JP2012030163A - Air cleaning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air cleaning system that can remove a silanol compound such as trimethyl silanol at a high removal rate.SOLUTION: The air cleaning system includes: a dehumidifier 13; an internal chemical filter 14; and a temperature control humidity controller 15. Air containing the silanol compound is filtered by the internal chemical filter 14 after relative humidity of the air is lowered to be 33% or less by the dehumidifier 13. The silanol compound is dimerized under the low-humidity environment to be removed by the internal chemical filter 14 at a high removal rate. The temperature and humidity controller 15 allows the air having passed through the internal chemical filter 14 to return to the normal relative humidity.

Description

  The present invention relates to an air purification system for removing a silanol compound capable of removing from the air a silanol compound that may cause an exposure failure or the like in an exposure process.

  It is known that a disilazane compound such as hexamethyldisilazane (HDMS) is used as a photoresist adhesive in the exposure process of the semiconductor manufacturing process. HDMS, for example, is sprayed on the wafer surface as a gas to replace the hydroxyl group on the wafer surface with a trimethylsilanol group, thereby hydrophobizing the wafer surface and improving the adhesion between the wafer surface and the resist agent. . HDMS may be hydrolyzed and float in the form of trimethylsilanol (TMS) in the form of a gas in the exposure apparatus. However, the suspended TMS may adhere to a lens or the like and cause fogging, which may cause exposure failure.

  Therefore, for example, as shown in Patent Document 1, air is circulated inside the exposure apparatus, and a chemical filter having an adsorbent such as activated carbon is disposed in the circulation path. Gaseous impurities such as TMS are removed by the chemical filter, so that the inside of the exposure apparatus is maintained at a certain level of cleanliness, thereby preventing exposure troubles and the like.

  Patent Document 2 discloses a contaminant removal apparatus in which an air washer, a dehumidifier, and a chemical filter are arranged from the upstream side in a circulation path inside an exposure apparatus. In this pollutant removal device, the air washer removes pollutants in the air by water vapor spray, and the chemical filter removes pollutants that could not be removed by the air washer, thereby improving the collection efficiency of pollutants. . Further, the dehumidifying device removes a certain amount of water vapor from the air saturated with the air washer so that the removal performance of the chemical filter does not deteriorate.

JP 2008-181968 A JP 2008-91746 A

  By the way, TMS is a low molecular weight substance, and is difficult to adsorb on activated carbon or the like, and is readily desorbed even if adsorbed. Therefore, it is difficult to remove efficiently with a chemical filter having a normal adsorbent. Therefore, conventionally, in order to remove the necessary amount of TMS, it has been necessary to make the chemical filter thicker or multilayer, or to use a large amount of an adsorbent such as activated carbon.

  On the other hand, although the pollutant removal apparatus in Patent Document 2 is considered to increase the TMS collection efficiency by the air washer and the chemical filter, since the air washer is provided, the apparatus itself becomes large. Moreover, in the dehumidifier, the air whose saturated water vapor amount has been obtained by the air washer is only returned to normal humidity or higher than normal (for example, 90%), and silanol compounds such as TMS are efficiently removed. In order to do this, dehumidification is not actively carried out. That is, the pollutant removal device is not configured to remove the silanol compound with a simple configuration and a high removal rate.

  The present invention has been made in view of the above problems, and provides an air purification system for removing a silanol compound capable of removing a silanol compound such as TMS with a high removal rate with a simple configuration. Objective.

  The air purification system according to the present invention removes the silanol compound by filtering the dehumidifying means that dehumidifies the air containing the silanol compound to a relative humidity of 33% or less, and the air dehumidified by the dehumidifying means. And a chemical filter.

  The air purification system preferably includes humidifying means for humidifying the air filtered by the chemical filter. For example, the air dehumidified by the humidifying means can be returned to normal humidity. The lower the relative humidity, the higher the removal rate of the silanol compound. For example, it is better that the relative humidity is 20% or less.

  A chemical filter is comprised with the filter base material to which many adsorbents were fixed, for example. The silanol compound is usually trimethylsilanol. The air purification system according to the present invention is used for purifying air inside the exposure apparatus, for example.

