JP2002325022A - Piezoelectric vibrator and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and highly precisely measure the frequency of a piezoelectric element piece corresponding to the miniaturization and high frequency and a piezoelectric oscillator at the time of manufacturing the piezoelectric vibrator. SOLUTION: The outline shapes of a plurality of crystal element pieces 22 are worked, and a recessed vibrator 23 is formed in a crystal wafer 21, and then a first exciting electrode 25a and a leading electrode to an outer peripheral reinforcing frame 24 are formed on one main surface 23a. A measuring terminal 28 is electrically and directly connected to the first exciting electrode so that the frequency of the crystal element piece can be measured, and an opposite main surface 23b of the vibrator is wet etched based on the measured result so that the frequency can be roughly adjusted. After the thickness of the vibrator is set, a second exciting electrode 25b and a leading electrode to the outer peripheral reinforcing frame are formed. A crystal vibrator 30 separated from the crystal wafer is mounted on a package 11, and the second exciting electrode is ion beam etched through a sealing hole 17 of a base 12, and then vacuum sealed. Thus, it is possible to finely adjust the frequency of the crystal vibrator, and to prevent the non-uniformity of the film thickness of the both vibrator electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a piezoelectric vibrator used for various electronic devices including OA devices such as information communication devices and computers, and consumer devices such as electronic timepieces. The present invention relates to a method for manufacturing a piezoelectric vibrating piece such as a crystal as a main vibration and a piezoelectric vibrator.

[0002]

2. Description of the Related Art Conventionally, various electronic devices such as OA devices such as information communication devices and computers, and consumer devices, for example, include a piezoelectric vibrator as a clock source of an electronic circuit, and the same piezoelectric vibrator and IC chip. Piezoelectric devices such as oscillators and real-time clock modules sealed in packages are widely used. With the recent downsizing and thinning of these electronic devices, piezoelectric devices are required to be even smaller and thinner, and surface-mount type devices suitable for mounting devices on circuit boards are often used. Have been.

[0003] In the field of information communication by mobile phones and the like,
In response to the increase in the communication frequency and the speed of the system due to the increase in the capacity and the speed of the information transmission, 9
There is a demand for a piezoelectric vibrator operating at a frequency of about 0 to 200 MHz. The frequency of a piezoelectric vibrator whose main vibration is in the thickness-shear mode using an AT-cut crystal vibrating piece is determined by the thickness of the piezoelectric vibrating piece, whose frequency is inversely proportional to that. Therefore, it is necessary to reduce the thickness of the vibrating portion of the vibrating piece made of quartz or another piezoelectric material. Therefore, for example, Japanese Patent Application Laid-Open No. 11-355094, Japanese Patent Application Laid-Open No. 11-205062,
As described in Japanese Patent Publication No. 8/038736, a thin vibrating portion and a thick reinforcing frame are integrally formed on the outer periphery of the vibrating portion to improve mechanical strength, to facilitate handling and mounting, and to cause chipping or cracking of the vibrating piece. A so-called inverted mesa type piezoelectric vibrator capable of realizing a high frequency while eliminating the problem has been proposed.

FIG. 6 shows an example of a process for manufacturing an inverted-mesa type AT-cut quartz-crystal vibrating piece by a conventional method. First, a crystal wafer 1 having a predetermined size is prepared and etched with an appropriate crystal etching solution to process a large number of crystal element pieces 2 having desired external shapes of the resonator element (FIG. 6A).
Next, the central portion of each crystal element piece 2 is half-etched to a predetermined depth from both front and back surfaces to a predetermined depth with a crystal etching solution to form a recessed shape of the vibrating portion 3 and a reinforcing frame 4 on the outer periphery thereof (FIG. 6). (B)). The concave shape of the vibrating part 3 can be formed by physical processing such as dry etching or mechanical polishing such as sand blasting in addition to wet etching. Next, the frequency of each crystal element piece 2 is measured (FIG. 6C).

