JP2006310706A - Cleaning method for optical component, immersion projection aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning an optical component by which a contaminant sticking to the optical component constituting a projection optical system comprised in an immersion projection aligner is easily removed. <P>SOLUTION: This is the method for cleaning the optical component used for the immersion projection aligner in which a mask is irradiated with exposing light, and then the pattern of the mask is transferred to a substrate through the projection optical system, and purified water is interposed between the surface of the substrate and the projection optical system. The cleaning method comprises a substrate releasing process (S12) for making the substrate release from a substrate stage on which the substrate is placed, a purified water supplying process (S14) for supplying the purified water to the space between the substrate stage and the projection optical system, an irradiating process (S15) for, by supplying the purified water in the purified water supplying process, making into contact with the purified water and irradiating the optical component contact to liquid, which constitutes the projection optical system and is arranged on the side nearest to the substrate stage, with the exposing light, and a purified water discharging process (S16) for discharging the purified water supplied in the purified water supplying process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used, for example, to transfer a mask pattern onto a photosensitive substrate in a lithography process for manufacturing a device such as a semiconductor element, an imaging element (CCD, etc.), a liquid crystal display element, or a thin film magnetic head. The present invention relates to a cleaning method for optical components used in a projection exposure apparatus using an immersion method, an immersion projection exposure apparatus including an optical component cleaned by the cleaning method, and an exposure method using the immersion projection exposure apparatus. is there.

  In lithography processes for manufacturing devices such as semiconductor elements and liquid crystal display elements, a projection exposure apparatus that transfers a mask pattern onto a substrate via a projection optical system is used. In this projection exposure apparatus, when excimer laser light is used as exposure light, a thin film-like contaminant adheres to the surface of the optical member through which the exposure light passes, and the adhered contaminant causes a decrease in transmittance and uneven illumination. It was a factor. Therefore, the contaminants attached to the surface of the optical member are removed by wiping with an etching solution containing hydrofluoric acid, and the etching solution remaining on the surface of the optical member is wiped with water or a cleaning organic solvent. A method for removing contaminants to be removed is used (see, for example, Patent Document 1).

International Publication No. 2004/050266 Pamphlet

  In recent years, there has been proposed an immersion projection exposure apparatus that performs exposure in a state where a space between a projection optical system and a substrate is filled with a predetermined liquid. The resolution of the projection exposure apparatus increases as the exposure wavelength λ used decreases and as the numerical aperture NA (brightness of the projection optical system) of the projection optical system increases. This resolution is normally expressed as resolution = k (process coefficient) × λ / NA, and the numerical aperture NA of the projection optical system is NA = n (refractive index of the medium through which exposure light passes) × sin θ (incident light of exposure light) Angle). Since exposure in a projection exposure apparatus other than immersion is performed in the atmosphere, n = 1, whereas in an immersion projection exposure apparatus, n is larger than 1, and the light incident angle θ of exposure light is changed. The numerical aperture NA of the projection optical system can be increased without any problem. That is, the resolution of the projection exposure apparatus can be improved to 1 / n times (the refractive index of the liquid is usually about 1.2 to 1.6). On the other hand, in the immersion projection exposure apparatus, when the numerical aperture NA is set to be the same as that of the projection exposure apparatus other than immersion, the beam incident angle θ of the exposure light can be reduced, so that the depth of focus is increased n times ( Improvement).

  In the above-described immersion projection exposure apparatus, ArF excimer laser light (wavelength 193 nm) is used as exposure light, and pure water having a refractive index of 1.44 is interposed between the projection optical system and the substrate. The photoacid generator (PAG) and amine, which are the eluates of the applied resist, are eluted in pure water, albeit in trace amounts. When exposure light is irradiated while the PAG and amine are dissolved in pure water, the PAG and amine are transformed and deposited to adhere to the surface of the optical member arranged on the most substrate side constituting the projection optical system as a contaminant. To do. Since the exposure light is absorbed by the attached contaminant or the exposure light is scattered by the attached contaminant, the transmittance of the projection optical system is deteriorated. Further, since the temperature of the optical member and pure water rises due to the exposure light absorbed by the adhering contaminants, the aberration of the projection optical system deteriorates.

  Therefore, it is necessary to remove contaminants attached to the surface of the optical member. Since the pollutant which is a modified product of PAG and amine is soluble in organic solvents such as alcohols and ketones, the pollutant can be removed by flowing an organic solvent instead of pure water. However, in order to remove contaminants by flowing an organic solvent instead of pure water, the substrate stage, lens holder, piping, etc. must be made of a material that can withstand the organic solvent, and the production cost of the projection exposure apparatus is reduced. Incurs an increase.

  An object of the present invention is to provide a cleaning method for an optical component that can easily remove contaminants attached to an optical component constituting a projection optical system included in an immersion projection exposure apparatus, and an optical component cleaned by the cleaning method. An immersion projection exposure apparatus and an exposure method using the immersion projection exposure apparatus are provided.

  The optical component cleaning method according to claim 1, wherein the mask is irradiated with exposure light, the pattern of the mask is transferred onto the substrate via the projection optical system, and the surface of the substrate and the projection optical system are transferred. A cleaning method for an optical component used in an immersion projection exposure apparatus including pure water, the substrate retracting step for retracting the substrate from a substrate stage on which the substrate is placed, the substrate stage, and the projection A pure water supply step for supplying the pure water between the optical system and the pure water supplied by the pure water supply step, thereby contacting the pure water and constituting the projection optical system; It includes an irradiation step of irradiating the wetted optical component disposed on the substrate stage side with the exposure light, and a pure water discharge step of discharging the pure water supplied by the pure water supply step. .