  An exposure apparatus according to the present invention is disposed in order from the upstream side in a chamber that houses an exposure main body, an air circulation path that circulates air discharged from the chamber and supplies the air to the chamber again, and an air circulation path. A dehumidifying means and a chemical filter are provided, and the air dehumidified by the dehumidifying means so that the relative humidity is lower than the inside of the chamber is filtered by the chemical filter.

  Also in the exposure apparatus, it is preferable that the air dehumidified to a relative humidity of 33% or less by the dehumidifying means is filtered by the chemical filter. In addition, the exposure apparatus may further include a humidifying unit disposed on the downstream side of the chemical filter in the air circulation path. In this case, the dehumidified air is supplied to the chamber after being humidified. For example, a wafer subjected to a hydrophobic treatment with a photoresist adhesive containing a disilazane compound is disposed inside the chamber.

  An air purification method according to the present invention is an air purification method for purifying air containing a silanol compound, wherein the air dehumidified to a relative humidity of 33% or less is filtered with a chemical filter to remove the silanol compound. It is characterized by.

  In the present invention, the air containing the silanol compound is filtered by the chemical filter after the silanol compound is dimerized in a considerable amount by dehumidification. Since the dimer of the silanol compound is easily adsorbed by the chemical filter and is difficult to desorb after being adsorbed, the removal rate of the silanol compound in the chemical filter can be improved.

It is the schematic which shows the exposure apparatus with which the air purification system of this invention is applied. It is an enlarged view which shows a chemical filter. It is a schematic diagram which shows the aeration test apparatus of Example 1 in the aeration experiment 1. It is a schematic diagram which shows the aeration test apparatus of Example 2 in the aeration experiment 1. It is a graph which shows the result of ventilation test 1. It is a schematic diagram which shows the aeration test apparatus in the aeration experiment 2.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic view showing an exposure apparatus to which an air purification system according to an embodiment of the present invention is applied. As shown in FIG. 1, the exposure apparatus 10 has a structure in which an internal chamber 12 and an air circulation path 30 are provided inside an external chamber 11, and an exposure main body 20 is disposed inside the internal chamber 12. Is done.

  The air circulation path 30 is a passage for circulating the air inside the internal chamber 12. Inside the air circulation path 30, a dehumidifying device 13, an internal chemical filter 14, and a temperature control device 15 that constitute an air purification system are arranged in this order from the upstream side along a fixed path S to be described later.

  The exposure main body 20 includes an illumination optical system 21, a reticle 22, a projection optical system 23, and a wafer stage 24, and a wafer W is placed on the wafer stage 24. The wafer W has a surface hydrophobized with a photoresist adhesive containing a disilazane compound represented by the following general formula (1) and then coated with a photoresist agent.

R ₃ SiNHSiR ₃ (1)
In the formula (1), R is an alkyl group having 1 to 3 carbon atoms such as methyl and ethyl, but a part of R may be a hydrogen atom, or a halogen atom such as a fluorine atom or a chlorine atom. As the disilazane compound, hexamethyldisilazane (HDMS) in which R is all methyl in the above formula (1) is generally used.

  The illumination optical system 21 includes a relay lens system, a condenser lens, and the like, and makes the laser beam emitted from the light source 26 provided outside the external chamber 11 enter the reticle 22. The reticle 22 is a photomask having a predetermined mask pattern, and the mask pattern is imaged on the wafer W arranged on the wafer stage 24 via the projection optical system 23, and the wafer W is subjected to exposure processing. Done.

  A fan (not shown) is provided inside the air circulation path 30 and the like, and the air inside the external chamber 11 is circulated along the fixed path S by the fan. Specifically, the air in the air circulation path 30 is supplied into the internal chamber 12 through the internal supply port 16, circulates inside the internal chamber 12, and is discharged to the air circulation path 30 through the internal discharge port 17. Is done. The air discharged from the internal discharge port 17 passes through the dehumidifying device 13, the internal chemical filter 14, and the temperature control device 15 in this order in the air circulation path 30 and again through the internal supply port 16 to the internal chamber. 12 is supplied inside. A part of the air inside the internal chamber 12 is exhausted to the outside via the local discharge port 18, and the external air is supplied to the inside of the air circulation path 30 via the external supply port 19.

