JP4784815B2 - High-order mode thin film resonator, piezoelectric thin film, and method for manufacturing piezoelectric thin film - Google Patents

Description

  The present invention relates to a thin film resonator for extracting a signal having a specific frequency from a broadband signal. Such a thin film resonator is used in most communication devices, but is often used particularly in a mobile phone that requires a resonator that can operate at a small size and a high frequency.

  An RF filter for extracting a signal in a specific frequency band is used in a communication device such as a mobile phone or a wireless LAN transmitter / receiver. In an RF filter, a large number of resonators that resonate at a frequency within a used frequency band are usually used. Since the frequency band used in these communication devices is as high as several hundred MHz to several GHz, the resonator needs to cope with such a high frequency.

  In recent years, a thin film resonator called FBAR (Film Bulk Acoustic Resonator) has attracted attention as a resonator capable of realizing a high resonance frequency (see Patent Document 1). The FBAR has a structure in which a piezoelectric thin film is placed on a substrate having a cavity, and a pair of electrodes is provided so as to sandwich the piezoelectric thin film. Here, the cavity is provided in the substrate so that the piezoelectric thin film can freely vibrate without being constrained by the substrate. In FBAR, since the resonance frequency is inversely proportional to the thickness of the piezoelectric thin film, the resonance frequency can be increased as the thickness of the thin film is reduced. In fact, it has been confirmed that a frequency filter using FBAR can obtain good filter characteristics even at a high frequency of several GHz.

  Further, SMR (Solidly Mounted Resonator) is known as another thin film resonator (see Patent Document 2). The SMR has a structure in which an acoustic multilayer film in which high impedance layers and low impedance layers made of materials having different acoustic impedances are alternately stacked is disposed under a resonance part in which a piezoelectric thin film is sandwiched between electrodes. Each of the high-impedance layer and the low-impedance layer has a thickness that is 1/4 times the wavelength of the ultrasonic wave having the same frequency as the resonance frequency of the resonance part. If such a structure is used, the sound wave radiated from the piezoelectric thin film toward the substrate is reflected at the boundary of each acoustic multilayer film, and the reflected waves are in phase with each other and do not cancel each other. Thereby, the vibration of the thin film resonator is prevented from leaking to the substrate, and the loss of vibration energy is prevented. SMR, like FBAR, can obtain a high resonance frequency of several GHz by thinning the piezoelectric thin film.

  In conventional FBAR and SMR, zinc oxide (ZnO) or aluminum nitride (AlN) is often used for piezoelectric thin films. ZnO has the advantage of higher electromechanical conversion efficiency than other piezoelectric materials. On the other hand, AlN has the advantage that the ultrasonic velocity of the ultrasonic wave propagating inside is faster than other piezoelectric bodies and the resonance frequency can be easily increased.

Japanese Patent Laid-Open No. 2001-203558 ([0003] to [0004], FIG. 1) Japanese Unexamined Patent Publication No. 2004-235886 ([0010] to [0011], FIG. 1)

As described above, the resonance frequency of the thin film resonator can be increased by thinning the piezoelectric thin film. However, it is not desirable to make the thin film too thin in order to maintain the physical strength of the thin film. In particular, since FBAR has a structure in which a thin film floats above a cavity, a certain level of thin film strength is required. For this reason, there is a limit to increasing the resonance frequency only by the thickness of the thin film.
The problem to be solved by the present invention is a thin film resonator capable of obtaining a higher resonance frequency than before without thinning the piezoelectric thin film, a piezoelectric thin film used for the thin film resonator, and production of the piezoelectric thin film It is to provide a method .

