JP2001036160A - Manufacture of electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a vibrator, improved in productivity, concerning the manufacturing method of a vibrator which is used in a mobile communication apparatus or the like. SOLUTION: In a diaphragm plate 1 and a retaining plate 2, which are composed of rotation Y plates of single crystal of the same material, surfaces of the crystal axis of an X-axis where polarization axes become positive are bonded mutually, and a bonded body 3 is eliminated. An aperture part 7 is formed at a prescribed position of the retaining plate 2 of the bonded body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electronic component used for a vibrator or a filter used in a mobile communication device or the like.

[0002]

2. Description of the Related Art In a vibration mode used in a vibrator having a frequency of several MHz or more, such as a thickness shear vibration or a thickness longitudinal vibration, an electronic component such as a vibrator or a filter has an oscillation frequency which is inversely proportional to a thickness of a vibrating portion of the vibrator. I do. In other words, it is necessary to make the diaphragm constituting the vibrator thin at a high frequency.
It is necessary to have the following thickness. In order to obtain such a thin diaphragm, the thick holding plate and the diaphragm are joined in advance, and the diaphragm is mechanically polished or chemically corroded. Thereafter, electrodes must be formed on the upper and lower surfaces of the diaphragm in order to utilize vibration modes such as thickness shear vibration and thickness longitudinal vibration, and the lower holding plate must be removed without damaging the diaphragm.

[0003]

However, since the diaphragm is thin, it is difficult to remove the diaphragm by mechanical means, and when chemical corrosion is taken, the material of the holding plate is changed to the material of the diaphragm. It is difficult to remove the retaining plate without chemically damaging the diaphragm by using an etchant or corrosive gas that corrodes the retaining plate but does not corrode the diaphragm. There was a problem that the properties were poor.

The present invention solves the above-mentioned conventional problems and provides a method for manufacturing an electronic component with improved productivity.

[0005]

In order to achieve the above object, the present invention provides a vibration plate and a holding plate to be joined using lithium niobate or lithium tantalate of the same rotating Y plate,
In order to match the thermal expansion coefficients, at least the X-axis direction of the in-plane crystal axes of both plates is matched and joined, and the joined surfaces are both surfaces whose polarization direction is +. .

[0006]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, a vibrating plate and a holding plate made of a single-crystal rotating Y plate of the same material are arranged on the plane of the X-axis crystal axis where the polarization direction is +. And a second step of thinning the diaphragm of the joined body, and forming a protective film made of a metal or an organic material on the upper and lower surfaces of the thinned joined body. A third step, and a fourth step of forming an opening at a predetermined position of the holding plate of the joined body having the protective film,
Since the diaphragm is thinned by joining it to the holding plate with the same coefficient of thermal expansion, the mechanical strength increases, handling is easy, and it does not bend against changes in ambient temperature. In addition, the surface of the joined body on the holding plate side has a negative polarity, so the chemical corrosion rate is high, and when the removal of the holding plate is completed and the diaphragm is exposed, vibration occurs. The surface on the polarization + side of the plate is exposed, and since the corrosion rate is low on this surface, the corrosion stops here. Therefore, the holding plate corresponding to the lower surface of the portion that becomes the vibrating portion in the plane of the diaphragm is This has the effect that the diaphragm can be removed without damaging it.

According to a second aspect of the invention, a vibration plate and a holding plate made of a single crystal rotating Y plate of the same material are joined to each other by joining the surfaces of the X-axis crystal axis where the polarization direction is + to form a joined body. A first step of forming, a second step of thinning the diaphragm of the bonded body, a third step of forming a protective film on the surface of the diaphragm of the thinned bonded body, and a protective film Forming a slit portion in the diaphragm having: a step of forming a protective film on the surface of the holding plate of the joined body; and forming an opening in a predetermined position of the holding plate of the joined body having the protective film. 4 and has a function of mitigating stress caused by a difference in thermal expansion from the package when the resonator or the filter is mounted on the package.

