JP4003491B2 - Method and apparatus for adjusting frequency characteristics of piezoelectric element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a frequency characteristic adjusting method and apparatus for a piezoelectric element, and more particularly to a technique for adjusting a frequency characteristic while etching a piezoelectric element.
[0002]
[Prior art]
In general, a piezoelectric element using a piezoelectric material such as a crystal is used in a circuit for generating a reference signal such as a clock, an oscillation circuit, a signal filter, or the like. In particular, surface acoustic wave elements have come to be used with higher signal frequencies. For such a piezoelectric element such as a surface acoustic wave element, it is desired to make the frequency characteristics such as the resonance frequency highly accurate and stable. However, since the frequency characteristics of the individual elements vary due to variations in the manufacturing process of the piezoelectric elements, it is necessary to adjust the frequency characteristics of the individual piezoelectric elements to achieve high accuracy and stability.
[0003]
As described above, the methods described in JP-A-7-30355, JP-A-9-55636, JP-A-11-308065, and the like have been used as methods for increasing the accuracy or stabilizing the frequency characteristics of the piezoelectric element. Can be mentioned.
[0004]
Japanese Patent Application Laid-Open No. 7-30355 describes a method of adjusting the frequency characteristics of a piezoelectric element by generating a local plasma between the piezoelectric element and the discharge electrode and etching the surface of the piezoelectric element. .
[0005]
In JP-A-9-55636, a surface acoustic wave element is transferred to an etching position, and the surface acoustic wave element is irradiated with plasma to measure the frequency characteristics of the surface acoustic wave element. A method is described in which etching is carried out until the desired frequency reaches a desired value, and then carried out.
[0006]
Japanese Patent Application Laid-Open No. 11-308065 describes a method in which etching is stopped by spraying a reactive gas on a quartz oscillator under atmospheric pressure while monitoring the oscillation frequency, and the etching is stopped when the oscillation frequency reaches a reference value.
[0007]
[Problems to be solved by the invention]
However, with the recent increase in the frequency of piezoelectric elements, there is an increasing demand for higher accuracy and stabilization of frequency characteristics, and when adjusting the frequency by the above method, the adjustment is performed efficiently. If processing is to be performed, it is necessary to increase the etching rate, so that sufficient accuracy and reproducibility of the frequency characteristics cannot be obtained, and in order to obtain sufficient accuracy and reproducibility of the frequency characteristics, Since it is necessary to perform the processing under a condition with a low etching rate, there is a problem that the processing efficiency is lowered due to the time and effort.
[0008]
Therefore, the present invention solves the above problems, and the problem is that when adjusting the frequency of a piezoelectric element such as a surface acoustic wave element, sufficient accuracy and reproducibility of frequency characteristics can be ensured. At the same time, it is an object of the present invention to provide a novel method capable of increasing the processing efficiency and an apparatus that can be used for the method.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the frequency characteristic adjustment method for a piezoelectric element according to the present invention is a frequency adjustment method for a piezoelectric element in which the frequency characteristic is adjusted by etching the piezoelectric element, and the frequency characteristic of the piezoelectric element is predetermined. A rough adjustment step in which etching is performed until a state is reached and a fine adjustment step in which the piezoelectric element is etched at a lower speed than the rough adjustment step are continuously performed.
[0010]
According to the present invention, the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the processing efficiency are achieved by continuously performing the fine adjustment step of performing the etching at a low speed after the rough adjustment step of performing the etching at a high speed. Frequency adjustment can be performed quickly and easily.
[0011]
According to another aspect of the invention, there is provided a method for adjusting a frequency characteristic of a piezoelectric element, wherein the frequency characteristic is adjusted by etching the piezoelectric element so that the frequency characteristic of the piezoelectric element is in a predetermined state. The coarse adjustment step for performing the etching until the fine adjustment step for etching the piezoelectric element at a lower speed than the rough adjustment step is sequentially performed by the same processing means.
[0012]
According to the present invention, it is not necessary to perform both steps using different processing means by sequentially performing the fine adjustment step for performing etching at a low speed by the same processing means after the rough adjustment step for performing etching at a high speed. In addition, it is possible to achieve both the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the processing efficiency, and it is possible to adjust the frequency quickly and easily.
