JP2009267200A - Exposure device and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device which suppresses the reduction of an operation rate due to washing process and is capable of maintaining stable optical characteristics. <P>SOLUTION: An immersion exposure device 200 which has a liquid 170 filled between a projection optical system 130 and a substrate 150 to be exposed and exposes the substrate 150 through the liquid 170 includes: a liquid supply line 172 for supplying the liquid 170 between the last face of the projection optical system and a stage 152 facing the last face; a washing station 190 for supplying gas 180 between a lens last face 138 and a substrate stage 152 to be exposed in a state that the liquid 170 is supplied by the liquid supply line 172; and an illuminating device 100 for irradiating the lens last face 138 by ultraviolet rays 198 during supply of gas 180 between the lens last face 138 and the substrate stage 152 to be exposed. The washing station 190 is provided on the substrate stage 152 to be exposed and has a gas supply port 191 and a gas recovery port 192. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to an exposure apparatus and a device manufacturing method.

    Conventionally, a reduction projection exposure apparatus has been used when a fine semiconductor element such as a semiconductor memory or a logic circuit is manufactured by using a photolithography technique. The reduction projection exposure apparatus projects an image of a circuit pattern drawn on a reticle (mask) 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. For this reason, the resolution can be improved by shortening the wavelength of light and increasing the NA. In recent years, with the demand for semiconductor device miniaturization, the wavelength of exposure light has been shortened, and the wavelength of ultraviolet rays used from an KrF excimer laser (wavelength of about 248 nm) to an ArF excimer laser (wavelength of about 193 nm) has become shorter. Yes.

  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, exposure is performed 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). According to immersion exposure, the effective wavelength of exposure light is shortened and the NA of the projection optical system is apparently increased, so that the resolution can be improved.

    The NA of the projection optical system is NA = n × sin θ where n is the refractive index of the medium. For this reason, NA can be increased to n by filling a medium having a refractive index higher than the refractive index of air (n> 1).

  In addition, since the higher the refractive index, the higher the resolution, so an immersion exposure system that uses a liquid with a high refractive index (high refractive index liquid) has been proposed as a successor to the immersion exposure system that uses pure water. (See Patent Documents 1 and 2).

    However, an immersion exposure apparatus using a high refractive index liquid has the following problems, unlike an immersion exposure apparatus using pure water.

    The first problem of the immersion exposure apparatus using a high refractive index liquid is contamination of the final lens of the projection optical system. Exposure light such as an ArF excimer laser causes oxidation and decomposition reactions of a high refractive index liquid made of a hydrocarbon compound, and the generated substance adheres to the lens surface. Adherents are a problem because they reduce the transmittance of exposure light and cause uneven illumination.

A second problem of the immersion exposure apparatus using a high refractive index liquid is a reduction in the operation rate of the exposure apparatus due to the introduction of a cleaning process. As a final lens cleaning method, there has been proposed a cleaning method in which the lens surface is dried and then irradiated with exposure light (see Non-Patent Document 1).
WO2005 / 114711 Publication WO2005 / 119371 Proc. SPIE Vol. 6520, 652035 (2007)

    However, the conventional method of recovering the immersion liquid under the lens and re-forming the immersion area after cleaning includes an immersion liquid recovery process, a lens surface drying process, an immersion area re-formation process, and an immersion liquid. Several hours of downtime occur, such as the temperature stabilization process. Considering the frequency of cleaning such as once every few days, an increase in apparatus downtime due to the introduction of the cleaning process is a serious problem.

  Therefore, the present invention provides an exposure apparatus that can suppress a reduction in operating rate accompanying the introduction of a cleaning process and can maintain stable optical characteristics.

  An exposure apparatus according to one aspect of the present invention is an exposure apparatus that fills a liquid between a projection optical system and at least a part of a substrate, and exposes the substrate through the liquid. A liquid supply means for supplying the liquid between a surface and a stage facing the final surface, and the liquid supply means supplies the liquid between the final surface of the projection optical system and the stage. Gas supply means for supplying a gas to the projection optical system, and irradiation means for irradiating the final surface of the projection optical system with ultraviolet rays while the gas is supplied between the final surface of the projection optical system and the stage. The gas supply means includes a gas supply port that is provided on the stage and supplies the gas, and a gas recovery port that recovers the gas supplied from the gas supply port.

