JPH10335236A - Aligner, optical cleaning method thereof and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner capable of keeping high optical performance by removing deposits such as water content or organic substances, every if they are deposited on the surface of an optical element. SOLUTION: This aligner comprises illumination optical systems 2-9 for illuminating a pattern on a projection master plate 10 which an optical beam from an optical source and a projection optical system 11 for imaging the means which has passed through the pattern on a photosensitive substrate 12, thereby exposing this substrate. A light diffuse means 13 is removably disposed in any one of spaces in the aligner, so as to expand an optical beam to the substrate 12, larger than the size of the optical beam for exposing the substrate 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention manufactures devices such as semiconductor devices such as LSIs, imaging devices such as CCDs, liquid crystal display devices, and thin-film magnetic heads (hereinafter collectively referred to as semiconductor devices). The present invention relates to a projection exposure apparatus for exposing a pattern on a projection original such as a mask (or reticle) to a photosensitive substrate such as a wafer in an optical lithography process, and particularly to an optical cleaning method.

[0002]

2. Description of the Related Art An optical lithography process is a main process for manufacturing a semiconductor device. With the increase in the degree of integration of a semiconductor device, a projection exposure apparatus used in the optical lithography process has made great progress. I have. The resolving power of the projection optical system mounted on the projection exposure apparatus is represented by the relationship of R = k × λ / NA, as is well known by the Rayleigh equation. Here, R is the resolution of the projection optical system,
λ is the wavelength of light for exposure, NA is the numerical aperture of the projection optical system, k
Is a constant determined by the process in addition to the resolution of the resist. As can be seen from the above equation, in order to realize the resolution required for the projection optical system in response to the high integration of semiconductor devices, the wavelength of the light source for exposure must be shortened, and the numerical aperture of the projection optical system must be reduced. Efforts to increase the NA are continuing. In recent years, KrF with an output wavelength of 248 nm
(Krypton fluoride) excimer laser as the light source for exposure,
Exposure apparatuses having a projection optical system having a numerical aperture of 0.6 or more have been commercialized, and exposure of fine patterns as large as 0.25 μm has been realized.

In particular, recently, as a light source following a KrF excimer laser, an ArF having an output wavelength of 193 nm is used.
(Argon fluoride) excimer lasers are attracting attention. If an exposure apparatus using this ArF excimer laser as an exposure light source can be realized, 0.18 μm to 0.13-0.
It is expected that fine processing down to 15 μm will be possible. The output wavelength of this ArF excimer laser (19)
In the wavelength range of 3 nm), materials that can be used as lenses are limited to two types at this stage, synthetic quartz glass and calcium fluoride (fluorite), from the viewpoint of transmittance. Therefore, as an optical material for this type of exposure apparatus, a material having sufficient transmittance and internal uniformity has been developed. In the case of synthetic quartz glass, the internal transmittance is 0.995 / cm or more, and calcium fluoride is used. Has reached negligible levels of internal absorption. When an ArF excimer laser is used as the light source for exposure, the material for the antireflection film coated on the surface of the optical material is also the output wavelength of the KrF excimer laser (248 nm).
The selection range is much narrower than that in the wavelength range of m), and the degree of freedom in design is greatly restricted. However, due to vigorous development efforts, the loss on each lens surface is 0.005.
The following levels have been realized.

[0004]

In an exposure apparatus using an ArF excimer laser as a light source, the characteristics of an optical member such as a lens are changed by heat generated by absorption of light by an optical material or an anti-reflection film, and this is a characteristic of an image forming characteristic. It becomes a fluctuation factor. Therefore, it is essential to achieve as high a transmittance as possible and to make the change in thermal characteristics as small as possible. However, in the case of light in the deep ultraviolet region of 200 nm or less, even if the absorption by the optical material and the antireflection film is reduced to the above level, when the optical components for the exposure apparatus are handled in the working environment in the air, Due to moisture and organic matter
The inventors' experiments have revealed that there is a problem that the transmittance of an optical component such as a lens rapidly decreases. The amount of absorption is, for example, 0.1 per lens.
01, which is larger than the absorption inside the optical component and the absorption by the antireflection film, and is the largest absorption factor.

A method of irradiating an ultraviolet ray as a method of cleaning the adhered matter adhered to the surface of the optical component is disclosed in, for example, Japanese Patent Application Laid-Open No.
This is known from 294705. However,
This technique relates to a method of cleaning a single optical component, and does not disclose a method of cleaning the entire optical component or a main part of the exposure device after the optical component is assembled as an exposure device. In addition, although a temporary cleaning effect is exhibited by the irradiation of ultraviolet light, the surface of the optical component is activated by the ultraviolet light, and when left in a normal working environment thereafter, it becomes easier to adsorb ambient moisture and organic substances. This has been found by experiments of the present inventors.

[0006] Therefore, even if the optical parts are cleaned with ultraviolet rays, it is practically impossible to construct a projection optical system by assembling optical parts such as lenses in a state where they are completely isolated from moisture and organic substances. Is not possible in
This is a major obstacle in realizing an optical system of an exposure apparatus for an ArF excimer laser. The present invention has been made in view of the above problems, and even when moisture and organic substances adhere to the surface of an optical element, these adhered substances are eliminated to maintain high optical performance. An object of the present invention is to provide an exposure apparatus, a method for cleaning an exposure apparatus, and a method for manufacturing a semiconductor device using the method.

[0007]

According to the present invention, when exposing a photosensitive substrate, the optical components of the exposing apparatus are self-cleaned by exposure light. Light cleaning is performed even when the cleaning is not performed, thereby solving the above problem. Further, in the present invention, the transmittance of the projection optical system or the illumination optical system or the illuminance distribution on the image plane of the projection optical system changes due to some factors during the exposure process, or the illumination coherency is changed during the exposure process. In such a case, the transmittance of the projection optical system or the illumination optical system and the illuminance distribution on the image plane of the projection optical system may change, so that the exposure operation is temporarily stopped not only before the exposure process but also during the exposure process. Then, light cleaning is performed to solve the above problem. That is, the exposure apparatus according to the present invention is provided with an optical unit that enlarges an optical path on the photosensitive substrate side from a predetermined space in the exposure apparatus to be larger than a light beam when exposing the photosensitive substrate. As the optical means, a light diffusing means is inserted into the predetermined space so that a light flux on the photosensitive substrate side with respect to a predetermined space in the exposure apparatus is larger than a light flux when performing exposure of the photosensitive substrate. It is preferable that they are removably arranged.

In addition, a shutter is disposed between the projection optical system and the photosensitive substrate so as to be insertable and removable so as to prevent the photosensitive substrate from being exposed by the cleaning light. The replacement of the photosensitive substrate, the alignment process, and the like can be performed in parallel, thereby making it possible to reduce the decrease in throughput due to the optical cleaning process. In addition, the surface on the side of the projection optical system of the shutter is used as a reflection surface, and the cleaning light that has passed through the projection optical system is reflected back to the projection optical system to further enhance the light cleaning effect. In addition, a transmitted light detector that measures the intensity of the light beam transmitted through the projection optical system is provided on the stage on which the photosensitive substrate is mounted, or the light beam reflected by the reflecting surface of the shutter surface is provided on a predetermined optical path in the exposure apparatus. A reflected light detector for measuring the intensity of the light, and an incident light detector for measuring the intensity of the light beam incident from the light source side on the optical path closer to the light source than the projection optical system. The system was configured to be able to measure the change in transmittance of the system, so that the start and end of the optical cleaning step could be determined based on the measurement result.

[0009]

FIG. 1 shows a first embodiment of the present invention. A light beam emitted from the ArF excimer laser 1 is shaped by the beam shaping optical system 2 into a shape corresponding to the shape of the incident surface of the fly-eye lens 3, then divided by the fly-eye lens 3, and emitted from the fly-eye lens 3. A plurality of secondary light sources are formed in the vicinity. The luminous flux from the multiple secondary light sources is
After the shape is restricted by the aperture stop 4, the front group 5 of the condenser lens
a is superimposed on the field stop 6 by the condenser lens rear group 5b to form uniform illumination light. The uniform illumination light formed on the field stop 6 is enlarged or reduced at a desired magnification by the front group 7 of the field stop image forming optical system and the rear group 9 of the field stop image forming optical system. Light up. The fine pattern formed on the mask 10 is projected and exposed by a projection optical system 11 onto a wafer 12 as a photosensitive substrate.

The front group 5a of the condenser lens, the rear group 5b of the condenser lens, the front group 7 of the imaging optical system and the rear group 9 of the imaging optical system
A condenser optical system for condensing light from a plurality of secondary light sources formed by a fly-eye lens 3 as an optical integrator and illuminating the mask 10 in a superimposed manner is configured. Note that the optical integrator is not limited to the fly-eye lens 3 configured by bundling a large number of rod-shaped optical elements, but may be an internal reflection type rod-shaped optical member. Without limitation, a plurality of optical integrators may be arranged in series.

As described above, when the wavelength is extremely short, such as the light beam emitted from the ArF excimer laser 1, the surfaces of the optical elements from the illumination optical systems 2 to 9 to the projection optical system 11 are exposed to air. Water and organic substances floating on the surface are attached and contaminated, causing a decrease in the transmittance of the refraction element and a decrease in the reflectance of the reflection element. These contaminants are self-cleaned by the light beam from the ArF excimer laser 1 when the light beam from the ArF excimer laser 1 passes to perform the exposure of the wafer 12. Go being. Therefore, in the present embodiment, prior to exposure of the wafer 12, a light beam from the ArF excimer laser 1 is passed through each optical element, so that contamination on the surface of the optical element can be cleaned.

First, the effect of cleaning is greater as the energy density is higher. Therefore, the projection optical system 11 can be used without considering the time loss required for attaching and detaching the mask 10.
If attention is paid only to the above cleaning, it is preferable to perform cleaning with the mask 10 removed. However, the numerical aperture of the projection optical system is configured so as to capture not only the light flux from the illumination optical system that has passed through the mask 10 but also the diffracted light diffracted by the mask 10. It is smaller than the numerical aperture of the optical system. Therefore, in a state where the mask 10 is removed, a portion that is not exposed to light is generated around the lens constituting the projection optical system, and a portion that is not cleaned is generated around the lens. Further, even when viewed only in a portion where light is irradiated, there is a possibility that an insufficiently cleaned portion may occur because the energy density is lower at the peripheral portion of the lens than at the central portion. Similarly, even if optical cleaning is performed with the mask 10 mounted, the peripheral portion of the lens has a lower energy density than the central portion, so that insufficient cleaning may occur.

For this reason, in this embodiment, instead of the mask 10 located between the rear group 9 of the field stop imaging optical system and the projection optical system 11, a diffusing plate 13 as light diffusing means is arranged.
The diffusion plate 13 is driven to be inserted into and removed from the optical path by an insertion device 22. The insertion device 22 is controlled by a control device 21. With this configuration, when light cleaning is to be performed, the light incident on the projection optical system 11 can be diffused by inserting the diffusion plate 13 into the optical path. In this case, a light beam having a light amount sufficient to obtain a sufficient cleaning effect is applied. At this time, the diffusion angle Δ by the diffusion plate 13 is such that the numerical aperture of the illumination optical system when performing cleaning irradiation is NA _i and the numerical aperture of the projection optical system is N
When the A _p, is preferably set to Δ ≧ NA _p -NA _i. It is not necessary to reduce the numerical aperture of the illumination optical system during light cleaning.
_i is preferably the maximum numerical aperture of the illumination optical system.

Here, as the light diffusing means, a material obtained by roughly rubbing quartz or fluorite, a diffraction grating, etc.
Those utilizing diffraction, reflection and the like can be mentioned. If the diffusion angle Δ is too large or the loss of light amount is large only by rough rubbing, the surface is treated with a chemical such as hydrofluoric acid (hydrogen fluoride) after rough rubbing to control the diffusion angle Δ. Is possible. When a diffraction grating is used, the diffraction angle can be controlled by appropriately setting the grating interval.

In this embodiment, the projection optical system 11
By disposing the shutter 14 that is driven into and out of the optical path by the driving device 23 between the and the wafer 12,
Prevents the wafer 12 from being exposed during light cleaning,
Thus, the wafer exchange and the alignment process during the light cleaning can be performed at the same time. Further, the surface of the shutter 14 on the side of the projection optical system 11 is formed as a reflection mirror, and the cleaning light that has passed through the projection optical system 11 is reflected and reversed to further enhance the cleaning effect.
At this time, by configuring the driving device 23 so that the direction of the normal line of the reflection mirror can be tilted in an arbitrary direction without matching the optical axis of the projection optical system, a more efficient cleaning effect can be obtained.

In this embodiment, the diffusion plate 13 is inserted in the optical path instead of the mask 10. However, the diffusion plate 13 may be inserted on the light source 1 side of the mask 10 or on the wafer 12 side of the mask 10. it can. In this case, cleaning may be performed while the mask 10 to be exposed is arranged.
However, in this case, the energy of the cleaning light incident on the projection optical system 11 is reduced by the transmittance of the mask 10, so that the cleaning time increases. On the other hand, if the cleaning is performed by removing the mask 10, the cleaning time is shortened.
The time required for insertion and removal of the device is required. Therefore, when the time required for attaching and detaching the mask 10 is longer, the cleaning may be performed while the mask 10 is arranged. Further, the place where the diffusion plate 13 is arranged may be any side as far as the front side of the portion requiring light cleaning. Therefore, if desired, it can be arranged inside the illumination optical system or inside the projection optical system. However, when the diffusing plate 13 is disposed inside the illumination optical system, the effective diameter of the optical system subsequent to the diffusing plate 13 cannot be sufficiently large according to the numerical aperture of the illumination optical system. A sufficient effective diameter is required.

In this embodiment, the stage 15 on which the wafer is placed is used to measure the light intensity on the wafer surface.
A transmission light detector 16 for measuring the intensity of a light beam transmitted through the projection optical system 11 is attached to the transmission light detector 1.
The output of 6 is input to the transmittance measuring device 20. With this configuration, the ArF excimer laser 1 and the projection optical system 1
The change in the total transmittance of all the optical elements up to 1 is measured as follows. That is, the stage 15 is driven to dispose the transmitted light detector 16 in the optical path of the projection optical system 11, and the shutter 14 is opened to measure the output of the transmitted light detector 16. Then, this output is monitored, and the state where the output is saturated is stored in the transmittance measuring device 20 as the best light intensity. After that, the light intensity at the present time is
By comparing with the best light intensity stored in 0,
The total transmittance of all the optical elements at the present time can be immediately known. Therefore, it is possible to easily determine whether or not the cleaning process should be started and whether or not to end the cleaning process.

Note that the transmittance measuring device 20 includes a stage 1
Transmitted light detector 16 as a photoelectric detector provided on 5
Is measured on the image plane of the projection optical system 11 to determine whether or not to start the optical cleaning step, but the present invention is not limited to this. That is, the transmittance measuring device 2
0 measures the transmittance distribution on the image plane of the projection optical system 11, that is, the illuminance distribution, based on the output of the transmitted light detector 16 serving as a photoelectric detector provided on the stage 15; It is needless to say that the configuration may be such that it is determined whether or not the distribution is obtained, and whether or not the light cleaning process is started is determined based on the determination.

FIG. 2 shows a second embodiment of the present invention.
In the configuration of FIG. 1, when the shutter 14 is closed, the light intensity cannot be measured on the wafer surface. Therefore, in the configuration of FIG. 2, the aperture stop 4 in the illumination optical system is used.
A half mirror between the lens and the front lens group 5a,
A reflected light detector 17 for measuring the intensity of the light beam incident on the half mirror from the reflection surface side of the shutter 14 is provided in the reflected light path. According to this configuration, Ar
It is possible to constantly monitor the change in the total transmittance of the forward path of the optical element from the F excimer laser 1 to the aperture stop 4 and the round trip path of the optical element from the front lens group 5a to the projection optical system 11. Therefore, the transmittance can be measured in real time during the cleaning step, which is useful for determining the end of the cleaning step. The position at which the half mirror is interposed does not particularly matter, and can be interposed at any position in the illumination optical system or the projection optical system.

FIG. 3 shows a third embodiment of the present invention.
In the configuration shown in FIG. 1 or FIG. 2, the ArF excimer laser 1 is used.
It is erroneously recognized that the transmittance has changed by that amount. Therefore, in the configuration of FIG. 3, in addition to providing the transmitted light detector 16 on the stage 15, a half mirror is arranged between the aperture stop 4 in the illumination optical system and the front group 5 a of the condenser lens, so that the ArF excimer laser 1 side. An incident light detector 18 for measuring the intensity of this light beam is provided on the reflected light path of the light beam incident on the half mirror, and the transmittance is obtained based on the difference between the outputs of the incident light detector 18 and the transmitted light detector 16. Things. According to this configuration, the projection optical system 1 can be moved from the front lens group 5a regardless of a change in the output of the ArF excimer laser 1.
The change in transmittance of the optical element up to 1 can be measured. The transmittance measuring device 20 shown in FIG. 3 is a transmission light detector 1 as a photoelectric detector provided on the stage 15.
6, the transmittance distribution on the image plane of the projection optical system 11, that is, the illuminance distribution is measured, and it is determined whether or not a predetermined illuminance distribution is obtained. It may be configured to judge whether or not.

FIG. 4 shows a fourth embodiment of the present invention.
In the configuration of FIG. 3, when the shutter 14 is closed, the light intensity cannot be measured on the wafer surface. Therefore, in the configuration of FIG. 4, a half mirror is arranged between the aperture stop 4 in the illumination optical system and the condenser lens front group 5a, and the reflected light path of the light beam incident on the half mirror from the ArF excimer laser 1 side is provided. Incident light detector 18 for measuring the intensity of light flux
And a reflected light detector 17 for measuring the intensity of the light beam entering the half mirror from the reflection surface side of the shutter 14 is provided. The output of the incident light detector 18 and the reflected light detector 17 is provided. The transmittance is obtained based on the difference. According to this configuration, regardless of the change in the output of the ArF excimer laser 1, and with the shutter 14 closed,
The change in the transmittance of the optical element from the front lens group 5a to the projection optical system 11 can be constantly monitored.

In each of the above embodiments, the description has been made mainly on the fact that the light cleaning step is performed prior to the exposure step. However, during the exposure step, the transmittance of the projection optical system 11 and the illumination optical system and the projection optical system The illuminance distribution on the image plane of the system 11 may change. For this reason, it is preferable to temporarily stop the exposure operation during the exposure process and periodically execute the optical cleaning process. Further, when the illumination coherency (σ value) is changed by changing the aperture diameter of the aperture stop 4 in the illumination optical system during the exposure process, the projection optical system 11 and the illumination optical system need to perform exposure. And the desired illuminance distribution on the image plane of the projection optical system 11 may not be obtained. Therefore, when changing the illumination coherency (σ value), it is preferable to temporarily stop the exposure operation during the exposure step and perform the light cleaning step. It should be noted that the σ value as the illumination coherency is determined by setting the numerical aperture of the illumination optical system to N.
_Let A _i be the numerical aperture of the projection optical system and NA _p be the definition of σ = NA _i / NA _p .

[0023]

As described above, according to the present invention, in particular, Ar
In a projection exposure apparatus using a far-ultraviolet wavelength such as an F excimer laser, moisture and organic substances adhering to an optical system constituting the exposure apparatus can be removed by light cleaning, so that a good reticle pattern image can be formed on a photosensitive substrate. Can be transferred to That is, in the optical lithography step including the exposure method, even if the transmittance of the projection optical system is reduced, the transmittance of the projection optical system can be sufficiently recovered by newly adopting the light cleaning step, Since a finer pattern can be transferred onto the photosensitive substrate, a highly integrated semiconductor device such as an LSI can be manufactured. In addition, if the light cleaning process according to the present invention is used when manufacturing a projection optical system, the assembly and adjustment work of the projection optical system under a normal working environment becomes possible, and the transmittance of the projection optical system is sufficiently secured. can do.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a third embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... ArF excimer laser 2 ... Beam shaping optical system 3 ... Fly eye lens 4 ... Aperture stop 5a ... Condensing lens front group 5b ... Condensing lens rear group 6 ... Field stop 7 ... Field stop imaging optical system 9 ... Field stop imaging optical system rear group 10 mask 11 projection optical system 12 wafer 13 diffuser 14 shutter 15 stage 16 transmitted light detector 17 reflected light detector 18 incident light detector 20 transmission Rate measuring device 21 ... Control device 22 ... Insertion device 23 ... Drive device

Claims (13)

[Claims] An illumination optical system for illuminating a pattern formed on a projection original with a light beam from a light source, and a projection for exposing the photosensitive substrate by forming an image of a light beam transmitted through the pattern on a photosensitive substrate. In an exposure apparatus having an optical system, the light flux on the photosensitive substrate side than a predetermined space in both of the optical systems is larger than the light flux when performing exposure of the photosensitive substrate, An exposure apparatus, wherein a light diffusing unit is disposed in a predetermined space so as to be insertable and removable. 2. An exposure apparatus according to claim 1, wherein said light diffusing means is arranged in place of said projection original. 3. The exposure apparatus according to claim 1, wherein a shutter is disposed between the projection optical system and the photosensitive substrate so as to be insertable and removable. 4. An exposure apparatus according to claim 3, wherein a surface of said shutter on a side of said projection optical system is formed as a reflection surface. 5. The exposure apparatus according to claim 4, wherein a direction of a normal line of said reflection surface is variable. 6. The exposure according to claim 1, wherein a transmission light detector for measuring the intensity of a light beam transmitted through the projection optical system is provided on a stage on which the photosensitive substrate is mounted. apparatus. 7. The exposure apparatus according to claim 4, further comprising a reflected light detector for measuring the intensity of the light beam reflected by the reflection surface, in any one of the optical paths in the exposure apparatus. 8. The exposure apparatus according to claim 6, wherein an incident light detector for measuring the intensity of a light beam incident from the light source side is provided on an optical path closer to the light source than the projection optical system. 9. An illumination optical system for illuminating a pattern formed on a projection original, and a projection optical system for exposing the photosensitive substrate by forming a light beam transmitted through the pattern on a photosensitive substrate. In the light cleaning method of the exposure apparatus, a step of removing the photosensitive substrate out of an optical path or inserting a shutter immediately before the photosensitive substrate; and a method of removing the photosensitive substrate from a predetermined space in both the optical systems. Inserting a light diffusing means into the predetermined space so that a light beam on the substrate side is larger than a light beam when performing exposure of the photosensitive substrate. . 10. An illumination optical system for illuminating a pattern formed on a projection original, and a projection optical system for imaging a light beam transmitted through the pattern on a photosensitive substrate to expose the photosensitive substrate. In a method of manufacturing a semiconductor device using an exposure apparatus, a step of exposing the photosensitive substrate by arranging the photosensitive substrate in an optical path, and removing the photosensitive substrate out of the optical path or immediately before the photosensitive substrate After inserting the shutter, the predetermined space so that the light flux on the photosensitive substrate side is larger than the light flux when performing exposure of the photosensitive substrate than the predetermined space in the two optical systems. Inserting a light diffusing means into the semiconductor device. 11. An illumination optical system for illuminating a pattern formed on a projection original with a light beam from a light source, and a projection for exposing the photosensitive substrate by forming an image of the light beam via the pattern on the photosensitive substrate. In an exposure apparatus having an optical system, a light beam on the photosensitive substrate side than a predetermined space in both of the optical systems is provided with optical means for expanding the light beam when performing exposure of the photosensitive substrate. An exposure apparatus characterized in that: 12. An illumination optical system for illuminating a pattern formed on a projection original with a light beam from a light source, and a projection for exposing the photosensitive substrate by forming an image of the light beam through the pattern on the photosensitive substrate. In an optical cleaning method for an exposure apparatus having an optical system, during the exposure step of the exposure apparatus or prior to the exposure step of the exposure apparatus, the photosensitive substrate side more than a predetermined space in both the optical systems. A light cleaning method, comprising a step of expanding a light beam more than a light beam when exposing the photosensitive substrate. 13. A method for manufacturing a semiconductor device, comprising an exposure step of illuminating a pattern formed on a projection original with a light beam from an illumination optical system and exposing the pattern onto a photosensitive substrate via a projection optical system. During the exposure step or prior to the exposure step, the light flux on the photosensitive substrate side is larger than a predetermined space in the two optical systems than the light flux when exposing the photosensitive substrate. A method for manufacturing a semiconductor device, comprising the steps of: