JP2007300604A - Surface acoustic wave device and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device having excellent characteristics capable of improving insertion loss in a pass band and improving the balance of the pass band and a communication device using the same.
SOLUTION: First and second surface acoustic wave elements 14 and 15 are formed on a piezoelectric substrate 1, and the surface acoustic wave elements 14 and 15 are surface acoustic wave resonators 16 to which an unbalanced input / output terminal 17 is connected. Are connected in parallel, and the balanced input / output terminals 18 and 19 are connected to the IDT electrodes 3 and 6 at the center of the surface acoustic wave elements 14 and 15, and the IDT electrodes 3 and 3 at the center of the surface acoustic wave elements 14 and 15 are connected. 6 and ground lead wires 20, 21 and signal lead wires 22, 23 connecting the surface acoustic wave resonator 16 and the surface acoustic wave elements 14, 15 intersect via insulators 24, 25. Thus, capacitors 26 and 27 are provided at the connection between the surface acoustic wave resonator 16 and the surface acoustic wave elements 14 and 15.
[Selection] Figure 1

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 for mobile communication equipment 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 order to reduce the size, weight, and cost of mobile communication devices, the number of components used has been reduced, and the addition of new functions to surface acoustic wave filters has been required. For example, there is a demand for an unbalanced input-balanced output type surface acoustic wave filter or a balanced input-unbalanced output type surface acoustic wave filter (hereinafter referred to as a balanced type surface acoustic wave filter).

  In order to satisfy this requirement, a longitudinally coupled double mode filter is often used. In addition, as an RF filter, there is a great demand to match one input terminal of an unbalanced connection with an input / output impedance of 50Ω and the other balanced connection with an input / output impedance of 100 to 200Ω.

  Here, the unbalanced input-balanced output type surface acoustic wave filter means a surface acoustic wave filter having an unbalanced input and a balanced output. The balanced input-unbalanced output type surface acoustic wave filter means a surface acoustic wave filter having a balanced input and an unbalanced output. Note that balanced input or balanced output means that a signal is input or output as a potential difference between two signal lines, and the signals of each signal line have the same amplitude and the phases are reversed. On the other hand, unbalanced input or unbalanced output means that a signal is input or output as the potential of one line with respect to the ground potential.

  FIG. 12 is a plan view schematically showing an electrode structure of a conventional balanced surface acoustic wave filter. In the balanced surface acoustic wave filter, surface acoustic wave filters 212 and 213 connected in parallel on a piezoelectric substrate 201 are arranged. The surface acoustic wave filters 212 and 213 respectively include three IDT electrodes 202, 203, 204 and 205, 206 and 207, and reflector electrodes 208, 209 and 210 and 211 disposed on both sides thereof.

  The surface acoustic wave filters 212 and 213 are connected in parallel and connected to the unbalanced signal terminal 214. The IDT electrodes 202, 204 and 205, 207 connected to the unbalanced signal terminal 214 are subjected to surface acoustic waves by applying an electric field to a pair of comb-like electrodes opposed to each other. The excited surface acoustic wave propagates to the center IDT electrodes 203 and 206. Further, the phase of the central IDT electrode 203 is opposite to the phase of the central IDT electrode 206 by 180 °, and finally the balanced output from one of the central IDT electrodes 203 and 206 is performed. Signals are transmitted to the signal terminals 215 and 216, and balanced output is performed. With such a structure, a balanced-unbalanced conversion function is realized.

  By using the conventional balanced surface acoustic wave filter shown in FIG. 12, an unbalanced-balanced conversion function can be realized. However, this balanced surface acoustic wave filter has deteriorated balance (amplitude balance and phase balance). Here, the balance includes an amplitude balance and a phase balance. The amplitude balance is such that a signal is input or output as a potential difference between two signal lines, and the amplitude magnitude (absolute value) of the signal of each signal line is more excellent. Similarly, the degree of phase balance is better as the phase difference of each signal is equal to 180 °.

  On the other hand, a balanced surface acoustic wave device shown in FIG. 13 has also been proposed. As an example of this structure, JP-A-11-97966 can be shown. Of the first-stage longitudinally coupled double-mode surface acoustic wave filters having three IDT electrodes 202, 203, and 204 sandwiched between reflector electrodes 210 and 211 on both sides, an unbalanced terminal is connected to the central IDT electrode 203. 221 is connected. The IDT electrodes 202 and 204 are connected in cascade to the second-stage IDT electrodes 205 and 207, respectively, and the IDT electrode 206 at the center of the second stage is divided into two and connected to the balanced signal terminals 222 and 223 in opposite phases. Yes. This provides an unbalanced input with an input impedance of 50Ω and a balanced output with an output impedance of 200Ω.

  13 is a longitudinally coupled surface acoustic wave in which three IDT electrodes are arranged close to each other in the propagation direction of the surface acoustic wave and reflector electrodes are arranged on both sides of the two-stage surface acoustic wave element in FIG. A configuration in which elements are further connected in cascade to form a surface acoustic wave filter can also be used. However, even with this configuration, the amplitude balance and the phase balance are not sufficient.

  Further, in Japanese Patent Application Laid-Open No. 2002-84164, in a conventional dual mode surface acoustic wave resonator filter, an IDT electrode arranged at the center of three IDT electrodes arranged in the propagation direction of the surface acoustic wave is an even pair. A structure that improves the degree of balance has been proposed. However, since the polarity of the outermost electrode finger of the center IDT electrode and the polarity of the outermost electrode finger of the IDT electrode adjacent to the center IDT electrode are different on the left and right, the parasitic capacitance formed at each balanced signal terminal is different. Therefore, the balanced surface acoustic wave filter having such a structure is not good in amplitude balance and phase balance.

Therefore, the conventional balanced surface acoustic wave filter is required to improve the amplitude balance and the phase balance. Further, the communication device using the conventional balanced surface acoustic wave device has not been sufficiently sensitive.
JP 11-97966 A JP 2002-84164 A

  Accordingly, an object of the present invention is to provide a surface acoustic wave device in which the balance (amplitude balance and phase balance) of a balanced surface acoustic wave filter is improved. Another object of the present invention is to provide a communication device with excellent sensitivity.

  The surface acoustic wave device according to the present invention includes a surface acoustic wave resonator at the front stage provided with an IDT electrode and three or more odd-numbered IDT electrodes connected in parallel to the surface acoustic wave resonator. Grounding for connecting the first and second surface acoustic wave elements, the signal extraction wiring connecting the IDT electrode on the front stage side and the IDT electrode on the rear stage side, and the IDT electrode and the reference potential electrode on the rear stage side A capacitor composed of a lead wire, a part of the signal lead wire, a part of the ground lead wire facing the part of the signal lead wire, and an insulator sandwiched between a part of both wires; One unbalanced input / output terminal connected to the IDT electrode on the side and two balanced output / input terminals connected to the IDT electrode on the rear stage side.

  In the surface acoustic wave device of the present invention, preferably, the width of the grounding lead line and the width of the signal lead line in the capacitor are different.

  In the surface acoustic wave device according to the present invention, preferably, the insulator is formed of silicon oxide or polyimide resin.

  In the surface acoustic wave device of the present invention, preferably, the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator.

  In the surface acoustic wave device according to the present invention, preferably, the reference potential electrode includes the front surface acoustic wave resonator, the rear surface acoustic wave element, the signal lead wire, the ground lead wire, and the capacitor. The annular electrode is formed so as to surround the unbalanced input / output terminal and the balanced output / input terminal.

