WO2000042639A1

WO2000042639A1 - Method and apparatus for projection exposure

Info

Publication number: WO2000042639A1
Application number: PCT/JP2000/000126
Authority: WO
Inventors: Satoru Oshikawa
Original assignee: Nikon Corporation
Priority date: 1999-01-13
Filing date: 2000-01-13
Publication date: 2000-07-20
Also published as: AU2003400A

Abstract

A projection exposure device (1) irradiates the pattern of a mask (3) with exposure light and transfers the image of the pattern to a substrate (2). The device comprises a casing (11) enclosing at least part of the path of the exposure light, and a source (16) for supplying inert gas to the casing (11) through pipes (12, 14). The tubes (12, 14) include inner walls formed of a material, such as stainless steel or tetrafluoroethylene, incapable of producing impurity gases.

Description

Description Projection exposure apparatus and projection exposure method

The present invention relates to a projection exposure apparatus that transfers an image of a mask pattern projected by exposure light onto a substrate, for example, a projection exposure apparatus and a projection exposure method suitably used in a manufacturing process of a semiconductor element or a liquid crystal display element. About. Background art

In the photolithography process, which is an important part of the manufacturing process of devices such as semiconductor devices and liquid crystal display devices, the circuit pattern of a photomask or reticle (hereinafter simply referred to as a “reticle”) is transmitted through a projection optical system. A projection exposure apparatus that transfers a wafer onto a substrate such as a wafer or a glass plate coated with a photosensitive agent is used. In recent years, as the degree of integration of semiconductor integrated circuits has increased, such a projection exposure apparatus has been designed to sequentially transfer a pattern to a plurality of exposure regions on a substrate while sequentially moving the substrate in a step-and-repeat manner. The so-called stepper is the mainstream.

In such a projection exposure apparatus such as a stepper, a laser beam is often used as exposure light emitted from a light source. In particular, in recent years, the circuit pattern of semiconductor devices has been steadily miniaturized, and accordingly, the exposure wavelength has been shortened to cope with this. For example, an ArF excimer laser having a wavelength of 193 nm has been developed. Are being used.

However, for example, when exposure light such as an ArF excimer laser is used, the emission spectrum line overlaps the oxygen absorption spectrum region, so that the light utilization efficiency is reduced by the absorption by oxygen, and It causes ozone generation. In particular, ozone is not only harmful, but also has an adverse effect on light use efficiency (transmittance), and furthermore, causes a chemical reaction with ions and suspended matter in the air, causing white turbidity on the surfaces of optical elements such as lenses. This causes a decrease in the performance of the projection exposure apparatus. In addition, when exposure light such as ArF excimer laser is used, impurity gases such as sulfuric acid component, nitric acid component, ammonia, amines, and siloxanes in the atmosphere are converted by a reaction such as a photochemical reaction. It changes into substances such as ammonium sulfate and ammonium nitrate, and these substances tend to adhere to the surface of an optical element such as a lens, which also has the problem of deteriorating the light use efficiency of the optical element.

In order to avoid the above problems, projection exposure apparatuses that use an ArF excimer laser or the like as the exposure light have conventionally employed an atmosphere in the optical path of the exposure light, such as nitrogen gas or helium gas, which is inert to photochemical reactions. For example, a technique of replacing with an inert gas such as US Pat. No. 5,559,584 (corresponding Japanese application: Japanese Patent Application Laid-Open No. Hei 6-260385, See Kaihei 6-2608686).

However, the conventional projection exposure apparatus as described above has the following problems.

First, in order to replace the atmosphere of the exposure light with an inert gas, an inert gas is supplied to the projection exposure apparatus from a gas supply source such as a gas cylinder through a supply pipe. Resin-based materials such as tubes are frequently used, and impurity gas (so-called outgas) is generated from the supply pipe itself, which causes deterioration of the light use efficiency of the optical element described above.