A method for manufacturing a piezoelectric thin film according to the present invention made to solve the above-described problems is as follows.
A temperature gradient is formed on the substrate in one direction parallel to the surface of the substrate, and particles made of any one of ZnO and AlN are formed on the surface of the substrate obliquely with respect to the substrate surface and in the incident direction. Producing a first piezoelectric layer by causing the projection onto the surface to be incident in the same direction as the temperature gradient;
A temperature gradient is formed on the substrate in a direction different from the direction by 180 °, and particles made of the same material as the material are obliquely incident on the surface of the first piezoelectric layer and incident on the substrate. A step of producing a second piezoelectric layer by causing the projection onto the surface to be incident so that the direction of projection differs by 180 ° from the production of the first piezoelectric layer;
It is characterized by having.
Further, the high-order mode thin film resonator according to the present invention is a thin film resonator in which a piezoelectric thin film made of either ZnO or AlN is provided between upper and lower electrodes.
Piezoelectric thin film is a one produced by the above method, on the [0001] first pressure conductor layer direction is oriented substantially parallel to one direction on the surface of the piezoelectric thin film, the material and thickness is the same as the first piezoelectric layer [0001] direction and the second pressure collector layer oriented in the first piezoelectric layer and 180 ° different directions, characterized in that it is formed directly.

As shown in FIG. 1, both ZnO and AlN have a wurtzite structure represented by the general formula ^{An + Bn-} (n is an integer) and a hexagonal crystal. In the wurtzite structure, layers composed of ^{An +} (layer A) and layers composed of B ^n- (layer B) are alternately stacked, and the layer B is located at a distance from the two layers A above and below the same distance. It is arranged at a position shifted in one direction of the c-axis. That is, the wurtzite structure has polarity in the c-axis direction. In the present application, the direction in which the A layer deviates from the B layer is defined as the [0001] direction.

  The piezoelectric thin film may be formed by alternately laminating a plurality of first piezoelectric layers and second piezoelectric layers. Here, the total number of layers in the piezoelectric thin film including the first piezoelectric layer and the second piezoelectric layer may be an even number or an odd number. For example, when the first piezoelectric layer, the second piezoelectric layer, the first piezoelectric layer, the second piezoelectric layer,... Are stacked in this order from the top, the lowest layer may be the second piezoelectric layer. It may be the first piezoelectric layer.

The thin film resonator of the present invention can be fixed on a substrate having a cavity. As a result, the FBAR can be configured.
Further, in the thin film resonator of the present invention, an acoustic multilayer film in which two types of layers having a thickness of 1/4 of an ultrasonic wave having a resonance frequency of the thin film resonator and having different acoustic impedances are alternately laminated. Can be fixed to one side. Thereby, the SMR can be configured.

Embodiments and effects of the invention

  The thin film resonator according to the present invention includes a piezoelectric thin film and upper and lower electrodes sandwiching the piezoelectric thin film, as in the conventional thin film resonator. The difference from the conventional thin film resonator is that, in the present invention, the piezoelectric thin film has two [0001] directions that are substantially parallel to the surface of the piezoelectric thin film, and the directions are 180 ° different from each other. 1 piezoelectric body layer, 2nd piezoelectric body layer).

  In a conventional thin film resonator, when an AC electric field having the resonance frequency is applied between the electrodes, the piezoelectric thin film vibrates in the opposite direction on the upper surface and the lower surface, and the wavelength is twice the thickness of the piezoelectric thin film. A standing wave (first-order mode standing wave) is formed. On the other hand, in order to form a standing wave having a wavelength equal to the thickness of the piezoelectric thin film (second-order mode standing wave), vibrations must be in phase on the upper and lower surfaces of the piezoelectric thin film. As long as a single piezoelectric thin film was used, even if an AC electric field was applied between the electrodes, such vibration could not be generated in the piezoelectric thin film, and a standing wave of the second mode could not be formed.

  On the other hand, the thin film resonator of the present invention uses a piezoelectric thin film composed of two piezoelectric layers whose [0001] directions differ by 180 °, so that when an alternating electric field having a resonance frequency is applied between the electrodes, Slip vibrations are generated in the first and second piezoelectric layers in opposite directions. Thereby, a standing wave is formed in the thin film by a transverse wave in a propagation direction perpendicular to the surface. At this time, since the upper surface of the first piezoelectric layer and the lower surface of the second piezoelectric layer slide in the same direction, the vibrations have the same phase, so that the formed standing wave becomes a secondary mode.

