JP6156390B2 - Method for removing silanol compound, chemical filter and exposure apparatus - Google Patents

Description

  The present invention relates to a silanol compound removing method for removing a silanol compound in air to be treated containing the silanol compound. The present invention also relates to a chemical filter and an exposure apparatus for carrying out the method for removing the silanol compound.

  In industries such as semiconductors and liquid crystals, control of air in clean rooms and product surfaces is important to ensure product yield, quality, and reliability. In particular, in the semiconductor industry field, circuit patterns are miniaturized as products are highly integrated, so that the exposure wavelength has become shorter in the exposure process used for semiconductor manufacturing. At present, a KrF excimer laser having a wavelength of 248 nm and an ArF excimer laser having a wavelength of 193 nm are used as a light source.

  In semiconductor manufacturing, when a hydroxyl group is present on the wafer surface, the resist is repelled. Therefore, as a wafer processing process, hexamethyldisilazane (HMDS) is used to remove the hydroxyl group of the wafer before applying the photoresist and increase the hydrophobicity. ) Is used. When this HMDS is hydrolyzed, trimethylsilanol is produced. And in the said exposure process, trimethylsilanol raise | generates photochemical reaction with light with a short wavelength with high energy, adheres to the exposure lens of an exposure apparatus, causes a haze (cloudiness), and causes exposure trouble.

  From such a background, Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-295765) discloses that silanols are brought into contact with a fibrous inorganic compound in which a hydroxyl group is present, and the silanols are chemically bonded to the fibrous inorganic compound. A method for purifying a substrate to be collected and removed is disclosed.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2011-166085) includes a large number of adsorbents composed of a porous body, and at least a part of the large number of adsorbents includes a metal catalyst (platinum or palladium). A supported chemical filter is disclosed. The chemical filter employs a method in which a silanol compound is dimerized in a filter portion on which a metal catalyst is supported, and the dimer is adsorbed on a filter portion on which the metal catalyst is not supported.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2012-30164) describes a dehumidifying means that dehumidifies air containing a silanol compound to a relative humidity of 33% or less, and air dehumidified by the dehumidifying means. An air purification system comprising a chemical filter for filtering and removing the silanol compound is disclosed.

  Note that the relative humidity of the air in the optical system space of the exposure apparatus for semiconductor manufacture and the air in the clean room for semiconductor manufacture is usually adjusted to 30 to 55%.

JP 2009-295765 A (Claims) JP 2011-166085 A (Claims) JP 2012-30164 A (Claims)

  However, in Cited Document 1, a mechanism for maintaining the surface temperature of the inorganic fiber compound at 70 to 300 ° C. is necessary, and it is practical to mount it on an exposure apparatus or the like in which the temperature and humidity are extremely precisely controlled. It will also be expensive.

  Further, in Cited Document 2, an expensive metal catalyst is used, a part on which the metal catalyst is supported, and a part for adsorbing the dimer of the silanol compound are required, so that the filter layer becomes thick. It is not economical.

  In Cited Document 3, since a dehumidifying device for dehumidifying is required, the cost increases.

  Therefore, the subject of this invention is providing the removal method of the silanol compound with the high removal effect of the silanol compound in to-be-processed air.

  As a result of intensive studies to solve the above-described problems in the prior art, the present inventors have made (1) bringing a silanol compound, particularly trimethylsilanol, into contact with activated carbon into which an oxygen-containing functional group has been introduced. The silanol compound can be dimerized by the action of the oxygen-containing functional group, and by dimerizing the silanol compound, it can be easily adsorbed on the activated carbon, and the amount of the oxygen-containing functional group in the activated carbon can be reduced. By increasing the amount to 0.5 mmol / g or more, the effect of removing silanol compounds, particularly trimethylsilanol compound, is enhanced. (2) However, the activated carbon having an oxygen-containing functional group of 0.5 mmol / g or more Those having many micropores with small pore diameters have high silanol compounds when the relative humidity of the air to be treated is about 45% or less. Although the removal effect is shown, when the relative humidity of the air to be treated is about 50 to 55%, the removal effect of the silanol compound becomes lower than that of about 45% or less, and (3) 0.5 mmol Even if the relative humidity of the air to be treated is about 50 to 55% by adjusting the pore size distribution of activated carbon having an oxygen-containing functional group of / g or more and increasing the number of micropores having a large pore size, 45% As a result, the inventors have found that the reduction in silanol compound removal performance can be reduced as compared with the case of less than about the case, and have completed the present invention.

  That is, the present invention (1) is activated carbon having an oxygen-containing functional group, the amount of oxygen-containing functional groups per 1 g of the activated carbon having the oxygen-containing functional group is 0.5 mmol / g or more, and a nitrogen adsorption isotherm In the differential pore volume distribution obtained by the MP method, the activated carbon having an oxygen-containing functional group having a peak top of the micropores in the range of 0.8 to 1.1 nm is brought into contact with the air to be treated containing the silanol compound. The silanol compound is dimerized, and the dimer of the produced silanol compound is adsorbed on the activated carbon having the oxygen-containing functional group to remove the silanol compound in the air to be treated. The present invention provides a method for removing silanol compounds.

  Further, the present invention (2) is activated carbon having an oxygen-containing functional group, the amount of oxygen-containing functional group per 1 g of the activated carbon having the oxygen-containing functional group is 0.5 mmol / g or more, and a nitrogen adsorption isotherm In the differential pore volume distribution determined by the MP method from the present invention, activated carbon having an oxygen-containing functional group having a peak top of a micropore peak of 0.8 to 1.1 nm is used ( The present invention provides a chemical filter for carrying out the silanol compound removal method of 1).

