JP4817237B2 - Piezoelectric element frequency adjusting device and frequency adjusting method - Google Patents

Description

  The present invention relates to a frequency adjusting apparatus and method used for manufacturing a piezoelectric element.

Piezoelectric elements such as crystal resonators, ceramic resonators, and SAW filters form the core of electronic components for frequency control and selection, and have become indispensable devices for recent information communication and electronic devices.
In the quartz resonator, the frequency is determined by the thickness of the quartz blank and the electrode, so these controls are important. Therefore, in the manufacturing process of the crystal unit, there is a frequency adjustment process for adjusting individual frequencies while measuring individual frequencies, which is a characteristic process that is not found in other electronic devices. Here, electrodes are formed on the cut-out crystal blank by sputtering film formation, etc., and then incorporated into the case. At this stage, a frequency variation of several hundred to 3000 ppm occurs, and this is a frequency variation of ± 2 ppm or less. A frequency adjustment process is required.

  In the frequency adjustment of the crystal resonator, a method of adjusting to the desired frequency by changing the electrode film thickness while measuring each frequency is adopted. There are two methods for changing the electrode film thickness: a vacuum deposition method and an ion beam etching method, and a vacuum deposition method using a resistance heating evaporation source has been put into practical use at an early stage.

  In the vapor deposition type frequency adjustment method, an adjustment electrode film is vapor-deposited from a resistance heating evaporation source on a base electrode film formed on a crystal piece through a metal mask. It has a relatively simple structure and is easy to control from a high deposition rate to a low deposition rate. Disadvantages include a multi-layer structure in which an adjustment electrode film is formed on the base electrode film, and particularly the adhesion and packing density of the adjustment electrode film tend to deteriorate, and vapor deposition occurs when the electrode becomes smaller as the crystal unit becomes smaller In the formulas, the base electrode film and the adjustment film are liable to be misaligned. In addition, the continuous operation time is limited to 8 hours or less due to the replenishment of the vapor deposition material and the cleaning due to contamination of the vapor deposition material.

  On the other hand, in the frequency adjustment method by ion beam etching, even if the electrode film is not multilayered or the positional deviation between the base electrode film and the adjustment film occurs, the crystal etching rate is extremely higher than the etching rate of the metal electrode film. Since the electrode film is selectively etched because it is low, there is little deterioration in device characteristics at the time of frequency adjustment in principle compared with the vapor deposition type. Furthermore, the ion beam etching method is advantageous over the vapor deposition method in that it does not require replenishment of the evaporating material and can be operated continuously for a long time.

  For this reason, the ion beam etching method was promising early on, and in the 1980s, research and development began by various crystal device manufacturers and equipment manufacturers. However, in the ion beam etching type, a phenomenon occurs in which the frequency shifts immediately after the frequency adjustment, which is a major cause that hinders practical use, and the ion beam etching type frequency adjustment apparatus starts to spread after 1999.

  FIG. 9 shows an example of frequency shift. Here, ion beam etching is performed for 2 to 4 seconds. Since the crystal resonator electrode is etched by ion beam etching, the frequency increases. There is a phenomenon that the frequency decreases immediately after the etching is finished. The shift amount at this time is as high as 300 ppm, which is much larger than the target ± 2 ppm, and the shift amount tends to increase as the adjustment rate is increased. It was difficult.

Therefore, paying attention to the fact that the frequency adjustment amount and the frequency shift amount after etching can be approximated by a linear expression, data of the frequency adjustment amount and the frequency shift amount after etching are acquired in advance by experiments to obtain an approximate expression. A method of reducing the frequency variation with respect to a desired frequency by offsetting the point at which etching is terminated from the frequency measurement result before frequency adjustment using the method is used (Patent Document 1).
JP 2003-204236 A

