JPH0929020A - Method for using air filter and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exclude organic matters in the air in a clean room. SOLUTION: An organic matter removing process mentioned as under is applied to an air filter 6 provided in an air introduction passage of a clean room. The air filter 6 is put in a stainless autoclave 1 and a cap is put on, and air of high purity is introduced from a cylinder 2 and passed through the inside of the autoclave 1 while maintaining the temperature in the autoclave 1 at 100 deg.C. The air filter 6 to which the above process is applied is provided in the air introduction passage of the clean room.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using and a method of manufacturing an air filter used in a clean room used in factories and laboratories related to semiconductors, foods, pharmaceuticals, biotechnology.

[0002]

2. Description of the Related Art Conventionally, in a clean room used in semiconductors, foods, pharmaceuticals, biotechnology-related factories and laboratories, a dry air filter for collecting airborne particulate matter is used as an air introduction path. It is installed and the air passing through it is introduced into the room.

In such a clean room, when a silicone sealing material is used for the interior, low molecular weight siloxanes volatilized from this diffuse into the air in the clean room, so that the products manufactured in the clean room are contaminated. It has been pointed out that there is a possibility that it will be carried out (Fujimoto, Fukui; “Analysis technology of impurities in clean room air” Air Purification, Vol. 32, No. 3, P. 1).
6-25 (1994)). In particular, in semiconductor manufacturing factories, the presence of siloxanes in the air in a clean room is said to reduce the product yield.

Therefore, the present applicants have proposed a method of constructing the interior of a clean room with an inorganic material (Japanese Patent Laid-Open No. 62-86248 and Japanese Utility Model Laid-Open No. 62-56).
No. 614, Japanese Utility Model Laid-Open No. 62-124102, etc.), for example, the wall material is a fitting type partition made of an inorganic non-combustible material, and the silicone sealing material is not used.

[0005]

However, even if the interior of the clean room is devised in this way, various organic gases containing low-molecular-weight siloxanes are present in the air in the clean room. No effective measures were taken to eliminate it.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to prevent the presence of organic substances such as low molecular weight siloxanes in the air in a clean room. To do.

[0007]

Means for Solving the Problems As a result of extensive studies to achieve the above object, the cause of the presence of low-molecular weight siloxanes in the air in a clean room is due to the air filter installed in the air introduction path. The present invention was completed by discovering that

That is, perhaps because of the prejudice that the air filters used in clean rooms are clean, the possibility of organic substances being generated from the constituent materials of the air filters has not been studied until now.

On the other hand, the present inventors put such an air filter in an autoclave, introduce high-purity air into the autoclave, pass the air discharged from the autoclave through the activated carbon, and adsorb it on the activated carbon. When a sample obtained by eluting the obtained substance in a solvent was analyzed by a gas chromatograph (GC) device, a large amount of organic matter was unexpectedly detected. In addition, this sample was analyzed by gas chromatography / mass spectrum (GC /
When analyzed by a MS) apparatus, it was found that this sample contained low molecular weight siloxanes, hydrocarbons, aromatic carboxylic acid esters, phosphoric acid esters, phenols and the like.

Therefore, in the invention according to claim 1, after the dry air filter for collecting the suspended particulate matter in the air is subjected to the treatment for removing the organic matter, the air filter is installed in the air introduction path of the clean room. Provided is a method of using an air filter, which is characterized by being installed.

According to a second aspect of the present invention, in the method of using the air filter according to the first aspect, the treatment for removing the organic matter is performed by placing the air filter in a closed container at least the inner surface of which is made of an inorganic material. It is characterized in that it is a process in which a clean gas is passed through the container while the temperature of the air filter is kept within a predetermined range.

The invention according to claim 3 is a method for manufacturing a dry air filter used in a clean room for collecting suspended particulate matter in the air, wherein at least the inner surface of the air filter is inorganic as a finishing treatment. Put in a closed container made of a material, while maintaining the temperature of the air filter at a predetermined value, a clean gas is passed through the container to perform a process of removing organic substances from the air filter. A method for manufacturing an air filter is provided.

