Title: Position detecting method, position detecting apparatus, exposure method, exposure apparatus, making method thereof, and device and device manufacturing method
Abstract: In order to find the positional relation between the reference coordinate system XY which defines the movement of a substrate W and the arrangement coordinate system αβ which corresponds to a plurality of divided areas on the substrate W divided by street lines Sα and Sβ, the substrate W and an observation field are moved relatively. By allowing position detecting method marks Mk on the substrate W to visit the observation field, the street lines Sα and Sβ are detected in the observation field during the observation field. According to the results of the detection, an approximate arrangement coordinate system is corrected. The positional relation between the reference coordinate system XY and the arrangement coordinate system αβ is caught with high accuracy enough to allow the observation field to visit the position detection mark (Mk). Thus, by obtaining the arrangement coordinate system of the divided area in high speed with high accuracy, the highly precise exposure might be performed with improved throughput.
Patent Number: 6,985,209 Issued on 01/10/2006 to Yoshida
| Inventors:
|
Yoshida; Koji (Chiyoda-ku, JP)
|
| Assignee:
|
Nikon Corporation (Tokyo, JP)
|
| Appl. No.:
|
695829 |
| Filed:
|
October 30, 2003 |
Foreign Application Priority Data
| Jun 15, 1998[JP] | 10-183311 |
| Current U.S. Class: |
355/55; 355/53 |
| Current Intern'l Class: |
G03B 27/52 (20060101); G03B 27/42 (20060101) |
| Field of Search: |
355/52,53,55,67,77
356/399-401
250/548
430/22,30,311
|
References Cited [Referenced By]
U.S. Patent Documents
| 4711567 | Dec., 1987 | Tanimoto.
| |
| 5162656 | Nov., 1992 | Matsugu et al.
| |
| 5440394 | Aug., 1995 | Nose et al.
| |
| 5525808 | Jun., 1996 | Irie et al.
| |
| 5682242 | Oct., 1997 | Eylon.
| |
| 6002487 | Dec., 1999 | Shirata.
| |
| 6141107 | Oct., 2000 | Nishi et al.
| |
| 6225012 | May., 2001 | Nishi et al.
| |
| 6278957 | Aug., 2001 | Yasuda et al.
| |
| 2001/0016293 | Aug., 2001 | Nishi et al.
| |
| Foreign Patent Documents |
| 60-245134 | Dec., 1985 | JP.
| |
| 9-36202 | Feb., 1997 | JP.
| |
| 9-036202 | Feb., 1997 | JP.
| |
| 62-124751 | Jun., 1997 | JP.
| |
Primary Examiner: Nguyen; Henry Hung
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. A position detecting method for detecting positions of a plurality of divided
areas divided by street lines on the substrate, by using an observation optical
system, said position detecting method comprising:
performing image pickup of a boundary between at least one said street lines
and at least one of said divided areas on said substrate, while relatively moving
said substrate and an observation field of said observation optical system in a
direction perpendicular to an optical axis direction of the observation optical system;
detecting a positional change of said boundary in a different direction from
a direction of said relative movement, based on image information obtained in said
image pickup during the relative movement; and
detecting a positional relation between a reference coordinate system that defines
a movement of said substrate, and an arrangement coordinate system that corresponds
to an arrangement of said plurality of divided areas on the substrate, based on
the detected positional change of said boundary.
2. The position detecting method according to claim 1, wherein
in said performing image pickup, said image pickup of said boundary is performed
at regular intervals during said relative movement.
3. The position detecting method according to claim 1, wherein
said positional change of said boundary is detected in a direction substantially
perpendicular to a direction of said relative movement in a two-dimensional plane
including the direction of the relative movement.
4. The position detecting method according to claim 3, wherein
the detection of said positional change of said boundary is performed during
said relative movement.
5. The position detecting method according to claim 3, wherein
said positional relation is detected, based on a positional change of said at
least one of said street lines in a direction perpendicular to the direction of
said relative movement while the relative movement is performed.
6. The position detecting method according to claim 5, wherein
prior to the detection of said at least one of said street lines, an outer edge
of said substrate is measured, and
based on the measurement result, said positional relation between said reference
coordinate system and said arrangement coordinate system is detected with predetermined
accuracy lower than accuracy with which the positional relation is detected while
the relative movement is performed.
7. The position detecting method according to claim 6, wherein
said substrate is rotated so that an axis direction of said reference coordinate
system is parallel to an axis direction of said arrangement coordinate system,
based on said positional relation detected with said predetermined accuracy.
8. The position detecting method according to claim 5, wherein
said observation field is relatively moved with respect to said substrate along
said at least one of said street lines.
9. The position detecting method according to claim 8, wherein
in the detection of said at least one of said street lines, a positional change
of a border between said at least one of said divided areas and said at least one
of said street lines within said observation field is measured by observing a moving
picture within said observation field while relatively moving said substrate and
the observation field, and
said positional relation is detected based on the measurement result of the positional
change of said border.
10. The position detecting method according to claim 9, wherein
when it is presumed that said border is out of range of said observation field,
the relative movement of said substrate and said observation field is corrected
so that the border is continuously caught within the observation field.
11. The position detecting method according to claim 9, wherein
in the detection of said at least one of said street lines, an image formed by
a total quantity of light that reaches each point within said observation field
is picked up during a predetermined pickup time, and
said positional change of said border within the observation field is measured
based on the pickup result.
