WO2000022656A1

WO2000022656A1 - Exposure system

Info

Publication number: WO2000022656A1
Application number: PCT/JP1999/005633
Authority: WO
Inventors: Osamu Yamashita
Original assignee: Nikon Corporation
Priority date: 1998-10-13
Filing date: 1999-10-13
Publication date: 2000-04-20
Also published as: TW439114B; AU6121899A

Abstract

An exposure system which is provided with an illuminating optical system for applying an illuminating light (IL) from a light source (1) to a reticle (R), which exposes a wafer (W) as a photosensitive substance to an illuminating light via the reticle (5), and which comprises a supply device (31, 32, 43, 46) for supplying a gas (e.g. helium gas) high in transmittance to an illuminating light to a sealed chamber (lens barrel, etc.) including at least a part (e.g. a projection optical system (PL), an illuminating optical system, the light source (1)) of an illuminating light path, a recovering device (33, 34) for recovering at least part of the supplied gas, and a purifying device (35, 37, 80) for removing from the recovered gas substances which change optical characteristics in a gas-supplied atmosphere.

Description

Description of exposure equipment Technical field

The present invention relates to an exposure apparatus used for transferring a mask pattern onto a substrate in a lithographic process for producing, for example, a semiconductor device, a liquid crystal display device, or a thin film magnetic head. Background art

For example, in an exposure apparatus such as a stepper used for manufacturing a semiconductor device, it is required to particularly increase a resolution in order to cope with an improvement in the degree of integration and fineness of the semiconductor device. Since the resolution is almost proportional to the wavelength of the illumination light, the exposure wavelength has been gradually shortened conventionally. In other words, the illumination light is changed from the visible g-line (wavelength 436 nm) by the mercury lamp to the ultraviolet i-line (wavelength 365 nm), and recently KrF excimer laser light (wavelength 248 nm) is used. It's swelling. And, now, A r F excimer one laser light (wavelength 193 nm), F ₂ laser beam (wavelength 157 nm), has been further studied using the Ar ₂ laser beam (wavelength 126 nm). In addition, conventional: X-ray lithography studies have shown that 13-nm or 7-nm light, which is very close to X-rays in the so-called extreme ultraviolet (EUV or XUV) region, and even 1-nm X-rays Use is also being considered.

However, in the wavelength range below the ArF excimer laser light, that is, in the vacuum ultraviolet range (VUV) below about 200 nm, absorption by oxygen in the air occurs, generating ozone and reducing the transmittance. . Therefore, for example, in an exposure apparatus using an ArF excimer laser beam, a so-called nitrogen purge is performed in which most of the gas in the optical path of the illumination light is replaced with nitrogen. Furthermore, a wavelength range shorter than the wavelength of A rF excimer laser (more than about 190 nm), an absorption at nitrogen, especially F ₂ laser about a wavelength range. In this case, if the area passing through nitrogen is a very narrow area, the absorption amount is small and there is not much hindrance to the exposure. No longer available. Therefore, when using light in the wavelength range of about 190 nm or less, it is necessary to replace most of the optical path of the light with another gas that transmits the light, or to create a vacuum.

As described above, when illuminating light in the wavelength range of about 190 nm or less is used in an exposure apparatus, most of the optical path is replaced with extremely pure nitrogen or a gas having a smaller absorption rate than nitrogen. Or a vacuum is desirable. However, if a large part of the optical path is evacuated as in the latter case, the structure must withstand the vacuum, which increases the manufacturing cost of the exposure apparatus.

In order to deal with such problems, the optical path of the illumination light is partially or entirely configured to be a sealed space, and an inert gas with high transmittance of the exposure light (for example, helium Gas) or pressurized supply of the gas into the sealed space in consideration of leakage. Note that, for example, when the projection optical system is a catadioptric system, the helm may be used in an exposure apparatus using an ArF excimer laser.

However, for example, in an optical element unit that is used in illumination optical systems and projection optical systems and has multiple optical elements such as lenses and mirrors arranged in a lens barrel, antireflection coating on the inner surface of the lens barrel and fixing of the optical elements are fixed. Contaminants such as organic substances and water are generated from adhesives and fillers used for cleaning, and condensed and adhere to the surface of the optical element, causing a reduction in the illuminance of illumination light and uneven illuminance. May deteriorate.

In addition, helium (H e) has the highest performance as an inert and safe gas, but its extremely low abundance in the earth's crust and the atmosphere, and its small atomic weight means that the above-mentioned sealed space cannot be used. However, there is a disadvantage that the operating cost of the exposure apparatus is increased because it is easy to leak from gaps between the cover and the lens barrel, etc., which constitute the lens, and the amount of consumption is large. Disclosure of the invention

Accordingly, an object of the present invention is to prevent the surface of an optical element or the like existing on the optical path of the illumination light from being contaminated when a gas having a high transmittance (inert) is supplied to at least a part of the optical path of the illumination light. An object of the present invention is to provide an exposure apparatus that can sufficiently prevent the gas consumption and reduce the amount of gas used. According to the present invention, in an exposure apparatus that irradiates an illumination light from a light source to a mask and transfers an image of a pattern formed on the mask onto a predetermined surface, at least a part of an optical path of the illumination light includes: A supply device that supplies a gas that transmits the illumination light, a recovery device that recovers at least a part of the gas supplied to the optical path of the illumination light, and an influence on transfer accuracy of the pattern image onto the predetermined surface. An exposure apparatus is provided, comprising: a purifying apparatus that removes an applied substance from the collected gas.

Here, the substance that affects the transfer accuracy of the image of the pattern on the predetermined surface includes, for example, a substance that changes optical characteristics. The transfer accuracy refers to the line width accuracy of the pattern, the transfer position accuracy of the pattern, or the displacement accuracy between the patterns when the pattern is transferred onto the photosensitive substrate surface as a predetermined surface. The substance that changes the optical properties is not particularly limited, but includes, for example, a substance that deteriorates the optical properties, a substance that changes the illuminance and the illuminance distribution of the illumination light, and more specifically, , Impurities generated from gases (air, nitrogen gas, helium gas, etc.) existing in the space in the optical path of illumination light, molecules of organic substances generated from adhesives or fillers for fixing the optical element to the lens barrel The impurities generated from the inner wall of the lens barrel (painted surface for anti-reflection, etc.) (for example, water molecules, molecules of carbon at the opening, or other substances that diffuse illumination light), or the surface of optical elements Purified liquid (ether, water, etc.) that has remained is vaporized. These contaminants or contaminants generated by the reaction of these contaminants with the illumination light aggregate and adhere to the surface of the optical element, thereby deteriorating the characteristics of the optical element and reducing the illuminance of the illumination light and the like. This causes the illuminance distribution to fluctuate.

According to the present invention, since a part of the gas supplied on the optical path is recovered by the recovery device, the substance that changes the optical characteristics existing on the optical path is removed from the optical path, Variations in characteristics are prevented. In addition, since the substance that changes the optical characteristics is removed from the collected gas by the purifier to purify the gas, the gas can be reused (recycled). Therefore, the use amount of the gas can be saved, and the operation cost can be greatly reduced when the gas is expensive.

In the above configuration, although not particularly limited, gas purified by the purification device Is supplied again to the optical path of the illumination light through the supply device, thereby forming a circulation system. However, a new gas may be always supplied by the supply device, and the recovered gas may be recovered (purified) and injected (enclosed) into a cylinder or the like, or supplied to another exposure device or the like. The supply destination of the gas by the supply device may be a space including the entire optical path of the illumination light (all the optical paths from the light source to the object to be exposed via the illumination system and the projection optical system). The space may include a part thereof, and may be, for example, a light source, all or a part of an illumination system, or a whole or a part of a projection optical system. Further, a space between the projection optical system and the photosensitive substrate (so-called wafer chamber) or a space between the illumination optical system and the projection optical system (so-called mask chamber) may be used.

Of course, the operations of the supply device, the recovery device, and the purification device may be always performed. However, it is more efficient to provide a control device and control the operations according to the fluctuation of the optical characteristics. As the control by the control device, a storage device in which control data including a time and a time at which the purifying device should be operated is stored in advance, and the purifying device is operated according to the control data stored in the storage device. Can be. Alternatively, a detection device for detecting the transmittance of a projection optical system that projects the pattern image of the mask onto the photosensitive substrate is provided, and when the amount of change in the detected transmittance exceeds a predetermined value, the purification is performed. The device can also be activated.

Further, a chamber defined by the supply device to include at least a part of an optical element in an optical path of the illumination light for supplying the gas (for example, a chamber defined by a chamber, a lens barrel, or the like). A supply port connected to the supply device and a discharge outlet connected to the recovery device, and an on-off valve controllable by the control device at each of the discharge port and the supply port. When not operated, the on-off valve can be closed. In this case, the gas present in the optical path is stabilized by opening the on-off valve to purify the gas at times other than the exposure processing, and closing the enclosing valve at the time of the exposure processing. A stable exposure process can be performed. In this case, before the cleaning device is operated, the contaminant is irradiated with the illumination light so that the contaminant attached to the surface of the optical element is floated using a light cleaning effect. By recovering and purifying the contained gas, the re-adhesion of contaminants to the optical element is prevented, and the occurrence of reduced illuminance and uneven illuminance is reduced. In addition, as a gas to be supplied and recovered, for example, an inert gas such as helium (He) or nitrogen (N2) can be used. In particular, helium is safe and has high transmittance even when using illumination light in the wavelength range of about 150 nm or less, and has a thermal conductivity that is about 6 times that of nitrogen (N ₂ ). Therefore, it has an excellent cooling effect on optical elements.

