JP3381806B2 - Vacuum exhaust gas filter - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to vacuum exhaust gas filters for semiconductor manufacturing processes. More specifically, the present invention relates to a vacuum exhaust gas filter that can quickly capture gas, mist, and dust-like substances discharged from a vacuum exhaust system of a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, since gas, mist and dusty substances discharged from a vacuum exhaust system are harmful, it is generally equipped with a detoxification equipment. Conventionally, as an adsorbent used for such a detoxification equipment, an ion exchange resin and a zeolite have been mentioned, but there is a drawback that a large equipment is required because of a slow capturing speed. In addition, the length of the piping that connects the detoxification equipment to the vacuum pump becomes longer, and the gas becomes mist or dust and easily precipitates in the piping, causing clogging of the piping. However, it has a drawback that the operation rate is lowered at present. Further, there is a drawback that the adsorbent needs to be replaced even if the adsorbent has a remaining adsorbing ability because the deposition occurs in the detoxification equipment and the pressure loss increases.

[0003]

The object of the present invention is to eliminate the above-mentioned drawbacks and to capture with a filter before the gas discharged through a vacuum pump becomes mist or dust and deposits in piping. Therefore, it is an object of the present invention to provide a filter that facilitates maintenance of the exhaust system and reduces the cost burden on the user.

[0004]

The above-mentioned object of the present invention is to achieve acrylonitrile containing 50% by weight or more of acrylonitrile.
0.1-6.0 m obtained by treating a ronitrile fiber
This is achieved by a vacuum exhaust gas filter for a semiconductor manufacturing process vacuum exhaust system, which comprises an aggregate of fibers containing mol / g of ionic groups. As such an ionic group, a cation is preferable, and the aggregate of fibers is 0.01 to 0.5.
The invention is more preferably achieved by having a density of 0 g / cm ³ and by forming the aggregate into a hollow cylindrical shape.

The present invention will be described in detail below. Acrylonitri
Acrylonitrile fiber containing 50 wt% or more of
As the fiber containing the ionic group obtained by the treatment ,
The content of the ionic group is 0.1 to 6.0 mmol / g.
Ri, the following method is needed use suitably.

As a fiber containing an anionic group, the method described in Japanese Patent No. 1453805 is suitable. That is, the starting acrylic fiber is a fiber formed of an AN polymer containing 50% by weight or more of acrylonitrile (hereinafter referred to as AN), and may be in the form of short fiber, tow, non-woven fabric, or the like. As a method of imparting an anionic group to the AN fiber, a nitrile group (hereinafter, referred to as a CN group) is converted into a carboxyl group by alkaline hydrolysis.

The concentration of the aqueous alkali metal hydroxide solution used during the hydrolysis treatment is 6.0 mol / 1000 g or more, and the metal hydroxides used are Na, K and L.
Examples thereof include hydroxides of alkali metals such as i or a mixture thereof. Further, it is desirable that the treatment amount of the alkali metal hydroxide aqueous solution is 4 parts by weight or more per 1 part by weight of the fiber. The reaction conditions such as temperature conditions or treatment time when the above alkali metal hydroxide aqueous solution is allowed to act include the sample form of the fiber, the fine structure of the polymer such as crystallinity, the alkali metal hydroxide aqueous solution concentration, etc. However, it is impossible to unambiguously define the preferred condition range, but in general, the higher the temperature, the higher the reaction rate and the advantageous effect of the treatment. It is desirable to use the temperature conditions of. The anionic group referred to here has the property of becoming an anion by being ionized in an aqueous medium, and includes, for example, a sulfonic acid group and a phosphoric acid group in addition to the carboxyl group.

Fibers containing cationic groups are described in the literature Stella Dragan, G .; Grigoriu, D
ie Angewandte Makromoleku
lare Chemie 200 (1992) 27-
The method described in 36 is preferred. That is, A
By treating an AN-based fiber containing 50% by weight or more of N with a chemical agent containing an amino group, an amino group is imparted by a reaction with a CN group. The bath conditions for the amination treatment here are H ₂ O / CN group = 2/1, amine / CN group = 5/1, treatment temperature = 108 ° C., treatment time =
2 to 15 hours.

The drug is N, N-dimethyl-1,2.
-Diaminoethane, N, N-dimethyl-1,3-diaminopropane, N, N-diethyl-1,3-diaminopropane and the like can be mentioned. The term "cationic group" as used herein has a property of becoming a cation by being ionized in an aqueous medium. For example, an amino group, a secondary amino group, and a
There are primary amino groups, quaternary ammonium groups, and the like.

