JP2001060548A - Exposure method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the deterioration of the light quantity of exposure beams by efficiently removing substances whose absorption is large from the optical path of exposure beams. SOLUTION: The pattern of a reticle 13 is transferred through a projecting optical system 18 to a wafer 19 under exposing lights IL in a vacuum ultraviolet region. The inside of the projecting optical system 18 is divided into mutually isolated plural lens chambers 76A-76F (a lens chamber 76G is integrated with the lens chamber 76D), so that a light absorbing substrate generated in one lens chamber can be prevented from being mixed in another lens chamber. An oxygen concentration sensor S3A for detecting the concentration of oxygen as a light-absorbing substance is arranged in the lens chambers 76A-76E, and a gas in the lens chambers 76A-76F is sucked though an exhaust pipe 71A based on the measured value, and the lens chambers 76A-76F are packed with a purge gas transmitted via the exposing lights IL through and exhaust pipe 70A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of projecting a mask pattern in a lithography process for manufacturing a device such as a semiconductor device, an image pickup device (CCD or the like), a liquid crystal display device, a plasma display device, or a thin film magnetic head. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus for transferring an image onto a substrate via an optical system.
UV light).

[0002]

2. Description of the Related Art In recent years, a projection exposure apparatus used for transferring a reticle pattern as a mask onto a wafer (or a glass plate or the like) coated with a photosensitive material as a substrate via a projection optical system. In the field of technology, further improvement in the resolution of the projection optical system is required as the integrated circuit becomes finer and higher in density. The resolution of the projection optical system increases as the wavelength (exposure wavelength) of the exposure light used as the exposure beam decreases and as the numerical aperture (NA) of the projection optical system increases. For this reason, the exposure light used in the projection exposure apparatus is becoming shorter and shorter each year, and the numerical aperture of the projection optical system is also increasing.

[0003] The currently mainstream exposure light has a wavelength of 248.
nm KrF excimer laser light, but a shorter wavelength ArF excimer laser light (wavelength 193) in a substantially vacuum ultraviolet region.
nm) is also being put to practical use. Recently, in order to cope with further miniaturization and higher density of integrated circuits, a wavelength of 157
use of nm of F ₂ laser has been attempted. In a projection exposure apparatus, it is also required to shorten the exposure time for each wafer to improve the throughput of the exposure process. In order to improve the throughput in this way, it is necessary to increase the illuminance of the exposure light, that is, the amount of light applied to the reticle per unit time. However,
When the wavelength of the exposure light is shortened, the absorption by a refraction member (such as a lens) and the absorption by a gas (atmosphere) on an optical path gradually increase.

That is, when the wavelength of the exposure light becomes 160 nm or less, which is even shorter in the vacuum ultraviolet region, the transmittance is relatively high in the glass material (optical material) of the refractive member used in the illumination optical system and the projection optical system. Good ones are quartz doped with fluorine or the like, fluorite (CaF ₂ ), magnesium fluoride (MgF
₂ ) and lithium fluoride (LiF). The wavelength of the exposure light is 180 nm in the vacuum ultraviolet region.
When the temperature is less than or equal to the level, substances such as oxygen, water vapor, carbon dioxide, organic substances, and halides contained in the atmosphere of the optical path of the exposure light (the ozone is assumed to be sufficiently removed) (hereinafter, referred to as “light absorbing substances”) ) Increases the exposure light absorption. Further, the absorption of oxygen in the light-absorbing substance is increased from the exposure light having a wavelength of about 200 nm, that is, a light near the vacuum ultraviolet region. In addition, a trace amount of organic substances and the like in the atmosphere around the optical member in the projection exposure apparatus may cause a photochemical reaction by vacuum ultraviolet light to generate a cloudy substance. The amount of decrease in the amount of light increases.

Further, when the amount of the light-absorbing substance increases, not only does the amount of exposure light reaching the wafer decrease, but also the accuracy of the exposure amount control decreases, causing variations in the line width of the circuit pattern transferred onto the wafer. In addition, the circuit wiring of the manufactured electronic device may be defective, and the yield of the final product may be reduced. Therefore, when vacuum ultraviolet light is used as the exposure light, the exposure light passes through the reticle and the projection optical system and reaches the surface of the wafer with sufficient illuminance to perform exposure at a practical throughput. It is necessary to form the member from the above-mentioned material having a relatively good transmittance, and to remove or reduce a substance having a high absorption rate for the exposure light such as the above-mentioned light absorbing substance from the optical path of the exposure light.

[0006]

As described above, in a conventional projection exposure apparatus, the wavelength of exposure light is shortened.
In order to reduce the absorption of the exposure light accompanying this, it is necessary to remove or reduce the light absorbing material from the optical path.
For this purpose, a method of drawing the optical path of the exposure light into a vacuum is conceivable.However, in this method, it is necessary to store the optical path of the exposure light in a firm airtight chamber that can withstand the evacuation, and for example, a wafer cassette under atmospheric pressure and When a wafer is exchanged between the two, it is necessary to go through a decompression chamber (preliminary chamber), which may increase manufacturing costs and decrease throughput. Therefore, at present, a method has been developed in which most of the atmosphere on the optical path of the exposure light is replaced (purged) by a gas through which the exposure light is transmitted, that is, a gas having a higher transmittance to the exposure light than the above-described light absorbing substance. Have been.

For example, as a method of replacing the atmosphere on the optical path of the exposure light in the projection optical system with a gas through which the exposure light passes,
A space (hereinafter, referred to as a “lens room”) surrounded by two predetermined lenses that constitute the projection optical system is isolated from other spaces, the hermeticity (airtightness) inside the space is increased, and the lens room is opened. There has been proposed a method of supplying the gas to the gas. At this time, it has been proposed to provide a plurality of lens chambers in the projection optical system. However, even in this configuration, the airtightness between the plurality of lens chambers has not been considered much in the past. However, in the case where the gas can easily flow between the plurality of lens chambers, if degassing including a light absorbing substance is generated from a partition wall or the like in a certain lens chamber, the degassing is performed by another degassing. Since the exposure light easily flows into the lens chamber, the transmittance of the exposure light is reduced even in another lens chamber, and the transmittance may be largely reduced as a whole.

Conventionally, no detailed study has been made on the arrangement of the gas supply and exhaust ports in the lens chamber. For this reason, the gas containing the light absorbing substance may locally stay inside the lens chamber, and the transmittance of the exposure light may be partially reduced. Therefore, it is now desired to develop a method capable of replacing all the gas in the lens chamber with a gas through which the exposure light passes as efficiently as possible.

Similarly, in an illumination optical system and the like, a space with high airtightness is formed in a part of the optical path of exposure light, and a gas in the highly airtight space is replaced with a gas through which the exposure light passes. In such a case, it is necessary to reduce the influence on other parts and to efficiently perform the replacement. In view of the above, an object of the present invention is to provide an exposure method capable of efficiently removing a substance having a large absorption of an exposure beam from an optical path of the exposure beam and maintaining a high light intensity of the exposure beam.

Another object of the present invention is to provide an exposure apparatus capable of performing such an exposure method.

[0011]

According to a first exposure method of the present invention, a first object (13) is illuminated with an exposure beam and a second object (1) is exposed with an exposure beam having passed through the pattern of the first object.
In the exposure method for exposing 9), the gas containing impurities inside and the gas through which the exposure beam passes are independently supplied to a plurality of hermetic chambers (76A to 76F) provided on the optical path of the exposure beam. The air supply is controlled. In the present invention, an impurity refers to a substance having a low transmittance to the exposure beam, and the type of the impurity varies depending on the wavelength of the exposure beam. In addition, the airtight room of the present invention is a room which is substantially isolated from other spaces and is substantially sealed, and therefore has a small flow of gas between the other spaces.

According to the present invention, for example, the gas cannot be mutually circulated between the plurality of hermetic chambers, or the amount of the gas circulated between the plurality of hermetic chambers is reduced, and the plurality of hermetically sealed chambers are independently provided inside. By providing an exhaust port for the gas of the above, and a gas supply port for the gas through which the exposure beam passes, the gas supply through which the exposure beam passes and the exhaust of the gas inside can be mutually transmitted to the plurality of hermetic chambers. Control independently. This allows the gas in the plurality of hermetic chambers to smoothly flow from the upstream (air supply port) side to the downstream (exhaust port) side, thereby efficiently exhausting the gas containing impurities. Furthermore, since the gas containing impurities exhausted from the hermetic chamber can be prevented from flowing into or flowing back into another hermetic chamber, even if degassing containing impurities occurs from a certain hermetic chamber, the exposure beam Can be kept high as a whole.

Next, in a second exposure method according to the present invention, an exposure beam illuminates a first object (13) with an exposure beam and exposes a second object (19) with an exposure beam passing through the pattern of the first object. In the method, an exhaust port (51B1 to 51B) is provided to an airtight chamber (76A) provided on the optical path of the exposure beam.
Exhausting gas containing impurities through B3),
The gas through which the exposure beam is transmitted is supplied through the gas supply ports (50B1 to 50B3), and at least one of the gas discharge port and the gas supply port is provided.

