Photocopying – Projection printing and copying cameras – Detailed holder for photosensitive paper
Reexamination Certificate
2000-12-15
2002-12-17
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for photosensitive paper
C355S053000, C355S075000
Reexamination Certificate
active
06496248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to stage devices and exposure apparatus and methods. In particular, the invention relates to stage devices that may be used in an exposure apparatus in which an energy beam having a wavelength of 200 nm or less is used for exposure, and to an exposure-apparatus and method using the stage device.
2. Description of Related Art
Hitherto, various types of exposure apparatus have been used in lithographic processes in the manufacture of semiconductor devices, liquid crystal display devices, and the like. Recently, reduction-projection exposure apparatus of a step-and-repeat type (steppers) and scanning projection exposure apparatus of a step-and-scan type (scanning stepper) are relatively widely used.
In these types of exposure apparatus, patterns of reticles (masks) are transferred onto a plurality of shot regions on a wafer (substrate). To that end, a wafer stage is driven in two-dimensions, in directions X and Y, by a driving mechanism including, for example, a linear motor. A reaction force generated by driving the wafer stage has been discharged by being mechanically transmitted to a floor (ground) by using a frame member disposed on a base (for example, a floor or a base plate as the foundation of the apparatus) vibrationally (dynamically) isolated from the stage, as described in, for example, U.S. Pat. No. 5,528,118.
In the case of the scanning stepper, a reticle stage in addition to the wafer stage must be driven in a given scanning direction. In order to deal with the reaction force generated by driving the reticle stage, a counter-mass structure that relies upon the law of conservation of momentum is generally used along a scanning direction (refer to, for example, U.S. patent application Ser. No. 09/260,544). The counter-mass structure moves in a direction opposite to the direction in which the stage moves in order to discharge (absorb) the reaction force. Movement of the counter-mass also maintains the center of gravity in the movement direction constant to avoid swaying of the apparatus. Another method for discharging a reaction force generated by moving a reticle stage is a method in which the reaction force is mechanically discharged to a base, such as a floor (ground), by using a frame member (see, for example, U.S. patent application Ser. No. 08/416,558).
In the known projection-exposure apparatus, a reaction force resulting from driving a stage is discharged to a base. Vibrations caused in the base by the reaction force have been damped by a vibration isolator, such as an anti-vibration table (vibration-elimination table) on which the projection optical system and stage are mounted, thereby suppressing vibration of the projection optical system and the stage caused by the reaction force.
Recently, vibration isolation has been improved by disposing multiple vibration-isolation tables in an exposure apparatus in situations where the effect of a reaction force, due to driving a stage, on the accuracy of exposure, although small, is non-negligible, even when the reaction force is discharged to a frame disposed directly on a base.
Semiconductor devices and the like have been more highly integrated over the years, thereby making circuit patterns smaller. Thus, projection-exposure apparatus have been required to have higher resolution. In order to improve resolution, it is known to increase the numerical aperture of the projection optical system (NA-increase) and to shorten the wavelength of the exposure beam. A most effective method for improving resolution is to shorten the wavelength of the exposure beam because the NA-increase decreases the depth of focus. Therefore, the wavelength of exposure beams has been decreasing over the years, and an exposure apparatus having, as a light source, an ArF-excimer laser having an output wavelength of 193 nm is at the stage of practical application. Moreover, exposure apparatus having light sources with even shorter wavelengths, such as an F
2
-laser (output wavelength of 157 nm) and an Ar
2
-laser (output wavelength of 126 nm), are being considered.
It is believed that the device rule (practical minimum line width) will be 0.1 &mgr;m or less in the future. There is almost no doubt that an electron beam exposure apparatus (hereinafter referred to as “EB-exposure apparatus”) will be one of the dominant alternatives as an exposure apparatus for realizing exposure of such microscopic patterns.
Vacuum ultraviolet radiation beams from, for example, the F
2
-laser, are difficult to transmit through air. Therefore, the overall light path thereof must be enclosed in a chamber or the like, and the air in the chamber must be replaced by inert gas such as nitrogen or helium, so as to remove the air from the section through which the light path is to be formed. That is, in an exposure apparatus using a vacuum ultraviolet light source, the reticle stage and the wafer stage are enclosed in respective chambers.
Similarly, in an EB-exposure apparatus, the wafer stage and the like are enclosed in evacuated chambers.
In an exposure apparatus using a near-ultraviolet light source such as an ArF-excimer laser, at least one part of the light path is preferably enclosed in a chamber or the like. The chamber or the like is preferably purged by replacing the air therein with clean air from which organic substances and the like have been removed, or with an inert gas such as nitrogen or helium.
However, in these exposure apparatus provided with chambers for enclosing the light paths, it is difficult to use the technology as it is, which is disclosed in, for example, U.S. Pat. No. 5,528,118 described above, to discharge the reaction force caused by driving, for example, wafer stages.
SUMMARY OF THE INVENTION
Accordingly, it is a first object of the invention to provide a stage device in which a reaction force generated by driving a stage can be discharged to the outside while maintaining the stage in a predetermined gas atmosphere condition.
It is a second object of the invention to provide an exposure apparatus in which the accuracy of exposure can be improved.
According to a first aspect of the invention, a stage device includes a stage, an airtight chamber, a driver and a reaction-force-discharging structure. The stage supports an object such as, e.g., a mask or a substrate. The airtight chamber receives the stage in a hermetic state. The driver is disposed in the airtight chamber and includes a movable member connected to the stage and a stationary member that cooperates with the movable member to generate a driving force to drive the stage. The reaction-force-discharging structure discharges a reaction force that is applied to the stationary member when driving the stage to the outside of the airtight chamber via a transmitting member, at least part of the transmitting member being connected to the airtight chamber.
In the present specification, the phrase “cooperates” as used, for example, in “a stationary member that cooperates with the movable member to generate a driving force” means that a driving force is generated by an interaction such as an electromagnetic (or magnetic) interaction between the stationary member and the movable member.
In the stage device according to this aspect of the invention, when the stage is driven by the driver disposed in the airtight chamber, a reaction force is generated by that driving and is applied to the stationary member. The reaction force is discharged to the outside of the airtight chamber by the reaction-force-discharging structure via the transmitting member, at least a portion of which is connected to the airtight chamber. When the airtight chamber receiving the stage is set to a predetermined gas atmosphere (including air from which organic substances and the like have been removed), the reaction force caused by driving the stage can be discharged to the outside while maintaining the predetermined atmosphere.
In this case, the airtight chamber may receive the stage and the driver, and the airtight chamber may be formed by a cham
Nguyen Henry Hung
Nikon Corporation
Oliff & Berridg,e PLC
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