  According to the cleaning method for an optical component according to claim 1, pure water that is in contact with the wetted optical component is circulated, and the surface of the wetted optical component is cleaned by irradiating with exposure light. By elution of the applied resist, contaminants adhering to the wetted optical component can be easily removed. Accordingly, it is possible to prevent a decrease in the transmittance of the projection optical system and a deterioration in the aberration of the projection optical system due to contaminants adhering to the surface of the wetted optical component.

  According to a second aspect of the present invention, there is provided a cleaning method for cleaning an optical component comprising: a cleaning substrate installation step of installing a cleaning substrate on which the resist is not applied on the substrate stage after the substrate is retracted by the substrate retracting step. Further, the pure water supply step is characterized in that the pure water is supplied between the surface of the cleaning substrate and the projection optical system.

  According to the optical component cleaning method of the second aspect, since the wetted optical component is cleaned in a state where the cleaning substrate is installed on the substrate stage, exposure is performed for cleaning the wetted optical component. It is possible to prevent the substrate stage from being damaged by the exposure light irradiation without the light reaching the substrate stage.

  The optical component cleaning method according to claim 3 further includes a transmittance measuring step of measuring the transmittance of the wetted optical component, and the transmittance of the wetted optical component measured by the transmittance measuring step. The liquid-contact optical component is washed when the value is lower than a predetermined allowable value.

  According to the method for cleaning an optical component described in claim 3, only when the wetted optical component needs to be cleaned based on the measurement result of the transmittance of the wetted optical component in the transmittance measuring step. Cleaning can be performed.

  According to a fourth aspect of the present invention, there is provided a method for cleaning an optical component comprising: a transmittance re-measurement step of re-measuring the transmittance of the wetted optical component after the wetted optical component is cleaned; A contaminant wiping step of wiping the contaminant remaining on the surface of the wetted optical component with an organic solvent when the transmittance of the wetted optical component remeasured by the measuring step is lower than a predetermined allowable value; It is characterized by including.

  According to the cleaning method for an optical component according to the fourth aspect, after the wetted optical component is cleaned, the transmittance of the wetted optical component is remeasured, and based on the remeasurement result, the wetted optical component is cleaned. Since the contaminant remaining on the surface is wiped off, the contaminant adhering to the surface of the wetted optical component can be reliably removed.

  The optical component cleaning method according to claim 5 is characterized in that the organic solvent is a solvent of alcohols or ketones.

  The optical component cleaning method according to claim 6, wherein a contaminant that adheres to a surface of the wetted optical component exposes the mask pattern on the substrate when the resist is applied on the substrate. The eluate from is a substance that has been transformed, precipitated, or deposited.

  The optical component cleaning method according to claim 7 is characterized in that the pure water has a resistivity of 1 MΩcm or more and a TOC (Total Organic Carbon) value of less than 1 ppm.

  The optical component cleaning method according to claim 8 is characterized in that the exposure light is ArF excimer laser light. According to the cleaning method for optical parts according to claims 5 to 8, contaminants adhering to the surface of the wetted optical part can be satisfactorily removed.

  The exposure apparatus according to claim 9 irradiates the mask with exposure light, transfers the pattern of the mask onto the substrate via the projection optical system, and purely between the surface of the substrate and the projection optical system. An immersion projection exposure apparatus with water interposed therein, comprising a wetted optical component cleaned by the optical component cleaning method according to any one of claims 1 to 8.

  According to the exposure apparatus of the ninth aspect, since the wetted optical component cleaned by the optical component cleaning method according to any one of the first to eighth aspects is provided, the wetted optical component is provided. Therefore, it is possible to prevent the deterioration of the transmittance of the projection optical system and the deterioration of the aberration of the projection optical system due to the contaminants adhering to the surface of the projection, and it is possible to perform the exposure well.

  The exposure method according to claim 10 irradiates the mask with exposure light, transfers the pattern of the mask onto the substrate via the projection optical system, and purely between the surface of the substrate and the projection optical system. An exposure method using an immersion projection exposure apparatus with water interposed, comprising a wetted optical component cleaned by the optical component cleaning method according to any one of claims 1 to 8. And an exposure step of projecting and exposing the pattern of the mask onto the substrate using the projection optical system.

  According to the exposure method of the tenth aspect, since the exposure is performed using the wetted optical component washed by the optical component cleaning method according to any one of the first to eighth aspects, It is possible to prevent deterioration of the transmittance of the projection optical system and deterioration of the aberration of the projection optical system due to contaminants adhering to the surface of the optical component, and it is possible to perform exposure satisfactorily.

  The exposure method according to claim 11 irradiates the mask with exposure light, transfers the pattern of the mask onto the substrate via the projection optical system, and purely between the surface of the substrate and the projection optical system. An exposure method using an immersion projection exposure apparatus with water interposed between the substrate stage and the projection optical system, wherein the substrate is retracted from a substrate stage on which the substrate is placed. A pure water supply step for supplying the pure water to the substrate, and the pure water is supplied by the pure water supply step so that the pure water is brought into contact with the pure water, and the projection optical system is arranged closest to the substrate stage side. A cleaning step of irradiating the wetted optical component with the exposure light; a pure water discharge step of discharging the pure water supplied by the pure water supply step; and a substrate on which the substrate is placed on the substrate stage. Installation process and surface of the substrate A liquid supply step of supplying the pure water between the projection optical system, characterized in that it comprises an exposure step of exposing a pattern of the mask on the substrate.

