JPH0880486A - Electrolytic ultrapure water, producer thereof, production, cleaning device and cleaning method - Google Patents

Abstract

PURPOSE: To reduce the running cost in cleaning, to make the working environ ment safe and make the water harmless. CONSTITUTION: An ultrapure water injection line 8 is communicated with a chelating agent injection part 9, a mixing tank 2 is provided on one end of the injection line 8, and the mixing tank 2 is communicated with an electrolytic cell 3. A cathode 10 and an anode 11 are inserted into the electrolytic cell 3, and a porous diaphragm 12 is furnished between the cathode 10 and anode 11. The cathode 10 is connected to the negative electrode 13 in a battery 4 and the anode 11 to the positive electrode in the battery 4. A member 15 is provided in the electrolytic cell 3. One end of a catholyte feed line 16 and one end of an anolyte feed line 17 are provided in the electrolytic cell 3, and the feed lines 16 and 17 are communicated with the mixing tank 2 through a bypass line 18. A treating tank 6 is provided at the other ends of the feed lines 16 and 17, and the treating tank 6 is communicated with a waste liq. tank 7 through a waste water line 19. As a result, the running cost is reduced in the cleaning stage, the working environment is made safe, and the waste water is made harmless.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrolyzed water of ultrapure water, an apparatus for producing the same, a method for producing the same, a cleaning apparatus and a cleaning method, and more particularly, it is used for cleaning a semiconductor substrate.

[0002]

2. Description of the Related Art Regarding the conventional method for cleaning a semiconductor substrate,
This will be described below. First, a chemical solution used for cleaning is prepared, and the silicon substrate is cleaned with this chemical solution. In particular,
By controlling the pH of this chemical solution to a predetermined value, the particles are removed by slightly etching the silicon substrate and the metal contamination on the surface is removed. Then, the silicon substrate is washed with ultrapure water. At this time, until the specific resistance value of this ultrapure water is recovered to about 18 MΩcm,
Wash with water.

[0003]

By the way, recently, there is a tendency that the diameter of semiconductor wafers is increased, and accordingly, the amount of chemicals and ultrapure water used for cleaning a silicon substrate and the amount of drainage are increased. ing. Further, since it is necessary to separately use an alkaline chemical solution and an acidic chemical solution depending on the purpose of cleaning the silicon substrate, it is inevitable that a cleaning apparatus having a chemical solution supply system is upsized. Therefore, there is a problem that the running cost in the cleaning process increases due to an increase in the amount of the chemical liquid and the ultrapure water used and an increase in the size of the cleaning device. Further, since the chemical solution used for cleaning the silicon substrate is a substance that is harmful and harmful to the human body, it is necessary to pay sufficient attention to the handling of the chemical solution, and it is difficult to handle the chemical solution. Furthermore, this chemical liquid may have an adverse effect on the environment if the waste liquid is not sufficiently treated.

The present invention has been made in consideration of the above circumstances, and an object thereof is ultrapure water which makes it possible to reduce the running cost in the cleaning process, to make the working environment safe and to make the drainage harmless. To provide the electrolyzed water, its producing device, its producing method, cleaning device and cleaning method.

[0005]

In order to solve the above problems, the present invention comprises cathode water or anode water separated by electrolyzing ultrapure water to which a predetermined amount of a chelating agent is added. It is characterized by that.

Further, an injection means for injecting the supporting electrolyte into the ultrapure water, an electrolytic cell for electrolyzing the ultrapure water in which the supporting electrolyte is injected by the injecting means, and an electrode provided in the electrolytic cell And are provided.

The method further comprises a step of adding a supporting electrolyte to the ultrapure water and a step of electrolyzing the ultrapure water to which the supporting electrolyte is added to generate cathode water and anode water. Is characterized by.

The supporting electrolyte is EDTA or HE.
It is characterized by being a chelating agent of any one of DTA, NTA, DTPA and TTHA. Further, electrolyzed water generated by electrolysis of ultrapure water is supplied, and a first processing tank in which a semiconductor substrate is cleaned by the electrolyzed water and electrolytic water used for cleaning in the first processing tank are sent. It is characterized by comprising: a second treatment tank in which the electrolyzed water is mixed and neutralized; and a drainage means for draining the water neutralized in the second treatment tank.

In addition, a step of generating electrolyzed water by electrolysis of ultrapure water, a step of cleaning the semiconductor substrate with the electrolyzed water, a step of mixing and neutralizing the electrolyzed water used for the cleaning, And a step of draining the harmonized water. Further, the electrolyzed water is characterized in that it is either cathode water, anode water, or a mixed water of cathode water and anode water, depending on the purpose of cleaning.

