The present invention relates to a stage apparatus used for, e.g., a fine moving stage for finely aligning a substrate such as a wafer or a master such as a reticle in an exposure apparatus or the like, an exposure apparatus, and a device manufacturing method.
Control techniques for industrial and information devices are increasing in precision and speed as such devices become complicated, advanced, and miniaturized. Exposure apparatuses for manufacturing xe2x80x9csemiconductor devicesxe2x80x9d which support various types of such devices are also rapidly increasing in speed and precision, and demands are arising for nm-order alignment precision and the like.
A generally known alignment mechanism for a wafer and reticle in an exposure apparatus is a stage apparatus constituted by a fine moving stage having a microtranslation mechanism and fine rotation mechanism, and a coarse moving stage having a large-stroke moving mechanism in the translational direction.
Such an exposure apparatus finely aligns, controls, and exposes a wafer or reticle on the fine moving stage so as to make it coincide with the image or object plane by the fine moving stage mounted on the coarse moving stage while the coarse moving stage makes large-stroke movement.
In general, both the coarse and fine moving stages often use linear motors, which utilize a Lorentz force, as the actuator of the alignment mechanism.
However, the fine moving stage of the exposure apparatus has recently been found to suffer from the following problems.
(1) As chips, wafers, and reticles increase in size, the fine moving stage also increases in size. Pushing up the fine moving stage by a linear motor using a Lorentz force consumes a large amount power.
Especially the actuator of the fine moving stage is often attached near a wafer or reticle. Compared to the coarse moving stage, the fine moving stage greatly influences the wafer or reticle to thermally deform it, resulting in very low final exposure precision.
(2) Demands are arising for a high-speed exposure apparatus, and the acceleration of the coarse moving stage is being increased. This means that the acceleration applied from the coarse moving stage to the fine moving stage also increases. When the coarse moving stage accelerates the fine moving stage, a moment force proportional to the acceleration of the coarse moving stage acts on the fine moving stage due to the difference between the barycenter of the fine moving stage and a xe2x80x9cpoint of applicationxe2x80x9d where the actuator of the coarse moving stage pushes the fine moving stage.
Hence, as the speed increases, the actuator of the fine moving stage becomes bulky in order to withstand the moment force, and the amount of heat generated by the actuator increases to adversely influence the exposure precision. In other words, a bulky actuator increases heat, which is a vicious cycle.
As a means for solving these problems, there is provided a method of compensating for the weight of the fine moving stage by using the repulsion and attraction forces of a magnet or electromagnet. In this case, it is difficult to hold the posture of the fine moving stage by compensation with only the magnet, so a spring is also used to hold the posture.
FIGS. 5A and 5B schematically show a conventional wafer stage for compensating for the weight by magnetic repulsion. This wafer stage comprises a fine moving stage 101 having a support surface 101a for supporting a wafer WO, a coarse moving stage 102 having a large-stroke moving mechanism (not shown), first to third spring members 103a to 103c for holding the posture of the fine moving stage 101 on the coarse moving stage 102, and first to third magnetic units 104a to 104c for compensating for the weight by a so-called magnetic repulsion force for supporting the weight of the fine moving stage 101. The magnetic units 104a to 104c are respectively made up of magnets 141a to 141c fixed to the upper surface of the coarse moving stage 102 and magnets 142a to 142c fixed to the lower surface of the fine moving stage 101 so as to face the corresponding magnets 141a to 141c. 
The weight of the fine moving stage 101 is compensated for by the magnetic repulsion forces of the magnets 141a to 141c and 142a to 142c of the magnetic units 104a to 104c. When the wafer W0 is aligned near the image plane of a projection optical system (not shown), the weight of the fine moving stage 101 is canceled by the magnetic repulsion force.
The three spring members 103a to 103c for compensating for the posture of the fine moving stage 101 have the same spring constant, which is set to minimize the restoring forces of the springs while the wafer W0 is near the image plane.
The fine moving stage 101 has a pair of bar mirrors 110 for detecting the position of the fine moving stage 101 by a laser interferometer or the like. This wafer stage is equipped with a control system for feeding back the detected position information of the fine moving stage 101 to the actuator of the coarse moving stage 102.
The three posture compensation spring members 103a to 103c are generally arranged at positions Z1 to Z3 at equal intervals of 120xc2x0 on a circle of a radius r having a geometrical center O of the fine moving stage 101 as its center.
In this prior art, however, the barycenter of a structure formed from the members and fine moving stage is at a position different from the geometrical center of the fine moving stage, i.e., the geometrical centroid of a triangle formed by the support points Z1 to Z3 of the spring members 103a to 103c under the influence of the members such as the bar mirrors fixed to the fine moving stage for holding a wafer. The restoring forces of the three spring members necessary for pushing up the fine moving stage only in the +Z direction without rotating it and for keeping it at a predetermined pushed-up position and posture are different.
Accordingly, holding the posture by the three springs having the same spring constant causes the following problems even if the magnets compensate for the weight of the fine moving stage. Assume that the fine moving stage is vertically displaced in the xe2x88x92Z direction without rotating it, and the springs uniformly deflect. In this case, the sum of the restoring forces of the three springs not only translates the fine moving stage in the +Z direction but also rotates it.
More specifically, if an external force acts on the fine moving stage owing to some factor while position control by the actuator of the fine moving stage stops, or if position control stops due to an emergency stop caused by an accident while the fine moving stage is displaced in the xe2x88x92Z direction by the actuator, restoring motion of the fine moving stage in the +Z direction and tilt motion exceeding a moving stroke in the rotational direction occur, scoring or damaging the stage.
There is proposed a method of compensating for the weight of the fine moving stage by magnets, compensating for the posture by springs, and generating a uniform weight compensation force by the magnets in almost the entire range of the Z-direction stroke on the fine moving stage. Even this method requires a posture holding means using coil springs or leaf springs because compensation by only magnets is unstable. This method cannot solve the static unbalance.
There is also proposed a method of directly compensating for the weight of the fine moving stage by springs. Even this method cannot solve the above problems.
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide a stage apparatus which uses at least three spring members in order to compensate for the weight of a stage for setting a wafer or reticle, can improve the stability of a compensation function by the spring members, and can effectively avoid scoring of or damage to the stage, to provide an exposure apparatus including the stage, and to provide a method of manufacturing a device by using the exposure apparatus.
To achieve the above object, according to the present invention, there is provided a stage apparatus comprising:
a stage;
a member fixed to said stage; and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative position relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from the other spring constants.
According to a preferred embodiment of the present invention, it is preferable that the at least three spring members include coil springs.
According to a preferred embodiment of the present invention, it is preferable that the at least three spring members include air cylinders.
According to a preferred embodiment of the present invention, it is preferable that the at least three spring members include leaf springs.
According to a preferred embodiment of the present invention, it is preferable that the weight compensation mechanism further includes a magnet.
According to a preferred embodiment of the present invention, it is preferable that the apparatus further comprises an actuator for vertically driving said stage.
According to a preferred embodiment of the present invention, it is preferable that the actuator includes a linear motor.
According to a preferred embodiment of the present invention, it is preferable that the apparatus further comprises at least three actuators for vertically driving said stage, wherein a supporting force generated by each of the spring members and applied to said stage and a driving force generated by each of the actuators and applied to said stage are exerted on the same axis.
According to a preferred embodiment of the present invention, it is preferable that the member includes a mirror.
According to a preferred embodiment of the present invention, it is preferable that the at least three spring members are arranged at positions a constant distance from the geometrical center of said stage.
According to a preferred embodiment of the present invention, it is preferable that the at least three spring members include n spring members, and the n spring members are arranged at vertexes of a regular n-side polygon having the geometrical center of said stage as a center.
According to the present invention, there is provided a stage apparatus comprising:
a stage;
a member fixed to said stage; and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when said stage is statically balanced.
According to the present invention, there is provided a stage apparatus comprising:
a coarse moving stage;
a fine moving stage mounted on said coarse moving stage;
a member fixed to said fine moving stage; and
a weight compensation mechanism which has at least three spring members for compensating for a weight of a structure including said fine moving stage and said member and is interposed between said coarse moving stage and said fine moving stage, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative positional relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from the other spring constants.