[0013]
In the present invention, the coarse adjustment step and the fine adjustment step are performed while measuring the frequency characteristics of the piezoelectric element, and the coarse adjustment step shifts to the fine adjustment step when a measured value reaches a predetermined value. In the fine adjustment step, it is preferable to stop the etching when the measured value reaches a target value.
[0014]
According to the present invention, while measuring the frequency characteristics of the piezoelectric element, the coarse adjustment step shifts to the fine adjustment step when the measurement value reaches a predetermined value, and the fine adjustment step causes the measurement value to reach the target value. Since the etching is stopped, the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the processing efficiency can be achieved at a higher level.
[0015]
In the present invention, the etching of the piezoelectric element is preferably performed by bringing plasma generated by a discharge electrode into contact with the piezoelectric element.
[0016]
According to the present invention, the frequency characteristics can be adjusted with higher accuracy by etching the piezoelectric element with plasma in the present invention.
[0017]
In the present invention, the distance between the discharge electrode and the piezoelectric element for generating the plasma is such that the etching rate is in the vicinity of the maximum value in the coarse adjustment step, and the stable region in which the extreme value of the etching rate is avoided in the fine adjustment step. It is preferable to select such that
[0018]
According to the present invention, the etching rate in the coarse adjustment step can be increased, the control rate can be improved by reducing the etching rate in the fine adjustment step, and the etching rate itself can be stabilized. Therefore, it is possible to improve both the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the improvement of the processing efficiency.
[0019]
In each of the above inventions, it is desirable that the coarse adjustment step and the fine adjustment step are continuously performed by changing only the etching conditions using the same etching apparatus. This makes it possible to reduce the complexity and processing time of processing operations compared to the case where processing is performed sequentially with different devices or processing is performed by changing the etching means, and the increase in size and equipment cost of the device is suppressed. Is possible.
[0020]
Next, the piezoelectric element frequency characteristic adjusting apparatus according to the present invention is a piezoelectric element frequency characteristic adjusting apparatus that adjusts the frequency characteristic by etching the piezoelectric element, the etching means for etching the piezoelectric element, Etching adjusting means for adjusting the etching intensity of the etching means, and a rough adjustment step for controlling the etching adjusting means to etch the piezoelectric element until the frequency characteristic reaches a predetermined state, and thereafter, adjusting the piezoelectric element. And a control unit that sequentially performs a fine adjustment step of performing etching at a lower speed than the rough adjustment step.
[0021]
According to the present invention, by performing the fine adjustment step of performing the etching at a low speed after the rough adjustment step of performing the etching at a high speed, the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the processing efficiency can be achieved. It is possible to achieve both. Particularly, since the rough adjustment step and the fine adjustment step are sequentially performed by controlling the etching adjustment means by the control means, the rough adjustment step and the fine adjustment step are performed by different apparatuses or separately. This eliminates the need for the etching means, so that complicated work is not necessary, and the apparatus can be downsized and the equipment cost can be reduced.
[0022]
In the present invention, there is provided frequency measuring means for measuring the frequency characteristics of the piezoelectric element, and the control means shifts to the fine adjustment step when the measured value reaches a predetermined value in the coarse adjustment step, and the fine adjustment step. In the adjustment step, it is preferable to perform control so that the etching is stopped when the measured value reaches the target value.
[0023]
According to the present invention, while measuring the frequency characteristics of the piezoelectric element, the coarse adjustment step shifts to the fine adjustment step when the measurement value reaches a predetermined value, and the fine adjustment step causes the measurement value to reach the target value. Since the etching is stopped, the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the processing efficiency can be achieved at a higher level.
[0024]
In the present invention, the etching means preferably has a discharge electrode for generating plasma, and the piezoelectric element is etched by the plasma.
[0025]
In the present invention, it is preferable that the etching means has a discharge electrode for generating plasma, and the discharge electrode is made of a metal whose main component is aluminum.
[0026]
In the present invention, the distance between the discharge electrode and the piezoelectric element for generating the plasma is such that the etching rate is in the vicinity of the maximum value in the coarse adjustment step, and the stable region in which the extreme value of the etching rate is avoided in the fine adjustment step. It is preferable to select such that
[0027]
According to the present invention, the etching rate in the coarse adjustment step can be increased, the control rate can be improved by reducing the etching rate in the fine adjustment step, and the etching rate itself can be stabilized. Therefore, it is possible to improve both the accuracy and reproducibility of the frequency characteristics of the piezoelectric element and the improvement of the processing efficiency.
[0028]
Next, the piezoelectric element of the present invention has been subjected to frequency adjustment by any one of the frequency adjustment methods described above.
[0029]
The surface acoustic wave device of the present invention has been subjected to frequency adjustment by any one of the frequency adjustment methods described above.
[0030]
Furthermore, the piezoelectric element of the present invention has been subjected to frequency adjustment by any one of the frequency adjusting devices described above.
[0031]
Further, the surface acoustic wave device of the present invention has been subjected to frequency adjustment by any one of the frequency adjusting devices described above.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of a method and apparatus for adjusting frequency characteristics of a piezoelectric element according to the present invention will be described in detail with reference to the accompanying drawings.
[0033]
FIG. 1 is a schematic configuration diagram showing the overall configuration of a frequency characteristic adjusting apparatus for a piezoelectric element according to the present invention. The apparatus 10 includes a chamber 11, a discharge electrode 12, and a discharge electrode 14 disposed so as to face the discharge electrode 12. AC power supplied from the power supply circuit 18 is supplied between the discharge electrode 12 and the discharge electrode 14 via the matching box 19. The insulating material 13 insulates between the discharge electrodes 12 and 14. The discharge electrode 14 is connected to a circuit through the chamber 11. The discharge electrode 14 is provided with an opening 14a.
[0034]
The discharge electrodes 12, 14 are preferably made of aluminum. Aluminum is difficult to be etched with a fluorinated gas or the like, which will be described later, and it is possible to prevent defective characteristics such as frequency shift from occurring in the piezoelectric element after etching. For example, when a stainless steel material is used, Ni, Cr or the like adheres to the piezoelectric element by sputtering, which causes a frequency shift that occurs after processing.
[0035]
A support member 15 disposed in the chamber 11 is disposed opposite to the opening 14 a of the discharge electrode 14. A piezoelectric element 21 such as a surface acoustic wave element is disposed on the support member 15, and probes 15a and 15b are provided in conductive contact with the piezoelectric element 21, and these probes 15a and 15b are configured by a network analyzer or the like. It is connected to the detection device 17. For example, when a pair of electrodes (for example, aluminum electrodes) is formed on the piezoelectric element 21, the probes 15a and 15b are brought into contact with the pair of electrodes. As a result, the frequency characteristic of the piezoelectric element 21 can be measured by the detection device 17.
[0036]
A drive mechanism 15 c that can move the support member 15 in the chamber 11 is provided. By this drive mechanism 15 c, the distance between the discharge electrode 14 and the piezoelectric element disposed on the support member 15 can be adjusted.
[0037]
Furthermore, a mask 15d is disposed on the discharge electrodes 12 and 14 side of the piezoelectric element 21 as necessary. The mask 15d may also serve as a work presser that presses the piezoelectric element 21.
[0038]
The detection device 17 is connected to the control device 20. In the present embodiment, the detection device 17 measures the frequency characteristic of the piezoelectric element 21 disposed on the support member 15 and outputs detection data corresponding to the characteristic frequency (for example, the resonance frequency) of this frequency characteristic. It is configured as follows. The frequency characteristic is not limited to the above characteristic frequency, and may be various parameters that depend on the frequency characteristic, for example, a half width of a frequency peak, a dispersion value, an integral value, a temperature coefficient, and the like.
[0039]
The control device 20 is configured to receive the detection data from the detection device 17 and control the power supply circuit 18 in accordance with the relationship between the detection data and a set value set inside. More specifically, when the characteristic frequency represented by the detection data reaches a predetermined value Fs, a switching control signal is output, and the power supply circuit 18 is controlled to control the discharge electrode 12 in the chamber 11. 14 outputs a switching control signal for switching the discharge state between the two. Further, when the characteristic frequency reaches the target value Fx, a stop control signal is output, and the power supply circuit 18 is controlled to stop the discharge between the discharge electrodes 12 and 14 in the chamber 11.
