JP2009208055A - Photocatalyst filter unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst filter unit which does not release contamination gas primarily comprising hexamethyl disilazane and trimethyl silanol even when accumulating the contamination gas therein, can easily remove a deposited decomposition product on a photocatalyst filter, has a long life of an optical source, has a resistance to an alkalline gas too and can avoid the deposition of salt. <P>SOLUTION: The photocatalyst filter unit comprises: a photocatalyst filter 4, 4a disposed in a body frame 3 provided with opening parts 2, 2a on the both ends so as to face at least the both opening parts 2, 2a; a cold cathode fluorescent lamp 5 disposed between the both photocatalyst filters 4, 4a; and a fluorine resin tube 6 capable of freely transmitting photocatalytic action inducing light irradiated from the cold cathode fluorescent lamp 5, with which the cold cathode fluorescent lamp 5 is covered, whereby photocatalyst filter 4, 4a can decompose the contamination gas primarily comprising hexamethyl disilazane and trimethyl silanol, can prevent the deposition of the decomposition product to the photocatalyst filter 4, 4a and can easily remove the deposited decomposition product. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photocatalytic filter unit which is installed in a clean room or the like and removes contaminants mainly hexamethyldisilazane (HMDS) and decomposition product trimethylsilanol (TMS). In the body, a photocatalytic filter is provided facing both openings, and a cold cathode fluorescent lamp covered with a fluororesin tube through which photocatalytic reaction inducing light can pass is provided. The present invention relates to a photocatalytic filter unit.

  Manufacturing processes of semiconductors, liquid crystals, organic EL, etc. are often performed in a clean room because they are extremely disliked from contamination. In this clean room, it is necessary to appropriately and highly remove contaminants that enter or occur due to various factors. Contaminants are roughly classified into fine particles and gas. Contaminated fine particles are removed by a HEPA filter or ULPA filter, and contaminated gases are removed by an adsorption filter. Naturally, the adsorbing filter for removing pollutant gas may accumulate and re-release because the adsorbed pollutant gas is not decomposed. Also, the adsorbing filter may release the gas that is the source of contamination from its material structure. In addition, since the amount of adsorption is limited, periodic replacement work is required to maintain the specified removal performance, and it is difficult to regenerate the replaced adsorption filter. As a result, running costs tend to increase.

Therefore, the following are known as means for eliminating the disadvantages of the adsorption filter as described above.
Japanese Patent Laid-Open No. 2000-300936 JP 2003-053194 A JP 2006-255529 A

  Patent Document 1 uses a photocatalytic filter for removing pollutant gas, decomposes the pollutant gas by its photocatalytic action, and does not have the possibility of accumulating pollutant gas and releasing it again like an adsorption filter. is there.

  In Patent Document 2, a photocatalytic filter is formed by forming a film of a photocatalyst such as titanium oxide on a ceramic or metal base material so that it can be washed with water. That is, as a result of decomposing the pollutant gas by the photocatalytic action of the photocatalytic filter, decomposition products such as sulfates and nitrates are deposited on the photocatalytic filter, and the decomposition products inhibit the photocatalytic action. Therefore, the decomposition product can be easily removed by washing with water or the like, so that the performance of the photocatalytic filter can be maintained and regenerated.

Patent Document 3 discloses a photocatalytic filter comprising a ceramic base layer and a photocatalytic layer formed on the surface of the ceramic base layer, and a light source that is arranged adjacent to the photocatalytic filter and that can emit light that induces photocatalytic action. And the ceramic base layer is composed of SiO ₂ as a main component and about 21 wt% of Al ₂ O _3, and the photocatalyst layer is composed of TiO ₂ as a main component and includes SiO ₂ , and TiO ₂ in the photocatalyst layer. The weight ratio of SiO ₂ to is about 8: 2, and the surface of the photocatalyst layer is adjusted to be weakly acidic. As a result, since the amount of SiO _{2 in the} photocatalyst layer is much weaker and acidic, the adsorption and removal of basic gas such as ammonia gas, which is a polluting gas, is selectively enhanced, and in addition, the decomposition products deposited on the photocatalyst filter are It can be easily removed by washing with water, and the performance of the photocatalytic filter can be maintained and regenerated.

