JP3397945B2 - Antistatic device and antistatic method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, to prevent electrification of a liquid such as pure water supplied for the purpose of cooling, lubrication, removal of cutting debris, etc. when cutting a silicon wafer. The present invention relates to an antistatic device and an antistatic method.

[0002]

2. Description of the Related Art When a silicon wafer on which an electronic circuit is formed is vertically and horizontally cut and divided into individual chips, pure water may be emitted to the cutting blade (blade) and the silicon wafer for the above purpose. Done. By the way, pure water has a specific resistance value of about several to 15 (MΩ · cm) at room temperature (theoretical limit value: 18.25 [MΩ · cm]), specifically, about 3 to 10 (MΩ · cm). Therefore, it is liable to be charged to a high voltage due to friction with the blade, friction at the time of radiation, etc., and there is a concern that the high electric field may electrostatically damage the electronic circuit.

Therefore, conventionally, in order to suppress the charging voltage of pure water to a low level, an antistatic device shown in FIG. 6 has been adopted.

As shown in the figure, the initial flushing type antistatic device has a storage tank 8 for storing pure water 7 supplied through a water supply pipe 6 from a tank (not shown) as a liquid supply source. There is. One end of a gas hose 10 is connected near the bottom of the storage tank 8, and the other end of the gas hose is connected to a jet port of a carbon dioxide gas cylinder 11.

That is, carbon dioxide gas is injected and mixed (dissolved) in the pure water 7 stored in the storage tank 8. The pure water 7 thus mixed with carbon dioxide has a specific resistance value of about 1 to 2 (MΩ · cm) or less.

Pure water 7 whose specific resistance value has been lowered as described above
Reaches the nozzle 14 through another water supply pipe 13, and is emitted from the nozzle 14 to the silicon wafer 16 and the cutting blade 17. Pure water is charged by friction with the blade 17 or the like, but the charging voltage can be suppressed to a low level because the specific resistance value is low. As a result, the electrostatic breakdown of the electronic circuit element during the cutting of the silicon wafer on which the electronic circuit is formed is suppressed.

[0007]

However, such a conventional apparatus has a problem that it requires a lot of labor to replenish the cylinder of carbon dioxide gas and to maintain the adjustment of the mixing amount and the like. Furthermore, neutralization treatment is required during drainage.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its main purpose is to effectively charge a liquid used for cutting a substrate, etc., with little effort. It is an object of the present invention to provide an antistatic device and an antistatic method capable of preventing, and also to provide an antistatic device capable of exhibiting other effects as well.

[0009]

An antistatic device according to the present invention comprises a water supply pipe for supplying a liquid from a liquid supply source, a storage tank having an open upper surface for storing the liquid, and an atmosphere for the liquid in the storage tank. Atmosphere supply means for supplying as bubbles, ultrasonic excitation means capable of irradiating ultrasonic waves into the storage tank, and a water supply pipe for guiding the liquid in the storage tank irradiated with ultrasonic waves by the ultrasonic excitation means to a nozzle The nozzle is configured to guide and radiate a liquid whose specific resistance value is lowered by irradiating the liquid in the storage tank with ultrasonic waves. The liquid from the liquid supply source of the antistatic device according to the present invention is injected from the upper part of the storage tank. The liquid of the antistatic device according to the present invention is characterized in that it is injected from below a liquid surface of the liquid stored in the storage tank.
The delivery of the liquid from the storage tank of the antistatic device according to the present invention is performed from the lower portion of the storage tank. The antistatic device according to the present invention is characterized in that the atmosphere is supplied to the outside of a transmission region of ultrasonic waves emitted by the ultrasonic wave excitation means.

[0010]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is, for example, when pure water is radiated for the purpose of cooling the blade when cutting a silicon wafer on which an electronic circuit is formed by using a cutting blade. It is carried out in order to reduce the specific resistance value in order to suppress the electrification.

That is, the specific resistance value is reduced by irradiating the radiated pure water with ultrasonic waves in advance.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an antistatic device as a first embodiment of the present invention will be described with reference to the accompanying drawings. However, in the following description, the same reference numerals are used for the same components as those of the conventional apparatus shown in FIG.

FIG. 1 shows a state in which the antistatic device according to the present invention is applied to the work of cutting the silicon wafer 16 using the cutting blade 17.

As shown in the figure, the antistatic device is provided with a rectangular parallelepiped storage tank 21, and pure water 7 supplied from a tank (not shown) as a liquid supply source through the water supply pipe 6 is stored in the storage tank 21. Stored in.

The water supply pipe 6 is connected near the bottom of the storage tank 21, and the pure water in the storage tank 21 is connected to the nozzle 1
The water supply pipe 13 that leads to 4 is connected to the upper portion of the storage tank 21.

