 or unbalanced output terminal 12 and the surface acoustic wave elements 31 and 32 were connected. All the signal lead-out wirings 19 to 22 form cross wiring portions 23 to 26 arranged so as to cross each other through the insulators 15 to 18, and the cross wiring portions 23 to 26 are odd numbers. The IDT electrodes 2 to 7 are formed symmetrically around the IDT electrodes 3 and 6 disposed in the center, and the resistances generated by the respective cross wiring portions 23 to 26 are substantially the same.

  With this configuration, the resistance and capacitance in the two cross wiring portions 23 and 24 and the cross wiring portions 25 and 26 are substantially the same as described above. Ripple can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band. Furthermore, since the cross wiring portions 23, 24 and 25, 26 are formed symmetrically around the IDT electrodes 3 and 6 disposed in the center in the odd number of IDT electrodes 2-4 and 5-7, The resistance and capacitance introduced in the equivalent circuit of the surface acoustic wave device can be finely and precisely adjusted in the first surface acoustic wave element 31 and the second surface acoustic wave element 32, and the amplitude balance In addition, the degree of phase balance can be improved.

  FIG. 3 shows a plan view of another example of the embodiment of the surface acoustic wave device of the present invention. As shown in FIG. 3, the surface acoustic wave device according to the present invention preferably has a surface acoustic wave between the surface acoustic wave elements 31 and 32 and the unbalanced input terminal 12 or the unbalanced output terminal 12. A resonator 33 is disposed, and the unbalanced input terminal 12 or unbalanced output terminal 12 and the surface acoustic wave resonator 33 are connected.

  Thereby, the electric capacity of the IDT electrode is the same as that of a conventional surface acoustic wave device including a surface acoustic wave element having three IDT electrodes and reflector electrodes on both sides thereof and a surface acoustic wave resonator. By doing so, the crossing width of the IDT electrodes of the surface acoustic wave elements 31 and 32 can be reduced to half, and the resistance loss can be reduced as compared with the conventional surface acoustic wave device. Insertion loss can be improved. In addition, since the first and second surface acoustic wave elements 31 and 32 are connected in parallel via the surface acoustic wave resonator 33, the resistance loss can be reduced as compared with the conventional surface acoustic wave device. Therefore, the insertion loss of the surface acoustic wave device can be improved.

  FIG. 4 shows a plan view of another example of the embodiment of the surface acoustic wave device of the present invention. As shown in FIG. 4, the surface acoustic wave device according to the present invention preferably has surface acoustic wave resonators 34, 34, downstream of the first and second surface acoustic wave elements 31, 32 as the previous stage. 35 is arranged, and the front stage and the rear stage are connected.

  FIG. 5 shows a plan view of another example of the embodiment of the surface acoustic wave device of the present invention. As shown in FIG. 5, the surface acoustic wave device according to the present invention preferably has the third and fourth elasticities in the rear stage of the first and second surface acoustic wave elements 31 and 32 as the front stage. Surface wave elements 36 and 37 are arranged, and the front stage and the rear stage are connected via surface acoustic wave resonators 34 and 35, respectively.

  Thus, as described above, the resistance and capacitance in the cross wiring portions 23 and 24 and the resistance and capacitance in the cross wiring portions 25 and 26 are substantially the same, so that the current flowing through the signal lead wires 19 and 20 or The currents flowing through the signal lead wires 21 and 22 are substantially the same, and the ripple in the passband can be greatly reduced. Therefore, it is possible to improve the insertion loss in the pass band. In addition, the attenuation outside the passband can be greatly reduced.

  In this case, the electric power of the IDT electrode is compared with a conventional surface acoustic wave device in which one surface acoustic wave element is provided in the front stage, one surface acoustic wave element is provided in the rear stage, and one surface acoustic wave resonator is provided between the two. If the same capacity is used, the crossing widths of the surface acoustic wave resonators 34 and 35 and the surface acoustic wave elements 31, 32, 36, and 37 can be reduced to half, and the first and second Since the surface acoustic wave elements 31 and 32 are connected in parallel, the resistance loss can be reduced as compared with the conventional surface acoustic wave device, so that the insertion loss of the surface acoustic wave device can be improved.

  In the third and fourth surface acoustic wave elements 36 and 37 in the subsequent stage, the cross wiring portions 23a and 24a are formed at the crossing portions of the signal lead wires 19a and 20a and the ground lead wire 27a, so that Cross wiring portions 25a and 26a are formed at intersections between the lead wirings 21a and 22a and the ground lead wiring 28a, and resistances and capacitances in the cross wiring portions 23a and 24a, and resistances and capacitances in the cross wiring portions 25a and 26a. Are almost the same. In addition, 15a-18a is an insulator. In the third and fourth surface acoustic wave elements 36 and 37, 2a to 7a are IDT electrodes, and 8a to 11a are reflector electrodes.

  FIG. 6 shows a plan view of another example of the embodiment of the surface acoustic wave device of the present invention. As shown in FIG. 6, the surface acoustic wave device of the present invention has a long electrode finger in a direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate 1 on the piezoelectric substrate 1. A plurality of odd-numbered IDT electrodes 2 to 4 and 5 to 7 and a plurality of odd-numbered IDT electrodes 2 to 4 and 5 to 7 are arranged on both sides, and are long electrode fingers in a direction perpendicular to the propagation direction. Are formed, and the first and second surface acoustic wave elements 31, 32 are formed of IDT electrodes and the first and second surface acoustic wave elements 31, 32, respectively. The first and second surface acoustic wave elements 31 are connected in parallel via surface acoustic wave resonators 34 and 35 which are made of reflector electrodes and to which the unbalanced input terminal 12 or the unbalanced output terminal 12 is connected. 32 is a balanced output section or balanced input section. A surface acoustic wave device in which the balanced output terminals 13 and 14 or the balanced input terminals 13 and 14 are connected to the IDT electrodes 3 and 6 at the center of the first and second surface acoustic wave elements 31 and 32, respectively. The ground lead wires 27 and 28 connected to the IDT electrodes 3 and 6 at the center of the first and second surface acoustic wave elements 31 and 32, the surface acoustic wave resonators 34 and 35, and the first and first surface acoustic wave elements 31 and 32, respectively. The signal lead-out wirings 19 to 22 connected to the two surface acoustic wave elements 31 and 32 respectively form cross wiring portions 23 to 26 arranged so as to cross each other through the insulators 15 to 18. The cross wiring portions 23 to 26 are formed symmetrically around the IDT electrodes 3 and 6 disposed at the center of the odd number of IDT electrodes 2 to 4 and 5 to 7, and Live by wiring parts 23-26 That resistance is substantially the same.

  Thereby, the electric current which flows through wiring becomes substantially the same, and the ripple in a pass band can be reduced significantly. Therefore, it is possible to improve the insertion loss in the pass band. Furthermore, since the cross wiring portions 23, 24 and 25, 26 are formed symmetrically around the IDT electrodes 3 and 6 disposed in the center in the odd number of IDT electrodes 2-4 and 5-7, The resistance and capacitance introduced in the equivalent circuit of the surface acoustic wave device can be finely and precisely adjusted in the first surface acoustic wave element 31 and the second surface acoustic wave element 32, and the amplitude balance In addition, the degree of phase balance can be improved.

  Furthermore, with the above configuration, it is necessary to provide a grounding pad electrode or the like between the first and second surface acoustic wave resonators 34 and 35 and the first and second surface acoustic wave elements 31 and 32. The pattern of the grounding pad electrode or the like can be laid out in an outer region other than between the surface acoustic wave elements 31 and 32 or between the surface acoustic wave elements 31 and 32 and the surface acoustic wave resonators 34 and 35. Therefore, the surface area of the surface acoustic wave device can be reduced by reducing the device area as much as possible.

  The number of electrode fingers of the IDT electrodes 2 to 7, the reflector electrodes 8 to 11, and the surface acoustic wave resonators 33 to 35 ranges from several to several hundreds. Is shown in a simplified manner.

  As the piezoelectric substrate 1 for the surface acoustic wave device, 36 ° ± 3 ° Y-cut X-propagation lithium tantalate single crystal, 42 ° ± 3 ° Y-cut X-propagation lithium tantalate single crystal, 64 ° ± 3 ° Y Cut X Propagation Lithium Niobate Single Crystal, 41 ° ± 3 ° Y Cut X Propagation Lithium Single Crystal, 45 ° ± 3 ° X Cut Z Propagation Lithium Tetraborate Single Crystal has a large electromechanical coupling coefficient and frequency temperature Since the coefficient is small, it is preferable as the piezoelectric substrate 1. Of these pyroelectric piezoelectric single crystals, if the piezoelectric substrate 1 has a significantly reduced pyroelectric property due to solid solution of oxygen defects or Fe, the reliability of the device is good. The thickness of the piezoelectric substrate 1 is preferably about 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate 1 becomes brittle, and if it exceeds 0.5 mm, the material cost and component dimensions are increased, which is not suitable for use.

  The IDT electrode and the reflector electrode are made of Al or an Al alloy (Al—Cu type, Al—Ti type) and are formed by a thin film forming method such as a vapor deposition method, a sputtering method, or a CVD method. An electrode thickness of about 0.1 to 0.5 μm is suitable for obtaining characteristics as a surface acoustic wave device.