  In the surface acoustic wave device of the present invention, it is preferable that the grounding lead wire is provided on one of the first and second surface acoustic wave elements.

  In the surface acoustic wave device according to the present invention, preferably, both the first and second surface acoustic wave elements are provided with the grounding lead wires, and the two ground lead wires each form a capacitor. To do.

  In the surface acoustic wave device of the present invention, preferably, the materials of the insulators constituting the two capacitors are different from each other.

  In the surface acoustic wave device of the present invention, preferably, the insulators constituting the two capacitors have different thicknesses.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, wherein the transmission signal is superimposed on a carrier wave signal to be an antenna transmission signal, and the unnecessary signal of the antenna transmission signal is attenuated. A band-pass filter including a surface acoustic wave device; and a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to an antenna through a duplexer.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, comprising an antenna, a low-noise amplifier that amplifies an antenna reception signal that is received by the antenna and passes through a duplexer, and the low-noise amplifier. A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the amplified antenna reception signal; and a mixer for separating the reception signal from the carrier signal of the antenna reception signal that has passed through the bandpass filter. Is.

  The surface acoustic wave device of the present invention is a signal extraction device for connecting the front and rear surface acoustic wave elements each having three or more odd number of IDT electrodes, and the front side IDT electrode and the rear side IDT electrode. A grounding lead wire for connecting a wiring, at least one of the IDT electrodes on the front side and the back side and a reference potential electrode, a part of the signal lead wire, and a part for grounding facing a part of the signal lead wire A capacitance composed of a part of the lead-out wiring and an insulator sandwiched between a part of both wirings, one unbalanced input / output terminal connected to the IDT electrode on the front stage side, and the IDT electrode on the rear stage side And two balanced input / output terminals connected to each other.

  In the surface acoustic wave device of the present invention, preferably, the width of the grounding lead line and the width of the signal lead line in the capacitor are different.

  In the surface acoustic wave device according to the present invention, preferably, the insulator is formed of silicon oxide or polyimide resin.

  In the surface acoustic wave device of the present invention, preferably, the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator.

  In the surface acoustic wave device of the present invention, it is preferable that the reference potential electrode includes the front surface and the rear surface acoustic wave elements, the signal extraction wiring, the ground extraction wiring, the capacitance, and the unbalanced input / output. It is an annular electrode formed so as to surround the terminal and the balanced output / input terminal.

  In the surface acoustic wave device of the present invention, preferably, the materials of the insulators constituting the two capacitors are different from each other.

  In the surface acoustic wave device of the present invention, preferably, the insulators constituting the two capacitors have different thicknesses.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, wherein the transmission signal is superimposed on a carrier wave signal to be an antenna transmission signal, and the unnecessary signal of the antenna transmission signal is attenuated. A band-pass filter including a surface acoustic wave device; and a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to an antenna through a duplexer.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, comprising an antenna, a low-noise amplifier that amplifies an antenna reception signal that is received by the antenna and passes through a duplexer, and the low-noise amplifier. A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the amplified antenna reception signal; and a mixer for separating the reception signal from the carrier signal of the antenna reception signal that has passed through the bandpass filter. To do.

  A surface acoustic wave device according to the present invention includes a first stage surface acoustic wave resonator including an IDT electrode and a second stage surface including three or more odd-numbered IDT electrodes connected in parallel to the surface acoustic wave resonator. A first and second surface acoustic wave elements; a signal lead-out line connecting the front-stage IDT electrode and the rear-stage IDT electrode; a ground lead-out line connecting the rear-stage IDT electrode and the reference potential electrode; Connected to part of signal lead-out wiring, part of ground lead-out wiring facing part of signal lead-out wiring, and insulator sandwiched between parts of both wirings, and IDT electrode on the front side By providing one unbalanced input / output terminal and two balanced input / output terminals connected to the IDT electrode on the rear stage side, a structure such as a peripheral electrode pattern that causes parasitic capacitance can be formed. Different If this is the case, the signals transmitted to the balanced input / output terminals may have different amplitudes, and the phase may deviate from the reverse phase, resulting in degradation of the balance. The electric capacity introduced in the equivalent circuit of the surface acoustic wave element is adjusted in the first and second surface acoustic wave elements by the capacity formed between the first and second surface acoustic wave elements It is possible to improve the amplitude balance and the phase balance.

  In addition, the above configuration eliminates the need for a grounding pad electrode or the like between the surface acoustic wave resonator and the first and second surface acoustic wave elements (longitudinal resonator type surface acoustic wave filter). The surface acoustic wave resonator and the longitudinally coupled resonator type surface acoustic wave filter can be made as close as possible, and a pattern such as a grounding pad electrode can be formed between the surface acoustic wave elements or between the surface acoustic wave resonator and the surface acoustic wave element. The surface acoustic wave device can be greatly reduced in size by reducing the area occupied by the surface acoustic wave element, the surface acoustic wave resonator, and the wiring pattern as much as possible.

  In the surface acoustic wave device of the present invention, it is preferable that the electrical capacitance generated in the capacitance can be controlled more finely because the width of the grounding lead wire and the width of the signal lead wire are different.

  In the surface acoustic wave device according to the present invention, preferably, the insulator is formed of silicon oxide or polyimide resin, so that insulation is reliably ensured at the intersection between the signal lead-out wiring and the ground lead-out wiring. can do. Furthermore, an appropriate capacitance can be inserted between the surface acoustic wave resonator and the first and second surface acoustic wave elements, and the first surface acoustic wave element and the second surface acoustic wave element are connected to each other. It is possible to adjust the balance of signals between them, and the balance of the surface acoustic wave device can be improved.

  In the surface acoustic wave device of the present invention, preferably, the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator, so that the electrical capacitance generated in the capacitor can be controlled more finely. .

  In the surface acoustic wave device according to the present invention, preferably, the reference potential electrode includes a front surface acoustic wave resonator, a back surface acoustic wave element, a signal lead wire, a ground lead wire, a capacitor, and an unbalanced input / output terminal. Since the ring-shaped electrode is formed so as to surround the balanced input / output terminal, the ground lead-out wiring is connected to the ring-shaped electrode formed around the surface acoustic wave element. There is no need to arrange the ground pad electrode, and it is possible to combine the reference potential electrodes into one, and the surface area of the surface acoustic wave resonator, the surface acoustic wave element, and the wiring pattern can be reduced as much as possible. It is possible to reduce the size of the apparatus.

  In the surface acoustic wave device according to the present invention, preferably, one of the first and second surface acoustic wave elements is provided by providing a ground lead wire on one of the first and second surface acoustic wave elements. Capacitors can be provided to improve the amplitude balance and the phase balance.

  In the surface acoustic wave device according to the present invention, preferably, both the first and second surface acoustic wave elements are provided with grounding lead wires, and the two ground lead wires each form a capacitance. Further, the amplitude balance and the phase balance can be further improved.

  In the surface acoustic wave device of the present invention, preferably, the materials of the insulators constituting the two capacitors are different from each other, so that the electric capacitance generated in each capacitor can be controlled separately.

  In the surface acoustic wave device of the present invention, preferably, the thicknesses of the insulators constituting the two capacitors are different from each other, so that the electric capacitance generated in each capacitor can be controlled separately.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, which is a mixer that superimposes a transmission signal on a carrier wave signal to make an antenna transmission signal, and an elastic surface that attenuates an unnecessary signal of the antenna transmission signal By including a band-pass filter including a wave device and a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to the antenna via the duplexer, severe insertion loss and A communication device that can satisfy the degree of balance is obtained, power consumption is reduced, and a communication device with extremely good sensitivity can be realized.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, which is amplified by an antenna, a low-noise amplifier that amplifies an antenna reception signal that is received by the antenna and passes through the duplexer, and a low-noise amplifier. A bandpass filter including a surface acoustic wave device that attenuates an unnecessary signal of the received antenna signal and a mixer that separates the received signal from the carrier signal of the antenna received signal that has passed through the bandpass filter. Thus, it is possible to obtain a communication device that can satisfy the severe insertion loss and balance that has been achieved, reduce power consumption, and have extremely good sensitivity.

  The surface acoustic wave device according to the present invention includes front and rear surface acoustic wave elements each including three or more odd-numbered IDT electrodes, and signal lead-out wiring connecting the front-stage IDT electrodes and the rear-stage IDT electrodes. , A ground lead wire connecting at least one of the IDT electrodes on the front side and the back side and the reference potential electrode, a part of the signal lead wire, and a part of the ground lead wire facing a part of the signal lead wire , And a capacitor composed of an insulator sandwiched between a part of both wires, one unbalanced input / output terminal connected to the IDT electrode on the front stage, and two balances connected to the IDT electrode on the rear stage By providing an input / output terminal, signals transmitted to the balanced input / output terminal are mutually different if the structure of the surrounding electrode pattern or the like that causes parasitic capacitance is different between the front stage and the rear stage. However, due to the above configuration, the equivalent circuit of the surface acoustic wave element is caused by the capacitance formed between the previous stage and the rear stage. The electric capacity introduced above can be adjusted in the front and rear stages, and the amplitude balance and the phase balance can be improved.

  In the surface acoustic wave device of the present invention, it is preferable that the electrical capacitance generated in the capacitance can be more finely controlled because the width of the grounding lead wire and the width of the signal lead wire in the capacitor are different.

  In the surface acoustic wave device according to the present invention, preferably, the insulator is formed of silicon oxide or polyimide resin, so that insulation is reliably ensured at the intersection between the signal lead-out wiring and the ground lead-out wiring. can do. Furthermore, an appropriate capacity can be inserted between the front-stage and rear-stage surface acoustic wave elements, and the balance of signals between the front-stage and rear-stage surface acoustic wave elements can be adjusted. The degree of balance can be improved.

  In the surface acoustic wave device of the present invention, preferably, the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator, so that the electrical capacitance generated in the capacitor can be controlled more finely. .

  In the surface acoustic wave device according to the present invention, preferably, the reference potential electrode includes front and rear surface acoustic wave elements, signal lead wires, ground lead wires, capacitors, unbalanced input / output terminals, and balanced output terminals. Since the ground electrode is connected to the annular electrode formed around the surface acoustic wave element, the ground pad electrode is arranged between the surface acoustic wave elements. This eliminates the need for a single reference potential electrode, and reduces the area occupied by the surface acoustic wave element and the wiring pattern as much as possible, thereby reducing the size of the surface acoustic wave device.

  In the surface acoustic wave device according to the present invention, preferably, the insulating materials constituting the two capacitors are different from each other, so that the electric capacitance generated in each capacitor can be controlled separately.

  In the surface acoustic wave device of the present invention, preferably, the thicknesses of the insulators constituting the two capacitors are different from each other, so that the electric capacitance generated in each capacitor can be controlled separately.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, which is a mixer that superimposes a transmission signal on a carrier wave signal to make an antenna transmission signal, and an elastic surface that attenuates an unnecessary signal of the antenna transmission signal A bandpass filter including a wave device, and a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to the antenna through the duplexer, thereby severe insertion loss that has been required conventionally In addition, it is possible to obtain a communication apparatus that can satisfy the degree of balance, reduce power consumption, and have extremely good sensitivity.

  The communication device of the present invention is a communication device having the surface acoustic wave device of the present invention, which is amplified by an antenna, a low-noise amplifier that amplifies an antenna reception signal that is received by the antenna and passes through the duplexer, and a low-noise amplifier. By providing a bandpass filter including a surface acoustic wave device that attenuates unnecessary signals of the received antenna signal and a mixer that separates the received signal from the carrier signal of the antenna received signal that has passed through the bandpass filter, A device that can satisfy the required severe insertion loss and balance can be obtained, and a communication device with reduced power consumption and extremely good sensitivity can be realized.

  An embodiment of a surface acoustic wave device of the present invention will be described in detail with reference to the drawings. A resonator type surface acoustic wave filter having a simple structure will be described as an example. For the purpose of explanation, the size of each electrode, the distance between electrodes, the number of electrode fingers, the interval, and the like are schematically illustrated.

  As shown in FIG. 1, an embodiment of a surface acoustic wave device of the present invention includes a surface acoustic wave resonator 16 provided in the front stage and two surface acoustic wave elements provided in the rear stage. The front-stage surface acoustic wave resonator 16 is connected in parallel with the two subsequent-stage surface acoustic wave elements.

  The front surface acoustic wave resonator 16 includes an IDT electrode 11 and reflector electrodes 12 and 13 provided on the piezoelectric substrate 1. The IDT electrode 11 and the reflector electrodes 12 and 13 include a plurality of electrode fingers that are long in the direction orthogonal to the propagation direction of the surface acoustic wave propagating on the surface of the piezoelectric substrate 1. The reflector electrode 12 and the reflector electrode 13 are disposed on the left side and the right side of the IDT electrode 11, respectively.

  The latter two surface acoustic wave elements are composed of a first surface acoustic wave element 14 and a second surface acoustic wave element 15. The first and second surface acoustic wave elements are composed of an odd number of three or more IDT electrode groups and reflector electrodes provided on both sides of the IDT electrode group.

  The first surface acoustic wave element 14 includes an IDT having a plurality of long electrode fingers on the piezoelectric substrate 1 along the direction of propagation of the surface acoustic wave propagating on the surface of the piezoelectric substrate 1 in a direction orthogonal to the propagation direction. An IDT electrode group composed of electrodes 2, 3 and 4 is provided. A reflector electrode 8 is provided on the left side of the IDT electrode group, and a reflector electrode 29 is provided on the right side.

  The second surface acoustic wave element 15 includes an IDT electrode group including IDT electrodes 5, 6, and 7. The IDT electrodes 5, 6, and 7 include a plurality of electrode fingers that are long in the direction orthogonal to the propagation direction of the surface acoustic wave propagating on the surface of the piezoelectric substrate 1. The reflector electrode 30 is provided on the left side of the IDT electrode group, and the reflector electrode 10 is provided on the right side.

  An unbalanced input / output terminal 17 (unbalanced input terminal or unbalanced output terminal) is connected to the IDT electrode 11 constituting the preceding surface acoustic wave resonator 16. A balanced input / output terminal 18 (balanced input / output terminal or balanced input terminal) is connected to the central IDT electrode 3 in the IDT electrode group constituting the first surface acoustic wave element 14 in the subsequent stage. The balanced input / output terminal 19 is also connected to the central IDT electrode 6 in the IDT electrode group constituting the second surface acoustic wave element 15 in the subsequent stage.

  Of the three IDT electrodes 2 to 4 constituting the first surface acoustic wave element 14, two IDT electrodes 2 and 4 are connected in parallel with the IDT electrode 11 on the preceding stage by a signal lead-out wiring 22. Of the three IDT electrodes constituting the first surface acoustic wave element 15, the two IDT electrodes 5 and 7 are connected in parallel with the IDT electrode 11 on the preceding stage by the signal lead-out wiring 23.

  In the IDT electrode group constituting the first surface acoustic wave element 14, a ground lead wire 20 is connected to the central IDT electrode 3. In the IDT electrode group constituting the second surface acoustic wave element 15, the ground lead-out wiring 21 is also connected to the central IDT electrode 6.

  The ground lead wires 20 and 21 connect the IDT electrodes 3 and 6 on the rear stage side and the reference potential electrode (annular electrode) 28, respectively. The reference potential electrode 28 is a ground electrode or the like, but is not necessarily a ground electrode, and may be an electrode held at a certain potential.

  The ground lead wire 20 and the signal lead wire 22 intersect with each other through an insulator 24. The ground lead wire 21 and the signal lead wire 23 intersect with each other through an insulator 25. Capacitors 26 and 27 are formed at these intersections, respectively. In other words, the capacitor 26 includes a part of the signal lead-out wiring 22, a part of the ground lead-out wiring 20 facing the part of the signal lead-out wiring 22, and the insulator 24 sandwiched between part of both the wirings 20 and 22. Consists of. Similarly, the capacitor 27 has an insulation sandwiched between a part of the signal lead-out line 23, a part of the ground lead-out line 21 facing the part of the signal lead-out line 23, and a part of both the lines 21 and 23. It is composed of a body 25.

  In the conventional configuration, when the structures of the electrode patterns around the first and second surface acoustic wave elements that cause parasitic capacitance are different from each other, the signals transmitted to the balanced output terminals have different amplitudes. The phase was shifted from the reverse phase and the balance was deteriorated. However, in one embodiment of the present invention, by providing the capacitors 26 and 27, the capacitance introduced in the equivalent circuit of the surface acoustic wave device is applied to the first surface acoustic wave element 14 and the second surface acoustic wave element 15. It is possible to adjust, and the amplitude balance and the phase balance can be improved.

  FIG. 14 is a plan view showing capacitors 26 and 27 in an equivalent circuit for the surface acoustic wave device of the present invention shown in FIG. As shown in FIG. 14, there is an electrical capacitance between a part of the signal lead-out lines 22 and 23 and a part of the ground lead-out lines 20 and 21 facing a part of the signal lead-out lines 21 and 23. It is formed.

  Further, the first surface acoustic wave element 14 and the second surface acoustic wave element 15 are connected in parallel via the surface acoustic wave resonator 16, so that the insertion loss in the pass band of the surface acoustic wave elements 14 and 15 is achieved. Thus, a balanced surface acoustic wave device can be realized without deterioration. This balanced surface acoustic wave element is an unbalanced input-balanced output type surface acoustic wave filter or a balanced input-unbalanced output type surface acoustic wave filter having an unbalanced-balanced conversion function or a balanced-unbalanced conversion function. It is.

  According to the configuration of the embodiment of the present invention, it is not necessary to provide a grounding pad electrode or the like between the surface acoustic wave resonator 16 and the surface acoustic wave elements 14 and 15. As a result, the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15 can be made as close as possible, and a pattern such as a grounding pad electrode is formed on the surface acoustic wave resonator 16 and the first and second surface acoustic wave resonators. It is possible to lay out outside the region sandwiched between the surface acoustic wave elements 14 and 15 and outside the region sandwiched between the first and second surface acoustic wave elements 14 and 15. Therefore, the surface acoustic wave device can be miniaturized by reducing the area occupied by the surface acoustic wave resonator 16, the first and second surface acoustic wave elements 14 and 15, and the wiring pattern as much as possible.

  As the insulators 24 and 25 used for the capacitor, silicon oxide or polyimide resin is preferably used. As a result, the insulation between the signal extraction electrodes 22 and 23 and the ground extraction electrodes 20 and 21 can be kept good. A desired capacitance can be formed between the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15 by adjusting the area of the extraction electrode and the thickness of the insulators 24 and 25. The balance of the surface acoustic wave device can be improved by the added capacity.

  A part of the grounding lead wires 20 and 21 is connected to an annular electrode 28 formed on the piezoelectric substrate 1 so as to surround the surface acoustic wave device. Thus, the capacitance introduced into the equivalent circuit of the surface acoustic wave device by the capacitors 26 and 27 formed between the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15 in the same manner. Can be adjusted in the first surface acoustic wave element 14 and the second surface acoustic wave element 15, and the amplitude balance and the phase balance can be improved.

  Further, with this configuration, the grounding lead electrodes 20 and 21 are connected to the annular electrode 28 formed around the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15. There is no need to arrange a ground pad electrode between the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15 and between the first and second surface acoustic wave elements 14 and 15. Further, the reference potential electrodes can be combined into one, and the area occupied by the surface acoustic wave resonator 16, the first and second surface acoustic wave elements 14 and 15, and the wiring pattern can be reduced as much as possible. The surface acoustic wave device can be downsized.

  In addition, an annular conductor pattern is formed at a location facing the annular electrode 28 on the external circuit board, and the annular electrode 28 and the annular conductor are joined together with a solder connection body or the like, so that the surface acoustic wave device has a circuit with a face-down structure. It can also be set as the structure which mounted on the board | substrate and sealed those outer peripheral parts with the soldering connection body etc. In this case, it is possible to ensure sufficient airtightness for the surface acoustic wave device, and to provide a surface acoustic wave device that is small and excellent in reliability.

  Further, as shown in FIG. 1, the grounding lead electrodes 20 and 21 are annularly formed in a state where the capacitors 26 and 27 are formed on at least one of the first surface acoustic wave element 14 or the second surface acoustic wave element 15. It may be connected to the electrode 28.

  Another embodiment of the surface acoustic wave device of the present invention is shown in FIG. While the surface acoustic wave device shown in FIG. 1 has two capacitors, the surface acoustic wave device shown in FIG. 2 has one capacitor. That is, a capacitance is connected to one of the ground lead wires between the surface acoustic wave resonator 16 and the first surface acoustic wave element 14 or between the surface acoustic wave resonator 16 and the second surface acoustic wave element 15. Should just be provided.

  In FIG. 2, a ground lead electrode 20 connected to the IDT electrode 3 of the first surface acoustic wave element 14 and a signal lead wiring 22 connecting the surface acoustic wave resonator 16 and the surface acoustic wave element 14 are shown. Capacitors 26 may be formed at the intersections. In this case, the balance of the surface acoustic wave device is improved by adjusting the capacitance applied to either the first surface acoustic wave element 14 or the second surface acoustic wave element 15 as in the case of FIG. Can be made. In FIG. 2, reference numeral 35 denotes a reference potential electrode.

  Instead of the ground lead electrode 20 and the signal lead wire 22 in FIG. 2, a ground lead electrode is connected to the IDT electrode 6 of the second surface acoustic wave element 15, and the surface acoustic wave resonator 16 and the surface acoustic wave element 15 are connected. May be connected by a signal lead-out wiring, and a capacitor may be formed at the intersection of these.

  FIG. 3 shows another embodiment of the surface acoustic wave device of the present invention. In FIG. 1, the reflector electrodes 29 and 30 are formed as one reflector electrode 31 in FIG. That is, each of the first and second surface acoustic wave elements 14 and 15 includes one reflector electrode 31 in which reflector electrodes are integrally formed at a location where they are adjacent to each other. The surface acoustic waves excited by the two surface acoustic wave elements 14 and 15 cancel each other at the reflector electrode 31 on the plus side and the minus side, respectively, and the reflection characteristics are improved. As a result, the generation of minute ripples in the passband can be further suppressed.

  Further, by forming one reflector electrode 31 at a location where the first and second surface acoustic wave elements 14 and 15 are adjacent to each other, the first and second surface acoustic wave elements 14 and 15 are shared. The occupied area can be reduced, and the surface acoustic wave device can be reduced in size.

  As shown in FIG. 4, the surface acoustic wave device according to another embodiment of the present invention includes surface acoustic wave elements 111 and 112 at the front and rear stages. The front and rear surface acoustic wave elements 111 and 112 are connected in cascade.

  On the piezoelectric substrate 101, IDT electrodes 102 to 107 and reflector electrodes 108 to 111 are provided along the propagation direction of the surface acoustic wave propagating on the surface of the piezoelectric substrate 1. The IDT electrodes 102 to 107 each include three IDT electrodes 102 to 104 and 105 to 107, and the reflectors 108, 109, 110, and 111 are arranged outside each set.

  That is, on the piezoelectric substrate 101, three IDT electrodes 102 to 104 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 surface of the piezoelectric substrate 101, and 105, 107, and the front stage composed of reflector electrodes 108, 109 and 110, 111, which are arranged on both sides of IDT electrodes 102-104 and 105-107, respectively, and have a plurality of long electrode fingers in the direction orthogonal to the propagation direction; The surface acoustic wave elements 112 and 113 at the subsequent stage are connected in cascade to form a surface acoustic wave device.

  An unbalanced input / output terminal 122 is connected to the preceding surface acoustic wave element 112. There is signal input / output via unbalanced input / output terminals. For example, an unbalanced input signal is input to the unbalanced input / output terminal 122 or an unbalanced output is output from the unbalanced output terminal 122.

  Two balanced input / output terminals are connected to the subsequent surface acoustic wave element 113. When the unbalanced input terminal 122 is connected to the preceding surface acoustic wave element 112, two balanced output terminals are connected to the subsequent surface acoustic wave element 113. When the unbalanced output terminal 122 is connected to the front surface acoustic wave element 112, two balanced input terminals are connected to the subsequent surface acoustic wave element 113.

  A ground lead wire 114 connected to the IDT electrode 106 of the surface acoustic wave element 113 at the front stage or the rear stage is provided. A signal lead-out wiring 115 for cascading the front surface acoustic wave element 112 and the rear surface acoustic wave element 113 is provided.

  The ground lead wire 114 and the signal lead wire 115 intersect three-dimensionally via the insulator 117, and the capacitor 118 is a part of the signal lead wire and a part of the signal lead wire facing the ground lead wire. It is formed by an insulator sandwiched between a part and part of both wirings.

  That is, a grounding lead line 114 connected to the IDT electrode 106 of the subsequent surface acoustic wave element 113, and a signal lead line 115 for cascading the surface acoustic wave element 112 and the surface acoustic wave element 113 in the subsequent stage are provided. And are arranged so as to intersect with each other via an insulator 117. A capacitor 118 having a structure in which the insulator 117 is sandwiched between the ground lead wiring 114 and the signal lead wiring 115 is provided at the intersection.

  If the surface acoustic wave element 112 at the front stage and the surface acoustic wave element 113 at the rear stage have different structures such as peripheral electrode patterns that cause parasitic capacitance, the signals transmitted to the balanced output signal terminals have amplitudes with each other. In other cases, the phase may be out of phase and the balance may deteriorate. However, since the surface acoustic wave device according to an embodiment of the present invention includes the capacitor 118, the capacitance introduced on the equivalent circuit can be adjusted between balanced outputs (or balanced inputs). That is, since the amplitude and phase of the output signals of the two balanced output signal terminals 123 and 124 can be adjusted, 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 between the surface acoustic wave element 112 at the front stage and the surface acoustic wave element 113 at the rear stage, and the surface acoustic wave element 112 at the front stage and the elasticity at the rear stage are eliminated. The surface acoustic wave element 113 can be made as close as possible, and a pattern such as a grounding pad electrode can be laid out outside the region sandwiched between the surface acoustic wave elements, and the surface acoustic wave element area can be reduced as much as possible. The surface acoustic wave device can be downsized.

  The thickness of the insulator 117 is preferably about 0.5 to 6 [mu] m, and if it is less than 0.5 [mu] m, a large electric capacity is generated, which adversely affects the electrical characteristics of the surface acoustic wave device. On the other hand, if the thickness exceeds 6 μm, the possibility that the upper wiring electrode is disconnected increases.

  The insulator 117 is formed by a method such as a build-up method. When the insulator 117 is formed, a plurality of insulating layers 117 may be stacked. Further, by mixing the insulator 117 with insulator particles made of alumina ceramic or the like or metal particles made of silver or the like, or making the insulator 117 a porous body in which a large number of bubbles are formed, the insulator The dielectric constant of 117 can be adjusted to the desired one.

  In a portion where the ground lead wiring 114 and the signal lead wiring 115 intersect with each other via the insulator 117, that is, in the capacitor 118, the insulator 117 of the ground lead wiring 114 and the signal lead wiring 115 is provided. The width (referred to as width b) of the one disposed above is formed larger than the remaining width (referred to as width a), and when adjusting the capacitance, the width b is reduced by laser light or etching. You can also follow.

  Alternatively, the width b is first set to be the same as the width a, and when the capacitance is adjusted, the width b is made larger than the width a by forming a solder layer or a metal layer at the portion of the width b. Can also be increased.

  That is, the capacity adjustment method for the capacity of the surface acoustic wave device is as follows: 1) a method in which insulator particles or metal particles having a different dielectric constant are mixed in the insulator; and 2) the width and signal of the ground lead-out wiring at the capacity portion. And 3) forming a first capacitor on the first surface acoustic wave element side and a second capacitor on the second surface acoustic wave element side. For example, a method of making the material or thickness of the second capacity insulator different from the material or thickness of the second capacity insulator.

  Another embodiment of the surface acoustic wave device of the present invention is shown in FIG. In the surface acoustic wave device shown in FIG. 4, the ground extraction electrode 114 is connected to the center IDT electrode 106 of the subsequent surface acoustic wave element 113, but in the example of FIG. 114 is connected to the common electrode of the IDT electrode 103 at the center of the surface acoustic wave element 112 in the preceding stage. In this case, similarly to the surface acoustic wave device shown in FIG. 4, the capacitance introduced on the equivalent circuit by the capacitor 118 formed between the surface acoustic wave element 112 at the front stage and the surface acoustic wave element 113 at the rear stage. It is possible to adjust between balanced outputs (or balanced inputs), and the amplitude balance and the phase balance can be improved. Similarly to the above, it is not necessary to provide a grounding pad electrode between the surface acoustic wave element 112 at the front stage and the surface acoustic wave element 113 at the rear stage, and the surface acoustic wave element 112 at the front stage and the elasticity at the rear stage are eliminated. The surface acoustic wave element 113 can be made as close as possible, and a pattern such as a grounding pad electrode can be laid out outside the surface acoustic wave element, and the surface acoustic wave device area is reduced as much as possible. It becomes possible to reduce the size.

  FIG. 6 shows a plan view of another embodiment relating to the surface acoustic wave device of the present invention. In the above configuration, the grounding lead wires 114 and 118, the front surface acoustic wave element 112, and the rear surface acoustic wave element 113 are provided between the front surface acoustic wave element 112 and the rear surface acoustic wave element 113. Two capacitors 118 and 121 are formed at intersections with the signal lead wires 115 and 116 connected in cascade. In this case, similarly to the above, the balance of the surface acoustic wave device can be improved by adjusting the capacitance added to both of the two cascade-connected portions.

  As the insulators 117 and 120 used for the capacitor, silicon oxide or polyimide resin is preferably used. Thereby, it is possible to maintain good insulation between the signal extraction electrodes 115 and 116 and the ground extraction electrodes 114 and 118, and by adjusting the area of the extraction electrodes and the thickness of the insulators 117 and 120. A desired capacity can be formed between balanced outputs (or balanced inputs), and the balance of the surface acoustic wave device can be improved by the added capacity.

  As shown in FIG. 6, in the above configuration, a part of the ground lead-out wiring 114 is connected to the annular electrode 128 formed on the piezoelectric substrate 101 so as to surround the surface acoustic wave device. Thus, in the same manner as described above, the capacitance introduced on the equivalent circuit of the surface acoustic wave element is reduced by two capacitors 118 formed between the surface acoustic wave element 112 at the front stage and the surface acoustic wave element 113 at the rear stage. Adjustments can be made at the balanced output (or balanced input), and the amplitude balance and the phase balance can be improved.

  Further, with this configuration, since the ground extraction electrode 114 is connected to the annular electrode 128 formed around the surface acoustic wave device, there is no need to arrange a ground pad electrode between the surface acoustic wave elements. It is possible to combine the reference potential electrodes into one, and the surface acoustic wave device area can be reduced as much as possible to reduce the surface acoustic wave device in size.

  Further, the surface acoustic wave device is formed by forming an annular conductor pattern at a location on the circuit board facing the annular electrode 128, mounting the surface acoustic wave device with a face-down structure, and sealing with a solder connector or the like. When formed, the surface acoustic wave device can ensure sufficient airtightness, and a surface acoustic wave device that is small in size and excellent in reliability can be provided.

  In addition, as shown in FIG. 6, the grounding lead electrodes 114 and 119 are connected to the cascade connection portions of both the front surface acoustic wave element 112 and the rear surface acoustic wave element 113 with capacitors 118 and 121 formed therein. It may be connected to the annular electrode 128.

  In addition, as a piezoelectric substrate for a 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-propagating lithium niobate single crystal, 41 ° ± 3 ° Y-cut X-propagating lithium niobate single crystal, 45 ° ± 3 ° X-cut Z-propagating lithium tetraborate single crystal are preferred. Since these have a large electromechanical coupling coefficient and a small frequency temperature coefficient, they are preferable as piezoelectric substrates.

  Of these pyroelectric piezoelectric single crystals, a piezoelectric substrate whose pyroelectricity is remarkably reduced by solid solution of oxygen defects or Fe is excellent in terms of device reliability. The thickness of the piezoelectric substrate is preferably about 0.1 to 0.5 mm because it has few disadvantages of being fragile, has a low material cost, and can easily reduce the component dimensions.

  On one main surface on which the surface acoustic wave element of the piezoelectric substrate is formed, a conductive connection body such as a conductor bump made of Au, solder or the like for flip-chip connecting the surface acoustic wave device face-down to an external circuit substrate or the like is provided. , Formed on the unbalanced input / output terminal 17, the balanced input / output terminals 18 and 19, the reference potential electrode (annular electrode 28) and the like.

  The IDT electrode and the reflector electrode are made of Al or an Al alloy (Al—Cu system, Al—Ti system), 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 filter.

  In addition, since the number of electrode fingers of the IDT electrode, electrode of the reflector electrode, and electrode fingers of the surface acoustic wave resonator ranges from several to several hundreds in the embodiment of the device, the elastic surface is simplified. In FIG. 1, the shapes thereof are simplified.

Furthermore, in the embodiment of the surface acoustic wave device, SiO ₂ , SiN _x , Si, and Al ₂ O ₃ are formed as protective films on the electrodes and the surface acoustic wave propagation portions on the surface of the piezoelectric substrate, and are formed of conductive foreign matter. 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 the band-pass filter included in these circuits is used. 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, 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. Therefore, if the surface acoustic wave device of the present invention is employed, a communication device with reduced power consumption can be provided because the insertion loss of the surface acoustic wave device is improved. Moreover, since the S / N ratio is improved by improving the insertion loss, the sensitivity of the communication device can be improved.

  FIG. 15 shows an example of a block circuit diagram of a high-frequency circuit having a bandpass filter incorporated in a mobile phone as a communication device. The transmission signal (high frequency signal) is superposed on the carrier wave signal by the mixer 220 to form an antenna transmission signal. The unnecessary signal is attenuated by the surface acoustic wave device 221 that is a bandpass filter, amplified by the power amplifier 222, and then the isolator 223. And the surface acoustic wave duplexer (duplexer) 215 and radiated from the antenna 214. The antenna reception signal received by the antenna 214 passes through the surface acoustic wave demultiplexer 215 and is amplified by the low noise amplifier 216. After the unnecessary signal is attenuated by the surface acoustic wave device 217 which is a bandpass filter, the amplifier The signal is re-amplified at 218 and converted to a low frequency signal by the mixer 219.

  In the above-described embodiment, for the sake of simplicity, three IDTs 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. An example of a surface acoustic wave element provided with electrodes is shown. However, the present invention is not limited to this, and an odd number of five or more IDT electrodes may be provided. Other configurations can be changed as appropriate without departing from the gist of the present invention.

  A specific example of the surface acoustic wave device shown in FIG. 1 will be described.

Al (99% by mass) -Cu (Cu) is formed on a large number of surface acoustic wave device formation regions on a LiTaO ₃ single crystal piezoelectric substrate (a mother substrate for multi-chip production) 1 having a 38.7 ° Y-cut propagation in the X direction. A fine electrode pattern such as first and second surface acoustic wave elements 14 and 15 made of an alloy was formed. 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 layer is spin-coated on the metal layer to a thickness of about 0.5 μm, patterned to a desired shape by a reduction projection exposure apparatus, and an unnecessary portion of the photoresist layer is developed with an alkaline developer by a developing apparatus. Dissolve to reveal the desired pattern. Thereafter, the metal layer was etched by an RIE apparatus, patterning was completed, and a pattern of each electrode constituting the surface acoustic wave device was obtained.

Next, a protective film was formed on a predetermined region of the electrode. That is, a SiO ₂ layer having a thickness of about 0.1 μm was formed on each electrode pattern and the piezoelectric substrate 1 by a CVD (Chemical Vapor Deposition) apparatus.

  Next, patterning is performed by photolithography for the formation of the extraction electrodes arranged to cross each other through an insulator, and the extraction electrodes 22 and 23 are formed on the intersections with the ground extraction wirings 20 and 21. An insulator was formed. Next, a connection electrode for connecting the ground lead wires 20 and 21 drawn from the common electrode of the IDT electrodes 3 and 6 and the annular electrode 28, and the ground lead wires of the lead electrodes 22 and 23. In order to form a connection electrode provided on the insulator on the intersection with 20 and 21, patterning was performed by photolithography.

At that time, since the SiO ₂ layer hinders electrical connection at the connection portion between the connection electrode and the grounding lead wires 20 and 21 and the annular electrode 28, the portion is formed into the SiO ₂ layer by dry etching using an RIE apparatus or the like. Etching was performed to open the window.

Furthermore, using a RIE apparatus or the like, a conductive connector for flip-chip connecting the surface acoustic wave device face-down to an external circuit board or the like is provided on one main surface of the piezoelectric substrate 1 where the surface acoustic wave element is formed. Were formed by etching the SiO ₂ layer. Thereafter, using a sputtering apparatus, an unbalanced input / output terminal, a balanced input / output terminal, and a reference potential electrode (annular electrode) having a structure in which a Cr layer, an Ni layer, and an Au layer were laminated on a window were formed. Each thickness of the unbalanced input / output terminal, the balanced input / output terminal, and the reference potential electrode was about 1.0 μm. After that, the photoresist, unnecessary Cr layer, Ni layer, and Au layer are simultaneously removed by lift-off method, and unbalanced input / output terminals, balanced input / output terminals, and reference potential electrodes are completed to form conductive connectors. did.

  Next, a conductive connection body for flip chip connection made of solder was formed on each of the unbalanced input / output terminal, the balanced input / output terminal, and the reference potential electrode by a printing method.

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 formation surface of the reference potential electrode or the like as the bottom surface and bonded. Thereafter, baking was performed in an N ₂ atmosphere to complete a packaged surface acoustic wave device. The package used was a 2.5 × 2.0 mm square laminate structure formed by laminating ceramic layers.

  Further, as a sample of Comparative Example 1, a surface acoustic wave device having a surface acoustic wave resonator 16 and first and second surface acoustic wave elements 14 and 15 as shown in FIG. 22 and 23 and the grounding lead electrodes 20 and 21 are not formed, and the grounding pad electrode 29 is provided between the surface acoustic wave resonator 16 and the first and second surface acoustic wave elements 14 and 15. , 30 were formed in the same process as in the above example.

  The other configuration of the surface acoustic wave device used as the sample of Comparative Example 1 is the same as the configuration of the surface acoustic wave device shown in FIG.

  Next, the characteristics of the surface acoustic wave devices of Example 1 and Comparative Example 1 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).

  FIG. 8 shows a graph of frequency characteristics in the vicinity of the pass band obtained as a result of the measurement. FIG. 8 is a graph showing the frequency dependence of insertion loss representing the transmission characteristics of a surface acoustic wave device as a frequency filter. The filter characteristics of Example 1 were very good. That is, as shown by the solid line in FIG. 8, good filter characteristics with improved insertion loss were obtained.

  On the other hand, as indicated by the wavy line in FIG. 8, the insertion loss of the filter characteristics in the passband of Comparative Example 1 is degraded. The surface acoustic wave device of Example 1 was able to improve the insertion loss of the passband by 0.3 dB as compared with Comparative Example 1.

  FIG. 9 shows a phase balance diagram in the vicinity of the passband for the surface acoustic wave devices of Example 1 and Comparative Example 1. As shown by the solid line in FIG. 9, the degree of phase balance in Example 1 was very good with a stable and flat characteristic within the passband. As shown by the wavy line in FIG. 9, the phase balance of Comparative Example 1 does not have stable characteristics in the passband. Thus, in this embodiment, the balance can be greatly improved in the pass band.

  Thus, in Example 1, the surface acoustic wave device with improved insertion loss and improved balance could be realized. Further, the surface acoustic wave device of Example 1 was downsized by about 10% in the area of the main surface on which the surface acoustic wave elements and the like were formed, compared with the surface acoustic wave device of Comparative Example 1.

  A specific example of the surface acoustic wave device shown in FIG. 4 will be described.

38.7 ° Y-cut-Propagation made of Al (99% by mass) -Cu (1% by mass) alloy on piezoelectric substrate 101 (mother substrate for multi-cavity) made of LiTaO ₃ single crystal with X-direction propagation An electrode pattern was formed.

  The pattern of each electrode was produced by performing photolithography using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the piezoelectric substrate 101 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 on the metal layer to a thickness of about 0.5 μm, patterned into a desired shape with a reduction projection exposure apparatus, and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing apparatus. The desired pattern was revealed. Thereafter, the metal layer was etched by an RIE apparatus, patterning was completed, and a pattern of each electrode constituting the surface acoustic wave device was obtained.

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

After that, patterning is performed by photolithography, and an etching process is performed to make the SiO ₂ layer portion corresponding to the connection portion between the grounding lead electrode 14 and the common electrode of the IDT electrode 6 into a window portion by dry etching with an RIE apparatus or the like. It went by. Furthermore, patterning was performed by photolithography, and the SiO ₂ layer at portions other than the capacitor 18 was etched by an RIE apparatus or the like, and the thickness was adjusted to 0.2 μm and processed.

Thereafter, a grounding lead electrode 14 was formed with an Al—Cu alloy using a sputtering apparatus. Furthermore, patterning was performed by photolithography, and etching was performed to open a flip chip connection window in the SiO ₂ layer with an RIE apparatus or the like. Thereafter, using a sputtering apparatus, an unbalanced input / output terminal, a balanced input / output terminal, and a reference potential electrode (annular electrode) having a structure in which a Cr layer, an Ni layer, and an Au layer were laminated on a window were formed. Each thickness of the unbalanced input / output terminal, the balanced input / output terminal, and the reference potential electrode was about 1.0 μm. After that, the photoresist, unnecessary Cr layer, Ni layer, and Au layer are simultaneously removed by lift-off method, and unbalanced input / output terminals, balanced input / output terminals, and reference potential electrodes are completed to form conductive connectors. did.

  Next, a conductive connection body for flip chip connection made of solder was formed on each of the unbalanced input / output terminal, the balanced input / output terminal, and the reference potential electrode by a printing method.

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 formation surface of the reference potential electrode or the like as the bottom surface and bonded. Thereafter, baking was performed in an N ₂ atmosphere to complete a packaged surface acoustic wave device. The package used was a 2.5 × 2.0 mm square laminate structure formed by laminating ceramic layers.

  Further, as a sample of Comparative Example 2, in the front surface acoustic wave element 12 and the back surface acoustic wave element 13 as shown in FIG. 10, the intersections of the signal extraction electrodes 15 and 16 and the ground extraction electrode are formed. However, a surface acoustic wave device in which a grounding pad electrode 25 was formed between the surface acoustic wave element 12 at the front stage and the IDT electrode 13 at the rear stage 2 was manufactured in the same process as described above.

  The other configuration of the surface acoustic wave device in the 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 Example 2 and Comparative Example 2 were measured. A signal of 0 dBm was input, and measurement was performed under the conditions of a frequency of 840 to 1040 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).

  FIG. 11 shows a phase balance diagram in the vicinity of the passband in the surface acoustic wave devices of Example 2 and Comparative Example 2. As shown by the solid line in FIG. 11, the phase balance of the surface acoustic wave device of Example 2 was very good with a stable and flat characteristic within the passband. Compared with the phase balance of the surface acoustic wave device of Comparative Example 2 shown by the wavy line in FIG. 11, the surface acoustic wave device of Example 2 was able to improve the balance in the pass band.

  As described above, in Example 2, it was possible to realize a surface acoustic wave device that suppressed generation of minute ripples generated in the passband, improved insertion loss, and improved balance. In addition, the surface acoustic wave device of Example 2 was smaller than the surface acoustic wave device of Comparative Example 2 by about 10% in the area of the main surface on which the surface acoustic wave elements and the like were formed.

FIG. 1 is a plan view showing an example of an embodiment relating to a surface acoustic wave device of the present invention. FIG. 2 is a plan view showing another example of the embodiment relating to the surface acoustic wave device of the present invention. FIG. 3 is a plan view showing still another example of the embodiment relating to the surface acoustic wave device of the present invention. FIG. 4 is a plan view showing still another example of the embodiment relating to the surface acoustic wave device of the present invention. FIG. 5 is a plan view showing still another example of the embodiment relating to the surface acoustic wave device of the present invention. FIG. 6 is a plan view showing still another example of the embodiment relating to the surface acoustic wave device of the present invention. FIG. 7 is a plan view showing an electrode structure of the surface acoustic wave device of Comparative Example 1. FIG. 8 is a diagram showing frequency characteristics of insertion loss in the passband and the vicinity thereof for the surface acoustic wave devices of Example 1 and Comparative Example 1. FIG. 9 is a diagram showing the frequency dependence of the degree of phase balance in the passband and the vicinity thereof for the surface acoustic wave measures of Example 1 and Comparative Example 1. FIG. 10 is a plan view schematically showing an electrode structure of the surface acoustic wave device of Comparative Example 2. FIG. 11 is a diagram showing the frequency dependence of the degree of phase balance in the passband of the surface acoustic wave device of Example 2 and Comparative Example 2 and in the vicinity thereof. FIG. 12 is a plan view showing an example of an electrode structure of a conventional surface acoustic wave device. FIG. 13 is a diagram showing the frequency characteristics of insertion loss in the passband of the conventional surface acoustic wave device and in the vicinity thereof. FIG. 14 is a plan view showing the capacitance of the surface acoustic wave device of the present invention shown in FIG. 1 with an equivalent circuit. FIG. 15 is a block circuit diagram of a high-frequency circuit having a band-pass filter incorporated in a mobile phone that is a communication device of the present invention.

Explanation of symbols

1: piezoelectric substrate 14: first surface acoustic wave element 15: second surface acoustic wave element 16: surface acoustic wave resonators 2-7: IDT electrodes 8, 20, 21, 10: reflector electrodes 20, 21: Grounding lead wires 22, 23: Signal lead wires 24, 25: Insulators 26, 27: Capacitance 17: Unbalanced input / output terminals 18, 19: Balanced output input terminals

Claims (20)

A surface acoustic wave device,
A surface acoustic wave resonator of the previous stage comprising an IDT electrode;
First and second surface acoustic wave elements in the subsequent stage respectively including three or more odd-numbered IDT electrodes connected in parallel to the surface acoustic wave resonator;
A signal extraction wiring connecting the IDT electrode on the front stage side and the IDT electrode on the rear stage side;
A ground lead-out wiring connecting the IDT electrode on the rear side and the reference potential electrode;
A capacitor composed of a part of the signal lead-out line, a part of the ground lead-out line facing the part of the signal lead-out line, and an insulator sandwiched between a part of both lines;
One unbalanced input / output terminal connected to the IDT electrode on the front stage side;
Two balanced input / output terminals connected to the IDT electrode on the rear stage side;
A surface acoustic wave device comprising:   2. The surface acoustic wave device according to claim 1, wherein a width of the ground lead wire and a width of the signal lead wire in the capacitor are different.   3. The surface acoustic wave device according to claim 1, wherein the insulator is made of silicon oxide or polyimide resin.   The surface acoustic wave device according to claim 3, wherein the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator.   The reference potential electrode includes the front surface acoustic wave resonator, the back surface acoustic wave element, the signal lead wire, the ground lead wire, the capacitor, the unbalanced input / output terminal, and the balanced output terminal. The surface acoustic wave device according to any one of claims 1 to 4, wherein the surface acoustic wave device is an annular electrode formed so as to surround the substrate.   The surface acoustic wave device according to claim 1, wherein the ground lead-out wiring is provided on one of the first and second surface acoustic wave elements.   6. The elastic surface according to claim 1, wherein the grounding lead wiring is provided in both the first and second surface acoustic wave elements, and the two grounding lead wirings respectively form a capacitance. Wave equipment.   The surface acoustic wave device according to claim 7, wherein materials of the insulators constituting the two capacitors are different from each other.   The surface acoustic wave device according to claim 7 or 8, wherein thicknesses of the insulators constituting the two capacitors are different from each other. A communication device having the surface acoustic wave device according to claim 1,
A mixer that superimposes a transmission signal on a carrier wave signal to form an antenna transmission signal;
A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the antenna transmission signal;
A communication apparatus comprising: a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to an antenna through a duplexer. A communication device having the surface acoustic wave device according to claim 1,
An antenna,
A low-noise amplifier that amplifies an antenna reception signal received by the antenna and passed through a duplexer;
A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the antenna reception signal amplified by the low noise amplifier;
A communication device comprising: a mixer that separates a received signal from a carrier signal of the antenna received signal that has passed through the bandpass filter. A surface acoustic wave device,
Front and back surface acoustic wave elements each including three or more odd-numbered IDT electrodes;
A signal extraction wiring connecting the IDT electrode on the front stage side and the IDT electrode on the rear stage side;
A grounding lead line connecting at least one of the IDT electrodes on the front side and the rear side and a reference potential electrode;
A capacitor composed of a part of the signal lead-out line, a part of the ground lead-out line facing the part of the signal lead-out line, and an insulator sandwiched between a part of both lines;
One unbalanced input / output terminal connected to the IDT electrode on the front stage side;
A surface acoustic wave device comprising two balanced input / output terminals connected to the IDT electrode on the rear stage side.   13. The surface acoustic wave device according to claim 12, wherein a width of the ground lead wiring and a width of the signal lead wiring in the capacitor are different.   The surface acoustic wave device according to claim 12 or 13, wherein the insulator is made of silicon oxide or polyimide resin.   The surface acoustic wave device according to claim 14, wherein the insulator includes insulator particles or metal particles having a dielectric constant different from that of the insulator.   The reference potential electrode is formed so as to surround the front and rear surface acoustic wave elements, the signal lead-out wiring, the ground lead-out wiring, the capacitor, the unbalanced input / output terminal, and the balanced output terminal. The surface acoustic wave device according to claim 12, wherein the surface acoustic wave device is an annular electrode.   The surface acoustic wave device according to any one of claims 12 to 16, wherein materials of the insulator constituting the two capacitors are different from each other.   The surface acoustic wave device according to claim 12, wherein thicknesses of the insulators constituting the two capacitors are different from each other. A communication device having the surface acoustic wave device according to claim 12,
A mixer that superimposes a transmission signal on a carrier wave signal to form an antenna transmission signal;
A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the antenna transmission signal;
A communication apparatus comprising: a power amplifier that amplifies the antenna transmission signal and outputs the amplified antenna transmission signal to an antenna through a duplexer. A communication device having the surface acoustic wave device according to claim 12,
An antenna,
A low-noise amplifier that amplifies an antenna reception signal received by the antenna and passed through a duplexer;
A bandpass filter including the surface acoustic wave device for attenuating an unnecessary signal of the antenna reception signal amplified by the low noise amplifier;
A communication device comprising: a mixer that separates a received signal from a carrier signal of the antenna received signal that has passed through the bandpass filter.

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