JP2003051732A - Piezoelectric resonator, filter and electronic communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric resonator that has a stable resonance response against a temperature change regardless of the change in film thickness ratio. SOLUTION: In the piezoelectric resonator 10 that has a resonance part 20 comprising a lower layer film 14 placed on a substrate 12 and a laminator placed on the lower layer film and in which the laminator is configured by layering at least a piezoelectric film 26, an intermediate film 28, and a piezoelectric film 30 between a couple of upper and lower electrodes, the film thickness ratio of each film being components of the resonance part is selected so that it is stimulated by an n multiple wave (n is an integer of 2 or over) of a fundamental wave, at least one of the films has a positive resonance frequency temperature coefficient and at least one of the films has a negative resonance frequency temperature coefficient, the film thickness of the intermediate film is selected such that the entire resonance frequency temperature coefficient of the piezoelectric resonator can be adjusted or adjustable to nearly zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator in which a piezoelectric material or a dielectric material is formed into a thin film to form a resonance part as a multilayer structure, and more specifically, it is used in a filter, an oscillator or the like and has a VHF band. , UHF band, and further relates to a piezoelectric resonator that vibrates in the thickness longitudinal direction in a super high frequency band higher than that.
The present invention also relates to a filter and electronic communication equipment using this piezoelectric resonator.

[0002]

2. Description of the Related Art In the case of a piezoelectric resonator utilizing longitudinal vibration of thickness, an extremely thin piezoelectric film is interposed between electrodes by utilizing the fact that its resonance frequency is inversely proportional to the thickness of the piezoelectric film. Some of them are mounted to obtain a resonance response in an ultrahigh frequency band.

In the case of such a piezoelectric resonator, it is desired that the resonance frequency temperature coefficient (TCF) be small, preferably zero, in order to stabilize the resonance response.

Since a piezoelectric film generally has a negative resonance frequency temperature coefficient, and the thin film alone does not necessarily have a good resonance response to a temperature change, for example, a ZnO thin film as a piezoelectric film having a negative resonance frequency temperature coefficient. Against
The temperature coefficient of the resonance frequency of the piezoelectric resonator as a whole is brought close to zero by stacking another SiO2 thin film having a positive temperature coefficient of the resonance frequency for adjusting the temperature coefficient and setting the film thickness of both thin films appropriately. There is a device that stabilizes the resonance response to temperature changes.

However, such ZnO thin film and S
In the case of a piezoelectric resonator in which the film thickness ratio of each iO2 thin film is adjusted, the proportion of the ZnO thin film in the resonance region is smaller than that of the SiO2 thin film, the vibration of the ZnO thin film is blocked by the SiO2 thin film, and a good resonance response is obtained. It has the drawback of being difficult.

As a solution to this, Japanese Patent Laid-Open No. 58-58
As disclosed in Japanese Patent No. 137317, a SiO2 thin film is provided in the middle of a ZnO thin film, and the thickness of the SiO2 thin film is set to Z.
A piezo-resonator has been proposed which attempts to achieve a good resonance response by making the size smaller than that of the nO thin film.

[0007]

By the way, in the piezoelectric resonator described in the above publication, since the ZnO thin film is vertically symmetrical with the SiO2 thin film in between, the vibration node is located in the SiO2 thin film, and Even if it suppresses even harmonics, it is for the fundamental wave.

However, in the case of the fundamental wave, the horizontal axis is Zn.
As shown in FIG. 8 in which the film thickness ratio between the O thin film and the SiO 2 thin film and the resonance frequency temperature coefficient on the vertical axis are shown in FIG. 8, the resonance frequency temperature coefficient deviates from the vicinity of zero due to a slight change in the film thickness ratio. The allowable range of the film thickness ratio that can control the frequency temperature coefficient near zero is extremely narrow. In FIG. 8, the fundamental wave and the second harmonic wave are shown.

Therefore, when the fundamental wave is used as in the conventional piezoelectric resonator, the temperature coefficient of the resonance frequency easily deviates from around zero due to the variation of the film thickness ratio between the ZnO thin film and the SiO2 thin film, and the resonance response deteriorates. There is room for improvement in reliability, and since it is necessary to control the film thickness ratio with high precision in the production thereof, it is a factor that significantly reduces the productivity of the piezoelectric resonator.

