JP2002319540A - Method for using optical catalyst, optical system, projection aligner, and optical catalyst optical system unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for using an optical catalyst in a low-oxygen atmosphere in which generation of CO2 which is a causative agent for a decreased transmission coefficient which is a reactive product when an organic polymer, being an impurity of an ultraviolet light optical system, is decomposed is suppressed, and to provide an optical system and an aligner using the optical catalyst. SOLUTION: The optical catalyst is irradiated with ultraviolet light in a low-oxygen atmosphere to decompose an organics in a gas into a low-end hydrocarbon, thus CO2 which absorbs ultraviolet light is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for using a photocatalyst, and an optical system and a projection exposure apparatus using the same.

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, projection exposure apparatuses used in optical lithography processes, which are important for the manufacture thereof, have made great progress. This high integration is largely due to the shortening of the exposure light wavelength.
In recent years, a krypton fluoride excimer laser (KrF excimer laser) having an output wavelength of 248 nm has been put into practical use as a light source for exposure. More recently, an argon fluoride excimer laser (ArF excimer laser) having an output wavelength of 193 nm has been used. Practical use of a projection exposure apparatus as a light source is also in progress.

[0003] Light having a wavelength of about 120 nm to 200 nm belongs to the vacuum ultraviolet region, and the light hardly passes through the air. This is because light energy is absorbed by substances such as oxygen molecules and CO ₂ molecules in the air. Since the ArF excimer laser is also light in the above-mentioned wavelength range, the light absorbing substance contained in the air in the exposure optical path absorbs the exposure light, so that it is difficult to perform exposure in an air atmosphere as in the related art. Therefore, it has been proposed to replace the air in the exposure light path with an inert gas or the like and reduce the concentration of oxygen molecules, CO ₂ molecules, and the like to perform exposure.
In a projection exposure apparatus using an ArF excimer laser or a shorter wavelength light source, the exposure light is absorbed by impurities present in the exposure light path of the optical system (illumination optical system and projection optical system), and the There is a problem that the transmittance of the system is reduced. This impurity may be a substance originating inside the exposure apparatus, a substance originating from an inert gas introduced into the exposure optical path, a substance existing in the clean room, or the like, existing in the optical system in a gaseous state or a solid state. Or liquid and adhere to the surface of the optical element.

[0004] Among them, to reduce impurities in the exposure light path, it can be expected that the impurities are decomposed to some extent by irradiation with the exposure light. That is, by irradiating the exposure light to the impurities attached to the surface of the optical element, there is an effect of desorbing the impurities, whereby relatively low-molecular impurities are removed to some extent. However, it was difficult to desorb a substance having a large molecular weight by light irradiation. In recent years, attempts have been made in recent years to oxidatively decompose an organic polymer as an impurity using a photocatalyst. Here, the photocatalyst refers to a substance which has an action of decomposing surrounding substances by generating electrons and holes on its surface when receiving light energy. Usually, the photocatalyst is used in an atmosphere in which sufficient oxygen exists, and active electrons are generated by the reaction of electrons and holes generated on the surface with oxygen to decompose organic substances. The light energy required to generate electrons and holes is provided by light of a wavelength having energy above the band gap of the substance.

[0005]

However, when organic substances are decomposed in an atmosphere having a sufficient amount of oxygen using a photocatalyst, CO ₂ is generated as one of the final products. This is because carbon, which is one of the elements constituting the organic matter, becomes CO ₂ by an oxidation reaction. When CO ₂ is generated in the exposure light path, it absorbs the ultraviolet light as the exposure light, so that the transmittance is reduced. Therefore, when the oxidative decomposition reaction of the organic substance is continuously performed by the photocatalyst, there is a problem that the exposure becomes difficult due to a decrease in transmittance. In addition, since the photocatalyst was considered to work in an atmosphere where oxygen is sufficiently present, the effect was low in a low oxygen atmosphere, and it was questioned that organic impurities in the gas in the exposure optical path in the exposure apparatus were removed. There was a problem. The present invention solves the above problems, suppresses the production of CO ₂ which is a reaction product when an organic polymer is decomposed, a method of using a photocatalyst in a low oxygen atmosphere, and an optical system using the photocatalyst. An object of the present invention is to provide an exposure apparatus.

[0006]

According to a first aspect of the present invention, there is provided a method of using a photocatalyst for decomposing an organic substance by irradiation of ultraviolet light, wherein the organic substance is decomposed into a lower hydrocarbon in a low oxygen atmosphere. .

[0007] With this configuration, the generation of CO ₂ can be further suppressed. According to a second aspect of the present invention, in the method of using the photocatalyst according to the first aspect, the low oxygen atmosphere has an oxygen concentration of 3% or less. With this configuration, generation of CO ₂ can be further suppressed.

[0008] The invention of claim 3 uses the photocatalyst of claim 1.
Wherein the photocatalyst is TiO._TwoOr Nb_TwoO_FiveOr T
a_TwoO_FiveIt is characterized by being. With this configuration, CO_Two
Can be further suppressed. The invention of claim 4 is claim 1
In the method for using a photocatalyst, the photocatalyst is K_FourNb ₆O₁₇Ma
Or KCa_TwoNb_ThreeO_TenOr KSr_TwoNb_ThreeO_TenIs characterized by
are doing.