In addition, when the recovery device recovers, for example, air in which helium is diffused, the purification device treats oxygen in the mixed gas with an oxygen absorbing material, and cools nitrogen to separate it from helium. Should be extracted. Alternatively, by cooling the gas mixture to the liquid air temperature and removing the generated liquid, it is possible to easily extract only helium still in a gaseous state. It is desirable that the cleaning device is shared by a plurality of exposure devices. Thereby, the equipment cost of the purification device is reduced. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic configuration diagram in which a part of a projection exposure apparatus and a hair circulation apparatus according to a first embodiment of the present invention is shown in section.

FIG. 2 is a schematic configuration diagram in which a plurality of projection exposure apparatuses and one helium circulation apparatus according to a second embodiment of the present invention are partially sectioned,

FIG. 3 is a schematic configuration diagram in which a part of a main part of a projection exposure apparatus according to a third embodiment of the present invention is shown in cross section.

FIG. 4 is a flowchart of a cleaning process performed by the control device of the projection exposure apparatus according to the third embodiment of the present invention;

FIG. 5 is a flowchart of another cleaning process performed by the control device of the projection exposure apparatus according to the third embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail with reference to the accompanying drawings. First embodiment A first embodiment of the present invention will be described with reference to FIG. In the first embodiment, the present invention is applied to a projection exposure apparatus for manufacturing a semiconductor in which a majority of the optical path of the illumination light is supplied with a Helium gas. FIG. 1 shows a schematic configuration of a projection exposure apparatus and a helium circulation apparatus of the present embodiment.

In Fig. 1, a projection exposure system is installed in a clean room on a floor F1 on a certain floor of a semiconductor manufacturing plant, and a projection is performed in a so-called machine room (utility space) on a floor F2 below that floor. A helium circulation device is installed to supply helium gas to the exposure device and to collect and purify it. By installing a device that easily generates dust and is a source of vibration on a floor different from the floor where the projection exposure apparatus is installed, the cleanliness in the clean room where the projection exposure apparatus is installed is improved. It can be set very high and the effect of vibration on the projection exposure apparatus can be reduced. Also, an F ₂ laser light source 3 is placed on the floor F 2, to reduce the occupied area of the floor F 1 by the apparatus main body (footprint), and may reduce the vibration of the apparatus main body. However, since helium is light and easily rises, the helium circulating apparatus of the present embodiment may be placed on the floor where the projection exposure apparatus is installed. In the helium circulation device, the supply device may be disposed on the floor F2, and the recovery device may be disposed on the floor F1 or on the floor.

First, in a clean room on the floor F 1, vibration isolation 2 A, 2 box-like case 1 through B is installed, F ₂ laser light source 3 as an illumination light source in the casing 1 (oscillation wavelength 1 5 7 nm), a beam-matching unit (BMU) 4 including a movable mirror etc. for positionally matching the optical path with the exposure main body, and a light-blocking pipe 5 through which the illumination light passes. Have been. In addition, a box-shaped airtight environment chamber 7 is installed next to the case 1, and a vibration isolator 25 A, 2 is provided in the environment chamber 7 on the floor F1 to attenuate vibration from the floor. The surface plate 24 is installed via 5 B, and the exposure main body 26 is installed on the surface plate 24. A sub-chamber 6 having good airtightness is installed from the pipe 5 protruding from the case 1 to the inside of the environment chamber 7, and the sub-chamber 6 houses most of the illumination optical system.

At the time of exposure, the ultraviolet pulse light IL having a wavelength of 157 nm as illumination light emitted from the F ₂ laser light source 3 in case 1 passes through the BMU 4 and the pipe 5 and is sub-channeled. Number 6 In the sub-chamber 6, the ultraviolet pulse light IL is incident on the fly-eye lens 11 through a variable attenuator 8 serving as an optical attenuator and a beam shaping optical system including lens systems 9A and 9B. An aperture stop system 12 of an illumination system for changing illumination conditions in various ways is disposed on the exit surface of the fly-eye lens 11.

The ultraviolet pulse light IL emitted from the fly-eye lens 11 and passing through a predetermined aperture stop in the aperture stop system 12 passes through the reflection mirror 13 and the condenser lens system 14 and enters the reticle blind mechanism 16. Fixed illumination field stop (fixed blind) having a slit-shaped opening of Further, in the reticle blind mechanism 16, a movable blind 15 B for changing the width of the illumination visual field in the scanning direction is provided separately from the fixed blind 15 A.

The ultraviolet pulse light IL shaped like a slit by the reticle blind mechanism 16 passes through the imaging lens system 17, the reflection mirror 18, and the main condenser lens system 19 on the reticle R circuit pattern area. The slit-shaped illumination area is illuminated with a uniform intensity distribution. In the present embodiment, the space from the light-exiting surface of the light-blocking pipe 5 to the main condenser lens system 19 is housed in the sub-chamber 6, and the space from the inside of the pipe 5 to the light-emitting surface of the F ₂ laser light source 3 is also sealed. And communicates with the space in the sub-chamber 6. In the space inside the subchamber 6, helium whose temperature is controlled to a predetermined purity or more at two locations from a helium circulation device downstairs through a branch pipe 31a and a branch pipe 31b of a pipe 31 is provided. Gas (H e) is being supplied.

The piping 31 is provided with an opening / closing valve V11, and the control system 45 controls the opening and closing of the closing valve VI1 to switch between supplying and stopping helium gas to the projection exposure apparatus. be able to. Further, a closing valve VI 3 is provided in the branch pipe 31 a of the pipe 31, and an opening / closing valve VI 4 is provided between the branch pipe 31 b and the projection optical system PL. ) Is provided with an on-off valve V 15. In addition, the helium gas whose temperature is controlled to have a purity equal to or higher than a predetermined purity is contained in the case 1 containing the F 2 laser light source 3 and the BMU 4 via the branch pipe 3 1 c of the pipe 31 and the opening / closing valve VI 2. Is supplied. Therefore, by opening and closing the opening / closing valves V 12 to V 15 independently by the control system 45, at least one of the case 1, the sub-chamber 6 (illumination optical system), and the projection optical system PL is desired. Helium It is possible to supply gas. Since helium has a small molecular weight and easily leaks, a part of the helium that naturally leaks from the sub-chamber 6 rises and accumulates in the space 7 a near the ceiling of the environmental chamber 7.

Under the ultraviolet pulse light IL, an image of the circuit pattern in the illumination area of the reticle R is transferred to the slit-shaped exposure area of the resist layer on the wafer W via the projection optical system PL. The exposure region is located on one of a plurality of shot regions on the wafer. The projection optical system PL of the present embodiment is a dioptric system (refractive system). However, since glass materials that can transmit such short-wavelength ultraviolet light are limited, the projection optical system PL is connected to a power dioptric system. (The catadioptric system) or a reflective system may be used to increase the transmittance of the ultraviolet pulse light IL in the projection optical system PL. In the following description, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of Figure 1 in a plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of Figure 1 I do.

At this time, the reticle R is sucked and held on the reticle stage 20, and the reticle stage 20 can move at a constant speed in the X direction (scanning direction) on the reticle base 21 and the X, Y, and rotation directions. It is mounted so that it can be moved slightly. The two-dimensional position and rotation angle of the reticle stage 20 (reticle R) are controlled by a drive control unit (not shown) equipped with a laser interferometer.

On the other hand, the wafer W is held by suction on the wafer holder 22, the wafer holder 22 is fixed on the wafer stage 23, and the wafer stage 23 is placed on the surface plate 24. The wafer stage 23 adjusts the focus position (position in the Z direction) and the tilt angle of the wafer W by an autofocus method so that the surface of the wafer W is aligned with the image plane of the projection optical system PL, and Performs constant-speed scanning in the X direction and stepping in the X and Y directions. The two-dimensional position and rotation angle of the wafer stage 23 (wafer W) are also controlled by a drive control unit (not shown) equipped with a laser interferometer. At the time of scanning exposure, the reticle R is scanned in the + X direction (or -X direction) at a speed Vr in the + X direction (or -X direction) through the reticle stage 20 through the reticle stage 20 to synchronize with the wafer stage. The wafer W is scanned in the -X direction (or + X direction) at a speed /? Vr (? Is a projection magnification from the reticle R to the wafer W) with respect to the exposure area via 23. T / JP99 / 05633 Also, as in the sub-chamber 6, the entire space inside the lens barrel of the projection optical system PL (space between multiple lens elements) is also branched from the helium circulating device downstairs into the piping 31. Helium gas whose temperature is controlled at a predetermined concentration or higher is supplied through the pipe 31b and the on-off valve V14. The helm leaking from the projection optical system PL barrel also rises and accumulates in the space 7 a near the ceiling of the environmental chamber 7.

