JP3514224B2 - Piezoelectric resonator, filter and electronic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric resonator, a filter, and an electronic device, and more particularly, to a piezoelectric resonator, a filter, and an electronic device using elastic vibration of a piezoelectric layer.

[0002]

2. Description of the Related Art The resonance frequency of a piezoelectric thin-film resonator utilizing the thickness vibration of a piezoelectric substrate is inversely proportional to the thickness of the piezoelectric substrate. However, the thickness of the piezoelectric substrate itself has been reduced to a practical high frequency limit of several hundred MHz in the fundamental mode due to its mechanical strength and restrictions on handling.

In order to solve such a problem, a piezoelectric thin film resonator has been conventionally proposed, and has been proposed as a filter or a resonator. As shown in FIG. 1, the piezoelectric thin-film resonator 1 is formed by partially etching the Si substrate 2 using a microfabrication method so that a part of the Si substrate 2 has a thickness of several μm.
A thin film support 3 having the following thickness is formed, and a ZnO piezoelectric thin film 4 having a pair of excitation electrodes 5a and 5b on both surfaces is provided thereon.

In such a piezoelectric thin-film resonator 1, the thin-film supporting portion 3 can be thinned by using a fine processing technique, and the piezoelectric thin-film 4 can be formed thin by sputtering or the like. There is a possibility that high-frequency characteristics can be extended up to this point.

However, the temperature coefficient of the elastic constant of ZnO is about -160 ppm / ° C., and the temperature coefficient of the elastic constant of Si is about −3 ppm.
Since the temperature coefficient of the resonance frequency of ZnO and Si has a negative value in both cases, the combination of the piezoelectric thin film 4 made of ZnO and the thin film support 3 made of Si has the resonance frequency in the fundamental mode. Has the disadvantage that the temperature characteristics of the sample are poor.

In the piezoelectric thin film resonator 6 shown in FIG.
The SiO ₂ thin film 7 is formed on the surface of the Si substrate 2 by thermal oxidation or the like, and the Si substrate 2 is partially etched to form the thin film support 3 with the SiO ₂ thin film 7, and the excitation electrodes 5 a, Piezoelectric thin film 4 having 5b on both sides
Is provided.

The temperature coefficient of the elastic constant of ZnO is about -160.
ppm / ° C, temperature coefficient of elastic constant of SiO ₂ is about + 200p
pm / ° C., and the sign of the temperature coefficient of the resonance frequency is different between ZnO and SiO _2.
By setting the ratio of the film thickness of the thin film support portion 3 made of SiO ₂ to a certain appropriate value (roughly 2: 1), the temperature coefficient of the resonance frequency in the fundamental mode can be reduced, The frequency temperature characteristics can be stabilized (Japanese Patent Application Laid-Open No. 58-121817).

FIG. 3 is a sectional view showing a piezoelectric thin film resonator 9 having another structure. This is a floating structure (air bridge structure)
A piezoelectric thin-film resonator 9 having a thin-film support portion 12 made of SiO ₂ formed on an Si substrate 10 via an air gap 11, and formed to float from the Si substrate 10. The excitation electrodes 14a, 1
A ZnO piezoelectric thin film 13 having 4b on both sides is provided.

In this piezoelectric thin-film resonator 9, as in the case of the piezoelectric thin-film resonator 6 shown in FIG. 2, the ratio between the thickness of the ZnO piezoelectric thin film 13 and the thickness of the SiO ₂ thin-film support portion 12 is set to an appropriate value. By setting, the temperature coefficient of the resonance frequency is reduced,
The temperature characteristics of the resonance frequency can be stabilized.

[0010]

In the second piezoelectric thin film resonator 6, the temperature coefficient of the resonance frequency can be offset by combining the ZnO piezoelectric thin film 4 and the SiO ₂ thin film support 3. Further, in the third piezoelectric thin film resonator 9, the temperature coefficient of the resonance frequency can be canceled by combining the ZnO piezoelectric thin film 13 and the SiO ₂ thin film support portion 12.

However, while ZnO is a piezoelectric material,
Since SiO ₂ is a non-piezoelectric material, these piezoelectric thin-film resonators have low resonance response and poor resonance characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and it is an object of the present invention to stabilize the temperature characteristics of the resonance frequency, and to provide a good resonance characteristic with a large resonance response. It is to provide a piezoelectric resonator. It is still another object of the present invention to provide a filter and an electronic device using the piezoelectric resonator.

[0013]

Means for Solving the Problems and Actions According to Claim 1
Mounted piezoelectric resonatorIs AlNOne or more layers consisting of
Piezoelectric layer and one or multiple layers of ZnO
Body layer, and at least a part of the laminate
So that it does not touch the board
A small number of piezoelectric layers constituting the laminate are arranged on the substrate.
At least one set of electrodes sandwiches at least one layer
It is characterized by having been provided.The piezoelectric capacitor according to claim 2.
The pendulum is a single layer with a positive temperature coefficient of resonance frequency or
A plurality of piezoelectric layers and one layer whose temperature coefficient is negative or
A plurality of piezoelectric layers are laminated, and the laminated body is at least
A part is placed on the substrate so as to float from the substrate,
Any of the piezoelectric layers constituting the laminate may be any of the electrodes.
Providing at least one set of electrodes to be sandwiched between the poles
It is characterized by having. The piezoelectric resonator according to claim 3.
Is one or more layers whose temperature coefficient of resonance frequency is positive
Piezoelectric layer and one or more layers whose temperature coefficient is negative
And a piezoelectric layer of at least one
Is placed on the substrate so as to float from the substrate,
Sandwich at least one of the piezoelectric layers constituting the laminate
And at least one set of electrodes at a temperature of the resonance frequency.
The piezoelectric layer having a negative coefficient is made of ZnO, LiNb
O _3. LiTaO ₃ , PbZr _X Ti _{( 1 -X)} O
₃ [0 ≦ x ≦ 0 . 52] as a main component.
It is characterized by having been constituted as. Claim 4
Has a positive temperature coefficient of the resonance frequency.
Alternatively, a plurality of piezoelectric layers and one layer having a negative temperature coefficient
Alternatively, a plurality of piezoelectric layers are laminated, and the laminate is
At least a part should be lifted off the substrate
At least one of the piezoelectric layers constituting the laminated body
At least one set of electrodes is provided so as to sandwich the layer,
The piezoelectric layer having a positive temperature coefficient of frequency is formed of AlN,
PbZr _X Ti _{( 1 -X)} O ₃ [0 . 54 ≦ x ≦ 1]
It is characterized by being constituted as a component. Claim 5
The described piezoelectric resonator has a positive temperature coefficient of resonance frequency
One or more piezoelectric layers and the temperature coefficient is negative
One or more piezoelectric layers are laminated on the substrate in three layers
Then, the laminate is floated at least partially from the substrate.
And placed on the substrate to form the piezoelectric body
At least one set sandwiching at least one body layer
Of the upper and lower piezoelectric layers sandwiching the central piezoelectric layer.
It is characterized in that the thickness is almost equal.