    According to another aspect of the present invention, there is provided a device manufacturing method comprising: exposing a substrate using the exposure apparatus; and developing the exposed substrate.

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

  ADVANTAGE OF THE INVENTION According to this invention, the exposure apparatus which can suppress the fall of the operation rate by introduction of a washing | cleaning process, and can maintain the stable optical characteristic can be provided. Moreover, according to the present invention, a device manufacturing method using such an exposure apparatus can be provided.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, the schematic configuration of the immersion exposure apparatus in the present embodiment will be described. FIG. 1 is a schematic diagram of an immersion exposure apparatus in the present embodiment. The immersion exposure apparatus fills a liquid between the projection optical system and at least a part of the substrate, and exposes the substrate through the liquid.

    As shown in FIG. 1, an immersion exposure apparatus 200 includes an illumination apparatus 100 including a laser 101 as a light source, a reticle 120 (mask) on which a pattern is formed, and a reticle stage 122 on which the reticle 120 is mounted. Have Further, the immersion exposure apparatus 200 includes a projection optical system 130, an exposure target substrate 150 (wafer) on which a pattern on the reticle 120 is projected by the projection optical system 130, and an exposure target substrate stage on which the exposure target substrate 150 is mounted. 152.

    A liquid 170 as a medium exists between the substrate stage 152 to be exposed and the projection optical system 130. The liquid 170 is supplied from the outside via the liquid supply line 172. The liquid 170 flowing from the liquid supply line 172 passes through the liquid supply port 175 provided in the projection optical system casing 135, the final surface of the projection optical system (lens final surface 138), the substrate stage 152 to be exposed, and the like. Supplied during. As described above, the liquid supply line 172 is a liquid supply unit that supplies the liquid 170 between the final surface of the projection optical system and the exposure target substrate stage 152 on which the exposure target substrate 150 is mounted. Further, the liquid 170 supplied between the final surface of the projection optical system and the substrate stage 152 to be exposed passes through the liquid recovery line 173 via the liquid recovery port 171 provided in the casing 135 of the projection optical system. Discharged.

    The liquid supply unit of this embodiment supplies the liquid 170 between the final surface of the projection optical system 130 and the substrate stage 152 to be exposed, but is not limited to this. The cleaning in this embodiment can be performed on a stage different from the exposed substrate stage 152 on which the substrate (wafer) is mounted. In this case, the liquid supply means of the present embodiment is configured to supply the liquid 170 between the final surface of the projection optical system and the stage facing the final surface.

    The lens final surface 138 of the projection optical system is in contact with the liquid 170 partially or entirely. During exposure, the immersion exposure apparatus 200 drives the substrate stage 152 to be exposed using the stage drive unit 160 to move the substrate to be exposed 150 directly below the lens final surface 138 of the projection optical system. In this manner, the immersion exposure apparatus 200 exposes the pattern formed on the reticle 120 onto the exposed substrate 150 via the liquid 170.

    The immersion exposure apparatus 200 of the present embodiment is a step-and-scan projection exposure apparatus, but is not particularly limited thereto. The present embodiment can also be applied to other types of exposure apparatuses such as a step-and-repeat method.

The illumination device 100 includes a light source unit including a laser 101 as a light source and a beam shaping optical system 102. As the laser 101, an ArF excimer laser with a wavelength of about 193 nm, a KrF excimer laser with a wavelength of about 248 nm, or an F ₂ laser with a wavelength of about 157 nm can be used. In this embodiment, the type and number of the lasers 101 are not limited, and the type of the light source unit is not limited.

  The liquid 170 is supplied from the liquid supply line 172 via the liquid supply port 175 between the lens final surface 138 of the projection optical system and the substrate stage 152 to be exposed. The liquid 170 is recovered by the liquid recovery line 173 via the liquid recovery port 171 arranged around the lens final surface 138 of the projection optical system. Thereby, a liquid immersion region filled with the liquid 170 can be formed between the lens final surface 138 of the projection optical system and the substrate to be exposed 150.

