Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1998-06-18
2001-05-15
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S077000, C356S401000
Reexamination Certificate
active
06233040
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus for manufacturing a semiconductor integrated circuit and a device manufacturing method which can use the exposure device and, more particularly, to improvement of driving of a substrate stage on which a substrate such as a wafer two-dimensionally moves in an exposure reference plane.
2. Description of the Related Art
In the lithography process in manufacturing a semiconductor integrated circuit, a reduction-projection type exposure device using a step-and-repeat scheme, i.e., a so-called stepper is popularly used.
FIG. 7
shows the arrangement of the stepper. Referring to
FIG. 7
, reference numeral
71
denotes a wafer;
72
, an X stage constituting a wafer stage;
73
, a Y stage constituting a wafer stage;
74
, an X-stage drive linear motor;
75
, a Y-stage drive linear motor;
76
, a measurement mirror,
77
, an X-stage position measurement laser beam;
78
, a Y-stage position measurement laser beam;
79
, an X-stage position measurement laser interferometer;
80
, a Y-stage position measurement laser interferometer;
81
, a reduction-projection lens; and
82
, a reticle. This device also comprises a light source for ultraviolet rays, X-rays, or the like (not shown).
In such a semiconductor reduction exposure device, a micropattern drawn on the reticle
82
is reduced to ⅕ by the reduction-projection lens
81
by means of a light source for ultraviolet rays, X-rays, or the like to expose and transfer the reduced pattern onto the wafer
71
. At this time, the wafer
71
is sequentially exposed while an X-Y drive called step-and-repeat is repeated by the X and Y wafer stages
72
and
73
. This X-Y drive depends on a position measured by the laser interferometers
79
and
80
to drive linear motors
74
and
75
, thereby positioning the wafer stages
72
and
73
.
FIG. 4
shows a conventional drive method for a wafer stage in the X-Y drive. The abscissa indicates time, and the ordinate indicates a velocity. Reference symbols S
1
to S
4
denote lines representing the difference between velocity patterns caused by the difference between stage moving amounts. The line S
1
having a small stage moving amount represents a velocity pattern in which, after the stage is maximally accelerated, the maximum deceleration is performed, such that the velocity does not reach the highest velocity V
1
, to move the stage to a target position. In contrast to this, the line S
4
having a larger stage moving amount represents a pattern in which a stage is maximally accelerated to the highest velocity V
1
, constant-velocity movement at the highest velocity V
1
is performed, and maximum deceleration is performed to move the stage to a target position.
As basic performances required in the stepper shown in
FIG. 7
, superposition precision and throughput are known. The wafer stage is an important mechanism which affects the performances. The positioning precision of the wafer stage considerably influences the superposition precision, and the drive time of the wafer stage considerably influences the throughput.
The drive time and positioning precision of the wafer stage are conflicting elements, and it is considerably difficult to improve both performances, i.e., both the drive time and the positioning precision. More specifically, increases in maximum acceleration and highest velocity of the velocity pattern of the wafer stage largely contribute to shortening of drive time. However, when the maximum acceleration and the highest velocity are increased, the amplitude of vibration of the stepper body serving as a base for supporting the wafer stage increases. The vibration serves as a disturbance to degrade the positioning precision of the wafer stage. For example, as shown in
FIG. 5A
, the drive time of a velocity pattern p
2
is shorter than the drive time of a velocity pattern p
1
such that the highest velocity of the velocity pattern p
2
is increased. However, as shown in corresponding
FIG. 5B
, the amplitude of vibration of the body increases because a body displacement h
2
in the velocity pattern p
2
is larger than a body displacement h
1
in the velocity pattern p
1
. In particular, residual vibration upon completion of the drive operates as a disturbance in positioning to cause degradation of the positioning precision.
For this reason, the maximum acceleration and the highest velocity of the velocity pattern of the wafer stage in a conventional stepper are set to satisfy the highest superposition precision required in the stepper, and these acceleration and velocity are fixed.
SUMMARY OF THE INVENTION
In a semiconductor exposure apparatus having a global alignment function, wafer stage precision in alignment measurement is very important. This is because a positioning error of the wafer stage in alignment measurement influences superposition precision of all shots in a wafer in exposure.
As shown in
FIG. 6
, the moving distance of the wafer stage in alignment measurement is longer than the moving distance in exposure. For this reason, the positioning precision of the wafer stage is influenced by the highest velocity or the maximum acceleration of the wafer stage more easily in exposure than in alignment measurement.
More specifically, since the maximum acceleration and the highest velocity of the wafer stage are constant in the above conventional art, when the maximum acceleration and the highest velocity of the wafer stage are increased to increase throughput, the wafer stage precision in alignment measurement is degraded, and the superposition precision of all the shots are degraded.
It is an object of the present invention to provide an exposure device which can obtain a high throughput without degrading superposition precision, and a device manufacturing method which can use the exposure device.
In order to achieve the object, according to the present invention, an exposure device for performing exposure to a substrate on a substrate stage while moving and positioning the substrate stage is characterized by comprising setting means for setting the value of a drive parameter for driving the substrate stage as different values depending on the types of movement of the substrate stage.
According to this arrangement, the value of the drive parameter is appropriately set according to the difference of demands for the positioning precision and the throughput depending on the types of movement of the substrate stage, so that the positioning precision and the throughput can be made compatible with each other.
In a preferred embodiment of the present invention, an exposure device has a global alignment function, and the setting means can set the value of a drive parameter in movement to alignment measurement shots and the value of a drive parameter in another movement as different values. For example, the drive parameter corresponds to the highest velocity or the maximum acceleration of the substrate stage.
The setting means sets the highest velocity or/and the maximum acceleration in movement to alignment measurement shots to be lower than the highest velocity or/and the maximum acceleration in another movement (i.e., a movement other than movement to alignment movement shots), respectively. In addition, when the exposure device is a scanning exposure device, the setting means can set the value of a drive parameter in movement to alignment shots, the value of a drive parameter in scanning exposure, and the value of a drive parameter in the remaining movement (i.e., a movement other than (a) movement to alignment shots and (b) scanning exposure) as values which are different from each other.
As described above, the highest velocity and the maximum acceleration in alignment measurement which considerably influence positioning precision are set to be lower values to give priority to the positioning precision, and the highest velocity and the maximum acceleration in exposure or another movement which slightly influence the positioning precision are set to be higher values t
Adams Russell
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Kim Peter B
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