JP2004254173A - Method of manufacturing crystal vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing by which a uniform developing state and etching state can be obtained on the surface of a crystal wafer in performing developing and etching by an overflow method or a downflow method. <P>SOLUTION: In the method of forming a crystal resonator from a crystal wafer in a step of exposing and developing a photoresist film formed on the crystal wafer, a developer is put into an overflow tank or a downflow tank, the crystal wafer held by a wafer holding tool is dipped therein, and a vibration source is connected to the wafer holding tool to develop the wafer while applying vibration. Doing the above process can solve a problem that the temperature difference in a dissolved substance occurs on the surface of the crystal wafer at the time of developing and etching, and this difference causes ununiformity of the developing state and the etching state in the crystal wafer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a quartz oscillator used as a reference signal source for a timepiece or a mobile communication device.
[0002]
[Prior art]
A so-called tuning-fork type crystal resonator having two vibrating legs is widely used as a reference signal source of a clock or a mobile communication device. Since the resonance frequency of such a crystal resonator is determined by the width and length of the legs, it is manufactured by a photolithography technique in order to obtain a uniform width and length of the legs (for example, see Patent Document 1). FIG. 6 is a flow chart showing an outline of a manufacturing process of the crystal unit. The quartz oscillator is cut out from a rough quartz crystal, polished, and formed using a photolithography technique starting from a rectangular quartz wafer adjusted to a predetermined thickness. (A) First, an Au film is formed on the front and back surfaces of a quartz wafer by sputtering using Cr as a base. (B) A photoresist is applied on both sides of the Au film. For coating, for example, spin coating is used. (C) After the step of drying at a predetermined temperature (prebaking), (d) the completed pattern of the crystal unit is exposed. (E) The pattern exposed on the photoresist is developed in a developer. The developing method will be described later in detail. (F) Au and Cr are etched using the developed photoresist pattern as a mask. The remaining Au and Cr patterns at this time become the outer shape of the crystal unit. (G) Thereafter, the photoresist is stripped. (H) New photoresist is applied to both sides, (i) after pre-baking, (j) the pattern of the gold plating film used for frequency adjustment is exposed and developed, and (k) gold plating is applied. (L) The photoresist on which the gold plating film is formed is peeled off, and (m) a new photoresist is applied to both sides. (N) After pre-baking, (o) the photoresist film is exposed to a pattern to be an electrode. (P) After development, (q) the crystal is etched with a mixed solution of hydrofluoric acid and ammonium fluoride using the pattern of the Au film with Cr as a base formed in (f) earlier as a mask, and An outer shape is formed. The detailed method of the etching will be described later. (R) The Au and Cr films are removed by etching except for the portion covered with the photoresist film for the electrode pattern previously formed in (o) and (p). (S) Pd is deposited using Ti as a base while rotating the wafer. As a result, electrode films on the front and back surfaces and side surfaces are formed. (T) The photoresist film for the electrode is peeled off, and the Ti and Pd films are left only in the portion that becomes the electrode by so-called lift-off. (U) Unnecessary Au and Cr films are removed by etching. At this time, in order to leave a Pd film, Au is dissolved in an etching solution, but an etching solution in which iodine which does not dissolve Pd is dissolved in a potassium iodide solution is used. Thus, a crystal resonator having electrodes and a tuning-fork type outer shape is completed.
[0003]
Although the developing method and the etching method use different liquids, the same tools and equipment can be used. Therefore, the description will be made together. The liquid in the text indicates a developing solution or an etching solution.
[0004]
The following methods are used for the developing method and the etching method. FIG. 7 shows the overflow method. The overflow method is a method in which the liquid is supplied from the lower surface by the pump 5 and overflows from the upper part of the inner tank 7 in a state where the wafer holding jig 3 containing the crystal wafer 1 is immersed in the liquid. A flow from the lower part to the upper part is generated inside the inner tank 7. The overflowed liquid is recovered from the lower part of the outer tank 9, connected to the pump 5 and circulated and supplied to the lower part of the inner tank 7.
[0005]
FIG. 8 shows the downflow method. The down-flow method is a method in which a liquid is sucked by a pump 5 from a lower part of an inner tank 7 and a liquid is circulated and supplied to a lower part of an outer tank 9 in a state where the wafer holding jig 3 containing the crystal wafer 1 is immersed in the liquid. It is. The liquid flows from the upper part of the outer tank 9 to the upper part of the inner tank 7, and a flow from the upper part to the lower part occurs in the inner tank 7.
[0006]
The overflow method and the downflow method have a merit that a uniform flow can be generated inside the inner tank 7 and therefore, there is an advantage that a development state and an etching state are unlikely to be different at each point in the quartz wafer 1 and are used frequently. It is.