With this configuration, generation of CO ₂ can be further suppressed. According to a fifth aspect of the present invention, in the method of using the photocatalyst according to the first aspect, the organic substance is an impurity present in an optical system used for light having a wavelength of 200 nm or less. With this configuration, generation of CO ₂ can be further suppressed.

According to a sixth aspect of the present invention, in the method of using the photocatalyst according to the first aspect, the organic substance is an impurity present in an optical system of a projection exposure apparatus having a light source having a light having a wavelength of 200 nm or less as a light source. . With this configuration, generation of CO ₂ can be further suppressed.

A seventh aspect of the present invention is the method of using the photocatalyst according to any one of the first to sixth aspects, wherein the temperature of the low oxygen atmosphere is adjusted. With this configuration, generation of CO ₂ can be further suppressed. The invention according to claim 8 is characterized in that, in the method for using a photocatalyst according to claim 1, an adsorption step of adsorbing the organic substance and the lower hydrocarbon on the surface of the photocatalyst is provided.

With this configuration, the generation of CO ₂ can be further suppressed. According to a ninth aspect of the present invention, in the method of using the photocatalyst according to the first aspect, a photocatalyst replacement step of replacing a part or all of the photocatalyst is included. With this configuration
The generation of CO ₂ can be further suppressed.

According to a tenth aspect of the present invention, in the ultraviolet light optical system comprising an optical element and a member holding the optical element, all or a part of the inside of the optical system can be hermetically sealed and has a low oxygen atmosphere. Wherein a photocatalyst is provided inside the optical system. With this configuration, generation of CO ₂ can be further suppressed.

According to an eleventh aspect of the present invention, in the optical system of the eighth aspect, the low oxygen atmosphere has an oxygen concentration of 3% or less. With this configuration, generation of CO ₂ can be further suppressed. The invention of claim 12 is an optical system of claim 10, wherein the photocatalyst is characterized in that TiO ₂ and Nb ₂ O ₅ or Ta ₂ O _5.

With this configuration, the generation of CO ₂ can be further suppressed. The invention according to claim 13 is the optical system according to claim 10, wherein the photocatalyst is K ₄ Nb ₆ O ₁₇ or KCa ₂ Nb ₃ O ₁₀ or KSr
₂ Nb ₃ O ₁₀ With this configuration, C
O2 generation can be further suppressed.

According to a fourteenth aspect of the present invention, in the optical system of the tenth aspect, the optical system is an optical system of a projection exposure apparatus that uses light having a wavelength of 200 nm or less as a light source.
With this configuration, generation of CO ₂ can be further suppressed. Claim 1
According to a fifth aspect of the present invention, in the optical system according to the tenth aspect, a filter is provided in the optical system.

With this configuration, generation of CO ₂ can be further suppressed. According to a sixteenth aspect, in the fifteenth optical system,
It is characterized in that all or a part of the gas in contact with the photocatalyst passes through the filter. With this configuration, generation of CO ₂ can be further suppressed.

The invention of claim 17 is the invention of claims 10 to 16
In the above optical system, a means for adjusting the temperature of the low oxygen atmosphere is provided. With this configuration, CO
₂ can be further suppressed. The invention according to claim 18, wherein an exposure light source for emitting ultraviolet light, an illumination optical system for irradiating the ultraviolet light to a mask, and a wafer coated with a photosensitive agent for illumination light passing through the mask on which a circuit pattern is drawn. In a projection exposure apparatus comprising a projection optical system for forming an image on the top and a stage for moving the wafer to an appropriate exposure position, the illumination optical system and the projection optical system are all or part thereof.
It is characterized in that it can be sealed and has a low oxygen atmosphere, and a photocatalyst is provided inside the projection exposure apparatus.

With this configuration, the generation of CO ₂ can be further suppressed. According to a nineteenth aspect, in the exposure apparatus of the eighteenth aspect, the low oxygen atmosphere has an oxygen concentration of 3% or less. With this configuration, generation of CO ₂ can be further suppressed.

In a twentieth aspect, in the exposure apparatus according to the eighteenth aspect, the photocatalyst is TiO _2, Nb ₂ O _5, or Ta ₂ O _5.
It is characterized by being. With this configuration, generation of CO ₂ can be further suppressed. The invention of claim 21 is the invention of claim 18
Wherein the photocatalyst is K ₄ Nb ₆ O ₁₇ or KCa
₂ Nb ₃ O ₁₀ or KSr ₂ Nb ₃ O ₁₀ .

With this configuration, the generation of CO ₂ can be further suppressed. According to a twenty-second aspect, in the exposure apparatus of the eighteenth aspect, a filter is provided in the exposure apparatus. With this configuration, generation of CO ₂ can be further suppressed.

According to a twenty-third aspect of the present invention, in the exposure apparatus of the twenty-second aspect, all or a part of the gas in contact with the photocatalyst passes through the filter. With this configuration
The generation of CO ₂ can be further suppressed. According to a twenty-fourth aspect of the present invention, in the exposure apparatus of the eighteenth to twenty-third aspects, a means for adjusting the temperature of the low oxygen atmosphere is provided.

