JP4604907B2 - Method and apparatus for purifying ultrapure water - Google Patents

Description

  The present invention relates to a method and apparatus for purifying ultrapure water. Specifically, the present invention attaches to the surface of an electronic material from ultrapure water used in a wet cleaning process for cleaning the surface of an electronic material such as a silicon substrate for semiconductor, and lowers semiconductor performance in a later process. The present invention relates to a method and apparatus for purifying ultrapure water that highly removes fearful impurities.

  Ultrapure water used for wet cleaning of electronic material surfaces such as silicon substrates for semiconductors is required to have a very high level of cleaning. In response to this, an ultrapure water production system has already been established for removing not only turbidity, viable bacteria, and ions, but also extremely small amounts of organic substances, colloids, and ultrafine particles. We have realized the supply of ultrapure water that satisfies the required water quality.

  However, due to the recent increase in the level of cleaning requirements associated with ultrafine and high density processing of semiconductor electronic materials, especially in wet cleaning processes that require strict cleanliness, ultrapure water used for wet cleaning is further increased. There has been a demand for cleaning. In particular, thorough removal has been desired for organic substances and metal impurities that adhere to the surface of an electronic material and may deteriorate semiconductor performance in a later process.

  Therefore, means for further purifying only a part of ultrapure water that requires specially high water quality near the point of use will be studied, and microfiltration membranes with ion adsorption capacity will be adopted for that application. (For example, JP-A-11-260787). However, ion adsorption microfiltration membranes do not always have a sufficient ability to remove trace amounts of impurities, and organic substances are not particularly targeted for removal. For this reason, a problem remains in order to cope with the recent increase in cleaning requirement level.

  By the way, the surface of an electronic material such as a semiconductor silicon substrate is easily contaminated because impurities such as dissolved organic matter are easily adsorbed. On the contrary, a silicon purifier is used that captures impurities in the chemical solution by dispersing the silicon fine particles in the cleaning chemical or by bringing the chemical solution into contact with the particulate silicon by utilizing this phenomenon. However, the impurities in the chemical solution are not completely removed only by contact with the silicon fine particles. In addition, since silicon fine particles are brought into contact with ultrapure water, there is a problem that silicon is oxidized and eluted into water. Therefore, it is difficult to apply the silicon contact method as it is to the purification of ultrapure water.

For this reason, due to the recent increase in the level of cleaning requirements associated with ultra-fine processing and high density of semiconductor electronic material processing, ultra-pure water used for wet cleaning, which requires particularly strict cleanliness, is further purified. The current situation is that sufficient measures have not been taken.
JP-A-11-260787

  The present invention may adhere to the surface of an electronic material from ultrapure water used in a wet cleaning process for cleaning the surface of an electronic material such as a silicon substrate for a semiconductor, and may deteriorate semiconductor performance in a later process. It is an object of the present invention to provide a method and apparatus for purifying ultrapure water that can remove impurities to a high degree.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors contact ultrapure water in advance with silicon and / or silicon oxide, and then contact with a structure having ion exchange capacity and adsorption capacity. Thus, it has been found that impurities that may adhere to the surface of the electronic material and effluents from silicon and / or silicon oxide can be highly removed.

The present invention has been achieved based on such findings, and the gist thereof is as follows.
[1] A method for purifying ultrapure water in which ultrapure water is brought into contact with granular silicon and / or granular silicon oxide and then brought into contact with a structure having ion exchange capacity and adsorption capacity. A method for purifying ultrapure water, wherein the adsorbing structure has one or more functional groups selected from the group consisting of a cation exchange group, an anion exchange group, and a chelate-forming group .
[2] The method for purifying ultrapure water according to [1], wherein the structure having ion exchange ability and adsorption ability is composed of fibers having a fiber diameter of 0.01 to 1 μm .
[3 ] A device for purifying ultrapure water comprising a packed bed of granular silicon and / or granular silicon oxide, and a structure having an ion exchange capacity and an adsorption capacity provided downstream of the packed bed , Purification of ultrapure water , wherein the structure having exchange ability and adsorption ability has one or more functional groups selected from the group consisting of a cation exchange group, an anion exchange group, and a chelate-forming group apparatus.
[ 4 ] The apparatus for purifying ultrapure water according to [ 3 ], wherein the structure having ion exchange capacity and adsorption capacity is composed of fibers having a fiber diameter of 0.01 to 1 μm .

