Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
1997-12-23
2001-02-06
LaBalle, Clayton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06184596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stage construction incorporating a movable stage whose position can be fixed, which is used in a semiconductor exposure device or in a sample analysis device such as a photoelectron spectroscopy device, an X ray microscope, an electron microscope, or the like.
2. Description of the Prior Art
When performing exposure of a wafer using a semiconductor exposure device, it is necessary to fix the position of the wafer accurately with regard to its six spatial degrees of freedom, conventionally designated as X, Y, Z, &thgr;, &agr;, and &bgr;. Further, in a photoelectron spectroscopy device, an X ray microscope, an electron microscope, or the like, in the same manner it is necessary to fix the position of the sample for analysis accurately with regard to its six degrees of freedom. In this field, in the prior art, assemblies of stages with 1-axis movement, 2-axis movement, or 3-axis movement have been superposed in combination as required, so that the combination can be utilized as a six axis stage construction. Such stages achieve the desired accuracy of position fixing by incorporating suitable assemblies, including driving mechanisms such as linking mechanisms, ball screws, planetary screws, linear screws, or the like, speed reducing mechanisms such as gears or the like, and friction bearings such as cross roller guides, V-flat sliding groove guides and the like.
However, reduction in mass is difficult to realize for such prior art stage constructions, due to the bulk of the main body of the stage construction becoming large. Accordingly the inertia of the movable parts of such a stage construction becomes great, so that it is difficult to increase the speed of their movement, and also improvement of the accuracy of position fixing becomes difficult. Further, due to the existence of at least two faces which are in sliding mechanical contact, one upon a fixed stage and one upon a movable stage, the cleanliness of the environment provided by such a stage construction is inevitably deteriorated due to generation of dust from the movement mechanism. Yet further, if the stage construction is to be used under high vacuum conditions, the problem arises that the vacuum level will be reduced, since lubricant needs to be used between these mechanically contacting faces.
In order to implement non-contact operation of such a stage construction, it is possible to levitate the movable stage by floating it upon air bearings, and to drive it using a linear motor; but the cleanliness of the environment is degraded since the air gushing out from the air bearing will inevitably stir up dust, and for example the yield rate of a semiconductor process utilizing this stage construction is deteriorated. Furthermore, due to the use of a flow of air for levitating the movable stage, it is fundamentally impossible to apply this expedient to a stage which is intended to operate under vacuum conditions.
SUMMARY OF THE INVENTION
The objective of the present invention is to propose a stage construction incorporating a magnetically levitated movable stage which, along with making possible high speed movement and high accuracy positioning of the movable stage due to reduction in its mass, can also be used under vacuum conditions without any compromise of environmental cleanliness.
In order to attain the above described objective, the present invention proposes, according to a first aspect thereof, a stage construction incorporating a magnetically levitated movable stage, comprising a fixed stage and a magnetically levitated movable stage which is driven in mutually perpendicular X, Y, and Z axis directions with respect to the fixed stage by magnetic action between the movable stage and the fixed stage, the Z axis direction being a direction in which the fixed stage and the movable stage are lined up. And the fixed stage comprises a magnet and a closed plenum in which the magnet is sealed, while the movable stage comprises a magnetic material which is opposed to the magnet and which experiences an attractive or repulsive magnetic force with respect to the magnet.
The portion of the fixed stage which is located between the magnet and the magnetic material may desirably be made from a material of low magnetic permeability.
Further, in order to attain the above described objective, the present invention proposes, according to another aspect thereof, a stage construction, incorporating a magnetically levitated movable stage, comprising a fixed stage and a magnetically levitated movable stage which is driven in mutually perpendicular X, Y, and Z axis directions with respect to the fixed stage by magnetic action between itself and the fixed stage. And the fixed stage comprises an electromagnet and a closed plenum in which the electromagnet is sealed, while the movable stage comprises a magnetic material which is opposed to the electromagnet and which experiences an attractive or repulsive magnetic force with respect to the electromagnet.
In this case as well, the portion of the fixed stage which is located between the electromagnet and the magnetic material may desirably be made from a material of low magnetic permeability.
Further, it is also desirable to supply a coolant medium to the plenum, and also to cover a surface of the electromagnet with a material which has a high coefficient of thermal conductivity.
It is also beneficial to supply the coolant medium to a coolant conduit which is provided between the plenum of the fixed stage and a surface of the fixed stage which opposes the movable stage. In this case, it is desirable to make this coolant conduit from a material which has low magnetic permeability.
Further, in order to attain the above described objective, the present invention proposes, according to another aspect thereof, a stage construction incorporating a magnetically levitated movable stage, comprising a fixed stage and a magnetically levitated movable stage which is driven with respect to the fixed stage by magnetic action between the movable stage and the fixed stage in mutually perpendicular X, Y, and Z linear directions and in &agr;, &bgr;, and &thgr; rotational directions respectively defined around the X, Y, and Z directions. And driving force is exerted upon the movable stage along the Z linear direction, and in the a rotational direction and in the &bgr; rotational direction, by attractive or repulsive magnetic force which is generated between a first group of magnets provided to one of the movable stage and the fixed stage and a first group of electromagnets provided to the other of the stages, while driving force is exerted upon the movable stage along the X linear direction and the Y linear direction, and in the &thgr; rotational direction, by crosswise current flow in an electrical conductor provided in the other of the stages crosswise to and within magnetic flux which is generated between a second group of magnets provided to the one of the stages and a second group of electromagnets provided to the other of the stages.
In this case, it is desirable for each electromagnet comprised in the second group of electromagnets to comprise a first coil wound around the Z linear direction and a second coil wound around a direction perpendicular thereto, with the electrical conductor within which the crosswise current flows being comprised in the second coil.
Or, it is desirable for each electromagnet comprised in the second group of electromagnets to comprise a first coil wound around the Z linear direction, a second coil wound around a direction perpendicular thereto, and a third coil wound around a direction perpendicular both to the Z linear direction and also to the perpendicular direction, while the electrical conductor within which the crosswise current flows is comprised in the second coil and/or in the third coil.
The movable stage may desirably be driven over the fixed stage, with a magnet which only generates attractive magnetic force being included within the first group of magnets.
Further, this s
LaBalle Clayton
Nikon Corporation
Pillsbury Madison & Sutro LLP
LandOfFree
Stage construction incorporating magnetically levitated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stage construction incorporating magnetically levitated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stage construction incorporating magnetically levitated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2610114