12. The position detecting method according to claim 1, wherein
said positional change of said boundary is detected by obtaining image information
through picking up an image of said boundary.
13. The position detecting method according to claim 1, wherein
said relative movement of said substrate and said observation field is performed
so that a predetermined number of position detection marks, which are chosen from
a plurality of position detection marks formed on said at least one of said street
lines, are caught within the observation field in predetermined order,
a position of the chosen predetermined number of position detection mark is detected, and
based on the detection result, said positional relation is detected with higher
accuracy than accuracy with which the positional relation is detected while the
relative movement is performed.
14. A position detecting apparatus that detects positions of a plurality of divided
areas divided by street lines on a substrate, said position detecting apparatus comprising:
a substrate stage that holds said substrate;
an observation system that performs image pickup of said substrate by using an
observation optical system;
a driving unit that drives said substrate stage in a direction perpendicular
to an optical axis direction of said observation optical system; and
a processing unit that is electrically connected to the observation system, and
obtains a positional relation between a reference coordinate system that defines
a movement of the substrate stage, and an arrangement coordinate system that corresponds
to an arrangement of said plurality of divided areas on the substrate, based on
image information regarding a boundary between at least one of said street lines
and at least one of said divided areas obtained by the observation system while
the substrate stage is moved by said driving unit.
15. The position detecting apparatus according to claim 14, wherein
said observation system observes a positional change of said boundary in a direction
substantially perpendicular to a moving direction of said substrate stage during
the movement of said substrate stage.
16. The position detecting apparatus according to claim 15, further comprising:
a control system that is electrically connected to said driving unit, and controls
the driving unit so that said at least one of said street lines is detected by
said observation system while moving said substrate stage, when detecting a mark
on said substrate.
17. The position detecting apparatus according to claim 16, wherein
said control system controls said driving unit so that said observation field
of said observation system follows a route to a predetermined position detection
mark that is chosen from the position detection marks formed on said at least one
of said street lines, and
the control system further detects a position of the chosen predetermined position
detection mark and detects a position of each divided area based on the detection
result of the chosen predetermined position detection mark.
18. The position detecting apparatus according to claim 17, wherein
said route is along a street line.
19. The position detecting apparatus according to claim 14, wherein
said observation system comprises an image pickup apparatus that obtains image
information by performing image pickup of a substrate surface.
20. An exposure method in which a predetermined pattern is transferred to a divided
area on a substrate by emitting an energy beam, said exposure method comprising:
detecting a position of said divided area formed on said substrate by using the
position detecting method according to claim 1, prior to said transfer.
21. An exposure apparatus that transfers a predetermined pattern to a divided
area on a substrate by emitting an energy beam, said exposure apparatus comprising:
an illumination system that emits said energy beam; and
the position detecting apparatus according to claim 14 that detects a position
of said at least one of said divided areas.
22. A making method of a position detecting apparatus that detects a plurality
of divided areas divided by street lines on a substrate, said method comprising:
providing a substrate stage that holds said substrate;
providing an observation system that performs image pickup of said substrate
by using an observation optical system;
providing a driving unit that drives said substrate stage in a direction perpendicular
to an optical axis direction of said observation optical system; and
providing a processing unit that is electrically connected to the observation
system, and obtains a positional relation between a reference coordinate system
that defines a movement of the substrate stage, and an arrangement coordinate system
that corresponds to an arrangement of said plurality of divided areas on the substrate,
based on image information regarding a boundary between at least one of said street
lines and at least one of said divided areas obtained by said observation system
while the substrate stage is moved by said driving unit.
23. A device manufacturing method comprising a lithographic process, wherein
a predetermined pattern is transferred onto a divided area divided by street
lines on said substrate, by using the exposure method according to claim 20.
24. A device manufactured by using the device manufacturing method according
to claim 23.
25. The position detecting method according to claim 1, wherein:
based on said detected positional relation between said reference coordinate
system and said arrangement coordinate system, a direction of the relative movement
is changed while relatively moving said substrate and said observation field.
Description
TECHNICAL FIELD
The present invention relates to a position detecting method, position detecting
apparatus, an exposure method, exposure apparatus, and a making method thereof,
as well as a device and device manufacturing method. More particularly, the present
invention relates to a position detecting method to detect a position of a plural
divided areas which are formed on a substrate; an apparatus on which the position
detecting method in applied; an exposure used when semiconductor devices are manufactured
in lithographic process, in the method, exposure is conducted found on the result
obtained by using the position detecting method; an exposure apparatus on which
the exposure method is applied, and a making method thereof; as well as a device
which is manufactured by using the exposure apparatus and a manufacturing method thereof.
BACKGROUND ART
Conventionally, in a lithographic process for manufacturing a semiconductor
device, liquid crystal display device and so forth, an exposure apparatus has been
used. In such an exposure apparatus, patterns formed on a mask or reticle (to be
genetically referred to as a "reticle" hereinafter) are transferred through a projection
optical system onto a substrate such as a wafer or glass plate (to be referred
to as a "substrate or wafer" herein after, as needed) coated with a resist or the like.
