U.S. patent application number 12/481447 was filed with the patent office on 2009-12-10 for apparatus for scanning sites on a wafer along a short dimension of the sites.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Michael B. Binnard, Eric Peter Goodwin, David M. Williamson.
Application Number | 20090305171 12/481447 |
Document ID | / |
Family ID | 41400005 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090305171 |
Kind Code |
A1 |
Goodwin; Eric Peter ; et
al. |
December 10, 2009 |
APPARATUS FOR SCANNING SITES ON A WAFER ALONG A SHORT DIMENSION OF
THE SITES
Abstract
An exposure apparatus (210) for transferring a mask pattern
(346) from a mask (212) to a substrate (214) includes a first site
(315) having a first site dimension (348) along a first axis and a
second site dimension (350) along a second axis that is
perpendicular to the first axis. The second site dimension (350) is
larger than the first site dimension (348). The exposure apparatus
(210) includes an illumination system (218), a mask stage assembly
(222), a substrate stage assembly (224), and a control system
(228). The illumination system (218) generates an illumination beam
(235) that is directed at the mask (212). The mask stage assembly
(222) retains and positions the mask (212) along the first axis
relative to the illumination beam (235). The substrate stage
assembly (224) retains and positions the substrate (214) along the
first axis. The control system (228) controls the illumination
system (218), the mask stage assembly (222), and the substrate
stage assembly (224) so that a portion of the mask pattern (346) is
transferred to a portion of the first site (315) while the mask
stage assembly (222) is moving the mask (212) along the first axis,
and the substrate stage assembly (224) is moving the substrate
(214) along the first axis.
Inventors: |
Goodwin; Eric Peter;
(Tucson, AZ) ; Williamson; David M.; (Tucson,
AZ) ; Binnard; Michael B.; (Belmont, CA) |
Correspondence
Address: |
Roeder & Broder LLP
5560 Chelsea Avenue
La Jolla
CA
92037
US
|
Assignee: |
Nikon Corporation
Tokyo
JP
|
Family ID: |
41400005 |
Appl. No.: |
12/481447 |
Filed: |
June 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61060411 |
Jun 10, 2008 |
|
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|
61078251 |
Jul 3, 2008 |
|
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61078254 |
Jul 3, 2008 |
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61104477 |
Oct 10, 2008 |
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Current U.S.
Class: |
430/322 ;
355/67 |
Current CPC
Class: |
G03B 27/54 20130101;
G03F 7/70358 20130101 |
Class at
Publication: |
430/322 ;
355/67 |
International
Class: |
G03F 7/20 20060101
G03F007/20; G03B 27/54 20060101 G03B027/54 |
Claims
1. An exposure apparatus for transferring a first mask pattern to a
substrate, the substrate including a first site having a first site
dimension along a first axis and a second site dimension along a
second axis that is perpendicular to the first axis, wherein the
second site dimension is larger than the first site dimension, the
exposure apparatus comprising: an illumination system that
generates a first illumination beam that is used to generate a
first pattern beam that contains the first mask pattern; a
substrate stage assembly that retains and positions the substrate
along the first axis; and a control system that controls the
illumination system, and the substrate stage assembly so that the
first mask pattern is transferred to the first site while the
substrate stage assembly is moving the substrate along the first
axis.
2. The exposure apparatus of claim 1 further comprising a
projection optical assembly that focuses the first pattern beam on
the substrate; wherein the projection optical assembly includes a
used field having a first field dimension along the first axis and
a second field dimension along the second axis, wherein the first
field dimension is smaller than the second field dimension.
3. The exposure apparatus of claim 2 wherein the first field
dimension is shorter than the first site dimension and the second
field dimension is equal to or greater than the second site
dimension.
4. The exposure apparatus of claim 1 further comprising a first
mask that includes the first mask pattern and a first mask stage
assembly that retains and positions the first mask along the first
axis relative to the first illumination beam, wherein the first
pattern beam is created by directing the first illumination beam at
the first mask pattern, and wherein the control system controls the
first mask stage assembly so that the first mask stage assembly is
moving the first mask along the first axis while the first mask
pattern is being transferred to the first site.
5. The exposure apparatus of claim 4 further comprising a second
mask stage assembly that retains and positions a second mask,
wherein the illumination system generates a second illumination
beam that is directed at the second mask, wherein the second
illumination beam illuminates a second mask pattern of the second
mask to generate a second pattern beam, and wherein the optical
assembly focuses the first pattern beam and the second pattern beam
on the substrate.
6. The exposure apparatus of claim 5 wherein the substrate further
includes a second site, and wherein the control system controls the
illumination system, the mask stage assemblies and the substrate
stage assembly to transfer an image of the first mask pattern to
the first site, and an image of the second mask pattern to the
second site.
7. The exposure apparatus of claim 6 wherein the control system
controls the substrate stage assembly to continuously move the
substrate along the first axis when transferring the images to the
first site and the second site.
8. The exposure apparatus of claim 7 wherein the control system
controls the substrate stage assembly to move the substrate a
movement step along the second axis after the second mask pattern
is transferred to the second site.
9. The exposure apparatus of claim 4 wherein the control system
controls the illumination system, the first mask stage assembly and
the substrate stage assembly so that the entire first mask pattern
is transferred to the first site while the first mask stage
assembly is moving the first mask along the first axis, and the
substrate stage assembly is moving the substrate along the first
axis.
10. The exposure apparatus of claim 1 wherein the control system
controls the substrate stage assembly to move the substrate a
movement step along the second axis after the first mask pattern is
transferred to the first site.
11. A process for manufacturing a wafer that includes the steps of
providing a substrate having a first site and a second site, and
transferring the first mask pattern to the first site and the
second site of the substrate with the exposure apparatus of claim
1.
12. A method for transferring a first mask pattern to a substrate,
the substrate including a first site having a first site dimension
along a first axis and a second site dimension along a second axis
that is perpendicular to the first axis, wherein the second site
dimension is larger than the first site dimension, the method
comprising the steps of: directing a first pattern beam that
contains the first mask pattern at the substrate; positioning the
substrate along the first axis with a substrate stage assembly; and
controlling the illumination system, and the substrate stage
assembly with a control system so that the first mask pattern is
transferred to the first site while the substrate stage assembly is
moving the substrate along the first axis.
13. The method of claim 12 wherein the step of directing includes
the steps of illuminating the first mask pattern with a first
illumination beam from an illumination system to generate the first
pattern beam, and focusing the first pattern beam on the substrate
with an optical assembly.
14. The method of claim 13 wherein the step of focusing includes
the optical assembly including a used field having a first field
dimension along the first axis and a second field dimension along
the second axis, wherein the first field dimension is smaller than
the second field dimension.
15. The method of claim 14 wherein the step of focusing includes
the first field dimension being shorter than the first site
dimension and the second field dimension being equal to or greater
than the second site dimension.
16. The method of claim 13 further comprising the steps of
positioning a second mask with a second mask stage assembly,
generating a second illumination beam that is directed at the
second mask with the illumination system, illuminating a second
mask pattern of the second mask with the second illumination beam
to generate a second pattern beam, and focusing the first pattern
beam and the second pattern beam on the substrate with the optical
assembly.
17. The method of claim 16 wherein the substrate further includes a
second site, and wherein the step of controlling includes the step
of controlling the illumination system, the mask stage assemblies
and the substrate stage assembly with the control system so that an
image of the first mask pattern is transferred to the first site,
and an image of the second mask pattern is transferred to the
second site.
18. The method of claim 17 wherein the step of controlling includes
the step of controlling the substrate stage assembly with the
control system to continuously move the substrate along the first
axis when transferring the images to the first site and the second
site.
19. The method of claim 17 further comprising the step of moving
the substrate a movement step along the second axis after the
second mask pattern is transferred to the second site.
20. The method of claim 12 wherein the step of controlling includes
the step of controlling the illumination system, and the substrate
stage assembly with the control system so that the entire first
mask pattern is transferred to the first site while the substrate
stage assembly is moving the substrate along the first axis.
21. The method of claim 1 2 further comprising the step of
controlling the substrate stage assembly with the control system to
move the substrate a movement step along the second axis after the
first mask pattern is transferred to the first site.
Description
RELATED APPLICATIONS
[0001] This application claims priority on U.S. Provisional
Application Ser. No. 61/060,411, filed Jun. 10, 2008 and entitled
"SYSTEM ARCHITECTURE FOR ACHIEVING HIGHER SCANNER THROUGHPUT"; on
U.S. Provisional Application Ser. No. 61/078,251, filed Jul. 3,
2008 and entitled "HIGH NA CATADIOPTRIC PROJECTION OPTICS FOR
IMAGING TWO RETICLES ONTO ONE WAFER"; on U.S. Provisional
Application Ser. No. 61/078,254 filed on Jul. 3, 2008 and entitled
"X-SCANNING EXPOSURE SYSTEM WITH CONTINUOUS EXPOSURE"; and on U.S.
Provisional Application Ser. No. 61/104,477 filed on Oct. 10, 2008.
As far as is permitted, the contents of U.S. Provisional
Application Ser. Nos. 61/060,411, 61/078,251, 61/078,254 and
61/104,477 are incorporated herein by reference.