FIG. 7 shows how to measure the frequency of each crystal element piece of the crystal wafer 1. As shown in the figure, a quartz wafer 1 is placed on an electrode plate 6 having a counter electrode 5 at a position corresponding to each vibrating part 3 and several tens of The measuring terminal 7 is arranged with a slight gap of about μm, and the frequency is measured by a measuring device including a frequency meter 8 or the like. Based on this measurement,
The front and back main surfaces 3a and 3b of the vibrating portion 3 are further wet-etched to roughly adjust the frequency, and the thickness of the vibrating portion 3 is adjusted to a required predetermined frequency range (FIG. 6D).
Thereafter, an electrode film is formed on each of the front and back surfaces of each crystal element piece 2 by sputtering in a wafer state, and the excitation electrode 9 and an extraction electrode therefrom are formed by using photolithography technology. 10 is obtained (FIG. 6E). Further, by forming the excitation electrode 9 and the extraction electrode after separating the crystal element piece 2 from the crystal wafer 1, the crystal vibrating piece 10 can be obtained.

FIG. 8 shows a crystal resonator completed by separating the crystal resonator element 10 obtained in this manner from the crystal wafer 1 and sealing them in packages 11. The package 11 shown in FIG. 1 includes a rectangular box-shaped base 12 on which insulating material thin plates are laminated, and a metal lid 14 joined to the upper end of the base 12 via a seal ring 13 by, for example, seam welding. Is mounted on the connection terminal 15 on the bottom surface of the base 12 at the base end portion 10a where the extraction electrode is provided with a conductive adhesive 16 in a cantilever manner. In addition, base 12
In the case where a sealing hole 17 communicating with the inside of the package is formed in the bottom surface of the package, the quartz vibrating piece 10 is mounted on the base 12 and the lid 14 is joined to the base, and then the sealing hole 17 is sealed. Before closing with the material 18, fine adjustment of the frequency can be performed by ion beam etching the excitation electrode of the vibrating section 3 through the sealing hole 17.

[0007]

However, in the conventional method described above, since the resonance frequency of the piezoelectric element piece is measured in a non-contact manner, the measuring terminal 7 and the adjacent main surface 3 of the vibrating portion 3 are measured.
Since energy leaks from the gap with a, there is a problem that the measurement tends to be unstable especially at a high frequency, and that accurate measurement is difficult. For example, FIG. 9 shows an example of the result of measuring the frequency of the AT-cut crystal element piece having such an inverted mesa structure as described above. From this figure, it can be seen that a large harmonic component other than the main vibration (fundamental wave) is detected in close proximity, and its influence is large.

Further, the measuring terminal 7 usually has a tip shape corresponding to the excitation electrode 9. Depending on the position of the tip on the main surface 3a of the vibrating portion, the measurement of the frequency becomes unstable, and There is a possibility that the specification of the (fundamental wave) becomes difficult due to the influence of harmonics detected in proximity thereto. In particular, as the piezoelectric element piece is miniaturized, the measuring terminal 7 is
It is difficult to accurately arrange them at desired positions.

Further, the excitation electrode 9 is ideally
It is preferable to form the film thickness evenly on the front and back main surfaces 3a and 3b because there is no variation in frequency and no reduction in vibration characteristics. However, in the above-described conventional method, the frequency is adjusted by forming the excitation electrodes 9 having the same thickness on the both main surfaces and then etching one of the excitation electrodes. In 3b, there is a problem that the thickness of the excitation electrode 9 is not uniform, and the frequency tends to vary.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the size of the piezoelectric vibrator, especially in the manufacture of a piezoelectric vibrating piece and a piezoelectric vibrator in a thickness-shear vibration mode. It is another object of the present invention to provide a method capable of accurately and accurately measuring the frequency of a piezoelectric element piece in response to a higher frequency.

Another object of the present invention is to make the thickness of the excitation electrodes formed on the front and back main surfaces of the vibrating portion of the piezoelectric vibrating reed uniform,
An object of the present invention is to provide a piezoelectric vibrating reed and a method of manufacturing a piezoelectric vibrator that can eliminate frequency variations.

[0012]

According to the present invention, in order to achieve the above object, a piezoelectric element piece having a predetermined outer shape and dimensions is prepared, and a first main surface of a vibrating portion of the piezoelectric element piece is provided. Forming a first excitation electrode, measuring the resonance frequency of the piezoelectric element using the first excitation electrode, and etching the second main surface of the vibrating portion of the piezoelectric element according to the measurement result. Thus, there is provided a method of manufacturing a piezoelectric vibrating reed, comprising the steps of adjusting the resonance frequency of the piezoelectric element reed and forming a second excitation electrode on the second main surface of the vibrating portion of the piezoelectric element reed. You.

