JP2000008083A - Gas-dissolved water production equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent metal impurities in the form of microparticles from mixing into hydrogen-dissolved water through being entrained by hydrogen gas when hydrogen-dissolved water is produced by introducing hydrogen gas which is generated using an electrolytic device into a gas-dissolving device to dissolve the hydrogen gas in pure water. SOLUTION: This gas-dissolved water production equipment has a gas-feed pipe 7 between an electrolytic device 1 and a gas-dissolving device 2, wherein, the gas-feed pipe 7 is equipped with a gas-liquid separator 12 and furthermore, the gas-feed pipe 7 which is connected between the gas-dissolving device 2 and the gas-liquid separator 12, is equipped with a filter device 13 to remove metal impurities in the form of microparticles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a gas-dissolved water by dissolving a gas in pure water. The present invention relates to an apparatus for producing gas-dissolved water for cleaning electronic component members requiring a surface.

[0002]

2. Description of the Related Art Wet processing of an object to be processed such as an electronic component, which is required to obtain an extremely clean surface, will be described below with reference to a wet processing of a silicon wafer used in LSI manufacturing.

In the LSI manufacturing process, an insulating film of, for example, SiO ₂ is formed on a silicon wafer, a predetermined pattern of windows is formed on the insulating film to expose metal silicon under the insulating film, and then wet processing is performed. , Depending on the purpose, p
An element is formed by repeating the process of guiding a negative or n-type element and embedding a metal wiring such as Al, for example.

In a step of introducing a p-type or n-type element or a step of embedding a metal wiring, foreign matter such as fine particles, metal,
If impurities such as organic substances and natural oxide films are attached, defective element characteristics such as a metal-silicon wiring defect and an increase in contact resistance occur.

Therefore, in the LSI manufacturing process, the surface wet processing step is a very important step for manufacturing a high-performance device, and it is necessary to remove impurities adhering to the wafer surface as much as possible.

Conventionally, wet processing of a semiconductor wafer has been performed using, for example, the following technique. That is, using a mixture of a sulfuric acid / hydrogen peroxide solution, a hydrochloric acid / hydrogen peroxide solution, an ammonia / hydrogen peroxide solution, a hydrofluoric acid solution, an ammonium fluoride solution, and the like, and a semiconductor surface, Organic substances, fine particles, metals, and the like adhering to the semiconductor surface without impairing the flatness at the atomic level
In order to remove the natural oxide film, for example, a wet process including the following steps is performed. (1) Sulfuric acid / hydrogen peroxide cleaning (sulfuric acid: hydrogen peroxide solution = 4: 1, volume ratio) 130 ° C. for 10 minutes (2) Ultrapure water cleaning 10 minutes (3) Hydrofluoric acid cleaning (0.5% hydrofluoric acid) 1 minute (4) Ultrapure water washing 10 minutes (5) Ammonia hydrogen peroxide washing (ammonia water: hydrogen peroxide solution: ultrapure water = 0.05: 1: 5, volume ratio) 80 ° C. 10 minutes (6) Ultrapure water cleaning 10 minutes (7) Hydrofluoric acid cleaning (0.5% hydrofluoric acid) 1 minute (8) Ultrapure water cleaning 10 minutes (9) Hydrochloric acid peroxide cleaning (HCl: Hydrogen peroxide water: Ultrapure water = 1: 1: 6, volume ratio) 80 ° C. 10 minutes (10) Ultrapure water cleaning 10 minutes (11) Hydrofluoric acid cleaning (hydrofluoric acid 0.5%) 1 minute (12) Ultrapure water cleaning 10 minutes (13) ) Spin drying or IPA steam drying

Here, the role of each of the above wet treatment steps will be described. The (1) sulfuric acid / hydrogen peroxide cleaning is mainly for removing organic substances adhering to the surface. The cleaning of ammonia hydrogen peroxide (5) is mainly for removing adhered particles on the surface, and the cleaning of hydrogen peroxide (9) is mainly for removal of metal impurities adhered on the surface. The hydrofluoric acid cleaning of (2), (7) and (11) is for removing a natural oxide film on the surface.

[0008] Further, the wet treatment of an object to be wet, such as an electronic component, for which an extremely clean surface is required, will be described below with reference to the wet treatment of a glass substrate used for manufacturing a liquid crystal display device.

In the liquid crystal display device manufacturing process, a gate metal wiring made of, for example, Cr is formed on a glass substrate, a gate insulating film made of silicon nitride is further formed, and an amorphous silicon i layer and an amorphous silicon n + layer are formed. Film, and further Al / Cr (Al and Cr
Alloy? ) Is formed. After that, a predetermined pattern of windows is formed in the metal wiring and the amorphous silicon n ⁺ layer to expose the amorphous silicon i layer, and then, an interlayer insulating film made of silicon nitride is further formed to form an element.

At the interface between the gate metal wiring and the gate insulating film and at the interface between the gate insulating film and the amorphous silicon i-layer, if foreign matter such as fine particles, impurities such as metal, organic matter, or natural oxide film are attached, metal-silicon Defective device characteristics such as defective wiring and increased contact resistance occur.

Therefore, in the liquid crystal display device manufacturing process, the surface wet treatment step after the formation of the thin film is a very important step for manufacturing a high-performance device, and it is necessary to remove impurities adhering to the surface as much as possible. There is.

As a method for bringing a wet processing chemical or ultrapure water into contact with the surface of a semiconductor wafer substrate or a glass substrate for a liquid crystal display device as described above, a chemical generally called a batch cleaning method (or A method of immersing a plurality of substrates together in a wet processing tank containing pure water or ultrapure water is often used, but the chemicals in the wet processing tank are circulated and filtered to prevent contamination of the chemicals during the wet processing. Rinsing or rinsing method includes overflow rinsing, in which ultrapure water is supplied from the bottom of the tank and overflows from the top of the tank when rinsing with pure water or ultrapure water. There is also a device such as a quick dump rinse that stores pure water or ultrapure water and drains it from the bottom of the tank at once. In recent years, besides the batch cleaning method, a method of applying a chemical, pure water, or ultrapure water to the substrate surface in a shower, or applying a chemical, pure water, or ultrapure water to the center by rotating the substrate at high speed A so-called single wafer wet treatment method such as a wet treatment method is also employed.

By the way, the rinsing treatment with pure water or ultrapure water, which is carried out after the step of removing the deposits by chemicals in the above-mentioned wet treatment system, is for rinsing (rinsing) the chemicals remaining on the substrate surface. Pure water or ultrapure water is usually used as the rinse water. This is because the contaminants may adhere to the substrate surface again after the adhered substance removing step using chemicals, that is, after the substrate surface is already in a clean state with no attached impurities, and the significance of the wet treatment is lost. Because it is For this purpose, pure water or ultrapure water, that is, high-purity water from which fine particles, colloidal substances, organic substances, metals, anions, dissolved oxygen, etc. have been removed to an extremely low concentration, is used as the rinsing water for removing chemicals. ing.

[0014] Such pure water or ultrapure water is conventionally produced by the following method.

That is, raw water is subjected to coagulation sedimentation, sand filtration, activated carbon filtration, reverse osmosis membrane, two-bed / column ion exchanger, mixed-bed ion exchanger, precision filter, etc.
In the next pure water treatment system, the primary pure water is obtained by processing, and immediately before the use point where the wet processing of the object to be cleaned is performed,
Ultrapure water is obtained by an ultrapure water production apparatus that further processes the pure water in a secondary pure water treatment system.

Such an ultrapure water production apparatus is essentially
The secondary pure water is stored in a primary pure water tank, and the secondary pure water is sequentially subjected to secondary treatment using a membrane treatment device such as an ultraviolet irradiation device, a mixed bed polisher, an ultrafiltration membrane device or a reverse osmosis membrane device. Fine particles, colloidal substances, organic substances, metals, anions and the like remaining in the water are permanently removed to obtain ultrapure water (secondary pure water) suitable for wet treatment of the object to be wet. The ultrapure water, which is the permeate of the membrane treatment device of the secondary pure water treatment system, is generally branched from the middle of the circulation line to the use point and sent, and the remaining ultrapure water is circulated through the circulation line. It is configured to return to the primary pure water tank through a return pipe (return pipe) of the line.

Incidentally, the ammonia hydrogen peroxide washing (5) is used for removing fine particles, and it is effective for the removal of fine particles that the water quality of the cleaning liquid is reductive. For example, in a liquid with an oxidation-reduction potential of about +400 mV vs NHE, such as ultrapure water, the fine particles and the object to be cleaned have electric potentials of opposite signs to each other, so they are attracted by electrical attraction. Inside, the zeta potentials of both have the same sign, so that a repulsive force is generated, and the fine particles are separated from the surface and float in the cleaning solution without re-adhering.
This is achieved by dissolving a reducing gas in a solution such as ultrapure water to create a cleaning solution having reducing properties, and by using this, a high-temperature, high-concentration chemical solution as described in (5) above is not used. This means that particulate removal is possible. Further, the washing with hydrochloric acid and hydrogen peroxide in the above (9) is used for removing metals, and it is effective to remove metals that the water quality of the washing solution is oxidizing. Therefore, a cleaning liquid having a high oxidizing property can be prepared by dissolving an oxidizing gas such as ozone in a liquid having an oxidation-reduction potential of about +400 mV like ultrapure water. The metal can be removed without using a high-temperature and high-concentration chemical solution as in 9).

A gas supply source for dissolving in pure water or ultrapure water is, for example, gas generation by a water electrolysis method. In this case, by applying a voltage in a predetermined electrolytic cell to electrolyze water, oxygen or ozone as an oxidizing gas is obtained on the anode side, which is the positive electrode side, and the cathode electrode side, which is the cathode side. Produces hydrogen as a reducing gas. Oxidizing water or reducing water can be easily obtained by dissolving the oxidizing or reducing gas in pure water or ultrapure water. For example, the oxidation-reduction potential of ozone-dissolved water obtained by dissolving the oxidizing gas ozone is about 1500 mV vs NHE
The oxidizing power can oxidize and remove metals and organic substances on the substrate, and the oxidation-reduction potential of hydrogen-dissolved water obtained by dissolving hydrogen as a reducing gas is about −25.
0 mV vs NHE, which has the effect of removing fine particles on the substrate by its reducing power.

[0019]

The gas generated by the electrolysis of water is led to a gas dissolving tank via a gas-liquid separator.
Here, the gas comes into contact with pure water or ultrapure water to be dissolved, and gas-dissolved water is obtained. Here, stainless steel is often used for the housing of the electrolytic cell for electrolysis of water because of its high strength and low corrosion resistance.
Electrodes are arranged between the housing on the anode side and the housing on the cathode side. Generally, lead oxide (PbO ₂ ) is used for generating ozone and platinum (Pt) is used for generating hydrogen. Therefore, solid electrolyte membranes (SPE) that can lower the electrolysis voltage are often used. The supply of electricity to the electrode is performed directly to the electrode power supply part on the electrode of the metal substrate, but when using SPE to deposit the electrode material on the ion exchange membrane, a metal called a power supply is separately arranged in the electrolytic cell,
Power is supplied via this.

By the way, in supplying the electrolysis product gas,
Iron oxide () in electrolysis gas or water vapor in electrolysis gas
There is a problem that fine metal impurities mainly composed of (Fe ₂ O ₃ ) are contained. This is due to the oxidation of iron at crystal defects in the stainless steel housing material, electrolytic corrosion due to the potential difference between the stainless steel housing material and the electrode material, and the fluoropolymer matrix ion exchange membrane used in SPE. of fluorine ions (F ^-) corrosion and elution with a stainless steel is considered not entirely clear for the cause.

As described above, when metal impurities are contained in the electrolysis product gas or the water vapor in the electrolysis product gas, the metal impurities adhere to the gas permeable membrane in the gas dissolving tank and cause a reduction in gas permeability. In extreme cases, metal impurities enter the gas-dissolved water through the gas permeable membrane, and when the electronic components are cleaned using the gas-dissolved water, the surface of the electronic components is affected by the metal impurities. The problem of contamination occurs.

The present invention has been made in view of the above points,
Provided is a gas-dissolved water production apparatus capable of separating and removing a mist-like metal impurity accompanying a gas supplied to pure water or a metal impurity contained in water vapor in a gas, thereby reliably preventing contamination by the metal impurity. With the goal.

[0023]

According to the present invention, there is provided (1) a gas-liquid contact portion for contacting pure water flowing through a pure water supply pipe with gas flowing through a gas supply pipe; In a gas-dissolved water producing apparatus for producing gas-dissolved water by dissolving gas in water, a filter device for removing metal impurities is provided at an arbitrary position of a gas supply pipe. (2) a gas-dissolved water producing device, (2) a gas-dissolved water producing device according to the above (1), wherein the gas-liquid contact portion is a gas-dissolved device provided with a gas permeable membrane, and (3) an electrolysis device provided with an electrolytic device. The gas-dissolved water producing apparatus according to the above (2), wherein a gas is generated by the method, and the generated gas is supplied to the gas dissolving apparatus through a gas supply pipe.
(4) The gas-dissolved water production apparatus according to (3), wherein a filter device for removing metal impurities is provided at an arbitrary position of a gas supply pipe connected between the gas dissolution apparatus and the electrolysis apparatus. 5) The gas-dissolved water producing apparatus according to the above (1) or (3), wherein the gas is hydrogen gas.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an example of an apparatus for producing hydrogen-dissolved water. In the figure, reference numeral 1 denotes an electrolytic device, 2 denotes a gas dissolving device, and the electrolytic device 1 is a solid electrolyte membrane (SPE).
An anode chamber 4 and a cathode chamber 5 are defined through the anode chamber 4. A pure water supply pipe 6 for supplying pure water to the electrolytic device 1 is provided.
And a gas supply pipe 7 for supplying and supplying hydrogen gas generated by the electrical separation of water. Reference numeral 8 denotes a gas outlet pipe for allowing oxygen gas generated in the anode chamber 4 to flow out.

The pure water supply pipe 6 is branched and connected to the gas dissolving apparatus 2 in addition to the electrolysis apparatus 1, and the gas supply pipe 7 is also connected to the gas dissolving apparatus 2. The gas dissolving apparatus 2 has a gas supply passage 10 and a pure water supply passage 11 partitioned by a gas permeable membrane 9.
Are connected.

A gas-liquid separator 12 and a filter device 13 are connected to the gas supply pipe 7. The filter device 13 can be provided at an arbitrary position of the gas supply pipe 7 and may be provided between the gas-liquid separator 12 and the gas dissolving device 2 as shown in FIG. Gas-liquid separator 1
2 may be provided.

14 is a gas-dissolved water outlet pipe for discharging gas-dissolved water, 15 is a valve for adjusting the supply pressure of hydrogen gas, and 16 is hydrogen combustion for burning excess hydrogen gas to render it harmless. Catalyst, 17 is an alkaline chemical tank, 18
Is an alkali injection pump, and 19 is a drain outlet pipe for draining drain from the gas-liquid separator.

The filter device 13 is for removing particulate metal impurities contained in hydrogen gas. The filter used in this device may be any filter that is generally used for filtering gas. For example, a filter that applies a charge opposite to that of the charged particles to adsorb fine particles with a different sign, such as an electrostatic filter, or a microporous membrane filter, a material that physically removes the filter, such as a nonwoven fabric filter, may be used as a material.
Including cotton and wool. Industrially produced filters are made of materials such as polyolefins and metal oxides, and have a shape that captures fine particles on the filter surface called a membrane filter and a filter that has a depth called a pre-filter, and entangles the fiber. As described above, the type is roughly classified into a type in which fine particles are captured, but the present invention can use any type. Filter pore size is 1
It is preferably less than μm. This filter device 1
The number 3 is not limited to one, and a plurality of filter devices can be provided in the gas supply pipe 7.

As the gas permeable film 9 in the gas dissolving device 2, a film made of a gas-philic material such as silicon or a film made of a water-repellent material such as a fluororesin is provided with a large number of fine holes through which gas can pass. For example, one configured to transmit gas but not water can be used. The gas permeable membrane 9 can be configured as, for example, a hollow fiber-like structure. When the gas permeable membrane 9 is formed in a hollow fiber-like structure, a method of dissolving gas from the inner space side of the hollow fiber to the outside is used as a gas dissolving method. Any of the methods of permeating gas from the outside of the hollow fiber to the inside of the hollow fiber can be adopted.

In the present invention, pure water refers to water from which impurities in water have been removed using activated carbon, an ion exchange resin, a filtration membrane, or the like, and is a concept including water called ultrapure water. Here, ultrapure water refers to raw water such as industrial water, tap water, well water, river water, lake water, etc., which is treated with a pretreatment device such as coagulation sedimentation, filtration, coagulation filtration, and activated carbon treatment. By removing coarse suspended substances, organic substances, etc., and then treating them with a primary pure water production device mainly composed of a desalination device such as an ion exchange device and a reverse osmosis membrane device, fine particles, colloidal materials, organic materials, metal ions A secondary pure water production system that removes most of the impurities such as anions and anions, and further irradiates this primary pure water with an ultraviolet irradiation device, a mixed bed polisher, a membrane treatment device equipped with an ultrafiltration membrane or a reverse osmosis membrane. And high-purity pure water from which impurities such as fine particles, colloidal substances, organic substances, metal ions, anions and the like are removed as much as possible by circulating treatment.

Next, the operation of the present invention will be described.

[0033] Pure water is supplied from the pure water supply pipe 6 to the electrolyzer 1, where the water is electrolyzed. Hydrogen gas is generated in the cathode chamber 5 by the electrolysis of water, and the hydrogen gas flows out of the gas supply pipe 7 together with water in the form of a gas-liquid mixture. The gas-liquid mixture enters the gas-liquid separator 12 through the gas supply pipe 7, where it is separated into hydrogen gas and water, and the separated hydrogen gas flows into the filter device 13 through the gas supply pipe 7.