[0040]
A shutter device 16 is disposed between the discharge electrodes 12 and 14. The shutter device 16 includes a shutter plate 16a configured to be movable, and the discharge is stopped by extending the shutter plate 16a between the discharge electrodes 12 and 14 so that the plasma can be extinguished. It is configured.
[0041]
Further, the chamber 11 contains a reactive gas having reactivity with the piezoelectric element 21 from the gas supply device 22, for example, halogen such as CF ₄ , C ₂ F ₆ , HF, F ₂ , and COF ₂ (halogen). Various gases (comprised of compounds) are mixed with other oxygen or inert gas as necessary. Further, an exhaust device 23 is connected to the chamber 11, and the inside of the chamber 11 is maintained at a predetermined pressure during processing.
[0042]
FIG. 2 is a graph showing a process of etching the piezoelectric element 21 using the apparatus 10 described above. Here, the vertical axis represents the resonance frequency (oscillation frequency) of the piezoelectric element 21, and the horizontal axis represents time. First, the piezoelectric element 21 is disposed on the support member 15 in the chamber 11, and the reaction gas is introduced from the gas supply device 22 while maintaining the pressure in the chamber 11 at a predetermined pressure by the exhaust device 23. The pressure in the chamber 11 is, for example, 0.1 to 400 [Pa], preferably 1 to 100 [Pa]. This pressure is set according to the type and composition of the reaction gas, the type of the piezoelectric element 21 and the like. Then, a high frequency voltage is supplied between the discharge electrodes 12 and 14, and the shutter plate 16a is opened and discharged to generate plasma. Plasma is irradiated to the piezoelectric element 21 from the opening 14a of the discharge electrode 14, and etching is started. The discharge frequency is also appropriate, for example 13.56 MHz.
[0043]
At the beginning of the etching process, the rough adjustment step is executed under the condition that the etching rate is relatively high. In the coarse adjustment step Ts1, the power supplied from the power supply circuit 18 to the discharge electrodes 12 and 14 is increased, for example, 200 W. The etching rate in this rough adjustment step is, for example, 300 to 400 [ppm / sec].
[0044]
During the etching, the detection device 17 performs sampling every 0.05 [sec], for example, measures the characteristic frequency of the piezoelectric element 21, for example, the resonance frequency, and sends output data to the control device 20. The detection device 17 can be constituted by a network analyzer or the like. When this characteristic frequency reaches the predetermined value Fs, the coarse adjustment step Ts1 ends, and the control device 20 sends a switching control signal to the power supply circuit 18 to reduce the power supplied from the power supply circuit 18. For example, the power supplied from the power supply circuit 18 is switched from 200W to 80W. Then, the process proceeds to a fine adjustment step Ts2 in which etching is performed at a smaller etching rate than the above rough adjustment step. In general, however, since there is a switching time Td necessary for switching the power when shifting from the coarse adjustment step Ts1 to the fine adjustment step Ts2, the period Tx1 during which etching is performed at the original high etching rate of the coarse adjustment step Ts1. Is continued until a time point delayed by the switching time Td from the coarse adjustment step Ts1, and thereafter, the etching is performed at the original low etching rate of the fine adjustment step Ts2 during a period Tx2 delayed by the switching time Td.
[0045]
In the transition from the coarse adjustment step Ts1 to the fine adjustment step Ts2, the shutter plate 16a is temporarily extended, and the power is switched in a state where the plasma between the discharge electrodes 12 and 14 is extinguished. The shutter plate 16a may be opened after the switching is completed. Thus, the etching is temporarily stopped at the end of the rough adjustment step Ts1, and then the fine adjustment step Ts2 is started at a low etching rate. In this case, it is possible to prevent the occurrence of problems due to plasma instability during the switching period.
[0046]
The etching rate in the fine adjustment step is significantly lower than that in the coarse adjustment step, and becomes, for example, 80 to 100 [ppm / sec]. Then, when the characteristic frequency reaches the target value Fx, the shutter plate 16a is extended and the etching is stopped. This etching can be stopped by interrupting the power supply, for example, by extending the shutter plate 16a to shut off the discharge electrodes 12 and 14.