BACKGROUND
[0002] Exposure apparatuses for semiconductor processing 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 positions a reticle, a projection optical assembly,
and a wafer stage assembly that positions a semiconductor
wafer.
[0003] As illustrated in prior art FIG. 1A, each wafer 1P is
typically divided into a plurality of rectangular shaped integrated
circuits 2P (sometimes referred to as "sites"). Further, each site
2P has a first site dimension 3P along a first axis (e.g. the X
axis), and a second site dimension 4P along a second axis (e.g. the
Y axis). Typically, the second site dimension 4P is greater than
the first site dimension 3P. For example, a common site 2P has a
first site dimension 3P of twenty-six millimeters and a second site
dimension 4P of thirty-three millimeters.
[0004] There are two kinds of exposure apparatuses that are
generally known and currently used. The first kind is commonly
referred to as a Stepper lithography system. In a Stepper
lithography system, the reticle is fixed (except for slight
corrections in position) and the wafer stage assembly moves the
wafer to fixed chip sites where the illumination source directs an
illumination beam at an entire reticle pattern on the reticle. This
causes the entire reticle pattern to be exposed onto one of the
chip sites of the wafer at one time. At the time of exposure, the
reticle and the wafer are stationary. After the exposure, the wafer
is moved ("stepped") to the next site for subsequent exposure.
[0005] The second kind of system is commonly referred to as a
Scanner lithography system. In a Scanner lithography system, the
reticle stage assembly moves the reticle in one direction along a
scan axis 5P (the second axis) concurrently with the wafer stage
assembly moving the wafer in one direction along the scan axis 5P
during the exposure of a first site 1S. With this system, the
illumination beam is slit shaped and illuminates only a portion of
the reticle pattern on the reticle. This causes a slit shaped
pattern beam 6P to be imaged onto the wafer 1P. This pattern beam
6P exposes only a portion of the first site 1S at a given moment,
and the entire reticle pattern is exposed and transferred to the
first site 1S over time as the reticle pattern is moved relative to
the illumination beam. After exposure of the first site 1S, the
wafer 1P is stepped along a step axis 7P (the first axis) and
subsequently a second site 2S is scanned while moving the wafer 1P
in the opposite direction along the scan axis 5P. With this design,
each site 1S, 2S is scanned along the second axis (the longer
dimension of the site).
[0006] In FIG. 1A, dashed line 11P illustrates an exposure pattern
11P of the first row of sites 2P on the wafer 1P. The exposure
pattern 11P comprises a plurality of scanning operations 13P and a
plurality of stepping operations 15P, wherein the scanning
operations 13P and the stepping operations 15P alternate so that
the exposure proceeds in a scan-step-scan-step-scan fashion. As
illustrated, and as noted above, the scanning of each site 2P
occurs across the second site dimension 4P and the steps between
each site 2P occurs along the first axis. This typically results in
scanning times and stepping times that are nearly equal to each
other.
[0007] The throughput capacity of an exposure apparatus used in
lithography is often quoted in the number of wafers that can be
printed per hour (WPH). Throughput depends on many factors, such as
the reticle stage and wafer stage performances, nozzle capabilities
(for immersion type exposure apparatuses), and available power for
the illumination system.
[0008] Additionally, the optical assembly is one of the limiting
factors in the performance of a lithography system. More
specifically, the optical assembly is thought of as limiting the
performance in terms of the resolution, or smallest printable
feature. One design tradeoff that is utilized includes keeping a
used field of the optical assembly as small as possible to minimize
aberrations. For example, FIG. 1B illustrates a field of view 17P
(illustrated with a dashed circle) for a prior art optical assembly
having a numerical aperture (NA) of 1.30. In this example, the
field of view 17P defines a substantially rectangular used field
19P. In the example provided above, to expose a site that is
twenty-six millimeters by thirty-three millimeters, the used field
19P has a first field dimension 21P of about twenty-six millimeters
along the first axis, and a second field dimension 23P of about
five millimeters along the second axis. These measurements are
specified at the wafer plane. The corresponding dimensions at the
reticle plane are determined by the magnification ratio of the
projection optical assembly. For example, in a 4.times. reduction
machine, the reticle dimensions are 4.times. bigger.
[0009] Additionally, in order to further minimize or correct
aberrations at such a high NA, the optical assembly is
catadioptric. This requires the used field 19P to be off-axis in
order to avoid obscurations from the relative surfaces. In one
prior art design, the closest edge of the used field 19P has an
offset distance 25P of about 2.5 millimeters from an optical axis
27P. This means the diagonal of the point in the used field 19P
farthest from the optical axis 27P is 15.01 millimeters, and the
field of view 17P has a field diameter of 30.02 millimeters, as
explained in Equation 1.
2* {square root over (13.sup.2+(5+2.5).sup.2)}=30.02 mm (Equation
1)
[0010] Using the specifications for one embodiment of a prior
system, where there are 125 chips per wafer, each chip is
16.times.32 mm, average wafer stage acceleration of 2.5G in the X
axis and the Y axis, an average reticle stage acceleration of 10G,
and a wafer stage scan velocity of 0.7 m/s, the maximum possible
throughput is 246 WPH (assuming no overhead time between
wafers).
[0011] As is known, there is a never ending search to increase the
throughput in exposure apparatuses.
SUMMARY
[0012] The present invention is directed to an exposure apparatus
for transferring a first mask pattern from a first mask to a
substrate. The substrate includes a first site having a first site
dimension along a first axis and a second site dimension along a
second axis that is perpendicular to the first axis. The second
site dimension is larger than the first site dimension.
[0013] In one embodiment, the exposure apparatus includes an
illumination system, a first mask stage assembly, a substrate stage
assembly, and a control system. The illumination system generates a
first illumination beam that is directed at the first mask. The
first mask stage assembly retains and positions the first mask
along the first axis relative to the first illumination beam. The
substrate stage assembly retains and positions the substrate along
the first axis. The control system controls the illumination
system, the first mask stage assembly and the substrate stage
assembly so that a portion of the first mask pattern is transferred
to a portion of the first site while the first mask stage assembly
is moving the first mask along the first axis, and the substrate
stage assembly is moving the substrate along the first axis.
[0014] With this design, one or more of the sites of the substrate
are scanned along their short dimension. As a result thereof, the
throughput of the exposure apparatus can be improved.
[0015] In certain embodiments, the first illumination beam
illuminates the first mask pattern to generate a first pattern
beam. In this embodiment, the exposure apparatus further comprises
an optical assembly that focuses the first pattern beam on the
substrate. Additionally, the optical assembly includes a used field
having a first field dimension along the first axis and a second
field dimension along the second axis, wherein the first field
dimension is smaller than the second field dimension. In one such
embodiment, the second field dimension is between approximately
thirty millimeters and thirty-five millimeters. Further, in this
embodiment, the first field dimension can be between approximately
1.5 mm and 5 mm. Still further, in one embodiment, the first field
dimension is shorter than the first site dimension and the second
field dimension is equal to or greater than the second site
dimension. As provided herein, the design of the optical assembly
provided herein allows for the scanning of the sites along their
short dimension.
[0016] In one embodiment, the exposure apparatus further comprises
a second mask stage assembly that retains and positions a second
mask. In this embodiment, the illumination system generates a
second illumination beam that is directed at the second mask.
Additionally, the second illumination beam illuminates a second
mask pattern of the second mask to generate a second pattern beam.
Further, in this embodiment, the optical assembly focuses the first
pattern beam and the second pattern beam on the substrate.
[0017] In some embodiments, the substrate may further include a
second site, and the control system may control the illumination
system, the mask stage assemblies and the substrate stage assembly
to transfer an image of the first mask pattern to the first site,
and an image of the second mask pattern to the second site. In one
such embodiment, the control system controls the substrate stage
assembly to continuously move the substrate at a constant velocity
along the first axis when transferring the images to the first site
and the second site. With this design, multiple sites can be
exposed between stepping of the substrate. This improves the
throughput of the exposure apparatus.
