JP3338435B2 - Method for producing liquid in which hydrogen ion or hydroxide ion and redox substance coexist by electrolysis of pure water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolysis of high-purity water, which is suitable for cleaning or surface treatment of semiconductors. It is to provide seeded water and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Water pH and redox capacity are very important factors in the field of cleaning or surface treatment. In the following, first, a general idea of how the pH and the oxidation-reduction ability play in the field of cleaning and how the pH and the oxidation-reduction ability are controlled will be described.

[0003] Contaminants to be cleaned are classified into ionic substances, reaction products, and liquid or particulate substances. Contamination forms of ionic substances include adsorption by ion exchange on glass surfaces, adhesion of ions on semiconductor and metal surfaces by electrostatic attraction, and intrusion by diffusion of ions into semiconductor, metal, and ceramic surface layers. It is roughly divided into Contamination by reaction products falls into this category due to the deposition and deposition of impurities in water, such as boiler scale, and oxide films or rust generated on metal surfaces.

On the other hand, the mechanism of contamination by particulate matter is complicated. Attachment by a chemical bond, attachment by a physicochemical bond such as van der Waals force or hydrogen bond, and physical attachment by an electrostatic force or a magnetic force.

Among the above contaminants, ionic substances are:
It is common to wash with high-purity water such as pure water or ultrapure water. In the case of a semiconductor or the like, the electric resistivity is about 18%.
Ultra-pure water of MΩ / cm (that is, water with almost no ions) is used. Further, the reaction product is usually washed with a chemical. For the scale and the like, a drug in which an acid and a chelating agent are combined is used. In particular, citric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid and the like have both functions, and therefore these drugs are often used.

[0006] On the other hand, the removal rate of the oxide film on the metal surface by dissolution is strongly dependent on the pH and the redox ability. For example, ferric oxide (Fe ₃ O ₄ ) constituting an oxide film of iron
Is well soluble in acidic and reducing aqueous solutions having a pH of about 4 or less. Representative agents for dissolving these oxide films include a combination of oxalic acid, citric acid, and ethylenediaminetetraacetic acid. Here, oxalic acid is an acid and also acts as a reducing agent. On the other hand, the surface oxide film of chromium steel dissolves in an oxidizing solution. Representative agents include a combination of sodium hydroxide and potassium permanganate, or a combination of hydrofluoric acid and nitric acid.

In the field of semiconductor silicon wafer cleaning, there is a case where cleaning is performed by etching a surface layer. In this case, a combination of ammonia water and peroxide water, sodium hydroxide, nitric acid and the like are used as the cleaning liquid. As in the case of silicon wafer cleaning, a method of oxidatively decomposing or dissolving contaminants is applied to remove liquid or film-like contaminants. Specifically, in the case of oxidative decomposition,
There is a combination of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ), or a combination of ammonium hydroxide (NH ₄ OH) and H ₂ O ₂ . When dissolving an inorganic substance, hydrochloric acid (HCl) and H ₂ O ₂ , H ₂ S
O ₄ and H ₂ O ₂ , HCl and nitric acid (HNO ₃ ), and a combination of H ₂ SO ₄ and HNO ₃ . When an organic substance is dissolved, an organic chlorine-based solvent such as trichloroethane or dichloroethane is used.

As is apparent from the above description, the pH of water
And redox capacity play an important role in cleaning and surface treatment. In order to make the pH of water acidic or alkaline and to provide redox ability, there are a method of adding a chemical agent and a method of utilizing electrolysis. In order to shift the pH to acidic using a chemical, an acid is used,
Cl ⁻ , SO ²⁻ , NO as counter ions of ⁺ ions
^3- and anions such as CH ₃ COO ⁻ are present. On the other hand, in order to shift the pH to alkaline, a base is used, so that Na ⁺ , K ⁺ , Ca ^2+, etc. are used as counter ions of OH ⁻ ions. It is necessary that metal ions coexist. It is impossible ions added to the water ^- this way without counterions when using chemicals H ⁺ or OH.

As a method of controlling the pH without using a chemical, an electrolysis method is generally known. Specifically, a diaphragm such as an ion exchange membrane is provided between a cathode and an anode. Is known. However, the conventional diaphragm electrolysis has the following conditions. In other words, the cathode pole,
Since there is a structural distance between the diaphragm and the anode, it is necessary to lower the electric resistance of the solution in order to perform electrolysis,
For this purpose, it was essential to add an electrolyte, that is, salts to water. When a solution to which a salt composed of an anion and a cation is added is electrolyzed, the anion moves to the anode and the cation moves to the cathode. As a result, the anode compartment becomes acidic and the cathode compartment becomes alkaline. Therefore, in the conventional electrolysis method, the counter ion increases as the H ⁺ ion or the OH ⁻ ion increases. As a typical technique for such electrolysis, a method for producing caustic soda (NaOH) by electrolysis of saline is known. It cannot be applied to technology that uses water as raw water, and no suggestion is given.

