U.S. patent application number 10/703205 was filed with the patent office on 2004-07-08 for control system and method for improving tracking accuracy of a stage through processing of information from previous operations.
Invention is credited to Hashimoto, Hideyuki, Hirano, Kazuhiro, Itakura, Yoshiji, Kawaguchi, Ryoichi, Makinouchi, Susumu, Yang, Pai-Hsueh, Yuan, Bausan.
Application Number | 20040128918 10/703205 |
Document ID | / |
Family ID | 32685157 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040128918 |
Kind Code |
A1 |
Yang, Pai-Hsueh ; et
al. |
July 8, 2004 |
Control system and method for improving tracking accuracy of a
stage through processing of information from previous
operations
Abstract
A precision assembly (10) includes a stage assembly (220) having
a first stage (208), a first mover assembly (210) and a control
system (24). The first mover assembly (210) moves the first stage
(208) during a first iteration (300) and a subsequent second
iteration (302) having a similar movement to the first iteration
(300). The first iteration (300) generates positioning data that is
sent to the control system (24) to control the first mover assembly
(210) to adjust movement of the first stage (208) during the second
iteration (302) based on at least a portion of the positioning data
from the first iteration (300). The positioning data can include
the position of the first stage (208) along a first axis, a second
axis and/or a third axis. The stage assembly can also include a
second stage (206) and a second mover assembly (204) that moves the
second stage (206) synchronously with the first stage (208). The
second stage (206) generates positioning data that is used by the
control system (24) to adjust movement the first mover assembly
(210) of the first stage (208) to improve synchronization of
movement of the stages. The precision assembly (10) can also
include one or more sensors (23) that monitor movement of one or
more components of the precision assembly (10) other than the stage
assembly (220). Positioning data of such movement is sent to the
control system (24) to control movement of the first stage
(208).
Inventors: |
Yang, Pai-Hsueh; (Palo Alto,
CA) ; Yuan, Bausan; (San Jose, CA) ;
Makinouchi, Susumu; (Kanagawa, JP) ; Itakura,
Yoshiji; (Kumagava, JP) ; Hirano, Kazuhiro;
(Ageo, JP) ; Hashimoto, Hideyuki; (Kumagaya,
JP) ; Kawaguchi, Ryoichi; (Tokyo, JP) |
Correspondence
Address: |
The Law Office of Steven G. Roeder
5560 Chelsea Avenue
La Jolla
CA
92037
US
|
Family ID: |
32685157 |
Appl. No.: |
10/703205 |
Filed: |
November 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60424506 |
Nov 6, 2002 |
|
|
|
Current U.S.
Class: |
52/7 |
Current CPC
Class: |
G03F 7/70725
20130101 |
Class at
Publication: |
052/007 |
International
Class: |
E04H 003/26 |
Claims
What is claimed is:
1. A stage assembly comprising: a first stage; a first mover
assembly that moves the first stage during a first iteration and a
subsequent second iteration, the first iteration having a first
intended trajectory of the first stage, the second iteration having
a second intended trajectory of the first stage that is similar to
the first intended trajectory of the first stage, positioning data
being generated during the first iteration; and a control system
that receives the positioning data, the control system controlling
the first mover assembly to adjust movement of the first stage
during the second iteration based on at least a portion of the
positioning data.
2. The stage assembly of claim 1 wherein the control system
includes a memory buffer that stores the positioning data.
3. The stage assembly of claim 1 wherein movement of the first
stage includes movement along a first axis and wherein the
positioning data includes the position of the first stage along the
first axis.
4. The stage assembly of claim 3 wherein movement of the first
stage includes movement along a second axis that is orthogonal to
the first axis, and wherein the positioning data includes the
position of the first stage along the second axis.
5. The stage assembly of claim 4 wherein movement of the first
stage includes movement about a third axis that is orthogonal to
the first and second axes, and wherein the positioning data
includes the position of the first stage about the third axis.
6. The stage assembly of claim 1 wherein movement of the first
stage includes movement about a first axis, and wherein the
positioning data includes the position of the first stage about the
first axis.
7. The stage assembly of claim 1 wherein at a time t1.sub.1 during
the first iteration the first stage has an intended position and an
actual position, wherein the difference between the intended
position and the actual position at time t1.sub.1 is a t1.sub.1
following error, and wherein the positioning data includes the
t1.sub.1 following error.
8. A precision apparatus including the stage assembly of claim 7,
the precision apparatus further comprising a second stage assembly
having a second stage and a second mover assembly that moves the
second stage synchronously with the first stage, wherein the
positioning data includes second stage positioning information, the
control system adjusting movement of the first mover assembly based
at least partly on the second stage positioning information to
improve synchronization of movement of the stages.
9. The precision apparatus of claim 8 wherein the second stage
moves during a first iteration and a subsequent second iteration,
the first iteration of the second stage having a first intended
trajectory, the second iteration of the second stage having a
second intended trajectory that is similar to the first intended
trajectory of the second stage, and wherein the positioning data
includes second stage positioning information during the first
iteration of the second stage.
10. The stage assembly of claim 7 wherein at a time t2.sub.1 during
the first iteration the first stage has an intended position and an
actual position, wherein the difference between the intended
position and the actual position at time t2.sub.1 is a t2.sub.1
following error, and wherein the positioning data includes the
t2.sub.1 following error.
11. The stage assembly of claim 1 wherein the first stage moves
along an actual trajectory during the first iteration, and wherein
the positioning data includes at least a portion of the actual
trajectory of the first stage during the first iteration.
12. The stage assembly of claim 1 wherein the control system
includes a noise filter that is applied to the positioning data to
remove the high frequency noise from the positioning data.
13. The stage assembly of claim 1 wherein control system updates
the positioning data using an adaptive algorithm.
14. The stage assembly of claim 13 wherein the control system
selectively pauses updating of the positioning data.
15. The stage assembly of claim 13 wherein the updated positioning
data is used in a model-based control law.
16. The stage assembly of claim 1 wherein the control system
includes a non-model based control law that is applied to the
positioning data.
17. The stage assembly of claim 1 wherein the first mover assembly
moves the first stage in a third iteration that precedes the first
iteration, wherein positioning data is generated from the third
iteration, and wherein the control system controls the first mover
assembly to adjust movement of the first stage during the second
iteration based on the positioning data generated during the third
iteration.
18. The stage assembly of claim 1 wherein the first iteration and
the second iteration each have substantially similar points in time
within each corresponding iteration that include time t1, time t2
and time t3, wherein time t1 is prior to time t2, and time t2 is
prior to time t3, and wherein the control system controls the first
mover assembly to adjust movement of the first stage at time t2 of
the second iteration based on the positioning data generated at
time t3 of the first iteration.
19. The stage assembly of claim 18 wherein the control system
controls the first mover assembly to adjust movement of the first
stage at time t2 of the second iteration based on the positioning
data generated at time t2 of the first iteration.
20. The stage assembly of claim 1 wherein the second intended
trajectory of the first stage is identical to the first intended
trajectory of the first stage.
21. The stage assembly of claim 1 wherein the first stage is a
reticle stage that retains a reticle.
22. The stage assembly of claim 1 wherein the first stage is a
wafer stage that retains a wafer.
23. A precision assembly including an illumination source and the
stage assembly of claim 1 positioned near the illumination
source.
24. The precision assembly of claim 23 further comprising a sensor
that senses the movement of a portion of the exposure apparatus
other than the stage assembly, wherein the positioning data
includes the movement of the portion of the exposure apparatus
being monitored by the sensor.
25. The precision assembly of claim 24 wherein the portion of the
exposure apparatus is at least a portion of an optical
assembly.
26. The precision assembly of claim 24 wherein the portion of the
exposure apparatus is at least a portion of an apparatus frame.
27. A device manufactured with the precision assembly according to
claim 23.
28. A wafer on which an image has been formed by the precision
assembly according to claim 23.
29. A precision assembly comprising: a first stage assembly
including a first stage and a first mover assembly that moves the
first stage; a second stage assembly including a second stage and a
second mover assembly that moves the second stage synchronously
with the first stage, positioning data being generated that
includes the position of the second stage; and a control system
that receives the positioning data, the control system controlling
the first mover assembly to adjust movement of the first stage
based on the position of the second stage to improve
synchronization of movement of the stages.
30. The precision assembly of claim 29 wherein the control system
includes a memory buffer that stores the positioning data.
31. The precision assembly of claim 29 wherein the control system
includes a noise filter that is applied to the positioning data to
remove the high frequency noise from the positioning data.
32. The precision assembly of claim 29 wherein control system
updates the positioning data using an adaptive algorithm.
33. The precision assembly of claim 32 wherein the control system
selectively pauses updating of the positioning data.
34. The precision assembly of claim 32 wherein the updated
positioning data is used in a model-based control law.
35. The precision assembly of claim 29 wherein the control system
includes a non-model based control law.
36. The precision assembly of claim 29 wherein the first stage is a
reticle stage that retains a reticle, and wherein the second stage
is a wafer stage that retains a wafer.
37. The precision assembly of claim 29 wherein the first mover
assembly moves the first stage during a first iteration and a
subsequent second iteration having a similar movement to the first
iteration of the first stage, at least a portion of the positioning
data being generated from the first iteration of the first stage,
and wherein the control system controls the first mover assembly
during the second iteration of the first stage based on at least a
portion of the positioning data that is generated from the first
iteration of the first stage.
38. The precision assembly of claim 37 wherein the second mover
assembly moves the second stage during a first iteration and a
subsequent second iteration having a similar movement to the first
iteration of the second stage, at least a portion of the
positioning data being generated from the first iteration of the
second stage, and wherein the control system controls the second
mover assembly during the second iteration of the second stage
based on at least a portion of the positioning data that is
generated from the first iteration of the second stage.
39. The precision assembly of claim 37 wherein at a time t2.sub.1
during the first iteration the first stage has an intended position
and an actual position, wherein the difference between the intended
position and the actual position at time t2.sub.1 is a t2.sub.1
following error, and wherein the positioning data includes the
t2.sub.1 following error.
40. The precision assembly of claim 37 wherein the first stage
moves along an actual trajectory during the first iteration, and
wherein the positioning data includes at least a portion of the
actual trajectory of the first stage during the first
iteration.
41. The precision assembly of claim 37 wherein the first mover
assembly moves the first stage in a third iteration that precedes
the first iteration, wherein positioning data is generated from the
third iteration, and wherein the control system controls the first
mover assembly to adjust movement of the first stage during the
second iteration based on the positioning data generated from the
third iteration.
42. The precision assembly of claim 37 wherein the first iteration
and the second iteration each have substantially similar points in
time within each corresponding iteration that include time t1, time
t2 and time t3, wherein time t1 is prior to time t2, and time t2 is
prior to time t3, and wherein the control system controls the first
mover assembly to adjust movement of the first stage at time t2 of
the second iteration based on the positioning data generated at
time t3 of the first iteration.
43. The precision assembly of claim 42 wherein the control system
controls the first mover assembly to adjust movement of the first
stage at time t2 of the second iteration based on the positioning
data generated at time t2 of the first iteration.
44. The precision assembly of claim 42 wherein the control system
controls the first mover assembly to adjust movement of the first
stage at time t2 of the second iteration based on the positioning
data generated at times t1 and t2 of the first iteration.
45. The precision assembly of claim 29 wherein the control system
includes a noise filter that is applied to the positioning data to
remove the high frequency noise from the positioning data.
46. The precision assembly of claim 29 wherein control system
updates the positioning data using an adaptive algorithm.
47. The precision assembly of claim 46 wherein the control system
selectively pauses updating of the positioning data.
48. The precision assembly of claim 46 wherein the updated
positioning data is used in a model-based control law.
49. The precision assembly of claim 29 wherein the control system
includes a non-model based control law.
50. The precision assembly of claim 29 further comprising a sensor
that senses the movement of a portion of the exposure apparatus
other than the stage assembly, wherein the positioning data
includes the movement of the portion of the exposure apparatus
being monitored by the sensor.
51. The precision assembly of claim 50 wherein the portion of the
precision assembly is at least a portion of an optical
assembly.
52. The precision assembly of claim 50 wherein the portion of the
precision assembly is at least a portion of an apparatus frame.
53. A device manufactured with the preision assembly according to
claim 29.
54. A wafer on which an image has been formed by the precision
assembly according to claim 29.
55. A precision assembly comprising: a first stage assembly
including a first stage and a first mover assembly that moves the
first stage; a sensor that monitors the position of a portion of
the precision assembly other than the stage assembly, the sensor
providing positioning data including the position of the portion of
the precision assembly being monitored by the sensor; and a control
system that receives the positioning data, the control system
controlling the first mover assembly to adjust movement of the
first stage based on at least a portion of the positioning
data.
56. The precision assembly of claim 55 wherein the portion of the
precision assembly being monitored by the sensor includes at least
a portion of an optical assembly.
57. The precision assembly of claim 55 wherein the portion of the
precision assembly being monitored by the sensor includes at least
a portion of an apparatus frame.