[0018] The present invention is further directed to a method for
transferring a first mask pattern from a first mask to a substrate,
a method for making an exposure apparatus, and a method of
manufacturing a wafer with the exposure apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] 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:
[0020] FIG. 1A is a simplified illustration of a prior art exposure
pattern on a wafer;
[0021] FIG. 1B is a simplified illustration of a field of view for
a prior art optical assembly;
[0022] FIG. 2 is a schematic illustration of a first embodiment of
an exposure apparatus having features of the present invention;
[0023] FIG. 3A is a simplified top illustration of a substrate and
an exposure pattern having features of the present invention;
[0024] FIG. 3B is a simplified top illustration of a field of view
for an optical assembly having features of the present
invention;
[0025] FIG. 3C is a simplified top illustration of the mask and a
portion of the substrate at the beginning of a scanning procedure
on a first site;
[0026] FIG. 3D is a simplified top illustration of the mask and a
portion of the substrate at the end the scanning procedure on the
first site;
[0027] FIG. 3E is a simplified top illustration of the mask and a
portion of the substrate at the beginning of a scanning procedure
on a second site;
[0028] FIG. 3F is a simplified illustration of an optical assembly
having features of the present invention;
[0029] FIG. 4 is a schematic illustration of a second embodiment of
an exposure apparatus having features of the present invention;
[0030] FIG. 5A is a simplified top view of an embodiment of a
substrate exposed by the exposure apparatus of FIG. 4;
[0031] FIG. 5B is a simplified illustration of a field of view of
an embodiment of an optical assembly having features of the present
invention;
[0032] FIG. 6A is a simplified side view of a first mask, a second
mask, an optical assembly, and a substrate at a beginning of an
exposure of a first site;
[0033] FIG. 6B is a simplified side view of the first mask, the
second mask, the optical assembly, and the substrate at a beginning
of an exposure of a second site;
[0034] FIG. 6C is a simplified side view of the first mask, the
second mask, the optical assembly, and the substrate at a beginning
of an exposure of a third site;
[0035] FIG. 6D is a simplified side view of the first mask, the
second mask, the optical assembly, and the substrate at a beginning
of an exposure of a fourth site;
[0036] FIGS. 7A-7I illustrate one embodiment of the exposure of
four sites;
[0037] FIGS. 8A-8I illustrate another embodiment of the exposure of
four sites;
[0038] FIGS. 9A-98I illustrate yet another embodiment of the
exposure of four sites;
[0039] FIGS. 10A-10D illustrate one embodiment of the exposure of
one site;
[0040] FIGS. 11A-11D illustrate another embodiment of the exposure
of one site;
[0041] FIG. 12 is a schematic illustration of the first mask, the
second mask, the substrate, and an embodiment of an optical
assembly having features of the present invention;
[0042] FIG. 13 is a simplified perspective view of portion of
another embodiment of an exposure apparatus having features of the
present invention;
[0043] FIG. 14 is a simplified top view of an embodiment of a
substrate exposed utilizing the exposure apparatus illustrated in
FIG. 13;
[0044] FIG. 15A is a flow chart that outlines a process for
manufacturing a device in accordance with the present invention;
and
[0045] FIG. 15B is a flow chart that outlines device processing in
more detail.
DESCRIPTION
[0046] FIG. 2 is a schematic illustration of a precision assembly,
namely an exposure apparatus 210 that transfers features from a
mask 212 to a substrate 214 such as a semiconductor wafer that
includes a plurality of sites 315 (illustrated in FIG. 3A). The
design of the exposure apparatus 210 can be varied to achieve the
desired throughput, and quality and density of the features on the
substrate 214. In FIG. 2, the exposure apparatus 210 includes an
apparatus frame 216, an illumination system 218 (irradiation
apparatus), a projection optical assembly 220, a mask stage
assembly 222, a substrate stage assembly 224, a measurement system
226, and a control system 228. Further, the exposure apparatus 210
mounts to a mounting base 230, e.g., the ground, a base, or a
floor, or some other supporting structure.
[0047] As an overview, in certain embodiments, the projection
optical assembly 220 is designed to have a larger field of view 331
(illustrated in FIG. 3B) and/or one or more of the sites 315 of the
substrate 214 are scanned along their short dimension. Further, in
certain embodiments, the exposure apparatus 410 (illustrated in
FIG. 4) is designed to use multiple masks 412 to sequentially
expose adjacent sites 315. These features can increase the
throughput capabilities of the exposure apparatuses 210, 410.
[0048] 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 axes. It should be
noted that any of these axes can also be referred to as the first,
second, and/or third axes.
[0049] The exposure apparatus 210 discussed herein is particularly
useful as a photolithography system for semiconductor manufacturing
that transfers features from a reticle (the mask 212) to a wafer
(the substrate 214). However, the exposure apparatus 210 provided
herein is not limited to a photolithography system for
semiconductor manufacturing. The exposure apparatus 210, for
example, can be used as an LCD photolithography system that exposes
a liquid crystal display device pattern onto a glass plate or a
photolithography system for manufacturing a thin film magnetic
head. Further, in certain embodiments, the concepts of the present
invention can be utilized in a maskless exposure apparatus.
[0050] The apparatus frame 216 is rigid and supports the components
of the exposure apparatus 210. The apparatus frame 216 illustrated
in FIG. 2 supports the mask stage assembly 222, the projection
optical assembly 220, the illumination system 218, and the
substrate stage assembly 224 above the mounting base 230.
[0051] The illumination system 218 includes an illumination source
232 and an illumination optical assembly 234. The illumination
source 232 emits an illumination beam 235 (irradiation) of light
energy. The illumination optical assembly 234 guides the
illumination beam 235 from the illumination source 232 to near the
mask 212. The illumination beam 235 illuminates the mask 212 to
generate a pattern beam 236 (e.g. images from the mask 212) that
exposes the substrate 214. In one embodiment, the illumination beam
235 is generally slit shaped and illuminates only a portion of the
mask 212 at any given moment. Similarly, the pattern beam 236 is
generally slit shaped and exposes only a portion of the substrate
214 at any given moment. In the embodiment illustrated in FIG. 2,
the mask stage assembly 222 moves the mask 212 back and forth along
the first axis (e.g. the X axis) during scanning of the sites
315.
[0052] In FIG. 1, the mask 212 is at least partly transparent, and
the illumination beam 235 is transmitted through a portion of the
mask 212. Alternatively, the mask 212 can be reflective, and the
illumination beam 235 can be directed at the mask 212 and reflected
off of the mask 212.
[0053] The illumination source 232 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 an F.sub.2 laser (157 nm). Alternatively,
the illumination source 232 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.
[0054] The projection optical assembly 220 projects and/or focuses
the pattern beam 236 from the mask 212 to the substrate 214.
Depending upon the design of the exposure apparatus 210, the
projection optical assembly 220 can magnify or reduce the pattern
beam 236. In one non-exclusive embodiment, the projection optical
assembly 220 reduces the pattern beam 236 by a reduction factor of
four. As a result thereof, during the exposure of a site 315, the
mask stage assembly 222 must move the mask 212 a distance that is
four times greater than a distance in which the substrate stage
assembly 224 moves the substrate 214. Stated in another fashion, if
the projection optical assembly 220 has a reduction factor of 4,
the substrate 214 is moved at a rate that is one fourth that of the
mask 212.
[0055] In certain embodiments, as discussed in more detail below,
the projection optical assembly 220 includes a plurality of optical
elements 220A (illustrated in phantom in FIG. 2) that are designed
and arranged so that the projection optical assembly 220 will have
a relatively large field of view 331 so that one or more of the
sites 315 of the substrate 214 can be scanned along their short
dimension. A discussion of possible fields of view 331 for the
projection optical assembly 220 is described in more detail
below.
[0056] The mask stage assembly 222 holds and positions the mask 212
relative to the projection optical assembly 220 and the substrate
214. The mask stage assembly 222 can include (i) a mask stage 237
having a chuck (not shown) for holding the mask 212, and (ii) a
mask stage mover assembly 238 that moves and positions the mask
stage 237 and the mask 212. For example, the mask stage mover
assembly 238 can move the mask stage 237 and the mask 212 along the
Y axis, along the X axis, and about the Z axis. Alternatively, for
example, the mask stage mover assembly 238 could be designed to
move the mask stage 237 and the mask 212 with more than three
degrees of freedom, or less than three degrees of freedom. For
example, the mask stage mover assembly 238 can include one or more
linear motors, rotary motors, planar motors, voice coil actuators,
or other type of actuators. In the embodiment illustrated in FIG.
2, the mask stage mover assembly 238 moves the mask 212 along the
first axis (e.g. the X axis) during scanning of the sites 315.
[0057] Somewhat similarly, the substrate stage assembly 224 holds
and positions the substrate 214 with respect to the pattern beam
236. The substrate stage assembly 224 can include (i) a substrate
stage 240 having a chuck (not shown) for holding the substrate 214,
and (ii) a substrate stage mover assembly 242 that moves and
positions the substrate stage 240 and the substrate 214. For
example, the substrate stage mover assembly 242 can move the
substrate stage 240 and the substrate 214 along the Y axis, along
the X axis, and about the Z axis. Alternatively, for example, the
substrate stage mover assembly 242 could be designed to move the
substrate stage 240 and the substrate 214 with more than three
degrees of freedom, or less than three degrees of freedom. For
example, the substrate stage mover assembly 242 can include one or
more linear motors, rotary motors, planar motors, voice coil
actuators, or other type of actuators. In the embodiment
illustrated in FIG. 2, the substrate stage mover assembly 242 moves
the substrate 214 along the first axis (e.g. the X axis) during
scanning of the sites 315 and moves the substrate 214 along the
second axis (e.g. the Y axis) while stepping in between scanning of
the sites 315.
[0058] The measurement system 226 monitors movement of the mask 212
and the substrate 214 relative to the projection optical assembly
220 or some other reference. With this information, the control
system 228 can control the mask stage assembly 222 to precisely
position the mask 212 and the substrate stage assembly 224 to
precisely position the substrate 214. For example, the measurement
system 226 can utilize multiple laser interferometers, encoders,
and/or other measuring devices.
[0059] The control system 228 is connected to the illumination
system 218, the mask stage assembly 222, the substrate stage
assembly 224, and the measurement system 226. The control system
228 receives information from the measurement system 226, and
controls the illumination system 218 and the stage assemblies 222,
224 to precisely position the mask 212 and the substrate 214 and
expose the sites 315. The control system 228 can include one or
more processors and circuits. In FIG. 2, the control system 228 is
illustrated as a single unit. It should be noted that in
alternative embodiments the control system 228 can be designed with
multiple, spaced apart controllers.
[0060] FIG. 3A is a simplified top view of one non-exclusive
embodiment of a substrate 214 that has been processed with the
exposure apparatus 210 of FIG. 2. In this embodiment, the substrate
214 is a generally disk shaped, thin slice of semiconductor
material, e.g. a semiconductor wafer, that serves as a substrate
for photolithographic patterning. Typically, the disk shaped
substrate 214 is divided into a plurality of rectangular shaped
sites 315 (e.g. chips) that are organized into a plurality of rows
(along the X axis) and columns (along the Y axis). As used herein,
the term "site" shall mean an area on the substrate 214 to which
the entire or a portion of the mask pattern 346 (illustrated in
FIG. 3C) has been transferred. For example, for a semiconductor
wafer, each site 315 is one or more integrated circuits that
include a number of connected circuit elements that were
transferred to the substrate 214 by the exposure apparatus 210 of
FIG. 2. In this example, each site 315 contains one or more
integral die piece(s) that can be sliced from the wafer.
[0061] In one embodiment, each site 315 is generally rectangular
shaped and has a first site dimension 348 (measured along the X
axis) that is less than a second site dimension 350 (measured along
the Y axis). In one non-exclusive embodiment, each site 315 has a
first site dimension 348 of approximately twenty-six (26)
millimeters, and a second site dimension 350 of approximately
thirty-three (33) millimeters. Alternatively, for example, each
site 315 can have a first site dimension 348 that is greater than
or less than twenty-six (26) millimeters, and a second site
dimension 350 that is greater than or less than thirty-three (33)
millimeters. For example, each site 315 can have a first site
dimension 348 of approximately sixteen (16) millimeters, and a
second site dimension 350 of approximately thirty-two (32)
millimeters.
[0062] The size of the substrate 214 and the number of sites 315 on
the substrate 214 can be varied. For example, the substrate 214 can
have a diameter of approximately three hundred millimeters.
Alternatively, the substrate 214 can have a diameter that is
greater than or less than three hundred millimeters and/or the
substrate 214 can have a shape that is different than disk shaped
(e.g. rectangular shaped). For example, the substrate 214 can be
circularly shaped with a diameter approximately four hundred fifty
millimeters.
[0063] Further, for simplicity, in the embodiment illustrated in
FIG. 3A, the substrate 214 is illustrated as having fifteen
separate sites 315. Alternatively, for example, the substrate 214
can be separated into greater than or fewer than fifteen sites
315.
[0064] In FIG. 3A, the sites 315 have been labeled "1" through "15"
(one through fifteen). In this example, (i) the sites 315 labeled
"1" through "3" are aligned in a first column along the Y axis;
(ii) the sites 315 labeled "4" through "6" are aligned in a second
column along the Y axis; (iii) the sites 315 labeled "7" through
"9" are aligned in a third column along the Y axis; (iv) the sites
315 labeled "10" through "12" are aligned in a fourth column along
the Y axis; and (v) the sites 315 labeled "13" through "15" are
aligned in a fifth column along the Y axis. Additionally, the
labels "1" through "15" represent one non-exclusive embodiment of a
sequence in which the mask pattern 346 can be transferred to the
sites 315 on the substrate 214. More specifically, as provided
herein, the exposure apparatus 210 can first transfer the mask
pattern 346 to the site 315 labeled "1" (sometimes referred to as
the "first site"). Next, the exposure apparatus 210 can move the
mask 212 (illustrated in FIG. 2) and the substrate 214, and
transfer the mask pattern 346 to the site 315 labeled "2"
(sometimes referred to as the "second site"). Subsequently, and
sequentially, the exposure apparatus 210 can move the mask 212 and
the substrate 214 to sequentially transfer the mask pattern 346 to
the sites 315 labeled "3", "4", "5", . . . and "15".
[0065] Moreover, FIG. 3A includes an exposure pattern 352
(illustrated with a dashed line) which further illustrates the
order in which the mask pattern 346 is transferred to sites "1"
through "3" in the first column. In this example, (i) the sites 315
labeled "1" through "3" are sequentially exposed as the substrate
214 is moved in a weaving (boustrophedonic) fashion and the mask
212 is moved back and forth. More specifically, the exposure
pattern 352 comprises a plurality of scanning operations 354 and a
plurality of stepping operations 356, wherein the scanning
operations 354 and the stepping operations 356 alternate so that
the exposure proceeds in a scan-step-scan-step-scan fashion. As
provided herein, the scanning 354 of each site 315 occurs as the
substrate 214 is moved along a scan axis 358 (i.e., the X axis)
across the first site dimension 348, and the stepping 356 in
between exposures of sites 315 occurs as the substrate 214 is moved
along a step axis 360 (i.e., the Y axis).
[0066] It should be noted that with the design illustrated in FIG.
3A, the scanning operations 354 occur while the substrate 214 is
moved along the first site dimension 348 and stepping operations
356 occur while the substrate 214 is moved along the second site
dimension 350. This results in shorter scanning times and longer
stepping times compared to the prior art.
[0067] It should also be noted that in this example, the site 315
that is exposed first and the order in which the columns are
exposed can be different than that illustrated in FIG. 3A. Further,
the site 315 that is first exposed can be located away from the
edge of the substrate 214
[0068] Additionally, FIG. 3A illustrates the pattern beam 236 that
is directed at the first site "1" on the substrate 214. The pattern
beam 236 is discussed in more detail with reference to FIGS.
3C-3E.
[0069] FIG. 3B is a simplified illustration of one embodiment of a
field of view 331 (illustrated with a dashed circle) of the
projection optical assembly 220 (illustrated in FIG. 2). As used
herein, the term field of view 331 shall mean the maximum image
area over which the projection optical assembly 220 can provide a
sufficiently accurate image of the mask pattern. As provided
herein, in certain embodiments, the field of view 331 of the
projection optical assembly 220 must be relatively large in order
to transfer a relatively large pattern beam 236 (illustrated in
FIG. 3A) to the site 315.
[0070] In one embodiment, the field of view 331 defines a
rectangular shaped used field 362 (illustrated with a box with
"X"'s) that includes a first field dimension 364 that is measured
along the first axis (the X axis) and a second field dimension 366
that is measured along the second axis (the Y axis). In this
embodiment, the second field dimension 366 is larger than the first
field dimension 366.
[0071] In certain embodiments, the projection optical assembly 220
is designed so that the first field dimension 364 is less than the
first site dimension 348 (illustrated in FIG. 3A) and the second
field dimension 366 is equal to or greater than the second site
dimension 350.
[0072] In one non-exclusive example, each site 315 has a first site
dimension 348 of twenty-six (26) millimeters and a second site
dimension 350 of thirty-three (33) millimeters. In this example,
the second field dimension 366 can be approximately thirty-three
(33) millimeters, and the first field dimension 364 is less than
twenty-six (26) millimeters. As non-exclusive examples, the first
field dimension 364 can be approximately 2, 3, 4, 5, or 5.5
millimeters. Further, as non-exclusive examples, the second field
dimension 366 can be approximately 29, 30, 31, 32, 34, or 35
millimeters
[0073] Further, comparing prior art FIG. 1B and FIG. 3B, the used
field 362 of FIG. 3B has been rotated by approximately 90 degrees
from the orientation of the used field 19P in the prior art (as
illustrated in FIG. 1B). In one non-exclusive embodiment, in order
to minimize the impact of the orientation change, the edge of the
used field 362 can be moved closer to an optical axis 368 of the
projection optical assembly 220. In this embodiment, for example,
the offset distance 368A is about 1.25 millimeters, instead of the
prior art design of 2.50 millimeters illustrated in FIG. 1B.
Further, the first field dimension 364 of the used field 362 is
less than the prior art design described above. The resulting
maximum field point is now 16.92 millimeters for a field diameter
368B of 33.84 millimeters as calculated in Equation 2.
2 * 16.5 2 + ( 2.5 + 1.25 ) 2 = 33.84 mm ( 33 mm field height ) (
Equation 2 ) ##EQU00001##
[0074] Additionally, it is important to look at the approximate
gain in throughput obtained by increasing the size of the used
field 362 of the projection optical assembly 220 and changing the
scan direction from across the second site dimension 350 to across
the first site dimension 348.
[0075] More specifically, utilizing a slightly larger used field
362 size of 33 millimeters by 2.5 millimeters for optical assembly
220, scanning the used field 362 across the first site dimension
348 instead of across the second site dimension 350, with an
average wafer stage acceleration of 2.5G in X axis and Y axis, an
average mask 212 acceleration of 10G, and a substrate 214 scan
velocity of 0.7 m/s, the maximum throughput is 274 wafers per hour.