  The present invention (3) provides an exposure apparatus having the chemical filter of the present invention (2).

  ADVANTAGE OF THE INVENTION According to this invention, the removal method of the silanol compound with the high removal effect of the silanol compound in to-be-processed air can be provided. Moreover, according to this invention, the chemical filter with the high removal effect of the silanol compound in to-be-processed air can be provided. Further, according to the present invention, it is possible to provide an exposure apparatus with few exposure obstacles due to adhesion of trimethylsilanol to the exposure lens.

It is a typical graph which shows the differential pore volume distribution of activated carbon. It is a figure which shows the trimethylsilanol removal test apparatus used in the Example. It is a graph which shows the relationship between the 90% removal lifetime of an Example and a comparative example, and the relative humidity of to-be-processed air.

  The method for removing a silanol compound of the present invention is activated carbon having an oxygen-containing functional group, the amount of the oxygen-containing functional group per 1 g of the activated carbon having the oxygen-containing functional group is 0.5 mmol / g or more, and the nitrogen adsorption isotherm. In the differential pore volume distribution obtained by the MP method from the line, the treated air containing the silanol compound is contacted with activated carbon having an oxygen-containing functional group whose peak top of the micropore is 0.8 to 1.1 nm. The silanol compound is dimerized, and the produced dimer of the silanol compound is adsorbed on the activated carbon having the oxygen-containing functional group to remove the silanol compound in the air to be treated. And a method for removing the silanol compound.

  The activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention is an activated carbon into which an oxygen-containing functional group has been introduced. That is, the activated carbon having an oxygen-containing functional group is activated carbon in which an oxygen-containing functional group is bonded to a carbon atom of the activated carbon. In other words, the activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention is activated carbon that has been subjected to oxidation treatment, and activated carbon into which an oxygen-containing functional group has been introduced by oxidation treatment.

  Examples of the oxygen-containing functional group include a carbonyl group, a hydroxyl group, a lactone group, a carboxyl group, a quinone group, and a carboxylic anhydride group. The activated carbon having an oxygen-containing functional group preferably has at least one or more of a carbonyl group, a hydroxyl group, a lactone group and a carboxyl group as the oxygen-containing functional group, and at least a carbonyl group, a hydroxyl group It is particularly preferable to have a lactone group and a carboxyl group.

  The amount of the oxygen-containing functional group per 1 g of the activated carbon having an oxygen-containing functional group is 0.5 mmol / g or more, preferably 0.8 to 3.0 mmol / g, particularly preferably 1.0 to 2.5 mmol / g. It is. When the amount of the oxygen-containing functional group per 1 g of the activated carbon having the oxygen-containing functional group is within the above range, the effect of removing the silanol compound is enhanced.

In addition, the amount of oxygen-containing functional groups per gram of activated carbon having oxygen-containing functional groups and the amount of each functional group are determined as follows. First, activated carbon having an oxygen-containing functional group is vacuum-dried for 8 to 10 hours in a constant temperature dryer adjusted to 115 ° C., and then allowed to cool in a desiccator containing silica gel as a desiccant. Next, four 50 ml stoppered Erlenmeyer flasks (A, B, C, D) are prepared, and 1 g of cooled activated carbon is accurately weighed to 0.1 mg in each Erlenmeyer flask. Next, an N / 10 sodium hydrogen carbonate aqueous solution was added to the Erlenmeyer flask (D), an N / 10 sodium carbonate aqueous solution was added to the Erlenmeyer flask (C), an N / 10 sodium hydroxide aqueous solution was added to the Erlenmeyer flask (B), and an Erlenmeyer flask (A ) 25 ml of N / 10 sodium ethoxide ethanol solution is added to the solution and shaken at 160 rpm at 25 ° C. for 24 hours. After shaking, the supernatant and precipitate are separated by centrifugation, and 10 ml of the supernatant is accurately weighed into a 20 ml beaker and titrated with N / 10 hydrochloric acid until the pH is 4 using a pH meter. Next, the consumption of each base per gram of activated carbon is calculated from the hydrochloric acid titration amount according to the following formula.
Base consumption (mmol / g) = (0.1 × (10-HCl titration) × 25) / 10
As a result of titration, the consumption of sodium bicarbonate was D (mmol / g), the consumption of sodium carbonate was C (mmol / g), the consumption of sodium hydroxide was B (mmol / g), and the consumption of sodium ethoxide When the amount was A (mmol / g), the amount of oxygen-containing functional groups per gram of activated carbon was “A (mmol / g)”, and the amount of carbonyl groups was “A-B (mmol / g). ) ", The amount of hydroxyl groups is" BC (mmol / g) ", the amount of lactone groups is" CD (mmol / g) ", and the amount of carboxyl groups is" D (mmol / g) ".

  The activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention has a micropore peak peak top of 0.8 to 1 in a differential pore volume distribution determined by an MP method from a nitrogen adsorption isotherm. .1 nm, preferably 0.9-1.0 nm. When the peak top of the micropore peak in the differential pore volume distribution of the activated carbon having an oxygen-containing functional group is in the above range, the removal effect of the silanol compound is high, and the relative humidity of the air to be treated is 50 to 55. Even if it is%, there exists an effect that the fall of the removal effect of the silanol compound when compared with the case of about 45% or less can be made small.