58. The precision assembly of claim 55 wherein the precision
assembly includes a second stage assembly having a second stage and
a second mover assembly that moves the second stage synchronously
with the first stage, wherein the positioning data includes the
position of the first and second stages, and wherein the control
system controls at least one of the mover assemblies to adjust
movement of the first stage based on the positioning data to
improve synchronization of movement of the stages.
59. The precision=assembly=of claim 58 wherein the second mover
assembly moves the second stage during a first iteration and a
subsequent second iteration having a similar movement to the first
iteration of the second stage, at least a portion of the
positioning data being generated during the first iteration of the
second stage, and wherein the control system controls the second
mover assembly during the second iteration of the second stage
based on at least a portion of the positioning data that is
generated during the first iteration of the second stage.
60. The precision assembly of claim 58 wherein the first stage is a
reticle stage that retains a reticle, and wherein the second stage
is a wafer stage that retains a wafer.
61. The precision assembly of claim 55 wherein the first mover
assembly moves the first stage during a first iteration and a
subsequent second iteration having a similar movement to the first
iteration of the first stage, at least a portion of the positioning
data being generated from the first iteration of the first stage,
and wherein the control system controls the first mover assembly
during the second iteration of the first stage based on at least a
portion of the positioning data that is generated during the first
iteration of the first stage.
62. The precision assembly of claim 61 wherein at a time t2.sub.1
during the first iteration the first stage has an intended position
and an actual position, wherein the difference between the intended
position and the actual position at time t2.sub.1 is a t2.sub.1
following error, and wherein the positioning data includes the
t2.sub.1 following error.
63. The precision assembly of claim 62 wherein the first stage
moves along an actual trajectory during the first iteration, and
wherein the positioning data includes at least a portion of the
actual trajectory of the first stage during the first
iteration.
64. The precision assembly of claim 61 wherein the first mover
assembly moves the first stage in a third iteration that precedes
the first iteration, wherein positioning data is generated from the
third iteration, and wherein the control system controls the first
mover assembly to adjust movement of the first stage during the
second iteration based on the positioning data generated from the
third iteration.
65. The precision assembly of claim 61 wherein the first iteration
and the second iteration each have substantially similar points in
time within each corresponding iteration that include time t1, time
t2 and time t3, wherein time t1 is prior to time t2, and time t2 is
prior to time t3, and wherein the control system controls the first
mover assembly to adjust movement of the first stage at time t2 of
the second iteration based on the positioning data generated at
time t3 of the first iteration.
66. The precision assembly of claim 65 wherein the control system
controls the first mover assembly to adjust movement of the first
stage at time t2 of the second iteration based on the positioning
data generated at time t2 of the first iteration.
67. The precision assembly of claim 65 wherein the control system
controls the first mover assembly to adjust movement of the first
stage at time t2 of the second iteration based on the positioning
data generated at times t1 and t2 of the first iteration.
68. The precision assembly of claim 55 wherein the control system
includes a noise filter that is applied to the positioning data to
remove the high frequency noise from the positioning data.
69. The precision assembly of claim 55 wherein control system
updates the positioning data using an adaptive algorithm.
70. The precision assembly of claim 69 wherein the control system
selectively pauses updating of the positioning data.
71. The precision assembly of claim 69 wherein the updated
positioning data is used in a model-based control law.
72. The precision assembly of claim 55 wherein the control system
includes a non-model based control law.
73. A device manufactured with the precision assembly according to
claim 55.
74. A wafer on which an image has been formed by the precision
assembly according to claim 55.
75. A method for positioning one or more stages of a precision
assembly, the method comprising the steps of: moving the first
stage during a first iteration and a subsequent second iteration
with a first mover assembly, the second iteration having a similar
movement to the first iteration; generating positioning data from
the first iteration that is sent to a control system; and
controlling the first mover assembly with the control system to
adjust movement of the first stage during the second iteration
based on at least a portion of the positioning data.
76. The method of claim 75 wherein the step of generating
positioning data includes sending the positioning data to a memory
buffer that stores the positioning data.
77. The method of claim 76 wherein the step of generating
positioning data includes sending positioning data that includes
the position of the first stage along a second axis that is
orthogonal to the first axis.
78. The method of claim 77 wherein the step of generating
positioning data includes sending positioning data that includes
the position of the first stage about a third axis that is
orthogonal to the first and second axes.
79. The method of claim 75 wherein the step of generating
positioning data includes sending positioning data that includes
the position of the first stage about a first axis.
80. The method of claim 75 wherein the step of moving the first
stage includes the first stage having an intended position at a
time t1 during the first iteration and an actual position at time
t1.sub.1, wherein the difference between the intended position and
the actual position at time t1 is a t1 following error, and wherein
the positioning data includes the t1.sub.1 following error.
81. The method of claim 80 wherein the step of moving the first
stage includes the first stage having an intended position at a
time t2.sub.1 during the first iteration and an actual position at
time t2.sub.1, wherein the difference between the intended position
and the actual position at time t2.sub.1 is a t2.sub.1 following
error, and wherein positioning data includes the t2.sub.1 following
error.
82. The method of claim 75 further comprising the step of
processing the positioning data with a noise filter to remove high
frequency noise.
83. The method of claim 75 further comprising the step of updating
the positioning data using an adaptive algorithm.
84. The method of claim 83 wherein the step of updating the
positioning data is selectively paused by the control system.
85. The method of claim 75 further comprising the step of
generating positioning data using a sensor that senses movement of
a portion of the precision assembly other than the stage
assembly.
86. The method of claim 75 further comprising the steps of moving a
second stage with a second mover assembly synchronously with the
first stage, generating positioning data from movement of the
second stage that is sent to the control system, and controlling
the first mover assembly with the control system based on the
positioning data from movement of the stages to adjust movement of
the first stage to improve synchronization of movement of the
stages.
87. The method of claim 85 wherein the first stage is a reticle
stage that retains a reticle and the second stage is a wafer stage
that retains a wafer.
88. A method for manufacturing a device that includes the method of
claim 75.
89. A method for manufacturing a wafer on which an image has been
formed that includes the method of claim 75.
90. A method for positioning one or more stages of a precision
assembly, the method comprising the steps of: moving the first
stage with a first mover assembly; moving a second stage with a
second mover assembly synchronously with the first stage;
generating second stage positioning data that includes the position
of the second stage; and controlling movement of the first mover
assembly with a control system based on the second stage
positioning data to improve the synchronization of movement of the
stages.
91. The method of claim 90 further comprising the steps of
generating first stage positioning data that includes the position
of the first stage, and controlling movement of the second mover
assembly with the control system based on the first stage
positioning data to improve the synchronization of movement of the
stages.
92. The method of claim 90 wherein the step of generating
positioning data includes sending the positioning data to a memory
buffer that stores the positioning data.
93. The method of claim 90 wherein the step of moving the first
stage includes moving the first stage during a first iteration and
a subsequent second iteration with the first mover assembly, the
second iteration having a similar movement to the first iteration,
and generating positioning data from the first iteration that is
sent to the control system, and wherein the step of controlling
movement of the first mover assembly includes controlling the first
mover assembly with the control system to adjust movement of the
first stage during the second iteration based on at least a portion
of the positioning data from the first iteration of the first
stage.
94. The method of claim 94 wherein the step of moving the first
stage includes the first stage having an intended position at a
time t1.sub.1 during the first iteration and an actual position at
time t1.sub.1, wherein the difference between the intended position
and the actual position at time t1.sub.1 is a t1.sub.1 following
error, and wherein the positioning data of the first stage includes
the t1.sub.1 following error.
95. The method of claim 94 wherein the step of moving the first
stage includes the first stage having an intended position at a
time t2.sub.1 during the first iteration and an actual position at
time t2.sub.1, wherein the difference between the intended position
and the actual position at time t2.sub.1 is a t2.sub.1 following
error, and wherein positioning data of the first stage includes the
t2.sub.1 following error.
96. The method of claim 90 further comprising the step of
generating positioning data using a sensor that senses movement of
a portion of the precision assembly other than the stage
assembly.
97. The method of claim 90 wherein the first stage is a reticle
stage that retains a reticle and the second stage is a wafer stage
that retains a wafer.
98. A method for manufacturing a device that includes the method of
claim 90.
99. A method for manufacturing a wafer on which an image has been
formed that includes the method of claim 90.
100. A method for positioning one or more stages of a stage
assembly of an precision assembly, the method comprising the steps
of: moving a first stage with a first mover assembly; monitoring
movement of a portion of the precision assembly other than the
stage assembly with a sensor; generating positioning data with the
sensor, the positioning data including the position of the portion
of the precision assembly being monitored by the sensor; and
controlling movement of the first mover assembly with a control
system to adjust movement of the first stage based on at least a
portion of the positioning data.
101. The method of claim 100 wherein the step of generating
positioning data includes generating positioning data of the
position of at least a portion of an optical assembly of the
precision assembly.
102. The method of claim 100 wherein the step of generating
positioning data includes generating positioning data of the
position of at least a portion of an apparatus frame of the
precision assembly.
103. The method of claim 100 further comprising the steps of moving
a second stage with a second mover assembly synchronously with the
first stage, and generating positioning data that includes the
position of the second stage, and wherein the step of controlling
movement includes controlling movement of the first mover assembly
to adjust movement of the first stage based on the second stage
positioning data to improve synchronization of movement of the
stages.
104. The method of claim 103 wherein the first stage is a reticle
stage that retains a reticle, and wherein the second stage is a
wafer stage that retains a wafer.
105. The method of claim 100 wherein the step of moving the first
stage includes moving the first stage during a first iteration and
a subsequent second iteration having a similar movement to the
first iteration, and generating first stage positioning data from
movement of the first stage during the first iteration, and wherein
step of controlling movement of the first mover assembly includes
controlling movement of the first mover assembly during the second
iteration based on at least a portion of the positioning data that
is generated from the first iteration of the first stage.
106. The method of claim 105 wherein the positioning data that is
generated from the first iteration of the first stage includes a
following error equal to the difference between an intended
position and an actual position of the first stage.
107. The method of claim 105 wherein the positioning data that is
generated from the first iteration of the first stage includes at
least a portion of an actual trajectory of the first stage during
the first iteration.
108. The method of claim 100 further comprising the step of
processing the positioning data with a noise filter to remove high
frequency noise.
109. The method of claim 100 further comprising the step of
updating the positioning data using an adaptive algorithm.
110. The method of claim 109 wherein the step of updating the
positioning data is selectively paused by the control system.
111. A method for manufacturing a device that includes the method
of claim 100.
112. A method for manufacturing a wafer on which an image has been
formed that includes the method of claim 100.
113. A first stage assembly comprising: a first stage having a
first intended trajectory and a second intended trajectory that is
similar to the first intended trajectory; a first mover assembly
that moves the first stage along a first actual trajectory that
emulates the first intended trajectory and a subsequent, second
actual trajectory that emulates the second intended trajectory,
positioning data being generated during the first actual
trajectory; and a control system that receives the positioning
data, the control system controlling the first mover assembly to
adjust the second actual trajectory of the first stage based on at
least a portion of the positioning data.
114. The stage assembly of claim 113 wherein the first intended
trajectory includes a first starting point and the second intended
trajectory includes a second starting point, and wherein the first
starting point is the same as the second starting point.
115. The stage assembly of claim 114 wherein the first intended
trajectory includes a first intended motion and the second intended
trajectory includes a second intended motion, and wherein the first
intended motion is similar to the second intended motion.
116. The stage assembly of claim 113 wherein the first intended
trajectory includes a first intended motion and the second intended
trajectory includes a second intended motion, and wherein the first
intended motion is the same as the second intended motion.
117. The stage assembly of claim 116 wherein the first intended
trajectory includes a first starting point and the second intended
trajectory includes a second starting point, and wherein the first
starting point is similar to the second starting point.
118. The stage assembly of claim 116 wherein the first intended
trajectory includes a first starting point and the second intended
trajectory includes a second starting point, and wherein the first
starting point is the same as the second starting point.
119. A stage assembly comprising: a first stage having (i) a first
intended trajectory that includes a first point and a first
movement, and (ii) a second intended trajectory that includes a
second point and a second movement, the second point being the same
as the first point, the second movement being similar to the first
movement; a first mover assembly that moves the first stage along a
first actual trajectory that emulates the first intended
trajectory, and a second actual trajectory that emulates the second
intended trajectory, positioning data being generated during the
first actual trajectory; and a control system that receives the
positioning data, the control system controlling the first mover
assembly to adjust the second actual trajectory of the first stage
based on at least a portion of the positioning data.
120. The stage assembly of claim 119 wherein the first movement is
the same as the second movement.
121. A stage assembly comprising: a first stage having (i) a first
intended trajectory that includes a first point and a first
movement, and (ii) a second intended trajectory that includes a
second point and a second movement, the second point being similar
to the first point, the second movement being the same as the first
movement; a first mover assembly that moves the first stage along a
first actual trajectory that emulates the first intended
trajectory, and a second actual trajectory that emulates the second
intended trajectory, positioning data being generated during the
first actual trajectory; and a control system that receives the
positioning data, the control system controlling the first mover
assembly to adjust the second actual trajectory of the first stage
based on at least a portion of the positioning data.