[0010]

According to the present invention, the amount of ultrapure water used can be reduced as compared with the conventional cleaning method by cleaning with only electrolytic water without using any chemical solution. At the same time, since the chemical liquid supply system is not required because the chemical liquid is not used, it is possible to prevent the cleaning device from increasing in size. Further, since it is not necessary to use the chemical liquid, the cleaning device can be easily handled and the operational safety of the cleaning device can be improved. Further, by mixing and neutralizing the electrolyzed water after the cleaning treatment in the second treatment tank, the waste water can be discarded while being rendered harmless to the environment.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an electrolyzed water producing apparatus and a semiconductor substrate cleaning apparatus according to first to third embodiments of the present invention. The electrolyzed water generating apparatus 1 is composed of a mixing tank 2 for mixing a chelating agent and ultrapure water, an electrolytic tank 3 for electrolyzing water, a Daniel battery 4, and the like. The semiconductor substrate cleaning apparatus 5 includes a processing tank 6 for cleaning a silicon substrate, a drainage tank 7, and the like.

That is, the ultrapure water injection line 8 is communicated with the chelating agent injection section 9. A mixing tank 2 is provided at one end of the injection line 8, and the mixing tank 2 is in communication with the electrolytic tank 3. A cathode 10 and an anode 11 made of platinum electrodes are inserted in the electrolytic cell 3, and a porous diaphragm 12 is provided between the cathode 10 and the anode 11. The cathode 10 is a negative electrode (Zn /
ZnSO ₄ aq) 13 and the anode 11 is a positive electrode (Cu / CuSO ₄ aq) 1 in the battery 4.
4 is electrically connected. A member 15 is provided in the electrolytic cell 3 for uniformly mixing the chelate in the ultrapure water and spreading the chelate into the electrolytic cell 3. This member 15 has a larger diameter than the holes of the porous diaphragm 12. Has a much larger hole.

One end of each of the cathode water supply line 16 and the anode water supply line 17 is provided in the electrolytic cell 3, and the cathode water supply line 16 and the anode water supply line 1 are provided.
Each of 7 is connected to the mixing tank 2 via an electrolytic water bypass line 18. The electrolytic water bypass line 18 is connected to the mixing tank 2. The cathode water supply line 16
And the treatment tank 6 at the other end of each of the anode water supply line 17
Is provided, and the treatment tank 6 is communicated with the drainage tank 7 through the drain line 19.

A method for producing electrolytic water using the apparatus for producing electrolytic water according to the first embodiment of the present invention and a method for cleaning a semiconductor substrate using the apparatus for cleaning a semiconductor substrate will be described below.

First, ultrapure water (not shown) is injected into the ultrapure water injection line 8. Next, the chelating agent injecting section 9 injects a chelating agent (not shown) into the ultrapure water injecting line 8.
As a result, the chelating agent and ultrapure water are injected into the mixing tank 2 through the ultrapure water injection line 8 and mixed in the mixing tank 2. Since this mixing tank 2 plays a role of a buffer for the direct supply of ultrapure water, it becomes possible to always supply a constant flow rate of ultrapure water to the electrolysis tank 3 by this mixing tank 2. As a result, ultrapure water whose chelate concentration is controlled to, for example, 50 to 100 ppm is formed.
The chelating agent functions as a supporting electrolyte for electrolyzing ultrapure water. The supporting electrolyte does not contain a metal element such as Na, for example, EDTA (ethylenediamine-tet).
racetic acid), HEDTA (hydroxyet
hyl ethylenediamine-triacetic acid), NTA (nitri
lotriacetic acid), DTPA (diethylenetriamine pe)
ntaacetic acid) or TTHA (triethylenetetramine-
A chelate such as hexaacetic acid) is used. this is,
This is because it is required that the cleaning water for the silicon substrate does not contain metal and halogen. Since the chelate has a property of coordinating a metal, when the chelate is used for cleaning the silicon substrate, the chelate is contaminated with metal from an external factor, that is, the metal is adsorbed on the surface of the silicon substrate. It has the effect of suppressing pollution. In addition to the above, sulfuric acid or nitric acid may be used as the supporting electrolyte. However, if S (sulfur) remains on the surface of the silicon substrate and the handling risk is taken into consideration, a chelate may be used as the supporting electrolyte. It is suitable to use.

After this, the ultrapure water having the chelate concentration controlled is sent to the electrolytic cell 3 and is evenly distributed in the electrolytic cell 3 by the member 15 in the electrolytic cell 3. Next, this ultrapure water is electrolyzed by the voltage applied from the Daniel battery 4 to the cathode 10 and the anode 11, and is separated into cathode water and anode water (not shown) through the porous diaphragm 12. The cathode water is alkaline with excess hydroxide ions, and the anode water is acidic with excess protons. Here, in order to obtain a constant flow rate of the cathode water and the anode water, it is sufficient to always supply a constant flow rate of ultrapure water to the electrolytic cell 3. The reason why the inside of the electrolytic cell 3 is partitioned by the porous diaphragm 12 is to efficiently separate the cathode water and the anode water.

Next, the cathode water and the anode water are supplied to the treatment tank 6 of the cleaning apparatus 5 through the cathode water supply line 16 and the anode water supply line 17. At this time, in the treatment tank 6, the cathode water and the anode water are mixed at a predetermined mixing ratio to form electrolyzed water controlled to PH7 to PH8. When mixed in this way, the cathode water and the anode water left unsupplied in the treatment tank 6 are returned to the mixing tank 2 through the electrolytic water bypass line 18, and are mixed again with the unelectrolyzed ultrapure water. 2 is supplied. Then, the silicon substrate previously put in the processing bath 6 is washed with the electrolyzed water.

During wet cleaning after metal sputtering,
Since the electrolyzed water is controlled to PH7 to PH8, it is possible to prevent the metal existing on the surface of the silicon substrate, in particular, the wiring material Al or Cu from being dissolved or corroded. This is because both Al and Cu are in the passive state in the case of electrolyzed water of PH7 to PH8, and even if electromotive force is generated between Al and Cu in this electrolyzed water, it does not depend on the electrode potential. Is. That is, according to the potential PH diagram (corrosion diagram), Al is PH4 to PH8, C
Since u is in the passivation region at PH7 to PH9, Al and Cu
Both of them are in the passive area. This is the case of electrolyzed water of PH7 to PH8.

After this, the electrolyzed water in the treatment tank 6 is sent to the drainage tank 7 through the drain line 19. Next, in this drainage tank 7, the electrolyzed water is neutralized by being mixed with cathode water or anode water. After this, this neutralized electrolyzed water is discarded.

According to the first embodiment, by using only electrolyzed water without using any chemicals, the amount of ultrapure water used can be reduced as compared with the conventional cleaning method.
At the same time, since the chemical liquid supply system is not required because the chemical liquid is not used, it is possible to prevent the cleaning device from increasing in size. As a result, the running cost in the cleaning step can be reduced as compared with the conventional method.

Further, by washing with electrolyzed water, it is not necessary to use a chemical solution which is a harmful substance to the human body, which has been used in the conventional washing method. Therefore, the cleaning device can be handled easily and the operational safety of the cleaning device can be improved.

Further, the waste water is discarded in a state of being harmless to the environment by mixing and neutralizing the electrolyzed water after the cleaning treatment in the drainage tank 7. Therefore, there is no possibility of adversely affecting the environment. That is, unlike the conventional method, since it is not necessary to use a chemical solution that may have an adverse effect on the environment in the cleaning process, there is no possibility of having an adverse effect on the environment.

Further, since the hydrogen bonds between water molecules are dissociated by electrolysis and the number of hydrogen bonds in water is reduced, the water molecule group (cluster) is reduced. Therefore, the surface tension is reduced, which is effective for cleaning a silicon substrate having a fine pattern or trench.

Further, since electrolyzed water has a stronger oxidizing power or reducing power than a normal acidic or alkaline solution, it is excellent in the ability to remove contamination on the surface of a silicon substrate. A method for producing electrolyzed water and a method for cleaning a semiconductor substrate according to the second embodiment of the present invention will be described below. In this case, the description of the same parts as those in the first embodiment will be omitted.

After the ultrapure water is separated into cathode water and anode water by electrolysis, the cathode water is supplied to the treatment tank 6 through the cathode water supply line 16. Next, the silicon substrate (not shown) that has been previously placed in the processing tank 6 during the manufacturing process of the semiconductor device is washed with the cathode water. After this,
The cathode water in the treatment tank 6 is sent to the drainage tank 7 through the drain line 19 and discarded. Next, the separated anode water is supplied to the treatment tank 6 through the anode water supply line 17, and the silicon substrate in the treatment tank 6 is washed with the anode water. As a result, during the manufacturing process, for example, RI
Damage and contamination that occur after E (Reactive Ion Etching) is performed are removed.