    As the material of the liquid 170, a substance having a high exposure wavelength transmittance and a good matching with the resist process is selected. The liquid 170 is, for example, a hydrocarbon compound, and for example, an alicyclic hydrocarbon compound such as decalin, bicyclohexyl, or cyclohexane is used. When a hydrocarbon compound is used as the liquid 170, contaminants formed by the reaction between the light from the laser 101 and the hydrocarbon compound adhere to the final lens of the projection optical system 130. For this reason, a gas supply means described later is particularly required.

    However, the liquid 170 of the present embodiment is not limited to the hydrocarbon compound, and pure water may be used, for example. When pure water is used as the liquid 170, it does not react with the light from the laser 101. However, contaminants generated from the resist on the exposed substrate 150 may adhere to the final lens of the projection optical system 130. For this reason, even when pure water is used as the liquid 170, a gas supply means described later is required.

    The cleaning station 190 (gas supply means) has a gas supply port 191 for supplying the gas 180 onto the substrate stage 152 to be exposed, and a gas recovery port 192 for recovering the supplied gas 180. The cleaning station 190 is provided on the substrate stage 152 to be exposed. At the time of cleaning, the cleaning station 190 is driven by the stage driving unit 160 to move immediately below the lens final surface 138 of the projection optical system. As an example, the gas recovery port 192 is disposed so as to surround the gas supply port 191. Since FIG. 1 is a sectional view, the gas recovery port 192 is shown as being provided on the left and right of the gas supply port 191.

    Here, it is preferable to incline the side wall 156 of the gas recovery port toward the lens final surface 138. According to such a configuration, the gas 180 can be easily supplied to a local position directly below the lens final surface 138. Note that the gas supply port 191 and the gas recovery port 192 are not limited to the above arrangement method, and may be another arrangement method.

    By using the gas supply port 191 and the gas recovery port 192, the final lens surface 138 of the projection optical system and the exposure target are exposed while the liquid 170 is held between the casing 135 of the projection optical system and the substrate stage 152 to be exposed. A gas 180 can be formed between the substrate stage 152 and the substrate stage 152. As described above, the cleaning station 190 supplies the gas 180 between the lens final surface 138 of the projection optical system 130 and the substrate stage 152 to be exposed in a state where the liquid 170 is supplied from the liquid supply line 172. It is.

    The arrangement of the cleaning station 190 is not limited to the substrate stage 152 to be exposed. The cleaning station 190 may be disposed so as to face the final lens of the projection optical system 130. For example, a cleaning station may be provided on a stage different from the exposed substrate stage 152 for mounting the exposed substrate 150.

    The gas 180 supplied from the gas supply port 191 includes at least oxygen or water. For example, the gas 180 preferably contains 1 wt% or more of oxygen, or contains water having a relative humidity of 10% or more and 80% or less at a temperature of 23 ° C. and 1 atm. The pressure and flow rate of the gas 180 supplied to the immersion exposure apparatus 200 can be controlled to an arbitrary value using a control device (not shown). Moreover, the opening part of the gas supply port 191 is comprised with a slit, several pinholes, or a porous body.

    The gas recovery port 192 is preferably the same size as the final surface of the projection optical system. However, the present invention is not limited to this, and it may be larger than the final surface of the projection optical system as long as it can be disposed inside the liquid supply port 175. Further, it is preferable to provide a space between the gas recovery port 192 and the final surface of the projection optical system in order to prevent the liquid 170 from scattering when the gas 180 is supplied.

    Further, it is preferable to provide a space between the liquid supply port 175 and the liquid recovery port 171 and the exposed substrate stage 152 so that the liquid 170 can be held when the gas region is formed by the gas 180. For this reason, the plane of the substrate stage 152 to be exposed includes a first plane 157 and a second plane 158 lower than the first plane 157, and a step is formed by the first plane 157 and the second plane 158. Yes. In the substrate stage 152 to be exposed, a recess including a side wall 155 and a second flat surface 158 is formed around the cleaning station 190. As described above, by providing the space by the concave portion including the side wall 155 and the second flat surface 158, the liquid 170 can be stably held even when the gas 180 is supplied and the pressure of the liquid 170 fluctuates.

    In FIG. 1, a gas supply port 191 and a gas recovery port 192 are provided on the exposed substrate stage 152 facing the final surface of the projection optical system 130. However, it is not limited to this arrangement. You may arrange | position in the space of the side surface of the last lens of the projection optical system 130, or the position adjacent to the liquid supply port 175.

