JP2007053239A - Aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower concentration of oxygen and water content in an inert gas purge vessel in a short time by replacing the atmosphere in an atmosphere reservoir with inert gas in a short time, relating to replacement in the vessel with the inert gas. <P>SOLUTION: To replace the inside of a purge area with purge gas, it is temporarily replaced with a gas having a specific gravity significantly different from the atmosphere such as helium, and then replaced with a desired gas such as nitrogen. Here, by tilting a lens barrel 36 and a motor 32 in perpendicular direction otherwise by devising internal form, a top and a bottom are generated in the interior. Ventilation holes 37 and 38 are provided here, and the internal gas of the motor and lens barrel is replaced using difference in specific gravity of gas. A function is provided, on replacing helium with nitrogen, that measures change amount of focusing point of a lens and detects completion of replacement to nitrogen, by detecting that the change amount has come to be a specified value or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a short-wavelength laser that easily activates atmospheric gas as exposure light and is also susceptible to absorption by oxygen and moisture, replaces the exposure light passage path in the apparatus with an inert gas, and projects the mask pattern into an optical pattern. The present invention relates to a technique that is preferably applied to an exposure apparatus that irradiates a photosensitive substrate through a system, and that can quickly replace a portion such as a lens housing or an actuator that is difficult for an inert gas to enter and is not easily replaced with an inert gas.

  Conventionally, in a manufacturing process of a semiconductor element formed from an ultrafine pattern such as LSI or VLSI, a reduced projection in which a circuit pattern drawn on a mask is reduced and projected onto a substrate coated with a photosensitive agent. An exposure apparatus is used. As the mounting density of semiconductor elements has increased, further refinement of the pattern line width has been demanded, and the resolution has been improved in response to the development of the resist process and the miniaturization of the exposure apparatus.

  As means for improving the resolution of the exposure apparatus, there are a method of changing the exposure wavelength to a shorter wavelength and a method of increasing the numerical aperture (NA) of the projection optical system.

For exposure wavelength, practical application of ArF excimer laser having an emission wavelength of about 193nm in recent the KrF excimer laser is performed with an oscillation wavelength of about 248 nm, a fluorine with an oscillation wavelength of about 157nm short wavelength _{(F 2} Excimer lasers are being used.

In the deep ultraviolet, particularly ArF excimer laser having a wavelength near 193 nm and fluorine (F ₂ ) excimer laser having an oscillation wavelength near 157 nm, there are a plurality of oxygen (O ₂ ) absorption bands in the band near these wavelengths. It is known.

  For example, a wavelength of 157 nm of a fluorine excimer laser generally corresponds to a wavelength region called vacuum ultraviolet. In this wavelength region, the absorption of light by oxygen molecules is large, so almost no light is transmitted in the atmosphere. In an environment where the oxygen and moisture concentrations are sufficiently reduced by reducing the pressure to near vacuum or replacing with inert gas. Only light can pass through.

According to Non-Patent Document 1, the absorption coefficient of oxygen with respect to light having a wavelength of 157 nm is about 190 atm ⁻¹ cm ⁻¹ . This means that when light having a wavelength of 157 nm passes through a gas having an oxygen concentration of 1% at 1 atmosphere, the transmittance per 1 cm is T = exp (−190 × 1 cm × 0.01 atm) = 0.150
It shows that there is only it.

Further, oxygen absorbs the light to generate ozone (O ₃ ). This ozone further increases the light absorption and significantly reduces the transmittance. Further, it is also known that various products resulting from the photochemical reaction of the laser adhere to the surface of the optical element, and so-called chemical contamination occurs that lowers the light transmittance of the optical system. This occurs because exposure light causes photochemical reaction of impurities in the air with oxygen, and a product (cloudy substance) resulting from such reaction adheres to the glass member, resulting in an opaque “cloudiness” on the glass member. Occurs. Here, as a substance that causes “cloudiness”, for example, ammonium sulfate (NH ₄ ) ₂ produced by sulfur dioxide (SO ₂ ) absorbing light energy to be in an excited state and reacting (oxidizing) with oxygen in the air. sO _4, and the like typically. This ammonium sulfate has a white color, and when it adheres to the surface of an optical member such as a lens or mirror, it becomes the “cloudy” state. The exposure light is scattered and absorbed by ammonium sulfate, resulting in a decrease in the transmittance of the optical system.

