JPS5836848B2 - Method for forming side electrodes of tuning fork type piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for shaping side electrodes of an ultra-small tuning fork type piezoelectric vibrator which is shaped by corrosion removal processing.

An object of the present invention is to easily form side electrodes on a tuning fork type piezoelectric vibrator formed by corrosion removal processing, and to obtain a higher performance tuning fork type piezoelectric vibrator at a low cost.

BACKGROUND ART In recent years, with the spread of crystal oscillation type electronic wristwatches, crystal resonators used as time standards are required to be further downsized, have higher performance, and have a fixed price.

For this reason, instead of the conventional machined crystal resonator,
Quartz crystal resonators made by corrosion-removal processing have been put into practical use, and their widespread use is expected.

However, although this crystal resonator is superior in terms of size and cost reduction compared to conventional mechanically processed resonators, it is insufficient in terms of performance.

It is inferior in terms of performance, especially in terms of high CI value,
This is a major impediment to the widespread use of ultra-compact resonators that require corrosion removal processing.

The reason for the high CI value is that the crystal resonator formed by conventional corrosion removal processing does not have electrodes on its side surface, which is the corrosion processing surface.

FIG. 1 shows an example of a conventional quartz crystal resonator which does not have side electrodes and has been subjected to corrosion removal processing.

FIG. 1A shows a plan view of the crystal resonator, and its M-M'
Representative examples of processing steps in cross section are shown in FIGS. 1B-F.

In FIG. 1A, 1 is a crystal oscillator, 2 and 3 are two electrodes provided on the surface of the crystal oscillator, and electrodes 2 and 3 are provided on the back surface of the crystal oscillator, respectively. In-phase electrodes 4 and 5 are provided in a mirror image relationship with the surface electrodes with respect to the plane of the crystal resonator.

The general process of removing corrosion of the crystal resonator shown in FIGS. A step of forming an electrode-shaped photoresist 8 on the conductive thin film 6 shown in FIG. The process of performing corrosion removal processing on the external shape 1 of the vibrator, by etching the conductive thin film 6 using the photoresist 8 shown in FIG. 1E as a corrosion-resistant film,
The process includes a step of forming electrodes 2, 3, 4.5, and a step of removing the photoresist shown in FIG. 1F.

As mentioned above, in the case of a crystal resonator made by conventional corrosion removal processing, the electrodes are formed only on the front and back surfaces, with electrodes formed on the side surface which is the corrosion processed surface, so when an electric field is applied, the lines of electric force are localized. However, it has the disadvantage that efficient excitation cannot be performed, resulting in a high CI value.

For this reason, attempts have been made to form side electrodes on a crystal resonator by corrosion removal processing, and FIG. 2 shows an example of a conventional corrosion removal processing crystal resonator having side electrodes.

FIG. 2A is a plan view of a conventional crystal resonator having side electrodes, where 9 is a crystal resonator, and two electrodes 12 and 13 provided on the surface of the crystal resonator 10 and 11 are side electrodes. It is.

Further, FIG. 2B shows a diagram in which the negative pattern of the electrode is formed with photoresist, and 14 is the photoresist.

FIGS. 2C to 2G are explanatory diagrams showing an example of the conventional corrosion removal processing process on the o-o' cross section of the crystal resonator, and FIG. It is an explanatory view showing an example of a conventional corrosion removal processing process in a cross section.

2C and 2H, a photoresist 14 with a negative pattern of electrodes shown in FIG. 2B is formed on a two-layer conductive thin film 16.17 having the external shape of a vibrator formed on a crystal thin plate 15. The steps, D and I in FIG. 2, are the steps of removing corrosion from the crystal thin plate into the external shape of the vibrator using the conductive thin film as a corrosion-resistant film, and the steps E and J in FIG. 2 are by sputtering from the surface.
A conductive thin film 18 that is the same as the conductive thin film 16 and a conductive thin film 19 that is the same as the other conductive thin film 17 are formed, and then a conductive thin film 20 that is the same as the conductive thin film 16 is formed by sputtering from the back side. and the process of forming a conductive thin film 21 that is the same as the other conductive thin film 17; FIGS. This is a process in which layers are removed layer by layer through corrosion processing.

The crystal resonator having side electrodes produced by the conventional manufacturing method described above has the following drawbacks.

(1) In order to reliably peel off the photoresist using the lift-off method and remove the conductive thin film formed on the photoresist, it is necessary to thicken the photoresist, which reduces the pattern accuracy of the photoresist. do.

Therefore, it is difficult to form minute electrode shapes to be provided in ultra-small vibrators.