Furthermore, SiO ₂ , SiN _x , Si, Al ₂ O ₃ is formed as a protective film on the surface acoustic wave propagation part on the surface of the surface acoustic wave device and the piezoelectric substrate 1 according to the present invention. It is also possible to prevent energization and improve power durability.

  In addition, the surface acoustic wave device of the present invention can be applied to a communication device. That is, at least one of a receiving circuit and a transmitting circuit is provided and used as a bandpass filter included in these circuits. For example, the transmission signal output from the transmission circuit is put on the carrier frequency by the mixer, the unnecessary signal is attenuated by the band pass filter, and then the transmission signal is amplified by the power amplifier and transmitted from the antenna through the duplexer. A communication device equipped with a transmission circuit capable of receiving signals or receiving a received signal with an antenna, amplifying the received signal that has passed through the duplexer with a low-noise amplifier, and then attenuating an unnecessary signal with a band-pass filter, and a carrier frequency with a mixer Can be applied to a communication apparatus including a receiving circuit that separates a signal from the signal and transmits the signal to a receiving circuit that extracts the signal. Accordingly, when the surface acoustic wave device of the present invention is employed, the insertion loss of the surface acoustic wave device is improved, and therefore an excellent communication device with reduced power consumption and remarkably good sensitivity can be provided.

  In the description of the above-described embodiment, for the sake of simplicity, there are many electrode fingers that are long in the direction orthogonal to the propagation direction along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate 3. Although an example in which two IDT electrodes are arranged has been shown, the present invention is not limited to this, and an odd number of five or more IDT electrodes may be arranged. It is possible to make appropriate changes without departing from the scope.

  Examples of the surface acoustic wave device (surface acoustic wave filter) of the present invention will be described below.

A specific example of the surface acoustic wave device shown in FIG. 3 will be described. A fine electrode pattern made of Al (99 mass%)-Cu (1 mass%) was formed on the LiTaO ₃ single crystal piezoelectric substrate 1 that propagated in the X direction with a 38.7 ° Y-cut. Each electrode pattern was produced by photolithography using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the piezoelectric substrate 1 was ultrasonically cleaned with acetone, IPA (isopropyl alcohol) or the like to remove organic components. Next, after sufficiently drying the piezoelectric substrate 1 with a clean oven, a metal layer to be each electrode was formed. A sputtering apparatus was used for forming the metal layer, and an Al (99 mass%)-Cu (1 mass%) alloy was used as the material of the metal layer. The thickness of the metal layer at this time was about 0.18 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm on the metal layer, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is removed with an alkaline developer by a developing apparatus. To dissolve the desired pattern. Thereafter, the metal layer was etched by an RIE apparatus, patterning was completed, and each electrode pattern constituting the surface acoustic wave device was obtained.

Thereafter, a protective film and insulators 15 to 18 were formed on a predetermined region of the electrode. That is, a SiO ₂ film serving as a protective film and insulators 15 to 18 was formed to a thickness of about 1.0 μm on each electrode pattern and the piezoelectric substrate 1 by a CVD (Chemical Vapor Deposition) apparatus.

Further, patterning was performed by photolithography, and the SiO ₂ film other than the insulators 15 to 18 was etched by an RIE apparatus or the like to adjust the film thickness to 0.2 μm. Thereafter, using a sputtering apparatus, signal lead electrodes 19 to 22 were formed of an Al—Cu alloy. Further, patterning was performed by photolithography, and the flip-chip window opening portion was etched by an RIE apparatus. Thereafter, a pad electrode mainly composed of Al was formed using a sputtering apparatus. The film thickness of the pad electrode at this time was about 1.0 μm. Thereafter, the photoresist and unnecessary Al were removed at the same time by a lift-off method, and a pad electrode for forming a conductor bump for flip-chipping the surface acoustic wave device on an external circuit board or the like was completed.

  Next, a flip-chip conductor bump made of Au was formed on the pad electrode using a bump bonding apparatus. The conductor bump had a diameter of about 80 μm and a height of about 30 μm.

Next, the piezoelectric substrate 1 was diced along a dividing line, and divided into each surface acoustic wave device (chip). Thereafter, each chip was accommodated in a package with a flip chip mounting apparatus with the electrode pad forming surface facing down and bonded. Thereafter, baking was performed in an N ₂ atmosphere to complete a packaged surface acoustic wave device. As the package, a 2.5 × 2.0 mm square laminated structure formed by laminating ceramic layers was used.

