Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-03-09
2003-11-25
Font, Frank G. (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S055000, C355S072000, C355S075000, C355S077000, C250S492200, C250S492220, C430S311000
Reexamination Certificate
active
06654100
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a stage device and an exposure apparatus, and to a method of manufacturing a device, and more specifically to a stage device that drives a stage on which an object is mounted, an exposure apparatus provided with the stage device as, for example, a driving device of a substrate, and to a method of manufacturing a device using the exposure apparatus.
2. Description of Related Art
Conventionally, in a lithographic process to manufacture a semiconductor element, a liquid crystal display element, or the like, an exposure apparatus has been used that transfers a pattern formed on a mask or a reticle (hereafter referred to as “reticle”) onto a substrate (hereafter referred to as “wafer”) such as a glass plate or a wafer, where a resist or the like is coated, through a projection optical system.
In this type of exposure apparatus, in order to position a wafer at an exposure position with high accuracy, a stage device has been used to control a position and a posture in six degrees-of-freedom, such as X, Y, Z, &thgr;
X
, &thgr;
Y
,&thgr;
Z
,of a wafer holder that holds the wafer. It is common in this type of stage device to drive an XY stage in the two-dimensional X-Y direction by a Y-axis driving linear motor and a pair of X-axis driving linear motors. In addition, a &thgr;
Z
table mounted on the X-Y stage, and a three degrees-of-freedom driving table (Z leveling table), mounted on the &thgr;
Z
table, drive a wafer holder that holds a wafer in three degrees-of-freedom directions such as Z, &thgr;
X
,and &thgr;Y.
In general, the XY stage moves on a holding plate (a stage base) having a smooth reference surface. Additionally, the XY stage is non-contactingly supported over the reference surface by a non-contact bearing, for example, an air bearing, arranged at the bottom of the XY stage with a clearance of several &mgr;m. Therefore, a posture of the XY stage with respect to the reference surface can be constantly maintained, and a long life expectancy can be expected by avoiding the effects of mechanical friction.
Meanwhile, in a conventional exposure apparatus, when an exposure operation for a wafer mounted on an XY stage is completed, wafer replacement and alignment (search alignment, fine alignment) are performed, then exposure is performed, and then wafer replacement is again performed. Thus, three significant operations, such as: (1) wafer replacement; (2) alignment; (3) exposure; and (4) wafer replacement, or the like, are repeated. Because of this, time (hereafter referred to as “overhead time”) for wafer replacement and alignment causes deterioration of throughput. Therefore, many “plurality of stages” arrangements have been suggested in which a plurality of stages are prepared, wafer replacement and alignment are performed on a separate stage during wafer exposure on one stage, and throughput is improved by such simultaneous parallel processing (e.g., see Japanese Laid-Open Patent Application No. 8-51069 and WO98/24115).
In an exposure apparatus with a plurality of stages as described above, compared to a single-stage type exposure apparatus, a stage moving area is naturally enlarged. Therefore, a reference surface used during stage movement, and as a result, a holding plate on which the reference surface is formed, needs to be enlarged (making its area large). The holding plate, particularly the reference surface, becomes a reference during stage movement. Thus, extremely high accuracy processing for the surface is required in order to suitably maintain stage stability and position controllability. However, it is extremely difficult to fabricate a large holding plate with a high surface accuracy. In addition, the cost increases as the reference surface area increases. Furthermore, as the holding plate becomes enlarged, it is difficult to support the holding plate without affecting the reference surface by warping due to its own weight. As a result, this deteriorates controllability of the position of the stage.
These shortcomings are not limited to a plurality of stages, but apply to an exposure apparatus with a single stage as well. In addition, in future exposure apparatus, as a wavelength for exposure is shortened, there is a high possibility of using a catadioptric system as a projection optical system. A diameter of a bottom part of this catadioptric system is large, so a distance between an exposure part and an alignment part or a wafer replacement part naturally becomes long. Furthermore, this is not limited to a catadioptric system, but even in a dioptric system, when a diameter of a projection optical system is enlarged in order to improve a numerical aperture, in the same manner, a distance between an exposure part and an alignment part or a wafer replacement part naturally becomes long. This causes enlargement of the holding plate due to an area increase in a range where the stage moves. In addition to this, the time between wafer replacement alignment and exposure naturally takes long, so this causes deterioration of throughput. Therefore, one problem to be solved is how this time can be shortened in order to improve throughput.
Additionally, when an exposure operation that improves throughput, an alignment operation, and a substrate replacement operation are simultaneously performed in a parallel manner by a plurality of stages, vibration due to driving one stage is transmitted to the other stages via the holding plate, so controlling the position of each stage deteriorates.
SUMMARY OF THE INVENTION
This invention is made in consideration of the above-mentioned circumstances. One object of the invention is to provide a stage device that can suitably maintain control of the position of the stage.
Another object of this invention is to provide an exposure apparatus that improves exposure accuracy with respect to a substrate on a stage and simultaneously improves throughput.
A further object of this invention is to provide a method of manufacturing a device with improved productivity, resulting in a device having a high level of integration.
A stage device according to one aspect of the invention is provided with a movable stage that holds an object. A first reference member on which a first movement reference surface is formed, is used as a reference when the stage moves. A second reference member on which a second movement reference surface, different from the first movement reference surface, is formed is provided. In addition, a switching device switches between a first state in which the stage is movable along the first movement reference surface, and a second state in which the stage is movable along the second movement reference surface.
According to this aspect of the invention, the switching device switches between a first state in which the stage is movable along the first movement reference surface and a second state in which the stage is movable along the second movement reference surface. Because of this, there is no inconvenience for stage movement even if the first reference member on which the first movement reference surface is formed is arranged physically separated from the second reference member on which the second movement reference surface is formed. Compared to the case on which the first movement reference surface and the second movement reference surface are formed on the same reference member, an area of the reference surface of the respective reference members can be made smaller. Therefore, for example, even if holding plates are used as the first reference member and as the second reference member, the respective reference surfaces can be processed with high accuracy. Thus, processing difficulty of the reference surfaces can be overcome. At the same time, stage stability can be ensured during movement in which the first and second reference surfaces are used as references, and positional controllability of the stage can be maintained.
In this case, the first and second reference members can be similar types of members, or can be constituted by different types
Brown Khaled
Font Frank G.
Nikon Corporation
Oliff & Berridg,e PLC
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