  According to the exposure method of claim 11, pure water that comes into contact with the wetted optical component is circulated, irradiated with exposure light, and the surface of the wetted optical component is washed to be applied to the substrate. As a result of the dissolution of the resist, contaminants adhering to the wetted optical component can be easily removed. Therefore, it is possible to prevent a decrease in the transmittance of the projection optical system and a deterioration in the aberration of the projection optical system due to contaminants adhering to the surface of the wetted optical component, and it is possible to perform exposure satisfactorily.

  The exposure method according to claim 12 includes a cleaning substrate installation step of installing a cleaning substrate on which the resist is not applied on the substrate stage after the substrate is retracted by the substrate retracting step; The method further includes a cleaning substrate retracting step of retracting the cleaning substrate from the substrate stage after the pure water is discharged by the water discharging step.

  According to the exposure method of claim 12, since the wetted optical component is cleaned in a state where the cleaning substrate is installed on the substrate stage, the exposure light irradiated for cleaning the wetted optical component is the substrate. The substrate stage can be prevented from being damaged by exposure light irradiation without directly reaching the stage.

  The exposure method according to claim 13 further includes a transmittance measuring step of measuring a transmittance of the wetted optical component, wherein the transmittance of the wetted optical component measured by the transmittance measuring step is a predetermined value. The liquid-contact optical component is washed when it is lower than an allowable value.

  According to the exposure method of the thirteenth aspect, the wetted optical component is cleaned only when it is necessary to clean the wetted optical component based on the measurement result of the wetted optical component in the transmittance measuring step. be able to.

  The exposure method according to claim 14, wherein a contaminant adhering to the surface of the wetted optical component is eluted from a resist applied on the substrate when the mask pattern is exposed on the substrate. It is characterized in that the substance is a modified, precipitated or deposited substance.

  The exposure method according to claim 15 is characterized in that the pure water has a resistivity of 1 MΩcm or more and a TOC (Total Organic Carbon) value of less than 1 ppm.

  According to the exposure methods of the fourteenth and fifteenth aspects, contaminants adhering to the surface of the wetted optical component can be satisfactorily removed.

  According to the optical component cleaning method of the present invention, pure water that comes in contact with the wetted optical component is circulated, exposed to exposure light, and cleaned on the surface of the wetted optical component. As a result of the dissolution of the resist, contaminants adhering to the wetted optical component can be removed. Accordingly, it is possible to prevent a decrease in the transmittance of the projection optical system and a deterioration in the aberration of the projection optical system due to contaminants adhering to the surface of the wetted optical component.

  In addition, according to the exposure apparatus of the present invention, since the wetted optical component cleaned by the optical component cleaning method of the present invention is provided, the projection optical system transmits through the contaminants adhering to the surface of the wetted optical component. It is possible to prevent the reduction of the rate and the deterioration of the aberration of the projection optical system, and the exposure can be performed satisfactorily.

  In addition, according to the exposure method of the present invention, pure water that comes into contact with the wetted optical component is circulated, and the surface of the wetted optical component is washed by irradiating exposure light and being applied to the substrate. By elution of the resist, contaminants attached to the wetted optical component can be removed. Therefore, it is possible to prevent a decrease in the transmittance of the projection optical system and a deterioration in the aberration of the projection optical system due to contaminants adhering to the surface of the wetted optical component, and it is possible to perform exposure satisfactorily.

  A projection exposure apparatus (immersion projection exposure apparatus) according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a step-and-repeat projection exposure apparatus according to this embodiment. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward.

As shown in FIG. 1, the projection exposure apparatus includes an ArF excimer laser light source as an exposure light source, and includes an illumination optical system 1 including an optical integrator (homogenizer), a field stop, a condenser lens, and the like. The exposure light IL made up of ultraviolet pulsed light having a wavelength of 193 nm emitted from the light source passes through the illumination optical system 1 and illuminates the pattern provided on the reticle (mask) R. The light that has passed through the reticle R passes through a telecentric projection optical system PL on both sides (or one side on the wafer W side) and passes through an exposure area on the wafer (substrate) W coated with a photoresist (resist) at a predetermined projection magnification. Reduced projection exposure is performed at β (for example, β is 1/4, 1/5, etc.). As the exposure light IL, KrF excimer laser light (wavelength 248 nm), F ₂ laser light (wavelength 157 nm), or the like may be used.

  The reticle R is held on the reticle stage RST, and the reticle stage RST is provided with a mechanism for finely moving the reticle R in the X direction, the Y direction, and the rotation direction. The positions of the reticle stage RST in the X direction, the Y direction, and the rotational direction are measured and controlled in real time by a reticle laser interferometer (not shown).

  The wafer W is fixed on a Z stage (substrate stage) 9 through a wafer holder (not shown). The Z stage 9 is fixed on an XY stage (substrate stage) 10 that moves along an XY plane substantially parallel to the image plane of the projection optical system PL, and the focus position (position in the Z direction) of the wafer W. And control the tilt angle. The positions of the Z stage 9 in the X direction, the Y direction, and the rotation direction are measured and controlled in real time by a wafer laser interferometer 13 using a moving mirror 12 positioned on the Z stage 9. The XY stage 10 is placed on the base 11 and controls the X direction, Y direction, and rotation direction of the wafer W.