The nitrogen adsorption isotherm is obtained by measuring changes in pressure and the amount of adsorption while keeping the material at a constant temperature by a nitrogen gas adsorption method. In the MP method, an adsorption isotherm is obtained by adsorbing nitrogen to an adsorbent (porous carbon material), and the adsorption isotherm is converted into a pore volume with respect to the thickness t of the adsorption layer (t plot). And a pore distribution curve is obtained based on the curvature of this plot (the amount of change in the pore volume with respect to the amount of change in the thickness t of the adsorption layer). The differential pore volume distribution obtained by the MP method from the nitrogen adsorption isotherm indicates the relationship between the pore diameter calculated by the MP method from the nitrogen adsorption isotherm and its volume, and as shown in FIG. It relates to the pore volume obtained by plotting the pore diameter (nm) on the axis and dV / dD (change ratio of the pore volume V (cm ³ / g) to the amount of change of the pore diameter D (nm)) on the vertical axis. It is a distribution map. FIG. 1 is a schematic graph showing the differential pore volume distribution of activated carbon.

  In the differential pore volume distribution, the peak top of the micropore peak is in the range of 0.8 to 1.1 nm. The position of the peak top of the peak seen in the micropore range of the differential pore volume distribution diagram is , 0.8 to 1.1 nm. Micropores refer to pores having a pore diameter greater than 0 nm and 2 nm or less. Therefore, in the differential pore volume distribution obtained by the MP method from the nitrogen adsorption isotherm, the activated carbon having the peak top of the micropores in the range of 0.8 to 1.1 nm is finer than 0 nm which is the micropores and 2 nm or less. For the pores, when the value of dV / dD with respect to the pore diameter was determined from the nitrogen adsorption isotherm by the MP method, the value of the pore diameter when the maximum value of dV / dD was 0.8 to 1.1 nm. Is in range.

  In FIG. 1, the differential pore volume distribution indicated by symbol X has a peak top at a position where the pore diameter is 0.9 nm in the range from 0 nm to 2 nm. Therefore, in the activated carbon having the differential pore volume distribution of X, the peak top of the micropore peak is 0.9 nm in the differential pore volume distribution. Further, in FIG. 1, the differential pore volume distribution indicated by the symbol Y has a peak top at a position where the pore diameter is 0.7 nm in the range from 0 nm to 2 nm. Therefore, in the activated carbon having the differential pore volume distribution of Y, the peak top of the micropore peak is 0.7 nm in the differential pore volume distribution.

The activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention has pore diameters of pores having a pore diameter of more than 0 nm and 2 nm or less in a differential pore volume distribution determined by the MP method from a nitrogen adsorption isotherm. Ratio of pore volume of pores having a pore diameter of 0.7 to 1.2 nm to the volume ((total sum of pore volumes of pores having a pore diameter of 0.7 to 1.2 nm (cm ³ / g) / fine The total pore volume (cm ³ / g)) × 100) of pores having a pore diameter of more than 0 nm and 2 nm or less is preferably 70 to 100%, particularly preferably 80 to 100%, and more preferably 90 to 100%. It is. The ratio of the pore volume of pores having a pore diameter of 0.7 to 1.2 nm to the pore volume of pores having a pore diameter of more than 0 nm and not more than 2 nm in the differential pore volume distribution of activated carbon having an oxygen-containing functional group is By being in the above range, the silanol compound removal effect is high, and even if the relative humidity of the air to be treated is 50 to 55%, the removal effect of the silanol compound when compared with the case where it is about 45% or less. The effect that reduction can be made small increases.

BET specific surface area of the activated carbon with oxygen-containing functional groups according to the method for removing the silanol compound of the present invention is preferably 1700 m ² / g or more, particularly preferably 1900~2600m ² / g. When the BET specific surface area of the activated carbon having an oxygen-containing functional group is in the above range, the removal effect of the silanol compound is high, and even if the relative humidity of the air to be treated is 50 to 55%, it is about 45% or less. The effect that the fall of the removal effect of the silanol compound when compared with the case can be made small increases.

Micro pore volume of the activated carbon with oxygen-containing functional groups according to the method for removing the silanol compound of the present invention is preferably 1.0 cm ³ / g or more, particularly preferably 1.05~1.25cm ³ / g. The micropore volume refers to the total pore volume of pores having a pore diameter greater than 0 nm and 2 nm or less. When the micropore volume of the activated carbon having an oxygen-containing functional group is within the above range, the removal effect of the silanol compound is high, and even if the relative humidity of the air to be treated is 50 to 55%, it is about 45% or less. The effect that the fall of the removal effect of the silanol compound when compared with the case can be made small increases.

  The activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention has, in addition to micropores, mesopores having a pore diameter of more than 2 nm and not more than 50 nm, and macropores having a pore diameter of more than 50 nm.

  Examples of a method for producing activated carbon having an oxygen-containing functional group include a method of oxidizing activated carbon in a gas phase or a liquid phase.

  Although it does not restrict | limit especially as activated carbon used as the raw material of manufacture of the activated carbon which has an oxygen-containing functional group, A coconut shell type | system | group activated carbon, a wood charcoal type activated carbon, a pitch type activated carbon, and a phenol resin type activated carbon are mentioned. The physical properties or properties of the raw material activated carbon are appropriately selected according to the physical properties or properties of the activated carbon having an oxygen-containing functional group to be produced.

  As a method of oxidizing activated carbon in the gas phase, a method of oxidizing activated carbon with ozone gas, a method of oxidizing with chlorine gas, a method of air oxidation by heating in air, a combination of oxygen treatment and nitrogen oxide treatment, oxygen Examples thereof include low-temperature plasma treatment with gas or air.

  In addition, as a method of oxidizing activated carbon in the liquid phase, activated carbon is converted into ozone aqueous solution, nitric acid aqueous solution, hydrogen peroxide aqueous solution, sulfuric acid solution, chloric acid solution, iodic acid solution, hypochlorous acid solution, bromine aqueous solution, permanganic acid. The method of immersing in a potassium solution etc. is mentioned. After the activated carbon is oxidized in the liquid phase, the oxidized activated carbon is sufficiently washed with pure water and dried at about 80 to 120 ° C.

