JP4567488B2 - Method for adjusting frequency of piezoelectric device - Google Patents

Description

  The present invention relates to a frequency adjustment method for a piezoelectric device using ion etching, and more particularly to a frequency adjustment method for a piezoelectric device whose resonance frequency of a piezoelectric diaphragm mounted on the piezoelectric device is a fundamental wave of 100 MHz or higher.

  In the manufacture of piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators, the frequency adjustment method of the piezoelectric device is to further deposit metal on the metal excitation electrode provided on the surface of the piezoelectric diaphragm in the piezoelectric device. An evaporation method for obtaining a desired vibration frequency and an ion etching method for obtaining a desired frequency by making ions collide with a metal excitation electrode film provided on the surface of a piezoelectric vibration plate for etching are used.

  In the frequency adjustment method of a piezoelectric device using the ion etching method, first, the piezoelectric base plate is cut and polished into an arbitrary shape such as a strip shape. Next, a plurality of the piezoelectric element plates are juxtaposed, covered with a mask in which electrode shapes are formed on both main surfaces of the piezoelectric element plates, and a metal or an alloy such as gold is deposited on the mask to An excitation electrode film is formed on the piezoelectric diaphragm.

  At this time, the deposition amount of the electrode film formed on the piezoelectric element plate is set so as to be lower than a desired frequency. That is, an excitation electrode film having a film thickness larger than the thickness of the excitation electrode film capable of obtaining a desired frequency is formed on the front and back main surfaces of the piezoelectric element plate. After that, the piezoelectric diaphragm on which the excitation electrode film is formed is mounted inside a ceramic package or the like, and the electrode terminal provided on the package and the excitation electrode film are electrically connected by a conductive adhesive or a bump. A piezoelectric device in a state is formed.

  Next, the piezoelectric device formed in this way is attached to the holder, and the excitation electrode film is configured by beaming and colliding the ions generated by the ion gun with the excitation electrode film of the piezoelectric diaphragm in the piezoelectric device. Metal molecules to be blown out of the piezoelectric device. Thus, a desired vibration frequency can be obtained by thinning the film thickness of the excitation electrode film to a film thickness that can physically obtain a desired frequency.

  The following prior art documents are disclosed for the frequency adjustment method described above.

JP-A-4-196707 JP 2001-285002 A JP-A-4-116167

  In addition, the applicant has not found any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the prior art document information described above.

  In the frequency adjustment method of the piezoelectric device as described above, an ion gun that generates ions and ejects the ions is used. In the control of the frequency adjustment rate by the ions ejected from the ion gun in the conventional frequency adjustment method, the frequency adjustment rate is controlled by varying the current applied to the ion gun power source.

  However, in the frequency adjustment process, etching is first performed at a relatively fast adjustment rate (the applied voltage to the ion gun is large) to the vicinity of the desired excitation frequency, and then the etching is performed in several stages and then the adjustment rate is reduced. The final desired excitation frequency is obtained, but the frequency adjustment rate at each stage is different, so it is difficult to adjust the frequency in a wide frequency range with one ion gun.

  Further, in the frequency adjustment using the method of changing the voltage applied to the ion gun power source, it is difficult to control the rate at a minute frequency adjustment rate, and therefore the frequency of the piezoelectric diaphragm must be measured every time the applied voltage is changed. For example, when 200 piezoelectric devices are used as one pallet and the frequency adjustment process is performed with two applied voltage changes, accurate rate control cannot be performed without frequency measurement 600 times, resulting in extremely high productivity. Becomes worse.

  Further, when measuring the frequency, the measurement contact terminal of the frequency measuring device is generally brought into contact with an electrode pad formed on a piezoelectric device on which a piezoelectric diaphragm is mounted, and the electrode pad is electrically connected. The frequency of the piezoelectric diaphragms connected to each other is measured, but if an elastic body such as a spring is used to generate the contact pressure at that time, a minute error occurs every measurement. Therefore, accurate frequency adjustment is difficult, and in particular, in a so-called high-frequency piezoelectric diaphragm that excites at 100 MHz or more in fundamental vibration, the influence of the error becomes large. Further, by varying the voltage applied to the ion gun power source, it becomes difficult to accurately specify the state of ions, and therefore the accuracy of frequency adjustment may be deteriorated.