(2) The photoresist formed into the tuning fork part is likely to peel off or change its shape during the corrosion removal process of the crystal thin plate, and therefore short circuits between the electrodes at the fork part are likely to occur.

(3) The photoresist formed on the tuning fork portion obstructs the circulation of the corrosive solution during the etching process of the crystal thin plate, and the shape of the tuning fork portion is deteriorated.

Next, FIG. 3 shows another example of a conventional corrosion-removed crystal resonator having side electrodes.

FIG. 3A is a plan view of the crystal resonator in this example, and FIG. 3B is a cross-sectional view taken along the Q)-Q' cross section, where 22 is the crystal resonator, and 23 and 24 are the surfaces of the crystal resonator. There are two electrodes on the back side of the crystal resonator.
3.24 and electrically in-phase electrodes 25 . 26 is formed in a mirror image relationship with the front and back electrodes with respect to the plane of the crystal resonator.

27, 28 and 29, 30 are side electrodes used in this embodiment.

In this example, after the corrosion removal process of the external shape of the vibrator and the corrosion process of the front and back electrodes, as shown in FIG. 3C,
Masks 31 and 32 having hole shapes that allow a conductive thin film to be formed by sputtering only on the side surfaces of the tuning fork arm and the connections between the side surfaces and the front and back electrodes are brought into close contact with the crystal resonator, and the side electrodes are formed by sputtering. It is something to do.

FIG. 3D is a sectional view taken along the line R-R'.

The crystal resonator shown in this example has the following drawbacks.

(1) The dimensional accuracy of the mask must be at least less than the width of the outer electrode of the crystal resonator, but in general, the dimensional accuracy of the mask is about ±15 factors of the plate thickness, so in order to improve the dimensional accuracy, The thickness of the mask must be made thinner.

However, if the thickness of the mask is made thinner, it becomes easier to break and workability becomes worse, so the thickness of the mask is 100 mm.
The limit is considered to be around μm.

Therefore, it is difficult to apply it to minute electrode shapes provided in ultra-small vibrators.

(2) It takes time and effort to align the mask and the crystal resonator and to fix the mask and the crystal resonator evenly and closely together.

Further, if the precision of alignment between the mask and the crystal resonator is poor, or if the crystal resonator and the mask are not in close contact due to warping of the mask, intervening dust, etc., a short circuit between the electrodes will occur.

Furthermore, if the mask and the crystal resonator are not fixed evenly and some parts are strongly fixed, the crystal resonator will crack and the mask will be damaged.

As mentioned above, it is even more difficult to apply the conventional quartz crystal resonator having side electrodes processed by corrosion removal processing due to miniaturization of the crystal resonator.

The present invention enables the side electrodes of an ultra-small tuning fork type piezoelectric vibrator to be easily formed by corrosion removal processing, and provides a piezoelectric vibrator with higher performance at a lower cost. As shown in the figure.

FIG. 4 DG shows a sectional view of the tuning fork arm.

4A and 4D are the crystal resonators shown in FIG. 1.

Photoresists 33 and 34 are formed on the front and back surfaces of the crystal resonator, respectively, as shown in FIGS. 4B and 4E.

The photoresist has a conductive thin film formed at least on the side surfaces of the tuning fork arms of the crystal resonator and the connecting portions between the side surfaces and the front and back electrodes, and a conductive thin film is formed in the vicinity of the tuning fork part and most of the front and back electrodes. It has a shape that does not affect its appearance.

Next, as shown in FIG. 4F, a conductive thin film 35 is sputtered from the front surface, and then a conductive thin film 36 is sputtered from the back surface.

Next, when the photoresists 33 and 34 are removed using a lift-off method, the conductive thin films 35 and 36 formed on the photoresists 33 and 34 become the photoresists 33 and 34. 3
As shown in FIGS. 4C and 4, side electrodes 37 and 38 connected to the front and back electrodes are formed.

As described above, the present invention has the following advantages.

1. The accuracy of the vibrator external shape, electrode shape, and electrode shape is improved because the process is the same as that of a piezoelectric vibrator, which involves corrosion removal processing of the external shape of the vibrator and the shape of the front and back electrodes, or conventional corrosion removal processing without side electrodes. It has good properties and can be easily applied to ultra-small piezoelectric vibrators.

2. Since the shape of the photoresist is relatively thick, even if the thickness of the photoresist is increased to ensure the lift-off method, the alignment accuracy with the vibrator can be satisfied using conventional photolithography technology, so the mask Short circuits between electrodes due to misalignment rarely occur.

3. Since the photoresist and the vibrator are in close contact with each other,
No short circuit between electrodes occurs due to the conductive thin film wrapping around during sputtering.