  In particular, in the short wavelength region where the exposure light is shorter than 248 nm shorter than the i-line, such as a KrF excimer laser, the exposure light causes a stronger photochemical reaction and the exposure light is absorbed by the above-mentioned “clouding”. The amount of light that scatters and reaches the substrate is reduced.

  When the amount of light decreases, the time required for substrate exposure increases correspondingly and productivity decreases.

Therefore, in order to ensure sufficient productivity, in the optical path of the exposure optical system and the position measurement optical system of the projection exposure apparatus using far ultraviolet rays as the light source such as ArF excimer laser and fluorine (F ₂ ) excimer laser, nitrogen or the like is used. A method has been adopted in which the oxygen concentration and water concentration present in the optical path are kept at a low level of several ppm order or less by means of purging with an inert gas.
, “Photochemistry of Small Molecules” (Hideo Okabe, AWiley-Interscience Publication, 1978, 178 pages)

As described above, in an exposure apparatus using ultraviolet rays, particularly ArF excimer laser light or fluorine (F ₂ ) excimer laser light as a light source, the absorption of exposure light by oxygen and moisture is large, so that sufficient transmittance and stability can be obtained. In order to reduce the oxygen and moisture concentrations in the optical path and to maintain these concentrations, the optical components are sealed in a highly sealed container, and an inert gas is always allowed to flow.

However, the exposure apparatus may open the nitrogen-filled space and replace internal parts in some cases for reasons such as maintenance and changes in illumination conditions, and external air enters the inert gas-filled space for these operations. There can be a thing. In addition, when used as an inert gas in a large amount such as N ₂ or He ₂ , there is a concern that harm to the human body due to suffocation may occur. Therefore, it is necessary to ensure safety by stopping the supply of inert gas during the maintenance work. Therefore, a large amount of air enters the container during the maintenance work.

  After the work, it is necessary to replace with an inert gas again. Further, even when the exposure apparatus is stopped for a long period of time, the atmosphere enters the inert gas purge area, so that replacement with an inert gas is required at the start of operation of the apparatus.

  However, there are many measurement systems and exposure lenses in the current semiconductor exposure apparatus, and the cylindrical lens barrel and actuators such as motors for holding these lenses have a semi-sealed structure, and nitrogen is contained inside. It has a structure that does not easily flow in and tends to accumulate air. Oxygen and moisture come out from the atmosphere accumulated in this part for a long time, the laser transmittance decreases, and impurities existing in the atmosphere cause adhesion of impurities to optical parts due to photochemical reaction. It can be considered that the transmittance of parts is reduced.

  In particular, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and in replacing the inert gas in the inert gas purge vessel with the inert gas, the replacement of the atmospheric pool portion from the atmosphere to the inert gas is shortened. The purpose is to reduce the oxygen and moisture concentration in the container in a short time.

  In order to achieve the above object, when replacing the gas purge area of the semiconductor exposure apparatus from the atmosphere to an inert gas, a gas having a specific gravity different from that of the atmosphere is once entered, and then the gas to be finally replaced is flowed in, In addition, gas inflow / outflow holes are provided at the uppermost and lowermost parts of the space having a substantially sealed structure such as a motor and a lens barrel. When the cover is removed during installation or maintenance and the purge area is opened to the atmosphere, the air flows into the purge area. When the opening time is long, the atmosphere enters into a substantially sealed space such as a motor or a lens barrel by diffusion movement. Once this substantially sealed space is replaced with the atmosphere, even if nitrogen is subsequently introduced into the purge area, the replacement speed is very slow because the inside of the substantially sealed space is only replaced by diffusion motion. In order to increase the nitrogen replacement speed of these substantially sealed spaces, the uppermost part and the lowermost part in the vertical direction are provided in the substantially sealed spaces such as a motor and a lens barrel. For the method of providing the uppermost and lowermost parts, it is effective to tilt the motor slightly and attach it to the motor. It is also effective to tilt the lens barrel, but if it is difficult to tilt it due to optical performance, the lens barrel By providing a taper inside, it becomes possible to provide the uppermost part and the lowermost part one by one in the substantially sealed space. Holes of such a size that gas can pass without resistance are formed in the uppermost part and the lowermost part.