When measuring the frequency of the piezoelectric element piece, the measuring terminal can be brought into direct contact with or electrically connected to the excitation electrode, so that energy leakage or displacement of the measuring terminal as in the prior art can occur. Since unstable measurement can be eliminated, more accurate and highly accurate frequency measurement can be performed. Moreover, in order to adjust the frequency of the piezoelectric element piece, only one main surface of the vibrating portion needs to be etched, so that the processing is simpler and shorter than in the past, and the control is easy, so that high accuracy is achieved. Can be adjusted to the frequency.

In one embodiment, the frequency of the piezoelectric element piece can be finely adjusted with high accuracy by further including the step of adjusting the resonance frequency of the piezoelectric element piece by etching the second excitation electrode.

In this case, with respect to the film thickness reference value of the excitation electrode determined based on the desired frequency, it is preferable that the first excitation electrode is formed thinner and the second excitation electrode is formed thicker. By etching the second excitation electrode, the thickness of both excitation electrodes can be made more uniform, so that the frequency can be adjusted with higher accuracy and the variation in frequency can be eliminated.

In one embodiment, the piezoelectric element piece is an AT-cut quartz element piece. Conventionally known various piezoelectric materials can be used for the piezoelectric element piece. In particular, the AT-cut quartz material has a substantially constant etching rate and is easy to control the etching.
This is preferable because the main surface of the vibrating portion can be uniformly processed to a desired thickness.

According to another aspect of the present invention, the piezoelectric vibrating reed manufactured by the above-described method of the present invention is hermetically sealed in a package, so that the frequency can be adjusted with high precision, and miniaturization and high frequency can be achieved. The present invention provides a method for manufacturing a piezoelectric vibrator suitable for employment.

In one embodiment, a surface-mounted type piezoelectric vibrator is formed by mounting a piezoelectric vibrating reed on a base of a package, bonding a lid to the base, and sealing the piezoelectric vibrating reed. it can.

In this case, after the piezoelectric vibrating reed is mounted on the base, the second excitation electrode of the piezoelectric vibrating reed is etched to further adjust the resonance frequency, so that the frequency of the piezoelectric vibrator is increased. Can be fine-tuned to accuracy.

Further, with respect to the film thickness reference value of the excitation electrode determined based on a desired frequency, the first excitation electrode is formed thinner and the second excitation electrode is formed thicker. Since the thicknesses of the two excitation electrodes can be made more uniform by etching the two excitation electrodes, the frequency of the piezoelectric vibrator can be adjusted with higher accuracy, and the frequency variation is eliminated.

In another embodiment, the base has a sealing hole communicating with the inside of the package, and after the piezoelectric vibrating reed is mounted on the base and the lid is joined to the base, before the sealing hole is closed. The method further includes a step of adjusting the resonance frequency by dry-etching the second excitation electrode through the sealing hole, thereby eliminating the influence of joining the lid to the base and achieving high-precision frequency. And the package can be sealed in a vacuum or in a predetermined gas atmosphere.

In one embodiment, the piezoelectric vibrating reed is an AT-cut quartz vibrating reed. In particular, the AT-cut quartz material has a substantially constant etching rate and is easy to control the etching. It is preferable because it can be processed to a thickness of.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for manufacturing a piezoelectric vibrating reed and a piezoelectric vibrator according to the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, quartz which has been widely used as a piezoelectric material is used for the piezoelectric element piece and the piezoelectric vibrating piece, and the same reference numerals are given to the same components in each drawing.