In addition, a nitrogen circulator (38 to 40, 82 to 88, 95, etc.) downstairs inside the environmental chamber 7 keeps the oxygen content extremely low and controls the temperature of nitrogen gas (N ₂ ) is supplied. Then, the nitrogen gas circulated in the environmental chamber 7 is returned to the nitrogen circulating device through, for example, an exhaust hole on the bottom side of the environmental chamber 7, a pipe 95 connected to the side face thereof, and an opening / closing valve V19 thereof. ing.

As described above, in the present embodiment, the light path of the ultraviolet pulse light IL from the emission surface of the F ₂ laser light source 3 to the main condenser lens system 19 and the light path of the ultraviolet pulse light IL in the projection optical system PL are: Helium gas, which has high transmittance even for light of about 0 nm or less, is supplied. In addition, from the main condenser lens system 19 to the entrance surface of the projection optical system PL, and from the exit surface of the projection optical system PL to the surface of the wafer W, the transmittance for light of about 190 ηm or less is very small. Although the nitrogen gas is supplied with poor quality, the optical path passing through the nitrogen gas is extremely short, so the amount of absorption by the nitrogen gas is also small. Thus, ultraviolet pulse light IL emitted from the F ₂ laser light source 3, since the whole and to a high transmittance (efficiency) reaches the surface of the wafer W, can reduce the exposure time (scanning exposure time), the exposure The throughput of the process is improved.

Helium has a thermal conductivity approximately six times better than that of nitrogen, so the thermal energy accumulated by the irradiation of the ultraviolet pulse light IL in the optical element in the illumination optical system and the optical element in the projection optical system PL Are efficiently transmitted to the cover of the sub-chamber 6 and the lens barrel of the projection optical system PL through the helm. In addition, the thermal energy of the cover of the sub-chamber 6 and the lens barrel of the projection optical system PL is supplied to the outside such as downstairs by the temperature-controlled air in the clean room or the temperature-controlled nitrogen gas in the environment chamber 7. Efficiently waste heat. Accordingly, the temperature rise of the illumination optical system and the optical element of the projection optical system PL is extremely low, and the deterioration of the imaging performance is minimized. Furthermore, helium has a very small change in refractive index with changes in atmospheric pressure. Therefore, for example, the amount of change in the refractive index in the projection optical system PL is extremely small, and also in this regard, stable imaging performance is maintained.

Next, the helium circulation device of the present embodiment will be described in detail. In the environmental chamber 7, the helium leaked from the sub-chamber 6 and the helium leaked from the projection optical system PL rise because they are lighter than nitrogen and accumulate in the space 7a near the ceiling. However, the gas in the space 7 a is a mixed gas containing helium, nitrogen, and air entering from outside the environmental chamber 7.

In the present embodiment, a pipe 33 is connected to the space Ίa from the outside of the environmental chamber 7, and the pipe 33 passes through an opening provided in the floor F 1 and communicates with the helium circulating device downstairs. . Further, the case 1 is connected to the pipe 33 by the pipe 92, and the pipe 92 is provided with the closing valve V16. In addition, the illumination optical system (sub channel, '6) and the projection optical system PL are also connected to the pipe 33 by pipes 93, 94, respectively, and the pipes 93, 94 are respectively provided with opening / closing valves V 17, VI 8 is provided. Therefore, by opening and closing the open / close valves VI 6 to V 18 independently by the control system 45, at least one of the case 1, the illumination optical system (sub-chamber 6), and the projection optical system PL is desired. As a result, it is possible to recover helium gas containing organic matter and dust. A suction pump (or fan) 34 is disposed in the middle of the pipe 33 on the bottom side of the floor F 1, and the gas mixture sucked from the space 7 a by the pipe 33 and the pump 34 is Head downstairs to the helium circulator. Then, the mixed gas that has passed through the pump 34 reaches the dust collecting and draining device 35, where minute dust and moisture are removed to avoid clogging of the adiabatic compression / cooling passage. The mixed gas that has passed through the dust collection and drainage device 35 reaches the refrigeration device 37 via the pipe 36, where it is cooled to the temperature of liquid nitrogen by adiabatic compression cooling. As a result, the components of nitrogen and air are liquefied, so that the components of air containing liquefied nitrogen and helium as gas can be easily separated. The air component mainly composed of nitrogen (N ₂ ) liquefied in the refrigerating device 37 is collected in a cylinder 40 via a pipe 38 and a suction pump 39 arranged in the middle of the pipe 38. . Air components such as nitrogen vaporized in the cylinder 40 can be reused (recycled), for example. On the other hand, helium, which remains as a gas in the refrigeration system 37, is supplied to the pipe 41 and a suction pump 5633

(Or a fan) 42 to the first inlet of the mixing temperature controller 43.

In addition, a purification device that removes and separates air, nitrogen, and other pollutants as impurities from helium gas by the dust collection and drainage device 35 and the refrigeration device 37 is configured. Chemical filters suitable for separating and removing contaminants contained in the helium gas in order to regenerate high-purity helium gas by further separating and removing contaminants that may remain without being removed, etc. Of the refrigeration unit 37 (piping 36) or the post-stage (piping 41) Is desirably provided.

In the present embodiment, a removing device 80 for removing impurities contained in the mixed gas is provided between the dust collecting and draining device 35 and the refrigerating device 37. The removal device 80 is an activated carbon filter (for example, Giga Soap manufactured by Niyuyu Co., Ltd.), or Zeolite Filter Yuichi, or a combination thereof, and includes an environmental chamber 7, an illumination optical system, Silicon organic substances such as siloxane (a substance having a Si-0 chain as an axis) or silazane (a substance having a Si-N chain as an axis) existing in the projection optical system PL are removed.

Here, one of the siloxanes, a substance called “cyclic siloxane”, in which the chain of Si— となっ is formed into a ring, is included in the silicone adhesive, sealing agent, paint, etc. used in projection exposure equipment. This is generated as degassing due to aging. Cyclic siloxane easily adheres to the surface of a photosensitive substrate or an optical element (such as a lens), and when exposed to ultraviolet light, is oxidized to become a SiO ₂ -based cloudy substance on the optical element surface. As silazane, there is HMDS (hexamethyldisilazane) used as a pretreatment agent in the resist coating step. HMDS reacts with water and changes (hydrolyzes) into a substance called silanol. Silanol easily adheres to the surface of a photosensitive substrate, an optical element, or the like, and is further oxidized when exposed to ultraviolet light to become a SiO ₂ -based cloudy substance on the surface of the optical element. Silazane generates ammonia by the above-mentioned hydrolysis, and when this ammonia coexists with siloxane, the surface of the optical element is further easily clouded.

By the way, organic substances adhering to the surface of the optical element of the illumination optical system or projection optical system, etc. 633

(Hide port carbon) is separated by light cleaning and is mixed into the helium gas. In the present embodiment, the removing device 80 also removes the hydroforce. Furthermore, in addition to the above-mentioned silicon-based organic substances, plasticizers (such as phthalsan esters) and flame retardants (phosphoric acid, chlorine-based substances) are also generated as degassed wiring and plastics in the environmental chamber 7. However, in the present embodiment, these plasticizers and flame retardants are also removed by the removal device 80. Even if ammonium ions, sulfate ions, and the like floating in the clean room enter the environment chamber 7, these ions are also removed by the removing device 80.

High-purity helium gas is supplied from a cylinder 46 filled with high-purity helium gas at a high pressure to the second inlet of the mixing temperature controller 43 through a pipe 47 and an on-off valve 48. Supplied. The liquefied helium may be stored in the cylinder 46. Further, a helium concentration meter for measuring the concentration (or purity) of helium in the pipe 41 through which the purified helium passes through the refrigerating device 37, etc., near the inlet to the mixing temperature control device 43. 44 is installed, and this measurement data is supplied to the control system 45. The control system 45 opens the on-off valve 48 when the concentration of the collected helium measured by the helium concentration meter 44 does not reach the predetermined allowable value, and the mixing temperature is measured from the column 46. Add high-purity helium into the controller 43. Then, when the helium concentration measured by the helium concentration meter 44 is equal to or more than the allowable value, the control system 45 closes the on-off valve 48. In addition, the closing valve 48 is closed even during the period in which the exposure operation is not performed. Note that an oxygen concentration meter may be used instead of the helium concentration meter 44.

In addition, an impurity concentration sensor (oxygen concentration sensor or helium concentration sensor, not shown) is installed near the inlet to the purification device consisting of the dust collection / drainage device 35, refrigeration device 37, etc. The measurement result of the impurity concentration sensor is supplied to the control system 45. A factory pipe provided with a flow path switching valve (not shown) is connected between the pump 34 and the purification device. The flow path switching valve is switched by the control system 45 based on the measurement result of the impurity concentration sensor.