The gain is 28 WPH, or an 11.5% gain in throughput over the prior
art described in the background. Alternatively, in certain
embodiments, the idea of scanning the used field 362 across the
first field dimension 364 could be used to decrease the
requirements for acceleration and maximum scanning velocity of the
substrate stage assembly 224 (illustrated in FIG. 2) and/or the
mask stage assembly 222 (illustrated in FIG. 2), while still
maintaining the same or better throughput than is possible in the
prior art.
[0076] FIG. 3C is a simplified top illustration of the mask 212 and
a portion of the substrate 214 in a side-by-side arrangement, at
the start of an exposure of the first site 1 (illustrated as a
box). It should be noted that the components of the exposure
apparatus 210 (illustrated in FIG. 2) are not shown in FIGS. 3C-3E
for clarity. Further, it should also be noted that the mask 212 and
the substrate 214 are shown in a side-by-side arrangement during
exposure and that FIGS. 3C-3E are only illustrated in this
configuration so that the relative positions of these components
can be better understood. Additionally, in these Figures, the mask
pattern 346 is illustrated as being approximately the same size as
each site 315. However, in the event that the projection optical
assembly 220 has a reduction factor of 4, the mask pattern 346 can
be four times larger than the size of each site 315. Moreover, FIG.
3C also illustrates at least a portion of sites 2 through 9. In
this embodiment, each site 315 includes a site left side 315A, an
opposed site right side 315B, and a site center 315C (only one is
illustrated with a FIG. 3C illustrates that the mask 212 includes
the mask pattern 346 (illustrated as a box) that includes the
features that are to be transferred to the substrate 214. In this
embodiment, the mask pattern 346 includes a pattern left side 346A,
and opposed pattern right side 346B, and a pattern center 346C
(illustrated as with a "+").
[0077] At the start of exposure of the first site 1, the control
system 228 (illustrated in FIG. 2) controls the illumination system
218 (illustrated in FIG. 2) to generate the slit shaped
illumination beam 235 (illustrated as "o"'s) that is directed at
the mask 212, and controls the mask stage assembly 222 (illustrated
in FIG. 2) to position the mask 212 so that the mask pattern 346 is
illuminated near the pattern left side 346A. This causes the
resulting pattern beam 236 (illustrated as "\"'s) to be directed at
a corresponding portion of the first site 1. In the illustrations,
the left side of the mask pattern area corresponds to the left side
of the substrate site. Depending on the optical design, however,
the image may be reversed, so the right side of the mask pattern
area corresponds to the left side of the substrate site.
[0078] At the beginning of the exposure of the first site 1, (i)
the pattern center 346C is located at a first mask position, which
is referenced as Xm1 along the scan axis 358 and Ym1 along the step
axis 360, and (ii) the site center 315C of the first site 1 is
located at a site first position, which is referenced as Xs1 along
the scan axis 358 and Ys1 along the step axis 360.
[0079] Further, at the beginning of the exposure, the control
system 228 (illustrated in FIG. 2) (i) controls the mask stage
assembly 222 so that the mask 212 is being moved at a constant
velocity in a first scan direction 370A (from right to left in FIG.
3A) along the scan axis 358 (the X axis), and (ii) controls the
substrate stage assembly 224 (illustrated in FIG. 2) so that the
substrate 214 is also being moved at a constant velocity in the
first scan direction 370A along the scan axis 358. With the present
design, in certain embodiments, both the mask 212 and the substrate
214 are moved synchronously in the same scan direction 370A.
Further, for example, if the projection optical assembly 220
(illustrated in FIG. 2) has a reduction factor of four, the mask
212 is moved at a rate that is four times greater than that of the
substrate 214. Alternatively, the mask 212 and substrate 214 can be
moved in opposite directions along the scan axis 358 during
scanning of the sites 315.
[0080] Additionally, as illustrated in FIG. 3C, the pattern beam
236 is generally rectangular slit shaped and includes a first beam
dimension 372 along the first axis (the X axis) and a second beam
dimension 374 along the second axis (the Y axis). In this
embodiment, the second beam dimension 374 is larger than the first
beam dimension 372. In certain embodiments, the exposure apparatus
210 (illustrated in FIG. 2) is designed so that the first beam
dimension 372 is less than the first site dimension 348
(illustrated in FIG. 3A) and the second beam dimension 374 is equal
to the second site dimension 350 (illustrated in FIG. 3A). In one
non-exclusive example, each site 315 has a first site dimension 348
of twenty-six (26) millimeters and a second site dimension 350 of
thirty-three (33) millimeters. In this example, the second beam
dimension 374 can be approximately thirty-three (33) millimeters,
and the first beam dimension 372 is less than twenty-six (26)
millimeters. As non-exclusive examples, the first beam dimension
372 can be approximately 2, 3, 4, 5, or 5.5 millimeters.
Alternatively, for example, the second beam dimension 374 can be
approximately 29, 30, 31, 32, 34, or 35 millimeters.
[0081] FIG. 3D is a simplified top illustration of the mask 212 and
a portion of the substrate 214 in a side-by-side arrangement, at
the end of the exposure of the first site 1. At this time, the
control system 228 (illustrated in FIG. 2) controls the
illumination system 218 (illustrated in FIG. 2) to generate the
slit shaped illumination beam 235 (illustrated as "o"'s) that is
directed at the mask 212, and controls the mask stage assembly 222
(illustrated in FIG. 2) to position the mask 212 so that the mask
pattern 346 is illuminated near the pattern right side 346B. This
causes the resulting pattern beam 236 (illustrated as "\"'s) to be
directed at a portion of the first site 1.
[0082] At the end of the exposure of the first site 1, (i) the
pattern center 346C is located at a second mask position, which is
referenced as Xm2 along the scan axis 358 and Ym1 along the step
axis 360, and (ii) the site center 315C of the first site 1 is
located at a site second position, which is referenced as Xs2 along
the scan axis 358 and Ys1 along the step axis 360.
[0083] It should be noted that (i) the difference between the first
mask position Xm1 and the second mask position Xm2 along the scan
axis 358 is referred to herein as a mask exposure distance 376, and
(ii) the difference between the first substrate position Xs1 and
the second substrate position Xs2 along the scan axis 358 is
referred to herein as a site exposure distance 378. In this
example, (i) the mask exposure distance 376 is the distance in
which the mask 212 is moved along the scan axis 358 during the
exposure (i.e., the scanning operation 354 as illustrated in FIG.
3A) of the first site 1, and (ii) the site exposure distance 378 is
the distance in which the substrate 314 is moved along the scan
axis 358 during the exposure of the first site 1.
[0084] For clarity, in FIG. 3D, the mask exposure distance 376 is
illustrated as being equal to the site exposure distance 378.
Alternatively, in the event the projection optical assembly 220
(illustrated in FIG. 1) has a reduction factor of four, the mask
exposure distance 376 is four times larger than the site exposure
distance 378.
[0085] Referring to FIGS. 3C and 3D, it should also be noted that
the entire mask pattern 346 is scanned to the first site 1 during
movement of the mask 212 the mask exposure distance 376.
Additionally, the exposure of the first site 1 is halted once the
pattern beam 236 is directed at the pattern right side 346B.
[0086] Further, it should be noted that during the exposure of the
sites 315 (i.e., during the scanning operations 354), the control
system 228 controls the mask stage assembly 222 so that the mask
212 is approximately not moved along the step axis 360 (the Y
axis), and the control system 228 controls the substrate stage
assembly 224 (illustrated in FIG. 2) so that the substrate 214 is
approximately not moved along the step axis 360 (the Y axis).
Moreover, during scanning, both the mask 212 and the substrate 214
are moved at a constant velocity along the scan axis 358.
[0087] FIGS. 3E is a simplified top illustration of the mask 212
and a portion of the substrate 214 in a side-by-side arrangement,
at the start of an exposure of the second site 2. At this time, the
control system 228 (illustrated in FIG. 2) controls the
illumination system 218 (illustrated in FIG. 2) to generate the
slit shaped illumination beam 235 (illustrated as "o"'s) that is
directed at the mask 212, and controls the mask stage assembly 222
(illustrated in FIG. 2) to position the mask 212 so that the mask
pattern 346 is illuminated near the pattern right side 346B. This
causes the resulting pattern beam 236 (illustrated as "\"'s) to be
directed at a corresponding portion of the second site 2.
[0088] At the beginning of the exposure of the second site 2, (i)
the pattern center 346C is again located at the second mask
position, which is referenced as Xm2 along the scan axis 358 and
Ym1 along the step axis 360, and (ii) the site center 315C of the
first site 1 is located at a site third position, which is
referenced as Xs2 along the scan axis 358 and Ys2 along the step
axis 360.
[0089] Basically, in between exposures (i.e., during the stepping
operations 356 as illustrated in FIG. 3A), (i) the substrate 214 is
stepped with the substrate stage assembly 224 (illustrated in FIG.