After the gas region is formed with the gas 180 inside the liquid 170, the final lens surface 138 of the projection optical system can be cleaned by irradiating the final lens surface 138 of the projection optical system with ultraviolet rays. By irradiating ultraviolet rays in a gas 180 containing oxygen or water, the reaction proceeds as shown in the following formulas (1) to (4). As a result, the oxide of the high refractive index liquid (liquid 170) adhering to the final surface of the projection optical system 130 can be decomposed and removed into carbon monoxide, carbon dioxide, or the like. In the following formula, O ( ¹ D) represents an excited oxygen atom.

O ₂ + UV → O + O (1)
O ₂ + O → O ₃ (2)
O ₃ + ultraviolet light → O ( ¹ D) + O ₂ (3)
H ₂ O + O ( ¹ D) → 2OH (4)
As the ultraviolet irradiation method, there are a method of using exposure light from the laser 101 of the light source unit as cleaning ultraviolet light, or a method of separately preparing an irradiation means for irradiating an ultraviolet light source different from the laser 101. According to the method using the exposure light from the laser 101, a scattering reticle can be used as the reticle 120. By using the scattering reticle, it is possible to uniformly irradiate the entire lens final surface 138 of the projection optical system.

    On the other hand, as another ultraviolet light source, a low-pressure mercury lamp, a deuterium lamp, an excimer lamp, or the like can be used. In particular, the low-pressure mercury lamp emits 185 nm and 254 nm and reacts as shown by the following formulas (5) to (8) to generate ozone, excited oxygen, and OH radicals having strong oxidizing power. it can. As a result, the deposit that is an oxide of the high refractive index liquid (liquid 170) can be efficiently decomposed and removed into carbon monoxide, carbon dioxide, or the like.

O ₂ +185 nm → O + O (5)
O ₂ + O → O ₃ (6)
O ₃ +254 nm → O ( ¹ D) + O ₂ (7)
H ₂ O + O ( ¹ D) → 2OH (8)
As described above, the illumination apparatus 100 irradiates the lens final surface 138 of the projection optical system with the ultraviolet rays 198 while the gas 180 is supplied between the lens final surface 138 of the projection optical system and the substrate stage 152 to be exposed. Irradiation means.

    Hereinafter, based on each Example, the structure of this invention is demonstrated in detail.

  First, an exposure apparatus in Embodiment 1 of the present invention will be described. The exposure apparatus of the present embodiment is an immersion exposure apparatus that removes contaminants attached to the final surface of the projection optical system by supplying a gas into the immersion area and irradiating an ArF excimer laser as ultraviolet rays. .

    FIG. 2 is a partial schematic view of the immersion exposure apparatus in the present embodiment. The immersion exposure apparatus shown in the figure is a step-and-scan exposure apparatus using an ArF excimer laser as a light source. Decalin having a refractive index of 1.64 is used as the liquid 170 (high refractive index liquid) supplied between the lens final surface 138 of the projection optical system and the substrate stage 152 to be exposed.

    The liquid 170 (decalin) is supplied from the liquid supply line 172 via the liquid supply port 175 between the lens final surface 138 of the projection optical system and the substrate stage 152 to be exposed. The supplied liquid 170 is recovered by the liquid recovery line 173 via the liquid recovery port 171. The exposed substrate 150 mounted on the exposed substrate stage 152 is moved directly below the lens final surface 138 of the projection optical system, and the exposed substrate 150 is exposed with an ArF excimer laser through the liquid 170. Thereby, the pattern formed on the reticle 120 can be transferred onto the exposed substrate 150 with high resolution.

    By the way, when the immersion exposure apparatus of this example was operated continuously for 5 days, an exposure abnormality considered to be exposure unevenness was detected. Note that the illuminance of the ArF excimer laser was 1 mJ / cm 2 per pulse on the exposed substrate 150. When the final lens surface 138 of the projection optical system was observed with a fiberscope, particle-like deposits were observed. The cause of uneven exposure is considered to be this deposit.

    In order to remove the deposits attached to the final lens surface 138 of the projection optical system, the final lens surface 138 of the projection optical system of the present embodiment is cleaned by the following procedure.

