Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1999-05-25
2001-04-03
Lee, Eddie C. (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S071000, C355S072000, C355S077000
Reexamination Certificate
active
06211946
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stag unit having a means for limiting the moving range of a moving table on which a target positioning object is mounted, a drive table driven by a linear motor and capable of easily performing origin detection, and a scanning exposure apparatus for manufacturing semiconductor elements or the like by using the same.
2. Related Background Art
To manufacture semiconductor elements, liquid crystal display elements, or the like by using the photolithography technique, a projection exposure apparatus is conventionally used, in which a pattern formed on a reticle (or a photomask) is exposed, through a projection optical system, onto a wafer (or a glass plate) coated with a photoresist.
In recent years, one chip pattern of a semiconductor element or the like tends to become larger. For this reason, a projection exposure apparatus for exposing a pattern on a reticle, which has a larger size, onto a wafer is required. To meet such a requirement for increasing the exposure area with a so-called step and repeat type projection exposure apparatus for performing full exposure of the entire pattern on the reticle, the projection optical system must be made larger. However, this results in an increase in manufacturing cost of a projection optical system having high imaging performance on the entire surface of the wide exposure field.
Therefore, a so-called step and scan type scanning exposure apparatus has received a great deal of attention. In this apparatus, after each shot area of the wafer is moved to the scan start position, the reticle, which is being illuminated, is scanned in a direction crossing the optical axis of the projection optical system. In synchronism with this scanning, the wafer is scanned in the direction crossing the optical axis of the projection optical system, thereby exposing the pattern of the reticle onto each shot area of the wafer.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a stage unit arranged in a scanning exposure apparatus which illuminates a mask on which a transfer pattern is formed, scans the mask in the first direction (Y direction or −Y direction) as a predetermined scanning direction, and synchronously scans a photosensitive substrate in a direction corresponding to the scanning direction, thereby sequentially exposing the pattern of the mask onto the photosensitive substrate, comprising a base, a scanning stage arranged to be freely moved in the first direction on the base, a fine adjustment stage, arranged to be freely moved, with respect to the scanning stage, within predetermined ranges in the first direction of a target scanning object and a second direction perpendicular to the first direction, for mounting the target scanning object thereon, a first electromagnetic actuator for driving the fine adjustment stage in the second direction with respect to the scanning stage, and a second electromagnetic actuator for driving the fine adjustment stage in the first direction with respect to the scanning stage with a larger thrust than that of the first electromagnetic actuator.
In this case, as each of the first and second electromagnetic actuators, an electromagnetic actuator of a moving magnet type in which a stationary member having a coil is fixed on the scanning stage side is used. Cooling means for cooling the stationary member of each of the first and second electromagnetic actuators by circulating a predetermined cooling fluid is preferably arranged.
In addition, a movable mirror fixed on the fine adjustment stage, and an interferometer for irradiating a measurement light beam on the movable mirror to detect a displacement of the fine adjustment stage with respect to the scanning stage are provided. The cooling means preferably circulates the cooling fluid from a portion near an optical path of the light beam from the interferometer.
Furthermore, one of the first and second electromagnetic actuators is preferably constituted by a pair of electromagnetic actuators which are parallelly arranged.
In the scanning exposure apparatus, a largo inertial force in the first direction as the scanning direction is applied to the fine adjustment stage particularly at the start and end of scanning. According to the stage unit of the present invention, however, an actuator having a small thrust is used as the electromagnetic actuator for driving the fine adjustment stage in the second direction (X direction or −X direction) because the inertial force applied to the fine adjustment stage in the second direction which is not the scanning direction can be almost neglected. With this arrangement, the shape and weight of the movable member of the electromagnetic actuator can be reduced. For this reason, the overall weight of the fine adjustment stage is reduced, thereby improving the control performance of the stage. In addition, the capacity of the coil of the electromagnetic actuator in the second direction can also be reduced. Since a heat generation amount from the coil is also decreased, heat deformation of each stage is minimized, thereby minimizing the adverse influence of heat to the measurement equipment for position measurement.
When each of the first and second electromagnetic actuators is an electromagnetic actuator of a moving magnet type, and the cooling means for cooling the stationary member of each of the first and second electromagnetic actuators by circulating the predetermined cooling liquid is arranged, the fine adjustment stage is separated from the coil as a heat source. For this reason, the heat deformation of the fine adjustment stage can be minimized as compared to a case wherein an electromagnetic actuator of a moving coil type is used.
When the stationary member as a heat source is liquid-cooled, the total heat generation amount is minimized. It is mechanically easy to cool the stationary member in this manner.
The movable mirror fixed on the fine adjustment stage, and the interferometer for irradiating the measurement light bean on the movable mirror to detect the displacement of the fine adjustment stage with respect to the scanning stage are arranged, and the cooling fluid is circulated from the portion near the optical path of the light beam from the interferometer. In this case, when the cooling fluid has the largest cooling capability, the electromagnetic actuators are sequentially cooled from the portion near the optical path. For this reason, temperature adjustment of a gas on the optical path is stably performed, thereby maintaining a high measurement precision.
When one of the first and second electromagnetic actuators is constituted by a pair of electromagnetic actuators which are parallelly arranged, driving in the rotational direction is enabled by applying thrusts to the pair of electromagnetic actuators in opposite directions.
According to the present invention, there is provided a stage unit comprising a moving table for mounting a target positioning object thereon, a base for mounting the moving table thereon to be freely moved in a predetermined direction, driving means for driving the moving table in the predetermined direction with respect to the base, switch means for stopping an operation of the driving means when the moving table moves beyond an allowable movement range in the predetermined direction, and push-back means for generating a biasing force for pushing back the moving table to the allowable movement range side before the switch means operates.
In this case, the biasing force of the push-back means is preferably larger than the frictional force between the moving table and the bass. At the same time, the biasing force is preferably a force within a range smaller than that of the driving force in the normal operation of the driving means.
An elastic member is used as an example of the push-back means.
A linear motor is used as an example of the driving means.
According to the present invention, when the moving table moves beyond the allowable movement range because of r
Horikawa Hiroto
Ohtomo Toshiya
Kim Peter B.
Lee Eddie C.
Nikon Corporation
Oliff & Berridg,e PLC
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