  An illuminance sensor 40 is provided on the Z stage 9 to measure the exposure dose and the illuminance distribution for irradiating the Z stage 9 (wafer W). The illuminance sensor 40 receives part of the exposure light via the projection optical system PL and outputs information related to the received light to the main control system 14 described later. The main control system 14 measures the transmittance of the wetted optical component 4 based on the exposure light dose and illuminance distribution via the projection optical system PL output from the dose sensor 40.

  The main control system 14 provided in the projection exposure apparatus adjusts the position of the reticle R in the X direction, the Y direction, and the rotational direction based on the measurement values measured by the reticle laser interferometer. That is, the main control system 14 adjusts the position of the reticle R by outputting a control signal to a mechanism incorporated in the reticle stage RST and finely moving the reticle stage RST.

  Also, the main control system 14 adjusts the focus position (position in the Z direction) and the tilt angle of the wafer W in order to adjust the surface on the wafer W to the image plane of the projection optical system PL by the auto focus method and the auto leveling method. I do. That is, the main control system 14 outputs a control signal to the wafer stage drive system 15 and drives the Z stage 9 by the wafer stage drive system 15 to adjust the focus position and the tilt angle of the wafer W. Further, the main control system 14 adjusts the position of the wafer W in the X direction, the Y direction, and the rotation direction based on the measurement values measured by the wafer laser interferometer 13. That is, the main control system 14 outputs a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to thereby change the position of the wafer W in the X direction, the Y direction, and the rotational direction. Make adjustments.

  At the time of exposure, the main control system 14 outputs a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to sequentially step each shot area on the wafer W to the exposure position. Move. That is, the operation of exposing the pattern image of the reticle R onto the wafer W by the step and repeat method is repeated.

  In this projection exposure apparatus, the immersion method is applied, and while the pattern image of the reticle R is transferred onto the wafer W, there is a resistivity between the wafer W and the wetted optical component 4. The pure water 7 is 1 MΩcm or more and the TOC (Total Organic Carbon) value is less than 1 ppm. The projection optical system PL includes a lens barrel 3 that houses a plurality of optical elements constituting the projection optical system PL, and only the surface of the wetted optical component 4 is used to prevent corrosion of the lens barrel 3 made of metal. Is configured to come into contact with the pure water 7.

  FIG. 2 is a diagram showing the positional relationship between the wetted optical component 4 and the wafer W and the two pairs of discharge nozzles and inflow nozzles that sandwich the wetted optical component 4 on the wafer W side in the X direction. FIG. 3 is a diagram showing a positional relationship between the wetted optical component 4 on the wafer W side and two pairs of discharge nozzles and inflow nozzles that sandwich the wetted optical component 4 on the wafer W side in the Y direction. The projection exposure apparatus according to this embodiment includes a liquid supply device 5 that controls the supply of pure water 7 and a liquid recovery device 6 that controls the discharge of pure water 7.

  As shown in FIG. 2, the liquid supply device 5 includes a discharge nozzle 21 a on the + X direction side of the wetted optical component 4 via the supply tube 21, and a −X direction of the wetted optical component 4 via the supply tube 22. A discharge nozzle 22a is connected to the side. Further, in the liquid supply device 5, as shown in FIG. 3, a discharge nozzle 27 a is provided on the + Y direction side of the wetted optical component 4 via the supply tube 27, and − of the wetted optical component 4 via the supply tube 28. A discharge nozzle 28a is connected to the Y direction side. The liquid supply device 5 receives pure water 7 from the discharge nozzles 21a, 22a, 27a, and 28a through the at least one supply pipe in the supply pipes 21, 22, 27, and 28 from the wafer. Supply on W.

  As shown in FIG. 2, in the liquid recovery device 6, inflow nozzles 23 a and 23 b are provided on the −X direction side of the liquid contact optical component 4 via the recovery tube 23, and the liquid contact optical component 4 is connected via the recovery tube 24. Inflow nozzles 24a and 24b are connected to the + X direction side. Further, in the liquid recovery apparatus 6, as shown in FIG. 3, inflow nozzles 29 a and 29 b are provided on the −Y direction side of the liquid contact optical component 4 via the recovery tube 29, and the liquid contact optical component is connected via the recovery tube 30. 4, inflow nozzles 30a and 30b are connected to the + Y direction side. The liquid recovery device 6 includes at least one recovery pipe in the recovery pipes 23, 24, 29, 30 from at least one inflow nozzle in the inflow nozzles 23a and 23b, 24a and 24b, 29a and 29b, 30a and 30b. The pure water 7 is recovered from the wafer W via

  Next, a method for supplying and collecting pure water 7 will be described. In FIG. 2, when stepping the wafer W in the direction of the arrow 25A indicated by the solid line (−X direction), the liquid supply device 5 supplies the pure water 7 via the supply pipe 21 and the discharge nozzle 21a, and the liquid The recovery device 6 recovers the pure water 7 supplied by the liquid supply device 5 through the recovery pipe 23 and the inflow nozzles 23a and 23b. On the other hand, in FIG. 2, when the wafer W is stepped in the direction of the arrow 26A indicated by the chain line (+ X direction), the liquid supply device 5 supplies the pure water 7 via the supply pipe 22 and the discharge nozzle 22a. The liquid recovery device 6 recovers the pure water 7 supplied by the liquid supply device 5 through the recovery pipe 24 and the inflow nozzles 24a and 24b. In FIG. 3, when the wafer W is step-moved in the direction of the arrow 31A indicated by the solid line (−Y direction), the liquid supply device 5 supplies the pure water 7 via the supply pipe 27 and the discharge nozzle 27a. The liquid recovery device 6 recovers the pure water 7 supplied by the liquid supply device 5 through the recovery pipe 29 and the inflow nozzles 29a and 29b. When the wafer W is moved stepwise in the + Y direction, the liquid supply device 5 supplies the pure water 7 via the supply pipe 28 and the discharge nozzle 28a, and the liquid recovery device 6 sets the recovery pipe 30 and the inflow nozzle 30a, The pure water 7 supplied by the liquid supply device 5 through 30b is recovered.