In the filter device 13, mist-like metal impurities mixed in the hydrogen gas or water vapor in the hydrogen gas are captured by the filter of the device 13 and separated and removed from the hydrogen gas. As a result, clean hydrogen gas containing no metal impurities is led to the gas dissolving device 2 through the gas supply pipe 7.

On the other hand, pure water is supplied from the pure water supply pipe 6 to the gas dissolving apparatus 2, and an alkaline solution is added to the pure water from an alkali chemical tare 17 to make the supplied pure water alkaline. You. This aims to obtain alkaline hydrogen water having high detergency by making the pH of the hydrogen-dissolved water alkaline. As an alkaline solution to be added, ammonium hydroxide (NH ₄ O
H), trimethylammonium hydroxide (T
MAH) or the like, and the pH is usually adjusted to 8.0 to 11.0.

In the gas dissolving apparatus 2, the hydrogen gas passes through the gas permeable membrane 9 and comes into contact with the pure water flowing in the pure water supply passage 11, and the hydrogen gas dissolves in the pure water to obtain hydrogen dissolved water. This hydrogen-dissolved water flows out of the gas-dissolved water outflow pipe 14 and is sent to, for example, a use point such as a semiconductor manufacturing plant and used as cleaning water.

The oxygen gas generated in the anode chamber 4 of the electrolyzer 1 is discharged out of the system through a gas outlet pipe 8.

In the above embodiment of the present invention, the case where hydrogen gas is cultivated in pure water has been described, but the present invention is not limited to this. That is, as another embodiment of the present invention, it is also possible to produce oxygen-dissolved water by introducing oxygen gas generated in the anode chamber 4 of the electrolysis apparatus 1 to the gas culturing apparatus 2 and dissolving this oxygen gas in pure water. Alternatively, ozone can be produced in the anode chamber 4, and the ozone can be dissolved in pure water in the gas dissolving device 2 to produce ozone-dissolved water. In this case, an acid solution is generally added to the supplied pure water in order to make the pH of the gas-dissolved water acidic.

In producing oxygen-dissolved water or ozone-dissolved water as described above, the present invention provides a filter device 13 in the same manner as described above to separate and remove fine metal impurities contained in gas. is there.

The present invention is not limited to the case where the gas is supplied from the electrolysis apparatus 1, and a gas such as hydrogen gas may be supplied from a gas cylinder to the gas supply pipe 7 and supplied.

Further, in the present invention, a gas such as a hydrogen gas may be directly supplied to pure water flowing in the pure water supply pipe 6 without providing the gas dissolving device 2 to obtain gas dissolved water. In short, a pure water flowing through the pure water supply pipe and a gas-liquid contacting part where the gas flowing through the gas supply pipe is in contact with the gas-liquid contacting part have a structure in which the gas is dissolved in the pure water. Any device configuration compromises.

[0042]

The present invention relates to a gas-dissolved water producing apparatus for producing gas-dissolved water by dissolving a gas supplied from a gas supply pipe into pure water supplied from a pure water supply pipe. Since a filter device for removing metal impurities is provided at the point of, fine-grained metal impurities mixed in the gas can be separated and removed reliably, and as a result, clean gas can be removed. It has the effect of dissolving in pure water to obtain high purity gas-dissolved water.

Therefore, for example, when a gas dissolving apparatus having a gas permeable membrane is used, according to the present invention, there is no risk of contamination of the gas permeable membrane, and the performance of the gas dissolving apparatus can be maintained satisfactorily. It can provide expensive equipment.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the apparatus for producing gas-dissolved water of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis apparatus 2 Gas dissolving apparatus 6 Pure water supply pipe 13 Filter apparatus

Claims (5)

[Claims] A gas-liquid contact portion is provided for contacting pure water flowing through a pure water supply pipe with gas flowing through a gas supply pipe, and the gas is dissolved in the pure water at the gas-liquid contact portion to remove gas-dissolved water. A gas-dissolved water producing apparatus, wherein a filter device for removing metal impurities is provided at an arbitrary position of a gas supply pipe. 2. The gas-dissolved water producing apparatus according to claim 1, wherein the gas-liquid contact section is a gas dissolving apparatus provided with a gas permeable membrane. 3. The gas-dissolved water producing apparatus according to claim 2, wherein an electrolytic apparatus is provided to generate gas by electrolysis of water, and the generated gas is supplied to the gas dissolving apparatus through a gas supply pipe. 4. A gas-dissolved water producing apparatus according to claim 3, wherein a filter device for removing metal impurities is provided at an arbitrary position of a gas supply pipe connected between the gas-dissolving apparatus and the electrolytic apparatus. 5. The gas-dissolved water producing apparatus according to claim 1, wherein the gas is hydrogen gas.