JP2011104480A - Apparatus and method for decomposition of gaseous pollutant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for decomposition of gaseous pollutant with improved removal efficiency of the gaseous pollutant. <P>SOLUTION: The apparatus for decomposition of gaseous pollutant includes: a container 1 into which gas 6 containing a trimethylsilanol is introduced; a photocatalyst 2 provided in the container 1; a light source 4 that generates a light to activate the photocatalyst 2; and a dehumidifying means 5 to lower the humidity in the container 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus and method for decomposing gaseous pollutants.

  In recent years, in clean rooms that manufacture the most advanced semiconductor elements, chemical contamination such as gaseous contaminants (AMC: Airborne Molecular Contaminants) in addition to fine particles has become a major problem as semiconductors are highly integrated and devices are becoming finer. It has become. AMC is adsorbed on the surface of a silicon wafer or the surface of a glass substrate, causing a problem in the product.

  Trimethylsilanol (TMS) is known as one of AMC. TMS is generated from a silicon seal material used as a seal material in a clean room.

  TMS also occurs for the following reasons. In the photolithography process in semiconductor manufacturing, hexamethyldisilazane is used to improve the adhesion between the resist and the wafer. This hexamethyldisilazane is easily hydrolyzed. When hexamethyldisilazane is hydrolyzed, TMS and ammonia gas are generated.

  The following methods have been examined as a countermeasure against conventional TMS contamination.

  Patent Document 1 discloses that a conventional semiconductor manufacturing apparatus equipped with a fan filter unit in which a dust removing filter and a chemical filter are combined cannot sufficiently prevent generation of haze and rupture of a resist film. In order to solve this problem, it has been proposed to use a fan filter unit that identifies a causative substance and does not generate the causative substance. Also disclosed is a method for manufacturing a semiconductor device capable of preventing the generation of haze and the rupture of a resist film.

  Patent Document 2 discloses that a sealing material used in a clean room for manufacturing a semiconductor element is a fluorine-based sealing material, and further has electrical insulation, mechanical stability, aging resistance, and processing. A method of suppressing the generation of TMS by covering the surface of a sealing material exposed in a clean room with a material excellent in property and adhesiveness is shown. In the photolithography process, a TMS countermeasure is taken in which a chemical filter using activated carbon is installed at the outside air inlet into the apparatus. Furthermore, a method is also shown in which a spare buffer chamber filled with an inert gas is provided in a semiconductor manufacturing apparatus, and a semiconductor element member contaminated in the spare buffer chamber is heat-treated.

  As described above, the conventional countermeasures against TMS contamination are mainly the use of a member that does not generate TMS and the adsorption removal by a chemical filter. However, these countermeasures are limited in improving the removal efficiency. Therefore, the conventional countermeasure against TMS contamination is a cause of reducing the product yield.

Japanese Patent Laid-Open No. 11-45845 JP 2007-27783 A

  It is an object of the present invention to provide a gaseous pollutant decomposition apparatus and decomposition method capable of improving the removal efficiency of gaseous pollutants.

  The apparatus for decomposing gaseous pollutants according to one aspect of the present invention includes a container into which a gas containing trimethylsilanol is introduced, a photocatalyst provided in the container, and a light source that generates light for activating the photocatalyst. And dehumidifying means for lowering the humidity in the container.

  A method for decomposing a gaseous pollutant according to an aspect of the present invention includes a step of exposing a gas containing trimethylsilanol to an atmosphere having an absolute humidity of a certain value or less to generate hexamethyldisiloxane (HMDSO) from the trimethylsilanol. And a step of decomposing the trimethylsilanol by oxidation by a photocatalytic reaction.

  ADVANTAGE OF THE INVENTION According to this invention, the decomposition apparatus and decomposition method of gaseous pollutant which can aim at the improvement of the removal efficiency of gaseous pollutant can be implement | achieved.

The figure which shows typically schematic structure of the TMS decomposition | disassembly apparatus of 1st Embodiment. The figure which shows the time change of the density | concentration of TMS and HMDSO after passing through a photocatalyst about each of TMS and HMDSO. The figure which shows the time change of the density | concentration of the carbon dioxide which generate | occur | produced by the photocatalytic reaction about each of TMS and HMDSO. The figure which shows the relationship between absolute humidity and HMDSO density | concentration. The figure which shows the lifetime of embodiment and the conventional TMS decomposition | disassembly apparatus. The figure which shows typically schematic structure of the TMS decomposition | disassembly apparatus of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the outline | summary of the removal apparatus and removal method of the gaseous pollutant of embodiment is demonstrated.

  The present inventors include a container in which oxidative decomposition of TMS is performed, a member (photocatalyst member) including a photocatalyst provided in the container, a light source that generates light for activating the photocatalyst, The TMS decomposition apparatus provided with the dehumidification filter installed in was produced.