  Next, a method for controlling the supply amount and recovery amount of pure water 7 will be described. FIG. 4 is a diagram showing a state in which pure water 7 is being supplied and recovered. As shown in FIG. 4, when the wafer W is moving in the direction of the arrow 25A (−X direction), the pure water 7 supplied from the discharge nozzle 21a flows in the direction of the arrow 25B (−X direction). These are recovered by the inflow nozzles 23a and 23b. The pure water 7 is always filled between the wetted optical component 4 and the wafer W by adjusting the supply amount and the recovery amount of the pure water 7 based on the moving speed of the XY stage 10 (wafer W).

  Next, a cleaning method for the liquid contact optical element 4 constituting the projection optical system PL included in the projection exposure apparatus according to this embodiment will be described with reference to the flowchart shown in FIG. When ArF excimer laser light is used as the exposure light IL as in the projection exposure apparatus according to this embodiment, and pure water 7 having a refractive index of 1.44 is interposed between the wetted optical component 4 and the wafer W, A photoacid generator (PAG), amine, and the like, which are eluates of the resist applied on the wafer W, are eluted in a small amount in the pure water 7. When the exposure light IL is irradiated in a state where PAG, amine and the like are dissolved in pure water 7, they are transformed and deposited, and adhere to and deposit on the surface of the wetted optical component 4 as a contaminant.

  That is, as a result of chemical analysis using an infrared absorption spectrum, the pollutant shows almost the same absorption spectrum as that of PAG and amine. It is considered that the eluted PAG and amine are aggregated by ArF excimer laser light irradiation, adsorbed on the wetted optical component 4 and stabilized.

  Since the exposure light IL is absorbed by contaminants (PAG, amine, etc.) deposited on the surface of the wetted optical component 4 or the exposure light IL is scattered by the deposited contaminants, the wetted optical component 4 and thus the projection. The transmittance of the optical system PL is deteriorated. Further, since the exposure light IL is absorbed by the accumulated contaminants, the temperatures of the liquid-contact optical component 4 and the pure water 7 are increased, so that the aberration of the projection optical system PL is deteriorated. Therefore, it is necessary to clean the wetted optical component 4 in order to remove contaminants attached to the surface of the wetted optical component 4.

  First, the main control system 14 measures the transmittance of the wetted optical component 4 based on the exposure light dose and the illuminance distribution through the projection optical system PL measured and output by the illuminance sensor 40 (step). S10, transmittance measurement step).

  Next, it is determined whether or not the transmittance of the wetted optical component 4 measured in step S10 is smaller than a predetermined allowable value (step S11). When it is determined in step S11 that the transmittance of the wetted optical component 4 is smaller than a predetermined allowable value, the main control system 14 retracts the wafer W from the Z stage 9 (step S12, substrate retracting process). . Specifically, the main control system 14 outputs a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15, thereby retracting the wafer W and the Z stage 9 (not shown). Until the wafer W is retracted.

  Next, the main control system 14 installs a cleaning substrate on which the resist is not applied on the Z stage 9 from which the wafer W has been retracted in Step S12 (Step S13, cleaning substrate installation step). Specifically, the main control system 14 outputs a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to move it to the place where the cleaning substrate is received. A substrate for use is placed on the Z stage 9. Then, the cleaning substrate is disposed under the projection optical system PL, that is, the wetted optical component 4 by driving the XY stage 10 by the wafer stage driving system 15.

  Next, the main control system 14 supplies pure water between the wetted optical component 4 and the cleaning substrate (step S14, pure water supply process). Specifically, the main control system 14 outputs a control signal to the liquid supply device 5, and the liquid supply device 5 supplies the supply pipe 21, the discharge nozzle 21a, the supply pipe 22, the discharge nozzle 22a, the supply pipe 27, and the discharge. Cleaning pure water is supplied between the wetted optical component 4 and the cleaning substrate through the nozzle 27a and at least one of the supply pipe 28 and the discharge nozzle 28a. The pure water for cleaning has a resistivity of 1 MΩcm or more and a TOC (Total Organic Carbon) value of less than 1 ppm, like the pure water 7 for exposure. The pure water for cleaning supplied by the liquid supply device 5 is recovered by the liquid recovery device 6 from the recovery pipe 23 and the inflow nozzles 23a and 23b, the recovery pipe 24 and the inflow nozzles 24a and 24b, the recovery pipe 29 and the inflow nozzle 29a, 29b, and at least one of the recovery pipe 30 and the inflow nozzles 30a and 30b. That is, by repeatedly supplying and collecting pure water for cleaning, the pure water between the wetted optical component 4 and the cleaning substrate circulates.