The storage tank 21 has an open upper surface,
Standing waves of ultrasonic waves are easily generated and cavitation
The generation of (bubbles) is promoted, the chemical action due to the high temperature (the gas temperature inside the bubbles becomes about 5500 ° C.) at the time of compressive destruction of the bubbles is promoted, and the specific resistance value decreases. Moreover, the storage tank 21 is formed to be relatively long, and by making the storage tank long in this way, the area of the water surface in the storage tank 21 becomes large, and the rate of the pure water 7 naturally contacting the atmosphere increases. There is. Therefore, in addition to the above-mentioned chemical action, the amount of the in-air component that acts to reduce the specific resistance value of the pure water 7 increases, contributing to the prevention of static electricity. However, although it is not yet confirmed what the atmospheric component is, it is presumed that it is probably carbon dioxide gas, and its effect has already been confirmed by experiments and actual work.

As shown in FIG. 1, a vibrator 23 is mounted on the bottom surface of the bottom of the storage tank 21. The electrode (not shown) of the oscillator 23 is connected to the output terminal of the oscillator 26 by the connection cable 25, and the oscillator 23 is connected to the oscillator 2
It is driven by a pulse voltage applied from 6 to generate ultrasonic vibration. The vibrator 23 and the oscillator 26 are collectively referred to as ultrasonic excitation means.

The ultrasonic waves emitted from the vibrator 23 are applied to the pure water 7 in the storage tank 21. By this ultrasonic irradiation, the specific resistance value of the pure water 7 is, for example, about 3 to 5 (MΩ · c).
m) to less than 1 (MΩ · cm). The pure water 7 whose specific resistance value has been reduced in this way is guided by the water supply pipe 13 to reach the nozzle 14, and is emitted from the nozzle 14 to the silicon wafer 16 and the cutting blade 17. Pure water is charged by friction with the blade 17, friction during radiation, etc., but the charging voltage is suppressed to a very low level because of the extremely low specific resistance value, and there is no adverse effect on the electronic circuit formed on the silicon wafer 16. Does not reach.

The theoretical support that the specific resistance value of pure water is lowered by the irradiation of ultrasonic waves as described above is currently in the analysis stage, but a sufficient effect has been confirmed in experiments and actual work. It has also been elucidated that a large number of experiments have repetitiveness that always gives a constant result.

An experiment was conducted on the reduction of the specific resistance value due to the irradiation of ultrasonic waves, and the result will be described here.

In this experiment, the measurement conditions and the like were set as follows.

First, as shown in FIG. 2, the pure water 7 in the processing tank 21 is not directly measured, but a beaker 28 is installed in the pure water 7 and the pure water 7 poured into the beaker 28 is measured. Was measured. This is because it is inefficient to replace the pure water in the large processing tank 21 for each of a number of repeated experiments. However, passing through the beaker 28 is rather disadvantageous with respect to the passage of ultrasonic waves to the pure water 7 injected into the beaker as a test solution, and therefore, the pure water 7 outside the beaker 28 is immersed in. Regarding (the original measurement target), it is obvious that the specific resistance value is lowered at a higher efficiency than the pure water in the beaker 28.

The beaker 28 has a volume of 1 (liter), and 800 (cc) of pure water 7, specifically, deionized water is used in the beaker 28.
ter) was injected. Then, the dimension indicated by symbol D in FIG. 2, that is, the separation distance of the bottom surface of the beaker 28 from the bottom portion of the processing tank 21 was set to about 20 (mm).

The frequency of the ultrasonic waves generated by the vibrator 23 was set to 200 (kHz), and the power density was changed variously.

Under these conditions, the oscillator 23
Was vibrated, and the specific resistance value was measured every time an arbitrary time elapsed from the start of ultrasonic irradiation. This measurement operation was repeated many times while changing the power density while replacing the pure water 7 in the beaker 28.

A representative one of various measurement results obtained by the above experiment is shown in FIG. FIG. 3 is a graph showing the relationship between the elapsed time and the specific resistance value.

As is clear from the results shown in FIG. 3, the specific resistance value which was about 3 (MΩ · cm) before the ultrasonic irradiation was 0.5 (MΩ · cm) at 60 (seconds) after the start of irradiation. Decreased to
After that, it further decreased with time, and reached 0.06 (MΩ · cm) at 360 (seconds) from the start of irradiation.
Ultrasonic irradiation was stopped here. After this, a few minutes later, when only the measurement was performed again, the specific resistance value was 0.
It was kept at 06 (MΩ · cm).

From the above results, it is clear that sufficient effects can be obtained even when the apparatus shown in FIG. 1 is subjected to actual work. That is, the irradiation of ultrasonic waves reduces the specific resistance value of pure water from about 3 (MΩ · cm) to 1 (MΩ · cm) or less in a short time of seconds (or minutes). This decrease in the specific resistance value is sufficient to suppress the generation of static electricity.