[0047]
In the present embodiment, as described above, after performing the coarse adjustment step with a high etching rate, the fine adjustment step with a low etching rate is performed, so that the characteristic frequency of the piezoelectric element is increased without reducing the processing efficiency. Accuracy and stability can be achieved. Further, the coarse adjustment and fine adjustment of the frequency characteristics of the piezoelectric element can be continuously performed by only one etching means, that is, the plasma generation means by the discharge electrodes 12 and 14 (that is, the coarse adjustment step and the fine adjustment step). Can be performed sequentially by the same processing means), so there is no need for complicated operations such as transferring the piezoelectric element to another device or moving the piezoelectric element in the vicinity of another discharge electrode in the device. In addition, an increase in equipment cost due to an increase in the size of the apparatus 10 by providing a plurality of sets of discharge electrodes and the necessity of a plurality of apparatuses (for example, a coarse adjustment apparatus and a fine adjustment apparatus) is avoided. be able to.
[0048]
In the present embodiment, the gap G (see FIG. 1) between the discharge electrode 14 and the piezoelectric element 21 can be adjusted by the drive mechanism 15c. The interval G is an important parameter that determines the action of plasma on the piezoelectric element 12. Since the power to be supplied is different, the plasma generation state is different between the coarse adjustment step and the fine adjustment step. Therefore, the dependency on the etching rate interval G is also different between the coarse adjustment step and the fine adjustment step. Different.
[0049]
In this case, since the etching efficiency is most important in the coarse adjustment step, the etching process can be efficiently performed by setting the interval G to an interval at which the maximum value of the etching rate can be obtained. On the other hand, since the controllability of etching is the most important in the fine adjustment step, the interval G is shifted from the interval at which the maximum value of the etching rate is obtained. The inclination angle of the graph showing the dependence on the interval G) is small, and it is preferable to set the value so that more stable etching is performed.
[0050]
By the way, as described above, since the plasma generation state is different between the coarse adjustment step and the fine adjustment step, the dependency of the etching rate on the interval G is also different from each other. Therefore, the interval at which the maximum value of the etching rate in the coarse adjustment step is obtained and the interval at which the maximum value of the etching rate in the fine adjustment step are usually different from each other.
[0051]
In the present embodiment, in view of the above situation, the interval G is an interval at which the maximum value of the etching rate is obtained in the coarse adjustment step, and is more than the maximum value of the etching rate in the fine adjustment step. The interval is set so that the etching rate is stable. As a result, a larger etching rate can be obtained in the coarse adjustment step, so that the processing efficiency can be further increased.On the other hand, in the fine adjustment step, the etching rate can be reduced and the controllability of the etching amount can be improved. Variation in the etching rate due to instability of the film can be suppressed.
[0052]
In the case of setting the interval G, for example, the dependency between the etching rate measured in advance in the etching conditions of the coarse adjustment step and the interval G, and the etching rate and interval measured in advance in the etching conditions of the fine adjustment step. The dependence between G and G is measured experimentally, and the relationship as described above, that is, the interval at which the maximum value of the etching rate is obtained in the coarse adjustment step and the etching in the fine adjustment step. What is necessary is just to obtain | require the value which satisfy | fills both that it exists in the area | region where the etching rate stabilized more, and it remove | deviated from the maximum value of a rate, and adjusts so that the space | interval G may be matched with this value using the said drive mechanism 15c. In the present embodiment, the gap G is set within a range of 2 to 6 mm.
[0053]
In the present invention, it is possible to continuously perform the coarse adjustment step and the fine adjustment step when adjusting the frequency characteristics by etching the piezoelectric element, or the coarse adjustment step and the fine adjustment step are the same process. Since it can be performed sequentially by means, it is possible to make a quick adjustment, and it is not necessary to set up to perform processing with another processing apparatus or another processing electrode, and without complicating the apparatus configuration, In addition, the conveyance work of the piezoelectric element can be made unnecessary.
[0054]
The method and apparatus for adjusting the frequency of the piezoelectric element of the present invention are not limited to the illustrated examples described above, and it is needless to say that various changes can be made without departing from the scope of the present invention. For example, the type, pressure, power, interval G, etc. of the reactive gas can be appropriately selected depending on the type of piezoelectric element (crystal, BaTiO ₃ , ZnO, etc.).
[0055]
【The invention's effect】
As described above, according to the present invention, it is possible to achieve both high accuracy and stabilization of the frequency characteristics of the piezoelectric element and improvement of the processing efficiency of the adjustment work.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a configuration of an embodiment of an apparatus used in a method for adjusting a frequency characteristic of a piezoelectric element according to the present invention.