  In contrast to the conventional thin film resonator, the thin film resonator of the present invention does not vibrate in the opposite direction on the upper surface and the lower surface. ) Can be prevented.

  Thus, in the thin film resonator of the present invention in which a high-order standing wave of the second order mode is formed, the thickness of the piezoelectric thin film remains the same, and the resonance wavelength is half that of the conventional thin film resonator, that is, The resonance frequency can be doubled.

The thin film resonator of the present invention has the following advantageous effects because the [0001] direction is oriented in a direction parallel to the plane of the thin film.
Temporarily, a [0001] direction is oriented in one direction perpendicular to the surface in the first piezoelectric layer, and a thin film resonator having a piezoelectric thin film oriented in a direction different from that in the second piezoelectric layer by 180 ° is manufactured. If possible, the thin film resonator can form a standing wave of a secondary mode in the piezoelectric thin film similarly to the thin film resonator of the present invention. However, in order to produce such a piezoelectric thin film, it is necessary to produce a thin film in which the [0001] direction is oriented in one direction perpendicular to the surface, and then adhere the thin films whose [0001] direction differs by 180 °. There is. In practice, it is difficult to produce such a piezoelectric thin film, and it is not practical.
On the other hand, the piezoelectric thin film used in the thin film resonator of the present invention is a method invented by the present inventor (Japanese Patent Laid-Open No. 2004-244716, Japanese Acoustical Society 2004 Autumn Research Presentation Proceedings II Volume 1169- (See page 1170). According to this method, a temperature gradient is formed in one direction parallel to the surface of the substrate, and a material such as ZnO is deposited on the substrate, so that the [0001] direction is higher from the lower temperature of the substrate. It is possible to produce a thin film oriented so as to face the surface. Therefore, first, by this method, a first piezoelectric layer having a [0001] direction oriented in one direction parallel to the surface is manufactured, and then the direction of the temperature gradient of the substrate is changed by 180 ° to thereby change the first piezoelectric layer. A second piezoelectric layer is fabricated on the substrate. Accordingly, it is possible to easily obtain a piezoelectric thin film in which the [0001] direction is oriented in one direction parallel to the surface in the first piezoelectric layer and in the second piezoelectric layer in a direction different from that by 180 °.
Further, since the transverse wave does not propagate in the air, the vibration energy of the resonator can be prevented from leaking outside.

  In the present invention, the piezoelectric thin film may be formed by alternately laminating a plurality of first piezoelectric layers and second piezoelectric layers. As a result, while the thickness of the piezoelectric thin film is kept the same as that of the prior art, harmonics of the third mode or higher can be formed in the piezoelectric thin film, and the resonance frequency can be further increased.

  The thin film resonator of the present invention can be applied to either FBAR or SMR. Both have the same configuration as the conventional FBAR and SMR, except that two piezoelectric layers having a piezoelectric polarization direction different by 180 ° are used.

  As an embodiment of the thin film resonator according to the present invention, an FBAR 10 using ZnO as a material for a piezoelectric thin film will be described with reference to FIG. The silicon (Si) substrate 11 has a cavity 12 passing through it at the center. A lower electrode 13 is provided on the Si substrate 11, and a piezoelectric thin film 14 in which a first piezoelectric layer 141 made of ZnO and a second piezoelectric layer 142 also made of ZnO are laminated in this order is provided thereon. Then, the upper electrode 15 is provided on the piezoelectric thin film 14. Here, the first piezoelectric layer 141 is oriented in one direction (right direction in FIG. 2) in which the [0001] direction is parallel to the surface, and the second piezoelectric layer 142 is oriented in the first piezoelectric layer 141 in the [0001] direction. It is formed so as to be oriented in a direction (left direction in FIG. 2) different from that of 180 °. In the region 16 sandwiched between the lower electrode 13 and the upper electrode 15, both the thickness of the first piezoelectric layer 141 and the thickness of the second piezoelectric layer 142 are t = 2 μm. In this embodiment, a copper thin film having a thickness of 0.8 μm was used for the lower electrode 13, and a gold thin film having a thickness of 0.2 μm was used for the upper electrode 15.

