Optics: measuring and testing – By light interference – For dimensional measurement
Reexamination Certificate
2002-02-12
2004-11-16
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By light interference
For dimensional measurement
Reexamination Certificate
active
06819433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exposure apparatus which includes an interferometer system which measures the position and displacement of an object in the vertical direction and is used to manufacture a liquid crystal board or semiconductor device.
BACKGROUND OF THE INVENTION
FIGS. 13 and 14
show an example of a measuring means for an alignment apparatus used in a conventional semiconductor exposure apparatus or the like.
FIG. 13
is a perspective view showing the arrangement of a measuring system using a laser interferometer.
FIG. 14
is a front view showing the overall conventional semiconductor exposure apparatus having the measuring system.
In
FIG. 14
, reference numeral
7
denotes an illumination unit for illuminating a reticle pattern;
8
, a reticle having a pattern to be transferred;
9
, a projection lens for projecting a reticle pattern onto a wafer;
10
, a lens barrel support which supports the projection lens
9
;
11
, a stage surface plate;
13
, an X stage;
14
, a Y stage;
15
, an X stage driving guide/X linear motor; and
16
, a Y stage driving guide/Y linear motor. A top stage
2
for precise alignment is mounted on the X and Y stages. The top stage
2
moves a long stroke in the X- and Y-axis directions by the guides
15
and
16
and an actuator. Further, the top stage
2
moves a short stroke in the Z-axis direction and rotational directions &ohgr;X, &ohgr;Y, and &thgr; by a Z actuator
17
which drives the top stage
2
with respect to the X stage
13
.
In
FIG. 13
, reference numeral
1
denotes a wafer chuck which supports a wafer (not shown). The top stage
2
constitutes a stage which supports the wafer chuck
1
. Reference numeral
3
denotes an X mirror which is attached to the top stage
2
and has a reflecting surface perpendicular to the X-axis;
4
, a Y mirror which is attached to the top stage
2
and has a reflecting surface perpendicular to the Y-axis;
5
a
,
5
b
, and
5
c
, X interferometers for measuring an X position; and
6
a
and
6
b
, Y interferometers for measuring a Y position. The X interferometers
5
a
,
5
b
, and
5
c
, and Y interferometers
6
a
and
6
b
are fixedly supported by a lens barrel support
10
shown in FIG.
14
.
In alignment by an apparatus conventionally called an alignment apparatus, a laser beam is sent to strike each predetermined position on a reflecting mirror attached to a stage. Position variation information at the beam incident position along the beam incident direction is acquired from the reflected beam to perform position detection. Alignment control is done based on the detection result. As a rotational direction detection means, pieces of position variation information at two beam incident positions along a single axis are obtained. More specifically, the measuring system in
FIG. 13
detects positions in the X, &thgr;, and &ohgr;Y directions from pieces of position variation information based on the X interferometers
5
a
,
5
b
, and
5
c
and in the Y and &ohgr;X directions by the Y interferometers
6
a
and
6
b
. Alignment control along the five axes except for the Z-axis is performed based on pieces of position detection information by the laser interferometers.
Referring back to
FIG. 14
, reference numerals
12
denote Z displacement sensors such as linear encoders or electrostatic capacitance sensors arranged in the above-described stage. The Z displacement sensors
12
measure displacement of the top stage
2
with respect to the X stage
13
at three positions, and can measure displacements of the top stage
2
in the Z and tilt directions. The Z tilt direction of the top stage
2
with respect to the lens barrel support
10
can be measured from the measurement values of the Z displacement sensors
12
and those of three interferometers (not shown) for performing Z measurement of the stage surface plate
11
with respect to the lens barrel support
10
. Z-axis alignment control is executed based on the detection results.
Alternatively, Z measurement of the top stage
2
may be directly performed using an interferometer, as shown in FIG.
15
. In
FIG. 15
, reference numeral
18
denotes a mirror attached to the lens barrel support
10
in order to perform Z measurement;
19
, a mirror which is integrally made up of an X mirror and a Z measuring mirror which forms an acute angle with the X mirror, and reflects, to the Z direction, measurement light incident parallel to the plane in which the top stage
2
moves; and
20
, a Z measuring interferometer
20
. This measuring method can directly measure the Z position and displacement of the top stage
2
by using the lens barrel support
10
as a measurement reference.
The alignment apparatus using the above Z position detection means suffers from the following problems.
In the prior art shown in
FIGS. 13 and 14
, Z position information of the top stage is obtained from the positional relationship between the X stage and the top stage. A measurement error occurs due to deformation of the stage guide when the stage accelerating/decelerating inertial force or stage weight acts as a moving load, or by deformation of the surface stage or structure which supports the stage. This inhibits precise alignment.
In the prior art shown in
FIG. 15
, the X or Y measuring mirror and the Z measuring mirror having an inclined surface are integrated. The X or Y measuring mirror which must exhibit high precision undergoes processing or mirror adhesion for Z measurement. This decreases the flatness and alignment precision. The alignment precision also decreases owing to an increase in weight or deformation caused by changes in adhesive over time.
SUMMARY OF THE INVENTION
The present invention has been proposed to solve the conventional problems, and has as its object to provide an exposure apparatus including an interferometer system that enable Z-direction measurement using a lens barrel support as a measurement reference and enable high-precision alignment by only mounting a bar mirror on a stage.
To solve the above problems, an exposure apparatus according to the present invention, having a projection optical system for projecting a pattern formed on a master onto a substrate, a stage capable of moving with respect to the projection optical system while holding at least one of the substrate and master, and a lens barrel support which supports the projection optical system, includes: an interferometer system having an interferometer for measuring a Z position and displacement of the stage with respect to the lens barrel support by using a Z measuring mirror which is arranged on the stage and has a reflecting surface substantially parallel to an XY plane.
More specifically, the exposure apparatus comprises a projection optical system for projecting a pattern formed on a master onto a substrate, a stage capable of moving with respect to the projection optical system while holding the substrate or master, and a lens barrel support which supports the projection optical system, and includes an interferometer system having an interferometer for measuring the position or displacement of the stage with respect to the lens barrel support. In this arrangement, the interferometer is arranged on at least one of the X and Y movable portions of the stage. Measurement light emitted by the interferometer is guided almost perpendicularly to the XY plane. The measurement light is reflected by a first reflecting surface attached to the lens barrel support toward the center of the lens barrel support, and travels toward a second reflecting surface at the center.
The measurement light is reflected by the second reflecting surface to almost perpendicularly strike a bar mirror having a reflecting surface almost parallel to the moving plane of the stage. Z measurement is performed by the reflected measurement light.
In the exposure apparatus, the interferometer system desirably includes a plurality of interferometer systems arranged on the apparatus. The interferometer may be mounted on either of the stage and a movable portion which follows th
Iwamoto Kazunori
Takai Ryo
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lyons Michael A.
Turner Samuel A.
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