  As a sample of the comparative example, in the surface acoustic wave resonator 33 and the first and second surface acoustic wave elements 31 and 32 as shown in FIG. 8, the signal lead electrodes 19 and 22 on one side and the ground lead electrode A surface acoustic wave device in which the cross wiring portions 23 and 26 where the three-dimensional crossings 27 and 28 are formed was manufactured in the same process as described above.

  The other configuration of the surface acoustic wave device shown in FIG. 8 used as a sample of the comparative example is the same as that of the surface acoustic wave device shown in FIG.

  Next, the characteristics of the surface acoustic wave devices of the present example and the comparative example were measured. A signal of 0 dBm was input, and measurement was performed under conditions of a frequency of 1640 to 2140 MHz and a measurement point of 801 points. The number of samples is 30, and the measuring instrument is a multi-port network analyzer (“E5071A” manufactured by Agilent Technologies).

  A graph of frequency characteristics in the vicinity of the passband is shown in FIG. The solid line in FIG. 10 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the surface acoustic wave filter. The filter characteristics of this example product were very good. That is, as shown by the solid line in FIG. 10, no ripple was observed in the passband of the surface acoustic wave filter of this example product, and good filter characteristics with improved insertion loss were obtained.

  On the other hand, as shown by the broken line in FIG. 10, ripples are generated in the passband of the surface acoustic wave filter of the comparative example, and the insertion loss is deteriorated.

  As described above, in this example, it was possible to realize a surface acoustic wave device that improved the insertion loss by suppressing the occurrence of ripples generated in the passband.

It is a top view which shows one example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the other example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the other example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the other example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the other example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the other example of embodiment about the surface acoustic wave apparatus of this invention. It is a top view which shows the conventional surface acoustic wave apparatus. It is a top view which shows the surface acoustic wave apparatus of a comparative example. It is a top view which shows the equivalent circuit of the surface acoustic wave apparatus of FIG. It is a diagram which shows the frequency characteristic of the insertion loss in the pass band of the surface acoustic wave apparatus of an Example and a comparative example, and its vicinity.

Explanation of symbols

1: piezoelectric substrate 31: first surface acoustic wave element 32: second surface acoustic wave element 36: third surface acoustic wave element 37: fourth surface acoustic wave elements 33 to 35: surface acoustic wave resonator 2 -7: IDT electrodes 8-11: reflector electrodes 27, 28: grounding lead wires 19-22: signal lead wires 15-18: insulator 12: unbalanced input / output force terminals 13, 14: balanced output (On) force terminal

Claims (6)

On a piezoelectric substrate, wherein along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate, three and IDT electrode having a plurality of long electrode fingers in the direction perpendicular to the propagation direction, the three IDT electrodes are respectively disposed on both sides, the surface acoustic wave device having a reflector electrode having a plurality of long electrode fingers in the direction perpendicular to the propagation direction,
An unbalanced input terminals being electrically connected to said surface acoustic wave element,
A grounding lead line connected to the bus bar electrode on the unbalanced input terminal side of the IDT electrode disposed in the center among the three IDT electrodes ;
In order to electrically connect the unbalanced signal terminal and the bus bar electrode on the unbalanced input terminal side of the IDT electrode arranged next to the IDT electrode arranged in the center among the three IDT electrodes. A first signal lead-out wiring ,
For electrically connecting the unbalanced signal terminal and the bus bar electrode on the unbalanced input terminal side of the IDT electrode disposed on the other side of the IDT electrode disposed in the center among the three IDT electrodes. A second signal lead-out wiring ,
A first cross wiring portion and the grounding lead-out wire and the first signal lead-out lines is the intersection via an insulator,
A second cross wiring portion that is a portion where the ground lead wire and the second signal lead wire intersect via an insulator;
Wherein the first cross-wiring portion and the second intersecting wiring portion, together are symmetrically formed around the IDT electrode disposed at the center among the three IDT electrodes, wherein the first A surface acoustic wave device characterized in that the resistance and capacitance generated by the cross wiring portion and the second cross wiring portion are substantially the same. The surface acoustic wave device according to claim 1, wherein a resistance generated by the first cross wiring portion and the second cross wiring portion is 1.5Ω or less . Between the surface acoustic wave element and the unbalanced input terminal, it is arranged a surface acoustic wave resonator, wherein said unbalanced input terminal and said surface acoustic wave resonator is connected The surface acoustic wave device according to claim 1 or 2. 4. The surface acoustic wave device according to claim 2, wherein a capacitance generated by the first cross wiring portion and the second cross wiring portion is 0.1 pF or less . 5. The insulator is made of a SiO ₂ film and a polyimide resin laminated on the SiO ₂ film.
A surface acoustic wave device comprising a resin layer .   A communication apparatus comprising at least one of a receiving circuit and a transmitting circuit having the surface acoustic wave device according to claim 1.

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