JP4524916B2 - High frequency piezoelectric device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high frequency piezoelectric device, and more particularly to a miniaturized high frequency piezoelectric vibrator and a dual mode piezoelectric filter.
[0002]
[Prior art]
Piezoelectric vibrators are widely used from communication devices to electronic devices because of their small size and the ability to easily obtain a stable frequency. Particularly in recent years, with the increase in the carrier frequency of wireless devices, there is a strong demand for further increase in the frequency of piezoelectric vibrators used in piezoelectric oscillators.
4 (a) and 4 (b) are diagrams showing the configuration of a conventional high-frequency piezoelectric vibrator using an AT-cut quartz substrate, where FIG. 4 (a) is a plan view and FIG. 4 (b) is a cross section taken along QQ. FIG. A recess 12 is formed on one main surface of the quartz substrate 11, and an electrode 13 is disposed at substantially the center on the opposite side of the plane, and a lead electrode 14 is extended from the electrode 13 toward the end of the quartz substrate 11. It is connected to the pad electrode 15 provided in the thick part of the annular surrounding part of the quartz substrate 11. A full-surface electrode 16 is attached to the recessed side of the quartz substrate 11 to constitute a high-frequency piezoelectric vibrator. FIG. 4B is a cross-sectional view taken along the line QQ, in which one end on the concave side and the bottom surface of the package (not shown) are conductively fixed by a cantilever support using a conductive adhesive 17. This is to prevent the thin vibrating portion of the recessed portion 12 from being distorted by the adhesive.
[0003]
FIG. 5A is a diagram for explaining the process of forming the high-frequency quartz substrate 11 shown in FIG. 4, and a gold AT cut quartz substrate (wafer) 21 processed into a thin plate of about 80 μm is formed on the entire surface. The thin film is attached using a vapor deposition apparatus or a sputtering apparatus, and a resist film is applied on the thin film, and the resist film is exposed through a mask. When the exposed resist film is peeled off using a release agent, a gold thin film in which the exposed shape is arranged in a matrix form is exposed. After the gold thin film is dissolved in aqua regia etc. to expose the quartz substrate surface, the exposed surface is immersed in an etching solution containing ammonium fluoride as a main component and etched, and then the resist film is peeled off. As shown in FIG. 5A, a wafer 21 in which individual substrates 22 having recesses are arranged in a matrix is obtained. At this time, the dividing etching grooves 23, 23, 23,... For dividing into the individual substrates 22 are simultaneously formed in the vertical and horizontal directions.
[0004]
Further, in order to adjust the frequency of the individual piezoelectric substrates 22 arranged in a matrix shape to a desired frequency, an etching solution is dropped on the individual recesses using a computer-controlled device, and the etching time is controlled. The frequency of each piezoelectric substrate 22 is adjusted. For this reason, the thin portion that is the vibrating portion needs to be surrounded by a higher wall surface.
FIG. 5B is an enlarged perspective view of the piezoelectric substrate 22 obtained by dividing the wafer 21 into individual pieces along the etching groove 23, and includes a thin portion 24 that is a vibrating portion and an annular surrounding portion that holds the thin portion 24. 25 is integrally formed. Moreover, FIG.5 (c) is sectional drawing in QQ.
[0005]
[Problems to be solved by the invention]
However, in the conventional high-frequency piezoelectric vibrator as described above, the thin-walled portion is used to protect the thin-walled portion that is the vibrating portion from vibration and impact and to finely adjust the frequency of the vibrating portion using an etching solution. And an annular surrounding portion formed integrally with each other. Therefore, there has been a problem that the size of the piezoelectric substrate is larger than the size of the piezoelectric substrate that is originally required to maintain the vibration. Further, as shown in FIG. 4B, the high-frequency piezoelectric vibrator has a so-called cantilevered support structure, so that the mass of the annular surrounding portion acts as a bending moment on the vibration portion. There is also a problem that the temperature characteristic exhibited by the part deviates from the cubic curve exhibited by the original cutting angle.
The present invention has been made to solve the above problems, and an object thereof is to provide a miniaturized high-frequency piezoelectric vibrator.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the high-frequency piezoelectric device according to the present invention includes a thin rectangular vibrating portion, and a thick holding portion that holds only three sides of the periphery of the rectangular vibrating portion. Is a high-frequency piezoelectric device that is integrally constructed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
1A and 1B are diagrams showing the configuration of a high-frequency vibrator according to the present invention, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along QQ. A concave portion 2 is formed on one main surface of the quartz substrate 1, an electrode 3 is disposed at substantially the center on the opposite plane side, and a lead electrode 4 is extended from the electrode 3 toward the end of the quartz substrate 1. It is connected to the pad electrode 5 provided in the thick part of the annular surrounding part of the quartz substrate 1. A full-surface electrode 6 is attached to the concave side of the quartz substrate 1 to constitute a high-frequency piezoelectric vibrator. Note that the coordinate axis of the crystal is shown in the left corner of FIG.