According to a third aspect of the present invention, between the second step and the third step of the first aspect, the surface of the diaphragm of the thinned joined body is made of the same material as the diaphragm. A second vibrating plate, and a step of thinning the second vibrating plate. Since a vibrating part having a structure in which the vibrating portion has a structure in which the polarization is reversed and bonded can be formed, a minimum of Next vibration 2
The next mode has an effect of manufacturing a vibrator having no possibility of abnormal oscillation or a filter having a wide bandwidth.

According to a fourth aspect of the present invention, the third step of the second aspect and the step of forming a protective film on the surface of the holding plate of the joined body are performed at the same time, thereby improving the productivity. Having.

(Embodiment 1) Hereinafter, a method of manufacturing an electronic component according to Embodiment 1 of the present invention will be described using a vibrator as an example.

FIG. 1 is a diagram for explaining a method of manufacturing a vibrator according to the first embodiment of the present invention.

First, the vibrating plate 1 and the holding plate 2 made of a single crystal rotating Y plate of the same material such as lithium niobate or lithium tantalate are mirror-polished to a predetermined thickness to oxidize a strong acid and a strong alkali. The surface is activated and dried by washing with a neutral cleaning solution.

Next, as shown in FIG.
The surface of the crystal axis of the X-axis where the polarization axis of the substrate and the holding plate 2 is + is overlapped and joined in a clean atmosphere such as a clean room to form a joined body 3. The arrow 4 in FIG. 1A indicates the polarization axis of the diaphragm 1 and the holding plate 2. Then, in order to improve the adhesive strength between the vibration plate 1 and the holding plate 2,
Heat to a temperature of about 300 ° C.

The thickness of the vibration plate 1 and the holding plate 2 is preferably as thin as possible. When using a plate with a size of 3 inches Φ,
Considering handling, it is desirable to be about 100 μm. In addition, as for the holding plate, it is better that the in-plane thickness variation is small, and it is desirable that the thickness be 1 μm or less.

Next, as shown in FIG.
The diaphragm 1 is thinned to a predetermined thickness t1 by a mechanical or chemical method. This thickness t1 is equal to the desired frequency f
It is proportional to the reciprocal of 1, and its proportionality constant has a value determined by the vibration mode used. The method of thinning is, for example,
It can be performed by a processing method using free abrasive grains by single-side polishing or fixed abrasive grains using a flat polishing machine or the like. In any case, the holding plate 2 side of the joined body 3 is fixed, and the vibration plate 1 side is polished or ground. Therefore, this surface serves as a reference for processing, and the thickness of the vibration plate 1 is controlled. Therefore, the material for the holding plate 2 is required to have a very small thickness variation. Further, with respect to the polishing machine or the grinding machine, the surface of the fixing jig for fixing the joined body 3 needs to be a highly accurate flat surface. In addition, in order to fix the entire surface evenly, 10 μm
It is preferable to use a ceramic material or the like in which pores are uniformly formed on the entire surface, and to fix them by vacuuming. In addition, when using a plane polishing machine, if this fixing jig is ground in advance with the same grindstone as the grindstone used for thinning, in-plane thickness variation can be eliminated, and a large number of large plates can be removed. The yield can be improved when manufacturing the vibrator. The diaphragm 1 is backed by the holding plate 2 and has high rigidity as a whole, so that the diaphragm 1 can be thinned to several μm.

Next, as shown in FIG.
A protective film 5 composed of two layers of chromium and gold is formed on the surface on the side of the vibration plate 1. The protective film 5 is formed in order to prevent the vibrating plate 1 from being attacked from the surface when the joined body 3 is immersed in a corrosive liquid. Therefore, the material of the protective film 5 may be an organic material as long as the material can withstand a later holding plate corrosion process. The reason for forming two layers of chromium and gold here is as follows. Gold alone cannot be adhered to lithium niobate or lithium tantalate. A chromium film is first formed as an underlayer to a thickness of about 100 ° to 100 ° by a method such as vacuum evaporation or sputtering to form an adhesion layer. A film having a thickness of about 2000 to 1 μm is formed by a method such as vacuum evaporation or sputtering. Titanium or the like may be used as a base, but chromium having high resistance is used because it is necessary to withstand a mixed acid of hydrofluoric acid and nitric acid.

