Radiation imagery chemistry: process – composition – or product th – Registration or layout process other than color proofing
Reissue Patent
1999-03-25
2003-05-06
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Registration or layout process other than color proofing
C430S005000, C356S399000, C356S400000, C356S401000, C355S053000
Reissue Patent
active
RE038113
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of driving a mask stage and a method of mask alignment. More particularly, the present invention relates to a method of driving a stage, which is suitably applied to a case where a reticle-side stage is driven in a scan direction in a slit-scan exposure type projection exposure apparatus, and a method of mask alignment in the projection exposure apparatus.
2. Related Background Art
When a semiconductor element, a liquid crystal display element, a thin film magnetic head, or the like is manufactured in a photolithography process, a projection exposure apparatus for transferring a pattern on a photomask or a reticle (to be generally referred to as a “reticle” hereinafter) onto a substrate (a wafer, glass plate, or the like) coated with a photosensitive material is used.
As a conventional projection exposure apparatus, a step-and-repeat type reduction projection exposure apparatus (stepper) for sequentially exposing a pattern image on a reticle onto each of shot areas by sequentially moving the shot areas of a wafer into an exposure field of a projection optical system is popularly used.
In recent years, since patterns on semiconductor devices or the like tend to be miniaturized, it is required to increase the resolution of a projection optical system. For this reason, in order to increase the resolution, a technique for decreasing the wavelength of exposure light, a technique for increasing the numerical aperture of the projection optical system, and the like have been examined. However, with either technique, it becomes difficult to maintain high accuracy of imaging performance (a distortion, curvature of field, and the like) on the entire exposure field when an exposure field as large as that in the prior art is to be assured. For this reason, an apparatus which is currently reconsidered its use is a so-called slit-scan exposure type projection exposure apparatus.
In the slit-scan exposure type projection exposure apparatus, a pattern on a reticle is exposed onto a wafer, wherein the reticle and wafer are being synchronously scanned relative to a rectangular or arcuated illumination area (to be referred to as a “slit-like illumination area” hereinafter).
Therefore, when a pattern with the same area as that in the stepper system is to be exposed onto a wafer, the exposure field of the projection optical system in the slit-scan exposure system can be set to be smaller than that in the stepper system. As a result, accuracy of imaging performance in the exposure field may be improved.
The mainstream of the conventional reticle size is 6″, and the mainstream of the projection magnification of the projection optical system is x⅕. However, as the area of the circuit pattern of, e.g., a semiconductor element increases, the 6 ″ reticle cannot serve its purpose at the x⅕ magnification. For this reason, a projection exposure apparatus in which the projection magnification of the projection optical system is changed to, e.g., x¼ must be designed. In order to cope with such an increase in area of a pattern to be transferred, the slit-scan exposure system is advantageous.
In a projection exposure apparatus of this type (stepper), a reticle must be aligned in advance on a reticle stage. For this purpose, a reticle alignment device is arranged on a reticle mark on the reticle. Such a reticle alignment device is disclosed in U.S. Pat. No. 4,710,029. In an alignment system disclosed in U.S. Pat. No. 4,710,029, light reflected by an alignment mark on a reticle is incident on a sensor via a vibration mirror and a slit. When the output from the sensor is synchronously detected by a driving signal of the vibration mirror, the position of the alignment mark relative to a slit is detected. The position of the alignment mark is detected based on a signal from the sensor in the alignment system, and the reticle is moved by a servo system, so that the alignment mark accurately coincides with the slit. As a result, alignment of the reticle with respect to the apparatus main body is executed.
SUMMARY OF THE INVENTION
In such a slit-scan exposure system, when the moving path of the reticle stage for driving a reticle is curved with respect to a desired path (for example, the moving path has a predetermined curvature with respect to a desired linear path), each shot area on a wafer undesirably has an intra-shot distortion according to the curve (curvature) of the moving path of the reticle stage. Furthermore, when the characteristics of an intra-shot distortion vary from one exposure apparatus to another, such a variation results in a matching error between different layers on the wafer. When the reticle stage is controlled by a method of measuring the position of the reticle stage by interfering light components reflected by a stationary mirror and a movable mirror provided to the reticle stage using an optical interferometer, such a curve of the path of the reticle stage is caused by a curve of the movable mirror.
The present invention has been made in consideration of the above situation, and has as its object to provide a method of driving a stage, which can prevent generation of an intra-shot distortion even when a movable mirror provided to a stage at the side of reticle (mask) has a curve in a slit-scan exposure type exposure apparatus.
In order to achieve the above object, according to the first invention, there is provided a method of driving a mask stage using the mask stage which mounts a mask formed with a predetermined pattern and is movable in a predetermined scan direction, a movable mirror which is arranged on the mask stage and has a reflection surface substantially parallel to the scan direction, measurement means for measuring a coordinate position, in a direction perpendicular to the scan direction, of the mask stage by radiating a measurement beam into the movable mirror, a substrate stage which mounts a photosensitive substrate and is movable in a direction substantially parallel to the scan direction, an illumination system for illuminating a predetermined area on the mask with illumination light, a projection optical system for projecting the pattern on the mask onto the photosensitive substrate, and an exposure device for sequentially exposing the pattern on the mask onto the photosensitive substrate while synchronously scanning the mask stage and the substrate stage in the scan direction with respect to an optical axis of the projection optical system, comprising:
the first step of placing the mask on the mask stage;
the second step of calculating a curved amount of the movable mirror by measuring the coordinate position, in the direction perpendicular to the scan direction, of the mask stage by the measurement means while scanning the mask stage in the scan direction; and
the third step of moving the mask stage in the direction perpendicular to the scan direction to correct the curved amount of the movable mirror calculated in the second step when the mask stage is scanned in the scan direction with respect to the optical axis.
According to the second invention, there is provided a method of driving a mask stage using a mask guide which is formed with a guide portion extending in predetermined scan direction, the mask stage which is mounted on the mask. Guide to be movable in the scan direction, and mounts a mask formed with a predetermined pattern, a movable mirror which is attached to the mask stage, and has a reflection surface substantially parallel to the scan direction, measurement means for measuring a coordinate position, in a direction perpendicular to the scan direction, of the mask stage by radiating a measurement beam into the movable mirror, a substrate stage which is movable in the direction substantially parallel to the scan direction and mounts a photosensitive substrate, an illumination system for illuminating a predetermined area on the mask with illumination light, a projection optical system for projecting the pattern on the mask ont
Murakami Seiro
Nishi Kenji
Miles & Stockbridge P.C.
Nikon Corporation
Rosasco S.
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