JPH11284480A - Piezoelectric thin film resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust simply a thin film element resonance frequency in a short time by providing a piezoelectric thin film made of a specified material and a dielectric thin film also made of a specified material between a pair of exciting electrodes, so as to build up a thin film element resonating at a frequency corresponding to a sum of the thickness of the piezoelectric thin film and the dielectric thin film. SOLUTION: A piezoelectric thin film element is made by providing a piezoelectric thin film 13 and a dielectric thin film 14 between a lower electrode 16 and an upper electrode 15, via an insulation film 2 on a substrate 1 having an opening 21. A sound wave propagates through a composite layer, consisting of the piezoelectric thin film 13 and the dielectric thin film 14 in the thickness direction and causes a resonance in that direction. the piezoelectric thin film 13 is made of a composite oxide material such as lead titanate. Since the piezoelectric constant of the piezoelectric thin film 13 can be managed with comparatively high accuracy, the sum of the thickness of the piezoelectric thin film 13 and that of the dielectric thin film 14 is managed with high accuracy within a prescribed range, and the accuracy of the resonance frequency is improved. The dielectric thin film 14 is made of an oxide material such as magnesium oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric thin film element using a piezoelectric thin film, and more particularly to a piezoelectric thin film element which can be used in a filter or a resonator operating in a frequency range from several hundred MHz to GHz band.

[0002]

2. Description of the Related Art In recent years, with the development of mobile communication, the demand for filters and resonators used at relatively high frequencies has been increasing. Above all, a vibrator using a piezoelectric body can be reduced in size and weight. Higher frequency of the type is being studied. A vibrator using the volume vibration (bulk vibration) of a piezoelectric body vibrates at a predetermined frequency by utilizing the fact that the piezoelectric body resonates at a wavelength proportional to its thickness, and therefore vibrates at a high frequency. For this purpose, it is necessary to reduce the thickness of the piezoelectric body. For example, when an element of this type is applied to a communication device such as a mobile communication device, the frequency used in these devices is a high frequency ranging from several hundred MHz to a GHz band. It is necessary to reduce the thickness to 1 to 2 microns or less. As a vibrator of this type, there is a crystal oscillator, and since this crystal oscillator is manufactured by polishing a single crystal crystal used as a piezoelectric body, there is a certain limit in thinning, and in the above high frequency band, Can not be used.

Accordingly, recently, a piezoelectric thin film element utilizing volume vibration, which can be used for mobile communication, using a piezoelectric thin film formed to a thickness of about 1 to 2 μm by various thin film forming methods. Is being considered. That is, in the piezoelectric thin film element, thin film electrodes are formed on both sides of a piezoelectric thin film formed to a thickness of about 1 to 2 microns by a thin film forming method, and by applying an AC voltage to the electrodes, It resonates at a frequency corresponding to the thickness of the piezoelectric thin film. In this configuration, in order to prevent loss of vibration energy, a floating structure in which the substrate below the resonance section is removed and the resonance section is lifted is usually adopted. As a manufacturing method of this floating structure,
It is well known that an upper structure is formed using gallium arsenide (GaAs) as a substrate, and the substrate is etched away from the back surface of the substrate with an etchant such as sulfuric acid to form an element. It is also possible to form the upper structure by using silicon (Si) as the substrate and to remove the substrate under the piezoelectric film by anisotropic etching of Si from the back surface of the substrate with alkali such as potassium hydroxide. is there.

[0004] An example of a conventionally reported device is as follows. For example, in the device disclosed in Japanese Patent Application Laid-Open No. Hei 6-350154, a lower thin film electrode,
By forming a piezoelectric film and an upper thin-film electrode and removing the substrate from the back surface of the substrate, the substrate below the portion serving as the vibrating portion is removed, thereby realizing a floating structure.

[0005]

However, in the case of an element utilizing the volume vibration of the piezoelectric thin film, the resonance frequency which is the operating frequency is uniquely determined according to the thickness of the piezoelectric body as described above. Therefore, in order to vibrate at a specific frequency, extremely accurate film thickness control is required.
When the film thickness is reduced to increase the frequency, it becomes more difficult to control the film thickness. Therefore, in practice, it is difficult to set a predetermined resonance frequency only by controlling the film thickness, and it is necessary to adjust the frequency using some method. Since there is no method, there is a problem that the cost involved in the adjustment process increases and the element price cannot be reduced. Also, in a vibrator utilizing surface acoustic waves, the resonance frequency is determined by the electrode pattern, so it is necessary to accurately form the electrode pattern. It is difficult to set the resonance frequency, and it is necessary to use some frequency adjustment method. Therefore, even in a vibrator utilizing surface acoustic waves,
It had similar problems.