122. A method for positioning a first stage of a stage assembly of
a precision assembly, the method comprising the steps of: providing
a first stage having a first intended trajectory and a second
intended trajectory that is similar to the first intended
trajectory; moving the first stage with a first mover assembly
along a first actual trajectory that emulates the first intended
trajectory and a subsequent, second actual trajectory that emulates
the second intended trajectory; generating positioning data from
the first actual trajectory that is sent to a control system; and
controlling the first mover assembly with the control system to
adjust the second actual trajectory of the first stage based on at
least a portion of the positioning data.
123. The method of claim 122 wherein the step of providing a first
stage includes the first intended trajectory having a first
starting point that is the same as a second starting point of the
second intended trajectory.
124. The method of claim 123 wherein the step of providing a first
stage includes the first intended trajectory having a first
intended motion that is similar to a second intended motion of the
second intended trajectory.
125. The method of claim 122 wherein the step of providing a first
stage includes the first intended trajectory having a first
intended motion that is the same as a second intended motion of the
second intended trajectory.
126. The method of claim 125 wherein the step of providing a first
stage includes the first intended trajectory having a first
starting point that is similar to a second starting point of the
second intended trajectory.
127. The method of claim 125 wherein the step of providing a first
stage includes the first intended trajectory having a first
starting point that is the same as a second starting point of the
second intended trajectory.
Description
RELATED APPLICATION
[0001] This Application claims the benefit on U.S. Provisional
Application Serial No. 60/424,506, filed on Nov. 6, 2002. The
contents of U.S. Provisional Application Serial No. 60/424,506 are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a control system
for controlling the trajectory and alignment of one or more
stages.
BACKGROUND
[0003] An exposure apparatus is one type of precision assembly that
are commonly used to transfer images from a reticle onto a
semiconductor wafer during semiconductor processing. A typical
exposure apparatus includes an illumination source, a reticle stage
assembly that retains a reticle, an optical assembly, a wafer stage
assembly that retains a semiconductor wafer, a measurement system,
and a control system.
[0004] In one embodiment, the wafer stage assembly includes a wafer
stage that retains the wafer, and a wafer mover assembly that
precisely positions the wafer stage and the wafer. Somewhat
similarly, the reticle stage assembly includes a reticle stage that
retains the reticle, and a reticle mover assembly that positions
the reticle stage and the reticle. The control system independently
directs current to the wafer mover assembly and the reticle mover
assembly to generate one or more forces that cause the movement
along a "trajectory" of the wafer stage and the reticle stage,
respectively.
[0005] The size of the images and features within the images
transferred onto the wafer from the reticle are extremely small.
Accordingly, the precise positioning of the wafer and the reticle
relative to the optical assembly is critical to the manufacture of
high density, semiconductor wafers. In some embodiments, numerous
identical integrated circuits are derived from each semiconductor
wafer. Therefore, during this manufacturing process, the wafer
stage and/or the reticle stage can be cyclically and repetitiously
moved to emulate an intended trajectory. Each intended trajectory
that is similar to a previous intended trajectory of one of the
stages is also referred to herein as an "iteration" or "cycle".
[0006] Unfortunately, during the movement of the stages, a
following error of the wafer stage and/or the reticle stage can
occur. The following error is defined by the difference between the
intended trajectory of the wafer stage and/or the reticle stage and
an actual trajectory of the stage at a specified time. For example,
the following error can occur due to lack of complete rigidity in
the components of the exposure apparatus, which can result in a
slight time delay between current being directed to the mover
assembly and subsequent movement of the stage.
[0007] Additionally, alignment errors can occur even if the stages
are properly positioned relative to each other. For example,
periodic vibration disturbances of various mechanical structures of
the exposure apparatus can occur. More specifically, oscillation or
resonance of the optical assembly and/or other supporting
structures can inhibit relative alignment between the stages and
the optical assembly. As a result of the following errors and/or
the vibration disturbances, precision in the manufacture of the
semiconductor wafers can be compromised, potentially leading to
production of a lesser quality semiconductor wafer.
[0008] Attempts to decrease following errors include the use of a
feedback control loop. In these types of systems, during movement
of one of the stages, the measurement system periodically provides
information regarding the current position of the stage. This
information is utilized by the control system to adjust the level
of current to the mover assembly in an attempt to achieve the
intended trajectory. Unfortunately, this method is not entirely
satisfactory and the control system does not always precisely move
each stage along its intended trajectory.
[0009] In light of the above, there is a need for a control system
that can improve the accuracy in the positioning of the stage.
Further, there is a need for a control system that can accurately
adjust the positioning of the wafer stage and/or the reticle stage
to produce higher quality semiconductor wafers.
SUMMARY
[0010] The present invention is directed to a stage assembly that
includes a first stage, a first mover assembly that moves the first
stage, and a control system. In one embodiment, the first mover
assembly moves the first stage in a first iteration and a
subsequent second iteration having a similar movement to the first
iteration. In one embodiment, the control system collects
positioning data during the first iteration that is utilized during
the second iteration to control the first mover assembly to adjust
movement of the first stage during the second iteration.
[0011] The control system can include a memory buffer that stores
the positioning data. Movement of the first stage can include
movement along an X axis, a Y axis and/or about a Z axis. The
positioning data can include the position of the first stage along
or about any or all of these axes.
[0012] For example, at a time t1.sub.1 during the first iteration,
the first stage can have an intended position and a measured,
actual position that can be different than the intended position.
The difference between the intended position and the actual
position at time t1.sub.1 is referred to herein as a t1.sub.1
following error. In one embodiment, the positioning data includes
the t1 following error. Further, at a time t2.sub.1 during the
first iteration the first stage can also have an intended position
and an actual position that can be different than the intended
position, referred to herein as a t2.sub.1 following error. The
positioning data can also include the t2.sub.1 following error.
[0013] Moreover, the first iteration and the second iteration can
each have correspondingly relative similar time points within each
iteration that include time t1, time t2 and time t3. In this
embodiment, time t1 is prior to time t2, and time t2 is prior to
time t3. In one embodiment, the control system controls the first
mover assembly to adjust movement of the first stage at time t2 of
the second iteration based on the positioning data generated at
time t3 of the first iteration.
[0014] In another embodiment, the first mover assembly can move the
first stage in a third iteration that precedes the first iteration.
The control system collects positioning data during the third
iteration that is used by the control system for adjusting current
to the first mover assembly to control movement of the first stage
during the second iteration based on the positioning data generated
during the third iteration.
[0015] In still another embodiment, the stage assembly can include
a second stage and a second mover assembly that moves the second
stage synchronously with the first stage. Positioning data from
movement of the second stage is used to more accurately control
positioning of the first stage. For example, the control system can
adjust current to the first mover assembly based at least partially
on the positioning data generated from the second stage. With this
design, the control system can improve synchronization of movement
of the stages.
[0016] In yet another embodiment, the present invention is directed
toward an exposure apparatus including a stage assembly having a
first stage and a first mover assembly, a sensor that provides
positioning data relating to movement of a portion of the exposure
apparatus other than the stage assembly. The exposure apparatus
also includes a control system that receives the positioning data.
The control system controls the first mover assembly to adjust
movement of the first stage based on at least a portion of the
positioning data.
[0017] The present invention is also directed to an exposure
apparatus, a wafer, a device, a method for positioning one or more
stages of a stage assembly of a precision assembly, a method for
making an exposure apparatus, a method for making a wafer, and a
method for making a device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The novel features of this invention, as well as the
invention itself, both as to its structure and its operation, will
be best understood from the accompanying drawings, taken in
conjunction with the accompanying description, in which similar
reference characters refer to similar parts, and in which:
[0019] FIG. 1 is a schematic view of an exposure apparatus having
features of the present invention;
[0020] FIG. 2A is a perspective view of a stage assembly having
features of the present invention;
[0021] FIG. 2B is a perspective view of a portion of the stage
assembly in FIG. 2A;
[0022] FIG. 2C is a perspective view of an actuator pair having
features of the present invention;
[0023] FIG. 2D is a perspective view of another stage assembly
having features of the present invention;
[0024] FIG. 3A is a simplified example of two iterations of the
stage, each iteration including an intended trajectory;
[0025] FIG. 3B is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0026] FIG. 3C is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0027] FIG. 3D is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0028] FIG. 3E is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0029] FIG. 3F is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0030] FIG. 3G is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0031] FIG. 3H is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0032] FIG. 31 is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0033] FIG. 3J is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0034] FIG. 3K is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0035] FIG. 3L is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0036] FIG. 3M is another simplified example of two iterations of
the stage, each iteration including an intended trajectory;
[0037] FIG. 4A is a graph including curves illustrating an intended
trajectory and an actual trajectory as a function of time during
movement of a stage over a plurality of iterations;
[0038] FIG. 4B is a graph illustrating a following error of the
stage in FIG. 4A as a function of time;
[0039] FIG. 4C is a graph illustrating actual trajectory as a
function of time during movement of the stage over a plurality of
iterations;
[0040] FIG. 5A is a block diagram that illustrates a first
embodiment of a control system for controlling a stage
assembly;
[0041] FIG. 5B is a block diagram that illustrates a second
embodiment of a control system for controlling the stage
assembly;
[0042] FIG. 6 is a Bode diagram illustrating magnitude and phase
plotted against frequency of a zero-phase FIR (Finite Impulse
Response) filter during information processing;
[0043] FIG. 7A is a Bode diagram illustrating magnitude and phase
plotted against frequency of a low-pass filter with phase lag
during information processing;
[0044] FIG. 7B is another Bode diagram illustrating magnitude and
phase plotted against frequency utilizing the low pass filter
forward and backward to render low pass effect with zero phase
during information processing;
[0045] FIG. 8 is a graph illustrating a series of curves including
acceleration, position, Y following error, X following error, and
theta Z following error, as a function of time of a stage in a
stage assembly having features of the present invention;
[0046] FIG. 9A is a graph illustrating the following error and a
vibration disturbance over time during the first several iterations
of a stage in a stage assembly having features of the present
invention;
[0047] FIG. 9B is a graph illustrating the following error and the
vibration disturbance over time during subsequent iterations of the
stage of FIG. 9A;
[0048] FIG. 10 is a flow chart that outlines a process for
manufacturing a device in accordance with the present invention;
and
[0049] FIG. 11 is a flow chart that outlines device processing in
more detail.
DESCRIPTION
[0050] FIG. 1 is a schematic illustration of a precision assembly,
namely an exposure apparatus 10, having features of the present
invention. The exposure apparatus 10 illustrated in FIG. 1 includes
an apparatus frame 12, an illumination system 14 (irradiation
apparatus), an assembly 16 such as an optical assembly, a reticle
stage assembly 18, a wafer stage assembly 20, a measurement system
22, one or more sensors 23, and a control system 24. The specific
design of the components of the exposure apparatus 10 can be varied
to suit the design requirements of the exposure apparatus 10.
[0051] As provided herein, the control system 24 utilizes a
position compensation system that improves the accuracy in the
control and relative positioning of at least one of the stage
assemblies 18, 20.
[0052] A number of Figures include an orientation system that
illustrates an X axis, a Y axis that is orthogonal to the X axis,
and a Z axis that is orthogonal to the X and Y axis. It should be
noted that these axes can also be referred to as the first, second
and third axes.
[0053] The exposure apparatus 10 is particularly useful as a
lithographic device that transfers a pattern (not shown) of an
integrated circuit from a reticle 26 onto a semiconductor wafer 28.
The exposure apparatus 10 mounts to a mounting base 30, e.g., the
ground, a base, or floor or some other supporting structure.
[0054] There are a number of different types of lithographic
devices. For example, the exposure apparatus 10 can be used as
scanning type photolithography system that exposes the pattern from
the reticle 26 onto the wafer 28 with the reticle 26 and the wafer
28 moving synchronously. In a scanning type lithographic device,
the reticle 26 is moved perpendicularly to an optical axis of the
assembly 16 by the reticle stage assembly 18 and the wafer 28 is
moved perpendicularly to the optical axis of the assembly 16 by the
wafer stage assembly 20. Scanning of the reticle 26 and the wafer
28 occurs while the reticle 26 and the wafer 28 are moving
synchronously.
[0055] Alternatively, the exposure apparatus 10 can be a
step-and-repeat type photolithography system that exposes the
reticle 26 while the reticle 26 and the wafer 28 are stationary. In
the step and repeat process, the wafer 28 is in a constant position
relative to the reticle 26 and the assembly 16 during the exposure
of an individual field. Subsequently, between consecutive exposure
steps, the wafer 28 is consecutively moved using the wafer stage
assembly 20 perpendicularly to the optical axis of the assembly 16
so that the next field of the wafer 28 is brought into position
relative to the assembly 16 and the reticle 26 for exposure.
Following this process, the images on the reticle 26 are
sequentially exposed onto the fields of the wafer 28 so that the
next field of the wafer 28 is brought into position relative to the
assembly 16 and the reticle 26.
