JP6753384B2 - Product cleaning method - Google Patents

Description

The present invention relates to a metal contamination inhibitor and a metal contamination preventive film for reducing the metal contamination property of ultrapure water, and particularly when the product is washed with ultrapure water, trace metals in the ultrapure water are added to the product. The present invention relates to a metal contamination inhibitor and a metal contamination preventive film capable of easily preventing metal contamination of a product due to adhesion, and a metal contamination prevention method and a product cleaning method using the metal contamination inhibitor.

In cleaning a wafer to be a substrate for semiconductor manufacturing, rinsing cleaning with ultrapure water is performed after cleaning various chemicals. For this rinsing cleaning, high-purity ultrapure water from which impurities in water have been highly removed is used.

However, even ultrapure water for wafer cleaning still contains trace metals, and metal contamination of the wafer due to adhesion of trace metals in ultrapure water to the wafer during cleaning becomes a problem. There is.

Conventionally, in order to suppress metal contamination in the product cleaning process to a lower level, in the production of ultrapure water, deminer purification treatment, application of low-eluting piping members and charged UF membranes, special piping cleaning, etc., or a combination thereof Purification of pure water is being promoted. However, all of them lead to an increase in the cost of the ultrapure water production equipment, and when applied to the existing equipment, there are problems such as a long suspension period due to the remodeling work.

Patent Documents 1 and 2 describe that polystyrene sulfonic acid, polystyrene-based quaternary ammonium salt, etc. in ultrapure water cause wafer contamination, and it is necessary to reduce their content in ultrapure water. Has been done.

Patent Document 3 describes a cleaning agent for electronic materials containing a quaternary ammonium salt (B) of an organic acid (A), which removes particles without leaving the influence of alkali metals on the wafer surface. It is stated that it will be possible. Specifically, Patent Document 3 enables advanced cleaning by preventing particles removed by cleaning from the object to be cleaned from reattaching to the cleaning surface during cleaning. However, there is no description about the reduction of contamination by trace metals in ultrapure water.

Patent Document 4 discloses a cleaning agent for removing particles containing polystyrene sulfonate as a surfactant, but similarly, there is no description about reduction of contamination by trace metals in ultrapure water.

Japanese Unexamined Patent Publication No. 2003-334550 Japanese Unexamined Patent Publication No. 2004-283747 JP-A-2007-335856 Japanese Unexamined Patent Publication No. 2014-141668

The present invention provides a metal contamination inhibitor capable of reducing the adhesion of trace metals in ultrapure water, particularly ultrapure water for cleaning products, and suppressing metal contamination to be cleaned, and this metal contamination inhibitor. It is an object of the present invention to provide a metal contamination prevention film, a metal contamination prevention method, and a product cleaning method used.

As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by adding a polymer having an ion exchange group to ultrapure water, and completed the present invention. I let you.
That is, the gist of the present invention is as follows.

[1] Metal contamination that is a metal contamination inhibitor added to the ultrapure water in order to reduce the contamination by trace metals in the ultrapure water, and is characterized by containing a polymer having an ion exchange group. Inhibitor.

[2] The metal contamination inhibitor according to [1], wherein the polymer is a polymer having a sulfonic acid group or a quaternary ammonium group.

[3] The metal pollution inhibitor according to [1] or [2], wherein the polymer has a molecular weight of 100,000 or more.

[4] The metal contamination inhibitor according to [2] or [3], wherein the polymer is polystyrene sulfonic acid.

[5] In any one of [1] to [4], a metal pollution inhibitor characterized in that the trace metal is a metal having a divalent value or higher.

[6] A metal contamination inhibitor, which is added on the upstream side of the separation membrane in any one of [1] to [5].

[7] A method for preventing metal contamination of a product in contact with water by a trace amount of metal in ultrapure water, wherein the ultrapure water is contaminated with the metal according to any one of [1] to [6]. A method for preventing metal contamination, which comprises adding an inhibitor.

[8] The metal contamination prevention method according to [7], wherein the metal contamination inhibitor is added to the ultrapure water, and then water is passed through the separation membrane module to bring the membrane permeated water into contact with the product.

[9] A product cleaning method, which comprises cleaning the product with ultrapure water to which the metal contamination inhibitor according to any one of [1] to [6] has been added.