In the present embodiment, the work is cutting of the silicon wafer 16 and the liquid used is pure water. However, other various methods such as only cleaning the silicon wafer are performed according to the contents of the work. It is of course possible to use the above liquids, and the present invention can be applied to these various liquids.

Further, although the silicon wafer is used as the antistatic target in this embodiment, the present invention may also be applied to other substrates such as liquid crystal glass and other articles other than the substrate. That is, it is effective when dealing with an article that is unfavorable to being exposed to a high electric field.

As is clear from the above description, according to the present invention, the specific resistance value is lowered by the chemical action by previously irradiating the liquid used for the required work such as the cutting of the silicon wafer with ultrasonic waves. , To prevent static electricity.
Therefore, complicated operations such as replenishment of carbon dioxide cylinders, adjustment and maintenance of mixing amount, and neutralization treatment of acidified wastewater as in the past are almost unnecessary, and labor is required only by operating a switch for ultrasonic irradiation. It is possible to prevent static electricity without spending, and to surely and effectively prevent it.

By the way, in the structure shown in FIG. 1, the vibrator 23 is mounted on the lower surface of the bottom of the storage tank 21,
It may be mounted on the outer surface of the side portion of the storage tank 21, or may be provided on the inner surface side of the bottom portion and the side portion. That is, the mounting position of the vibrator 23 to the storage tank 21 is not limited to that of the present embodiment, and the point is that the ultrasonic waves are effectively transmitted to the liquid in the storage tank.

Further, the vibrator 23 may not be attached to the storage tank 21, but may be simply put into the storage tank. However, as in the present embodiment, the oscillator 23 is replaced with the storage tank 21.
It is possible to apply ultrasonic waves most efficiently under the same conditions by mounting the same on the.

Further, the above-mentioned experiments revealed the following.

First, the larger the energy of the ultrasonic waves to be irradiated, the lower the specific resistance value in a shorter time.

Secondly, the higher the frequency of the applied ultrasonic waves, the more effective. Specifically, a high frequency is more effective than about 30 (kHz). This is because, for example, one wavelength of 1 (MHz) is λ = 1.5 (mm) in water, and strong ultrasonic waves occur at this pitch. Therefore, if the water depth is constant, there are many strong ultrasonic waves. It is because

Next, an antistatic device as a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. However, the antistatic device of the second embodiment is configured similarly to the antistatic device of the first embodiment shown in FIG. 1 except for the portions described below, and the configuration and operation of the entire device are Since the description is duplicated, it is omitted and only the main part is described.

Further, in the following description and FIGS. 4 and 5, the same or corresponding components as those of the antistatic device of the first embodiment are designated by the same reference numerals.

As shown in FIG. 4, in the antistatic device of the second embodiment, near the front and rear end portions of the storage tank 21,
For example, two air supply pipes (bubblers) 31 are arranged parallel to each other so as to be immersed in the pure water 7. As shown in FIG. 5, these air supply pipes 31 are provided with a large number of small pores 31a arranged in a row over substantially the entire length thereof, and the air supplied from one end is bubbled into the pure water 7 through the pores 31a.
3 (see FIG. 4). This air supply pipe 31 is 1
Books also show good effects.

The air supply pipe 31 and a pressurizing pump (not shown) that pressurizes the atmosphere to a predetermined pressure and sends it to the air supply pipe 31 are collectively referred to as an air supply means.

By supplying the atmosphere as bubbles 33 into the pure water 7 as described above, the rate of contact of the pure water 7 with the atmosphere is increased and the specific resistance value of the pure water 7 is reduced in the atmosphere. The amount of the component to be melted in is increased, and it is more effective together with the action of lowering the specific resistance value by the chemical action due to the ultrasonic irradiation.

Here, as shown in FIG.
Are supplied to the outside of the transmission area E of the ultrasonic waves emitted by the vibrator 23. According to this configuration, the ultrasonic waves are not reflected by the bubbles 33, and the efficiency of the ultrasonic waves passing through the pure water 7 is maintained high.

As described above, it is preferable that the ultrasonic waves emitted from the vibrator 23 have a high frequency. In that case,
Since the directivity is also large, the above-mentioned transmission area E is almost accurately determined, and it is easy to supply the bubble 33 outside this area.

In addition, in the antistatic device, as shown in FIG. 4, a water supply pipe 6 for guiding pure water supplied from a tank (not shown) as a liquid supply source into the storage tank 21.
Is connected to the upper part of the storage tank 21. That is,
Pure water is poured into the storage tank 21 from above. According to this configuration, the new pure water injected from the water supply pipe 6 causes a flow along the water surface in the storage tank 21. Therefore, the rate at which this newly injected pure water comes into contact with the atmosphere increases, the amount of penetration of the components in the atmosphere that acts to reduce the specific resistance value of the pure water increases, and the chemical waves generated by the ultrasonic irradiation described above It is more effective together with the action of lowering the specific resistance value.