  The temperature / humidity adjusting device 15 is disposed upstream of the internal supply port 16, and the air supplied from the air circulation path 30 to the inside of the internal chamber 12 is supplied to the constant humidity (for example, relative humidity) by the temperature / humidity adjusting device 15. The humidity is adjusted to about 45% to 55%). An external chemical filter 25 is disposed upstream of the external supply port 19, and air from the outside is supplied to the air circulation path 30 after removing gaseous contaminants by the external chemical filter 25. . In the present embodiment, air from the outside is supplied, for example, downstream of the internal chemical filter 14 and upstream of the temperature and humidity control device 15.

  As shown in FIG. 2, the internal chemical filter 14 is a filter substrate 50 in which an infinite number of adsorbents 51 are fixed by a known binder. The internal chemical filter 14 is for removing contaminants in the air including a silanol compound and a disiloxane compound described later, and filtering the air.

  The filter base material 50 has a mat shape and has a three-dimensional network skeleton structure composed of a foam such as polyurethane foam. However, the filter base 50 is a fiber composed of organic fibers or inorganic fibers instead of the foam. A substrate, a honeycomb structure, or a pleated structure may be used. The adsorbent 51 is made of a porous material such as a crushed shape, a powder shape, or a particle shape. Examples of the porous body include those capable of adsorbing gaseous organic substances such as activated carbon, silica, zeolite, alumina, and porous glass by physical adsorption. Among these, activated carbon is preferable. This is because activated carbon easily adsorbs silanol compounds and disiloxane compounds.

  The external chemical filter 25 may be a chemical filter having the same configuration as that of the internal chemical filter 14, but may have a different configuration. In addition, the chemical filters 14 and 25 may not be those in which an adsorbent is fixed to a filter base material, and may be those in which an adsorbent is filled in, for example, a container or a column.

  The dehumidifying device 13 is a device that dehumidifies the air passing therethrough, for example, a column filled with a hygroscopic agent inside, a device in which the hygroscopic agent is fixed to a substrate similar to the filter substrate described above, or a known dryer A device or the like is used.

As described above, the wafer W is hydrophobized by the photoresist adhesive containing the disilazane compound, and the interior of the chamber 12 is kept at a constant relative humidity. Therefore, the silanol compound of the general formula (2) generated by the hydrolysis reaction of the disilazane compound (see the reaction formula (2) ′) floats inside the internal chamber 12 and is discharged from the internal discharge port 17. The air contains a silanol compound.
R ₃ SiNHSiR ₃ + 2H ₂ O → 2R ₃ SiOH + NH ₃ ... (2) ′

R ₃ SiOH (2)
The silanol compound has only one SiOH group as shown in Formula (2). In the formula (2), R is an alkyl group having 1 to 3 carbon atoms such as methyl and ethyl, but a part of R may be a hydrogen atom, or a halogen atom such as a fluorine atom or a chlorine atom. The silanol compound is generally a decomposition product of HDMS, and is trimethylsilanol (TMS) in which R is all methyl in the formula (2).

  The air containing the silanol compound discharged from the internal discharge port 17 first passes through the dehumidifying device 13 in the air circulation path 30. The air containing the silanol compound is dehumidified by passing through the dehumidifying device 13, and the relative humidity thereof is at least lower than the relative humidity inside the internal chamber 12 and is sent to the internal chemical filter 14.

The silanol compound is difficult to dimerize in a normal humidity atmosphere inside the exposure apparatus 10 (for example, around 50% relative humidity). However, silanol compounds are dimerized by dehydration condensation as shown in the following formula (3) in an environment with low chemical stability and relatively low relative humidity, and change to disiloxane compounds that are dimers. It becomes easy. Therefore, the silanol compound contained in the air is changed into a considerable amount of a disiloxane compound when the air is dehumidified by the dehumidifier 13.
2R ₃ SiOH → R ₃ SiOSiR ₃ + H ₂ O (3)
In the formula (3), the disiloxane compound (R ₃ SiOSiR ₃ ) is generally hexamethyldisiloxane which is a dimer of TMS.