According to the present invention, since at least one of the exhaust port and the air supply port is provided in plurality, the gas in the airtight chamber is supplied when air is supplied and exhausted to the airtight chamber. The flow path (flow velocity distribution) and the flow rate can be easily controlled, and the impurities can be prevented from locally staying in the airtight chamber. Further, for example, by providing a plurality of exhaust ports corresponding to the plurality of intake ports, or by increasing the number of exhaust ports, the gas in the hermetic chamber is downstream (exhaust port) from the upstream (supply port) side. Since the gas flows smoothly to the side, the gas containing impurities can be efficiently exhausted.

Next, a first exposure apparatus according to the present invention illuminates a first object (13) with an exposure beam, and exposes a second object (19) with an exposure beam passing through the pattern of the first object. In the apparatus, a plurality of airtight chambers (76A to 76F) provided on an optical path of the exposure beam are independently exhausted from each other to exhaust gas containing impurities therein and supply gas passing through the exposure beam. Air supply / exhaust mechanism (35-38)
And a densitometer (S3A to S3F) for measuring the concentration of the impurity in at least a part of the plurality of airtight chambers. According to such an exposure apparatus, the first exposure method of the present invention can be performed.

Next, a second exposure apparatus according to the present invention illuminates a first object (13) with an exposure beam and exposes a second object (19) with an exposure beam having passed through the pattern of the first object. In the apparatus, an airtight chamber (76A) arranged on the optical path of the exposure beam, and an air supply pipe (50B1 to 50B3) for supplying a gas through which the exposure beam passes to the airtight chamber (50B1 to 50B3). 70B1 to 70B3),
From the airtight chamber (76A) to the exhaust port (51B1-51B)
3) Exhaust pipes (71B1 to 71B3) for exhausting gas containing impurities through the exhaust pipe and the exhaust beam and the exposure beam of the gas containing impurities inside the hermetic chamber through the exhaust pipe and the air supply pipe. A supply / exhaust mechanism (35-38) for supplying permeated gas, and a plurality of exhaust ports and at least one of the air supply ports are provided.
According to such an exposure apparatus, the second exposure method of the present invention can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. This example is a step-and-step method using vacuum ultraviolet light as the exposure beam.
The present invention is applied to a scanning projection exposure apparatus. FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus of this embodiment. In FIG. 1, the projection exposure apparatus of this embodiment uses a fluorine laser (F ₂ laser) having an oscillation wavelength of 157 nm as an exposure light source 1. . Vacuum ultraviolet light, such as fluorine laser light, is greatly absorbed by light-absorbing substances such as oxygen, water vapor, hydrocarbon-based gas (carbon dioxide, etc.), organic substances, and halides that are present in the normal atmosphere. In order to prevent attenuation, it is necessary to suppress the concentration of the gas of the light absorbing substance corresponding to these impurities of the present invention to about 10 ppm or less. Therefore, in the present embodiment, the gas on the optical path of the exposure beam is converted into a gas through which the exposure beam passes, that is, nitrogen (N ₂ ) gas, helium (He), neon (N
e), it is chemically stable with a high transmittance to an exposure beam such as a rare gas composed of argon (Ar), krypton (Kr), xenon (Xe), or radon (Rn), and the light-absorbing substance is highly (Hereinafter referred to as “purge gas”). The nitrogen gas and the rare gas are collectively referred to as an inert gas.

The nitrogen gas can be used as a gas (purge gas) through which the exposure beam passes up to a wavelength of about 150 nm even in a vacuum ultraviolet region.
The light substantially acts as a light-absorbing substance with respect to light of about nm or less. Therefore, it is desirable to use a rare gas as a purge gas for an exposure beam having a wavelength of about 150 nm or less. Among rare gases, helium gas is desirable from the viewpoint of stability of refractive index and high thermal conductivity. However, helium is expensive. May be used. Also,
As the purge gas, not only a single kind of gas may be supplied, but also a mixed gas such as a gas obtained by mixing nitrogen and helium at a predetermined ratio may be supplied.

Hereinafter, the configuration of the projection exposure apparatus of this embodiment will be described in detail. First, the exposure light (illumination light for exposure) IL composed of a laser beam having a wavelength of 157 nm as an exposure beam emitted from the exposure light source 1 is shaped into a cross-sectional shape by the shaping optical system 2 in the first sub-chamber 31. The light enters a fly-eye lens 3 as an optical integrator (homogenizer) for uniforming the illuminance distribution. The exposure light IL emitted from the fly-eye lens 3 reaches the field stop (reticle blind) 8 through the first relay lens 5, the mirror 6 for bending the optical path, and the second relay lens 7, and the illumination field becomes a rectangular area that is elongated. Stipulated. The exposure light IL that has passed through the field stop 8 passes through the first condenser lens 9, the second condenser lens 10, the mirror 11 for bending the optical path, and the third condenser lens 12, and the pattern surface (lower surface) of the reticle 13 as a mask. Is illuminated. An illumination optical system is composed of an exposure light source 1, a shaping optical system 2, a fly-eye lens 3, relay lenses 5, 7, mirrors 6, 11, a field stop 8, condenser lenses 9, 10, 12, and the like. The system 2 to the condenser lens 12 are housed in a highly airtight box-shaped first sub-chamber 31.

In the present embodiment, the surface on the exit side of the fly-eye lens 3 is a surface which has an optical Fourier transform relationship with the pattern surface of the reticle 13 by the optical system including the relay lens 5 and the condenser lens 12, ie, It is arranged so as to match the pupil plane IP of the illumination optical system. An aperture switching member 4 for determining the numerical aperture of the exposure light is rotatably disposed on the pupil plane IP. Around the rotation axis of the aperture switching member 4, an aperture stop for normal illumination, a small coherence An aperture stop (σ stop) of an illumination system including an aperture stop for a factor (σ value), an aperture stop for annular illumination, an aperture stop for modified illumination having a plurality of apertures, and the like is arranged. Main control system (not shown) that controls operation
By controlling the rotation angle of the aperture switching member 4 via the drive motor 47, a desired σ aperture can be set on the optical path of the exposure light IL.

In FIG. 1, the exposure light IL transmitted through the reticle 13 is projected onto a wafer 19 as a substrate via a projection optical system 18 to project the pattern of the reticle 13 onto a projection magnification β (β is 1/4, (1/5 etc.) to form a reduced image. The wafer 19 is made of, for example, a semiconductor such as silicon or SOI.
(silicon on insulator) or the like, on which a photoresist is applied. The reticle 13 and the wafer 19 of this example correspond to the first object and the second object (substrate to be exposed) of the present invention, respectively. In the following description, the Z axis is taken parallel to the optical axis PAX of the projection optical system 18, the X axis is taken parallel to the plane of FIG. 1 in a plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of FIG. I do. In this case, the illumination area on the reticle 13 has an elongated slit shape in the Y direction, and the scanning direction of the reticle 13 and the wafer 19 at the time of exposure is the X direction.

In the present embodiment, the reticle 13 is held on a reticle stage 14, and the reticle stage 14 continuously moves the reticle 13 on a reticle base 15 in the X direction, and finely moves in the X, Y, and rotational directions. 1
3 is corrected. Moving mirror 16 fixed to end of reticle stage 14 and reticle stage drive system 1
The position and rotation angle of the reticle stage 14 are measured by the laser interferometer 7, and the reticle stage drive system 17 controls the operation of the reticle stage 14 based on the measured values. Reticle stage 14, Reticle base 1
The reticle stage system is composed of the second sub-chamber 32 having a high airtightness.
Is housed inside.

On the other hand, the wafer 19 is held on a wafer stage 20 via a wafer holder (not shown), and the wafer stage 20 continuously moves the wafer 19 on the wafer base 21 in the X direction. The step moves in the X and Y directions. The position and the rotation angle of the wafer stage 20 are measured by the movable mirror 22 fixed to the end of the wafer stage 20 and the laser interferometer in the wafer stage drive system 23, and based on the measured values, the wafer stage drive system 23 The operation of the wafer stage 20 is controlled. Further, based on information on the focus positions (positions in the direction of the optical axis PAX) at a plurality of measurement points on the wafer 19 measured by an auto focus sensor (not shown), the wafer stage 20 performs the auto focus method on the wafer 19.
By controlling the focus position and tilt angle of
During the exposure, the surface of the wafer 19 is continuously adjusted to the image plane of the projection optical system 18. A wafer stage system is constituted by the wafer stage 20, the wafer base 21, and the like. This wafer stage system is housed in a highly airtight box-shaped third sub-chamber 33.

At the time of exposure, when the exposure of one shot area on the wafer 19 is completed, the next shot area is moved to the scanning start position by the step movement of the wafer stage 20, and then the reticle stage 14 and the wafer stage 2 are moved.
0 is synchronously scanned in the X direction using the projection magnification β of the projection optical system 18 as the speed ratio, that is, the operation of scanning the reticle 13 and the shot area on the wafer 19 while maintaining the imaging relationship is a step.・ Repeated in the AND scan method. Thus, the pattern images on the reticle 13 are sequentially transferred to the respective shot areas on the wafer 19.

As described above, in the projection exposure apparatus of this embodiment, the gas in the space including the optical path of the exposure light IL is exposed to the exposure light I.
A supply / exhaust mechanism for replacing (purging) with a gas (purging gas) through which L passes is provided. That is, a part of the illumination optical system, the reticle stage system, and the wafer stage system respectively include sub-chambers 31, 32,
The space between the optical members of the projection optical system 18 is housed in the lens 33 and is a highly airtight lens chamber. A high-purity purge gas is supplied into the sub-chambers 31 to 33, and a high-purity purge gas is also supplied to each lens chamber in the projection optical system 18.

Further, the boundary between the first sub-chamber 31 and the upper part of the second sub-chamber 32, the boundary between the lower part of the second sub-chamber 32 and the upper part of the projection optical system 18, and the lower part of the projection optical system 18. Covers (e.g., bellows) 40-each having a certain degree of flexibility but not so much deforming are provided at the boundary with the upper part of the third sub-chamber 33.
42 are provided, and their boundaries are substantially sealed by the covers 40 to 42, so that the optical path of the exposure light is almost completely sealed. For this reason, there is almost no mixing of the gas containing the light absorbing substance from the outside into the optical path of the exposure light, and the attenuation of the exposure light can be extremely suppressed.

The supply / exhaust mechanism of this embodiment includes an exhaust device 35 including a vacuum pump and a recovery device 3 for recovering purge gas.
6. A storage device 37 for storing a high-purity purge gas, and an air supply device 38 for adjusting the temperature of the purge gas and supplying the purge gas to the outside.
And so on. The exhaust device 35 sucks the gas in the projection optical system 18 through the exhaust pipes 71A and 75B and the valve V4 as required until a predetermined vacuum state is obtained, and collects the sucked gas through the pipe 72. 36. The recovery device 36 controls the gas in the sub-chambers 31, 32, and 33 via an exhaust pipe with valves V11, V9, and V10 and an exhaust pipe 75A, respectively, by gas flow control using a substantially steady flow near the atmospheric pressure. The gas in the plurality of lens chambers of the projection optical system 18 is collected by gas flow control via the exhaust pipes 71A and 75B and the valve V3. In the case of gas flow control, it is necessary to supply a purge gas having a flow rate substantially equal to the flow rate of the gas to be exhausted. The gas in the plurality of lens chambers of the projection optical system 18 of the present example can be exhausted by any of a suction method with a reduced pressure to a certain degree of vacuum and a gas flow control method without a reduced pressure.

The recovery device 36 separates the purge gas from the recovered gas and the gas supplied from the exhaust device 35, temporarily accumulates the separated purge gas, and if necessary accumulates the accumulated purge gas. The gas is supplied to the air supply device 38 via the pipe 73. The accumulating device 37 supplies the purge gas compressed or liquefied therein to a high pressure, as necessary, to the air supply device 38 via a pipe 74 provided with a valve V2. The air supply device 38 is connected to the pipe 7
3 and 74, the temperature of the purge gas supplied was adjusted, and the HEPA filter (high efficiency particulate a) was used.
The above-mentioned light-absorbing substances and the like are removed from the purge gas by filter parts 68A and 68B including a dust filter such as an ir-filter) and a chemical filter for removing the above-mentioned light-absorbing substances containing a trace amount of organic substances.

The material removed by the filter sections 68A and 69B may be a substance which adheres to the optical element used in the projection exposure apparatus and causes clouding thereof, or a substance floating in the optical path of the exposure beam and the illumination optical system. A substance that changes the transmittance (illuminance) or the illuminance distribution of the system or the projection optical system 18 or a substance that adheres to the surface (photoresist) of the wafer 19 and deforms the pattern image after the development processing is also included. . As a part of the filters in the filter sections 68A and 68B, an activated carbon filter (for example, Gigasorb (trade name) manufactured by Nitta Corporation), a zeolite filter, or a filter combining these can be used. This allows
Silicon-based organic substances such as siloxane (a substance having an Si-O chain as an axis) or silazane (a substance having an Si-N chain as an axis) are removed.

The purge gas that has passed through the filter section 68A is supplied into the sub-chambers 31, 32, and 33 via an air supply pipe 69A with a valve V1 and branch air supply pipes with valves V7, V5, and V6, respectively. The purge gas that has passed through the filter section 68B is supplied to a plurality of lens chambers in the projection optical system 18 via an air supply pipe 69B having a valve V8 and an air supply pipe 70A having a plurality of branch pipes. In this case, the valves V1 to V11 are valves that can be opened and closed electromagnetically, and their opening and closing operations are controlled independently of each other by a control device 34 composed of a computer, and the exhaust device 35, the recovery device 36, and the storage device The operation of the air supply device 37 and the air supply device 38 is also controlled by the control device 34. Then, the supply operation of the purge gas from the air supply device 38 and the selective opening / closing operation of the valves V <b> 1, V <b> 5 to V <b> 8 allow any one of the inside of the sub-chambers 31 to 33 and the plurality of lens chambers in the projection optical system 18. On the other hand, the purge gas can be supplied at a desired flow rate.

The first sub-chamber 31, the second sub-chamber 32, the projection optical system 18, and the third sub-chamber 3
Oxygen concentration sensors S1 to S4 for detecting the concentration of oxygen gas in the light-absorbing substance are respectively installed inside 3, and the oxygen concentration is continuously measured at a predetermined sampling rate. The interior of the projection optical system 18 is divided into a plurality of lens chambers as described later, and oxygen concentration sensors S3A to S3F are provided in most of the lens chambers (see FIG. 2).
Is installed. Accordingly, the oxygen concentration sensor S3 in FIG.
Represents the plurality of oxygen concentration sensors S3A to S3F. Examples of the oxygen concentration sensors S1 to S4 include a galvanic cell type oxygen concentration meter, a polarographic type oxygen concentration meter, a zirconia type oxygen concentration meter,
Alternatively, a yellow phosphorus emission type oxygen sensor or the like can be used. The measured values of the oxygen concentration are supplied to the control device 34,
If any one of the oxygen concentration sensors S1 to S4 detects an oxygen gas having a predetermined allowable concentration or higher, the control device 3
According to the command of 4, the gas in the space where the oxygen gas is detected is replaced with the purge gas until the oxygen gas concentration becomes equal to or lower than the allowable concentration.

Next, the projection optical system 18 of this embodiment will be described in detail. FIG. 2 is a cross-sectional view showing the internal configuration of the projection optical system 18 in FIG. 1. In FIG. 2, the projection optical system 18 including the catadioptric optical system of the present embodiment uses a primary image (a primary image of the reticle 13 pattern). A first image forming optical system for forming an intermediate image I, and a wafer 1 as a photosensitive substrate at a reduced magnification of a secondary image of a reticle pattern based on light from the primary image I.
9 and a second imaging optical system for forming the optical system on the second imaging optical system 9.

The first image forming optical system includes, in order from the reticle side, a first lens group G1 having a positive refractive power, an aperture stop (not shown), and a second lens group G2 having a positive refractive power. Have been. An aperture stop 25 is arranged near an optical Fourier transform plane for the pattern surface of the reticle 13 between the first lens group G1 and the second lens group G2, that is, near the pupil plane PP of the projection optical system 18. Optical axis P at the center of
A circular center shielding plate CS centering on AX is installed. The central shielding plate CS is a member for shielding a light beam passing through a predetermined area around the optical axis PAX in the vicinity of the pupil plane PP. It is desirable to be arranged at a position shifted by a predetermined amount toward the reticle 13 along the PAX.

The first lens group G1 includes, in order from the reticle side, a positive meniscus lens L11 having an aspherical convex surface facing the reticle side, and a positive meniscus lens L12 having an aspherical convex surface facing the reticle side. And a positive meniscus lens L13 having an aspherical concave surface facing the wafer side. The second lens group G2 includes, in order from the reticle side, a biconcave lens L21 having a reticle side surface formed into an aspherical shape, a biconvex lens L22 having a reticle side surface formed into an aspherical shape, and a wafer side A positive meniscus lens L23 having an aspherical convex surface facing the surface thereof, and a positive meniscus lens L24 having an aspherical concave surface facing the wafer side.
It is composed of

On the other hand, the second image forming optical system has a surface reflecting surface R1 having a concave surface facing the wafer side in order from the reticle side, and a circular opening portion 61 centered on the optical axis PAX at the center. A mirror M1, a lens component L2, and a sub-mirror M2 having a reflecting surface R2 provided on the lens surface on the wafer side are provided. A circular opening centered on the optical axis PAX is provided at the center of the sub-mirror M2. A part 62 is formed. According to another viewpoint, the sub-mirror M2 and the lens component L2 constitute a back reflector, and the lens component L2 constitutes a refraction part of the back reflector. In this case, the imaging magnification of the first imaging optical system is β1,
Assuming that the imaging magnification of the imaging optical system is β2, for example,
It is desirable that the relationship of 0.7 <| β1 / β2 | <3.5 is satisfied.

In the example of FIG. 2, the imaging magnification β1 of the first imaging optical system is 0.6249, the imaging magnification β2 of the second imaging optical system is 0.4000, and the projection from the reticle 13 to the wafer 19 is performed. The magnification β is 0.25 (１ ／ times).
An example of detailed lens data of the projection optical system 18 shown in FIG. 2 is disclosed in Japanese Patent Application No. 10-370143 filed by the present applicant.

All the optical elements (G1, G2, M1, L2, M2) constituting the projection optical system 18 are arranged along a single optical axis PAX. Further, the primary mirror M1 is arranged near the position where the primary image I is formed, and the secondary mirror M2 is
9 is arranged in the vicinity. Also, in this example,
An image forming light beam composed of exposure light IL from the pattern of the reticle 13 forms a primary image (intermediate image) I of the reticle pattern via the first image forming optical system, and the image forming light beam from the primary image I is The light is reflected by the secondary mirror M2 via the opening 61 of the primary mirror M1 and the lens component L2. The light reflected by the sub-mirror M2 passes through the lens component L2 and is reflected on the surface reflection surface R1 of the primary mirror M1.
Then, a secondary image of the reticle pattern is formed at a reduced magnification on the surface of the wafer 19 via the lens component L2 and the opening 62 of the secondary mirror M2.

As described above, the projection optical system 18 has a primary mirror M1 and a secondary mirror M1 having openings 61 and 62 (portions where no physical through-hole or reflection surface is formed) near the optical axis PAX. Since M2 is included, the imaging optical path originating from an arbitrary point on the reticle 13 and reaching the wafer 19 is substantially shielded (centered) in the vicinity of the pupil plane between the primary image I and the wafer 19. Shielded). However, if there is a light beam passing near the optical axis PAX in the vicinity of the pupil plane, this light beam is not reflected by the primary mirror M1 and the secondary mirror M2, but simply passes through the openings 61 and 62 and passes through the wafer. 19 and is superimposed on the original projected image.

The position occupied by the superimposed light in the entire image-forming light flux changes according to the position on the reticle 13. In this case, since the characteristics of the image formed on the wafer 19 change according to the position on the reticle 13, if the fineness or integration degree of the pattern of the reticle 13 further improves in the future, the amount of change of the image will increase. It may exceed the allowable range. Therefore, in this example, the pupil plane PP of the projection optical system 18 formed between the reticle 13 and the primary image (intermediate image) I
Is disposed near the center shield plate CS as described above. The center shielding plate CS can also be called a center shielding stop. The central shielding plate CS shields each light beam passing through the pupil plane PP with the primary mirror M1 and the secondary mirror M2 (opening 6).
1, 62), and a size that does not block an effective imaging light flux. Thus, the central shielding portion of each light beam can be uniformly set as the center portion of the light beam, and the image does not change depending on the position.

In this embodiment, the projection optical system 18 is
Fluorite is used for all refractive optical components (lens components) to be formed.
Chi CaF_TwoThe crystal is used. Also, as the exposure light
F _TwoThe oscillation center wavelength of the laser light is 157.6 nm.
Color for light with a wavelength range of 157.6 nm ± 10 pm
Aberrations are corrected, and spherical aberration, astigmatism,
Various aberrations such as distortion and distortion are also well corrected. Change
In addition, the surface change of the reflection surface of the primary mirror M1 due to the temperature change is suppressed.
In order to maintain good imaging performance, the surface
The support member for supporting the launch surface R1 is provided with a linear expansion coefficient of 3 ppm / ° C.
The following substances, for example Titanium Silicate Glass
ate Glass). With titanium silicate glass
For example, Corning ULE (Ultra Low Expa
nsion: trade name) can be used.

The projection optical system 18 of this embodiment is of a straight cylinder type in which all optical elements constituting the catadioptric optical system are arranged along a single optical axis PAX. In addition to this, it is possible to design and manufacture a lens barrel by using a technique that is an extension of the conventional straight-tube type refraction system, and it is possible to achieve high accuracy without difficulty in manufacturing.

That is, in this example, the lenses L11 to L13 and L21 to L24 constituting the first imaging optical system are respectively held on the upper inner surface of the lens barrel 30 via the lens frames, and the second imaging optical system is The constituent primary mirror M1 and lens component L2 (sub-mirror M2) are held on the lower inner surface of the lens barrel 30 via supporting portions M1a and M2a, respectively.
The optical path of the exposure light IL up to 24 is a lens chamber 76A to 76C, 76G, 76 which is a space closed by two adjacent lenses, these lens frames, and the lens barrel 30 in order.
D, 76F. However, the lenses L21, L
Since the lens room 76G, which is a space sealed by the lens frame 22 and these lens frames, is an extremely narrow space, the lens room 76G
G communicates with a lens chamber 76D below it through a plurality of air supply / exhaust vents 77 provided in the lens frame.
In other words, the very narrow lens chamber 76G is substantially integrated with the fairly wide lens chamber 76D adjacent thereto.

Further, the lens component L2
The optical path of the exposure light IL to (the secondary mirror M2) is
4. The lens passes through a lens chamber 76E which is a space sealed by the lens frame, the lens component L2, and the lens barrel 30. The lens chambers 76A to 76F in the projection optical system 18 have high airtightness and are strictly isolated from each other so that gas inside them cannot flow. However, exceptionally, only the narrow lens chamber 76G is substantially integrated with the adjacent lens chamber 76D.
You may be isolated from D. The lens chambers 76A to 76F in the lens barrel 30 of the projection optical system 18 correspond to the hermetic chamber of the present invention. Although the lens barrel 30 in FIG. 2 is integrally represented, the lens barrel 30 may be actually configured by a plurality of lens barrels arranged in series along the optical axis PAX.

In FIG. 2, supply ports 50A1 to 50A5 for supplying purge gas are provided to the lens barrels 30 on the side surfaces of a plurality of lens chambers 76A to 76F inside the projection optical system 18.
A7 and exhaust ports 51A1 to 51A7 for exhausting a gas containing a light absorbing substance are provided, and an air supply port 50A1 is provided.
The branch pipe of the air supply pipe 70A is connected to each of the exhaust pipes 51A1 to 51A7.
Are connected. The air supply pipe 71A is the air supply pipe 69
B, and is connected to the air supply device 38 of FIG.
A is connected to the exhaust device 35 and the recovery device 36 of FIG. 1 via the exhaust pipe 75B. Also, the lens chambers 76A to 76A
Oxygen concentration sensors S3A to S3F are arranged in 6E, respectively, and the measurement values of the oxygen concentration sensors S3A to S3F are supplied to the control device 34 in FIG. In this case, although the oxygen concentration sensors are not provided in the relatively narrow lens chambers 76F and 76G, for example, a space for disposing the sensors is provided in the lens frame on the side surface, and these lens chambers 76F and 76G are provided.
An oxygen concentration sensor may be arranged on each of F and 76G.

In this case, the interior of the lowermost lens chamber 76E of the projection optical system 18 has a primary mirror M having an opening 61 at the center.
It is almost divided into two by one. Therefore, in order to prevent the gas containing the light absorbing substance from locally staying in the lens chamber 76E, the gas supply port 50A5 and the gas discharge port 51A are provided above the primary mirror M1.
5, and an air supply port 50A6 and an exhaust port 51A6 are also provided below the primary mirror M1. As for the oxygen gas concentration sensor, oxygen concentration sensors S3E and S3F are provided above and below the primary mirror M1, respectively. in this way,
It is desirable that the number of air supply ports, exhaust ports, sensors (such as oxygen concentration sensors) for detecting light-absorbing substances, etc., installed in one lens chamber be appropriately adjusted according to the structure of the airtight chamber.

The exhaust ports 5 of the lens chambers 76A to 76E
1A1 to 51A6 are provided at positions lower than the air supply ports 50A1 to 50A6 arranged to face each other. However, since the lens chamber 76F is narrow, the exhaust port 51A
The height of 7 is the same as that of the air supply port 50A7. When a gas having a relatively smaller molecular weight than the light-absorbing substance such as nitrogen or helium is supplied as the purge gas, an exhaust port such as this example is used to efficiently exhaust the gas containing the light-absorbing substance by the flow of the purge gas. 51A1 to 51A6 are connected to the air supply port 5
It is desirable to provide below 0A1-50A6.
Conversely, when a gas having a relatively higher molecular weight than the light absorbing substance is supplied as a purge gas, the exhaust ports 51A1 to 51A
6 is preferably provided above the air supply ports 50A1 to 50A6.

When a sensor (oxygen concentration sensors S3A to S3F) for detecting a light-absorbing substance is installed, if the molecular weight of the light-absorbing substance to be detected is relatively larger than the purge gas, a corresponding airtight chamber (lens) Room 76A ~
76E), or in a space where the hermetic chamber is divided as much as possible. Conversely, if the molecular weight of the light-absorbing substance to be detected is relatively smaller than that of the purge gas, it is desirable to install the sensor as high as possible in the airtight chamber or the divided space.

In this embodiment, in order to increase the transmittance of the exposure light IL at the time of exposure, the lens chambers 76A to 76A in the projection optical system 18 are used.
F (the lens chamber 76G is included in the lens chamber 76D)
The inside gas is replaced with a purge gas through which the exposure light IL passes. The exposure light IL of this example is an F ₂ laser (wavelength: 157 nm)
Therefore, a nitrogen gas can be used as the purge gas, but a helium gas or another rare gas may be used when importance is placed on the stability of the imaging characteristics and the cooling property.

The purge gas in each of the lens chambers 76A to 76F can be supplied even if the same purge gas is supplied to each of the lens chambers.
A different type of barge gas may be supplied to each lens chamber.

When the exposure operation is started, FIG.
The controller 34 replaces the gas inside the sub-chambers 31, 32, 33 with a purge gas by, for example, the above-described gas flow control method. Then, the projection optical system 18
As for the control device 34, the valves V3, V
8, the valve V4 is opened, and the exhaust device 35 is operated to reduce the pressure inside the lens chambers 76A to 76F in the projection optical system 18 in FIG. Thereafter, the exhaust device 35 is stopped, the valve V4 is closed, the valve V8 is opened, and the air supply device 38 is operated to fill the inside of the lens chambers 76A to 76F with the purge gas to the atmospheric pressure. Thereafter, the oxygen concentration sensors S3A-
The oxygen concentration is typically measured as the residual concentration of the light absorbing substance by S3F, and the pressure reduction and the filling of the purge gas are repeated until the maximum value of the measured residual concentration becomes equal to or less than the allowable concentration.
Then, after the maximum value of the residual concentration becomes equal to or less than the allowable concentration, the control device 34 of FIG.
8. By controlling the opening / closing operation of V3 and the operation of the recovery device 36 and the air supply device 38, the maximum value of the residual concentration of the light-absorbing substance in the lens chambers 76A to 76F becomes less than the allowable concentration by the gas flow control method. Replacement (purge) is performed as described above.

At this time, as shown in FIG. 2, since the lens chambers 76A to 76F of the projection optical system 18 are independent of each other, the purge gas supplied from the air supply pipe 70A is supplied to the air supply port in the lens chamber 76A, for example. Exhaust port 51A from 50A1
1 flows smoothly toward each lens chamber 76.
A purge gas flows through the exhaust ports 51A1
It flows smoothly toward 51A7. As a result, the lens room 7
The gas containing the light absorbing material mixed into the 6A-76F or the degassing containing the light absorbing material generated inside the gas flows from the exhaust ports 51A1 through 51A7 along the flow direction of the purge gas supplied from the air supply ports 50A1 through 50A7, respectively. Exhaust pipe 7
After being exhausted to the 1A side, the inside of the lens chambers 76A to 76F is filled with a high-purity purge gas. Accordingly, the transmittance of the exposure light IL passing through the projection optical system 18 is maintained at a high level, and the illuminance (pulse energy of the pulse light) of the exposure light IL incident on the wafer 19 is increased. Since the exposure time can be shortened, the throughput is improved. Further, since the flow of gas in the projection optical system 18 is stabilized and the fluctuation of the refractive index distribution is reduced, the imaging characteristics of the projection image transferred onto the wafer 19 are stably maintained, and the projection image is finally formed. The line width uniformity of the circuit pattern is improved.

Even if the degassing containing the light absorbing substance occurs in the widest lens chamber 76E, the degassing does not flow into the adjacent lens chamber 76F or the like, and the inside of the adjacent lens chamber 76F or the like is contaminated. It is not done. Further, since the residual concentration of the light absorbing substance in the lens chamber 76E is controlled by the oxygen concentration sensors S3E and S3F, the concentration of the light absorbing substance in the lens chamber 76E does not exceed the allowable concentration.

As sensors for detecting light-absorbing substances as impurities, oxygen concentration sensors S3A to S3F are used.
Besides ozone (O ₃ ), water vapor, and carbon dioxide (CO
Sensors for detecting hydrocarbon-based molecules such as ₂ ) may be provided in the lens chambers 76A to 76E, respectively. Further, these sensors may be provided in the lens chambers 76F and 76G. In this case, the concentration of a plurality of types of light-absorbing substances is measured in each lens chamber, and the purge gas is supplied such that the maximum value of the residual concentration of each light-absorbing substance falls below a predetermined allowable concentration. Further, the allowable concentration of the light absorbing substance may be set to a different value for each of the lens chambers 76A to 76E (further, 76F and 76G). For example, the lens chambers 76B and 7 have a short optical path of the exposure light IL.
By setting the allowable density in the lens chambers 76A and 76E having a longer optical path than that of the projection optical system 1C, the projection optical system 1
8 can maintain a high transmittance for the exposure light IL as a whole.

Further, instead of the sensor for detecting the concentration of the light-absorbing substance or together with the sensor for detecting the concentration of the light-absorbing substance, sensors for measuring the concentration of the purge gas are provided in the lens chambers 76A to 76E (further, Lens room 76
F, 76G). In this configuration, the purge gas concentration may be directly measured in each lens chamber, and the purge gas may be supplied such that the minimum value of the measured value is equal to or higher than a predetermined allowable level. Also in this configuration, the allowable levels of the concentration of the purge gas in the plurality of lens chambers may be set to different values.

Although each of the lens chambers 76A to 76G in the projection optical system 18 of this embodiment has extremely high airtightness, the projection optical system 18 corrects various aberrations of the projection optical system 18. There is also a lens driving mechanism (not shown) for performing such operations, so that outside air may gradually enter into the lens chamber via the fixing members of these lens driving mechanisms. Further, although very small, outgassing containing the light absorbing substance from the lens driving mechanism or the like may escape into the lens chamber. Since the amount of such outside air and the amount of degassing tend to increase substantially in proportion to the internal surface area of the corresponding lens chamber, in this example, the internal surface area of each of the lens chambers 76A to 76G is also taken into consideration. It is desirable to control at least one of the supply amount of the purge gas and the exhaust amount. Specifically, the flow rate of the purge gas may be increased in a lens chamber having a larger internal surface area.

When the projection optical system 18 is provided with a lens driving mechanism for correcting various aberrations including the imaging characteristics of the projection optical system, an exhaust port of a lens chamber provided with the lens driving mechanism is provided. What is necessary is just to provide in the vicinity of a lens drive mechanism or to include a lens drive mechanism. With this configuration, there is no possibility that outside air enters the lens chamber via the fixing member or the like of the lens driving mechanism. In addition, impurities such as organic substances generated from parts constituting the lens driving mechanism are
There is no danger of entering the lens chamber.

Next, a second embodiment of the present invention will be described with reference to FIG. In this example, a plurality of exhaust ports for exhausting gas from the hermetic chamber and a plurality of air supply ports for supplying purge gas to the hermetic chamber are provided. A mechanism for replacing the gas in the lens chamber 76A with the purge gas will be described. FIG. 3 is a cross-sectional view showing a lens chamber 76A of the projection optical system 18 as an airtight chamber of the present embodiment. In FIG. 3, the lens barrel 30 surrounding the lens chamber 76A has approximately 6 optical axes.
Three exhaust ports 51B1, 51B2, 51B3 at 0 ° intervals
Are formed, and three air supply ports 50B1, 50B2, and 50B3 are formed so as to be substantially symmetrically opposed to these exhaust ports. The exhaust ports 51B1 to 51B3 are connected to the exhaust pipe 75B (the exhaust device 35 and the recovery device 36) of FIG. 1 via the exhaust pipes 71B1 to 71B3, respectively.
The air supply ports 50B1 to 50B3 are connected to the air supply pipes 70B1 to 70B1, respectively.
Air supply pipe 69B of FIG. 1 (air supply device 38) via 70B3
The lens chamber 76A is connected to the exhaust ports 51B1 to 51B.
The internal gas is exhausted through B3, and the purge gas is supplied through air supply ports 50B1 to 50B3.

In this embodiment, the air supply ports 50B1 to 50B3
Valves VB1 to VB3 and VB4 to VB6, which can be opened and closed, are installed near the exhaust ports 51B1 to 51B3, respectively, and supply ports 50B1 to 50B3 and exhaust ports 51 are provided.
B1 to 51B3 can be opened and closed independently. Further, an oxygen concentration sensor (not shown) for detecting oxygen as a light-absorbing substance, and a sensor for detecting another light-absorbing substance as necessary are provided in the lens chamber 76A. The exhaust from the lens chamber 76A and the supply of the purge gas to the lens chamber 76A are performed so that the residual concentration becomes equal to or lower than the allowable concentration.

In this embodiment, as an example, when the use of the projection exposure apparatus in FIG. 3 starts, if the concentration of the light absorbing substance in the lens chamber 76A is high, the valves VB1 to VB
B3 is closed, valves VB4 to VB6 are opened, and exhaust port 51 is opened.
The gas is exhausted from B1 to 51B3 and the lens chamber 76A is exhausted.
The inside is evacuated. Thereafter, the valves VB4 to VB6 are closed, the valves VB1 to VB3 are opened, and the air supply ports 50B1 to 50B1 are opened.
By supplying the purge gas into the lens chamber 76A through 50B3, the inside of the lens chamber 76A can be efficiently replaced with a high-purity purge gas.

After replacing the gas in the lens chamber 76A with the purge gas, the valves VB1 to VB6 are closed and the exposure is performed while maintaining the lens chamber 76A in a highly airtight state. Thereafter, only when the residual concentration of the light-absorbing substance such as oxygen detected by a sensor (not shown) may exceed the allowable concentration, the valves VB1 to VB6 are opened to open the exhaust ports 51B1 to 51B1.
Exhaust of gas from 51B3 and air supply ports 50B1-50
The purge gas is supplied via B3. As a result, the purge gas supplied from the air supply ports 50B1 to 50B3 is
Each flows through the inside of the lens chamber 76A along the flow path indicated by the dotted line to the corresponding exhaust ports 51B1 to 51B3,
At that time, the gas containing the light absorbing substance is also exhausted.

In this embodiment, the supply / exhaust mechanism is more complicated than in the first embodiment, but the valve VB1 provided near the intake ports 50B1 to 50B3 and the exhaust ports 51B1 to 51B3 is provided.
To VB6, the airtight state of the lens chamber 76A can be increased.
When the concentration of the light absorbing substance in A is high, the lens chamber 76
A can be efficiently replaced with a purge gas. When an expensive gas such as helium gas is used as the purge gas, the concentration of the light-absorbing substance in the lens chamber 76A may exceed the allowable concentration, or the concentration of the purge gas may be lower than a predetermined allowable level. It is also possible to open the valves VB1 to VB6 and perform purging only when there is a risk of becoming. Thereby, the operation cost of the projection exposure apparatus can be reduced.

Note that, in the embodiment of FIG.
Although three B1 to 51B3 and three air supply ports 50B1 to 50B3 are provided, two or four or more exhaust ports and air supply ports may be provided respectively. Further, the installation positions of the valves VB1 to VB6 are set to positions as close as possible to the inner wall of the lens barrel 30 in order to reduce irregularities in the lens chamber 76A and prevent the light absorbing substance as impurities from staying in the lens chamber 76A. It is desirable to do. Further, in order to more efficiently exhaust the gas containing the light absorbing substance and supply the purge gas, the distal ends of the exhaust pipes 71B1 to 71B3 (the exhaust port 51B).
1 to 51B3) and the distal end portions (air supply ports 50B1 to 50B3) of the air supply pipes 70B1 to 70B3, respectively.
It is desirable to be within 6A.

Further, when the gas containing the light absorbing substance is prevented from locally staying in the lens chamber and the lens chamber is efficiently replaced with the purge gas, the air supply ports 50B1 to 50B
Open the valves VB1 to VB3 of B3 and set the exhaust port 5
The opening and closing of valves VB4 to VB6 of 1B1 to 51B3 may be controlled at predetermined time intervals. For example, the valves VB5 and VB6 are closed, the valve VB4 is opened, and the gas in the lens chamber is evacuated.
The valve VB6 is closed, the valve VB5 is opened, and the gas in the lens chamber is exhausted.
B5 may be closed and the valve VB6 may be opened to exhaust the gas in the lens chamber.

The opening / closing control of the valves VB4 to VB6 of the exhaust ports 51B1 to 51B3 is not limited to this configuration, and two valves may be simultaneously opened and one valve may be closed.

Next, a third embodiment of the present invention will be described with reference to FIG. In this example, the number of air supply ports and the number of exhaust ports are adjusted so that the purge gas can be more efficiently replaced. FIG. 4 is a cross-sectional view showing a lens chamber 76A of the projection optical system 18 of the present embodiment. In FIG. 4, a lens barrel 30 surrounding the lens chamber 76A is shown.
Has one air inlet 50C and five air outlets 51C1-
51C5 are formed at substantially equal angular intervals about the optical axis, a purge gas is supplied to the air supply port 50C via an air supply pipe 70C, and the exhaust pipes 71C1 to 51C5 are supplied from the exhaust ports 51C1 to 51C5.
The gas containing the light absorbing substance in the lens chamber 76A is exhausted through C1 to 71C5. At this time, the purge gas flows in the lens chamber 76A substantially along the flow path indicated by the dotted line. As described above, in this example, the number of the air supply ports 50C for flowing the purge gas and the exhaust ports 51C1 to 51C5
And the number of installations are different from each other.

The method of supplying and exhausting the purge gas includes a method in which the purge gas is pressurized on the supply side and flows into an airtight chamber (hereinafter, referred to as a “supply and pressurization method”), and a method in which the gas is released on the exhaust side. There is a method in which the pressure is reduced to suck the gas in the hermetic chamber (hereinafter, referred to as an “exhaust pressure reducing method”). In this example, it is assumed that the purge is performed by the former air supply and pressurization method, and the purge gas is supplied into the lens chamber 76A by pressurization, and the gas in the lens chamber 76A is supplied by indirect pressurization. Since the air is exhausted, the number of air inlets is reduced (the total cross-sectional area of the air inlets in the lens chamber 76A is reduced).
By increasing the number of exhaust ports (to increase the total sectional area of the exhaust ports in the lens chamber 76A), purging can be performed more efficiently. Therefore, in the embodiment of FIG. 4, one air supply port 50C and one exhaust port 51C1 are provided.
Although five to 51C5 are provided, two or more air supply ports may be provided, and the number of exhaust ports may be provided more than the number of the air supply ports.

Conversely, when purging is performed by the exhaust pressure reduction method, the purge gas can be efficiently replaced by setting the number of air supply ports to be greater than the number of exhaust ports. Note that, in this example as well, valves that can be opened and closed are respectively provided near the air supply port and the exhaust port, and when the concentration of the light-absorbing substance increases or the concentration of the purge gas decreases in the lens chamber 76A. Only the purge gas may be supplied.

Next, a fourth embodiment of the present invention will be described with reference to FIG. At the time of maintenance of the projection exposure apparatus, the work may be performed by opening the airtight chamber inside the illumination optical system or the projection optical system to the air (atmosphere) in the clean room. A large amount of air enters the air. After such work, when performing exposure with the airtight chamber closed again, if a gas having a very small molecular weight compared to air, such as helium gas, is used as a purge gas, the molecular weight of helium gas and the molecular weight of air will be reduced. Due to the difference from the (average molecular weight), the helium gas tends to be unevenly distributed, for example, in the upper part of the lens chamber of the projection optical system as an airtight chamber, and air containing the light absorbing substance tends to stay in the lower part of the lens chamber. Therefore, in the present embodiment, the supply port and the exhaust port are provided so as to eliminate the bias of the distribution of the purge gas due to such a difference in molecular weight.

FIG. 5 is an end view along a longitudinal section showing a lens chamber 76A of the projection optical system 18 of this embodiment. In FIG. 5, an air supply port 50D is provided in the lens barrel 30 above the lens chamber 76A.
1, 50D2 are formed, and exhaust ports 51D1, 51D2 are formed in the lens barrel 30 below the lens chamber 76A.
0D1 and 50D2 are connected to air supply pipes 70D1 and 70D2 for supplying a purge gas, and have exhaust ports 51D1 and 51D2.
D2 is an exhaust pipe 71 for exhausting a gas containing a light absorbing substance.
D1 and 71D2. In addition, air supply port 50D
Three or more pairs of 1, 50D2 and exhaust ports 51D1, 51D2 may be provided at substantially equal angular intervals about the optical axis.

In this embodiment, the purge gas flowing in the air supply pipes 70D1 and 70D2 flows into the lens chamber 76A from the air supply ports 50D1 and 50D2, and the gas containing the light absorbing material in the lens chamber 76A is discharged to the exhaust port 51D1. , 51D2 to the exhaust pipes 71D1, 71D2. Similarly, when a gas having a slightly smaller molecular weight (average molecular weight) than air, such as nitrogen gas or neon gas, is used as a purge gas, the exhaust ports 51D1, 51D2 are connected to the air supply ports 50D1, 50D2 as shown in FIG. It is good to arrange it lower than. When a gas having a small molecular weight such as helium gas is used as the purge gas, the purge gas is supplied from the upper portion of the lens chamber 76A because the purge gas tends to move upward as described above. By exhausting air having a high molecular weight (gas containing a light absorbing substance) from the lower part of the lens chamber 76A, it is possible to prevent the light absorbing substance from staying in the lower part of the lens chamber 76A,
The replacement with the purge gas can be performed more efficiently.

Conversely, when a gas having a molecular weight larger than that of air, such as argon gas or krypton gas, is used as the purge gas, the purge gas is introduced from the lower part of the airtight chamber, and the gas inside the airtight chamber is removed from the upper part of the airtight chamber. It is desirable to be configured to exhaust air. That is, it is desirable to consider the positions of the supply port and the exhaust port according to the magnitude of the molecular weight (density at the same atmospheric pressure) of the purge gas with respect to air. In this example, it is also possible to adopt a configuration in which an openable and closable valve is provided in the vicinity of the supply port and the exhaust port, or a configuration in which the number of the supply ports and the exhaust ports (the total cross-sectional area) are different. Of course.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a projection optical system 1 of the present example.
8 is an end view along a longitudinal section showing a lens chamber 76A of No. 8;
In FIG. 6, a substantially U-shaped air supply section 50E at the tip of an air supply pipe 70E for supplying a purge gas is provided with a lens barrel 30.
Is provided inside the lens chamber 76A through the through hole, and approximately U at the end of an exhaust pipe 71E for exhausting a gas containing a light absorbing substance.
The V-shaped exhaust part 51E also passes through the lens barrel 30 through the lens barrel 76.
A is installed inside A so as to face the air supply unit 50E. The air supply unit 50E and the exhaust unit 51E are respectively arranged along the inner surface of the lens barrel 30 so as not to block the exposure light, and the air supply unit 50E and the exhaust unit 51E are provided with a large number of small ventilation holes 50Ea and 51Ea, respectively. The purge gas is supplied and the internal gas is exhausted through these ventilation holes.

Further, the air holes 50E corresponding to the air supply port and the air exhaust port are provided so that the purge gas can easily flow in the portion where the light absorbing material easily stays, such as the uneven portion in the lens chamber 76A.
The positions of a and 51Ea are adjusted. By adjusting the shape, size, installation position, and the like of the air supply port and the exhaust port, the flow path of the purge gas in the lens chamber 76A can be finely adjusted. Therefore, even in a place where a large number of fine structures are installed such as inside the projection optical system and the light-absorbing substance tends to stay, the purge gas can be efficiently supplied, and the light-absorbing substance can be efficiently supplied. Can be prevented from deteriorating due to stagnation locally and uneven distribution in the lens chamber 76A.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. In each of the above-described embodiments, a method in which pipes such as an air supply pipe and an exhaust pipe are provided independently of the lens barrel of the projection optical system and the gas in the projection optical system is replaced with a purge gas (hereinafter referred to as a “small tube utilization method”). However, in this example, the lens barrel has a double structure composed of an inner cylinder and an outer cylinder, and a space between the inner cylinder and the outer cylinder (hereinafter, referred to as “inter-cylinder space”). (Hereinafter, referred to as “inter-cylinder space utilization method”).

FIG. 7 shows the lens chamber 76A of the projection optical system 18A when the inter-cylinder space utilization method is applied to the embodiment of FIG.
FIG. 8 is a cross-sectional view showing a lens chamber 76A of the projection optical system 18A of FIG. 7 surrounded by an inner cylinder 30A.
A is further surrounded by an outer cylinder 30B, and the space between the inner cylinder 30A and the outer cylinder 30B is symmetrically divided into a first inter-cylinder space 70F and a second inter-cylinder space 71F. Further, the air supply ports 50F1 to 50F1 are provided in the inner cylinder 30A in contact with the first inter-cylinder space 70F.
50F3 is formed, and exhaust ports 51F1 to 51F3 are formed in the inner cylinder 30A that is in contact with the second inter-cylinder space 71F. Valves VF1 to VF6 that can be opened and closed near air supply ports 50F1 to 50F3 and exhaust ports 51F1 to 51F3, respectively. Is installed. Then, the air supply device 38 shown in FIG.
9B, a purge gas is supplied to the inter-cylinder space 70F of FIG. 7, and the supplied purge gas is supplied to the supply ports 50F1 to 50F.
3 and the gas containing the light absorbing material in the lens chamber 76A is supplied to the lens chamber 76A through the exhaust ports 51F1 to 51F1.
51F3 flows to the inter-cylinder space 71F,
The gas in F is collected through the exhaust pipe 75B of FIG.
Alternatively, it is configured to be sucked by the exhaust device 35.

Similarly, FIG. 8 is a cross-sectional view showing the lens chamber 76A of the projection optical system 18B when the inter-cylinder space utilization method is applied to the embodiment of FIG. Inner tube 30A and outer tube 30B surrounding 18B lens chamber 76A
An air supply port 50G at the tip of an air supply pipe 70G for supplying purge gas is provided through an inter-cylinder space 71G between the inner cylinder 30G and five exhaust ports 51G1 to 51G in an inner cylinder 30A in contact with the inter-cylinder space 71G.
51G5 are formed. And the air supply device 3 of FIG.
8 to the air supply pipe 69B and the air supply pipe 70G of FIG.
0G), a purge gas is supplied into the lens chamber 76A, and the gas containing the light-absorbing substance in the lens chamber 76A is discharged from the exhaust port 5A.
The gas flows into the inter-cylinder space 71G through 1G1 to 51G5, and the gas in the inter-cylinder space 71G is sucked into the recovery device 36 or the exhaust device 35 via the exhaust pipe 75B in FIG.

In the method using a thin tube, the surface area of the inner wall of the supply pipe and the exhaust pipe is relatively small, and the conventional piping equipment having high airtightness and low leakage can be diverted. There are advantages to be able to supply. On the other hand, in the inter-cylinder space utilization method of the present embodiment, since the purge gas moves in the inter-cylinder space, a purge gas having substantially the same temperature as that in the inter-cylinder space can be supplied into the lens chamber 76A.
There is an advantage that adverse effects on exposure due to temperature fluctuations of the gas inside (such as fluctuations in the imaging characteristics of the projection optical system) can be reduced.

It is needless to say that the inter-cylinder space utilization method of this example can be applied to other embodiments other than the above-described embodiments of FIGS. In addition, the narrow tube utilization method and the inter-cylinder space utilization method are used in such a manner that a narrow tube utilization method is used for purging a predetermined airtight chamber and a cylinder space utilization method is used for purging other airtight chambers. It may be. In each of the above embodiments, the case where the gas in the lens chamber in the projection optical system is replaced with the purge gas has been described. However, the same effect can be obtained by similarly performing the replacement with the purge gas in the airtight chamber such as the illumination optical system. Of course, it can be obtained. The number, shape, and installation position of the air supply and exhaust ports are determined by the concentration (or total amount) of the light-absorbing substance allowed in the corresponding airtight chamber, the time allowed for replacement with the purge gas, and the airtight chamber. It is desirable to optimize according to the pressure resistance and the like of the member surrounding the.

It should be noted that the air supply mechanism or the exhaust mechanism is
It is not necessary to limit the system to only the system. For example, an oxygen gas supply device that supplies oxygen gas into the hermetic chamber may be provided separately from the supply device that supplies the purge gas. In this case, before the purge gas is filled into the hermetic chamber, oxygen gas is supplied into the hermetic chamber where the chemical contamination has occurred, and the exposure light is irradiated to excite the oxygen molecules to partially ozone the ozone. Ozone molecules can be reacted with contaminants adhering to the optical member or the like to separate the contaminants from the optical member or the like using the high activity of the ozone molecules, that is, ozone cleaning can be performed. When vacuum ultraviolet light is used as an exposure beam, ozone molecules are generated only in the vicinity of the optical member irradiated with vacuum ultraviolet light because vacuum ultraviolet light hardly passes through a gas containing oxygen molecules. Therefore, there is an advantage that ozone cleaning can be performed more efficiently. As described above, by further providing the oxygen gas supply device for supplying the oxygen gas, the cleaning degree of the optical member used in the projection exposure apparatus can be increased, and more accurate exposure can be performed.

Further, as described above, when a large amount of light-absorbing substance is present in the hermetic chamber before filling with the purge gas, it is possible to supply the purge gas after once evacuating by a vacuum pump or the like. This is the most efficient, and has the advantage that the apparatus does not need to be so high in strength when the purge gas is flown into the hermetic chamber after evacuating to eliminate the pressure difference with the outside.

In the above embodiment, the gas in the sub-chambers 31, 32 and 33 and the gas in the lens chamber in the projection optical system are collected by the collecting device 36, and the purge gas is separated from the collected gas. Then, the purge gas is supplied to the air supply device 38 again, but the present invention is not limited to this configuration. For example, the sub-chambers 32 and 33 have a shorter optical path length than the illumination optical system and the projection optical system, accommodate movable parts such as a wafer stage and a reticle stage, and frequently exchange wafers and reticles. Alternatively, the allowable concentration of the light absorbing substance may be set higher than that of the illumination optical system or the projection optical system. Therefore, as a modified example of the above embodiment, when the collected purge gas is recycled, the sub-chambers 31, 32, 3
3. Instead of supplying the collected purge gas to all of the projection optical systems, the recovery gas is collected in the sub-chambers 32 and 33 where the allowable concentration of the light-absorbing substance does not necessarily need to be set lower than in the projection optical system and the sub-chamber 31. The purge gas stored in the storage device 37 may be supplied to the sub chamber 31 and the lens chamber in the projection optical system.

In the above embodiment, the F ₂ laser beam was used as the exposure beam. However, for example, an ArF excimer laser beam (wavelength 193 nm), Kr
₂ laser beam (wavelength 147 nm), or Ar ₂ laser beam (wavelength 126 nm) exposure apparatus that uses such, and even application of the present invention to an exposure apparatus that uses vacuum ultraviolet light having a wavelength of about 200nm~100nm as exposure beam can do.

Further, for example, a wavelength of 248 is used as an exposure beam.
The present invention is also applicable to a case where a harmonic of a solid-state laser such as a YAG laser having an oscillation spectrum at any of nm, 193 nm, and 157 nm or in the vicinity thereof is used. As an exposure beam, a single-wavelength laser in the infrared or visible range oscillated from, for example, a DFB semiconductor laser or a fiber laser is doped with, for example, erbium (Er) (or both erbium and ytterbium (Yb)). The present invention is also applicable to a case where harmonics amplified by a fiber amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal are used.

Specifically, assuming that the oscillation wavelength of the single-wavelength laser is in the range of 1.51 to 1.59 μm, the eighth harmonic whose generation wavelength is in the range of 189 to 199 nm, or whose generation wavelength is 151 A 10th harmonic within the range of １５159 nm is output. In particular, the oscillation wavelength is set to 1.544 to 1.55.
When the wavelength is within the range of 3 μm, an eighth harmonic within the range of 193 to 194 nm, that is, ultraviolet light having substantially the same wavelength as the ArF excimer laser can be obtained, and the oscillation wavelength is 1.57 to 1.5.
When it is within the range of 8 μm, 10th harmonic within the range of 157 to 158 nm, that is, ultraviolet light having substantially the same wavelength as the F ₂ laser can be obtained.

Although the projection optical system of the above embodiment is a catadioptric system, the present invention can be applied to a case where a projection optical system composed of a refraction system or a reflection system is used.
Further, in each of the above embodiments, the present invention is applied to a step-and-scan type projection exposure apparatus, but the present invention is applied to a batch exposure type projection exposure apparatus such as a stepper, and furthermore, a projection optical system. It is apparent that the present invention can be applied to a proximity type exposure apparatus or the like which does not use the above.

In the illumination optical system and the projection optical system according to the above-described embodiments, the respective optical members are arranged in a support member or a lens barrel in a predetermined positional relationship, and the adjustment is performed. Is installed in a column (not shown). In addition to the assembly adjustment, the stage system, the laser interferometer, and the supply and exhaust mechanism for purging the inside of the apparatus are assembled and adjusted, and the respective components are electrically, mechanically, or optically connected. Thus, the projection exposure apparatus of the above embodiment is assembled. The work in this case is desirably performed in a clean room where the temperature is controlled.

Then, a device such as a semiconductor element is manufactured by subjecting the wafer exposed by the above-mentioned projection exposure apparatus to a developing step, a pattern forming step, a bonding step and the like. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention.

[0088]

According to the first exposure method of the present invention, the gas in the plurality of hermetic chambers smoothly flows from the supply port side to the exhaust port side, so that the gas containing impurities can be efficiently exhausted. Furthermore, even in the case where degas including impurities is generated from a certain hermetic chamber, it is possible to prevent the degas from flowing into or flowing back into another hermetic chamber. Accordingly, a substance having a large absorption with respect to the exposure beam can be efficiently removed, and the light amount of the exposure beam can be maintained high, so that the throughput in manufacturing a device such as a semiconductor element can be improved.

According to the second exposure method of the present invention,
It is easy to control the flow path and flow rate of the gas in the airtight chamber when supplying and exhausting air to the airtight chamber, and it is possible to prevent impurities having a large absorption for the exposure beam from locally staying in the airtight chamber. . Further, since the gas in the airtight chamber can be uniformly circulated in a certain direction, a substance having a large absorption for the exposure beam can be efficiently removed, and the light amount of the exposure beam can be maintained high.

Next, according to the exposure apparatus of the present invention, the exposure method of the present invention can be implemented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a projection optical system 18 in FIG.

FIG. 3 is a cross-sectional view showing a schematic configuration of a lens chamber 76A as an airtight chamber according to a second embodiment of the present invention.

FIG. 4 shows a lens chamber 76A according to a third embodiment of the present invention.
It is a cross-sectional view which shows schematic structure of.

FIG. 5 shows a lens chamber 76A according to a fourth embodiment of the present invention.
It is an end elevation along a longitudinal section which shows.

FIG. 6 shows a lens chamber 76A according to a fifth embodiment of the present invention.
It is an end elevation along a longitudinal section which shows.

FIG. 7 shows a lens chamber 76A according to a sixth embodiment of the present invention.
It is a cross-sectional view which shows schematic structure of.

FIG. 8 is a transverse sectional view showing another example of the sixth embodiment.

[Explanation of symbols]

1: exposure light source, 13: reticle, 18: projection optical system, 1
9: Wafer, 35: Exhaust device, 36: Recovery device, 37 ...
Storage device, 38: air supply device, 50A1 to 50A7: air supply port, 51A1 to 51A7: exhaust port, 70A: air supply pipe, 7
1A: exhaust pipe, 76A to 76G: lens chamber, M1: primary mirror, M2: secondary mirror, S1 to S4, S3A to S3F: oxygen concentration sensor, V1 to V11, VB1 to VB6: valve

Claims (9)

[Claims] Illuminating a first object with an exposure beam;
An exposure method for exposing a second object with an exposure beam having passed through a pattern of an object, wherein a plurality of hermetic chambers provided on an optical path of the exposure beam are each independently evacuated to gas containing impurities therein; An exposure method comprising controlling supply of gas through which a beam passes. Illuminating a first object with an exposure beam;
In an exposure method for exposing a second object with an exposure beam having passed through a pattern of an object, a gas containing impurities therein is exhausted through an exhaust port to an airtight chamber provided on an optical path of the exposure beam. An exposure method, comprising: supplying a gas through which the exposure beam passes through an air port, and providing a plurality of at least one of the exhaust port and the air supply port. 3. The exposure method according to claim 1, wherein the concentration of the impurities is monitored when the gas and the impurities are exhausted from inside the hermetic chamber. 4. The method according to claim 1, wherein an exhaust of the gas containing the impurities and a supply of a gas transmitted through the exposure beam are controlled in accordance with the surface area of the inner wall of the airtight chamber. 4. The exposure method according to claim 3. Illuminating a first object with an exposure beam;
An exposure apparatus for exposing a second object with an exposure beam having passed a pattern of an object, wherein a plurality of hermetic chambers provided on an optical path of the exposure beam are each independently evacuated to gas containing impurities therein and the exposure beam. An exposure apparatus comprising: a supply / exhaust mechanism configured to supply a gas through which air passes; and a densitometer that measures a concentration of the impurity in at least a part of the plurality of hermetic chambers. 6. illuminating a first object with an exposure beam;
An exposure apparatus for exposing a second object with an exposure beam having passed through a pattern of an object, wherein the exposure beam is transmitted through an airtight chamber disposed on an optical path of the exposure beam via an air supply port to the airtight chamber. An air supply pipe for supplying gas; an exhaust pipe for exhausting gas containing impurities from the hermetic chamber via an exhaust port; and a gas containing impurities inside the hermetic chamber via the exhaust pipe and the air supply pipe. And an air supply / exhaust mechanism for supplying air through which the exposure beam passes, wherein at least one of the exhaust port and the air supply port is provided in plurality. 7. The exposure apparatus according to claim 6, wherein the exhaust port and the air supply port are vertically displaced from each other. 8. The exposure apparatus according to claim 6, wherein an end of the air supply pipe and an end of the exhaust pipe are drawn into the hermetic chamber. 9. The exposure apparatus according to claim 5, wherein the airtight chamber is a lens chamber.