[0056] However, the use of the exposure apparatus 10 provided
herein is not limited to a photolithography system for
semiconductor manufacturing. The exposure apparatus 10, for
example, can be used as an LCD photolithography system that exposes
a liquid crystal display device pattern onto a rectangular glass
plate or a photolithography system for manufacturing a thin film
magnetic head. Further, the present invention can also be applied
to a proximity photolithography system that exposes a mask pattern
from a mask to a substrate with the mask located close to the
substrate without the use of a lens assembly.
[0057] The apparatus frame 12 is rigid and supports the components
of the exposure apparatus 10. The apparatus frame 12 illustrated in
FIG. 1 supports the assembly 16 and the illumination system 14
above the mounting base 30.
[0058] The illumination system 14 includes an illumination source
34 and an illumination optical assembly 36. The illumination source
34 emits a beam (irradiation) of light energy. The illumination
optical assembly 36 guides the beam of light energy from the
illumination source 34 to the assembly 16. The beam illuminates
selectively different portions of the reticle 26 and exposes the
wafer 28. In FIG. 1, the illumination source 34 is illustrated as
being supported above the reticle stage assembly 18. Typically,
however, the illumination source 34 is secured to one of the sides
of the apparatus frame 12 and the energy beam from the illumination
source 34 is directed to above the reticle stage assembly 18 with
the illumination optical assembly 36.
[0059] The illumination source 34 can be a g-line source (436 nm),
an i-line source (365 nm), a KrF excimer laser (248 nm), an ArF
excimer laser (193 nm) or a F.sub.2 laser (157 nm). Alternatively,
the illumination source 34 can generate charged particle beams such
as an x-ray or an electron beam. For instance, in the case where an
electron beam is used, thermionic emission type lanthanum
hexaboride (LaB.sub.6) or tantalum (Ta) can be used as a cathode
for an electron gun. Furthermore, in the case where an electron
beam is used, the structure could be such that either a mask is
used or a pattern can be directly formed on a substrate without the
use of a mask.
[0060] The assembly 16 can be an optical assembly, for example,
that projects and/or focuses the light passing through the reticle
26 to the wafer 28. Depending upon the design of the exposure
apparatus 10, the assembly 16 can magnify or reduce the image
illuminated on the reticle 26. The assembly 16 need not be limited
to a reduction system. It could also be a 1.times. or a
magnification system.
[0061] When far ultra-violet rays such as the excimer laser is
used, glass materials such as quartz and fluorite that transmit far
ultra-violet rays can be used in the assembly 16. When the F.sub.2
type laser or x-ray is used, the assembly 16 can be either
catadioptric or refractive (a reticle should also preferably be a
reflective type), and when an electron beam is used, electron
optics can consist of electron lenses and deflectors. The optical
path for the electron beams should be in a vacuum.
[0062] Also, with an exposure device that employs vacuum
ultra-violet radiation (VUV) of wavelength 200 nm or lower, use of
the catadioptric type optical system can be considered. Examples of
the catadioptric type of optical system include the disclosure
Japan Patent Application Disclosure No. 8-171054 published in the
Official Gazette for Laid-Open Patent Applications and its
counterpart U.S. Pat. No. 5,668,672, as well as Japan Patent
Application Disclosure No. 10-20195 and its counterpart U.S. Pat.
No. 5,835,275. In these cases, the reflecting optical device can be
a catadioptric optical system incorporating a beam splitter and
concave mirror. Japan Patent Application Disclosure No. 8-334695
published in the Official Gazette for Laid-Open Patent Applications
and its counterpart U.S. Pat. No. 5,689,377 as well as Japan Patent
Application Disclosure No. 10-3039 and its counterpart U.S. Patent
Application No. 873,605 (Application Date: 6-12-97) also use a
reflecting-refracting type of optical system incorporating a
concave mirror, etc., but without a beam splitter, and can also be
employed with this invention. As far as is permitted, the
disclosures in the above-mentioned U.S. patents, as well as the
Japan patent applications published in the Official Gazette for
Laid-Open Patent Applications are incorporated herein by
reference.
[0063] The reticle stage assembly 18 holds and positions the
reticle 26 relative to the assembly 16 and the wafer 28. Somewhat
similarly, the wafer stage assembly 20 holds and positions the
wafer 28 with respect to the projected image of the illuminated
portions of the reticle 26. The stage assemblies 18, 20 are
described in more detail below.
[0064] In photolithography systems, when linear motors (see U.S.
Pat. Nos. 5,623,853 or 5,528,118) are used in a reticle stage
assembly 18 or a wafer stage assembly 20, the linear motors can be
either an air levitation type employing air bearings or a magnetic
levitation type using Lorentz force or reactance force.
Additionally, the stage can move along a guide, or it can be a
guideless type of stage. As far as is permitted, the disclosures in
U.S. Pat. Nos. 5,623,853 and 5,528,118 are incorporated herein by
reference.
[0065] Alternatively, the reticle stage and/or the wafer stage
could be driven by a planar motor. The planar motor drives the
stage by an electromagnetic force generated by a magnet unit having
two-dimensionally arranged magnets and an armature coil unit having
two-dimensionally arranged coils in facing positions. With this
type of driving system, either the magnet unit or the armature coil
unit is connected to the stage and the other unit is mounted on the
moving plane side of the stage.
[0066] Movement of the stages as described above generates reaction
forces that can affect performance of the photolithography system.
Reaction forces generated by motion of the wafer stage can be
mechanically transferred to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,528,100 and published
Japanese Patent Application Disclosure No. 8-136475. Additionally,
reaction forces generated by motion of the reticle stage can be
mechanically transferred to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,874,820 and published
Japanese Patent Application Disclosure No. 8-330224. As far as is
permitted, the disclosures in U.S. Pat. Nos. 5,528,100 and
5,874,820 and Japanese Patent Application Disclosure No. 8-330224
are incorporated herein by reference.
[0067] Typically, numerous integrated circuits are derived from a
single wafer 28. Therefore, the process may involve a substantial
number of repetitive, identical or substantially similar movements
of portions of the reticle stage assembly 18 and/or the wafer stage
assembly 20. Each such repetitive movement is also referred to
herein as an iteration, iterative movement or cycle, as defined in
greater detail below.
[0068] The measurement system 22 monitors movement of the reticle
26 and the wafer 28 relative to the assembly 16 or some other
reference. With this information, the control system 24 can control
the reticle stage assembly 18 to precisely position the reticle 26
and the wafer stage assembly 20 to precisely position the wafer 28
relative to the assembly 16. For example, the measurement system 22
can utilize multiple laser interferometers, encoders, and/or other
measuring devices.
[0069] Additionally, one or more sensors 23 can monitor and/or
receive information regarding one or more components of the
exposure apparatus. For example, the exposure apparatus 10 can
include one or more sensors 23 positioned on or near the assembly
16, the frame 12, or other suitable components. As explained below,
information from the sensor(s) 23 can be provided to the control
system 24 for processing as provided herein. In the embodiment
illustrated in FIG. 1, the exposure apparatus 10 can include two
spaced apart, separate sensors 23 that are secured to the apparatus
frame 12 and two spaced apart, separate sensors 23 that are secured
to the assembly 16. Alternatively, the sensors 23 can be positioned
elsewhere. Further, the type of sensor 23 can be varied. For
example, one or more of the sensors 23 can be an accelerometer, an
interferometer, a gyroscope, and/or other types of sensors.
[0070] The control system 24 receives information from the
measurement system 22 and other systems and controls the stage
mover assemblies 18, 20 to precisely and synchronously position the
reticle 26 and the wafer 28 relative to the assembly 16 or some
other reference. The control system 24 includes one or more
processors and circuits for performing the functions described
herein. The control system 24 is described in greater detail
below.
[0071] A photolithography system (an exposure apparatus) according
to the embodiments described herein can be built by assembling
various subsystems, including each element listed in the appended
claims, in such a manner that prescribed mechanical accuracy,
electrical accuracy, and optical accuracy are maintained. In order
to maintain the various accuracies, prior to and following
assembly, every optical system is adjusted to achieve its optical
accuracy. Similarly, every mechanical system and every electrical
system is adjusted to achieve its respective mechanical and
electrical accuracies. The process of assembling each subsystem
into a photolithography system includes mechanical interfaces,
electrical circuit wiring connections and air pressure plumbing
connections between each subsystem. Needless to say, there is also
a process where each subsystem is assembled prior to assembling a
photolithography system from the various subsystems. Once a
photolithography system is assembled using the various subsystems,
a total adjustment is performed to make sure that accuracy is
maintained in the complete photolithography system. Additionally,
it is desirable to manufacture an exposure system in a clean room
where the temperature and cleanliness are controlled.
[0072] FIG. 2A is a perspective view of a stage assembly 220 that
is used to position a device 200, and a control system 224. The
stage assembly 220 can be used as the wafer stage assembly 20 in
the exposure apparatus 10 of FIG. 1. In this embodiment, the stage
assembly 220 would position the wafer 28 (illustrated in FIG. 1)
during manufacturing of the semiconductor wafer 28. As provided
herein, the stage assembly 220 can also include a portion or all of
the control system 224. Alternatively, the stage assembly 220 can
be used to move other types of devices 200 during manufacturing
and/or inspection, to move a device under an electron microscope
(not shown), or to move a device during a precision measurement
operation (not shown).
[0073] Still alternatively, for example, the stage assembly 220
could be used as the reticle stage assembly 18 in the exposure
apparatus 10 of FIG. 1. In this example, the stage assembly 220
would position the reticle 26 (illustrated in FIG. 1) during
manufacturing of the semiconductor wafer 28.
[0074] In the embodiment illustrated in FIG. 2A, the stage assembly
220 includes a stage base 202, a coarse stage mover assembly 204, a
coarse stage 206, a fine stage 208 and a fine stage mover assembly
210. The design of the components of the stage assembly 220 can be
varied. For example, in FIG. 2A, the stage assembly 220 includes
one coarse stage 206 and one fine stage 208. Alternatively,
however, the stage assembly 220 could be designed to include
greater or fewer than one coarse stage 206 or greater or fewer than
one fine stage 208. As used herein, the terms coarse stage 206 and
fine stage 208 can be used interchangeably with the first stage and
the second stage, in either order. It should also be recognized
that the stage assembly 220 illustrated and described herein is
only one example of possible types of stage assemblies, and is in
no way intended to limit the scope of the present invention.
Further, the stage assembly 220 can be constructed in accordance
with industry standards that are generally known to those skilled
in the art.
[0075] In FIG. 2A, the stage base 202 is generally rectangular
shaped. Alternatively, the stage base 202 can be another shape. The
stage base 202 supports some of the components of the stage
assembly 220 above the mounting base 30 illustrated in FIG. 2A.
[0076] The design of the coarse stage mover assembly 204 can be
varied to suit the movement requirements of the stage assembly 220.
In one embodiment, the coarse stage mover assembly 204 includes one
or more movers, such as rotary motors, voice coil motors, linear
motors utilizing a Lorentz force to generate a driving force,
electromagnetic actuators, planar motors, or some other force
actuators.
[0077] In FIG. 2A, the coarse stage mover assembly 204 moves the
coarse stage 206 relative to the stage base 202 along the X axis,
along the Y axis, and about the Z axis (collectively "the planar
degrees of freedom"). Additionally, the coarse stage mover assembly
204 could be designed to move and position the coarse stage 206
along the Z axis, about the X axis and/or about the Y axis relative
to the stage base 202. Alternatively, for example, the coarse stage
mover assembly 204 could be designed to move the coarse stage 206
with less than three degrees of freedom.
[0078] In FIG. 2A, the coarse stage mover assembly 204 includes a
planar motor. In this embodiment, the coarse stage mover assembly
204 includes a first mover component 212 that is secured to and
moves with the coarse stage 206 and a second mover component 214
(illustrated in phantom) that is secured to the stage base 202. The
design of each component can be varied. For example, one of the
mover components 212, 214 can include a magnet array having a
plurality of magnets and the other of the mover components 214, 212
can include a conductor array having a plurality of conductors.
[0079] In FIG. 2A, the first mover component 212 includes the
magnet array and the second mover component 214 includes the
conductor array. Alternatively, the first mover component 212 can
include the conductor array and the second mover component 214 can
include the magnet array. The size and shape of the conductor array
and the magnet array and the number of conductors in the conductor
array and the number of magnets in the magnet array can be varied
to suit design requirements.
[0080] The first mover component 212 can be maintained above the
second mover component 214 with vacuum pre-load type air bearings
(not shown). With this design, the coarse stage 206 is movable
relative to the stage base 202 with three degrees of freedom,
namely along the X axis, along the Y axis, and rotatable around the
Z axis. Alternatively, the first mover component 212 could be
supported above the second mover component 214 by other ways, such
as guides, a rolling type bearing, or by the magnetic levitation
forces and/or the coarse stage mover assembly 204 could be designed
to be movable with up to six degrees of freedom. Still
alternatively, the coarse stage mover assembly 204 could be
designed to include one or more electromagnetic actuators.