  In Patent Document 1, since the pollutant gas is decomposed by the photocatalytic action of the photocatalyst filter, there is no possibility that the pollutant gas accumulates and re-releases, but decomposition products generated by the decomposition of the pollutant gas accumulate on the photocatalyst filter. This decomposition product inhibits the photocatalytic action, causes a drop in performance, necessitates replacement of the photocatalytic filter, and is extremely difficult to regenerate, resulting in high running costs as in the case of an adsorption filter.

In Patent Document 2, since the pollutant gas is decomposed by the photocatalytic action of the photocatalyst filter, there is no possibility that the pollutant gas is accumulated and re-released, and even if the decomposition product is deposited on the photocatalyst filter, it can be easily removed by washing with water. However, a HMDS (abbreviation for hexamethyldisilazane) process is performed to make the wafer surface hydrophobic in the lithography process in the pre-process of semiconductor manufacturing and to improve the adhesion to the photoresist (photosensitive resin). HMDS reacts with moisture in the air and hydrolyzes to HMSO, in which ammonia (NH ₃ ) is liberated and further hydrolyzed to produce TMS (trimethylsilanol). These substances are produced in the lithography process. It becomes a serious obstacle. However, in this document, the decomposition removal performance due to the photocatalytic action of HMDS, NH ₃ , and TMS accompanying this HMDS treatment is not clear, and the yield of the product is liable to fall.

Further, in Patent Document 3, since the pollutant gas is decomposed by the photocatalyst filter, there is no possibility that the pollutant gas is accumulated and re-released, and even if the decomposition product is deposited on the photocatalyst filter, it can be easily removed by washing with water. The decomposition removal performance of No. ₃ is also good. However, the hot cathode fluorescent lamp as a light source has a relatively short life, and the glass of the lamp is chemically weak against the presence of NH ₃ , and is generated by reacting with SO ₄ ²⁻ and Cl ₂ in the air. When ammonium sulfate or ammonium chloride adheres to the glass surface, the photocatalytic action-induced light irradiation is weakened accordingly, and when the hot cathode fluorescent lamp is replaced, these attached ammonium salts may scatter and become a contamination source.

Therefore, the present invention has been made in view of the above circumstances, there is no possibility that contaminated gas accumulates and is re-released, and it can be easily removed even if decomposition products accumulate on the photocatalytic filter, and in the lithography process. Provides a photocatalytic filter unit that has good HMDS, NH ₃ , and TMS decomposition and removal performance in conjunction with HMDS treatment, and that has a long light source life, is resistant to alkaline gases, and can protect the adhesion of generated salts. The task is to do.

The present invention has been proposed in order to achieve the above-mentioned problems, and is characterized by having the following configuration.
That is, according to the first aspect of the present invention, a photocatalytic filter is provided at least at both openings in a body having openings at both ends, and a cold cathode fluorescent lamp is provided between the two photocatalytic filters. In the photocatalytic filter unit, the cold cathode fluorescent lamp is covered with a fluororesin tube through which photocatalytic induction light emitted from the cold cathode fluorescent lamp is transmissive, and hexamethyldisilazane (HMDS) contained in the air. ) And trimethylsilanol (TMS) are mainly removed.

  The invention according to claim 2 is a photocatalyst comprising one or more photocatalyst filters and the same number of cold cathode fluorescent lamps as the photocatalyst filters arranged alternately between the cold cathode fluorescent lamps and the photocatalytic filter. It is a filter unit.

  According to a third aspect of the present invention, there is provided the photocatalytic filter, wherein the photocatalytic filter is formed by forming a concave / convex surface on the surface of a ceramic three-dimensional network structure porous body using a surface layer forming ceramic and supporting the photocatalyst on the concave / convex surface. Is a unit.

  The invention according to claim 4 is the photocatalyst filter unit according to claim 1, 2, or 3, wherein the photocatalyst of the photocatalyst filter is titanium oxide.