The temperature is set according to the type of air filter and the type of organic gas which is not desired to be present in the clean room, but is preferably 70 ° C. or higher and 180 ° C. or lower, more preferably 90 ° C. or higher and 140 ° C. or higher. It is below ℃. Then, in order to keep the temperature of the air filter contained in the container within a predetermined range, the container itself may be heated to raise the internal air, or the temperature of the gas passing through the container. May be controlled to a range according to the predetermined range.

As a clean gas to be passed through the container,
Air and nitrogen that do not contain organic substances and are of high purity (purity 98
% Or more), and those containing carbon dioxide or water vapor as impurities can be used. Such gas may be introduced into the container from a cylinder containing high-purity air or nitrogen into the container through a clean pipe, or may be introduced into room air through a filter which has been previously cleaned. . In the latter case, it is necessary to clean the filter used with high-purity air (or nitrogen).

The passing speed of the gas is not particularly limited, but it is 5 to 20 per air filter to be treated.
It is preferably 1 / min. According to the method of using the air filter of claim 1, since the air that has passed through the air filter that has been subjected to the removal treatment of organic substances is introduced into the clean room from the air introduction path, the concentration of the organic gas in the clean room is reduced. To be done.

According to the method of using the air filter of the second aspect, in addition to the function of the first aspect, the organic substances contained in the constituent members of the air filter are easily volatilized and volatilize into a gaseous state. The resulting organic matter is entrained in the clean gas passing through the container and is efficiently removed to the outside of the container.

According to the method of manufacturing an air filter of claim 3, the organic matter contained in the constituent members of the air filter is easily volatilized, and the volatilized and gaseous organic matter passes through the container. The resulting air filter is unlikely to become a source of contamination of organic substances because it is efficiently removed outside the container by being entrained in such a gas.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to specific examples. FIG. 1 is a schematic diagram showing a processing apparatus for removing organic substances from the air filter used in this example.

This apparatus has a stainless steel autoclave (closed vessel) 1 and a cylinder 2 filled with high-purity (99.99% or more) air. In FIG. 1, the lid of the autoclave 1 is opened. It shows the state.

A gas inlet 11 is provided in the lower portion of the cylindrical peripheral wall of the autoclave 1, and a gas outlet 12 is provided in the upper portion of the peripheral wall opposite to the gas inlet 11. The gas inlet 11 of the autoclave 1 and the cylinder 2 are connected by a clean pipe 3, and the pipe 4 connected to the gas outlet 12 is connected with an activated carbon tube 5 filled with 40 g of activated carbon. ing.

The activated carbon tube 5 is for collecting the organic substances in the gas generated in the autoclave 1 and discharged from the gas outlet 12, and has a high purity (9
2) at 250 ° C while passing nitrogen of 9.9999% or more)
It is treated by heating for a time, and it is confirmed that the activated carbon inside the GC / MS device has not been adsorbed by organic substances.

Inside the autoclave 1, there is a net-like bottom plate 13 made of stainless steel. The bottom plate 13 has a size such that its air passage surface can be placed substantially horizontally depending on the size of the air filter 6 to be treated. It has become. The gas introduction port 11 is located below the bottom plate, and the introduced gas passes through the bottom plate 13 and passes through the air filter 6 from below. Further, in the peripheral wall of the autoclave 1, although not particularly shown, a heater including a conventionally known coil-shaped heating wire and the like is disposed,
The inside of the autoclave 1 is heated by this heater. <Treatment of various filters under the same conditions: No. 1-9>
By using the above-mentioned device, as a dry type air filter which is conventionally arranged in the air introduction path of a clean room, UL
PA Filter (Ultra Low Penetra
ion air filter), HEPA filter (High Efficiency Particle)
Air filters), a pre-filter, and a filter for removing sea salt particles were used to perform a treatment for removing organic substances from these filters.