  The lower the relative humidity of the air dehumidified by the dehumidifier 13 and sent to the chemical filter 14, the higher the ratio of dimerizing the silanol compound. However, considering practicality and the like, the rate of increase in dimerization is remarkably increased 33. % Or less is preferable. Further, when it is necessary to dimerize TMS at a higher rate, for example, the relative humidity may be set to 20% or less.

  Since the disiloxane compound which is a dimer has a molecular weight larger than that of the silanol compound, the disiloxane compound is more easily adsorbed by the adsorbent 51 of the internal chemical filter 14 than the silanol compound. It becomes difficult to detach from the agent 51. In addition, even if the silanol compound adsorbed on the adsorbent 51 is not dimerized, it is actively dimerized as low-humidity air continues to flow through the filter 14. Thus, after dehumidifying the air, when the air is filtered by the internal chemical filter 14, the silanol compound contained in the air is positively dimerized and removed by the internal chemical filter 14 at a high removal rate. become. As the removal rate increases, the filter 14 with degraded performance can remove the required amount of silanol compound, resulting in a longer period of use of the filter 14 and sufficient removal of the silanol compound even when the thickness is thin. it can.

  As described above, the temperature / humidity control device 15 is disposed on the downstream side of the internal chemical filter 14. Therefore, the circulating air whose relative humidity has been reduced by the dehumidifying device 13 is humidified by the temperature and humidity control device 15 and the relative humidity is increased again, and then supplied to the inside of the internal chamber 12. Therefore, the relative humidity inside the internal chamber 12 can be maintained at a constant humidity as described above.

  In this embodiment, air is dehumidified by supplying low-humidity air to the air circulation path 30 from the outside instead of being dehumidified by the dehumidifier 13, and the dehumidified air is supplied to the internal chemical filter 14. It may be supplied. Similarly, humidification of the circulating air may be performed by supplying high-humidity air from the outside via the external supply port 19 instead of being performed by the temperature control device 15.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the configurations of the following examples.

[Ventilation test 1]
In Examples 1 to 5 and Comparative Example 1, air containing TMS was aerated at a predetermined relative humidity inside the aeration test apparatus, and the rate of change of TMS to hexamethyldisiloxane (hereinafter abbreviated as “D2”). It was confirmed.

[Example 1]
In the aeration test apparatus 40 according to the first embodiment, as shown in FIG. 3, a nitrogen gas cylinder 41, a flow meter 42, and a TMS generation source 43 are connected in order from the upstream side, and six layers are formed on the downstream side of the TMS generation source 43. The column 44 in which the chemical filters 44A to 44F of FIG. The ventilation test apparatus 40 was arranged in a constant temperature and humidity chamber 47 except for the nitrogen gas cylinder 41 so that the temperature of ventilation inside the apparatus 40 was 23 ° C. The constant temperature and humidity chamber 47 was shielded from light to avoid the influence of light. As the constant temperature and humidity chamber 47, PR-1KT manufactured by Espec Corporation was used.

  The TMS generation source 43 is configured by disposing an inner container 45 having an opening at the top and containing liquid TMS inside the outer container 46 forming a part of the ventilation path. The chemical filters 44A to 44F were obtained by cutting out Gigasorb L (trade name, manufactured by Nitta Corporation) formed by adhering activated carbon to urethane foam into a cylindrical shape having a diameter of 19 mm and a height of 20 mm.

  The nitrogen gas cylinder 41 supplies nitrogen gas having a relative humidity of 0% and a nitrogen purity of 99.999%, and the flow rate measured by the flow meter is 5.1 liters / minute (surface wind speed in the column 44 is 0.3 m / second). Thus, nitrogen gas was passed through the ventilation path of the device 40. The TMS generation source 43 contained vaporized TMS in a certain ratio in the air ventilated inside the device 40. A part of TMS was dimerized to D2, and the chemical filter in the column 44 collected TMS and D2. The column 44 had the multilayer (six layers) chemical filters 44A to 44F as described above so that substantially all of TMS and D2 contained in the air could be collected. Nitrogen gas aeration was continued for 72 hours.

