JP2003060479A - Piezoelectric resonator, filter, duplexer, and resonant- frequency adjusting method of the piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make adjustable easily the resonant frequency of a piezoelectric resonator. SOLUTION: The piezoelectric resonator 1 has a substrate 11, a lower barrier layer 12 provided below the substrate 11, an upper barrier layer 13 provided on the substrate 11, a lower electrode 14 provided on the upper barrier layer 13, a piezoelectric thin film 15 provided on the lower electrode 14, and an upper electrode 16 provided on the piezoelectric thin film 15. Furthermore, the piezoelectric resonator 1 has an impedance-adjusting portion 20 provided on the piezoelectric thin film 15, connected with the upper electrode 16, has a grounding electrode 17 provided under the lower barrier layer 12, and is provided at a position facing the impedance-adjusting portion 20. The impedance-adjusting portion 20 includes one or more cutting planned portions, capable of being cut to vary its impedance, corresponding to the states of the cuttingly predetermined portions. By selecting the states of the impedance-adjusting portion 20, the resonant frequency of the piezoelectric resonator 1 is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator including a piezoelectric vibrator and used in mobile communication equipment and the like, a filter including the piezoelectric resonator, a duplexer including the filter, and resonance of the piezoelectric resonator. The present invention relates to a frequency adjustment method.

[0002]

2. Description of the Related Art In mobile communication devices such as mobile phones, which have become extremely popular in recent years, miniaturization and higher frequencies have been promoted year by year. Therefore, electronic components used in mobile communication devices are also required to be downsized and have a high frequency that can be supported.

Some mobile communication devices are equipped with a duplexer for switching between a transmission signal path and a reception signal path in order to share one antenna for transmission and reception. This duplexer includes a filter that passes a transmission signal and blocks a reception signal, and a filter that passes a reception signal and blocks a transmission signal.

In recent years, a surface acoustic wave filter may be used as the filter in the duplexer. The surface acoustic wave filter has characteristics that it can handle frequencies up to 2 GHz and can be made smaller than a ceramic filter. However, in the future, when the operating frequency of the mobile communication device becomes 2 GHz or more, there are many technical problems under the present circumstances for the surface acoustic wave filter to cope with such frequency.

Therefore, recently, Japanese Patent Laid-Open No. 2000-27807 has been proposed.
As shown in Japanese Patent Publication No. 8, a device called a thin film bulk acoustic resonator (hereinafter, also referred to as FBAR) is drawing attention. This FBAR is a piezoelectric resonator that utilizes resonance in the thickness direction of the piezoelectric thin film. In the FBAR, the resonance frequency can be changed by changing the thickness of the piezoelectric thin film. Further, it is considered that FBAR can support frequencies up to several GHz.

By the way, in the FBAR, in order to obtain a predetermined resonance frequency, it is necessary to accurately control the thickness of the piezoelectric thin film and the electrode. However, it is difficult to perfectly control these thicknesses. Therefore, it is necessary to adjust the resonance frequency of the FBAR by some method.

As a method of adjusting the resonance frequency of the FBAR, there are pamphlets of International Publication No. 98/15984,
U.S. Pat. No. 5,780,713 and U.S. Pat. No. 5,587,620 propose a method of changing the thickness of an electrode or the like by etching or film formation after fabrication of FBAR.

Further, in Japanese Unexamined Patent Publication No. 4-329705, in an oscillator using a stripline having a triplate structure as a resonance element, a strip conductor forming the stripline is trimmed to increase its inductance component. There is disclosed a technique for adjusting the resonance frequency of the strip line, and thus the oscillation frequency of the oscillator.

Further, in Japanese Patent Laid-Open No. 64-37102, the resonance frequency of the dielectric coaxial resonator is trimmed by trimming the electrodes on the substrate electrically connected to the inner conductor of the dielectric coaxial resonator. A technique for adjusting the is disclosed.

Further, in Japanese Patent Laid-Open No. 63-268297, a technique for forming an inductance line in an inner layer of a multi-layer substrate and forming a part of desired inductance by an outer-layer conductor in a high frequency circuit using the multi-layer substrate. Is disclosed.

[0011]

[Problems to be Solved by the Invention] However, FBA
The method of adjusting the resonance frequency of the FBAR by changing the thickness of the electrodes and the like after the fabrication of R has a problem that a large-scale device is required for etching and film formation of the electrodes and the like. Further, in this method, it may be necessary to evacuate the chamber containing the FBAR in order to etch the electrodes or form a film. In this case, there is a problem that it takes a lot of time to adjust the resonance frequency of the FBAR.

Further, in the method of trimming the strip conductor shown in JP-A-4-329705 and the method of trimming the electrode shown in JP-A-64-37102, the resonance frequency can be easily adjusted. In addition, there is a problem that it is difficult to make an accurate adjustment.

Further, JP-A-63-268297 describes that the inductance can be adjusted because a part of the desired inductance is formed by the outer layer conductor. Whether or not to adjust the inductance is not specifically described.

The present invention has been made in view of the above problems. A first object of the present invention is to provide a piezoelectric resonator having a piezoelectric vibrator and capable of easily adjusting a resonance frequency, and the piezoelectric resonator. To provide a filter and a duplexer including the filter.

A second object of the present invention is to provide a method of adjusting the resonance frequency of a piezoelectric resonator in which the resonance frequency of the piezoelectric resonator provided with the piezoelectric vibrator can be easily adjusted.

[0016]

The piezoelectric resonator of the present invention comprises:
A piezoelectric thin film having piezoelectricity, a piezoelectric vibrator having two electrodes arranged on both surfaces of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film, and connected to at least one of the two electrodes, An impedance adjusting unit that includes at least one part to be cut, which is a part that can be cut, and whose impedance changes according to the state of the part to be cut.

In the piezoelectric resonator of the present invention, the impedance of the impedance adjusting section can be changed by selecting the state of the planned cutting portion of the impedance adjusting section. This makes it possible to adjust the resonance frequency of the piezoelectric resonator including the piezoelectric vibrator and the impedance adjusting unit.

In the piezoelectric resonator of the present invention, the impedance adjusting portion may have an inductance that changes according to the state of the portion to be cut.

Further, in the piezoelectric resonator of the present invention, the inductance of the impedance adjusting section may be changed in the range of 0 to 10 nH.

Further, in the piezoelectric resonator of the present invention, the inductance of the impedance adjusting section may be changed in the range of 0 to 3 nH.

Further, the piezoelectric resonator of the present invention is 0.5 to 1
It may be used in the frequency band of 0 GHz.

Further, the piezoelectric resonator of the present invention is 0.8 to 6
It may be one used in the frequency band of GHz.

In addition, in the piezoelectric resonator of the present invention, the piezoelectric vibrator further has a substrate that supports the piezoelectric thin film and the electrode, and the impedance adjusting unit is provided on one of the two electrodes that is farther from the substrate. It may be connected.

The filter of the present invention comprises at least one piezoelectric resonator of the present invention.

The duplexer of the present invention is provided with a first filter that passes a transmission signal and blocks a reception signal, and a second filter that passes a reception signal and blocks a transmission signal, and is connected to an antenna. At least one of the first filter and the second filter is configured to include at least one piezoelectric resonator of the present invention.

The resonance frequency adjusting method for a piezoelectric resonator according to the present invention comprises a piezoelectric thin film having piezoelectricity, and a piezoelectric thin film disposed on both sides of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film.
A method of adjusting a resonance frequency of a piezoelectric resonator including a piezoelectric vibrator having two electrodes, the method comprising: one or more planned cutting portions that are connected to at least one of the two electrodes and can be cut; An impedance adjusting unit whose impedance changes according to the state of the cut portion is provided, and the resonance frequency of the piezoelectric resonator is adjusted by selecting the state of the cut portion.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the configuration of a piezoelectric resonator according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. 1 is an exploded perspective view of the piezoelectric resonator according to the present embodiment, FIG. 2 is a plan view showing electrodes of the piezoelectric resonator according to the present embodiment, and FIG. 3 is a sectional view taken along the line AA of FIG. 4 is a sectional view taken along the line BB of FIG. Note that the piezoelectric thin film is omitted in FIG.

The piezoelectric resonator 1 according to the present embodiment is arranged so that the base 11, the lower barrier layer 12 arranged adjacent to the lower surface of the base 11, and the upper surface of the base 11 are adjacent to each other. And an upper barrier layer 13. The piezoelectric resonator 1 further includes a lower electrode 14 disposed on the upper barrier layer 13, a piezoelectric thin film 15 disposed on the lower electrode 14, and an upper electrode disposed on the piezoelectric thin film 15. 16 and 16. The piezoelectric resonator 1 is further arranged below the lower barrier layer 12, the impedance adjusting portion 20 arranged on the piezoelectric thin film 15 and connected to the upper electrode 16, and below the lower barrier layer 12, the base 11, and the upper barrier layer. 13 and a ground electrode 17 arranged at a position facing the impedance adjusting unit 20 with the piezoelectric thin film 15 interposed therebetween.

The substrate 11 is for supporting the other components of the piezoelectric resonator 1. The base 11 is provided with a cavity 11a. For the base 11, for example, a Si substrate is used.

As will be described later, the lower barrier layer 12
Is used as a mask for forming the cavity 11a in the base 11. Therefore, the opening 12a is formed in the lower barrier layer 12 at a position corresponding to the cavity 11a. Silicon nitride (SiN _x ) is used as the material of the lower barrier layer 12, for example.

The upper barrier layer 13 is a cavity 11 of the base 11.
It is an insulating layer that separates the base 11 and the lower electrode 14 so that the lower electrode 14 can be arranged at a position corresponding to a.
The material of the upper barrier layer 13 is, for example, silicon nitride (Si
N _X ) is used.

The piezoelectric thin film 15 is a thin film having piezoelectricity. ZnO, for example, is used as the material of the piezoelectric thin film 15. Each of the lower electrode 14 and the upper electrode 16 is mainly made of metal, and is formed, for example, by stacking an Au layer on a Cr layer. The impedance adjusting unit 20 is made of a conductor patterned into a predetermined shape. The impedance adjustment unit 20 may be made of the same material as the upper electrode 16.

The lower electrode 14 has a signal electrode 14A and ground electrodes 14B, 14C and 14D. These electrodes 14A to 14D are arranged on the same plane. The signal electrode 14A includes a first portion 14Aa arranged at a position corresponding to the cavity 11a of the base 11, and a second portion 14Ab extending in one direction and connected to the first portion 14Aa at the central portion. I'm out. The ground electrode 14B is arranged in parallel with the second portion 14Ab of the signal electrode 14A. The ground electrodes 14C and 14D are the first electrodes of the signal electrode 14A.
Are arranged on both sides of the portion 14Aa. Ground electrode 14
B, 14C and 14D are designed to be grounded. In addition, the signal electrode 14A and the ground electrodes 14B, 14C, 14D
The impedance between and is set to, for example, 50Ω.

The upper electrode 16 is arranged at a position corresponding to the cavity 11a of the base 11. Therefore, the lower electrode 14
The first portion 14Aa of the signal electrode 14A and the upper electrode 1
6 are opposed to each other via the piezoelectric thin film 15.

