JPH11195576A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner capable of reducing the deterioration of its performance at any exposure wavelength for a long time of period by coating a high transmitting, fading resistant, and hydrophobic substance for the wavelength of an exposure light on a surface of an optical device existing in an optical light path, and putting a trap mechanism for a hydrophilic impurity in a vessel. SOLUTION: At least a part of an optical system is covered by a chamber capable of being sealed from an outside air and the inside of the chamber is purged by an impurity, metallic compound, organic compound, and the like, and oxidizing gas with its moisture removed. The vessel has a mechanism of trapping a hydrophilic material and at least a part of a lens surface and a mirror 206 surface, through which the exposing light enters are coated by a hydrophobic substance transparent for ultraviolet radiation of wavelengths from 160 to 380 nm. The ultraviolet light passing through a reticle 14 enters a sealing chamber 102 which seals a demagnifying exposing lens group 15 disposed in a mirror cylinder 16 and transcribes a pattern of the reticle 14 on a semiconductor wafer 17 through a demagnifying exposing lens group 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing a semiconductor device, and more particularly to an exposure apparatus such as a stepper exposure apparatus including a reduction exposure system.

[0002]

2. Description of the Related Art A stepper exposure apparatus reduces a pattern on a reticle or mask (collectively referred to as a reticle in this specification) to 1/10 to 1/5 to expose a photoresist film or the like on a semiconductor wafer. An image is formed on an object. With the increase in integration and miniaturization of semiconductor devices, the exposure wavelength of a stepper exposure apparatus has been shortened from a g-line of a mercury lamp to an i-line, and further, a KrF laser beam of an excimer laser or an ArF
Shortening the wavelength to laser light is in progress. The ultraviolet light used for these exposures has a high photon energy and causes a chemical change in a photoreceptor such as an irradiated photoresist.
A reticle pattern is formed on an exposure target.

FIG. 4 shows a conventional stepper exposure apparatus.
In FIG. 4, a lamp 41 that emits ultraviolet light and a condenser lens 42 for irradiating light emitted from the lamp 41 onto a reticle 44 are arranged in a lens barrel 401 of an illumination system. Emitted from lamp 41, condenser lens 4
The light collimated in 2 irradiates the reticle 44. Further, the ultraviolet light that has passed through the opening of the reticle 44 passes through the inside of the projection system barrel 402, is focused by the reduction projection system lens group 45, and exposes the photoresist film applied on the semiconductor wafer 47. Note that the semiconductor wafer 47 is mounted on an XY stage 49 fixed on a base 48. The photoresist film applied on the semiconductor wafer 47 is removed by a shutter, a diaphragm, etc., which are omitted in FIG.
After exposing with an appropriate illuminance, the XY stage 49 is moved,
Exposure is repeatedly performed in the same procedure.

In order to increase the processing speed of the stepper, it is necessary to stabilize and stabilize the amount of light transmitted through all the lens groups of the illumination system and the exposure system, and to minimize flare and uneven illuminance on the object to be exposed. Must be suppressed. Usually, an antireflection film for an exposure wavelength is formed on the lens surface in order to increase transmittance and suppress flare. Further, on the mirror surface, an enhanced reflection film composed of a metal and a dielectric multilayer film is formed in order to increase the reflectance and increase the amount of light.

[0005]

If the g-line and i-line steppers are used for a long period of time, the lens surfaces constituting the illumination system lens group 42 and the projection system reduction lens group 45 in FIG. Clouds and organic matter accumulate on the portion irradiated with the ultraviolet exposure light. In general, the surfaces of these optical elements such as lenses and mirrors are coated with an antireflection film or an antireflection film for the exposure wavelength, and the reflectivity changes due to cloudiness and the deposition of organic substances. As the transmittance of the entire system decreased, scattering of exposure light also occurred. If the fogging and the organic substance adhere to the surface of the optical element constituting the optical system, the illuminance on the object to be exposed may become uneven. Further, when the deposit adhering to the lens group surface absorbs the exposure light, similarly, the transmittance of the lens decreases and the transmittance in the lens surface becomes uneven. Further, absorption of the exposure light causes a temperature change of the lens and the like, thereby deteriorating the exposure performance. In such a state, the projected illuminance of the stepper decreases, illuminance unevenness occurs, flare and the like increase, and the performance as a whole degrades, such as a shift in focus position and deterioration in resolution performance.