    At the time of exposure, the liquid 170 is supplied from the liquid supply line 172 via the liquid supply port 175 between the lens final surface 138 of the projection optical system and the substrate 150 to be exposed on the substrate stage 152 to be exposed. The supplied liquid 170 is recovered by the liquid recovery line 173 via the liquid recovery port 171. In this way, the liquid 170 is held between the final lens surface 138 of the projection optical system and the substrate to be exposed 150 to form an immersion area.

    During cleaning, the cleaning station 190a provided on the substrate stage 152 to be exposed is moved directly below the lens final surface 138 while the liquid 170 is supplied between the lens final surface 138 of the projection optical system and the substrate 150 to be exposed. To do. In this way, the cleaning station 190a is arranged to face the lens final surface 138 of the projection optical system.

    As shown in FIG. 2, the cleaning station 190a has a gas supply port 191a and a gas recovery port 192a disposed around the gas supply port 191a. The gas 180 is supplied from the gas supply port 191 a toward the lens final surface 138 through the gas supply line 194. The gas supply line 194 has a tube through which gas passes inside the substrate stage 152 to be exposed, and is connected to an external flexible tube. In addition, the gas 180 recovered from the gas recovery port 192a is discharged to the outside through the gas recovery line 196. The gas recovery line 196 has a tube through which gas passes inside the substrate stage 152 to be exposed, and is connected to an external flexible tube.

    The side wall 159a of the gas supply port is inclined inward and is configured to become narrower as it approaches the tip. With such a configuration, the gas 180 can be locally supplied toward the lens final surface 138. Further, the side walls 156a and 156c of the gas recovery port are inclined so as to be directed toward the lens final surface 138. In particular, the inclined surface of the side wall 156a (outer side wall) of the gas recovery port is curved. With such a configuration, the gas 180 supplied to the lens final surface 138 can be efficiently recovered, and the gas 180 can be held at a local position.

    After the immersion area is moved onto the cleaning station 190a, the gas 180 is blown from the gas supply port 191a to the lens final surface 138, and the blown gas 180 is collected from the gas recovery port 192a. The liquid 170 can be removed from directly under the lens final surface 138 by performing the operation of blowing the gas 180 for 2 minutes or more, for example.

    After removing the liquid 170 from directly under the lens final surface 138, the lens final surface 138 is irradiated with an ArF excimer laser. At this time, by setting the scattering reticle at the reticle position, the ArF excimer laser as the exposure light can uniformly irradiate the lens in the projection optical system 130, particularly the lens final surface 138.

    By supplying a gas 180 containing oxygen from the gas supply port 191a and irradiating an ArF excimer laser, the reaction proceeds as represented by the formulas (1) to (4). As a result, the oxide resulting from the liquid 170 adhering to the lens final surface 138 of the projection optical system can be decomposed and removed into carbon monoxide, carbon dioxide, or the like.

    For example, when the oxygen concentration in the gas 180 supplied from the gas supply port 191a is 40 wt% and the irradiation time of the ArF excimer laser is 30 minutes, the deposit on the lens final surface 138 is removed. When it was actually cleaned under these conditions, no deposit was observed in the observation of the final lens surface 138 with a fiberscope. Further, even when the substrate to be exposed was exposed, no exposure abnormality due to exposure unevenness was detected. However, the present invention is not limited to this condition, and deposits can be effectively removed at other oxygen concentrations and irradiation times.

    There is a correlation between the oxygen concentration in the gas 180 supplied from the gas supply port 191a and the cleaning effect of the deposits. Although it has been confirmed that if the oxygen concentration is 1 wt% or more, a deposit cleaning effect can be obtained, it is more preferable to set the oxygen concentration to 20 wt% or more for cleaning in a shorter time.

    Moreover, the same cleaning effect as oxygen can be obtained by including water in the gas. Actually, at a temperature of 23 ° C. and 1 atm, a gas having a relative humidity of 10% or more is supplied to the lens final surface 138 and irradiated with ultraviolet rays 198 (ArF excimer laser) to effectively remove the deposits. did it.

    Next, the cleaning operation in this embodiment will be described. FIG. 3 is a flowchart showing the operation of the cleaning method in this embodiment.