[10] The product cleaning according to [9], wherein the metal contamination inhibitor is added to the ultrapure water, water is passed through the separation membrane module, and the product is washed with the obtained membrane permeated water. Method.

[11] A metal contamination prevention film characterized by adhering or fixing the metal contamination inhibitor according to any one of [1] to [6].

By adding the metal contamination inhibitor of the present invention to ultrapure water, a polymer having an ion exchange group can adsorb trace metals in ultrapure water by an ion exchange reaction to suppress adhesion to the product. .. That is, the metal contamination property of ultrapure water can be reduced only by adding the metal contamination inhibitor of the present invention to ultrapure water.
Therefore, according to the metal contamination prevention film and the metal contamination prevention method of the present invention using the metal contamination inhibitor of the present invention, it is possible to effectively prevent metal contamination of the product by trace metals in ultrapure water. Further, according to the product cleaning method of the present invention, when cleaning a product with ultrapure water, metal contamination of the product can be prevented and efficient cleaning can be performed.

It is a system diagram which shows the cleaning experimental apparatus used in Experiment I. It is a graph which shows the result of Examples I-1, I-2 and Comparative Examples I-1 to I-5 of Experiment I. It is a system diagram which shows the UF membrane experimental apparatus used in Experiments II and III. It is a graph which shows the result of the comparative example II-1 of experiment II. It is a graph which shows the result of Example II-1 of Experiment II. It is a graph which shows the result of Example III-1 of Experiment III.

Embodiments of the present invention will be described in detail below.

The ultrapure water to which the metal contamination inhibitor of the present invention is added is high-purity water used in semiconductors, electronic parts, precision instruments, medical fields, etc., and is usually made of materials, parts, instruments, etc. (the present invention). In some cases, these are collectively referred to as a "product").

In the present invention, the trace metal in the ultrapure water to be reduced is a trace metal that cannot be removed in the manufacturing process of the ultrapure water and remains in the ultrapure water.

Trace metals in ultrapure water include monovalent metals such as Na, K, Li, and Ag, Mg, Al, Ca, Cr, Mn, Fe, Ni, Co, Cu, Zn, Sr, Cd, Ba, and Pb. Etc. are divalent or higher valent metals, and these are present as metal ions in ultrapure water. Usually, the amount of trace metals in ultrapure water used for cleaning various products is 1 ng / L or less, for example, about 0.01 to 0.5 ng / L as the concentration of each metal, and the total concentration thereof is It is 5 ng / L or less, for example, about 0.01 to 1 ng / L.

In the present invention, these trace metals are adsorbed on the polymer having an ion exchange group by an ion exchange reaction with the polymer having an ion exchange group to prevent adhesion to the product. From the viewpoint of this ion exchange reactivity, the metal contamination inhibitor of the present invention is particularly effective for polyvalent metal ions.

The ion exchange group of the polymer having an ion exchange group used in the present invention may be any as long as it can adsorb metal ions by an ion exchange reaction with metal ions, and is a carboxyl group, a sulfonic acid group, a quaternary ammonium group, or a tertiary group. Examples include an amino group.

Of these, a sulfonic acid group or a quaternary ammonium group is preferable from the viewpoint of ion exchange reactivity. The sulfonic acid group has an excellent ability to adsorb metal cations.

The polymer having an ion exchange group may have only one kind of these ion exchange groups, or may have two or more kinds.

Specific examples of the polymer having an ion exchange group include a polymer having a sulfonic acid group such as polystyrene sulfonic acid (PSA) and a polystyrene-based quaternary ammonium salt such as a polytrimethylbenzylammonium salt and a polytrimethylstyrylalkylammonium salt. Examples thereof include polymers having a quaternary ammonium group such as. The metal contamination inhibitor of the present invention may contain only one kind of the polymer having these ion exchange groups, or may contain two or more kinds.

The molecular weight of the polymer having an ion exchange group (in the present invention, the molecular weight is the weight average molecular weight in terms of polyethylene glycol by gel permeation chromatography) is preferably 10,000 or more. A polymer having a molecular weight of 10,000 or more has an effect of preventing contamination by metal adsorption by an ion exchange reaction. However, especially in a low concentration region, a polymer having a large molecular weight is superior in the above effect and therefore has an ion exchange group. The molecular weight of the polymer is preferably 100,000 or more. The molecular weight of the polymer having an ion exchange group is preferably 100,000 or more in terms of the removal effect by the separation membrane described later.