In the piezoelectric resonator according to any one of the first to fifth aspects , AlN or one or a plurality of piezoelectric layers having a positive temperature coefficient of the resonance frequency, and ZnO or a negative temperature coefficient thereof. Since one or a plurality of piezoelectric layers are laminated, by appropriately setting the thickness of each piezoelectric layer,
The temperature coefficient of the resonance frequency of the entire laminate can be made substantially zero. Moreover, since both the layer having a positive temperature coefficient and the layer having a negative temperature coefficient of the resonance frequency are constituted by the piezoelectric layer, the resonance response of the piezoelectric resonator is improved and its resonance characteristics are improved. it is cut with <br/> be improved.

[0015] Therefore, according to the piezoelectric resonator according to claim 1 to 5, the temperature characteristics of the resonance frequency is stable and can be resonant responses even greater resonance characteristics to produce a good piezoelectric resonator.

According to a sixth aspect of the present invention, there is provided a piezoelectric resonator according to the first aspect.
Alternatively , in the piezoelectric resonator described in any one of 3 to 5 , any one of the piezoelectric layers included in the multilayer body is sandwiched between any one of the electrodes.

In the piezoelectric resonator according to the second or sixth aspect , since all the piezoelectric layers are sandwiched between the electrodes, all the piezoelectric layers are inputted by inputting an excitation electric signal to the electrodes. Is excited. Therefore, the resonance response of the piezoelectric resonator can be made extremely large, and a piezoelectric resonator having strong resonance characteristics can be manufactured.

According to a seventh aspect of the present invention, there is provided a piezoelectric resonator according to the second aspect.
Alternatively , the piezoelectric layer having a negative temperature coefficient of the resonance frequency in the piezoelectric resonator described in 4 to 6 is made of ZnO, LiNb.
_{O 3, LiTaO 3, PbZr X} Ti (1 -X) O
₃ [0 ≦ x ≦ 0.52], characterized in that it is composed mainly of a piezoelectric material.

ZnO, LiNbO ₃ , LiTaO ₃ , P
bZr _X Ti _(1-X) O ₃ [0 ≦ x ≦ 0.52]
8. The piezoelectric device according to claim 3 , wherein each of the piezoelectric materials is a piezoelectric material, and the temperature coefficient of the resonance frequency has a negative value .
In the case of a piezoelectric resonator, by combining with a piezoelectric layer having a positive temperature coefficient of resonance frequency, a piezoelectric resonator having good resonance characteristics can be manufactured.

[0020] The piezoelectric resonator according to the eighth aspect is characterized in that :
The piezoelectric layer having a positive temperature coefficient in the piezoelectric resonator described in 2, 3, or 5 to 7 is formed of AlN, PbZr _X Ti _{( 1
-X)} O ₃ [0.54 ≦ x ≦ 1] as a main component.

AlN, PbZr _X Ti _(1-X) O
₃ [0.54 ≦ x ≦ 1] is a piezoelectric, moreover since the temperature coefficient of the resonant frequency has a positive value, claim 4
Alternatively, in the piezoelectric resonator described in 8, a piezoelectric resonator having good resonance characteristics can be manufactured by combining with a piezoelectric layer having a negative temperature coefficient of resonance frequency.

It should be noted that PbZr _X Ti _(1-X) O ₃ is
Since both the positive and negative frequency temperature coefficients can be obtained by changing the composition, a piezoelectric resonator having good resonance characteristics can be manufactured by combining both positive and negative piezoelectric layers.

The piezoelectric resonator according to claim 9, claim 1-4 or 6-8 by laminating piezoelectric layers of three layers on the substrate
Wherein the thicknesses of the upper and lower piezoelectric layers sandwiching the central piezoelectric layer are substantially equal.

In the piezoelectric resonator according to the fifth or ninth aspect , the thicknesses of the upper and lower piezoelectric layers sandwiching the central piezoelectric layer among the three piezoelectric layers are substantially equal. The three stacked piezoelectric layers have a symmetrical structure with respect to the center plane of the center piezoelectric layer. Therefore, even if a thermal stress is generated due to a temperature change, the stress can be balanced, so that the laminated piezoelectric layers are hardly broken and warpage is hardly generated.

The filter according to the tenth aspect is the first aspect.
The piezoelectric resonator according to any one of the first to ninth aspects is used.

According to the eleventh aspect of the present invention, there is provided the electronic apparatus according to the first aspect.
The piezoelectric resonator according to any one of the first to ninth aspects is used.

[0027] A filter according to claim 10 and claim 1.
Since the electronic device described in 1 uses the piezoelectric resonator according to the present invention, it is possible to obtain a filter and an electronic device with a small frequency temperature change. Further, since the characteristics of the resonator are improved, the filter characteristics of the filter and the electronic device can be improved.

[0028]

(First Embodiment) FIG. 4 is a sectional view showing the structure of a piezoelectric thin-film resonator 21 according to a first embodiment of the present invention. In this piezoelectric thin film resonator 21,
An AlN thin film 23A is formed on the upper surface of a Si substrate 22,
A cavity 24 is provided by opening the center of the substrate 22. At this time, the portion corresponding to the cavity 24 of the AlN thin film 23A becomes the thin film support 27. Also, on the lower surface of the Si substrate 22,
An SiO ₂ film 28 is formed. On the upper surface of the thin film support 27, a piezoelectric thin film 25Z made of ZnO is formed. One excitation electrode 26a is provided from the lower surface of the AlN thin film 23A to the end of the Si substrate 22, and a part of the excitation electrode 26a is exposed from the AlN thin film 23A. The other excitation electrode 26b is also provided on the upper surface of the piezoelectric thin film 25Z.

Thus, the piezoelectric thin film 25Z and the thin film support 27
The excitation electrodes 26a,
26b is provided, and the ZnO piezoelectric thin film 25Z and the thin film support 27 vibrate in thickness when an electric signal for excitation is applied.

FIGS. 5 (a) to 5 (i) are schematic diagrams showing the steps of manufacturing the piezoelectric thin film resonator 21. FIG. Although not shown in FIG. 4, the etching of the Si substrate 22 is controlled by the SiO ₂ film 30 on the upper surface of the Si substrate 22 as described below. First, a (100) plane Si substrate 22 is prepared, and an SiO ₂ film 28 is formed on the back surface of the Si substrate 22 by sputtering. Next, a resist film 29 is formed on the SiO ₂ film 28, and the resist film 29 is patterned by photolithography to form an opening [FIG.
(A)]. The SiO ₂ film 28 is selectively etched with hydrofluoric acid or the like through the opening of the resist film 29, and an opening is made in the SiO ₂ film 28 in accordance with the opening of the resist film 29 (FIG. 5B).

After the resist film 29 formed on the back surface of the Si substrate 22 is removed, a CVD
The SiO ₂ film 30 is formed by a sputtering method or a sputtering method (FIG. 5C). Thereafter, using the SiO ₂ film 28 as a mask, the Si substrate 22 is anisotropically etched from the lower surface side with an etchant such as TMAH. By this anisotropic etching, the central portion of the Si substrate 22 is opened, and SiO ₂
A cavity 24 is formed below the film 30 (FIG. 5D). As a result, the periphery of the SiO ₂ film 30 is supported by the Si substrate 22, and the central portion of the SiO ₂ film 30 is
Floating from the i-substrate 22.