  In the method as described above, the relationship between the frequency adjustment amount and the frequency shift amount after etching must be obtained in advance by experiments. The relationship between the frequency adjustment amount and the frequency shift amount after etching differs depending on the frequency. Even if the frequency is the same, the frequency adjustment amount and the frequency shift after etching are different when the piezoelectric substrate shape, electrode size, ion beam irradiation area, adjustment rate, etc. are different. The relationship of quantity is also different. Therefore, it is necessary to obtain this data every time the type of piezoelectric element is changed. It is necessary for an engineer to be involved in such data acquisition and condition setting, and it is difficult for a general worker alone to fully exploit the apparatus capability. In addition, when the number of samples is originally small, it is difficult to divide the number into conditions. If the conditions cannot be determined, the desired adjustment accuracy cannot be obtained and the yield is deteriorated and finally obtained. The number further decreases. This is not a problem if it is mass production of small varieties, but this condition is a problem that cannot be ignored for small-lot production of many varieties.

  A first aspect of the present invention includes an etching source for etching a piezoelectric element, a control unit that controls the amount of etching, and a calculation unit that provides control information to the control unit. A frequency adjusting device for a piezoelectric element that adjusts the resonance frequency of the piezoelectric element, wherein the calculation means derives a thermal stress distribution in the piezoelectric element based on the material characteristics of the etched piezoelectric element and the power for etching, and the thermal stress The frequency adjustment device is configured to calculate, as control information, a shift amount of the resonance frequency generated after etching based on the distribution, and the control unit corrects the adjustment amount of the resonance frequency based on the shift amount. Here, the etching source was an ion gun for ion beam etching, and the power for etching was the power of the ion beam.

  The second aspect of the present invention is an ion gun for ion beam etching of a piezoelectric element, control means for controlling the start / end of etching, a frequency monitor for detecting the resonance frequency of the piezoelectric element and outputting it to the control means, and control means The piezoelectric element frequency adjusting device includes a calculation means for providing control information to the piezoelectric element, and adjusts a resonance frequency of the piezoelectric element by etching the piezoelectric element. The frequency detected by the frequency monitor is adjusted before the piezoelectric element is adjusted. When the resonance frequency is fr and the difference between the resonance frequencies before and after the adjustment by etching is Δfr, the control unit calculates the adjustment amount D of the resonance frequency based on at least Δfr, and the calculation unit calculates the piezoelectric element to be etched. Deriving the thermal stress distribution in the piezoelectric element based on the material properties and the power of the irradiated ion beam, based on the thermal stress distribution The shift amount ΔDx with respect to the target adjustment amount Dx is calculated, and Dx and ΔDx are provided as control information to the control means. The control means compares D with (Dx + ΔDx), and D = (Dx + ΔDx). This is a frequency adjusting device configured to finish etching at the time.

  The third aspect of the present invention is an ion gun for ion beam etching of a piezoelectric element, a control means for controlling the start / end of etching, a frequency monitor for detecting the resonance frequency of the piezoelectric element and outputting it to the control means, and a control means The piezoelectric element frequency adjusting device includes a calculation means for providing control information to the piezoelectric element, and adjusts a resonance frequency of the piezoelectric element by etching the piezoelectric element. The frequency detected by the frequency monitor is adjusted before the piezoelectric element is adjusted. When the resonance frequency is fr and the difference between the resonance frequencies before and after the adjustment by etching is Δfr, the control unit calculates the adjustment amount D of the resonance frequency based on at least Δfr, and the calculation unit calculates the piezoelectric element to be etched. Deriving the thermal stress distribution in the piezoelectric element based on the material properties and the power of the irradiated ion beam, based on the thermal stress distribution Then, a shift amount ΔD (t) of the adjustment amount D with respect to the ion beam irradiation time t from the start of etching is derived, and ΔD (t) and the target adjustment amount Dx are provided as control information to the control means. This is a frequency adjusting device configured to compare D with (Dx + ΔD (t)) and end etching when D = (Dx + ΔD (t)).

Here, in the first to third aspects, the material characteristic is composed of physical constant data and shape characteristic data representing the shape of the piezoelectric element, the electric power is calculated from the etching rate, and the arithmetic means includes a plurality of types of piezoelectric elements. And a shift amount is calculated from the physical constant data corresponding to the selected type among a plurality of types, the input shape characteristic data, and the etching rate.
In addition, the piezoelectric element is a crystal resonator, and the shape characteristic data is a size and a cut angle type related to the shapes of the crystal and electrodes constituting the crystal resonator.

