JPH09141058A - Refining membrane for semiconductor wafer treating liquid and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous membrane having a function to selectively capture trace metal ions simultaneously with filtration in particular in the stage of refining a positive type resist treating soln. of semiconductor wafer and wafer washing liquid. SOLUTION: This process for producing a filter membrane comprises coating a functional group having a wire cylindrical structure, a functional group having a silotherm structure regenerated with hot water and a functional group forming a complex and this method for treating the semiconductor wafer comprises using the same. When the method is applied to the refining of the semiconductor wafer treating liquid, not only the filtration is effected but metal ions are extremely selectively removed. The loss of org. alkalis is lessened in an org. alkaline liquid. The purity of the washing water is thus improved. An HBMF 2 in particular has an effect of removing a slight amt. of metals from the inside of pure water and has further the particle removal performance equal to or better than that of a general filter. Then, the minority carrier recombination life time when the wafer is subjected to treating and washing by using the ultrapure water treated by the filter membrane is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to purification for maintaining high quality of a positive resist processing solution for semiconductor wafers and wafer cleaning water by removing a trace amount of metal ions by an ion exchange reaction with an organic acid, The present invention relates to a porous membrane having a function of selectively capturing trace metal ions simultaneously with filtration.

[0002]

2. Description of the Related Art Conventionally, the removal of a trace amount of metal ions contained in an organic alkaline developer for treating a positive resist has been an important issue for maintaining the electrical characteristics of a wafer. Further, for the wafer itself, especially for a silicon wafer that requires a large amount of handling, a cleaning step after mirror polishing is indispensable, and it has been desired to use pure water containing as few metal ions as possible. From this point of view, for example, JP-A-57-1390
No. 42 proposes that a polyacrylic gel-based weakly acidic ion exchange resin is introduced into an organic alkaline solution to selectively remove a trace amount of metal ions dissolved in the organic alkaline solution. Further, with respect to the wafer cleaning water, it is a large scale to repeatedly install ion exchange equipment for ion exchange as necessary, so that various measures have been taken in using a surfactant. For example, JP-A-4-7830 discloses a polymer. The use of surfactants has been proposed as facilitating subsequent rinse with rinse water.

[0003]

However, in the above-mentioned method for treating an organic alkaline solution, it is unavoidable that some of the alkali ions are lost, and metal ions also remain in the solution to a considerable extent. Further, even when the above-mentioned polymer surfactant is used, only the ion-exchange ability of the organic carboxylic acid is utilized, and therefore there is a demand for further improvement in performance in removing metal ions. Furthermore, when using ultrapure water once prepared at the point of use, install the current ion exchange device at the point of use each time in order to avoid deterioration of purity due to the mixing and elution of trace impurities from the line in the middle. Was not always easy due to process restrictions. The task was to solve these inconveniences easily.

[0004]

Against this background, processing liquids for various semiconductor wafers are purified to selectively select metal ions contained in the processing liquid, and organic alkali is directly added to the liquid. Various studies were conducted to selectively remove only the retained metal ions. First, it was noted that organic alkalis are structurally larger than metal ions, while many metal ions have complex-forming ability unlike organic alkali cations. Furthermore, the process in which these problems occur is originally a process in the process close to the final process in which the amount of metal ions contained is small, so the objective is to improve the filtration process installed immediately before the point of use of the semiconductor processing liquid. We repeated examination to achieve. As a result, a polymer having an organic acid and an organic base, which are directly and indirectly bonded before and after ion exchange, is disclosed on, for example, Japanese Patent Publication No. 4-75051 so that the filtration performance is not lost on the existing porous membrane. A film coated in this manner was applied to the purification of the semiconductor wafer processing solution, and metal ions were extremely selectively removed not only by filtration, but the loss of organic alkali in the organic alkaline solution was reduced. Then, they found that the purity was extremely improved, and completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Here, a polymer having an organic acid and an organic base which are directly and indirectly bonded before and after ion exchange is:
A polymer in which an organic acid and an organic base are bound by a neutralization reaction before ion exchange, a polymer having a serpentine cage structure, a polymer formed from a benzoin derivative monomer, an organic acid monomer, and an organic base monomer, so-called silotherm The structure means a polymer in which a metal ion bonded to an organic acid after ion exchange is coordinate-bonded to an organic base, that is, a polymer in which an organic acid and an organic base are indirectly bonded via a metal ion. Hereinafter, for the sake of simplicity, these polymers are referred to as a polymer composed of an organic acid and an organic base forming a hybrid structure. Organic bases mean amines, sulfides and phosphines as well as their respective quaternary ammonium bases, tertiary sulfonium bases and quaternary phosphonium bases. For the sake of simplicity, various amines which are nitrogen compounds and a quaternary ammonium salt group will be described below, but they are not meant to be limiting.