In general, the semiconductor device is manufactured by using the exposure apparatus,
and it is composed of a plurality of circuit pattern layers on a wafer. Therefore,
the positioning of the shot area on the wafer and the reticle (to be referred to
as "alignment" hereinafter) must be precisely performed when they are overlaid
in the exposure apparatus. In order to position them in the apparatus precisely,
the position of the wafer must be detected correctly, and the techniques, for example,
disclosed in the publication of Japanese unexamined patent application (refer to
as "Japan laid-open", hereinafter) No. H9-92591, have been proposed.
In such conventional position detecting methods, enhanced global alignment (to
be referred to as "EGA" hereinafter) is widely employed. In EGA, fine alignment
marks, which are positioning marks transferred together with circuit patterns on
the wafer, are measured at a plurality of positions within the wafer, in order
to precisely detect positional relations of the reference coordinate system and
the arrangement coordinate system (to be referred to as "wafer coordinate system"
hereinafter). Wherein, the reference coordinate system defines the movement of
the wafer, and the arrangement coordinate system defines the arrangement of the
respective shot areas on the wafer. The arrangement coordinate of the respective
shot areas are then obtained by the least-squares approximation or the like, and
stepping is performed by using the calculated result in accordance with the accuracy
of the wafer stage on exposure. EGA is disclosed in, for example, Japan laid-open
No. S61-44429 and its corresponding U.S. Pat. No. 4,780,617. In order to use such
EGA, the fine alignment mark formed on the predetermined position on the wafer
is observed by high magnifying power. However, the observation field is essentially
narrow under the observation with high magnifying power. Therefore, prior to perform
fine alignment, the following detection for the reference coordinate system and
the arrangement coordinate system is preformed to catch fine alignment marks certainly
within the narrow observation field.
At first, the outer edge of the wafer, an object in the positioning detection,
is observed. The positional relation between the reference coordinate system and
the arrangement coordinate system are detected in the predetermined accuracy derived
from the position of the notch in the outer edge, the position of the orientation
flat or the outer edge of the wafer. This detection procedure is referred to as
"rough alignment".
Then, the observation apparatus is moved to the wafer or vice versa, that is,
relative movement of the observation apparatus and the wafer according to the positional
relations of the first approximation arrangement coordinate system obtained by
rough alignment and the reference coordinate system. A plurality of search alignment
marks is caught within the relatively wider observation field, and the search alignment
marks are observed. Based on the search alignment marks observed as mentioned above,
the positional relation between the reference coordinate system and the arrangement
coordinate system is detected in higher accuracy than that obtained in the rough
alignment. Such detection procedure is referred to as "search alignment" hereinafter.
The observation field of the observation unit is set in an enough range to catch
the search alignment mark when the inaccuracy is included in the positional relation
between the reference coordinate system and the arrangement coordinate system detected
in the rough alignment. Further, the accuracy for the detection of the positional
relation between the reference coordinate system and the arrangement coordinate
system is set in an enough range for the fine alignment performed in next.
As mentioned above, the rough alignment and the search alignment are sequentially
performed. Then, the wafer is moved against the observation unit or vise versa,
according to the positional relation between the reference coordinate system and
the second-approximated arrangement coordinate system, which is obtained in the
search alignment. After that, a plurality of fine alignment marks on the wafer
is caught in a narrow observation field to perform fine alignment.
In conventional position detecting methods, three alignments such as rough alignment,
search alignment and fine alignment are sequentially conducted. Among them, both
in the search alignment and rough alignment, the positions of a plurality of marks
to be observed must be detected after they are caught in the observation field,
wherein the wafer is moved to the observation unit or vise versa. Therefore, it
takes much time to detect the positions of the shot areas by using the conventional method.
On the other hand, in the exposure apparatus, high through put is needed because
this apparatus is employed for mass production of semiconductor devices. Therefore,
the alignment procedure composed of three steps as mentioned above becomes a problem
on the way to accomplish the high through put. Accordingly, it is expected that
the new technology to shorten the alignment time, maintaining the present accuracy
of the alignment.
The present invention has been made in consideration of the above-mentioned situation.
The first object of the present invention is to provide the position detecting
method and a position detecting apparatus to conduct the position detection with
high accuracy in a short time.
The second object of the present invention is to provide the exposure method
and the exposure apparatus with high accuracy and high through put depending on
the rapid and precise position detection.
The third object of the present invention is to provide the device on which fine
patterns are precisely formed.
DISCLOSURE OF INVENTION
In the first aspect of the present invention, the present invention is a position
detecting method for detecting a position of a plurality of divided area formed
on the substrate, comprising: moving a substrate to an observation field relatively;
detecting a positional relation between a reference coordinate system which defines
said movement of a substrate and an arrangement coordinate system corresponding
to said plurality of a divided area while the relative movement is performing.
According to the position detecting method, the equal position detection
performed in the search alignment may be conducted during the period necessary
for fine alignment, in which the substrate and the observation field are relatively
moved. Conventionally, this period has been not used for the measurement for alignment.
Therefore, the conventional search alignment step may be skipped, and the positional
relation between the reference coordinate system and the arrangement coordinate
system is detected rapidly.
In the first position detecting method of the present invention, the divided
area
on the substrate is divided by street lines, and the positional relation is detected
based on a detection result of the street line while the relative movement is performing.
In this case, the street line is detected within the observation field, moving
the substrate and the observation field relatively, when the two coordinates systems
are detected. One of the coordinate system is the reference coordinate system for
defining the movement of the substrate and the other is the arrangement coordinate
system corresponding to the arrangement of a plurality of the divided areas divided
by the street lines on the substrate. The street line formed on the substrate is
substantially parallel to the coordinate axis of the arrangement coordinate system.