The exposure wavelength is excimer KrF laser (248
nm) and ArF laser (193 nm).
When the energy density of photon energy increases,
Organic substances that are easily decomposed and removed from the lens surface are oxidized and removed from the lens surface by laser irradiation, and when laser irradiation is stopped, organic substances are re-adhered. There was a problem such as the change in illuminance.

On the other hand, there is a problem that new active species are formed from impurity substances in the atmosphere where the optical system is placed due to high photon energy, and new deposits which are not generated by low energy light are deposited. there were.

In order to solve the above problems, Japanese Patent Laid-Open No.
Improvements to filling the barrel with gas such as N ₂ are disclosed -201702 a non-oxidizing gas in. Japanese Patent Application Laid-Open No. Hei 7-273016 discloses an improvement measure for preventing performance deterioration by preventing sticking to a lens or the like with a seal glass and making the seal glass replaceable.

However, the inside of the lens barrel is filled with N ₂ ,
Although the oxidation reaction can be suppressed, the lens barrel contains a large amount of contaminants including oxygen, such as adhesives for fixing the lens and the lens barrel, and organic substances attached to the inner surface of the lens barrel. It is very difficult to completely prevent oxidation. Further, it is impossible to prevent the deposition of deposits due to oxidation.
Furthermore, even if the impurity substance causing the adhesion is very low in concentration, it is adsorbed and concentrated on the lens surface and reacts on the lens surface. It was very difficult in practice. That is, it is not enough to prevent the adhesion of impurities inside the lens barrel, the dissociation of impurities due to ultraviolet light, and the deterioration of optical performance due to deposition due to a synthesis reaction or the like.

[0010] Further, there is a problem that conventional measures cannot cope with the problem, for example, it is very difficult to replace the reduction exposure system lens group.

An object of the present invention is to provide an exposure apparatus in which the performance is not deteriorated for a long time at any exposure wavelength.

[0012]

In order to achieve the above object, an exposure apparatus according to the present invention passes light emitted from a light source on an optical path including an optical element such as a lens or a mirror, and passes the light on an object to be exposed through a reticle. In an exposure apparatus, at least a part of the optical element is covered with a sealed container and can be purged with a clean oxidizing gas to reduce the impurity concentration in the container, and the surface of the optical element existing on the optical path is exposed. A coating of a substance having high light transmittance and high light resistance and hydrophobicity at the wavelength of light is provided, and a hydrophilic impurity trap mechanism is provided in the container so that the hydrophilic impurity gas can be adsorbed and removed.

[0013]

According to a preferred embodiment of the present invention, there is provided an exposure apparatus for passing a light beam from a light source through an optical system including a lens and a mirror, and exposing the light onto an object to be exposed through a reticle. At least a part of the optical system is covered with a container capable of blocking the outside air, and the inside of the container is purged with an oxidizing gas from which impurities such as metal compounds and organic compounds and moisture have been removed. It has a mechanism for trapping a substance having a group, and at least a part of a lens surface or a mirror surface on which exposure light is incident is coated with a substance that is transparent to ultraviolet light of 160 nm to 380 nm and has hydrophobicity. It is characterized by having.

The hydrophobic substance coated on the lens surface has, for example, a refractive index of 1.35 or more at an exposure wavelength.
It is made of a material having a low refractive index in the range of 1.52, and is positioned on the outermost surface as a part of a multilayer film configuration that realizes antireflection performance of exposure light. As the hydrophobic substance, for example, CaF
Compounds containing ₂ or CaF ₂ are preferably used. In addition, the hydrophobic substance coated on the surface of the optical element has a sufficiently low exposure light absorptance (for example, 0.1%).
% Or less), other than CaF ₂ or the like. In that case, it is desirable that the extinction coefficient k and the film thickness d (nm) of the hydrophobic coating satisfy the following conditions. d <20 nm k * d <0.02 nm In the trapping mechanism, the substance used for the trap may be a hydrophilic coating, TiO ₂ or Ti
A coating of a compound containing O ₂ , silicic acid or a gel-like substance based on silicic acid, or a substance based on activated carbon or activated ash can be used. Preferably, the hydrophilic substance forming the hydrophilic coating has a static contact angle with water of 30 ° or less, and the hydrophobic substance has a static contact angle with water of 50 ° or more.

The hydrophilic substance used in the trap is T
If a compound coating comprising iO ₂ or TiO _2, further it is preferable to provide a mechanism for irradiating ultraviolet light shorter than 380nm in the hydrophilic material surface.