Next, an electrode material is deposited on the surface of the SiO ₂ film 30 by a lift-off deposition method to form one excitation electrode 26a (FIG. 5E). Also, by reactive sputtering, SiO ₂ is applied from above the excitation electrode 26a.
An AlN thin film 23A is formed on the surface of the film 30 [FIG.
(F)]. At this time, a part of the excitation electrode 26a is
It is exposed from the thin film 23A.

Next, ZnO is deposited by reactive sputtering using a metal mask to form a ZnO piezoelectric thin film 25Z on the AlN thin film 23A (FIG. 5 (g)).
Further, an electrode material is deposited on the ZnO piezoelectric thin film 25Z by a lift-off vapor deposition method to form the other excitation electrode 26b.
Is formed [FIG. 5 (h)]. Next, the exposed portion of the SiO ₂ film 30 is removed by wet etching with an HF-based etchant or dry etching with RIE, thereby exposing the lower surface of the excitation electrode 26a and the AlN thin film 23A [FIG. )]. Thus, the piezoelectric thin film resonator 21 having the structure as shown in FIG. 4 is manufactured.

Since the temperature coefficient of the resonance frequency of ZnO has a negative value while the temperature coefficient of the resonance frequency of AlN has a positive value, the ZnO piezoelectric thin film 25Z and the AlN thin film support 27 are joined. According to the piezoelectric thin film resonator 21 thus set, the temperature coefficient of the resonance frequency can be made substantially zero by appropriately setting the film thickness ratio between the ZnO piezoelectric thin film 25Z and the thin film support 27.

FIG. 6 shows the thickness T of the ZnO piezoelectric thin film 25Z.
When changing the ratio of the thickness _{T AlN} of the AlN thin film support portion 27 _(T AlN _/ T _ZnO) relative to _ZnO, shows a change in the temperature coefficient of the resonant frequency of the piezoelectric thin film resonator 21. By experimentally obtaining such data, the optimum film thickness ratio can be obtained, and the temperature coefficient of the resonance frequency of the piezoelectric thin film resonator 21 can be made substantially zero.

Further, in the conventional piezoelectric thin-film resonator, the thin-film supporting portion only has a function of supporting the piezoelectric thin film for causing the piezoelectric vibration, whereas the piezoelectric thin-film resonator 21 of the present invention has Since both ZnO and the thin film support 27 constituting the ZnO piezoelectric thin film 25Z are made of a piezoelectric material, when an electric signal is applied to the ZnO piezoelectric thin film 25Z and the thin film support 27 through the excitation electrodes 26a and 26b, the thin film support 27 Elastic vibration (thickness vibration) is generated in both the piezoelectric thin film 25Z and the ZnO piezoelectric thin film 25Z, a large resonance response can be obtained, and strong resonance characteristics can be realized.

(Second Embodiment) FIG. 7 is a sectional view showing a piezoelectric thin-film resonator 31 according to a second embodiment of the present invention. In the piezoelectric thin film resonator 31, the Si substrate 22
A ZnO thin film 23Z is formed on the upper surface of the substrate, and a cavity 24 is formed in the center of the Si substrate 22. Also, an AlN piezoelectric thin film 25A is formed on the ZnO thin film 23Z. Also, Al
An excitation electrode 26 is provided on an upper surface and a lower surface of a vibration portion formed of a laminate of the N piezoelectric thin film 25A and the thin film support 27, respectively.
b, 26a.

The piezoelectric thin-film resonator 31 is different from the first embodiment in that the thin-film supporting portion and the piezoelectric material of the ZnO piezoelectric thin film are replaced with each other. By appropriately setting the thickness and the thickness of the AlN piezoelectric thin film 25A, the temperature coefficient of the resonance frequency can be stabilized. Furthermore, since both the thin film support 27 and the AlN piezoelectric thin film 25A vibrate piezoelectrically, the resonance impedance of the piezoelectric thin film resonator 31 can be increased, and strong resonance characteristics can be obtained.

(Third Embodiment) FIG. 8 is a sectional view showing a piezoelectric thin film resonator 32 according to a third embodiment of the present invention. The piezoelectric thin-film resonator 32 has an A
1N thin film 23A is formed, and S
A cavity 24 is formed in the center of the i-substrate 22, and the AlN thin film 2 is formed.
A ZnO piezoelectric thin film 25Z is formed on 3A, and an AlN piezoelectric thin film 25A is further formed thereon. Also, Al
Exciting electrodes 26b and 26a are provided on the upper surface and the lower surface of a vibrating portion formed of a laminate of the N piezoelectric thin film 25A, the ZnO piezoelectric thin film 25Z, and the thin film support 27, respectively.

This piezoelectric thin-film resonator 32 is also made of a ZnO piezoelectric thin-film 2 by reactive sputtering using a metal mask.
After the 5Z is formed, it is manufactured in the same manner as in the first embodiment except that the AlN piezoelectric thin film 25A is formed by reactive sputtering using a metal mask.

In such a laminate having a three-layer structure,
By appropriately setting the ratio between the thicknesses of the thin film support 27, the ZnO piezoelectric thin film 25Z, and the AlN piezoelectric thin film 25A, the temperature coefficient of the resonance frequency can be made substantially zero, and the temperature characteristics can be stabilized. .

Further, three piezoelectric thin films 23A, 25Z,
Since the entire laminate including the piezoelectric thin film 25A is made of a piezoelectric material, when an electric signal is applied to the piezoelectric thin films 25A, 25Z and the thin film support 27 through the excitation electrodes 26a, 26b, the thin film support 27, the piezoelectric thin film 25A, Elastic vibration occurs in all of the 25Z, a large resonance response can be obtained, and strong resonance characteristics can be realized.

Further, the piezoelectric thin film resonator 3 having the above structure
In the case of No. 2, if the thickness t1 of the thin film support portion 27 (piezoelectric thin film 23A) and the thickness t2 of the AlN piezoelectric thin film 25A are made equal, the structure of the stacked body becomes substantially symmetrical about the piezoelectric thin film 25Z in the vertical direction. Therefore, it becomes difficult for the laminate to mechanically warp due to a temperature change.

(Fourth Embodiment) FIG. 9 is a sectional view showing a piezoelectric thin film resonator 33 according to a fourth embodiment of the present invention. In the piezoelectric thin film resonator 33, the Si substrate 22
A ZnO thin film 23Z is formed on the upper surface of the substrate, and a cavity 24 is formed in the center of the Si substrate 22. Further, an AlN piezoelectric thin film 25A is formed on the ZnO thin film 23Z, and a ZN piezoelectric thin film 25A is further formed thereon.
An nO piezoelectric thin film 25Z is formed. Also, the ZnO piezoelectric thin film 25Z, the AlN piezoelectric thin film 25A, and the thin film support 27
Excitation electrodes 26b and 26a are provided on the upper surface and the lower surface of the vibrating portion made of the laminated body.