More specifically, new pure water from the water supply pipe 6 is injected from below the liquid surface 7a of a large amount of pure water 7 already stored in the storage tank 21. With this configuration, the liquid surface is not disturbed by the injection, and therefore, unlike the case of supplying pure water from above the liquid surface, bubbles (unlike bubbles due to cavitation) do not occur, It is preferable from the viewpoint of preventing reflection of sound waves. Bubbles due to cavitation are instantly compressed and destroyed after generation, and disappear, so there is almost no effect of ultrasonic reflection.

On the other hand, the pure water is sent out from the storage tank 21.
It is made from the lower part of the storage tank 21. That is, another water supply pipe 13 for guiding pure water to the silicon wafer 16 and the cutting blade 17 is connected near the bottom of the storage tank 21. According to this configuration, bubbles generated in the storage tank 21 due to some action (different from bubbles generated by cavitation), particularly bubbles 33 generated when the air supply pipe 31 is used are generated in the silicon wafer. 16, it is prevented from flowing into the blade 17. Therefore, it is possible to prevent the pure water containing the bubbles from causing a cavitation phenomenon due to friction with the blade 17, which contributes to the prevention of static electricity generation.

The present invention is not limited to the configuration of each of the above-described embodiments, and various configurations can be realized by combining some of the configurations included in each of the embodiments with each other or by applying them. Is.

[0049]

As described above, according to the present invention,
The specific resistance value is lowered by a chemical action by previously irradiating a liquid used for a required work such as cutting of a silicon wafer with an ultrasonic wave, thereby preventing the electrification. Therefore, there is almost no need for complicated operations such as replenishment of carbon dioxide cylinders, maintenance of mixed amount adjustment, neutralization of acidified waste water, etc. as in the past, and almost no complicated work is required. Therefore, it is possible to prevent static electricity without spending labor and to surely and effectively prevent it. In addition, in the present invention, the following various types of antistatic devices are adopted, and unique effects are exhibited. First,
An antistatic device that includes an air supply unit that supplies the liquid stored in the storage tank with atmospheric air as bubbles can be used. Secondly, there is an antistatic device configured so that liquid supplied from a tank or the like as a liquid supply source is injected into the storage tank from above the storage tank. In these configurations, the rate at which the liquid comes into contact with the atmosphere increases, the amount of penetration of the components in the atmosphere that acts to reduce the specific resistance value of the liquid increases, and the resistivity due to the chemical action due to the ultrasonic irradiation described above increases. It is more effective in combination with the effect of reducing the value.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of an antistatic device according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a main part of an experimental device manufactured to confirm the effect of the antistatic device shown in FIG.

FIG. 3 is a graph summarizing data obtained by the experimental apparatus shown in FIG.

FIG. 4 is a vertical cross-sectional view of a main part of an antistatic device as a second embodiment of the present invention.

FIG. 5 is a perspective view of an air supply pipe included in the configuration shown in FIG.

FIG. 6 is a perspective view of a main part of a conventional device.

[Explanation of symbols]

6,13 Water supply pipe 7 Pure water (liquid) 14 nozzles 16 Silicon wafer 17 Cutting blade (blade) 21 Storage tank 23 oscillator 26 oscillators 31 Air supply pipe 33 bubbles

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Claims (5)

(57) [Claims] 1. A water supply pipe for supplying a liquid from a liquid supply source,
A storage tank having an open upper surface for storing liquid, an atmosphere supply means for supplying the atmosphere in the liquid in the storage tank as bubbles, an ultrasonic wave excitation means capable of irradiating ultrasonic waves into the storage tank, and the ultrasonic wave excitation means The nozzle is provided with a water supply pipe that guides the liquid in the storage tank irradiated with ultrasonic waves to the nozzle,
An antistatic device characterized in that the liquid in the storage tank is irradiated with ultrasonic waves to guide and radiate a liquid having a reduced specific resistance value. 2. The antistatic device according to claim 1, wherein the liquid from the liquid supply source is injected from the upper part of the storage tank. 3. The antistatic device according to claim 1, wherein the liquid is injected from below a liquid surface of the liquid stored in the storage tank. 4. The antistatic device according to claim 1, wherein the liquid is delivered from the storage tank from a lower portion of the storage tank. 5. The antistatic device according to claim 1, wherein the atmosphere is supplied to the outside of a transmission region of the ultrasonic wave generated by the ultrasonic wave excitation means.