JPH05121985A - Manufacture of piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To easily manufacture a subminiature vibrator with an excellent characteristic by adhering two substrates, incorporating and enclosing closely a piezoelectric element chip and cutting the adhered substrates. CONSTITUTION:After an oxide film 13 is formed on a silicon wafer 11, a photo resist 14 is coated to the wafer and it is etched to form a throughhole 4 and a cavity 16 containing a crystal vibrator. After a surface insulation film 17 is formed by oxidation, the oxide film on the adhered face is removed and a 1st substrate 12 is formed. Then an electrode wiring 18 for the crystal vibrator is implemented to the rear side of the substrate 12, conductive paste 19 is dropped on the surface of the substrate 12, a crystal vibration chip 5 is connected tentatively, curing processing is implemented in a high temperature dryer and the connection is finished. The substrate 12 and a 2nd substrate 20 are inserted between the sets of electrodes provided with a heater and after they are heated to a prescribed temperature, a voltage is applied and adhering processing is implemented and the wafer is cut by a dicer with high precision. Thus, the miniaturization of the crystal vibrator is easily realized.

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, which is used as an electronic component mounted on an industrial or consumer electronic circuit board.

[0002]

2. Description of the Related Art In recent years, due to the development of microcomputer technology, it has been applied in a wide range of advanced fields from the industrial field to the consumer field. One of the main technologies is digital circuit technology, and the demand for a high-precision oscillator for generating a reference signal as a component for generating a signal clock is increasing.
As high-precision oscillators, low-frequency piezoelectric vibrators for wristwatches to high-frequency piezoelectric vibrators for personal computers and various communication devices have been put to practical use. In particular, as the latter high-frequency piezoelectric vibrator, the demand for AT vibrators whose frequency accuracy is high on the order of PPM is growing rapidly, and in place of the conventional metal can encapsulation of disk-shaped piezoelectric vibrators, other There is a demand for a surface-mount type microminiature piezoelectric vibrator that can be mounted similarly to electronic components.

[0003]

DISCLOSURE OF THE INVENTION The present invention is to easily manufacture a vibrator which is ultra-small in size and excellent in characteristics as compared with the conventional piezoelectric vibrator.

[0004]

In order to solve such a problem, the present invention joins a first substrate and a second substrate in order to hermetically contain a piezoelectric vibrator piece. The piezoelectric vibrator is obtained by cutting.

The details of the present invention will be described below with reference to examples.

[0006]

EXAMPLE 1 A perspective view of a crystal resonator as an example of the piezoelectric vibrator of the present invention is shown in FIG. 1, and a method for manufacturing a wafer batch type crystal resonator will be described with reference to FIG. A first substrate 12 is formed by the following steps using a silicon wafer 11 having an outer shape of 4 inches and a thickness of 500 microns and a plane orientation (100). That is, after the entire surface of a silicon wafer is oxidized to form an oxide film 13, a photoresist 14 is applied and photoetching is performed by a photomask, and a through hole 15 for electrode wiring and a cavity portion 16 for accommodating a crystal resonator piece are provided. Formation. Then, the entire surface is wet-oxidized again to form the surface insulating film 17, and then the oxide film on the bonding surface is completely or partially removed. After that, electrode deposition for the crystal resonator wiring is performed on the back surface of the first substrate 12 to form the electrode wiring 18 by the photoetching method. After that, the conductive silver paste 19 is weighed and dropped in the vicinity of the through hole 15 on the surface of the first substrate 12, and the crystal oscillator piece having a width of 1.5 × a length of 5.4 × a thickness of 0.08 (unit: mm). 5 is temporarily connected. The wafer batch substrate is cured in a high temperature dryer to cure the conductive adhesive, and the connection between the crystal oscillator electrode and the wiring electrode is completed. Further, as the transparent second substrate 20 facing the first substrate, a second substrate made of glass having a thermal expansion coefficient close to that of the first substrate (the difference in the linear expansion coefficient between the first substrate and the second substrate will be described later). 30% or less between the bonding temperature and room temperature) is used. The second substrate forms a cavity by photoetching with a photomask. The first substrate and the second substrate are aligned by alignment marks and sandwiched between a pair of electrode plates equipped with a heating device. In order to perform anodic bonding between the first substrate and the second substrate, the heating device is heated and heated, and when the temperature of the substrate reaches a predetermined temperature of 200 to 400 ° C., the first substrate is heated. A positive potential is applied to the electrode in contact with the substrate, and a negative potential is applied to the electrode in contact with the second substrate. The potential difference between the positive potential and the negative potential is 200 to 1000.
Set the bolt to an arbitrary value and start anodic bonding. Immediately after applying the voltage, a charging current having a capacity in the gap between the first substrate and the second substrate and an ion current moving between the interfaces flow, and the value thereof decreases with the passage of time. When the current value becomes smaller than a predetermined value, the end point of anodic bonding is set, and the process is ended. Since the anodic bonding method has a higher bonding strength than bonding methods such as bonding, practical strength can be obtained by bonding in a small area. A dicing machine equipped with a diamond wheel can perform precision cutting at a peripheral speed of 70 m / sec at a cutting speed of 1 to 10 mm / sec. In order to reduce the wear of the diamond wheel due to cutting,
By applying a voltage between the object to be cut and the diamond wheel and suppressing the elution of ions in the glass, the durable life of the diamond wheel can be increased.
The crystal unit thus formed is shown in FIG. Figure 1
FIG. 3 shows an AA ′ sectional view and a BB ′ sectional view of the quartz oscillator of FIG. In the crystal oscillator, the silicon substrate 1 is used as the first substrate, the glass substrate is used as the second substrate, and the crystal oscillator piece placed on the cavity 2 of the silicon substrate and the electrode from the crystal oscillator piece are taken out. The side electrode 3 (the first electrode 6 and the second electrode 7) is provided on the side surface of the silicon substrate 1 by providing the through hole 4 for This crystal oscillator is characterized by its small size and high dimensional accuracy, and can be mass-produced at a low price by the wafer batch method.