That is, the relation between the relative movement direction of the substrate
to the observation field and the direction along the axis of the arrangement coordinate
may be obtained by detecting the street line in the observation field. The relative
movement direction is decided in the reference coordinate system. Furthermore,
the street line is detected in the observation field, moving the substrate to the
observation field or vice versa, i.e., relative movement. As a result, the relation
between the direction of the street line is formed and that of the relative movement
is detected accurately, because the detection is not performed based on the street
line having short length caught at the moment in the observation field, but that
having enough length caught there. Accordingly, the positional relation between
the reference coordinate system and the arrangement coordinate system may be detected
in high speed, holding its accuracy.
The street lines divide an area to form divided areas on the substrate. In its
extension direction, there are usually two directions being perpendicular each
other to divide the divided area into matrices. Accordingly, when the direction
of the substrate is not decided prior to the detection of the street line, even
though one street line is detected, it is not determine that the street line is
extended which direction described above for the arrangement of the divided area.
Considering these, in the first position detecting method of the present
invention, prior to the detection of the street line, an outer edge of the substrate
is measured to obtain a result, and a positional relation between the reference
coordinate system and the arrangement coordinate system is detected by using the
result with a predetermined accuracy, which is lower than that detected while the
substrate is moving to an observation field relatively.
In this case, the outer edge of the substrate is measured to determine uniquely
the relation between the arrangement direction of the divided area and the extension
direction of the street line, which is caught in the observation field, by using
the result. For example, when the divided areas are arranged in matrices and the
extension directions of two street lines are perpendicular each other, the rotation
direction is obtained less than 45° found on the measurement of the outer
edge of the substrate. Accordingly, when one street line is detected, it is recognized
that the street line is extended to which array direction in the divided area on
the substrate.
When the positional detection is detected with the predetermined accuracy, the
substrate may be rotated so that a direction along an axis of the reference coordinate
system is substantially parallel with the direction along an axis of the arrangement
coordinate system based on the positional relation detected with the predetermined
accuracy. This rotation is performed according to the positional relation detected
with the predetermined accuracy based on the measurement result of the outer shape
of the substrate. In this case, in performing the relative movement of the substrate
and the observation field in below, since the relative movement direction may be
set as the one of the axis direction of the reference coordinate system, the relative
movement is controlled easily.
Further, in the first position detecting method of the present invention,
the observation field is moving to the substrate relatively along the street line.
In this case, since the particular street line is continuously detecting, the accuracy
in the position detection between the reference coordinate system and the arrangement
coordinate system derived from the detection of the street line may be improved.
In the detection of the street line, a positional change of a border between
the
divided area and the street line is measured by observing of a moving picture in
the range of the observation field to obtain a result, while the relative movement
is performed, and the positional relation is detected based on a measurement result
of the change of the border. In this case, the positional change between the border
of the divided area and the street line is measured by observing the moving picture
in the observation field while the substrate and the observation field are moving
relatively. Accordingly, the positional relation between the reference coordinate
system and the arrangement coordinate system is detected in high accuracy and high
speed. At that time, the relative movement of the substrate and the observation
field is not discontinued, and the image-pick up apparatus having high-speed shutter,
of which speed is enough high compared to that of the relative movement, is not
needed, conducting the image pick-up in the observation field.
When it is presumed that the border is out of the range of the observation field,
the relative movement of the substrate to the observation field may be corrected
so that the border in the range of the observation field is continuously caught.
According to the described above, since the border is continuously caught in the
observation field, and it is assured to observe the border between the divided
area and the street line extending over the enough length of the street line. Therefore,
the relation between the direction of the street line is formed and that of the
relative movement is detected reliably in high accuracy.
Since the substrate and the observation field is relatively moved when the
street line is detected, the images obtained as the image picked-up result generally
become blur images. When the object moves to the camera (i.e., the observation
field) during pick-up time, if the time for picking up image is not enough short
against the velocity of the relative movement (i.e., the shutter speed is enough
high). Then, the blur image is formed by the overlapped images caught at each moment.
That is, the blur image is formed by the total amount of the light which reached
each points in the observation field during the predetermined pick-up time. However,
even though generating such blur image, the moving velocity of the border between
the divided area and the street line becomes enough slow in the observation field,
when the observation field is moved relatively along the street line. The moving
direction of the border is perpendicular to that of the relative movement in the
observation field. On the contrary, in the area corresponding to the divided area,
the blur image having the brightness corresponding to mean reflectance of the divided
area is formed. In the area corresponding to the street line, the image having
the brightness corresponding to mean reflectance of the street line is formed.
In general, the mean reflectance in the divided area is different from that in
the street line.
In detection of the street line, an image formed by the total amount of the light
which reached respective point in the range of the observation field during predetermined
time is picked-up; and the positional change of the border in the range of the
observation field is measured based on the image pick-up result. In this case,
the positional change of the border between the divided area and the street line
in the observation field, i.e., the positional relation between the reference coordinate
system and the arrangement coordinate system, may be detected by using the image
pick-up result, the blur image, positively. For example, in the above-mentioned
case, the border between the divided area and the street line is detected by detecting
the turning point of the brightness in the obtained image. Then, the positional
relation between the reference coordinate system and the arrangement coordinate
system is detected based on the detection result. Accordingly, the positional relation
between the reference coordinate system and the arrangement coordinate system is
detected accurately, when the relative movement velocity of the substrate and the
observation field is fast. As a result, the image pick-up apparatus of which image
pick-up time is relatively long and is commercially available may be used.
In the first position detection method of the present invention, the relative
movement of the substrate to the observation field is performed to catch a predetermined
number of position detection mark, which is chosen from a plurality of the position
detection mark formed on the street line, in the observation field with predetermined
order; the position of the chosen position detection mark is detected; based on
the detection result, the positional relation may be detected with higher accuracy
than that detected during the relative movement.
With this, the street line is detected while the predetermined number of the
position detection marks formed on the street line, i.e., fine alignment marks,
are moved in the observation field. Then, according to the detection result, the
positional relation between the reference coordinate system and the arrangement
coordinate system is detected in the predetermined accuracy. The substrate and
the observation field moves relatively along the street line. The target position
for movement of the position detection mark for the position detection mark to
be visited is corrected by using the detected positional detection, during this
relative movement of the substrate and the observation field. Correcting the target
position as mentioned above, based on the corrected target position, the position
detection marks are sequentially detected by moving the substrate and the observation
field relatively. After detecting the predetermined number of the position detection
marks, based on such position detection results, the positional relation between
the reference coordinate system and the arrangement coordinate system are detected
in high accuracy by using, for example, EGA method. Accordingly, in the present
invention, since fine alignment is performed without conducting the conventional
search alignment, the positional relation between the reference coordinate system
and the arrangement coordinate system are detected rapidly, keeping with its high accuracy.
In the second aspects of the present invention, the present invention is the
second
position detecting method for detecting position of a plurality of divided areas
which are divided by street lines on a substrate by detecting a plurality of position
detection mark formed on said street line, wherein the street line is detected
when said plurality of position detection mark is sequentially detected, and a
moving route of said substrate is decided by using a detection result.
According to this, the street line is detected while the observation field
moves to a plurality of the position detection marks formed on the street line,
i.e., fine alignment marks. According to the detection result, the positional relation
between the reference coordinate system and the arrangement coordinate system is
detected in the predetermined accuracy. By using the detected positional relation,
the target position for the position detection mark to be detected is corrected
during this relative movement of the substrate and the observation field. Thus
correcting the target position for movement, the position detection marks are sequentially
detected based on the corrected target position as mentioned above. Then, after
detecting the predetermined number of the position detection marks, the positional
relation between the reference coordinate system and the arrangement coordinate
system is detected based on the detection result in high accuracy by using, for
example, the EGA method. Accordingly, since fine alignment is performed without
conducting the conventional search alignment, the positional relation between the
reference coordinate system and the arrangement coordinate system are detected
rapidly, keeping with its high accuracy.
Also in the second position detecting method of the present invention, similarly
to the first position detecting method, prior to the detection of the street line,
an outer edge of the substrate is measured and a positional relation between the
reference coordinate system and the arrangement coordinate system may be detected
by using the result. In this case, when one street line is detected, it is recognized
that the street line is extended to which array direction of the divided area on
the substrate.
Furthermore, similarly to the case of the first position detecting method,
by using the positional detection obtained from the measurement result of the outer
edge of the substrate, the substrate may be rotated so that a direction along an
axis of the reference coordinate system is substantially parallel with the direction
along an axis of the arrangement coordinate system. In this case, the same effects
that brought by the first position detecting method of the present invention is brought.
In the second position detecting method of the present invention, similarly to
the first position detection method, the observation field may be moved against
the substrate relatively along the street line. In this case, similarly to the
first position detection method, since the particular street line is continuously
detected, the accuracy of the detection in the positional detection between the
reference coordinate system and the arrangement coordinate system derived from
the detection of the street line may be improved.
In the detection of the street line, a positional change of the border between
the divided area and the street line in the observation field may be measured by
observing a moving picture in the range of the field, while moving the substrate
to the observation field relatively. In this case, the positional change of the
border between the divided area and the street line in the field is measured by
observing the moving picture in the field during the relative movement of the substrate
and the observation field. Accordingly, the positional relation between the reference
coordinate system and the arrangement coordinate system may be detected in high
accuracy and high speed, when the image in the observation field is picked up.
At that time, the relative movement is not discontinued, or the image pick-up apparatus
having high-speed shutter, of which speed is enough high compared to that of the
relative movement is not used.
Furthermore, similarly to the first position detecting method, when
it is presumed that the border is out of the observation field, the relative movement
of the substrate and the observation field may be corrected so as to catch continuously
the border in the range of the observation field. In the detection of the street
line, the image formed by the total amount of the light reached respective point
in the observation field during predetermined time is picked-up. Then, the positional
change of the border in the field may be measured by using the picked up image
result. In this case, the same effect that brought by the first position detecting
method is brought.
In the third aspect of the present invention, the present invention is a position
detecting apparatus for detecting a plurality of divided area on a substrate comprising:
a position of a substrate stage which holds said substrate; a driving unit which
drives said substrate stage; and an observation system which observes said substrate
while said substrate is moved by said driving unit.
According to this, the substrate may be observed by the observation system
while the substrate held by the substrate stage is moving. Therefore, the position
detecting method is performed by the apparatus and the positional relation between
the reference coordinate system and the arrangement coordinate system may be detected
in high speed.