  Next, in step S14, the main control system 14 is supplied with pure water for cleaning between the wetted optical component 4 and the cleaning substrate, and the cleaning is performed between the wetted optical component 4 and the cleaning substrate. With pure water circulating, the exposure light IL is irradiated onto the cleaning substrate through the wetted optical component 4 (step S15, irradiation step). By irradiating the wetted optical component 4 with the exposure light IL, PAG, amine, and the like deposited on the surface of the wetted optical component 4 are decomposed by the exposure light that is ArF excimer laser light, and the wetted optical component 4. Peel from the surface. Then, it flows with the circulating pure water and is discharged from between the wetted optical component 4 and the cleaning substrate.

  Next, the main control system 14 discharges pure water supplied between the wetted optical component 4 and the cleaning substrate (step S16, pure water discharge step). Specifically, the main control system 14 outputs a control signal to the liquid recovery device 6, and the liquid recovery device 6 collects the recovery pipe 23 and the inflow nozzles 23a and 23b, the recovery pipe 24 and the inflow nozzles 24a and 24b, and the recovery. For cleaning shared between the wetted optical component 4 and the cleaning substrate by the liquid supply device 5 through at least one of the pipe 29 and the inflow nozzles 29a and 29b, and the recovery pipe 30 and the inflow nozzles 30a and 30b. Collect pure water.

  Next, the main control system 14 remeasures the transmittance of the wetted optical component 4 based on the exposure light irradiation amount and the illuminance distribution measured by the illuminance sensor 40 (step S17, transmittance remeasurement step). . Next, it is determined whether or not the transmittance of the wetted optical component 4 remeasured in step S17 is smaller than a predetermined allowable value (step S18). If it is determined in step S18 that the transmittance of the wetted optical component 4 is smaller than a predetermined allowable value, that is, if contaminants remain on the surface of the wetted optical component 4, the wetted optical component 4 Is wiped off with an organic solvent (step S19, wiping step). The organic solvent used for wiping is a solvent of alcohols or ketones. Examples of alcohols include methanol, ethanol, propanol, and butanol. Examples of ketones include acetone, methyl ethyl ketone, and cyclopentanone.

  Next, the main control system 14 measures the transmittance of the liquid contact optical component 4 again based on the exposure light irradiation amount and the illuminance distribution measured by the illuminance sensor 40, and the transmittance of the liquid contact optical component 4 is determined. It is confirmed that the value is equal to or greater than a predetermined allowable value (step S20).

  If it is determined in step S11 that the transmittance of the wetted optical component 4 is equal to or greater than a predetermined allowable value, the main control system 14 does not need to clean the wetted optical component 4, and therefore exposure. To resume. Further, when it is determined in step S18 that the transmittance of the wetted optical component 4 is equal to or greater than a predetermined allowable value, the main control system 14 does not need to wipe the surface of the wetted optical component 4; The cleaning substrate is retracted from the Z stage 9, the wafer is placed on the Z stage 9, and exposure is resumed.

  According to the projection exposure apparatus according to this embodiment, pure water that comes into contact with the wetted optical component is circulated, and the surface of the wetted optical component is washed by irradiating with exposure light and applied to the substrate. As a result, the contaminant attached to the wetted optical component can be easily removed. Accordingly, it is possible to prevent a decrease in the transmittance of the projection optical system and a deterioration in the aberration of the projection optical system due to contaminants adhering to the surface of the wetted optical component.

  In this embodiment, when cleaning the wetted optical component, the wafer is retracted from the Z stage before irradiating the exposure light, and the cleaning substrate is set on the Z stage. The wafer may be retracted from the stage, and the exposure light may be irradiated without installing the cleaning substrate.

  Further, in this embodiment, it is determined whether or not the wetted optical component is cleaned based on the measurement value of the illuminance sensor, but the wetted optical component is cleaned at a predetermined interval. Also good.

Further, in this embodiment, after the wetted optical component is cleaned, further wiping is performed with an organic solvent. However, only cleaning may be performed.
(Experiment 1)
A quartz glass substrate to which PAG (contaminant) according to Experiment 1 was attached was prepared and cleaned. FIG. 6 is a diagram showing a configuration of a tester 50 for producing and cleaning a quartz glass substrate to which the PAG according to Experiment 1 is attached. As shown in FIG. 6, the tester 50 includes a liquid supply device 52, a sample holder 54, a pump 56, and a liquid recovery device 58. One surface of the sample holder 54 is optically polished parallel plate quartz. A glass substrate 54a is installed.

First, an aqueous solution in which PAG is dissolved in pure water to a concentration of 3 ppm is prepared and supplied by the liquid supply device 52. The aqueous solution supplied by the liquid supply device 52 travels in the direction of the arrow A in the figure and fills the inside of the sample holder 54. The aqueous solution that has passed through the inside of the sample holder 54 travels in the direction of arrow B in the figure, and is recovered by the liquid recovery device 58 via the pump 56. Here, an ArF excimer laser beam (193 nm) is applied to a quartz glass substrate 54a whose one surface is in contact with the aqueous solution in the sample holder 54 from the direction of arrow C in the drawing with a fluence of 1.5 mJ / cm ² shot. As a result of 3 × 10 ⁶ shot irradiation, PAG adhered to the surface of the quartz glass substrate 54a.