  The fourth aspect of the present invention comprises an etching source for etching a piezoelectric element, a control means for controlling the amount of etching, and an arithmetic means for providing control information to the control means. A method of adjusting a resonance frequency, wherein a thermal stress distribution in a piezoelectric element is derived based on material characteristics of the piezoelectric element to be etched and power for etching by an arithmetic means, and after etching based on the thermal stress distribution. The step of calculating the generated resonance frequency shift amount as control information, the step of starting the control means, and the control means determine the etching end point based on the target adjustment amount and the calculated shift amount, and perform the etching. It is a method consisting of an end step. Here, the etching source was an ion gun for ion beam etching, and the power for etching was the power of the ion beam.

  According to the present invention, it is not necessary to obtain the amount of frequency shift by experiments in advance, the condition setting time can be greatly shortened, and it is possible to cope with a large variety of small-quantity production.

Example 1.
FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 22 is a crystal oscillator, 15 is an ion gun for ion beam etching of the crystal oscillator 22, 30 is a control unit for starting / ending etching by turning on / off the ion gun 15, and 11 is a crystal oscillator. A frequency monitor 10 for measuring the resonance frequency of 22 is an arithmetic means for providing control information described later to the control unit 30. As will be described later, the control unit 30 determines the timing for ending the etching based on information input from the frequency monitor 11 and the calculation means 10.

FIG. 2 is a schematic view showing a frequency adjusting device having an in-line structure of three chambers of a crystal resonator according to the present invention. It has a three-chamber inline configuration of a preparation chamber 1, an etching chamber 2, and an extraction chamber 3. A carrier 27 carrying a plurality of crystal resonators 22 is set on the transport rail 9 of the preparation chamber 1. After exhausting to 10 −3 Pa or less, the gate valve 12 is opened, and the crystal resonator 22 mounted on the carrier 27 is conveyed to the front of the ion gun 15. The etching chamber 2 is provided with a plurality of (three in this embodiment) ion guns 15 in order to shorten the etching time of the crystal resonator, and from the upstream (left side), H (for high rate), M ( Medium rate) and L (low rate), each provided with a shutter 7, a contact mechanism 8 with a crystal resonator 22, and a frequency monitor (network analyzer) 11 of the resonance frequency of the crystal resonator 22. ing. These are controlled by the control unit 30, and the crystal resonator 22 is adjusted to a desired frequency.
The crystal resonator 22 whose frequency has been adjusted in the etching chamber 2 is opened after the gate valve 13 is opened and sent to the take-out chamber 3 for each carrier 27 by the transport rail 9. Is done. The control unit 30 is connected to the calculation means 10.

  FIG. 3 is a schematic view of the ion gun 15 used in FIG. A cylindrical anode 18, a hot cathode 17, an ion extraction acceleration grid 21, and a shielding grid 20 are provided inside the ion gun. An inert gas introduction pipe 16 is connected to the ion gun body 15. The midpoint of the transformer, the ion gun body 15 and the shielding grid 20 are at the same potential. A low-voltage DC discharge power source E1 and a discharge current monitor mechanism 25 are connected between this potential and the anode 18. The discharge current monitor output of the discharge current monitor mechanism 25 is applied to a discharge current control circuit 24 that controls an AC power regulator 26 for power control of the hot cathode 17. In addition, a constant voltage direct current high voltage power supply E <b> 2 is connected between the shielding grid 20 and the acceleration grid 21. That is, the discharge current control circuit 24 responding to the discharge current monitor output controls the supply of power to the hot cathode so that the discharge current becomes constant. The discharge current control circuit 24 turns on / off the ion gun 15 based on a signal from the control unit 30. The opening / closing operation of the shutter 7 is also controlled by the control unit 30.