  The oxidation conditions of the activated carbon are selected as appropriate, but the condition that the amount of oxygen-containing functional groups per 1 g of activated carbon is 0.5 mmol / g or more, preferably 0.8 to 3.0 mmol / g, particularly Preferably, a condition of 1.0 to 2.5 mmol / g is selected.

  Then, by oxidizing the activated carbon, a part of the carbon of the activated carbon is oxidized and converted to an oxygen-containing functional group, and activated carbon having an oxygen-containing functional group is obtained.

  In the silanol compound removal method of the present invention, the activated carbon having an oxygen-containing functional group is brought into contact with the air to be treated containing the silanol compound.

  The air to be processed is not particularly limited, but is air containing a silanol compound such as air in an optical system installation space of an exposure apparatus for manufacturing a semiconductor.

  The silanol compound contained in the air to be treated is a compound having a silanol group (—Si—OH). As the silanol compound, a silanol compound having a molecular weight of 300 or less is preferable, and a silanol compound having a molecular weight of 200 or less is particularly preferable. More preferably, examples of the silanol compound include trimethylsilanol and triethylsilanol. And in the removal method of the silanol compound of this invention, when a to-be-processed air contains a trimethylsilanol, there exists a remarkable effect.

  The content of the silanol compound in the air to be treated is not particularly limited. For example, in the case of air in an optical system installation space of an exposure apparatus for manufacturing a semiconductor, it is usually 0.3 to 8.0 ppb.

  The method of bringing the air to be treated into contact with the activated carbon having an oxygen-containing functional group is not particularly limited. For example, the activated carbon having an oxygen-containing functional group is formed by filling activated carbon having an oxygen-containing functional group into a filling container. Examples thereof include a method of allowing the air to be treated to pass through the activated carbon layer, a method of supporting the activated carbon having an oxygen-containing functional group on a carrier, and allowing the air to be treated to pass through the carrier.

  The temperature at which the air to be treated is brought into contact with the activated carbon having an oxygen-containing functional group is 5 to 40 ° C, preferably 10 to 30 ° C.

  The supply of the air to be treated when the air to be treated is brought into contact with the activated carbon having the oxygen-containing functional group is appropriately selected depending on the content of the silanol compound in the air to be treated, the amount of the activated carbon having the oxygen-containing functional group, and the like. The

In the method for removing a silanol compound of the present invention, an activated carbon having an oxygen-containing functional group is brought into contact with activated carbon having an oxygen-containing functional group by bringing the treated air containing the silanol compound into contact with the activated carbon having an oxygen-containing functional group as shown in the following formula (1). The unshared electron pair of the oxygen atom of the oxygen-containing functional group and the hydrogen atom of the silanol group in the silanol compound are bonded to each other, and then to the unshared electron pair of the oxygen atom of the oxygen-containing functional group present in the vicinity Two silanol compounds to which the hydrogen atom of the silanol group is bonded are considered to undergo dehydration condensation and dimerization. The dimerization reaction is “2R ₃ SiOH → R ₃ SiOSiR ₃ + H ₂ O”.
Formula (1):

  The present inventors have found that dimerization of the silanol compound occurs even at a low temperature of 5 to 40 ° C., preferably 10 to 30 ° C., due to the action of the oxygen-containing functional group introduced into the activated carbon, and the silanol compound is dimerized. Since the molecular weight of the object to be removed can be increased, it can be easily adsorbed on the activated carbon, and the amount of oxygen-containing functional groups in the activated carbon is within a specific range, thereby removing the silanol compound. Found to be higher. And the amount of the oxygen-containing functional group per 1 g of the activated carbon having an oxygen-containing functional group is 0.5 mmol / g or more, preferably 0.8 to 3.0 mmol / g, particularly preferably 1.0 to 2.5 mmol. It was found that the effect of removing the silanol compound is enhanced by setting the amount to / g. Therefore, according to the silanol compound removal method of the present invention, even low-molecular weight silanol compounds such as trimethylsilanol, which have been conventionally considered difficult to adsorb and remove with activated carbon due to its low molecular weight, are adsorbed on activated carbon. Can be removed. Moreover, according to the removal method of the silanol compound of this invention, the removal of the silanol compound in to-be-processed air can be performed at 5-40 degreeC, Preferably it is 10-30 degreeC low temperature.

  Furthermore, the present inventors have found that the amount of oxygen-containing functional group is 0.5 mmol / g or more, preferably 0.8 to 3.0 mmol / g, particularly preferably 1.0 to 2.5 mmol / g. Even if the activated carbon has a functional group, the activated carbon having many micropores with small pore diameters has a silanol compound removal performance when the relative humidity of the air to be treated is 50 to 55%, compared with the case where the relative humidity is about 45% or less. Found that it would be lower. When the relationship between the relative humidity and the amount of moisture adsorbed by the activated carbon was repeatedly examined, activated carbon with a peak top of the micropore peak in the differential pore volume distribution of less than 0.8 nm was found to increase the relative humidity from low to high. When the humidity is changed, when the relative humidity is about 45% or less, the moisture in the air is hardly absorbed. However, when the relative humidity becomes higher than about 45%, the moisture starts to be absorbed, and when the relative humidity becomes higher than about 50%. On the other hand, activated carbon with a peak top of the micropore peak in the differential pore volume distribution of 0.8 to 1.1 nm changes the relative humidity from low humidity to high humidity. When the relative humidity is about 55% or less, the moisture in the air is hardly absorbed and the moisture starts to be absorbed when the relative humidity becomes higher than about 55%. Begin increases have found that it is when it becomes higher than the relative humidity of approximately 60%. From these, the amount of oxygen-containing functional groups per gram is 0.5 mmol / g or more, preferably 0.8 to 3.0 mmol / g, particularly preferably 1.0 to 2.5 mmol / g. By adjusting the pore distribution of the activated carbon having an oxygen functional group so that the peak top of the micropore peak in the differential pore volume distribution is 0.8 to 1.1 nm, Even if the relative humidity is higher than 45% and 55% or less, or even 50 to 55%, the decrease in the removal performance of the silanol compound when compared with the case where it is 45% or less can be reduced. I found.

