JPH0563485A - Frequency adjustment device for piezoelectric body by ion beam - Google Patents

Abstract

(57) [Summary] [Purpose] To enable accurate frequency adjustment without causing an error in the resonance frequency due to thermal shock. [Constitution] In the case where a piezoelectric resonator provided with an electrode made of a metal thin film is irradiated with an ion beam to adjust the resonance frequency by reverse sputtering, the center of the plate surface where the resonance frequency rises due to thermal shock caused by the irradiation of the ion beam. Part and the peripheral portion of the plate surface where the resonance frequency is lowered are simultaneously subjected to reverse sputtering, and the irradiation area of the peripheral portion is set to an area that cancels the frequency change caused by thermal shock in the central portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam frequency adjusting apparatus for adjusting the resonance frequency by irradiating a piezoelectric resonator with an ion beam to perform reverse sputtering, and particularly to a frequency error due to thermal shock. Regarding the removal of.

[0002]

2. Description of the Related Art Conventionally, the resonance frequency of a piezoelectric resonator is adjusted by, for example, forming a piezoelectric body into a predetermined shape and forming an electrode made of a metal thin film by vacuum vapor deposition or the like. By evaporating the metal, the resonance frequency is accurately adjusted by the effect of adding the mass. However, in such a device, the resonance frequency changes only in the direction of decreasing with the addition of mass. For this reason, if the frequency drops below the target frequency, the frequency cannot be recovered, and it must be discarded, which has been an obstacle to frequency adjustment.

Therefore, in a vacuum atmosphere, a piezoelectric resonator,
For example, there has been considered a frequency adjustment method by reverse sputtering in which an electrode of a quartz oscillator is irradiated with an ion beam to knock out its atoms and molecules to reduce the mass and thereby increase the frequency. According to such frequency adjustment, the resonance frequency can be raised after the electrodes are formed, and by combining with the conventional frequency adjustment by vacuum deposition, the rise and fall of the resonance frequency can be controlled arbitrarily. However, in the frequency adjustment by such a method, the quartz piece is locally and rapidly heated by the irradiation of the ion beam, and the resonance frequency greatly changes. This is a change in frequency due to thermal shock, and shows a change in resonance frequency as shown in FIG. 2, for example. That is, when the irradiation of the ion beam is started at time t0, the resonance frequency gradually rises from fs with the lapse of time, and when the irradiation is stopped at time t1 when it reaches the target frequency f0,
The resonance frequency gradually decreases to fb, which is a so-called frequency back phenomenon. This decrease in the resonance frequency causes an adjustment error, and the amount of decrease in the frequency at this time is not constant, so accurate frequency adjustment is required. There was a problem that I could not do.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an ion beam capable of performing accurate frequency adjustment without causing an error in the resonance frequency due to thermal shock. An object of the present invention is to provide a frequency adjusting device.

[0005]

According to the present invention, a piezoelectric resonator provided with an electrode made of a metal thin film is irradiated with an ion beam to adjust the resonance frequency by reverse sputtering. Simultaneous reverse sputtering is performed on the central part of the plate surface where the resonance frequency rises and the peripheral part of the plate surface where the resonance frequency decreases, and the irradiation area of the peripheral part cancels out the frequency change caused by thermal shock in the central part. It is characterized by having an area.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the front view of the crystal resonator shown in FIG. 1 by way of example of adjusting the resonance frequency of the crystal resonator. In FIG. 1, reference numeral 1 denotes, for example, an AT-cut crystal piece, which is a synthetic quartz crystal cut at a predetermined angle with respect to the crystal axis, formed into a round plate, and polished to a thickness corresponding to a desired resonance frequency. Then, the excitation electrode 2 is formed so as to face the front and back plate surfaces of the crystal piece 1 and is led out to the peripheral portion of the plate surface. The crystal piece 1 holds the lead-out end portion of the electrode 2 by a holding member 4 implanted in the base 3 and electrically leads it out. The base 3 is hermetically sealed by covering the base 3 with a cover (not shown) after frequency adjustment. The frequency is adjusted as follows. That is, an inert gas such as argon or krypton is turned into plasma by a high frequency discharge or a direct current discharge in a low vacuum atmosphere of about 10 −2 Torr. Then, the ions of this plasma are extracted by an accelerating electrode to obtain an ion beam, which is then introduced into a processing chamber in a high vacuum atmosphere of about 10 -6 Torr and irradiated onto the plate surface of the crystal piece 1. In this case, when the electrode formation site of the crystal blank 1 is irradiated with an ion beam, the atoms and molecules of the substance forming the surface are knocked out from the surface of the electrode and the mass thereof is reduced. By doing so, the mass of the electrode is reduced, so that the mass addition effect is reduced and the resonance frequency is gradually increased. Further, the frequency change due to heat generation when irradiating the ion beam, that is, the frequency change due to thermal shock, the frequency increases at the central portion of the crystal piece 1, the frequency decreases at the peripheral portion of the crystal piece, and the ion beam irradiation is performed. When stopped, the frequency changes approximately in the opposite direction corresponding to the amount of change in the frequency. That is, as shown in FIG. 2, when the ion beam irradiation is started, the frequency change due to thermal shock is increased at the central portion (shown C) of the crystal piece and decreased at the peripheral portion (shown E), On the contrary, when the irradiation of the ion beam is stopped, it decreases at the central part and rises at the peripheral part. Further, the change in frequency due to such thermal shock is five times or more larger than that in the peripheral portion in the central portion, particularly in the portion where the electrodes are formed, and the changing directions are opposite to each other. Therefore, the ion beam irradiation area is set at the same time as the electrode formation area and the electrode non-formation area, and the irradiation area of the ion beam is set so that the absolute values of the frequency changes due to thermal shock are equal in both areas. 5 is irradiated with an ion beam to adjust the frequency.

With this configuration, the resonance frequency as a whole changes in the upward direction by irradiating the plate surface of the crystal resonator with the ion beam. Further, the change in frequency caused by the irradiation of the ion beam due to the thermal shock can cancel the change in the central part and the change in the peripheral part of the plate surface, and the effect of the thermal shock can be ignored in appearance. You can Therefore, the resonance frequency of the crystal piece to be frequency-adjusted with respect to the target resonance frequency is set to be slightly lower, and the plate surface is irradiated with an ion beam to perform the frequency adjustment. The irradiation of the ion beam is simultaneously performed on the central portion of the crystal piece and the peripheral portion corresponding to the frequency change due to the thermal shock of the central portion, so that the apparent frequency change due to the thermal shock does not occur. Therefore, it is possible to accurately adjust to the target frequency by performing ion beam irradiation to gradually increase the frequency and stopping the irradiation when the frequency reaches the target frequency. However, the resonance frequency can be adjusted efficiently and accurately, and when the frequency becomes too high, the frequency can be lowered again by adding a little mass on the electrode by vapor deposition or the like, and the readjustment can be performed. .. Note that the present invention is not limited to the above-described embodiment, and for example, the above-described embodiment describes an example using a crystal resonator using a round plate-shaped crystal piece, but a strip-shaped crystal piece may be used, Of course, it can be applied to an appropriate piezoelectric resonator such as tantalate, which is made of only crystal.

[0008]

As described in detail above, according to the present invention, it is possible to provide an ion beam frequency adjusting apparatus capable of performing accurate frequency adjustment without causing an error in the resonance frequency due to thermal shock. it can.

[0009]

[Brief description of drawings]

FIG. 1 is a front view of a crystal unit that performs frequency adjustment by the device of the present invention.

FIG. 2 is a diagram showing a change in frequency due to a thermal shock and an irradiation site of an ion beam.

FIG. 3 is a graph showing changes in ion beam irradiation time and frequency by a conventional frequency adjusting device.

[Explanation of symbols]

 1 Quartz piece 2 Excitation electrode 5 Irradiation area

Claims (1)

[Claims] 1. A method for adjusting a resonance frequency by irradiating a metal thin film of a piezoelectric resonator, in which an electrode made of a metal thin film is formed on a plate surface of a piezoelectric body, with an ion beam and performing reverse sputtering to adjust the resonance frequency. The reverse sputtering is performed simultaneously on the central portion of the plate surface where the resonance frequency rises and the peripheral portion of the plate surface where the resonance frequency decreases due to the thermal shock caused by the irradiation of A frequency adjusting device for a piezoelectric body using an ion beam, which performs reverse sputtering on an irradiation region having an area that cancels a generated change in frequency.