By the way, although the mechanism that causes the frequency shift as described above has not been elucidated for many years, the thermal stress caused by the temperature rise distribution due to the ion beam irradiation causes a change in the elastic constant of the piezoelectric substrate, resulting in a frequency shift. I found out that
As an example, FIG. 4 shows a calculation result of frequency fluctuations when an ion beam having a beam voltage of 300 V and an ion beam current density of 1 mA / cm ² is irradiated on an electrode diameter of 3 φ with a crystal resonator of φ7.4 and a frequency of 25 MHz.

The power density of an ion beam with a beam voltage of 300 V and an ion beam current density of 1 mA / cm ² is 300 mW / cm ² , and when irradiated into a 3φ electrode, it becomes 21 mW, which raises the temperature of the φ7.4 crystal.
FIG. 5 shows a temperature distribution change simulation result by the difference method at this time. Here, the crystal resonator is supported by the support, but it is assumed that the heat conduction in this portion is small and is thermally floating. It can be seen that the temperature near the center rises due to the beam irradiation and gradually diffuses to the periphery, but there is a temperature difference between the center and the periphery.

により位置rの熱応力を求めることが出来る。ここで、αは水晶の熱膨張率、Ｅは水晶のヤング率、ｂは水晶素板の半径、τは位置ｒでの温度上昇である。
図６（ａ）及び（ｂ）は図５の温度分布から式(1)(2)によって求めた熱応力分布である。 The thermal stress caused by this temperature distribution is the thermal stress of a solid disk using a cylindrical coordinate system,

The thermal stress at position r can be obtained by Here, α is the thermal expansion coefficient of the crystal, E is the Young's modulus of the crystal, b is the radius of the crystal base plate, and τ is the temperature rise at the position r.
FIGS. 6A and 6B are thermal stress distributions obtained from the temperature distribution of FIG. 5 by the equations (1) and (2).

である。ここで、ｕ:粒子変位、φ:電気ポテンシャル、ρ:密度、ｃ:弾性定数、ｅ:圧電定数、ε:誘電率である。圧電性を持つ解から、共振周波数ｆｒは基板の厚さをＨとして、

で与えられ、共振での変移成分は、

となる。 Next, a frequency change is obtained from the obtained thermal stress distribution.
The basic wave equation is

It is. Here, u: particle displacement, φ: electric potential, ρ: density, c: elastic constant, e: piezoelectric constant, and ε: dielectric constant. From the solution having piezoelectricity, the resonance frequency fr is H as the thickness of the substrate.

The shift component at resonance is given by

It becomes.

で与えられ、応力による弾性常数の変化は、

となる。 From Thurston's theory, the propagation velocity W of the sound wave in the crystal under the stress P is expressed as U: variation direction unit vector, N: propagation direction unit vector, and M: compression stress unit vector.

The change in elastic constant due to stress is given by

It becomes.

で与えられる。圧電定数と誘電率の変化は小さいので無視し、積分範囲をＶ=電極面積×基板厚さとすると、

となる。 The change in resonance frequency obtained from the perturbation method is

Given in. Since the change in piezoelectric constant and dielectric constant is small, it is ignored and the integration range is V = electrode area × substrate thickness.

It becomes.

となる。ここで、Ｍ_１、Ｍ_２はそれぞれ圧縮応力ベクトルＭのｘ軸方向、ｙ軸方向の単位ベクトルであり、Ｓはコンプライアンス、Ｃは材料変換後の弾性定数である。
上式からわかるように、共振周波数の変化Δω／ωは、熱応力Ｍを対象となる形状に関して全方向に積分した結果に深く関連している。

FIG. 7 shows a change in the resonance frequency of ATcut and BTcut with a frequency of 25 MHz obtained from Equation (3), that is, a comparison between the shift amount calculation result and the actual measurement value. The frequency change of the actually measured value is shown by subtracting the converted frequency change from the film thickness change. It can be seen that the calculated values and the measured values are in good agreement.
Furthermore, when formula (3) is further arranged,

It becomes. Here, M ₁ and M ₂ are unit vectors of the compressive stress vector M in the x-axis direction and y-axis direction, respectively, S is compliance, and C is an elastic constant after material conversion.
As can be seen from the above equation, the change Δω / ω in the resonance frequency is deeply related to the result of integrating the thermal stress M in all directions with respect to the target shape.