[0016]

According to the above construction, the lens and the mirror have an impurity substance having a hydrophilic group such as a hydroxyl group, a carboxyl group, a carbonyl group, an amino group or a sulfone group existing in the mirror holding environment. Since it is difficult to be adsorbed on the surface, it is possible to suppress a reaction such as dissociation or polymerization of the impurity substance due to exposure light on the surface. Further, it is possible to prevent the hydrophilic impurity substance dissociated and generated by the exposure light in the gas layer from depositing on the lens and mirror surfaces.

Furthermore, by purging with a gas from which impurities are removed as much as possible, the concentration of impurity substances in the atmosphere where the lens and mirror are installed is reduced, and the adhering substances are prevented from adsorbing or synthesizing on the lens and mirror surfaces. ,
Organic substances that cannot be completely removed can be oxidized and removed by irradiating ultraviolet rays in an oxidizing atmosphere. Further, by absorbing and removing the hydrophilic impurity substance in the optical element holding environment, the impurity concentration on the surface of the lens and the mirror can be reduced to a level that does not generate a reaction product due to ultraviolet rays, and the optical performance of the exposure apparatus is extended. Stabilizes over time.

An excimer (ArF) laser exposure lens whose performance has deteriorated is connected to a Fourier transform infrared spectrometer (hereinafter referred to as FTIR).
), And found that various compounds such as hydrocarbons, carboxylic acid compounds, acrylamide, sulfates, and silicates were deposited on the lens surface.

Analysis of the same unused lens system showed that
Various hydrocarbons were detected. Therefore, it can be determined that the carboxylic acid compound, acrylamide, sulfate, silicate and the like are formed by the reaction of the components in the atmosphere and the outgas components from the lens assembly. Normal,
It is known that various hydrocarbons adhere to the sample left in the air, and it is not possible to distinguish between hydrocarbons that adhere in the air and those that are formed by photochemical reactions, It has been clarified that it adheres to the lens surface during the normal lens making process and after cleaning.

Further, in order to examine on which surface the carboxylic acid compound, acrylamide, sulfate, silicate and the like are likely to adhere, the outermost surface layer of the antireflection film formed on the lens surface should be made hydrophilic. Irradiate a laser using a thin film mainly composed of SiO ₂ partially terminated with H and a thin film mainly composed of CaF ₂ having hydrophobicity in a use environment of an exposure apparatus. As a result, deposits were found only on the surface of the film having a hydrophilic surface, and no attachment was found on the hydrophobic surface. As described above, hydrocarbons generally adhere to almost all surfaces. Therefore, most surfaces show hydrophobicity. However, when ultraviolet rays such as an ArF laser are irradiated in an environment containing oxygen, the hydrocarbons adhere to the surface. Is removed, and a thin film mainly composed of SiO ₂ partially terminated with H becomes hydrophilic.

From the above results, the impurity substance having a hydrophilic group existing in the laser irradiation environment is adsorbed on the lens surface,
Then, it was found that reactions such as dissociation and synthesis by the irradiation energy of the ultraviolet laser were generated, and attached matter was generated. The present invention has been made based on the above background.

[0022]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a main part of an i-line exposure apparatus according to one embodiment of the present invention. In the figure, reference numeral 101 denotes an illumination system lens sealing chamber; 102, a projection system lens sealing chamber;
3 is an oxygen gas cylinder, 104 is a gas purifier, 105 is a gas discharge hole, 106 is an antireflection film using a hydrophobic material on the outermost surface, and 107 is a hydrophilic coating.

Embodiment 1 of the present invention will be described in detail with reference to FIG. In FIG. 1, reference numeral 11 denotes a light-emitting tube as a light source, which has a high-luminance light-emitting portion that emits ultraviolet light, far ultraviolet light, and the like. Ultraviolet rays emitted from the arc tube 11 are adjusted by a condenser lens 12 and optical components such as an i-line filter, a mirror, an optical integrator, and a zoom lens, which are omitted in the schematic diagram, so as to uniformly illuminate the reticle. The ultraviolet light that has passed through the reticle 14 is transmitted to the reduction exposure lens group 1 contained in the lens barrel 16.
Then, the pattern of the reticle 14 is transferred onto the semiconductor wafer 17 via the reduction exposure lens group 15. The semiconductor wafer 1
7 is mounted on an XY stage 19 fixed on a base 18. The lens barrel 16 includes an adhesive for bonding the reduction exposure lens group 15 and the lens barrel 16, a lens fixing jig, and the like, but is not shown in FIG.

Oxygen gas cylinder 103 and gas purifier 1
The oxygen gas purified by 04 is introduced into the sealing chamber 102. The oxygen gas used here is not only an organic solvent and an organic metal-based gas mixed into the clean room, but also an impurity gas that generates a solid by a photochemical reaction.
02, so as to keep the impurity level as low as possible. Lens barrel 1 in sealed chamber 102
6, a through hole 108 is formed so that the purified oxygen gas can efficiently reach the reduction exposure lens group 15. This oxygen gas is flowed into the sealing chamber 102 for a while to sufficiently replace the impurity gas in the lens barrel. Thereafter, exposure is performed while flowing oxygen gas.

In order to stabilize the optical performance of an exposure apparatus, it is necessary to stabilize the optical performance of an optical element irradiated with exposure light, that is, impurities that deteriorate optical performance such as lens transmittance and mirror reflectance. It is important to prevent the adhesion and deposition of ash. In general, a multilayer antireflection film or a multi-reflection film is formed on the surface of a lens or a mirror, and even a small amount of adhesion or deposition greatly changes the optical performance.

Although the inside of the sealing chamber 102 is purged with purified oxygen gas and maintained in an environment with very few impurities, the adhesive between the lens and the lens barrel and the surface of the lens barrel are kept in the lens barrel. There are impurities and the like adsorbed on the surface, and there is a limit no matter how much impurities are removed. The impurities present in the lens barrel repeatedly adsorb and desorb on the lens barrel inner surface,
Either is discharged through the through-hole 108 to the outside of the lens barrel together with oxygen as a purge gas. However, it takes a very long time to completely remove impurities, and the purge gas has to be stopped due to maintenance of the apparatus, and during this time, the inside of the lens barrel is re-contaminated. It is very difficult to perform exposure in an environment free from impurities.

Under these circumstances, in order to eliminate the adhesion and deposition of impurities on optical components such as lenses and mirrors, it is necessary not only to remove the impurities but also to remove the deposits and prevent the deposition. The deposits are various hydrocarbons, carboxylic acid compounds, acrylamide, and the like. The hydrocarbons adhere regardless of irradiation with ultraviolet rays, and can be oxidized and removed by irradiating with ultraviolet rays in an oxidizing atmosphere. For this purpose, in the present embodiment, the lens environment is set to an oxygen atmosphere, and the lens is configured to be oxidized and removed by irradiating ultraviolet exposure light. On the other hand, hydrophilic impurities having a hydroxyl group, a carboxyl group, a carbonyl group, an amino group, a sulfone group, etc. are decomposed and polymerized by the energy of ultraviolet rays, deposit as deposits, and cause deposits that cannot be removed by oxidation. May be.

[0028] The adhesion and retention time of such a hydrophilic impurity on the hydrophobic surface becomes very short for the hydrophilic surface. As a result, the probability of causing reactions such as dissociation and polymerization on the hydrophobic surface due to the energy of ultraviolet rays is reduced, and it is difficult to form deposits.

Therefore, in this embodiment, a multilayer antireflection film 106 made of a hydrophobic material is formed on the outermost surface of the lens in order to prevent a slight deposition. Although FIG. 1 shows that an antireflection film using a hydrophobic material is formed only on one lens, it is more preferable to coat the surface of all optical elements irradiated with exposure light. The hydrophobic material used here needs to have excellent light durability against ultraviolet exposure light to be used, and further, a material having high transmittance of ultraviolet exposure light and having no absorption must be used. As the hydrophobic coating, an organic material having an alkyl group, a phenyl group, or the like is generally used. However, in an ultraviolet exposure apparatus, extremely high-intensity ultraviolet rays are used, which is not desirable in terms of durability. Non-light-resistant coatings can be degraded by UV radiation and become a source of contamination. Therefore, an inorganic material having excellent light durability is more suitable. As the hydrophobic coating of this embodiment, since the outermost layer (air adjacent layer) of the antireflection coating on the lens surface is a coating having hydrophobicity, the refractive index is as low as about 1.35 to 1.52. Preferably, the material is a CaF ₂ coating and Ca
The F ₂ using a coating as a main component. CaF ₂
Since the coating has no absorption in the range of 160 nm to the visible region and has excellent light durability, it is a suitable material as the outermost surface coating of the antireflection film.