In addition, inert gas such as nitrogen supplied from a gas supply source such as a gas cylinder is generally subjected to only a process of drying to reduce moisture, and other impurity gas is mixed into the inert gas. In some cases.

As described above, there is a problem that the impurity gas generated from the pipe itself such as the supply pipe or the impurity gas mixed in the supplied inert gas adversely affects the optical performance only by adhering to the optical element. . Disclosure of the invention

The present invention has been made in consideration of the above problems, and has as its object to provide a projection exposure apparatus and a projection exposure method that can prevent a decrease in optical performance due to an impurity gas.

The projection exposure apparatus of the present invention exposes a pattern of a mask (reference numeral 3 in the figure, the same applies hereinafter). A projection exposure apparatus (1) that illuminates with light and transfers an image of the pattern onto a substrate (2), the casing (11) surrounding at least a part of an optical path of the exposure light, A supply device (16) for supplying an inert gas through a supply pipe (12, 14) into the interior of (11), wherein at least the inner peripheral surface of the supply pipe (12, 14) has impurities. It is formed of a gas generation suppressing material.

In the projection exposure apparatus of the present invention, at least the inner peripheral surface of the supply pipe (12, 14) is formed of an impurity gas generation suppressing material which generates less impurity gas than the conventionally used nylon tube. The generation of impurity gas from the supply pipe (12, 14) itself is suppressed. Therefore, the internal contamination of the inert gas introduced into the casing can be minimized, and the transmittance of the optical element such as a lens can be suppressed from being reduced, so that the original performance of the projection exposure apparatus can be sufficiently exhibited. In addition, since the performance degradation of the optical element, which has conventionally occurred, can be suppressed, the required performance can be maintained for a long period of time.

Here, the impurity gas includes a gas containing a substance that adheres to the surface of the optical element, and a light absorbing substance (oxygen, ozone, etc.) that absorbs exposure light.

Examples of the impurity gas generation suppressing materials are stainless steel, tetrafluoroethylene (so-called Teflon: registered trademark), tetrafluoroethylene-terfluoro (alkyl vinyl ether), and tetrafluoroethylene-hexafluoro. Examples include various fluoropolymers such as propene copolymers, but are not limited thereto. The supply pipe (12, 14) may be entirely formed of the above material, or only the inner peripheral surface of the supply pipe (12, 14) may be formed of the above material.

The supply pipe may be provided with a filter for removing impurities from an inert gas supplied through the supply pipe. In this case, impurities can be removed from the inert gas supplied to the casing, and the above-mentioned effect can be made more remarkable.

A distribution unit may be provided on a downstream side of the filter, and the distribution unit may be connected to the plurality of supply pipes connected to each unit of the casing. In this case, the number of fills can be minimized, and the above effects can be obtained with a minimum cost. On the other hand, a projection exposure method according to the present invention is a method of illuminating a pattern of a mask with exposure light and transferring an image of the pattern onto a substrate, wherein at least a part of an optical path of the exposure light is partially broken. An inert gas was supplied to the inside of the casing through a supply pipe at least an inner surface of which was formed of an impurity gas generation suppressing material, and an optical path of the exposure light was filled with the inert gas. In this state, the image of the pattern is transferred onto a substrate. According to this method, the same effect as described above can be obtained. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view showing one embodiment of the projection exposure apparatus according to the present invention.

FIG. 2 is a diagram showing an inert gas supply path in the projection exposure apparatus. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments of the present invention will be described with reference to FIG. 1 and FIG.

FIG. 1 schematically shows a configuration of a projection exposure apparatus according to an embodiment of the present invention. In this figure, reference numeral 1 denotes a projection exposure apparatus, 2 denotes a wafer (substrate), and 3 denotes a reticle (mask). Reference numeral 4 denotes a light source that emits exposure light, 5 denotes an illumination optical system that irradiates the reticle 3 with exposure light, 6 denotes a light transmission system that is disposed between the light source 4 and the illumination optical system 5, and 7 denotes a light source from the reticle 3. The projection optical system projects the exposure light onto the wafer 2.