  According to the present invention, ultrapure water is brought into contact with granular silicon and / or granular silicon oxide, so that impurities such as organic substances and metals in ultrapure water can adsorb granular silicon and / or granular silicon oxide. Can be removed. Further, by bringing ultrapure water into contact with a structure having ion exchange ability and adsorption ability (hereinafter sometimes referred to as “ion exchange / adsorption structure”), ion exchange and ion exchange ability of this structure can be achieved. It is possible to remove metal impurities that cannot be adsorbed by granular silicon and / or granular silicon oxide due to the adsorption capacity. Moreover, in the present invention, the treatment with the ion exchange / adsorption structure is performed after the treatment with the granular silicon and / or the granular silicon oxide, so that the elution into the ultrapure water is performed by the treatment with the granular silicon and / or the granular silicon oxide. Silicon oxide can be adsorbed and removed with an ion exchange / adsorption structure. For this reason, the problem of contamination due to elution of silicon oxide by the silicon contact method can be solved, and impurities such as organic substances and metals in ultrapure water can be highly removed.

  According to the present invention, the ultra-pure water used in the wet cleaning process for cleaning the surface of an electronic material such as a silicon substrate for a semiconductor adheres to the surface of the electronic material and may deteriorate the semiconductor performance in a later process. A certain impurity can be removed to a high degree and the yield of semiconductor products can be improved.

  In the present invention, the ion exchange / adsorption structure is preferably composed of fibers having a fiber diameter of 0.01 to 1 μm because of excellent adsorption efficiency. Moreover, it is preferable from the surface of ion exchange capability that this structure has 1 type, or 2 or more types of functional groups chosen from the group which consists of a cation exchange group, an anion exchange group, and a chelate formation group.

  Embodiments of a method and apparatus for purifying ultrapure water according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a method and apparatus for purifying ultrapure water according to the present invention, and FIG. 2 shows an electrospray deposition method suitable for manufacturing an ion exchange / adsorption structure according to the present invention. It is explanatory drawing of.

  In the ultrapure water purification method of the present invention, ultrapure water is brought into contact with granular silicon and / or granular silicon oxide and then brought into contact with an ion exchange / adsorption structure.

  The apparatus for purifying ultrapure water of the present invention comprises a packed bed of granular silicon and / or granular silicon oxide, and an ion exchange / adsorption structure provided at the subsequent stage of the packed bed. 1 can be adopted.

  In FIG. 1, 1 is a granular silicon filling container having a granular silicon filling layer 1A formed therein, and 2 is a granular silicon oxide filling container having a granular silicon oxide filling layer 2A formed therein. In the granular silicon filling container 1 and the granular silicon oxide filling container 2, the packed layers 1A and 2A are formed between the water collecting support plates 3A and 3B. Reference numeral 4 denotes an anion exchange / adsorption filter in which a fiber assembly into which an after-mentioned anion exchange group is introduced is accommodated, and reference numeral 5 denotes a cation exchange / into which a fiber assembly in which an after-mentioned cation exchange group is introduced is accommodated. It is an adsorption filter.

  In the present invention, the treatment with granular silicon and / or granular silicon oxide is performed prior to the treatment with ion exchange / adsorption structure, and after the treatment with granular silicon and / or granular silicon oxide, the treatment with ion exchange / adsorption structure is performed. Since the treatment is performed, an extremely high impurity removal treatment can be performed.

  As shown in FIG. 1, the treatment with granular silicon and / or granular silicon oxide uses a granular silicon filling container 1 and a granular silicon oxide filling container 2 and is filled with a mixture of granular silicon and granular silicon oxide. A filled container may be used. In addition, treatment with only one of the granular silicon filling container and the granular silicon oxide filling container may be performed, but the treatment with only the granular silicon has a high organic substance and relatively high adsorptivity (small ionization tendency compared to Si). Although metal can be adsorbed and removed, all kinds of metals cannot be adsorbed and removed, and treatment with only granular silicon oxide can adsorb and remove metal ions and hydrophilic organic substances, but it cannot adsorb and remove hydrophobic organic substances. Can be removed by the ion exchange / adsorption structure in the subsequent stage, but in order to reduce the load of the ion exchange / adsorption structure and increase the service life, it is possible to use a combination of granular silicon and granular silicon oxide. preferable.