[0010]

As described above, the generally known electrolysis method cannot be used for raw water such as pure water, which has almost no ions, at a time when it is not common knowledge to those skilled in the art. To provide a technique capable of causing H ⁺ or OH ⁻ to be present in excess in pure water or ultrapure water without adding an ionic substance, or to provide unprecedented pure water or H ⁺ or OH ⁻ using ultrapure water as raw water is provided to provide excess cleaning water. The above is further explained as follows. That is, when an acid or alkali and an oxidation-reduction agent are used in the cleaning water in the cleaning or surface treatment step, H ⁺
Alternatively, counter ions coexist with OH ⁻ ions, and after cleaning or surface treatment, the remaining of these ions becomes a problem. For example, in the case of cleaning metals, corrosion may occur if anions remain. In particular, it is well known that halogen ions such as Cl ⁻ accelerate corrosion. In the case of a semiconductor, it is necessary to avoid ionic impurities remaining on the surface regardless of anions and cations. It is known that when these ionic impurities remain, they serve as a trapping source for carriers and deteriorate the performance of the semiconductor. In order to remove these residual ions, it is necessary to perform sufficient rinsing after chemical cleaning. Particularly in the field of semiconductors, a large amount of water is used for rinsing. Specifically, several tons of water are required per silicon wafer. In recent years, the shortage of water resources has become a problem, and reducing the amount of water used is becoming an urgent and important issue from the viewpoint of securing production.

If cleaning or surface treatment can be performed with the decomposition products of H ₂₀ without using chemicals, the problem of residual ions is greatly reduced. By the way, H ₂ O is known to decompose according to the following oxidation-reduction reaction. Here, E. Is the standard redox potential.

O ₂ + H + e ⁻ ← HO ₂ E. = −0.13 V (1) 2H ⁺ + 2e ⁻ ← → H ₂ E. = + 0.0 V (2) O ₂ + 2H ⁺ 12e ⁻ ← → H ₂ O ₂ E. = + 0.69 V (3) H ₂ O ₂ + H ⁺ + e ⁻ ← OH. + H ₂ OE. = + 0.71 V (4) O ₂ + 2H ⁺ + 4e ⁻ ← → 2H ₂ O E. = + 1.229 V (5) HO ₂ + H ⁺ + e ⁻ ← → H ₂ O ₂ E. _{= + 1.495V (6) H 2} O 2 + 2H + + 2e - ← → 2H 2 O E. = + 1. 77 V (7) O ₃ + 2H ⁺ + 2e ⁻ ← → O ₂ + H ₂ O E. = + 2.07 V (8) OH ⁻ + H ⁺ + e ⁻ ← → H ₂ O E. = + 2.85 V (9) H ₂ O + e ⁻ ← → H · + OH ⁻ E. = −2.93 V (10) 2H ₂ O + 2e ⁻ ← → H ₂ + 2OH ⁻ E. _{= -0.828V (11) O 2 +} 2H 2 O + 4e - ← → 4OH - E. = −0.401V (12) O ₂ + H ₂ O + 2e ⁻ ← HO ₂ + OH ⁻ E. _{= -0.08 V (13) HO 2} - + H 2 O + 2e - ← → 3OH - E. = + 0.76 V (14) O ₃ + H ₂ O + 2e ⁻ ← → O ₂ + 2OH ⁻ E. = + 1.24 V (15) OH ⁻ + e ⁻ ← → OH ^- E. = + 2.02 V (16) As apparent from the above reaction formula, by a redox reaction, ^{H +} ions from the _{H 2} 0, OH ^- ions, H · radical, OH · _radical, H _2, O 2, HO _{2, O 3}
Electrolysis method is attracting attention as a method to generate such
The electrolytic reaction generally depends on the electrolyte of the aqueous solution, the electrode material, the current density and the electrolytic voltage. Therefore, by electrolysis,
Use of water (pure water, etc.) with the lowest possible electrolyte concentration, that is, impurities, should be used as the starting material, since the effect of including an electrolyte when producing decomposition products in water will be the same as adding a counter ion. is necessary. However, electrolysis of pure water or the like has not been conventionally considered.

Note that H ₂ O ₂ , H ₂ , O ₂ , O ₃
Redox species such as can be purified after electrolytic generation. These species made in the electrolyte solution,
It may be added to water containing H ⁺ ions or OH ⁻ ions. In either case, it is necessary to obtain water containing H ⁺ ions or OH ⁻ ions without adding a counter ion.

According to the present invention, the electric resistance is 0.01 MΩ / cm.
By electrochemically treating the above pure water or ultrapure water of 10 MΩ / cm or more, H
⁺ Ions or OH ⁻ ions are generated, and these are converted to H ₂ O ₂ , OH radical, H radical, H ₂ ,
An object of the present invention is to provide water suitable for cleaning and surface treatment by combining redox species such as O ₂ and O ₃ .