Further, FIG. 8 is a diagram showing a relationship between the pre-measurement frequency (adjustment amount) immediately after etching and before the resonance frequency shifts, and the post-measurement frequency (shift amount) after the resonance frequency is shifted. The dotted lines in the figure indicate the calculation results described above, and the beam voltage and adjustment rate are (1000 V, 1600 ppm / s), (900 V, 1300 ppm / s), (800 V, 1000 ppm / s), (700 V) from the bottom. , 700 ppm / s) and (500 V, 400 ppm / s). Each point in the figure is an actual measurement value, which almost coincides with the calculated line.
Therefore, if you know the crystal shape and dimensions of the crystal unit, the material constants such as the expansion coefficient, Young's modulus, and elastic constant of the crystal unit, and the electrode shape, size, ion beam irradiation area, and ion beam irradiation amount of the crystal unit, The frequency shift can be predicted.

  Next, returning to FIG. 1, the computing means 10 will be described. The computing means 10 is means for deriving ΔD in advance using the above principle. The memory 101 in the arithmetic means 10 stores crystal physical constant data (expansion coefficient α, Young's modulus E, density ρ, elastic constant c, piezoelectric constant e, dielectric constant ε, etc.) in advance. These are known values. In addition, for the desired etching adjustment rate, the current density of the ion beam, the applied voltage, and the power Xp determined thereby are calculated (in a known manner). Information on the crystal and electrode shapes in the crystal resonator to be etched and the crystal cut angle (hereinafter referred to as “shape characteristic data Xs”) is input to the computing means 10 by the operator before starting the etching. The

  Here, the shape characteristic data Xs is, for example, the diameter when the crystal is circular, and the length of the side when the crystal is square. Further, the resonance frequency before adjustment of the crystal resonator 22 is defined as fr, the difference between the resonance frequencies before and after the adjustment is defined as Δfr, the adjustment amount D is defined as D = Δfr / fr, the shift amount of D is defined as ΔD, and all the values are defined. Absolute value. Further, in addition to the previous paragraph, a target adjustment amount Dx that is a target value of the adjustment amount D is input by the operator.

  The calculation means 10 calculates the thermal stress distribution function M from the above physical constants, the calculated power Xp, and the input shape characteristic data Xs based on the above-described principle, and the thermal stress distribution function M Based on this, the shift amount ΔDx with respect to the target adjustment amount Dx is calculated, and the values of Dx and ΔDx are given to the control unit 30. Thereafter, the control unit 30 turns on the ion gun 15, and etching is started at the inputted etching rate (power Xp). The control unit 30 calculates Δfr and the adjustment amount D {D = Δfr / fr} from the resonance frequency detected by the frequency monitor 11. Of course, the calculation for obtaining Δfr or D from the detected resonance frequency may be performed by the frequency monitor 11 instead of the control unit 30. The control unit 30 compares D with (Dx + ΔDx), and turns off the ion gun 15 to end the etching when they become equal.

  For example, referring to FIG. 8, when (beam voltage, adjustment rate) is (1000 V, 1600 ppm / s) and the target adjustment amount Dx is | −1500 | = 1500 (ppm), the shift amount ΔDx is | −. Since 200 | = 200 (ppm) is calculated, if etching is performed until D calculated from the resonance frequency detected by the frequency monitor 11 reaches 1700 (ppm), the target 1500 ppm can be adjusted.

  In this embodiment, the start / end of etching is basically performed by turning on / off the ion gun 15, but may be performed by opening / blocking the beam by the shutter 7. Further, although the adjustment amount D = Δfr / fr (ratio) is defined, the above principle can be used even if D = Δfr or the like (absolute amount).