[0081] The control system 224 directs electrical current to one or
more of the conductors in the conductor array. The electrical
current through the conductors causes the conductors to interact
with the magnetic field of the magnet array. This generates a force
between the magnet array and the conductor array that can be used
to control, move, and position the first mover component 212 and
the coarse stage 206 relative to the second mover component 214 and
the stage base 202. The control system 224 adjusts and controls the
current level for each conductor to achieve the desired resultant
forces. Stated another way, the control system 224 directs current
to the conductor array to position the coarse stage 206 relative to
the stage base 202.
[0082] The fine stage 208 includes a device holder (not shown) that
retains the device 200. The device holder can include a vacuum
chuck, an electrostatic chuck, or some other type of clamp.
[0083] The fine stage mover assembly 210 moves and adjusts the
position of the fine stage 208 relative to the coarse stage 206.
For example, the fine stage mover assembly 210 can adjust the
position of the fine stage 208 with six degrees of freedom.
Alternatively, for example, the fine stage mover assembly 210 can
be designed to move the fine stage 208 with only three degrees of
freedom. The fine stage mover assembly 210 can include one or more
rotary motors, voice coil motors, linear motors, electromagnetic
actuators, or other type of actuators. Still alternatively, the
fine stage 208 can be fixed to the coarse stage 206.
[0084] FIG. 2B illustrates a perspective view of the coarse stage
206, the fine stage 208, and the fine stage mover assembly 210 of
FIG. 2A. In this embodiment, the fine stage mover assembly 210
includes three spaced apart, horizontal movers 216 and three spaced
apart, vertical movers 218. The horizontal movers 216 move the fine
stage 208 along the X axis, along the Y axis and about the Z axis
relative to the coarse stage 206 while the vertical movers 218 move
the fine stage 208 about the X axis, about the Y axis and along the
Z axis relative to the coarse stage 206.
[0085] In FIG. 2B, each of the horizontal movers 216 and each of
the vertical movers 218 includes an actuator pair. 226 comprising
two electromagnetic actuators 228 (illustrated as blocks in FIG.
2B). Alternatively, for example, one or more of the horizontal
movers 216 and/or one or more of the vertical movers 218 can
include a voice coil motor or another type of mover.
[0086] In FIG. 2B, (i) one of the actuator pairs 226 (one of the
horizontal movers 216) is mounted so that the attractive forces
produced thereby are substantially parallel with the X axis, (ii)
two of the actuator pairs 226 (two of the horizontal movers 216)
are mounted so that the attractive forces produced thereby are
substantially parallel with the Y axis, and (iii) three actuator
pairs 226 (the vertical horizontal movers 216) are mounted so that
the attractive forces produced thereby are substantially parallel
with the Z axis. With this arrangement, (i) the horizontal movers
216 can-make fine adjustments to the position of the fine stage 208
along the X axis, along the Y axis, and about the Z axis, and (ii)
the vertical movers 218 can make fine adjustments to the position
of the fine stage 208 along the Z axis, about the X axis, and about
the Y axis.
[0087] Alternatively, for example, two actuator pairs 226 can be
mounted parallel with the X direction and one actuator pair 226
could be mounted parallel with the Y direction. Still
alternatively, other arrangements of the actuator pairs 226 can be
utilized.
[0088] In one embodiment, the measurement system 22 (illustrated in
FIG. 1) includes one or more sensors (not shown in FIG. 2B) that
monitor the position of the fine stage 208 relative to the coarse
stage 206 and/or the position of fine stage 208 relative to another
structure, such as the assembly 16 (illustrated in FIG. 1).
Information from the measurement system 22 is provided to the
control system 224 as provided herein.
[0089] FIG. 2C is an exploded perspective view of an actuator pair
226 that can be used for one of the horizontal movers or one of the
vertical movers. More specifically, FIG. 2C illustrates two
attraction only, electromagnetic actuators 228 commonly referred to
as an E/I core actuators. Each E/I core actuator is essentially an
electo-magnetic attractive device. Each E/I core actuator 228
includes an E shaped core 236 ("E core"), a tubular shaped
conductor 238, and an I shaped core 240 ("I core"). The E core 236
and the I core 240 are each made of a magnetic material such as
iron, silicon steel or Ni--Fe steel. The conductor 238 is
positioned around the center bar of the E core 236.
[0090] The combination of the E core 236 and the conductor 238 is
sometimes referred to herein as an electromagnet, while the I core
240 is sometimes referred to herein as a target. As an example, the
opposing electromagnets can be mounted to the coarse stage 206
(illustrated in FIG. 2B) and the targets can be secured to the fine
stage 208 (illustrated in FIG. 2B) there between the opposing
electromagnets. In one embodiment, the I cores 240 are attached to
the fine stage 208 in such a way that the pulling forces of the
opposing actuator pairs 226 do not substantially distort the fine
stage 208. In one embodiment, the I cores 240 can be integrally
formed into the fine stage 208. However, the configuration of the
cores can be reversed and the I cores can be the secured to the
coarse stage 206 and the E cores can be secured to the fine stage
208.
[0091] In this embodiment, the measurement system 222 includes one
or more sensors 242 that measure a gap distance between the E core
236 and the I core 240 for each electromagnetic actuator 228. A
suitable sensor, for example, can include a capacitor sensor. By
measuring the gap distance, the relative positioning of the coarse
stage relative to the fine stage can be determined. This
positioning data can then be provided to the control system 224 for
processing as provided herein.
[0092] FIG. 2D is a perspective view of another embodiment of a
stage assembly 220D that can be used to position a device 200D, and
a control system 224D having features of the present invention. In
the embodiment illustrated in FIG. 2D, the stage assembly 220D
includes a stage base 202D, an X mover assembly 204D, a Y mover
assembly 206D, a stage 208D that retains the device 200D, and a
guide assembly 210D. In this embodiment, the X mover assembly 204D
includes a first X mover 250D and a second X mover 252D that move
the guide assembly 210D and the stage 208D along the X axis and
about the Z axis. The Y mover assembly 206D includes a Y mover 254D
that moves the stage 208D along the Y axis. However, the number of
X movers and Y movers can vary. In addition, the number of mover
assemblies can vary. Further, the design of the other components of
the stage assembly 220D can be varied. The stage assembly 220D is
described in greater detail in U.S. patent application Ser. No.
09/557,122 filed on Apr. 24, 2000. To the extent permitted, the
contents of U.S. patent application Ser. No. 09/557,122 are
incorporated herein by reference. The stage assembly 220D can be
constructed in accordance with industry standards that are
generally known to those skilled in the art and/or in accordance
with the stage assembly disclosed in U.S. patent application Ser.
No. 09/557,122 filed on Apr. 24, 2000.
[0093] The stage assembly 220D or the stage assembly 220
(illustrated in FIG. 2A) can be used to move the device 200, 200D
during one or more iterations. As defined herein, a first iteration
is said to be identical or similar to a second iteration if the
first iteration includes a first intended trajectory that is
identical or a similar to a second intended trajectory of the
second iteration. FIGS. 3A through 3M illustrate various
non-exclusive examples of the first intended trajectory and the
second intended trajectory of the stage that are identical or
similar.
[0094] Two or more intended trajectories can be considered
iterations or iterative movements relative to each other
under-various=circumstances. For example, as illustrated in FIG.
3A, the first intended trajectory 300A (solid line) can be
identical to the second intended trajectory 302A (dashed line).
Although in this Figure the trajectories 300A, 302A are illustrated
as being spaced apart for clarity, the trajectories 300A, 302A are
actually overlapping. In this example, the first intended
trajectory 300A includes (i) a first starting point 304A that is
the same as a second starting point 306A, e.g. same coordinate
position along X axis and Y axis, of the second intended trajectory
302A, and (ii) a first intended movement 308A (also referred to
herein as a "movement") that begins from the first starting point
304A that is the same as a second intended movement 310A that
begins from the second starting point 306A. The "starting point"
can be any point during an overall movement of the stage. As used
herein, however, the starting point is representative of the start
of the iteration. Moreover, each intended trajectory 300A, 302A can
also include a corresponding ending point 312A, 314A, which is
representative of the end of the iteration. The starting point
and/or the ending point can also be simply referred to herein as a
"point".
[0095] As provided above, each intended trajectory 300A, 302A
includes a corresponding ending point (represented by arrows 312A,
314A). Thus, the first intended trajectory 300A includes the first
starting point 304A, the first movement 308A and the first ending
point 312A. Somewhat similarly, the second intended trajectory 302A
includes the second starting point 306A, the second movement 310A
and the second ending point 314A. In this embodiment, the first
ending point 312A is the same as the second ending point 314A.
[0096] Alternatively, as illustrated in FIG. 3B, two or more
intended trajectories can be considered iterations if the first
intended trajectory 300B is similar to the second intended
trajectory 302B. For example, the first intended trajectory 300B
includes (i) the first starting point 304B that is similar to the
second starting point 306B of the second intended trajectory 302B,
and (ii) the first movement 308B is the same as the second movement
310B. For example, in this embodiment, the first movement 308B is
considered to be the same as the second movement 310B when each
movement 308B, 310B is exactly the same distance, along exactly the
same axis, and in the same direction. In another embodiment, the
first movement 308B can be considered the same as the second
movement 310B when each movement 308B, 310B follows the same
coordinate positions.
[0097] FIG. 3C illustrates another embodiment=wherein the first
intended trajectory 300C can be similar to the second intended
trajectory 302C. In this embodiment, (i) the first starting point
304C is the same as the second starting point 306C of the second
intended trajectory 302C, and (ii) the first movement 308C is
similar to the second movement 310C.
[0098] FIG. 3D illustrates yet another embodiment wherein the first
intended trajectory 300D can be similar to the second intended
trajectory 302D. In this embodiment, (i) the first starting point
304D is similar to the second starting point 306D of the second
intended trajectory 302D, and (ii) the first movement 308D is
similar to the second movement 310D.
[0099] The definition of similar points can be varied to suit the
design requirements of the precision apparatus 10 (illustrated in
FIG. 1), and can apply to both starting points and ending points.
In one embodiment, the first point of the first intended trajectory
is similar to the second point of the second intended trajectory if
the distance between the first point and the second point is less
than approximately 500 percent of the length of the first intended
movement of the stage. In alternative embodiments, the first point
is similar to the second point if the distance between the first
point and the second point is less than approximately 200 percent,
100 percent, 50 percent, 25 percent, 10 percent, 5 percent, 1
percent, 0.1 percent or 0.01 percent of the total distance of the
intended movement of the stage during the iteration. For example,
if the distance between the first and second points is 1.0
millimeter, and the length of first movement is 10.0 millimeters,
the distance between the first and second points is 10 percent of
the first movement. Depending upon the settings for the control
system 24 (illustrated in FIG. 1), the distance between the first
and second points in this example may or may not be considered
similar.
[0100] In another embodiment (not shown), the first movement is
similar to the second movement if the first ending point is similar
to the second ending point, and the length of the first movement is
within approximately 100 percent of the length of the second
movement. In alternative embodiments, the first movement can be
similar to the second movement if the first ending point is similar
to the second ending point, and the length of the first movement is
within approximately 75 percent, 50 percent, 25 percent, 10
percent, 5 percent, 1 percent or 0.1 percent of the length of the
second movement. Alternatively stated, in one embodiment the first
movement can be considered similar to the second movement if each
movement is approximately the same distance along approximately the
same axis.
[0101] Additionally, although the stage can be capable of moving
along or about more than one axis simultaneously, similar
iterations can occur based on movement of the stage along one of
the axes. For example, in a step-and-repeat photolithography
system, movement of the stage along the Y axis may be substantially
repeated over time regardless of whether movements of the stage
along the X axis and about the Z axis are repetitious. Moreover, in
alternative embodiments, movement along the Y axis can be
repetitious, if the stage is positioned in the same or different
locations along the X axis. In another example, movement of the
stage about the Z axis may be substantially repeated over time
regardless of whether movements of the stage along the X and Y axes
are repetitious.
[0102] In yet another example of similar iterations, more than one
component of movement, i.e. along the X axis and the Y axis, may be
substantially repeated over time. In still another example, rather
than simple back-and-forth movements along the Y axis, the stage
can guidelessly and simultaneously be moving in a plane that
includes the X axis and the Y axis. Additionally, the stage can
guidelessly and simultaneously be moving along the X axis, the Y
axis and/or about the Z axis. It is further recognized that any
combination of intended trajectories of the stage along or about
one or more of the axes that are similar or repetitious are
referred to herein as iterations or iterative movements.
[0103] FIG. 3E illustrates another embodiment wherein the first
intended trajectory 300E can be similar to the second intended
trajectory 302E. In this embodiment, the first starting point 304E
is the same as the second starting point 306E, and (ii) the first
movement 308E is substantially symmetrical to the second movement
310E relative to the X axis.
[0104] FIG. 3F illustrates another embodiment wherein the first
intended trajectory 300F can be similar to the second intended
trajectory 302F. In this embodiment, the first starting point 304F
is the same as the second starting point 306F, and (ii) the first
movement 308F is substantially symmetrical to the second movement
310F relative to the Y axis.