In the position detecting apparatus of the present invention, this apparatus
may
further comprise a control system for controlling the driving unit to detect the
street line, which divides the area on the substrate into the divided area, by
using the observation system, moving said substrate stage, when the position detection
marks on the substrate are detected. In this case, the control system moves the
substrate stage through the driving unit so as to detect the street line in the
observation field, when the substrate is observed. Accordingly, the positional
relation between the reference coordinate system and the arrangement coordinate
system may be detected accurately in high speed.
In the position detecting apparatus of the present invention, the control system
may be the structure wherein the driving unit is controlled by the control unit
so as to trace the route to the predetermined position detection mark which are
chosen among the position detection marks formed on the street line by the observation
field; the position of the predetermined position detection marks chosen are detected,
and the position of the divided area is respectively detected by using the detection
result of the predetermined detection mark.
With this, the control system moves the substrate stage to sequentially catch
the predetermined number of the position detection marks formed on the street line,
i.e., fine alignment marks, in the observation field of the observation system.
During the movement of the substrate stage, the observation system detects the
street line. The control system detects the positional relation between the reference
coordinate system and the arrangement coordinate system by using the detection
result in the predetermined accuracy, and the target position for movement for
the position detection mark to be detected is corrected, while the substrate stage
is moving. The control system thus corrects the target position for the movement,
and the substrate stage is moved based on the target position for the movement,
and then the position detection mark is sequentially detected. The control system
detects the positional relation between the reference coordinate system and the
arrangement coordinate system, according to detection result of the predetermined
number of the position detection marks, by using, for example, EGA method, in high
accuracy. According to the detection result, the positional relation between the
reference coordinate system and the arrangement coordinate system is detected in
the predetermined accuracy. Accordingly, in the present invention, since fine alignment
is performed without conducting the conventional search alignment, the positional
relation between the reference coordinate system and the arrangement coordinate
system are detected rapidly, keeping with its high accuracy. The route may be along
the street line.
The forth aspect of the present invention, the present invention is the exposing
method wherein a predetermined pattern is transferred to a divided area on a substrate
by emitting an energy beam comprising, prior to the transfer, detecting a position
of said divided area formed on the substrate by using the position detecting method
of the present invention. According to this, the position of the divided area formed
on the substrate may be accurately detected by using the position detecting method
of the present invention in high speed; then, the predetermined patterns are transferred
to the substrate by exposing second layer and subsequent layers for the divided
area. Accordingly, multilayer exposure is conducted to form multilayer patterns,
holding the overlay accuracy in enhanced through put.
In the fifth aspect of the present invention, the present invention is the exposure
apparatus for transferring the predetermined pattern to the divided area on the
substrate by emitting energy beam comprising: an illumination system for emitting
the energy beam; and the position detection apparatus of the present invention
for detecting the position of the divided area. With this, the predetermined pattern
is transferred onto the divided area after high speed and high accuracy position
detection is performed by detecting the position of the divided area formed on
the substrate with the position detecting apparatus of the present invention. Therefore,
the multilayer exposure may be conducted to form multilayer patterns, holding the
overlay accuracy among layers in enhanced through put.
In the sixth aspect of the present invention, the present invention is the making
method for an exposure apparatus wherein the predetermined pattern is transferred
to the predetermined divided area on a substrate by emitting energy beam comprising:
providing the illumination system for emitting the energy beam; providing the substrate
stage for holding the substrate; providing the driving unit for driving the substrate
stage; providing a observation system for observing the substrate during movement
the substrate stage by the driving unit. According to this, the illumination system,
position detecting apparatus, and other various parts and devices are connected
and assembled mechanically, optically and electrically, and adjusted, thereby the
exposure apparatus for transferring the pattern onto the substrate may be produced.
The making method for the exposure apparatus of the present invention may further
comprise providing the control system for controlling the driving unit to detect
the street line, which divides the area on the substrate into the divided area,
in the observation system, moving the substrate stage, when the mars on the substrates
are detected. In this case, the apparatus as follows is made, wherein the control
unit moves the substrate stage in the observation field of the observation system
through the driving unit, observing the substrate by the observation system.
Furthermore, in the lithography step, the device having fine patterns
on it may be manufactured by exposing the substrate with the exposure apparatus
of the present invention to transfer the predetermined pattern onto the substrate.
Accordingly, the present invention is the device produced by using the exposure
apparatus of the present invention in another view point, and also it is the manufacturing
method of device by using the exposure method of the present invention to transfer
the predetermined pattern onto the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing the schematic arrangement of an exposure apparatus
according to one embodiment.
FIG. 2 is a view for explaining the rough alignment detection system of the
apparatus in FIG. 1.
FIG. 3 is a perspective view for explaining the principle of scanning exposure
performed by the apparatus in FIG. 1.
FIG. 4 is a flow chart of an alignment procedure prior to exposure for the second
layer and subsequent layers.
FIG. 5 is a view showing arrangements as an example of chip areas and street
lines on the wafer.
FIG. 6 is a view showing as an example of sites of position detection marks formed.
FIGS. 7A to 7C are views for explaining the image in the observation field.
FIG. 8 is a flow chart for explaining the device manufacturing method by using
the exposure apparatus shown in FIG. 1.
FIG. 9 is a flow chart showing the processing step in FIG. 8.