The piezoelectric thin-film resonator 33 is different from the piezoelectric thin-film resonator 32 of the third embodiment in that the thin-film support 27 and the ZnO
Since the piezoelectric materials of the piezoelectric thin film 25Z and the AlN piezoelectric thin film 25A are replaced with each other, the film thickness of the thin film support portion 27 and the film thickness of each of the piezoelectric thin films 25A and 25Z are appropriately set as in the third embodiment. Thereby, the temperature characteristics of the resonance frequency can be stabilized. Further, since the thin film support 27 and each of the piezoelectric thin films 25A and 25Z vibrate piezoelectrically, the resonance response of the piezoelectric thin film resonator 33 is increased,
Strong resonance characteristics can be obtained. Further, by making the structure of the laminate approximately symmetrical in the vertical direction, mechanical warpage of the laminate due to a temperature change can be reduced.

(Fifth Embodiment) FIG. 10 shows a fifth embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a piezoelectric thin-film resonator according to the embodiment. The piezoelectric thin-film resonator 34 has an A
1N thin film 23A is formed, and S
An AlN thin film 23A is formed by forming a cavity 24 in the center of the i-substrate 22, and a ZnO piezoelectric thin film 2 is formed thereon.
5Z is formed, and an AlN piezoelectric thin film 25A is further formed thereon. The AlN piezoelectric thin film 25A and ZnO
Excitation electrodes 26a are provided on the boundary of the piezoelectric thin film 25Z and the lower surface of the thin film support portion 27 so as to be electrically connected to each other, and the upper surface of the AlN piezoelectric thin film 25A and the ZnO piezoelectric thin film 2
Excitation electrodes 26b are provided at the boundaries of the 5Z and AlN thin film support portions 27, respectively, so that they are electrically connected to each other.

In the piezoelectric thin film resonator 34 having such a structure, the AlN piezoelectric thin film 25A and the ZnO piezoelectric thin film 25Z
And the thin film support portion 27 are connected in parallel, so that the piezoelectric thin films 25A, 25Z are passed through the excitation electrodes 26a, 26b.
When an electric signal is applied to the thin film support 27, elastic vibration is generated in the thin film support 27 and each of the piezoelectric thin films 25A and 25Z, and a large resonance response can be obtained.
Strong resonance characteristics can be realized.

Also in such a three-layered laminated body, by appropriately setting the ratio of the thicknesses of the AlN thin film support 27, the ZnO piezoelectric thin film 25Z and the AlN piezoelectric thin film 25A, the temperature of the resonance frequency can be improved. The coefficient can be made substantially zero, and the temperature characteristics can be stabilized.

Further, in the piezoelectric thin film resonator 34 having such a structure, the thin film support portion 27 (AlN thin film 23A)
If the thickness t1 of the AlN piezoelectric thin film 25A is made equal to the thickness t2 of the AlN piezoelectric thin film 25A, the structure of the stacked body becomes substantially symmetrical with respect to the piezoelectric thin film 25Z in the vertical direction. It becomes difficult.

The piezoelectric thin film resonator 3 having such a structure is
4 also, AlN and ZnO were exchanged, and an AlN piezoelectric thin film was formed on the ZnO piezoelectric thin film.
A piezoelectric thin film may be formed.

(Sixth Embodiment) FIG. 11 shows a sixth embodiment of the present invention.
It is sectional drawing which shows the piezoelectric thin film resonator 41 by embodiment. This is a piezoelectric thin film resonator 41 having a floating structure (air bridge structure), and a thin film support portion 44A made of AlN is placed on a glass substrate 42 via an air gap 43.
Is formed, and a piezoelectric thin film 45Z made of ZnO is formed on the thin film support portion 44A. Also, the ZnO piezoelectric thin film 45
The excitation electrodes 46b and 46b are provided on the upper and lower surfaces of the vibrating portion formed by the laminate of Z and the thin film support portion 44A, respectively.
46a is provided.

In this manner, the excitation electrodes 46a and 46b are provided on both surfaces of the vibrating portion composed of the laminate of the ZnO piezoelectric thin film 45Z and the thin film support 44A. The ZnO piezoelectric thin film 45Z and the thin film support 44A receive the excitation electric signal. When added, it vibrates in thickness.

FIGS. 12A to 12F are diagrams schematically showing the steps of manufacturing the piezoelectric thin film resonator 41. FIG. First, a sacrifice layer 47 made of ZnO is formed on a glass substrate 42 by a sputtering method, and the sacrifice layer 47 is etched while leaving a part to be an air gap 43 (FIG. 12A). Next, an excitation electrode 46a is formed of Al on the sacrificial layer 47 by a vacuum deposition method and a lift-off method (FIG. 12).
(B)].

The sacrificial layer 47 is formed by a reactive sputtering method.
A thin film support 44A made of AlN is formed on the substrate [FIG. 12 (c)]. Thereafter, the sacrifice layer 47 is formed using an acetic acid aqueous solution.
Is etched to form an air gap 43 on the lower surface of the thin film supporting portion 44A, and the thin film supporting portion 44A is floated from the upper surface of the glass substrate 42 (FIG. 12D). Next, a ZnO piezoelectric thin film 45 is formed on the upper surface of the thin film support 44A by sputtering.
Z is formed (FIG. 12E), and an excitation electrode 46b is formed on the ZnO piezoelectric thin film 45Z by a vacuum evaporation method using a metal mask (FIG. 12F). In this way,
A piezoelectric thin film resonator 41 having a floating structure as shown in FIG. 11 is manufactured.

The temperature coefficient of the resonance frequency of ZnO has a negative value, while the temperature coefficient of the resonance frequency of AlN has a positive value. In the piezoelectric thin film resonator 41 having the thin film 45Z formed thereon, the temperature coefficient of the resonance frequency can be made substantially zero by appropriately setting the film thickness ratio between the ZnO piezoelectric thin film 45Z and the thin film support 44A.

Further, in the conventional piezoelectric thin film resonator having a floating structure, the thin film supporting portion has only a function as a thin film for supporting the piezoelectric thin film. Since both ZnO forming the ZnO piezoelectric thin film 45Z and AlN forming the thin film support portion 44A are piezoelectric materials, when an electric signal is applied to the ZnO piezoelectric thin film 45Z and the thin film support portion 44A through the excitation electrodes 46a and 46b, Thin film support 44A and ZnO piezoelectric thin film 45
Elastic vibration occurs in both Z, a large resonance response can be obtained, and strong resonance characteristics can be realized.

According to the piezoelectric thin film resonator 41 having such a floating structure, it is not necessary to cut the back surface of the substrate 42 by etching, so that there is an advantage that the substrate is not limited to a substrate made of a specific material such as glass.

The piezoelectric thin film resonator 41 of this embodiment
In the above, ZnO and AlN may be exchanged, and the AlN piezoelectric thin film may be formed on the ZnO thin film support.

(Seventh Embodiment) FIG. 13 shows a seventh embodiment of the present invention.
It is sectional drawing which shows the piezoelectric thin film resonator 51 by embodiment. This piezoelectric thin-film resonator 51 has an A
1N thin film 23A is formed, and S
An AlN thin film 23A is formed by forming a cavity 24 in the center of the i-substrate 22, and a ZnO piezoelectric thin film 2 is formed thereon.
5Z is formed, and an AlN piezoelectric thin film 25A is further formed thereon. Further, an excitation electrode 26b is formed on the upper surface of the AlN piezoelectric thin film 25A, and an excitation electrode 26a is provided at the boundary between the thin film support 27 and the ZnO piezoelectric thin film 25Z.