Through holes 15a and 15b are formed in the piezoelectric thin film 15 at positions corresponding to both ends of the second portion 14Ab of the signal electrode 14A. In the piezoelectric thin film 15, through holes 15c and 15d are formed at positions corresponding to both ends of the ground electrode 14B, and through holes 15c are formed at positions corresponding to both ends of the ground electrode 14C.
e and 15f are formed, and through holes 15g and 15h are formed at positions corresponding to both ends of the ground electrode 14D.

As shown in FIG. 2, the ground electrodes 14C, 1
The 4Ds are connected to each other by a wire 19 passing through the through holes 15e and 15g. Signal electrode 14A
Is connected to a circuit using the piezoelectric resonator 1 through the through holes 15a and 15b.

The portion of the piezoelectric resonator 1 other than the impedance adjusting section 20 and the ground electrode 17 constitutes a piezoelectric vibrator.

The impedance adjusting unit 20 is the upper electrode 1
6 is arranged on the same plane. The impedance adjusting unit 20 includes one or more planned cutting parts which are parts that can be cut, and the impedance changes according to the state of the planned cutting parts. In the present embodiment, in particular, the impedance adjusting unit 20 is designed so that the inductance changes according to the state of the planned cutting portion.

FIG. 1 and FIG. 2 show an example of the shape of the impedance adjusting section 20. The impedance adjusting unit 20 in this example has four branch portions 20A, 20B, 20C, 20D that extend in one direction and are arranged in parallel with each other.
And a connecting portion 20 that connects one ends of the branch portions 20A to 20D.
A connecting portion 2 that connects E and the other end of the branch portions 20A to 20D
It has 0F. The impedance adjusting unit 20 is provided near the connecting portion between the branch portion 20A and the connecting portion 20E.
It is connected to the upper electrode 16.

The impedance adjusting section 20 in this example
As shown in FIG. 2, there are 11 planned cutting portions 21a.
~ 21k are provided. The to-be-cut portion 21a is arranged at a portion of the impedance adjustment unit 20 that is connected to the upper electrode 16. The planned cutting portion 21b is the connecting portion 20.
In E, it is arranged in the vicinity of the connection portion with the branch portion 20A. The planned cutting portion 21c is, in the connecting portion 20F,
It is arranged near the connecting portion with the branch portion 20A. The to-be-cut portion 21d is arranged in the branch portion 20A in the vicinity of a connecting portion with the connecting portion 20E. Expected cutting part 21e
Is arranged in the branch portion 20A in the vicinity of a connecting portion with the connecting portion 20F. The planned cutting portion 21f is the connecting portion 2
At 0E, it is arranged between the branch portion 20B and the branch portion 20C and at a position close to the branch portion 20B. The to-be-cut portion 21g is arranged in the connecting portion 20F, between the branch portion 20B and the branch portion 20C, and at a position close to the branch portion 20B. The planned cutting portion 21h is, in the branch portion 20B,
It is arranged near the connecting portion with the connecting portion 20E. The to-be-cut portion 21i has a connecting portion 20F in the branch portion 20B.
It is located near the connection part with. Cutting section 21
j is a branch portion 20C and a branch portion 20D in the connecting portion 20E.
And is located at a position close to the branch portion 20C. The to-be-cut portion 21k is arranged in the connecting portion 20F, between the branch portion 20C and the branch portion 20D, and at a position close to the branch portion 20C.

The impedance adjusting section 20 includes the lower barrier layer 12, the base 11, the upper barrier layer 13 and the piezoelectric thin film 1.
Since it is opposed to the ground electrode 17 via 5, it becomes a micro-strip line. The impedance of the microstripline changes depending on its shape, including the change in inductance. Therefore, the shape of the impedance adjusting unit 20 changes, and the impedance of the impedance adjusting unit 20 changes depending on the state of each of the scheduled cutting portions 21a to 21k in the impedance adjusting unit 20, that is, whether or not they are cut.

Next, the piezoelectric resonator 1 according to the present embodiment will be described.
An example of the manufacturing method will be described. In this manufacturing method,
The substrate 11 was oriented so as to have a (100) plane.
A Si substrate was used. Then, the upper surface of the base 11 (front
Chemical vapor deposition (CV) on the bottom surface and the bottom surface, respectively.
D) method, 200 nm thick silicon nitride (SiN
_X) A film was formed. A nitride film formed on the upper surface of the base 11.
The silicon film becomes the upper barrier layer 13 and is formed on the lower surface of the base 11.
The formed silicon nitride film becomes the lower barrier layer 12.

Next, an opening 12a was formed in the lower barrier layer 12 by photolithography and dry etching. The lower barrier layer 12 is used as a mask for forming the cavities 11a in the base 11 by etching later.

Next, a ground electrode 17 is formed on the lower surface of the lower barrier layer 12 so as to face the impedance adjusting section 20 to be formed later. The ground electrode 17 was formed by forming a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm in this order by a lift-off method as described below. That is, first, a resist pattern having an opening at a position where the ground electrode 17 should be formed was formed on the lower surface of the lower barrier layer 12 by photolithography. Next, a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm were formed in this order by sputtering to cover the resist pattern. Next, the resist pattern is removed, and C formed in the opening of the resist pattern is removed.
The r layer and the Au layer were used as the ground electrode 17.

Next, the lower electrode 14 was formed on the upper surface of the upper barrier layer 13. The lower electrode 14 was formed by forming a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm in this order by a lift-off method as described below. That is, first, a resist pattern having an opening at a position where the lower electrode 14 should be formed was formed on the upper surface of the upper barrier layer 13 by photolithography. Next, a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm were formed in this order by sputtering to cover the resist pattern. Next, the resist pattern is removed, and C formed in the opening of the resist pattern is removed.
The r layer and the Au layer were used as the lower electrode 14.

The lower electrode 14 has the signal electrode 14A and the ground electrodes 14B to 14D, and these electrodes 14A to 14D are arranged on the same plane. Moreover, the impedance between the signal electrode 14A and the ground electrodes 14B to 14D is set to 50Ω.

Next, a piezoelectric thin film 15 was formed by forming a ZnO layer having a thickness of about 1.2 μm so as to cover the lower electrode 14 by a sputtering method. Next, the through holes 15a to 15h were formed by removing a part of the piezoelectric thin film 15 using acetic acid.

Next, the upper electrode 16 is formed on the upper surface of the piezoelectric thin film 15.
And the impedance adjustment part 20 was formed. The upper electrode 16 and the impedance adjusting section 20 were formed by forming a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm in this order by a lift-off method as described below. That is, first, a resist pattern having an opening at a position where the upper electrode 16 and the impedance adjusting section 20 should be formed was formed on the upper surface of the piezoelectric thin film 15 by photolithography. Next, a Cr layer having a thickness of about 5 nm and an Au layer having a thickness of about 100 nm were formed in this order by sputtering to cover the resist pattern. Next, the resist pattern was removed, and the Cr layer and the Au layer formed in the opening of the resist pattern were used as the upper electrode 16 and the impedance adjusting section 20. The width of the line in the impedance adjusting unit 20 was 20 μm.

The portion of the piezoelectric thin film 15 arranged between the first portion 14Aa of the signal electrode 14A and the upper electrode 16 is the portion that resonates. The size of this part is 15
The rectangle was 0 μm and 150 μm in width.

Next, using the lower barrier layer 12 as a mask, K
The base 11 was etched from the lower surface (back surface) side using OH to form a cavity 11a. The base 11 made of a Si substrate oriented so as to have a (100) plane is anisotropically etched with KOH. As a result, the base 11
As shown in FIG. 3 and FIG. 4, a cavity 11a having a shape in which the width gradually widens toward the lower side was formed. In addition,
During the etching of the substrate 11, the surface of the ground electrode 17 was protected in order to prevent the ground electrode 17 from being affected by the etching solution.

Next, the ground electrodes 14C and 14D were connected to each other by the wire 19 by the wire bonding method.

Next, the operation of the piezoelectric resonator 1 according to this embodiment and the resonance frequency adjusting method will be described. In the piezoelectric resonator 1, a high frequency excitation voltage is applied to the signal electrode 14A of the lower electrode 14 and the upper electrode 16. This excitation voltage is applied to the piezoelectric thin film 15. As a result, a portion of the piezoelectric thin film 15 disposed between the first portion 14Aa of the signal electrode 14A and the upper electrode 16 is excited, and a longitudinal wave traveling in the thickness direction is generated in this portion.
This portion resonates when the frequency of the excitation voltage is a predetermined resonance frequency.

The resonance frequency of the piezoelectric resonator 1 changes depending on the inductance of the impedance adjusting section 20. This will be described with reference to FIGS. 5 and 6. FIG. 5 is a circuit diagram showing a circuit configuration of the piezoelectric resonator 1, and FIG. 6 is a circuit diagram showing an equivalent circuit of the piezoelectric resonator 1. As shown in FIG. 5, the piezoelectric resonator 1 includes two terminals 2 and 3, and a piezoelectric vibrator 10 and an impedance adjusting unit 20 provided between the terminals 2 and 3. The piezoelectric vibrator 10 and the impedance adjusting unit 20 are connected in series. The piezoelectric vibrator 10 is a part of the piezoelectric resonator 1 other than the impedance adjustment unit 20 and the ground electrode 17. Further, in FIG. 5, the impedance adjusting unit 20 is represented by a semi-fixed inductor. One end of the piezoelectric vibrator 10 is connected to the terminal 2. The other end of the piezoelectric vibrator 10 is
It is connected to one end of the impedance adjusting unit 20. The other end of the impedance adjusting unit 20 is connected to the terminal 3.

As shown in FIG. 6, the equivalent circuit of the piezoelectric vibrator 10 includes an inductor 31, a capacitor 32, and a resistor 33 connected in series, and a capacitor 34 connected in parallel to the series circuit formed by them. Composed of and.
Here, the inductance of the inductor 31 is Lm, the capacitance of the capacitor 32 is Cm, the resistance value of the resistor 33 is Rm, and the capacitance of the capacitor 34 is Co. The inductance Lm is called an equivalent inductance, the capacitance Cm is called an equivalent capacitance, and the resistance value Rm is called a resonance resistance. The capacitance Co is a braking capacitance.

In FIG. 6, the connection point between the capacitor 34 and the inductor 31 corresponds to the signal electrode 14A of the lower electrode 14, and the connection point between the capacitor 34 and the resistor 33 corresponds to the upper electrode 16. The equivalent circuit of the piezoelectric resonator 1 is similar to the equivalent circuit of the piezoelectric vibrator 10 described above, except that the impedance adjusting unit
Will be added. In FIG. 6, the impedance adjusting unit 20 is represented by an inductor whose inductance is Lv. One end of this inductor is connected to the connection point between the capacitor 34 and the resistor 33.

The resonance frequency ωr of the piezoelectric resonator 1 represented by the equivalent circuit of FIG. 6 is represented by the following equation (1).

[0057] ωr = 1 / √ {(Lm + Lv) Cm} (1)

As can be seen from the equation (1), the piezoelectric resonator 1
The resonance frequency ωr of changes with the inductance Lv of the impedance adjusting unit 20.

The inductance Lv of the impedance adjusting unit 20 changes depending on the state of each of the planned cutting portions 21a to 21k, that is, whether each of the planned cutting portions 21a to 21k is cut.

An example of the relationship between the states of the respective cut-off portions 21a to 21k and the inductance Lv of the impedance adjusting section 20 will be described below. In this example, the impedance adjuster 20 is capable of selecting one of the four states shown in FIGS. Further, in this example, the upper electrode 16 is grounded directly or via the impedance adjusting unit 20.