The coating having a snake-cage structure is formed by modifying a polymer coated with a porous film in advance to bind a quaternary ammonium hydroxide and a polymerizable organic acid by a neutralization reaction to bind this organic acid. It can be obtained by polymerization on a porous membrane. Methods for synthesizing these quaternary ammonium hydroxides are already known, and for example, a mixture or copolymer for copolymerization of styrene and a few% of divinylbenzene is mixed with, for example, monochloromethyl methyl ether before and after coating by Friedel-Crafts. In the presence of a catalyst, a side chain monohalogenated methyl halide is introduced into a benzene nucleus and a tertiary amine is added to the benzene nucleus to easily obtain the compound, which is then synthesized by treating with an alkali metal hydroxide. The polymerizable organic acid is preferably an unsaturated organic acid such as acrylic acid, methacrylic acid, vinylacetic acid, allylacetic acid, maleic acid or itaconic acid.

When the porous film thus obtained is applied, the organic alkali cations in the organic alkali solution for wafer processing to be purified are less likely to pass through the snake cage structure, while the metal ions are resistant to the snake cage structure. It can be presumed that it moves inside and approaches the carboxyl group of the starting organic acid to be bound and removed. That is, the ion exchange of the organic alkali cations is suppressed and the metal ions are relatively removed, so that the intended target is achieved.

The polymer having a silotherm structure has triallylamine, methyldiallylamine, ethyldiallylamine and 1,4-bis (N, N) as amines, as is apparent from JP-A-51-148683, which discloses the production method.
-Diallylaminomethyl) benzene, 2,4,6-tris (N, N-diallylaminomethyl) toluene, 1,
An amine selected from 2,4-tris (N, N-diallylaminomethyl) benzene, 1,6-bis (N, N-diallylamino) hexane, n-propyldiallylamine, and benzyldiallylamine is used. It is obtained by forming a polymer on a porous film using an organic acid and a monomer composed of unsaturated benzoin or its ether derivative. When the porous membrane thus obtained is applied, it has a feature that it is regenerated as a filtration membrane and an ion exchange membrane by backwashing with heated hot water as well as ion exchange.

For a polymer having a structure forming a complex, the positional relationship between the element serving as a ligand and the carboxyl group is important, and a certain distance relationship within the molecular structure is represented by iminodiacetic acid. Since it is required, it is preferable that the amine and the organic acid have a predetermined structure so that an alternating copolymer of unsaturated alkylamine and unsaturated fatty acid is formed. The introduction of amine is facilitated by replacing the above-mentioned tertiary amine with primary and secondary amines and performing a dehydrohalogenation reaction.
In addition to the unsaturated aliphatic organic acid described above, the organic acid may be iminodiacetic acid introduced into the side chain alkyl by dehydrohalogenation reaction in the same manner as the introduction of a secondary amine, and one obtained by the introduction described above, A halo-substituted various aliphatic organic acid may be reacted and introduced into the secondary amine portion. When the porous membrane obtained in this manner is applied, ion exchange is accompanied by complex formation, thereby enabling relatively selective removal of metal ions in the case of removing ions in the organic alkaline solution.

Further, it has been found that the formation of the coated porous film having the above-mentioned structure together also has an important feature because the versatility and applicability are increased. By the way, the above-mentioned various organic acids are monomers that can be converted into organic acids such as ester and organic nitrile in order to easily and surely proceed the various reactions, for example, methyl acrylate, methyl methacrylate, acrylonitrile and methacrylonitrile. It is also possible to replace it with and coat it to lead to an organic acid.

The polymer formation will be described in detail. In the context of the porous membrane, the functional groups of the porous membrane are used, and if not, alkali treatment or various kinds of radiation is used to form active sites to graft. It is preferable to polymerize, but it is also possible to cover the membrane so as to physically surround the membrane so as to have a strong structure in which the inside of the hole extends from the front side to the back side of the membrane. Even if the polymer to be a film is polymerized on the surface all at once, for example, a nitrogen-containing polymer is first coated to have the above-described snake cage structure,
Further, a quaternization treatment may be performed to bond an unsaturated organic acid, and then the polymerization reaction may be performed again. The reaction after the first polymerization does not necessarily mean only the polymerization reaction, but also means that a substitution reaction or an addition reaction that modifies the polymer later such as a reaction between an active halogen atom and iminodiacetic acid is promoted. To do.

The existing porous membrane is intended to be made of various polyolefins or halogen-substituted products thereof, polyether sulfone, polycarbonate, polyamide, and other materials having a nominal pore diameter of 0.02 μm to several μm. is there. If the filtration performance is not lost, the pore size originally possessed by the porous membrane may be reduced, but the effect does not matter if the intended sieve effect and the flow rate are within the preset allowable range. It is assumed that the porous membrane having the above-mentioned pore diameter is processed to have a predetermined pore diameter, and that it is naturally taken. As a factor having a large influence on the pore size in the coating, the viscosity during the polymerization is important particularly when the polymer is formed on the film surface. If the chain length is too long, the viscosity becomes so high that it becomes difficult to control the pore size. Therefore, when using a polymerization initiator, it is important to use the polymerization initiator in several times the usual method. Hereinafter, specific examples of the present invention will be described in Examples.