[0008]
The feature of the present invention resides in the structure of the piezoelectric substrate 1 and, as shown in FIG. 1B, among the thick annular surrounding portions, the thick portion α of the annular surrounding portion in the −X-axis direction is made extremely small. This is because the size and frequency temperature characteristics are improved.
[0009]
The perspective view shown in FIG. 2A is a diagram for explaining the process of forming the piezoelectric substrate 1 of the high-frequency crystal resonator shown in FIG. 1, and is a large AT-cut quartz substrate processed into a thin plate of about 80 μm. (Wafer) A gold thin film is deposited on the entire surface of the wafer 1a by using a vapor deposition apparatus or a sputtering apparatus, and a resist film is applied on the thin film, and the resist film is exposed through a mask. When the exposed resist film is peeled off using a release agent, a gold thin film in which the exposed shape is arranged in a matrix form is exposed. After the gold thin film is dissolved in aqua regia etc. to expose the quartz substrate surface, the substrate 1a is immersed in an etching solution containing ammonium fluoride as a main component and etched, and then the resist film is peeled off. As shown in FIG. 2A, a wafer 1a in which individual piezoelectric substrates 1b having concave portions are arranged in a matrix is obtained. At this time, the etching grooves 7, 7, 7,... For dividing into individual pieces are also formed at the same time. Furthermore, as described above, in order to adjust the frequency of the individual piezoelectric substrates 1b arranged in a matrix to a predetermined frequency, an etching solution is dropped into the individual recesses using a computer-controlled device, and the etching time is reduced. Is controlled to adjust the frequency of each piezoelectric substrate 1b.
[0010]
FIG. 2B shows a part of an enlarged cross-sectional view taken along the line Q-Q of FIG. 2A, and a dividing etching groove 7 is formed at the end of the annular surrounding portion in the X-axis direction. It is. 2C is a perspective view of FIG. 2C, and a cross-sectional view of FIG. As can be seen from FIGS. 2C and 2D, the thick wall portion of the annular surrounding portion in the −X-axis direction is formed to be extremely thin. Thus, by forming a high-frequency piezoelectric substrate, it is suitable for a small size, and the influence of distortion due to the weight of the annular surrounding portion α is extremely small.
[0011]
FIG. 3 shows a modification of the present invention, in which the etching grooves 7 for division arranged orthogonal to the X-axis direction are provided at the boundary between the thick part and the thin part of the annular surrounding part. Since the depth of the groove 7 depends on the width of the opening, the depth of the groove 7 can be controlled by reducing the width of the opening. Therefore, since it can form without penetrating the groove | channel 7, it becomes possible to adjust each piezoelectric substrate 1b to a predetermined frequency.
[0012]
The high-frequency piezoelectric substrate constituting the present invention can also be applied to a dual mode piezoelectric filter.
Although the present invention has been described above using an AT-cut quartz substrate, the present invention is not limited to quartz and can be applied to any piezoelectric material that can be etched.
[0013]
【The invention's effect】
Since the present invention is configured as described above, the invention described in claim 1 can constitute a small high-frequency piezoelectric piezoelectric device, and exhibits an excellent effect that the frequency-temperature characteristic exhibits a smooth cubic curve. The invention described in claim 2 can realize a piezoelectric device smaller than that of the device of claim 1, and at the same time exhibits an excellent effect of exhibiting a better frequency temperature characteristic.
[Brief description of the drawings]
FIG. 1A is a plan view showing a configuration of a small high-frequency piezoelectric vibrator according to the present invention, and FIG. 1B is a cross-sectional view.
2A is a view showing a part of an enlarged cross-section of a quartz substrate in which individual piezoelectric substrates are arranged in a matrix shape by etching a large AT-cut wafer. FIG.
FIG. 3A is a partially enlarged cross-sectional view of a wafer in a modified embodiment of the present invention, and FIG. 3B is a cross-sectional view of a high-frequency piezoelectric vibrator.
4A is a plan view of a conventional high-frequency piezoelectric vibrator, and FIG. 4B is a transmission men's.
5A is a perspective view showing a state in which high-frequency crystal substrates obtained by etching an AT-cut crystal wafer are arranged in a matrix, and FIG. 5B is a perspective view of a high-frequency piezoelectric substrate divided into individual pieces. FIG. 2C is a cross-sectional view.
[Explanation of symbols]
1, 1 b, ・ Piezoelectric substrate 1 a, wafer 2, 8, recess 3, electrode 4, lead electrode 5, pad electrode 6, entire surface electrode 7. . Etched groove 9, α ·· Annular enclosure

Claims (1)

A high-frequency piezoelectric device in which a thin rectangular vibrating part and a thick holding part that holds only three sides of the periphery of the rectangular vibrating part are integrally formed.

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