[0105] FIG. 3G illustrates another embodiment wherein the first
intended trajectory 300G can be similar to the second intended
trajectory 302G. In this embodiment, the first starting point 304G
is the same as the second starting point 306G, and (ii) the first
movement 308G is substantially symmetrical to the second movement
310G relative to the origin (which can also be referred to as the
0, 0 coordinate). Additionally, the first movement 308G diverges
from the second movement 310G.
[0106] FIG. 3H illustrates another embodiment wherein the first
intended trajectory 300H can be similar to the second intended
trajectory 302H. In this embodiment, the first movement 308H is
substantially symmetrical to the second movement 310H relative to
the origin (which can also be referred to as the 0, 0 coordinate).
However, in this embodiment, the starting points are neither
identical nor similar.
[0107] FIG. 31 illustrates another embodiment wherein the first
intended trajectory 3001 can be similar to the second intended
trajectory 3021. In this embodiment, the first starting point 3041
is the same as the second starting point 3061, and (ii) the first
movement 3081 is substantially symmetrical to the second movement
3101 relative to the origin (which can also be referred to as the
0, 0 coordinate). Additionally, the first movement 3081 converges
toward the second movement 3101.
[0108] FIG. 3J illustrates still another embodiment wherein the
first intended trajectory 300J is similar to the second intended
trajectory 302J. As illustrated in FIG. 3J, the first intended
trajectory 300J has a first starting point 304J, a first movement
308J and a first ending point 312J. The second intended trajectory
302J has a second movement 310J that includes the first starting
point 304J, the entire first movement 308J and the first ending
point 312J. Stated another way, the first intended trajectory 300J
is only a portion of the second intended trajectory 302J. Although
in this Figure the trajectories 300J, 302J are illustrated as being
spaced apart for clarity, the trajectories 300J, 302J are actually
overlapping. Alternatively, the first trajectory 300J and the
second trajectory 302J could be reversed so that the second
movement 310J comprises essentially a portion of the first movement
308J.
[0109] FIG. 3K shows yet another embodiment wherein the first
intended trajectory 300K is similar to the second intended
trajectory 302K. As illustrated in FIG. 3K, the first intended
trajectory 300K has a first starting point 304K that is different
than a second starting point 306K of the second intended trajectory
302K. Further, the first intended trajectory 300K has a first
ending point 312K that is different than a second ending point 314K
of the second intended trajectory 302K. However, in this
embodiment, the first movement 308K is substantially similar to the
second movement 310K. In other words, the first and second
movements 308K, 310K have a substantially similar length, and have
a similar length of movement along both the X axis and the Y axis.
Alternatively, the length of movement for the first and second
movements 308K, 310K can be substantially similar along either one
of the X or Y axes.
[0110] FIG. 3L illustrates an additional embodiment that describes
a first iteration 300L that is similar to a second iteration 302L.
This example includes the first iteration 300L having a first
movement 308L that includes a first intended trajectory structure,
and the second iteration 302L having a second movement 310L that
includes a second intended trajectory structure that is the same as
the first intended trajectory structure. As used herein, the
"intended trajectory structure" is a function of (i) the shape of
the intended trajectory, (ii) the percentage of time during the
intended trajectory that is represented by acceleration, constant
velocity and/or deceleration, (iii) the location of the starting
point of the intended trajectory, and/or (iv) the timing of the
acceleration, constant velocity and/or deceleration during the
intended trajectory.
[0111] In the embodiment illustrated in FIG. 3L, the first intended
trajectory 300L has a similar starting point 304L as the second
intended trajectory 302L, as defined previously. Further, the first
intended trajectory 300L includes a first acceleration 320L during
approximately the first 30 percent of the first movement 308L of
the stage, a first constant velocity 324L during the next 40
percent of the first movement 308L of the stage, and a first
deceleration 328L during the next 30 percent of the first movement
308L of the stage. The total length of the first movement 308L of
the stage in this example is 100 millimeters.
[0112] The second intended trajectory 302L includes a second
acceleration 322L during the first 30 percent of the second
movement 310L of the stage, a second constant velocity 326L during
the next 40 percent of the second movement 310L of the stage, and a
second deceleration 330L during the next 30 percent of the second
movement 310L of the stage. The total length of the second movement
310L of the stage in this example is 200 millimeters. Further, the
shapes of the intended trajectories 300L, 302L are similar, i.e.
substantially proportional to one another. Stated another way, the
second intended trajectory 302L is proportionately larger than the
first intended trajectory 300L. Importantly, the percentages
provided in this example are provided for ease of discussion only.
Any suitable combination of percentages can be used. Further, the
first and second trajectories could be reversed.
[0113] FIG. 3M illustrates another embodiment showing two
iterations having similar intended trajectories 300M, 302M. This
embodiment is somewhat similar to the embodiment illustrated in
FIG. 3L, however the first intended trajectory 300M has a different
first starting point 304M than the second starting point 306M of
the second intended trajectory 302M. In this embodiment, the first
starting point 304M is similar to the second starting point 306M as
defined previously herein. Further, in this embodiment, the first
iteration 300M is similar to the second iteration 302M if the first
intended trajectory structure and second intended trajectory
structure are substantially similar to one another, as described
previously with respect to FIG. 3L.
[0114] The foregoing examples of iterations that include identical
and/or similar intended trajectories are not intended to represent
an exclusive listing of all possible embodiments of "identical" or
"similar" iterations and/or intended trajectories. However, the
examples provided herein are illustrative of certain movements of
the stage that can be considered similar, and therefore useful, in
predicting and adjusting future movements of the stage. The
foregoing examples are in no way intended to limit the scope of the
present invention, and numerous other possible "similar" intended
trajectories, although not explicitly illustrated or described,
could be encompassed by the scope of the present invention.
[0115] FIG. 4A is a graph illustrating an overview of an actual and
an intended simplified back-and-forth type of iterative movement of
a stage, such as the fine stage 208 illustrated in FIG. 2A, or the
stage 208D illustrated in FIG. 2D, along a single axis as a
function of time over the course of a plurality of substantially
similar iterations of the stage. Curve 410 (shown as a solid line)
illustrates the actual trajectory of the stage, and curve 412
(shown as a dashed line) illustrates the intended trajectory of the
stage. The spacing between the curves 410, 412 has been exaggerated
for illustrative purposes.
[0116] It is recognized that FIG. 4A can also be representative of
movement of one or more stages other than the fine stage 208 shown
in FIG. 2A and/or the stage 208D illustrated in FIG. 2D. For
example, the movements described herein can be applied to a stage
assembly that does not include a plurality of stages.
Alternatively, the stage assembly can include more than two
stages.
[0117] For convenience, FIG. 4A includes a first iteration 400, a
second iteration 0.402, a third iteration 404 and a portion of a
fourth iteration 406, which is also referred to herein as the
"current iteration". Alternatively, the first, second, third and
fourth iteration can include only a portion of each of the
iterations 4007406 illustrated in FIG. 4A, provided the portions of
the iterations are substantially similar in movement. Stated
another way, the iterations 400-406 illustrated in FIG. 4A are
provided as a single example for ease of discussion, and are in no
way intended to limit the scope of possible iterative movements
that can be controlled by the control system 24 (illustrated in
FIG. 1) provided herein.
[0118] The intended trajectory 412 and number of iterations during
the manufacture of an object such as a semiconductor wafer can
vary. In this example, the intended trajectory 412 of the stage is
substantially similar from one iteration to the next. The control
system 24 provided herein is particularly useful to control the
actual trajectory 410 of the stage over a plurality of iterations
400-406 having a substantially similar intended trajectory 412.
However, the control system 24 can also be effectively utilized to
control the actual trajectory 410 of the stage based on positioning
data generated from movements of the stage resulting from somewhat
different intended trajectories 412, as provided in greater detail
below.
[0119] The actual trajectory 410 of an iteration can be
substantially similar to the actual trajectory 410 of the previous
iteration, although the actual trajectories 410 for each iteration
400-406 may not necessarily be identical. For example, as
illustrated in FIG. 4A, during the first iteration 400, at times
t1.sub.1, t2.sub.1, t3.sub.1, t4.sub.1 and t5.sub.1, the measured
position of the stage is located at positions P.sub.1, P.sub.2,
P.sub.3, P.sub.4 and P.sub.5, (hereinafter the "actual position")
respectively. Although only times t1.sub.1 through t5.sub.1 are
shown in FIG. 4A for clarity, a greater or a fewer number of times
can be used in the alternative, or in addition to any of times
t1.sub.1 through t5.sub.1.
[0120] Somewhat similarly, the second iteration 402 includes times
t1.sub.2 through t5.sub.2, the third iteration 404 includes times
t1.sub.3 through t5.sub.3, and the fourth iteration 406 includes
t1.sub.4 through t3.sub.4. Each of the times t1 through t5 of the
second iteration 402 and times t1.sub.3 through t5.sub.3 the third
iteration 404 have an actual position that is similar, although not
necessarily identical, to a corresponding actual position P.sub.1
through P.sub.5, respectively. Each of the times t1 through t3 of
the fourth iteration 406 has an actual position point that is
similar, although not necessarily identical, to a corresponding
actual position P.sub.1 through P.sub.3, respectively.
[0121] Additionally, in one embodiment the intended and/or actual
trajectory of the stage at times t1.sub.1 and t1.sub.2, for
example, can have a substantially similar or identical position
along the X and Y axes. Similarly, at times t2.sub.2 and t2.sub.3,
the intended and/or actual trajectory of the stage can have a
substantially similar or identical position along the X and Y
axes.
[0122] Alternately, the intended trajectory of the stage at times
t1 and t1.sub.2 can have a substantially similar position along the
Y axis and a different position along the X axis. In other words,
although the intended and/or the actual trajectory along the Y axis
may not change from the first iteration 400 to the second iteration
402, the intended and/or actual trajectory along the X axis may be
different from the first iteration 400 to the second iteration.
This example can be applied to any two or more iterations, along or
about any axes.
[0123] It is recognized that the second and third iterations 402,
404, although similar in movement to previous first and second
iterations 400, 402, respectively, can vary somewhat as a result of
the additional information collected and utilized by the control
system 24 and subsequent adjustments that the control system 24
makes in directing current to the one or more mover assemblies to
cause forces that more accurately move the stage, as provided
herein. Further, it is also recognized that the iterations 400-406
have been denoted as the first, second, third and fourth iterations
for the sake of convenience. However, any iteration can be the
first, second, third or fourth iteration, and that the labels
"first", "second", "third" and "fourth" do not necessarily imply a
particular sequencing of the iterations.
[0124] The control system 24 provided herein can include one or
more control modes. In one embodiment, the control system includes
a first control mode and a second control mode. As an overview, the
first control mode includes the processing of positioning data
received by the control system during a single iteration, e.g. the
first iteration 400, to control future movement of the stage also
during the first iteration 400. The second control mode includes
the processing of positioning data received by the control system
during at least one iteration, e.g. the first iteration 400 and the
second iteration 402, to control future movement of the stage
during the second iteration 402 and/or third iteration 404, as one
example.
[0125] As provided in greater detail below, the positioning data
can include various types of information to be received and/or
processed by the control system. For example, the positioning data
can include "time-dependent" positioning data or "position
dependent" positioning data. Time-dependent positioning data
includes any information relating to the intended and/or actual
position of the stage at various times. For instance, an example of
time-dependent positioning data includes information regarding a
following error of the stage, e.g. the difference between the
intended position and the actual position of the stage at various
times. Position-dependent positioning data includes information
regarding the position of other components of the exposure
apparatus that can influence position of the stage. Examples of
position-dependent positioning data can include information
regarding vibration of the assembly 16 (illustrated in FIG. 1)
and/or the apparatus frame 12 (illustrated in FIG. 1).
[0126] The first control mode can be described with reference to
the first iteration 400 in FIG. 4A. In a simplified example, in
order to determine the amount of current that the control system 24
needs to direct to the mover assemblies to position the stage in
accordance with the intended trajectory 410 of the stage at time
t4.sub.1, time-dependent positioning data is provided to the
control system 24 from one or more of the previous times t1.sub.1
through t3.sub.1. This positioning data is analyzed by the control
system 24 along with the intended trajectory 410 to determine the
force that is required to move the stage at time t4.sub.1. With
this positioning data, the control system 24 applies an appropriate
control law to determine the amount of current to direct to the
mover assemblies to obtain the required force distribution for
moving the stage to the extent necessary for proper positioning of
the stage. The number of data points t1.sub.1 through t3.sub.1 used
in this analysis can vary. Further, the time duration between data
points can vary. The first control mode can be used for movement of
the stage with one or more degrees of freedom, i.e. along the X, Y
and/or Z axes, and/or about the X, Y and/or Z axes, including any
combination of these directions. The control system 24 can also be
used to determine the current to be directed to the coarse stage
206, either in conjunction with the stage, or in the alternative.
Further, the control system 24 can be utilized to synchronously
position a plurality of stages as provided herein.