[0013]

【Example】

Example 1 Production of Porous Membrane Coated with Polymer Consisting of Organic Acid and Base Having Hybrid Structure 100 ml of dimethyl sulfoxide was put into a 500 ml flask and stirred to obtain α-allyl-α-benzoylbenzyl methyl ether. 1.33 g, triallylamine hydrochloride 6.94 g, 10.0 wt% methanol solution of causticum (corresponding to causticum 40.0 mmol), 4-chloromethylvinylbenzene 7.63 g, methyl acrylate 8.60 g and 4,4′- 24 of 100 ml of a solution of 0.500 g of azobis (4-cyanovalerianic acid) in an equal mixture of dimethyl sulfoxide and methanol
Supplied over time. During this time, the temperature inside the flask is from room temperature to 7
The temperature was controlled so as to linearly increase to 0.0 ° C. The flask was cooled to room temperature, and the content liquid was made of ultra-high molecular weight polyethylene (molecular weight: 1,000,000), the diameter was 47.0 mm, and the thickness was 1
20 circular porous membranes having a diameter of 00μ, a pore diameter of 0.2μ, and an opening ratio of 60.0% were decanted gently into a cylindrical container arranged so as not to contact each other. Then, the lower valve of the cylindrical container was opened to remove the liquid content, and the porous membrane in a wet state was stored in the cylindrical container and heat-treated overnight in a dryer at 80.0 ° C. Remove the cylindrical container from the dryer, wash the porous membrane with dimethyl sulfoxide and water, and confirm that the eluate is gone.
It was transferred to an autoclave of 1 l and 300 ml of dimethyl sulfoxide was provided, and the porous membrane was dipped and kept at a temperature of 120 ° C. while being vibrated, and trimethylamine hydrochloride was added.
100 ml of a dimethylsulfoxide solution consisting of 955 g, 0.950 g of iminodiacetonitrile and 10.0 wt% methanol solution (corresponding to 50.0 mmol of potassium hydroxide) was added by a pressure pump over 2.00 hours and further 3.00. Continue to react for hours. After cooling to room temperature, the filter membrane is taken out and repeatedly washed with a 10.0 wt% acrylic acid aqueous solution, and the process is continued until the consumption of acrylic acid is exhausted. After the completion of washing, the filter membrane is taken out, immersed in a dimethylsulfoxide solution of 5.00 wt% of methyl acrylate, treated at 70 ° C. for 1 hour, and then 10.0 w
in a t% methanol solution for 3.00 hours and further in water for 1.
Reflux treatment was performed for 00 hours. After cooling, the filtration membrane was taken out and washed repeatedly with a 10.0 wt% aqueous solution of acrylic acid until the consumption of acrylic acid was exhausted, followed by washing with water and drying under reduced pressure to coat a polymer having a hybrid structure with an organic acid and a base. To obtain a porous membrane (hereinafter, a porous membrane produced in the same manner is abbreviated as HBMF2).

Example 2 Improvement of wafer carrier lifetime by removing trace metals in pure water with HBMF2 and cleaning wafers with this pure water A cleaning tank (20 liters) made of quartz as shown in FIG. 1, a pump and HBMF2 A system was assembled in which the cartridge filter used was connected to the piping. This HB
Cartridge filter using MF2 has an effective filtration area of 60
It has an attachable structure of 00 cm ² . After operating the pump to thoroughly clean the line and confirming that there is no metal elution from the line, fill the quartz cleaning tank with ultrapure water from the ultrapure water supply source, and place 12 6-inch wafers (P-type). Immerse and connect with a short tube instead of the cartridge filter.
It was processed for 4 hours at a circulation rate of 20 liters per minute. Then, the wafer is taken out and oxidized with dry oxygen at 1000 ° C. for 1 hour, and the μ-PCD method (for details, refer to the following literature: J. Atsum.
i, S. Otsuka, S. Munehira and K. Kajiyama: Pro-ceedin
gs of the 1st Int. Symp. on Cleaning Tech. in Semi
conductor Device Manufacturing, The Electrochem. S
oc., Pro-ceedings Vol. 90-9, p.59 (1989)) and measured the carrier lifetime as a reference value. Then, H
BMF2 was attached, another wafer of the same lot was immersed in the same number of wafers in the same tank, and immersion treatment was performed while circulating for 24 hours, and the carrier lifetime was measured as described above. This 2
Seed wafers of 2 for each seed wafer
The average value of the carrier lifetime measured at each location is shown in FIG. From this result, it is clear that the circulation of the ultrapure water treated with HBMF2 makes the carrier lifetime sufficiently long. Further, the metal on each wafer was extracted with an aqueous solution of hydrochloric acid for each two wafers of the above-mentioned two kinds, and the content thereof was measured by a mass spectrometer ICP-MS.
The measurement result of each metal is shown in FIG. As is clear from this figure, it is understood that the metal ions have been removed by HBMF2.