[0015]

It is known that an electrochemical reaction strongly depends on a reaction overpotential, which is a measure of the likelihood of an electrode reaction. Since the ideal hydrogen overvoltage of platinum is as very small as 0 V, H ⁺ ions adsorbed on the surface of platinum, which is the cathode, are easily reduced to hydrogen atoms and then quickly changed to H ₂ gas. FIG.
Even if platinum is used for the anode and the cathode in the electrolytic cell of No. 1 and Nafion 117 is used as the ion exchange membrane, no change in pH can be obtained. Therefore, if carbon having a hydrogen overvoltage of 0.6 V higher than platinum is used for the electrode, H ⁺
The ion reduction reaction is less likely to occur, and H around the electrode is reduced.
^{+ The} ion concentration increases. By passing water through the electrode in such a situation, H ⁺ ions are partially removed.
As a result, acidic water having no counter ion and a high H ⁺ ion concentration can be obtained. Some of the H ⁺ ions are reduced to H radicals (H atoms) or H ₂ gas, so that the electrolytic solution contains a reducing chemical species. Thus, an acidic and reducing liquid containing no counter ion is obtained. It is desirable that carbon be fired at a relatively low temperature of 500 ° C. to 800 ° C. Since low-temperature fired carbon has a large electric resistance, for example, carbon fired at 1000 ° C. or more may be further coated with carbon fired at 500 to 800 ° C. In order to obtain such a liquid, an electrode material having a higher hydrogen overvoltage than platinum may be used, and is not limited to a carbon electrode. Mercury and its metal compounds, lead and the like are also useful. The ion exchange membrane is not limited to Nafion 117, but is preferably a material in which a —SO ₃ H group or a —COOH group is bonded to a fluororesin. It is desirable that the current density is low as the electrolysis condition,
A value of about 20 mA / cm ² or less is suitable. It is desirable that the flow velocity on the electrode surface is high, and the linear velocity on the electrode surface is 1 cm.
/ Sec is desirable. When an acid is put into the intermediate chamber in the electrolytic cell shown in FIG. 2, anions are eliminated by the cation exchange resin membrane, and H ⁺ ions can be supplied to the cathode chamber. Is obtained.

In order to obtain an aqueous solution containing H ⁺ ions or OH ⁻ ions having no counter ion, it is necessary to use pure water or ultrapure water as raw water. Electrolyzing pure water is usually difficult due to high electrical resistance,
This becomes possible by using the electrolytic cell shown in FIG. 1 or FIG.

The structure of these electrolytic cells will be described below.

As shown in FIG. 1, an electrolytic cell 4 having a structure in which a cathode 2 and an anode 3 are closely attached to both sides of an ion exchange membrane 1 is used. The cathode chamber 9 is provided with an inlet 5 and an outlet 6, and the anode chamber 10 is provided with an inlet 7 and an outlet 8. In such a configuration, for example, a cation exchange group (-
When a cation exchange membrane into which (SO ₃ H group) is introduced is used,
Electrolysis voltage can be reduced to several volts (V), and electrolysis of pure water or ultrapure water can be easily performed.

At the anode electrode, an oxidizing substance such as O ₂ or O ₃ is generated, which is transferred to the cathode chamber via the ion exchange membrane, and the performance of the reduced species generated at the cathode electrode may be reduced. Conceivable. When these problems are concerned, the electrolytic cell shown in FIG. 2 is effective. In the electrolytic cell 25 shown in FIG.
Reference numeral 3 denotes a cathode electrode, 14 denotes an anode electrode, 15 denotes an inlet of the cathode chamber 21, 16 denotes the same outlet, 17 denotes an inlet of the anode chamber 22, 18 denotes the same outlet, 19 denotes an inlet of the intermediate chamber 23, and 20 denotes the same outlet. . By passing water having a reduced dissolved oxygen concentration (DO) through the intermediate chamber 23, the permeation of oxidizing substances generated at the anode electrode is prevented. Dissolved oxygen concentration (DO) using high purity nitrogen N ₂ (or argon Ar) gas
Lower.

In the electrolytic cell shown in FIG. 1, for example, when platinum is used for the anode and the cathode, and Nafion 117 manufactured by DuPont is used as the ion exchange membrane, the reaction of the formula (5) is performed at the anode and the reaction at the cathode is performed. The reaction of equation (2) occurs. Specifically, H ⁺ ions generated at the anode are reduced to H ₂ at the cathode, and no change in pH is observed with the water in the anode chamber and the water in the cathode chamber. However, the water in the anode chamber becomes oxidizing due to generation of O ₂ , and the water in the cathode chamber becomes reducing due to generation of H _2, but the object of the present invention is not achieved because there is no change in pH.