As described above in detail, the present invention has the following effects.
According to the first aspect of the present invention, when air containing a pollutant gas mainly composed of hexamethyldisilazane (HMDS) and trimethylsilanol (TMS) is allowed to flow from one of the openings of the aircraft into the aircraft, Through the other photocatalyst filter, through the vicinity of the cold cathode fluorescent lamp, and further through the other photocatalyst filter and out of the airframe from one of the other openings. At that time, by both photocatalytic filters irradiated with photocatalytic action inducing light from the cold cathode fluorescent lamp, immediately HMDS and TMS are mainly decomposed and removed, and by decomposing the pollutant gas mainly containing HMDS and TMS, Newly generated decomposition products such as salts are guarded by a fluororesin tube and do not adhere to the surface of the cold cathode fluorescent lamp. Therefore, there is no possibility that pollutant gases mainly composed of HMDS and TMS accumulate and re-release, and furthermore, the use of a cold cathode fluorescent lamp as a light source has a long life and is strong against alkaline gases, and the generated decomposition. There is an effect that can prevent the adhesion of the product.

  Since the air containing pollutant gas mainly composed of HMDS and TMS passes through one or more photocatalyst filters and cold cathode fluorescent lamps installed alternately, the invention according to claim 2 further increases HMDS and TMS accordingly. Decomposes the main polluting gas. Therefore, the above effect can be further enhanced.

  In the invention according to claim 3, since the surface of the ceramic three-dimensional network structure porous body is formed with an uneven surface by the surface layer forming ceramic, and the photocatalyst is supported on the uneven surface, the surface area is dramatically increased. The photocatalyst is difficult to fall off due to the wider and uneven anchor effect. Therefore, in addition to the above effects, the performance of the photocatalytic filter can be improved and maintained, and there is an effect that it can be regenerated.

In the invention according to claim 4, when the photocatalyst is titanium oxide, a high catalytic effect is obtained and the polluted gas mainly composed of HMDS and TMS is decomposed. Therefore, in addition to the above effects, there is an effect that the decomposition removal performance of HMDS, NH ₃ and TMS accompanying the HMDS process in the lithography process is improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a plan view of a photocatalytic filter unit showing an embodiment of the present invention, FIG. 2 is a partially broken sectional view of the photocatalytic filter unit of FIG. 1, and FIG. 3 is a partially broken sectional view of the photocatalytic filter unit of FIG. FIG. 4 is an explanatory view of the photocatalytic filter of the photocatalytic filter unit of FIG. 1, and FIG. 5 is a cross-sectional view of the air cleaning device in which the photocatalytic filter unit of the present invention is incorporated. In the drawing, a photocatalytic filter unit 1 is provided with a photocatalytic filter 4, 4 a facing at least both openings 2, 2 a in an airframe 3 having openings 2, 2 a at both ends, and both photocatalytic filters 4, The cold cathode fluorescent lamp 5 is provided between 4a, and this cold cathode fluorescent lamp 5 is covered with a fluororesin tube 6 through which photocatalytic induction light irradiated from itself is freely transmitted, and is in the air. Hexamethyldisilazane (HMDS) and trimethylsilanol (TMS) contained are mainly removed.

  In this photocatalyst filter unit 1, a photocatalyst filter 4b and a cold cathode fluorescent lamp 5a are further provided between the cold cathode fluorescent lamp 5 and the photocatalyst filter 4a so as to be interposed between the opening 2 and the opening 2a. The photocatalytic filter 4, the cold cathode fluorescent lamp 5, the photocatalytic filter 4b, the cold cathode fluorescent lamp 5a, and the photocatalytic filter 4a are interposed. Note that the photocatalytic filters 4, 4 a, and 4 b are partitioned and installed by a partition plate 9.

  The airframe 3 has a rectangular parallelepiped shape, and has openings 2 and 2a at both ends thereof. The other portions are closed during a driving operation. A power supply box 7 for supplying electricity to the cold cathode fluorescent lamp 5 is built in the side of the machine body 3, and the side plate 8 and the like can be opened and closed for maintenance needs, and the photocatalytic filters 4, 4 a, 4 b and cold cathode fluorescent light can be opened. The structure is such that the lamps 5 and 5a can be easily removed and attached.

