Photocopying – Projection printing and copying cameras – Detailed holder for photosensitive paper
Reexamination Certificate
1999-05-19
2001-09-04
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for photosensitive paper
C355S053000
Reexamination Certificate
active
06285444
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to a positioning system for carrying and accurately positioning a workpiece, and to an exposure method or a device manufacturing method using such a positioning system. In another aspect, the invention is concerned with a position measuring method for accurately measuring the position of an article.
FIG. 29
shows an example of a conventional positioning system to be used in a semiconductor exposure apparatus, for example.
Denoted in the drawing at
104
is a wafer chuck for carrying a wafer (not shown) thereon, and denoted at
105
is a top stage of a stage system for supporting the wafer chuck
104
. It can be moved by means of guides and actuators (not shown) in X- and Y-axis directions with long strokes, and also it can be moved in a Z-axis direction and rotated in rotational directions &thgr;x, &thgr;y and &thgr;z with short strokes.
Denoted at
130
is a control box which includes a computing circuit and a driving circuit, for example. Denoted at
131
a
is an X reflection surface mounted to the top stage
105
, and denoted at
132
b
is a Y mirror reflection surface mounted to the top stage. Denoted at
133
a
,
133
b
and
133
c
are interferometers for measurement with respect to the X direction. Denoted at
134
a
and
134
b
are interferometers for measurement with respect to the Y direction. These interferometers
133
a
-
133
c
and
134
a
-
134
b
are fixedly supported by a base (not shown) which functions as a reference for the measurement.
Conventionally, for the positioning of a system called a positioning system, position detection is first made by projecting laser light to predetermined positions on a reflection mirror mounted on a stage whereby positional change information about the beam incidence positions along the beam incidence direction is produced on the basis of reflected light. Based on the result of this position detection, the positioning control is accomplished. As regards the method of detecting a rotational direction of the top stage
105
, it can be detected by detecting positional change information about the beam incidence positions at two locations along the same axis direction. Namely, in the measuring system of
FIG. 29
, position detection with respect to the Y-axis direction and &thgr;x direction is performed on the basis of positional change information detected by using the interferometers
133
a
,
133
b
and
133
c
. Then, positioning control with respect to five axial directions, excluding the Z-axis, is accomplished on the basis of the position detection information using laser interferometers.
As regards the position detecting means for the Z-axis direction, generally, it comprises a linear encoder or an electro-capacitance sensor provided within the stage to be moved, and the positioning control with respect to the Z-axis direction is performed on the basis of the result of detection by the detecting means.
In such a positioning system using Z-axis position detecting means as described above, positional information about the top stage with respect to the Z direction is detected by using a sensor mounted on the stage which is to be moved with a long stroke. This causes the following inconveniences.
(1) Since the positional information cannot be directly detected from the base (measurement reference) on which the laser interferometer is mounted, a plurality of sensors have to be disposed in series to perform the measurement. The measurement is, therefore, influenced by the precision of guide means, causing a measurement error.
(2) Inertia during stage acceleration and deceleration or the weight of the stage itself, acting as a movement load, will cause deformation of the stage guide or deformation of the base or the structure supporting the stage. This causes a measurement error and interferes with high precision positioning.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a positioning system with long-stroke movability in X and Y directions, by which measurement in the Z-axis direction is enabled in a simple structure and by which high precision positioning is assured.
In accordance with an aspect of the present invention, there is provided a positioning system, comprising: a movable member being movable along a reference plane containing first and second directions; and a position measuring device for measuring positional information related to the movable member; wherein the movable member includes an element having a reflection surface inclined with respect to the reference plane; and wherein said position measuring device includes measuring means for causing a measurement beam to be reflected by said inclined reflection surface and for detecting positional information related to the movable member with respect to a direction intersecting the reference plane.
In one preferred form of this aspect of the present invention, the inclined reflection surface includes a reflection surface portion for reflecting the measurement beam, projected thereto from said position measuring device substantially parallel to the reference plane, in a direction intersecting the reference plane.
In one preferred form of this aspect of the present invention, the positioning system further comprises a fixed mirror mounted on a stationary member and having a reflection surface with a direction of a normal thereto extending to intersect the reference plane, wherein the measurement beam reflected by said inclined reflection surface is then reflected by said fixed mirror backwardly along the beam path.
In one preferred form of this aspect of the present invention, the measurement beam reflected by said inclined reflection surface advances in a direction away from the reference plane.
In one preferred form of this aspect of the present invention, the measurement beam reflected by said inclined reflection surface advances in a direction close to the reference plane.
The position measuring device may detect the positional information related to the movable member with respect to a direction intersecting the reference plane, on the basis of a reflection beam reflected by the fixed mirror.
The inclined reflection surface may comprise a reflection surface inclined by 45 deg. with respect to the reference plane.
The direction intersecting the reference plane may be substantially orthogonal to the reference plane.
The measurement beam impinging on said inclined reflection surface and a reflected beam reflected by said inclined reflection surface may define an acute angle therebetween.
A measurement beam substantially parallel to the reference plane may be used to detect information about the movable member with respect to six axial directions.
The movable member may include a first mirror to be used for position measurement to the movable member with respect to the first direction, and a second mirror to be used for position measurement to the movable member with respect to the second direction.
The first mirror may serve to reflect a measurement beam, substantially parallel to the first direction, in a direction substantially parallel to the first direction.
The second mirror may serve to reflect a measurement beam, substantially parallel to the second direction, in a direction substantially parallel to the second direction.
The first and second directions may intersect with each other substantially at a right angle.
The inclined reflection surface may be provided integrally with at least one of said first and second mirrors.
The position measuring device may include first and second measuring means for performing measurement in relation to two different locations on said first mirror, third and fourth measuring means for performing measurement in relation to two different locations on said second mirror, fifth measuring means for performing measurement in relation to a third location placed out of a straight line connecting the two locations on said first mirror, and sixth measuring means for detecting a reflection beam coming via said inclined reflection surface.
The p
Akutsu Kotaro
Osanai Eiji
Adams Russell
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Hung Henry
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