This piezoelectric thin film resonator 51 is
7 and the excitation electrode 26a are manufactured in the same manner as in the third embodiment except that the formation order is reversed.

In such a laminate having a three-layer structure,
By appropriately setting the ratio between the thicknesses of the thin film support 27, the ZnO piezoelectric thin film 25Z, and the AlN piezoelectric thin film 25A, the temperature coefficient of the resonance frequency can be made substantially zero, and the temperature characteristics can be stabilized. .

In the piezoelectric thin film resonator 51, the AlN piezoelectric thin film 25A and the ZnO piezoelectric thin film 25Z are
a, 26b, the excitation electrodes 26a, 2b
When an electric signal is applied to both piezoelectric thin films 25A and 25Z through 6b, elastic vibration is generated in the piezoelectric thin films 25A and 25Z, a large resonance response can be obtained, and strong resonance characteristics can be realized. On the other hand, the thin film support 2 made of AlN
7 is located between the excitation electrodes 26a and 26b,
Since N is a piezoelectric material, when a signal voltage is applied to the excitation electrodes 26a and 26b, a voltage is also applied to the thin film support 27 by dielectric polarization, thereby contributing to the improvement of the resonance characteristics of the piezoelectric thin film resonator 51.

Further, in the piezoelectric thin film resonator 51 having such a structure, if the thickness t1 of the thin film support portion 27 (piezoelectric thin film 23A) is made equal to the thickness t2 of the AlN piezoelectric thin film 25A, the piezoelectric thin film 25Z , The structure of the laminate is substantially symmetrical in the vertical direction, so that the laminate is less likely to be mechanically warped due to a temperature change.

(Eighth Embodiment) FIG. 14 shows a ninth embodiment of the present invention.
It is sectional drawing which shows the piezoelectric thin film resonator 52 by embodiment. In this embodiment, in the configuration of the thin film support 27 and the piezoelectric thin films 25Z and 25A, which are the same as the piezoelectric thin film resonator 51 of FIG. 13, the excitation electrodes 26b and 26a are connected to the upper surface of the ZnO piezoelectric thin film 25Z and the lower surface of the thin film support 27. Is formed.

In the piezoelectric thin-film resonator 52, the thin-film support portion 27 and the ZnO piezoelectric thin film 25Z are connected to the excitation electrodes 26a, 26
b, when an electric signal is applied to the thin film support portion 27 and the ZnO piezoelectric thin film 25Z through the excitation electrodes 26a and 26b, the thin film support portion 27 and the ZnO piezoelectric thin film 25Z
Elastic vibration is generated, a large resonance response can be obtained, and strong resonance characteristics can be realized. On the other hand, the AlN piezoelectric thin film 25A is located between the excitation electrodes 26a and 26b, but since AlN is a piezoelectric material, the excitation electrodes 26a and 26b
When a signal voltage is applied to 26b, the AlN piezoelectric thin film 25
A voltage is also applied to A by dielectric polarization, which contributes to the improvement of the resonance characteristics of the piezoelectric thin-film resonator 52. Therefore, also in this embodiment, the temperature characteristics of the resonance frequency are stable and have strong resonance characteristics, and the piezoelectric thin films 25Z, 25
It is possible to manufacture the piezoelectric thin film resonator 52 in which the A and the thin film support portion 27 are less likely to warp.

(Ninth Embodiment) FIG. 15 shows a ninth embodiment of the present invention.
It is sectional drawing which shows the piezoelectric thin film resonator 53 by 2nd Embodiment. The piezoelectric thin-film resonator 53 has a Z
An nO thin film 23Z is formed, and S
A cavity 24 is formed at the center of the i-substrate 22. The AlN piezoelectric thin film 25A is formed on the ZnO thin film 23Z, and the ZnO piezoelectric thin film 25Z is further formed thereon. Also, Z
An excitation electrode 26b is formed on the upper surface of the nO piezoelectric thin film 25Z, and an excitation electrode 26a is provided at the boundary between the ZnO thin film support 27 and the AlN piezoelectric thin film 25A.

In the piezoelectric thin film resonator 53, the ZnO piezoelectric thin film 25Z and the AlN piezoelectric thin film 25A are
a, 26b, the excitation electrodes 26a, 2b
When an electric signal is applied to both piezoelectric thin films 25Z and 25A through 6b, elastic vibration is generated in the piezoelectric thin films 25Z and 25A, a large resonance response can be obtained, and strong resonance characteristics can be realized. On the other hand, the thin film support 2 made of ZnO
7 is located between the excitation electrodes 26a and 26b,
Since O is a piezoelectric material, when a signal voltage is applied to the excitation electrodes 26a and 26b, a voltage is also applied to the ZnO thin film support portion 27 by dielectric polarization, thereby contributing to the improvement of the resonance characteristics of the piezoelectric thin film resonator 53.

Accordingly, also in this embodiment, the temperature characteristics of the resonance frequency are stable and have strong resonance characteristics, and further, the piezoelectric thin films 25Z, 25A and the thin film support portion 27 are unlikely to be warped with a change in temperature. The piezoelectric thin film resonator 53 can be manufactured.

(Tenth Embodiment) FIG. 16 is a sectional view showing a piezoelectric thin-film resonator 54 according to a tenth embodiment of the present invention. In this embodiment, the piezoelectric thin film resonator 5 shown in FIG.
3, the excitation electrodes 26b and 26a are formed on the upper surface of the AlN piezoelectric thin film 25A and on the lower surface of the thin film support 27 in the same configuration of the thin film support 27 and the piezoelectric thin films 25A and 25Z.

In this piezoelectric thin-film resonator 54, the AlN piezoelectric thin film 25A and the thin-film support 27 are formed by the excitation electrodes 26b, 26b.
a, when an electric signal is applied to the AlN piezoelectric thin film 25A and the thin film support 27 through the excitation electrodes 26a and 26b, the AlN piezoelectric thin film 25A and the thin film support 27
Elastic vibration is generated, a large resonance response can be obtained, and strong resonance characteristics can be realized. On the other hand, the ZnO piezoelectric thin film 25Z is located between the excitation electrodes 26a and 26b, but since ZnO is a piezoelectric material, the excitation electrodes 26a and 26b
When a signal voltage is applied to 26b, the ZnO piezoelectric thin film 25
A voltage is also applied to Z by dielectric polarization, which contributes to the improvement of the resonance characteristics of the piezoelectric thin-film resonator 54. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin-film resonator 54 having stable temperature characteristics of the resonance frequency and strong resonance characteristics.

(Eleventh Embodiment) FIG. 17 is a sectional view showing a piezoelectric thin film resonator 55 according to an eleventh embodiment of the present invention. In this piezoelectric thin-film resonator 55, the AlN thin film 23A is formed on the upper surface of the Si
A cavity 24 is formed at the center of the. A ZnO piezoelectric thin film 25Z is formed on the AlN thin film 23A. Also, ZnO
The excitation electrodes 26b, 26 are provided on the upper and lower surfaces of the piezoelectric thin film 25Z.
a is provided.