[0007]
FIG. 9 is a diagram showing a flow velocity distribution near the surface of a quartz wafer according to these conventional methods. The length of the arrow indicates the magnitude of the flow velocity, and the direction of the arrow indicates the direction of the flow velocity. The horizontal axis indicates the distance from the quartz wafer surface. As shown in FIG. 9, since the flow velocity on the surface of the quartz wafer is small, the dissolved substance does not easily leave the surface, and the concentration of the dissolved substance varies near the surface, so that the developed state and the etched state obtained are uniform. did not become.
[0008]
FIG. 10 is an example showing the boundary 15 of the photoresist 13 developed by the conventional method, and it can be seen that the boundary 15 is disturbed.
[0009]
Further, as an example of a cleaning process by a conventional method, it is performed that a megasonic of 500 kHz to 3 MHz is applied to a downflow tank to increase the cleaning efficiency (for example, see Patent Document 2). When megasonic, that is, ultrasonic vibration is applied to the downflow tank itself, bubbles are generated inside the liquid, and the bubbles adhere to the surface of the crystal wafer, or bubbles are directly generated on the surface of the crystal wafer. It has been found that since the location where bubbles are generated is isolated from the liquid, development and etching may become non-uniform only in that portion, which is not preferable. This is because a large amount of energy is required to apply ultrasonic vibration to the entire tank and exert an influence on the quartz wafer, and bubbles are generated in a portion where the vibration energy is concentrated.
[0010]
[Patent Document 1]
JP-A-5-315883 (pages 3-4, FIG. 1-2)
[Patent Document 2]
JP-A-9-64146 (pages 4 to 7, FIGS. 3 and 5)
[0011]
[Problems to be solved by the invention]
As described above, in the above-described conventional technology, the flow velocity on the surface of the quartz wafer is small due to the uniform flow, and the concentration of the dissolved material near the surface is uneven because the dissolved substance does not quickly leave the surface of the quartz wafer. Therefore, there is a problem that the developed state and the etched state are not uniform in the quartz wafer. Also, when megasonic, that is, ultrasonic vibration is applied to the downflow tank itself, bubbles are generated inside the liquid, and these bubbles adhere to the surface of the crystal wafer, or bubbles are directly generated on the surface of the crystal wafer, Since the location where the bubbles are generated is isolated from the liquid, there has been a problem that the development and etching may be non-uniform only at that location.
[0012]
In order to solve the above problems, an object of the present invention is to provide a manufacturing method capable of obtaining a uniform developed state and an etched state on the surface of a quartz wafer during development and etching by an overflow method and a downflow method.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a method of manufacturing a crystal unit according to the present invention is a method of forming a crystal unit from a crystal wafer, and developing a photoresist film formed on the crystal wafer after exposure. In the process, the developer is put into an overflow tank or a downflow tank, the crystal wafer held by the wafer holding jig is immersed therein, and a vibration generating source is connected to the wafer holding jig to apply vibration. It is characterized by performing development.
[0014]
The method for manufacturing a crystal resonator according to the present invention is a method for forming a crystal resonator from a crystal wafer, wherein the step of processing the crystal wafer into a predetermined shape by etching includes: The quartz wafer held in a wafer holding jig is immersed in the tank, and a vibration generating source is connected to the wafer holding jig to perform etching while applying vibration.
[0015]
In the method for manufacturing a crystal resonator according to the present invention, the frequency of the vibration applied to the wafer holding jig is 10 kHz to 500 kHz.
[0016]
According to the method for manufacturing a crystal resonator of the present invention, the vibration applied to the wafer holding jig is transmitted to the crystal wafer, and the vibrating crystal wafer disperses the dissolved substance remaining on the crystal wafer surface from the surface of the crystal wafer. Therefore, the concentration of the dissolved substance on the surface of the quartz wafer is not increased, and uniform development and etching can be performed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a view showing an embodiment of a method for manufacturing a crystal unit according to the present invention, which is applied to an overflow method, in which a vibration source 11 is connected to a wafer holding jig 3 immersed in an overflow tank. is there. The overflow method is a method in which the liquid is supplied from the lower surface by the pump 5 and overflows from the upper part of the inner tank 7 in a state where the wafer holding jig 3 containing the crystal wafer 1 is immersed in the liquid. A flow from the lower part to the upper part is generated inside the inner tank 7. The overflowed liquid is recovered from the lower part of the outer tank 9, connected to the pump 5 and circulated and supplied to the lower part of the inner tank 7.