In this embodiment, the hydrophobic coating is used as the outermost coating of the anti-reflection film. However, the coating does not necessarily have to contribute to the anti-reflection coating. A similar effect can be obtained for prevention. With this thickness, it can be used even if it absorbs at the exposure light wavelength, and the extinction coefficient k and the film thickness d (n
It is desirable that the relationship of m) is d <20 nm and k * d <0.02. This translates to 0.1% absorption
If the absorption exceeds this, the temperature of the optical element rises, and the exposure performance deteriorates. If the film thickness is too large, the reflection characteristics will be affected. For example, in the case of a coating having a low refractive index such as CaF ₂ , coating the antireflection film or the surface of the half mirror will result in a change in the reflectance. 20
If the thickness is not more than nm, the coating can be applied without considering the optical performance, except in special cases.

Conventionally, a material having a high refractive index has been used for the surface of a dielectric mirror. In the case of a mirror, as shown in this embodiment, the outermost surface is coated with a material having a low refractive index such as CaF _2. Even so, there is almost no effect on the reflection characteristics. That is, in the case of a mirror, the thickness does not need to be particularly limited as long as there is no absorption. However, usually, the extinction coefficient is not 0, and it is desirable that the extinction coefficient is within the above range in terms of absorption.

In order to minimize the concentration of hydrophilic impurities in the lens holding environment, a hydrophilic coating 107 is applied to the inner surface of the lens barrel and trapped. Lens barrel 16
Since the impurities that cannot be completely removed from the gas introduced into the inside can be trapped in the vicinity of the lens, it is very effective in reducing the concentration of the impurity gas adsorbed on the lens surface. A hydrophobic film such as a hydrocarbon adheres to the surface of the hydrophilic coating 107 over time, but this hydrophobic film can be constantly oxidized and removed like the lens surface, and the impurity trap can be stably performed for a long period of time. . As the hydrophilic coating 107, an inorganic material which has a low vapor pressure and does not generate gas is suitable, and a metal oxide such as hydrogen-terminated SiO ₂ is suitable.

In this embodiment, the hydrophilic coating 107 is applied to the inner surface of the lens barrel to trap the hydrophilic impurities.
As a trap for hydrophilic impurities, a trap having a large surface area and capable of adsorbing and removing a large amount of hydrophilic impurities, such as silicic acid or a gel-like substance mainly composed of silicic acid, or a substance mainly composed of activated carbon. I just want it.

In this way, it is possible to prevent deposition of deposits on the surface of the lens or mirror that change the optical performance of the exposure apparatus, and to further remove the attached hydrocarbon, thereby stabilizing the performance of the exposure apparatus for a long period of time. Can be done.

In this embodiment, an i-line exposure apparatus has been described.
Even in an exposure apparatus such as g-line, excimer KrF, or ArF, the optical performance is stabilized by the effect of removing deposits on the surfaces of optical elements such as lenses and mirrors and preventing deposition. In this embodiment, oxygen gas is used as the purge gas,
Even if an inert gas such as N ₂ or Ar is mixed with the oxygen gas, it is sufficient that the oxygen gas removal performance is not changed. A suitable oxygen concentration is 0.5% or more. As the purge gas, it is desirable to use a gas which can maintain an environment in which impurities in the lens barrel are removed as much as possible and which has a small difference in refractive index from the atmosphere. Oxygen gas or a mixture of oxygen gas and N ₂ or Ar gas is preferable. Gas and the like are suitable.

When the exposure wavelength is 193 nm for excimer ArF, the oxygen gas existing on the optical path absorbs the exposure light and must be removed as much as possible. So in this case,
It is not preferable to use oxygen gas as the oxidizing gas.
In such a case, measures such as removing ozone attached to the lens or the hydrophilic surface by periodically flowing ozone gas between exposures are taken.

In this embodiment, the embodiment in which only the contraction exposure system lens is prevented from being adhered is shown. However, the illumination system lens can also be provided by using a gas introduction mechanism, a circulation hole, a discharge hole, and a hydrophobic surface coating. It goes without saying that exactly the same processing is possible.

Deposits are likely to be formed on the atmosphere side of the exposure light irradiating portions of the sealing chambers 101 and 102, but anti-adhesion glass or the like is arranged in this portion to facilitate attachment / detachment and replacement.