Next, in the electrolytic cell of FIG. 1, when platinum is used for the anode and cathode electrodes as the anion exchange membrane as the ion exchange membrane, unlike the cation exchange membrane, the surface of platinum which is the cathode electrode has H ⁺ Ions do not exist. Specifically, Nafion 117 is reacted with ethylenediamine (NH ₂ CH ₂ CH ₂ NH ₂ ) as an anion exchange membrane,
Fluororesin of a film _{to -SO 2} NHCH 2 CH 2 NH 2 group is attached as an exchange group may be used. When electrolysis is performed in a state where H ⁺ ions are insufficient, the cathode reaction is (1).
As shown by the equation (0) or the equation (11), a reductive decomposition reaction of H ₂ O occurs. As is apparent from these equations, OH ⁻ ions are generated around platinum. At the same time, H radicals or H ₂ gas are generated. In this way, alkaline and reducing water without counterions is obtained.

As the anion exchange membrane, fluororesin-S
The membrane is not limited to a membrane to which O ₂ NHCH ₂ CH ₂ NH ₂ groups are bonded, and any exchange membrane to which cation exchange groups are bonded can be used. In this case, a higher electrolytic current density is desirable, and 5 mA / cm ² or more is suitable. The water flow speed is desirably 1 cm / sec or more as a linear speed on the electrode surface. As the electrode, a metal that is stable in an alkaline solution such as platinum, palladium, stainless steel, gold, silver, carbon steel, nickel alloy, and steel is desirable. 1000 ℃
Graphite fired at the above high temperature is also effective.

On the other hand, water is oxidatively decomposed by anodic electrolysis, and H ⁺ ions are generated from H ₂ O according to the equation (5) or (8). When a cation exchange membrane is used for the ion exchange membrane in the electrolytic cell of FIG. 1, H ⁺
The ions move to the cathode compartment, and the pH of the solution in the anode compartment
Does not change. When an anion exchange membrane is used, H ⁺ ions do not move to the cathode chamber but stay in the anode chamber, and the pH shifts to the acidic side. At this time, if the OH ⁻ ions generated at the cathode electrode are removed by passing water, the change in pH on the anode side increases. Further, as can be seen from the equations (5) and (8), the anode electrolyte generates O ₂ or O ₃ gas, and has an oxidation performance. As an anion exchange membrane, -SO ₂ NH ₂ CH
A membrane to which an anion exchange group such as a ₂ CH ₂ NH ₂ group is bonded is desirable, but the anion exchange group is not limited to a special exchange group. 2 mA / electrolysis current density
cm ² or more is desirable, and the water flow rate is 1 cm /
sec or more is desirable. As an electrode material, platinum, palladium, and lead oxide (β-PbO ₂ ), which are stable to an anodic reaction, are desirable.

Further, as a method different from the electrolyte, H ⁺ ions or OH ion exchange resins ^- a method of obtaining a water containing ions. For example, when immersing the ion-exchange resin having a -SO ₃ H group in pure water or ultrapure water, -SO ₃ as part of the -SO ₃ H group following formula _{^{H ← → -SO 3 - + H}} + Partially dissociated. Since the dissociated H ⁺ ions migrate into water, the use of water makes it possible to use water containing H ⁺ ions without adding a counter ion. On the other hand, as redox species, H ₂ , O ₂ , H ₂
O ₂ , O _{3 and the} like can be generated by electrolysis. The redox species containing no impurity ions can be obtained by electrolytically producing these redox species using an electrolyte solution in order to increase the electrolysis efficiency and then purifying them. H ⁺
By adding the redox species to the water in which the ions are present, the water of the present invention can be obtained. As a cation exchange resin, an ion exchange resin in which —SO ₃ H groups are bonded to a fluororesin, and a styrene-divinylbenzene (DVB) resin—
An ion exchange resin to which an SO ₃ H group is bonded is desirable. Specifically, Nafion NR-50 manufactured by DuPont and Amberlite manufactured by Organo (trade name: Amberlite)
e) IR-116, IR-118, IR-120B, I
R-122, Diaion manufactured by Mitsubishi Kasei Corporation (trade name: D
iaion) SK102, SK104, SK1B, SK
110, SK116, Dowex (trade name; Dowex) manufactured by Dow Chemical Company, HCR-W2, HCR-S, H
GR-W and the like.

On the other hand, when preparing water containing OH ^- ions, it is preferable to use an anion exchange resin. Nafion NR-50 and NH ₂ CH ₂ CH ₂ as anion exchange groups
The NH ₂ styrene -DVB besides reacted resin -
N ⁺ _{(CH 3) 3 groups,} -NC ₂ H 5 OH (CH
₃ ) An ion exchange resin in which _two groups are bonded is desirable. Specifically, Amberlite IRA-401, IRA-40
2, IRA-400, IRA-430, IRA-41
1, IRA-410 (manufactured by Organo), Diaion
SA11A, SA12A, SA10A, SA21A, S
A20A (Mitsubishi Kasei), Dowex SBP-P,
SBR, SAR (manufactured by Dow Chemical Company) and the like. Thus OH ^- _H 2 in water containing ions, O
By adding ₂ , O ₃ or H ₂ O ₂ , the water of the present invention can be obtained.