(Embodiment 2) The crystal unit described in Embodiment 1 above is one in which a silicon oxide film is formed as a first substrate on a silicon substrate to form an insulating film, and electrical wiring is formed thereon. It was However, in this method, since the silicon oxide film is thin, stray capacitance is formed between the silicon layer of the first substrate and the wiring electrode. When the electrode width is reduced to minimize the area of the electrode wiring portion on the first substrate in order to suppress the stray capacitance, there is a contradictory constraint that the wiring resistance increases. However, in the frequency band where the oscillation frequency exceeds several tens of MHz, it is difficult to design satisfying this constraint, and it is necessary to further reduce the stray capacitance. Therefore, in this embodiment, the electrode wiring is performed on the glass substrate instead of the wiring on the silicon substrate. Less than,
The structure of the crystal resonator of this embodiment will be described with reference to FIG. A minute through hole is formed in the glass substrate 21 as the first substrate by electric discharge machining or laser machining, and through hole plating is performed by electroless selective plating to form a wiring electrode 22 penetrating the glass substrate 21. Thereafter, the electrode connecting portion of the crystal oscillator piece is conductively bonded and fixed to the through-hole electrode by using a conductive silver paste. In addition, in order to prevent the disturbance of the frequency due to the disturbance of the crystal unit, the receiving unit 23 that supports the node of the vibration mode of the crystal unit.
In the wiring electrode forming step. High frequency oscillation AT
Since the crystal oscillator has a small oscillation amplitude, the thickness of the electrode formed on the glass substrate is sufficient, but FIG. 5 shows other crystal oscillator pieces having an oscillation state at a lower frequency with a larger amplitude. Such an escape space 24 may be provided. On the other hand, the silicon substrate as the second substrate is provided with a cavity 2 as a space for accommodating the crystal piece by an etching method.
To form. The glass substrate 21 on which the crystal oscillator piece is thus mounted is placed in the above-described anodic bonding apparatus so as to face the silicon substrate 25, and is anodically bonded in the same manner as in the above method. In the present embodiment, the cavity is provided in the silicon substrate, but by providing the cavity in the glass substrate and eliminating the pattern of the silicon substrate, alignment between the substrates is unnecessary, and the process can be simplified.