  Either the treatment with granular silicon or the treatment with granular silicon oxide may be performed first. Therefore, as shown in FIG. 1, it is limited to the case where the granular silicon oxide filling container 2 is provided after the granular silicon filling container 1. Alternatively, the granular silicon filling container may be installed after the granular silicon oxide filling container. Further, the granular silicon filling layer and the granular silicon oxide filling layer may be formed in the same filling container.

  Further, in FIG. 1, there is no particular limitation on the order of installation of the anion exchange / adsorption filter 4 and the cation exchange / adsorption filter 5, and the anion exchange / adsorption filter 4 may be provided at the subsequent stage of the cation exchange / adsorption filter 5. . Also, the anion exchange / adsorption filter and the cation exchange / adsorption filter can be formed in the same container. In addition to a combination of anion exchange / adsorption filter and cation exchange / adsorption filter, a fiber aggregate introduced with a chelate group, a combination of a cation exchange / adsorption filter and an anion exchange / adsorption filter, or a chelate group was introduced. A combination of a fiber assembly and a cation exchange / adsorption filter or an anion exchange / adsorption filter may be used. Even in this case, there is no particular limitation on the installation order of each replacement / adsorption filter.

  There is no particular limitation on the direction of water flow to each filling container or filter, and it may be an upward flow or a downward flow. However, in general, the filling containers 1 and 2 are preferably downward flowing water. . In the upward flow, the upper part of the packed bed may flow and be crushed.

  There is no restriction | limiting in particular in the granular silicon used in this invention, For example, what used the crushed material of the silicon substrate as a base | substrate and the surface was adjusted to the shape of bare silicon can be used. It is also possible to use spherical silicon produced by melting silicon, silicon deposited on another substrate surface by a CVD method, silicon deposited by a sol-gel method, or the like. The particle size of the granular silicon used here is preferably small from the viewpoint of the specific surface area, but is preferably large from the viewpoint of pressure loss when passing ultrapure water. From these two points, an optimum particle size can be set in order to obtain the desired treatment effect, and it is usually preferable that the average particle size is about 0.1 to 5 mm.

  Further, as the granular silicon oxide used in the present invention, the above-mentioned granular silicon is brought into contact with an oxidizing agent such as ozone-dissolved water, ozone gas, hydrogen peroxide water, ozone + hydrogen peroxide water, and the surface is oxidized with silicon. A material on which a material film is formed is preferably used, but silicon dioxide, glass wool, quartz, glass balls, and the like may also be used. Also for this granular silicon oxide, for the same reason as in granular silicon, the particle size is preferably about 0.1 to 5 mm in average particle size.

  In addition, the ion exchange / adsorption structure used in the present invention is composed of fibers having a fiber diameter of 0.01 to 1 μm, particularly an aggregate of fibers having an average fiber diameter of 0.05 to 0.5 μm. Preferably, one or more functional groups selected from the group consisting of a cation exchange group, an anion exchange group, and a chelate-forming group for imparting ion exchange capability to such a fiber assembly are introduced. In particular, an aggregate of polymer fibers into which such a functional group is introduced is preferable.

  Here, the anion exchange group basically means one having an amine, and particularly preferably one having an quaternary ammonium group. Moreover, a sulfonic acid group, a phosphoric acid group, a carboxyl group, etc. are used suitably for a cation exchange group. As the chelate-forming group, an iminodiacetic acid group, a mercapto group, an ethylenediamine group, or the like is preferably used.

  The structure having ion exchange capacity and adsorption capacity used in the present invention is not particularly limited, and examples thereof include a porous film as disclosed in JP-A-11-260787. Compared to the body, an aggregate of fibers with a very small fiber diameter has a very large specific surface area, which is very efficient for removing impurities, especially in a dilute system such as an ultrapure water system. Show. Therefore, the structure according to the present invention is preferably composed of an assembly of nanofibers having a fiber diameter of about 0.01 to 0.1 μm.