  Therefore, in the silanol compound removal method of the present invention, the relative humidity of the air to be treated is higher than 45% and lower than or equal to 55%, or even 50 to 55%, and the relative humidity is lower than 45%. When compared, the decrease in the removal effect of the silanol compound is small and the effect of removing the silanol compound is high. Therefore, when the relative humidity of the air to be treated is higher than 45% and 55% or lower, and further 50 to 55%, the silanol compound removal method of the present invention has an oxygen-containing functional group amount of 0. Compared to the silanol compound removal method using activated carbon having an oxygen-containing functional group of less than 0.5 mmol / g, the effect of removing the silanol compound is enhanced. Further, the pore diameter of the pore having a pore diameter of 0.7 to 1.2 nm with respect to the pore volume of the pore having a pore diameter distribution of greater than 0 nm and 2 nm or less in the differential pore volume distribution of the activated carbon having an oxygen-containing functional group By setting the volume ratio in the above range, setting the BET specific surface area of the activated carbon having an oxygen-containing functional group in the above range, setting the micropore volume of the activated carbon having an oxygen-containing functional group in the above range, etc., the effect can be obtained. Get higher.

  Moreover, in the removal method of the silanol compound of this invention, even if the relative humidity of the to-be-processed air is higher than 45% and 55% or less, and also 50-55%, compared with the case where relative humidity is 45% or less. Since the decrease in the removal performance of the silanol compound can be reduced, the effect of removing the silanol compound is high and stable when the relative humidity of the air to be treated is in the range of 30 to 55%. Further, the pore diameter of the pore having a pore diameter of 0.7 to 1.2 nm with respect to the pore volume of the pore having a pore diameter distribution of greater than 0 nm and 2 nm or less in the differential pore volume distribution of the activated carbon having an oxygen-containing functional group By setting the volume ratio in the above range, setting the BET specific surface area of the activated carbon having an oxygen-containing functional group in the above range, setting the micropore volume of the activated carbon having an oxygen-containing functional group in the above range, etc., the effect can be obtained. Get higher.

  The method for removing a silanol compound of the present invention is an activated carbon having an oxygen-containing functional group in which the amount of oxygen-containing functional group is less than 0.5 mmol / g even when the relative humidity of the air to be treated is 45% or less. Compared with the silanol compound removal method using, the effect of removing the silanol compound is enhanced. Further, the pore diameter of the pore having a pore diameter of 0.7 to 1.2 nm with respect to the pore volume of the pore having a pore diameter distribution of greater than 0 nm and 2 nm or less in the differential pore volume distribution of the activated carbon having an oxygen-containing functional group By setting the volume ratio in the above range, setting the BET specific surface area of the activated carbon having an oxygen-containing functional group in the above range, setting the micropore volume of the activated carbon having an oxygen-containing functional group in the above range, etc., the effect can be obtained. Get higher.

  The chemical filter of the present invention is a chemical filter for carrying out the silanol compound removal method of the present invention, and is an activated carbon having an oxygen-containing functional group, and the oxygen-containing functional group per 1 g of the activated carbon having the oxygen-containing functional group. In the differential pore volume distribution determined by the MP method from the nitrogen adsorption isotherm, the oxygen-containing functional group in which the peak top of the micropore peak is in the range of 0.8 to 1.1 nm It is a chemical filter characterized by using activated carbon having

  The activated carbon having an oxygen-containing functional group according to the chemical filter of the present invention is the same as the activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention. In other words, the chemical filter of the present invention uses activated carbon having an oxygen-containing functional group according to the silanol compound removal method of the present invention.

  The chemical filter of the present invention is activated carbon having an oxygen-containing functional group, and the amount of the oxygen-containing functional group per 1 g of the activated carbon having the oxygen-containing functional group is 0.5 mmol / g or more. In the differential pore volume distribution obtained by the MP method, activated carbon having an oxygen-containing functional group with a peak top of the micropores in the range of 0.8 to 1.1 nm is filled in a gas-filled container, and the activated carbon layer A chemical filter in which is formed.

  Further, the chemical filter of the present invention is activated carbon having an oxygen-containing functional group, the amount of oxygen-containing functional groups per 1 g of the activated carbon having the oxygen-containing functional group is 0.5 mmol / g or more, and the nitrogen adsorption isotherm. In the differential pore volume distribution obtained from the line by the MP method, there is a chemical filter in which activated carbon having an oxygen-containing functional group having a peak top of a micropore peak of 0.8 to 1.1 nm is supported on a carrier. It is done.

  In the chemical filter of the present invention in which activated carbon having an oxygen-containing functional group is supported on the carrier, the carrier on which the activated carbon having an oxygen-containing functional group is supported is not particularly limited and is used as a carrier for a chemical filter. For example, an inorganic fibrous base material (paper) composed of inorganic fibers is formed into a honeycomb structure or a pleated structure, and an organic fibrous base material (paper) composed of organic fibers is honeycomb. Examples thereof include an organic fibrous carrier molded into a structure or a pleated structure. Among these, as the carrier, a pleated structure is preferable because it can increase the amount of activated carbon per unit volume and has a low pressure loss.

