JP3382100B2 - Electrolytic ionic water generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic ionized water generator, and more particularly to the structure of electrodes arranged in an electrolytic cell.

[0002]

2. Description of the Related Art Conventionally, ionized water produced by an ionized water producing apparatus has been used in various fields, especially in the production of semiconductor devices and liquid crystals. In the manufacture of semiconductor devices, it is used for cleaning semiconductor substrates such as silicon semiconductors with ionized water obtained by electrolyzing pure water or ultrapure water, and for polishing. Up to now, fluorocarbon solvents such as CFCs have been used for cleaning semiconductor substrates in the manufacture of semiconductor devices, but they have begun to be shunned because they adversely affect the living environment. Instead, pure water or ultrapure water is used instead. Has come to be used as the safest solvent. Pure water is high-purity water having a resistivity of about 5 to 18 MΩcm in which impurities such as ions, fine particles, microorganisms, and organic substances are almost removed. Ultrapure water is extremely high-purity water having a higher purity than that of pure water obtained by removing suspended substances, dissolved substances, and highly efficiently from water by an ultrapure water production apparatus. By electrolyzing these waters (hereinafter collectively referred to as pure water), ionic water such as highly oxidative anodic ionic water (acidic water) and strongly reducing cathodic ionic water (alkaline water) is generated. It

In the manufacture of semiconductor devices and liquid crystals,
It is also considered to clean the surface of the substrate using pure water or ultrapure water such as anodic ion water or cathodic ion water.
FIG. 9 shows a conventional electrolytic ionized water generator. Electrolysis tank 50
Includes a cathode chamber 52 and an anode chamber 53, a cathode 541 is disposed in the cathode chamber 52, and an anode 542 is disposed in the anode chamber 53. Then, these electrodes 54 (cathode 541,
The anodes 542) are both made of platinum or titanium. In order to efficiently separate the cathode ionized water 58 formed in the cathode chamber 52 and the anode ionized water 59 formed in the anode chamber 53, the cathode chamber and the anode chamber are formed of a porous diaphragm 56 such as ceramic or polymer. It is partitioned. The cathode 541 of the electrolytic cell 50 is connected to the negative electrode 67 of the DC power supply 66, and the anode 542 is connected to its positive electrode 68. Electrolyzer 5
At 0, the power supply voltage from the power supply 66 is applied to the pure water supplied from the ultrapure water supply pipe 61 of the electrolytic cell 50, for example,
The diluted electrolyte solution 51 added with a supporting electrolyte such as ammonium chloride is electrolyzed. As a result of this electrolysis cathode 5
The cathode ion water generated on the 41 side is alkaline water, and the anode ion water generated on the anode 542 side is acidic water.

Cathode ionized water 58 produced in the cathode chamber 52
Is supplied to the outside from the cathode ionized water supply pipe 62,
The anode ionized water 59 generated in the anode chamber 53 is supplied to the outside from the anode ionized water supply pipe 63. Since alkaline water is usually generated in the cathode chamber 52, for example, when using a polishing apparatus used for manufacturing a semiconductor device, in order to perform polishing using alkaline water,
Alkaline water is supplied to the polishing cloth of the polishing apparatus by using the cathode ionized water supply pipe 62 connected to the electrolytic cell 50 as the ionized water supply pipe. In this case, the acidic water generated in the anode chamber 53 is unnecessary and is discarded. Therefore, the anode ionized water supply pipe 63 is connected to the ionized water discharge pipe for discharging ionized water. Further, in order to perform polishing using acidic water, the anode ionized water supply pipe 63 connected to the electrolytic cell 50 serves as an ionized water supply pipe to supply the acidic water to the polishing cloth. In this case, the alkaline water generated in the cathode chamber 52 is unnecessary and is discarded. Therefore, the cathode ionized water supply pipe 62 is connected to the ionized water discharge pipe for discharging ionized water. As described above, the electrolytic cell 50
Is separated into two tanks by the diaphragm 56, and each electrode is arranged in each separated tank, so that alkaline water or acidic water can be taken out from each tank depending on the purpose.

As described above, the ionic water includes alkaline water and acidic water, which are diluted in the electrolytic cell, for example, HC.
Ionized water having an arbitrary pH is produced by electrolyzing an electrolytic solution of 1, HNO ₃ , NH ₄ Cl, NH ₄ F, or the like. However, in this method, the metal ions contained in the electrolyte solution and the metal ions generated from the electrodes are also attracted to the electric field generated at the electrodes, and a large amount of metal ions enter the electrolytic cell, especially the alkaline cell (cathode chamber), and the purity of the electrolytic ion water is increased. Had lowered.
Recently, there has been an increasing demand for using ionized water for cleaning wafers in the manufacture of semiconductor devices. In such a current situation, in semiconductor devices, minute amounts of metal impurities have a great influence on device characteristics, so that highly purified ionized water is required.

[0006]

When using electrolytic ion water for cleaning semiconductor substrates, it is essential that there be no particles or metal contamination. When a metal electrode is used, the electrode is usually manufactured in a general room, and various metal elements are contained in the electrode. Even if an electrode coated with a noble metal such as Pt, which has high oxidation resistance, is used, various metal elements including Pt elute on the anode side even though they are trace amounts, and are contained in the electrolytic ion water produced. Will end up. Such a phenomenon is the same even when an electrode made of a metal oxide is used. It is also known to use carbon for the electrode, but when a carbon electrode is used for an electrolytic cell, oxygen is generated by electrolysis of water, and particularly carbon is generated on the anode side as shown in the following formula (1). Electrodes are significantly consumed by reacting with oxygen. C + O ₂ → CO ₂ ↑ (1) As a result, the electrode surface is attacked and carbon fragments are spilled from the electrode. The carbon pieces cause particles. The present invention provides an apparatus for producing electrolyzed ionized water of ultrapure water or pure water, which enables reduction of running costs in cleaning processes, pollution of wastewater, and improvement of work environment safety.

[0007]

In order to solve the above problems, the present invention is characterized in that a carbon electrode in which carbon fragments are less likely to be missing is used to generate electrolytic ionized water without metal contamination. I am trying. Crystalline carbon electrodes such as graphite formed by firing have many pores,
An uneven surface is formed on the surface. A carbon electrode is also a desirable material from the viewpoint of increasing the electrolysis efficiency because of its large surface area. Therefore, after forming the molded body of the electrode, a carbon layer such as an amorphous layer is formed on the surface. Since the carbon layer is deposited even inside the pores on the surface of the molded body, the bonds between the carbon elements are strengthened to make it difficult for the carbon pieces to be lost. Also, because the electrode surface is covered with a filter, even if carbon fragments are missing,
It is possible to prevent particles from being captured by the filter and being mixed into the electrode ion water. Further, by adding hydrochloric acid at a high concentration to the anode side, the reaction of the formula (1) in the electrode reaction is remarkably reduced, and the reaction from the oxygen generation main body to the chlorine generation main body becomes a problem on the anode side. Carbon deficiency can be sufficiently suppressed.

The electrolytic ionized water producing apparatus of the present invention comprises an electrolytic cell for electrolysis comprising an anode chamber containing an anode and a cathode chamber containing a cathode, and a supporting electrolyte having a predetermined concentration in the electrolytic cell. A means for supplying a prepared electrolyte solution is provided, and the electrode is formed of a crystalline carbon molded body, and an amorphous carbon layer is formed on the surface thereof. At least a part of the electrode may be covered with a filter at a predetermined interval. The electrolytic bath may have an electrolytic ion water supply line for supplying the generated electrolytic ion water, and a filter may be arranged at a predetermined position on the electrolytic ion water supply line.
A filter may be arranged on at least a part of the inner wall of the electrolytic cell. The means for supplying the electrolyte solution comprises a first means for supplying the electrolyte solution to the anode chamber.
Second means for supplying the electrolyte solution to the cathode chamber
You may make it consist of the means of. The first means is
An electrolyte solution containing a supporting electrolyte composed of hydrochloric acid may be supplied to the anode chamber, and the second means may supply an electrolyte solution containing a supporting electrolyte composed of ammonia to the cathode chamber. The electrolyte solution may be composed of ultrapure water or pure water supplied from an ultrapure water supply line and a supporting electrolyte. The electrolyzer may include a cleaning water supply line for supplying cleaning water and a cleaning water discharge line for discharging the cleaning water.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an electrolytic cell of an electrolytic ionized water generator. The electrolytic cell 1 is divided into an anode chamber 2 and a cathode chamber 3, which are separated by an ion exchange membrane 6 arranged at the boundary. A carbon electrode, which is a feature of the present invention, is installed in the electrolytic cell 1. Carbon electrode
It is composed of an anode 4 and a cathode 5, and the anode 4 is an anode chamber 2 and a cathode 5.
Are arranged in the cathode chamber 3. Both ends of the anode 4 and the cathode 5 are fixed to the upper lid of the electrolytic cell 1. Although not shown, the anode 4 is connected to the positive electrode of the power source, and the cathode 5 is
It is connected to the negative pole of the power supply. Ultrapure water to which a supporting electrolyte is added or pure water is supplied from the lower portion of the electrolytic cell 1 through electrolyte-added ultrapure water supply lines 8 and 9. A first electrolyte-added ultrapure water supply line 8 is connected to the anode chamber 2, and a second electrolyte-added ultrapure water supply line 9 is connected to the cathode chamber 3.
Are connected. The electrolyzed ionic water is generated by electrolyzing the ultrapure water added with the supporting electrolyte, that is, the electrolyte solution, which is supplied from the supply lines 8 and 9 by energizing about 10 to 20 V between the electrodes 4 and 5. Acidic water is produced in the anode chamber 2 with the anode 4, and alkaline water is produced in the cathode chamber 3 with the cathode 5. The electrolytic cell 1 is, for example, 1
It is a square of 0 × 10 cm to 30 × 30 cm, and the height is about 20 to 50 cm.

