JP2008182167A - Exposure apparatus, exposure method, and exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus which reduces variation in transmissivity of liquid to have superior exposure performance. <P>SOLUTION: The exposure apparatus has a projection optical system configured to project an image of a reticle pattern onto a substrate, and exposes the substrate via a liquid supplied to a space between the substrate and the projection optical system. The exposure apparatus includes an oxygen removal unit configured to reduce dissolved oxygen in the liquid, and a degassing unit configured to reduce a dissolved gas in the liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure apparatus, an exposure method, and an exposure system.

  2. Description of the Related Art A reduction projection exposure apparatus has been conventionally used when a fine semiconductor element such as a semiconductor memory or a logic circuit is manufactured using a photolithography technique. The reduction projection exposure apparatus projects an image of a circuit pattern drawn on a reticle onto a substrate such as a wafer by a projection optical system to transfer the circuit pattern.

  The minimum dimension (resolution) that can be transferred by the reduction projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength and the higher the NA, the better the resolution. In recent years, with a demand for miniaturization of semiconductor elements, an exposure apparatus having a high resolution is required to transfer a finer pattern. For this reason, the wavelength of exposure light has been shortened, and the wavelength of ultraviolet rays used for exposure has been shortened from an KrF excimer laser (wavelength: about 248 nm) to an ArF excimer laser (wavelength: about 193 nm).

  Under such circumstances, immersion exposure has attracted attention as a technique for further improving the resolution while using a light source such as an ArF excimer laser. In immersion exposure, the effective wavelength of exposure light is set by filling the space between the final lens closest to the wafer side of the projection optical system and the wafer with liquid (that is, making the medium on the wafer side of the projection optical system liquid). The resolution is improved by shortening the wavelength and apparently increasing the NA of the projection optical system. The NA of the projection optical system is NA = n × sin θ where n is the refractive index of the medium. Therefore, NA is increased to n by satisfying a medium having a refractive index higher than the refractive index of air (n> 1). can do.

In addition, since the higher the refractive index, the higher the resolution is expected, the immersion exposure apparatus using a liquid having a high refractive index (high refractive index liquid) as a successor technique of the immersion exposure apparatus using pure water. Has been proposed (see Patent Document 1).
JP 2006-4964 A U.S. Pat. No. 4,346,164 JP 2005-136374 A

  However, the present inventor compared the high refractive index liquid and pure water. The immersion exposure apparatus using the high refractive index liquid is different from the immersion exposure apparatus using pure water as follows. It was found to have

  A first problem related to an immersion exposure apparatus using a high refractive index liquid is that the liquid needs to be reused. This is because the high refractive index liquid is higher in cost and environmental burden than pure water.

  In order to solve such a first problem, an immersion exposure apparatus as described below has already been proposed (see Patent Documents 2 and 3).

  The immersion exposure apparatuses of Patent Documents 2 and 3 remove impurities from the collected liquid (that is, purify the liquid collected by the purification means) and reuse the liquid. In general, an inspection means for inspecting the purity of the purified liquid is arranged after the purification means. For example, Patent Document 3 proposes a method for detecting the amount of particles and impurities, and a method for measuring physical characteristics such as electrical resistance and refractive index. However, as a result of intensive studies by the inventor, it has been found that such an inspection means cannot accurately detect the purity of the liquid. That is, in the conventional immersion exposure apparatus, it is not sufficiently guaranteed whether the liquid being circulated (that is, reused) is of good quality, so that the liquid that is not of good quality (that is, cannot be reused) is removed. It may be reused. The problem of how to circulate a high-quality liquid in an immersion exposure apparatus using a high refractive index liquid is a unique problem not found in an immersion exposure apparatus using pure water.

  A second problem related to an immersion exposure apparatus using a high refractive index liquid is that the transmittance of the high refractive index liquid is likely to decrease. In a high refractive index liquid, oxygen is more easily dissolved than pure water, and the transmittance in the ultraviolet wavelength region is greatly reduced when exposed to the atmosphere. In addition, the conventional immersion exposure apparatus has a deaeration unit that reduces all dissolved gas for the purpose of suppressing the generation of bubbles. However, such deaeration unit cannot sufficiently reduce dissolved oxygen, Dissolved oxygen reduces the liquid permeability. In addition, there is a concern about reactions such as decomposition by exposure light, and a decrease in transmittance due to such reactions is also assumed. When the liquid transmittance decreases, the temperature of the liquid increases due to the absorption of exposure light, and the refractive index changes. Such a change in the refractive index of the liquid causes an exposure aberration. Therefore, in order to maintain the exposure performance (imaging performance), it is necessary to strictly manage the transmittance of the liquid. In addition, when correcting the exposure aberration caused by the temperature change of the liquid, it is preferable to maintain the liquid transmittance constant. When the transmittance of the liquid varies, it is necessary to control the aberration correction amount according to the variation.

  Accordingly, an object of the present invention is to provide an exposure apparatus that reduces fluctuations in the transmittance of liquid.

  An exposure apparatus according to an aspect of the present invention includes a projection optical system that projects an image of a reticle pattern onto a substrate, and exposes the substrate through a liquid supplied between the projection optical system and the substrate. The exposure apparatus includes a deoxygenation unit that reduces dissolved oxygen in the liquid and a deaeration unit that reduces dissolved gas in the liquid.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, it is possible to provide an exposure apparatus that reduces fluctuations in liquid transmittance.