[0127] The second control mode can selectively be used by the
control system 24 depending upon the requirements of the stage
assembly. During the second control mode, the control system 24
receives positioning data used for positioning the stage from
various sources, as provided in detail below. The positioning data
is used to position the stage, or other stages, with greater
accuracy.
[0128] The second control mode includes the features of the first
control mode described above, as well as the processing of
positioning data received by the control system 24 during one or
more previous iterations, e.g. the first iteration 400, the second
iteration 402 and/or the third iteration 404, to control movement
of the stage during the fourth iteration 406. In contrast with the
first control mode, the positioning data from a previous iteration,
but at a later point in time during the previous iteration, can be
used in controlling movement of the stage during the current
iteration. For example, to determine the level of current to direct
to the mover assembly at time t3.sub.4, positioning data from times
t4.sub.1 and t5.sub.1 from the first iteration 400, times t4.sub.2
and t5.sub.2 from the second iteration 402, and/or times t4.sub.3
and t5.sub.3 from the third iteration 404 can be used. This
positioning data can be used in conjunction with or in the
alternative to positioning data from times t1.sub.1 through
t3.sub.1 of the first iteration 400, times t1.sub.2 through
t3.sub.2 of the second iteration 402, and/or times t1.sub.3 through
t3.sub.3 of the third iteration 404, or any portions thereof. With
this design, a greater amount of positioning data factors into
controlling the stage with the control system 24.
[0129] Moreover, the second control mode can also utilize
positioning data from the current iteration, e.g. the fourth
iteration 406, to control the actual trajectory 410 during the
current iteration 406, as provided above during the first control
mode. In alternative embodiments, the control system 24 can include
either the first control mode or the second control mode.
[0130] Thus, the second control mode of the control system 24 can
take into account both intra-iteration and inter-iteration trends
in the positioning data. With this design, with each successive
iteration, the positioning error is decreased. Stated another way,
over time the actual trajectory 410 of the stage becomes closer and
closer to the intended trajectory 412.
[0131] FIG. 4B illustrates an example of the following error 414 of
the stage over the first, second, third and fourth iterations
400-406 based on the intended trajectory 412 and the actual
trajectory 410 illustrated in FIG. 4A. The following error 414
shown in FIG. 4B has been exaggerated for illustrative purposes. As
provided herein, the control system 24 (illustrated in FIG. 1)
utilizes the following error 414 from prior iterations to control
movement of the stage during the current and future iterations.
[0132] FIG. 4C is a graph that illustrates two simplified
back-and-forth iterative movements of one or more of the stages
illustrated in FIG. 2A or 2D, for example, which include a first
iteration 400C and a second iteration 404C, separated in time by a
period of other non-iterative movements 402C of the stage. In this
embodiment, the second control mode of the control system provided
herein does not necessarily require the iterations to be
consecutive. For example, referring to FIG. 4C, the control system
can store positioning data from the first iteration 400C to be used
for positioning the stage during the second iteration 404C.
[0133] The control system provided herein can identify when an
intended movement or trajectory of the stage is similar to a
previous movement or trajectory of the stage. Once this occurs, the
control system can draw from the previously stored positioning data
in order to adjust the amount of current to direct to the mover
assembly for more accurately positioning the stage in accordance
with the intended trajectory of the stage. For purposes of
controlling movement of the stage during the second iteration 404C,
the control system can disregard the movements of the stage, and
any positioning data received, during the irrelevant, non-iterative
time period 402C. Rather, the control system utilizes the
positioning data from the first iteration 400C, and/or any other
similar iterations prior to the first iteration 400C, for
controlling movement of the stage during the second iteration
404C.
[0134] FIG. 5A is a schematic diagram illustrating the basic steps
of a first embodiment of the control system 524A including the
first control mode 500 and the second control mode 501 to control
movement of the stage illustrated in FIG. 2A and/or 2D, for
example. As previously provided, the steps outlined in FIG. 5A can
also be used to control movement of the coarse stage 206, and/or
other stages of the precision apparatus-10, either concurrently or
separately. It is recognized that not all steps of the first
control mode 500 and/or the second control mode 501 illustrated in
FIG. 5A are required in each embodiment of the present invention.
The sensing and control functions can be used to control the stage
assembly of FIG. 2A, another stage assembly of the exposure
apparatus, or another type of stage assembly.
[0135] As provided above, with the first control mode 500, the
control system 524A analyzes positioning data from within a single
iteration to improve positioning of the device to be positioned,
i.e. the reticle, the wafer and/or other objects. An intended
trajectory 512 of the stage is determined based on the desired path
of the device. The intended trajectory 512 can be along the X axis,
the Y axis and/or about the Z axis. Additionally, the intended
trajectory 512 can also include components about the X axis, about
the Y axis and/or along the Z axis, or any combination of these
axes.
[0136] In one embodiment, during the first control mode 500, one or
more points in time along the intended trajectory 512 are compared
with points in time from the actual trajectory 510 to determine
whether the stage is properly positioned, and to determine whether
the stage will be properly positioned in the immediate future. The
actual trajectory 510 is determined by the measurement system 22
(illustrated in FIG. 1) which generates a sensor signal. The
measurement system 22 measures the current position of the stage,
and thus the object, relative to the assembly 16 (illustrated in
FIG. 1). The sensor signal is then sent to the control system 524A.
Each sensor signal provides information relating to the actual
position of the stage in one or more degrees of freedom at a
specific point in time.
[0137] The following error 514A for the stage is determined by
computing the difference between the intended trajectory 512 and
the actual trajectory 510 at a specific point in time. Based on the
extent of the following error 514A, a control law during feedback
control 506A determines the extent to which the current to the one
or more mover assemblies is adjusted, if at all. The control law
during feedback control 506A may be in the form of a PID
(proportional integral derivative) controller, proportional gain
controller or a lead-lag filter, or other commonly known law in the
art of control, for example.
[0138] Once the control law during feedback control 506A determines
the current to be applied, the current is distributed to the one or
more mover assemblies as appropriate (at step 507). The mechanical
system, which includes the mover assemblies, then moves the stage
at step 508, causing the stage to more accurately emulate the
intended trajectory 512 of the stage. The measurement system
measures the position of the stage, which is then used to determine
the position of the center of gravity (CG) and/or the position of
the object using coordinate transformation at step 509. Information
regarding the position of the object is then compared with a
desired position of the object based on the intended trajectory 512
in order to increase positioning accuracy. The first control mode
500 can continue in this manner until the present iteration has
concluded. Upon commencement of a subsequent iteration, new data
regarding the following error 514A is continually generated from
within the current iteration. This new data regarding the following
error 514A is used in a similar manner during the first control
mode 500 as described above.
[0139] The second control mode 501 of the control system 524A
collects and assimilates the positioning data in order to determine
the appropriate amount of current to direct to the mover assemblies
to move the stage with increased accuracy. Positioning data can
include one or more of the types of data described herein.
Importantly, the positioning data does not need to include all
types of data described, although it may.
[0140] The second control mode 501 of the control system 524A can
compensate for one or more types of repetitive activities. These
repetitive activities can include position-dependent activities
such as following errors 514A, and/or periodical, time-dependent
disturbances, e.g. unwanted vibration of portions of the mechanical
system.
[0141] The second control mode 501 of the control system 524A can
include the first control mode 500, in addition to a position
compensation system (indicated in dashed box 515) having one or
more steps that further increase the accuracy of the positioning
and alignment of one or more of the stages. The steps included in
the functioning of the position compensation system 515 of the
second control mode 501 can vary. The position compensation system
515 can receive and process data from previous iterations to
continually decrease the following error 514A and/or offset the
effects of any vibration disturbances of the mechanical system in
the current and future iterations. In addition, it is recognized
that the position compensation system 515 can also be applied to
work with a plurality of stages simultaneously, in order to
synchronously control movement of a plurality of stages to decrease
the following errors 514A, 514B for a first stage and a second
stage, for example, and offset the effects of any vibration
disturbances of the mechanical system in the current and future
iterations.
[0142] In the embodiment illustrated in FIG. 5A, positioning data
from one or more iterative movements of the stage is collected and
provided to a memory buffer 516 for use during future iterations.
The size of the memory buffer 516 can vary, provided the memory
buffer 516 is of sufficient size to accommodate the data to be
transmitted to the memory buffer 516.
[0143] Further, the number of iterations from which positioning
data is collected, and the length of time the positioning data is
stored in the memory buffer 516 can be varied. For example, in one
embodiment, positioning data from only one prior iteration is
stored in the memory buffer 516, which can thereafter be purged
upon storage of the positioning data from the next iteration. In
alternative embodiments, positioning data from more than one prior
iteration is stored in the memory buffer 516. For instance,
positioning data from the previous 2, 3, 5, 10, 50, 100, 500 or
more iterations can be stored in the memory buffer 516 before being
systematically purged, if at all. Still alternatively, positioning
data from a different number of iterations can be stored.
[0144] For example, the positioning data can include the intended
trajectory 512 at various points in time (illustrated by dotted
line 517). Further, the positioning data can include the following
error 514A of the stage. The intended trajectory data 517 and the
following error data 514A are stored in the memory buffer 516. The
amount of positioning data and the duration of time between the
collection of positioning data that is provided to the memory
buffer 516 during each iteration can vary.
[0145] The positioning data can also include a compilation of
following errors 514A, 514B from two or more stages in the exposure
apparatus 10, also known as a synchronization error. The
synchronization error is a measurement of how accurately two or
more stages are moving relative to each other, compared with the
intended trajectory 512 of each of the respective stages. For
example, movement of the reticle stage and the wafer stage emulates
the intended trajectory 512 of each respective stage in order to
synchronously move relative to the assembly 16 (illustrated in FIG.
1), for example, and/or to each other. Sensors 523 or another
suitable measurement device can be used to monitor whether the
actual movement of the stages is properly synchronized. This
synchronization error data taken at various points in time can be
provided to the memory buffer 516.
[0146] Additionally, the positioning data to be provided to the
memory buffer 516 can include the actual position of the stage
(illustrated by dotted line 519) at various points in time along
the actual trajectory 510 from one or more iterations. Further, the
positioning data can include data relating to the movement of the
stage, including the position, velocity and/or the acceleration of
the stage. This positioning data can be in the form of the CG of
the stage assembly, the position of the object and/or the position
of the stage, the velocity and/or the acceleration of the stage,
all at various times, as non-exclusive examples. It is recognized
that the amount of current to be directed to the mover assembly can
differ depending upon the location of the stage, which impacts the
CG of the stage assembly. The number of actual position data points
519 and the duration of time between the actual position data
points 519 provided to the memory buffer 516 can vary.
[0147] The positioning data can further include information
relating to the current directed to the mover assemblies
(illustrated by dotted line 520) during previous iterations and/or
during the current iteration. The control system 524A can monitor
and provide to the memory buffer 516 data that includes the
specific current directed to each actuator from each mover assembly
acting on the stage(s).
[0148] Further, position-dependent positioning data including
sensor information (illustrated by dotted line 522), e.g.
information from one or more sensors 523 such as an accelerometer,
is also provided to the memory buffer 516. For example, one or more
accelerometers 523 can be secured to the lens of the assembly 16,
the apparatus frame 12 or to other structures of the exposure
apparatus 10. The sensors 523 can sense and monitor the position
and/or movement at various times, including the vibration,
velocity, acceleration and other movements of the structures to
which they are attached, and provide information regarding such
positions and/or movements to the memory buffer 516. The position
and/or movement of the structures being monitored can be in the
form of relative position, and need not necessarily be absolute
position. This position-dependent positioning data can be taken
during the current iteration, or from previous iterations.
[0149] Additionally, positioning data can be provided to the memory
buffer 516 immediately following application of the feedback
control step 506A from the first control mode of the control system
524A (illustrated by dotted line 526), i.e. prior to application of
the position compensation system 515 to control the current to the
one or more mover assemblies.
[0150] Moreover, because the stage is capable of moving with one or
more degrees of freedom, positioning data for each of the
applicable principal axes over one or more iterations, i.e. along
the X axis, along the Y axis and/or about the Z axis, or any
applicable combination of these axes, can likewise be provided to
the memory buffer 516.
[0151] Once a sufficient amount of positioning data has been
received by the memory buffer 516, this information can be
processed (indicated in step 528) by the control system 524A.
During information processing 528, useful information can be
extracted from the positioning data that has been collected in the
memory buffer 516. Further, the positioning data can be transformed
as necessary into information that can be utilized by the control
system 524A to more accurately move and position the stage.
[0152] The specific processes utilized by the control system 524A
to process the positioning data can be varied. For example, the
information processing step 528 can include coordinate
transformation of the sensor information 522. For example,
positioning data can include data relating to the position or
movement of various portions of the mechanical system of the
precision apparatus 10. More specifically, positioning data can
include the position of the lens assembly of the optical assembly
at various times, which can be a measurement reference for the
wafer stage. Oscillation of the lens assembly, for example, can
cause excitation of the wafer stage. By using coordinate
transformation, the sensor information 15-522 from a sensor 523
such as an accelerometer that is attached to the lens assembly can
be used to suppress vibrations that may occur in the wafer stage as
a result of oscillation of the lens assembly or other parts of the
mechanical system.