If the control system 45 determines that the collected gas contains impurities of a predetermined value or more based on the measurement result of the impurity concentration sensor, the control system 45 sets the collected gas The flow path is switched from the purification device to the factory piping, and the collected gas is discharged through the factory piping. On the other hand, when the concentration of the impurities contained in the recovered gas falls below a predetermined value, the control system 45 switches the flow path of the recovered gas from the factory piping to the purifier to purify the gas.

One possible reason for the contamination of the recovered gas with impurities is that after the exposure operation has been stopped for a period of time, the exposure light is applied to the optical elements that constitute the illumination optical system and projection optical system. Has just started. Immediately after exposure light exposure, organic impurities accumulated on the surface of the optical element for a certain period of time are decomposed by the light cleaning effect. As described above, if the gas recovered from the space contains many impurities exceeding the purifying range of the purifying device, not only the life of the purifying device is shortened, but also the purifying efficiency of the purifying device is deteriorated. there is a possibility. Therefore, as described above, the impurity concentration of the gas supplied to the purification device is monitored, and a gas having an impurity concentration corresponding to the allowable range of the purification device is supplied to the purification device, and the allowable range of the purification is determined. If it exceeds, exhausting it through the factory piping can improve the life and purification efficiency of the purification device.

Further, the mixing temperature controller 43 mixes the purified helium and the helium from the cylinder 46 within a predetermined pressure range to control the temperature to a predetermined temperature, and controls the temperature and pressure-controlled helium. To pipe 31. The components from the dust collection and drainage device 35 to the mixing temperature control device 43 constitute the helium circulation device of the present embodiment. In addition, the pipe 31 passes through the opening provided in the floor F 1 on the upper floor and reaches the inside of the clean room on the upper floor, and at the middle of the pipe 31 and on the bottom side of the floor F 1. A blower (or fan) 32 is installed. The helium gas having a concentration equal to or higher than a predetermined value within a predetermined atmospheric pressure range by the mixing temperature controller 43 and controlled to a predetermined temperature is supplied to a pipe 31 and then blown by a pump 32. While being supplied to the inside of the case 1 of the projection exposure apparatus on the floor F1, the inside of the sub-chamber 6, and the inside of the projection optical system PL via the branch pipes 31a, 31b and 31c of the pipe 31. I have.

Here, in the present embodiment, the control system 45 closes the on-off valve VI 1 of the pipe 31 and opens the on-off valves V 16 to V 18 of the pipes 92 to 94, and the pump 3 4 The gas (helium) in case 1, subchamber 6, and projection optics PL Etc.). At this time, it is desirable to close an on-off valve (not shown) provided near the inlet of the pipe 33 so that the mixed gas in the upper space 7a of the environmental chamber 7 does not flow into the pipe 33. Thereafter, the opening / closing valves V 16 to V 18 are closed, and the opening / closing valve VI 1 is opened to supply helmets to the case 1, the sub-chamber 6, and the projection optical system PL. The on-off valves V12 to V15 are closed in order from the one at which the concentration reaches a predetermined value. After all the on-off valves VI2 to V15 are closed, the on-off valve V11 is closed. Although not shown, a helium densitometer or an oximeter is provided in each of the case 1, the sub-chamber 6, and the projection optical system PL, and the control system 45 is based on the output of the densitometer. To control the opening and closing of the open / close valves V12 to V15. Also, when the Helium concentration in Case 1, Sub-chamber 6, and one of the projection optical system PL, for example, the projection optical system PL, becomes lower than a predetermined value, open / close valves VII and VI 4 to supply helium. I do. At this time, the main control system (not shown), which controls the entire projection exposure apparatus, checks the operation of the apparatus itself. For example, when the exposure processing of the wafer is in progress, the supply of the helium is continued until the exposure processing is completed. The main control system sends an instruction to the control system 45 to wait for the start.

As described above, in the present embodiment, most of the Helium gas supplied so as to flow through most of the optical path of the illumination light (ultraviolet pulse light IL) of the projection exposure apparatus passes through the pipe 33 from above the environmental chamber 7. As it is collected in the helium circulation device downstairs, the amount of expensive helium used can be reduced. Therefore, the operating cost of the projection exposure apparatus can be reduced while increasing the transmittance to the illumination light and increasing the cooling efficiency of the optical element.

In the above embodiment, a cylinder for storing the collected helium (for example, a nitrogen cylinder similar to the nitrogen cylinder 40 described above) is provided between the refrigerating device 37 and the mixing temperature adjusting device 43 in FIG. ) May be further provided. In this case, in order to be able to store a large amount, it is desirable that the helm be compressed to about 100 to 200 atm by a compressor and stored in the cylinder. This reduces the volume to approximately 1/1000 to 1/200. Furthermore, helium may be liquefied and stored by a liquefier using a turbine or the like. Liquefaction can reduce the volume of the helm to almost 1/700 / 05633. When the highly compressed or liquefied helium is reused as described above, for example, when it is returned to a state of about 1 atm, the temperature decreases due to expansion. It is also desirable to provide a buffer space for keeping the pressure constant. In addition, an open / close valve is installed before (upstream) the mixing temperature controller 43 to adjust the amount of helium taken in from a cylinder (not shown) for storing the recovered helium, or to adjust its flow path (pipe 4). The opening and closing of 1) may be controlled. By using this on-off valve and the on-off valve 48 of the pipe 47 together, the concentration of the helm sent to the pipe 31 can be more easily adjusted.

In the above embodiment, the Helium gas is supplied so as to circulate most of the optical path of the illumination light, but further covers the entire optical path, and also has the cooling efficiency of the reticle stage 20 and the wafer stage 23. In order to increase the pressure, helium gas may be supplied to the entire inside of the environmental chamber 7. Even in this case, most of the helium is recovered, so the increase in operating costs is small. Further, in the above embodiment, the helium purified by the mixing temperature controller 43 and the high-purity helium are mixed, but when the concentration (purity) of the purified helium is low, However, there is a possibility that the density of the helium supplied to the projection exposure apparatus cannot be rapidly increased to an allowable level even if the lithography is simply mixed. In such a case, the purified helium is stored in another cylinder, and the purity is further increased in another recycling factory, etc., and the high-purity helium in the cylinder 46 is supplied to the projection exposure apparatus. May be supplied.

In the above-described projection exposure apparatus, the case 1, the sub-champ 6, and the projection optical system PL are filled (filled) with helium using the opening / closing valves V11 to V18, respectively. In the embodiment, since the helium circulation device is provided, for example, while the opening / closing valves V 16 to V 18 are closed, the amount of helm leaking from the case 1, the sub-chamber 6, and the projection optical system PL can be reduced. Correspondingly, the helium may be constantly supplied while adjusting the flow rate of the helium, or helium may be constantly supplied at a predetermined flow rate with the open / close valves V11 to V18 open. In the latter case, it is not particularly necessary to provide the on-off valves V11 to V18.

In this case, a Helium concentration sensor or an oxygen concentration sensor that measures the Helium concentration in each space of Case 1, Subchamber 6, and the projection optical system PL is placed. May be monitored to determine whether the helium concentration has reached an allowable value. If the helium concentration in each space is reduced, that is, if light-absorbing substances (oxygen or organic impurities, etc.) that absorb the exposure light in each space are present at a predetermined value or more, purification is performed. Helium of high purity instead of supplying helium again

It should be supplied from 4-6. If helium of high purity is supplied from the cylinder 46 and the helium concentration in the space does not reach the predetermined value, there is a possibility that the helium leaks in the space. A warning may be issued to notify the operator or the operation of the exposure apparatus may be automatically stopped.

Also, the pipes 92 to 94 (and the on-off valves V 16 to V 18) connecting the case 1, the sub-chamber 6, and each of the projection optical system PL to the pipe 33 need not be provided. At this time, the on-off valves V11 to V15 may not be further provided. In this case, helium leaks from the case 1, the sub-chamber 6, and the projection optical system PL, so that the helium is replenished, that is, the helium is constantly maintained so that the helium concentration is maintained at an allowable value or more. Or it may be supplied at any time (regularly). Further, in the present embodiment has assumed that the housing and the F ₂ laser light source 3 and the BMU 4 in case 1, apart from storage B MU 4 and the housing and the F ₂ laser light source 3, F ₂ laser light source 3 Helium may be supplied to the housing and the housing. At this time, the F ₂ laser light source 3 and the housing may be mechanically connected, and a glass plate through which the F ₂ laser is transmitted may be provided as a partition plate for both.

Although the above-described exposure apparatus is installed in a clean room, it is desirable that the air pressure in case 1, the sub-chamber 6, and the environmental chamber 7 be set higher than the air pressure in the clean room. By doing so, it is possible to prevent impurities in the clean room from flowing into each space. Further, the air pressure in the sub-chamber 6 housed in the environmental chamber 7 and the projection optical system PL is set higher than the air pressure in the environmental chamber 7. Since drive mechanisms such as a reticle stage and a wafer stage are arranged in the environment chamber, impurities generated from these drive mechanisms can be prevented from flowing into the sub-chamber 6 and the projection optical system PL.