  Hereinafter, an exposure apparatus according to one aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted. Here, FIG. 1 is a schematic block diagram showing the configuration of the exposure apparatus 1 of the present invention.

  As shown in FIG. 1, the exposure apparatus 1 includes an illumination device 10, a reticle stage 25 on which a reticle 20 is placed, a projection optical system 30, a wafer stage 45 on which a wafer 40 is placed, and a circulation means 100. Have.

  The exposure apparatus 1 performs immersion exposure for exposing the wafer 40 with the pattern of the reticle 20 through the liquid L between the optical element (final lens) closest to the wafer 40 and the optical element of the projection optical system 30 and the wafer 40. Device. In the present embodiment, the exposure apparatus 1 is a step-and-scan projection exposure apparatus, but a step-and-repeat projection exposure apparatus can also be used.

  The illumination device 10 illuminates a reticle 20 on which a transfer circuit pattern is formed, and includes a light source unit and an illumination optical system.

The light source unit includes a laser 11 as a light source and a beam shaping optical system 12. As the laser 11, an ArF excimer laser with a wavelength of about 193 nm, a KrF excimer laser with a wavelength of about 248 nm, an F ₂ laser with a wavelength of about 157 nm, or the like can be used. In this embodiment, an ArF excimer laser having a wavelength of about 193 nm is used as the light source. However, the type and number of lasers 11 are not limited, and the type of light source is not limited.

  The beam shaping optical system 12 converts the aspect ratio of the light beam from the laser 11. The beam shaping optical system 12 forms a light beam having a size and a divergence angle necessary for illuminating the optical integrator 14.

  The illumination optical system is an optical system that illuminates the reticle 20, and in this embodiment, the condensing optical system 13, the optical integrator 14, the aperture stop 15, the condensing lens 16, the bending mirror 17, and the masking blade. 18 and an imaging lens 19. The illumination optical system can realize various illumination modes such as annular illumination and quadrupole illumination.

  The condensing optical system 13 efficiently introduces a light beam having a desired shape into the optical integrator 14. The condensing optical system 13 includes an exposure amount adjustment unit that can change the exposure amount of the reticle 20.

  The optical integrator 14 is for uniformizing the illumination light that illuminates the reticle 20, and in the present embodiment, a fly-eye lens is used.

  The aperture stop 15 is disposed at a position conjugate with the pupil plane 32 of the projection optical system 30. The aperture shape of the aperture stop 15 corresponds to an effective light source shape formed on the pupil plane 32 of the projection optical system 30.

  The condensing lens 16 condenses a plurality of light beams emitted from the secondary light source in the vicinity of the emission surface of the optical integrator 14.

  The mirror 17 reflects the light beam collected by the condenser lens 16. The masking blade 18 is uniformly illuminated by the plurality of light beams.

  The masking blade 18 is a field stop composed of a plurality of movable light shielding plates. The masking blade 18 has an opening having a substantially rectangular opening shape corresponding to the effective area of the projection optical system 30. The light beam transmitted through the opening of the masking blade 18 is used as illumination light for illuminating the reticle 20.

  The imaging lens 19 images the opening (opening shape) of the masking blade 18 on the reticle 20.

  A pattern for exposing the wafer 40 is formed on the reticle 20.

  The reticle stage 25 supports the reticle 20.

  The projection optical system 30 projects an image of the pattern of the reticle 20 onto the wafer 40. As the projection optical system 30, a refractive system or a catadioptric system can be used. As the final lens closest to the wafer in the projection optical system 30, a plano-convex lens or a meniscus lens can be used.

  A photoresist is applied to the surface of the wafer 40. In this embodiment, the wafer 40 is used as the substrate, but a glass plate or other substrate can be used instead of the wafer 40.

  The wafer stage 45 supports the wafer 40 via a holding unit 45a such as a wafer chuck.

  The circulation unit 100 supplies the liquid L between the final lens of the projection optical system 30 and the wafer 40 via the supply nozzle 102. The circulation unit 100 collects the liquid L supplied between the final lens of the projection optical system 30 and the wafer 40 via the recovery nozzle 104.

  The oxygen reducing means 50 supplies a gas other than oxygen around the liquid L so that the oxygen concentration around the liquid L is lower than the oxygen concentration in the atmosphere. The gas supplied by the oxygen reduction means is preferably a gas having high permeability to exposure light, and for example, nitrogen, helium, argon, or the like is used. Inexpensive nitrogen is more suitable because of the large consumption of gas. By reducing the oxygen concentration around the liquid L, it is possible to suppress a decrease in the transmittance of the liquid L caused by the dissolution of oxygen.

  As the liquid L, a liquid that has good transmittance with respect to the wavelength of the exposure light, does not attach dirt as much as possible to the projection optical system 30, and has good matching with the resist process is used. The liquid L is pure water or a hydrocarbon-based liquid, and can be selected according to the photoresist applied to the wafer 40 and the wavelength of exposure light. The final lens of the projection optical system 30 can be coated to protect the influence from the liquid L.

  The circulation means 100 includes a purification means 110 that improves the purity of the recovered liquid L, a deoxygenation means 120 that removes dissolved oxygen in the liquid L, a degassing means 125 that removes dissolved gas in the liquid L, and a liquid L Measuring means 130 for measuring the transmittance of the light. In the present embodiment, the measuring unit 130 includes three measuring units 130A to 130C. The circulation means 100 includes a pump for transferring the liquid L, a flow rate control unit for controlling the transfer amount of the liquid L, a temperature adjusting unit for adjusting the temperature of the liquid L, and a liquid L purified after being recovered with a new liquid. It further has a mixing means for mixing.