  TMS gas was introduced into a container that is in a low humidity environment by a dehumidifying filter. As a result, hexamethyldisiloxane (HMDSO), which is a dimer of TMS, was generated in the container. It is considered that HMDSO was generated because the dehydration condensation reaction of TMS occurred because the inside of the container was in a low humidity environment.

  The reason for generating HMDSO from TMS is that HMDSO, which is a dimer, can be more efficiently oxidatively decomposed than TMS. Hereinafter, this point will be further described.

  When TMS is oxidatively decomposed by a photocatalytic reaction, the concentration of carbon dioxide generated as a reaction product decreases with time. This decrease in the concentration of carbon dioxide means a decrease in photocatalytic activity.

  However, HMDSO, which is a dimer of TMS, is oxidatively decomposed by a photocatalytic reaction, but the concentration of carbon dioxide generated as a reaction product does not decrease over time. This means that when HMDSO is oxidatively decomposed by a photocatalytic reaction, a decrease in the activity of the photocatalyst is suppressed and HMDSO can be efficiently oxidatively decomposed.

  The photocatalyst is, for example, titanium oxide. Titanium oxide has a high photocatalytic activity and is useful for the decomposition of TMS.

  The light source is, for example, a light source that generates ultraviolet light having a wavelength of 380 nm or less. The reason for using ultraviolet light having a wavelength of 380 nm or less is that the photocatalytic reaction is promoted.

  The ultraviolet light is, for example, ultraviolet light generated by corona discharge generated by applying a high voltage between the electrodes. In this case, the corona discharge generates ultraviolet light necessary for causing a photocatalytic reaction, and also generates ozone that contributes to oxidative decomposition, so that TMS can be decomposed and removed more effectively.

  In addition, if a chemical filter that adsorbs TMS is installed in the subsequent stage of the above TMS decomposition apparatus (container, photocatalyst member, light source, dehumidification filter), TMS that could not be removed by oxidative decomposition can be removed by adsorption, which is more effective. TMS can be removed.

  Hereinafter, the TMS decomposition apparatus according to the embodiment will be described in more detail.

  FIG. 1 is a diagram schematically illustrating a schematic configuration of the TMS decomposition apparatus according to the first embodiment.

  The TMS decomposition apparatus of this embodiment generates a light for activating the photocatalyst member 3, a photocatalyst member 3 including the photocatalyst 2 provided in the vessel 1 in which the oxidative decomposition of TMS is performed. A light source 4 and a dehumidifying filter 5 installed in the container 1 are provided.

  As the light source 4, an ultraviolet lamp (manufactured by Toshiba Lighting & Technology Co., Ltd.) having a wavelength of 380 nm or less was used. At this time, instead of the ultraviolet lamp, an LED lamp that can emit ultraviolet light, or a lamp that generates ultraviolet light by corona discharge generated by applying a high voltage between the electrodes may be used.

  Here, as the photocatalyst member 3 including the photocatalyst 2, a titanium oxide sol (photocatalyst 2) is formed on the surface of a ceramic three-dimensional network substrate (size: 65 × 70 × 6 mm, porosity: 80 to 90%). An average particle system: 30 nm) was used, and a photocatalyst carrier fixed by heat treatment was used.

  At this time, the concentration of the photocatalyst of the photocatalyst carrier relative to the three-dimensional network substrate was 12 wt%. The concentration of the photocatalyst is not limited to 12 wt%, and may be in the range of 8-20 wt%, for example.

  As a material for the photocatalyst carrier, in addition to a ceramic substrate, a honeycomb substrate made of activated carbon or silica gel may be used. The photocatalyst member 3 and the light source 4 are arranged so that the upper surface of the photocatalyst member 3 and the light emission surface of the light source 4 are parallel to each other.

  Here, as the dehumidifying filter 5, a filter using silica gel as a dehumidifying agent was used. Instead of silica gel, zeolite, activated carbon or activated carbon fiber as a dehumidifying agent may be used.

  The dehumidifying filter 5 was provided at the front stage of the apparatus, that is, at the inlet side for introducing the gas 6 (in front of the photocatalytic member 3). Thereby, HMDSO produced by dehydrating and condensing TMS can be efficiently supplied to the photocatalytic member 2.

  The gas 6 introduced from the entrance (not shown) of the TMS decomposition apparatus passes through the dehumidifying filter 4. At this time, the absolute humidity in the container 1 is set to 30% or less (low humidity) by the dehumidifying filter 4. As a result, TMS in the gas 6 undergoes dehydration condensation, and HMDSO is generated from TMS.

  The gas containing HMDSO passes through the photocatalytic member 3. At this time, the photocatalytic member 3 is irradiated with light (ultraviolet light) from the light source 4. In addition, the photocatalyst member 3 is arranged so that the gas containing HMDSO is introduced from the direction perpendicular to the side surface (the surface on the gas introduction side) of the photocatalyst member 2.