BEST MODE FOR CARRYING OUT THE INVENTION
An exposure method and exposure apparatus according to an embodiment of the present
invention will be described below with reference to FIGS. 1 to 9.
FIG. 1 shows the schematic arrangement of an exposure apparatus
100 according
to one embodiment of the present invention. The exposure apparatus
100 is
a scanning type projection exposure apparatus comprising a position detecting apparatus
based on a so-called step-and-scan exposure method.
The exposure apparatus
100 comprises: the illumination system
10
for emitting illumination light for exposing the wafer, reticle stage RST serving
as a mask stage for holding the reticle R as a mask; a projection optical system
PL; the wafer stage WST for moving two-dimensionally the wafer W as the substrate
within the X-Y plane; the rough alignment detecting system RAS for observing outer
edge of the wafer W; the alignment detecting system AS as the observing system
for observing fine alignment mark as position detecting marks or street lines,
and the control system for controlling thereof.
The illumination system
10 includes: the light unit; a shutter, the secondary
light source forming optical system, a beam splitter, a condenser lens system,
a reticle blind, and an image lens system, which are not shown in FIG. 1. The respective
components of the illumination system
10 are disclosed Japan laid-open No.
H9-320956. As the light source unit, followings are used: KrF excimer laser beam
(wavelength=248 nm), ArF excimer laser beam (wavelength=193 nm), F
2
laser beam (wavelength=157 nm), Kr
2 (krypton dimer) laser beam (wavelength=146
nm), Ar
2 (argon dimer) laser beam (wavelength=126 nm), high harmonic
generation devices such as copper vapor laser or YAG laser harmonics, an ultra-high
pressure mercury vapor lamp (e.g., g-line or i-line), or the like. Alternatively,
instead of the light, which is emitted from the above-mentioned light source, beam
such as charged electron x-ray and electron beam might be used.
Function of the illumination system
10 composed as described above
is briefly explained. The light beam, which is emitted from the light source, reaches
the secondary light source forming optical system when the shutter is opened, thereby
many secondary light sources are formed at the emission terminal of the secondary
light source optical system. The illumination light from the secondary light source
that passes through both the beam splitter and the condenser lens system, and reach
the reticle blind. Then the illumination light passed through the reticle blind
is emitted to the mirror M through the image lens system.
The mirror M bends the optical path of the illumination light beam IL vertically
down load, and then the light beam illuminates the illumination area IAR portion
(see FIG. 3) formed as the rectangular shape on the reticle R, which is held on
the reticle stage RST.
The reticle R is fixed on the reticle stage RST, for example, by vacuum chucking.
In order to position the reticle R, the reticle stage RST is structured so that
it can be finely driven two-dimensionally (in the X-axis direction, the Y-axis
direction perpendicular to the X-axis direction, and the rotational direction around
the Z-axis perpendicular to the X-Y plane) within a plane perpendicular to an optical
axis IX (coinciding with an optical axis AX of the projection optical system PL,
which will be described later) of the illumination optical system.
The reticle stage RST can be moved on a reticle base (not shown in FIGS.) in
a predetermined scanning direction (Y-axis direction in this case) at a designated
scanning velocity by a reticle driving portion (not shown in FIGS.) structured
of a linear motor or the like. It has a movement stroke which the entire surface
of the reticle R can at least cross the optional axis IX of the illumination optical system.
On the reticle stage RST, a moving mirror
15 for reflecting a laser beam
from a reticle laser interferometer (to be referred to as a "reticle interferometer"
hereinafter)
16 is fixed. The reticle interferometer
16 detects the
position of the reticle stage RST within the stage movement plane at all times
by for example, a resolution of about 0.5 to 1 nm. In practice, a moving mirror
which has a reflecting surface perpendicular to the scanning direction (Y-axis
direction) and a moving mirror which has a reflecting surface perpendicular to
the non-scanning direction (X-axis direction) are mounted on the reticle stage
RST. Also, the reticle interferometer
16 is arranged on one axis in the
scanning direction, and on two axes in the non-scanning direction. However, in
FIG. 1, these are represented as the moving mirror
15 and reticle interferometer
16.
Positional information of the reticle stage RST is sent from the reticle
interferometer
16 to a stage control system
19 and to the main controller
20 via the stage control system
19. The stage control system
19
drives the reticle stage RST through a reticle driving portion (not shown in FIGS.)
by instructions from the main controller
20 based on the positional information
of the reticle stage RST.
A reticular alignment system (not shown in FIGS.) determines the initial position
of the reticle stage RST so that the reticle R is accurately positioned at a predetermined
reference position. Therefore, the position of the reticle r can be measured with
a sufficiently by only measuring the position of the moving mirror
15 with
the reticle interferometer
16.
The projection optical system PL is arranged below the reticle stage RST in FIG.
1. The direction of the optical axis AX (which coincides with the optical axis
IX of the illumination optical system) of the projection optical system PL is the
Z-axis direction. In order to make the projection optical system PL double telecentric,
a refraction optical system configured of a plurality of lens elements arranged
at predetermined intervals along the optical axis AX is employed. The projection
optical system PL is a reduction optical system having a predetermined projection
magnification of, for example, ⅕, ¼ or ⅙. Therefore, when the
illumination area IAR of the reticle R is illuminated with the illumination light
IL from the illumination optical system, a reduced image (partial inverted image)
of the circuit pattern of the reticle R in the illumination area IAR is formed
on the wafer W which surface is coated with a photo-resist.