The first state shown in FIG. 7 is the planned cutting portion 2
Only the planned cutting portion 21a of 1a to 21k is cut. In the first state, the upper electrode 16 is grounded. In this first state, since the impedance adjusting unit 20 is separated from the upper electrode 16, the length of the line of the impedance adjusting unit 20 connected to the upper electrode 16 is 0 mm.
Is. In the first state, the inductance Lv of the impedance adjusting unit 20 connected to the upper electrode 16 has an inductance of 0 nH.
Is.

The second state shown in FIG. 8 is the planned cutting portion 2
Only the planned cutting portions 21b and 21c of 1a to 21k are cut. In the second state, the impedance adjuster 20 is grounded at the end opposite to the upper electrode 16 with the branch 20A interposed therebetween. In the second state, the impedance adjusting unit 2 connected to the upper electrode 16
The line length of 0 is 0.6 mm. In the second state,
The inductance Lv of the impedance adjusting unit 20 connected to the upper electrode 16 was about 0.5 nH.

The third state shown in FIG. 9 is the planned cutting portion 2
Cut-scheduled portions 21d, 21e, 21 of 1a to 21k
Only f and 21g are cut. In the third state, the impedance adjuster 20 is grounded at the end opposite to the upper electrode 16 with the branch 20A interposed therebetween. In the third state, the length of the line of the impedance adjusting unit 20 connected to the upper electrode 16 is 1.2 mm. In the third state, the inductance Lv of the impedance adjusting unit 20 connected to the upper electrode 16 is about 1.0 n.
It was H.

The fourth state shown in FIG. 10 is the planned cutting portions 21d, 21e, 21 of the planned cutting portions 21a to 21k.
Only h, 21i, 21j, and 21k are cut off. In the fourth state, the impedance adjuster 20 is grounded at the end opposite to the upper electrode 16 with the branch 20A interposed therebetween. In this fourth state, the upper electrode 16
The length of the line of the impedance adjusting unit 20 connected to is 1.8 mm. In the fourth state, the inductance L of the impedance adjustment unit 20 connected to the upper electrode 16
v was about 1.5 nH.

A laser beam, for example, is used to cut the planned cutting portions 21a to 21k. Further, when the planned cutting parts 21a to 21k are cut, the planned cutting parts 21a to 21k are cut with a certain width so that a large capacitance component does not occur in the impedance adjusting section 20 due to the cut part. Is preferred.

Although not shown, the impedance adjusting section 20 cuts the planned cutting sections 21d, 21e, 21h, and 21i of the planned cutting sections 21a to 21k and cuts both ends of the branch section 20C. The fifth state of the impedance adjusting unit 20 may be settable.

FIG. 11 is a plan view showing a probe used to measure the characteristics of the piezoelectric resonator 1. The probe 40 has three terminals 41A, 41B, 41C. One end of a cable 42 is connected to the probe 40. Although not shown, two conductors are inserted in the cable 42. One end of one conductor has a terminal 41B
And one end of the other conducting wire is connected to the terminals 41A and 41C.

When measuring the characteristics of the piezoelectric resonator 1, 2
One probe 40 is used. The terminals 41A, 41B, 41C of the one probe 40 are connected to the first port of the network analyzer via the lead wire in the cable 42 connected to the probe 40. The terminals 41A, 41B, 41C of the other probe 40 are connected to the second port of the same network analyzer via the lead wire in the cable 42 connected to the probe 40.

Terminals 41A, 41 of one probe 40
B and 41C are through holes 15c and 15 respectively.
a, 15h, one end of the ground electrode 14B, one end of the second portion 14Ab of the signal electrode 14A, the ground electrode 1
Touch one end of 4D. Terminal 4 of the other probe 40
1A, 41B and 41C are through holes 15 respectively.
It is inserted into d, 15b, 15f and contacts the other end of the ground electrode 14B, the other end of the second portion 14Ab of the signal electrode 14A, and one end of the ground electrode 14C.

The network analyzer includes the signal electrode 14
Two probes 40 through the second portion 14Ab of A
Signals are exchanged between the terminals 41B of 1 to measure the characteristics of the piezoelectric resonator 1. The ground electrodes 14B, 14C, 14
D is grounded via the terminals 41A and 41C of the two probes 40 and the network analyzer.

Next, the results of experimentally determining the frequency characteristics of the circuit including the piezoelectric resonator 1 for each of the four states shown in FIGS. 7 to 10 will be described. Here, FIG.
The circuit shown in (1) was constructed and the frequency characteristics of the signal attenuation in this circuit were obtained. The circuit shown in FIG. 12 includes a signal line 50, an input end 51 provided at one end of the signal line 50,
The output end 52 provided at the other end of the signal line 50 and the signal line 5
And a piezoelectric resonator 1 connected to 0. The end of the piezoelectric resonator 1 on the piezoelectric vibrator 10 side is connected to the signal line 50, and the impedance adjusting unit 2 of the piezoelectric resonator 1 is connected.
The end on the 0 side is grounded.

FIGS. 13 to 16 show the results of experimentally obtaining the frequency characteristics of the circuit shown in FIG. 12 for each of the four states shown in FIGS. 7 to 10. 13 to 16, the frequency at which the attenuation amount is maximum is the resonance frequency of the piezoelectric resonator 1. In the first state, as shown in FIG. 13, the resonance frequency was 1.81 GHz and the attenuation amount at the resonance frequency was -16.5 dB. In the second state, as shown in FIG. 14, the resonance frequency is 1.80 GHz, and the attenuation amount at the resonance frequency is −
It was 16.7 dB. In the third state, as shown in FIG. 15, the resonance frequency was 1.79 GHz and the attenuation amount at the resonance frequency was -16.9 dB. In the fourth state, as shown in FIG. 16, the resonance frequency is 1.7.
8 GHz, and the amount of attenuation at the resonance frequency is -16.
It was 9 dB.