That is, the bottom plate 13 in the autoclave 1
Place one air filter 6 horizontally on top of the autoclave and seal it with a lid.
While maintaining the temperature of the inside at 100 ° C, a flow rate of 10 (l / l
(min), introducing high-purity air from the cylinder 2 into the autoclave 1 was continued for 8 hours. The temperature is measured by a thermocouple (not shown) arranged immediately above the air filter 6.

Then, in order to investigate the state of removal of organic substances from the filter by this treatment, the amount of organic substances collected by the activated carbon in the activated carbon tube 5 during the treatment was analyzed by a GC device and the kind thereof was analyzed by a GC / MS device. . As an analytical sample, the activated carbon in the activated carbon tube 5 after the treatment was put into a flask with a stopper containing 50 ml of carbon disulfide and left to stand for 2 hours or more, whereby the organic matter adsorbed by the activated carbon was converted into carbon disulfide. The eluted liquid was used.

Regarding the amount of collected organic matter,
An internal diameter of 0.52 mm coated with polysiloxane by a Hitachi GC device "G-5000 (FID)"
It was measured by performing quantitative analysis using a glass capillary column having a length of 30 mm and using toluene as a reference substance. That is, a calibration curve of toluene was prepared in advance, and the total weight of organic substances was measured in terms of toluene.

Regarding the type of the collected organic matter, the GC / MS device "M-200" manufactured by Hitachi, Ltd. is used.
"0" was identified by qualitative analysis of each peak component using the same column as above.

On the other hand, after the above treatment, the heating of the heater was stopped and the internal temperature was returned to room temperature, the lid of the autoclave 1 was opened, and the condition of the filter after treatment was checked. Especially when treated at a high temperature, it is carefully examined whether the filter medium is peeled off from the outer frame due to the deterioration of the sealant or the like.
And, when such a problem occurs, the filter appearance after the treatment is "X", otherwise "○"
Was evaluated.

Further, for the evaluation of the above treatment, the filter after this treatment was put into the same autoclave 1 as described above, and the temperature near the filter installation position in the autoclave 1 was maintained at 100 ° C. , Flow rate 10
The introduction of high-purity air from the cylinder 2 into the autoclave 1 at (l / min) was continued for 5 hours (total flow rate of passing aeration 3.0 m ³ ), and the amount of collected organic matter was collected in the same manner as above. The types of organic substances that were used were analyzed. As a result, the amount and type of organic substances remaining in the filter even after the organic substance removal process can be known.

When the autoclave used once for the organic substance removing process is reused, it is necessary to prevent the organic substances generated in the previous process from remaining in the autoclave 1 and the pipe 4. For that purpose, autoclave 1
After removing the treated filter from the inside, the inner surface of the autoclave 1 is first wiped with a clean cloth, then with a cloth soaked with ethanol, and then with a dry clean cloth. In addition, the air outlet 1 of the autoclave 1
The pipe 4 connected to 2 is removed, the inside is washed with ethanol, and then clean air is blown in to dry it. In addition, the activated carbon tube 5 is replaced with a new one for each treatment.

Further, using the autoclave 1 and the pipe 4 after washing, the apparatus was assembled without connecting the activated carbon tube 5, and the temperature inside the autoclave 1 was kept at 120 ° C. without the filter, and the temperature was raised from the cylinder 2. The supply of pure air is continued for more than 5 hours. After that, connecting the activated carbon tube 5 to the pipe 4 and introducing high-purity air into the autoclave 1 in the same manner as described above is continued for 4 hours, and the gas passing through the autoclave 1 is introduced into the activated carbon tube 5. Thereafter, the organic matter adsorbed by the activated carbon in the activated carbon tube 5 is analyzed in the same manner as described above, and when it is confirmed that the activated carbon does not adsorb the organic matter,
This device is used for the next process.

Tables 1 and 2 below show the results of the type of filter, the treatment conditions, the state of removal and remaining of organic substances, and the appearance of the filter after treatment for each sample.

[0032]

[Table 1]

[0033]

[Table 2]

Sample Nos. 2 to 7 in Tables 1 and 2
Is the above-mentioned organic matter removal treatment for each type of filter, but sample No. 1 is ULPA-1 which has not been subjected to the above-mentioned organic matter removal treatment, and the residual amount of organic matter is remarkably higher than the others. It contained high and low molecular weight siloxanes, hydrocarbons, aromatic carboxylic acid esters, and phosphoric acid esters.