  In the photocatalyst member 3, HMDSO is decomposed by a photocatalytic reaction by the photocatalyst 2 to generate carbon dioxide. Therefore, the gas 7 containing carbon dioxide is discharged from the outlet (not shown) of the TMS decomposition apparatus.

  Using the above-described TMS decomposition apparatus, TMS concentration and HMDSO concentration at the exit of the TMS decomposition apparatus were measured for TMS and HMDSO when the photocatalyst 2 was not irradiated with ultraviolet light. In addition, the amount of carbon dioxide generated was compared for each of the cases where ultraviolet light was irradiated and not, and the superiority of HMDSO was examined. Specifically, it is as follows.

The TMS concentration 50ppm of at the entrance to the TMS cracker, is introduced into the TMS cracker under conditions of a flow rate 3.0 L / min, the ultraviolet light in the ultraviolet light intensity 2.0 mW / cm ² to the photocatalyst 2 with the light source 4 When irradiated, the TMS and carbon dioxide concentrations at the outlet of the TMS decomposition apparatus were measured (Experiment 1).

The HMDSO concentration at the entrance of 20ppm of TMS cracker, is introduced into the TMS cracker under conditions of a flow rate 3.0 L / min, the ultraviolet light in the ultraviolet light intensity 2.0 mW / cm ² to the photocatalyst 2 with the light source 4 The concentrations of HMDSO and carbon dioxide at the outlet of the TMS decomposition apparatus when irradiated were measured (Experiment 2).

  In the case where ultraviolet light was not irradiated in Experiment 2, the concentrations of HMDSO and carbon dioxide at the outlet of the TMS decomposition apparatus were measured as in Experiment 2 (Experiment 3).

  In the case where ultraviolet light was not irradiated in Experiment 1, the concentrations of TMS and carbon dioxide at the outlet of the TMS decomposition apparatus were measured as in Experiment 1 (Experiment 4).

  FIG. 2 shows changes over time in the concentrations of TMS and HMDSO at the outlet of the TMS decomposition apparatus in the above four experiments 1-4.

  In FIG. 3, the time change of the density | concentration of the carbon dioxide in the exit of a TMS decomposition apparatus in the said four experiments 1-4 is shown.

  As shown in FIG. 2, when TMS is introduced (Experiment 1 and Experiment 4), TMS is removed (decomposed) after passing through the photocatalyst regardless of the presence or absence of ultraviolet irradiation, so the TMS concentration at the outlet of the TMS decomposition apparatus is The value is very low at the start of measurement. However, as shown in FIG. 2, it can be seen that the TMS concentration at the outlet of the TMS decomposition apparatus tends to increase with the passage of time. This is presumably because TMS is adsorbed on the surface of the photocatalyst and the catalytic action is lowered.

  When UV irradiation is present (Experiment 1), the performance of decomposing TMS is higher than when there is no UV irradiation (Experiment 4), and the TMS concentration at the outlet of the TMS decomposition apparatus is lower, but the surface of the photocatalyst TMS was adsorbed on the catalyst, and the catalytic action decreased with time.

  On the other hand, when HMDSO is introduced (Experiment 2 and Experiment 3), there is no change in the HMDSO concentration at the exit of the TMS decomposition apparatus (Experiment 3) if there is no ultraviolet irradiation, and if there is ultraviolet irradiation, TMS The HMDSO concentration at the outlet of the cracker is approximately halved (Experiment 2). That is, it was confirmed that HMDSO was decomposed by the photocatalytic reaction.

  Moreover, from FIG. 3, when there was ultraviolet irradiation (Experiment 1 and Experiment 2), the generation of carbon dioxide was confirmed, and it was confirmed that TMS and HMDSO were decomposed by the photocatalytic reaction. However, when there was no ultraviolet irradiation (Experiment 3 and Experiment 4), carbon dioxide was not detected.

  Furthermore, from FIG. 3, even when there is ultraviolet irradiation, when TMS is introduced (Experiment 1), the concentration (generated amount) of carbon dioxide decreases with time, but when HMDSO is introduced. (Experiment 2) shows that the concentration (production amount) of carbon dioxide hardly changes over time. That is, with respect to decomposition (removal) using a photocatalytic reaction, it is more efficient to decompose TMS by dehydrating and condensing it into HMDSO and then decomposing with photocatalyst, rather than decomposing TMS with photocatalyst. It turns out that decomposition becomes possible.

  FIG. 4 is a diagram showing the relationship between the absolute humidity in the container of the TMS decomposition apparatus and the concentration of HMDSO (HMDSO concentration) generated by decomposition of TMS introduced into the container by a photocatalytic reaction. The TMS concentration at the entrance of the TMS decomposition apparatus was 50 ppm.