Electrolytic ionized water drainage lines 10 and 11 (that is, acidic water drainage line 10 and alkaline water drainage line 11) are formed in the anode chamber 2 and the cathode chamber 3, respectively, from which electrolytic ionized water is discharged. As for the electrolyte concentration of the electrolyte solution, the electrolyte solution on the side of the anode chamber has a hydrochloric acid content of 1,000 to
It is suitable that the electrolyte solution on the cathode chamber side is about 100,000 ppm and ammonia is about 10 to 500 ppm.
To increase the conductivity, hydrochloric acid may be added to the electrolyte solution supplied to the cathode chamber side in an amount of 10 to 500 ppm in accordance with the amount of ammonia. The pH of the electrolyte solution is 8-9.
Try to be around. Electrolytic ionized water drainage line 10,
Reference numeral 11 is also an electrolytic ion water supply line for supplying electrolytic ion water to other devices such as a wafer cleaning device. During electrolysis, electrolytic ionized water discharge lines 10, 1
The opening / closing valves 18 and 19 of 1 are opened, and the acidic water branch line 2 which is a branch line of the electrolytic ion water discharge lines 10 and 11 is opened.
7 and the opening / closing valve 20 of the alkaline water branch line 28,
21 is closed. FIG. 3 is a perspective view and a partial side view of an electrode (anode). The anode 4 in this embodiment is plate-shaped as shown. The present invention has various possible shapes as other embodiments. In addition to a plate shape, a round bar shape, a polygonal column, or the like can be used. The anode is obtained by molding crystalline carbon such as graphite and firing it with heat of about 1000 ° C. to 1200 ° C. for several hours to several hundred hours.

The fired molded body 41 is porous and has irregularities on its surface. The molded body 41 is dipped in an amorphous carbon material and fired to form the carbon layer 42 even in the pores. Since the carbon layer 42 is in close contact with the surface of the molded body 41 along the irregularities, it strengthens the bond between the carbon elements and makes it difficult for the carbon pieces to drop out. In addition to this, as the means for forming the carbon layer 42, a low pressure CVD method, a vacuum vapor deposition method, or the like is used. The electrodes (anode 4 and cathode 5) in the electrolytic cell 1 are covered with, for example, a filter 7 having a high cleanliness of silica. The degree of coverage may be a part or the whole. In the figure, what is partially covered is shown. A space of about 3 to 10 mm is provided between the electrode and the filter. The filter 7 and the electrolytic cell 1 main body are joined, for example, by sandwiching packings 24 and 25 between them and fixing them with screws 26. Although carbon fragments are expected to be missing from the anode 4 and the cathode 5 by electrolysis, the missing carbon fragments are captured by the filter 7 and are not included in the electrolytic ion water. As a material for the filter 7, for example, there is a ceramic filter obtained by baking and hardening quartz used for a dry filter. The ceramic filter is made of, for example, a molded body of three layers having different particle sizes, and impurities can be sufficiently removed. FIG. 4 is a perspective view of the filter 7.