  The method for producing such an assembly of nanofibers is not particularly limited. For example, the sea-island spinning technology disclosed in Japanese Patent Application Laid-Open No. 2004-162244 and the book “Advanced Industrial Excavation Strategy Using Nanofiber Technology” p. Although the electrospray deposition method described in 113- is mentioned, it is more convenient to use the electrospray deposition method in which nanofibers can be directly spun into a film. As a method for producing a fiber assembly having a functional group as described above by using the electrospray deposition method, a method of forming a polymer compound having a functional group originally into a film by the electrospray deposition method, A method of introducing a functional group by a graft polymerization method after forming a film using a polymer compound as a material can be employed.

  Hereinafter, a method for producing a fiber assembly by an electrospray deposition method will be described with reference to FIG.

  In FIG. 2, a DC high voltage is applied between the capillary 11 and the substrate electrode 12 by the power supply 13, and the charged molten polymer or polymer solution from the capillary 11 draws in the electric field toward the electrode 12. Spatter as you can. At this time, the polymer is divided into a plurality of fibers, attracted so as to vortex toward the electrode, and deposits on the electrode to obtain an aggregate of fibers. Note that a sheet-like support may be disposed on the electrode 12 and deposited on the support.

  The polymer solution in the container 14 is supplied to the capillary 11 via the pump 15.

  The tip diameter of the capillary 11 is preferably about 0.1 to 500 μm. The distance between the capillary 11 and the electrode 12 is preferably about 1 to 50 cm. The applied voltage between the capillary 11 and the electrode 12 is preferably about 1 to 100 kV.

  The structure of the resulting aggregate of fibers changes in structure depending on conditions such as a material to be used, a solvent, an applied voltage, a distance between electrodes, and a solution feeding speed.

  As described above, the average fiber diameter of the fiber assembly is preferably 0.01 to 0.1 μm. By reducing the fiber diameter, the specific surface area can be increased, but if it becomes thinner than 0.01 μm, there is a problem in strength.

  The fiber aggregate is preferably laminated on the support in terms of strength, moldability and the like, and is fixed as necessary. The fiber assembly may be synthesized directly on the support, or may be laminated on the support after synthesis. As described above, if a support is disposed on the electrode 12, the fibers are deposited directly on the support and integrated.

  In order to fix the fiber assembly on the support, there are a method of welding with heat, a solvent, etc. and a method of bonding using a binder material, but a method of heat welding is used to reduce the elution of impurities as much as possible. preferable.

  The support for laminating is not particularly limited as long as it has continuous voids, but filter paper, filter cloth, woven fabric, nonwoven fabric, hollow fiber body, porous body and the like are preferable. The pore diameter or interfiber distance is not particularly limited, but is preferably 0.1 to 100 μm, particularly preferably 0.1 to 50 μm. If it is too large, the fibers enter the pore diameter and cause pressure loss. On the other hand, if it is smaller than 0.1 μm, the support itself causes pressure loss. The thickness of the support is preferably about 0.1 to 10 mm.

  In addition, although there is a limit to the size of the fiber aggregate obtained from one capillary, a wide area fiber aggregate can be formed by arranging the capillary. Further, it is possible to freely control the thickness by taking a long spraying time.

  The material for the support and fiber assembly (starting material) is not particularly limited, but an organic polymer is better. For example, polystyrene, polyester, polyethylene, polypropylene, aliphatic polyamide, aromatic polyamide, polyimide, polysulfone, polyethersulfone, cellulose acetate, cellulose nitrate, polyacrylonitrile, polyvinylidene fluoride, polyfluorinated ethylene, polycarbonate, polyvinyl alcohol, polylactic acid , Poly (2-vinylpyridine), poly (4-vinylpyridine), polystyrene sulfonic acid, polyvinyl sulfonic acid, polyacrylic acid, polymethacrylic acid, polyvinyl amide and the like are used, but not limited thereto Copolymers composed of monomers may also be used.

  Examples of organic polymer solvents include benzene, toluene, xylene, ethylbenzene, cresol, cyclohexane, dichloromethane, dichloroethane, trichloroethane, trichloroethylene, cyclohexanone, 1,4-dioxane, tetrahydrofuran, methyl ethyl ketone, acetone, N, N-dimethylformamide, N , N-dimethylacetamide, N-methyl-2-pyrrolidone, methyl acetate, water, methanol, ethanol, etc. are used, but not limited thereto.

  In order to produce a fiber assembly having the above-mentioned functional group, it is not necessary to introduce a functional group if it is synthesized using an organic polymer having an original functional group as described above. However, when a water-soluble polymer is used as a starting material for the fiber assembly, insolubilization treatment such as cross-linking is necessary for application to water. In addition, when a fiber assembly has a support body, you may introduce | transduce a functional group also to a support body.

  The method for introducing a functional group is appropriately selected depending on the type of polymer. For example, in the case of a fiber assembly synthesized with polystyrene, a strong cation exchange fiber assembly into which a sulfonic acid group has been introduced can be obtained by heat treatment in the presence of paraformaldehyde and sulfuric acid. Further, a strong anion exchange fiber aggregate can be obtained by chloromethylating polystyrene and then quaternizing ammonium. In addition, after treatment with formaldehyde and an acylaminomethylating agent in the presence of an acid catalyst and a lubricant, it is hydrolyzed under an acid or base catalyst to be converted to an aminomethyl group, and further treated with monochloroacetic acid, A chelate fiber aggregate into which iminodiacetic acid groups are introduced can be obtained.

  For example, in the case of a fiber assembly synthesized with poly (4-vinylpyridine), it can be cross-linked and quaternized by bringing dibromobutane or the like into contact and reacting, and a strong anion exchange fiber assembly is obtained.

  In addition, even an organic polymer that cannot directly introduce an ion exchange group can be introduced by radical polymerization of a reactive functional group such as styrene or glycidyl methacrylate using radiation or UV. is there.

  Polystyrene does not need to introduce such reactive functional groups, and sulfonic acid groups can be easily introduced and can be suitably used. Poly (4-vinylpyridine) is also preferable because it can be easily crosslinked and quaternized.

  The functional group-introduced fiber assembly thus produced preferably has an ion exchange capacity of, for example, about 1 to 10 meq / g.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

In the following examples and comparative examples, a 6-inch N-type substrate in which bare silicon and a silicon oxide film are mixed is used as a target for wet cleaning, and a cassette equipped with the five silicon substrates is stored in a clean bench. After flowing ultrapure water for rinsing at 2 L / min for 5 days in an overflowing Teflon vessel, the amount of metal contamination on the surface of the substrate was measured with a total reflection X-ray fluorescence analyzer, thereby purifying ultrapure water. A degree evaluation test was conducted. The lower limit of detection by this measurement method is titanium 3 × 10 ¹⁰ atoms / cm ² , chromium 1.5 × 10 ¹⁰ atoms / cm ² , iron 1 × 10 ¹⁰ atoms / cm ² , nickel 0.7 × 10 ¹⁰ atoms / cm 2. ² , copper 0.6 × 10 ¹⁰ atoms / cm ² and zinc 0.6 × 10 ¹⁰ atoms / cm ² .

  Moreover, the detection lower limit in the measurement of the TOC value of ultrapure water was 0.3 ppb.

The ultrapure water subjected to the purification has a TOC value of 0.6 ppb, and SiO ₂ has a water quality that is not detected.

Example 1
<Preparation of granular silicon filled container>
A spherical silicon n-type having a particle diameter of 3 to 5 mm was filled in a PFA (perfluoroalkoxy fluororesin) container having an internal volume of 300 ml. An aqueous solution containing 0.5 wt% hydrofluoric acid and 0.5 wt% hydrogen peroxide was passed through the container at a flow rate of 40 ml / min for 5 min from the top of the filling container, and then rinsed with 1 L of ultrapure water. By making it into the shape of bare silicon, it was set as the granular silicon (bare silicon) filling container.

<Production of granular silicon oxide filled container>
A spherical silicon n-type having a particle diameter of 3 to 5 mm was filled in a PFA container having an internal volume of 300 ml. An aqueous solution containing 0.5 wt% hydrofluoric acid and 0.5 wt% hydrogen peroxide was passed through the container at a flow rate of 40 ml / min for 5 min from the top of the filling container, and then rinsed with 1 L of ultrapure water. Further, ultrapure water in which ozone 5 mg / L was dissolved was passed from the top at a flow rate of 1 L / min for 10 minutes to oxidize the silicon surface, and a granular silicon oxide (silicon with oxide film) filling container was obtained.

<Preparation of cation exchange / adsorption filter>
A fiber assembly is produced by an electrospray deposition method shown in FIG. 2 using a solution in which polystyrene having an average molecular weight of 320,000 (manufactured by Aldrich) is dissolved in dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.) at a concentration of 10 wt%. did. The operating conditions of the electrospray deposition method are an applied voltage of 20 kV, a distance between electrodes of 10 cm, a liquid feeding speed of 0.05 mL / min, and a capillary tip diameter of 0.1 mm. The obtained fiber aggregate was an aggregate of polystyrene fibers having an average fiber diameter of 0.05 μm.

  10 g of the obtained fiber assembly was immersed in 100 ml of 80 wt% sulfuric acid solution to which 1 g of paraformaldehyde was added, and heated at 60 ° C. for 30 minutes to introduce sulfonic acid groups. After the reaction, the fiber assembly was treated with alkali, washed thoroughly with water, and the ion exchange capacity was measured. As a result, it was 3.2 meq / g.

  10 g of the obtained cation exchange group-introduced fiber assembly was cut out to 47 mmφ and placed in a flat membrane container (filter holder) made of PFA to obtain a cation exchange / adsorption filter.

<Preparation of anion exchange / adsorption filter>
Using a solution in which poly (4-vinylpyridine) having an average weight molecular weight of 160,000 was dissolved in ethanol (water content 2 wt%) so as to be 15 wt%, a fiber assembly was formed by an electrospray deposition method shown in FIG. Manufactured. The operating conditions of the electrospray method are an applied voltage of 15 kV, a distance between electrodes of 10 cm, a liquid feeding speed of 0.01 mL / min, and a capillary diameter of 0.1 mm. The obtained fiber assembly was a poly (4-vinylpyridine) fiber assembly having an average fiber diameter of about 0.05 μm.

  The obtained fiber assembly was immersed in 100 ml of 40 wt% dibromobutane-n-hexane solution at 10 ° C. for 30 seconds to form quaternary ammonium groups. The treated fiber assembly was treated with hydrochloric acid and then sufficiently washed with water. The ion exchange capacity was measured and found to be 2.9 meq / g.

  10 g of the obtained anion exchange group-introduced fiber aggregate was placed in a flat membrane container made of PFA similar to the above to obtain an anion exchange / adsorption filter.

<Purification of ultrapure water>
A granular silicon filling container, a granular silicon oxide filling container, a cation exchange / adsorption filter, and an anion exchange / adsorption filter are piped in this order, and ultrapure water is passed in series at a downward flow of 0.5 L / min. The purified ultrapure water thus obtained was passed through the above-mentioned silicon substrate-fitted Teflon vessel for 5 days.

After the test, none of titanium, chromium, iron, nickel, copper and zinc was detected from the five silicon substrates. The TOC value of ultrapure water before treatment was 0.6 ppb, whereas the TOC value of purified ultrapure water was 0.3 ppb, and no SiO ₂ was detected from this purified ultrapure water. It was.

Example 2
Ultrapure water was purified and evaluated in the same manner as in Example 1 except that the connection order of the purified silicon filled container and the granular silicon oxide filled container was reversed.

After the test, none of titanium, chromium, iron, nickel, copper and zinc was detected from the five silicon substrates in the same manner as in Example 1. The TOC value of ultrapure water before treatment was 0.6 ppb, whereas the TOC value of purified ultrapure water was 0.3 ppb, and no SiO ₂ was detected from this purified ultrapure water. It was.

Comparative Example 1
Without purifying ultrapure water, water was passed through a Teflon vessel equipped with 5 silicon substrates for 5 days.

After the test, titanium and nickel were not detected from the five silicon substrates, but chromium, iron, copper and zinc were detected, and the concentrations thereof were chromium 8 × 10 ¹⁰ atoms / cm ² and iron 3 × 10 ^11. Atomic / cm ² , copper 6 × 10 ¹⁰ atoms / cm ² , and zinc 2 × 10 ¹¹ atoms / cm ² . The TOC value of this ultrapure water was 0.6 ppb, and no SiO ₂ was detected.

Comparative Example 2
In Example 1, ultrapure water was purified and evaluated in the same manner as in Example 1 except that the cation exchange / adsorption filter and the anion exchange / adsorption filter were not used.

After the test was completed, titanium, chromium, iron, nickel and zinc were not detected from the five silicon substrates, but copper was detected, and the concentration was 6 × 10 ¹⁰ atoms / cm ² . In addition, the TOC value of ultrapure water before treatment was 0.6 ppb, whereas the TOC value of purified ultrapure water was 0.3 ppb. From purified ultrapure water, SiO ₂ was detected at 55 ppb. It was done.