Accordingly, it is an object of the present invention to provide a piezoelectric thin-film element having a structure capable of adjusting the frequency in a short time and easily, and which can be manufactured at low cost.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional example. That is, the piezoelectric thin-film vibrator according to the present invention, in a piezoelectric thin-film vibrator provided with a piezoelectric thin film between a pair of excitation electrodes, further provided a first dielectric thin film between the pair of excitation electrodes, The resonance is performed at a frequency corresponding to the combined thickness of the piezoelectric thin film and the thickness of the first dielectric thin film.

In the piezoelectric thin-film vibrator, a capacitance element is formed by forming a capacitance-forming electrode on the upper excitation electrode of the pair of excitation electrodes via a second dielectric thin film. Is preferred. Thus, the resonance frequency can be changed by changing the capacitance value of the capacitance element.

Further, in the above-mentioned piezoelectric thin film vibrator,
In order to obtain stable piezoelectric characteristics, the piezoelectric thin film is at least selected from the group consisting of zinc oxide, aluminum nitride, lead titanate, lead zirconate titanate, barium titanate, lithium niobate and lithium tantalate. 1
Preferably, it is formed to include two piezoelectric materials.

Further, in the piezoelectric thin film vibrator, the first dielectric thin film may be formed of magnesium oxide, aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide,
It is preferable that the insulating layer is formed to include at least one dielectric selected from the group consisting of titanium oxide and niobium oxide.

In the piezoelectric thin-film vibrator, the first dielectric thin film is formed on the upper surface of the piezoelectric thin film so that the first dielectric thin film has a function as a mask when the piezoelectric thin film is etched. Preferably, it is formed on almost the entire surface.

In the present invention, the piezoelectric thin-film vibrator may be provided on a substrate via an insulating film, and an opening may be formed on the substrate directly below the piezoelectric thin-film vibrator.

Further, in the piezoelectric thin-film vibrator, first and second pad electrodes are formed on the substrate located outside the opening with the insulating film interposed therebetween. The second pad electrode is connected to the lower electrode of the pair of excitation electrodes, and the second pad electrode is connected to the upper electrode or the capacitance forming electrode of the pair of excitation electrodes. You may do so.

In the piezoelectric thin-film vibrator, the second
It is preferable that the pad electrode and the electrode located above the pair of excitation electrodes or the capacitance forming electrode be connected by a conductive bridge.

According to another aspect of the present invention, there is provided a piezoelectric thin film vibrator comprising a pair of excitation electrodes and a piezoelectric thin film, wherein at least one of the pair of excitation electrodes is provided. The capacitor is formed by forming a capacitor forming electrode on the electrode via a dielectric thin film, and the resonance frequency can be adjusted using the capacitor.

[0016]

Embodiments of the present invention will be described below. Embodiment 1 FIG. The piezoelectric thin film element according to the first embodiment is an element in which a vibrating portion is formed on a substrate having an opening 21 via an insulating film 2, and the vibrating portion is, as shown in FIG.
Two types of layers, a piezoelectric thin film 13 and a dielectric thin film 14, are provided between the lower electrode 16 and the upper electrode 15.
(Exciting electrode) and the lower electrode 16 (exciting electrode) are vibrated by the piezoelectric thin film 13 and the dielectric thin film 1.
4 is resonated at a frequency corresponding to the total thickness. In the first embodiment, the vibrating part is provided on the insulating film 2 (a part that can vibrate freely) located immediately above the opening 21.

In the piezoelectric thin film element of the first embodiment configured as described above, sound waves propagate in the composite layer of the piezoelectric thin film 13 and the dielectric thin film 14 in the thickness direction, and resonate in the thickness direction. Cause Therefore, the resonance frequency of the piezoelectric thin film element according to the first embodiment is mainly determined by the piezoelectric constant of the piezoelectric thin film 13 and the total thickness of the thickness of the piezoelectric thin film 13 and the thickness of the dielectric thin film 14. The first embodiment
As the material of the piezoelectric thin film 13, a lead-based piezoelectric material represented by zinc oxide, aluminum nitride, lead titanate or lead zirconate titanate, barium titanate and its modified material, lithium niobate, lithium tantalate, etc. It is preferable to use a composite oxide of an alkali metal and niobium or tantalum, and by using these materials, relatively stable piezoelectric characteristics can be obtained.