2) so that the second site 2 is being moved towards the field of
view 331 (illustrated in FIG. 3B) of the projection optical
assembly 220 (illustrated in FIG. 2), and (ii) the position of the
mask pattern 346 is reset along the scan axis 358 to the second
mask position Xm2 with the mask stage assembly 222 (illustrated in
FIG. 2). It should be noted that the mask pattern 346 is moved past
the second mask position Xm2 after the exposure because the mask
212 is moved at a constant velocity during the entire exposure and
the mask 212 must be decelerated after the exposure. The mask is
subsequently accelerated back toward the second mask position Xm2
prior to the next exposure, so that the mask 212 can again be moved
at a constant velocity from the second mask position Xm2 to the
first mask position Xm1 during the subsequent exposure of the
second site 2.
[0090] It should also be noted that the difference between the site
first position Ys1 and the site third position Ys2 along the step
axis 358 is referred to herein as a site step distance 380. In this
example, the site step distance 380 is the distance in which the
substrate 314 is moved along the step axis 360 between the exposure
of the first site 1 and the exposure of the second site 2 (i.e.,
during the stepping operation 356).
[0091] Further, at the beginning of the exposure, the control
system 228 (illustrated in FIG. 2) (i) controls the mask stage
assembly 222 so that the mask 212 is being moved at a constant
velocity in a second scan direction 370B (from left to right in
FIG. 3A) along the scan axis 358 (the X axis) from the second mask
position Xm2 back toward the first mask position Xm1, and (ii)
controls the substrate stage assembly 224 (illustrated in FIG. 2)
so that the substrate 214 is also being moved at a constant
velocity in the second scan direction 370B along the scan axis 358
from Xs2 back toward Xs1. With the present design, in certain
embodiments, both the mask 212 and the substrate 214 are moved
synchronously in the same scan direction 370B. Further, for
example, if the projection optical assembly 220 (illustrated in
FIG. 2) has a reduction factor of four, the mask 212 is moved at a
rate that is four times greater than that of the substrate 214.
Alternatively, as noted above, the mask 212 and substrate 214 can
be moved in opposite directions along the scan axis 358 during
scanning of the sites 315.
[0092] FIG. 3F is a simplified illustration of one non-exclusive
embodiment of the projection optical assembly 220. In this
embodiment, the projection optical assembly 220 includes the
plurality of spaced apart optical elements 220A and an optical
housing 382A. In this embodiment, the projection optical assembly
220 has an optical axis 382B and the optical elements 220A are
aligned along the optical axis 382B.
[0093] As provided herein, the design, positioning, and number of
optical elements 220A can be varied to achieve the relatively large
field of view 331 (illustrated in FIG. 3B) and described above so
that one or more of the sites 315 (illustrated in FIG. 3A) of the
substrate 214 (illustrated in FIG. 3A) can be scanned along their
short dimension. In FIG. 3F, the projection optical assembly 220 is
illustrated as having eleven optical elements 220A. Alternatively,
the projection optical assembly 220 can be designed with greater or
fewer than eleven optical elements 220A. As provided herein, the
number of optical elements 220A can be greater than what is typical
utilized in prior art projection optical assemblies to cancel
off-axis aberrations. In FIG. 3F, the optical elements 220A are
aligned along the common optical axis 382B. Alternatively, the
optical path can be folded to allow for the use of additional
optical elements 220A for aberration correction without increasing
the distance between the mask and the substrate.
[0094] In one embodiment, one or more of the optical elements 220A
is a lens that is made of high quality fused silica (SiO2).
Alternatively, one or more of the optical elements 220A can be made
of another material.
[0095] In one embodiment, in order to achieve a larger field of
view 331, one or more of the optical elements 220A can have an
element diameter 320B that is greater than approximately three
hundred fifty millimeters (350 mm). For example, in alternative
non-exclusive embodiments, one or more of the optical elements 220A
can have an element diameter 320B that is greater than
approximately 360, 370, 375, 380, 385, or 390 millimeters.
[0096] Further, in order to achieve a larger field of view 331 with
less off-axis aberrations, a separation distance 320C between a top
of an uppermost element 320U of the projection optical assembly 220
and a bottom of a lowermost element 320L can be greater than
approximately 1.4 meters. For example, in alternative non-exclusive
embodiments, the separation distance 320C can be greater than
approximately 1.5, 1.6, 1.7, 1.8, 1.9, or 2 meters for a NA=1.3
system.
[0097] FIG. 4 is a schematic illustration of a second embodiment of
an exposure apparatus 410 having features of the present invention.
In FIG. 4, the exposure apparatus 410 includes an apparatus frame
416, an illumination system 418, an optical assembly 420, a first
mask stage assembly 422A, a second mask stage assembly 422B, a
substrate stage assembly 424, a measurement system 426, and a
control system 428. Many of these components are similar in design
to the corresponding similarly named components described above and
illustrated in FIG. 2.
[0098] In this embodiment, the exposure apparatus 410 utilizes
multiple masks 412A, 412B to transfer images to a substrate 414
that includes a plurality of sites 415. With this embodiment, in
certain embodiments, the masks 412A, 412B are substantially
identical in design, and at least two adjacent sites 415 on the
substrate 414 can be sequentially exposed without stopping the
substrate 414 and without changing the movement direction of
substrate 414. Stated in another fashion, at least two sites 415
can be scanned without stepping the substrate 414. This allows for
higher overall throughput for the exposure apparatus 410.
[0099] Further, in this embodiment, the exposure apparatus 410 is a
scanning type photolithography system (i) that first exposes a
first mask pattern 429A from the first mask 412A onto one of the
sites 415 of the substrate 414 while the first mask 412A and the
substrate 414 are moving synchronously, and (ii) that subsequently
exposes a second mask pattern 429B from the second mask 412B onto
an adjacent site 415 on the substrate 414 while the second mask
412B and the substrate 414 are moving synchronously. Alternatively,
the masks 412A, 412B can be different in design and the exposure
apparatus 410 can be used to scan both the first mask pattern 429A
and the second mask pattern 429B onto the same site 415,
simultaneously or at different times.
[0100] An additional discussion of a multiple mask exposure system
is disclosed in concurrently filed application Ser. No. ______,
entitled "EXPOSURE APPARATUS THAT UTILIZES MULTIPLE MASKS"
(PA1017-00/4990/Roeder Ref. No.11269.156), which is assigned to the
assignee of the present invention, and is incorporated by reference
herein as far as permitted.
[0101] An additional discussion regarding another type of exposure
apparatus is disclosed in concurrently filed application Ser. No.
______, entitled "EXPOSURE APPARATUS WITH SCANNING ILLUMINATION
BEAM" (PAO1003-00/04982/Roeder Ref. No. 11269.177), which is
assigned to the assignee of the present invention, and is
incorporated by reference herein as far as permitted.
[0102] The illumination system 418 generates a first illumination
beam 435A (irradiation) of light energy that is selectively
directed at the first mask 412A, and a second illumination beam
435B (irradiation) of light energy that is selectively directed at
the second mask 412B. In certain embodiments, the illumination
system 418 generates both illumination beams 435A, 435B at the same
time. Alternatively, in certain designs, the illumination system
418 will sequentially generate the illumination beams 435A, 435B
during the sequential exposure of the sites 415.
[0103] In one embodiment, the illumination system 418 includes (i)
a first illumination source 432A that emits the first illumination
beam 435A; (ii) a first illumination optical assembly 434A that
guides the first illumination beam 435A from the first illumination
source 432A to near the first mask 412A; (iii) a second
illumination source 432B that emits the second illumination beam
435B; and (iv) a second illumination optical assembly 434B that
guides the second illumination beam 435B from the second
illumination source 432B to near the second mask 412B.
Alternatively, the illumination system 418 can be designed with a
single illumination source that generates an illumination beam that
is split or selectively redirected to create the multiple separate
illumination beams 435A, 435B.
[0104] The first illumination beam 435A illuminates the first mask
412A to generate a first pattern beam 436A (e.g. images from the
first mask 412A) that exposes the substrate 414. Similarly, the
second illumination beam 435B illuminates the second mask 412B to
generate a second pattern beam 436B (e.g. images from the second
mask 412B) that exposes the substrate 414.
[0105] The optical assembly 420 projects and/or focuses the first
pattern beam 436A and the second pattern beam 436B onto the
substrate 414. In the embodiment illustrated in FIG. 4, the optical
assembly 420 includes (i) a first optical inlet 421A that receives
the first pattern beam 436A, (ii) a second optical inlet 421B that
receives the second pattern beam 436B, and (iii) an optical outlet
421C that directs both pattern beams 436A, 436B at the substrate
414. Further, in this embodiment, (i) the first optical inlet 421A
includes a first inlet axis 421D, (ii) the second optical inlet
421B includes a second inlet axis 421E, and (iii) the optical
outlet 421C includes an outlet axis 421F. The optical assembly 420
is described in more detail below.
[0106] The first mask stage assembly 422A holds and positions the
first mask 412A relative to the optical assembly 420 and the
substrate 414. Similarly, the second mask stage assembly 422B holds
and positions the second mask 412B relative to the optical assembly
420 and the substrate 414. Further, the substrate stage assembly
424 holds and positions the substrate 414 with respect to the
pattern beams 436A, 436B. The stage assemblies 422A, 422B, 424 can
be similar in design to the corresponding components described
above with reference to FIG. 2.