For sample No. 8, the cylinder 2 was removed, the air outlet of the blower in the laboratory was connected to the air inlet 11 of the otoclave 1, and the air in the laboratory was introduced into the autoclave 1. This is an example of performing the above processing.
In this case, since dust had adhered to the filter after the treatment, it was judged that the filter was not suitable for use in a clean room, and the treatment for evaluation was not performed.

As shown in the section "Type of collected organic matter" in Tables 1 and 2, the type and content of the organic matter contained differ depending on the type of filter, and are common to all the filters used here. Then, n = 4 to 11 cyclic dimethylpolysiloxane (D4 to D11) represented by the following formula (1) and an aliphatic hydrocarbon having 10 to 16 carbon atoms (from decane to hexadecane) are contained. It was

-[(CH ₃ ) ₂ SiO] _n- (1) HEPA-1, ULPA-1, and fan filters contain dioctyl phthalate (DOP), phosphate ester, etc. in addition to the above. Was there. Also, HEPA-2,
In addition to this, the ULPA-2 and the filter for sea salt removal contained aromatic hydrocarbons such as toluene and xylene, and phenols.

Then, each of the samples was subjected to the above-mentioned organic substance removal treatment to obtain n of the cyclic dimethylpolysiloxane.
Almost all of the compounds of 4 to 8 (D4 to D8) were removed, but those of n = 9 or more (D9 to D11) were not removed. The molecular weight of D8 (hexadecamethylcyclooctasiloxane) was 592, and it is considered that most of the lower molecular weight compounds were removed by the above treatment.

Here, the cyclic dimethylpolysiloxane has been pointed out in the above-mentioned documents and the like as a substance having a problem when it exists in the semiconductor manufacturing atmosphere. In addition, since cyclic dimethylpolysiloxane having a molecular weight of more than 600 has a high vapor pressure, it is difficult to volatilize, and it is unlikely that it is contained in the air in the clean room that is kept at room temperature (around 20 ° C). The organic substance having a molecular weight of 600 or less may be removed.

Therefore, according to the above treatment, most of the cyclic dimethylpolysiloxane having n of 8 or less is removed from the filter. Therefore, if the filter after the treatment is installed in the air introduction path of the clean room, the inside of the clean room will be reduced. It is possible to create an atmosphere that does not contain organic substances that pose a problem in semiconductor manufacturing.

Regarding the aliphatic hydrocarbon, in each sample, decane having 10 to 13 carbon atoms to tridecane was removed, but tetradecane having 14 or more carbon atoms to hexadecane was not removed. Here, at a normal operating temperature, an aliphatic hydrocarbon having more carbon atoms than tridecane having a carbon number of 13 (molecular weight 184) is unlikely to exist in the clean room.
Most of what should be removed by the treatment is removed. Therefore, by installing the filter after the treatment in the air introduction path of the clean room, the inside of the clean room can be made an atmosphere containing no aliphatic hydrocarbon.

Regarding aromatic hydrocarbons, No. 3
In No. 7 and No. 7, toluene and xylene accounted for about 90% of the organic matter contained in the filter before treatment, and most of them were removed but were slightly detected.

Most of the phenols and esters were removed by the above treatment. Furthermore, comparing the amounts of organic substances contained in the filters before and after the treatment, it can be seen that a large amount of organic substances are removed by the treatment. <Investigation of organic matter removal state by treatment condition: No. 9 to 17
> The above-mentioned organic substance removal treatment was performed by changing the treatment temperature and the treatment time for each sample. In addition, for the filters after the treatment, the treatment for the above-mentioned evaluation is performed in No.
The same conditions were used.

Tables 3 and 4 below show the results of the type of filter, the treatment conditions, the state of removal and remaining of organic substances, and the appearance of the filter after treatment for each sample.