By forming the piezoelectric thin film 13 using the above-described piezoelectric material, the piezoelectric constant of the piezoelectric thin film 13 can be managed with relatively high accuracy, so that the thickness of the piezoelectric thin film 13 and the thickness of the dielectric thin film 14 are reduced. By accurately managing the total thickness of the components within a certain range, the accuracy of the resonance frequency can be expected to be improved. Therefore, in the piezoelectric thin film element of the first embodiment, it is preferable that the dielectric thin film 14 can form the film thickness more accurately than the piezoelectric thin film 13.

In the piezoelectric thin film element of the first embodiment, since the sound wave propagates in the thickness direction in the composite layer of the piezoelectric thin film 13 and the dielectric thin film 14, the dielectric thin film 14 It is preferable to use a material having an acoustic impedance relatively close to However, as for the acoustic impedance, it is sufficient that the density is not remarkable. If it is a compound-based film, especially an oxide-based film, it can be used with almost no problem in terms of impedance. Regarding the crystal structure, the crystal structure of the piezoelectric thin film 13 and the crystal structure of the dielectric thin film 14 do not need to be the same or similar. Further, needless to say, the dielectric thin film 14 is required to have high insulation properties. In this specification, the term “dielectric thin film” or “dielectric film” means a film made of an insulating material having no piezoelectricity.

The dielectric constant of the dielectric thin film 14 is not particularly limited when it is electrically connected in parallel with the piezoelectric thin film.
When they are connected in series as in the first embodiment, it is sufficient that the circuit has sufficient voltage application capability and that a sufficient voltage can be applied to the piezoelectric thin film 13. However, it is preferable that the capacitance of the dielectric thin film 14 is set to be equal to or less than the capacitance of the piezoelectric thin film 13. Materials satisfying the requirements described above and suitable for the dielectric thin film 14 include magnesium oxide, aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride,
Tantalum oxide, titanium oxide, niobium oxide, and the like can be given.

As described above, the piezoelectric thin film vibrator according to the first embodiment uses the dielectric thin film 14 having a good thickness controllability to combine the piezoelectric thin film 13 with the dielectric thin film 14. Since the thickness can be formed with high accuracy, resonance can be performed at a frequency closer to a predetermined frequency.

Next, a procedure for manufacturing the piezoelectric thin film element of the first embodiment will be described. First, for example, if the main surface is (1
A plasma CVD (Chemical v) process using silane and oxygen as reaction gases at a film forming temperature of 300 ° C. is performed on a GaAs substrate 1 formed to have a (00) plane.
a film thickness of about 2 by an apour deposition method.
A 00 nm silicon dioxide film (insulating film 2) is formed.
Next, on the insulating film 2, a titanium film having a thickness of 30 nm,
A lower electrode having a two-layer structure composed of a platinum film having a thickness of 0 nm is formed by an evaporation method. The lower electrode is patterned as described below, and the lower electrode 16, the pad electrode 17,
It becomes 18. Next, using a target made of lead titanate with an excess of 20 mol% of lead on a lower electrode, a titanium film was formed by sputtering at a film forming pressure of 1 Pa and a substrate temperature of 600 ° C. in a mixed gas of argon gas and oxygen gas. A piezoelectric thin film made of lead oxide is formed to a thickness of 0.95 μm.

Next, a dielectric thin film made of a silicon dioxide thin film is formed on the piezoelectric thin film by the same plasma CVD as described above so as to have a thickness of 0.05 μm (that is, the total thickness of the dielectric thin film and the piezoelectric thin film 13 is reduced to 0.05 μm). 1 μm). Next, an electrode having the same two-layer structure as the lower electrode is formed on the dielectric thin film made of the silicon dioxide film, and then the upper electrode 15 having a predetermined shape is formed by using a lift-off method. Here, although not shown, the upper electrode 15 has a two-layer structure of a titanium film and a platinum film. Thereafter, the dielectric thin film made of a silicon dioxide film is wet-etched with a resist using a 1% hydrofluoric acid aqueous solution to form an upper electrode 1.
The dielectric thin film 14 is formed by performing patterning to have the same shape as 5. Further, unnecessary portions of the piezoelectric thin film were removed by etching with a resist mask and a mixed solution of hydrochloric acid and nitric acid at 70 ° C.
A 100 μm square piezoelectric thin film 15 is formed.