4. During sputtering, there is no need to fix the device to a jig, just place it on the substrate, which simplifies the process.

Next, an application example of the present invention is shown in FIG.

In FIG. 5A, a photoresist 39 is applied only to the surface of the vibrator 1.
FIG. 5B shows a cross-sectional view of a tuning fork arm in which a conductive thin film 40 is sputtered only from the surface of the vibrator 1. FIG.

In this case, the conductive thin film 40 is formed not only on the front surface and side surfaces but also on a part of the back surface.

Therefore, by removing the photoresist 39 using a lift-off method, side electrodes connected to the front and back electrodes are formed as shown in FIG. 5C.

As described above, the present invention can simply add side electrodes to a crystal resonator that has been subjected to corrosion removal processing, but the present invention is not limited to crystal resonators, and can be applied to lithium tantalate, lithium niobate, etc. The present invention can be applied to any tuning fork type voltage vibrator whose external shape is modified by processing, and the electrode structure is not limited to this example.

The present invention has the advantage that without sacrificing the characteristics of ultra-miniaturization and low cost of piezoelectric vibrators produced by corrosion removal processing, it is also possible to easily obtain performance comparable to relatively large piezoelectric transducers produced by conventional machining. The effect is very strong.

[Brief explanation of the drawing]

FIG. 1A shows a plan view of a conventional quartz crystal resonator without side electrodes by corrosion removal processing, and B-F is a cross-sectional view showing an example of its manufacturing method. FIG. 2A is a plan view of a conventional quartz crystal resonator having side electrodes processed by corrosion removal, B is a plan view of the resist arrangement, and C-L is a process sectional view showing an example of the manufacturing method. Figures 3A and 3B are a plan view and a cross-sectional view of a conventional corrosion-removed crystal resonator with side electrodes, and CD is another example of a plan view and cross-sectional view showing a method of manufacturing a crystal resonator using a mask. . FIG. 4 shows an embodiment of the present invention, where A, B, and C are process plan views of the manufacturing method of the present invention, and DG is a cross-sectional view of the process. FIG. 5 shows an application example of the present invention, and A, B, and C are process cross-sectional views of the manufacturing method of the present invention. 1... Crystal resonator, 2, 3... Surface electrode, 4, 5... Back electrode, 6... Conductive thin film, 7... ... Crystal thin plate, 8 ... Photoresist, 9 ... Crystal resonator, 10.11.
...Surface electrode, 12, 13...Side electrode, 14...Photoresist, 15...
Crystal thin plate, 16, 17, 18, 19, 20, 21...
... Conductive thin film, 22 ... Crystal resonator, 23
, 24... Surface electrode, 25, 26...
Back electrode, 27. 2B, 29.30...Side electrode, 31.32...Mask, 33,34...
... Photoresist, 35, 36 ... Conductive thin film, 37. 38...Side electrode, 39.
... Photoresist, 40 ... Conductive thin film.

Claims (1)

[Scope of Claims] 1. A side electrode type of a tuning fork type piezoelectric vibrator, in which a conductive thin film is formed on each of the front and back planes of a voltage conductive thin plate which has been subjected to corrosion removal processing in the outer shape of the tuning fork type piezoelectric vibrator. In the precept method,
A first step of forming electrode shapes on the front and back surfaces using the conductive thin film, a second step of covering with photoresist up to the portions of the front and back surfaces where the electrodes are formed, up to the ends thereof;
Sputtering a conductive thin film from each of the front and back planes,
a third step of forming a conductive thin film over almost the entire external shape of the tuning fork type piezoelectric vibrator; the photoresist formed by each of the steps; and a conductive film formed on the photoresist. and a fourth step of removing the thin film. 2. In a method for forming side electrodes of a tuning fork type piezoelectric vibrator, in which a conductive thin film is formed on each of the front and back planes of a piezoelectric thin plate that has been subjected to a corrosion removal process in the external shape of the tuning fork type piezoelectric vibrator,
a first step of forming electrodes on the front and back surfaces using the conductive thin film; a second step of covering with a photoresist up to a portion of the plane on which the electrodes are formed that does not reach the edge of either the front or back surface; , sputtering a conductive thin film from either the front or back plane covered with photoresist in the step, to cover the entire surface of either the front or back plane of the external shape of the tuning fork type piezoelectric vibrator; a third step of forming a conductive thin film on the side surfaces, and a fourth step of removing the photoresist formed in each of the above steps and the conductive thin film formed on the photoresist. A side electrode type precept method for a tuning fork type piezoelectric vibrator consisting of.