Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2000-03-14
2001-12-18
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C356S399000, C356S400000, C356S401000, C356S500000
Reexamination Certificate
active
06331885
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a scanning type exposure apparatus and a scanning exposure method used when a circuit device such as a semiconductor circuit element and a liquid crystal display element is produced in accordance with a lithography step. In particulars the present invention relates to a scanning type exposure apparatus and an exposure method preferably used to perform scanning exposure with a large mask having a size of not less than 9 inches. The present invention also relates to a device produced with the exposure method.
Especially, the present invention generally includes the following five concepts in order to achieve the common objects of the present invention as described later on. The first concept relates to a scanning exposure method and a scanning exposure apparatus in which a substrate is moved in synchronization with a mask having a large pattern or a plurality of comparted patterns so that the large pattern is transferred to the substrate in a stitching manner, or the plurality of patterns are transferred to an identical area of the substrate in a superimposing or overlay manner. The second concept relates to a stage apparatus, for example, a triangular stage and a scanning exposure apparatus including the same, the stage apparatus having a reflecting mirror extending obliquely with respect to a movement direction of the stage, and an interferometer for transmitting a measuring beam (length-measuring beam) to the reflecting mirror. The third concept relates to an unbalanced load-preventive stage apparatus for supporting a second movable member and a first movable member in a floating manner over a base board respectively, and a scanning exposure apparatus including the stage apparatus. The fourth concept relates to the timing control for the stepping movement (stepping) of a substrate in a direction perpendicular to a scanning direction and the scanning movement of the substrate in the scanning direction when the next comparted area is subjected to scanning exposure after scanning exposure of a certain area comparted on the substrate is completed, in the scanning exposure for synchronously moving a mask and the substrate. The fifth concept relates to the control of the rate of acceleration during movement of a mask or a substrate to shorten the settling time for synchronizing the mask and the substrate during scanning exposure. These concepts are specifically described and explained in the opening of the chapter of “Best Mode for Carrying Out the Invention” of this document.
DESCRIPTION OF THE RELATED ART
At present, in the production site for manufacturing the semiconductor device, a reduction production exposure apparatus, i.e., a so-called stepper, which uses, as a illumination light beam, the i-ray of a mercury lamp having a wavelength of 365 nm, is used to mass-produce circuit devices (for example, 64 M (mega) bit D-RAM) having a minimum line width of about 0.3 to 0.35 &mgr;m. Simultaneously, an exposure apparatus begins to be introduced to mass-produce next-generation circuit devices having a degree of integration of 1 G (giga) bit D-RAM class with a minimum line width of not more than 0.25 &mgr;m.
A prevailing exposure apparatus for producing the next-generation circuit device is a scanning type exposure apparatus based on the step-and-scan manner in which an illumination light beam is an ultraviolet pulse laser beam having a wavelength of 248 nm supplied from a KrF excimer laser light source or an ultraviolet pulse laser beam having a wavelength of 193 nm supplied from an ArF excimer laser light source. A mask or a reticle (hereinafter generally referred to as “reticle”) on which a circuit pattern is depicted, and a wafer as a photosensitive substrate are subjected to relative one-dimensional scanning with respect to a projection field of a reduction projection optical system. Thus, the entire circuit pattern on the reticle is transferred to the inside of one shot area on the wafer to perform the scanning exposure operation which is repeated together with the stepping action between shots.
A micro-scan exposure apparatus made by Perkin-Elmer is firstly commercially produced, and it is commercially available as a scanning type exposure apparatus based on the step-and-scan manner, which carries a reduction projection optical system comprising a refraction optical element (lens element) and a reflection optical element (for example, concave mirror). The micro scan exposure apparatus is explained in detail, for example, in SPIE, Vol. 1 1088 pp. 424 to 433. That is, a part of a pattern on a reticle is projected onto a wafer via an effective projection area limited to have a circular arc slit-shaped configuration, while the reticle and the wafer are relatively moved at a velocity ratio in conformity with the projection magnification (¼ reduction). Thus, a shot area on the wafer is subjected to exposure.
Another projection exposure system based on the step-and-scan manner is known, in which an excimer laser beam is used as an illumination light beam to combine a so-called scan-and-stitching method which is a method for limiting an effective projection area of a reduction projection optical system having a circular projection field to be a polygonal configuration (hexagon) so that both ends of the effective projection area are partially overlapped with each other. Such a projection exposure system is disclosed, for example, in Japanese Patent Application Laid-Open No. 2-229423 and U.S. Pat. No. 4,924,257 corresponding thereto. A projection exposure apparatus, which adopts such a scanning exposure system, is also disclosed, for example, in Japanese Patent Application Laid-Open No. 4-196513 and U.S. Pat. No. 5,473,410 corresponding thereto, Japanese Patent Application Laid-Open No. 4-277612 and U.S. Pat. No. 5,194,893 corresponding thereto, and Japanese Patent Application Laid-Open No. 4-307720 and U.S. Pat. No. 5,506,684 corresponding thereto.
A reticle having a size of not more than 6 inches is used for the conventional scanning type exposure apparatus as described above. The device rule is not less than 0.2 &mgr;m L/S (line and space). Therefore, the scanning exposure has been performed by using a projection optical system having a projection magnification of ¼.
However, in the case of the scanning type exposure apparatus based on the step-and-scan manner, the exposure is performed while moving a reticle stage and a wafer stage at predetermined scanning velocities. Therefore, it is necessary to perform, before the start of the exposure, the pre-scanning (acceleration until arrival at the target velocity (scanning velocity during the exposure)+settling operation until convergence of the velocity to the target velocity within a predetermined error range after completion of the acceleration). In the case of the scanning type exposure apparatus based on the step-and-scan manner, when the pattern on the reticle is successively transferred to a plurality of shot areas (hereinafter appropriately referred to as “shots”) on the wafer, the exposure is successively performed for the next shot by alternately scanning the reticle (reciprocating scanning) in ordinary cases in order to improve the throughput. For this reason, it is necessary to perform the following operation. That is, after completion of the transfer of the reticle pattern to one shot, the reticle is further moved from the exposure end point by the same distance as the movement distance during the pre-scanning before the start of the exposure to return the reticle to the scanning start position for the next shot exposure (over-scanning). Therefore, when the exposure is performed for a shot area having a size equivalent to a shot size for a full field exposure apparatus based on, for example, the step-and-repeat system, there is a possibility that the throughput is lowered as compared with the full field exposure apparatus, due to the pre-scanning and the over-scanning to be performed before and after the scanning exposure (
Adams Russell
Fuller Rodney
Nikon Corporation
Oliff & Berridg,e PLC
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