  In the chemical filter of the present invention in which activated carbon having oxygen-containing functional groups is supported on the carrier, the method for supporting activated carbon having oxygen-containing functional groups is not particularly limited. For example, in the chemical filter of the present invention in which activated carbon having an oxygen-containing functional group is supported on a carrier, the activated carbon having an oxygen-containing functional group may be supported on a carrier by using a binder, or an inorganic fiber Activated carbon having oxygen-containing functional groups may be supported by a sheet of quality or organic fiber so as to be supported.

  And, into the chemical filter of the present invention, air to be treated containing a silanol compound, for example, air in an optical system installation space of an exposure apparatus for manufacturing a semiconductor is introduced, and the air to be treated is passed through the chemical filter, The method for removing a silanol compound of the present invention can be carried out using the chemical filter of the present invention by bringing the air to be treated into contact with activated carbon having an oxygen-containing functional group supported on a carrier.

  As described above, the activated carbon having an oxygen-containing functional group according to the method for removing a silanol compound of the present invention has a relative humidity of air to be treated higher than 45% and 55% or lower, and even 50 to 55%. The chemical filter of the present invention in which such activated carbon is used because the decrease in the removal performance of the silanol compound when compared with the case where the relative humidity is 45% or less is small and the removal performance of the silanol compound is high. When the relative humidity of the air to be treated is higher than 45% and lower than or equal to 55%, and further 50 to 55%, the oxygen-containing functional group has an oxygen-containing functional group of less than 0.5 mmol / g. Compared to a chemical filter using activated carbon, the silanol compound removal performance is enhanced. Moreover, the chemical filter of this invention has the effect that the removal performance of a silanol compound is high and stable in the range whose relative humidity of to-be-processed air is 30 to 55%. In addition, the chemical filter of the present invention is a chemical that uses activated carbon having an oxygen-containing functional group in which the amount of the oxygen-containing functional group is less than 0.5 mmol / g even when the relative humidity of the air to be treated is 45% or less. Compared to the filter, the silanol compound removal performance is enhanced.

  The exposure apparatus of the present invention is an exposure apparatus having the chemical filter of the present invention.

  The chemical filter according to the exposure apparatus of the present invention is the same as the chemical filter of the present invention.

  The structure of the exposure apparatus of the present invention is not particularly limited, and may be any exposure apparatus that is usually used for semiconductor manufacturing.

  The exposure apparatus of the present invention is provided with an optical system installation space in which an optical system member and an exposure object are installed and can be shielded from external air. Further, the exposure apparatus of the present invention extracts the air in the optical system installation space and returns the air in the optical system installation space back to the optical system installation space and the air in the clean room in the optical system installation space. And an external air intake path for intake. In the exposure apparatus of the present invention, the chemical filter of the present invention is installed in each of the circulation path and the external air intake path.

  The exposure apparatus of the present invention includes a relay lens system, a condenser lens system, a projection optical system lens (hereinafter also referred to as an optical system member), and an installation portion for an exposure object. In the exposure apparatus of the present invention, the optical system member and the exposure object are installed in a small chamber that can be cut off from the outside air, so that the space of the installation part in which the optical system member and the exposure object are installed ( Hereinafter, it is also referred to as an optical system installation space.) Is cut off from outside air.

  In the exposure apparatus of the present invention, air in the optical system installation space is extracted and returned to the optical system installation space, and the air circulation path in the optical system installation space and the air in the clean room are taken into the optical system installation space. An external air intake path, and the chemical filter of the present invention is installed in each of the circulation path and the external air intake path. In the exposure apparatus of the present invention, the air in the optical system installation space extracted from the optical system installation space in the circulation path is extracted by passing through the chemical filter installed in the circulation path. In addition, silanol compounds in the air in the optical system installation space, particularly trimethylsilanol, are removed. The air from which silanol compounds such as trimethylsilanol have been removed is returned to the optical system installation space again. In the exposure apparatus of the present invention, in the external air intake path, the air taken in from the clean room passes through the chemical filter installed in the external air intake path, so that the air in the clean room taken in The silanol compound, especially trimethylsilanol, is removed. The air from which silanol compounds such as trimethylsilanol have been removed is supplied to the optical system installation space.

(Analysis method and evaluation method)
<Measurement method of oxygen-containing functional group amount>
The activated carbon to be measured was vacuum-dried for 8 to 10 hours in a constant temperature dryer adjusted to 115 ° C., and then allowed to cool in a desiccator containing silica gel as a desiccant. Next, four 50 ml stoppered Erlenmeyer flasks (A, B, C, D) were prepared, and 1 g of cooled activated carbon was accurately weighed to 0.1 mg in each Erlenmeyer flask. Next, an N / 10 sodium hydrogen carbonate aqueous solution was added to the Erlenmeyer flask (D), an N / 10 sodium carbonate aqueous solution was added to the Erlenmeyer flask (C), an N / 10 sodium hydroxide aqueous solution was added to the Erlenmeyer flask (B), and an Erlenmeyer flask (A ) 25 ml of N / 10 sodium ethoxide ethanol solution was added to the solution and shaken at 160 rpm at 25 ° C. for 24 hours. After shaking, the mixture was separated into a supernatant and a precipitate by centrifugation, and 10 ml of the supernatant was accurately weighed in a 20 ml beaker and titrated with N / 10 hydrochloric acid until the pH reached 4 using a pH meter. Next, the consumption of each base per gram of activated carbon was calculated from the hydrochloric acid titration amount by the following formula.
Base consumption (mmol / g) = (0.1 × (10-HCl titration) × 25) / 10
The consumption of sodium bicarbonate is D (mmol / g), the consumption of sodium carbonate is C (mmol / g), the consumption of aqueous sodium hydroxide is B (mmol / g), and the consumption of sodium ethoxide is A (Mmol / g), the oxygen-containing functional group amount per 1 g of activated carbon is “A (mmol / g)”, and the carbonyl group amount is “A-B (mmol / g)”. Is “BC (mmol / g)”, the amount of lactone group is “CD (mmol / g)”, and the amount of carboxyl group is “D (mmol / g)”.