With this configuration, generation of CO ₂ can be further suppressed. The invention according to claim 25, wherein an optical element, an optical system for ultraviolet light comprising a member for holding the optical element, a vent capable of exchanging gas with the optical system, and a container connected via the vent. And a photocatalyst optical system unit comprising a photocatalyst provided in the container, wherein the inside of the optical system and the inside of the container are in a low oxygen atmosphere.

With this configuration, the generation of CO ₂ can be further suppressed. According to a twenty-sixth aspect of the present invention, in the photocatalytic optical system unit of the twenty-fifth aspect, the container has an inlet for introducing a gas from outside. With this configuration
The generation of CO ₂ can be further suppressed.

According to a twenty-seventh aspect of the present invention, in the photocatalytic optical system unit of the twenty-fifth aspect, all or a part of the gas introduced from the inlet contacts the photocatalyst. With this configuration, generation of CO ₂ can be further suppressed.

According to a twenty-eighth aspect of the present invention, in the photocatalytic optical unit of the twenty-fifth aspect, the low oxygen atmosphere has an oxygen concentration of 3% or less. With this configuration, generation of CO ₂ can be further suppressed. The invention of claim 29 is based on claim 2
5. In the photocatalytic optical unit of 5, the photocatalyst is TiO ₂ ,
It is characterized by Nb ₂ O ₅ and Ta ₂ O ₅ .

With this configuration, the generation of CO ₂ can be further suppressed. The invention according to claim 30 is the photocatalytic optical unit according to claim 25, wherein the photocatalyst is K ₄ Nb ₆ O ₁₇ or KCa ₂ Nb ₃ O
₁₀ or KSr ₂ Nb ₃ O ₁₀ . With this configuration, generation of CO ₂ can be further suppressed.

According to a thirty-first aspect of the present invention, in the photocatalytic optical unit according to the twenty-fifth aspect, the optical system is an optical system of a projection exposure apparatus using light having a wavelength of 200 nm or less as a light source. With this configuration, generation of CO ₂ can be further suppressed.

According to a thirty-second aspect, in the photocatalytic optical unit according to the twenty-fifth aspect, a filter is provided in the photocatalytic optical unit. With this configuration, generation of CO ₂ can be further suppressed. The invention of claim 33 is
The photocatalytic optical unit according to claim 32, wherein all or a part of the gas in contact with the photocatalyst passes through the filter.

With this configuration, generation of CO ₂ can be further suppressed. According to a thirty-fourth aspect, in the photocatalytic optical unit according to the twenty-fifth to thirty-fourth aspects, a means for adjusting the temperature of the low oxygen atmosphere is provided. With this configuration, generation of CO ₂ can be further suppressed.

According to a thirty-fifth aspect of the present invention, in the photocatalytic optical system unit according to the twenty-fifth aspect, the photocatalyst is provided on a substrate surface. With this configuration, generation of CO ₂ can be further suppressed. According to a thirty-sixth aspect, in the photocatalytic optical system unit according to the thirty-fifth aspect, the photocatalyst is obtained by adhering a photocatalyst raw material to the substrate surface and firing the photocatalyst raw material.
It is characterized by being 0.1 μm or less.

With this configuration, the generation of CO ₂ can be further suppressed. According to a thirty-seventh aspect of the present invention, in the photocatalytic optical system unit according to the thirty-fifth aspect, the substrate is configured to be singly replaceable, or a plurality of all or partly replaceable configurations.

With this configuration, generation of CO ₂ can be further suppressed.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

[0035]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a method for using a photocatalyst according to the present invention. As shown in FIG. 1, a quartz plate having TiO ₂ adhered to its surface as a photocatalyst 1 is placed inside a sealable container 3 made of stainless steel. As the ultraviolet light irradiating means 2, a mercury lamp is installed inside the container 3 so that the surface of TiO ₂ is irradiated with the light. In order to confirm the effect, cyclic siloxane as an organic substance as an impurity is put in the container 3, and air is evacuated to about 0.25 atm by a vacuum pump (not shown). Nitrogen gas is introduced from outside via a valve (not shown)
The gas pressure inside is adjusted to about 1 atm. At this time, the oxygen concentration in the container is about 5%. The mercury lamp of the ultraviolet irradiation means 2 is turned on, and the photocatalyst 1 is irradiated with ultraviolet light for 30 minutes. After the irradiation, a predetermined amount of the internal gas in the container 3 is extracted, and the extracted internal gas is set for gas chromatography. According to the analysis result of internal gas by gas chromatography,
Most of the decomposition products are CH ₄ , and the detected amount of CO ₂ is extremely small. This indicates that the cyclic siloxane mixed in the container 3 is decomposed into a lower hydrocarbon mainly composed of CH ₄ , and hardly generates CO ₂ .