In the piezoelectric thin-film resonator 55, since the ZnO piezoelectric thin film 25Z is sandwiched between the excitation electrodes 26a and 26b, the piezoelectric thin film 25 is passed through the excitation electrodes 26a and 26b.
When an electric signal is applied to Z, elastic vibration occurs in the piezoelectric thin film 25Z, and a resonance response can be obtained. on the other hand,
The thin film support 27 is located between the excitation electrodes 26a and 26b, but since AlN is a piezoelectric material, the excitation electrode 26
When a signal voltage is applied to the piezoelectric thin film resonator 55a and 26b, a voltage is also applied to the thin film support 27 by dielectric polarization.
Can be improved. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin film resonator 55 having stable temperature characteristics of the resonance frequency and strong resonance characteristics.

(Twelfth Embodiment) FIG. 18 is a sectional view showing a piezoelectric thin-film resonator 56 according to a twelfth embodiment of the present invention. In this embodiment, the piezoelectric thin film resonator 5 shown in FIG.
5, the excitation electrodes 26b and 26a are connected to the thin film support 2 and the ZnO piezoelectric thin film 25Z.
7 are formed on the upper and lower surfaces.

In this piezoelectric thin-film resonator 56, since the thin-film support 27 is sandwiched between the excitation electrodes 26a and 26b,
When an electric signal is applied to the thin film support 27 through the excitation electrodes 26a and 26b, elastic vibration is generated in the thin film support 27, and a resonance response can be obtained. On the other hand, ZnO
The piezoelectric thin film 25Z is located between the excitation electrodes 26a and 26b, but since ZnO is a piezoelectric material, the excitation electrode 26
a, 26b when a signal voltage is applied to the ZnO piezoelectric thin film 2
A voltage is also applied to 5Z by dielectric polarization, and the resonance characteristics of the piezoelectric thin-film resonator 56 can be improved. Therefore,
Also in this embodiment, it is possible to manufacture the piezoelectric thin-film resonator 56 having stable temperature characteristics of the resonance frequency and strong resonance characteristics.

(Thirteenth Embodiment) FIG. 19 is a sectional view showing a piezoelectric thin-film resonator 57 according to a thirteenth embodiment of the present invention. In the piezoelectric thin film resonator 57, a ZnO thin film 23Z is formed on the upper surface of the Si
A cavity 24 is formed at the center of the. An AlN piezoelectric thin film 25A is formed on the ZnO thin film 23Z. Also, AlN
The excitation electrodes 26b, 2 are provided on the upper and lower surfaces of the piezoelectric thin film 25A.
6a is provided.

In this piezoelectric thin film resonator 57, since the AlN piezoelectric thin film 25A is sandwiched between the excitation electrodes 26b, 26a, the piezoelectric thin film 25 passes through the excitation electrodes 26a, 26b.
When an electric signal is applied to A, elastic vibration is generated in the AlN piezoelectric thin film 25A, and a resonance response can be obtained.
On the other hand, the thin film support 27 is located between the excitation electrodes 26a and 26b, but since the ZnO is a piezoelectric material, when a signal voltage is applied to the excitation electrodes 26a and 26b, the thin film support 27 is also in a dielectric state. A voltage is applied by the polarization, and the resonance characteristics of the piezoelectric thin film resonator 57 can be improved. Therefore,
Also in this embodiment, it is possible to manufacture the piezoelectric thin film resonator 57 having a stable resonance frequency temperature characteristic and a strong resonance characteristic.

(Fourteenth Embodiment) FIG. 20 is a sectional view showing a piezoelectric thin film resonator 58 according to a fourteenth embodiment of the present invention. In this embodiment, the piezoelectric thin film resonator 5 shown in FIG.
7, the excitation electrodes 26b and 26a are connected to the thin film support 2 and the AlN piezoelectric thin film 25A.
7 are formed on the upper and lower surfaces.

In the piezoelectric thin-film resonator 58, since the thin-film support portion 27 is sandwiched between the excitation electrodes 26a and 26b, the thin-film support portion 27 passes through the excitation electrodes 26a and 26b.
When an electric signal is applied to the thin film supporting member 27, an elastic vibration is generated in the thin film supporting portion 27, and a resonance response can be obtained. On the other hand, A
The 1N piezoelectric thin film 25A is located between the excitation electrodes 26b and 26a, but since AlN is a piezoelectric material, when a signal voltage is applied to the excitation electrodes 26a and 26b, the AlN piezoelectric thin film 25A is also inductively polarized. A voltage is applied, and the resonance characteristics of the piezoelectric thin film resonator 58 can be improved. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin film resonator 58 having stable resonance frequency temperature characteristics and strong resonance characteristics.

(Fifteenth Embodiment) FIG. 21 is a sectional view showing a piezoelectric thin-film resonator 59 according to a fifteenth embodiment of the present invention. In this piezoelectric thin-film resonator 59, the AlN thin film 23A is formed on the upper surface of the Si
A cavity 24 is formed at the center of the. A ZnO piezoelectric thin film 25Z is formed on the AlN thin film 23A.
An N piezoelectric thin film 25A is formed. Only one layer of the three-layer structure including the thin film support 27 and the piezoelectric thin films 25Z and 25A is sandwiched between the excitation electrodes 26a and 26b.

In this piezoelectric thin-film resonator 59, only one layer of the thin-film support portion 27 and the piezoelectric thin films 25Z and 25A is sandwiched between the excitation electrodes 26b and 26a.
When an electric signal is applied through 6a and 26b, an elastic vibration is generated there and a resonance response can be obtained.
On the other hand, the remaining two layers are located between the excitation electrodes 26a and 26b, but both are formed of a piezoelectric material. Therefore, when a signal voltage is applied to the excitation electrode 26, a voltage is applied due to dielectric polarization. Thus, the resonance characteristics of the piezoelectric thin film resonator 59 can be improved. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin-film resonator 59 which has stable temperature characteristics of resonance frequency, has strong resonance characteristics, and is less likely to warp against temperature changes.

(Sixteenth Embodiment) FIG. 22 is a sectional view showing a piezoelectric thin-film resonator 60 according to a sixteenth embodiment of the present invention. In the piezoelectric thin film resonator 60, a ZnO thin film 23Z is formed on the upper surface of the Si
A cavity 24 is formed at the center of the. An AlN piezoelectric thin film 25A is formed on the ZnO thin film 23Z, and a ZnO thin film 25A is further formed thereon.
An O piezoelectric thin film 25Z is formed. Only one layer of the three-layer structure including the thin film support 27 and the piezoelectric thin films 25A and 25Z is sandwiched between the excitation electrodes 26b and 26a.