By the above method, an acidic and reducing or oxidizing aqueous solution and an alkaline and reducing or oxidizing aqueous solution can be obtained without adding a counter ion. In the case of cleaning the iron-based metal surface oxide film, an acidic and reducing aqueous solution is effective. For washing the aluminum-based metal having the amphoteric oxide film, an acidic or alkaline and reducing aqueous solution is effective. Humoral used when washing, such as a silicon wafer is dependent on the contamination forms, firstly H ⁺ ions or OH ^- solution combining ion and the oxidizing substances are suitable. On the other hand, an alkaline and reducing aqueous solution is effective for washing vinyl chloride resin, acrylic resin and the like.

[0027]

Test Example 1 Test Example 1 In the electrolytic cell shown in FIG. 1, 80 mesh platinum was used for the anode and activated mesh glass carbon (RVC) was used for the cathode. The size of platinum is 80 × 60mm
The dimensions of the RVC are 90 × 70 × 25 mm and its surface area is about 800 m ² / g.

This electrolytic cell was incorporated in the apparatus shown in FIG. 26 indicates an electrolytic cell, 27 indicates a cathode chamber, and 28 indicates an anode chamber. A pipe 31 is connected to the cathode chamber, and a tank 29 is provided on the outlet side. The water accumulated in the tank is recirculated to the electrolytic cell using the circulation pump 30. Fluorine resin such as tetrafluoroethylene resin was used as the material of the equipment and piping. The capacity of the tank is 3 liters and the circulating water volume is 1 liter /
min. The electrolysis current is set to 0.5A and about 1MΩ
/ Cm of pure water was subjected to constant current electrolysis. The pH was measured with a glass electrode, and the oxidation-reduction potential was determined using silver / silver chloride (A
g / AgCl) electrode was measured using platinum as the sample electrode.

FIG. 4 shows the change over time in pH. The pH shifted to the acidic side with the start of electrolysis, and after about 10 minutes, about 4.65.
Became. SO ₄ as anion that may elute
² and F ^- there is. When the electrolyte was sampled and analyzed using ion chromatography, each concentration was 0.1 ppm or less. When 0.01 N sodium hydroxide (NaOH water) was titrated to this electrolyte,
The amount of NaOH used was less than the theoretical value for the measured pH, but the pH returned to neutral. These results indicate that H ⁺ ions are generated in the electrolyte. On the other hand, a value of about -0.527 V was obtained as the oxidation-reduction potential. In general, the oxidation-reduction potential of water at pH 4.6 is about +0.25 V, and the oxidation-reduction potential of the electrolytic solution is more negative than this potential, indicating that the solution is reducible.

In order to confirm the effect of this electrolytic solution, heating was performed at 700 ° C. for about 2 minutes in air, and Fe ₃
The carbon steel on which O ₄ was formed was immersed in the tank described above and washed. FIG. 5 shows the change with time of the elution amount of the oxide. In the figure, the curve 1 shows the result of washing in the electrolytic solution in the above-mentioned tank, and the curve 2 shows the result of washing in pure water. The elution amount of the oxide in the electrolytic solution is larger by one digit or more than the elution amount of the oxide in pure water, which indicates the effectiveness of the present invention.

Test Example 2 Using the electrolytic cell shown in FIG.
A 80-mesh platinum mesh with a size of 60 cm was used, and a carbon electrode with an outer size of 80 x 60 mm was used as a cathode. The carbon electrode uses polycarbodiimide as a starting material,
A sheet having a thickness of 0.5 mm and a shape shown in FIG.
It was fired at 0 ° C. After the same resin was further coated on the surface of this electrode, it was fired again at about 750 ° C. The intermediate chamber has dimensions of 90 × 70 × 25 cm, and contains Nafion NR50, which is a cation exchange resin, for about 160.
g. Nafion 117 as a cation exchange membrane was used as an ion exchange membrane as a diaphragm. This electrolytic cell was incorporated in the device shown in FIG.

In FIG. 7, the electrolytic cell 32 is a cathode chamber 3.
3. It comprises an intermediate chamber 34 and an anode chamber 35.
Ultrapure water is supplied from the ultrapure water production device 36 to the electrolytic cell using a pump 37. The solution subjected to cathodic electrolysis is supplied to a pipe 39.
And is stored in the tank 38. The overflowing liquid is discharged via a pipe 40. Pass degassed pure water to the intermediate room. Pure water is put into the degassing tank 41, and the water is bubbled from the N ₂ gas cylinder 42 through the pipe 44 using the bubbler 43. Pure water with DO reduced by bubbling is supplied to the intermediate chamber using the piping 46 and the circulation pump 45. Stop valves 47 and 4 are provided at the exit and entrance of the intermediate chamber.
8 and the material of the liquid contact surface of the equipment / piping was fluororesin as in Test Example 1.

At a flow rate of 1 liter / min, 16.5 MΩ /
cm of ultrapure water was passed through the electrolytic cell in one direction, and constant current electrolysis was performed at an electrolytic current of 0.25A. The flow rate is also 0 in the intermediate chamber.
Water degassed with N ₂ gas was passed at 5 liter / min. DO was about 20 ppb. The glass electrode and the platinum electrode were put in the tank 38, and the pH and the oxidation-reduction potential were measured. The pH will be in the range of 6-5 and the redox potential will be about-
It was 0.65V. The oxidation-reduction potential is in a more negative direction than in Example 1, and it is considered that a stronger reducing species is generated. One of the reduced species candidates is, for example, H (hydrogen radical).

Next, in the above-mentioned electrolytic cell, Nafion 117 provided in the cathode chamber and the intermediate chamber was removed, and Nafion NR filled in the intermediate chamber was brought into direct contact with the carbon electrode. At this time, the valves 47 and 48, which are the inlet and outlet valves of the intermediate chamber, were closed. Constant current electrolysis was performed at the same flow rate of 1 liter / min and electrolysis current of 0.25 A as in the above electrolysis conditions.
The pH was between 5 and 4, and a more acidic liquid was obtained.

Test Example 3 In the electrolytic cell shown in FIG. 1, an anion exchange membrane in which --SO ₃ NHOH ₂ OH ₂ NH ₂ groups were bonded to a fluororesin was used as an ion exchange membrane, and 8 was used as an anode and a cathode.
Platinum of 80 × 60 mm with 0 mesh was used. 1MΩ incorporating the electrolytic cell apparatus of Test Example 1 in the same manner as FIG. 3
/ Cm of pure water was circulated at a flow rate of 1 liter / min, and constant current electrolysis was performed at an electrolysis current of 1.5 A. A glass electrode, a platinum electrode and the tank 2 were put into the tank 2 to measure pH and oxidation-reduction potential. FIG. 8 shows the change over time in pH. As is apparent from the figure, the pH reached 10.5 after about 15 minutes. The oxidation-reduction potential became about -1.0V. The redox potential was about -0.1 V when an aqueous solution having a pH of 10.5 was prepared by adding NaOH to pure water. The oxidation-reduction potential of the electrolyte is -0.1
It is in a direction more base than V and shows strong reducing properties. Thus, an alkaline reducing electrolyte was obtained without adding a counter ion.

The cleaning effect of this electrolytic solution was confirmed for a printed substrate soldered. One printed board of about 50 × 50 mm was placed in an electrolyte of pH 10 in a tank 2 for 3 hours.
The other printed circuit boards were immersed in pure water having a resistance of 1 MΩ / cm for 30 seconds. After immersion, the surface of each printed circuit board was rinsed with pure water. The amount of ions remaining on the surface of the print substrate was evaluated by measuring the conductivity of the waste liquid that had been washed off. FIG. 9 shows the relationship between the number of times of washing and the conductivity of the waste liquid. In the figure, curve 1 shows the case where the printed board is immersed in pure water, and curve 2 shows the case where the printed board is immersed in the electrolytic solution. As can be seen from the figure, the conductivity of the waste liquid decreases rapidly when immersed in the electrolytic solution. This indicates that the electrolytic solution has a higher cleaning effect than pure water.

Test Example 4 In the electrolytic cell shown in FIG. 2, platinum of 80 mesh and dimensions of 80 × 60 mm was used for the anode and cathode, Nafion 117 was used as the ion exchange membrane, and Nafion N was used for the intermediate chamber.
160 g of R50 were charged. In this example, Nafion 11
7 between the cathode and the cathode, 100
A mesh net was inserted as a spacer. A glass electrode and a platinum electrode were immersed in a tank in which this electrolytic cell was incorporated into a one-through system shown in FIG. 6, and the pH and the oxidation-reduction potential of the electrolytic solution were measured. Ultrapure water having an electric resistance of 16.5 MΩ / cm was passed at a flow rate of 1 liter / min, and an electrolytic current of 1.
Constant current electrolysis was performed at 5 A. The pH was between 9.5 and 10, and the oxidation-reduction potential was about -0.8V. It has been proved that the insertion of the spacer reduces the amount of H ⁺ ions adsorbed on the surface of the platinum cathode to cause reductive decomposition of H ₂ O.

Test Example 5 In the electrolytic cell of FIG. 1, -SO ₂ NH was added to the ion exchange membrane.
Using an anion-exchange membrane having OH ₂ 0H ₂ NH ₂ group,
80 × 60m with 80 mesh for anode and cathode
m of platinum was used. This electrolytic cell was used in the same manner as in Test Example 2 and FIG.
Was installed in the circulation type device shown in (1). However, unlike the test example 2, the anode chamber was connected to the circulation line. That is, the anode electrolyte was circulated. A glass electrode and a platinum electrode were immersed in the tank.

Pure water having an electric resistance of 1 MΩ / cm was circulated at a flow rate of 1 liter / min, and was subjected to constant current electrolysis at a current of 0.5 A. FIG. 10 shows the change over time in pH. PH after 15 minutes
Reached 4.75. The oxidation-reduction potential is + 0.4V
And an acidic electrolyte solution was obtained.

Test Example 6 In the electrolytic cell shown in FIG.
Approximately 160 g of Nafion NR-50 was filled in the intermediate chamber using platinum having a mesh size of 80 × 60 mm. In this example, the ion exchange membrane between the anode and Nafion NR-50 was removed, and Nafion 117 was inserted only between the cathode and Nafion NR-50. Test Example 2
It was incorporated into the device shown in FIG. However, unlike Test Example 2, the anode chamber was connected to a one-through line. Specifically, the anode chamber is 33 and the cathode chamber is 35
And Further, the valves 48 and 47 at the entrance and exit of the intermediate chamber were closed. Ultrapure water of 16.5 MΩ / cm was flowed through the electrolytic cell at a flow rate of 1 liter / min in a one-through manner, and was electrolyzed at a constant current of 1.5 A. The glass electrode and the platinum electrode were put in the tank 38, and the pH and the oxidation-reduction potential were measured. The pH dropped to 5-4 and the redox potential was about 0.45V. When the pH is simply adjusted to 5 to 4 using an acid, the oxidation-reduction potential becomes 0.2.
０．３0.3V. It can be seen that the potential of the electrolyte is more noble than this potential and is oxidizing. Further, since O ₃ was generated from the electrolytic solution, it is considered that O ₃ contributed to this oxidation-reduction potential.

Test Example 7 The ion exchange group (Na form) of a strongly acidic styrene-based cation exchange resin IR-120B (manufactured by Organo) was first converted from -SO ₃ Na to -SO ₃ H form with concentrated sulfuric acid. Then, the ion exchange resin was sufficiently washed with pure water. 10 final washings
0 ml was sampled, and 10 cc of an aqueous solution of 0.01 mol (M) of barium chloride was added thereto, but no precipitation was observed. From this result, it is determined that the amount of SO ₄ ^2- ions eluted from the ion exchange resin is 0.1 ppm or less.

Take 5 g of ion exchange resin, and add about 1 M
Add 100 cc to Ω / cm pure water and leave for 10 minutes. The supernatant was taken and the pH was measured with a glass electrode. A value of 3.6 was obtained. 0.01 in 40 ml of supernatant
When 0.4 ml of M NaOH aqueous solution was added, the pH of the glass electrode was 6.3. From this result, it can be seen that H ⁺ ions are present in the supernatant. That is, an acidic liquid was obtained without adding a counter ion.
By adding 30% H ₂ O ₂ to this, an acid and oxidizing liquid can be obtained without adding a counter ion.

The effect of this solution was evaluated by the speed of removing fingerprints attached to the glass surface. 40 ml of the above acidic water
Solution containing 1 g of 30% H ₂ O ₂ and 30% pure water
A liquid to which 1 g of H ₂ O ₂ was added was prepared. Two glasses with fingerprints were prepared, immersed in each liquid, and left in a container for about 1 hour. Observation of the surface condition for one hour revealed that the fingerprint on the surface of the glass immersed in the acidic liquid was removed, but the fingerprint remained on the pure water. From these results, the effectiveness of the acidic and oxidizing liquid is judged.

Test Example 8 In the electrolytic cell shown in FIG.
Dimensions with platinum 80 × 60 mm, the cathode electrode trial
In the same manner as in Experimental Example 2, a carbon electrode having carbon fired at about 750 ° C. was used for the surface layer, and both Nafion 117 and Nafion 324 having higher anion elimination ability than Nafion 117 were used as a membrane. The intermediate chamber was filled with 170 g of Amberlite 15 (manufactured by Organo Corporation). This electrolytic cell was incorporated in the device shown in FIG.

Ultrapure water is supplied from the ultrapure water producing apparatus 36 shown in FIG. The solution subjected to cathodic electrolysis is stored in a tank 38 via a pipe 39. The overflowed liquid is discharged through the pipe 40. In the intermediate chamber tank 41, H ⁺
In order to supply more ions, a solution in which polyacrylic acid is dissolved at 0.01M is added. The polyacrylic acid itself does not move to the cathode chamber by the cation exchange membrane. This liquid is bubbled from a N ₂ gas cylinder 42 via a pipe 44 using a bubbler 43. The liquid in which the dissolved oxygen concentration (DO) has been reduced by bubbling is supplied to the intermediate chamber using the piping 46 and the circulation pump 45.

At a flow rate of 1 liter / min, 16.5 MΩ
/ Cm of ultrapure water is allowed to flow in the cathode chamber in one direction. In this state, a constant current analysis at an electrolytic current of 0.25 A was performed. A deaerated aqueous solution of polyacrylic acid was passed through the intermediate chamber at 0.5 L / min. Tank 3
8, a glass electrode and a platinum electrode were inserted, and the pH and the oxidation-reduction potential were measured. The pH dropped to 5-4 and the redox potential was about -0.7V. By placing the polyacrylic acid solution in the intermediate chamber, a stronger acidic liquid was obtained than in Test Example 2.