[0045]

[Table 3]

[0046]

[Table 4]

Table 3 summarizes ULPA-1, but No. 9 has a treatment temperature of 23 ° C., which is room temperature.
The aliphatic hydrocarbons D4 to D8 and decane to tridecane are not removed even after the time treatment. Also, No. 110
Since the treatment temperature is 70 ° C., the removal degree of organic substances is higher than that of No. 9, but D8 and DOP remain.

Nos. 11 to 13 have treatment temperatures of 130 to 19
Since it is as high as 0 ° C., compared with No. 2, even if the total flow rate of high-purity air is low, it has the same or higher organic substance removing effect. But,
Regarding No. 13, when the filter after the treatment was inspected, it was found that the adhesive bonding the aluminum frame and the filter cloth had deteriorated, and the treatment temperature was too high at 190 ° C.

Table 4 shows a summary of ULPA-2. Since No. 14 has a low treatment temperature of 50 ° C., D4 to D8 which are components to be removed and decane to tridecane of the aliphatic hydrocarbon are aromatic. Hydrocarbons were also not removed. In addition, since No. 15 had a relatively low treatment temperature of 70 ° C., tridecane, an aliphatic hydrocarbon, remained among the components to be removed. No. 16 and 17 have a processing temperature of 1
Since it is as high as 30 ℃ and 160 ℃, tridecane is also D4-D8.
Was also removed. Further, the phenols contained in ULPA-2 are not removed by the treatment at 130 ° C. or lower,
It was found to be removed by treatment at 160 ° C. <Evaluation test of clean room with treated filter: No.18-26> The walls and floor of the clean room are made of inorganic material or organic material, and four kinds of filters installed at the air sampling port and clean air As the filter installed at the outlet, a filter that has been subjected to the organic substance removal treatment (treated filter) or a filter that has not been treated (untreated filter) under the conditions shown in Table 1 is used, and the room temperature is 23 ° C. The fan was operated so that the air flow rate from the air outlet was 40% and the air flow rate from the air outlet was 0.5 m / s, and the organic substances contained in the air in the clean room after 24 hours were analyzed.

As a method for analyzing the organic substances contained in the air in this clean room, about 10 liters of air at a height of 1.5 m from the floor located away from the outlet in the clean room, and Tenax trap are used. Collect the sample into a collecting tube, and collect the Tenax collecting tube from a TCT (Thermal Desorption Corporation) which is an accessory device of the above-mentioned GC / MS device.
ld Trap Injector), the organic matter was desorbed from there and concentrated, and then introduced into the GC / MS apparatus to analyze the content of the organic matter and the type of the contained organic matter.

As a wall made of an inorganic material constituting a clean room, a fitting type panel (inorganic partition) made of an inorganic non-combustible material was used, and this panel was assembled without using an organic sealing material. As the floor made of an inorganic material, a floor surface with a stainless steel plate attached was used. Further, a duct having an inner surface coated with aluminum was used as the duct connecting the air sampling port and the clean air blowing port.

Further, it was confirmed by the following method that these are made of a material in which substantially no organic matter is generated. That is, the material cut into a few mm square is put in a vial and sealed, and the gas generated when it is heated to 150 ° C.
Inject into C / MS instrument and analyze. Then, the generated organic substances are quantified from the obtained total ion chromatogram and mass spectrometry data, and the compound name of each peak is qualitatively analyzed and confirmed. As a result, if the amount of organic substances generated per 1 g of the sample is 10 μg or less in terms of toluene, it is considered that the material does not substantially generate organic substances.

As a result of analyzing the above-mentioned inorganic partition by this method, it was found to be 0.1 per 1 g of the sample in terms of toluene.
μg. Therefore, in the clean room composed of the wall made of the inorganic partition and the stainless steel surface floor, when the internal air contained organic matter, the organic matter was installed at the air sampling port and the blowing port. It can be judged that it was caused by the filter.

In Nos. 18 to 21, a fan filter incorporating ULPA-1 was installed at the outlet, and in Nos. 22 to 26, ULPA-2 was used as a circulating fan without using a fan filter. Built in.

Tables 5 and 6 show the filter construction, interior material construction, and organic matter analysis results of each sample in the clean room.

[0056]

[Table 5]

[0057]

[Table 6]

As can be seen from Table 5, in No. 18, since all the filters that have been subjected to effective organic substance removal treatment are used, the amount of organic substances contained in the air in the clean room is It was a low value of 263 ng / m ³ . This is a remarkably low value of 1/100 as compared with the value of 25800 ng / m ^{3 in} the case of No. 21 which is the same as No. 19 except that all the filters are not subjected to the above treatment, It can be seen that the concentration of organic substances in the air in the clean room is significantly reduced by using the filter after performing the above treatment. Further, in the air in this clean room, cyclic dimethyl polysiloxane, which is a defective substance when present in the semiconductor manufacturing atmosphere, was not detected.

No. 21 has a filter configuration of No. 21.
Same as No. 18, but since the walls and floor of the clean room are organic materials, the amount of organic substances contained in the air in the clean room is 823000 ng / m ^{3 which} is abnormally high. Dioctyl phthalate (DOP) and dibutyl phthalate (DBP) due to the plasticizer were detected.

Further, in No. 19, since the pre-filter and the medium-performance filter were untreated, the organic matter content was doubled as compared with No. 18, but No. 20
Compared with, the organic matter content was extremely low. Therefore, it is not necessary to perform the above-mentioned organic substance removal treatment on all the filters, and it can be said that it is effective that the above treatment is applied to a high-performance filter such as a ULPA filter or a HEPA filter.

On the other hand, Nos. 22 to 26 shown in Table 6 are examples of the case where the air in the clean room is circulated by the circulation fan, and No. 22 assumes that all the filters have been subjected to the organic substance removal treatment. The concentration of organic substances in the air in the clean room is the lowest.
The o.24 was partially untreated, but the high-performance filter was subjected to the above-mentioned treatment, so that the organic matter concentration was relatively low. On the other hand, in Nos. 25 and 26, as in Nos. 20 and 21 in Table 5, the organic matter concentration was high.

In the apparatus for removing organic matter used in this embodiment, the high-purity air introduced into the autoclave 1 passes through the air passage surface of the air filter 6 from the lower side to the upper side. However, the flow path of the introduced air does not necessarily have to pass through the air filter 6 in this way. However, it is preferable that the flow path of the introduced air passes through the air filter 6 in this way, because the volatilized organic substances are entrained in the introduced air and are most efficiently removed from the autoclave 1.

[0063]

As described above, claims 1 and 2
According to the method of using the air filter described above, since the concentration of the organic gas in the clean room is reduced, it is possible to reduce the contamination of organic substances in the clean room.

In particular, according to the method of claim 2, since the removal efficiency of the organic substances is high, the time required for the organic substance removal processing can be shortened. Further, according to the method for producing an air filter of claim 3, since an air filter which is unlikely to be a source of pollution of organic matter is obtained, if the obtained air filter is used in a clean room, organic matter pollution in the clean room can be reduced. .

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus used in Examples for an organic substance removal treatment of an air filter.

[Explanation of symbols]

 1 Autoclave (closed container) 2 Cylinder (clean gas) 6 Air filter

Claims (3)

[Claims] 1. An air characterized in that a dry air filter for collecting airborne particulate matter is subjected to a treatment for removing organic substances, and then the air filter is arranged in an air introduction path of a clean room. How to use the filter. 2. The treatment for removing the organic matter is carried out by placing the air filter in a closed container at least the inner surface of which is made of an inorganic material and keeping the temperature of the air filter within a predetermined range. The method of using the air filter according to claim 1, which is a process of passing a clean gas. 3. A method for producing a dry air filter for collecting airborne particulate matter used in a clean room, wherein as a finishing treatment, the air filter is placed in a closed container at least the inner surface of which is made of an inorganic material. ,
With the temperature of the air filter held at a predetermined value,
A method for producing an air filter, comprising a step of passing a clean gas through the container to remove organic substances from the air filter.