[0107] The control system 428 receives information from the
measurement system 426 and controls the stage assemblies 422A,
422B, 424 to precisely position the masks 412A, 412B and the
substrate 414. Further, the control system 428 can control the
operation of the illumination system 418 to selectively and
independently generate the illumination beams 435A, 435B.
[0108] FIG. 5A is a simplified top view of one non-exclusive
embodiment of a substrate 414 that can be exposed with the exposure
apparatus 410 described above. The design of the substrate 414 is
similar to the substrate 214 described above and illustrated in
FIG. 3A. However, in FIG. 5A, the order in which the sites 415 are
exposed is different. More specifically, two sites 415 are scanned
along the X axis (e.g. the short dimension of the sites 415) before
being stepped along the Y axis.
[0109] In this embodiment, the substrate 414 is illustrated as
having thirty-two separate sites 415, with each site 415 having a
first site dimension 548 (measured along the X axis) that is less
than a second site dimension 550 (measured along the Y axis). In
one non-exclusive embodiment, each site 415 has a first site
dimension 548 of approximately twenty-six (26) millimeters, and a
second site dimension 550 of approximately thirty-three (33)
millimeters.
[0110] In FIG. 5A, the sites 415 have been labeled "1" through "32"
(one through thirty-two). In this example, the labels "1" through
"32" represent one non-exclusive embodiment of the sequence in
which the mask patterns 436A, 436B can be transferred to the sites
415 on the substrate 414. More specifically, as provided herein,
the exposure apparatus 410 can transfer the first mask pattern 429A
from the first mask 412A to the site 415 labeled "1" (sometimes
referred to as the "first site"). Next, the exposure apparatus 410
can transfer the second mask pattern 429B from the second mask 412B
to the site 415 labeled "2" (sometimes referred to as the "second
site"). Subsequently, the exposure apparatus 410 can transfer the
second mask pattern 429B from the second mask 412B to the site 415
labeled "3" (sometimes referred to as the "third site"). Next, the
exposure apparatus 410 can transfer the first mask pattern 429A
from the first mask 412A to the site 415 labeled "4" (sometimes
referred to as the "fourth site"). Subsequently, the exposure
apparatus 410 can continue repeating the sequencing of the
transferring of the first mask pattern 429A and the second mask
pattern 429B (i.e., in a first, second, second, first sequence) to
the sites 415 labeled "6", "7", "8", . . . and "32". In an
alternative embodiment, the exposure apparatus 410 can alternate
between transferring the first mask pattern 429A and the second
mask pattern 429B to the sites 415 labeled "1", "2", "3", "4", "5",
. . . and "32" (i.e., the first mask pattern 429A is transferred to
all the odd numbered sites 415, and the second mask pattern 429B is
transferred to all the even numbered sites 415).
[0111] Moreover, FIG. 5A includes an exposure pattern 552A
(illustrated with a dashed line) which further illustrates the
order in which the mask patterns 429A, 429B are transferred to
sites 415. In this example, the exposure pattern 552A again
includes a plurality of scanning operations 552B and a plurality of
stepping operations 552C, wherein the scanning operations 552B and
the stepping operations 552C alternate so that the exposure
proceeds in a scan-step-scan-step-scan fashion. In this embodiment,
the scanning 552B occurs as the substrate 414 is moved along a scan
axis 558 (the X axis), and the stepping 552C occurs as the
substrate 414 is moved along a step axis 560 (the Y axis).
[0112] It should be noted that with the use of multiple masks 412A,
412B (illustrated in FIG. 4), two adjacent sites 415 (e.g. 1 and 2)
can be scanned sequentially while moving the substrate 414 at a
constant velocity along the scan axis 558. As a result thereof, the
substrate 414 does not have to be stepped and reversed in direction
between the exposures of the sites 415. Instead, for the embodiment
illustrated in FIG. 5A, the substrate 414 is only stepped between
the exposure of pairs of adjacent sites 415 aligned on the scan
axis 558. Stated in another fashion, with the present design, there
is one stepping motion for every two sites 415 scanned. This
results in fewer steps and significantly improved throughput from
the exposure apparatus 410.
[0113] It should be noted that in this example, the site 415 that
is exposed first and the order in which the sites 415 are exposed
can be different than that illustrated in FIG. 5A. Further, the
site 415 that is first exposed can be located away from the edge of
the substrate 414.
[0114] FIG. 5B is a simplified illustration of one embodiment of a
field of view 531 (illustrated with a dashed circle) of the optical
assembly 420 (illustrated in FIG. 4). As provided herein, in
certain embodiments, the field of view 531 of the optical assembly
420 must be relatively large in order to transfer a relatively
large pattern beam 436A, 436B (illustrated in FIG. 4) to the site
415 (illustrated in FIG. 5A).
[0115] In one embodiment, the field of view 531 defines (i) a first
used field 562A (illustrated as a box with solid lines) in which
the first pattern beam 436A (illustrated in FIG. 4) exits the
optical assembly 420, and (ii) and a spaced apart second used field
562B (illustrated as a box with dashed lines) in which the second
pattern beam 436B (illustrated in FIG. 4) exits the optical
assembly 420. In one embodiment, the first used field 562A and the
second used field 562B are substantially similar in shape and size.
As illustrated, the first used field 562A has a rectangular shape
that includes a first field dimension 564 that is measured along
the first axis (the X axis) and a second field dimension 566 that
is measured along the second axis (the Y axis). In this embodiment,
the second field dimension 566 is larger than the first field
dimension 564.
[0116] In certain embodiments, the optical assembly 420 is designed
so that the first field dimension 564 is less than the first site
dimension 548 (illustrated in FIG. 5A) and the second field
dimension 566 is equal to the second site dimension 550
(illustrated in FIG. 5A). In one non-exclusive example, each site
415 has a first site dimension 548 of twenty-six (26) millimeters
and a second site dimension 550 of thirty-three (33) millimeters.
In this example, the second field dimension 566 can be
approximately thirty-three (33) millimeters, and the first field
dimension 564 is less than twenty-six (26) millimeters. As
non-exclusive examples, the first field dimension 564 can be
approximately 2, 2.5, or 3 millimeters.
[0117] In one embodiment, the optical assembly 420 has a numerical
aperture (NA) of at least approximately 1.30. In order to minimize
or correct aberrations of the optical assembly 420 at such a high
NA, the optical assembly 16 can be catadioptric. In one embodiment,
the used fields 562A, 562B are off-axis in order to avoid
obscurations from the relative surfaces. Stated in another fashion,
in the embodiment illustrated in FIG. 5B, (i) the first used field
562A is offset from an optical axis 568 of the optical assembly 420
a first offset distance 568A, (ii) the second used field 562B is
offset from the optical axis 568 a second offset distance 568B, and
(iii) the first used field 562A and the second used field 562B are
spaced apart a separation distance 568C. Moreover, the used fields
562A, 562B are positioned on opposite sides of the optical axis
568, and the used fields 562A, 562B are substantially parallel to
each other. In one non-exclusive embodiment, each offset distance
568A, 568B is approximately 2.5 millimeters, and the separation
distance 568C is approximately 5 millimeters. Alternatively, the
offset distances 568A, 568B can be greater than or less than 2.5
millimeters.
[0118] FIGS. 6A-6D further illustrate one non-exclusive embodiment
of how a substrate 414 can be exposed utilizing the exposure
apparatus 410 illustrated in FIG. 4. More specifically, FIG. 6A is
a simplified side view of the first mask 412A, the second mask
412B, the optical assembly 420, and the substrate 414 at a
beginning of an exposure of a first site 1. At the start of
exposure of the first site 1, the control system 428 (illustrated
in FIG. 4) controls the illumination system 418 (illustrated in
FIG. 4) to generate the slit shaped first illumination beam 435A
that is directed at the first mask 412A, and controls the first
mask stage assembly 422A (illustrated in FIG. 4) to position the
first mask 412A so that the first mask pattern 429A is illuminated
near a right side of the pattern 429A. This causes a resulting
first pattern beam 436A to be directed by the optical assembly 420
at the right side of the first site 1.
[0119] Additionally, as illustrated in FIG. 6A, the first pattern
beam 436A is initially directed toward the first optical inlet 421A
along the first inlet axis 421D. The first pattern beam 436A is
subsequently redirected and focused within the optical assembly 420
until the first pattern beam 436A is ultimately directed by the
optical assembly 420 from the optical outlet 421C offset from the
outlet axis 421F. More particularly, the first pattern beam 436A is
directed by the optical assembly 420 through the optical outlet
421C toward a right side of the first site 1.
[0120] Further, at the beginning of the exposure of the first site
1, the control system 428 (i) controls the first mask stage
assembly 422A so that the first mask 412A is being moved at a
constant velocity in a first scan direction 558A (from left to
right in FIG. 6A) along the scan axis 558 (the X axis), and (ii)
controls the substrate stage assembly 424 (illustrated in FIG. 4)
so that the substrate 414 is also being moved at a constant
velocity in the first scan direction 558A along the scan axis 558.