  As the deoxygenating means 120, a bubbler that removes dissolved oxygen by bubbling a gas other than oxygen can be used. The gas used in the bubbler is preferably a gas that is highly permeable to exposure light, and for example, nitrogen, helium, argon, or the like is used.

  In combination with the bubbling, the liquid in the vessel for bubbling is stirred to efficiently perform the deoxygenation treatment. In addition, by generating fine bubbles using a porous body or the like, the area where the liquid and the gas come into contact can be increased, and the deoxygenation treatment can be performed efficiently. As a porous body, what was manufactured with materials, such as a tetrafluoroethylene resin (PTFE), SUS, SiO2, SiC, can be used.

  As the deoxygenating means 120, any means may be used as long as it is a method of bringing a gas other than oxygen into contact with the liquid L. For example, the liquid L may be put into the container, and the liquid L may be simply stirred while flowing a gas other than oxygen. Alternatively, the liquid L may be formed into fine droplets, and the atmosphere around the droplets may be a gas other than oxygen.

  As the deaeration means 125, a deaeration filter that removes dissolved gas by flowing a liquid through one of the gas permeable membranes and depressurizing the other can be used. As the gas permeable membrane, for example, a fluororesin such as tetrafluoroethylene resin (PTFE) is used. In order to increase the contact area between the gas permeable membrane and the liquid, the gas permeable membrane may be processed into a hollow fiber shape having a diameter of about 100 μm. Dissolved gas can be efficiently removed by forming a bundle of several tens to several hundreds of hollow fibers of fluororesin, flowing a liquid therein, and reducing the pressure outside the hollow fibers. Conversely, the inside of the hollow fiber may be decompressed and the liquid may flow outside the hollow fiber. The purpose of the deaeration means 125 is to reduce the dissolved gas concentration and shorten the lifetime of the bubbles. As a result, exposure defects due to bubbles can be prevented.

  The shortening of the bubble life can also be realized by using a different kind of gas from the gas supplied by the oxygen reduction means 50 in the deoxygenation means 120. The periphery of the liquid L supplied between the final lens of the projection optical system 30 and the wafer 40 is replaced with, for example, nitrogen by the oxygen reduction means 50. Therefore, bubbles generated in the liquid L on the wafer 40 are nitrogen bubbles. In order to shorten the bubble life of nitrogen, the nitrogen concentration in the liquid L may be reduced. Since the nitrogen concentration in the liquid L can be reduced by bubbling with a gas other than nitrogen such as helium, the lifetime of the bubbles can be shortened. However, since the gas used for bubbling is saturated in the liquid, the gas component used for bubbling may form bubbles due to pressure fluctuation or temperature fluctuation. Therefore, it is preferable to provide the deaeration means 125 after the deoxygenation means 120. A gas other than nitrogen such as helium is more expensive than nitrogen. Therefore, two deoxygenating means 120 may be provided in series, deoxygenation may be performed first by nitrogen bubbling, and then denitrogenation may be performed by helium bubbling. By performing nitrogen bubbling before helium bubbling, it is possible to reduce the amount of helium gas used.

  When the shortening of the bubble life is realized only by the degassing means 125, there is a concern about the enlargement of the degassing means 125. Moreover, in order to cope with a high pressure loss, there is a possibility that a problem such as an increase in the size of the liquid feed pump may occur. However, in addition to the deaeration unit 125, by changing the type of gas used in the oxygen reduction unit 50 and the deoxygenation unit 120, an increase in the size of the deaeration unit 125 can be suppressed and exposure defects due to bubbles can be prevented. Is possible.

  As a method for measuring the transmittance of the liquid L, the measuring means 130 uses a method of passing the liquid L through a cell made of a light-transmitting material such as quartz and measuring the transmittance of the cell. Since the transmittance to be measured is the transmittance with respect to the wavelength of the exposure light, it is preferably the transmittance with respect to the wavelength of about 248 nm for the KrF excimer laser and the transmittance with respect to the wavelength of about 193 nm for the ArF excimer laser. The measuring means 130 is a spectrophotometer having a configuration in which light having a wavelength of exposure light is selected from a light source such as a D2 lamp using a diffraction grating and the like, incident on the cell, and then transmitted light is detected by a photoreceiver such as a photomultiplier. A meter (i.e. a normal spectrophotometer) is used.

  Some liquids L can predict the transmittance with respect to the wavelength of the exposure light from the transmittances of other wavelengths. In this case, the measuring means 130 can be configured to measure the transmittance for wavelengths other than the exposure light. For example, the emission line of a low-pressure mercury lamp (185 nm) or excimer lamp (172 nm) can be used depending on the wavelength, and the spectroscope may be omitted. The measuring means 130 can appropriately use a double beam method using a chopper or the like, a lock-in amplifier method, or a method of measuring light intensity before and after the cell in order to improve measurement accuracy. Similarly, from the viewpoint of measurement accuracy, the measured thickness of the liquid L is preferably in the range of 1 mm to 100 mm, and preferably in the range of 10 mm to 50 mm.

  The measuring unit 130A measures the transmittance of the liquid L collected from the exposure position where the wafer 40 is exposed. The measuring unit 130B measures the transmittance of the liquid L purified by the purifying unit 110. The measuring unit 130 </ b> C measures the transmittance of the liquid L supplied between the projection optical system 30 and the wafer 40.

  FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus 1. FIG. 2 shows the projection optical system 30, the wafer 40, the wafer stage 45, the liquid L, and the circulation means 100.

  In the circulation means 100, the liquid L recovered from the recovery nozzle 104 is processed by the deoxygenation means 120A, and the transmittance is measured by the measurement means 130A. When the transmittance value of the liquid L measured by the measuring unit 130A is high, the liquid L is transferred to the purifying unit 110. On the other hand, when the transmittance value of the liquid L measured by the measuring means 130A is low, the liquid L is transferred to the waste liquid tank 140.

  The liquid L purified by the purifying means 110 is measured for transmittance by the measuring means 130B. When the transmittance value of the liquid L measured by the measuring unit 130B is high, the liquid L is transferred to the mixing unit 150. On the other hand, when the value of the transmittance of the liquid L measured by the measuring unit 130B is low, the liquid L is transferred again to the purifying unit 110. Note that when the value of the transmittance of the liquid L is extremely low, the liquid L is transferred to the waste liquid tank 140. In addition, waste liquid containing impurities discharged during the purification of the purification means 110 is also transferred to the waste liquid tank 140.

  The mixing unit 150 mixes the new liquid supplied from the new liquid tank 152 and the liquid L purified by the purification unit 110. The mixing ratio of the new liquid and the purified liquid L is determined based on the transmittance value of the liquid L measured by the measuring means 130B, and the new liquid and the purified liquid L are mixed at the determined mixing ratio. To do.

  The mixed liquid is stored in the supply tank 154. The liquid L supplied from the supply tank 154 is processed by the deoxygenation means 120. In FIG. 2, the supply tank 154 and the deoxygenation means 120 are shown separately. However, the deoxidation process may be performed by providing a bubbler as a deoxygenation means in the supply tank 154. Further, the dissolved gas in the liquid L is reduced by the deaeration means 125 arranged on the downstream side of the deoxygenation means 120. The liquid L that has been subjected to deoxygenation treatment and deaeration treatment is measured for the transmittance of the liquid L by the measuring means 130C. Based on the transmittance of the liquid L measured by the measuring unit 130C, an aberration correction amount for focus and exposure amount is determined and corrected when exposure is performed. The deaeration unit 125 may be downstream of the measurement unit 130C.

  Hereinafter, various forms of the circulation means 100 will be described in detail.

  In the first embodiment, the circulation unit 100 includes a nitrogen bubbler (deoxygenation unit) 120 and a deaeration filter (deaeration unit) 125 as shown in FIG. FIG. 3 is a partial block diagram showing a part of the configuration of the exposure apparatus 1.

  In the exposure apparatus 1 of Example 1, a hydrocarbon-based high refractive index liquid having a refractive index of 1.64 is used as the liquid L supplied between the projection optical system 30 and the wafer 40.

  Although the environment around the exposure position of the exposure apparatus 1 is replaced with nitrogen by the oxygen reducing means 50, a small amount of oxygen dissolves in the liquid L, thereby reducing the transmittance of the liquid L. When the dissolved oxygen concentration in the liquid L was measured immediately before the exposure position, it was 0.1 ppm or less when the nitrogen bubbler 120 and the degassing filter 125 were operated. On the other hand, the dissolved oxygen concentration measured in a state where the nitrogen bubbler 120 was stopped and only the degassing filter 125 was operated was 2 ppm. When the dissolved oxygen concentration is 2 ppm, the transmittance of the liquid L is reduced by about 0.7% / mm. The reduction in transmittance of 0.7% / mm greatly contributes to the amount of aberration that occurs, so that an exposure apparatus having only the deaeration filter 125 cannot provide good imaging performance. On the other hand, since the exposure apparatus having the nitrogen bubbler 120 in addition to the deaeration filter 125 can supply the liquid L having a high transmittance, it can provide stable imaging characteristics.

  In the second embodiment, the circulation unit 100 includes a bubbler (deoxygenation unit) 120 and a deaeration filter (deaeration unit) 125 as in FIG. 3 of the first embodiment. However, the gas used in the bubbler is helium.

  In the exposure apparatus 1 of Example 2, a hydrocarbon-based high refractive index liquid having a refractive index of 1.64 is used as the liquid L supplied between the projection optical system 30 and the wafer 40.

  Although the environment around the exposure position of the exposure apparatus 1 is replaced with nitrogen by the oxygen reducing means 50, a small amount of oxygen dissolves in the liquid L, thereby reducing the transmittance of the liquid L. When the dissolved oxygen concentration in the liquid L was measured immediately before the exposure position, it was 0.1 ppm or less when the helium bubbler 120 and the degassing filter 125 were operated. In contrast, the dissolved oxygen concentration measured with the helium bubbler 120 stopped and only the deaeration filter 125 operated was 2 ppm. When the dissolved oxygen concentration is 2 ppm, the transmittance of the liquid L is reduced by about 0.7% / mm. The reduction in transmittance of 0.7% / mm greatly contributes to the amount of aberration that occurs, so that an exposure apparatus having only the deaeration filter 125 cannot provide good imaging performance. On the other hand, since the exposure apparatus having the helium bubbler 120 in addition to the deaeration filter 125 can supply the liquid L with high transmittance, it can provide stable imaging characteristics.

  Moreover, since the gas used in the oxygen reduction means 50 is different from the gas used in the deoxygenation means 120, defects caused by bubbles can be suppressed.

  In the third embodiment, the circulation unit 100 includes a deoxygenation unit 120 and a deaeration unit 125 as shown in FIG. 4, and the liquid L is transmitted between the exposure position where the wafer 40 is exposed and the purification unit 110. It has measuring means 130A for measuring the rate. FIG. 4 is a partial block diagram showing a part of the configuration of the exposure apparatus 1.

  In the exposure apparatus 1 of Example 3, a hydrocarbon-based high refractive index liquid having a refractive index of 1.64 is used as the liquid L supplied between the projection optical system 30 and the wafer 40.

  At the exposure position of the exposure apparatus 1, the liquid L comes into contact with the final lens of the projection optical system 30, the wafer 40, the top plate of the wafer stage 45, the surrounding air, etc., and the transmittance decreases. In particular, since a photoresist is applied to the wafer 40, substances such as a residual solvent, a photoacid generator, and a base in the photoresist are mixed into the liquid L, and the transmittance of the liquid L is reduced. Further, although the environment around the exposure position is replaced with nitrogen by the oxygen reducing means 50, a trace amount of oxygen dissolves in the liquid L, and the transmittance of the liquid L may be lowered. Furthermore, since KrF excimer laser and ArF excimer laser, which are exposure light, have strong energy, there is a concern that the liquid L itself is broken and the transmittance is lowered as a result.

  In the circulation unit 100 shown in FIG. 4, the liquid L collected from the exposure position for exposing the wafer 40 through the collection nozzle 104 is processed by the deoxygenation unit 120A, and the transmittance is measured by the measurement unit 130A. As described above, the cause of the decrease in the transmittance of the liquid L includes mixing of eluate from a photoresist or the like, decomposition of the liquid L itself by exposure light, and mixing of oxygen. The purification means 110 mainly removes eluate and decomposition products. Therefore, the deoxygenating means 120A is arranged in front of the measuring means 130A for the purpose of separating the decrease in the transmittance of the liquid L due to the mixing of oxygen from other factors.

  In the third embodiment, the measurement unit 130A includes a D2 lamp as a light source, a diffraction grating that extracts light having a wavelength of 193 nm from light emitted from the D2 lamp, a quartz cell that circulates the liquid L and transmits measurement light, and transmission. And a detector for detecting light intensity. The quartz cell was configured so that the liquid L to be measured had a thickness of 10 mm.

  When the transmittance value per 10 mm thickness of the liquid L measured by the measuring means 130A is 10% or more, the liquid L is sent to the purifying means 110, and when the transmittance value per 10 mm thickness of the liquid L is less than 10%, The liquid L was set to be sent to the waste liquid tank 140. Note that the transmittance determination reference value can be changed according to the purification capability of the purification means 110.

  When the transmittance value per 10 mm thickness of the liquid L measured by the measuring means 130A is 10% or more, the purification condition of the purifying means 110 is further controlled according to the measured transmittance value. Here, the purification conditions are the processing time, processing frequency, processing temperature, etc. in the purification means 110. For example, when the transmittance value is as low as about 20% per 10 mm thickness, the number of treatments in the purifying means 110 is set to 5 times so that the transmittance of the liquid L is sufficiently recovered. On the other hand, when the transmittance value is as high as around 70% per 10 mm thickness, the number of treatments in the purification means 110 is set to one.

  The liquid L purified by the purification means 110 is stored in the supply tank 154. The liquid L supplied from the supply tank 154 is supplied between the projection optical system 30 and the wafer 40 via the supply nozzle 102 after passing through the deoxygenating means 120 and the degassing means 125. The circulation unit 100 appropriately includes a liquid temperature adjusting unit, a particle filter, a chemical filter, and the like (not shown) between the deaeration unit 125 and the supply nozzle 102.

  When the wafer 40 was exposed using the exposure apparatus 1 having the circulation means 100 shown in FIG. 4 and the image performance was inspected, the best focus position drift did not occur and stable image performance was exhibited. In addition, when measuring means similar to the measuring means 130A is disposed after the deoxygenating means 120 and the transmittance stability of the liquid L is inspected, the transmittance per 10 mm thickness is stable in the range of 80 ± 3%. Confirmed that.

  By disposing the measuring means 130A for measuring the transmittance of the liquid L between the exposure position and the purifying means 110, the liquid L having an extremely low transmittance among the liquids L whose transmittance has decreased at the exposure position. Can be eliminated. By excluding the liquid L having a low transmittance, the load on the purification means 110 can be maintained within an appropriate range, and a sufficient purification effect can be maintained. Further, contamination in the apparatus (for example, the purification means 110) caused by the liquid L having a low transmittance can be prevented. Furthermore, it is possible to control the purification condition of the purification unit 110 based on the transmittance value of the liquid L measured by the measurement unit 130A.

  As described above, by disposing the measuring unit 130A between the exposure position and the purification unit 110, the quality of the liquid L collected from the exposure position can be accurately managed. Further, by controlling the purification conditions of the purification unit 110 based on the transmittance value of the liquid L, it is possible to provide an exposure apparatus that reduces the variation in the transmittance of the liquid L.

  In the fourth embodiment, as shown in FIG. 5, the circulation unit 100 measures the transmittance of the liquid L between the liquid L purified by the purification unit 110 and the mixing unit 150 that mixes the new liquid. 130B. FIG. 5 is a partial block diagram showing a part of the configuration of the exposure apparatus 1.

  In the exposure apparatus 1 of Example 4, a hydrocarbon-based high refractive index liquid having a refractive index of 1.64 is used as the liquid L supplied between the projection optical system 30 and the wafer 40.

  In the circulation unit 100 shown in FIG. 5, the liquid L collected from the exposure position for exposing the wafer 40 via the collection nozzle 104 is purified by the purification unit 110, and the transmittance is measured by the measurement unit 130B. The measuring unit 130B is the same as the measuring unit 130A of the third embodiment.

  When the transmittance value per 10 mm thickness of the liquid L in the measuring unit 130B is 75% or more, the liquid L is sent to the mixing unit 150 and mixed with a new liquid. At this time, the mixing ratio of the new liquid and the purified liquid L was controlled based on the measured transmittance value so that the transmittance of the mixed liquid was 85% per 10 mm thickness.

  When the transmittance value per 10 mm thickness of the liquid L in the measuring unit 130B is 50% or more and less than 75%, the liquid L is sent again to the purifying unit 110 and purified. At this time, purification conditions such as the number of treatments were controlled based on the measured transmittance value.

  When the transmittance value per 10 mm thickness of the liquid L in the measuring unit 130 </ b> B is less than 50%, it is determined that the reuse of the liquid L is difficult, and the liquid L is sent to the waste liquid tank 140.

  The purified liquid L and the new liquid are mixed by the mixing means 150 and stored in the supply tank 154. The liquid L supplied from the supply tank 154 is supplied between the projection optical system 30 and the wafer 40 via the supply nozzle 102 after passing through the deoxygenating means 120 and the degassing means 125. The circulation unit 100 appropriately includes a liquid temperature adjusting unit, a particle filter, a chemical filter, and the like (not shown) between the deaeration unit 125 and the supply nozzle 102.

  When the wafer 40 was exposed using the exposure apparatus 1 having the circulation means 100 shown in FIG. 5 and the image performance was inspected, the best focus position drift did not occur and stable image performance was shown. Further, when the measuring means similar to the measuring means 130B is disposed after the deoxygenating means 120 and the transmittance stability of the liquid L is inspected, the transmittance per 10 mm thickness is stable in the range of 85 ± 1%. Confirmed that.

  Thus, by arranging the measuring means 130B between the purifying means 110 and the mixing means 150, the quality of the purified liquid L can be managed with high accuracy. Further, by controlling the mixing ratio with a new liquid on the basis of the transmittance value of the purified liquid L, it is possible to provide an exposure apparatus that reduces the variation in the transmittance of the liquid L.

  In the fifth embodiment, as shown in FIG. 6, the circulation unit 100 measures the transmittance of the liquid L between the deoxygenation unit 120 that removes dissolved oxygen in the liquid L and the exposure position at which the wafer 40 is exposed. It has measuring means 130C. FIG. 6 is a partial block diagram showing a part of the configuration of the exposure apparatus 1.

  In the exposure apparatus 1 of Example 5, a hydrocarbon-based high refractive index liquid having a refractive index of 1.64 is used as the liquid L supplied between the projection optical system 30 and the wafer 40.

  In the circulation unit 100 shown in FIG. 6, the liquid L collected from the exposure position for exposing the wafer 40 via the collection nozzle 104 is purified by the purification unit 110 and stored in the supply tank 154. The liquid L supplied from the supply tank 154 passes through the deoxygenating means 120 and the degassing means 125, and then the transmittance is measured by the measuring means 130C.

  The measuring unit 130C is the same as the measuring unit 130A of the third embodiment.

  The liquid L whose transmittance is measured by the measuring unit 130 </ b> C is supplied between the projection optical system 30 and the wafer 40 via the supply nozzle 102. The circulation unit 100 appropriately includes a new liquid tank (not shown), a mixing unit that mixes a new liquid and the purified liquid L, a liquid temperature adjusting unit, a particle filter, a chemical filter, and the like.

  In the fifth embodiment, the focus position at the time of exposure is corrected based on the measured value of transmittance by the measuring unit 130C. It is preferable that the correction value for the focus position is uniquely determined in advance for the transmittance value of the liquid L. However, since there may be a case where it depends on a positional relationship between adjacent shots, a distance from the scanning exposure start position, or the like, a focus or exposure amount correction value that takes these into consideration may be required.

  In immersion exposure, managing the transmittance of the liquid L is very important for maintaining the imaging performance. By measuring the transmittance of the liquid L just before being supplied between the projection optical system 30 and the wafer 40, the exposure operation can be stopped if the liquid L with a low transmittance is supplied. Further, the aberration correction amount such as the focus position and the exposure amount varies depending on the transmittance of the liquid L. By accurately measuring the transmittance of the liquid L, it is possible to control the aberration correction amount and maintain good imaging performance.

  When the exposure apparatus 1 having the circulation means 100 shown in FIG. 6 was used to expose the wafer 40 while correcting the focus position and exposure amount, and the image performance was inspected, stable image performance was shown. The transmittance value of the liquid L measured by the measuring unit 130C was in the range of 80 ± 5% per 10 mm thickness.

  Thus, by disposing the measuring unit 130C between the deoxygenating unit 120 and the exposure position, the quality of the liquid L supplied to the exposure position can be accurately managed. Further, by controlling the aberration correction amount based on the transmittance value of the liquid L, it is possible to provide an exposure apparatus that realizes good imaging performance.

  Next, the exposure apparatus 1 of Example 6 will be described. FIG. 7 is a block diagram showing a part of the configuration of the exposure apparatus of the sixth embodiment.

  In the exposure apparatus 1 of Embodiment 6, the liquid L collected from between the projection optical system 30 and the wafer 40 is temporarily stored in the tank 160, and the transmittance of the liquid L stored in the tank 160 is measured by the measuring unit 130. is doing. Then, the transmittance of the liquid L is managed based on the measurement result of the measuring means 130. In addition, as the measurement means 130, the thing similar to the measurement means 130A of Example 3 is used.

  The exposure apparatus of Embodiment 6 has a plurality of tanks 160 as shown in the block diagram of FIG. By having the purification means 110 and the liquid L permeability measuring means 130 for each tank 160, the purification process can be performed for each tank 160 until the collected liquid L permeability is restored.

  By managing the transmittance of the liquid L for each tank 160, the liquid L having a stable transmittance can be supplied to the exposure position.

  In FIG. 7, the measuring means 130 is provided for each tank 160, but the number of the tanks 160 and the measuring means 130 is not necessarily the same. It is also possible to use one measuring unit 130 with a plurality of tanks. Similarly, it is possible to use one purification means 110 in a plurality of tanks.

  Further, a deoxidizing means 120 such as a bubbler may be provided in the tank 160. Since the purification treatment and the deoxygenation treatment can be performed for each tank, the transmittance can be managed with high accuracy. Furthermore, the liquid permeability can be controlled by adjusting the oxygen concentration contained in the gas to be bubbled. By controlling the liquid permeability using the dissolved oxygen concentration as a parameter, the difference in permeability between tanks can be reduced. As a result, when the supply source tank is switched, the exposure conditions can be prevented from changing greatly.

  In the seventh embodiment, as shown in FIG. 8, a measuring unit 130 </ b> C that measures the transmittance of the liquid L is provided between the deoxygenating unit 120 that removes the dissolved oxygen of the liquid L and the exposure position that exposes the wafer 40. The exposure apparatus 1A will be described. FIG. 8 is a partial block diagram showing a part of the configuration of an exposure apparatus 1A as one aspect of the present invention.

  In the exposure apparatus 1A, pure water having a refractive index of 1.44 was used as the liquid L supplied between the projection optical system 30 and the wafer 40. In addition, when using pure water for the liquid L, as shown in FIG. 8, it is not necessary to circulate the liquid L (it is not necessary to recycle).

  The liquid L stored in the supply tank 154 is sent to the oxygen removing means 120 for processing, and the transmittance is measured by the measuring means 130C.

  In the seventh embodiment, the measurement unit 130C includes a D2 lamp as a light source, a diffraction grating that extracts light having a wavelength of 193 nm from light emitted from the D2 lamp, a quartz cell that circulates the liquid L and transmits measurement light, and transmission. And a detector for detecting light intensity. The quartz cell was configured so that the liquid L to be measured had a thickness of 20 mm.

  The liquid L whose transmittance is measured by the measuring unit 130 </ b> C is supplied between the projection optical system 30 and the wafer 40 via the supply nozzle 102. The exposure apparatus 1A appropriately includes a liquid temperature adjusting unit, a particle filter, a chemical filter, and the like (not shown) between the supply tank 154 and the supply nozzle 102.

  In the seventh embodiment, the focus position at the time of exposure is corrected based on the measured value of transmittance by the measuring unit 130C. It is preferable that the correction value for the focus position is uniquely determined in advance for the transmittance value of the liquid L. However, since there may be a case where it depends on a positional relationship between adjacent shots, a distance from the scanning exposure start position, or the like, a focus or exposure amount correction value that takes these into consideration may be required.

  Using the exposure apparatus 1A, the wafer 40 was exposed while correcting the focus position and exposure amount, and the image performance was examined. As a result, stable image performance was shown. The transmittance value of the liquid L measured by the measuring means 130C was in the range of 83 ± 3% per 10 mm thickness.

  As described above, the exposure apparatus 1 or 1A includes at least one of the measurement units 130A to 130C that measure the transmittance of the liquid L. Therefore, the exposure apparatus 1 or 1A can accurately manage the transmittance of the liquid L, can reduce fluctuations in the transmittance of the liquid L, and can realize excellent exposure performance. Further, by disposing measuring means at two or more locations between the exposure position and the purification means 110, between the purification means 110 and the mixing means 150, and between the deoxygenation means 120 and the exposure position, Variations in the transmittance of the liquid L can be further reduced.

  When supplying the liquid L from the external liquid supply / recovery device to the exposure apparatus 1, the exposure apparatus 1 may not include the measurement units 130 </ b> A to 130 </ b> C and the circulation unit 100. For example, the external liquid supply / recovery device is a circulator having the same configuration as the circulation means 100 described above, and the liquid L permeation rate is measured in the liquid supply / recovery device, and the permeation of the liquid L is determined based on the measurement result. The rate should be managed. An exposure apparatus that exposes the wafer via a liquid L supplied between the projection optical system and the wafer, and a measuring unit that measures the transmittance of the liquid L are circulated through the liquid L supplied to the exposure apparatus. An exposure system having a circulating device that constitutes the image forming apparatus also constitutes one aspect of the present invention.

