JP3358107B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly, to an exposure apparatus having an excimer laser, a harmonic laser, and a mercury lamp light source for emitting light in the ultraviolet region, particularly, a spectrum light overlapping the absorption spectrum of oxygen. .

[0002]

2. Description of the Related Art In a lithography process for manufacturing a semiconductor device or a liquid crystal substrate, an exposure apparatus for exposing a pattern image of a reticle (photomask or the like) onto a photosensitive substrate via a projection optical system is used. In recent years, semiconductor integrated circuits have been developed in the direction of miniaturization, and in the lithography process, a method of shortening the exposure wavelength of a lithography light source has been considered as a means for further miniaturization.

At present, an exposure apparatus employing a KrF excimer laser having a wavelength of 248 nm as a stepper light source has already been developed. Also, a harmonic of a wavelength variable laser such as a Ti-sapphire laser, a fourth harmonic of a YAG laser having a wavelength of 266 nm, a fifth harmonic of a YAG laser having a wavelength of 213 nm, a mercury lamp having a wavelength of around 220 nm or 184 nm, and an ArF having a wavelength of 193 nm Excimer lasers and the like have attracted attention as candidates for short-wavelength light sources.

In a conventional exposure apparatus using a g-line, an i-line, a KrF excimer laser or a mercury lamp that emits light having a wavelength of about 250 nm as a light source, the emission spectrum lines of these light sources have oxygen absorption as shown in FIG. It did not overlap with the spectral region, and there was no inconvenience due to a decrease in light use efficiency due to oxygen absorption and ozone generation due to oxygen absorption. Therefore, these exposure apparatuses were basically able to perform exposure in an air atmosphere.

However, as shown in the figure, in a light source such as an ArF excimer laser, the emission spectrum line overlaps with the oxygen absorption spectrum region. Inconvenience due to the occurrence occurs. For example, if the transmittance of ArF excimer laser light in a vacuum or in an inert gas such as nitrogen or helium is 100% / m, the free-run state (natural emission state), that is, about 90% in an ArF broadband laser. / M, the transmittance is reduced to about 98% / m even when an ArF narrow band laser having a narrowed spectrum width and avoiding the oxygen absorption line as shown is used.

[0006] The decrease in transmittance is considered to be due to the absorption of light by oxygen and the effect of the generated ozone. The generation of ozone not only adversely affects the transmittance (light utilization efficiency), but also degrades the performance of the device due to the reaction with the optical material surface and other components and causes environmental pollution.

As described above, in an exposure apparatus having a light source such as an ArF excimer laser, it is necessary to fill the entire optical path with an inert gas such as nitrogen in order to avoid a decrease in light transmittance and generation of ozone. Is well known. In general, an exposure apparatus includes an illumination optical system for uniformly illuminating a reticle with light from a light source, a projection optical system for forming a circuit pattern formed on the reticle on a wafer, and supporting and moving the wafer appropriately. And stage means for positioning.

[0008]

The exposure apparatus having the above-mentioned structure is basically composed of a unit which is not driven from the light source to the projection optical system. Also, in the scanning optical system, even if the reticle is moved during exposure, the frequency of replacement is small. Further, although there is a drive unit for exchanging the σ stop inserted in the illumination optical system, there is no exchange during exposure and the exchange frequency is low. Therefore, if the space from the light source to the final optical member (such as a lens) of the projection optical system is surrounded by a container and the air in the container is replaced with an inert gas, the atmosphere of the inert gas is broken during one exposure process. Not much.

However, the stage means requires frequent replacement of wafers, and furthermore, it is necessary to always move the wafer stage two-dimensionally in order to transfer a circuit pattern to a plurality of exposure areas of one wafer. Therefore, the method of filling the inert gas by surrounding it with a container from the end of the projection optical system to the entire stage means has a disadvantage that the container becomes large and complicated. In addition, since the inert gas atmosphere is broken each time the wafer is replaced, it takes time to form the required inert gas atmosphere again,
There is a disadvantage that the throughput is reduced.

The present invention has been made in view of the above problems, and has as its object to provide an exposure apparatus capable of performing exposure in a required inert gas atmosphere and having improved throughput.

