JP2001036369A - Production of high frequency piezoelectric vibration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress production cost and to improve producing efficiency. SOLUTION: The principle planes, on which recesses are not formed, of two piezoelectric diaphragms 1 and 2 are stuck mutually by an adhesive agent 3 and in the state of performing masking to principle planes to form recesses, so as to form prescribed recesses with metal films 10 and 20, the diaphragms are immersed in an etching liquid so that recesses can be formed. Afterwards, these two piezoelectric diaphragms 1 and 2 are separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating device such as a quartz vibrator or a quartz filter used as a receiving unit of a communication device or a clock source of a microcomputer. It is about.

[0002]

2. Description of the Related Art As the frequency of communication equipment and the operating frequency of microcomputers increase, piezoelectric vibrating devices such as quartz oscillators and quartz filters are also required to support higher frequencies. In general, a thickness shear vibration of an AT-cut quartz plate is often used as a quartz plate corresponding to a higher frequency, and as is well known, the frequency is determined by the thickness, and the frequency and the thickness are inversely proportional. For example, when a frequency of 100 MHz is obtained as the fundamental vibration frequency, about 16 μm
m ultra-thin piezoelectric diaphragms are required. In the processing of such an extremely thin plate, it is difficult to perform a polishing operation, and it has been difficult to improve a production yield.

To solve such a problem, FIG.
As shown in (f), a concave portion is provided in the central portion of the quartz plate,
A vibration region 91 having a thin wall is set at the bottom of the concave portion,
A reinforcing portion for reinforcing the vibration region with a thick portion around the
Has been invented. FIG. 6F is an internal cross-sectional view showing a conventional example, and the vibration region 9 of the thinned concave portion is shown.
A plurality of excitation electrodes 9a are formed in a vibrating region 91 of a quartz plate 9 having a thick reinforcing portion 92 formed around the plate 1 and a peripheral portion thereof. FIG. By adopting such a configuration, the vibration region can be made considerably thinner than before while maintaining the overall mechanical strength, and compared with the above-mentioned conventional single-thickness piezoelectric vibration plate, 16 μm or The formation of a vibration region having a thickness smaller than that was also achieved with a good yield.

In order to obtain a piezoelectric vibrator having such a structure,
For example, a manufacturing process using a photolithography technique as shown in each of FIGS. As shown in FIG. 6A, a Cr film 93 is formed on the front and back surfaces (both main surfaces) of the quartz plate 9 as a protective film.
And an Au film 94 are sequentially formed by a vacuum evaporation method or the like. FIG.
As shown in (b), after applying a resist liquid on the surface (one main surface) on which the concave portion is to be formed, patterning exposure is performed,
A resist film 95 having a predetermined pattern is obtained. Using the resist film 95 as a mask, a part of the Au film and the Cr film as the protective film is etched to obtain a protective film having a pattern corresponding to the concave portion. After that, the resist film is removed, and FIG.
As shown in (2), using the protective film as a mask, a part of the quartz plate is etched to form a concave portion. Then, after the protective film is peeled and removed, an excitation electrode is formed as shown in FIG.

[0005]

According to the above-described manufacturing method, it is necessary to form a protective film on the main surface of the quartz plate on which the concave portion is not formed. It is finally removed together with the protective film used for the formation. The thickness of the protective film is determined by the required frequency, that is, the etching time of the quartz plate. For example, Au
Although several hundred to several thousand angstroms of the film are required, these are eventually removed, which has been a factor of increasing the manufacturing cost.

In order to efficiently perform the etching without variation at the time of etching or the like, it is necessary to place a quartz plate in a jig at a predetermined interval and immerse the plate in an etching solution. There is also a problem that the number of installations is limited and mass production efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a method of manufacturing a high-frequency piezoelectric vibration device capable of suppressing the manufacturing cost and increasing the manufacturing efficiency. is there.

[0008]

In order to solve the above-mentioned problems, the present invention provides a piezoelectric vibrating plate having a concave portion formed at the center of one main surface of a piezoelectric vibrating plate whose frequency is determined by its thickness. A method for manufacturing a high-frequency piezoelectric vibration device, comprising: forming a thin piezoelectric vibration region in a central portion by forming the piezoelectric vibration region; and forming a thick reinforcing portion provided around the piezoelectric vibration region. The main surfaces of the two piezoelectric vibrating plates, each of which does not have a concave portion, are bonded to each other, and masking is performed so that a predetermined concave portion is formed on the main surface of the concave portion. After the formation, the two piezoelectric vibrating plates are separated.

According to a second aspect of the present invention, a concave portion is formed in a central portion of one main surface of a piezoelectric vibrating plate whose frequency is determined by a thickness, thereby forming a thin piezoelectric vibrating region in the central portion. And a method of manufacturing a high-frequency piezoelectric vibration device in which a thick reinforcing portion provided around the piezoelectric vibration region is formed. After being attached to a corrosive holding plate and masking so that a predetermined concave portion is formed on the main surface on which the concave portion is formed, the substrate is immersed in an etchant to form a concave portion. The manufacturing method may be characterized in that the diaphragm is separated from the holding plate.