    First, it is determined whether it is time to perform cleaning (step S101). In the exposure apparatus of this embodiment, the cleaning is set to be performed periodically, for example, by irradiating ultraviolet rays 198 (ArF excimer laser) for 10 minutes once a day. However, the present invention is not limited to this, and it may be set to perform cleaning when the exposure of one or a plurality of exposed substrates is completed, that is, when the exposed substrates are replaced.

    As shown in FIG. 3, when it is determined that it is not the cleaning time (NO), the determination in step S101 is repeated. If it is determined that the cleaning time has come (YES), the stage drive unit 152 moves the substrate stage 152 to be exposed, and the cleaning station 190 is disposed directly below the housing of the projection optical system 130 (step S102). At this time, the space between the cleaning station 190 (exposed substrate stage 152) and the housing of the projection optical system 130 is filled with the liquid 170.

    Next, the cleaning station 190a is activated. Specifically, the gas 180 starts to be supplied from the gas supply port 191a toward the lens final surface 138 of the projection optical system (step S103). It is determined whether or not a certain time has elapsed from the start of supply of the gas 180 (step S104), and when the certain time has elapsed, the gas 180 is started to be recovered using the gas recovery port 192a (step S105).

    Next, the last lens surface 138 is irradiated with ultraviolet rays 198 (ArF excimer laser) (step S106). By the irradiation with the ultraviolet rays 198, the deposits on the lens final surface 138 can be removed.

    After the irradiation with the ultraviolet ray 198, it is determined whether or not a certain time has passed (step S107). When the certain time has passed, the supply of the gas 180 is stopped (step S108). Even after the supply of the gas 180 from the gas supply port 191 a is stopped, the gas 180 remains between the lens final surface 138 of the projection optical system and the substrate stage 152 to be exposed. For this reason, the recovery of the gas 180 by the gas recovery port 192a is continued for a certain time after the supply of the gas 180 is stopped.

    It is determined whether or not a fixed time has passed since the supply of the gas 180 was stopped (step S109). When the fixed time has passed, the recovery of the gas 180 through the gas recovery port 192a is stopped (step S110). At this time, no gas 180 remains between the final lens surface 138 of the projection optical system 130 and the substrate stage 152 to be exposed. That is, the space between the housing 135 of the projection optical system and the exposed substrate stage 152 is filled with the liquid 170, including just below the lens final surface 138.

    Next, the substrate stage 152 to be exposed is moved, and the substrate to be exposed 150 before exposure is arranged immediately below the lens final surface 138 of the projection optical system (step S111). When the placement of the substrate to be exposed 150 is completed, the substrate to be exposed 150 is exposed (step S112). When the cleaning method of this embodiment is executed every time the exposure of one substrate to be exposed 150 is completed, the steps shown in FIG. 3 are repeated after the exposure in step S112 is completed.

    As described above, by periodically cleaning the lens final surface 138 of the projection optical system using the immersion exposure apparatus of this embodiment, the deposit can be removed before the deposit impedes the exposure performance. it can. As a result, stable exposure performance can be maintained. In addition, according to the present embodiment, since the lens final surface can be cleaned while maintaining the liquid immersion area, the downtime of the apparatus accompanying the cleaning process is shortened, and the reduction in productivity can be reduced. It is.

    Next, an exposure apparatus according to Embodiment 2 of the present invention will be described. The present embodiment is an immersion exposure apparatus that removes contaminants attached to the final lens surface of the projection optical system by supplying a gas into the immersion area and irradiating a low-pressure mercury lamp.

    FIG. 4 is a partial schematic diagram of the immersion exposure apparatus in the present embodiment. The immersion exposure apparatus in this embodiment is a step-and-scan exposure apparatus that uses an ArF excimer laser as a light source. In this embodiment, decalin having a refractive index of 1.64 is used as the liquid 170 (high refractive index liquid) supplied between the final lens surface 138 of the projection optical system and the substrate stage 152 to be exposed.

    The liquid 170 (decalin) is supplied from the liquid supply line 172 via the liquid supply port 175 between the lens final surface 138 of the projection optical system and the substrate 150 to be exposed, and the liquid recovery line 173 via the liquid recovery port 171. It is collected by. By exposing the substrate to be exposed with an ArF excimer laser through the liquid 170, the pattern formed on the reticle 120 is transferred onto the substrate 150 to be exposed with high resolution.