<Measurement of differential pore volume distribution>
The activated carbon to be measured was measured with bell soap mini manufactured by Nippon Bell Co., Ltd., and the nitrogen adsorption isotherm was determined. Subsequently, the differential pore volume distribution was determined by the MP method from the obtained nitrogen adsorption isotherm.

<Trimethylsilanol removal test>
As shown in FIG. 1, a test sample is sandwiched between hollow glass tubes 2 having an inner diameter of 20 mm and a length of 300 mm with a support member 4 so as to have a thickness of 5 mm or 7 mm (length in the ventilation direction of air to be treated). A test sample layer (activated carbon layer) 3 was formed to produce a trimethylsilanol removal test apparatus 1.
Next, 150 ppb of trimethylsilanol-containing air (temperature: 23 ° C., predetermined relative humidity) is supplied from the gas inlet 21, discharged from the gas outlet 22, and the air to be treated is supplied to the test sample layer 3 at a wind speed of 0.3 m / Aerated in seconds. Every time a predetermined time elapses, the trimethylsilanol-containing air on the gas inlet 21 side during ventilation and the trimethylsilanol-containing air on the gas outlet 22 side are collected by a dedicated analytical carbon-based adsorption tube, and the mass of the gas chromatograph Analysis was performed using an analyzer, and the concentration of trimethylsilanol in each collected air was analyzed. The trimethylsilanol removal rate for each elapsed time was determined by the following formula.
Trimethylsilanol removal rate (%) = ((trimethylsilanol concentration at the inlet side−trimethylsilanol concentration at the outlet side) / trimethylsilanol concentration at the inlet side) × 100

<90% removal life>
From the time-dependent change in the trimethylsilanol removal rate determined in the trimethylsilanol removal test, the time required for the trimethylsilanol removal rate to reach 90% was defined as 90% removal life (hours).

Example 1
Oxidation was performed by exposing 20 g of activated carbon a having an average particle size of crushed shape of 32/60 mesh (0.25 to 0.50 mm) and a specific surface area of 2400 m ² / g to 1% ozone atmosphere for 8 hours. . When the amount of oxygen-containing functional groups of the obtained activated carbon A having oxygen-containing functional groups was measured, the amount of oxygen-containing functional groups was 1.25 mmol / g, the amount of carbonyl groups was 0.41 mmol / g, and the amount of hydroxyl groups was 0.45 mmol. / G, the amount of lactone groups was 0.23 mmol / g, and the amount of carboxyl groups was 0.16 mmol / g. Further, when the differential pore volume distribution of the activated carbon A having an oxygen-containing functional group was obtained, the position of the peak top of the micropore peak was 0.9 nm, and the pore diameter was larger than 0 nm and smaller than 2 nm. The ratio of the pore volume of pores having a pore diameter of 0.7 to 1.2 nm to the pore volume was 94%. Moreover, the specific surface area of the activated carbon A having an oxygen-containing functional group was 2400 m ² / g, and the micropore volume of the pore diameter larger than 0 nm and 2 nm or less was 1.12 cm ³ / g.
Next, the trimethylsilanol removal test apparatus 1 shown in FIG. 1 is filled with activated carbon A having an oxygen-containing functional group, and 150 ppb of trimethylsilanol-containing air having a temperature of 23 ° C. and a relative humidity of 150 ppb of the relative humidity shown in Table 1. Trimethylsilanol removal test was conducted using the trimethylsilanol-containing air. The results are shown in Table 1.

(Comparative Example 1)
Oxidation was performed by exposing 20 g of activated carbon b having an average particle size of crushed shape of 32/60 mesh (0.25 to 0.50 mm) and a specific surface area of 1500 m ² / g to 1% ozone atmosphere for 8 hours. . The amount of oxygen-containing functional groups of the obtained activated carbon c having oxygen-containing functional groups was measured. The amount of oxygen-containing functional groups was 1.57 mmol / g, the amount of carbonyl groups was 0.35 mmol / g, and the amount of hydroxyl groups was 0.59 mmol. / G, the amount of lactone groups was 0.33 mmol / g, and the amount of carboxyl groups was 0.30 mmol / g. Further, when the differential pore volume distribution of the activated carbon c having an oxygen-containing functional group was obtained, the position of the peak top of the peak of the micropore was 0.7 nm, and the pore diameter was larger than 0 nm and smaller than 2 nm. The ratio of the pore volume of pores having a pore diameter of 0.7 to 1.2 nm to the pore volume was 43%. Moreover, the specific surface area of the activated carbon c having an oxygen-containing functional group was 1500 m ² / g, and the micropore volume larger than 0 nm and not more than 2 nm was 0.65 cm ³ / g.
Next, the trimethylsilanol removal test apparatus 1 shown in FIG. 1 is filled with activated carbon c having an oxygen-containing functional group, and the temperature is 23 ° C. and the relative humidity is 150 ppb of the relative humidity shown in Table 2 as air containing 150 ppb of trimethylsilanol. Trimethylsilanol removal test was conducted using the trimethylsilanol-containing air. The results are shown in Table 2.