  A gas such as helium having a large specific gravity with respect to the atmosphere is put in the purge area in the above-described form. A discharge hole is made at the bottom of the purge area. The two gases are less mixed due to the difference in specific gravity between the atmosphere and helium. Helium that has flowed into the purge area accumulates at the top of the purge area, and the air is pushed down from a discharge port provided at the bottom of the purge area.Helium that has accumulated in the upper part of the purge area gradually increases in volume and moves to the lower part of the purge area. To reach. When helium reaches the position of the uppermost hole provided in the motor and the lens barrel, helium penetrates from this hole, and the atmosphere in the motor and lens barrel is pushed out from the lowermost hole, and the internal atmosphere is replaced with helium. To go.

  Helium is introduced in excess of the purge area volume, and then nitrogen is introduced. The specific gravity of nitrogen is slightly lighter than that of the atmosphere, but is almost the same as the atmosphere and about 7 times heavier than helium when compared with the same volume. When nitrogen is introduced with the upper discharge port of the purge area opened, the nitrogen accumulates at the lower part of the purge area and gradually reaches the upper part according to the inflow amount. Since the upper outlet is bent downward, helium does not blow out into the atmosphere before nitrogen is introduced. At this time, in a substantially sealed space such as a motor or a lens barrel, nitrogen begins to enter from the bottom hole, and helium is discharged from the top hole, and the inside is replaced with nitrogen.

  As described above, holes are provided in the uppermost and lowermost portions of the substantially sealed space, and helium is allowed to flow before inflow of nitrogen, so that the atmosphere in the substantially sealed space in the purge area, which has been conventionally performed only by diffusion, is changed from nitrogen to nitrogen. The replacement becomes a replacement by gas inflow and outflow, and the replacement time can be drastically shortened.

  Conventionally, as a method of knowing the end of substitution from the atmosphere to nitrogen, the oxygen concentration at the outlet is measured, and when it falls below a specified value, the end of substitution is known and exposure is started. However, as described above, when replacing helium with nitrogen, neither gas contains oxygen, so even if the oxygen concentration is measured, it is not known that the gas has been replaced with nitrogen. This problem can be solved by installing a helium sensor in addition to the oximeter, but the cost increases. When the optical system in the purge area is a measurement system that performs mark position measurement, etc., the reticle or wafer or the lens in the measurement system is driven so that the mark on the reticle or wafer is observed and the mark is in focus. Focusing is performed every time, and it is possible to know that the replacement of helium with nitrogen is completed when the driving amount of the reticle, wafer, and lens necessary for focusing becomes below a certain level. This utilizes the property that the focal position of the measurement system varies depending on the difference in refractive index between helium and nitrogen.

  As mentioned above, although the detail was demonstrated about this invention, if it demonstrates further, it will show as follows about the 1st invention of this invention.

  (1) An exposure apparatus that illuminates a mask with exposure light from an exposure light source via an illumination optical system, and projects and exposes a pattern formed on the mask onto a photosensitive substrate via a projection optical system, Covering the optical path of exposure light from the exposure light source to the photosensitive substrate and the path through which the exposure light passes as a light source used in the measurement optical system, and when replacing the interior of the casing with the purge gas from the atmosphere, once with a specific gravity such as helium An exposure apparatus characterized by substituting with a desired gas such as nitrogen after substituting with a greatly different gas.

  According to the present invention, in a projection exposure apparatus using an ultraviolet light source such as an ArF excimer laser or an F2 excimer laser, when the purge area is opened to the atmosphere during installation or maintenance, the atmosphere in the purge area is quickly replaced with nitrogen. Can reduce downtime. For this reason, productivity is improved and semiconductor device manufacturing costs are reduced.

  The exposure apparatus of the present invention is an exposure apparatus that uses ultraviolet light as exposure light, replaces the exposure light passage path in the apparatus with an inert gas, and irradiates a photosensitive substrate with a mask pattern via a projection optical system. Applies to known ones.

