Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2002-04-30
2004-09-07
Mathews, Alan (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S072000, C355S077000
Reexamination Certificate
active
06788385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a stage device and an exposure apparatus, and more particularly, to a stage device having a plurality of stages, and an exposure apparatus having the stage device.
2. Description of Related Art
Various types of exposure apparatus are conventionally used in photolithographic processes for manufacturing semiconductor devices (ICs), liquid crystal display devices, and the like. In recent years, stepping projection exposure apparatus, such as a step-and-repeat reduction projection exposure apparatus (a so-called “stepper”) and a step-and-scan projection exposure apparatus (a so-called “scanning stepper”) have been mainly used.
Since this type of projection exposure apparatus is principally used to mass-produce semiconductor devices and the like, it has been inevitably necessary to increase the number of wafers to be exposed in a given period, that is, to enhance throughput.
Operation of the projection exposure apparatus is generally carried out in the following manner:
(a) First, a wafer is loaded onto a wafer table by a wafer loader in a wafer loading step.
(b) An alignment step is performed so as to find the positions of the shot areas on the wafer. The alignment step usually employs EGA (Enhanced Global Alignment). In this method, the positions of alignment marks (wafer marks) made in a plurality of sample shot areas selected beforehand from the shot areas of the wafer are sequentially measured, and layout data on all the shot areas is found by statistical calculations using the so-called least squares method or the like based on the results of measurement and the designed shot layout (see Japanese Unexamined Patent Application Publication No. 61-44429 and U.S. Pat. No. 4,780,617 corresponding thereto). This makes it possible to find the coordinate position of each shot area with high throughput and with relatively high precision.
(c) In the next exposure step, the shot areas on the wafer are sequentially positioned at an exposure position based on the coordinate positions thereof determined by EGA or the like and the previously measured base line distance, and an image of the pattern on the reticle is transferred onto the wafer via a projection optical system.
(d) In a wafer unloading step, the wafer on the wafer table, which has been exposed, is unloaded by using a wafer unloader. This step is performed simultaneously with the above-described wafer loading step (a). That is, the steps (a) and (d) form a wafer replacement step.
In the conventional projection exposure apparatus, broadly, three operations, wafer replacement, alignment, and exposure, are thus repeated on one wafer stage.
Accordingly, by concurrently performing at least parts of the above three operations, i.e., wafer replacement, alignment, and exposure, throughput can be made higher than that in a case in which the operations are sequentially performed. Exposure is not carried out during wafer replacement and alignment. In order to reduce the operating time, that is, to enhance throughput, for example, a stage for wafer replacement and alignment and a stage for exposure are concurrently and independently controlled.
An exposure apparatus having such two stages, which are independently movable, (hereinafter referred to as a “twin-stage type exposure apparatus”) is disclosed in, for example, U.S. Pat. No. 5,715,064.
In the exposure apparatus disclosed in the above publication, alignment is effected on one of the stages concurrently with exposure of a wafer on the other stage. In this case, throughput is markedly enhanced, compared with the case in which alignment and exposure are sequentially effected.
When two wafer stages are simply placed, however, the footprint of the exposure apparatus is increased.
In order to effect high-precision exposure, the wafer table with the wafer thereon must be driven for Z-driving so as to control the focusing and leveling of the wafer during alignment as well as exposure. Since two wafer stages are placed side by side on a surface plate in the conventional twin-stage type exposure apparatus, however, reaction force produced due to the Z-tilting driving of the wafer table on one of the wafer stages, which is subjected to exposure, may vibrate the wafer table on the other wafer stage, and this may result in lower exposure accuracy.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a stage device which has a footprint equivalent to that of a single-stage type stage device and which allows two stages to be independently and freely moved.
A second object of the present invention is to provide an exposure apparatus which reduces the footprint thereof and enhances throughput and exposure accuracy.
According to a first aspect of the present invention, there is provided a stage device having a first stage and a second stage, including: a first driving device having a first moving member and a first stationary member so as to drive the first stage in a first direction; a second driving device having a second moving member and a second stationary member so as to drive the second stage in the first direction; a first guide bar provided with the first stationary member so as to movably support one side of the first stage; and a second guide bar provided with the second stationary member so as to movably support one side of the second stage, the second guide bar being placed at a predetermined distance from the first guide bar in a second direction orthogonal to the first direction.
In the above stage device, the first stage is driven along the first guide bar in the first direction by the first driving device while it is supported on one side by the first guide bar. The second stage is driven along the second guide bar in the first direction by the second driving device while it is supported on one side by the second guide bar. In this case, the first guide bar and the second guide bar can be placed close to each other by, for example, adopting a structure in which the other end of the first stage opposite from the side supported by the first guide bar is placed above the second guide bar, that is, in which a part of the moving range of the first stage is set above the second guide bar. This makes it possible to independently and freely move two stages in a footprint slightly larger than that of a single-stage type stage device.
The stage device may further include a third driving device for driving at least one of the first guide bar and the second guide bar in the second direction. In this case, since the first guide bar and the second guide bar can be moved close to and apart from each other, any serious problem is not caused by the structure in which the other side of the first stage opposite from the side supported by the first guide bar is placed above the second guide bar and the other side of the second stage opposite from the side supported by the second guide bar is placed above the first guide bar, that is, in which the moving range of the first stage and the moving range of the second stage partly overlap with each other. Therefore, it is possible to independently and freely move the two stages in a footprint approximately equal to that of a single-stage type stage device. In particular, in a case in which the third driving device independently drives the first guide bar and the second guide bar in the second direction, the two stages can be independently and freely moved in two-dimensional directions. This further reduces the size of the stage device.
Preferably, the point of action of driving force in the first direction is set at the center of gravity of each of the first and second stages. This can prevent unnecessary rotation moment from acting on the first and second stages when the stages are driven in the first direction.
The stage device may further include: a first table disposed on the first stage so as to hold a first sample; a first minutely driving device connected to the first sta
Binnard Michael
Hazelton Andrew J.
Martinek Daniel
Martinek Robert
Tanaka Keiichi
Martinek Daniel
Mathews Alan
Nikon Corporation
Oliff & Berridg,e PLC
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