The ultraviolet irradiating means 2 includes a Kr
An ultraviolet laser such as an F excimer laser, an ArF excimer laser, or a nitrogen laser, an ultraviolet generating lamp such as an excimer lamp, a semiconductor light emitting element, a semiconductor laser, or the like may be used. Alternatively, as shown in FIG. 2, irradiation may be performed through a window 4 made of a material that transmits ultraviolet light such as synthetic quartz.

[0037]

Example 2 Photocatalyst was TiO_TwoBut not Nb_TwoO_FiveAfter using
Outside, the analysis of the gas inside the container 3 is performed in the same manner as in the first embodiment.
went. The results were almost the same as in Example 1. photocatalyst
To Ta _TwoO_Five, K_FourNb₆O₁₇, KCa_TwoNb_ThreeO_TenAnd KSr_TwoNb_ThreeO_TenSequentially
A similar analysis was performed instead, but the results were almost the same as in Example 1.
It was like.

[0038]

Example 3 The gas inside the container 3 was analyzed in the same manner as in Example 1 except that the oxygen concentration was 3%. As a result, the detected amount of CO ₂ was further lower than that of Example 1. Therefore, it is expected that the absorptance of ultraviolet light will be further reduced and that ultraviolet light can be used efficiently.

[0039]

Embodiment 4 FIG. 3 is a schematic diagram showing an optical system according to the present invention. A quartz plate having TiO ₂ adhered to its surface as a photocatalyst 11 is placed inside a sealable container 13 made of stainless steel. A mercury lamp is TiO ₂
Is placed inside the container 13 so that the light is irradiated onto the surface of the container 13. An ultraviolet optical system 15 composed of a glass optical element such as synthetic quartz is provided in the container 13. Depressurize the internal gas to about 0.25 atm, then fill with nitrogen gas to about 1 atm,
Adjust to a low oxygen atmosphere with an oxygen concentration of about 5%. Photocatalyst 11
Is irradiated with ultraviolet light from the ultraviolet light irradiating means 12 to decompose organic substances contained in the internal gas into lower hydrocarbons. In order to confirm the effect, a cyclic siloxane as an organic substance as an impurity is put in the container 13, and the photocatalyst 11 is irradiated with ultraviolet light for about 30 minutes. After the irradiation, the gas inside the container 13 was analyzed. The results were almost the same as in Example 1.

In place of the ultraviolet light irradiation means 12, the optical system 1
Ultraviolet light from a light source (not shown) used in 5 may be used as excitation light. The method is based on the optical system 15.
The photocatalyst 1 is provided by providing a leak in each optical element and a branch in the optical path.
1 may be irradiated, or the light of the light source light of the optical system 15 may be irradiated directly or indirectly. A filter using activated carbon may be provided in the container 13. The filter promotes the effect of capturing the decomposition product of the photocatalyst and preventing a decrease in transmittance. The filter is made of a substance that performs an adsorption reaction on the decomposition product, and zeolite or the like can be used in addition to activated carbon. It is efficient to capture the decomposition products immediately after the decomposition reaction. Therefore, as shown in FIG. 7, a photocatalyst unit 95 may be used in which filters 93 and 94 are attached to the photocatalyst 91 and a fan 97 is provided to form a gas flow. Filters 93 and 9
Reference numeral 4 is composed of an adsorptive substance such as activated carbon. Photocatalyst 9
1 is irradiated with ultraviolet light from an ultraviolet light irradiation means 92, and decomposition products decomposed by the photocatalyst 91 excited by the irradiation are captured by a filter 94. Further, a configuration excluding the filter 93 may be adopted.

[0041]

Embodiment 5 FIG. 4 is a conceptual diagram showing an exposure apparatus according to the present invention. The exposure apparatus of the present invention includes at least a surface 301
a, a wafer stage 301 on which a substrate W coated with a photosensitive agent placed on the substrate W can be placed, and vacuum ultraviolet light having a wavelength prepared as exposure light is applied to the wafer stage 301, and a mask prepared on the substrate W
An illumination optical system 101 for transferring an R pattern, a light source 100 for supplying exposure light to the illumination optical system 101, and a mask R for projecting an image of the pattern of the mask R on the substrate W are first arranged. And a projection optical system 500 placed between a surface P1 (object plane) of the substrate W and a second surface (image plane) matched with the surface of the substrate W. Illumination optical system 100
Also includes an alignment optical system 110 for adjusting the relative position between the mask R and the wafer W, and the mask R is disposed on a reticle stage 201 that can move in parallel to the surface of the wafer stage 301. Is done. The reticle exchange system 200 exchanges and transports the mask R set on the reticle stage 201. Reticle exchange system 20
Reference numeral 0 denotes a stage driver for moving the reticle stage 201 parallel to the surface 301a of the wafer stage 301. The projection optical system 500 has an alignment optical system applied to a scan type exposure apparatus.