Therefore, the present invention provides a piezoelectric resonator having at least a piezoelectric thin film and capable of setting the resonance frequency temperature coefficient to near zero by adjusting the film thickness ratio of a plurality of thin films having different resonance frequency temperature coefficients. By widening the allowable range of the film thickness ratio where the resonance frequency temperature coefficient can be set to near zero, it is possible to stabilize the resonance response with high accuracy, and greatly reduce the burden on high-precision management of the film thickness ratio. , Making it possible to improve its productivity is an issue to be solved.

[0011]

The piezoelectric resonator of the present invention comprises:
An inner thin film of at least one layer including at least a piezoelectric film is interposed between a pair of upper and lower opposing electrodes, and at least one of an upper surface of the upper electrode and a lower surface of the lower electrode has one or more outer thin films. , Each thin film constitutes a resonance part, and each thin film has at least one positive resonance frequency temperature coefficient, at least one negative resonance frequency temperature coefficient, and n-th harmonic wave (where n is The integer of 2 or more) is set to such a film thickness ratio that at least the outer thin film exists.

According to the present invention, since the film thickness ratio excited by the nth harmonic is set, it is possible to use a region in which the resonance frequency changes little with temperature even if the film thickness ratio of each film changes. As a result, the resonance response to the temperature change becomes stable. Further, since the intermediate film is provided between the two piezoelectric films, the resonance frequency temperature coefficient can be set to substantially zero by setting the film thickness of the intermediate film in the region.

As described above, according to the present invention, the variation of the temperature coefficient of the resonance frequency with respect to the variation of the film thickness, that is, the variation of the resonance frequency with respect to the temperature change can be suppressed to a small level, and the resonance response is extremely stable against the temperature change. A piezoelectric resonator can be provided.

In the present invention, preferably, the outer thin film is
A lower layer film formed of at least one layer provided on a substrate, wherein the inner thin film is at least a lower piezoelectric film, an intermediate film,
Each of the films, which is formed of a laminated body including an upper piezoelectric film and constitutes the resonance portion, is set to have a film thickness ratio at which it is excited by a double wave.

According to the present invention, even if the film thickness ratio of each film changes, the region in which the resonance frequency changes little with temperature can be used in the same manner as described above, so that the resonance response to the temperature change is stable. Will be things. Further, since the intermediate film is provided between the two piezoelectric films, the resonance frequency temperature coefficient can be set to substantially zero by setting the film thickness of the intermediate film in the region.

In the present invention, preferably, the inner thin film is
It is composed of a plurality of thin films having different resonance frequency temperature coefficients.

In the present invention, preferably, the outer thin film is
It is composed of a plurality of thin films having different resonance frequency temperature coefficients.

In the present invention, preferably, when the film thickness of the laminate is constant A, the film thickness of the lower layer film is B, and the film thickness ratio is expressed by A / (A + B), the n times The thickness ratio is set so that the wave is a double wave and the node of the double wave exists in the lower layer film.

In this case, with respect to the second harmonic wave, the thickness range of the lower layer film is changed to widen the allowable range of the film thickness ratio in which the temperature coefficient of the resonance frequency can be set to near zero, and the wide range is controlled by controlling the film thickness of the intermediate film. The temperature coefficient of the resonance frequency can be set to be close to zero within an allowable range, and the burden on highly accurate management of the film thickness ratio can be significantly reduced, so that the productivity can be significantly improved.

In the present invention, preferably, the resonance frequency temperature coefficient of the lower piezoelectric film and the upper piezoelectric film and the resonance frequency temperature coefficient of the intermediate film have opposite signs.

In the present invention, preferably, one of the lower piezoelectric film, the upper piezoelectric film and the intermediate film have the same resonance frequency temperature coefficient, and the lower piezoelectric film and the upper piezoelectric film have resonance frequency temperature coefficients. The coefficients are of opposite sign.

In the present invention, preferably, in the inner thin film, the intermediate layer is a piezoelectric film or a dielectric film.

In the present invention, preferably, the piezoelectric film having a positive resonance frequency temperature coefficient used for the inner thin film is an AIN film,
PbZr _x Ti _(1-x) O ₃ (where 0.54 ≦ X ≦ 1)
The negative piezoelectric film is a ZnO film.

In the present invention, preferably, the dielectric film having a positive temperature coefficient of resonance frequency used for the inner film is a film containing SiO ₂ as a main component, and the negative dielectric film is a film containing SiN as a main component. , Al ₂ O ₃ as a main component.

In the present invention, preferably, the lower layer film is Si.
It is either an O ₂ film, a SiN film, or a film containing Al ₂ O ₃ as a main component.

In the present invention, preferably, the lower layer film is a thermal oxide film and a laminated film of SiO ₂ film formed by a method other than thermal oxidation, a laminated film of SiN film and Al ₂ O ₃ film, and thermal oxidation. SiO ₂ film and Al ₂ O ₃ film formed by a method other than thermal oxidation or S
It is either a laminated film with a thin film selected from an iN film or a ZnO film, or one of these.

[0027]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below based on the embodiments shown in the drawings.

Referring to FIG. 1, in a piezoelectric resonator 10 of the present embodiment, a substrate 1 such as a (100) plane Si substrate is used.
A lower layer film 14 composed of at least one layer is formed as an outer thin film on the upper surface of 2, and a cavity 16 is provided by opening the central portion thereof.

A laminated body 18 is formed on the upper surface of the lower layer film 14.

The laminated body 18 constitutes a resonance part 20 together with the lower layer film 14, and is composed of a pair of upper and lower electrodes 22, 24.
At least a lower piezoelectric film 26, an intermediate film 28, and an upper piezoelectric film 30 are laminated in this order as an inner thin film in this order.

Each of the films 14 and 26 constituting the resonance part 20.
30 is set to a film thickness ratio that is excited in an n-times mode, that is, an n-times wave (where n is an integer of 2 or more) with respect to the fundamental wave, and in this embodiment, a thickness longitudinal resonance mode by the second wave. .

By setting the film thickness ratio, the double wave node is positioned not only in the intermediate film 28 but also in the lower film 14.

In the resonance part 20, the signs of the resonance frequency temperature coefficients of the lower layer film 14, the lower and upper piezoelectric films 26, 30 and the intermediate film 28 are combined in positive and negative, and the film of the intermediate film 28 is combined. The temperature coefficient of the resonance frequency of the entire piezoelectric resonator 10 can be adjusted or adjusted to near zero by setting the thickness.

The piezoelectric resonator 10 is characterized in that the lower layer film 14, the lower piezoelectric film 26, the intermediate film 28 and the upper piezoelectric film 30 are made of the following materials.

Lower layer film 14: SiO ₂ thin film (positive temperature coefficient TCF) Lower piezoelectric film 26: ZnO thin film (negative temperature coefficient TCF) Intermediate film 28: SiO 2 thin film (positive temperature coefficient TCF) Upper piezoelectric film 30: ZnO Thin Film (Negative Temperature Coefficient TCF) With respect to the piezoelectric resonator 10 having the above-described structure, the cross section of each film is schematically shown in FIG. 2 and the film thickness thereof will be described.

In FIG. 2, the film thickness of the laminated body 18 is represented by a constant A, and the film thickness of the lower layer film 14 is represented by B. Electrode 2
2 has a thickness of 0.15 μm, and the electrode 24 has a thickness of 0.1 μm.
Is.

When the film thickness ratio R is defined as A / (A + B), the film thickness ratio R changes with the film thickness B of the lower layer film 14.

In FIG. 2, the piezoelectric films 26 and 30 have the same film thickness, and the intermediate film 28 is located between the electrodes 22 and 24. In the film thickness ratio R of these films, the antinode of the second wave is located on the electrodes 22 and 24, and the node is the intermediate film 28.
And the lower layer film 14 are located.

Although not shown in the drawings in this embodiment, in the case of a resonance wave of a second harmonic wave or more, at least one thin film of piezoelectric film is interposed between a pair of upper and lower opposing electrodes. A piezoelectric resonator in which an outer thin film exists on at least one of the upper surface of the upper electrode and the lower surface of the lower electrode, and the node of the resonance wave exists in the outer thin film.

Next, referring to FIG. 3 in which the horizontal axis represents the film thickness ratio R and the vertical axis represents the resonance frequency temperature coefficient TCF, the resonance frequency temperature coefficient TC of the piezoelectric resonator 10 due to the change in the film thickness of the intermediate film 28.
F will be described.

In FIG. The characteristic line is that the thickness of the intermediate film 28 is 0.0 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.1 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.2 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.3 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.4 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.5 μm. The characteristic line is that the thickness of the intermediate film 28 is 0.6 μm. It is time for

From FIG. 3, as the film thickness of the intermediate film 284 increases, the resonance frequency temperature coefficient TCF approaches zero, and in particular, the film thickness of the intermediate film 28 becomes 0.
It can be seen that when the thickness is 5 to 0.6 μm, the resonance frequency temperature coefficient TCF converges to near zero over a wide range of the film thickness ratio R of 0.3 to 0.5.

Therefore, in the case of the second harmonic, the nodes are located inside the lower film 14 and the intermediate film 28, and the resonance frequency temperature coefficient TCF is set to almost zero by controlling the film thickness of the intermediate film 28. be able to.

Therefore, by appropriately selecting the film thickness of the intermediate film 28, the resonance frequency temperature coefficient TCF of the piezoelectric resonance portion 20 can be set to substantially zero.

In this embodiment, the film thickness ratio R and the intermediate film 2 are used.
By appropriately setting the film thickness of 8
The resonance frequency temperature coefficient TCF of 0 can be set to almost zero, and the resonance frequency temperature coefficient TCF can be maintained at almost zero even if the film thickness ratio R is slightly changed, and thus the temperature coefficient TCF can be maintained at zero. The resonance response of the piezoelectric resonance portion 20 becomes stable.

In the case of this embodiment, the lower layer film 14
The SiO ₂ thin film piezoelectric film 26 is made of ZnO thin film, the intermediate film 28 is made of SiO ₂ thin film piezoelectric film 30, and the ZnO thin film is made of constituent material. If this combination is the first combination, the same applies to the second to tenth combinations described below. The effect of can be obtained.

The combination will be exemplified below. In addition,
The structure of the piezoelectric resonator according to each of the second to seventh combinations is similar to that of FIG. 1, and therefore its drawing is omitted.

(Second combination) The lower layer film 14 is made of SiO ₂ ,
A thin film mainly containing one kind selected from SiN and Al ₂ O ₃ , one of the piezoelectric films 26 and 30 is a ZnO thin film, and an intermediate film 28.
Is a SiO ₂ thin film, and the other of the piezoelectric films 26 and 30 is AlN or P
_{bZrxTi (1-x) O 3} , ( It was I, 0.54 ≦ x ≦ 1) thin film composed mainly of one selected from.

In this case, since the piezoelectric film is a combination of the ZnO thin film and the AlN thin film, the ratio of the SiO ₂ thin film can be reduced and the resonance response can be further improved.

Further, in this case, when the n-th harmonic is the second harmonic, the SiO ₂ thin film between both piezoelectric films includes a node of the second harmonic, so that the region where the temperature change of the resonance frequency is small changes to the resonance frequency temperature. The coefficient can be set near zero.

The AlN thin film is used as a tensile stress for ZnO.
It is possible to balance the compressive stress and the stress of the thin film or the SiO ₂ thin film, and prevent destruction and characteristic deterioration due to deformation of the element.

(Third combination) One of the lower layer film 14 and the intermediate film 28 is a thin film containing one kind selected from SiO ₂ , SiN and Al ₂ O ₃ as a main component, the lower piezoelectric film 26 and the upper piezoelectric film 30. but, ZnO thin film, the other of the lower film 14 or the intermediate layer _{28, AlN, PbZrxTi (1-x} ) O 3, to the I (,
0.54 ≦ x ≦ 1) A thin film containing one kind selected from the main components.

In this case, since the piezoelectric film is a combination of the ZnO thin film and the AlN thin film, the ratio of the SiO ₂ thin film can be reduced and the resonance response can be further improved. In particular, since there is no SiO ₂ thin film between the electrodes, the resonance response is further improved.

Further, in this case, when the n-th harmonic is the second harmonic, the AlN thin film between the piezoelectric films includes the second-harmonic node, so that the region where the temperature change of the resonance frequency is small changes the resonance frequency temperature coefficient. Can be set near zero.

The AlN thin film was used as a tensile stress for ZnO.
It is possible to balance the compressive stress and the stress of the thin film or the SiO ₂ thin film, and prevent destruction and characteristic deterioration due to deformation of the element.

(Fourth Combination) One of the lower layer film 14 and the intermediate film 28 is a SiO ₂ thin film, and the lower piezoelectric film 26 and the upper piezoelectric film 30 are AlN, PbZrxTi _(1-x) O ₃ , and , 0.54 ≦ x ≦ 1), and the other of the lower layer film 14 and the intermediate film 28 is Si.
A thin film whose main component is one selected from N and Al ₂ O ₃ .

In this case, when the n-th harmonic is the second harmonic, the SiN thin film between the piezoelectric films includes the second-harmonic node, so that the region where the temperature change of the resonance frequency is small is zero. Can be set near.

It should be noted that the AlN thin film is used as a tensile stress for SiO
₂ It is possible to balance the compressive stress and the stress of the thin film, and prevent the destruction and characteristic deterioration due to the deformation of the element.

(Fifth Combination) One of the lower layer film 14 and the intermediate film 28 is a SiO ₂ thin film, and the lower piezoelectric film 26 and the upper piezoelectric film 30 are AlN, PbZrxTi _(1-x) O ₃ , (added. , 0.54 ≦ x ≦ 1), a thin film mainly composed of one kind selected from
O thin film.

In this case, when the n-th harmonic is the second harmonic, the ZnO thin film between the piezoelectric films includes a second-harmonic node, so that the region where the temperature change of the resonance frequency is small changes the resonance frequency temperature coefficient. Can be set near zero.

It should be noted that the AlN thin film is used as a tensile stress for ZnO.
It is possible to balance the compressive stress and the stress of the thin film or the SiO ₂ thin film, and prevent destruction and characteristic deterioration due to deformation of the element.

(Sixth Combination) The lower layer film 14 is made of SiN,
A thin film mainly composed of one selected from Al ₂ O ₃ , the lower piezoelectric film 26 and the upper piezoelectric film 30 is made of AlN, PbZrxT.
i _(1-x) O ₃ , a thin film mainly containing one kind selected from (however, 0.54 ≦ x ≦ 1) and the intermediate film 28 are made of SiN, A
A thin film containing, as a main component, one selected from l ₂ O ₃ .

In this case, when the n-th harmonic is the second harmonic, the SiN thin film between the piezoelectric films includes the second-harmonic node, so that the region where the temperature change of the resonance frequency is small changes the resonance frequency temperature coefficient. Can be set near zero.

(Seventh combination) Lower layer film 14 or intermediate film
One side is SiN, Al₂O₃Mainly one selected from
The lower piezoelectric film 26 and the upper piezoelectric film 30 are
1N, PbZrxTi _(1-x)O₃, (Dashi, 0.54 ≦
x ≦ 1), a thin film mainly composed of one kind selected from x), a lower layer
The other of the film 14 and the intermediate film 28 is a ZnO thin film.

In this case, since the piezoelectric film is a combination of the ZnO thin film and the AlN thin film, the ratio of the SiN thin film can be reduced and the resonance response can be further improved. Especially, since there is no SiN thin film between the electrodes, the resonance response is further improved.

The AlN thin film was used as a tensile stress for ZnO.
It is possible to balance the compressive stress and the stress of the thin film, and prevent destruction and characteristic deterioration due to deformation of the element.

(Eighth combination) The first, second, third,
In the fourth and fifth combinations, the lower layer film 14 is composed of two layers, as shown in FIG. 4, the lower side 14a being a thermal oxide film and the upper side 14b being a SiO ₂ thin film.

In this case, since the resonance frequency temperature coefficient of the lower layer film 14 is different between the lower side 14a and the upper side 14b, the resonance frequency temperature coefficient is made zero by finely adjusting the film thickness on each side 14a, 14b. It can be finely adjusted to the vicinity.

(Ninth Combination) In the sixth and seventh combinations, the lower layer film 14 has A on one side as shown in FIG.
The l ₂ O ₃ thin film, on the other hand, 14b is composed of at least two layers of SiN thin films.

In this case, further, since the lower layer film 14 is a combination of SiO ₂ thin films having different resonance frequency temperature coefficients, the resonance frequency temperature coefficient can be freely set. (Tenth Combination) In the first or eighth combination, as shown in FIG. 6, the lower layer film 14 has one 14a, which is a kind of thin film selected from a thermal oxide film and a SiO ₂ thin film, and the other one.
4b is composed of at least two layers of a kind of thin film selected from Al ₂ O ₃ , SiN and ZnO.

In this case, since the resonance frequency temperature coefficient of the lower layer film 14 is different between the lower side 14a and the upper side 14b, the resonance frequency temperature coefficient is made zero by finely adjusting the film thickness on each side 14a, 14b. It can be adjusted subtly and freely in the vicinity.

The piezoelectric resonator 10 of this embodiment according to any one of the first to tenth combinations described above is a π-type ladder filter as shown in FIG. 7A, and a T-type ladder filter as shown in FIG. 7B. The filter can be used by incorporating it into an L-shaped filter as shown in FIG. 7 (c). In the case of such a filter, the filter characteristic is stable with respect to the temperature change. In such a filter, a plurality of the piezoelectric resonators 10 described above are provided on the substrate 12, and the piezoelectric resonators 10 on the substrate 12 are connected to the electrodes 22 and 24 in the wiring configuration of FIG. As a result, it is possible to complete a filter having stable operation characteristics with respect to ambient temperature changes.

By mounting the piezoelectric resonator 10 of the present embodiment according to any one of the above-mentioned first to tenth combinations or the filter shown in FIG. 7 on a mobile phone, a wireless LAN, and various other electronic communication devices. When used for electronic communication operation of the electronic communication device, it is possible to stabilize operation characteristics with respect to changes in ambient temperature.

[0074]

As described above, according to the present invention,
An inner thin film of at least one layer including at least a piezoelectric film is interposed between a pair of upper and lower opposing electrodes, and at least one of an upper surface of the upper electrode and a lower surface of the lower electrode has one or more outer thin films. , Each thin film constitutes a resonance part, and each thin film has at least one positive resonance frequency temperature coefficient, at least one negative resonance frequency temperature coefficient, and n-th harmonic wave (where n is Since the (number of 2 or more) node is set to a film thickness ratio that exists in at least the outer thin film, a region in which the resonance frequency changes little with temperature even if the film thickness ratio in each film changes By being able to do so, the resonance response to the temperature change becomes stable. Further, since the intermediate film is provided between the two piezoelectric films, the resonance frequency temperature coefficient can be set to substantially zero by setting the film thickness of the intermediate film in the region. Therefore, it is possible to provide a piezoelectric resonator having a small resonance frequency temperature coefficient with respect to a change in film thickness, that is, a change in resonance frequency with respect to a temperature change can be suppressed to a small extent, and a resonance response extremely stable with respect to a temperature change. Become.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a main part of FIG.

3 is a characteristic diagram of the film thickness ratio and the resonance frequency temperature coefficient in the main part of FIG.

FIG. 4 is a sectional view of a piezoelectric resonator according to another embodiment of the present invention.

FIG. 5 is a sectional view of a piezoelectric resonator according to still another embodiment of the present invention.

FIG. 6 is a sectional view of a piezoelectric resonator according to still another embodiment of the present invention.

FIG. 7 is a circuit diagram of a filter using the piezoelectric resonator of the present invention.

FIG. 8 is a waveform diagram of a fundamental wave and a second harmonic wave in the piezoelectric resonator.

[Explanation of symbols]

10 Piezoelectric resonator 14 Underlayer film 20 Resonance part 22, 24 electrodes 26,30 Piezoelectric film 28 Intermediate film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H03H 9/58 H01L 41/18 101D 41/08 U (72) Inventor Yoshihiko Goto 2nd Tenjin, Nagaokakyo, Kyoto Prefecture No. 26-10 Murata Manufacturing Co., Ltd. (72) Inventor Tadashi Nomura 2-10-10 Tenjin, Nagaokakyo City, Kyoto Prefecture No. 26-10 Murata Manufacturing Co., Ltd. (72) Inventor Yukio Yoshino 2 26-10 Tenjin, Nagaokakyo City, Kyoto Prefecture Murata Manufacturing Co., Ltd.

