Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1997-09-08
2001-10-23
Gray, David M. (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S076000, C355S073000, C355S075000
Reexamination Certificate
active
06307616
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an exposure apparatus for the manufacture of microdevices such as, for example, semiconductor devices (e.g., ICs or LSIs), liquid crystal devices, image pickup devices (e.g., CCDs), or magnetic heads. More particularly, the invention is directed to an exposure apparatus with an original holding stage which is lightened in weight to increase the throughput of the apparatus.
In an exposure apparatus according a simultaneous exposure method, if a projection optical system is provided by lenses, the imaging region thereof has a circular shape. However, since a semiconductor integrated circuit is generally of a rectangular shape, the pattern transfer region in the case of the simultaneous exposure method has to be of a rectangular shape inscribed with the circular imaging region of the projection optical system. Thus, even the largest pattern transfer region is of a square shape with a side 1/{square root over (2)} of the diameter of the circle.
On the other hand, there has been proposed a scan exposure method (step-and-scan method) wherein a slit-like exposure region of a size approximately corresponding to the diameter of a circular imaging region of a projection optical system is used and wherein a reticle and a wafer are scanningly moved in synchronism with each other, whereby the pattern transfer region is enlarged. In this method, with a projection optical system having an imaging region of the same size, a larger pattern transfer region can be attained as compared with the step-and-repeat method wherein for each pattern transfer region the simultaneous exposure is performed by use of a projection lens. More specifically, with respect to the scan direction there is no limitation by the optical system and, therefore, a pattern transfer region corresponding to the stroke of the stage can be provided. Also, with respect to a direction perpendicular to the scan direction, a pattern transfer region of about 2 times larger can be provided.
In exposure apparatuses for the manufacture of semiconductor integrated circuits, enlargement of the pattern transfer region and improvement of resolution are desired to meet production of larger capacity chips. The capability of using a smaller projection optical system is advantageous with respect to optical performance and cost. Thus, the step-and-scan exposure method is very attractive.
In such a step-and-scan exposure apparatus, it is necessary to assure high precision registration of a reticle and a wafer. For example, a reticle placed on a reticle stage in response to reticle replacement is observed through a reticle alignment scope, and the position of the reticle with respect to a reference mark provided on the reticle stage is measured precisely. Regarding this reticle scope, the measurement range becomes narrower with higher measurement precision. For example, the measurement range of a reticle alignment scope in an exposure apparatus suitable to production of 256M devices will have a size of about 2 microns square.
With a conventional reticle hand mechanism, it is very difficult to place a reticle on a reticle stage with a precision (error) of about 2 microns. Thus, it may be possible to provide an X-Y-&thgr; fine motion mechanism on the reticle stage and, while changing the reticle alignment scope magnification to a lower magnification, to reduce the positional error of the reticle within the range of 2 microns. However, if such an X-Y-&thgr; fine motion mechanism is mounted on the reticle stage, the reticle stage becomes heavy. Particularly, for an exposure apparatus of a scan type wherein a reticle is to be scanningly moved, the movement speed of the stage becomes lower, which causes reduction of throughput. Further, the weight of the reticle stage may cause flexure of a stage base, causing degradation of exposure precision.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an exposure apparatus which is free from the problems described above.
It is another object of the present invention to provide a substrate handling method suitably usable in a scan type exposure apparatus, for example, by which at least one of the inconveniences described above can be removed.
It is a further object of the present invention to provide a substrate handling system suitably usable in a scan type exposure apparatus, for example, by which at least one of the inconveniences described above can be removed.
It is a yet further object of the present invention to provide a device manufacturing method based on such a scanning exposure apparatus as described above.
In accordance with an aspect of the present invention, there is provided a substrate handling method, comprising: a first step for holding a substrate with a hand mechanism; a second step for discharging a gas out of a gas pad provided on a stage, such that the substrate held by the hand mechanism is floated by a small amount relative to the gas pad; a third step for moving the hand mechanism such that the substrate is positioned finely with respect to the plane of the substrate; and a fourth step for stopping gas discharging from the gas pad.
In accordance with another aspect of the present invention, there is provided a substrate handling system, comprising: a hand mechanism for holding a substrate; and a gas pad provided on a stage and being adapted to hold a substrate with suction of gas, said gas pad further being adapted to provide gas suction and gas discharging interchangeably.
In accordance with a further aspect of the present invention, there is provided a substrate handling system, comprising: a hand mechanism for holding a substrate; and a gas pad provided on a stage and being adapted to hold a substrate with attraction through suction of gas; said hand mechanism being adapted to position the substrate finely, held by said hand mechanism, upon said gas pad and with respect to the plane of the substrate.
In accordance with a yet further aspect of the present invention, there is provided a device manufacturing method for manufacturing a device with an exposure process including a substrate holding method as recited above.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
REFERENCES:
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patent: 5281996 (1994-01-01), Bruning et al.
patent: 5471279 (1995-11-01), Takizawa
patent: 5498118 (1996-03-01), Nakahara
patent: 5715064 (1998-02-01), Lin
patent: 5858587 (1999-01-01), Yamane et al.
patent: 5883932 (1999-03-01), Chiba et al.
Murata Noriaki
Taji Kenichiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Gray David M.
Kim Peter B.
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