[Example 2]
In the aeration test apparatus 50 of Example 2, as shown in FIG. 4, the gas component removal column 51, the dehumidification columns 52 and 53, the hygrometer 54, and the TMS generation source 43 are sequentially connected from the upstream side. The column 44 was connected to the downstream side. On the downstream side of the column 44, a valve 57, a flow meter 42, and a pump 55 were further connected in this order. As the flow meter 42, the TMS generation source 43, and the column 44, the same ones as in Example 1 were used, and the entire apparatus 50 was disposed inside the constant temperature and humidity chamber 47 under the same conditions as in Example 1.

  The gas component removing column 51 has a diameter of 50 mm and a length of 6 cm, and Gigacoal A (trade name, manufactured by Nitta Corporation) is cut into a diameter of 50 mm and a height of 2 cm, Gigacoal C (trade name). , Manufactured by Nitta Co., Ltd.) were cut into a diameter of 50 mm and a height of 4 cm in this order from the upstream side. The dehumidifying column 52 was a column having a diameter of 50 mm and a length of 16 cm, and was filled with silica gel (manufactured by Kanto Chemical Co., Inc., silica gel blue, medium particles). The dehumidifying column 53 was a column having a diameter of 25 mm and a length of 10 cm, and was filled with calcium chloride (for drying) (manufactured by Kanto Chemical Co., Inc.). As the hygrometer 54, VIEWMEMORY THR-VM made by SYINYEI was used.

  In Example 2, the air in the constant temperature and humidity chamber 47 is sucked by the pump 55, the flow rate is adjusted by the valve 57, and the flow rate measured by the flow meter 42 is 5.1 liters / minute (surface air velocity in the column 44). The air was vented to the ventilation path of the device 50 so that the air flow rate was 0.3 m / sec. The aerated air was dehumidified by the dehumidifying columns 52 and 53 and the relative humidity measured by the hygrometer 54 was 13% while the gas component in the air was removed by the gas component removing column 51. Also in the second embodiment, similarly to the first embodiment, the TMS generation source 43 contains the vaporized TMS in the ventilation air at a certain ratio, and the chemical filters 44A to 44F are dimerized with the TMS in the ventilation air. D2 was collected. In Example 2, as in Example 1, aeration was continued for 72 hours.

[Example 3]
This was carried out in the same manner as in Example 2 except that the humidity inside the constant temperature and humidity chamber 47 was adjusted so that the relative humidity measured by the hygrometer 54 was 20%.

[Example 4]
This was carried out in the same manner as in Example 2 except that the dehumidifying columns 52 and 53 were omitted, the humidity inside the constant temperature and humidity chamber 47 was adjusted, and the relative humidity measured by the hygrometer 54 was 25%. .

[Example 5]
This was carried out in the same manner as in Example 2 except that the dehumidifying columns 52 and 53 were omitted, the humidity inside the constant temperature and humidity chamber 47 was adjusted, and the relative humidity measured by the hygrometer 54 was 33%. .

[Comparative Example 1]
This was carried out in the same manner as in Example 2 except that the dehumidifying columns 52 and 53 were omitted, the humidity inside the constant temperature and humidity chamber 47 was adjusted, and the relative humidity measured by the hygrometer 54 was 44%. .

  In each of Examples 1 to 5 and Comparative Example 1, after 72 hours of aeration, each of chemical filters 44A to 44F was placed in 20 ml of acetone, and the gaseous organic matter adsorbed on each filter was subjected to ultrasonic vibration over 2 hours. The amount of TMS and D2 adsorbed on each of the filters 44A to 44F was measured by GC-FID. Tables 1 and 2 show the adsorption amounts of TMS and D2 in weight% when the total adsorption amount and total adsorption amount of TMS and D2 of all the filters 44A to 44F in the column 44 are 100% by weight. FIG. 5 is a graph showing the relationship between D2 wt% and relative humidity.

In addition, the measurement conditions of GC-FID are as follows.
GC-FID: manufactured by Shimadzu Corporation, GC-2010
Column: Inert Cap 1MS Inner Diameter 0.25mm Length 60m
Column temperature: maintained at 40 ° C. for 5 minutes, then heated to 280 ° C. at 10 ° C./min. Then hold at 280 ° C for 21 minutes.
Carrier gas: He Column flow rate: 1.16 ml / min Injection volume: 1.0 μl Measurement time: 50 minutes

  As is clear from Tables 1 and 2 and FIG. 5, the lower the relative humidity, the more easily TMS changes to D2, and the rate of change to D2 can be significantly increased by setting the relative humidity to 33% or less. It was. Further, as shown in Examples 2 and 3, when the relative humidity is set to 20% and 13% or less, the change rate to D2 becomes about 70% or more and about 90% or more, and the change rate to D2 is further increased. We were able to.