Next, the nitrogen circulation device of the present embodiment will be described in detail. In this embodiment, while supplying nitrogen into the environmental chamber 7 through the piping 88, the piping 95, 33 The nitrogen is recovered from the chamber 7 through the chamber 7, that is, the nitrogen is circulated in the chamber 7. When the nitrogen concentration in the environmental chamber 7 reaches a predetermined value, the supply of nitrogen is stopped, and the piping 88 (or its branch passages 88a, 88b) and the piping 95 are deviated. The valve is closed with the on-off valve V 2 3 (or V 24, V 25), and V 19, and when the nitrogen concentration in the environment chamber 7 becomes lower than a predetermined value, the on-off valve V 2 3 (and V 24 and V 25) may be opened to supply nitrogen.

The nitrogen separated from the helium or the like in the refrigerating device 37 is recovered by a pump 39 through a pipe 38 to a cylinder 40. Further, the nitrogen in the cylinder 40 is sent to the temperature controller 86 through the pipe 81 by the pump 83. An open / close valve V 21 is provided in the pipe 81, and a nitrogen concentration meter (or oxygen concentration meter) 82 that measures the concentration of nitrogen sent to the temperature controller 86 is installed. The measured value of 2 is supplied to the control system 45. The control system 45 is an on-off valve for the piping 85 connecting the nitrogen cylinder 84 and the temperature controller 86 when the nitrogen concentration measured by the concentration meter 82 does not reach the predetermined value. V22 is released, and high-purity nitrogen is supplied from the cylinder 84 to the temperature controller 86. On the other hand, when the nitrogen concentration is equal to or higher than the predetermined value, the control system 45 keeps the on-off valve V22 closed. When the nitrogen concentration measured by the concentration meter 82 is extremely low, the on-off valve V 21 may be closed and only nitrogen from the cylinder 84 may be sent to the temperature controller 86. Then, when the nitrogen concentration measured by the concentration meter 82 reaches an allowable value (a value smaller than the above-mentioned predetermined value), the on-off valve V 21 is opened. Further, the temperature controller 86 mixes the recovered and purified nitrogen with the nitrogen from the cylinder 84 to control the temperature and pressure to a predetermined value. To supply. In the middle of the piping 88, a pump (or fan) 87 is provided on the bottom side of the floor F1 for blowing air. Nitrogen is supplied by this pump 87 to the branch piping 88a, 88g of the piping 88. It is fed into the environmental chamber 7 through b.

In the present embodiment, the outlet of the branch pipe 88a is provided between the projection optical system PL and the wafer W so that nitrogen flows between the projection optical system PL and the wafer W. On the other hand, the branch pipe 88b is branched into two, one outlet is installed between the condenser lens 19 and the reticle R, and the other outlet is connected between the reticle R and the projection optical system PL. is set up. Thus, in the present embodiment, the illumination optical system (condenser-one lens Since high-purity nitrogen can be supplied preferentially between 19) and the projection optical system PL, and between the projection optical system PL and the wafer W, the environment chamber 7 is filled with nitrogen and its concentration is increased. The supply amount of nitrogen can be reduced as compared with the case where the pressure is maintained at a predetermined value or more.

Note that there may be a plurality of outlets arranged between the condenser lens 19 and the reticle R and a plurality of outlets arranged between the projection optical system PL and the wafer W. In the present embodiment, nitrogen supplied between the condenser lens 19 and the reticle R and between the projection optical system PL and the wafer W is recovered from the chamber 7 through the pipes 95 and 33. However, apart from the pipes 95 and 33, at least one gas recovery pipe is separately provided between the condenser lens 19 and the reticle R, and between the projection optical system PL and the wafer W. It may be provided.

In this embodiment, the environment chamber 7 is set to a nitrogen atmosphere. However, for example, air from which impurities have been removed is supplied to the environment chamber 7 so that the space between the illumination optical system and the projection optical system PL and the It is only necessary to supply nitrogen between the optical system PL and the wafer W, and to make both spaces a nitrogen atmosphere. At this time, helium may be supplied instead of nitrogen. In this case, it is not necessary to provide a nitrogen circulating device. For example, the pipe 31 and the branch pipes 88a and 88b may be connected, and helium may be supplied to the two spaces. Further, as the air to be supplied to the environment chamber 7, chemically clean dry air (for example, having a humidity of about 5% or less) from which the above-described organic substances have been removed may be used. This configuration is particularly effective for a projection exposure apparatus using an ArF excimer laser as an exposure light source. In this case, nitrogen may be supplied to the case 1, the sub-chamber 6, and the projection optical system PL, or nitrogen may be supplied to the case 1, the sub-chamber 6, and the projection optical system PL. May be supplied with helium.

Further, the recovered nitrogen may be compressed to about 100 to 200 atm by a compressor, or may be liquefied by a liquefier using an evening bottle or the like and stored in a cylinder 40. The opening / closing valves V 24 and V 25 provided in the branch pipes 88 a and 88 b are provided between the illumination optical system and the projection optical system PL, and between the projection optical system PL and the wafer W. Nitrogen can be supplied to only one of the two spaces. When supplying them simultaneously, the opening / closing valves V 24 and V 25 need not be provided.

In the present embodiment, nitrogen is caused to flow between the illumination optical system and the projection optical system PL, and between the projection optical system PL and the wafer W, but branch pipes 88a and 88b are provided. Instead, a pipe 88 may be simply connected to the environmental chamber 7 to close the closing valve V23 when the nitrogen concentration in the environmental chamber 7 becomes equal to or higher than a predetermined value. Also, regardless of the presence or absence of the branch pipes 88a and 88b, nitrogen is supplied at a predetermined flow rate with the on-off valves V23 and V19, and the nitrogen is circulated in the environmental chamber 7. May be. In this case, it is not particularly necessary to provide the on-off valves V23 and V19. In this embodiment, nitrogen (or helium) or the like is supplied into the environment chamber 7. However, depending on the wavelength range of the illumination light for exposure, the environment chamber 7 is chemically clean and temperature controlled. It may be sufficient to supply supplied air. For example, if the exposure wavelength is about 190 nm or more, the inside of the environmental chamber 7 may be an air atmosphere. In this embodiment, most of the illumination optical system is housed in the sub-chamber 6 and a part of the sub-chamber 6 is installed in the environment chamber Ί. For example, all of the sub-chamber 6 is installed in the environment chamber 7. You may. In this case, the recovery rate of the helium leaking from the sub-chamber 6 can be improved. Also, in order to collect the helium leaking from a part of the sub-chamber 6 installed outside the environmental chamber 7, the sub-chamber 6 outside the environmental chamber 7 is covered with a housing, and a pipe 33 is connected to the upper part of the housing. May be. In this embodiment, a single gas (nitrogen, helium, etc.) is supplied to the case 1, the sub-chamber 6, and the projection optical system PL. However, for example, nitrogen and helium are mixed at a predetermined ratio. A gas may be supplied. In this case, the piping 31 of the nitrogen circulation device may be connected to the piping 31 of the steam circulation device downstream of the on-off valve V11. Note that the mixed gas is not limited to the combination of nitrogen and helium, but may be combined with neon, hydrogen, or the like. Further, the gas supplied to the environment chamber 7 may be the above-mentioned mixed gas. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment In this embodiment, helms from a plurality of projection exposure apparatuses are purified by a single helm circulation apparatus. In FIG. 2, portions corresponding to FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. The pipes 92-94 connecting the pipe 33 to each of the case 1, the sub-chamber 6, and the projection optical system PL shown in Fig. 1 and the pipe 95 connecting the pipe 33 to the environmental chamber 7 are shown. Omitted. In addition, the items described in the first embodiment that are not described in the second embodiment can be similarly applied to the second embodiment.

FIG. 2 is a cross-sectional view showing a plurality of projection exposure apparatuses and one helical circulation apparatus of the present embodiment. In FIG. 2, a plurality of environmental chambers 7A, 7B, and 7C are installed on a floor F1, and each of the environmental chambers 7A, 7B, and 7C has the same exposure as that of the exposure main unit 26 of FIG. The main body is installed, and an unillustrated illumination light source is arranged in close proximity. Helium gas of a predetermined purity or higher is supplied into the environmental chambers 7A, 7B, and 7C from a not-shown helm supply device (not shown). The mixed gas of helium, air, and nitrogen supplied to the environmental chambers 7A, 7B, and 7C and ascended to the space near the internal ceiling, flows through pipes 33A, 33B, and 33C, respectively. It is led to common piping 49. The common pipe 49 passes through an opening in the floor F1 and communicates with the helm circulation device on the floor F2 below the floor. The suction pump 34 is installed on the bottom side of the floor F 1 of the common pipe 49.

The helium, nitrogen, and air mixed gas collected through the common pipe 49 and the suction pump 34 in the lower-stage helm circulation device reaches the refrigerating device 37 via the dust collecting and draining device 35, and is refrigerated. The nitrogen liquefied in 37 is sealed in a cylinder 40. The helium that has not been liquefied in the refrigerating device 37 is further purified by a chemical filter (not shown) or the like, and compressed, for example, at a high pressure into a cylinder 50 for accumulating helium by a pipe 41 and a suction pump 42. Enclosed. This helium is supplied via a pipe 51 provided in a cylinder 50 to a regeneration plant for further increasing the purity or to a helium supply device shown in FIG.