Comparative Example 3
In Example 1, ultrapure water was purified and evaluated in the same manner as in Example 1 except that the granular silicon filled container and the granular silicon oxide filled container were not used.

After completion of the test, titanium, chromium, nickel, copper and zinc were not detected from the five silicon substrates, but iron was detected, and the concentration was 15 × 10 ¹⁰ atoms / cm ² . Further, the TOC value of ultrapure water before treatment was 0.6 ppb, whereas the TOC value of purified ultrapure water was 0.5 ppb, and SiO ₂ was not detected.

Comparative Example 4
In Example 1, purification of ultrapure water was performed in the same manner as in Example 1 except that water was passed in the order of a cation exchange / adsorption filter, an anion exchange / adsorption filter, a granular silicon filled container, and a granular silicon oxide filled container. And an evaluation test was conducted.

After the test, none of titanium, chromium, iron, nickel, copper and zinc was detected from the five silicon substrates in the same manner as in Example 1. The TOC value of ultrapure water before treatment was 0.6 ppb, whereas the TOC value of purified ultrapure water was 0.3 ppb. From this purified ultrapure water, SiO ₂ was 14 ppb. was detected.

  The results of the above examples and comparative examples are summarized in Table 1.

As is clear from Table 1, when ultrapure water is passed through all of the granular silicon-filled container, the granular silicon oxide-filled container, the cation exchange / adsorption filter, and the anion exchange / adsorption filter, the metal is the lower limit of detection. The TOC was further reduced as follows. However, SiO ₂ was detected in Comparative Example 4 in which water was passed through the ion exchange / adsorption filter in the former stage and then passed through the container filled with granular silicon and granular silicon oxide in the latter stage. In Comparative Example 1 using ultrapure water that was not purified, Comparative Example 2 in which all metals other than titanium and nickel adhered to the silicon substrate, and water was passed only through the granular silicon and granular silicon oxide filled containers. In Comparative Example 3 in which copper was passed through only the ion exchange / adsorption filter, iron was adhered to the silicon substrate. Moreover, in Comparative Example 2, the SiO ₂ concentration was increased by purification.

  From these results, after passing water through the granular silicon filled container and the granular silicon oxide filled container, the water is passed through the ion exchange / adsorption filter, so that organic matter, metal, etc. in ultrapure water can be obtained through extremely simple operation. Impurities can be adsorbed and removed, and ultrapure water can be refined to a higher degree than before. By using this purified ultrapure water to clean silicon substrates, it is possible to obtain a clean surface without metal adhesion. I understand that I can do it.

It is a systematic diagram which shows embodiment of the refinement | purification method and refiner | purifier of the ultrapure water of this invention. It is explanatory drawing of the electrospray deposition method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Granular silicon filling container 2 Granular silicon filling layer 2A Granular silicon oxide filling container 2B Granular silicon oxide filling layer 3A, 3B Water collecting support plate 4 Anion exchange / adsorption filter 5 Cation exchange / adsorption filter 11 Capillary 12 Electrode 13 Power supply

Claims (4)

A method for purifying ultrapure water in which ultrapure water is brought into contact with granular silicon and / or granular silicon oxide and then brought into contact with a structure having ion exchange capacity and adsorption capacity. A method for purifying ultrapure water, wherein the structure has one or more functional groups selected from the group consisting of a cation exchange group, an anion exchange group, and a chelate-forming group .   The method for purifying ultrapure water according to claim 1, wherein the structure having ion exchange capacity and adsorption capacity is composed of fibers having a fiber diameter of 0.01 to 1 µm. An apparatus for purifying ultrapure water comprising a packed bed of granular silicon and / or granular silicon oxide, and a structure having ion exchange capacity and adsorption capacity provided downstream of the packed bed , the ion exchange capacity and The ultrapure water purifier is characterized in that the adsorbing structure has one or more functional groups selected from the group consisting of a cation exchange group, an anion exchange group, and a chelate-forming group . 4. The apparatus for purifying ultrapure water according to claim 3, wherein the structure having ion exchange capacity and adsorption capacity is composed of fibers having a fiber diameter of 0.01 to 1 [mu] m.

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