  Furthermore, in the frequency adjustment method as described in Patent Document 3 disclosed as the above-mentioned prior art document information, there is a disclosure that the amount of ions can be changed with a mask as described in the same document. When the mask of the form is used, when the amount of ions is reduced, the etching area of ions irradiated onto the electrode film of the piezoelectric vibrator is very narrow and concentrated at one point, so that the balance of thickness and mass as a whole of the electrode film May worsen and adversely affect the vibration characteristics of the piezoelectric vibrator.

The present invention has been made in view of the above problems, and in a frequency adjustment method of a piezoelectric device using an ion etching method, an excitation beam formed on an ion beam exit and a piezoelectric diaphragm mounted on the piezoelectric device. between the mask plate disposed on the electrode film, placing the ion shield plate for changing the amount of ions emitted from the ion beam exit opening in an amount corresponding to the desired etch rate of該励vibration electrode film The ion shielding plate has a plurality of holes penetrating the front and back main surfaces of the ion shielding plate for allowing a desired amount of ions to pass through in a main surface region of the ion shielding plate through which the ion beam passes. The ion shielding plate in which the plurality of through holes are opposed to a predetermined one ion passage hole formed in the mask plate, and the size of the opening of the through hole or the number of through holes formed is different. Multiple A frequency adjustment method of a piezoelectric device, characterized by varying the etching rate amount by use.

  By using such a frequency adjustment method of the piezoelectric device, the amount of ion etching of the excitation electrode film of the piezoelectric diaphragm mounted on the piezoelectric device can be appropriately changed by a plurality of ion shielding plates. Thus, the frequency adjustment rate corresponding to a wide range of frequencies can be controlled, and the rate control at a minute frequency adjustment rate can be performed accurately and easily.

  In addition, since accurate rate control is possible, the frequency of measurement of the frequency of the piezoelectric diaphragm can be reduced, and the occurrence of errors for each frequency measurement can be minimized. There is an effect that it is possible to provide a piezoelectric device that is inexpensive and has extremely small variation in characteristics between products.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram illustrating an outline of a frequency adjustment method of a piezoelectric device according to the present invention, using a cross-sectional view of a piezoelectric vibrator which is one of piezoelectric devices. FIG. 2 is a plan view showing an embodiment of the ion shielding plate shown in FIG. 1, and there is a difference in the number of through holes formed in (a) and (b). FIG. 3 is a plan view showing another form of the ion shielding plate shown in FIG. 1, and there is a difference in the diameter of the opening of the through hole in (a) and (b). In addition, in order to clarify the explanation in each drawing, parts and parts of the structure are not shown. Each dimension in the drawings is also partially exaggerated, and the same reference numerals denote the same objects in each figure.

  First, as a mechanism for generating an ion beam, a gas tube is provided in the discharge chamber in the ion gun apparatus, and argon (Ar) gas, which is an inert gas, flows into the discharge chamber through the gas tube. The Ar gas in the discharge chamber is ionized by plasma generated by causing a direct current discharge between the cylindrical discharge electrode and the electrically heated filament to generate Ar + ions.

  The generated Ar + ions are attracted from the discharge chamber to the electrode plate to which a high voltage is applied, and are drawn out of the discharge chamber through an ion passage formed in the electrode plate. The electrode plate 16 has an effect of indirectly controlling the amount of Ar + ions exiting from the discharge chamber and protecting the ion acceleration electrode plate from collision of Ar + ions.

  Ar + ions that have passed through the electrode plate are further attracted and accelerated by the ion acceleration electrode plate to which a high voltage is applied. The ion accelerating electrode plate is also formed with an ion passage opening, and an ion beam is formed by Ar + ions that have passed through the ion passage opening. The excitation electrode film 13 is etched by the collision of Ar + ions with the excitation electrode film 13 formed in the above, and the excitation frequency of the piezoelectric diaphragm 12 is adjusted to a desired frequency. Note that the piezoelectric vibrator 10 is operated in a frequency adjustment process with a plurality of matrix arrangements as one pallet. Further, a mask plate 14 for protecting a structure other than the excitation electrode film 13 from the irradiated ion beam is disposed on the plurality of arranged piezoelectric vibrators 10. The ion beam is applied only to the excitation electrode film 13 through the ion passage hole 15 formed in the mask plate 14.