The projection exposure apparatus 1 emits one short-wavelength laser beam such as an ArF light source excimer laser from the light source 4 as exposure light.

The illumination optical system 5 includes various lenses such as a fly-eye lens, a relay lens, and a condenser lens, a field stop, and a blind. The illumination optical system 5 equalizes the luminous flux of the exposure light emitted from the light source 4 and sent through the light transmission system 6, and irradiates the reticle 3 with the exposure light.

As shown in FIG. 2, in the projection exposure apparatus 1, the illumination optical system 5 and the projection optical system 7 are housed inside the chamber 110. The inside of the chamber 110 is controlled by a temperature controller (not shown) so that the atmosphere is maintained at a predetermined temperature.

The optical path of the exposure light from the light source 4, i.e., the light source 4, the light transmission system 6, the illumination optical system 5, The projection optical system 7 is surrounded by a casing 11. One end of a supply pipe 12 for supplying an inert gas to the inside of each casing 11 is connected, and the other end of each supply pipe 12 is disposed, for example, inside the chamber 110. It is connected to the distribution unit 13. A supply pipe 14 is connected to the distribution section 13 for connection to a gas supply source such as a gas cylinder. Through this supply pipe 14, a gas supply source (not shown), for example, nitrogen gas, helium gas, etc. An inert gas that is inert to the gas is supplied to the distribution unit 13.

A filter 15 for removing an impurity gas in the inert gas supplied from a gas supply source (not shown) is provided in the supply pipe 14.

The supply pipe 12, the distribution section 13, the supply pipe 14, and the filter 15 constitute a supply device 16 for supplying an inert gas to the casing 11.

The distribution unit 13 distributes the inert gas to the supply pipes 12 that reach the light source 4, the light transmission system 6, the illumination optical system 5, and the projection optical system 7, and controls the supply pipes 12 by a control unit (not shown). Adjust the pressure and flow rate of the inert gas to be distributed.

The supply pipes 12, 14 are made of at least an impurity gas generation suppressing material that is a material that generates less gas than a conventionally used nylon tube, for example, a pipe made of stainless steel (hereinafter, referred to as “stainless steel pipe”), or Various fluoropolymers such as tetrafluoroethylene (so-called Teflon: registered trademark), tetrafluoroethylene-terfluoro (alkyl vinyl ether), tetrafluoroethylene-hexafluoropropene copolymer, etc. It is formed by a tube (hereinafter, simply referred to as “Teflon tube”). Stainless steels are classified into austenitic, ferritic and martensitic types. In particular, the stainless steel used in this embodiment is preferably an austenitic stainless steel. This is because austenitic stainless steels have better workability than others. In particular, iron is the main component, chromium 16.00 to 18.00% by weight, nickel 10.00 to: 14.00% by weight, molybdenum 2.00 to 3.00% by weight, silicon 1.00% by weight or less. It is preferable to use those containing 2.00% by weight or less of manganese, 0.08% by weight or less of carbon, 0.045% by weight or less of phosphorus, and 0.03% by weight or less. Of the supply pipes 12 and 14, it is preferable to use a stainless steel pipe for the fixed one, and to use a Teflon tube for the movable part and the place where the replacement is performed regularly. Here, the movable part includes, for example, a reticle blind する for changing an illumination area of a reticle arranged in the illumination optical system, and a plurality of aperture stops (transport zone, aperture diameter) for changing reticle illumination conditions. The aperture plate has a different aperture, an aperture for making four secondary light sources at positions eccentric from the optical axis, etc.). The inner and outer peripheral surfaces of the stainless steel pipe are preferably subjected to electrolytic polishing, while the Teflon tube is preferably cleaned in advance with a solvent or the like.

According to such a projection exposure apparatus, when an inert gas is supplied from a gas supply source or the like (not shown) through the supply pipe 14, the inert gas is removed after the impurity gas is removed through the filter 15. Are sent to the distribution unit 13. Then, in the distribution section 13, the inert gas is distributed to each of the supply pipes 12 so as to have a predetermined pressure and flow rate, and then the casings of the light source 4, the light transmission system 6, the illumination optical system 5, and the projection optical system 7 are provided. It is sent to 11 and the atmosphere of the optical path of the exposure light is replaced with an inert gas.

Also, as shown in FIG. 1, a desired inert gas atmosphere is formed between the final lens of the projection optical system 7 and the wafer 2 by an appropriate method. Specifically, the entire stage device 1 され on which the wafer 2 is placed from the lower end of the projection optical system 7 is surrounded by a container (not shown), and the container is filled with an inert gas. A method of continuously supplying an inert gas to an open space between the lower end and the wafer 2 to form an inert gas atmosphere can be employed. Further, between the illumination optical system and the projection optical system, that is, the reticle chamber in which the reticle is arranged is also surrounded by the casing 11, and the inside of the casing 11 may be replaced with an inert gas as described above. .

In addition, wiring and fiber cables (not shown) disposed in the casing 11 are also made of tetrafluoroethylene (registered trademark) tetrafluoroethylene, a material that suppresses the generation of impurity gases. — It is preferably coated with various fluoropolymer materials such as terfluoro (alkyl vinyl ether) and tetrafluoroethylene-hexafluoropropene copolymer. The wiring is used, for example, to supply electric power to a motor for driving a reticle blind and a palette plate. Also, fiber cables are used, for example, for reticles and wafers. It is used to emit alignment light to perform alignment. In such a projection exposure apparatus 1, the exposure light emitted from the light source 4 is made uniform through the light transmission system 6 and the illumination optical system 5 to uniformly illuminate the reticle 3, and any light on the reticle 3 The pattern forms an image on a predetermined exposure area on the wafer 2 via the projection optical system 7 and is projected and transferred.

After the transfer of the pattern to the exposure area is completed, the wafer 2 is moved to a predetermined position and positioned by the stage device 17, and the projection transfer of the pattern to the next exposure area is performed. In this manner, the projection transfer of the pattern onto the entire wafer 2 is performed by the so-called step-and-repeat method in which the movement and positioning of the wafer 2 and the projection transfer of the pattern are sequentially repeated.

As described above, in the projection exposure apparatus 1, the periphery of the light source 4, the illumination optical system 5, the light transmission system 6, and the projection optical system 7 are surrounded by the casing 11, and the inert gas is supplied into the interior. Is done.

As a result, the atmosphere in the optical path of the exposure light from the light source 4 to the wafer 2 is replaced with the inert gas, and the exposure light passes through the inert gas atmosphere. Therefore, it is possible to prevent the generation of ozone generated by the photochemical reaction of the exposure light with the air. As a result, the environment is not impaired, the light use efficiency (transmittance) of the exposure light is not reduced, and the surface of an optical element such as a lens or a mirror disposed on the optical path of the exposure light is not clouded. Therefore, the performance of the projection exposure apparatus 1 can be stably exhibited.

The supply pipes 12 and 14 for supplying inert gas to the casing 11 use stainless steel pipes or Teflon tubes, which are materials for suppressing the generation of impurity gases. Generation of outgas from the gas itself can be minimized, and internal contamination of the inert gas introduced into the casing 11 can be minimized. As a result, it is possible to suppress a decrease in the transmittance of optical elements such as lenses disposed in the light source 4, the light transmission system 6, the illumination optical system 5, the projection optical system 7, and the like, and to reduce the original performance of the projection exposure apparatus 1. We can show enough. Also, from a long-term perspective, it is possible to suppress the performance degradation of the optical element that has occurred conventionally, and to maintain the required performance for a long time. Further, since the supply pipe 14 is provided with a filter 15, impurity gas mixed with the inert gas supplied into the casing 11 can be removed. Can be enhanced.