The improvement of the electrode structure according to the present invention significantly reduces the loss of carbon fragments from the electrodes, but if electrolysis is continued for a long time, some carbon fragments remain in the filter 7. In order to eliminate this, an ultrapure water supply line for cleaning and a drain line are attached to the electrolytic cell 1. A first cleaning ultrapure water supply line 12 is connected to the upper part of the anode chamber 4, and a first cleaning ultrapure water drain line 14 is connected to the lower part. A second cleaning ultrapure water supply line 13 is connected to the upper part of the cathode chamber 5, and a second cleaning ultrapure water drain line 15 is connected to the lower part. When cleaning the inside of the filter, the electrolysis process is stopped and the opening / closing valves 18 and 19 of the electrolytic ion water discharge lines 10 and 11 are closed. And ultrapure water supply line for cleaning 1
The opening / closing valves 16 and 17 of 2 and 13 are opened, and the opening / closing valves 20 and 21 of the acidic water branch line 27 and the alkaline water branch line 28 and the opening / closing valves 22 and 23 of the ultrapure water supply lines 14 and 15 for cleaning are opened. After washing away the carbon pieces in the filter, the opening / closing valves 16, 17 and 20-2
3 is closed, and the open / close valves 18 and 19 of the electrolytic ionized water discharge lines 10 and 11 are opened to perform electrolysis. Further, particle filters 29 and 30 are installed in the electrolytic ion water drain lines 10 and 11 just in case.

FIG. 5 is a sectional view of a portion taken along the line AA 'in FIG. As shown in the figure, the electrode composed of the anode 4 and the cathode 5 is composed of a plurality of molded bodies. Filter 7
Surrounds the periphery of each molded body of each electrode. FIG. 6 is another embodiment of the filter. The impurities generated from the electrodes are removed in order to prevent the impurities from entering the generated electrolytic ion water. Therefore,
If it is attached to an electrolytic ion water drainage line that supplies electrolytic ion water to the outside, it is not necessary to arrange it so as to surround the electrodes. Therefore, here, the filter 7 made of high-purity ceramic is attached to the electrolytic ion water drainage line. Unlike FIG. 5 and FIG. 6, FIG. 7 is fixed to the inner surface of the electrolytic cell 1. There is little mixing of carbon fragments into electrolytic ionized water.

FIG. 2 is a system diagram of a semiconductor manufacturing apparatus in which the electrolytic ionized water generator shown in FIG. 1 is applied to cleaning semiconductor wafers. This system is basically composed of ultrapure water or an ultrapure water tank 45 containing pure water, an electrolytic ionized water generator including the electrolytic tank 1, and a semiconductor wafer cleaning tank 39. The ultrapure water supply line for cleaning and the drain line shown in FIG. 1 connected to the electrolytic cell 1 are not directly related to the cleaning of semiconductor wafers and therefore omitted in this figure. The ultrapure water tank 45 is provided with pure water or ultrapure water lines 31 and 3 for supplying pure water or ultrapure water to a cleaning process in manufacturing an apparatus for electrolysis or semiconductor devices.
2 are connected, and lines for supplying pure water or ultrapure water to these devices are arranged in these ultrapure water lines. The electrolyte solution supply line 8 supplies to the electrolytic cell 1 an electrolyte solution formed by mixing hydrochloric acid (HCl) supplied from the supporting electrolyte solution tank 48 and ultrapure water with a mixer 46. The electrolyte solution supply line 9 is formed by mixing hydrochloric acid (HCl) supplied from the supporting electrolyte solution tank 43, ammonia (NH ₃ ) supplied from the supporting electrolyte solution tank 49, and ultrapure water with a mixer 47. The electrolyte solution is supplied to the electrolytic cell 1.

For cleaning, in order to enhance the effect of removing particles and metal contamination, it is used in combination with other chemicals such as hydrofluoric acid, nitric acid and hydrochloric acid. Alkaline water is also used in combination with a liquid such as a surfactant. In addition, the concentration of the drug solution is preferably about 0.1 to 5%. These are sucked up and mixed by the pumps 35 and 36 from the chemical liquid tanks 33 and 34. The electrolytic ion water uniformly mixed by the mixers 37 and 38 is supplied to the cleaning tank 39 to clean the semiconductor substrate 40. When electrolyzed ion water is used for cleaning a semiconductor wafer, particles can be suppressed by using a metal-based electrode, but the metal becomes ions and is eluted from the anode. In the case of a carbon electrode alone, the surface is eroded by the oxidation of the anode (generation of CO ₂ ), carbon fragments are lost, and a large amount of particles are generated. In the present invention, the surface of the carbon electrode is covered with a carbon layer of amorphous carbon in order to make it difficult for the carbon electrode itself to be lost, and this serves as an adhesive to strengthen the bond between carbons. In addition, since it is considered that deficiency is inevitable as long as a carbon electrode is used, a filter is installed around the electrode for that purpose, and the generated particles are collected. Further, in the above embodiments, the case where there is one electrolysis cell for performing electrolysis has been described, but the present invention is not limited to this case, and a plurality of electrolysis cells 1, 1 ′, 1 ″ are provided as shown in FIG. 8. Can be used in combination.