Next, the lower electrode is patterned by ion milling to form a square lower electrode 16 of 250 μm × 150 μm. At this time, a pad electrode 17 for connecting to the upper electrode 15 is formed separately from the lower electrode 16 on the substrate 1 outside the piezoelectric thin film 13 at the same time, and the pad electrode 18 connected to the lower electrode 16 and the connection electrode 19 is formed. To form The pad electrode 17 is made of the titanium film 3
a and the platinum film 4a, and the pad electrode 18 is composed of the titanium film 3b and the platinum film 4b. Then, the upper electrode 15 and the pad electrode 17 are connected by forming a bridge 20. Here, the bridge 20 is a bridge 20 on the upper electrode 15.
After the resist is formed except for the connection portion with the bridge 20 on the pad electrode 17, the gold plating film is
It is formed by forming a μm and then removing the resist.

Finally, the substrate is polished to a thickness of about 100 μm, thinned, and then the opening 21 is formed by etching from the back surface of the substrate. As described above, the piezoelectric thin film element of Embodiment 1 can be manufactured. In the piezoelectric thin film element manufactured as described above, the piezoelectric thin film 13
Is 0.95 μm, and the resonance frequency of the element in which the thickness of the dielectric thin film 14 is 0.047 μm is 1.74 G
Hz. Furthermore, when ten different elements on a wafer were manufactured and evaluated by the same process, the resonance frequency of each element was in the range of 1.71 to 1.78 GHz, and the standard deviation of the resonance frequency was ± 0.03 GHz. there were.

The present inventors fabricated a device shown in FIG. 2 as a comparative example and compared it with a device fabricated based on the first embodiment. The piezoelectric thin film element of the comparative example of FIG. 2 is configured in the same manner as the first embodiment except that the dielectric thin film 14 is removed from the piezoelectric thin film element of the first embodiment of FIG. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. When ten piezoelectric thin film elements of this comparative example were manufactured and their resonance frequencies were measured, resonance was observed in the range of 1.60 (minimum) to 1.81 (maximum) GHz, and the variation of the resonance frequency was reduced. The standard deviation represented was ± 0.08 GHz. The piezoelectric thin film 13
Is 0.96 to 1.05 with respect to the target value of 1 μm.
It varied in the range of μm. From the above results, it is understood that the variation in the resonance frequency can be reduced by forming the dielectric thin film 14 as described in the first embodiment.

Embodiment 2 FIG. Next, a piezoelectric thin film element according to a second embodiment of the present invention will be described. As shown in FIG. 3, the piezoelectric thin film element according to the second embodiment has a structure similar to that of the first embodiment.
The piezoelectric thin film element of the above embodiment is further characterized in that a capacitance forming electrode 23 is formed on the upper electrode 15 with a dielectric thin film 22 interposed therebetween, and the other configuration is the same as that of the first embodiment. That is, in the piezoelectric thin film element of the second embodiment, after forming up to the upper electrode 15 in the same manner as in the first embodiment, a 0.1 μm thick silicon dioxide thin film 22 (dielectric thin film) is formed on the upper electrode 15 by plasma CVD. 22) is formed, and 100 μm × 100 μm is formed on the silicon dioxide film 22.
The corner capacitance forming electrode 23 was formed by vapor deposition and lift-off. Thereafter, as in the first embodiment, unnecessary portions of the piezoelectric thin film are removed by etching, patterning of the thin film for the lower electrode, the lower thin film electrode, the lower electrode pad, and the bridge are formed. Further, the opening 21 is formed. A piezoelectric thin film element was formed.

By manufacturing as described above, a capacitance constituted by the upper electrode 15, the silicon dioxide film 22, and the capacitance forming electrode 23 is formed on the piezoelectric thin film 13 in series with the piezoelectric vibrator. And its capacitance value was 4 pF. In addition, the resonance frequency of the piezoelectric thin film element manufactured as described above was 1.6 GHz.

In the piezoelectric thin-film vibrator manufactured as described above, the capacitance formed by the upper electrode 15, the silicon dioxide film 22, and the capacitance forming electrode 23 formed on the piezoelectric thin film 13 is adjusted by the frequency adjustment. (Capacitance element) for use. In the above example, the capacitor for frequency adjustment is formed using the silicon dioxide film 22, but the present invention is not limited to this, and another dielectric thin film may be used.

That is, in the piezoelectric thin film element of the second embodiment, the resonance frequency is changed within a range of several percent by changing the capacitance formed in series with the piezoelectric vibrator in the piezoelectric thin film element. That is, the capacitor for frequency adjustment is formed integrally with the element. The capacitance of the frequency adjustment capacitor can be changed by partially removing the capacitance forming electrode 23 on the dielectric thin film 22 using a laser or the like. Note that the dielectric thin film 22 is
The same material as described above can be applied.

If the capacitance of the capacitor 23 for frequency adjustment is changed by partially removing the electrode 23 for capacitance formation on the dielectric thin film 22, the weight of the electrode 23 for capacitance formation is consequently reduced. The resonance frequency is also changed by the weight change.
Therefore, in the second embodiment, the frequency is adjusted by changing the mass of the capacitance forming electrode 23 and the additional capacitance of the frequency adjusting capacitor. Here, in the configuration of the second embodiment, the mass of the capacitor forming electrode 23 is reduced by shaving the capacitor forming electrode 23, and the additional capacitance of the frequency adjusting capacitor is reduced. Since the frequency is changed (superimposed and changed) in the direction, the frequency adjustment width can be expanded by this step, and the operation time of the frequency adjustment can be shortened.

Embodiment 3 FIG. Hereinafter, a piezoelectric thin film element according to a third embodiment of the present invention will be described. Embodiment 3
Is the upper electrode 15 of the first embodiment.
Same as the first embodiment except that a dielectric thin film 24 formed substantially the same size as the piezoelectric thin film 13 is used instead of the dielectric thin film 14 formed substantially the same size as It is composed of That is, in the same way as in the first embodiment, the thickness-saving hand-held thin film element of the third embodiment has a thickness of 100 μm × 1.
After the formation of the thin film electrode 15 having a size of 00 μm square, the same shape as the piezoelectric thin film 13 in which the silicon dioxide film is finally left is used.
Light etching is performed with a 1% hydrofluoric acid aqueous solution so that the patterning becomes 00 μm × 100 μm. Then, unnecessary portions are removed by etching the piezoelectric thin film with a resist mask using a mixed solution of hydrochloric acid and nitric acid at 70 ° C.
The shape is 200 μm × 100 μm. At this time, the amount of side etching when etching the piezoelectric thin film is reduced by the presence of the silicon dioxide film 24 (dielectric thin film 24). Patterning accuracy can be improved.

Thereafter, patterning of the lower electrode 16, connection between the lower thin film electrode and the lower electrode pad, and the like are performed in the same manner as in the first embodiment. Further, after forming a bridge 20, an opening 21 is formed. The piezoelectric thin film element shown in FIG. 4 was formed. Using a total of ten piezoelectric thin film elements from each of the piezoelectric thin film elements shown in FIG. 4 using ten different wafers and measuring the results, the average resonance frequency was 1.55 GHz.
And the variation was ± 0.04 GHz. That is,
Even with the above configuration, it is possible to provide a piezoelectric thin film element that can reduce manufacturing variations as compared with the comparative example.

In the piezoelectric thin film element according to the third embodiment,
After forming the dielectric thin film 24 to a predetermined size on the piezoelectric thin film, the piezoelectric thin film 1 is formed using the dielectric thin film 24 as a mask.
3 is formed. By doing so, the dielectric thin film 24
Has a better adhesion to the piezoelectric thin film than a resist, so that the amount of side etching of the piezoelectric thin film 13 can be reduced and the piezoelectric thin film can be formed with high accuracy. That is, when the piezoelectric thin film is wet-etched with a strong acid such as hydrochloric acid or nitric acid, when only the resist is used as an etching mask, a phenomenon that the piezoelectric thin film under the mask is etched due to imperfect adhesion is observed. However, in the third embodiment, since the piezoelectric thin film is etched using the dielectric thin film having good adhesion to the piezoelectric thin film, the side etching amount of the piezoelectric thin film can be reduced. Although the dielectric thin film 24 is formed using silicon dioxide in the third embodiment, the present invention is not limited to this, and other dielectric materials can be used.