[0010] In each of the above manufacturing methods, a thin metal protective film may be formed on the bonding surface of the piezoelectric vibrating plate.
Thereby, the corrosion resistance due to the etchant on the bonding surface can be improved.

Also, a configuration may be adopted in which an adhesive used for bonding is wrapped around the end surface of the bonding surface to prevent the etching solution from penetrating into the bonded portion.

According to the first and second aspects, by bonding the two piezoelectric vibrating plates together, only the main surface necessary for forming the concave portion can be etched. Therefore, there is no need to form a protective film such as an Au film on the other main surface which is not involved in the formation of the concave portions as in the related art.

In addition, since a piezoelectric vibrating plate integrated into a pair is used at the time of forming a resist film and a protective film, or at the time of etching, handling is easy in manufacturing.
In addition, manufacturing efficiency can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment of the Invention
An MCF (monolithic crystal filter) using a cut quartz plate will be described as an example with reference to the drawings.

FIG. 1 is a view showing a manufacturing method according to the present invention, and FIG. 2 is a perspective view showing a state in which a large wafer is processed to obtain a large number of quartz plates. FIG. 1 shows a manufacturing process using two quartz plates, after forming concave portions in both, and before forming electrodes. FIG. 1A shows a quartz plate 1.
2 shows a state in which the main surfaces of the quartz plate 2 on which the concave portions are not formed are bonded together with the adhesive 3, and then the metal films (protective films) 10 and 20 are formed on the main surfaces other than the bonded surfaces. Each of the quartz plates 1 and 2 has a thickness of about 50 μm, and both main surfaces are mirror-finished by polishing. In this embodiment, the adhesive 3 uses a novolak-based polymer resin, but may also use an acrylate-based or hydroxystyrene-based polymer resin, or an epoxy-based adhesive, UV ( An (ultraviolet) curable adhesive may be used. The metal films 10 and 20 are formed using a thin film forming means such as a vacuum evaporation method, and Cr films 11 and 21 are formed in contact with the quartz plates 1 and 2, and Au films 12 and 22 are formed on the upper surfaces thereof.

FIG. 1B shows the formation of a resist film formed on the surface of the metal film. In this example, a positive type of OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd. is used for the resist film. A photoresist is uniformly applied on the metal films 10 and 20 by a spinner or the like, and is exposed through a photomask having a predetermined mask pattern (not shown). Thereafter, the unnecessary resist 41 is removed through a developing process and the like, and the resist film 4 having a predetermined mask pattern is obtained.

Then, using the resist film 4 as a mask, a part of the metal films 10 and 20 is etched, and the concave portions 1 are formed in the quartz plate.
Metal films 10a and 20a having a mask pattern for forming a and 2a are obtained. FIG. 1C shows a state where the concave portions 1a and 2a are formed in the quartz plate by etching using the patterned metal films 10a and 20a as a mask. The etching depth of the concave portion is controlled by parameters such as the type of the etching solution, the surrounding environment, and the etching time. In this example, etching is performed for about 4 hours using a mixed solution of hydrofluoric acid and ammonium fluoride as the etching solution. Thereby, an etching amount of about 35 μm is obtained. As a result, the thickness of the thin piezoelectric vibration region of the concave portion is about 15 μm.

FIG. 1D shows the state of the metal film 1 after the etching.
This shows a state in which the quartz plates 1 and 2 are separated by immersing 0a and 20a in a metal stripper and removing the adhesive 3 by immersing in a resin stripper. Thereby, two quartz plates having the thick reinforcing portions 13 and 23 and the thin piezoelectric vibrating regions 14 and 24 can be obtained.

Thereafter, as shown in FIG. 1E, excitation electrodes and extraction electrodes (not shown) are provided in the piezoelectric vibrating regions 14 and 24.
To form In this example, in order to obtain the MCF, the divided electrodes 15, 16, 25, 26 and the common electrodes 17, 27 are formed as excitation electrodes by a vacuum deposition method using a masking means.

In the above manufacturing example, an example is shown in which two quartz plates are attached, but in actual manufacturing, batch processing is often performed using a large wafer from the viewpoint of efficiency. FIG. 2 shows an example in which two large quartz wafers W1 and W2 are bonded together to obtain a large number of quartz plates 1 having concave portions 10.
Deep grooves W11 and W21 for small splitting are formed vertically and horizontally around each quartz plate. Note that it is of course possible to cut into small pieces by dicing or the like without forming this deep groove.

A second embodiment will be described with reference to FIG. Note that the same structural parts as those described in the above embodiment are described using the same numbers,
The description of the manufacturing method is partially omitted.