  From FIG. 4, it can be seen that when the absolute humidity is higher than 35%, the increase in the HMDSO concentration is not observed, but when the absolute humidity is 35% or less, particularly 30% or less, the increase in the HMDSO concentration is clearly seen. The same tendency was observed even when the TMS concentration was other than 50 ppm. That is, it was found that in order to reliably decompose TMS into HMDSO, it is important that the absolute humidity in the container 1 is not more than a certain value, that is, not more than 35%. When the absolute humidity was 30% and 50%, the amount of HMDSO produced was 1 to 3 ppm.

  Further, FIG. 4 shows that the HMDSO concentration is 10 ppm when the absolute humidity is 5% or less. The same tendency was observed even when the TMS concentration was other than 50 ppm. That is, it was found that HMDSO can be efficiently generated from TMS in a low humidity environment, particularly in a low humidity environment with an absolute humidity of 5% or less.

  The present inventors investigated the lifetime of the TMS decomposition apparatus using the photocatalyst of the embodiment and the lifetime of the TMS decomposition apparatus using the conventional chemical filter. The result is shown in FIG. Here, the time until the TMS removal rate falls below 90% is defined as the lifetime. The lifetime of the conventional TMS decomposition apparatus is 1000 hours, whereas the lifetime of the TMS decomposition apparatus of the present embodiment is 2000 hours, and the lifetime is doubled.

  Thus, when the TMS decomposition apparatus of the embodiment is used, HMDSO is generated from TMS by exposing a gas containing TMS (gaseous pollutant) in an atmosphere having an absolute humidity of a certain value or less, and HMDSO is decomposed by oxidation by a photocatalytic reaction. As a result, the TMS decomposition method capable of improving the removal efficiency (decomposition efficiency) of TMS can be implemented, and therefore, it is possible to suppress a decrease in product yield due to TMS contamination. Moreover, since the TMS decomposition apparatus of this embodiment has a long lifetime, the TMS decomposition apparatus of this embodiment and the TMS decomposition method using the same are advantageous in terms of reducing manufacturing costs.

(Second Embodiment)
FIG. 6 is a diagram schematically illustrating a schematic configuration of the TMS decomposition apparatus according to the second embodiment. 1 corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof is omitted.

  The TMS decomposition apparatus of this embodiment is different from that of the first embodiment in that a chemical filter 8 is further provided.

  The chemical filter 8 is a chemical filter using activated carbon, for example.

  The chemical filter 8 is provided behind the photocatalyst member 3 (apparatus outlet side), and the gas 7 that has passed through the photocatalyst member 3 passes through the chemical filter 8. The chemical filter 8 collects TMS that has not been oxidatively decomposed (not removed) by the photocatalytic member 3. Therefore, according to the present embodiment, TMS can be removed more effectively in the container 1.

  The TMS decomposition apparatus and method according to the embodiment described above are used, for example, for cleaning a clean room or a semiconductor manufacturing apparatus. The semiconductor manufacturing apparatus is, for example, an exposure apparatus that uses ArF or the like as a light source, or an optical system inspection apparatus.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment.

  For example, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  In addition, various modifications can be made without departing from the scope of the present invention.

1 ... container, 2 ... photocatalyst, 3 ... photocatalytic member, 4 ... a light source, 5 ... dehumidifying filter (dehumidifier), 6 ... introducing gas (TMS), 7 ... exhaust gas (CO _2), 8 ... chemical filter.

Claims (8)

A container into which a gas containing trimethylsilanol is introduced;
A photocatalyst provided in the container;
A light source for generating light for activating the photocatalyst;
A decomposing apparatus for gaseous pollutants, comprising dehumidifying means for lowering the humidity in the container.   The apparatus for decomposing gaseous pollutants according to claim 1, wherein the dehumidifying means is a dehumidifying filter provided with silica gel, zeolite, activated carbon, or activated carbon fiber.   2. The apparatus for decomposing gaseous pollutants according to claim 1, wherein the dehumidifying means is provided closer to the inlet side for introducing the gas than the photocatalyst.   The apparatus for decomposing a gaseous pollutant according to claim 1 or 2, wherein the dehumidifying means is capable of setting an absolute humidity in the container to 35% or less.   4. The gaseous pollutant decomposition apparatus according to claim 1, wherein the light source generates ultraviolet light by corona discharge.   The apparatus for decomposing a gaseous pollutant according to any one of claims 1 to 4, wherein the photocatalyst is titanium oxide. Exposing a gas containing trimethylsilanol in an atmosphere having an absolute humidity of a certain value or less to produce hexamethyldisiloxane from the trimethylsilanol; and
And a step of decomposing the trimethylsilanol by oxidation by a photocatalytic reaction.   The method for decomposing a gaseous pollutant according to claim 7, wherein the absolute humidity in the atmosphere is 35% or less.

Images