Next, as shown in FIG.
The protective film 5 is formed on the surface on the holding plate 2 side. In this case, the same material as that of the protective film 5 in the previous step may be applied under the same conditions. With the above-described configuration of chromium and gold, the protective film 5 can be formed at a time.

Next, as shown in FIGS. 1 (e) and 1 (f), a photosensitive resin (not shown in this drawing) is applied to both surfaces of the joined body 3, and The pattern other than the window 6 is held by a resin by baking and developing a pattern to be the window 6, and the protective film 5 corresponding to the window 6 is chemically corroded.

Next, as shown in FIG. 1 (g), an opening 7 is formed by chemically corroding the holding plate 2 through the window 6. The chemical corrosion of the holding plate 2 is performed by immersing the joined body 3 at a temperature of 70 ° C. or more using a mixed acid of hydrofluoric acid and nitric acid having a mixing ratio of 2: 1. Under these conditions, a corrosion amount of about 20 μm can be obtained in 3 hours. Therefore, if the thickness of the holding plate 2 is set to about 100 μm, the holding plate 2 may be immersed in the corrosive liquid for about 15 hours. Corrosion progresses,
When the flat surface of the diaphragm 1 is exposed, this surface is the surface on the polarization + side, and the rate of corrosion becomes 1/20 or less. Therefore, when this surface comes out, the chemical corrosion stops. On the negative side, the surface roughness sharply deteriorates as the corrosion progresses. On the positive side, the surface roughness does not deteriorate so much. Never. In addition, since the thickness of the diaphragm 1 is preserved, the frequency does not deviate from a target frequency. Further, the vibration plate 1 and the holding plate 2 are made of the same material, and are joined so that the directions of the crystal axes are aligned. Even if the holding plate 2 is partially removed, the holding plate 2 does not crack after being partially removed.

The holding plate 2 may be partially removed by a mechanical processing method. For example, an abrasive having an average particle size of about several μm is sprayed on the holding plate 2 side of the joined body 3 together with high-pressure air to be processed halfway. After that, the bonded body 3 is immersed in the above-mentioned corrosive liquid, and
Is chemically corroded until the lower surface of the is exposed. In this case, even if the holding plate 2 is relatively thick, the holding plate 2 can be efficiently removed. In this case, with respect to the resin on the holding plate 2 side formed in FIG. 1E, it is necessary to form a protective film of the resin in substantially the same pattern on the protective film 5 made of chromium and gold. This is to protect the periphery of the opening 7 from being processed by processing with an abrasive. However, the process of spraying the abrasive damages the resin protective film in the lateral direction. As a result, the protective film is damaged. Therefore, it is preferable that the resin protective film is placed about 10 μm inside the opening pattern of the metal protective film.

Finally, as shown in FIGS. 1 (h) and 1 (i), the protective film 5 on the front and back surfaces is subsequently peeled off, and electrodes are formed on the front and back of the opening 7 which becomes the vibrating portion of the vibrator. Then, it is mounted on a package, and after finely adjusting the frequency, sealing is performed to manufacture a vibrator.

In the present embodiment, the joining step shown in FIG. 1A has been described by a method of joining the vibration plate 1 and the holding plate 2 using direct joining. The bonding may be performed using another adhesive or the like as long as it can be performed. When direct bonding is used, chemicals hardly penetrate the bonding interface when the holding plate is chemically corroded, and the + side of the diaphragm is directly exposed to the outside in the state where the holding plate is removed by corrosion. Therefore, post-processing is not required. And, because there is nothing at the interface, it is easy to control the thickness by processing only the diaphragm with reference to the surface on the holding plate side.