  As shown in FIG. 4, the photocatalytic filters 4, 4 a, and 4 b are formed on the surface of the skeleton 11 of the ceramic three-dimensional network structure porous body 10 by sintering the surface layer forming ceramic particles 12 to form the uneven surface 13. The photocatalyst is supported on the uneven surface 13. Since the skeleton 11 of the three-dimensional network structure porous body 10 has a diameter of 100 μm to 1000 μm, and the surface layer forming ceramic particles 12 have a particle diameter of 1 μm to 50 μm, the three-dimensional network structure A good irregular surface 13 is formed on the skeleton 11 of the porous body 10 to have a sufficient surface area, and the photocatalytic action induced light by the cold cathode fluorescent lamp 5 reaches the inside of the photocatalytic filters 4, 4 a and 4 b. To achieve a highly efficient photocatalytic action.

The photocatalyst is a fine powder of anatase-type titanium oxide (TiO ₂ ), and contains approximately 20% of SiO ₂ as a binder while having this as a main component. And this titanium oxide is baked on the favorable uneven | corrugated surface 13 on the frame | skeleton 11 of the three-dimensional network structure porous body 10. FIG. Therefore, the baked titanium oxide is difficult to fall off due to the anchor effect of the uneven surface 13. For this reason, the photocatalytic filters 4, 4a and 4b can prevent performance degradation and dust generation due to dropping of the titanium oxide as the photocatalyst, and the performance can be improved and maintained, and can be regenerated. Since the photocatalyst contains about 20% of SiO _{2 in} addition to titanium oxide, the surface of the photocatalyst becomes weakly acidic, and the adsorption and decomposition of a basic gas such as ammonia gas can be promoted.

  Although the cold cathode fluorescent lamps 5 and 5a are excellent from the viewpoint of durability (up to 30,000 hours), the use of ammonium salt in the presence of pollutant gas, especially ammonia gas, etc. on the glass of the surface by use. The photocatalytic action-induced light that is attached and irradiates from itself, that is, the transmittance of ultraviolet rays is reduced. Further, during exchange, adhering substances such as ammonium salts may be scattered and become a source of contamination. For this reason, the cold cathode fluorescent lamps 5 and 5 a are covered with the fluororesin tube 6.

  This fluororesin tube 6 has a low gas permeability, in other words, a low gas adhesion, has a sufficiently high corrosion resistance, and also transmits ultraviolet rays irradiated from the cold cathode fluorescent lamps 5 and 5a. Is high. Therefore, the cold-cathode fluorescent lamps 5 and 5a covered with the fluororesin tube 6 are stable against ultraviolet rays without being directly attacked by pollutant gases in the air or adhering pollutant gases and contaminants derived therefrom. Thus, when the cold-cathode fluorescent lamps 5 and 5a are replaced during maintenance, the pollutant gas and the contaminants derived therefrom are scattered to almost never become a pollution source.

  A specific material of the fluororesin tube 6 is exemplified as follows. That is, PFA (perfluoroalkoxyalkane), PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), E / TFE (ethylene, tetrafluoroethylene copolymer), FEP (perfluoro (ethylene, polypropylene), tetra Fluoroethylene, hexafluoroethylene copolymer) and the like. PFA, PTFE, etc. are suitable in terms of availability and cost.

  The above-described photocatalytic filter unit 1 may be used alone in a place where air containing a pollutant gas mainly composed of hexamethyldisilazane (HMDS) and trimethylsilanol (TMS) circulates, or You may use it incorporating in the air purifying apparatus 20 as shown in FIG. The air cleaning device 20 is arranged in a device main body 23 having an air inlet 21 and an air outlet 22 in order from the air inlet 21 toward the air outlet 22, a fan 24, a pre-filter 25, the photocatalytic filter unit 1, and a rear filter 26. Is provided. The air cleaning device 20 is installed in a clean room such as semiconductor manufacturing.