  FIG. 7 is a graph showing the transmission characteristics of the quartz glass substrate 54a to which the PAG is attached. As shown by the broken line in FIG. 7, in the light with a wavelength of 193 nm (ArF excimer laser light), the surface reflection of the quartz glass substrate 54a with respect to the air is about 4.5% on each surface (incident surface and exit surface). The air permeability of the clean quartz glass substrate 54a is about 91%. On the other hand, as shown by the solid line in FIG. 7, the transmittance of the quartz glass substrate 54a with the PAG attached to pure water is 80% or less for light with a wavelength of 193 nm. % Or more.

  Next, a cleaning experiment was performed using the quartz glass substrate 54a to which the PAG was attached. First, the liquid supply device 52 of the tester 50 shown in FIG. 6 supplies pure water having a resistivity of 18 MΩcm and a TOC value of 4 ppb. The pure water supplied by the liquid supply device 52 travels in the direction of arrow A in FIG. The pure water that has passed through the sample holder 54 travels in the direction of arrow B in FIG. 6 and is collected by the liquid recovery device 58 via the pump 56. Pure water is circulated from the liquid supply device 52 to the liquid recovery device 58 by the pump 56.

Here, an ArF excimer laser beam (193 nm) is applied to the quartz glass substrate 54a, which is in contact with the surface of the sample holder 54 on which PAG adheres to pure water, in the direction of arrow C in the figure, at 1.5 mJ / cm ² shot. 2.9 × 10 ⁶ shots were irradiated at a fluence of. PAG was decomposed by laser light, and the decomposed product was gradually removed because it was dissolved little by little in pure water. The dashed-dotted line in FIG. 7 shows the transmission characteristics of the quartz glass substrate 54a after the PAG removal. It recovered to the same level as the transmittance of the clean quartz glass substrate 54a (broken line in the figure).

According to Experiment 1, the PAG that is a contaminant attached to the surface of the quartz glass substrate could be removed by circulating pure and irradiating with ArF excimer laser light.
(Experiment 2)
A quartz glass substrate to which the amine (contaminant) according to Experiment 2 was adhered was prepared and cleaned. In the same manner as in Experiment 1, an amine was adhered to a parallel flat quartz glass substrate that had been optically polished using a tester 50 shown in FIG. Specifically, an aqueous solution in which trioctylamine is dissolved in pure water to a concentration of 1 ppm is prepared and supplied by the liquid supply device 52. The aqueous solution supplied by the liquid supply device 52 travels in the direction of the arrow A in the figure and fills the inside of the sample holder 54. The aqueous solution that has passed through the inside of the sample holder 54 travels in the direction of arrow B in the figure, and is recovered by the liquid recovery device 58 via the pump 56. Here, ArF excimer laser light (193 nm) is applied to a quartz glass substrate whose one surface is in contact with the aqueous solution in the sample holder 54 with a fluence of 1.5 mJ / cm ² shot from the direction of arrow C in the figure. As a result of irradiation with x10 ⁶ shots, amine adhered to the quartz glass substrate.

  FIG. 8 is a graph showing the transmission characteristics of a quartz glass substrate to which an amine is attached. As shown in FIG. 8, in the case of light having a wavelength of 193 nm (ArF excimer laser light), the transmittance of a quartz glass substrate to which amine is attached is larger than the transmittance of a clean quartz glass substrate (indicated by a broken line in the figure). The rate (indicated by the solid line in the figure) deteriorated by 0.5%.

  Next, a cleaning experiment was performed using a quartz glass substrate to which amine was attached. First, the liquid supply device 52 of the tester 50 shown in FIG. 6 supplies pure water having a resistivity of 18 MΩcm and a TOC value of 4 ppb. The pure water supplied by the liquid supply device 52 travels in the direction of arrow A in FIG. The pure water that has passed through the sample holder 54 travels in the direction of arrow B in FIG. 6 and is collected by the liquid recovery device 58 via the pump 56. Pure water is circulated from the liquid supply device 52 to the liquid recovery device 58 by the pump 56.

Here, ArF excimer laser light (193 nm) was applied at 1.5 mJ / cm ² shot from the direction of arrow C in the figure to the quartz glass substrate in which the surface of the sample holder 54 in which amine was attached was contacted with pure water. Irradiated with 2.9 × 10 ⁶ shots at fluence. The amine was decomposed by the laser beam, and the decomposition product was gradually removed because it was gradually dissolved in pure water. As indicated by the one-dot chain line in FIG. 8, the transmittance of the quartz glass substrate after amine removal was restored to the same level as the transmittance of the clean quartz glass substrate (broken line in the figure).

  According to Experiment 2, the amine, which is a contaminant attached to the surface of the quartz glass substrate, could be removed by circulating pure and irradiating with ArF excimer laser light.

It is a figure which shows schematic structure of the projection exposure apparatus concerning Embodiment. It is a figure which shows the positional relationship of the liquid-contact optical component which comprises the projection optical system concerning Embodiment, and the discharge nozzle and inflow nozzle for X directions. It is a figure which shows the positional relationship of the liquid-contact optical component which comprises the projection optical system concerning Embodiment, and the discharge nozzle and inflow nozzle for Y directions. It is a figure for demonstrating the state by which supply and collection | recovery of pure water are performed between the liquid-contacting optical components concerning embodiment and a wafer. It is a flowchart for demonstrating the washing | cleaning method of the liquid-contact optical component concerning embodiment. It is a figure which shows the structure of the test device concerning the experiment 1. FIG. 4 is a graph showing transmission characteristics of a quartz glass substrate according to Experiment 1. 6 is a graph showing transmission characteristics of a quartz glass substrate according to Experiment 2.