(Embodiment 2) Hereinafter, a method of manufacturing an electronic component according to Embodiment 2 of the present invention will be described using a vibrator as an example.

FIG. 2 is a diagram for explaining a method of manufacturing a vibrator according to the second embodiment of the present invention. Here, the same reference numerals are given to the same manufacturing method and the same components as those in FIG. 2 of the present embodiment and the drawings of the first embodiment, and the detailed description is omitted.

First, as shown in FIG.
And the holding plate 2 are joined to form a joined body 3.

Next, as shown in FIG.
Diaphragm 1 is thinned.

Next, as shown in FIG.
And a second diaphragm 11 made of the same material as
Form 2

The joined body 3 and the second diaphragm 11 are both cleaned with a strong acid and strong alkali oxidizing cleaning solution to activate and dry the surface, and then are overlapped and joined in a clean atmosphere of a clean room. The arrow 13 in FIG. 2C indicates the polarization direction of the second diaphragm 11. That is, the bonding is performed such that the surface of the joined body 3 on the diaphragm 1 side and the surface of the second diaphragm 11 whose polarization direction is the negative side are opposed to each other. Joint 3
Since the surface on the side of the diaphragm 1 has a surface whose polarization direction is on the minus side, it means that the two are joined on the surface whose polarization direction is on the minus side. In this way, when the diaphragm 1 and the second diaphragm 11 are replaced by one new diaphragm 12, the diaphragm 12 has a polarization inversion structure.

Next, as shown in FIG.
Among them, the second diaphragm 11 is thinned. This is performed by grinding or polishing as in the case of making the diaphragm 1 thinner.
By this thinning, the two diaphragms of the three-layer assembly are made equal in thickness.

Normally, when only one diaphragm is used, primary,
Vibration occurs in odd vibration modes of next, fifth,.... In this way, when the two vibration plates are bonded to each other by reversing the polarization, an even number such as second, sixth, and tenth is obtained. Vibration mode can be vibrated. In the case of a vibrator made of lithium niobate or lithium tantalate utilizing thickness longitudinal vibration, tertiary vibration is used because primary vibration cannot efficiently confine vibration energy under the electrode. However, in this case, the primary vibration is on the lower frequency side than the tertiary vibration, so it is easy to oscillate, and there is a problem that it oscillates with the primary vibration depending on circuit conditions.
When configured as a filter, the bandwidth is 1
It becomes as narrow as 1/9 of the next vibration. In the present embodiment, in order to avoid this problem, there is no such a problem in the secondary vibration in which the two vibration plates are adhered by reversing the polarization, and the energy can be efficiently confined under the electrode. Therefore, oscillation can be efficiently performed. Moreover, since this vibration mode is the lowest order, it is easy to avoid oscillating at any other frequency. Also, the bandwidth as a filter characteristic is nine times as wide as that in the case where the third-order mode is used. If the thicknesses of the two diaphragms are different, the primary vibration mode is likely to vibrate, and depending on circuit conditions, there is a possibility that oscillation will occur in the primary vibration mode.
To prevent this, it is desirable that the difference between the thicknesses of the two diaphragms be 10% or less of the total thickness.

Subsequent steps are the same as those in the embodiment shown in FIG.

(Embodiment 3) Hereinafter, a method of manufacturing an electronic component according to Embodiment 3 of the present invention will be described using a vibrator as an example.

FIG. 3 is a view for explaining a method of manufacturing a vibrator according to the third embodiment of the present invention. Here, this embodiment differs from FIG. 1 in the first embodiment in that a slit portion is formed in the diaphragm. In the present embodiment, the same reference numerals are given to the same manufacturing method and the same components as those in FIG. 1 of the first embodiment, and the detailed description is omitted.

First, as shown in FIG.
And the holding plate 2 are joined to form a joined body 3.

Next, as shown in FIG.
Diaphragm 1 is thinned.