Further, although ultraviolet light as exposure light used in the exposure apparatus of the present invention is not limited, as described in the prior art, far ultraviolet light, particularly ArF excimer laser having a wavelength near 193 nm and fluorine having a wavelength near 157 nm (F ₂ ) Effective for excimer laser light.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of an exposure apparatus for carrying out the present invention. The exposure apparatus of the present embodiment generally includes a light source 1 composed of an F2 excimer laser, a light source lens system 2 that is an optical system that forms laser light L1 that is illumination light emitted from the light source 1 into a light beam having a predetermined shape, It comprises a projection lens system 3 that forms an image of a laser beam L1 formed in a predetermined shape by a light source lens system 2 on a wafer W1, which is a substrate, through a reticle R1. Further, a TTL (Through The Lens) microscope 4 using exposure light is provided as a function for measuring the positional relationship between the reticle R1 and the wafer W1. The light source of the TTL microscope is provided with an optical path switching mirror mechanism 5 in the light source lens system 2, and when using the TTL microscope, the mirror is placed in the optical path of the laser light L1 and the laser light L2 for the TTL microscope light source is taken out. The laser beam L2 is incident on the TTL microscope 4 through the laser introducing optical system 6.

  The light source lens system 2, the projection lens system 3, the TTL microscope 4 and the laser introduction optical system 6 to the TTL microscope are all arranged inside the purge containers 7-10. The purge vessels 7 to 10 are provided with a nitrogen supply device 11 for supplying nitrogen, which is an inert gas, and a flow rate controller 13 capable of variably controlling the flow rate provided in the nitrogen gas supply line 12 and the nitrogen gas supply line. Connected through. This flow controller also serves as a stop valve and can stop nitrogen.

  A nitrogen exhaust gas exhaust line 14 is provided in the upper part of the purge area. An on / off valve 15 is attached to the exhaust line 14 and can be opened and closed as necessary. At the end of the exhaust line, an oximeter 16 for monitoring that nitrogen purge is normally performed is attached. As a result, nitrogen is constantly flowing inside the purge vessels 7 to 10, and the oxygen concentration and the water concentration are suppressed below the levels necessary for the transmission of the F2 laser. In FIG. 1, only the nitrogen supply path to the TTL microscope purge container 9 is shown for the sake of simplification, but nitrogen is also supplied to the purge containers 7, 8, and 10 which are other nitrogen purge containers through the same path. The In addition to these nitrogen supply lines, a helium supply line is provided. Similarly to the nitrogen supply line, a helium supply device 17 and a flow rate controller 19 are provided, and helium can be introduced into the purge vessel through the helium supply line 18.

  A discharge line 20 for supplying helium is provided below the purge vessel 9. An on / off valve 15 is also attached here and can be opened and closed as necessary. During normal operation, helium does not flow into the purge vessel 9 by closing the flow rate controller 19. In FIG. 1, only the helium supply path to the TTL microscope purge container 9 is shown for simplification of the drawing, but helium can be introduced into the other purge containers 7, 8, 10 through the same path. ing.

  FIG. 2 is an internal detail view of the TTL microscope 4 of FIG. The laser beam L2 is introduced as illumination light, and the mark on the wafer and reticle is captured as an image by a CCD camera, and the positional relationship between the two marks is measured. This will be described with reference to FIG. The illumination light L2 is incident on the TTL microscope by the laser introducing optical system 6. The incident laser passes through the TTL microscope illumination optical system lens 21, σ stop 22, relay lens 23, NA stop 24, and objective lens 25, is reflected by the mirror 26, and is irradiated and imaged on the reticle mark and wafer mark surface. The return light passes through the relay lens 23 through the reverse path, passes through a phase changing element (not shown), is reflected by the polarization beam splitter 27, passes through the erector lens 28, and forms an image on the detection surface of the CCD camera 29. .

  The objective lens 25 and the mirror 26 are placed on a linear guide 30 so that a mark at a desired position can be observed, and can be moved by a ball screw 31 and a motor 32, whereby a desired position on the reticle and wafer surface. Can be observed. A seal glass 33 is provided in front of the erector lens 28 to seal the purge area, thereby separating the purge area and the non-purge area.

  The illumination optical system 21, the relay lens 23, and the objective lens 25 are housed in lens barrels 34, 35, and 36, respectively. In the above configuration, the lens barrels 34 to 36 and the inside of the motor 32 have a substantially sealed structure. When the inside of the purge container 9 is opened to the atmosphere for a long time during the installation or maintenance of the apparatus, the atmosphere intrudes into the substantially sealed space by diffusion, and the subsequent structure of nitrogen replacement makes it difficult for nitrogen to flow into the interior. Therefore, it is difficult to replace with nitrogen.

  Therefore, in the present embodiment, the lens barrels 34, 35, and 36 are tapered, and an upper discharge inlet 37 and a lower discharge inlet 38 are provided at the uppermost and lowermost portions, respectively. If allowed by the optical design, the lens barrel itself may be tilted to form the uppermost part and the lowermost part.

  Since it is difficult to taper the inside of the motor, the motor itself is tilted to form the uppermost part and the lowermost part, and the discharge inlets 37 and 38 are provided in the same manner as the lens barrel. Since this inclination is a slight amount and is absorbed by the coupling 39, there is no problem in the objective lens driving operation.

  As described above, the discharge inlet is provided at the uppermost part and the lowermost part of the substantially sealed space, and then helium is first introduced into the purge container 9 filled with the atmosphere. A helium flow controller 19 supplies a predetermined amount of helium, and at the same time, the on / off valve 15 of the purge container discharge line 14 is closed and the on / off valve 15 of the discharge line 20 is opened. While supplying helium, the nitrogen flow controller 13 is closed to stop the nitrogen inflow.

  Since helium weighs only about one-seventh the unit volume compared to the atmosphere, helium that has flowed in begins to accumulate in the upper portion of the purge vessel 9 without being mixed with the atmosphere, and only the atmosphere is gradually expelled from the discharge line 20. To go. FIG. 3 is an enlarged view showing the internal state of the motor 32 and the lens barrel 36 at this time.

  In FIG. 3, helium accumulates in the upper part of the container 9 and increases the volume to be tightened in the lower part. When the helium reaches the upper discharge inlet 37 provided on the uppermost part of the lens barrel 36 and the motor 32, the helium is discharged from the upper discharge inlet 37. The air flows into the motor and the lens barrel, and the air is pushed down from the lower discharge inlet 38. By continuing the inflow of helium that is equal to or more than the volume of the purge vessel 9 as it is, the entire area inside the purge vessel 9 including the inside of the motor and the barrel, which are substantially sealed spaces, is replaced with helium. After the inside of the container 9 is replaced with helium, the helium flow controller 19 stops the helium supply and simultaneously closes the on / off valve 15 of the discharge line 20. Next, nitrogen flow is started by the nitrogen flow controller 13, and at the same time the on / off valve 15 of the discharge line 14 is opened. Like the air, nitrogen is approximately seven times the weight per unit volume compared to helium, so most of the nitrogen supplied due to the difference in weight accumulates in the lower part of the purge vessel 9 without mixing with helium. Increase the volume at the top according to At the same time, helium is discharged from the discharge line 14 so as to be pushed out. The reason why the final outlet of the discharge line 14 is located below the container 9 is to prevent helium from being blown into the atmosphere as soon as the discharge line 14 is opened, so that the atmosphere does not flow backward. When the region occupied by nitrogen reaches the lower discharge inlet 38 of the motor and the lens barrel, nitrogen enters the motor 32 and the lens barrel 36 from here, and helium is pushed out from the upper discharge inlet.

  As a result, nitrogen is directly introduced from the discharge inlet into the motor or the lens barrel, which has been replaced with nitrogen from the atmosphere only by the diffusion effect, and the replacement is completed in a short time. The upper and lower surfaces of the purge vessel 9 are also inclined to provide the uppermost and lowermost portions, and the provision of the discharge inlet is also effective for increasing the nitrogen replacement time inside the purge vessel 9.

  In addition, it is not always necessary to provide holes in the uppermost and lowermost parts of the motor and the lens barrel. Providing holes in the vicinity can also be expected to be effective although there is a slight decrease in efficiency. Furthermore, it is preferable to provide one hole at the uppermost and lowermost points, but a hole can be formed. However, a certain effect can be expected even if holes are provided at the upper and lower parts without tapering the lens barrel. In this case, it becomes easier to replace by making a plurality of holes as shown in FIG.

  In this embodiment, the motor and the lens barrel are taken up as parts having a substantially sealed space existing in the purge container. Similarly, various actuators such as an air cylinder such as a part that becomes a substantially sealed space existing in the purge container. It can be applied to various sensors and other parts.

(Example 2)
In the first embodiment, the gas replacement method is described. In the second embodiment, a configuration for detecting the replacement is described. The oxygen concentration meter 16 shown in FIG. 1 of Embodiment 1 plays a role of monitoring that nitrogen purge is normally performed during normal operation of the exposure apparatus. Further, when the atmosphere is replaced with helium in Example 1, it is possible to detect the completion of the helium replacement by detecting the decrease in oxygen concentration. However, when replacing helium with nitrogen in Example 1, oxygen is not included in both gases, so the oxygen concentration meter cannot detect the replacement. Although it is possible to detect by providing a separate helium sensor, the cost increases accordingly. In the case of a scope having an optical system in the purge vessel as in the first embodiment for measurement and having a CCD camera 29, it is possible to know the replacement state of helium to nitrogen without providing a new sensor. it can.

  A description will be given below based on FIG. 5 showing the configuration of the replacement state detection of the present embodiment. Since most of FIG. 5 is the same as FIG. 1 of the first embodiment, it is denoted by the same reference numerals and description thereof is omitted. In FIG. 5, the reticle R1 described in the first embodiment is arranged under the TTL microscope. Below that, the projection optical system optical system 3 is arranged, and the mark M1 provided on the wafer-side imaging surface can be observed. The mark M1 is disposed on the wafer stage 40. The wafer stage 40 can be driven not only in the XY direction but also in the Z direction, that is, in the height direction, and has a scale for reading the driving amount.

  The wafer in which the contrast of the mark imaged on the CCD in the TTL microscope is highest when the wafer stage 40 is driven up and down while observing the mark M1 on the wafer-side imaging plane with a TTL microscope immediately before replacing helium with nitrogen. Find the stage position. This is a state in which the TTL microscope 4 is focused on the wafer mark M1. Similarly, the wafer stage 40 is driven up and down while observing the mark M1 on the wafer-side imaging plane in the same manner at regular intervals after the start of inflow of nitrogen, and the focus is searched for the position of the wafer stage where the contrast is highest. Nitrogen and helium have different absolute refractive indices. The amount of difference is only about 0.003%, but such a difference in refractive index is observed as a change in the focal position of several μm in terms of the wafer in the TTL microscope. When the focal position is compared between nitrogen and helium in the objective lens, the relative refractive index of the glass member and each gas is larger in helium, so that the focal position in helium is closer to the objective lens side.

  In the configuration of FIG. 5, when the focus position is found at regular intervals when replacing the inside of the container 9 from helium to nitrogen, the relationship between the time and the focus position is obtained as shown in the graph of FIG. In the graph, t0 is the time when the substitution from helium to nitrogen is started. At the point in time when the focal position almost does not change with time as shown by t1, almost all the gas in the purge container 9 is replaced with nitrogen, so it is considered that the focal position has not changed.

  That is, if t1 is obtained, it is possible to detect that the replacement of helium with nitrogen is completed. Actually, it is not necessary to wait for exposure or measurement with a TTL microscope until the focal position variation becomes completely zero with time, and there is no problem if the variation amount is sufficiently small with respect to the measurement accuracy. For this reason, it is possible to reduce the downtime of the apparatus by setting to perform exposure and TTL measurement when the fluctuation amount becomes the allowable value or less.

  In this embodiment, the focal point is found by driving the wafer stage up and down to find the position where the contrast of the mark imaged on the TTL microscope CCD is the highest. However, instead of moving the wafer stage up and down, The relay lens may be driven in the optical axis direction.

  In the present embodiment, the TTL microscope is described. Similarly, in the projection optical system, the focal length is different between helium and nitrogen, so that the replacement state can be detected by monitoring the change in focus. In the case of the projection optical system 3, the focal point can be changed in the same manner as in the TTL microscope. However, with respect to the light source lens system 2, the focus change in the process of substitution from helium to nitrogen cannot be observed with a TTL microscope. This is because the TTL microscope observes the wafer surface without going through the light source lens system.

  Accordingly, when detecting a change in the focal position of the light source lens system, it is necessary to separately provide a measurement system capable of observing the focus change while passing the laser beam through the light source lens system 2. For example, a slit pattern is provided at the image formation position on the reticle surface and the image formation position on the wafer surface, and a light quantity sensor is formed under the pattern on the wafer, so that the light quantity sensor is incident when the slit pattern is aligned with the focal position of both. Since the laser intensity to be strengthened is the strongest, it is conceivable to detect the focal position by detecting it.

Schematic representing the first embodiment of the present invention TTL microscope detailed view of the first embodiment of the present invention TTL microscope internal motor and lens barrel detailed view of the first embodiment of the present invention TTL microscope inner barrel alternative conceptual diagram of the first embodiment of the present invention Schematic representing the second embodiment of the present invention The figure which shows an example of the graph obtained by the measuring method of the 2nd Example of this invention

Explanation of symbols

L1 Exposure light source laser light L2 Measurement light source laser light R1 Reticle W1 Wafer M1 Wafer surface mark 1 Exposure light source 2 Light source lens system 3 Projection lens system 4 TTL microscope 5 Switching mirror mechanism 6 Laser introducing optical system 7 Light source lens system purge container 8 Projection lens system purge container 9 TTL microscope purge container 10 Laser introduction optical system purge container 11 Nitrogen supply device 12 Nitrogen supply line 13 Nitrogen flow controller 14 Upper gas discharge line 15 On-off valve 16 Oxygen concentration meter 17 Helium supply device 18 Helium supply line 19 Helium flow controller 20 Lower gas discharge line 21 TTL microscope illumination optical system 22 σ stop 23 relay lens 24 NA stop 25 objective lens 26 mirror 27 beam splitter
28 Elector lens 29 CCD camera 30 Objective lens driving linear guide 31 Objective lens driving ball screw 32 Objective lens driving motor 33 Seal glass 34 Illumination system lens barrel 35 Relay lens barrel 36 Objective lens barrel 37 Upper gas discharge inlet 38 Lower gas discharge inlet 39 Coupling 40 Wafer stage

Claims (5)

  An exposure apparatus that illuminates a mask with exposure light from an exposure light source via an illumination optical system, and projects and exposes a pattern formed on the mask onto a photosensitive substrate via a projection optical system, the exposure light source Covering the optical path of the exposure light from the light source to the photosensitive substrate and the path through which the exposure light passes as a light source used in the measurement optical system, and when replacing the interior of the housing from the atmosphere to purge gas, the specific gravity of the atmosphere such as helium is greatly different An exposure apparatus characterized by substituting with a desired gas such as nitrogen after substituting with a gas.   By providing vents in the upper and lower parts of parts that have a substantially sealed space such as the lens barrel and motor in the purge area, and by flowing gas into the sealed space such as the lens barrel and motor using the difference in specific gravity of the gas. 2. The exposure apparatus according to claim 1, wherein the internal gas is replaced with a desired gas.   By attaching tilted parts such as a lens barrel and motor in the purge area tilted in the vertical direction, the upper and lowermost parts are created in the internal space, and vents are provided here, using the difference in specific gravity of gas. 2. An exposure apparatus according to claim 1, wherein the internal gas is replaced with a desired gas by flowing the gas into a substantially sealed space such as a lens barrel or a motor.   By tapering the inner diameter of a part that has a substantially sealed space such as a lens barrel in the purge area, the top and bottom parts are created in a substantially sealed space such as a lens barrel, and vents are provided in each of these to provide a difference in specific gravity of gas. An exposure apparatus that uses a gas to flow into a substantially sealed space such as a lens barrel to replace the internal gas with a desired gas.   Means for measuring the amount of change in the imaging position of the lens when substituting the gas in the purge area from helium to nitrogen, or when substituting with a gas having a different absolute refractive index, such as substituting from nitrogen to helium; The exposure apparatus according to claim 1, wherein the exposure apparatus has a function of detecting completion of replacement when the amount of change becomes a predetermined value or less.