Explanation of symbols

  R ... reticle, RST ... reticle stage, PL ... projection optical system, W ... wafer, 1 ... illumination optical system, 4 ... wetted optical component, 5 ... liquid supply device, 6 ... liquid recovery device, 7 ... pure water, 9 ... Z stage, 10 ... XY stage, 14 ... Main control system, 21,22 ... Supply pipe, 23,24 ... Collection pipe, 40 ... Illuminance sensor.

Claims (15)

An immersion projection exposure apparatus in which a mask is irradiated with exposure light, the pattern of the mask is transferred onto a substrate via a projection optical system, and pure water is interposed between the surface of the substrate and the projection optical system. A method for cleaning optical components used,
A substrate retracting step for retracting the substrate from a substrate stage on which the substrate is placed;
A pure water supply step of supplying the pure water between the substrate stage and the projection optical system;
When the pure water is supplied by the pure water supply step, the exposure light is irradiated onto the wetted optical component that is in contact with the pure water and that is disposed closest to the substrate stage constituting the projection optical system. An irradiation process to perform,
A pure water discharge step of discharging the pure water supplied by the pure water supply step;
An optical component cleaning method comprising: And further comprising a cleaning substrate installation step of installing a cleaning substrate on which the resist is not applied on the substrate stage after the substrate is retracted by the substrate retracting step,
2. The optical component cleaning method according to claim 1, wherein the pure water supply step supplies the pure water between a surface of the cleaning substrate and the projection optical system. Further comprising a transmittance measuring step of measuring the transmittance of the wetted optical component;
3. The wetted optical component is cleaned when the transmittance of the wetted optical component measured in the transmittance measuring step is lower than a predetermined allowable value. Cleaning method for optical parts. A transmittance re-measurement step of re-measuring the transmittance of the wet-contact optical component after the wet-contact optical component is cleaned,
Contaminant wiping to wipe off contaminants remaining on the surface of the wetted optical component with an organic solvent when the transmittance of the wetted optical component remeasured by the transmittance remeasurement step is lower than a predetermined allowable value. Process,
The method for cleaning an optical component according to any one of claims 1 to 3, further comprising:   5. The optical component cleaning method according to claim 4, wherein the organic solvent is a solvent of alcohols or ketones.   The contaminant adhering to the surface of the wetted optical component is a substance in which the eluate from the resist applied on the substrate is modified, deposited and deposited when the mask pattern is exposed on the substrate. The optical component cleaning method according to claim 1, wherein the optical component is cleaned.   The optical component cleaning method according to any one of claims 1 to 6, wherein the pure water has a resistivity of 1 MΩcm or more and a TOC (Total Organic Carbon) value of less than 1 ppm.   The optical component cleaning method according to claim 1, wherein the exposure light is ArF excimer laser light. An immersion projection exposure apparatus in which a mask is irradiated with exposure light, the pattern of the mask is transferred onto a substrate via a projection optical system, and pure water is interposed between the surface of the substrate and the projection optical system. There,
An immersion projection exposure apparatus comprising a wetted optical component cleaned by the optical component cleaning method according to any one of claims 1 to 8. An immersion projection exposure apparatus that irradiates a mask with exposure light, transfers the mask pattern onto a substrate via a projection optical system, and interposes pure water between the surface of the substrate and the projection optical system. The exposure method used,
A projection exposure of the pattern of the mask onto the substrate using the projection optical system including the wetted optical component cleaned by the optical component cleaning method according to claim 1. The exposure method characterized by including the exposure process to perform. An immersion projection exposure apparatus that irradiates a mask with exposure light, transfers the mask pattern onto a substrate via a projection optical system, and interposes pure water between the surface of the substrate and the projection optical system. The exposure method used,
A substrate retracting step for retracting the substrate from a substrate stage on which the substrate is placed;
A pure water supply step of supplying the pure water between the substrate stage and the projection optical system;
When the pure water is supplied by the pure water supply step, the exposure light is irradiated onto the wetted optical component that is in contact with the pure water and that is disposed closest to the substrate stage constituting the projection optical system. Cleaning process to
A pure water discharge step of discharging the pure water supplied by the pure water supply step;
A substrate installation step of installing the substrate on the substrate stage;
A liquid supply step for supplying the pure water between the surface of the substrate and the projection optical system;
An exposure step of exposing the pattern of the mask onto the substrate;
An exposure method comprising: A cleaning substrate installation step of installing a cleaning substrate on which the resist is not applied on the substrate stage after the substrate is retracted by the substrate withdrawal step;
A cleaning substrate retracting step of retracting the cleaning substrate from the substrate stage after the pure water is discharged by the pure water discharging step;
The exposure method according to claim 11, further comprising: Further comprising a transmittance measuring step of measuring the transmittance of the wetted optical component;
13. The liquid-contact optical component is cleaned when the transmittance of the liquid-contact optical component measured in the transmittance measurement step is lower than a predetermined allowable value. Exposure method.   The contaminant adhering to the surface of the wetted optical component is a substance in which the eluate from the resist applied on the substrate is modified, deposited and deposited when the mask pattern is exposed on the substrate. The exposure method according to any one of claims 10 to 13, wherein the exposure method is provided.   The exposure method according to claim 10, wherein the pure water has a resistivity of 1 MΩcm or more and a TOC (Total Organic Carbon) value of less than 1 ppm.

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