JPH0829317B2 - Method for producing ultrapure water and apparatus used for the method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing ultrapure water and an apparatus used for the method.

In particular, it is suitable as a method and apparatus for producing ultrapure water for cleaning semiconductor wafers or chips (hereinafter abbreviated as semiconductor wafers), which are intermediate products in the electronic industry that produces LSIs and VLSIs.

[Prior Art] In the field of electronics industry that produces LSIs and VLSIs, a large amount of so-called ultrapure water is used for cleaning semiconductor wafers, which are intermediate products thereof.

As this ultrapure water, water whose ions, TOC and dissolved silica concentration are in the order of ppb and the number of fine particles is in the order of several particles / cc is used, and this water quality has a large effect on the product yield. affect.

Conventionally, as the ultrapure water, raw water such as industrial water, city water, well water, tap water, etc. is used for coagulation sedimentation device, sand filter, ion exchange resin, reverse osmosis device, vacuum degassing tower, ultraviolet irradiation device. Ultra pure water obtained by making pure water by a pure water producing apparatus combined with a mixed-bed polisher and treating it with an ultrafiltration device immediately before the point of use was used.

However, recently, as the integration density of LSI has increased, further improvement in the water quality of ultrapure water has been required in order to improve the yield.

Therefore, the conventional ultrafiltration device, which is the final filtration device, has a problem that there is a limit to the removal of ionic substances, TOC, fine particles, etc. Therefore, the reverse osmosis device is used as the end filtration device. An ultrapure water production system has also been filed (Japanese Patent Laid-Open No. 62-254805).

[Problems to be Solved by the Invention] However, when installing a reverse osmosis device at the end of an ultrapure water device, it is necessary to place a high-pressure pump in front of the reverse osmosis device. Here, the shaft, rotor, and impeller are used. Since the ionic substance is eluted by such high pressure pump parts, the specific resistance value of the water discharged from the pump is lowered, and the water quality is deteriorated such that the concentration of fine particles is increased.

The present invention eliminates the drawbacks of the prior art, more strictly removes ionic substances, TOC, fine particles and dissolved silica, and a method for producing ultrapure water capable of obtaining ultrapure water with higher purity, and a method thereof. An object is to provide an apparatus used in a manufacturing method.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configurations.

(1) Pure water produced by the pure water producing apparatus is pressurized by a high-pressure pump to 3 to 30 kg / cm ² , treated with an ion exchanger apparatus, and further reverse osmosis independent of the ion exchanger apparatus. A method for producing ultrapure water, which comprises obtaining ultrapure water by treating with a membrane device.

(2) A pure water production apparatus for obtaining pure water by treating raw water and pure water obtained by the pure water production apparatus
A high-pressure pump that boosts pressure to ~ 30 kg / cm ² , and a reverse osmosis membrane device that further purifies the treated water from the high-pressure pump to ultrapure water,
In the ultrapure water production apparatus comprising a recycling pipe for recycling excess ultrapure water that is not used at the point of use out of the ultrapure water after production into pure water, between the high pressure pump and the reverse osmosis membrane device. An apparatus for producing ultrapure water, comprising an ion exchanger device independent of the reverse osmosis membrane device.

 Hereinafter, the present invention will be described in detail.

In the present invention, between the high pressure pump and the reverse osmosis membrane,
The feature is that an ion exchanger is arranged. The drawing shows a flow chart for explaining the main configuration of the apparatus of the present invention. Ion exchanger (4 in the figure) eliminates ionic substances that are considered to be eluted from the parts of the high-pressure pump (3 in the figure), and then TOC is eliminated by reverse osmosis membrane (5 in the figure). Further, the concentration of fine particles and microorganisms and the concentration of dissolved silica can be eliminated to an extremely low concentration by both the ion exchanger and the reverse osmosis membrane.

In the present invention, the pure water producing apparatus (1 in the figure) is a generally known water treatment apparatus, coagulating sedimentation apparatus, sand filter, ion exchange resin, reverse osmosis apparatus, vacuum degassing tower, ultraviolet irradiation apparatus. , A mixed bed polisher, an ultrafiltration device, etc., or a device combining two or more devices. Pure water means industrial water, city water, well water, tap water, etc. , Water obtained by treatment with these devices. Most preferred is pure water obtained by performing the treatment with all the above-mentioned devices. If pure water of low quality is supplied as it is, the high-pressure pump, the ion exchanger and the reverse osmosis device that follow it will be contaminated and deteriorate quickly. Therefore, pure water of the highest purity should be used. preferable.

The pure water obtained as described above is stored in a pure water layer indicated by 2 in the figure, and then supplied to the high pressure pump. In the present invention, a commonly used high-pressure pump such as a spiral pump or a plunger pump can be used.
The operating pressure is required to be about 3 to 30 kg / cm ² , and more preferably about 3 to 10 kg / cm ² . If the pressure is too low, the water permeability may be low, and if it is too high, fine particles having a relatively large particle size may easily permeate the membrane.

As the ion exchanger used in the present invention, known ion exchange resins and ion exchange fibers can be used.

As an ion exchange resin, its diameter is 100-1000 μm
Are preferred. If it is less than 100 μm, the resin may become powdery and pressure loss may increase, and if it exceeds 1000 μm, the amount of ion exchange per unit volume becomes small. Further, as a preferred specific component thereof, chemical resistance, styrene-divinylbenzene copolymer excellent in heat resistance, methacrylic acid-divinylbenzene copolymer, or acrylic acid-divinylbenzene copolymer with an ion exchange group Examples thereof include gel-type and MR-type ion exchange resins into which is introduced.

In the present invention, as the ion exchange resin, JP-A-59 is used.
-166245, JP-A-62-11593, etc., such as polystyrene-based, polyphenol-based, polyvinyl alcohol-based, polyacrylic-based, polyethylene-based, polyamide-based synthetic organic polymers (ion exchange polymers) An insoluble synthetic organic ion-exchange fiber having an ion-exchange group introduced therein is used, the diameter of which is preferably 0.1 to 100 µ, and more preferably 1 to 100 µ. Among them, a fiber composed of an ion-exchange polymer and a reinforcing polymer, preferably, the ion-exchange polymer as the main component of the sheath component, the multi-core mixed and composite fiber with the reinforcing polymer as the core component as the base material. The ion-exchanged fibers described above are preferable because they have sufficient mechanical strength in operation and shape-preserving property. The proportion of reinforcing polymer is usually 10-90%
However, if it is too small, the mechanical strength becomes weak, and if it is too large, the amount of ion exchange and the amount of adsorption decrease. Therefore, the range of 20 to 80% is preferable.

As the ion-exchange polymer, poly (monovinyl aromatic compound), particularly polystyrene compound, is preferable because it has excellent chemical resistance and heat resistance and the operation can be repeated many times over a long period of time.

As the reinforcing polymer, poly-α-olefin is preferable because it has excellent chemical resistance.

Among these ion exchangers, in high-purity water at the ultrapure water level, TOC components and fine particles generated from the exchanger itself also become a major source of pollution, so ion-exchange fibers with a low elution rate of such contaminants. Are more preferable than the ion exchange resin.

As the reverse osmosis membrane used in the present invention, a composite type reverse osmosis membrane in which a porous support is coated with an active layer for controlling separation is used. Examples of the porous support include those having an active layer of crosslinked polyamide formed on the surface of a polysulfone support film by an interfacial polycondensation reaction. Other components of the active layer include aromatic polyamide, polyamic acid, polyamide hydrazide, polyimidazolone, polysulfonamide, polybenzimidazole, polybenzimidazolone and polyarylene oxide.

Further, the form of the membrane, flat membrane, tubular membrane, hollow fiber membrane,
It can take any known form such as a spiral wound membrane.

As shown in FIG. 1, the ion exchanger device containing the ion exchanger and the reverse osmosis membrane device containing the reverse osmosis membrane are not integrated, and both are separate structural units.
It is connected by the ultrapure water line as shown in.

The ultrapure water obtained as described above is supplied to the use point 7 in the figure through the recycle pipe 6 in the figure.

Well-known metals or plastics are used as the material for the piping. Among them, the elution rate of pollutants such as metals, organic substances, and fine particles from the surface of the piping is small, the surface smoothness is large, and the heat resistance and chemical resistance are excellent. It is desirable that As an example of those having such properties,
Examples of the metal include a stainless tube whose surface is subjected to composite electropolishing or passivation treatment, and examples of the plastic include hard vinyl chloride and polypropylene. More preferably, the elution rate of contaminants is low, polyvinylidene fluoride, Examples thereof include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin and polyether ether ketone.

A normal diaphragm valve is used as the point of use, and a material whose inner surface is subjected to complex electrolytic polishing with stainless steel (SUS316) is used as the material.

Furthermore, the extra ultrapure water that is not used at the point of use is
It is recycled to the pure water tank 2 in the figure by the recycling pipe. In the present invention, it may also be recycled to the pure production apparatus 1 in the figure.

[Examples] Examples are shown below, but the present invention is not limited thereto.

As the ion exchanger, a fiber mixture of 1 mm cut fiber-like cation exchange fiber and anion exchange fiber 0.2
As a reverse osmosis device, a spiral type element in which (composite reverse osmosis membrane) in which an active layer of crosslinked polyamide is formed on the surface of a polysulfone support membrane by loading (28 milliequivalents of cations and 24 milliequivalents of anions) is used as a reverse osmosis device. The following experiment was performed using the.

As raw water, city water is used, and a pure water production device consisting of a coagulating sedimentation device, a sand filter, an ion exchange resin, a reverse osmosis device, a vacuum degassing tower, an ultraviolet irradiation device, a mixed bed polisher, and an ultrafiltration device is used. Pure water was obtained. When ultrapure water was produced by using the obtained pure water at a flow rate of 180 / hr to produce ultrapure water, ultrapure water was obtained at a flow rate of 150 / hr after 3 hours.
Pure water that passes through the pure water production equipment and reaches the high-pressure pump,
Water quality analysis was conducted for each of the treated water that passed through the high-pressure pump and reached the ion exchanger, the treated water that passed through the ion exchanger and reached the reverse osmosis membrane, and the ultrapure water that passed through the reverse osmosis membrane. Is shown in Table 1.

[Effect of the Invention] The production method and apparatus of the present invention can provide ultrapure water having a low ionic substance, TOC, fine particle and silica concentration and excellent purity.

The obtained ultrapure water can be widely applied in the electronic industry field, pharmaceutical field, analysis field, and the like. Particularly, it is very effectively used in the electronic industry field where high-purity ultrapure water is desired for high integration of LSI.

[Brief description of drawings]

The drawings are flow charts for explaining the main configuration of the device of the present invention. 1 ... Pure water production device, 2 ... Pure water tank 3 ... High-pressure pump, 4 ... Ion exchanger 5 ... Reverse osmosis membrane, 6 ... Recycle piping 7 ... Use point

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruo Yokota 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Toray Co., Ltd. Shiga Works (72) Inventor Ken Noyori 1-1-1, Sonoyama, Shiga Prefecture (72) Inventor Tadahiro Omi 2-1-17-301 Yonegabukuro, Sendai City, Miyagi Prefecture (56) References JP-A 61-167404 (JP, A) JP-A 62-176507 ( JP, A) Actually open Sho 62-164903 (JP, U)

Claims (2)

[Claims] 1. Pure water produced by a pure water producing apparatus is pressurized by a high-pressure pump to 3 to 30 kg / cm ² and then treated by an ion exchanger apparatus, which is further independent of the ion exchanger apparatus. A method for producing ultrapure water, which comprises obtaining ultrapure water by treatment with a reverse osmosis membrane device. 2. A pure water producing apparatus for obtaining pure water by treating raw water, a high pressure pump for raising the pure water obtained by the pure producing apparatus to 3 to 30 kg / cm ² , and a high pressure pump. Ultra pure water comprising a reverse osmosis membrane device that further purifies treated water into ultra pure water, and a recycling pipe for recycling excess ultra pure water that is not used at the point of use out of the ultra pure water after production into pure water. An ultrapure water producing apparatus, characterized in that, in the water producing apparatus, an ion exchanger device independent of the reverse osmosis membrane device is provided between the high-pressure pump and the reverse osmosis membrane device.