Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1999-02-12
2001-07-10
Brown, Glenn W. (Department: 2858)
Photocopying
Projection printing and copying cameras
Step and repeat
Reexamination Certificate
active
06259509
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an exposure apparatus and a device manufacturing method using the same. More particularly, the invention is concerned with an exposure apparatus or an illumination system therefor having a movable portion such as a variable blind or zoom lens, for example. In another aspect, the invention is directed to a device manufacturing method using such an exposure apparatus.
Device manufacturing technology for the production of semiconductor devices, for example, has advanced remarkably and, along this trend, microprocessing techniques have improved considerably. Particularly, as regards optical processing techniques, it has accomplished a microprocessing technique of a submicron order resolution. The resolution can be improved by one of a method in which the numerical aperture (NA) of an optical system is adjusted while holding an exposure wavelength fixed and a method in which the exposure wavelength is shortened.
As regards the latter, the exposure wavelength has been changed from i-line (365 nm) to a recent KrF excimer laser having an emission wavelength of ultraviolet rays of about 248 nm. Further attempts are being made for next generation exposure light sources, using ArF excimer lasers having an emission wavelength of about 193 nm or using vacuum ultraviolet rays or soft X-rays (hereinafter, generally “X-rays”) having shorter wavelengths.
It is known that, when ultraviolet rays are used as an exposure light source, as a result of continued operation of the apparatus for a long term, there occurs deposition of ammonium sulfide (NH
4
) or silicon dioxide (SiO
2
) on the surface of an optical element disposed along a light path, damaging the optical characteristic notably. This phenomenon is attributable to a chemical reaction of chemical matter such as ammonia NH
3
, a sulfurous acid SO
2
or a Si compound contained in the ambience around the optical element, caused by irradiation with ultraviolet rays. In an attempt to prevent such deterioration of optical elements, the whole optical path of the illumination system is purged by an inert gas such as nitrogen or clean dry air, for example.
On the other hand, in order to meet a further enlargement of a chip size of semiconductor devices, the exposure method itself is being gradually changed from a step-and-repeat method in which a mask pattern is printed repeatedly with intervention of stepwise motion, to a step-and-scan method in which exposure is made while scanningly moving a mask and a wafer, followed by sequential movements to subsequent shots. In an exposure apparatus according to this step-and scan method, the exposure field has a slit-like shape and, therefore, there is an advantage that the exposure area can be enlarged without enlargement in the size of a projection optical system.
Generally, in such an exposure apparatus, there is a variable blind disposed along the optical path of an illumination system, for regulating the range of illumination for illuminating a mask having a circuit pattern formed thereon. This blind may comprise light blocking plates which are operable to set an illumination region of a rectangular shape as desired, in accordance with the type of the mask used. Specifically, step-and-repeat type exposure apparatuses may include a variable blind having light blocking plates with respect to a direction perpendicular to the mask and wafer scan direction, for setting an illumination range corresponding to the chip size as well as light blocking plates with respect to the scan direction, being movable in synchronism with the scan for variably setting the illumination range to a pattern region in the mask scan direction. An example is disclosed in U.S. Pat. No. 5,194,893.
A driving mechanism for such a variable blind may comprise a drive source and guides for regulating movement directions of the light blocking plates. Generally, the guide may comprise a contact type straight guide in which balls or rollers rotate or circulate while being in contact with a guide surface inside the guide. The drive source may generally comprise an output shaft rotation type motor and a feed screw. A driving mechanism based on such sliding motion or rolling motion may assure good positioning precision and easy driving speed control. On the other hand, at the guide, at the feed screw and at bearing elements inside the rotary motor, use of a lubricant agent such as grease is necessary to prevent wearing.
SUMMARY OF THE INVENTION
A lubricant agent contains chemical matters which may be deposited on an optical element, as described hereinbefore. These chemical matters gradually scatter into the ambient gas inside the purged space of the illumination system. As a result of operation of the exposure apparatus for a long term, therefore, these matters will be deposited on the optical element or elements, causing continuing deterioration such as a decrease of illuminance or non-uniformness of illumination, in mask illumination. Thus, it raises a problem peculiar to the exposure apparatus that chemical matters contained in grease or the like used for a driving mechanism inside the illumination system are adhered to optical elements due to intense illumination, damaging the optical performance. Further, there is another problem that a driving mechanism having sliding or rolling components easily creates particles which may be deposited to adjacent optical elements to cause non-uniformness of illumination.
In order to avoid these problems, a movable portion including a driving mechanism may be isolated from the purged space and it may be cleaned appropriately or may be replaced by a fresh one. However, such a maintenance operation leads to a decrease of operation efficiency of the apparatus. Also, addition of optical elements to the illumination system causes a decrease of illumination efficiency.
It is accordingly an object of the present invention to provide an illumination system and/or an exposure apparatus by which the reliability of the illumination system can be improved and the frequency of maintenance can be decreased.
It is another object of the present invention to provide a device manufacturing method using such a exposure apparatus.
In accordance with an aspect of the present invention, there is provided an exposure apparatus, comprising: an illumination system having a movable portion; and a driving mechanism for said movable portion, said driving mechanism including at least one of a non-contact type bearing and a non-contact type motor.
In accordance with another aspect of the present invention, there is provided an illumination system, comprising: an optical element disposed in an ambience of one of an inert gas and clean air; a movable portion disposed in said ambience; and a driving mechanism for said movable portion, said driving mechanism including at least one of a non-contact type bearing and a non-contact type motor.
In accordance with a further aspect of the present invention, there is provided a device manufacturing method including an exposure process using an exposure apparatus as recited above. The method may further include a step for applying a photoresist to a substrate before the exposure process, and a step for developing the photoresist after the exposure process.
In accordance with the present invention, a driving mechanism for a movable portion of an illumination system uses a non-contact type bearing or a non-contact type motor having no sliding or rolling portion. This removes the necessity of using a lubricant agent such as grease, and it prevents emission of chemical matters causing damage of optical elements. The reliability of the illumination system is improved, and the frequency of maintenance is reduced.
The same gaseous fluid as an ambience gas may be used as a lubricant gas for the gas bearing. This avoids the necessity of isolating the movable portion from the purged space of the optical system. The reliability and maintenance facilitation are further improved.
In accordance with a device manufacturing method according to
Miwa Yoshinori
Yamane Yukio
Brown Glenn W.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Leroux E P
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