Next, the operation of the photocatalytic filter unit 1 having the above configuration will be described in a state where the photocatalytic filter unit 1 is incorporated in the air cleaning device 20.
First, when the air cleaner 20 is turned on and the cold cathode fluorescent lamps 5 and 5a are turned on and then the fan 24 is driven, hexamethyldisilazane (HMDS) and trimethylsilanol (TMS) are mainly used. The air containing the pollutant gas is introduced into the apparatus main body 23 from the air inlet 21, and the prefilter 25 removes coarse particles and dust, etc., in the air containing the pollutant gas, and the next photocatalyst. The filter unit 1 is prevented from entering. The air that has entered the photocatalytic filter unit 1 from the opening 2 sequentially passes through the photocatalytic filter 4, the cold cathode fluorescent lamp 5, the photocatalytic filter 4b, the cold cathode fluorescent lamp 5a, and the photocatalytic filter 4b, and then passes through the opening 2a. Go out of unit 1.

  Strong oxidative decomposition action generated on the photocatalytic filters 4, 4 a, 4 b due to the ultraviolet irradiation from the cold cathode fluorescent lamps 5, 5 a in the process in which the air containing the pollutant gas passes through the photocatalytic filter unit 1. The pollutant gas mainly composed of HMDS and TMS in the air is decomposed and removed by the active oxygen and OH radicals having the above. That is, the pollutant gas mainly composed of HMDS and TMS that could not be decomposed and removed by the photocatalyst filter 4 is decomposed and removed by the next photocatalyst filter 4a. Further, it is decomposed and removed by the photocatalytic filter 4b.

  In the photocatalytic filter unit 1, the air which has been decomposed and removed mainly from HMDS and TMS, passes through the rear filter 26 and exits from the air purifier 10 through the air outlet 22. Thereafter, the filter 26 can remove finer particles than the prefilter 25, for example, fine particles of about 0.1 μm, and finally removes dust from the air cleaning device 20 including the photocatalytic filter unit 1. It removes so that these dusts are not put out in the clean room which is an installation place of the air purifier 20.

Next, the effect of the photocatalytic filter unit 1 of the present invention was demonstrated as follows.
<Test Example 1>
In the photocatalytic filter unit of the present invention, HMDS (hexamethyldisilazane) adjusted to a concentration of about 50 μg / m ³ is circulated at a wind speed of 0.5 m / sec, and sampling is performed on the upstream side and the downstream side of the photocatalytic filter unit, respectively. HMDS in the gas sampled on the upstream side and the downstream side was measured, and the removal performance of HMDS was calculated.
The experimental apparatus is as shown in FIG.
1. Measurement of HMDS Using a permeator, HMDS is generated and mixed with clean air pretreated before the air supply fan of the experimental apparatus shown in FIG. 6 to adjust the concentration on the upstream side of the photocatalytic filter unit to about 50 μg / m ³ . did. Two hours after the photocatalytic filter unit was turned on, the gas for measurement was collected by aeration from an adsorption tube (filled with activated carbon) connected upstream and downstream at a suction speed of 1 L / min. The gas collected by the adsorption tube was extracted with an organic solvent and measured with a gas chromatograph-mass spectrometer (GC-MS). In this measurement, a calibration curve of standard substances of TMS (trimethylsilanol) and M2 (hexamethyldisiloxane) is prepared, and TMS and M2 concentrations in the extract are obtained from this calibration curve, and this is used to extract TMS and M2. The concentration was calculated by multiplying the amount of solvent used to determine the mass of TMS and M2 and dividing by the amount of air sampled. Furthermore, it converted into the HMDS density | concentration from these density | concentrations.
2. Measurement of ammonia 2 hours after turning on the power of the photocatalytic filter unit, the gas for measurement is captured by aeration at a suction speed of 2 L / min from a two-stage linked impinger (absorbing liquid filling) connected upstream and downstream. Gathered. The absorption liquid after being collected by the two-stage connection impinger was used as a measurement test liquid, and measured by an ion chromatograph (IC). The concentration in the air was calculated by multiplying the concentration of the target component in the absorption liquid by the amount of the pretreatment liquid to obtain the mass of the target component collected in the absorption liquid and dividing this by the amount of air sampled. Furthermore, it converted into the HMDS density | concentration from these density | concentrations.

<Test Example 2>
HMDS was measured by the same method as in Test Example 1 except that HMDS (hexamethyldisilazane) adjusted to a concentration of about 50 μg / m ³ was passed through the photocatalytic filter unit of the present invention at a wind speed of 0.35 m / sec. .

