Optics: measuring and testing – By light interference – For dimensional measurement
Reexamination Certificate
1999-07-26
2001-09-04
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By light interference
For dimensional measurement
C356S508000
Reexamination Certificate
active
06285457
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates generally to an exposure apparatus for use in the manufacture of semiconductor devices or liquid crystal panels, for example. In another aspect, the invention is concerned with a device manufacturing method using such an exposure apparatus.
FIG. 9
shows an example of measuring means in a positioning system usable in a semiconductor exposure apparatus, for example, and specifically, it illustrates the arrangement of a measuring system based on laser interferometers.
Denoted in the drawing at
120
is a wafer chuck for carrying thereon a wafer, not shown. Denoted at
121
is a top stage for supporting the wafer chuck
120
. The top stage can be moved by a guide and an actuator (not shown) in a Y axis direction and through a long stroke, and also it can be moved in a Z axis direction and rotational directions of wX, wY and &thgr; through a short stroke.
Denoted at
130
is a control box including a calculating circuit and a driving circuit, for example. Denoted at
131
a
is the reflection surface of an X mirror mounted on the top stage
121
, and denoted at
131
b
is the reflection surface of a Y mirror mounted an the top stage
121
. Denoted at
133
a
,
133
b
and
133
c
are interferometers, respectively, for measuring positions of the top stage
121
in the X direction, at corresponding places thereof, and denoted at
134
a
and
134
b
are interferometers, respectively, for measuring positions of the top stage
121
in the Y direction, at corresponding places thereof. These interferometers
133
a
-
133
c
and
134
a
and
134
b
are fixedly supported by a base, not shown, which provides a reference for the measurement.
Conventionally, for the positioning with the use of a positioning system, laser light is projected to predetermined locations on a reflection mirror, and position detection is performed on the basis of reflected light therefrom and of information related to a change in position of incidence of the beam along the bean incidence direction. The positioning control is then made in accordance with the result of the detection. As regards detection with respect to rotational direction, it is made on the basis of information about a change in position of beam incidence at two locations along one and the same axial direction. Namely, in the measuring system of
FIG. 9
, on the basis of positional change information based on the interferometers
133
a
,
113
b
and
133
c
, position detection with respect to the Y-axis direction and wX direction is performed. Then, positioning control in regard to five-axis directions except the Z axis is performed in accordance with the position detection information based on the laser interferometers. The position detecting means in regard to the Z-axis direction may usually comprise a linear encoder or an electrostatic capacity sensor, for example, accommodated in a movement stage, and the positioning control with respect to the Z-axis direction is performed in accordance with the result of detection by it.
FIG. 10
shows a general structure of a semiconductor exposure apparatus having such a measuring system as described above.
Denoted in
FIG. 10
at
101
is an illumination system for illuminating a reticle pattern, and denoted at
102
is a reticle having a pattern to be transferred. Denoted at
103
is a projection lens for projecting the reticle pattern onto a wafer, and denoted at
104
is a barrel supporting member for supporting the projection lens
103
. Denoted at
107
a
is a light emitting portion of focus detecting means for measuring the distance between the wafer and the focal point of the projection lens
103
, and denoted at
107
b
is a light receiving portion of this focus detecting means. Denoted at
115
is an interferometer for controlling the position of a stage system, wherein denoted at
121
is a top stage, denoted at
110
is an X stage and denoted at
111
is a Y stage. Denoted at
117
is a guide with an X linear motor, for driving the X stage, and denoted at
118
is a guide with a Y linear motor, for driving the Y stage. Denoted at
125
is a Z actuator for moving the top stage
121
in the Z direction relative to the X stage
110
. Denoted at
122
are Z displacement sensors provided in the stage system described above. By using these Z displacement sensors
122
, any displacement of the top stage
121
with respect to the X stage
110
is measured at three locations, by which any displacement of the top stage in the Z direction as well as displacement thereof in a tilt direction can be measured.
The positioning system having such Z-axis position detecting means, however, involves the following problems.
(1) The positional information about the top stage in the Z direction is produced on the basis of the positional relation between the X stage and the top stage. Therefore, any deformation of the stage guide resulting from a movement load such as inertia produced during stage acceleration or deceleration or the weight of the stage itself, or any deformation of a base or a structure supporting the stage will cause a measurement error. This is a bar to high precision positioning.
(2) Any change in guiding precision or deformation of the base, for example, has to be compensated for by the Z actuator provided between the X stage and the top stage. This requires that the Z actuator between the X stage and the top stage has a large stroke.
(3) The measurement of displacement in the Z direction is based on a principle different from that of the measurement in the X and Y directions using interferometers. A difference in frequency characteristic will produce a measurement error.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an exposure apparatus, by which measurement of a position or displacement of a stage can be performed while taking a barrel supporting member as a reference, and by which high precision alignment is assured.
It is another object of the present invention to provide an exposure apparatus, by which Z-axis measurement can be done with a simple structure, and by which high precision alignment is assured.
In accordance with an aspect of the present invention, there is provided an exposure apparatus, comprising: a projection optical system; a barrel supporting member for supporting said projection optical system; a stage being movable relative to said projection optical system; a base for supporting said stage; base measuring means for measuring at least one of a position and a displacement of said base with respect to said barrel supporting member; and stage measuring means for measuring at least one of a position and a displacement of said stage with respect to said barrel supporting member.
In preferred forms of this aspect of the present invention, said stage measuring means may include a laser interferometer. Said interferometer may project measurement light to a reflection surface associated therewith, along a direction orthogonal to an optical axis of said projection optical system. Said stage may be provided with a reflection surface for obliquely reflecting measurement light projected from said interferometer. Said stage may be provided with a first reflection surface extending substantially perpendicularly to measurement light projected from said interferometer, and a second reflection surface for obliquely reflecting measurement light projected from said interferometer.
The measurement light being obliquely reflected may bear a component in the optical axis direction of said projection optical system. A plane containing the measurement light projected from said interferometer and the measurement light as obliquely reflected, may be substantially parallel to an optical axis of said projection optical system. There may he an acute angle defined between the measurement light as projected and the measurement light as obliquely reflected.
The exposure apparatus may further comprise stationary reflection means having a reflection surface for reflecting the obliquely reflected measurement light. Sa
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Font Frank G.
Natividad Phil
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