A container 23 capable of sealing such an exposure apparatus.
To be stored. The container 23 is made of stainless steel so that the internal gas can be exchanged. Inside this container 23,
As the photocatalyst 21, a quartz plate having TiO ₂ adhered to the surface is installed. As the ultraviolet light irradiation means 22, a mercury lamp is installed inside the container 23 so that the surface of the TiO ₂ is irradiated with the light. The inside of the container 23 is replaced with an inert gas, a nitrogen gas or the like, and the oxygen concentration is controlled so as to be 5% or less. The photocatalyst 21 is provided at a location in the optical system of the exposure apparatus that does not block exposure light during exposure and does not interfere with movable parts and the like. UV light irradiating means 22 is applied to photocatalyst 21 provided in container 23.
Irradiation with more ultraviolet light decomposes organic substances contained in the gas inside the container 23 into lower hydrocarbons. In order to confirm the effect, a cyclic siloxane as an organic substance as an impurity is put in the container 23, and the photocatalyst 21 is irradiated with ultraviolet light for about 30 minutes. After the irradiation, the gas inside the container 23 was analyzed. The results were almost the same as in Example 1. Further, ultraviolet light from the light source 100 may be used as light for excitation. The method uses the illumination optical system 101 and the projection optical system 50.
The light may be applied to the photocatalyst 21 by providing a leak light or a branch in the optical path of each optical element of 0, or the light from the light source 100 may be applied directly or indirectly. Only a part of the optical system may be sealed in a container, and a photocatalyst may be provided in a low oxygen atmosphere. Further, the illumination optical system 101 and the projection optical system 500 may be sealed as independent systems, and the photocatalyst 21 and the ultraviolet light irradiation means 22 may be provided respectively. Further, the photocatalyst 21 and the ultraviolet light irradiation means 22 may be provided in either the illumination optical system 101 or the projection optical system 500. A filter 26 using activated carbon may be provided in the container 23. The filter 26 captures the decomposition product of the photocatalyst 21 and promotes the effect of preventing a decrease in transmittance. The filter 26 is made of a substance that performs an adsorption reaction on decomposition products, and zeolite or the like can be used in addition to activated carbon. It is efficient to capture the decomposition products immediately after the decomposition reaction. For this reason, as shown in FIG. 7, a photocatalyst unit 95 may be used in which filters 93 and 94 are attached to the photocatalyst 91 and a fan 97 is provided to form a gas flow. The filters 93 and 94 are made of an adsorptive substance such as activated carbon. The photocatalyst 91 is irradiated with ultraviolet light from the ultraviolet light irradiation means 92, and the decomposition products decomposed by the photocatalyst 91 excited by the irradiation are captured by the filter 94. Further, a configuration excluding the filter 93 may be adopted.

[0043]

Embodiment 6 FIG. 5 is a conceptual diagram of an optical system according to the present invention. The container 33 is provided with an ultraviolet light optical system 35 composed of a glass optical element such as synthetic quartz. The container 33 is connected to the container 33 via a vent. The container 38 is provided with a photocatalyst 31 and an ultraviolet light irradiation means 32. The gas inside the container 33 and the container 38 is reduced to about 0.25 atm, and then filled with nitrogen gas to about 1 atm to adjust to a low oxygen atmosphere having an oxygen concentration of about 5%. The photocatalyst 31 is irradiated with ultraviolet light from the ultraviolet light irradiation means 32 to decompose organic substances contained in the gas inside the container 33 into lower hydrocarbons. An internal gas containing an organic substance is introduced into the container 38 from the container 33, and the organic substance is decomposed and the purified gas is returned to the container 33. At this time, it is effective to perform the inflow and outflow of the gas using a fan or the like. In addition, when a filter is provided in the gas flow path in contact with the photocatalyst 31 and the decomposed organic matter is captured, the effect of purification is improved. In addition, oxygen molecules and CO ₂
In order to reduce the concentration of molecules and the like, an inert gas is introduced through an inlet 39 provided in the container 38, and the air in the optical path is replaced with the inert gas. At this time, it is effective to form a gas flow path such that all or a part of the introduced inert gas comes into contact with the photocatalyst. At this time, ultraviolet light from a light source (not shown) used for the optical system 35 may be used as excitation light. The method may be such that light is leaked from each optical element of the optical system 35 or a branch is provided in the optical path to irradiate the photocatalyst 31 or the light of the light source light of the optical system 35 is used directly or indirectly. Irradiation may be performed. A filter 36 using activated carbon may be provided in the container 33 or the container 38. The filter 36 captures the decomposition product of the photocatalyst 31 and promotes the effect of preventing the transmittance of the optical system 35 from decreasing. The filter 36 is made of a substance that performs an adsorption reaction on decomposition products, and zeolite or the like can be used in addition to activated carbon. The filter 36 may be attached to a vent. In particular, in the case where the ventilation port has a configuration in which gas flows from the container 38 to the container 33, decomposition products can be effectively captured. It is efficient to capture the decomposition products immediately after the decomposition reaction. For this reason, as shown in FIG. 7, a photocatalyst unit 95 may be used in which filters 93 and 94 are attached to the photocatalyst 91 and a fan 97 is provided to form a gas flow. The filters 93 and 94 are made of an adsorptive substance such as activated carbon. The photocatalyst 91 is irradiated with ultraviolet light from the ultraviolet light irradiation means 92, and the decomposition products decomposed by the photocatalyst 91 excited by the irradiation are captured by the filter 94. Further, a configuration excluding the filter 93 may be adopted. Further, instead of the fan 97, a gas inflow / outflow fan of the container 33 and the container 38 may be used.