FIG. 1 shows a preferred embodiment of a process of manufacturing the inverted-mesa type AT-cut quartz resonator shown in FIG. 8 by applying the method of the present invention. First, a quartz wafer 21 having a predetermined size is prepared in the same manner as in the conventional process, and is etched using, for example, an etching solution for quartz made of a mixed solution of hydrofluoric acid and ammonium fluoride to have a desired external shape of the resonator element. A large number of crystal element pieces 22 are processed (FIG. 1A). Next, the central portion of each crystal element piece 22 is half-etched from the front and back surfaces to a predetermined depth with the above-mentioned crystal etching solution to a predetermined depth to reduce the thickness, thereby forming the concave shape of the vibrating portion 23 and the reinforcing frame 24 on the outer periphery thereof ( FIG. 1 (B)).

The etching liquid has a high etching rate for processing the outer shape of the vibrating piece, and has a low etching rate for processing the concave shape of the vibrating portion in order to more precisely control the thickness of the vibrating portion 23. It is preferable to use those having an etching rate. The recessed shape of the vibrating part 23 may be formed to a desired thickness by physical processing such as dry etching or mechanical polishing such as sand blasting in addition to the chemical processing by wet etching in the present embodiment. Can be.

Next, an electrode film is formed on one surface of each crystal element piece 22 by sputtering an electrode material or the like, and the first main surface 23a of the vibrating portion 23 is formed on the first main surface 23a of the vibrating portion 23 by photolithography. Of the excitation electrode 25a and a lead electrode from the excitation electrode 25a to the outer peripheral reinforcing frame (FIG. 1C). Thereafter, the frequency of the crystal element piece 22 is measured (FIG. 1).
(D)).

FIG. 2 schematically shows the procedure for measuring the frequency of the crystal resonator element in FIG. 1 (D). As shown in the figure, a quartz wafer 21 is placed on an electrode plate 27 having a counter electrode 26 at a position corresponding to a first excitation electrode 25a of each vibrating part 23, and a measuring terminal 28 is attached to each quartz element piece 22. Is electrically connected directly to the first excitation electrode 25a or to an extraction electrode from the first excitation electrode 25a.
It measures with the measuring device which consists of. FIG. 3 shows an example of the result of measuring the frequency in this manner. According to the present invention, since the measurement is performed by electrically connecting the measurement terminal 28 directly to the first excitation electrode 25a, the influence of the harmonic component is eliminated as shown in FIG. Can be easily detected, and its frequency can be measured accurately.

Next, based on the measurement result, the vibrating section 2
The frequency is roughly adjusted by further wet-etching the main surface 23b on the side opposite to 3 to adjust the thickness of the vibrating portion 23 to a required predetermined frequency range (FIG. 1).
(E)). Thereafter, an electrode film is formed by, for example, sputtering an electrode material on the opposite surface of each crystal element piece 22 in a wafer state, and using photolithography technology,
A first excitation electrode 25 is provided on the other main surface 23 b of the vibrating section 23.
By forming a second excitation electrode 25b paired with a and an extraction electrode from the second excitation electrode 25b to the outer peripheral reinforcing frame, a desired crystal vibrating piece 30 whose frequency is adjusted with high precision can be obtained (FIG. 1F). . Further, as described above in relation to the prior art, the excitation electrodes 25a or 25b and their extraction electrodes can be formed after each crystal element piece 22 is separated from the crystal wafer 21.

Further, according to the present invention, the thickness of the excitation electrode is calculated from the thickness of the vibrating portion 23 for a desired frequency and is set as a reference value to, and is first formed on one main surface 23a of the vibrating portion 23. The thickness ta of the first excitation electrode 25a is smaller than the reference value to of the film thickness, preferably, about 1/2 (= to / 2). The film thickness tb of the second excitation electrode 25b formed on the other main surface 23b is set to be larger than the reference value to of the film thickness. Preferably, as shown in FIG. 4 (A), α is a thickness that can absorb the variation in the frequency of the crystal element piece and the variation in the thickness of the excitation electrode by the subsequent frequency adjustment, and t represents the thickness.
b = (to / 2) + α. In the process of finely adjusting the frequency of the crystal resonator, which will be described later, the second excitation electrode 25b having a large thickness, as shown in FIG.
Dry etching to a thickness of 2. The thickness of the vibrating portion 23 used for calculating the film thickness reference value can be accurately and easily known from the thickness of the quartz wafer 21 and the etching amount thereof.

