Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2002-06-13
2004-04-13
Fuller, Rodney (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
C355S053000, C355S055000, C355S067000
Reexamination Certificate
active
06721031
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exposure apparatus suitable for manufacturing a semiconductor element, image sensing element, liquid crystal display element, thin-film magnetic head, and any other microdevices.
BACKGROUND OF THE INVENTION
Photolithography for manufacturing a semiconductor element or the like adopts an exposure apparatus which exposes a photosensitive substrate to the pattern image of a mask (e.g., reticle) via a projection optical system. Recently, semiconductor integrated circuits have been developed toward micropatterning, and the wavelength of a photolithography light source is being decreased in photolithography.
Such an exposure apparatus suffers a decrease in the intensity of exposure light under the influence of absorption of exposure light by oxygen in the use of, as exposure light, vacuum ultraviolet rays, particularly, light with a wavelength shorter than 250 nm such as a KrF excimer laser beam (wavelength: 248 nm), an ArF excimer laser beam (wavelength: 193 nm), or an F
2
laser beam (wavelength: 157 nm), harmonic light such as a YAG laser beam, or X-rays.
The prior art avoids a decrease in the transmittance of light as follows: a closed space which confines only an optical path is formed in an exposure apparatus having a light source such as an F
2
excimer laser, and gas in the closed space is purged with gas such as nitrogen not containing oxygen.
FIG. 32
is a view showing an exposure apparatus which executes exposure by supplying inert gas into a space defined by an optical member on the final stage of a projection optical system (lens barrel) and a photosensitive substrate (wafer) and forming an inert gas atmosphere in the space. In this exposure apparatus, a shielding member is arranged around the space in order to separate the space in the exposure region from an ambient atmosphere. Inert gas is supplied from the vicinity of the exposure region to the space.
The exposure apparatus shown in
FIG. 32
requires several sec until the oxygen concentration in the space in the exposure region decreases after a wafer stage is driven to load a wafer into the exposure region. This results in low throughput.
The same problem occurs when inert gas is supplied to the vicinity of a reticle. Also for the reticle, the exposure apparatus requires several sec until the oxygen concentration in a space surrounded by a shielding member decreases, which decreases the throughput.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to shorten a time required to purge, with inert gas, gas in an optical path space including a space (exposure region) through which exposure light passes, such as a space between a projection optical system and a substrate, a space between an illumination optical system which illuminates a mask (e.g., reticle) and a mask stage which holds the mask, and a space between the mask stage and the projection optical system, and/or to maintain the purity or concentration of inert gas in the optical path space at a proper level.
To achieve the above object, according to the present invention, there is provided an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate by using exposure light, comprising a stage, an optical system, and a gas flow formation mechanism which forms a flow of inert gas in an optical path space including a space through which exposure light passes between the stage and the optical system, wherein the gas flow formation mechanism forms a flow of inert gas having a spatially or temporally nonuniform distribution in the optical path space. This arrangement can shorten a time required to purge gas in an optical path space with inert gas, and/or maintain the purity or concentration of inert gas in the optical path space at a proper level.
According to a preferred aspect of the present invention, the gas flow formation mechanism forms a flow of inert gas having a nonuniform flow velocity distribution in the optical path space, as a flow of inert gas having a spatially nonuniform distribution.
More specifically, it is preferable that the gas flow formation mechanism comprise a supply mechanism which supplies inert gas to the optical path space, and that the supply mechanism supply inert gas having a nonuniform flow velocity distribution to the optical path space.
Alternatively, it is preferable that the gas flow formation mechanism comprise a supply mechanism which supplies inert gas to the optical path space, and an exhaust mechanism which exhausts gas containing inert gas from the optical path space, and that the exhaust mechanism exhaust the gas containing the inert gas from the optical path space so as to form a nonuniform flow velocity distribution in the optical path space.
According to another preferred aspect of the present invention, the nonuniform flow velocity distribution preferably includes a distribution in which a flow velocity is higher at a portion closer to the optical system. The flow of inert gas can be formed in a direction apart from the optical system, and gas in the optical path space can be efficiently exhausted.
Alternatively, according to still another preferred aspect of the present invention, the nonuniform flow velocity distribution preferably includes a distribution in which a flow velocity is higher at a portion closer to an optical axis of the optical system. The flow of inert gas can be formed from the optical path space toward an ambient space, and gas in the optical path space can be efficiently exhausted.
According to still another preferred aspect of the present invention, the supply mechanism preferably comprises two gas supply portions arranged at positions opposite to each other via the optical path space. This can further increase the exhaust efficiency.
As means for forming a flow of inert gas having a temporally nonuniform distribution, e.g., a flow of inert gas whose flow velocity temporally changes, according to still another preferred aspect of the present invention, the gas flow formation mechanism comprises a supply mechanism which supplies inert gas to the optical path space, and the supply mechanism changes a flow rate of inert gas supplied to the optical path space along with a lapse of time. Since gas in the optical path space can be stirred, the purge time can be shortened.
According to still another preferred aspect of the present invention, it is preferable that the gas flow formation mechanism comprise two gas supply portions arranged at positions opposite to each other via the optical path space, and that inert gas be supplied to the optical path space to make a flow of gas in the optical path space nonuniform.
The two gas supply portions preferably supply different supply amounts of inert gas to the optical path space or to change flow rates of inert gas along with a lapse of time. This can enhance the stirring effect.
It is more preferable that the gas flow formation mechanism comprise at least two supply mechanisms which supply inert gas to the optical path space, and that the at least two supply mechanisms be controlled to supply different supply amounts of inert gas from the respective supply mechanisms or to change flow rates of inert gas supplied from the respective supply mechanisms along with a lapse of time. This can further enhance the stirring effect.
The at least two supply mechanisms are controlled to change flow rates of inert gas supplied from the respective supply mechanisms to the optical path space along with a lapse of time while a sum of the flow rates of inert gas supplied from the respective supply mechanisms to the optical path space is kept almost constant. The stirring effect can be enhanced while the consumption amount of inert gas is kept constant.
The gas flow formation mechanism preferably changes a flow of inert gas formed in the optical path space in accordance with a change in positional relationship between the stage and the optical path space. Alternatively, it is preferable that the gas flow formation m
Hasegawa Noriyasu
Terashima Shigeru
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Fuller Rodney
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