[0153] In addition, the information processing 528 can include
signal smoothing. Positioning data received by the memory buffer
516 may include anomalous data or high frequency noise, for
instance. In order to smooth the positioning data, one or more data
filters can be utilized. In general, at least two types of filters
can be utilized during information processing 528. The first type
of filter includes a zero-phase finite impulse response (FIR)
filter, such as: 1 Q 1 ( z - 1 ) = 0.5 3 + 0.5 2 z - 1 + 0.5 z - 2
+ z - 3 + 0.5 2 z - 4 + 0.5 3 z - 5 + 0.5 3 z - 6 ( 0.5 3 + 0.5 2 +
0.5 + 1 + 0.5 + 0.5 2 + 0.5 3 ) z - 3
[0154] FIG. 6 is a graphical representation illustrating the
zero-phase FIR filter that can be used during information
processing 528 (illustrated in FIG. 5A) to remove high frequency
noise from the positioning data, without sacrificing the phase
accuracy at other frequencies. In FIG. 6, the magnitude of the
smoothing filter Q.sub.1(z.sup.-1) is plotted as a function of
frequency. Further, phase is plotted as a function of frequency.
FIG. 6 illustrates that the filter can have a magnitude attenuation
effect at high frequencies without sacrificing the phase accuracy
at low frequencies.
[0155] FIGS. 7A and 7B are graphical representations of a
zero-phase IIR filter that can be used during information
processing. 528 to remove high frequency noise from the positioning
data, without sacrificing the phase accuracy at other frequencies.
In these instances, a zero-phase forward and reverse filter can be
used, such as:
Q.sub.2(z.sup.-1)=Q.sub.LP(z.sup.-1)Q.sub.LP(z),
[0156] where Q.sub.LP(z.sup.-1) is a low pass IIR filter.
[0157] Alternatively, other suitable methods of smoothing the
positioning data can be used with the present invention.
[0158] Referring back to FIG. 5A, the information processing 528
can also include updating a model of the position compensation
system 515 by applying one or more parameter-updating algorithms to
incorporate the positioning data into the system model. For
example, if a neural network is employed to model the inverse
dynamics of the system, a backward propagation method can be used
to update the parameters of the position compensation system 515.
As a further example, autoregressive and moving average with
external input (ARMAX) can be used to model the closed-loop system,
including the mechanical system 508 and the feedback control 506A
and/or 506B, as follows:
A(z.sup.-1)y(t)=B(z.sup.-1)u(t-.alpha.)+C(z.sup.-1).epsilon.(t)
[0159] where y(t)=output, u(t)=input, and .epsilon.(t)=model
error.
[0160] When ARMAX is used to model the system, the parameters can
be updated using a recursive least squares method, as a
non-exclusive example. Alternatively, other suitable methods can be
used to update the parameters of the position compensation system
515.
[0161] Further, the information processing step 528 can include a
periodic evaluation of the performance of the control system 524A
to determine whether the parameters of the position compensation
system 515 need to continue to be updated. For example, once the
following errors 514A converge to below a predetermined threshold
level (which can vary), e.g. 5 nm, 10 nm, 25 nm or some other
suitable level, updating of the parameters can be temporarily
suspended until the following errors 514A exceed the specified
threshold, at which point the parameters can again be updated. With
this design, once the following errors 514A have been lowered to
below the specified threshold, any high frequency noise or other
anomalous data will not contaminate the output of the position
compensation system 515.
[0162] Following information processing, a control law 530 is
calculated by the control system 524A, and the control law 530 is
applied to the processed positioning data. In some embodiments, the
control law 530 is a function of both time and vibration
disturbance iterations. The control law can be model-based or
non-model-based.
[0163] For example, a model-based control law can include inverse
dynamics of the closed-loop system or a neural network. More
specifically, a model-based control law can include the following
equation, for example: 2 u j L ( t ) = k L i = 0 j - 1 A c ( z - 1
) B c ( z - 1 ) u j FB ( t + )
[0164] where
[0165] j--iteration#
[0166] t--time step in an iteration
[0167] .alpha.--time delay between system input and output
[0168] k.sub.L--learning control gain
[0169] u.sup.FB=G.sup.FB(z.sup.-1)e--feedback control
[0170] G.sup.FB(z.sup.-1)--feedback controller
[0171] e--following error
[0172] A non-model-based control law may be in the form of a PID
controller, as one example. For instance, a relatively simple
non-model-based P-type control law can be used, as follows: 3 u j L
( t ) = k L i = 0 j - 1 e i ( t + ) = u j - 1 L ( t ) + k L e j - 1
( t + )
[0173] where
[0174] j--iteration#
[0175] t--time step in an iteration
[0176] .alpha.--time delay between system input and output
[0177] k.sub.L--learning control gain
[0178] e--following error
[0179] A PD-type control law may have a faster iteration-wise
convergent rate of following errors 514A, such as: 4 u j L ( t ) =
k L i = 0 j - 1 s i ( t + ) = u j - 1 L ( t ) + k L s j - 1 ( t +
)
[0180] where s.sub.1(t)=e.sub.j(t)+k.sub.de.sub.j(t) is a
generalized following error 514A with an additional derivative
term.
[0181] Additionally, the control system 524A includes logics 532
which allow the position compensation system to be manually turned
on or off as necessary.
[0182] In the embodiment illustrated in FIG. 5A, once the control
law 530 has been applied to the processed positioning data, the
position compensation system 515 is then used as a force
feedforward to control the current that is directed to the one or
more mover assemblies at step 534A. Thus, the current that has been
determined as a result of the feedback control 506B of the first
control mode 500 is modified by the position compensation system
515 to more accurately position the stage.
[0183] FIG. 5B illustrates a second embodiment of the control
system 524B including the first control mode 500 and the second
control mode 501. In general, the functioning of the control system
524B in this embodiment is similar to the control system 524A
illustrated in FIG. 5A. However, the output of the position
compensation system 515 is used as a position feedforward control
to fine-adjust the following error 514B for the first control mode
500 of the control system 524B, as indicated by step 534B. The
constitution of the control system 524B in this embodiment provides
substantially the same effects and results of the control system
524A from the embodiment illustrated in FIG. 5A.
[0184] FIG. 8 is a series of curves illustrating the ability of the
control system to process the positioning data and to adapt in
directing current to the one or more mover assemblies over time.
With this design, the accuracy of movement of the one or more
stages within an exposure apparatus continues to increase while the
position compensation control is functioning.
[0185] Curve 800 represents a typical acceleration of a stage over
a plurality of iterations as a function of time. Curve 802
illustrates the actual trajectory of the stage of graph 800 over a
plurality of iterations. Curve 804 illustrates the following error
in a Y direction over time. Curve 806 illustrates the following
error in an X direction over time. Curve 808 illustrates the
following error in a theta Z direction (about the Z axis) over
time. As shown in curves 804-808, the following errors along the X
axis, along the Y axis and about the Z axis are relatively large
during the first several iterations. However, as the a greater
amount of positioning data is provided to the memory buffer and
processed by the control system with each successive iteration, the
following error in each direction decreases to a relatively low
level over time.
[0186] In one embodiment, in FIG. 8, R.sub.1, and R.sub.2, are
equal to 1 and 2, respectively; S.sub.1, S.sub.2, S.sub.3, S.sub.4,
and S.sub.5 are equal to 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm
respectively; U.sub.1 and U.sub.2 are equal to 2500 nm and 5000 nm
respectively; Q.sub.1 is equal to 2500 nm; and N.sub.1 is equal to
10 .mu.rad.
[0187] In another embodiment, in FIG. 8, R.sub.1, and R.sub.2, are
equal to 2 and 4, respectively; S.sub.1, S.sub.2, S.sub.3, S.sub.4,
and S.sub.5 are equal to 150 mm, 200 mm, 250 mm, 300 mm, and 350 mm
respectively; U.sub.1 and U.sub.2 are equal to 5000 nm and 10000 nm
respectively; Q.sub.1 is equal to 5000 nm; and N.sub.1 is equal to
20 prad.
[0188] In still another embodiment, in FIG. 8, R.sub.1, and
R.sub.2, are equal to 4 and 8, respectively; S.sub.1, S.sub.2,
S.sub.3, S.sub.4, and S.sub.5 are equal to 250 mm, 300 mm, 350 mm,
400 mm, and 450 mm respectively; U.sub.1 and U.sub.2 are equal to
10000 nm and 20000 nm respectively; Q.sub.1 is equal to 10000 nm;
and N.sub.1 is equal to 30 .mu.rad.
[0189] FIGS. 9A and 9B are graphs illustrating the effectiveness of
the control system at decreasing two different types of errors or
disturbances. FIG. 9A shows portions of the first three iterative
movements of a reticle stage. At this point, the position
compensation system is beginning to receive and process the
positioning data. Thus, the following error is relatively large.
Moreover, FIG. 9A illustrates a vibration disturbance 900 with a
frequency of approximately 32 Hertz that has been experimentally
imparted on the mechanical system of the exposure apparatus.
[0190] In one embodiment, in FIG. 9A, D.sub.1, D.sub.2 and D.sub.2,
are equal to 25 nm, 50 nm and 75 nm, respectively; and A.sub.1,
A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and A.sub.8
are equal to 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, and 8 nm
respectively.
[0191] In another embodiment, in FIG. 9A, D.sub.1, D.sub.2 and
D.sub.2, are equal to 50 nm, 100 nm and 150 nm, respectively; and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and
A.sub.8 are equal to 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35
nm, and 40 nm respectively.
[0192] In still embodiment, in FIG. 9A, D.sub.1, D.sub.2 and
D.sub.2, are equal to 100 nm, 200 nm and 300 nm, respectively; and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and
A.sub.8 are equal to 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70
nm, and 80 nm respectively.
[0193] FIG. 9B illustrates that after the position compensation
system has received and processed positioning data, over time, the
positioning error of the reticle stage and the vibration
disturbance 900 (illustrated in FIG. 9A) have each been
substantially reduced.
[0194] In one embodiment, in FIG. 9B, D.sub.1, D.sub.2 and D.sub.2,
are equal to 25 nm, 50 nm and 75 nm, respectively; and A.sub.1,
A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and A.sub.8
are equal to 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, and 8 nm
respectively.
[0195] In another embodiment, in FIG. 9B, D.sub.1, D.sub.2 and
D.sub.2, are equal to 50 nm, 100 nm and 150 nm, respectively; and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and
A.sub.8 are equal to 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35
nm, and 40 nm respectively.
[0196] In still embodiment, in FIG. 9B, D.sub.1, D.sub.2 and
D.sub.2, are equal to 100 nm, 200 nm and 300 nm, respectively; and
A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, and
A.sub.8 are equal to 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70
nm, and 80 nm respectively.
[0197] Semiconductor devices can be fabricated using the above
described systems, by the process shown generally in FIG. 10. In
step 1001, the device's function and performance characteristics
are designed. Next, in step 1002, a mask (reticle) having a pattern
is designed according to the previous designing step, and in a
parallel step 1003 a wafer is made from a silicon material. The
mask pattern designed in step 1002 is exposed onto the wafer from
step 1003 in step 904 by a photolithography system described
hereinabove in accordance with the present invention. In step 1005
the semiconductor device is assembled (including the dicing
process, bonding process and packaging process), finally, the
device is then inspected in step 1006.
[0198] FIG. 11 illustrates a detailed flowchart example of the
above-mentioned step 904 in the case of fabricating semiconductor
devices. In FIG. 11, in step 1101 (oxidation step), the wafer
surface is oxidized. In step 1102 (CVD step), an insulation film is
formed on the wafer surface. In step 1103 (electrode formation
step), electrodes are formed on the wafer by vapor deposition. In
step 1104 (ion implantation step), ions are implanted in the wafer.
The above mentioned steps 1101-1104 form the preprocessing steps
for wafers during wafer processing, and selection is made at each
step according to processing requirements.
[0199] At each stage of wafer processing, when the above-mentioned
preprocessing steps have been completed, the following
post-processing steps are implemented. During post-processing,
first, in step 1105 (photoresist formation step), photoresist is
applied to a wafer. Next, in step 1106 (exposure step), the
above-mentioned exposure device is used to transfer the circuit
pattern of a mask (reticle) to a wafer. Then in step 1107
(developing step), the exposed wafer is developed, and in step 1108
(etching step), parts other than residual photoresist (exposed
material surface) are removed by etching. In step 1109 (photoresist
removal step), unnecessary photoresist remaining after etching is
removed. Multiple circuit patterns are formed by repetition of
these preprocessing and post-processing steps.
[0200] While the particular precision apparatus 10 and control
system 24 as shown and disclosed herein are fully capable of
obtaining the objects and providing the advantages herein before
stated, it is to be understood that they are merely illustrative of
the presently preferred embodiments of the invention and that no
limitations are intended to the details of construction or design
herein shown other than as described in the appended claims.
* * * * *