Embodiment 4 FIG. Embodiment 4 according to the present invention
Is a device utilizing surface acoustic waves, and a piezoelectric film 113 is provided on a substrate 100 via an insulating film 102.
Are formed, and the comb-shaped electrodes 116 a,
116b is formed. Here, in particular, the fourth embodiment
In the piezoelectric thin film element of (1), capacitance forming electrodes 115a and 115b are formed on comb-shaped electrodes 116a and 116b via dielectric thin films 124a and 124b, respectively.
5a and 115b are connected to pad electrodes 117 and 118 via bridges 120a and 120b, respectively. Note that the pad electrodes 117 and 118 are formed of titanium films 103a and 103b and platinum 104a and
4b. That is, in the piezoelectric thin film element according to the fourth embodiment, the comb-shaped electrodes 116a and 116b are respectively connected to the pad electrodes 117 and 118 via the capacitors for frequency adjustment constituted by using the dielectric thin films 124a and 124b.
It is connected to the. Thereby, the electrodes 115a and 11a
The resonance frequency can be adjusted by changing the area of 5b by, for example, shaving using a laser.

In each of the embodiments described above, the electrodes of the vibrating section and the pad electrodes are connected by bridging. Thereby, disconnection at the connection portion can be prevented, and free vibration of the vibrating portion can be secured, so that vibration characteristics can be improved. However, the present invention is not limited to this, and connection may be made using ordinary surface wiring. Further, the material constituting the cross-linking itself may be a material having good conductivity, but can be simply formed by gold plating used in an ordinary microwave IC process or the like.

[0037]

As described in detail above, the piezoelectric thin film vibrator according to the present invention is provided with the first dielectric thin film in addition to the piezoelectric thin film, and has a thickness of the piezoelectric thin film and the first dielectric thin film. Since the resonance is performed at a frequency corresponding to the combined thickness of the thin film, the thickness can be accurately set, and the variation in the resonance frequency can be reduced. As a result, the frequency adjustment range can be reduced, so that the frequency can be adjusted in a short time, and the device can be manufactured at low cost.

In the piezoelectric thin-film vibrator, a capacitance element having a capacitance-forming electrode formed on the excitation electrode via a second dielectric thin film is formed, and the capacitance value of the capacitance element is determined. , The resonance frequency can be adjusted.

Further, in the piezoelectric thin film vibrator, the piezoelectric thin film is selected from the group consisting of zinc oxide, aluminum nitride, lead titanate, lead zirconate titanate, barium titanate, lithium niobate and lithium tantalate. By including at least one piezoelectric material, stable piezoelectric characteristics can be obtained, and the variation in resonance frequency can be further reduced. As a result, the frequency adjustment range can be further reduced, so that the frequency can be adjusted in a shorter time, and the device can be manufactured at lower cost.

Further, in the piezoelectric thin film vibrator, the first dielectric thin film may be made of magnesium oxide, aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide,
By including at least one dielectric selected from the group consisting of titanium oxide and niobium oxide, the total thickness of the piezoelectric thin film and the first dielectric thin film can be accurately controlled, and the resonance frequency can be reduced. Variation can be made extremely small.

In the piezoelectric thin-film vibrator, the first dielectric thin film is formed on almost the entire upper surface of the piezoelectric thin film, so that the first dielectric thin film can be masked when the piezoelectric thin film is etched. , And the shape of the piezoelectric thin film can be accurately formed.

According to the present invention, the piezoelectric thin film vibrator can be easily manufactured by providing the piezoelectric thin film vibrator on a substrate with an insulating film interposed therebetween.

Further, in the piezoelectric thin film vibrator, the first and second pad electrodes are further formed, and the first pad electrode is connected to the lower electrode of the pair of excitation electrodes. And the second pad electrode is connected to the first pad electrode.
By connecting to the upper electrode or the capacitance forming electrode of the pair of excitation electrodes, connection to an external circuit can be facilitated.

Further, in the piezoelectric thin film vibrator, the second
By connecting the pad electrode and the upper electrode of the pair of excitation electrodes or the capacitance forming electrode by conductive bridging, free vibration of the vibrating portion can be secured and stable. Resonance with small loss can be realized.

A piezoelectric thin-film vibrator according to another aspect of the present invention is configured such that a capacitance forming electrode is formed on at least one of the pair of excitation electrodes via a dielectric thin film. Since the capacitance element is formed, the resonance frequency can be easily adjusted using the capacitance element.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a piezoelectric thin film vibrator according to a first embodiment of the present invention, wherein (a) is a plan view,
(B) is a sectional view taken along line AA 'of (a),
(C) is a sectional view taken along line BB 'of (a).