The wafer stage WST can be in the Y-axis direction that is in the predetermined
scanning direction (Y-axis direction is shown as the right or left direction in
FIG. 1) or the X-axis direction that is perpendicular to the Y-axis direction (the
X-axis direction is shown as the perpendicular to the sheet of FIG. 1), for example,
by a two dimensional linear actuator. The substrate table
18 is fixed on
the wafer stage WST. The wafer holder
25 is mounted on the substrate table
18. The wafer W as a substrate is held on the wafer holder
25 by
vacuum chucking. The substrate stage is composed of the wafer stage WST, the substrate
table
18, and the wafer holder
25.
The substrate table
18 is mounted on the wafer stage WST of which position
is fixed in X-Y axis direction but allowing to move or tilt Z-axis direction. The
substrate table
18 is supported by three shafts, which are not shown in
the figures. These three shafts are independently driven by the wafer driving unit
21 in Z-axis direction to establish the face position of the wafer W held
on the substrate table
18 (the position in Z-axis direction and the tilt
on X-Y plane) in predetermined situation. Furthermore, the wafer holder
25
can rotate along the Z-axis. Accordingly, the wafer holder
25 is driven
in 6 degrees of freedom by the two-dimensional linear actuator or the driving unit.
However, the two dimensional linear actuator or the driving unit is shown in FIG.
1 as the typical example.
On the substrate table
18, a moving mirror
27 is fixed for reflecting
a laser beam from a wafer laser interferometer (to be referred to as a "wafer interferometer"
hereinafter)
28. The wafer interferometer
28 arranged externally
detects the position of the wafer W in the X-Y plane at all times with a resolution
of about 0.5 to 1 nm.
In the practice, a moving mirror which has a reflecting surface perpendicular
to the Y-axis direction, that is the scanning direction, and a moving mirror which
has a reflecting surface perpendicular to the X-axis direction, that is the non-scanning
direction, are on the substrate table
18. The wafer interferometer
28
is arranged on one axis in the scanning direction, and on two axes in the non-scanning
direction. However, in FIG. 1, these are represented as the moving mirror
27
and wafer interferometer
28. The positional information (or velocity information)
is sent to the stage control of system
19 and to the main controller
20
through the stage control system
19. The main controller
20 instructs
the stage control system
19 to control and drive the wafer stage WST via
a wafer driving unit
21. A control system is structured of main controller
20 and the stage control system
19.
Alternatively, on the substrate table
18, a reference mark
plate as mentioned in below, which is not shown in FIGS., is fixed. The mark plate,
on which several kinds of the reference marks are formed, is used to measure the
distance from the detection center in the alignment detection system AS to optical
axis in the projection optical system PL.
The rough alignment detection system RAS is held at the position distant from
the projection optical system PL and upward of it by using the holding member,
which is not shown in FIGS. The rough alignment detection system RAS is composed
of three rough alignment sensors
40a,
40b, and
40c,
all of which detect the position of three points on the outer edge of the wafer
W. Wafer W is carried by the wafer loader, not shown in FIGS., and it is held on
the wafer holder
25. These three rough alignment sensors
40a,
40b, and
40c are placed at the positions on circumference
of a circle which has predetermined radius (this radius is the almost same as that
of the wafer) so that the central angle is set to 120 degrees. Among them, the
rough alignment sensor
40a is placed at the position, wherein the
sensor
40a is capable of detecting a notch N (the notch is a V-shaped
cutout) formed on the wafer W held on the wafer holder
25. As the rough
alignment sensor, an image processing method sensor composed of an image pick-up
device and image processing circuit is used.
Return to FIG. 1, the alignment system AS is arranged at the side of the projection
optical system PL. In this embodiment, an off-axis alignment microscope is employed,
in which the microscope is composed of an imaging alignment sensor to observe the
street lines or marks for position detection (fine alignment marks) formed on the
wafer. The detailed structure of this alignment system AS is disclosed in, for
example, Japan laid-open No. H9-219354, and its correspondent, U.S. Pat. No. 5,859,707.
The disclosure described in the above is fully incorporated by reference herein,
as far as the law of the countries designated in a request or elected in a demand
for the application filed in the country of origin permits them. The image of the
wafer W observed in the alignment system AS is transmitted to the main controller
20.
The apparatus in FIG. 1 further includes a multiple focal position detection
system for detecting the positions of the range within the exposure area IA (to
be referred as "the area on the wafer which conjugates to above-mentioned illumination
area IAR": see FIG. 3) on the surface of the wafer W and the area around it in
the Z direction (the direction of the optical axis AX). The multiple focal position
detection system is one of a focus detection system based on the oblique incident
light method. The multiple focal position detection system, not shown in FIGS.,
is configured of an emitting optical system and a light-receiving optical system.
For example, the emitting optical system includes an optical fiber bundle, condenser
lens, pattern forming plate, lens, emitting object lens, and the like (none of
which are shown). The light-receiving optical system includes a condenser object
lens, a rotational direction vibration plate, and image forming lens, a light-receiving
slit plate, a light-receiving unit having many photosensors, and the like (none
of which are shown). The detailed structure of this multiple focal position detection
system is disclosed in, for example, Japan laid-open No. H6