[0019]
FIG. 2 is a view showing an embodiment of a method of manufacturing a crystal unit according to the present invention, which is applied to a downflow method, and a vibration is applied to a wafer holding jig 3 containing a crystal wafer 1 immersed in a downflow tank. This is an example in which the generation source 11 is connected. The down flow method is a method in which a liquid is sucked from the lower part of the inner tank 7 by the pump 5 and the liquid is circulated and supplied to the lower part of the outer tank 9. The liquid flows from the upper part of the outer tank 9 to the upper part of the inner tank 7, and a flow from the upper part to the lower part occurs in the inner tank 7.
[0020]
In both the overflow method and the downflow method, the vibration generated from the vibration generating source 11 is transmitted to the quartz wafer 1 through the wafer holding jig 3, thereby promoting the diffusion of the dissolved substance away from the quartz wafer 1.
[0021]
FIG. 3 is a view showing a flow velocity distribution near the surface of a quartz wafer when the present invention is used. The vibration transmitted from the vibration source 11 to the crystal wafer 1 through the wafer holding jig 3 gives a component of the flow velocity in a direction perpendicular to the surface of the crystal wafer, so that the dissolved substance quickly leaves the surface.
[0022]
FIG. 4 is an example showing the boundary 15 of the photoresist 13 developed by the manufacturing method of the present invention, and it can be seen that the boundary 15 is straight. As described above, when the present invention is used, uniform development can be performed. Although not shown in the drawing, this situation is the same in etching, and uniform etching can be performed by using the present invention.
[0023]
When vibration is applied to the wafer holding jig as in the present invention, bubbles are not generated inside the liquid or bubbles are generated on the surface of the quartz wafer. In the case of the present invention, it is sufficient if the wafer holding jig vibrates slightly and only a small amount of energy needs to be applied, so that no bubbles are generated. In the case of the present invention, a frequency of vibration of about 10 kHz to 500 kHz is sufficient.
[0024]
FIG. 5 is a diagram comparing the frequency distribution of a crystal resonator manufactured by the present invention with the frequency distribution of a crystal resonator manufactured by a conventional method. According to the present invention, since the outer shape of the crystal unit can be formed uniformly to a predetermined size, it can be seen that the spread of the frequency distribution is reduced.
[0025]
【The invention's effect】
As described above, according to the method for manufacturing a crystal resonator of the present invention, there is an effect that uniform development and etching can be performed. Further, since the effect can be obtained with a small energy, there is an effect that power consumption can be reduced. Further, there is an effect that a uniform crystal resonator having a small frequency distribution can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment according to the present invention, and is a diagram showing an example in which the present invention is applied to an overflow method.
FIG. 2 is a diagram showing an embodiment according to the present invention, and is a diagram showing an example in which the present invention is applied to a downflow method.
FIG. 3 is a diagram showing a flow velocity near the surface of a quartz wafer according to the present invention.
FIG. 4 is a diagram showing a state of a boundary line when a photoresist is developed according to the present invention.
FIG. 5 is a diagram comparing the frequency distribution of a crystal resonator manufactured according to the present invention with the frequency distribution of a crystal resonator manufactured by a conventional method.
FIG. 6 is a flowchart showing an outline of a manufacturing process of the crystal unit.
FIG. 7 is a diagram illustrating a method for manufacturing a crystal unit according to a conventional method, and is a diagram illustrating an overflow method.
FIG. 8 is a diagram illustrating a method of manufacturing a crystal unit according to a conventional method, and is a diagram illustrating a downflow method.
FIG. 9 is a diagram showing a flow velocity near the surface of a quartz wafer in a conventional method.
FIG. 10 is a view showing a state of a boundary line when a photoresist is developed by a conventional method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystal wafer 3 Wafer holding jig 5 Pump 7 Inner tub 9 Outer tub 11 Vibration source 13 Photoresist 15 Boundary line

Claims (3)

In a manufacturing method for forming a quartz oscillator from a quartz wafer, a step of exposing and developing a photoresist film formed on the quartz wafer is performed by placing a developing solution in an overflow tank or a downflow tank and placing the wafer in the overflow tank or downflow tank. A method for manufacturing a crystal resonator, comprising: immersing the crystal wafer held by a holding jig, and connecting a vibration source to the wafer holding jig to perform development while applying vibration. In a manufacturing method for forming a crystal resonator from a crystal wafer, the step of processing the crystal wafer into a predetermined shape by etching includes: placing an etchant in an overflow tank or a downflow tank; And dipping the quartz wafer held in the wafer and connecting a vibration source to the wafer holding jig to perform etching while applying vibration. 3. The method according to claim 1, wherein a frequency of the vibration applied to the wafer holding jig is 10 kHz to 500 kHz.

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