The amount of the metal contamination inhibitor added to the ultrapure water of the present invention is appropriately determined according to the amount of trace metal in the ultrapure water, and the ion exchange reaction between the polymer having an ion exchange group and the metal in the ultrapure water. It is preferable to add the mixture so as to have an equivalent ratio or more. Further, if the amount added is too large, the differential pressure rises due to leakage or retention of the metal contamination inhibitor to the treated water side, and the cost of the metal contamination inhibitor itself is high. Therefore, the ion exchange reaction equivalent ratio is 1 It is preferable to add the mixture in an amount of about 20 times, particularly 1.1 to 5 times.

If the amount added as a polymer having an ion exchange group is too small, the anticontamination effect of the polymer having an ion exchange group cannot be effectively obtained, and if it is too large, it may itself become a pollution factor. When water is passed through the separation membrane described later, the separation membrane tends to be clogged at an early stage, which is not preferable.

In the present invention, ultrapure water to which a metal contamination inhibitor is added is passed through a separation membrane module to remove a polymer having an ion exchange group that has adsorbed and captured metal in water, and then used for cleaning the product or the like. You may. By separating and removing the polymer having an ion exchange group that has adsorbed and captured the metal in this way, the metal contamination of ultrapure water can be further reduced.

In this case, since the metal ion in water exists as a cation except for some forms, a polymer having a cation exchange group is used as the polymer having an ion exchange group, and the metal cation is used as a polymer having a cation exchange group. It is preferable to adsorb and remove with a separation membrane. As the polymer having a cation exchange group, a polymer having a sulfonic acid group having a strong cation exchange ability, particularly polystyrene sulfonic acid is preferable.

As the separation membrane, a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, a reverse osmosis (RO) membrane, or the like can be used, and the molecular weight of adsorbing metal ions is 10,000 to 10,000. It is preferable to use a UF membrane because it can efficiently remove several millions of polymers. Further, from the viewpoint of the removal efficiency of the metal ion-adsorbing polymer, the fractional molecular weight of the UF membrane used is preferably about 1,000 to 100,000, particularly about 1,000 to 10,000.

As the separation membrane, various shapes can be used, but it is possible to use a hollow fiber membrane module of a type in which the added metal contamination inhibitor is quickly discharged to the concentrated water side and the metal contamination inhibitor does not remain. preferable.

When ultrapure water to which the metal contamination inhibitor of the present invention is added is passed through the separation membrane module, a part of the polymer having an ion exchange group in the metal contamination inhibitor is contained in the concentrated water and discharged to the outside of the system. However, the rest remains on the primary side (water supply side) in the separation membrane module and retains the metal trapping effect until all ion exchange groups are bonded to metal ions, so that the metal contamination inhibitor for ultrapure water The addition may be either continuous injection or intermittent injection.

If all the ion-exchange groups of the polymer having the ion-exchange groups in the added metal contamination inhibitor are bonded to the metal, the metal in the ultrapure water cannot be captured and removed. If the metal removal effect is reduced during the intermittent injection, additional injection of a metal contamination inhibitor may be performed, but the removal effect can be restored by adding an acid as described below. That is, when ultrapure water to which acid is added is passed through the separation membrane module, metal ions are desorbed and released from the polymer having an ion exchange group adsorbing metal remaining on the primary side of the separation membrane, and the ion exchange group is released. The polymer it has is regenerated. It is desirable to include the metal ions desorbed and released by the regeneration treatment in the membrane concentrated water and discharge it to the outside of the system because metal contamination on the permeated water side of the membrane can be prevented. The metal ions newly flowing into the primary side of the separation membrane are adsorbed and removed by the polymer having the regenerated ion exchange group. When applying continuous injection, use an internal pressure type hollow fiber membrane module because the added metal contamination inhibitor and regenerated metal ions do not stay in the module and are quickly discharged to the concentrated water side. Is preferable.

In this case, hydrochloric acid, nitric acid, or other strong inorganic acid can be used as the acid. The amount of acid added is preferably about 1 mg / L to 100 mg / L.

The metal contamination inhibitor of the present invention may contain components other than the polymer having an ion exchange group, but from the viewpoint of product contamination prevention, the metal contamination inhibitor of the present invention contains an ion exchange group. It is preferable that it contains only the polymer having.