  FIG. 3 shows the FBAR 20 in which the [0001] direction of ZnO of the piezoelectric thin film is oriented perpendicular to the plane of the thin film. The Si substrate 21, the cavity 22, the lower electrode 23, and the upper electrode 25 are the same as those of the FBAR 10 of this embodiment. The piezoelectric thin film 24 includes a first piezoelectric layer 241 whose [0001] direction is oriented in one direction perpendicular to the plane of the thin film (the lower direction in FIG. 3), and a direction that is 180 ° different from the orientation direction (upper direction in FIG. 3). The second piezoelectric layer 242 oriented in the [0001] direction is stacked.

  FIG. 4 shows an example of a conventional FBAR 30. The Si substrate 31, the cavity 32, the lower electrode 33, and the upper electrode 35 are the same as those of the FBAR 10 of this embodiment. The piezoelectric thin film 34 is made of a ZnO thin film whose c-axis is oriented in a direction perpendicular to the plane of the thin film.

A vibration mode formed in the piezoelectric thin film when an AC voltage is applied between the electrodes will be described with reference to FIG.
First, in the FBAR 30 of the comparative example, when an AC voltage having the same frequency as the resonance frequency of the FBAR is applied between the lower electrode 33 and the upper electrode 35, the upper surface and the lower surface of the piezoelectric thin film 34 are opposite in phase. (Fig. 5 (a)). That is, the vibration of the first mode in which ½ of the vibration wavelength is equal to the thickness of the piezoelectric thin film 34 is generated.
On the other hand, in the FBAR 10 of this embodiment, when an AC voltage having the same frequency as the resonance frequency of the FBAR is applied between the lower electrode 13 and the upper electrode 15, the first piezoelectric layer 141 and the second piezoelectric layer 142 are applied. Slip vibrations occur in opposite directions (FIG. 5 (b)). For example, when the lower surface of the first piezoelectric layer 141 moves to the left side of the drawing, the upper surface of the first piezoelectric layer 141 is on the right side, the lower surface of the second piezoelectric layer 142 is on the right side, and the second piezoelectric layer 142 is The upper surface moves to the left. Therefore, the vibration of the piezoelectric thin film 14 has the same phase on the upper surface and the lower surface of the piezoelectric thin film 14, and the center in the thickness direction (the boundary between the first piezoelectric layer 141 and the second piezoelectric layer 142). In the vicinity, the phase is opposite to that (FIG. 5B). Thereby, the vibration of the secondary mode in which the thickness of the piezoelectric thin film 14 is equal to the wavelength of vibration is generated.
Therefore, if the thickness of the piezoelectric thin film 14 (the sum of the thicknesses of the first piezoelectric layer 141 and the second piezoelectric layer 142) and the thickness of the piezoelectric thin film 34 are made the same, It can be seen that the resonance frequency of the FBAR 10 is twice the resonance frequency of the FBAR 30 of the comparative example.

Next, a manufacturing method of the FBAR 10 of this embodiment will be described with reference to FIG.
First, a mask 41 having a window in a region where the lower electrode 13 is to be formed is formed on the surface of the Si substrate 21, and a lower electrode material is vapor-deposited thereon (a) to produce the lower electrode 13. After removing the mask 41, a magnetron sputtering is performed on the Si substrate 11 and the lower electrode 13 while forming a temperature gradient in a direction parallel to the Si substrate 11 so that the temperature on the left side of the drawing is higher than the temperature on the right side. ZnO particles are sputtered by the above method and are caused to fly from the upper left to the lower right of the figure and enter the surface of the Si substrate 11 (c). As a result, the first piezoelectric layer 141 having the [0001] direction from the left side to the right side in the drawing is formed (d). Such control of the temperature gradient and the incident direction of the ZnO particles will be described later. Next, the Si substrate 11 is rotated by 180 ° about an axis perpendicular to the first piezoelectric layer 141 (one-dot chain line in (e)) (e) (by this, the [0001] direction of the first piezoelectric layer 141) From the right to the left in the figure). Next, on the first piezoelectric layer 141, as in (c), while forming a temperature gradient in the Si substrate 11 so that the temperature on the left side is higher than the temperature on the right side, the upper left side is directed to the lower right side. The ZnO particles are incident on the surface of the first piezoelectric layer 141 (f). As a result, the second piezoelectric layer 142 made of a ZnO thin film having a polarization in a direction different by 180 ° from the ZnO of the first piezoelectric layer 141 is formed (g). At this time, by making the production time of the first piezoelectric layer 141 equal to the production time of the second piezoelectric layer 142, the thicknesses of the first piezoelectric layer 141 and the second piezoelectric layer 142 can be made equal. . Further, a mask 42 provided with a window is formed in a region where the upper electrode 15 is to be formed, and the upper electrode material is vapor-deposited (h) thereon to produce the upper electrode 15. After removing the mask 42 (i), a region near the center of the piezoelectric thin film 14 in the Si substrate 11 is selectively etched to form the cavity 12 (j).

The first piezoelectric layer 141 and the second piezoelectric layer 142 were produced using the magnetron sputtering apparatus 50 shown in FIG. In the magnetron sputtering apparatus 50, a magnetron circuit 52 and a cathode 53 are provided in the lower part of the film forming chamber 51, and an anode 54 is provided in the upper part. Immediately below the anode 54, a substrate base 55 is provided at a position deviated from a line connecting the centers of the cathode 53 and the anode 54 (one-dot chain line in the drawing). The substrate table 55 has a surface inclined with respect to the center line, and by placing the substrate 58 on the surface, the substrate 58 can be disposed inclined with respect to the center line. On the cathode 53, a ZnO target 56 as a raw material for the first piezoelectric layer 141 and the second piezoelectric layer 142 is placed. Further, a gas source 57 of argon (Ar) gas and oxygen (O ₂ ) gas is connected to the film forming chamber 51.

A method for producing the first piezoelectric layer 141 and the second piezoelectric layer 142 using the magnetron sputtering apparatus 50 will be described. A substrate on which the lower electrode 13 shown in FIG. 6B is formed or a substrate on which the first piezoelectric layer 141 shown in FIG. Here, the end face (the left side of FIGS. 6 (c) and 6 (f)) of the substrate 58 where the temperature is desired to be raised is brought to the center (dashed line in FIG. 7) side of the apparatus. When Ar gas and O ₂ gas are introduced into the film forming chamber 51 and high frequency power is supplied to the cathode 53, a magnetic field and an electric field are formed in the film forming chamber 51, whereby the Ar gas and O ₂ gas are ionized. Emits electrons. The electrons move while drawing a toroidal curve by an electric field and a magnetic field, whereby plasma is generated near the ZnO target 56 and ZnO is sputtered from the ZnO target 56. The sputtered ZnO forms a uniaxial flow (raw material flow 59) toward the anode 54 , and deposits on this surface when it reaches the surface of the substrate 58. At this time, by arranging the substrate 58 to be inclined as described above, a temperature gradient is formed in the substrate 58, whereby the [0001] direction is oriented in one direction parallel to the substrate. A second piezoelectric layer 142 is formed.

  As shown in FIG. 8, in the magnetron sputtering apparatus 50, the substrate 58 is movable in a direction parallel to the surface of the substrate table 55, and a mask 61 having windows 62 only in a part of the region is provided on the surface of the substrate 58. May be. In this case, by forming the first piezoelectric layer 141 and the second piezoelectric layer 142 while moving the substrate 58 in the above-described direction, the first piezoelectric layer 141 and the first piezoelectric layer 141 are not provided on the substrate 58 without providing a resist mask or the like. The two piezoelectric layers 142 can be formed only within a predetermined range on the substrate 58. In addition, the thickness and quality of the first piezoelectric layer 141 and the second piezoelectric layer 142 can be made uniform in the plane.