The crystal vibrating piece 30 thus obtained is separated from the crystal wafer 21 and, as described above with reference to FIG.
Are sealed in a package 11 composed of a rectangular box-shaped base 12 having a through hole and a metal lid 14. The crystal vibrating piece 30 is cantilevered with the conductive adhesive 16 on the connection terminal 15 on the bottom surface of the base 12 at the base end 30a where the extraction electrode is provided, with the second excitation electrode 25b facing down. . After the lid 14 is joined to the upper end of the base 12 via the seal ring 13 by, for example, seam welding, the second excitation electrode 25b is dry-etched through the sealing hole 17 as shown in FIG. Perform ion beam etching. Therefore, it is preferable that the sealing hole 17 is disposed substantially at the center of the bottom surface of the base 12 corresponding to the position of the second excitation electrode 25b.

In this ion beam etching, the external terminals 3 drawn out from the connection terminals 15 to the outer surface of the package 11 are used.
By performing the measurement while measuring the frequency via 1, the frequency of the crystal resonator can be finely adjusted with high accuracy. As described with reference to FIGS. 4A and 4B, when the second excitation electrode 25b is formed thicker than the first excitation electrode 25b, the second excitation electrode 25b is removed by ion beam etching to thereby provide a dual excitation electrode. The unevenness of the film thickness of the electrodes 25a and 25b can be reduced. Since the thickness of the vibrating portion 23 and the film thickness of the first excitation electrode 25a are known before the film formation of the second excitation electrode 25b, it is possible to design the two excitation electrodes so that the film thicknesses thereof are equal. . In particular, as described above, the film thickness ta of the first excitation electrode 25a is set to the film thickness reference value of one.
/ 2 (= to / 2), the thickness tb of the second excitation electrode 25b
Is preferably set to a value (= to / 2 + α) obtained by adding a thickness (α) that can be absorbed by frequency adjustment to の of the film thickness reference value. This makes it possible to eliminate the variation in the frequency at the same time as the fine adjustment of the frequency with higher accuracy.

Finally, when the sealing hole 17 is hermetically closed with a sealing material 18 in a vacuum atmosphere or an inert gas atmosphere,
A quartz resonator having an inverted mesa structure corresponding to a higher frequency according to the present invention is completed. As the sealing material 18, for example, a high melting point Pb-Sn solder-based material such as Au-Sn solder or 9: 1 solder is used, and a metal ball 18 formed of these materials is used.
5 'is placed on a step 17' as shown in FIG. 5 (B) and welded by a batch-type vacuum sealing device, a laser device, an electron beam device, or the like, thereby closing the sealing hole 17.

The present invention is not limited to the above-described embodiment, and it will be apparent to those skilled in the art that various modifications and changes can be made to the above-described embodiment within the technical scope thereof. For example, the present invention can be similarly applied to piezoelectric element pieces made of various piezoelectric materials such as lithium tantalate and lithium niobate other than quartz. Further, in the above embodiment, a method is employed in which a large number of crystal element pieces are simultaneously processed in the state of a wafer and then divided into individual crystal vibrating pieces.
After cutting out a plurality of crystal element pieces from the wafer by dicing or the like, each of the crystal element pieces can be individually processed to produce a crystal vibrating piece. Further, the piezoelectric vibrating reed manufactured according to the present invention can be used for a piezoelectric oscillator and other various piezoelectric devices other than the piezoelectric vibrator.

[0034]

According to the present invention, the above-described configuration provides the following special effects. According to the present invention, in the process of manufacturing the piezoelectric vibrating piece and the piezoelectric vibrator, when measuring the frequency of the piezoelectric element piece, the measuring terminal can be directly contacted or electrically connected to the excitation electrode. As described above, there is no risk of energy leakage and displacement of the measuring terminals, so that accurate and high-precision measurement can be performed in accordance with the miniaturization and high frequency of the piezoelectric vibrator, and the frequency adjustment of the piezoelectric element piece. Is easy to control by etching only one main surface of the vibrating part, it is possible to adjust the frequency with high precision, and it is performed more easily and in a shorter time than before, thereby improving productivity and yield. be able to. In addition, since the thickness of the vibrating portion and the thickness of each excitation electrode formed on the front and back main surfaces can be controlled separately, the frequency can be adjusted with high precision, and the thickness of both excitation electrodes can be made uniform. Frequency variation can be eliminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a crystal wafer composed of FIGS. 1A to 1F showing a manufacturing process of a crystal resonator element according to the present invention in the order of steps.