Claims (14)

[Claims] 1. An inner thin film of at least one layer including at least a piezoelectric film is interposed between a pair of upper and lower opposing electrodes, and at least one of an upper surface of an upper electrode and a lower surface of a lower electrode has one or more layers. An outer thin film is present, and each thin film constitutes a resonance part, and each thin film has at least one positive resonance frequency temperature coefficient, at least one negative resonance frequency temperature coefficient, and an n-fold factor ( However, n
Is an integer of 2 or more) is set to a film thickness ratio such that at least the outer thin film is present in the piezoelectric resonator. 2. The outer thin film is at least one lower layer film provided on a substrate, and the inner thin film is formed of a laminated body including at least a lower piezoelectric film, an intermediate film, and an upper piezoelectric film, 2. The film thickness ratios of the respective films forming the constituent parts are set so that they are excited by a double wave or more.
2. The piezoelectric resonator according to. 3. The piezoelectric resonator according to claim 1, wherein the inner thin film is composed of a plurality of thin films having different resonance frequency temperature coefficients. 4. The piezoelectric resonator according to claim 1, wherein the outer thin film is composed of a plurality of thin films having different resonance frequency temperature coefficients. 5. When the thickness of the laminated body is constant A, the thickness of the lower layer is B, and the thickness ratio is expressed by A / (A + B), the node of the second harmonic wave is the lower layer. The piezoelectric resonator according to any one of claims 2 to 4, wherein the film thickness ratio is set so as to exist in the film. 6. The resonance frequency temperature coefficient of the lower piezoelectric film and the upper piezoelectric film and the resonance frequency temperature coefficient of the intermediate film have opposite signs. Piezoelectric resonator. 7. The resonance frequency temperature coefficient of one of the lower piezoelectric film and the upper piezoelectric film has the same sign as the resonance frequency temperature coefficient of the intermediate film, and the resonance frequency of the lower piezoelectric film is the same. The sign of the temperature coefficient and the sign of the resonance frequency temperature coefficient of the upper piezoelectric film are opposite to each other.
5. The piezoelectric resonator according to any one of 5 to 5. 8. The piezoelectric resonator according to claim 2, wherein in the inner thin film, the intermediate film is a piezoelectric film or a dielectric film. 9. The piezoelectric film having a positive sign of the resonance frequency temperature coefficient used for the inner thin film is an AIN film or PbZr _{x.
Ti (1-x) O 3} ( however, 0.54 ≦ X ≦ 1) is a film composed mainly of, 8 or claims 1, wherein the piezoelectric film is a negative a ZnO film 2. The piezoelectric resonator according to. 10. The dielectric film having a positive resonance frequency temperature coefficient used for the inner thin film is a film containing SiO ₂ as a main component, and the negative dielectric film is a film containing SiN as a main component or A.
The piezoelectric resonator according to any one of claims 1 to 8, which is a film containing l ₂ O ₃ as a main component. 11. The lower layer film is a SiO ₂ film or Si.
11. The piezoelectric resonator according to claim 2, which is either an N film or a film containing Al ₂ O ₃ as a main component. 12. The lower layer film is a laminated film of a thermal oxide film and a SiO ₂ film formed by a method other than thermal oxidation, a SiN film and an A film.
a laminated film with an l ₂ O ₃ film, a laminated film of a thermal oxide film or a SiO ₂ film formed by a method other than thermal oxidation and a thin film selected from an Al ₂ O ₃ film, a SiN film or a ZnO film, or The piezoelectric resonator according to claim 2, wherein the piezoelectric resonator is any one of these. 13. A filter comprising a plurality of the piezoelectric resonators according to any one of claims 1 to 12, wherein electrodes of the piezoelectric resonators are connected to each other in a filter circuit configuration. 14. An electronic communication device comprising one or a plurality of the piezoelectric resonators according to claim 1 and using the piezoelectric resonators for electronic communication operation.