[0011]

To solve the above problems, an illumination optical system for illuminating a mask on which a pattern is formed with exposure light from a light source, and a projection optical system for transferring an image of the pattern onto a substrate. An exposure apparatus comprising: a first container surrounding the illumination optical system; a second container surrounding the mask; a third container surrounding the projection optical system; and the first container; First gas supply means for supplying an inert gas to each of the second container and the third container; and supplying the inert gas toward the substrate along an optical axis of the projection optical system. An exposure apparatus comprising: a second gas supply unit; and an ionization unit configured to ionize the inert gas supplied to the second container surrounding the mask.

In this configuration, the ionization means is configured to ionize the inert gas supplied toward the substrate.

[0013] The first gas supply means may be arranged such that the pressure in the first container, the pressure in the second container, and the pressure in the third container are each equal to or higher than the atmospheric pressure. An inert gas is supplied to the first container, the second container, and the third container.

In this configuration, the inert gas to be ionized is nitrogen gas or helium gas.

[0015]

According to the present invention, there is provided an exposure apparatus comprising: an illumination optical system for illuminating a mask on which a pattern is formed with exposure light from a light source; and a projection optical system for transferring an image of the pattern to a substrate. In the apparatus, a first container surrounding the illumination optical system, a second container surrounding the mask, a third container surrounding the projection optical system, the first container, the second container First gas supply means for supplying an inert gas to each of the container and the third container, and second gas for supplying the inert gas toward the substrate along the optical axis of the projection optical system Since it has a supply unit and an ionization unit for ionizing the inert gas supplied to the second container surrounding the mask, it is possible to remove static electricity generated in the mask.

Further, the ionization means can further ionize the inert gas supplied toward the substrate.

The inert gas to be ionized is nitrogen gas or helium gas, and the inert gas is ionized by ultraviolet irradiation.

[0018]

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a configuration of an exposure apparatus according to an embodiment of the present invention. The illustrated device is, for example, A
A light source EXL that emits short-wavelength laser light such as an rF excimer laser is provided. A part of the light beam emitted from the light source EXL passes through a beam splitter (partial mirror) Mp, and the rest is reflected. The light transmitted through the beam splitter Mp is reflected by mirrors MI1, MI2 and MI3,
The reticle R is uniformly illuminated via an appropriate illumination optical member. An optical path from the light source EXL to the reticle R forms an illumination optical system IL. The illumination optical system IL is surrounded by a container, and the container is supplied with an inert gas such as a nitrogen gas via a valve V1.

The light transmitted through the reticle R is reflected by the projection optical system P
L through various optical members constituting the wafer stage W
S reaches the surface of the wafer W placed on the reticle R
Image the above pattern. The projection optical system PL is also surrounded by a container, and the container is supplied with nitrogen gas via a valve V2.

The container surrounding the illumination optical system IL communicates with the exhaust duct via the valve V3, the oxygen sensor S, and the rotary pump RP. On the other hand, the projection optical system P
The container surrounding L is connected to the exhaust duct via the valve V4, the oxygen sensor S, and the rotary pump RP. Light emitted from the light source EXL and reflected by the beam splitter Mp is reflected by a plurality of appropriately arranged mirrors M, and enters the gas cell GS via the lens L. Nitrogen gas is supplied to the gas cell GS via a pressure reducing valve RG. As shown in detail in FIG. 2, an orifice O is formed in the gas cell GS, and a lens L is arranged so as to seal the orifice O. Light incident into the gas cell GS via the lens L is configured to be focused on an axis connecting the gas supply port 10 and the gas discharge port 11. Thus, the nitrogen gas is ionized in the gas cell GS by the two-photon absorption effect of the ultraviolet light.

The ionized nitrogen gas discharged from the gas cell GS is supplied to a vessel surrounding the reticle R via a valve V5. The container surrounding the reticle R communicates with the exhaust duct via the valve V8, the oxygen sensor S, and the rotary pump RP. The ionized nitrogen gas discharged from the gas cell GS is further configured to be supplied to the lower end of the projection optical system PL via a valve V6 and to the wafer stage WS via a valve V7.

FIG. 3 is a perspective view schematically showing the configuration of the projection optical system PL and the wafer stage WS. As shown, the wafer W is placed on the wafer table 2 perpendicularly to the optical axis of the projection optical system PL and at regular intervals. On the quadrilateral wafer table 2, X is set along two orthogonal sides.
A direction interference mirror 7X and a Y direction interference mirror 7Y are provided. The X-direction interference mirror 7X and the Y-direction interference mirror 7Y are configured to reflect light from the interferometer units 6X and 6Y provided at opposing positions, respectively. Detection is performed at a resolution, and thus positional information of the wafer W can be obtained.

The wafer table 2 is mounted on an X stage 5, and the X stage 5 is reciprocated in the X direction by a driving mechanism 3X. The X stage 4 and the driving mechanism 3X are mounted on the Y stage 4, and the Y stage 4 is reciprocated in the Y direction by the driving mechanism 3Y. Further, the Y stage 4 and the driving mechanism 3
Y is placed on the base. Thus, the wafer table 2, the X stage 5, the driving mechanism 3X, the Y stage 4, the driving mechanism 3Y, the X direction interferometer unit 6X, the Y direction interferometer unit 6Y, the X direction interference mirror 7X, and the Y direction interference mirror 7Y Constitute a wafer stage mechanism WS.

FIGS. 4 (a) and 4 (b) are views showing the path of the nitrogen gas supplied between the projection optical system PL and the wafer W and the arrangement of the supply ports. In the present embodiment, a plurality of outlets 8 arranged, for example, circumferentially are provided at the lower end of the projection optical system PL. A nitrogen gas is supplied to the wafer W through the outlet 8 along the optical axis of the projection optical system PL, in other words, in a direction substantially perpendicular to the surface of the wafer W.

On the other hand, a plurality of other outlets 9 are provided on the wafer table 2. Via this outlet 9, nitrogen gas is also supplied in a direction substantially parallel to the wafer W surface. As shown in FIG. 4B, the outlets 9 may be arranged circumferentially on the wafer table 2 to supply nitrogen gas radially toward the optical axis of the projection optical system PL. Also,
By providing the outlet 9 'inside the X-direction interference mirror 7X and the Y-direction interference mirror 7Y provided on the wafer table 2, the outlet may not interfere with the wafer when the wafer W is replaced. .

In the exposure apparatus according to the embodiment of the present invention configured as described above, the illumination optical system IL and the projection optical system PL
And a container surrounding the reticle R, respectively, is connected to a rotary pump R via corresponding valves V3, V4 and V8.
It is evacuated sequentially by the action of P. The degree of vacuum in each container can be known based on the oxygen concentration detected by the corresponding oxygen sensor S. After the desired vacuum state is achieved, nitrogen gas is supplied to the containers surrounding the illumination optical system IL and the projection optical system PL via the valves V1 and V2, respectively, until the atmospheric pressure becomes higher than the atmospheric pressure. The container surrounding the reticle R is supplied with appropriately ionized nitrogen gas through the valve V5 until the pressure becomes equal to or higher than the atmospheric pressure. By the action of the ionized nitrogen gas, static electricity generated on the reticle R can be removed, and damage to the reticle R caused by static electricity can be prevented.

On the other hand, between the projection optical system PL and the wafer W, the ionized nitrogen gas is directed toward the wafer W via the valve V6 and the outlet 8 formed at the lower end of the projection optical system PL. The wafer W is supplied substantially vertically.
Further, ionized nitrogen gas is supplied above the wafer W substantially in parallel with the wafer W through a valve V7 and an outlet 9 provided on the wafer table 2 of the wafer stage WS. By the action of the ionized nitrogen gas, static electricity generated on the wafer W can be removed,
Damage and contamination of the wafer W due to static electricity can be prevented.

The ionized nitrogen gas is supplied almost continuously between the projection optical system PL and the wafer W during exposure projection of the wafer and when the wafer is replaced. Therefore, even when the wafer is replaced, the nitrogen gas atmosphere is not substantially broken. On the other hand, in the container surrounding the illumination optical system IL and the projection optical system PL, the internal components and the like are not usually replaced, and there is no need to further supply nitrogen gas after initial replacement with nitrogen gas. . On the other hand, in the container surrounding the reticle R, only when it is necessary to replace the reticle R, it is necessary to newly evacuate and supply the ionized nitrogen gas after the replacement.

As described above, in this embodiment, in the exposure apparatus in which the exposure wavelength overlaps with the absorption spectrum of oxygen, both the direction perpendicular to the wafer surface and the direction parallel to the wafer surface are provided between the final member of the projection optical system and the wafer. Is supplied continuously along the line. Therefore, projection exposure in an inert gas atmosphere can be performed at a replacement ratio substantially equal to that of the case where the space is replaced with an inert gas by being surrounded by a container from the lower end of the projection optical system to the entire wafer stage. Incidentally, when the nitrogen gas is supplied only in the direction perpendicular to the wafer surface, the inventor of the present application supplies the nitrogen gas from both directions as in the present invention, although the oxygen concentration in the exposed portion is about 10%. It has been confirmed that this can reduce the oxygen concentration to about 1%.

The wafer table is generally provided with a wafer suction / release mechanism. Therefore, by sharing the gas used when the wafer is detached with the inert gas used in the present invention, the piping structure of the gas circulation system can be simplified. Further, in the present embodiment, an example in which nitrogen gas is used as the inert gas has been described, but any inert gas having no oxygen absorption spectrum in the exposure wavelength region may be used.
For example, a gas such as helium may be used.

Further, in the present embodiment, an exposure apparatus using an ArF laser and using light in a wavelength range of 200 nm or less as an exposure light has been described as an example. It is apparent that the present invention can be effectively applied to resists that dislike the atmosphere, regardless of the exposure wavelength. Further, the projection optical system P
It goes without saying that the present invention can be effectively applied to any of the reflection system, the catadioptric system, and the refraction system.

[0032]

As described above, according to the present invention, an illumination optical system for illuminating a mask on which a pattern is formed with exposure light from a light source, and a projection optical system for transferring an image of the pattern to a substrate. A first container surrounding the illumination optical system, a second container surrounding the mask, a third container surrounding the projection optical system, and the first container. First gas supply means for supplying an inert gas to each of the second container and the third container, and supply of an inert gas toward the substrate along an optical axis of the projection optical system And a second gas supply means for ionizing the inert gas supplied to the second container surrounding the mask.
Static electricity generated in the mask can be removed, and damage to the mask due to the static electricity can be prevented.

[0033]

[0034]

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a gas cell used in the apparatus of FIG.

FIG. 3 is a perspective view schematically showing a configuration of a projection optical system and a wafer stage.

FIG. 4 is a diagram showing a path of an inert gas supplied between a projection optical system and a wafer and an arrangement of supply ports.

FIG. 5 is a diagram showing an absorption spectrum of oxygen.

[Explanation of symbols]

 2 Wafer table 3 Drive mechanism 4 X stage 5 Y stage 6 Interferometer unit 7 Interferometer mirror 8 Inert gas outlet of projection optical system 9 Inert gas outlet of wafer table

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-21013 (JP, A) JP-A-62-286226 (JP, A) JP-A-5-47650 (JP, A) JP-A 52-286 84976 (JP, A) JP-A-61-97918 (JP, A) JP-A-61-112317 (JP, A) JP-A-3-272127 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (6)

(57) [Claims] 1. A pattern is formed by exposure light from a light source.
An exposure apparatus including an illumination optical system for illuminating the mask, and a projection optical system for transferring an image of the pattern onto a substrate, a first container surrounding the illumination optical system, and a second container surrounding the mask. A container, a third container surrounding the projection optical system , and the first container , the second container, and the third container .
A first gas supply means for supplying an inert gas to each of the first gas supply means and an inert gas toward the substrate along an optical axis of the projection optical system;
An exposure apparatus comprising: second gas supply means for supplying an active gas; and ionization means for ionizing the inert gas supplied to the second container surrounding the mask . 2. The apparatus according to claim 1, wherein said ionization means further moves toward said substrate.
2. The exposure apparatus according to claim 1, wherein the inert gas thus supplied is ionized. 3. The first gas supply means is arranged such that the pressure in the first container, the pressure in the second container , and the pressure in the third container are each equal to or higher than the atmospheric pressure. The exposure apparatus according to claim 1, wherein an inert gas is supplied to the first container, the second container, and the third container. 4. The method according to claim 1, wherein the inert gas to be ionized is nitrogen gas or helium gas.
The exposure apparatus according to any one of claims 1 to 3 . Wherein said ionization means, said by irradiating ultraviolet rays to the inert gas, the exposure according to the inert gas from claim 1, wherein the ionizing to any one of claims 4 apparatus. Wherein said first, second, an exposure according to claims 1, characterized in that an oxygen sensor for measuring the respective oxygen concentration in the third vessel to claims 5 apparatus.