    By the way, when the immersion exposure apparatus of this example was operated continuously for 5 days, an exposure abnormality considered to be uneven exposure amount was detected. Note that the illuminance of the ArF excimer laser was 1 mJ / cm 2 per pulse on the exposed substrate 150. When the final lens surface 138 of the projection optical system was observed with a fiberscope, particle-like deposits were observed. For this reason, it is considered that the cause of the exposure unevenness is a deposit adhered to the lens final surface 138.

    In order to remove the deposits attached to the final lens surface 138 of the projection optical system, the final lens surface 138 of the projection optical system of the present embodiment is cleaned by the following procedure.

    The liquid 170 is supplied from the liquid supply line 172 through the liquid supply port 175 between the lens final surface 138 of the projection optical system 130 and the substrate to be exposed 150 on the substrate stage 152 to be exposed. The supplied liquid 170 is recovered by the liquid recovery line 173 via the liquid recovery port 171.

    As described above, the liquid 170 is held between the lens final surface 138 and the substrate to be exposed 150 to form a liquid immersion region. While the immersion area is held on the substrate stage 152 to be exposed, the substrate stage 152 is moved, and an immersion area formed by the liquid 170 is provided from the substrate 150 to the substrate stage 152 to be exposed. Move to the cleaning station 190b.

    The cleaning station 190b includes a gas recovery port 192b, a gas supply port 191b disposed around the gas recovery port 192b, and a low-pressure mercury lamp (not shown). In the exposure apparatus of this embodiment, unlike the first embodiment, a gas supply port 191b is provided around the gas recovery port 192b. Since FIG. 4 is a cross-sectional view, the gas supply port 191b is shown as being provided on the left and right of the gas recovery port 192b. The gas supply port 191b of this embodiment blows the gas 180 including the outside of the irradiation region of the lens final surface 138.

    The side wall 159 b of the gas supply port is inclined toward the lens final surface 138. With such a configuration, the gas supply port 191 b can locally supply the gas 180 toward the lens final surface 138. Further, the side wall 156b of the gas recovery port is inclined so that the tip is widened. With such a configuration, the gas 180 supplied to the lens final surface 138 can be efficiently recovered.

    The arrangement of the cleaning station 190b of this embodiment is effective not only for removing deposits caused by the liquid 170 but also for removing deposits caused by the resist formed on the substrate to be exposed 150. Deposits resulting from the resist also adhere outside the exposure light irradiation area. For this reason, according to the structure of the present embodiment in which gas is blown also outside the irradiation region of the lens final surface 138, the deposits caused by the resist can be effectively removed.

    After the immersion area is moved onto the cleaning station 190b, the gas 180 is sprayed from the gas supply port 191b to the lens final surface 138, and the sprayed gas 180 is recovered from the gas recovery port 192b. Actually, the liquid 170 could be removed from the final lens surface 138 by performing this spraying operation for 2 minutes or more. However, it is not limited to this, and spraying time can be changed according to other conditions.

    After the liquid 170 is removed from the lens final surface 138, the lens final surface 138 is irradiated with a low-pressure mercury lamp. The low-pressure mercury lamp may be arranged so that it can be irradiated from the lower surface of the lens, or may be arranged so that it can be irradiated via the projection optical system 130. When the gas 180 supplied from the gas supply port 191b contains oxygen and water and is irradiated with a low-pressure mercury lamp, the reaction proceeds as expressed in the equations (5) to (8). As a result, the oxide resulting from the liquid 170 adhering to the lens final surface 138 of the projection optical system can be decomposed and removed into carbon monoxide, carbon dioxide, or the like.

    Actually, the deposit on the lens final surface 138 was removed by setting the oxygen concentration in the gas supplied from the gas supply port 191b to 21 wt% and the irradiation time of the low-pressure mercury lamp to 60 minutes. At this time, in the observation of the lens final surface 138 with a fiberscope, no deposit was observed. Further, even when the substrate to be exposed was exposed, no exposure abnormality due to exposure unevenness was detected. However, the oxygen concentration of the gas 180 and the irradiation time of the low-pressure mercury lamp can be appropriately changed.