As described in the first embodiment (FIG. 1), the helium recovery device (33A to 33C, 34 to 42, 49, 50, 80) in FIG. 2 also serves as the nitrogen recovery device. Therefore, a plurality of projection exposure units and one nitrogen supply unit (piping 81 in Fig. 1) The nitrogen supply device supplies the nitrogen stored in the tank 40 to a plurality of projection exposure apparatuses. This makes it possible for a plurality of projection exposure apparatuses to double as one nitrogen circulation apparatus. As described above, in the present embodiment, a single helium circulating device and a nitrogen circulating device are used for a plurality of exposure devices, so that the purification cost is reduced. Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment actively purifies helium gas while purifying helium gas with respect to a lens unit (projection lens unit) constituting a part or all of the projection optical system PL in the first embodiment and the second embodiment. This specifically discloses the configuration to be performed. Note that the items described in the first embodiment, which are not described in the third embodiment, can be similarly applied to the third embodiment.

In the figure, three lenses 63, 64, 65 are provided at predetermined intervals in a lens barrel 62 of the projection lens unit 61, and are fixed by a retaining ring 66. Reference numeral 67 denotes a lens separating ring for maintaining a predetermined interval between the lens 64 and the lens 65. Actually, the projection lens unit 61 has many lenses, but only three of them are shown in FIG. 3 to simplify the explanation. Lens chambers R 1 and R 2 are defined between the lenses 63 and 64 and between the lenses 64 and 65 by these lenses and the inner wall of the lens barrel 62. The lens chamber R1 is provided with a gas supply port G1 to which the quick force bra Q1 is mounted and a gas discharge port G2 to which the quick breaker Q2 is mounted. On the other hand, the lens chamber R2 is provided with a gas supply port G3 to which the quick force bra Q3 is attached and a gas outlet G4 to which the quick coupler Q4 is attached.

One end of a pipe L1 is connected to the output side of a supply device 72 including a pump, a control valve, and the like controlled by the control device 71, and the other end of the pipe L1 is branched into two ends. Pipe L2 is connected to the gas supply port G1, and the other pipe L3 is connected to the gas supply port G3. Pipe L 2 and pipe L 3 are each controlled by the control device 7 1 Open / close valves (control valves) VI and V3 are installed. One end of a pipe L4 is connected to the input side of the purifier 73, and the other end of the pipe L4 is branched into two, one of which is connected to the gas outlet G2, and the other of which is connected to the gas outlet G2. L 6 is connected to gas outlet G 4. Opening / closing valves (control valves) V 2 and V 4 controlled by the control device 71 are interposed in the pipe L 5 and the pipe L 6, respectively. The output side of the purification device 73 is connected to the input side of the supply device 72 via a pipe L7. A cylinder 74 into which high-purity helium gas is press-fitted is connected to another input side of the supply device 72 via a pipe L8.

The purifying device 73 is a device for regenerating high-purity helium gas by separating and removing contaminants (solid fine particles, liquid fine particles, and gas) contained in the input helium gas as the gas to be purified. Chemical filters suitable for separating / removing contaminants contained in helium gas as shown below, other filtration devices, separation devices utilizing differences in the chemical properties of helium and contaminants, etc. It consists of a single or a combination of these. As an example of the contaminants to be separated and removed, the gas initially present in each of the lens chambers R 1 and R 2 of the lens unit 61, impurities contained therein, and optical elements such as lenses are fixed to the lens barrel. Of organic substances generated from adhesives or fillers, and impurities generated from the inner wall of the lens barrel (painted surface for anti-reflection, etc.) (for example, water molecules, molecules of hydro force, or other substances) Substances that diffuse the illumination light), purified liquid (ether, water, etc.) adhering to the optical element, etc., and substances produced by reacting with the illumination light, etc. What aggregates and adheres to the lens surface floats due to the light cleaning effect of illumination light, and is also the aforementioned silicon-based organic matter, plasticizer, flame retardant, etc., and is suitable for separating and removing these. Purification device It is adopted.

In addition, as the chemical filter used in the purifying device 73, an ion-exchange resin, ion-exchange fiber, or the like can be used as the ion-removal filter, and the surface area and the reaction rate are large and the molding process is easy. Therefore, ion exchange fiber is suitable for gas treatment. Ion exchange fibers are made, for example, by radiation graph polymerization from polypropylene fibers. As a filter for removing water and the like, an adsorbent such as activated carbon, silica gel, and zeolite can be used. The control device 71 is a device including a microcomputer for controlling the operation of the supply device 72, the purification device 73, and the valves V1 to V4 to perform the purification process at an appropriate timing. And a storage device 75 in which control data including the timing and time of performing the purification process is stored in advance. The control data is created so as to be most effective empirically, experimentally, or theoretically, and is stored in the storage device 75. Further, the storage device 75 stores the operation history of the exposure apparatus, that is, the exposure history such as the irradiation time of the illumination light to the illumination optical system or the projection optical system and the time during which the illumination light is not irradiated. Is also good. For example, when this lens unit is used for the first time after the completion of assembly, as described above, contaminants such as adhesives, fillers, paints, and cleaning agents may aggregate and adhere to the lens surface. However, since the light transmittance tends to decrease entirely or partially, a control system is created so that the purification process is performed relatively frequently. Since such phenomena tend to gradually decrease with the lapse of operation time, the frequency of purification is reduced according to the operation time, and after a certain amount of operation time has elapsed, The control data is created so that the purification process is performed diffusely and periodically.

In accordance with the control data created in this way, the control device 71 performs the processing shown in the flowchart of FIG. First, the control data is read from the storage device 75 (ST 1), and it is determined whether or not it is time to perform the purification process based on the data on the time to perform the purification process (ST 2). If it is time to carry out the purification treatment, pre-irradiation of illumination light is performed to remove contaminants adhering to the surface of the lens etc. by utilizing the light cleaning effect of ultraviolet rays. Float (ST 3). The preliminary illumination light irradiation time is determined in consideration of the past operation time of the exposure apparatus, that is, the exposure time of the illumination light to the optical system and the exposure history such as the time when the illumination light is not irradiated. . When the illumination light is preliminarily irradiated, a promoting gas such as ozone for promoting the light cleaning effect may be supplied into the optical path. Up to this point, the on-off valves V1 to V4 of the lens unit 61 are closed, so here, the on-off valves VI to V4 are opened (ST4), and the supply device 72 and Activate the purifier 73 to start circulation and purification of helium gas (ST 5).

That is, a new helium gas or purification device from the cylinder 74 is supplied by the supply device 72. Supply either one of the helium gas purified by 73 or a mixture thereof to the piping LI, L2, L3, and replace the inside of each lens chamber R1, R2 of the lens unit 61 with clean helium gas. I do. Helium gas containing suspended contaminants, which had been present in the lens chambers R 1 and R 2 of the lens unit 61, was recovered through the pipes L 5, L 6 and L 4 and sent to the purifier 73. Can be The contaminants contained in the helium gas are separated and removed by the purification device 73, and the purified helium gas is sent to the supply device 72 via the pipe L7. Will be Next, it is determined whether or not a predetermined time has elapsed from the start of the purification, based on the data on the time for performing the purification process (the time from the start to the end of the purification) set in the control data ( ST 6) When the predetermined time has elapsed, the operation of the supply device 72 and the purification device 73 is stopped (ST7), the on-off valves VI to V 4 are closed (ST8), and the purification process ends.

The control for performing the purification process by the controller 71 described above is performed in accordance with the control data stored and held in the storage device 75 in advance, but as shown in FIG. 5, the light transmittance is measured. Thus, control can be performed so as to perform the purification process according to the actual pollution situation. An illuminance sensor (detection device) 76 that detects the illuminance of the illumination light is provided on the wafer stage that holds the wafer to be exposed, and the illuminance of the illumination light is monitored to detect the light transmittance (ST 1). The variation of the light transmittance is compared with a predetermined value stored in the storage device 75 in advance (ST2), and when the detected variation of the light transmittance exceeds the predetermined value (larger). In this case, pre-irradiation of illumination light is carried out in advance to float contaminants adhering to the surface of the lens etc. using the light washing effect of ultraviolet rays (ST 3). Preliminary illumination light irradiation time is obtained from a difference between a predetermined value stored and held in the storage device and the detected variation in light transmittance. In other words, when the difference between the fluctuations is large, the irradiation time is long, and when the difference between the fluctuations is small, the irradiation time is short. In this state, since the on-off valves V1 to V4 of the lens unit 61 are closed, the on-off valves VI to V4 are opened (ST4), and the supply device 72 and the purification device 73 are operated. Start gas circulation and purification (ST 5).

That is, a new helm gas or a purification device from the cylinder 74 by the supply device 72. 73 Either one of the purified gas or a mixture thereof is supplied to the piping LI, L2, L3, and the interior of each lens chamber R1, R2 of the lens unit 61 is cleaned with clean gas. Replace. Helium gas containing suspended contaminants, which had been present in the lens chambers R 1 and R 2 of the lens unit 61, was recovered through the pipes L 5, L 6, and L 4, and was purified. Sent to Contaminants contained in the helium gas are separated and removed by the purification device 73, and the purified helium gas is sent to the supply device 72 via the pipe L7, thereby circulating the helium gas in the same manner. Is performed. Next, the light transmittance is detected again by the illuminance sensor 76 on the wafer stage (ST 6), and the fluctuation amount of the detected light transmittance is set in advance, and the predetermined value stored in the storage device 75 is stored. (ST7) which is equal to or smaller than the predetermined value used for comparison in ST2, and when the detected light transmittance variation does not exceed the predetermined value (if small) Next, the operation of the supply device 72 and the purification device 73 is stopped (ST8), the on-off valves VI to V4 are closed (ST9), and the purification process ends.

In the processing shown in FIG. 5, in ST1 and ST2 or ST6 and ST7, the illuminance is detected by the illuminance sensor provided on the wafer stage, and the amount of change in light transmittance is obtained. The variation is compared with a predetermined value, but a non-uniformity sensor for detecting the illuminance distribution of the illumination light is provided on the wafer stage, and the difference between the maximum value and the minimum value of the detected illuminance distribution is determined. Is compared with a predetermined value set in advance to perform the purification process, or the purification process can be terminated. The position of the illuminance sensor is not limited to the position on the wafer stage. Beam splitters are provided upstream and downstream of the lens unit 61 to monitor the illuminance of the branched light, and the illuminance and the illuminance distribution of the module are monitored. , The amount of change in illuminance, light transmittance, or the amount of change in light transmittance is compared with a predetermined value set correspondingly, and a purifying process is performed based on the result, or the purifying process is terminated. You may do so.

Either the control process shown in FIG. 4 or the control process shown in FIG. 5 can be selected and adopted, or a combination thereof can be used. In addition, these control processes are performed at times other than the exposure process of exposing and transferring the reticle pattern onto the wafer, for example, immediately before the start of the operation of the exposure apparatus, and the exposure process for one lot is completed. It may be performed immediately before performing the exposure processing on the next lot, or may be performed immediately before the exposure processing on the next wafer is completed after the exposure processing on one wafer is completed. This is because, if gas is circulated during the exposure processing, exposure accuracy may be adversely affected by pressure fluctuations and temperature fluctuations in the lens chambers R 1 and R 2 of the lens unit 61. As described above, the on-off valves V1 to V4 are opened only during the cleaning process, and the on-off valves V1 to V4 are closed during the exposure process, so that the inside of the lens chambers R1 and R2 of the lens unit 61 can be reduced. Is prevented from flowing and a stable state can be obtained.

In the example shown in FIG. 3, an on-off valve is provided in each of the pipes L 2, L 3, L 5, and L 6 so that the flow of helium gas can be controlled in each of the lens chambers R 1 and R 2. However, within a range where the gas flow rate flowing through the lens chambers R l and R 2 does not extremely decrease, the closing valves V 1 to V 4 are deleted and piping valves L 1 and L 4 are provided with on-off valves respectively. Thus, the flow of gas in each of the lens chambers Rl and R2 may be commonly controlled. In addition, as shown in Fig. 3, the gas supply ports G1, G3 and the gas discharge ports G2, G4 are not provided for all the lens chambers R1, R2. Piping may be provided only in the chamber.

The lens unit 61 shown in FIG. 3 is a lens unit used for the projection optical system. However, the lens unit to be purified is not limited to the lens unit having such a configuration, but may be another configuration used for the projection optical system. An exposure apparatus can be configured by applying the above-described gas purification system to a lens unit having a lens unit or a lens unit used in an illumination optical system. Further, the present invention is not limited to the lens unit, and can be similarly applied to an optical element unit using a lens and a reflecting mirror or an optical element unit using only a reflecting mirror.

In the above embodiment, helium gas is used as a gas having a high (inert) transmittance with respect to illumination light and a good thermal conductivity, but such a gas other than helium ( For example, the present invention can be applied to the case where high-purity nitrogen, neon (Ne), or a mixed gas of helium and nitrogen is used.

The first to third embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment belongs to the technical scope of the present invention. It is intended to include all design changes and equivalents.

For example, in each of the above embodiments, the exposure apparatus that employs a device that emits F excimer laser light (wavelength 157 nm) as a light source has been described. However, KrF excimer laser light (wavelength 248 nm) and A rF excimer laser beam (wavelength: 19 3 nra), those employing what emits Ar ₂ laser beam (wavelength 126 nm), in addition, a so-called extreme ultraviolet (EUV, or XUV) wavelength close to almost X-ray of the area 13 It can also be applied to an exposure device that employs a light source that emits light at 7 nm or 7 nm, or even X-rays at a wavelength of 1 nm.

In each of the above embodiments, the step-and-scan type reduced projection type scanning exposure apparatus (scanning stepper) has been described. However, for example, the entire surface of the reticle pattern is kept in a state where the reticle and the wafer are stationary. Irradiating the illuminating light for exposure to the reticle pattern

Step of Batch Exposure of (Shot Area) The present invention can be similarly applied to a reduction projection type exposure apparatus (stepper) of the repeat type, and further to an exposure apparatus of the mirror projection type or the proximity type. it can. Projection optical systems are not limited to those in which all optical elements are refractive elements (lenses), but are reflective elements.

The optical system may include only a mirror (such as a mirror), or may be a catadioptric optical system including a refracting element and a reflecting element (such as a concave mirror or a mirror). The projection optical system is not limited to the reduction optical system, but may be an equal-magnification optical system or an enlargement optical system.

In addition, a single-wavelength laser in the infrared or visible range emitted from a DFB semiconductor laser or a fiber laser is used as the exposure illumination light. For example, a fiber amplifier doped with erbium (or both erbium and dietary beams) is used. A harmonic that has been amplified by and converted to ultraviolet light using a nonlinear optical crystal may be used. For example, if the oscillation wavelength of a single-wavelength laser is in the range of 1.51 to 1.59 m, the 8th harmonic whose generation wavelength is in the range of 189 to 199 nm, or the generation wavelength of 151 to 159 nm The 10th harmonic within the range is output. In particular, if the oscillation wavelength is in the range of 1.544 to 1.553 m, an 8th harmonic in the range of 193 to 194 nm, that is, ultraviolet light having substantially the same wavelength as the ArF excimer laser can be obtained. To 1. 5 7-1. When the range of 5 8 m, 1 5 7~ 1 1 0 fold higher harmonics in the range of 5 8 nm, i.e. F ₂ laser and ultraviolet light having almost the same wavelength can be obtained. Assuming that the oscillation wavelength is in the range of 1.03 to 1.12 ^ 111, a 7th harmonic whose output wavelength is in the range of 147 to 160 nm is output, and especially the oscillation wavelength is 1.0. 0 9 9-1. When 1 0 6 111 within range, 7 harmonic in the range generation wavelength of 1 5 7-1 5 8, i.e. F ₂ laser and ultraviolet light having almost the same wavelength can be obtained . Note that a single-beam oscillation fiber laser is used as the single-wavelength oscillation laser.

The present invention is not limited to a projection exposure apparatus used for manufacturing a semiconductor device, a liquid crystal display, a thin film magnetic head, and an image pickup device (such as a CCD), but also includes a glass substrate or a silicon wafer for manufacturing a reticle or a mask. For example, the present invention can be applied to a projection exposure apparatus that transfers a circuit pattern. Where DUV (Far UV) light or VUV

(Vacuum ultraviolet light) In an exposure apparatus using light or the like, a transmission type reticle is generally used, and as a reticle substrate, quartz glass, quartz glass doped with fluorine, fluorite, magnesium fluoride, or quartz crystal is used. Are used. In addition, a reflective mask is used in an EUV exposure apparatus, and a transmission mask (stencil mask, membrane mask) is used in a proximity type X-ray exposure apparatus or a mask projection type electron beam exposure apparatus. For example, a silicon wafer is used.

By the way, the illumination optical system composed of a plurality of lenses and the projection optical system are incorporated into the main body of the exposure apparatus for optical adjustment, and the reticle stage and wafer stage consisting of many mechanical parts are attached to the main body of the exposure apparatus and wired. And pipes, and connect Case 1, the illumination optical system (subchamber 6), the projection optical system PL, and the environmental chamber 7 to the helium circulator and nitrogen circulator, etc. The operation of the exposure apparatus according to the above-described embodiment can be manufactured by performing the above operations. It is desirable to manufacture such an exposure apparatus in a clean room where the temperature, cleanliness, etc. are controlled.

Mechanical polishing, electrolytic polishing, puff polishing, chemical polishing, etc., are performed on the pipes and inner walls of the chamber described in this embodiment to reduce the surface roughness. It is advisable to take measures such as performing gas (baking) treatment to reduce the amount of outgassing from the surface of the structural material. In addition, helium gas and nitrogen gas Pipes supplied to the space should be made of a material with reduced generation of impurity gas (degas) (for example, stainless steel, tetrafluoroethylene, tetrafluoroethylene-terfluoro (alkyl vinyl ether), or tetrafluoride). It is desirable to use an ethylene-hexafluorobutene benzene copolymer or other various polymers).

A semiconductor device includes a step of designing the function and performance of the device, a step of manufacturing a reticle based on this design step, a step of manufacturing a wafer from a silicon material, and a step of forming a reticle pattern by the exposure apparatus of the above-described embodiment. It is manufactured through the steps of exposing to the wafer, light transfer, device assembly steps (including dicing, bonding, and packaging processes), and inspection steps.

In manufacturing a semiconductor device, in particular, in the step of exposing and transferring a reticle pattern onto a wafer, a gas that transmits the illumination light is supplied to at least a part of an optical path of the illumination light, and at least one of the gases is supplied. This is performed when the part is recovered and a substance that affects the transfer accuracy of the pattern image is removed from the recovered gas. Similarly, a gas that transmits illumination light is supplied between the projection optical system and the photosensitive substrate, and at least a part of the gas supplied to the space is recovered, and the gas is transmitted through the projection optical system. Then, the image of the pattern is transferred onto the photosensitive substrate. In addition, while performing the operation described in the first, second, and third embodiments, or after the operation, a step of exposure transfer is performed.

In addition, all disclosure contents of Japanese Patent Application No. 10-290 326 26 filed on October 13, 1998, including the specification, claims, drawings and abstract Is hereby incorporated by reference in its entirety.

Claims

The scope of the claims

1. An exposure apparatus that irradiates a mask with illumination light from a light source and transfers an image of a pattern formed on the mask onto a predetermined surface.

A supply device that supplies a gas that transmits the illumination light to at least a part of an optical path of the illumination light;

A recovery device that recovers at least a part of the gas supplied to the optical path of the illumination light.

An exposure apparatus, comprising: a purifying device that removes, from the collected gas, a substance that affects transfer accuracy of the image of the pattern onto the predetermined surface.

2. The exposure apparatus according to claim 1, wherein the purification device is connected to the supply device, and the gas purified by the purification device is supplied again to the optical path of the illumination light by the supply device. .

3. The exposure apparatus according to claim 1, wherein the gas is supplied to at least a part of the illumination system by the supply device.

4. The exposure apparatus according to claim 3, wherein the substance is removed from the gas by the purification device.

5. A projection optical system for projecting an image of the pattern of the mask onto the photosensitive substrate, further comprising:

The exposure apparatus according to claim 1, wherein the supply device supplies the gas to at least a part of the projection optical system.

6. The exposure apparatus according to claim 5, wherein the substance is removed from the gas by the cleaning device.

7. The exposure apparatus according to claim 1, wherein the supply device supplies the gas to the light source.

8. The exposure apparatus according to claim 1, wherein a substance that changes the illuminance or the illuminance distribution on the surface irradiated with the illumination light by the cleaning device is removed from the gas.

9. The substance includes a plurality of optics disposed between the light source and the predetermined surface. The exposure apparatus according to claim 1, further comprising: a control device that changes an optical characteristic of at least one optical element among the elements, and controls an operation of the purification device according to the change in the optical characteristic. apparatus.

10. A storage device in which control data including a time and a time when the purification device should be operated is stored in advance,

10. The exposure apparatus according to claim 9, wherein the control device operates the purifying device according to control data stored in the storage device.

11. A projection optical system for projecting an image of the pattern of the mask onto the photosensitive substrate;

Further comprising a detection device for detecting the transmittance of the projection optical system,

10. The exposure apparatus according to claim 9, wherein the control device activates the cleaning device when a variation amount of the transmittance detected by the detection device exceeds a predetermined value.

12. A supply port connected to the supply device and the recovery port in a chamber defined so that the supply device includes at least a part of an optical element in an optical path of the illumination light that supplies the gas. Provide an outlet connected to the device,

On-off valves controllable by the control device are provided at the discharge port and the supply port, respectively.

10. The exposure apparatus according to claim 9, wherein the control device closes the on-off valve when not operating the purifying device.

13. The exposure apparatus according to claim 12, wherein the control device irradiates the illumination light before operating the cleaning device to float contaminants attached to a surface of the optical element.

14. The exposure apparatus according to claim 12, further comprising a gas supply source for supplying a new gas.

15. The exposure apparatus according to claim 1, wherein the cleaning apparatus operates according to an exposure history.

16. The exposure apparatus according to claim 1, wherein at least a part of an optical path of the illumination light is a space including the mask or the predetermined surface.

17. The supply device includes: a light source that emits the illumination light in a first space in an optical path of the illumination light; A first supply mechanism that supplies a first gas that transmits light, and a second supply mechanism that supplies a second gas that transmits the illumination light to a second space different from the first space in an optical path of the illumination light. With 2 supply mechanism,

17. The exposure apparatus according to claim 16, wherein the purification device removes the substance from the collected gas and separates the first gas and the second gas.

18. The first space is a space including at least one optical element among a plurality of optical elements arranged between the light source and the predetermined surface,

The exposure apparatus according to claim 17, wherein the second space is a space including the mask or the predetermined surface.

19. An exposure apparatus that irradiates a mask with illumination light from a light source and transfers an image of a pattern formed on the mask onto a photosensitive substrate via a projection optical system, wherein the projection optical system, the photosensitive substrate, A supply device for supplying a gas that transmits the illumination light to a space between

An exposure apparatus, comprising: a recovery device configured to recover at least a part of the gas supplied to the space.

20. The gas according to claim 19, wherein the gas recovered by the recovery device includes another type of gas that transmits the illumination light, which is different from the gas that transmits the illumination light. Exposure equipment.

21. The gas that transmits the illumination light is one of nitrogen and helium, and the gas that transmits the other type of illumination light is the other of the nitrogen and the helium. 3. The exposure apparatus according to claim 1.

22. An exposure method for irradiating a mask with illumination light from a light source and transferring an image of a pattern formed on the mask onto a predetermined surface.

Supplying a gas that transmits the illumination light to at least a part of an optical path of the illumination light; collecting at least a part of the gas supplied to the optical path of the illumination light; an image of the pattern on the predetermined surface; An exposure method characterized by removing, from the collected gas, substances that affect the transfer accuracy of the light.

23. Reduce the light path of the illumination light again by removing the gas from which the substance has been removed. 23. The exposure method according to claim 22, wherein both are supplied to a part.

24. The exposure method according to claim 23, wherein the gas to be recovered is a gas in a space including the mask or the predetermined surface.

25. In an exposure method for irradiating an illumination light from a light source onto a mask and transferring an image of a pattern formed on the mask onto a photosensitive substrate via a projection optical system, the projection optical system, the photosensitive substrate, Supplying a gas that transmits the illumination light, and recovering at least a part of the gas supplied to the space.

26. In a method for manufacturing an apparatus for irradiating an illumination light from a light source onto a mask and transferring an image of a pattern formed on the mask onto a photosensitive substrate,

A supply pipe for supplying gas that transmits the illumination light is connected to a gas chamber that defines at least a part of an optical path of the illumination light,

Connecting a collection pipe for collecting at least a part of the gas supplied to the gas chamber to the gas chamber;

The method according to claim 1, wherein the collection pipe is connected to a purifying device that removes a substance that affects transfer accuracy of the image of the pattern onto the predetermined surface.

27. A method for manufacturing a semiconductor device by irradiating illumination light from a light source onto a mask and transferring an image of a pattern formed on the mask onto a predetermined surface,

A gas that transmits the illumination light is supplied to at least a part of an optical path of the illumination light, and at least a part of the gas supplied to the optical path of the illumination light is recovered.From the recovered gas, A manufacturing method for transferring an image of the pattern onto a predetermined surface while removing a substance which affects the transfer accuracy of the image of the pattern onto the predetermined surface.

28. A method for manufacturing a semiconductor device by irradiating illumination light from a light source onto a mask and transferring an image of a pattern formed on the mask onto a photosensitive substrate via a projection optical system,

A gas that transmits the illumination light is supplied between the projection optical system and the photosensitive substrate, and at least a part of the gas supplied to the space is recovered while passing through the projection optical system. Transferring the image of the pattern onto the photosensitive substrate. Manufacturing method

29. An exposure apparatus including an exposure apparatus body that irradiates a mask with illumination light from a light source and transfers an image of a pattern formed on the mask onto a predetermined surface, wherein at least a part of an optical path of the illumination light is provided. A supply device for supplying a gas that transmits the illumination light,

The exposure apparatus, wherein the supply device is installed in a space different from a space in which the exposure apparatus main body is installed.

30. a purifying device for removing, from the recovered gas, a substance that affects the transfer accuracy of the pattern image onto the predetermined surface;

30. The exposure apparatus according to claim 29, wherein the cleaning device is installed in a space different from a space in which the exposure device main body is installed.

31. The exposure apparatus according to claim 19, wherein the exposure apparatus main body is installed in a clean room, and the cleaning device or the recovery device is installed in a space adjacent to the clean room.