From the results shown in FIGS. 13 to 16, it is understood that in the present embodiment, the resonance frequency of the piezoelectric resonator 1 can be adjusted by selecting the state of the impedance adjusting section 20.

In the present embodiment, impedance adjusting section 20 may include one or more parts to be cut, which are parts that can be cut, and whose impedance changes according to the state of the part to be cut. Therefore, the shape of the impedance adjusting unit 20 and the method of adjusting the impedance (inductance) of the impedance adjusting unit 20 are not limited to the above-described shapes and methods. For example, in the impedance adjusting section 20 shown in FIG. 2, four branch sections 20A,
The inductance of the impedance adjusting unit 20 may be adjusted by selectively cutting each one of 20B, 20C, and 20D.

Now referring to FIGS. 17 and 18,
Another configuration example of the impedance adjusting unit 20 will be described. The impedance adjusting unit 20 shown in FIG. 17 has a conductor portion 61 formed in a zigzag shape. Conductor part 6
One end of 1 is connected to the piezoelectric vibrator 10. Conductor part 6
A terminal 62 is connected to the other end of 1. In addition, terminals 63 and 64 are connected to two locations in the middle of the conductor portion 61. In the impedance adjusting unit 20, the planned cutting portion 6 is provided in the middle of the conductor portion 61 between the terminal 62 and the terminal 63.
5 is provided, and a planned cutting portion 66 is provided in the middle of the conductor portion 61 between the terminal 63 and the terminal 64.

The impedance adjusting section 20 shown in FIG.
In, it is possible to select one of three states having different inductances. The first state is a state in which both the planned cutting portions 65 and 66 are not cut. In the first state, the terminal 62 is used as one terminal of the piezoelectric resonator 1. The second state is the planned cutting portion 65.
Is in a disconnected state. In the second state, the terminal 63
Is used as one terminal of the piezoelectric resonator 1.
The third state is a state where the planned cutting portion 66 is cut. In the third state, the terminal 64 is used as one terminal of the piezoelectric resonator 1. In the above-described first to third states, since the length of the conductor portion 61 connected to the piezoelectric vibrator 10 is different, the impedance adjusting portion 20 is different.
The inductance of is also different.

In the example shown in FIG. 17, the conductor portion 61
Although the terminals 63 and 64 are provided at two locations in the middle of the
The terminal may be provided at one place in the middle of 1, or the conductor portion 61
You may provide a terminal in three or more places on the way. In either case, the number of selectable states in the impedance adjusting section 20 is the number of terminals provided in the middle of the conductor section 61 plus one.

Impedance adjuster 20 shown in FIG.
Is a bonding pad 7 connected to the piezoelectric vibrator 10.
1 and a bonding pad 72 connected to the terminal 3,
It has four bonding wires 73 to 76 connecting between the bonding pads 71 and 72. In this impedance adjusting unit 20, each of the bonding wires 73 to
76 is the planned cutting section.

Impedance adjusting section 20 shown in FIG.
In, it is possible to select one of four states having different inductances. The first state is a state in which all the bonding wires 73 to 76 are not cut. The second state is the bonding wires 73-76.
One of the bonding wires is cut. The third state is the bonding wires 73-7.
In this state, two of the bonding wires 6 are cut. In the fourth state, the bonding wires 73 to
In this state, three bonding wires out of 76 are cut. In the above-mentioned first to fourth states, since the number of bonding wires connecting between the bonding pads 71 and 72 is different, the impedance of the impedance adjusting unit 20 is also different.

The bonding wires 73 to 76 are cut by
It can be easily performed using a jig 77 such as scissors or tweezers. Instead of cutting the bonding wires 73 to 76, for example, a hook jig is used to pull the bonding wires 73 to 76 so that at least one end of the bonding wires 73 to 76 has the bonding pads 71, 72.
You may move away from.

As described above, the piezoelectric resonator 1 according to this embodiment includes the piezoelectric vibrator 10 and the impedance adjusting section 20. The piezoelectric vibrator 10 includes a piezoelectric thin film 15 having piezoelectricity, and two electrodes 14A and 16 arranged on both surfaces of the piezoelectric thin film 15 for applying an excitation voltage to the piezoelectric thin film 15. There is. The impedance adjusting unit 20 is connected to at least one of the two electrodes 14A and 16 and includes one or more planned cutting parts which are parts that can be cut, and impedance (especially inductance) changes according to the state of the planned cutting parts. To do.

In the piezoelectric resonator 1 according to the present embodiment, the planned cutting portion of the impedance adjusting section 20 is predetermined, so the relationship between the state of the planned cutting section and the impedance (inductance) of the impedance adjusting section 20 is: , You can know in advance. Therefore, in the piezoelectric resonator 1, the impedance (inductance) of the impedance adjusting unit 20 can be changed by a known amount by selecting the state of the planned cutting portion of the impedance adjusting unit 20. As a result, according to the present embodiment,
It is possible to easily adjust the resonance frequency of the piezoelectric resonator 1 including the piezoelectric vibrator 10 and the impedance adjusting unit 20.

In the piezoelectric resonator 1 according to the present embodiment, the inductance of the impedance adjusting section 20 is 0 from the viewpoint of ease of manufacturing the impedance adjusting section 20.
It is preferable to change in the range of 10 to 10 nH, and 0 to 3 nH
It is more preferable to change within the range.

Further, the piezoelectric resonator 1 according to the present embodiment
Is preferably used in the frequency band of 0.5 to 10 GHz, and more preferably used in the frequency band of 0.8 to 6 GHz.

