Radiant energy – Means to align or position an object relative to a source or...
Reexamination Certificate
2001-05-30
2004-12-28
Wells, Nikita (Department: 2881)
Radiant energy
Means to align or position an object relative to a source or...
C250S492200, C250S398000, C310S012060, C310S091000, C318S566000
Reexamination Certificate
active
06835941
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a stage unit and its making method, and an exposure apparatus and its making method, and, more specifically, a stage unit which controls the position of a sample placed on itself and its making method, and an exposure apparatus which is equipped with the stage unit and transfers a predetermined pattern onto a wafer, and its making method.
BACKGROUND ART
In a lithography process for making a semiconductor device, liquid crystal display device, or the like, an exposure apparatus has been used. In such an exposure apparatus, patterns formed on a mask or reticle (to be generically referred to as a “reticle” hereinafter) are transferred through a projection optical system onto a substrate such as a wafer or glass plate (to be referred to as a “substrate” or “wafer” hereinafter, as needed) coated with a resist, etc. As apparatuses of this type, a static exposure type projection exposure apparatus, e.g., a so-called stepper, and a scanning exposure type projection exposure apparatus, e.g., a so-called scanning stepper are mainly used. Such an exposure apparatus is equipped with a stage unit, which is movable in two-dimensional directions while holding a wafer, to transfer a pattern formed on a reticle onto a plurality of shot areas on the wafer in turn.
In such a stage unit, the wafer is held on a wafer holder by vacuum chucking, etc. and fixed on a wafer table (movable body) to set the position of the wafer to a exposure position with high accuracy. Such wafer tables have been driven along a mechanical guide surface by a driving unit mechanically in contact with the wafer table and movable. Therefore, stage units have been equipped with X-stage to drive the wafer table in X direction and Y-stage to drive the wafer table together with X-stage in Y direction to move the wafer table on the X-Y plane.
Meanwhile, the development of a stage unit which controls the position of a wafer with high accuracy without being affected by the mechanical accuracy, etc. of a guide surface and performs positioning of the wafer by supporting a flat-plate-like shaped and movable body, on which the wafer is placed above a supporting member, by levitation and driving the movable body in a non-contacting manner to avoid mechanical friction and prolong the life of the stage is in progress. As such stage units, a variable magnetic reluctance driving method in which a linear pulse motor, as in a Sawyer motor, using the variable magnetic reluctance driving method is so structured that two axes are combined with each other, and a stage unit using a planar motor as a driving unit (driver) employing a Lorentz (electromagnetic) force method disclosed in, for example, Japanese Patent Laid-Open No. 58-175020 and U.S. Pat. No. 5,196,745 have been suggested.
Recently, wafers on which patterns are transferred by an exposure apparatus are being enlarged. Along with the enlargement of wafers, a wafer table as a table on which a wafer is placed is also enlarged and necessarily the weight of the wafer table is increased. Therefore it is necessary to drive the wafer table by a large force to move the wafer at high speed for the improvement of the through-put of the exposure apparatus.
Incidentally on driving the wafer table, the wafer table and a mover are moved together as one entity against a stator using a driving unit comprising the mover and the stator and on this occasion, a reaction to the force applied to the mover is induced in the stator. As a consequence, a vibration occurs and is transmitted to other members when the mover is mechanically connected with other members of the exposure apparatus, and then inflicts a bad effect on exposure accuracy. For example, when the mover is mechanically connected with a supporting member with respect to a projection optical system of the exposure apparatus, the projection optical system will vibrate and cause the degradation of the exposure accuracy.
Such a bad effect to the exposure accuracy generally becomes severer along with the increase of drive force of the mover. Therefore along with the enlargement of wafers, the mover is driven by a large force to move the wafer at high speed for the improvement of the through-put and the exposure accuracy will be degraded remarkably. That is, along with the enlargement of wafers it is getting difficult to improve both the through-put and the exposure accuracy.
The present invention has been made in view of the condition above. A first object of the present invention is to provide a stage unit that can move a placed sample at high speed and perform accurate positioning.
Also, a second object of the present invention is to provide an exposure apparatus that can improve both the through-put and the exposure accuracy by high speed movement of a substrate and highly accurate positioning.
DISCLOSURE OF INVENTION
From a first aspect, the present invention is a stage unit that is equipped with a driving unit including a mover and a stator; and a reaction canceling mechanism to apply to the stator a force canceling a reaction acting on the stator by electromagnetic interaction. This stage unit is referred to as a “first stage unit of the present invention” hereafter.
According to the present invention, the reaction canceling mechanism generates a force to cancel the reaction acting on the stator by using electromagnetic interaction excellent in controllability and linearity and applies it to the stator, thereby accurately canceling the reaction acting on the stator. Accordingly, even with the increase of the drive force of the mover, the vibration of the stator is prevented and the stage unit is capable of high accurate positioning while moving a sample placed on itself.
In the first stage unit of the present invention, if the reaction canceling mechanism can apply to any arbitrary point of the stator a force having an arbitrary magnitude and an arbitrary direction, the reaction canceling mechanism may generate one kind of force and apply it to an appropriate point (for example, applying a force having the same magnitude as the reaction and opposite direction to the point of reaction application of the stator) to cancel a reaction caused by driving the mover translationally. However, when the stator is rotationally driven or the point of the stator to which the reaction canceling mechanism applies the force is fixed, it is generally impossible to cancel the reaction just by giving the stator one kind of force.
Therefore, in the first stage unit of the present invention, it is preferred for the reaction canceling mechanism to generate a force to act on at least two points of the stator and cancel the reaction as a whole. In this case, if the reaction canceling mechanism can apply forces having an arbitrary magnitude and an arbitrary direction to at least two fixed points of the stator, the reaction acting on the stator by a translational driving, a rotational driving or the combination of the both can be canceled. Especially, when the reaction acting on the stator is a force along a predetermined plane, the reaction can be canceled by applying two kinds of forces being along the predetermined plane and having magnitude and direction corresponding to the reaction.
The aforementioned case shows a case where the reaction canceling mechanism can apply the force having an arbitrary magnitude and an arbitrary direction to the stator. However, in a case where the points of the stator to which the reaction canceling mechanism applies the forces are fixed and the direction of the force applied to each point is predetermined, the reaction generally can not be canceled just by applying two kinds of forces to the stator. In such a case, the reaction canceling mechanism generates forces having respective predetermined directions, which cancel the reaction as a whole, and applies them to at least three points of the stator, thereby being able to cancel the reaction acting on the stator by a translational driving, a rotational driving or the combination of the both. Especially, if the reaction acting on the st
Nikon Corporation
Wells Nikita
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