(Embodiment 3) As still another embodiment of the piezoelectric vibrator of the present invention, a method of manufacturing a high-precision crystal resonator having a small frequency drift will be described. Here, the anodic bonding apparatus is formed in a closed container and uses a rare gas such as nitrogen gas or argon / xenon or a mixed gas thereof as an inert gas. Sufficient gas replacement is performed in a gas, and anodic bonding is performed under the gas pressure or reduced pressure to bond the glass substrate as the first substrate and the silicon substrate as the second substrate. After that, the above-mentioned dicing device is used to cut into individual crystal oscillators to obtain a desired shape. A crystal oscillator anodically bonded in an inert gas has a crystal impedance dance because there is no oxidation of the electrode in the sealed cavity due to sufficient baking and inert gas in the manufacturing process, and there is little stress change to relax. Low,
It becomes a high-precision crystal unit with little frequency drift.

(Embodiment 4) FIG. 6 shows a quartz resonator having a ground electrode as another embodiment of the piezoelectric resonator of the present invention.
Here, the conductivity of the silicon substrate is used, and in addition to the first and second electrodes for wiring on the silicon oxide film, the third electrode 31 that contacts the silicon substrate is formed.
Conduct electricity to ground potential. As a result, the crystal oscillator is shielded and stable oscillation characteristics with little change in stray capacitance can be obtained.

The details of the present invention have been described above based on the embodiments, taking a crystal oscillator as an example. However, the container for the present piezoelectric element can be applied to a crystal oscillator in a frequency region other than 20 MHz applied to the present embodiment. Needless to say, the piezoelectric element is not limited to the crystal unit, and LiTaO
3, it can be utilized for other piezoelectric elements such as LiNbO3.

Further, although the bottom surface side member to be used has been polished on both sides, it may be smoothed by polishing only the joint surface side.

Further, although the wiring between the through hole portion and the side electrode portion is flat, a groove may be formed by etching and an electrode for wiring may be formed in the groove portion.

Finally, a Cr / Au bilayer film was used as the electrode film, but Cr, W, Al, Fe, Ni, Ta and Mo were used.
It may be a single layer film such as the above or a multilayer film thereof.

[0014]

According to the present invention, it is possible to easily realize miniaturization of a crystal resonator, which has been delayed in size reduction among electronic components which are being miniaturized as surface mount components, and further miniaturized. It solves the difficulty of assembly due to
By improving the assembly accuracy and reducing the stress generation, it is possible to reduce the oscillation frequency accuracy of the crystal unit and the frequency change over time.

[Brief description of drawings]

FIG. 1 is a perspective view of a substrate on which a crystal resonator according to the present invention is mounted.

FIG. 2 is a diagram showing a method of manufacturing a wafer batch type crystal unit according to the present invention.

FIG. 3 is an A- of the crystal unit shown in FIG. 1 according to the present invention.
Sectional drawing which shows an A'section and a BB 'section.

4A and 4B are an elevation view and a plan view showing another embodiment of the crystal oscillator of the glass substrate wiring according to the present invention.

5A and 5B are an elevation view and a plan view showing still another embodiment of the crystal oscillator of the glass substrate wiring according to the present invention.

FIG. 6 is a diagram showing ground wiring on the circuit board of the crystal unit according to the present invention.

[Explanation of symbols]

 1 Silicon substrate 2 Cavity 3 Side electrode 4 Through hole 5 Crystal oscillator piece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Ikusaka 3-3-5 Yamato, Suwa, Nagano Seiko Epson Corporation

Claims (4)

[Claims] 1. A first substrate on which a plurality of piezoelectric vibrator pieces are mounted, and a second substrate facing the substrate, wherein the first substrate and the second substrate are bonded to each other. A method for manufacturing a piezoelectric vibrator, comprising forming a bonded substrate in which a piezoelectric vibrator piece is hermetically contained, and cutting the bonded substrate. 2. A silicon wafer is used for one of the substrates,
2. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein an insulating film is formed on the surface of the silicon wafer, an electrode pattern is formed on the surface of the insulating film, and then the piezoelectric vibrator piece is mounted. 3. A piezoelectric vibrator piece after forming a cavity on one substrate by a selective etching method using a silicon wafer and using a glass substrate on the other substrate and forming an electrode pattern on the glass substrate. 2. The method for manufacturing a piezoelectric vibrator according to claim 1, wherein the silicon wafer and the glass substrate are mounted by anodic bonding. 4. A method of manufacturing a piezoelectric vibrator, characterized by performing anodic bonding in an atmosphere of an inert gas.