As can be seen from the equation (1), in the piezoelectric resonator 1 according to the present embodiment, the higher the resonance frequency ωr is set, the smaller (Lm + Lv) Cm may be. Therefore,
When the piezoelectric resonator 1 is used in the above preferable frequency band, the inductance L of the impedance adjusting unit 20
v can be small. Further, the smaller (Lm + Lv) Cm, the smaller the amount of change in Lv required to change the resonance frequency ωr by the same amount. Therefore, the piezoelectric resonator 1
Is used in the above-mentioned preferable frequency band, the amount of change in the inductance Lv of the impedance adjusting unit 20 can be small. From these facts, when the piezoelectric resonator 1 is used in the above-mentioned preferable frequency band, it becomes easy to manufacture the impedance adjusting section 20 and adjust the impedance (inductance).

Further, in the piezoelectric resonator 1 according to the present embodiment, the impedance adjusting section 20 has two electrodes 14A,
The electrode 16 is connected to the electrode 16 that is farther from the base 11. This makes it possible to easily perform the work of cutting the planned cutting portion of the impedance adjusting unit 20.

Next, the filter according to this embodiment will be described. FIG. 19 is a circuit diagram of the filter according to the present embodiment. The filter 80 according to the present embodiment is a ladder type filter. The filter 80 has two input terminals 81 and 82 and two output terminals 83 and 84. The input terminal 82 and the output terminal 84 are connected to each other.

The filter 80 further includes a piezoelectric resonator 1A as a series resonator provided between the input terminal 81 and the output terminal 83. The piezoelectric resonator 1A has a piezoelectric vibrator 10A and an impedance adjusting unit 20A which are connected in series. One end of the piezoelectric vibrator 10A is connected to the input terminal 81, and the other end is connected to one end of the impedance adjusting unit 20A. The other end of the impedance adjusting unit 20A is connected to the output terminal 83.

The filter 80 further includes a piezoelectric resonator 1B as a parallel resonator whose one end is connected to the connection point between the piezoelectric resonator 1A and the output terminal 83. Piezoelectric resonator 1B
Has a piezoelectric vibrator 10B and an impedance adjusting unit 20B which are connected in series. One end of the piezoelectric vibrator 10B is connected to a connection point between the piezoelectric resonator 1A and the output terminal 83, and the other end is connected to the impedance adjusting unit 20B.
Is connected to one end. The other end of the impedance adjusting unit 20B has an input terminal 82 and an output terminal 84.
It is connected to the.

The piezoelectric resonators 1A and 1B have the same structure as the piezoelectric resonator 1, and the piezoelectric vibrators 10A and 10B have the same structure as the piezoelectric vibrator 10.
The configurations of A and 20B are similar to those of the impedance adjusting unit 20.

FIG. 19 shows the basic configuration (minimum unit) of the filter 80 according to this embodiment. The filter 80 according to the present embodiment may have a configuration in which a plurality of circuits shown in FIG. 19 are connected in cascade.

In the filter 80 according to the present embodiment, the resonance frequency of at least one of the piezoelectric resonators 1A and 1B can be easily adjusted by changing the impedance (inductance) of at least one of the impedance adjusting units 20A and 20B. Is possible. Therefore, according to the present embodiment, the frequency characteristic of the filter 80 can be easily adjusted.

In the filter 80 according to this embodiment, one of the impedance adjusting units 20A and 20B may be omitted.

Next, the duplexer according to this embodiment will be described. FIG. 20 is a circuit diagram of the duplexer according to this embodiment. The duplexer 90 according to the present embodiment has antenna terminals 91 and 92 connected to an antenna (not shown) and transmission signal terminals 93 and 94 connected to a transmission circuit (not shown) that outputs a transmission signal to the antenna.
And reception signal terminals 95 and 96 connected to a reception circuit (not shown) for inputting a reception signal from the antenna.

The duplexer 90 further includes a first filter 97 that passes the transmission signal and blocks the reception signal, and a second filter 98 that passes the reception signal and blocks the transmission signal. The filters 97 and 98 each have two input terminals and two output terminals.

Two input terminals of the filter 97 are connected to the transmission signal terminals 93 and 94, respectively. Filter 9
The two output terminals of 7 are antenna terminals 91 and 92, respectively.
It is connected to the. Two input terminals of the filter 98 are connected to antenna terminals 91 and 92, respectively. The two output terminals of the filter 98 are the reception signal terminals 9 respectively.
5, 96 are connected.

In the duplexer 90 according to this embodiment, at least one of the filters 97 and 98 is configured to include at least one piezoelectric resonator 1 according to this embodiment. In the filter including the piezoelectric resonator 1, the frequency characteristic of the filter can be adjusted by changing the impedance of the impedance adjusting unit 20 to adjust the resonance frequency of the piezoelectric resonator 1. Therefore, according to the present embodiment, the frequency characteristic of the duplexer 90 can be easily adjusted.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, the piezo-resonator of the present invention may include two impedance adjusters connected to the two electrodes of the piezo-electric vibrator.

Although the ladder type filter is shown in FIG. 19, the filter of the present invention may have another structure as long as it includes at least one piezoelectric resonator of the present invention.

Further, in the present invention, the impedance adjusting section may be one whose impedance changes in accordance with the state of the planned cutting portion, and for example, may have capacitance changing in accordance with the state of the planned cutting portion. Good.

[0101]

As described above, the first to seventh aspects are as follows.
In the piezoelectric resonator according to any one of items 1 to 5, it is possible to change the impedance of the impedance adjustment unit by a known amount by selecting the state of the portion to be cut of the impedance adjustment unit. Therefore, according to the present invention, it is possible to easily adjust the resonance frequency of the piezoelectric resonator.