Example 2
In the first embodiment, the shift amount ΔDx corresponding to the power Xp of the ion beam and the target adjustment amount Dx is derived, and the control information provided from the calculation means 10 to the control unit 30 is Dx and ΔDx. In the figure, the shift amount ΔD is derived as a function ΔD (t) of t from the ion beam power Xp and the ion beam irradiation time t from the start of etching, and Dx and the function ΔD (t) are used as control information.
Although the basic configuration of the present embodiment is the same as that of the first embodiment shown in FIGS. 1 to 3, the control unit 30 needs to have a timer circuit therein.

In this embodiment, the control unit 30 calculates the value of ΔD (t) using an internal timer circuit (not shown), and turns off the ion gun 15 when D = (Dx + ΔD (t)). To finish etching. Instead of using ΔD as a function of t, Dx and ΔD (W (t)) can be used as control information as a function of total power W (t) {W (t) = Xp × t} applied with ΔD. Good.
In the present embodiment, the frequency monitor 11 is not necessary if the resonance frequency before adjustment is known in advance. Further, when it is not necessary to finally obtain an absolute resonance frequency in the adjustment, that is, when only a relative value before and after the adjustment is required, the frequency monitor 11 is not necessary.

  What is common in both embodiments is that the control means obtains the shift amount in relation to the thermal stress distribution generated from the start to the end of etching or the thermal stress distribution generated at the end of etching, and the control unit Is to control the ion gun to correct the shift amount. The difference is that, in the first embodiment, the control information is configured with the shift amount as a function of the adjustment amount on the crystal resonator side, whereas in the embodiment shown later, the shift amount is a function of the output value on the ion gun side. The control information is configured as follows.

  In the present embodiment, a piezoelectric element using a crystal resonator is shown as a preferred example, but other types of piezoelectric elements may be used. In other words, if the physical constants (expansion coefficient α, Young's modulus E, density ρ, elastic constant c, piezoelectric constant e, dielectric constant ε, etc.) of the material used for the piezoelectric element are known, the shape characteristics and etching of the piezoelectric element are known. Thermal stress distribution can be derived from the rate (ion beam power). Of course, for each of a plurality of types of materials, each physical constant data may be input to the memory and the corresponding physical constant data may be read according to the material selected by the operator. Then, it is possible to apply the principle of the present invention in which an adjustment amount shift is obtained based on the thermal stress distribution and the end point of etching is determined. Therefore, even if it is a piezoelectric element of the kind handled for the first time, if it is made of a known material, the frequency adjustment process can be performed simply by inputting a known value without acquiring prior measurement / experiment data. Can start.

  In this embodiment, the ion beam etching is used, but the same principle can be used even in the case of using reactive plasma etching. In this case, power (which may be an applied voltage) input for plasma generation can be applied as the power corresponding to the power Xp.

The block diagram which shows the crystal oscillator frequency adjusting device of this invention Schematic of a crystal resonator frequency adjustment device using an ion gun according to the present invention. Schematic of ion gun according to the present invention Diagram for explaining the present invention Temperature distribution diagram for explaining the present invention Thermal stress distribution diagram for explaining the present invention The figure which compares the calculation result of a frequency change in this invention, and a measured value Diagram for explaining the present invention Diagram explaining shift of resonance frequency

Explanation of symbols

1. Preparation room 2. 2. Etching chamber Extraction chamber 7. Shutter 8. Contact mechanism9. Transport rail 10. Calculation means 11. Frequency monitor 12. Gate valve 1
13. Gate valve 2
15. Ion gun 16. Gas introduction pipe 17. Hot cathode 18. Anode 19. Magnet 20. Shielding grid 21. Acceleration grid 22. Crystal resonator 24. Discharge current control circuit 25. Discharge current monitor mechanism 26. AC voltage regulator 27. Carrier 30. Control unit 101. memory

Claims (4)