[0016]

According to the present invention, generation of particles and metal contamination that occur when electrolyzing ultrapure water is suppressed, and highly clean electrolytic ionic water that can be used for cleaning semiconductor wafers can be generated.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electrolytic cell in an electrolytic ionized water generator of the present invention.

FIG. 2 is a schematic system diagram of an electrolytic ionized water generation device and a cleaning device of the present invention.

FIG. 3 is a perspective view of an anode of the present invention and a sectional view taken along the line AA ′.

FIG. 4 is a perspective view of a high-purity filter used in the present invention.

5 is a cross-sectional view of a portion taken along the line AA ′ in FIG.

FIG. 6 is a sectional view of the electrolytic cell of the present invention.

FIG. 7 is a sectional view of the electrolytic cell of the present invention.

FIG. 8 is a perspective view of the electrolytic cell of the present invention.

FIG. 9 is a cross-sectional view of a conventional electrolytic cell.

[Explanation of symbols]

1 ... Electrolyzer, 2 ... Anode chamber, 3 ... Cathode chamber, 4 ... Anode, 5 ... Cathode, 6 ...
Ion exchange membrane, 7 ... High purity filter, 8, 9
..Electrolyte-added ultrapure water supply line, 10 ... acid water drainage line, 11 ... alkaline water drainage line, 1
2, 13 ... Ultrapure water supply line for cleaning, 14, 15
..Ultra-pure water drain lines for cleaning, 16, 17, 18, 1
9, 20, 21, 22, 23 ... Open / close valve, 24,
25 ... Packing, 26 ... Fixing screw, 27 ...
・ Acid water branch line, 28 ... Alkaline water branch line, 29, 30 ... Particle filter, 3
1, 32 ... Ultrapure water line, 33, 34 ... Chemical solution tank, 35, 36, 49, 44, 70 ... Pump, 37, 38, 46, 47 ... Mixer, 39 ...
・ Cleaning tank, 40 ・ ・ ・ Semiconductor wafer, 41 ・ ・ ・
Molded body, 42 ... Carbon layer, 45 ... Ultrapure water tank, 48, 43, 49 ... Supporting electrolyte tank.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-263430 (JP, A) JP-A 8-126886 (JP, A) JP-A 55-149684 (JP, A) JP-A 62- 14987 (JP, A) JP-A-7-185547 (JP, A) Actual development: 6-52994 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/46 C25B 9 / 00 C25B 11/12

Claims (8)

(57) [Claims] 1. An electrolytic cell for electrolysis, which comprises an anode chamber containing an anode and a cathode chamber containing a cathode, and means for supplying an electrolytic solution in which a supporting electrolyte is adjusted to a predetermined concentration to the electrolytic cell. with the door, the electrode is made of molded article of crystalline carbon on its surface
Is an electrolytic ionized water generator characterized in that an amorphous carbon layer is formed . 2. The electrolytic ion water generator according to claim 1, wherein at least a part of the electrode is covered with a filter at a predetermined interval. 3. The electrolytic cell has an electrolytic ion water supply line for supplying the generated electrolytic ion water, and a filter is arranged at a predetermined position in the electrolytic ion water supply line. The electrolytic ionized water generator according to claim 1. 4. The electrolytic ionized water generator according to claim 1, wherein a filter is arranged on at least a part of an inner wall of the electrolytic cell. 5. The means for supplying the electrolyte solution comprises a first means for supplying the electrolyte solution to the anode chamber and a second means for supplying the electrolyte solution to the cathode chamber. The electrolytic ionized water generator according to claim 1. 6. The first means supplies an electrolyte solution containing a supporting electrolyte composed of hydrochloric acid to the anode chamber, and the second means
6. The means for supplying an electrolyte solution containing a supporting electrolyte made of ammonia to the cathode chamber.
The electrolyzed ionized water generator according to item 1. 7. The electrolytic ion according to claim 1, wherein the electrolyte solution comprises ultrapure water supplied from an ultrapure water supply line or pure water and a supporting electrolyte. Water generator. 8. The electrolytic cell is provided with a cleaning water supply line for supplying cleaning water and a cleaning water discharge line for discharging this cleaning water, according to any one of claims 1 to 7. Electrolytic ionized water generator.