The ionic group content of the fibers used in the filter is generally 0.1 to 6.0 mmol / g, preferably 1.0 to 5.5 mmol / g. In addition, when the ionic group is less than 0.1 mmol / g, the effect is hard to appear. If it exceeds 6.0 mmol / g, the tensile strength as a fiber becomes weak and the processability of a filter or the like becomes remarkably poor.

The density of the filter is 0.01 to 0.5.
0 g / cm ³ , preferably 0.02-0.40 g / cm
³ , more preferably 0.03 to 0.10 g / cm ³ . If the density is less than 0.01 g / cm ³ , it is likely to be deformed due to pressure change and the trapping function will not be exhibited.
On the other hand, when it exceeds 0.50 g / cm ³ , the air permeability is deteriorated, the pressure loss becomes large even with a small trapping amount, and the filter life becomes extremely short.

The filter is preferably formed in a hollow cylindrical shape. In this case, the ratio of diameter to height is generally 1: 0.5 to 20, preferably 1: 1 to 10. The hollow cylindrical shape is superior to other shapes in form stability against pressure change and moldability, and since the filter volume per equipment volume can be increased, the equipment volume can be reduced. The term "hollow cylindrical shape" as used in the present invention means that the outer shell of the filter has a hollow cylindrical shape, and includes, for example, a pleat shape and, in some cases, a hollow truncated cone shape.

The molding of the filter may be carried out by any method. For example, when the above-mentioned fiber containing an anionic group is used, 10 to 15% by weight of water is added and then the hollow is formed. It is charged into a cylindrical molding machine and blown with hot air at 60 ° C. to dry it. Examples of other methods include a method in which heat-fusible fibers are mixed and then heat-fused, a method in which a non-woven fabric or yarn is formed and then wound into a tubular object, and the like.

[0014]

The reason why the present invention rapidly captures gas, mist and dust-like substances has not been fully clarified, but it is generally considered as follows.

That is, the gas in contact with the filter is more likely to adhere to the fibers due to the mist or dust formation of the gas due to the temperature decrease and the action of the ionic groups.

Since the trapping efficiency of the gas, mist and dust-like substance is obviously different depending on the type of the ionic group, it is clear that the trapping is largely related to the electric action.

[0017]

The present invention will be described below with reference to Examples.
The scope of the invention is not limited to only these examples.

The amount of ionic groups, pressure loss, trapping amount, trapping efficiency and tensile strength were determined by the following methods.

(1) Carboxyl group (mmol / g) About 0.5 g of the test fiber dried to a constant weight is precisely weighed (Xg).
70 ml of 0.1N sodium hydroxide aqueous solution
Is added and left for 30 minutes, then filtered through a glass filter and washed with water by adding about 50 ml of ion-exchanged water. This washing with water is repeated 3 times. Phenolphthalein was added to the filtrate, and titration (Yml) was performed with a 0.1N-hydrochloric acid aqueous solution until the coloration disappeared, which was calculated from the following formula.

[Equation 1]

(2) Tertiary amino group (mmol / g) About 0.5 g of the test fiber dried to a constant weight is precisely weighed (Xg).
Then, add 70 ml of 0.1N hydrochloric acid aqueous solution to this and leave it for 30 minutes, then filter with a glass filter to obtain about 50 m.
l of ion-exchanged water is added and the mixture is washed with water. This washing with water is repeated 3 times. Phenolphthalein was added to the filtrate, and the mixture was washed with O. Titration with 1N-sodium hydroxide aqueous solution (Ym
l) and calculated from the following formula.

[Equation 2]

(3) Pressure loss (cm-Hg) A U-shaped manometer into which mercury was injected was connected before and after the filter, and the value was obtained by subtracting the height before the filter from the height of the mercury column after the filter. (4) Capture amount (g) It was calculated from the difference between the filter weight before use (Xg) and the filter weight after use (Yg). Captured amount (g) = Y−X

(5) Capture efficiency (%) It was calculated from the capture amount (Yg) with respect to the total gas amount (Xg) in the extended use time of the filter obtained from the known gas amount per unit time of the exhaust line used.

[Equation 3]

(6) Tensile Strength (g / d) JIS L 1015 7.7 Tensile Strength 7.7.
1 According to the standard test method.

Example 1 A fiber containing an anionic group was prepared by the following method.
An AN fiber containing 90% by weight of AN was subjected to alkali hydrolysis treatment under the conditions shown in Table 1. PH of obtained fiber is 2.5
After acidification treatment with a hydrochloric acid aqueous solution, dehydration and drying were performed, and the fiber No. 1-5 were obtained. Further, the fibers were left for 30 minutes in ammonia gas and the fiber in which the molar ratio of ammonium salt type carboxyl groups and acid type carboxyl groups was adjusted to 1: 1 was used for the filter production.