In the second embodiment, the same effect as in the first embodiment can be obtained. Further, when cathode water is used for cleaning the silicon substrate, the cathode water exerts excellent effects in removing particles on the surface of the silicon substrate and in silicon etching.

A method for producing electrolyzed water and a method for cleaning a semiconductor substrate according to the third embodiment of the present invention will be described below. In this case, the description of the same parts as those in the first embodiment will be omitted.

After the ultrapure water is separated into cathode water and anode water by electrolysis, the anode water is supplied to the treatment tank 6 through the anode water supply line 17. Next, a silicon substrate (not shown), which has been previously placed in the processing tank 6 during the manufacturing process of the semiconductor device, forms a trench, and then the CDE (Chemical Dry Etching) is performed after the polymer is removed to form the trench. In order to remove the residual contamination on the side wall,
It is washed with the anode water.

After this, this anode water is sent to the drainage tank 7 through the drainage line 19. Next, in the drainage tank 7, the anode water is neutralized by being mixed with cathode water. This neutralized anode water is discarded.

Also in the third embodiment, the same effect as in the first embodiment can be obtained. When anodic water is used for cleaning the silicon substrate, the anodic water exhibits an excellent effect of removing the metal and organic substances on the surface of the silicon substrate.

Further, in a normal acidic solution, it works effectively only for removing a metal having a greater ionization tendency than hydrogen (H), and C
Although u cannot be removed, anodic water has a strong oxidizing power, so Cu and organic contaminants can be removed. Incidentally, the cathode water and the anode water in the above-mentioned embodiment are properly used depending on the purpose of cleaning the silicon substrate.

[0032]

As described above, according to the present invention,
Cleaning is performed using only electrolyzed water without using any chemicals, the electrolyzed water after cleaning is mixed and neutralized, and waste water is discarded. Therefore, it is possible to reduce the running cost in the cleaning process, make the working environment safer, and render the drainage harmless.

[Brief description of drawings]

FIG. 1 is a schematic view showing an electrolyzed water producing apparatus and a semiconductor substrate cleaning apparatus according to first to third embodiments of the present invention.

[Explanation of symbols]

1 ... Electrolyzed water generator, 2 ... Mixing tank, 3 ... Electrolytic tank, 4 ...
Daniel battery, 5 ... Semiconductor substrate cleaning device, 6 ... Treatment tank, 7 ... Drainage tank, 8 ... Ultrapure water injection line, 9 ... Chelating agent injection section, 10 ... Cathode (Pt), 11 ... Anode ( Pt), 12 ...
Porous diaphragm, 13 ... Negative electrode (Zn / ZnSO ₄ aq), 14 ... Positive electrode (Cu / CuSO ₄ aq), 15 ... Member, 16 ... Cathode water supply line, 17 ... Anode water supply line, 18 ... Electrolyzed water bypass line , 19 ... Drainage line.

Claims (7)

[Claims] 1. Electrolyzed water of ultrapure water, which comprises cathode water or anode water separated by electrolyzing ultrapure water to which a predetermined amount of chelating agent has been added. 2. An injection unit for injecting a supporting electrolyte into ultrapure water, an electrolyzer for electrolyzing the ultrapure water in which the supporting electrolyte is injected by the injecting unit, and an electrode provided in the electrolytic tank. An electrolyzed water generation device comprising: 3. A step of adding a supporting electrolyte to the ultrapure water, and a step of electrolyzing the ultrapure water to which the supporting electrolyte is added to generate cathode water and anode water. And a method for producing electrolyzed water. 4. The supporting electrolyte is EDTA, HEDT
The electrolyzed water producing apparatus or the producing method thereof according to claim 2 or 3, which is a chelating agent of any one of A, NTA, DTPA and TTHA. 5. A first treatment tank to which electrolyzed water generated by electrolysis of ultrapure water is supplied, and the electrolyzed water is used to wash a semiconductor substrate, and an electrolysis used for washing in the first treatment tank. A cleaning process, comprising: a second treatment tank to which water is sent and in which the electrolyzed water is mixed and neutralized; and a drainage means for draining the water neutralized in the second treatment tank. apparatus. 6. A step of producing electrolyzed water by electrolysis of ultrapure water, a step of washing a semiconductor substrate with the electrolyzed water, a step of mixing and neutralizing the electrolyzed water used for the washing, and A cleaning method comprising: a step of draining the hydrated water. 7. The cleaning apparatus according to claim 5 or 6, wherein the electrolyzed water is any one of cathode water, anode water, or a mixed water of cathode water and anode water depending on a cleaning purpose. Cleaning method.