FIG. 2 is a perspective view showing how to measure the frequency of the crystal resonator element in FIG. 1 (D).

FIG. 3 is a diagram showing measurement results of the frequency of FIG. 2;

FIG. 4 is a partially enlarged cross-sectional view showing the crystal resonator element of FIG. 1 (F).

5A and 5B are longitudinal sectional views of the crystal resonator shown in FIGS. 5A and 5B showing a process of sealing the crystal resonator element in a package.

FIGS. 6A to 6E are cross-sectional views of a quartz crystal wafer including FIGS.

FIG. 7 is a perspective view showing how to measure the frequency of the crystal element piece in FIG. 6 (C).

FIG. 8 is a longitudinal sectional view showing a crystal resonator.

FIG. 9 is a diagram showing measurement results of the frequency in FIG. 7;

[Explanation of symbols]

 1,21 Quartz wafer 2,22 Quartz element piece 3,23 Vibration part 3a, 3b, 23a, 23b Main surface 4,24 Reinforcement frame 5,26 Counter electrode 6,27 Electrode plate 7,28 Measuring terminal 8,29 Frequency meter 9 Excitation electrode 10, 30 Quartz vibrating piece 10a, 30a Base end 11 Package 12 Base 13 Seal ring 14 Lid 15 Connection terminal 16 Conductive adhesive 17 Sealing hole 17 'Step 18 Seal material 18' Metal ball 25a First Excitation electrode 25b Second excitation electrode 31 External terminal

Claims (10)

[Claims] 1. A piezoelectric element piece having a predetermined outer shape and dimensions is prepared, a first excitation electrode is formed on a first main surface of a vibrating portion of the piezoelectric element piece, and the first excitation electrode is used. Measuring the resonance frequency of the piezoelectric element piece by etching the second main surface of the vibrating portion of the piezoelectric element piece according to the result of the measurement, thereby adjusting the resonance frequency of the piezoelectric element piece; A method of manufacturing a piezoelectric vibrating reed, comprising: forming a second excitation electrode on the second main surface of the vibrating portion of the piezoelectric element piece to manufacture a piezoelectric vibrating reed. 2. The method according to claim 1, further comprising the step of adjusting the resonance frequency of the piezoelectric element by etching the second excitation electrode. 3. The method according to claim 1, wherein the first excitation electrode is formed thinner and the second excitation electrode is formed thicker with respect to a thickness reference value of the excitation electrode determined based on a desired frequency. The method for manufacturing a piezoelectric vibrating reed according to claim 2. 4. The method for manufacturing a piezoelectric vibrating piece according to claim 1, wherein said piezoelectric element piece is an AT-cut quartz crystal element piece. 5. A method for manufacturing a piezoelectric vibrator, wherein the piezoelectric vibrating reed manufactured by the method according to claim 1 is hermetically sealed in a package. 6. The piezoelectric vibrator according to claim 5, wherein the piezoelectric vibrating reed is mounted on a base of the package, and a lid is bonded to the base to seal the piezoelectric vibrating reed. Method. 7. The method according to claim 1, further comprising a step of adjusting the resonance frequency by etching the second excitation electrode of the piezoelectric vibrating piece after mounting the piezoelectric vibrating piece on the base. Item 7. A method for manufacturing a piezoelectric vibrator according to item 6. 8. The method according to claim 1, wherein the first excitation electrode is formed thinner and the second excitation electrode is formed thicker with respect to a thickness reference value of the excitation electrode determined based on a desired frequency. The method for manufacturing a piezoelectric vibrator according to claim 7, wherein: 9. The base has a sealing hole communicating with the inside of the package, and closes the sealing hole after mounting the piezoelectric vibrating reed on the base and joining the lid to the base. 9. The method according to claim 8, further comprising the step of adjusting the resonance frequency of the second excitation electrode by dry-etching the second excitation electrode through the sealing hole. Method. 10. The method according to claim 5, wherein the piezoelectric vibrating reed is an AT-cut quartz vibrating reed.