The metal contamination inhibitor of the present invention may be added to ultrapure water in the preceding stage of the separation membrane module, or the metal contamination inhibitor is attached or immobilized on the separation membrane in advance, and this separation membrane (metal contamination inhibitory film). ) May be passed through the module having ultrapure water. In particular, it is preferable to attach or immobilize a metal contamination inhibitor on the primary surface of the separation membrane. When the metal removal effect of the metal contamination inhibitor adhered to or immobilized on the separation membrane is reduced, the metal removal effect can be restored by passing ultrapure water to which an acid is added.

The metal contamination inhibitor of the present invention can be used in a subsystem of an ultrapure water production apparatus. For example, when the subsystem is equipped with a non-regenerative mixed bed ion exchange resin device, a pump, and an UF membrane device, it is preferable to add a metal contamination inhibitor at the rear stage of the pump and the front stage of the UF membrane device. In this case, the water quality load due to the metal generated from the pump can be reduced by the metal pollution inhibitor. A metal contamination inhibitor may be added after the UF membrane apparatus. Instead of the UF membrane apparatus which is the final filter, a module having a metal contamination prevention film to which a metal contamination inhibitor is attached or immobilized may be provided. The configuration of the subsystem is not limited to this, and various ion exchange resin devices, UV oxidizing devices, degassing devices, and the like may be provided, or any of the units may be omitted.

In order to improve the ion exchange reaction rate, a buffer tank or the like may be provided to secure the reaction time, or a stirring means such as a line mixer may be provided. These means can be provided at any place after the place where the metal contamination inhibitor is added. The lower limit of the reaction time is preferably longer than 1 second.

The product cleaning method of the present invention for cleaning the product using the metal contamination inhibitor of the present invention will be described below.

In the product cleaning method of the present invention, the product is cleaned using ultrapure water to which the metal contamination inhibitor of the present invention is added in the above-mentioned suitable addition amount. As described above, the product may be washed with membrane permeated water obtained by passing water through the separation membrane module after adding the metal contamination inhibitor of the present invention.

The cleaning method is not particularly limited, and immersion cleaning, spray cleaning, or the like can be adopted.

The metal contamination inhibitor of the present invention is particularly suitable for rinsing cleaning of electronic parts such as wafers after chemical cleaning, and even if the metal is not highly purified ultrapure water, the metal of the present invention is simply used. Only by adding a predetermined amount of the anticontamination agent, or only by passing water through the separation membrane module after the addition, or by passing water through the separation membrane module (metal contamination prevention membrane module) to which the metal contamination inhibitor is attached or immobilized. Only by preventing metal contamination due to the adhesion of trace metals in ultrapure water to the product, it is possible to obtain a highly clean product and solve the problem of cost increase for high purification of ultrapure water. can do.

Hereinafter, the present invention will be described in more detail with reference to examples.

[Experiment I: Effect of suppressing metal adhesion to wafer]
<Experimental conditions>
After adding the metal to ultrapure water at 10 ng / L (mixed standard solution, each concentration) and the drug at 30 μg / L by the washing experimental apparatus shown in FIG. 1 (however, in Comparative Example I-1, the drug An experiment was conducted in which the mixture of the line mixer 1 (without addition) was supplied as cleaning water to the cleaning bath 2 to clean the wafer 3 in the cleaning bath 2.

The washed wafer was pulled out of the water and allowed to dry. The amount of metal adhering to the surface of the dried wafer was measured by gas phase inductively coupled plasma mass spectrometry (VPD-ICP-MS).

As the metal, Na, Al, Ca, Cr, Fe, Ni, Cu, and Zu were added, and the following chemicals were used.

Example I-1: Polystyrene sulfonic acid (PSA)
Example I-2: Polystyrene Quaternary Ammonium Salt (PSQ)
Comparative Example I-1: No drug added Comparative Example I-2: Crown ether (18-crown-6)
Comparative Example I-3: Ethylenediaminetetraacetic acid (EDTA)
Comparative Example I-4: Ethylenediaminetetramethylenephosphonic acid (EDTMP)
Comparative Example I-5: Gluconic Acid

<Results / Discussion>
The amount of metal adhered to the wafers of Examples I-1 and I-1 and Comparative Examples I-1 to 5 is shown in FIG.
As is clear from FIG. 2, PSA showed an adhesion-suppressing effect on all polyvalent metals, whereas other chemicals have selectivity depending on the metal type, and PSA is the most versatile to suppress adhesion. confirmed. Next to PSA, PSQ has a wide range of application, and chelating agents such as EDTA and EDTMP and other agents have been able to obtain an inhibitory effect on only some metals.