    Further, the operation at the time of cleaning in this embodiment is the same as that shown in FIG. 3 except that the gas supply port 191b and the gas recovery port 192b are used for supplying and recovering the gas, respectively, and the low-pressure mercury lamp is used as the ultraviolet ray 198. 3 is the same as that described in the first embodiment.

    As described above, by periodically cleaning the lens final surface 138 of the projection optical system using the immersion exposure apparatus of the present embodiment, the deposit is effectively removed before the deposit impedes the exposure performance. Can be removed. As a result, stable exposure performance can be maintained.

    In this embodiment, for example, periodic cleaning is performed once a day by irradiating a low-pressure mercury lamp for 20 minutes. However, the present invention is not limited to this, and it may be set so that cleaning is performed for each exposure of one or a plurality of exposed substrates. According to the exposure apparatus of the present embodiment, since the lens final surface 138 can be cleaned while the immersion area is held, the apparatus downtime associated with the cleaning process is shortened, and the reduction in productivity can be reduced. Is possible.

    A device (semiconductor integrated circuit element, liquid crystal display element, etc.) includes a step of exposing a substrate (wafer, glass plate, etc.) coated with a photosensitive agent using the exposure apparatus of any one of the embodiments described above, and the substrate It is manufactured by undergoing a development step and other known steps.

    According to each of the above embodiments, the final lens surface of the projection optical system can be cleaned while the liquid immersion area is formed. As a result, it is possible to shorten the time of the cleaning process, and it is possible to provide an immersion exposure apparatus having a high operation rate while using a high refractive index liquid.

    Therefore, according to each of the above-described embodiments, it is possible to provide an exposure apparatus that can suppress a reduction in operating rate accompanying the introduction of a cleaning process and can maintain stable optical characteristics. In addition, a device manufacturing method using such an exposure apparatus can be provided.

    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 diagram of the immersion exposure apparatus in a present Example. 1 is a partial schematic diagram of an immersion exposure apparatus in Embodiment 1. FIG. 3 is a flowchart showing the operation of the cleaning method in Embodiment 1. 5 is a partial schematic diagram of an immersion exposure apparatus in Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Illuminating device 101: Laser 102: Beam shaping optical system 120: Reticle 122: Reticle stage 130: Projection optical system 135: Projection optical system housing 150: Exposed substrate 152: Exposed substrate stage 155: Side walls 156, 156a 156b, 156c: gas recovery port side wall 157: first plane 158: second plane 159a, 159b: gas supply port side wall 160: stage drive unit 170: liquid 171: liquid recovery port 172: liquid supply line 173 : Liquid recovery line 175: Liquid supply port 180: Gas 190, 190a, 190b: Cleaning station (gas supply means)
191, 191 a, 191 b: gas supply port 192, 192 a, 192 b: gas recovery port 194: gas supply line 196: gas recovery line 198: ultraviolet ray 200: immersion exposure apparatus

Claims (6)

An exposure apparatus that fills a liquid between a projection optical system and at least a part of a substrate and exposes the substrate through the liquid,
Liquid supply means for supplying the liquid between a final surface of the projection optical system and a stage facing the final surface;
A gas supply means for supplying a gas between the final surface of the projection optical system and the stage in a state where the liquid is supplied by the liquid supply means;
Irradiation means for irradiating the final surface of the projection optical system with ultraviolet rays while the gas is supplied between the final surface of the projection optical system and the stage,
The exposure apparatus according to claim 1, wherein the gas supply unit includes a gas supply port that supplies the gas and a gas recovery port that recovers the gas supplied from the gas supply port.     The exposure apparatus according to claim 1, wherein the gas contains 1 wt% or more of oxygen.     2. The exposure apparatus according to claim 1, wherein the gas has a relative humidity of 10% or more at a temperature of 23 [deg.] C. and 1 atm.   The exposure apparatus according to claim 1, wherein the ultraviolet light is exposure light.   The exposure apparatus according to claim 1, wherein the liquid is a hydrocarbon compound. Exposing the substrate using the exposure apparatus according to any one of claims 1 to 5;
And developing the exposed substrate. A device manufacturing method comprising: