JPH02187190A - Ultrapure water making apparatus - Google Patents

Abstract

PURPOSE:To obtain ultrapure water of good quality by using an inorg. porous membrane as a filter membrane again filtering and treating pure water immediately before a course point. CONSTITUTION:The pure water 9 on a primary side stored in a pure water tank 10 is treated with a mixed bed type polisher 11, an ultraviolet ray irradiation apparatus 12 and a terminal filter membrane apparatus 13 using a hollow inorg. porous membrane as a filter membrane. Ultrapure water wherein the ion, fine particles and live bacteria remaining in the pure water 9 on the primary side are removed is obtained on the transmission side of the terminal filter membrane apparatus 13. The obtained ultrapure water is transferred to a course point part 14 by course point piping 17 and necessary ultrapure water is used herein as the washing water of a semiconductor wafer and the residual ultrapure water is recirculated to the pure water tank 10. The bacteria propagating on the surface of membrane are removed by supplying hot water to the membrane. By this method, effective sterilization can be performed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to the use of so-called ultrapure water, which is used as water for cleaning semiconductor wafers or chips, which are intermediate products, in the electronic industry that produces LSIs and VLSIs. It relates to the equipment to be manufactured.

<Prior art> In the electronics industry that produces LSIs and VLSIs, when cleaning intermediate products such as semiconductor wafers or chips (hereinafter referred to as semiconductor wafers), in order to improve the yield, the amount of ions and the amount of fine particles must be controlled. amount I)I
) Not only does it reduce the number of viable bacteria to the b order, but it also reduces the number of viable bacteria to 10
- Requires so-called ultrapure water, reduced to 1 particle/ml.

Conventionally, in producing such ultrapure water, raw water was processed through a coagulation sedimentation device, a sand filter, an activated carbon filter, a reverse osmosis membrane device, and two
Pure water is obtained by processing with a primary side pure water production device that combines a three-bed pure water production device, a mixed bed polisher, etc., and the purified water is further processed with an ultraviolet irradiation device, a mixed bed polisher, etc.
A microfiltration membrane (MF membrane) is used just before the final cleaning of the semiconductor wafer, that is, just before the point of use.
Ultrapure water is obtained by processing with a so-called terminal filtration membrane device such as a device or an ultrafiltration membrane (UF membrane) device, and this is used as water for washing.

In the filtration membrane equipment used at the end of such applications, even though the water to be treated is pure water obtained from the primary water purification equipment, and even though it is irradiated with ultraviolet rays immediately beforehand, Regardless, if ultrapure water production continues for a long time, the amount of viable bacteria and particles leaking into the ultrapure water that is permeated water will increase and exceed the permissible limit.

The reason for this is thought to be that general bacteria that are resistant to ultraviolet rays and exist in a small amount in the pure water that is the water to be treated by the filtration membrane device propagate on the membrane surface and the like.

Therefore, if the filtration membrane used is contaminated as described above, it is necessary to perform some kind of sterilization treatment.

The conventional sterilization treatment for the filtration membrane is 1 to 5.
% hydrogen peroxide solution, or an oxidizing agent solution such as a sodium hypochlorite solution, or a sterilization treatment using so-called chemicals, such as immersion in an acid, alkali solution, etc., or a filtration membrane at 70°C. This is a hot water sterilization treatment in which water is washed and sterilized using hot water as described above, and ultrapure water has been produced while performing such sterilization treatment periodically.

<Problems to be Solved by the Invention> The conventional microfiltration membranes and ultrafiltration membranes used in the above-mentioned terminal filtration membrane devices are made of synthetic polymers such as polysulfone, polyvinyl chloride, polyvinyl alcohol, or cellulose acetate. It is made from natural polymers such as
In short, it was made from organic matter.

Therefore, there are some difficulties in terms of heat resistance or chemical resistance.
Therefore, when the above-mentioned sterilization treatment is performed, the filtration membrane deteriorates, and when producing ultrapure water after sterilization treatment, the number of viable bacteria and particles in the ultrapure water that is permeated increases, or There were problems in that organic matter began to be eluted from the membrane itself and that the membrane had to be replaced more frequently. Furthermore, in order to prevent membrane deterioration, the temperature of the hot water and the concentration of the chemicals used are also limited, which sometimes results in insufficient sterilizing effects and the inability to obtain high-quality ultrapure water.

The present invention solves these problems by using a membrane with extremely excellent heat resistance and chemical resistance as the filtration membrane of the terminal filtration membrane device, thereby preventing the deterioration of the membrane during sterilization treatment as described above. It is our aim to provide an ultrapure water production device that eliminates the need for sterilization, enables sterilization under harsher conditions than conventional methods, and can therefore always stably obtain high quality ultrapure water with extremely low numbers of viable bacteria and particles. This is the purpose.

<Means for Solving the Problems> The present invention comprises a primary side pure water production device, 1, and an end filtration membrane device for refiltering the pure water obtained by the pure water production device immediately before the point of use. The filtration membrane device is an ultrapure water production device characterized by using an inorganic porous membrane as the filtration membrane.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention, where part A indicates a primary pure water production device, and part B indicates a secondary pure water production device including a terminal filtration membrane device. , again-
The area surrounded by the dotted chain line indicates the so-called use point where water is collected for cleaning semiconductor wafers.

The next-side pure water production device A is, for example, a coagulation sedimentation device 2.
, filtration device 3 using sand, anthracite, etc., pore size 10μ
Cartridge filter 4, reverse osmosis membrane device 5.2-bed 3-column pure water production device 6, mixed bed pure water production device 7.0゜4
It is composed of a cartridge filter 8 and the like having a diameter of about 5 to 0.8 microns, and processes the raw water 1 to produce so-called primary pure water 9 in which ions, fine particles, etc. are removed as much as possible.

Depending on the water quality of the raw water 1, the coagulation-sedimentation device 2 and the filtration device 3 may be omitted and both devices may be integrated into a so-called simple turbidity filtration device such as a coagulant body feed type filtration device or a micro floc type filtration device. Further, if the water quality is good, the raw water may be passed directly to the cartridge filter 4. Conversely, if a large amount of organic matter is present in the raw water 1, an activated carbon filter may be installed after the filtration device 3. Sometimes.

Furthermore, if the amount of ions in the raw water is small, the reverse osmosis membrane device 5 may be omitted, or the two-bed, three-column pure water production device 6 installed after the reverse osmosis membrane device 5 may be omitted. In some cases.

Furthermore, if necessary, an ultraviolet irradiation device may be installed in the primary side pure water production apparatus A, and a vacuum deaerator may be installed for the purpose of deoxidizing.

Next, the secondary deionized water production device B includes a deionized water tank 1 that stores the primary deionized water 9 obtained in the secondary deionized water production device A as described above.
0, a mixed bed polisher 11 that further processes the pure water 9;
It is composed of an ultraviolet irradiation device 12 and a terminal filtration membrane device 13 using an inorganic porous membrane as a filtration membrane, which is installed just before the point-of-use portion 14 surrounded by a dashed line.

The feature of the present invention is that as a filtration membrane of the terminal filtration membrane device 13,
As mentioned above, an inorganic porous membrane is used, and the inorganic porous membrane is a so-called ceramic membrane made of an inorganic material such as 5tO2 glass, alumina, or aluminum silicate. For example, 0.1~
Those with a pore size of several tens of microns, which generally belong to the category of precision filtration membranes, or those with a pore size of several tens of microns,
- It generally refers to a porous membrane that belongs to the category of ultrafiltration membranes, and it is preferable to use a membrane shaped into a hollow (tubular) shape. Hollow ceramic membranes having such fine pores have been developed recently, and membranes with diameters close to those of conventional hollow fiber membranes, such as a diameter of several digits, have already been put into practical use.

In addition, in the figure, 15 is a heat exchanger installed between the ultraviolet irradiation device 12 and the terminal filtration membrane device 13, and 16 is a heat medium supply pipe that supplies a heat medium such as hot water or steam to the heat exchanger 15. However, the heat exchanger 15 is used when the terminal filtration membrane device 13 is sterilized with hot water, and no heat medium is allowed to flow through the heat exchanger 15 in normal processing.

Further, 17 is a use point piping for transferring ultrapure water, which is permeated water of the terminal filtration membrane device 13, to the use point section, 18 is a non-permeable wood pipe for discharging non-permeated water of the filtration membrane device 13, Reference numeral 19 indicates blow pipes attached to appropriate positions of the use point piping 17, respectively.

In the secondary side pure water production apparatus B shown in FIG.
2 at the front stage and the mixed bed polisher 11 at the rear stage.

Effect> The present invention has the above-mentioned configuration, and in a normal process for producing ultrapure water, raw water 1 is first treated in the -primary side pure water production apparatus A in the same way as in the past, and ions, Primary pure water 9 from which fine particles and the like have been removed as much as possible is obtained, and the pure water 9 is temporarily stored in a pure water tank 10.

Next, the primary pure water 9 stored in the pure water tank 10 is passed through a mixed bed polisher 11, an ultraviolet irradiation device 12, and a terminal filtration membrane device 13 using the hollow inorganic porous membrane described above as a filtration membrane. The treatment is performed in this order to obtain so-called ultrapure water from the permeation side of the terminal filtration membrane device 13, in which ions, particulates, live bacteria, TOC, etc. remaining in the downstream pure water 9 are removed as much as possible. The obtained ultrapure water is transferred to the use point section 14 through the use point piping 17, where the necessary ultrapure water is used as water for cleaning semiconductor wafers, and the remaining ultrapure water is circulated to the pure water tank 10.