FIGS. 2A and 2B are diagrams showing a configuration of a piezoelectric thin-film vibrator of a comparative example, where FIG. 2A is a plan view and FIG.
It is sectional drawing about C 'line, (c) is D- of (a).
It is sectional drawing about the D 'line.

FIG. 3 is a diagram showing a configuration of a piezoelectric thin film vibrator according to a second embodiment of the present invention, wherein (a) is a plan view,
(B) is a sectional view taken along line CC ′ of (a),
(C) is a sectional view taken along line DD ′ of (a).

FIG. 4 is a diagram showing a configuration of a piezoelectric thin-film vibrator according to a third embodiment of the present invention, wherein (a) is a plan view,
(B) is a sectional view taken along line GG ′ of (a),
(C) is a sectional view taken along line HH 'of (a).

FIG. 5 is a diagram showing a configuration of a piezoelectric thin-film vibrator according to a fourth embodiment of the present invention, wherein (a) is a plan view,
FIG. 2B is a cross-sectional view taken along line II ′ of FIG.

[Explanation of symbols]

1,100 substrate, 2,102 insulating film, 3, 3a, 3
b Titanium film, 4, 4a, 4b Platinum film, 13, 113
Piezoelectric thin film, 14, 22, 24, 124a, 124b
Dielectric thin film, 15 upper electrode, 16 lower electrode, 1
7, 18, 117, 118 Pad electrode, 19 Connection electrode, 20, 120a, 120b Conductive bridge, 21 Opening, 23, 115a, 115b Capacitor forming electrode, 1
16a, 116b Comb electrodes.

Continued on the front page (72) Inventor Hideko Uchikawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (9)

[Claims] 1. A piezoelectric thin-film vibrator having a piezoelectric thin film between a pair of excitation electrodes, further comprising a first dielectric thin film between the pair of excitation electrodes, and a thickness of the piezoelectric thin film. A piezoelectric thin film vibrator characterized by resonating at a frequency corresponding to a thickness obtained by combining the thickness of the first dielectric thin film. 2. The piezoelectric thin-film vibrator according to claim 2, wherein a second one of the pair of excitation electrodes is provided on an excitation electrode located above.
The piezoelectric thin-film vibrator according to claim 1, wherein the capacitance element is formed by forming a capacitance-forming electrode via a dielectric thin film. 3. The piezoelectric thin film according to claim 1, wherein the piezoelectric thin film is at least one piezoelectric material selected from the group consisting of zinc oxide, aluminum nitride, lead titanate, lead zirconate titanate, barium titanate, lithium niobate and lithium tantalate. The piezoelectric thin-film vibrator according to claim 1, wherein the piezoelectric thin-film vibrator is formed including: 4. The method according to claim 1, wherein the first dielectric thin film is made of magnesium oxide, aluminum oxide, silicon oxide, silicon nitride,
The piezoelectric thin-film vibrator according to any one of claims 1 to 3, wherein the piezoelectric thin-film vibrator is formed to include at least one dielectric selected from the group consisting of silicon oxynitride, tantalum oxide, titanium oxide, and niobium oxide. 5. The piezoelectric thin-film vibrator according to claim 1, wherein the first dielectric thin film is formed on substantially the entire upper surface of the piezoelectric thin film. 6. The piezoelectric thin-film vibrator according to claim 1, wherein the piezoelectric thin-film vibrator is provided on a substrate via an insulating film, and an opening is provided on the substrate directly below the piezoelectric thin-film vibrator. A piezoelectric thin film vibrator on which is formed. 7. The piezoelectric thin-film vibrator further includes first and second pad electrodes formed on the substrate located outside the opening with the insulating film interposed therebetween, wherein the first pad electrode is connected to the first pad electrode. The second pad electrode is connected to the lower electrode of the pair of excitation electrodes, and the second pad electrode is connected to the upper electrode or the capacitance forming electrode of the pair of excitation electrodes. The piezoelectric thin-film vibrator according to claim 6. 8. The conductive pad according to claim 7, wherein the second pad electrode and the upper electrode of the pair of excitation electrodes or the capacitance forming electrode are connected by a conductive bridge. Piezoelectric thin film vibrator. 9. A piezoelectric thin-film vibrator comprising a pair of excitation electrodes and a piezoelectric thin film, wherein a capacitance forming electrode is provided on at least one of the pair of excitation electrodes via a dielectric thin film. A piezoelectric thin-film vibrator in which a capacitive element is formed by forming.