Here, in the present invention, as shown in FIG. 1, an ion shielding plate 16 is disposed between the ion beam exit 11 and the ion passage hole 15 formed in the mask plate 14. This ion shielding plate 16 has a form as shown in FIG. 2 or FIG. 3, and a plurality of penetrations are made in the ion beam irradiation regions on both the front and back main surfaces where the ion beam of the flat ion shielding plate 16 enters and exits. A hole 17 is formed. The plurality of through holes 17 are formed in the ion shielding plate 16 so as to face one predetermined ion passage hole 15 formed in the mask plate 14. By arranging the ion shielding plate 16 in which the number of through-holes 17 formed and the size of the opening are appropriately changed from a desired ion amount, the ion amount irradiated to the excitation electrode film 13 is directly and accurately controlled. As a result, the frequency adjustment rate can be stably controlled. Further, since the plurality of through holes 17 are formed so as to be evenly distributed over the entire ion beam irradiation region, the entire surface of the excitation electrode film 13 can be uniformly ion etched. 2 and 3, the ion shielding plate described in (a) shows a form in which the ion passage amount is smaller than that of the ion shielding plate described in (b). In addition, since the ion shielding plate 16 can be formed and replaced very easily, the amount of ion beam can be stably varied, and the frequency adjustment in a wide frequency range can be easily performed.

  In the embodiment of the present invention, since the ion irradiation amount in various combinations of the ion gun apparatus and the ion shielding plate 16 can be quantitatively derived, the etching rate of the excitation electrode film 13 is also very high in the actual rate amount. A close value can be predicted in advance by simulation or the like, and the number of times of excitation frequency measurement of the piezoelectric diaphragm 12 performed to confirm the etching state can be reduced. In the case of the piezoelectric vibrator 10 as disclosed in FIG. 1, the measurement contact terminal of the frequency measuring device is formed on the piezoelectric diaphragm 12 in order to measure the excitation frequency of the piezoelectric diaphragm 12 mounted therein. The external connection terminal 18 that is electrically connected to the excitation electrode film 13 is in pressure contact using an elastic force such as a spring.

  In the above embodiment, the outer shape of the ion shielding plate 16 is disclosed as square and circular. However, other shapes may be used, and the shape of the opening of the through hole formed in the ion shielding plate 16 may also be used in this embodiment. Shapes other than the disclosed shape may be used.

  In this embodiment, the piezoelectric vibrator, which is one of the piezoelectric devices, has been described. However, an integrated circuit element or the like in which at least an oscillation circuit is formed together with the piezoelectric diaphragm in the container constituting the piezoelectric device. Even in the mounted piezoelectric oscillator, the configuration and operational effects of the present invention can be similarly achieved. The present invention can also be applied to the case where a plate-like piezoelectric diaphragm is used as the piezoelectric diaphragm.

FIG. 1 is a configuration diagram illustrating an outline of a frequency adjustment method of a piezoelectric device according to the present invention using a cross-sectional view of a piezoelectric vibrator that is one of piezoelectric devices. FIG. 2 is a plan view showing an embodiment of the ion shielding plate shown in FIG. 1, and shows ion shielding plates having different numbers of through holes in (a) and (b). FIG. 3 is a plan view showing another form of the ion shielding plate shown in FIG. 1, and shows ion shielding plates having different opening diameters of through holes in (a) and (b).

Explanation of symbols

10 ... Piezoelectric vibrator (piezoelectric device)
DESCRIPTION OF SYMBOLS 11 ... Ion beam exit 12 ... Piezoelectric diaphragm 13 ... Electrode film for excitation 14 ... Mask plate 16 ... Ion shielding plate 17 ... Through-hole

Claims (1)

In the frequency adjustment method of the piezoelectric device using the ion etching method,
Between the ion beam exit and the mask plate disposed on the excitation electrode film formed on the piezoelectric diaphragm mounted on the piezoelectric device, the ion is supplied in an amount corresponding to a desired etching rate of the excitation electrode film. Place an ion shielding plate to change the amount of ions emitted from the beam exit ,
The ion shielding plate is formed with a plurality of holes penetrating the front and back main surfaces of the ion shielding plate for allowing a desired amount of ions to pass through in a principal surface region of the ion shielding plate through which the ion beam passes. The plurality of through holes are opposed to a predetermined one ion passage hole formed in the mask plate;
A method for adjusting the frequency of a piezoelectric device , wherein the etching rate is varied by using a plurality of ion shielding plates having different sizes of openings of the through holes or the number of formed through holes .

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