The amount of PSA added in Example I-1 is about 10 times the ion exchange reaction equivalent ratio, and the amount of PSQ added in Example I-2 is about 10 times the ion exchange reaction equivalent ratio.

[Experiment II: Metal reduction effect on UF membrane]
<Experimental conditions>
Using the UF membrane experimental apparatus shown in FIG. 3, 100 ng / L of metal (mixed standard solution, each concentration) and 30 μg / L of PSA (molecular weight 1 million) in ultrapure water (about 10 times the ion exchange reaction equivalent ratio). Water added so as to be (however, PSA was not added in Comparative Example II-1) was passed through the UF membrane module (fractional molecular weight: PEG conversion 12000) 4 as water supply, and water was supplied and treated water (membrane permeation water). ), The metal concentration in brine (concentrated water) was measured by inductively coupled plasma mass spectrometry (ICP-MS).

As the metal, Li, Na, Mg, Al, K, Ca, Cr, Mu, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb were used.

<Results / Discussion>
The metal concentrations in the water supply, treated water, and brine are shown in FIGS. 4 and 5.
As is clear from FIG. 4, when PSA is not added, there is no change in the concentration of any of the metals in the water supply, the treated water, and the brine. As is clear from FIG. 5, when PSA is added, the amount of multivalent metal having a divalent value or higher is reduced by about 95% in the treated water with respect to the water supply. Since the PSA removal rate in the UF membrane was 94% in a separate test, it is presumed that the PSA that captured the metal in the water was blocked by the UF membrane, which reduced the metal concentration in the treated water. To.

[Experiment III: Regeneration effect of PSA remaining on UF membrane]
<Experimental conditions>
The UF module used in Example II-1 was washed with ultrapure water for 7 days, loaded with a high concentration of metal and PSA, and then the UF membrane was again subjected to ultrapure water and nitric acid (relative to the amount of water flow). 0.001%) was passed through water for washing. Before loading and after each washing step, water to which each metal was added so as to be about 10 ng / L was passed, and the metal concentration of the treated water was analyzed by the ICP-MS method to determine the metal permeability (permeability of the metal). Example III-1).

<Results / Discussion>
The metal transmittance of the UF membrane after each step is shown in FIG.
As is clear from FIG. 6, the transmittance of the multivalent metal before the PSA loading was 5 to 10%, suggesting that the PSA loaded in the experiment of Example II-1 remained and the metal could be removed. Will be done. After loading, the metal almost permeated the UF membrane with a transmittance of 80 to 100%, but it was confirmed that the transmittance tended to decrease with each repetition of nitric acid washing. From this, it was confirmed that PSA remains on the primary side of the UF membrane, and the metal removing effect is reduced when the metal loading is continued, but the metal removing effect is restored by washing with an acid.

From the results of Examples II-1 and III-1, it was clarified that the metal concentration in the treated water can be reduced by continuously or intermittently injecting a polymer having a cation exchange group on the primary side of the UF membrane. It was also suggested that the cation exchange group of the polymer remaining on the primary side of the UF membrane can be regenerated by acid washing and can be applied as an on-site reproducible polisher.

1 Line mixer 2 Cleaning bath 3 Wafer 4 UF membrane module

Claims (2)

This is a product cleaning method for cleaning products with ultrapure water (excluding those with a pH of 5 or less) to which a metal contamination inhibitor is added to reduce the contamination by trace metals in ultrapure water.
The metal contamination inhibitor contains a polymer having an ion exchange group, and the polymer is polystyrene sulfonic acid having a weight average molecular weight of 100,000 or more .
A product cleaning method characterized in that ultrapure water to which the metal contamination inhibitor is added is used for cleaning the product without film treatment. In the product cleaning method according to claim 1, the amount of the metal contamination inhibitor added to the ultrapure water is 1 of the ion exchange reaction equivalent of the polymer having an ion exchange group and the trace amount of metal in the ultrapure water. A product cleaning method characterized by being up to 20 times.

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