In addition, a distribution section 13 is provided on the downstream side of the filter 15, and a plurality of supply pipes 12 connected to the casing 11 are connected to the distribution section 13. The number of the filters 15 can be minimized, and the above-described effects can be achieved with a minimum cost.

In the above embodiment, the positions of the distribution unit 13 and the filter 15 are not limited, and may be disposed inside the chamber 10 or outside the chamber 10. Good.

Also, for example, it is possible to supply the inert gas into the casing 10 with only one supply pipe instead of using a plurality of supply pipes 12. In this case, the distribution section 13 May be omitted.

In addition, the supply pipes 12, 14 are made of stainless steel pipes, Teflon tubes, etc., but other materials can be used as long as they generate little impurity gas from themselves. is there. Further, for example, only the inner peripheral surface and the outer peripheral surface of the supply pipes 12 and 14 may be formed of the above-described material. In this case, for the supply pipes 12 and 14 located outside the chamber 10, only the inner peripheral surface may be formed of the above-described material.

Further, in the present embodiment, the casing 11 to which the inert gas is supplied via the stainless steel pipe and the Teflon tube is one which has been washed with an ultrasonic wave or a solvent before being installed in the apparatus. Thereby, generation of impurity gas can be further suppressed.

Further, as the casing 11, especially the inner peripheral surface of the casing 11 that houses the light transmission system is usually coated with chrome, but since the coating itself may generate impurity gas, it is solid. It is preferred to form the casing 11 with metal.

In the above embodiment, the wiring and the fiber cable disposed in the casing 11 are also covered with the impurity gas generation suppressing material. As in the past, the nylon coating may be used, and the nylon coating may be wrapped or coated with aluminum foil. With this configuration as well, generation of impurity gas from the coating can be suppressed. However, it is most preferable that the wiring, the fiber cable, and the like be covered with an impurity gas generation suppressing material, and further be wound or covered with aluminum foil.

Similarly, an aluminum foil may be provided on the inner and outer peripheral surfaces of the inert gas supply pipes 12 and 14 and the tube.

Further, in the present embodiment, the filter 15 is provided in the supply pipe 14 to remove the impurity gas mixed with the inert gas supplied into the casing 11. For example, when using an air stage that drives the stage by lifting it with air pressure, the air supply for the air stage is used to remove the impurity gas present in the air supplied to the air stage. The tube may be provided with a filter. With such a configuration, the contamination of the air in the chamber can be further suppressed.

As the supply pipe for the air stage, the Teflon tube is desirably used as described above since the air stage is a movable member. As the air for the air stage, it is desirable to use the same or a different inert gas as the inert gas supplied into the casing 11. If the same gas as the inert gas supplied into the casing 11 is used, a decrease in the gas concentration in the casing can be prevented. Further, any filter may be used as the filter 15 as long as the impurity gas mixed in the inert gas can be removed. For example, the filter 15 can be an organic filter that removes silicon-based organic substances (for example, siloxane / silazane), or an activated carbon that removes plasticizers (such as phthalsan esters) and flame retardants (such as phosphoric acid and chlorine-based substances). Filter (for example, trademark “Gigasoap” manufactured by Niyu Corporation)） Zeolite Fill Yuichi or the like can be used.

In addition, the present invention has an object to prevent an impurity gas from being mixed into an inert gas supplied to an optical path of exposure light of a projection exposure apparatus. Any configuration other than the configuration described above may be used.

In this embodiment, the supply pipe for supplying the inert gas is used to suppress generation of impurity gas. Although the example using the supply pipe formed of the control material has been described, the discharge pipe for discharging the gas in the casing from the casing may be formed of the impurity gas generation suppressing material. Although the projection exposure apparatus 1 is of the step-and-repeat type, the present invention is also applicable to a scanning projection exposure apparatus that exposes the pattern of the reticle 3 by synchronously moving the reticle 3 and the wafer 2. Can be applied. The types of projection exposure apparatus are not limited to those used for semiconductor manufacturing, and include, for example, a liquid crystal projection exposure apparatus that exposes a liquid crystal display element pattern to a square glass plate, and a thin film magnetic head. The present invention can be widely applied to an exposure apparatus or the like for performing the above. Further, the projection optical system 7 may be any of a total reflection system, a total refraction system, and a catadioptric system, and the magnification may be not only a reduction system but also any of an equal magnification and an enlargement system.

The light source used as the exposure light in the projection exposure apparatus 1, A r F excimer not limited to one The one (1 9 3 nm), K r F excimer one The one (2 4 8 nm), F 2 laser one ( 157 nm), or a harmonic of a YAG laser or a metal vapor laser, or EUV (Extreme Ultra Violet) light with an emission spectrum at 5 to 5 nm (soft X-ray region), and even X-rays. Charged particle beam can also be used.

As the inert gas, for example, an inert gas such as nitrogen, helium, neon, argon, krypton, xenon, or radon may be used. Preferably, use is made of chemically clean dry air (air from which substances that cause lens fogging, such as ammonia ions floating in a clean room, or air with a humidity of 5% or less) are used. .

Further, the above-described configurations may be appropriately selected and combined, or any configuration may be combined with the present invention without departing from the gist of the present invention. Industrial applicability

In the projection exposure apparatus of the present invention, at least the inner peripheral surface of the supply pipe for supplying the inert gas to the casing is made of, for example, stainless steel, tetrafluoroethylene, tetrafluoroethylene, ethylene-terfluoro (alkyl vinyl ether), tetrafluoro. It is made of an impurity gas generation suppressing material such as various fluorine polymers such as ethylene-hexafluoropropene copolymer. Therefore, generation of impurity gas from the supply pipe itself is suppressed. As a result, the internal contamination of the inert gas introduced into the casing can be minimized, the transmittance of optical elements such as lenses can be suppressed, and the original performance of the projection exposure apparatus can be fully exhibited. . In addition, it is possible to maintain the required performance for a long time.

Claims

The scope of the claims

1. A projection exposure apparatus that illuminates a pattern of a mask with exposure light and transfers an image of the pattern onto a substrate, wherein the casing surrounds at least a part of an optical path of the exposure light; And a supply device for supplying an inert gas to the inside of the device via a supply tube, wherein at least an inner peripheral surface of the supply tube is formed of an impurity gas generation suppressing material.

2. The projection exposure apparatus according to claim 1, wherein the material for suppressing the generation of impurity gas is stainless steel, styrene tetrafluoride, tetrafluoroethylene monoterfluoro (alkyl vinyl ether), tetrafluoro. Projection exposure equipment using various fluoropolymers such as ethylene-hexafluoropropene copolymer.

3. The projection exposure apparatus according to claim 1, wherein the supply pipe is provided with a filter for removing impurities from an inert gas supplied through the supply pipe.

4. The projection exposure apparatus according to claim 3, wherein a distribution unit is provided downstream of the filter, and the distribution unit includes a plurality of supply pipes connected to each unit of the casing. Is connected to the projection exposure apparatus.

5. The projection exposure apparatus according to claim 1, wherein the power supply wiring disposed near the optical path of the exposure light is covered with an impurity gas generation suppressing material.

6. The projection exposure apparatus according to claim 5, wherein the impurity gas generation suppressing material is an aluminum foil.

7. A projection exposure method for illuminating a pattern of a mask with exposure light and transferring an image of the pattern onto a substrate, wherein at least a part of an optical path of the exposure light is surrounded by a casing, and the inside of the casing is formed. Transferring an image of the pattern onto a substrate in a state in which an inert gas is supplied through a supply pipe having at least an inner surface formed of an impurity gas generation suppressing material, and an optical path of the exposure light is filled with the inert gas. A projection exposure method that specializes in