In the piezoelectric thin-film resonator 60, only one layer of the thin-film support portion 27 and the piezoelectric thin films 25A and 25Z is sandwiched between the excitation electrodes 26a and 26b.
When an electric signal is applied through 6a and 26b, an elastic vibration is generated there and a resonance response can be obtained.
On the other hand, the remaining two layers are located between the excitation electrodes 26a and 26b, but are both formed of a piezoelectric material. Therefore, when a signal voltage is applied to the excitation electrodes 26a and 26b, the voltage is increased by dielectric polarization. And the resonance characteristics of the piezoelectric thin-film resonator 60 can be improved. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin-film resonator 60 having stable temperature characteristics of the resonance frequency, strong resonance characteristics, and less likely to be warped against a temperature change.

(Seventeenth Embodiment) Various embodiments of the diaphragm type piezoelectric thin film resonator have been described so far. For the piezoelectric thin film resonator having a floating structure, two or more piezoelectric thin film resonators are provided on the thin film supporting portion. Various embodiments are possible, such as those in which a thin film is formed, those in which only a part of the thin film support and the piezoelectric thin film are sandwiched between excitation electrodes, and those in which the combination of piezoelectric materials is changed.

For example, FIG. 23 is a sectional view showing a piezoelectric thin film resonator 61 having a floating structure (according to the seventeenth embodiment), showing a different embodiment of the piezoelectric thin film resonator 61 having a floating structure. In this piezoelectric thin film resonator 61, an AlN thin film support portion 44A having a floating structure is formed on a glass substrate 42 via an air gap 43, and a ZnO piezoelectric thin film 45Z is formed on the thin film support portion 44A. ZnO piezoelectric thin film 4
Exciting electrodes 46b and 46a are formed on the upper and lower surfaces of 5Z.

In the piezoelectric thin film resonator 61, the piezoelectric thin film 4
Since 5Z is sandwiched between the excitation electrodes 46b and 46a,
When an electric signal is applied to the piezoelectric thin film 45Z through the excitation electrodes 46a and 46b, elastic vibration occurs in the piezoelectric thin film 45Z, and a resonance response can be obtained. On the other hand, the thin film supporting portion 44A is located between the excitation electrodes 46a and 46b, but since AlN is a piezoelectric material, the excitation electrodes 46a and 46b
When a signal voltage is applied to 46b, a voltage is also applied to the thin film support portion 44A by dielectric polarization, and the resonance characteristics of the piezoelectric thin film resonator 61 can be improved. Therefore, also in this embodiment, it is possible to manufacture the piezoelectric thin film resonator 61 having stable resonance frequency temperature characteristics and strong resonance characteristics.

(Eighteenth Embodiment) FIG. 24 is a sectional view showing the structure of a piezoelectric resonator 62 according to an eighteenth embodiment of the present invention. In this embodiment, a cavity 24 is formed on the upper surface of the Si substrate 22 by etching the upper surface of the Si substrate 22, and the excitation electrode 26a, the AlN thin film 23A, and the ZnO thin film are formed on the Si substrate 22. 25 and an excitation electrode 26b. In addition, the Si substrate 22
Is provided with a SiO ₂ film 28 on the lower surface thereof. As a manufacturing procedure, the excitation electrode 26a and the AlN
After forming the thin film 23A, an etching solution is injected into the upper surface of the Si substrate 22 from an opening provided in the AlN thin film 23A,
A cavity 24 is provided by etching a part of the Si substrate 22 below the opening of the AlN thin film 23A. Then, A
A ZnO thin film 25Z is formed on the upper surface of the 1N thin film 23A,
The excitation electrode 26b may be provided thereon.

This embodiment corresponds to the first embodiment in which the cavity 24 is formed not from the back surface of the substrate but from the front surface. Such a piezoelectric resonator 30 has the same operation and effect as the first embodiment. Also in this embodiment, embodiments corresponding to the second to sixteenth embodiments are possible depending on the combination of the piezoelectric film and the electrodes.

In each of the above embodiments, the case where ZnO and AlN are combined as the piezoelectric material has been described. However, other than this, ZnO, LiNbO ₃ , LiTa
O ₃ , PbZr _X Ti _(1-X) O ₃ [0 ≦ x ≦ 0.5
2] a piezoelectric material having a negative temperature coefficient of the resonance frequency, AlN having a positive temperature coefficient of the resonance frequency,
A combination with a piezoelectric material such as PbZr _X Ti _(1-X) O ₃ [0.54 ≦ x ≦ 1] may be used.

(Nineteenth Embodiment) FIGS. 25A and 25B
(C) is a circuit diagram of a filter according to the nineteenth embodiment of the present invention. These filters are ladder filters configured by using the piezoelectric thin film resonator 71 according to the present invention.
(B) is a T-type filter 73, and (c) is a π-type filter 74.
It has become.

Since the filters 72, 73, and 74 use the piezoelectric thin-film resonator 71 according to the present invention, it is possible to obtain a filter having a small frequency temperature change. In addition, since the characteristics of the piezoelectric thin-film resonator 71 are improved, the filter characteristics are also improved. Further, if the piezoelectric thin-film resonator 71 is made of a three-layer structure such as the piezoelectric thin-film resonators 32, 34, and 51, and the upper and lower thin films sandwiching the central thin film are substantially equal in thickness, a filter resistant to destruction can be obtained. Can be.

Further, the piezoelectric thin film resonator and the filter according to the present invention are also used for electronic devices such as mobile phones and personal computers.

[0092]

According to the piezoelectric resonator according to the first aspect,
By appropriately setting the thickness of each piezoelectric layer, the temperature coefficient of the resonance frequency of the entire laminate can be made almost zero, and all the layers other than the electrodes are made of a piezoelectric material. Therefore, the resonance response of the piezoelectric resonator can be improved, and the resonance characteristics can be improved. Therefore, according to the piezoelectric resonator of the first aspect, it is possible to manufacture a piezoelectric resonator that has stable resonance frequency temperature characteristics, a large resonance response, and excellent resonance characteristics.

According to the piezoelectric resonator of the present invention, all the piezoelectric layers can be excited by inputting an excitation electric signal to the electrodes, so that the resonance response of the piezoelectric resonator is very large. Thus, a piezoelectric resonator having strong resonance characteristics can be manufactured.

ZnO, LiNbO ₃ , LiTaO ₃ , P
The bZr _X Ti _(1-X) O ₃ [0 ≦ x ≦ 0.52] is a piezoelectric substance, and has a negative temperature coefficient of the resonance frequency. According to the described piezoelectric resonator, a piezoelectric resonator having excellent resonance characteristics can be manufactured by combining the piezoelectric resonator with a piezoelectric layer having a positive temperature coefficient of the resonance frequency.

AlN, PbZr _X Ti _(1-X) O
₃ [0.54 ≦ x ≦ 1] is a piezoelectric material, and the temperature coefficient of the resonance frequency has a positive value.
According to the piezoelectric resonator described in (1), a piezoelectric resonator having good resonance characteristics can be manufactured by combining with a piezoelectric layer having a negative temperature coefficient of resonance frequency.

In the piezoelectric resonator according to the fifth aspect,
Since the three stacked piezoelectric layers have a symmetrical structure with respect to the center plane of the center piezoelectric layer, the stress can be balanced even if a thermal stress is generated due to a temperature change. Are less likely to break and warpage is less likely to occur.