[Ventilation test 2]
In the aeration test apparatus of the aeration test 2, as shown in FIG. 6, a column 80 in which six layers of chemical filters 83 </ b> A to 83 </ b> F are stacked is prepared as in the aeration test 1. However, in this test, about 450 g / m ² of TMS was adhered to the most upstream chemical filter 83A and used as a TMS generation source. On the side of the air outlet 82 of the column 80, there are a valve 84 for adjusting the flow rate of air, a flow meter 85 for measuring the flow rate of air vented to the column 80, and a pump 86 for ventilating the column 80 with air. Connected.

  The column 80 was aerated for 240 hours with air conditioned at 23 ° C. at 10.2 liters / minute (surface wind speed 0.6 m / second). A part of TMS was dimerized to D2, and TMS or D2 was desorbed from the chemical filter 83A by air ventilation, and flowed downstream.

  After the ventilation, the amounts of TMS and D2 adsorbed on the filters 83A to 83F were measured in the same manner as in the ventilation test 1. Further, regarding the chemical filters 83A to 83F before ventilation (0 hour), the weights of TMS and D2 were similarly measured as blanks. Table 3 shows the measured values in each layer and the ratio (wt%) of the adsorption amount of each layer when the total adsorption amount is 100 wt% for TMS and D2.

  As is apparent from the results in Table 3, most of the TMS was desorbed from the first-layer chemical filter, and the desorbed TMS was most adsorbed by the third-layer chemical filter. On the other hand, most of D2 was retained by the first-layer chemical filter, and most of D2 was adsorbed by the second-layer filter. That is, TMS is difficult to be adsorbed by the chemical filter and is easily desorbed once adsorbed, but the dimer (D2) is easily adsorbed to the chemical filter, and once adsorbed, it is difficult to desorb from the filter. Understandable.

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 12 Internal chamber 13 Dehumidifier (dehumidification means)
14 Internal chemical filter 15 Humidity control device (humidification means)
20 exposure body part 30 air circulation path 50 filter base material 51 adsorbent

Claims (11)

  A dehumidifying means for dehumidifying air containing silanol compounds to a relative humidity of 33% or less; and a chemical filter for removing the silanol compounds by filtering the air dehumidified by the dehumidifying means. Features an air purification system.   The air purification system according to claim 1, further comprising a humidifying unit that humidifies the air filtered by the chemical filter.   The air purification system according to claim 1, wherein the relative humidity is 20% or less.   The air purification system according to claim 1, wherein the chemical filter includes a filter base material on which a large number of adsorbents are fixed.   The air purification system according to claim 1, wherein the silanol compound is trimethylsilanol.   6. An exposure apparatus wherein internal air is purified by the air purification system according to any one of claims 1 to 5.   A chamber in which the exposure main body is disposed, an air circulation path that circulates the air discharged from the chamber and supplies it to the chamber again, and a dehumidification that is sequentially disposed in the air circulation path from the upstream side An exposure apparatus comprising: means and a chemical filter, wherein the air dehumidified by the dehumidifying means so that the relative humidity is lower than the inside of the chamber is filtered by the chemical filter.   8. The exposure apparatus according to claim 7, wherein the air dehumidified to a relative humidity of 33% or less by the dehumidifying means is filtered by the chemical filter.   8. The exposure according to claim 7, further comprising humidifying means disposed on the downstream side of the chemical filter in the air circulation path, wherein the dehumidified air is humidified and supplied into the chamber. apparatus.   8. The exposure apparatus according to claim 7, wherein a wafer hydrophobized with a photoresist adhesive containing a disilazane compound is disposed inside the chamber.   An air purification method for purifying air containing a silanol compound, wherein the air dehumidified to a relative humidity of 33% or less is filtered with a chemical filter to remove the silanol compound.

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