Further, in the piezoelectric resonator according to the seventh aspect, the impedance adjusting section is connected to one of the two electrodes that is farther from the base body. Therefore, according to the present invention, it is possible to easily perform the work of cutting the planned cutting portion of the impedance adjusting unit.

In the filter according to the eighth aspect, the resonance frequency of the piezoelectric resonator can be easily adjusted by changing the impedance of the impedance adjusting section. Therefore, according to the present invention, it is possible to easily adjust the frequency characteristic of the filter.

Further, in the duplexer according to claim 9,
At least one of the first filter and the second filter is
It is configured to include at least one piezoelectric resonator having an impedance adjusting unit. In the filter including this piezoelectric resonator, by changing the impedance of the impedance adjustment unit to adjust the resonance frequency of the piezoelectric resonator,
It is possible to adjust the frequency characteristic of the filter. Therefore, according to the present invention, it is possible to easily adjust the frequency characteristic of the duplexer.

Further, according to the method of adjusting the resonance frequency of the piezoelectric resonator of the tenth aspect, the impedance of the impedance adjusting unit is changed by a known amount by selecting the state of the planned cutting portion of the impedance adjusting unit. be able to. Therefore, according to the present invention, it is possible to easily adjust the resonance frequency of the piezoelectric resonator.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a piezoelectric resonator according to an embodiment of the present invention.

FIG. 2 is a plan view showing electrodes of a piezoelectric resonator according to an embodiment of the present invention.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 5 is a circuit diagram showing a circuit configuration of a piezoelectric resonator according to an embodiment of the present invention.

FIG. 6 is a circuit diagram showing an equivalent circuit of a piezoelectric resonator according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a first state of the impedance adjusting unit in the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a second state of the impedance adjusting unit in the embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a third state of the impedance adjusting unit in the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a fourth state of the impedance adjusting unit in the embodiment of the present invention.

FIG. 11 is a plan view showing a probe used for measuring the characteristics of the piezoelectric resonator according to the embodiment of the present invention.

FIG. 12 is a circuit diagram showing a circuit including a piezoelectric resonator according to an embodiment of the present invention.

FIG. 13 is a characteristic diagram showing a result of experimentally obtaining frequency characteristics of the circuit shown in FIG. 12 for the first state of the portion to be cut.

FIG. 14 is a characteristic diagram showing a result of experimentally obtaining the frequency characteristic of the circuit shown in FIG. 12 for the second state of the portion to be cut.

FIG. 15 is a characteristic diagram showing a result of experimentally obtaining frequency characteristics of the circuit shown in FIG. 12 for a third state of the portion to be cut.

16 is a characteristic diagram showing a result of experimentally obtaining frequency characteristics of the circuit shown in FIG. 12 with respect to a fourth state of a portion to be cut.

FIG. 17 is an explanatory diagram showing another configuration example of the impedance adjusting unit in the embodiment of the present invention.

FIG. 18 is an explanatory diagram showing still another configuration example of the impedance adjustment unit in the embodiment of the present invention.

FIG. 19 is a circuit diagram of a filter according to an embodiment of the present invention.

FIG. 20 is a circuit diagram of a duplexer according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric resonator, 10 ... Piezoelectric vibrator, 11 ... Substrate, 12
... lower barrier layer, 13 ... upper barrier layer, 14 ... lower electrode, 15 ... piezoelectric thin film, 16 ... upper electrode, 17 ... ground electrode, 20 ... impedance adjusting section, 21a-21k.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5J108 AA02 AA07 BB07 CC04 EE03                       FF07 FF10 FF11 JJ01 JJ04                       KK05 NB06                 5K011 DA27 EA01 JA01 KA05

Claims (10)

[Claims] 1. A piezoelectric vibrator having a piezoelectric thin film having piezoelectricity, and two electrodes arranged on both surfaces of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film; A piezoelectric resonator, which is connected to at least one of electrodes and includes one or more parts to be cut, which are parts that can be cut, and an impedance adjusting part whose impedance changes according to the state of the part to be cut. . 2. The piezoelectric resonator according to claim 1, wherein the impedance adjusting unit has an inductance that changes according to a state of the planned cutting portion. 3. The piezoelectric resonator according to claim 2, wherein the inductance of the impedance adjusting unit changes in the range of 0 to 10 nH. 4. The piezoelectric resonator according to claim 2, wherein the inductance of the impedance adjusting unit changes in the range of 0 to 3 nH. 5. The piezoelectric resonator according to claim 1, which is used in a frequency band of 0.5 to 10 GHz. 6. The piezoelectric resonator according to claim 1, wherein the piezoelectric resonator is used in a frequency band of 0.8 to 6 GHz. 7. The piezoelectric vibrator further has a base body that supports the piezoelectric thin film and electrodes, and the impedance adjusting unit is connected to one of two electrodes that is farther from the base body. 7. The method according to claim 1, wherein
2. The piezoelectric resonator according to any one of 1. 8. A filter comprising at least one piezoelectric resonator according to any one of claims 1 to 7. 9. A duplexer connected to an antenna, comprising: a first filter that passes a transmission signal and blocks a reception signal; and a second filter that passes a reception signal and blocks a transmission signal. At least one of the first filter and the second filter is configured to include at least one piezoelectric resonator according to any one of claims 1 to 7. 10. A piezoelectric resonance device comprising a piezoelectric vibrator having a piezoelectric thin film having piezoelectricity and two electrodes arranged on both surfaces of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film. A method for adjusting a resonance frequency of a child, comprising at least one planned cutting part that is connected to at least one of the two electrodes and can be cut, and impedance changes according to a state of the planned cutting part. A method of adjusting a resonance frequency of a piezoelectric resonator, comprising: adjusting a resonance frequency of the piezoelectric resonator by providing an impedance adjusting unit for selecting a state of the cutting unit.