According to the filter of the sixth aspect and the electronic device of the seventh aspect, it is possible to obtain a filter and an electronic device with a small frequency temperature change. Further, since the characteristics of the resonator are improved, the filter characteristics of the filter and the electronic device can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional piezoelectric thin-film resonator.

FIG. 2 is a cross-sectional view showing the structure of another conventional piezoelectric thin film resonator in which the temperature characteristic of the resonance frequency is improved.

FIG. 3 is a cross-sectional view showing the structure of another conventional piezoelectric thin-film resonator having a floating structure.

FIG. 4 is a sectional view showing the structure of the piezoelectric thin film resonator according to the first embodiment of the present invention.

5 (a) to 5 (i) are schematic views for explaining a manufacturing process of the piezoelectric thin film resonator of the above.

FIG. 6 is a diagram illustrating a relationship between a film thickness ratio between a piezoelectric thin film and a thin film supporting portion and a temperature characteristic of a resonance frequency in the piezoelectric thin film resonator.

FIG. 7 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a second embodiment of the present invention.

FIG. 8 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a third embodiment of the present invention.

FIG. 9 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a sixth embodiment of the present invention.

12 (a) to 12 (f) are schematic views for explaining a manufacturing process of the piezoelectric thin film resonator according to the first embodiment.

FIG. 13 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a seventh embodiment of the present invention.

FIG. 14 is a sectional view showing the structure of a piezoelectric thin-film resonator according to an eighth embodiment of the present invention.

FIG. 15 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a ninth embodiment of the present invention.

FIG. 16 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a tenth embodiment of the present invention.

FIG. 17 is a sectional view showing a structure of a piezoelectric thin-film resonator according to an eleventh embodiment of the present invention.

FIG. 18 is a sectional view showing a structure of a piezoelectric thin-film resonator according to a twelfth embodiment of the present invention.

FIG. 19 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a thirteenth embodiment of the present invention.

FIG. 20 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a fourteenth embodiment of the present invention.

FIG. 21 is a sectional view showing a structure of a piezoelectric thin film resonator according to a fifteenth embodiment of the present invention.

FIG. 22 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a sixteenth embodiment of the present invention.

FIG. 23 is a sectional view showing the structure of a piezoelectric thin-film resonator according to a seventeenth embodiment of the present invention.

FIG. 24 is a sectional view showing a structure of a piezoelectric thin film resonator according to an eighteenth embodiment of the present invention.

FIG. 25 is a nineteenth embodiment of the present invention, wherein (a)
Is an L-type filter, (b) is a T-type filter, and (c) is a π-type filter.

[Explanation of symbols]

22 Si substrate 23A AlN thin film 23Z ZnO thin film 24 cavities 25A, 25Z, 45Z piezoelectric thin film 26a, 26b, 46a, 46b Excitation electrode 27 Thin film support 42 glass substrate 43 Air gap 44A Thin film support

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 41/09 H01L 41/08 C 41/18 U H03H 9/54 S 41/18 101Z (JP, A) JP-A-60-126907 (JP, A) JP-A-60-68711 (JP, A) JP-A-7-254836 (JP, A) JP-A-4-349164 (JP, A) 58-137317 (JP, A) JP-A-7-30354 (JP, A) JP-A-3-148186 (JP, A) JP-B 5-32925 (JP, B2) (58) Int.Cl. ⁷ , DB name) H03H 9/17 C23C 14/06 C23C 14/08 H01L 21/205 H01L 41/083 H01L 41/09 H01L 41/18 H03H 9/54

Claims (11)

(57) [Claims] 1. A stacking a piezoelectric layer one layer or plural layers formed of piezoelectric layers and ZnO one layer or plural layers made of AlN, the laminate, so as to float at least a portion of the substrate A piezoelectric resonator, wherein at least one set of electrodes is provided on the substrate so as to sandwich at least one of the piezoelectric layers constituting the laminate. (2) One layer whose temperature coefficient of resonance frequency is positive
Or a plurality of piezoelectric layers and one layer having a negative temperature coefficient.
Or a plurality of piezoelectric layers, and the laminate is
At least a part is placed on the board so that it floats from the board.
And any of the piezoelectric layers constituting the laminated body
At least one set of electrodes sandwiched between the electrodes
A piezoelectric resonator comprising: (3) One layer whose temperature coefficient of resonance frequency is positive
Or a plurality of piezoelectric layers and one layer having a negative temperature coefficient.
Or a plurality of piezoelectric layers, and the laminate is
At least a part is placed on the board so that it floats from the board.
At least one of the piezoelectric layers constituting the laminate
At least one pair of electrodes is provided so as to sandwich
The piezoelectric layer having a negative wave number temperature coefficient is formed of ZnO, L
iNbO _3. LiTaO ₃ , PbZr _X Ti _{( One -X)}
O ₃ [0 ≦ x ≦ 0 . 52].
A piezo-resonator characterized in that it is configured as a component. (4) One layer whose temperature coefficient of resonance frequency is positive
Or a plurality of piezoelectric layers and one layer having a negative temperature coefficient.
Or a plurality of piezoelectric layers, and the laminate is
At least a part is placed on the board so that it floats from the board.
At least one of the piezoelectric layers constituting the laminate
At least one pair of electrodes is provided so as to sandwich
The piezoelectric layer having a positive wave number temperature coefficient is formed of AlN, P
bZr _X Ti _{( One -X)} O ₃ [0 . 54 ≦ x ≦ 1]
A piezo-resonator characterized in that it is configured as a component. (5) One layer whose temperature coefficient of resonance frequency is positive
Or a plurality of piezoelectric layers and one layer having a negative temperature coefficient.
Or a plurality of piezoelectric layers are laminated on a substrate in three layers,
Make sure the laminate is at least partially lifted off the substrate
And the piezoelectric layer constituting the laminate is disposed on the substrate.
At least one set of electrodes sandwiching at least one layer
The thickness of the upper and lower piezoelectric layers sandwiching the central piezoelectric layer
A piezoelectric resonator characterized by being substantially equal. 6. Any of the piezoelectric layers constituting the laminate, characterized in that it is sandwiched between one of the electrodes, the piezoelectric resonator according to claim 1 or 3-5. 7. The piezoelectric layer having a negative temperature coefficient of resonance frequency is made of ZnO, LiNbO ₃ , LiTaO ₃ , PbZr.
7. The piezoelectric resonance according to claim 2 , wherein the piezoelectric material is mainly composed of a piezoelectric material of _X Ti _{( 1 −X)} O ₃ [0 ≦ x ≦ 0.52]. 8. Child. 8. A piezoelectric layer having a positive temperature coefficient of resonance frequency is made of AlN, PbZr _X Ti _{( 1- X)} O ₃ [0.54.
≦ x ≦ 1] as a main component, the piezoelectric resonator according to claim 2, 3 or 5-7 . 9. The piezoelectric resonator according to claim 1-4 or 6-8 by laminating piezoelectric layers of three layers on the substrate,
A piezoelectric resonator, wherein upper and lower piezoelectric layers sandwiching a central piezoelectric layer have substantially the same thickness. 10. A filter using a piezoelectric resonator according to claim 1-9. 11. An electronic apparatus using the piezoelectric resonator according to claim 1-9.