The use of the exposure apparatus shown in FIG. 1 makes it possible to change the reflectance by adhering to the lens surface and to prevent or remove substances that scatter and absorb i-rays. Irradiation unevenness does not change, and stable exposure can be performed for a long period of time. In addition, it is not necessary to disassemble and clean the lens group, and the apparatus can be used efficiently.

[0040]

Embodiment 2 FIG. 2 shows a second embodiment of the present invention. FIG.
In 106, a hydrophobic coating, 201, 21
0 is an active oxygen generating catalyst having hydrophilicity, 202 is an ultraviolet lamp, 203 is a gas mixing / switching device, 204 is a gas purifier, 205 is a KrF excimer laser, 206 is a mirror, 207 is a nitrogen gas, 208 is an oxygen gas, Reference numeral 209 denotes a sealing box that can transmit ultraviolet light.

This embodiment will be described in detail with reference to FIG. The laser beam emitted from the laser 205 is
6. The reticle 14 is adjusted to be uniformly illuminated by the condenser lens 13 and optical components such as an optical integrator and a zoom lens which are omitted in the schematic diagram. The laser beam that has passed through the reticle 14 enters a sealing box 209 that seals the reduction exposure lens group 15 housed in the lens barrel 16, and further passes through the reduction exposure lens group 15 onto the wafer 17. Transfer the pattern.

In the optical system of FIG. 2, the lens barrel 16 includes an adhesive for bonding the reduction exposure lens group 15 and the lens barrel 16, a lens fixing jig, and the like, but is not shown. Further, although the hydrophobic coating 106 is illustrated as being coated only on the surface of one lens of the reduction exposure lens group 15, the other lens surface and the mirror 20
It is more desirable to apply it also to the surface of the condenser lens 6 and the condenser lens 13.

Prior to exposure, a gas obtained by mixing a nitrogen gas 207 and an oxygen gas 208 at a predetermined mixing ratio with a gas mixing / switching unit 203 and a gas cylinder regulator and a mass flow meter not shown in FIG. Then, the inside of the sealing box 209 is sufficiently purged. The nitrogen gas and oxygen gas used here are those from which impurities such as hydrocarbons, organic metals and NH ₄ which cause deposition are removed as much as possible.
4 is designed to extend its life.

After purging with a mixed gas of nitrogen and oxygen, the ultraviolet lamp 202 is turned on to irradiate the active oxygen generating catalyst 201 coated in the sealing box 209 with ultraviolet light. At this time, the active oxygen generating catalyst 201 is made of TiO ₂ or TiO ₂ whose surface is processed to have hydrophilicity.
A thin film of a compound containing ₂ can be used. The sealing box 209 is preferably made of a material having a high transmittance of ultraviolet rays, for example, quartz or the like so that the catalyst is effectively irradiated with ultraviolet rays.

TiO ₂ or TiO ₂ having hydrophilicity
The thin film of the compound containing contains functions as a trap for hydrophilic impurities in the sealing box 209. Hydrophilic Ti
Organic contaminants such as hydrophilic impurities and hydrocarbons adsorbed on the O ₂ surface change the hydrophilic TiO ₂ surface to hydrophobic, and the trapping effect gradually decreases. Here, it is known that TiO ₂ has an effect of removing organic contaminants adhering to the surface by irradiating ultraviolet rays of 380 nm or less. Also in this example, when the TiO ₂ thin film having the reduced trapping effect was irradiated with ultraviolet rays, it was found that the impurity substances attached to the TiO ₂ surface could be removed. That is, TiO _{2 in} an oxygen atmosphere
By irradiating the thin film with ultraviolet rays, the trap performance can be restored. The attached organic contaminants are changed into gas components such as H ₂ O and CO ₂ by the effect of active oxygen, and are discharged from the outlet 105 to the outside of the sealing box 209 by the purge gas. In this embodiment, since the structure is such that ultraviolet light is irradiated from the back side of the active oxygen generation catalyst thin film, the thickness of the thin film is 0.1 mm.
It is desirable that it is about 1 μm to 10 μm.

On the other hand, the active oxygen-generating catalyst 210 coated on the inner surface of the lens barrel 16 is constantly irradiated with the ultraviolet light in which the exposure light is scattered during the exposure. Then, it can function as an impurity trap. Since hydrophilic impurities are unlikely to adhere to the surface of the lens or mirror on which the hydrophobic coating 106 is applied, deposition of carboxylate, sulfate, silicate, and the like due to the reaction between the ultraviolet light and the deposit can be suppressed.