FIG. 2 is a graph showing a change with time of frequency in a process of adjusting a frequency characteristic of a piezoelectric element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Adjustment apparatus, 11 ... Chamber, 12 ... Discharge electrode, 13 ... Insulating material, 14 ... Discharge electrode, 15 ... Support member, 16 ... Shutter apparatus, 17 * ..Detection device 18 ... Power circuit 19 ... Matching box 20 ... Control device 21 ... Piezoelectric element 22 ... Gas supply device 23 ... Exhaust device

Claims (6)

A method of adjusting a frequency characteristic of a piezoelectric element, wherein a frequency characteristic is adjusted by etching a piezoelectric element in which an electrode pattern giving a desired frequency characteristic is formed on at least one surface of a plate-like substance having piezoelectricity,
The etching of the piezoelectric element is performed by bringing the plasma generated by the discharge electrode into contact with the piezoelectric element,
The distance between the discharge electrode for generating the plasma and the piezoelectric element until the frequency characteristic of the piezoelectric element reaches a predetermined state is selected so that the etching rate is close to the maximum value, and the etching of the piezoelectric element is performed. Coarse adjustment steps to be performed;
The distance between the discharge electrode for generating the plasma and the piezoelectric element is selected to be a stable region that avoids the extreme value of the etching rate, and the piezoelectric element is etched at a lower speed than the coarse adjustment step. And adjusting the frequency characteristics of the piezoelectric element. A method of adjusting a frequency characteristic of a piezoelectric element, wherein a frequency characteristic is adjusted by etching a piezoelectric element in which an electrode pattern giving a desired frequency characteristic is formed on at least one surface of a plate-like substance having piezoelectricity,
The etching of the piezoelectric element is performed by bringing the plasma generated by the discharge electrode into contact with the piezoelectric element,
The distance between the discharge electrode for generating the plasma and the piezoelectric element until the frequency characteristic of the piezoelectric element reaches a predetermined state is selected so that the etching rate is close to the maximum value, and the etching of the piezoelectric element is performed. Coarse adjustment steps to be performed;
The distance between the discharge electrode for generating the plasma and the piezoelectric element is selected to be a stable region that avoids the extreme value of the etching rate, and the piezoelectric element is etched at a lower speed than the coarse adjustment step. And a frequency characteristic adjustment method for a piezoelectric element, wherein the adjustment step is sequentially performed by the same processing means.   The coarse adjustment step and the fine adjustment step are performed while measuring the frequency characteristics of the piezoelectric element. In the coarse adjustment step, when the measured value reaches a predetermined value, the fine adjustment step is performed. Then, the etching is stopped when the measured value reaches the target value, and the method for adjusting the frequency characteristic of the piezoelectric element according to claim 1 or 2. A piezoelectric element frequency characteristic adjusting device for adjusting a frequency by etching a piezoelectric element,
Etching means having a discharge electrode for generating plasma;
Etching adjusting means for adjusting the etching strength of the etching means;
By controlling the etching adjusting means, the distance between the discharge electrode and the piezoelectric element for generating the plasma and the etching rate is in the vicinity of the maximum value until the frequency characteristic of the piezoelectric element reaches a predetermined state. The rough adjustment step for etching the piezoelectric element, and the distance between the discharge electrode and the piezoelectric element for generating the plasma are selected so as to be a stable region that avoids the extreme value of the etching rate, A control means for sequentially performing a fine adjustment step of etching the piezoelectric element at a lower speed than the rough adjustment step, and a frequency characteristic adjustment device for a piezoelectric element.   Frequency measuring means for measuring frequency characteristics of the piezoelectric element is provided, and the control means shifts to the fine adjustment step when the measurement value reaches a predetermined value in the coarse adjustment step, and measures in the fine adjustment step. 5. The frequency characteristic adjusting device for a piezoelectric element according to claim 4, wherein the control is performed so that the etching is stopped when the value reaches a target value.   6. The piezoelectric element according to claim 4, wherein the etching means has a discharge electrode for generating plasma, and the discharge electrode is made of a metal whose main component is aluminum. Frequency characteristic adjustment device.

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