The non-permeated water obtained from the non-permeated side of the terminal filtration membrane device 13 is circulated through the non-permeated water piping 18 to the primary pure water production device A or the pure water tank 10 for recovery.

As the production of ultrapure water as described above continues, bacteria will grow on the membrane surface of the inorganic porous membrane used in the terminal filtration membrane device 13, so the terminal filtration membrane device 13 must be sterilized periodically. Process. For example, when the filtration membrane device 13 is sterilized with hot water, it is carried out as follows.

That is, a heat medium such as hot water or steam is supplied to the heat exchanger 15 through the heat medium supply pipe 16, and the water supplied to the terminal filtration membrane device 13 is indirectly heated by the heat exchanger 15, for example. The hot water is heated to around 90°C, and the hot water is passed through the terminal filtration membrane device 13.
feed in the same direction as the filtration process. Next, the heat permeated water is passed through the use point piping 17, and the heat permeated water is passed through the use point piping 17.
After passing through the yarn, the yarn is blown out from the blow tube 19.

Further, a part of the hot water supplied to the terminal filtration membrane device 13 is blown from the non-permeable wood pipe 18 as non-permeable hot water.

In the ultrapure water production apparatus of the present invention, the filtration membrane used in the terminal filtration membrane device 13 is a so-called ceramic membrane made of an inorganic material such as glass as described above, so it is different from the conventional one made of an organic material. It has much better heat resistance than other filtration membranes, and usually has a heat resistance temperature of about 900°C. Therefore, in the sterilization treatment using hot water at the above-mentioned temperature, the filtration membrane does not deteriorate at all in terms of material or performance even if the treatment is repeated periodically. Therefore, during the production of ultrapure water as described above, viable bacteria and fine particles remaining in the downstream pure water can be effectively removed for a long period of time, and high quality ultrapure water can be stably produced. .

In addition, in the above-mentioned embodiment, the case where the filtration membrane device 13 is sterilized with hot water was explained, but in the device of the present invention, the filtration membrane device 13 is heated with high-temperature steam of 100° C. or higher, which is higher than the hot water. It is also possible to sterilize by directly supplying sterilization, and in that case, more complete sterilization can be achieved than with the above-mentioned hot water sterilization.

Furthermore, in the case of the so-called ceramic membrane used in the present invention, it is generally superior in chemical resistance compared to conventional organic membranes, and therefore sterilization treatment is carried out using solutions containing chemicals such as oxidizing agents, acids, and alkalis. It is also possible to carry out the sterilization using a sterilizing agent, and furthermore, it is also possible to use the solution by heating it during such sterilizing treatment.

In addition, when heat sterilization using the above-mentioned high-temperature steam or sterilization using the above-mentioned chemicals is performed, the constituent members of the filtration membrane device 13 other than the membrane, such as the container in which the filtration membrane is attached, must also have excellent heat resistance or chemical resistance. It goes without saying that it must be used.

Effect> As explained above, the ultrapure water production device of the present invention uses glass as the filtration membrane of the terminal filtration membrane device that finally filters the pure water obtained in the primary side pure water production device just before the point of use. Since we use an inorganic porous membrane made of materials such as alumina with excellent heat and chemical resistance, so-called ceramic membranes, the membrane can be sterilized by conventional sterilization methods using hot water or chemicals. However, the membrane does not deteriorate at all, and ultrapure water with an extremely low number of viable bacteria and particles can be stably obtained for a long period of time.

In addition, the above-mentioned ceramic membrane is particularly excellent in its heat resistance, and can usually withstand a temperature of about 900 degrees Celsius, so it can be sterilized under high-temperature conditions that cannot be applied to conventional organic membranes. Therefore, it becomes possible to perform more effective sterilization.

Furthermore, in conventional ultrapure water production equipment, organic membranes were used in the terminal filtration membrane devices as described above, so as the membranes deteriorated due to sterilization treatment, organic substances began to be eluted from the membranes themselves. Therefore, there was a problem that the quality of the obtained ultrapure water deteriorated, but the apparatus of the present invention uses an inorganic membrane, so there is no such concern at all.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention. 1...Raw water 2...Coagulation sedimentation device 3
...Filtering device 4.8...Cartridge filter 5...Reverse osmosis membrane device 6...Two-bed, three-column type pure water production device 7...Mixed bed type pure water production device 9...- Next side pure water 10...Pure water tank 11...
・Mixed bed polisher 12...UV irradiation device 13・
...Terminal filtration membrane device 14...Use point section 15...Heat exchanger 16
...Heating medium supply pipe 17...Use point l-piping

Claims (1)

[Claims] It is equipped with a primary side pure water production device and a terminal filtration membrane device that refilters the pure water obtained by the pure water production device just before the point of use, and the filtration membrane device is made of inorganic porous material as a filtration membrane. An ultrapure water production device characterized by using a membrane.