Example 3 The same measurement was performed using the system of Example 2.
However, in this embodiment, after supplying pure water into the quartz tank, N
Metals of a, Al, Fe, Cr, Ni, Cu and Zn were added to have a concentration of about 0.1 ppb, and 12 6-inch wafers were immersed for 1 hour, and the carrier lifetime was measured. Then, the liquid in the tank was attached with a cartridge filter of HBMF2, treated at the same circulation speed as in Example 2 for 24 hours, and then another 12 wafers were newly immersed for 1 hour, and the carrier lifetime was measured in the same manner. As shown in FIG. 4, HBMF
It was found that the wafer carrier lifetime was remarkably improved by using 2. Table 1 shows the results of measuring the respective metal concentrations in these two solutions. It is clear that the metal ions have been removed by HBMF2.

[0016]

[Table 1]

Example 4 Al ³⁺ , Fe by a disk-shaped sample of HBMF2
Measurement of ³⁺ Removal Capacity A sample cut out to a diameter of 47 mm was added to pure water to measure the removal capacity of Fe ³⁺ and Al ³⁺ . In addition, HBMF2 as a reference
The same measurement was performed using a UPE membrane having a diameter of 47 mm having the same pore size as the above. 47 mm of HBMF2 as shown in Table 2
The disk removed Fe ³⁺ and Al ³⁺ , but ion removal of the UPE film was not observed.

[0018]

[Table 2]

Example 5 Instead of the polyethylene porous membrane of Example 1, a porous membrane made of polytetrafluoroethylene (hereinafter abbreviated as PTFE) was treated in the same manner, and HBMF2 in pure water F was used.
e ³⁺ Ion removal capacity measurement. Diameter 4 as in Example 3
A 7 mm disk-shaped film was added to pure water to measure the Fe ³⁺ removal capacity. Also, HBM as a reference
The same measurement was performed using a 47 mm diameter PTFE membrane having the same pore size as F2. As shown in Table 3, 4 of HBMF2
The 7 mm disk removed Fe ³⁺ , but no ion removal of the PTFE membrane was observed.

[0020]

[Table 3]

[0021]

[Effects of the Invention] A polymer composed of various organic acids and organic bases having a hybrid structure is coated on an existing porous membrane so as not to lose its filtration performance, and this is used as a semiconductor wafer processing solution. When applied to purification, not only filtration but also metal ions are removed very selectively, the loss of organic alkali in organic alkali liquid is reduced, and the purity of washing water is greatly improved. In particular, HBMF2 is used to remove trace amounts of metal with pure water. It has the effect of removing it from the inside, and moreover, it has the same or more particle removal performance as compared with a general filter. Therefore, when the wafer is processed and washed using ultra pure water processed with this filtration film The minority carrier recombination lifetime can be improved and the contamination due to the metal of the wafer can be reduced. In addition, there is also an effect that deionization can be smoothly performed together with filtration without the purpose of separately installing ion exchange equipment.

[Brief description of the drawings]

FIG. 1 Quartz cleaning tank, pump and HBMF2
It is a figure which shows the system which connected the cartridge filter to piping using.

FIG. 2 is a diagram showing an average value of carrier lifetimes measured at four points on each wafer by collecting two samples from each of two kinds of wafers.

FIG. 3 is a mass spectrometer ICP-MS in which two kinds of wafers each having two wafers are subjected to extraction of metal on the wafers with an aqueous hydrochloric acid solution.
It is a figure which shows the density which measured the content with respect to each metal.

FIG. 4 is a result of treating the liquid in the tank with an HBMF2 cartridge filter for 24 hours at the same circulation speed as in Example 2 and then dipping another 12 wafers for 1 hour and similarly measuring the carrier lifetime. FIG.

Claims (3)

[Claims] 1. A porous membrane for purifying a semiconductor processing solution, which is coated with a polymer composed of an organic acid and a base having a hybrid structure. 2. A method for purifying an organic alkaline solution, which comprises filtering with a porous membrane for purifying a semiconductor processing liquid, which is coated with a polymer composed of an organic acid and a base having a hybrid structure. 3. A method for purifying wafer cleaning water, which comprises filtering with a porous membrane for purifying a semiconductor processing liquid, which is coated with a polymer composed of an organic acid and a base having a hybrid structure.