[0025]

[Table 1]

The anionic group type filter was produced by the following method. After opening the fiber containing an anionic group with a card machine, add 10 to 15% by weight of water with a sprayer and charge it into a hollow cylindrical molding machine with an outer diameter of 180 mm and an inner diameter of 90 mm to obtain a height of 130 mm. While being compressed, a hot air of 60 ° C. was blown in to dry it to obtain a molded body.

The obtained filter is a CV for semiconductor manufacturing.
It was attached after the vacuum pump of the D process vacuum exhaust system, and a gas, mist, and dust-like substance trapping experiment was conducted until the pressure loss across the filter during operation became 30 cm-Hg.
The characteristic values of the filter used and the capture results are shown in Table 2. In addition, the CVD referred to here is a chemical vapor.
Abbreviation for por position.

[0028]

[Table 2]

The trapping efficiency is 0.02 m for the amount of carboxyl groups.
At 5.6 mmol / g, it was about 6 times that of mol / g, and a clear effect of containing a carboxyl group was recognized. or,
In the trapped state, dust-like substances were laminated on both the gas inlet side and the outlet side on the filter surface. Since there are many deposits on the gas inlet side and the gas outlet side in the interior as well, it can be seen that gas passing through the filter facilitates gas mist formation or dust formation.

Example 2 A fiber containing a cationic group was prepared by the following method.
That is, an AN fiber containing 90% by weight of AN was subjected to a crosslinking treatment with hydrazine hydrate under the conditions shown in Table 3, followed by washing with water and an amination treatment with N, N-dimethyl-1,3-diaminopropane. It was Further, after washing with water, dehydration and drying, fiber No. Got 6-10.

[0031]

[Table 3]

The cationic group type filter was manufactured by the following method. After 4 parts by weight of the fiber containing a cationic group and 1 part by weight of the fiber of Table 1 (fiber No. 3) containing an anionic group were opened by a card machine and homogenized, 10 to 15 with a sprayer. A molded body was formed by the method of Example 1 by adding water in a weight percentage. The trapping experiment of the obtained filter was also conducted in the same manner as in Example 1, and the characteristic values of the filter and the trapping results are shown in Table 4.

[0033]

[Table 4]

The trapping efficiency is 0.1 mmo for the amount of tertiary amino groups.
A high result of 83% at 1 / g and 99% close to complete collection was obtained at 3.4 mmol / g or more. Also, in the trapped state, dust-like substances are laminated only on the gas inlet side on the filter surface,
Even inside, it adhered intensively to the gas inlet side. Furthermore, from the fact that no deposit was observed 2 cm or more from the surface on the gas inlet side in the thickness direction, it can be seen that the cationic group type filter is particularly excellent in trapping ability.

[0035]

[0036]

[0037]

[Comparative example]

Comparative Example 1 Polyester heat-sealing fibers containing no ionic groups were opened with a card machine and charged in the same molding machine as in Example 1 11
A 0 ° C. hot air was blown into the molded body. A capture experiment was conducted on the obtained filter in the same manner as in Example 1, and the results are shown in Table 5.

[0039]

[Table 5]

When the density is 0.07 g / cm ³ or less, the trapping efficiency is 1% or less, and the filter function is not exhibited. Density 0.
Even at 50 g / cm ³ , the trapping efficiency is as low as 4%, which is clearly inferior to the filter containing an ionic group. Further, in the trapped state, the dust-like substance is laminated only on the gas inlet side on the filter surface, and is almost evenly attached inside the filter, which indicates that the trapping is physical.

[0041]

As described above, by using this filter as an exhaust gas filter for a vacuum exhaust system for semiconductor manufacturing processes, no harm equipment is required and the exhaust system piping length can be shortened. Furthermore, since there is no maintenance of the exhaust system, it is possible to reduce costs and improve the operating rate. Further, it is possible to avoid the dangerous work such as directly handling the harmful substances.

Claims (4)

(57) [Claims] 1. Containing 50% by weight or more of acrylonitrile
0.1 ~ obtained by treating acrylonitrile fiber
A vacuum exhaust gas filter for a semiconductor manufacturing process vacuum exhaust system comprising an aggregate of fibers containing 6.0 mmol / g of ionic groups. 2. The filter according to claim 1, wherein the ionic group is a cation. 3. The density of the aggregate of fibers is 0.01 to 0.5.
It is 0 g / cm < ³ >, The filter of Claim 1 or 2 characterized by the above-mentioned. 4. The filter according to any one of claims 1 to 3, wherein the fiber aggregate is formed into a hollow cylindrical shape.