[0047]

As described above, according to the present invention,
An acidic or alkaline liquid having redox performance can be obtained without using anions such as Cl ⁻ , SO ₄ ²⁻ and NO ₃ ⁻ and cations such as Na ⁺ and K ⁺ .

According to the present invention, the following effects can be obtained.

The acidic and reducing liquid is effective for dissolving and removing an oxide film or rust on a metal surface, and for cleaning a surface while preventing oxidation of a silicon wafer. An even greater advantage is that Cl can promote metal corrosion after cleaning.
^{It is} a trap source for ions or electrons of silicon semiconductors; Since harmful ions such as Na ⁺ and K ⁺ ions do not remain, the amount of pure water or ultrapure water used for final cleaning can be reduced. The acidic oxidizing liquid is effective for decomposing and removing organic substances attached to the surface of a silicon wafer, glass, or the like. Cl remains on the surface, such as with the printed circuit board reducing the liquid alkaline ^- removal rate of such ion is greater than just pure water. When the electrolytic solution is used, the removal rate of the ionic impurities is increased, and the cooling water can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a configuration outline of an electrolytic cell used in the present invention,

FIG. 2 is a diagram showing a schematic configuration of an electrolytic cell used in the present invention;

FIG. 3 is a diagram showing a schematic configuration of a test apparatus used in Test Example 1.

FIG. 4 is a diagram showing the results of Test Example 1,

FIG. 5 is a diagram showing the results of Test Example 1,

FIG. 6 is a diagram showing a carbon electrode incorporated in the electrolytic cell used in Test Example 2,

FIG. 7 is a diagram showing a schematic configuration of a test apparatus used in Test Example 2;

FIG. 8 is a diagram showing the results of Test Example 3,

FIG. 9 shows the results of Test Example 5.

FIG. 10 shows the results of Test Example 6.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion exchange membrane, 2 ... Cathode pole, 3 ... Anode pole,
4 ... electrolyzer, 5 ... into the cathode chamber, 6 ... outlet in the cathode chamber,
7 ... Anode compartment inlet, 8 ... Anode compartment outlet, 9 ... Cathode compartment, 10 ... Anode compartment, 11, 12 ... Ion exchange membrane,
13: cathode electrode, 14: anode electrode, 15: cathode chamber inlet, 16: cathode chamber outlet, 17: anode chamber inlet, 18: anode chamber outlet, 19: intermediate chamber inlet, 20 ...
Intermediate chamber outlet, 21: cathode chamber, 22: anode chamber, 2
3 ... Intermediate chamber, 25 ... Electrolyzer, 26 ... Electrolyzer, 27 ... Cathode, 28 ... Anode, 29 ... Tank, 30 ... Circulation pump, 31 ... Piping, 32 ... Electrolyzer, 33 ... Cathode, 34 ... Intermediate chamber, 35 Anode chamber, # 6 Ultrapure water production equipment, 37 Pump, 38 Tank, 39 Pipe, 4
0: Waste liquid pipe, 41: Degassing tank, 42: Nitrogen cylinder, 43: Bubbler, 44: Nitrogen gas pipe, 45: Pump, 46: Pipe, 47: Intermediate chamber inlet, 48: Intermediate chamber outlet.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-14232 (JP, A) JP-A-64-90088 (JP, A) JP-A-3-39493 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C02F 1/46 C11D 7/02 H01L 21/304

Claims (4)

(57) [Claims] Claims: 1. A method for electrolyzing pure water or ultrapure water into said electrolyzed water.
Pure water or ultra-pure water that generates H ⁺ ions and redox substances
A method for producing washing water using water as raw water, wherein a cation exchange membrane and a cation exchange resin are held as a diaphragm structure for electrolysis, and carbon obtained by calcining an organic substance at 600 to 800 ° C. as a cathode electrode is held on the surface. A method for producing cleaning water using, as raw water, pure water or ultrapure water that generates H ⁺ ions and hydrogen atoms, hydrogen molecules, or hydrogen peroxide using electrodes. 2. A method for producing washing water using pure water or ultrapure water as raw water, which produces H ⁺ ions and an oxidation-reduction substance in the electrolytic water by electrolysis of pure water or ultrapure water, the method comprising: Using a cation exchange membrane and a cation exchange resin as a diaphragm structure, and platinum or β-type lead oxide as an anode,
A method for producing cleaning water using pure water or ultrapure water that generates H ⁺ , ozone, and oxygen molecules as raw water. 3. The method according to claim 1, wherein
Electrolysis of pure water or ultrapure water without adding ions
Pure water that produces H ⁺ ions and redox substances inside
A method for producing cleaning water using ultrapure water as raw water. 4. The method according to claim 1, wherein
Electrolysis of pure water or ultrapure water without adding ions
Pure water also generating ions and the oxidation-reduction substance ^- OH in
Is a method for producing cleaning water using ultrapure water as raw water.