Ion gun for ion beam etching of a piezoelectric element, control means for controlling the start / end of etching, a frequency monitor that detects the resonance frequency of the piezoelectric element and outputs it to the control means, and provides control information to the control means A piezoelectric element frequency adjusting device for adjusting the resonance frequency of the piezoelectric element by etching the piezoelectric element,
The frequency detected by the frequency monitor, a resonance frequency before the adjustment of the piezoelectric element as fr, the difference between the resonant frequency and the fr being adjusted by the etching when the .DELTA.fr, the control means is the resonant frequency An adjustment amount D = Δfr / fr is calculated,
The calculation means derives a thermal stress distribution in the piezoelectric element based on the temperature distribution of the piezoelectric element to be etched, calculates a shift amount ΔDx with respect to the target adjustment amount Dx based on the thermal stress distribution, and Dx and ΔDx To the control means as the control information,
A frequency adjusting device configured to compare D with (Dx + ΔDx) after the control means starts etching with the ion gun and terminate the etching when D = (Dx + ΔDx).
Ion gun for ion beam etching of a piezoelectric element, control means for controlling the start / end of etching, a frequency monitor that detects the resonance frequency of the piezoelectric element and outputs it to the control means, and provides control information to the control means A piezoelectric element frequency adjusting device for adjusting the resonance frequency of the piezoelectric element by etching the piezoelectric element,
The frequency detected by the frequency monitor, a resonance frequency before the adjustment of the piezoelectric element as fr, the difference between the resonant frequency and the fr being adjusted by the etching when the .DELTA.fr, the control means is the resonant frequency An adjustment amount D = Δfr / fr is calculated,
The calculation means derives a thermal stress distribution in the piezoelectric element based on the temperature distribution of the piezoelectric element to be etched, and shifts the adjustment amount D with respect to the ion beam irradiation time t from the start of etching based on the thermal stress distribution. Deriving the amount ΔD (t), and providing ΔD (t) and the target adjustment amount Dx as the control information to the control means;
After the control means starts etching the ion gun, D is compared with (Dx + ΔD (t)), and the frequency adjustment is configured to end the etching when D = (Dx + ΔD (t)). apparatus.
Ion gun for ion beam etching of a piezoelectric element, control means for controlling the start / end of etching, a frequency monitor that detects the resonance frequency of the piezoelectric element and outputs it to the control means, and provides control information to the control means A method of adjusting the resonance frequency of the piezoelectric element by etching the piezoelectric element by a computing means that comprises:
Regarding the frequency detected by the frequency monitor, when the resonance frequency before adjustment of the piezoelectric element is fr and the difference between the resonance frequency being adjusted by etching and fr is Δfr, the control means Calculating an adjustment amount D = Δfr / fr;
The calculation means derives a thermal stress distribution in the piezoelectric element based on the temperature distribution of the piezoelectric element to be etched, calculates a shift amount ΔDx with respect to the target adjustment amount Dx based on the thermal stress distribution, and Dx and ΔDx Providing the control means with the control information; and
After the control means starts etching the ion gun, D is compared with (Dx + ΔDx), and the etching is terminated when D = (Dx + ΔDx).
A method comprising:
Ion gun for ion beam etching of a piezoelectric element, control means for controlling the start / end of etching, a frequency monitor that detects the resonance frequency of the piezoelectric element and outputs it to the control means, and provides control information to the control means A method of adjusting the resonance frequency of the piezoelectric element by etching the piezoelectric element by a computing means that comprises:
Regarding the frequency detected by the frequency monitor, when the resonance frequency before adjustment of the piezoelectric element is fr and the difference between the resonance frequency being adjusted by etching and fr is Δfr, the control means Calculating an adjustment amount D = Δfr / fr;
The calculation means derives a thermal stress distribution in the piezoelectric element based on the temperature distribution of the piezoelectric element to be etched, and shifts the adjustment amount D with respect to the ion beam irradiation time t from the start of etching based on the thermal stress distribution. Deriving an amount ΔD (t) and providing ΔD (t) and a target adjustment amount Dx to the control means as the control information; and
After the control means starts etching the ion gun, D is compared with (Dx + ΔD (t)), and the etching is terminated when D = (Dx + ΔD (t)).
A method comprising:

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