According to the present invention, there is provided a stage apparatus comprising:
a coarse moving stage;
a fine moving stage mounted on said coarse moving stage;
a member fixed to said fine moving stage; and
a weight compensation mechanism which has at least three spring members for compensating for a weight of a structure including said fine moving stage and said member and is interposed between said coarse moving stage and said fine moving stage, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when said stage is statically balanced.
According to the present invention, there is provided an exposure apparatus comprising:
an illumination system for illuminating a master;
a master stage apparatus which moves while supporting the master;
a projection optical system for projecting a pattern of the master onto a substrate; and
a substrate stage apparatus which moves while supporting the substrate,
at least one of said master and substrate stage apparatuses having
a stage,
a member fixed to said stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative positional relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from the other spring constants.
According to the present invention, there is provided an exposure apparatus comprising:
an illumination system for illuminating a master;
a master stage apparatus which moves while supporting the master;
a projection optical system for projecting a pattern of the master onto a substrate; and
a substrate stage apparatus which moves while supporting the substrate,
at least one of said master and substrate stage apparatuses having
a stage,
a member fixed to said stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when said stage is statically balanced.
According to the present invention, there is provided an exposure apparatus comprising:
a projection optical system for projecting an image onto a substrate; and
a substrate stage apparatus which moves while supporting the substrate,
said substrate stage apparatus having
a stage,
a member fixed to said stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative positional relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from the other spring constants.
According to the present invention, there is provided an exposure apparatus comprising:
a projection optical system for projecting an image onto a substrate; and
a substrate stage apparatus which moves while supporting the substrate,
said substrate stage apparatus having
a stage,
a member fixed to said stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including said stage and said member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when said stage is statically balanced.
According to the present invention, there is provided a device manufacturing method comprising the steps of:
exposing a photosensitive agent on a substrate by using an exposure apparatus; and
developing the photosensitive agent on the substrate,
the exposure apparatus having
an illumination system for illuminating a master,
a master stage apparatus which moves while supporting the master,
a projection optical system for projecting a pattern of the master onto a substrate, and
a substrate stage apparatus which moves while supporting the substrate,
at least one of the master and substrate stage apparatuses having
a stage,
a member fixed to the stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including the stage and the member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative position relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from other spring constants.
According to the present invention, there is provided a device manufacturing method comprising the steps of:
exposing a photosensitive agent on a substrate by using an exposure apparatus; and
developing the photosensitive agent on the substrate,
the exposure apparatus having
an illumination system for illuminating a master,
a master stage apparatus which moves while supporting the master,
a projection optical system for projecting a pattern of the master onto a substrate, and
a substrate stage apparatus which moves while supporting the substrate,
at least one of the master and substrate stage apparatuses having
a stage,
a member fixed to the stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including the stage and the member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when the stage is statically balanced.
According to the present invention, there is provided a device manufacturing method comprising the steps of:
exposing a photosensitive agent on a substrate by using an exposure apparatus; and
developing the photosensitive agent on the substrate,
the exposure apparatus having
a projection optical system for projecting an image onto a substrate, and
a substrate stage apparatus which moves while supporting the substrate,
the substrate stage apparatus having
a stage,
a member fixed to the stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including the stage and the member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined based on a relative position relationship between the barycentric position of the structure and the at least three spring members so as to set at least one spring constant different from other spring constants.
According to the present invention, there is provided a device manufacturing method comprising the steps of:
exposing a photosensitive agent on a substrate by using an exposure apparatus; and
developing the photosensitive agent on the substrate,
the exposure apparatus having
a projection optical system for projecting an image onto a substrate, and
a substrate stage apparatus which moves while supporting the substrate,
the substrate stage apparatus having
a stage,
a member fixed to the stage, and
a weight compensation mechanism having at least three spring members for compensating for a weight of a structure including the stage and the member, a barycentric position of the structure deviating from a centroid of a polygon formed by support points of the at least three spring members,
wherein spring constants of the at least three spring members are determined to make application points of restoring forces of the at least three spring members coincide with the barycentric position of the structure when the stage is statically balanced.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.