[0044]

Embodiment 7 FIG. 6 is a conceptual diagram of an exposure apparatus according to the present invention. A container 44 containing the optical system of the exposure apparatus and a container 48 are connected to the container 44 via a vent. The container 48 is provided with a photocatalyst 41 and an ultraviolet light irradiation unit 42. Container 4
The pressure of the gas inside the chamber 4 and the container 48 is reduced to about 0.25 atm, then filled with nitrogen gas to about 1 atm, and adjusted to a low oxygen atmosphere having an oxygen concentration of about 5%. The photocatalyst 41 is irradiated with ultraviolet light from an ultraviolet light irradiation means 42 to decompose organic substances contained in the internal gas 43 into lower hydrocarbons. The internal gas 43 containing an organic substance is introduced into the container 48 from the container 44, and the organic substance is decomposed and the purified gas is returned to the container 44. At this time, it is effective to perform the inflow and outflow of the gas using a fan or the like. In addition, when a filter is provided in the gas flow path in contact with the photocatalyst 41 to capture the decomposed organic matter, the purification effect is improved. In order to reduce the concentration of oxygen molecules, CO ₂ molecules, etc., an inlet 4 provided in the container 48 is provided.
An inert gas is introduced through 9 and the air in the optical path is replaced with the inert gas. At this time, it is effective to form a gas flow path such that all or a part of the introduced inert gas comes into contact with the photocatalyst. One or more containers 48 may be attached to each of the illumination optical system 101 and the projection optical system 500. Alternatively, only the illumination optical system 101 or only the projection optical system 500 may be used, and only a part of the illumination optical system or the projection optical system may be covered with a container to which the container 48 is connected.

A filter 46 using activated carbon may be provided in the container 44 or the container 48. Filter 46
Promotes the effect of capturing the decomposition products by the photocatalyst 41 and preventing the transmittance of the irradiation optical system 101 and the projection optical system 500 in the exposure apparatus from being lowered. The filter 46 is made of a substance that performs an adsorption reaction on the decomposition product, and zeolite or the like can be used in addition to activated carbon. Filter 4
6 may be attached to a vent. In particular, vent 4
In the case of a configuration in which gas flows from 8 to the container 44, decomposition products can be effectively captured.

When the decomposition product is captured immediately after the decomposition reaction,
Efficient. Therefore, as shown in FIG.
A photocatalyst unit 95 may be used in which filters 93 and 94 are attached to the filter and a fan 97 is provided to form a gas flow. The filters 93 and 94 are made of an adsorptive substance such as activated carbon. The photocatalyst 91 is irradiated with ultraviolet light from the ultraviolet light irradiation means 92, and decomposition products decomposed by the photocatalyst 91 excited by the irradiation are filtered.
4 captured. Further, a configuration excluding the filter 93 may be adopted. Further, instead of the fan 97, a gas inflow / outflow fan of the containers 44 and 48 may be used. 3 to 6, in order to compensate for the decomposition reaction by the photocatalyst and the temperature change due to the ultraviolet light irradiation means itself, etc.
By providing the temperature control means 19 for the gas inside the optical system using a heater, a heat pipe, a Peltier element, or the like, it is possible to maintain the temperature of the optical element within a certain range, thereby maintaining the accuracy of the optical system.

FIG. 8 is a view showing a second embodiment of the photocatalytic unit. As shown in FIG. 8, a plurality of photocatalyst panels 51 may be arranged in the photocatalyst unit 96. The gas from which impurities are to be removed flows along the gas flow path formed by the photocatalyst panel 51. The photocatalyst panel 51 is irradiated with light for excitation from a light source (not shown). The surface of the photocatalyst panel 51 is coated with TiO ₂ .
The TiO _{2 on} the surface of the photocatalyst panel 51 has a property of adsorbing a decomposition product by a decomposition reaction on the surface. Therefore, decomposition products are adsorbed on the surface of the photocatalyst panel 51. For this reason, while the gas flows along the gas flow path, the impurities contained therein are decomposed into decomposition products and adsorbed on the surface of the photocatalyst panel 51 to be eliminated. Return to the attached device.

When impurities are adsorbed on the surface of the photocatalyst panel 51, the photocatalyst is deactivated and the photocatalytic reaction may not occur. The photocatalyst panels 51 have a structure that can be individually removed. Therefore, the deactivated photocatalyst panel 51 can be replaced with another usable photocatalyst panel 51, so that a photocatalytic reaction can be caused to occur again. Since the photocatalyst panel 51 can replace only the deactivated panel, the replacement efficiency is further improved.

TiO on the surface of the photocatalyst panel 51_TwoIs the base
After being attached to the plate surface, it is manufactured by sintering. Normal way
According to TiO_TwoHas a particle size of about several μm,
iO _TwoIs adjusted to fine particles having a particle size of 0.1 μm or less and fired.
Increases the surface area per unit volume and absorbs impurities.
The wearing efficiency is improved.

As a method for adjusting TiO ₂ to fine particles having a particle size of 0.1 μm or less, there is a method of hydrolyzing titanium alkoxide with an aqueous nitric acid solution and subjecting the filtered alkoxide to hydrothermal treatment. By this method, individual particles of TiO ₂ can be reduced to a diameter of about 0.01 μm. Fine particles of TiO ₂ prepared by this method are adhered to a substrate and fired. Thereby, the ability of adsorbing impurities on the surface of the photocatalyst panel 51 is increased, and the efficiency of removing impurities in the gas is improved.

A gas to which 100 ppm of decamethylcyclopentasiloxane was added as an impurity was flowed at a flow rate of 2 l / min through the photocatalyst unit 96 having the above configuration. Then, the photocatalyst panel 5
One surface was analyzed. FIG. 9 is a diagram showing the analysis results of elements on the surface of the photocatalyst panel 51 before and after flowing the gas. The horizontal axis shows values specific to each element, and the vertical axis shows
The detection amounts of each element are shown. The solid graph is before the gas flow, and the shaded graph is after the gas flow. The peak written as SiK in FIG. 9 indicates the presence of the Si element. As can be seen from the comparison of the peaks, after the gas was flowed, Si elements that were not present before the gas flow were detected. This is to detect silicon contained in the decomposition product of decamethylcyclopentasiloxane added as an impurity. Therefore, it was confirmed that the surface of the photocatalyst panel 51 had an effect of adsorbing decomposition products from impurities (decamethylcyclopentasiloxane). Therefore, by flowing a gas containing impurities through the surface of the photocatalyst panel 51, the impurities contained in the gas can be decomposed and the decomposition products can be adsorbed and removed.
6, the performance of the optical system and the projection exposure apparatus is further improved.

[0052]

As described above, according to the present invention, the generation of CO ₂ , which is a reaction product when an organic polymer is decomposed, is suppressed, so that impurities contained in the system can be reduced and the light source light can be reduced. It is possible to provide a method for using a photocatalyst in a low-oxygen atmosphere and a photosystem or an exposure apparatus using the photocatalyst, which reduce the absorption of light and improve the performance of the optical element and the optical system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a first embodiment of a method for using a photocatalyst according to the present invention.

FIG. 2 is a configuration diagram schematically showing a first embodiment of an optical system according to the present invention.

FIG. 3 is a configuration diagram schematically showing a second embodiment of the optical system according to the present invention.

FIG. 4 is a configuration diagram schematically showing a first embodiment of an exposure apparatus according to the present invention.

FIG. 5 is a configuration diagram schematically showing a first embodiment of a photocatalytic optical system unit according to the present invention.

FIG. 6 is a configuration diagram schematically showing a second embodiment of the photocatalytic optical system unit according to the present invention.

FIG. 7 is a configuration diagram schematically showing a first embodiment of a photocatalytic unit according to the present invention.

FIG. 8 is a configuration diagram schematically showing a second embodiment of the photocatalytic unit according to the present invention.

FIG. 9 is a view showing an analysis result of elements adsorbed on the surface of the photocatalytic panel according to the present invention.

[Explanation of symbols]

1, 11, 21, 31, 41, 91 Photocatalyst 2, 12, 22, 32, 42, 92 Ultraviolet light irradiation means 3, 13, 23, 33, 38, 44, 48 Sealable container 4 Ultraviolet light transmission window 15 , 35 Optical system 26, 36, 46 Filter 19 Temperature control means 39, 49 Inlet 51 Photocatalytic panel 95, 96 Photocatalytic unit 97 Fan 100 Ultraviolet laser 101 Illuminating optical system 500 Projection optical system R Reticle W wafer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03F 7/20 502 B01D 53/36 G F-term (Reference) 2H097 CA13 GB00 LA10 4D048 AA17 AB03 BA02Y BA07X BA14Y BA15Y BA24Y BA41X BA42Y EA01 4G069 AA03 BA04A BA04B BA48A BB04A BB06A BC03A BC09A BC12A BC55A BC56A CA10 CA15 EA08 EB19 5F046 BA04 CA04 DA04 DA27 DA30

Claims (37)

[Claims] 1. A method of using a photocatalyst for decomposing an organic substance by irradiating ultraviolet light, wherein the organic substance is decomposed into a lower hydrocarbon in a low oxygen atmosphere. 2. The method for using a photocatalyst according to claim 1, wherein the low oxygen atmosphere has an oxygen concentration of 3% or less. 3. The method for using a photocatalyst according to claim 1, wherein said photocatalyst is TiO _2, Nb ₂ O _5, or Ta ₂ O ₅ . 4. The method according to claim 1, wherein said photocatalyst is K ₄ Nb ₆ O ₁₇ or KCa ₂ Nb ₃ O ₁₀ or KSr ₂ Nb ₃ O
_{10. A} method for using a photocatalyst, which is ₁₀ . 5. The method for using a photocatalyst according to claim 1, wherein the organic substance is an impurity present in an optical system used for light having a wavelength of 200 nm or less. 6. The method of using a photocatalyst according to claim 1, wherein the organic substance is an impurity present in an optical system of a projection exposure apparatus having a light source having a light having a wavelength of 200 nm or less. 7. The method for using a photocatalyst according to claim 1, wherein the temperature of said low oxygen atmosphere is adjusted. 8. The method for using a photocatalyst according to claim 1, further comprising an adsorption step of adsorbing the organic substance and the lower hydrocarbon on the surface of the photocatalyst. 9. The method for using a photocatalyst according to claim 1, further comprising a photocatalyst replacement step of replacing a part or all of the photocatalyst. 10. An ultraviolet optical system comprising an optical element and a member holding the optical element, wherein all or a part of the inside of the optical system is sealable and has a low oxygen atmosphere, and An optical system comprising a photocatalyst provided inside the optical system. 11. The optical system according to claim 8, wherein the low oxygen atmosphere has an oxygen concentration of 3% or less. 12. The optical system according to claim 10, wherein said photocatalyst is TiO _2, Nb ₂ O ₅ or Ta ₂ O ₅ . 13. The optical system according to claim 10, wherein said photocatalyst is K ₄ Nb ₆ O _17, KCa ₂ Nb ₃ O ₁₀ or KSr ₂ Nb ₃ O ₁₀ . 14. An optical system according to claim 10, wherein said optical system is an optical system of a projection exposure apparatus using light having a wavelength of 200 nm or less as a light source. 15. An optical system according to claim 10, wherein a filter is provided in said optical system. 16. The optical system according to claim 15, wherein all or a part of the gas in contact with the photocatalyst passes through a filter. 17. The optical system according to claim 10, wherein
An optical system comprising means for adjusting the temperature of the low oxygen atmosphere. 18. An exposure light source for emitting ultraviolet light, an illumination optical system for irradiating the mask with the ultraviolet light, and an illumination light passing through the mask on which a circuit pattern is drawn is formed on a wafer coated with a photosensitive agent. In a projection exposure apparatus including a projection optical system for forming an image and a stage for moving a wafer to an appropriate exposure position, the illumination optical system and the projection optical system may be entirely or partially hermetically sealed and have low oxygen. A projection exposure apparatus in an atmosphere, wherein a photocatalyst is provided inside the projection exposure apparatus. 19. An exposure apparatus according to claim 18, wherein the low oxygen atmosphere has an oxygen concentration of 3% or less. 20. The exposure apparatus according to claim 18, wherein the light
The catalyst is TiO_TwoOr Nb_TwoO _FiveOr Ta_TwoO_FiveIs characterized by
Exposure equipment. 21. An exposure apparatus according to claim 18, wherein said photocatalyst is K ₄ Nb ₆ O _17, KCa ₂ Nb ₃ O ₁₀ or KSr ₂ Nb ₃ O ₁₀ . 22. An exposure apparatus according to claim 18, wherein a filter is provided in said exposure apparatus. 23. The exposure apparatus according to claim 22, wherein all or a part of the gas in contact with the photocatalyst passes through a filter. 24. An exposure apparatus according to claim 18, further comprising means for adjusting a temperature of said low oxygen atmosphere. 25. An optical element, an optical system for ultraviolet light comprising a member holding the optical element, a vent capable of exchanging gas with the optical system, and a container connected via the vent. A photocatalytic optical system unit comprising a photocatalyst provided in the container, wherein the inside of the optical system and the inside of the container are in a low oxygen atmosphere. 26. The photocatalytic optical system unit according to claim 25, wherein said container has an inlet for introducing a gas from outside. 27. A photocatalytic optical system unit according to claim 25, wherein all or a part of the gas introduced from said inlet contacts the photocatalyst. 28. The photocatalytic optical unit according to claim 25, wherein the low oxygen atmosphere has an oxygen concentration of 3% or less. 29. The photocatalytic optical unit according to claim 25, wherein said photocatalyst is TiO ₂ , Nb ₂ O ₅ , or Ta ₂ O ₅ . 30. The photocatalytic optical unit according to claim 25.
And the photocatalyst is K_FourNb ₆O₁₇Or KCa_TwoNb_ThreeO_TenOr KSr
_TwoNb_ThreeO_TenPhotocatalytic optical system unit
G. 31. A photocatalytic optical unit according to claim 25, wherein said optical system is an optical system of a projection exposure apparatus using light having a wavelength of 200 nm or less as a light source. 32. The photocatalytic optical unit according to claim 25, wherein a filter is provided in said photocatalytic optical unit. 33. The photocatalytic optical unit according to claim 32, wherein all or a part of the gas in contact with the photocatalyst passes through a filter. 34. A photocatalytic optical unit according to claim 25, further comprising means for adjusting the temperature of said low oxygen atmosphere. 35. The photocatalytic optical system unit according to claim 25, wherein said photocatalyst is provided on a substrate surface. 36. The photocatalytic optical system unit according to claim 35, wherein the photocatalyst is obtained by attaching a photocatalyst raw material to the surface of the substrate and firing the photocatalyst, and the photocatalyst raw material has a particle size of 0.1 μm or less. A photocatalytic optical system unit characterized by the above-mentioned. 37. The photocatalytic optical system unit according to claim 35, wherein said substrate has a structure that can be replaced by a single member or a structure that can be replaced entirely or partially by a plurality of substrates. unit.