In this example, two quartz plates 1 and 2 are attached to the holding plate 5 so as to face each other. The holding plate is, for example, P
A material having corrosion resistance to an etchant such as t or Au is used. Further, the core may be made of graphite and the surface thereof may be plated with high-purity SiC, or the core may be made of quartz and plated with Cr-Au to have corrosion resistance to an etching solution. And
As shown in FIG. 3A, positioning recesses 51 and 52 are formed on the front and back surfaces of the holding plate 5 when viewed in cross section. The quartz plates 1 and 2 are adhered to the positioning concave portions with adhesives 61 and 62, and the Cr films 11 and 21 and Au are respectively attached.
Metal films 10 and 20 including films 12 and 22 are formed. The positioning recess is not essential, but effectively functions for positioning and fixing in manufacturing. As shown in FIG. 3B, a resist film 4 is formed, and the metal film 1 is formed using the resist film 4 as a mask.
0 and 20 are etched into a predetermined pattern. Thereafter, as shown in FIG. 3C, the patterned metal film 10 is formed.
Etching is performed using a and 20a as masks to form recesses 1a and 2a in the quartz plate.

After completion of the etching, the metal films 10a and 20a are peeled off and removed as shown in FIG.
By separating and removing 62, each of the quartz plates 1 and 2 is separated from the holding plate 5. Thereafter, an excitation electrode is formed on the quartz plate having the separated concave portion. In this embodiment, a quartz oscillator is illustrated, and as shown in FIG. 3E, excitation electrodes 71 and 72 and an extraction electrode (not shown) are formed on the front and back of the piezoelectric oscillation region.

In each of the above embodiments, an example is shown in which quartz plates of the same outer size are bonded, but a quartz plate or a quartz wafer of a different size may be bonded. In this case, it is possible to perform flexible manufacturing, for example, to cope with multi-product production. However, it is necessary to form a protection film (resin or metal film) or the like for etching in a protruding region of a bonded surface of a crystal plate or a crystal wafer having a large external size.

Further, as shown in FIG. 4, in order to prevent the etching solution from penetrating into the bonded portions,
Thin metal films 18 and 28 as protective films on the bonding surface of No. 2
And then a quartz plate may be bonded with the adhesive 3. In order to reduce the cost of the metal film material,
The protective film may be formed only near the outer periphery of the bonding surface of the quartz plate.

Further, as shown in FIG. 5, an adhesive 3 is applied near the outer periphery of the adhesive bonding so as to cover the side surfaces of the bonded quartz plates 1 and 2 (shown at 29). In this case, unintended corrosion of the bonded surface of the quartz plate can be prevented. It is necessary that the coating on the side surface includes at least a circumferential bonded portion.

In each of the above embodiments, a quartz plate is exemplified as the piezoelectric body, but other piezoelectric bodies such as lithium tantalate and langasite may be used.

[0028]

According to the first and second aspects, by bonding two piezoelectric vibrating plates together, only the main surface necessary for forming the concave portion can be etched. Therefore, unlike the related art, Au having a film thickness enough to withstand the etching solution in direct contact with other main surfaces not involved in the formation of the concave portion is also used.
There is no need to form a protective film such as a film. Therefore, material costs during manufacturing can be reduced.

Further, since a piezoelectric vibrating plate integrated into a set of two is used at the time of forming a resist film and a protective film, or at the time of etching, handling is easy in manufacturing,
In addition, manufacturing efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process according to the present invention.

FIG. 2 is a diagram showing a manufacturing method according to the present invention.

FIG. 3 shows a manufacturing method according to the present invention.

FIG. 4 is a diagram showing a manufacturing method according to the present invention.

FIG. 5 is a diagram showing a manufacturing method according to the present invention.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

1, 2, 9 Quartz plate (piezoelectric vibration device) 10, 20 Metal film 1a, 2a Concave portion 14, 24, 91 Piezoelectric vibration region 13, 23, 92 Reinforcement portion 15, 16, 17, 25, 26, 27, 71, 72,9
a Excitation electrode 4 Resist film W1, W2 Quartz wafer

Claims (2)

[Claims] 1. A thin piezoelectric vibration region is formed in a central portion of a main surface of a piezoelectric vibrating plate whose frequency is determined by a thickness. A method for manufacturing a high-frequency piezoelectric vibrating device comprising a thick reinforcing portion provided on the periphery, wherein two principal surfaces of two piezoelectric vibrating plates, each having no concave portion, are bonded to each other and a concave portion is formed. A high-frequency piezoelectric vibration device characterized in that, after masking is performed so that a predetermined concave portion is formed on a main surface to be formed, the concave portion is formed by immersion in an etching solution, and the two piezoelectric vibration plates are separated. Manufacturing method. 2. A piezoelectric vibrating plate whose frequency is determined by its thickness has a concave portion formed in a central portion of one main surface thereof, thereby forming a thin piezoelectric vibrating region in the central portion and forming a piezoelectric vibrating region in the central portion. A method for manufacturing a high-frequency piezoelectric vibrating device comprising a thick reinforcing portion provided on the periphery, wherein a main surface of each of two piezoelectric vibrating plates, on which no concave portion is formed, is formed on a holding plate having corrosion resistance. After sticking and masking so that a predetermined concave portion is formed on the main surface forming the concave portion, after immersing in an etchant to form a concave portion, the two piezoelectric vibrating plates are removed from the holding plate. A method for manufacturing a high-frequency piezoelectric vibration device, comprising: separating the device.