As described above, an optical element such as a lens or a mirror is placed in a clean oxidizing gas atmosphere, a hydrophobic thin film is formed on the surface of the optical element, and a hydrophilic coating is applied to the inner surface of the container surrounding the element. At the same time, the hydrophilic coating is made of TiO ₂ or a TiO ₂ compound active oxygen generation catalyst thin film, and a mechanism for irradiating the active oxygen generation catalyst thin film with ultraviolet light to stabilize the optical performance of the exposure device for a long period of time. Can be maintained.

In this embodiment, a nitrogen / oxygen mixed gas is used. However, oxygen gas, or oxygen gas and Ar, N
A mixed gas of an inert gas such as e may be used, or air from which metal impurities, organic impurities, and the like have been removed may be used. However, it is desirable that an inexpensive, high-purity gas can be obtained, and that the refractive index be similar to that of the atmosphere.

In this embodiment, since exposure is performed by a KrF excimer laser, it is possible to perform exposure while introducing oxygen gas at 0.5% or more. However, when performing exposure with an ArF excimer laser, the oxygen gas on the optical path absorbs the exposure light. Therefore, the gas mixing / switching unit 203 does not introduce the oxygen gas during the exposure. At the time of switching or at regular time intervals, oxygen gas is introduced periodically and laser irradiation is performed to remove impurities adhering to the hydrophilic surface.

In this embodiment, not only the active oxygen generation catalyst thin film 210 coated on the inner surface of the lens barrel 16 but also the active oxygen generation catalyst thin film 201 is provided on the inner surface of the sealed box 209. UV irradiator 2 for irradiating this active oxygen generating catalyst thin film 201 outside
However, if the state in which the amount of contaminants is small can be maintained, impurities in the lens barrel 16 can be trapped by only the active oxygen generation catalyst thin film 210 coated on the inner surface of the lens barrel and exposure performance can be maintained.

Further, an ozone generator is installed between the oxygen gas 208 and the purifier 204, and even if an active gas such as an ozone gas is periodically introduced into the sealing box 209, the organic substance adhering to the hydrophilic surface can be obtained. The thin film can be removed, the trap effect can be maintained, and the effect of stabilizing the exposure performance can be obtained.

[0052]

[Embodiment 3] FIG. 3 shows that an ArF excimer laser is irradiated on a substrate in a clean room environment, the stationary contact angle of the substrate surface with water, the laser power is 10 mJ / cm ² , and the substrate is irradiated with 1 × 10 ⁸ shots. It is the graph which showed the relationship of the amount of deposited material.

As is apparent from the figure, as the static contact angle increases, the amount of deposits decreases. From the change in mass after the laser power of 10 mJ / cm ² and 1 × 10 ⁸ shots shown in the figure, if the static contact angle is 50 ° or more, almost no deposits are observed, and the specifications for stabilizing the performance of the exposure device Was found to be satisfactory. On the other hand, when the static contact angle is 3
If it is 0 ° or less, deposits are deposited, and an effect as an impurity trap can be expected.

From the above results, a hydrophobic coating is applied to the surface of the optical element such as a lens or a mirror to be irradiated with ultraviolet exposure light so that the static contact angle with water is 50 ° or more. By applying a hydrophilic coating such that the static contact angle with water is 30 ° or less on the inner surface of a container such as a lens barrel surrounding the element, adhesion of deposits to the optical element surface due to ultraviolet irradiation is suppressed, Optical characteristics can be stabilized. In addition, with such a configuration, the exposure amount, illuminance unevenness, and the like of the exposure apparatus can be stabilized, and the operation rate of the exposure apparatus can be improved.

In this example, a thin film of CaF ₂ and a compound thin film of CaF ₂ and SiO ₂ was used as the hydrophobic coating, and the static contact angle was changed by changing the composition ratio. This is because these inorganic materials are excellent in light durability even in the vacuum ultraviolet wavelength region, are not absorbed, and are stable materials, but they have hydrophobicity and light durability in the vacuum ultraviolet wavelength region. Any material that is excellent, without absorption, can be used, and fluorides are generally suitable. In the present embodiment, hydrogen-terminated SiO ₂ is used for the hydrophilic material. However, for the hydrophilic material, there is no problem of light durability against ultraviolet light and absorption, and various oxides, silica gel,
Activated carbon or the like having a large surface area and easily adsorbing hydrophilic impurities is suitable.