Next, as shown in FIG.
A protective film 5 is formed on the surface of the vibration plate 1 with a photosensitive resin or the like.

Next, as shown in FIG.
The slit portion 21 is formed.

The slit 21 can be provided by exposing and developing a pattern. This slit part 21
Through the diaphragm 1 of the joined body 3 through a method of spraying, for example, an abrasive having an average particle size of about several μm onto the diaphragm side of the joined body 3 together with high-pressure air from the diaphragm 1 of the joined body 3 It is. The working depth at this time is sufficient to penetrate the diaphragm 1 of the joined body 3. Another method for forming the slit portion 21 is as follows.
There is a method of irradiating the laser according to the pattern of the slit by omitting the step of forming the laser beam. Alternatively, the protective film 5 may be a laminated film of chromium and gold, and the protective film 5 may be further provided on the entire surface of the holding plate 2 to form a slit by a chemical corrosion method. In this case, since the diaphragm 1 is thin, if the temperature is raised to 70 ° C. or more with a 2: 1 mixture of hydrofluoric acid and nitric acid,
The slit 21 can be formed in about two hours.

Subsequent steps are the same as the steps shown in the first embodiment of the present invention, and detailed description will be omitted.

As described above, by processing the vibrator,
A slit is provided on the outer peripheral portion of the vibrating portion, and the vibrating portion 6 and its outer peripheral portion can be separated. As a result, stress generated when the resonator is mounted on the package and stress generated due to the difference in thermal expansion coefficient between the package and the resonator due to temperature changes after mounting are not directly transmitted to the vibrating part. It is possible to obtain a vibrator having high performance.

[0041]

As described above, according to the present invention, since the diaphragm is thinned by being joined to the holding plate having the same coefficient of thermal expansion, the mechanical strength is increased, the handling is easy, and even if the ambient temperature changes. Since there is no warping, the desired thickness can be obtained with high precision, and the surface of the joined body on the holding plate side has a polarization of −
The rate of chemical corrosion is high because of the surface that becomes, and when the removal of the holding plate is completed and the diaphragm is exposed, the surface on the polarization + side of the diaphragm is exposed, and the corrosion rate for this surface is Is slow, so that the corrosion stops here, so that the holding plate corresponding to the back surface of the portion that becomes the vibrating portion in the plane of the diaphragm can be removed without damaging the diaphragm, thereby improving productivity. This has the effect.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a vibrator according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of manufacturing a vibrator according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a method of manufacturing a vibrator according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration plate 2 Holding plate 3 Joined body 5 Protective film 7 Opening

Claims (4)

[Claims] A first step of joining a vibration plate and a holding plate made of a single crystal rotating Y plate of the same material to each other on a surface of an X-axis crystal axis whose polarization direction is + to form a joined body; A second step of thinning the diaphragm of the joined body, a third step of forming a protective film made of a metal or an organic material on the upper and lower surfaces of the thinned joined body, and a step of forming a joined body having the protective film. A fourth step of forming an opening at a predetermined position of the holding plate. 2. A first step of joining a vibration plate and a holding plate made of a single crystal rotating Y plate of the same material to each other on a plane of an X-axis crystal axis where the polarization direction is +, to form a joined body; A second step of thinning the diaphragm of the joined body, a third step of forming a protective film on the surface of the thinned diaphragm of the joined body, and forming a slit portion in the diaphragm having the protective film. An electronic component comprising: a forming step; a step of forming a protective film on a surface of a holding plate of the joined body; and a fourth step of forming an opening at a predetermined position of the holding plate of the joined body having the protective film. Manufacturing method. 3. Between the second step and the third step, a second diaphragm made of the same material as the diaphragm is joined to the surface of the diaphragm of the thinned joined body, 2. The method for manufacturing an electronic component according to claim 1, further comprising the step of thinning the diaphragm. 4. The method for manufacturing an electronic component according to claim 2, wherein the third step and the step of forming a protective film on the surface of the holding plate of the joined body are performed simultaneously.