(Comparative Example 2)
When the oxygen-containing functional group amount of the activated carbon b having a crushed shape average particle size of 32/60 mesh (0.25 to 0.50 mm) and a specific surface area of 1500 m ² / g was measured, the oxygen-containing functional group amount was 0. .39 mmol / g, the amount of carbonyl groups was 0.14 mmol / g, the amount of hydroxyl groups was 0.20 mmol / g, the amount of lactone groups was 0.02 mmol / g, and the amount of carboxyl groups was 0.03 mmol / g. Further, when the differential pore volume distribution of the activated carbon b was determined, the position of the peak top of the micropore peak was 0.7 nm, and the pore diameter relative to the pore volume of pores having a pore diameter of more than 0 nm and 2 nm or less. The ratio of the pore volume of pores having a diameter of 0.7 to 1.2 nm was 43%. Moreover, the specific surface area of the activated carbon b was 1500 m ² / g, and the micropore volume of the pore diameter larger than 0 nm and 2 nm or less was 0.65 cm ³ / g.
Next, the trimethylsilanol removal test apparatus 1 shown in FIG. 1 is filled with activated carbon b having oxygen-containing functional groups, and 150 ppb of trimethylsilanol-containing air having a temperature of 23 ° C. and a relative humidity of 150 ppb of the relative humidity shown in Table 3. Trimethylsilanol removal test was conducted using the trimethylsilanol-containing air. The results are shown in Table 3.

  FIG. 3 shows the relationship between the 90% removal life of the activated carbons of Example 1, Comparative Example 1 and Comparative Example 2 and the relative humidity of the air to be treated. As can be seen from the results, the activated carbon A of Example 1 has a higher removal life characteristic than the activated carbon b of Comparative Example 2 in the entire range of relative humidity of 35 to 55%, and the relative humidity of 50 to 55. It was found that the removal life characteristics at% showed a small reduction in the removal life characteristics when compared with the case where the relative humidity was 45% or less, and stable removal performance at a relative humidity of 35 to 55%. On the other hand, the activated carbon c of Comparative Example 1 shows a very high removal life characteristic compared to the activated carbon b of Comparative Example 2 when the relative humidity is 45% or less. However, when the relative humidity is 50% or more, the relative humidity is Compared with the case of 45% or less, the removal life characteristic was greatly reduced, and when the relative humidity was 55%, the removal life characteristic was lower than that of the active substance b of Comparative Example 2.

(Analysis of adsorption amount of dimer of silanol compound)
In Example 1-A, Comparative Example 1-B, and Comparative Example 2-B, activated carbon after the trimethylsilanol removal test (in Example 1, after 217.3 hours test, in Comparative Example 1, 234.1) 0.1 g of the sample after the time test and the sample after 99.3 hours in Comparative Example 2 were collected in a vial. Next, 2 mL of dichloromethane was added to the vial and shaken for extraction. Subsequently, the extract was quantitatively analyzed by GC-MS, and the ratio of the trimer of trimethylsilanol and trimethylsilanol in the substance adsorbed on the activated carbon was determined. As a result, in Example 1-A, trimethylsilanol was 5 mass%, and the dimer of trimethylsilanol was 95 mass%. In Comparative Example 1-B, the content of trimethylsilanol was 12% by mass and the dimer of trimethylsilanol was 88% by mass. In Comparative Example 2-B, trimethylsilanol was 76% by mass, and the trimethylsilanol dimer was 24% by mass.

Claims (9)

  Activated carbon having oxygen-containing functional groups, the amount of oxygen-containing functional groups per gram of activated carbon having oxygen-containing functional groups is 0.5 mmol / g or more, and differential pores determined by the MP method from nitrogen adsorption isotherms In the volume distribution, activated carbon having an oxygen-containing functional group having a peak top of a micropore peak at 0.8 to 1.1 nm is contacted with air to be treated containing a silanol compound to dimerize the silanol compound, A method for removing a silanol compound, comprising removing the silanol compound in the air to be treated by adsorbing the produced dimer of the silanol compound to activated carbon having the oxygen-containing functional group.   In the pore volume distribution, the ratio of the pore volume of pores having a pore diameter of 0.7 to 1.2 nm to the pore volume of pores having a pore diameter of more than 0 nm and 2 nm or less is 70 to 100%. The method for removing a silanol compound according to claim 1. ^3. The silanol compound according to claim 1, wherein the activated carbon having an oxygen-containing functional group has a specific surface area of 1700 m ² / g or more and a micropore volume of 1 cm ³ / g or more. Removal method.   The activated carbon having the oxygen-containing functional group has at least one or more of a carbonyl group, a hydroxyl group, a lactone group, and a carboxyl group as the oxygen-containing functional group. The removal method of the silanol compound of any one of Claims 1.   The method for removing a silanol compound according to any one of claims 1 to 4, wherein the silanol compound is trimethylsilanol.   The method for removing a silanol compound according to any one of claims 1 to 5, wherein a relative humidity of the air to be treated containing the silanol compound is 30 to 55%.   The method for removing a silanol compound according to any one of claims 1 to 5, wherein a relative humidity of the air to be treated containing the silanol compound is 50 to 55%.   Activated carbon having oxygen-containing functional groups, the amount of oxygen-containing functional groups per gram of activated carbon having oxygen-containing functional groups is 0.5 mmol / g or more, and differential pores determined by the MP method from nitrogen adsorption isotherms The silanol according to any one of claims 1 to 7, wherein activated carbon having an oxygen-containing functional group having a peak top of a micropore in a volume distribution of 0.8 to 1.1 nm is used. A chemical filter for carrying out a method for removing a compound.   An exposure apparatus comprising the chemical filter according to claim 8.