FIG. 9 (a) shows an SMR 70a as another embodiment of the thin film resonator according to the present invention. In the SMR 70a, a first piezoelectric layer 741a and a second piezoelectric layer 742a made of ZnO are provided between a film-like lower electrode 73 and an upper electrode 75, similar to the FBAR 10. Here, the first piezoelectric layer 741a is formed so that the [0001] direction is from the left side to the right side of the drawing, and the second piezoelectric layer 742a is formed so that the [0001] direction is from the right side to the left side of the drawing. . Under the lower electrode 73, an acoustic multilayer film 78a in which a plurality of low acoustic impedance layers 76a made of SiO ₂ and high acoustic impedance layers 77a made of Mo are alternately laminated is provided, and a substrate 79 is provided thereunder. The low acoustic impedance layer 76a and the high acoustic impedance layer 77a are formed to have a thickness of 1/4 of the wavelength when the ultrasonic wave having the same frequency as the resonance frequency of the SMR 70a propagates through each layer. The acoustic multilayer film 78a is the same as the acoustic multilayer film used in the conventional SMR, and can thereby prevent the resonance energy from leaking to the substrate 79 and being lost.

  FIG. 9B shows an SMR 70b in which the [0001] direction of ZnO of the piezoelectric thin film is oriented perpendicular to the surface of the thin film. The SMR 70b basically has the same configuration as the SMR 70a except that the first piezoelectric layer 741b and the second piezoelectric layer 742b are provided as in the FBAR 20.

  10, as a modification of the FBAR and SMR of the present invention, a plurality of first piezoelectric layers 8411, 8412,... And second piezoelectric layers 8421, 8422,. An example is shown. (a) is an FBAR in which the [0001] direction of ZnO is oriented in a direction parallel to the layer, (b) is an SMR in which the [0001] direction is oriented in a direction parallel to the layer, and (c) is a layer in the [0001] direction. FBARs oriented in the direction perpendicular to, and (d) shows SMR oriented in the direction perpendicular to the layer in the [0001] direction. In all cases, the thicknesses of the first piezoelectric layer and the second piezoelectric layer were set to the same values as those of the FBAR 10, SMR 70a, FBAR 20, and SMR 70b in which they were provided one by one. In (b) and (d), the thicknesses of the low acoustic impedance layer 86 and the high acoustic impedance layer 87 are set to the same values as those of the SMR 70a and the SMR 70b. Other than that, the substrate 81, the cavity 82, the upper electrode 83, the lower electrode 85, the acoustic multilayer film 88, and the substrate 89 have the same configuration as the FBAR 10, FBAR 20, SMR 70a, and SMR 70b.

  FIG. 11 shows the results of measuring the admittance characteristics of the manufactured FBAR 20. Here, after the thin film resonator comprising the lower electrode 13, the piezoelectric thin film 14 and the upper electrode 15 is fabricated in the process shown in FIG. 6, the substrate 11 is removed, and the thin film resonator is placed on the substrate having a cavity. And fixed one was used. Resonance was observed when an AC voltage having a frequency of 560 MHz was applied between the lower electrode 13 and the upper electrode 15. From this thickness, it is appropriate to consider that the transverse wave resonance of the secondary mode is generated from the thickness of the first piezoelectric layer 241 and the second piezoelectric layer 242. Note that the resonance (spurious) seen at a frequency of 280 MHz, which is smaller than that at a frequency of 560 MHz, is a transverse wave of a primary mode that was not completely canceled due to the fact that the manufactured lower electrode 13 was relatively thick. It is considered to be resonance. This can be almost eliminated by increasing the manufacturing accuracy.

The crystal structure figure which shows a wurtzite structure. The longitudinal cross-sectional view which shows one Example of FBAR which concerns on this invention. The longitudinal cross-sectional view which shows the example of FBAR with which the [0001] direction of ZnO of the piezoelectric material thin film was orientated in the direction perpendicular | vertical to a surface. The longitudinal cross-sectional view which shows an example of FBAR of a comparative example. The longitudinal cross-sectional view and graph for demonstrating the vibration mode of the piezoelectric material thin film in FBAR of a present Example and a comparative example. The longitudinal cross-sectional view which shows the manufacturing method of FBAR10 of a present Example. [0001] Fig. 3 is a longitudinal sectional view showing an apparatus for producing a ZnO thin film whose [0001] direction is in-plane oriented. The longitudinal cross-sectional view which shows the other example of a ZnO thin film manufacturing apparatus. The longitudinal cross-sectional view which shows the other Example of SMR of this invention. The longitudinal cross-sectional view which shows the other Example of FBAR and SMR of this invention. The graph which shows the measurement result of the admittance characteristic of FBAR10 of a present Example.

Explanation of symbols

10, 20, 30 ... FBAR
11, 21, 31, 81 ... Si substrates 12, 22, 32, 82 ... cavities 13, 23, 33, 73, 83 ... lower electrodes 14, 24, 34 ... piezoelectric thin films 141, 241, 741a, 741b, 8411 ... First piezoelectric layer 142, 242, 742a, 742b, 8421 ... second piezoelectric layer 15, 25, 35, 75, 85 ... upper electrode 41, 42 ... mask 50 ... magnetron sputtering apparatus 51 ... film forming chamber 52 ... magnetron Circuit 53 ... Cathode 54 ... Anode 55 ... Substrate table 56 ... ZnO target 57 ... Gas source 58 ... Substrate 59 ... Raw material flow 61 ... Mask 62 ... Windows 70a, 70b ... SMR
76a, 76b, 86 ... low acoustic impedance layers 77a, 77b, 87 ... high acoustic impedance layers 78a, 78b, 88 ... acoustic multilayer films

Claims (7)

A temperature gradient is formed on the substrate in one direction parallel to the surface of the substrate, and particles made of any one of ZnO and AlN are formed on the surface of the substrate obliquely with respect to the substrate surface and in the incident direction. Producing a first piezoelectric layer by causing the projection onto the surface to be incident in the same direction as the temperature gradient;
A temperature gradient is formed on the substrate in a direction different from the direction by 180 °, and particles made of the same material as the material are obliquely incident on the surface of the first piezoelectric layer and incident on the substrate. A step of producing a second piezoelectric layer by causing the projection onto the surface to be incident so that the direction of projection differs by 180 ° from the production of the first piezoelectric layer;
A method for producing a piezoelectric thin film, comprising: In thin-film resonator comprising providing a piezoelectric thin film made of any one of ZnO and AlN between the upper and lower electrodes,
Be one piezoelectric thin film was prepared by the method of claim 1, on the [0001] first pressure conductor layer direction is oriented substantially parallel to one direction on the surface of the piezoelectric thin film, high, characterized in that the material and thickness are the same as the first piezoelectric layer [0001] second pressure collector layer direction is oriented in the first piezoelectric layer and 180 ° different directions are formed directly Next mode thin film resonator.   3. The high-order mode thin film resonator according to claim 2, wherein the piezoelectric thin film is formed by alternately laminating a plurality of first piezoelectric layers and second piezoelectric layers.   4. The high-order mode thin film resonator according to claim 2, wherein the high-order mode thin film resonator is fixed on a substrate having a cavity.   An acoustic multi-layer film composed of two layers with different acoustic impedance and a thickness of 1/4 of the ultrasonic wave having the same frequency as the resonance frequency of the thin film resonator is fixed to one surface. The high-order mode thin film resonator according to claim 2 or 3, wherein Ri consists either ZnO and AlN, a piezoelectric thin film manufactured by the method of claim 1, [0001] first pressure direction is oriented substantially parallel to one direction on the surface of the piezoelectric thin film on the collector layer, the material and thickness are the same as the first piezoelectric layer [0001] direction and the second pressure collector layer oriented in the first piezoelectric layer and 180 ° different directions is formed directly A piezoelectric thin film characterized by comprising:   7. The piezoelectric thin film according to claim 6, wherein a plurality of first piezoelectric layers and second piezoelectric layers are alternately laminated.

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