<Control Example 1>
Instead of the photocatalytic filter unit of the present invention in Test Example 1, HMDS and ammonia were measured by the same method as in Test Example 1 except that a conventional photocatalytic filter unit was used. This conventional ceramic three-dimensional network structure porous body is mainly composed of silicon carbide (SiC), the photocatalyst is composed mainly of titanium oxide (TiO ₂ ), and the weight ratio α of SiO _{2 to} TiO ₂ α ( The surface of the photocatalyst is adjusted to be neutral with SiO ₂ / TiO ₂ ) of 0.11.

<Control Example 2>
HMDS was measured in the same manner as in Test Example 1 except that HMDS (hexamethyldisilazane) adjusted to a concentration of about 50 μg / m ³ was passed through the photocatalytic filter unit of Control Example 1 at a wind speed of 0.35 m / sec. did.
The results are shown in Table 1.

  According to the results of Table 1, the test examples 1 and 2 clearly have higher removal efficiency for both HMDS and ammonia than the control examples 1 and 2, demonstrating the superiority of the present invention.

  As described above, the first embodiment of the present invention has been described, but the specific configuration is not limited to this, and modifications and additions within the scope not departing from the gist of the present invention, other combinations in each claim, It should be understood that this is possible as appropriate.

The photocatalyst filter unit of the present invention can be used when there is no risk of re-release of the once trapped pollutant gas, and the decomposition product after decomposing the pollutant gas is easily removed even if it accumulates on the photocatalyst filter. Highly reliable, especially to improve the decomposition and removal performance of HMDS, NH ₃ , and TMS associated with HMDS treatment in lithography process, and has a long light source life and resistance to alkaline gases, and protects and prevents the adhesion of generated salts The availability becomes extremely high when it is desired to improve the performance.

  It is a top view of the photocatalyst filter unit which shows the embodiment of the present invention (example 1).   FIG. 2 is a partially broken cross-sectional view of the photocatalytic filter unit of FIG. 1 (Example 1).   FIG. 2 is a partially broken cross-sectional view of the photocatalytic filter unit of FIG. 1 (Example 1).   (Example 1) which is explanatory drawing of the photocatalyst filter of the photocatalyst filter unit of FIG.   It is sectional drawing of the state which incorporated the photocatalyst filter unit of this invention in the air purifying apparatus (Example 1).   It is a perspective view of the experimental apparatus for demonstrating the effect of the photocatalyst filter unit of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photocatalyst filter unit 2, 2a Opening part 3 Machine body 4, 4a, 4b Photocatalyst filter 5, 5a Cold cathode fluorescent lamp 6 Fluororesin tube 7 Power supply box 8 Side plate 9 Partition plate 10 Three-dimensional network structure porous body 11 Skeleton 12 Surface layer Ceramic particles for forming 13 Uneven surface 20 Air cleaning device 21 Air inlet 22 Air outlet 23 Device main body 24 Fan 25 Pre-filter 26 Post filter

Claims (4)

  A photocatalytic filter unit in which a photocatalytic filter is provided at least facing both the openings in the body having openings at both ends, and a cold cathode fluorescent lamp is provided between the photocatalytic filters. The cold cathode fluorescent lamp is covered with a fluororesin tube through which photocatalytic induction light radiated from itself is freely transmitted, and mainly contains hexamethyldisilazane (HMDS) and trimethylsilanol (TMS) contained in the air. A photocatalytic filter unit that is removed.   2. The photocatalytic filter unit according to claim 1, wherein one or more photocatalytic filters and the same number of the cold cathode fluorescent lamps as the photocatalytic filters are alternately disposed between the cold cathode fluorescent lamps and the photocatalytic filter.   3. The photocatalytic filter unit according to claim 1, wherein the photocatalytic filter is formed by forming a concave / convex surface on a surface of a ceramic three-dimensional network porous body with a surface layer forming ceramic and supporting the photocatalyst on the concave / convex surface. .   The photocatalytic filter unit according to claim 1, wherein the photocatalyst of the photocatalytic filter is titanium oxide.

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