  Further, when the exposure apparatus 1 circulates the liquid L, the transmittance of the recovered liquid L is measured, and the purification condition of the purification unit 110 or the mixing ratio of the mixing unit 150 is controlled based on the measurement result. An exposure method for adjusting the transmittance of the liquid L is provided. Such an exposure method can maintain the transmittance of the liquid L constant, and has the same effect as the exposure apparatus 1.

  In the exposure, the light beam emitted from the light source unit illuminates the reticle 20 by the illumination optical system. The pattern on the reticle 20 is imaged on the wafer 40 via the liquid L by the projection optical system 30. The liquid L used by the exposure apparatus 1 or 1A is accurately controlled in transmittance, and the variation in transmittance that affects the exposure performance is reduced. Therefore, the exposure apparatus 1 or 1A can provide a device (semiconductor device or liquid crystal display device) with higher throughput and higher quality than conventional devices.

  In the above embodiment, the exposure apparatus includes the circulation unit 100 that circulates the liquid L between the recovery nozzle 104 and the supply nozzle 102. However, the circulation unit 100 may be provided outside the exposure apparatus as a circulation device, and the exposure system may be configured by the exposure device and the circulation device.

  Next, an embodiment of a device manufacturing method using the exposure apparatus 1 or 1A will be described with reference to FIGS. FIG. 9 is a flowchart for explaining how to fabricate devices (semiconductor devices and liquid crystal devices). Here, an example of manufacturing a semiconductor device will be described. In step 1 (circuit design), a device circuit is designed. In step 2 (reticle fabrication), a reticle on which the designed circuit pattern is formed is fabricated. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the reticle and wafer. Step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 10 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the reticle onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to this device manufacturing method, it is possible to manufacture a higher quality device than before.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic block diagram which shows the structure of the exposure apparatus as 1 side surface of this invention. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. FIG. 2 is a partial block diagram showing a part of the configuration of the exposure apparatus shown in FIG. 1. It is a partial block diagram which shows a part of structure of the exposure apparatus as 1 side surface of this invention. It is a flowchart for demonstrating manufacture of a device. 10 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 9.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A Exposure apparatus 10 Illumination apparatus 20 Reticle 25 Reticle stage 30 Projection optical system 40 Wafer 45 Wafer stage 50 Oxygen reduction means 100 Circulation means 102 Supply nozzle 104 Recovery nozzle 110 Purification means 120, 120A Deoxygenation means 125 Deaeration means 130 , 130A, 130B, 130C Measuring means 140 Waste liquid tank 150 Mixing means 152 New liquid tank 154 Supply tank 160 Tank L Liquid

Claims (13)

In an exposure apparatus that includes a projection optical system that projects an image of a pattern of a reticle onto a substrate, and that exposes the substrate via a liquid supplied between the projection optical system and the substrate.
Deoxygenation means for reducing dissolved oxygen in the liquid by contacting the liquid with a gas other than oxygen; and
An exposure apparatus comprising: deaeration means for reducing dissolved gas in the liquid.   Characterized by comprising oxygen reducing means for providing an atmosphere having a lower oxygen concentration than the atmosphere by supplying a gas other than oxygen around a liquid supplied between the projection optical system and the substrate. The exposure apparatus according to claim 1.   3. An exposure apparatus according to claim 2, wherein the gas used in the deoxygenating means is different from the gas supplied by the oxygen reducing means.   4. An exposure apparatus according to claim 3, wherein the gas used in the deoxygenation means is helium and the gas supplied by the oxygen reduction means is nitrogen. 5. The exposure apparatus according to claim 1, wherein the deoxygenating unit includes a bubbler that reduces dissolved oxygen by bubbling a gas other than oxygen.   6. The exposure apparatus according to claim 1, wherein the degassing unit includes a degassing filter that reduces dissolved gas by flowing a liquid through one of the gas permeable membranes and reducing the pressure of the other. .   The exposure apparatus according to claim 1, wherein the deaeration unit is disposed between the deoxygenation unit and an exposure position at which the substrate is exposed.   The exposure apparatus according to claim 1, further comprising a measuring unit that measures the transmittance of the liquid.   The exposure apparatus according to claim 8, wherein the measuring unit is disposed on the downstream side of the deoxygenating unit.   9. The exposure apparatus according to claim 8, wherein the concentration of dissolved oxygen in the liquid is controlled based on the measurement result of the measuring means to adjust the transmittance of the liquid. Comprising purification means for improving the purity of the liquid recovered from between the projection optical system and the substrate;
The measuring means is disposed between an exposure position for exposing the substrate and the purification means,
The determination unit determines whether or not the liquid collected from between the projection optical system and the substrate can be reused based on a measurement result of the measurement unit, and controls a purification condition of the purification unit. Item 9. The exposure apparatus according to Item 8. An exposure method for exposing the substrate via a liquid supplied between the projection optical system and the substrate,
Circulating the liquid supplied between the projection optical system and the substrate;
The circulation step includes
An exposure method comprising: a step of reducing dissolved oxygen in the liquid recovered from between the projection optical system and the substrate; and a step of reducing dissolved gas increased in the step of reducing the dissolved oxygen. . An exposure apparatus that has a projection optical system that projects an image of a pattern of a reticle onto a substrate, and that exposes the substrate via a liquid supplied between the projection optical system and the substrate;
A circulation device for circulating the liquid supplied between the projection optical system and the substrate;
The exposure apparatus according to claim 1, wherein the circulation device includes a deoxygenation unit that reduces dissolved oxygen in the liquid and a deaeration unit that reduces dissolved gas in the liquid.