[0056]

Next, an embodiment of a device production method using the above-described exposure apparatus will be described.
FIG. 5 shows a micro device (a semiconductor chip such as an IC or an LSI,
2 shows a flow of manufacturing a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, and the like. In step 1 (circuit design), a device pattern is designed. Step 2 is a process for making a mask on the basis of the designed pattern. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 6 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern on the mask is printed and exposed on the wafer by the exposure apparatus having the above-described optical system. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the production method of this embodiment, it is possible to produce a highly integrated device, which was conventionally difficult to produce, at low cost.

[0059]

As described above, according to the present invention,
An exposure apparatus using ultraviolet light can be stably operated for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a lens system of an exposure apparatus according to one embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a lens system of an exposure apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a static contact angle and a deposit on a lens surface and an impurity trap coating according to an example of the present invention.

FIG. 4 is a schematic sectional view showing a lens system of an exposure apparatus according to a conventional technique.

FIG. 5 is a diagram showing a flow of manufacturing a micro device.

FIG. 6 is a diagram showing a detailed flow of a wafer process in FIG. 5;

[Explanation of symbols]

11: light source, 12: condenser lens, 14: reticle, 15: reduction exposure system lens, 16: lens barrel, 17: silicon wafer, 101, 102: sealing chamber, 103:
Oxygen gas, 104: gas purifier, 105: gas outlet,
106: hydrophobic coating, 107: hydrophilic coating, 108: through-hole for gas discharge, 201, 210: active oxygen generating catalyst having hydrophilicity, 202: ultraviolet lamp, 203: gas mixing / switching device, 204: gas purification , 205: KrF excimer laser, 206: mirror,
207: Nitrogen gas, 208: Oxygen gas, 209: Sealing box that can transmit ultraviolet rays.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Ryoji Bilo, Inventor 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hidehiro Kanazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inc.

Claims (10)

[Claims] 1. An exposure apparatus for passing an exposure light beam from a light source through an optical system and exposing an exposure target object through a reticle, comprising: a container for shielding at least a part of the optical system from outside air;
The optical system includes means for purging the inside of the container with an oxidizing gas from which impurities such as metal compounds and organic compounds and moisture have been removed, and a trap mechanism for trapping a substance having a hydrophilic group in the container. An exposure apparatus characterized in that at least a part of the surface of the optical element to be coated is coated with a substance that is transparent to ultraviolet light of 160 nm to 380 nm and has hydrophobicity. 2. The exposure light according to claim 1, wherein the optical element is a lens, and a hydrophobic substance coated on the surface of the lens is made of a low-refractive-index material whose refractive index is in a range of 1.35 to 1.52 at an exposure wavelength. 2. The exposure apparatus according to claim 1, wherein the exposure apparatus is a part of a multilayer film that realizes the anti-reflection performance of the above, and is located on the outermost surface of the multilayer film. 3. The method according to claim 1, wherein the hydrophobic substance is CaF ₂ or CaF _2.
3. The exposure apparatus according to claim 1, wherein the exposure apparatus is a compound containing 2. 4. An extinction coefficient k and a film thickness d (nm) of a hydrophobic substance coated on a surface of the optical element satisfy a condition of d <20 nm k * d <0.02 nm. Item 2. An exposure apparatus according to Item 1. 5. The exposure apparatus according to claim 1, wherein in the trap mechanism, a substance used for the trap is a hydrophilic coating. 6. The exposure apparatus according to claim 1, wherein a static contact angle of the hydrophobic substance with water is 50 ° or more, and a static contact angle of the hydrophilic coating with water is 30 ° or less. . 7. In the trap mechanism, the substance used for the trap is TiO ₂ or a coating of a compound containing TiO ₂ , and 380 nm is applied to the surface of the hydrophilic substance.
The exposure apparatus according to claim 1, further comprising a mechanism for irradiating ultraviolet rays having a wavelength shorter than m. 8. The exposure apparatus according to claim 1, wherein in the trap mechanism, a substance used for the trap is silicic acid or a gel-like substance containing silicic acid as a main component. 9. The exposure apparatus according to claim 1, wherein in the trap mechanism, a substance used for the trap is a substance containing activated carbon or activated ash as a main component. 10. A device manufacturing method, comprising manufacturing a device using the exposure apparatus according to claim 1.