With the present design, in certain embodiments, both the first
mask 412A and the substrate 412 are moved synchronously in the same
scan direction 558A. Further, for example, if the optical assembly
420 has a reduction factor of four, the first mask 412A is moved at
a rate that is four times greater than that of the substrate 414.
Alternatively, the first mask 412A and the substrate 414 can be
moved in opposite directions along the scan axis 558 during
scanning of the sites 415.
[0121] As the first mask 412A is being moved in the first scan
direction 558A, the first pattern beam 436A continues to illuminate
a portion of the first mask 412A from initially near the right side
toward the left side. At the same time, the substrate 414 is being
moved in the first scan direction 558A so that the first pattern
beam 436A is directed initially at the right side and continuously
and subsequently toward the left side of the substrate 414.
[0122] FIG. 6B is a simplified side view of the first mask 412A,
the second mask 412B, the optical assembly 420, and the substrate
414 at a beginning of an exposure of the second site 2.
[0123] At the start of exposure of the second site 2, the control
system 428 (illustrated in FIG. 4) controls the illumination system
418 (illustrated in FIG. 4) to generate the slit shaped second
illumination beam 435B that is directed at the second mask 412B,
and controls the second mask stage assembly 422B (illustrated in
FIG. 4) to position the second mask 412B so that a second mask
pattern 429B is illuminated near the right side of the pattern
429B. This causes a resulting second pattern beam 436B to be
directed by the optical assembly 420 at a portion of the second
site 2.
[0124] Additionally, as illustrated in FIG. 6B, the second pattern
beam 436B is initially directed toward a second optical inlet 421B
of the optical assembly 420 along a second inlet axis 421E. The
second pattern beam 436B is subsequently redirected and focused
within the optical assembly 420 until the second pattern beam 436B
exits the optical outlet 421C offset from the outlet axis 421F.
[0125] Further, at the beginning of the exposure of the second site
2, the control system 428 (i) controls the second mask stage
assembly 422B so that the second mask 412B is being moved at a
constant velocity in the first scan direction 558A along the scan
axis 558, and (ii) controls the substrate stage assembly 424
(illustrated in FIG. 4) so that the substrate 414 is also being
moved at a constant velocity in the first scan direction 558A. With
the present design, in certain embodiments, both the second mask
412B and the substrate 414 are moved synchronously in the same scan
direction 558A. Alternatively, the second mask 412B and the
substrate 414 can be moved in opposite directions along the scan
axis 558 during scanning of the sites 415.
[0126] It should be noted that with the design of the optical
assembly 420 as illustrated herein, the exposure of the first site
1 and the second site 2 occurs with the substrate 414 being moved
in the same first scan direction 558A at a substantially constant
velocity. This enables greater throughput for the exposure
apparatus 410 (illustrated in FIG. 4).
[0127] FIG. 6C is a simplified side view of the first mask 412A,
the second mask 412B, the optical assembly 420, and the substrate
414 at a beginning of an exposure of the third site 3. It should be
noted that after the exposure of the second site illustrated in
FIG. 6B, the substrate 414 is stepped into the page along the Y
axis.
[0128] During the exposure of the third site 3, the control system
428 (illustrated in FIG. 4) controls the illumination system 418
(illustrated in FIG. 4) to generate the slit shaped second
illumination beam 435B that is directed at the second mask 412B,
and controls the second mask stage assembly 422B (illustrated in
FIG. 4) to position the second mask 412B so that the second mask
pattern 429B is illuminated near its left side. This causes a
resulting second pattern beam 436B to be directed by the optical
assembly 420 at a portion of the third site 3.
[0129] Further, during the exposure of the third site 3, the
control system 428 (i) controls the second mask stage assembly 422B
so that the second mask 412B is being moved at a constant velocity
in a second scan direction 558B (from right to left in FIG. 6C,
opposite from the first scan direction 558A) along the scan axis
558 (the X axis), and (ii) controls the substrate stage assembly
424 (illustrated in FIG. 4) so that the substrate 414 is also being
moved at a constant velocity in the second scan direction 558B.
[0130] FIG. 6D is a simplified side view of the first mask 412A,
the second mask 412B, the optical assembly 420, and the substrate
414 at a beginning of an exposure of the fourth site 4. At the
start of exposure of the fourth site 4, the control system 428
(illustrated in FIG. 4) controls the illumination system 418
(illustrated in FIG. 4) to generate the slit shaped first
illumination beam 435A that is directed at the first mask 412A, and
controls the first mask stage assembly 422A (illustrated in FIG. 4)
to position the first mask 412A so that the first mask pattern 429A
is illuminated near its left side. This causes a resulting first
pattern beam 436A to be directed by the optical assembly 420 at a
portion of the fourth site 4. In certain embodiments, the exposure
of the fourth site 4 using reticle 412A can begin before the
exposure of the third site 3 using reticle 412B has finished.
[0131] During the exposure of the fourth site 4, the control system
428 (i) controls the first mask stage assembly 422A so that the
first mask 412A is being moved at a substantially constant velocity
in the second scan direction 558B along the scan axis 558, and (ii)
controls the substrate stage assembly 424 (illustrated in FIG. 4)
so that the substrate 414 is also being moved at a substantially
constant velocity in the second scan direction 558B.
[0132] It should be noted that with the design of the optical
assembly 420 as illustrated herein, the exposure of the third site
3 and the fourth site 4 occur with the substrate 414 being moved in
the same second scan direction 558B along the scan axis 558.
Further, the four sites 1-4 can be exposed with only one stepping
motion.
[0133] FIGS. 7A-7I further illustrate one embodiment of how four
sites labeled 1-4 can be exposed using the exposure apparatus 410
as illustrated in FIG. 4 and as described above. In these Figures,
the box with solid lines represents the first used field 762A, the
box with dashed lines represents the second used field 762B, and
the slashes represent the respective pattern beam. Further, in
these Figures, the arrow represents the direction in which the
substrate is being moved during scanning at that particular time.
During the exposure of the sites 1-4, the substrate is moved down
the page, then left, and then up. In FIGS. 7A-7I, it appears that
the used fields 762A, 762B move, however, the substrate is actually
being moved relative to the used fields 762A, 762B.
[0134] Starting with FIG. 7A, at the beginning of the exposure of
the first site 1, the first pattern beam 736A (illustrated with
slashes) is exposing the first site 1 and there is no second
pattern beam. At this time, the first used field 762A is positioned
over the first site 1, and the second used field 762B is not over
any of the sites 1-4.
[0135] Next, referring to FIG. 7B, after the first site 1 is
exposed, the first used field 762A is positioned over the second
site 2, and the second used field 762B is positioned over the first
site 1. At this time neither of the pattern beams is being
generated. The amount of time in which the two beams are off is
determined by the distance between the slits and the motion of the
stages.
[0136] Subsequently, referring to FIG. 7C, once the second used
field 762B is positioned over the second site 2, the second pattern
beam 736B (illustrated with slashes) begins to expose the second
site 2, and there is no first pattern beam.
[0137] Next, referring to FIG. 7D, while the second used field 762B
is still positioned over the second site 2, the second pattern beam
736B (illustrated with slashes) continues to expose the second site
2, and there is no first pattern beam.
[0138] Subsequently, upon the completion of the exposure of the
second site 2, the substrate is moved to the left. Referring to
FIG. 7E, once the second used field 762B is positioned over the
third site 3, the second pattern beam 736B (illustrated with
slashes) begins to expose the third site 3, and there is no first
pattern beam. At this time, the substrate is being moved up the
page.
[0139] Next, referring to FIG. 7F, while the second used field 762B
is still positioned over the third site 3, the second pattern beam
736B (illustrated with slashes) continues to expose the third site
3, and there is no first pattern beam.
[0140] Subsequently, referring to FIG. 7G, after the third site 3
is exposed, the first used field 762A is positioned over the third
site 3, and the second used field 762B is positioned over the
fourth site 4. At this time neither of the pattern beams are being
generated.
[0141] Next, referring to FIG. 7H, once the first used field 762A
is positioned over the fourth site 4, the first pattern beam 736A
(illustrated with slashes) begins to expose the fourth site 4, and
there is no second pattern beam.
[0142] Subsequently, referring to FIG. 7I, while the first used
field 762A is still positioned over the fourth site 4, the first
pattern beam 736A (illustrated with slashes) continues to expose
the fourth site 4, and there is no second pattern beam.
[0143] In this embodiment, the system is designed so that the
second site 2 is not exposed until after the exposure of the first
site 1 is fully completed, and the fourth site 4 is not exposed
until after the exposure of the third site 3 is fully completed.
This requires an A-B-B-A exposure sequence. The benefit of this
sequence is that there is never a time when both pattern beams are
required, so it is easier to use a single illumination source 432A,
432B (illustrated in FIG. 4). The drawbacks of this sequence are
(1) that the reticle stage acceleration must be proportional to the
substrate acceleration (e.g., in a 4.times. reduction system, the
reticle acceleration is four times the substrate acceleration), and
(2) that the scanning distance is longer than that required for the
sequence described below for FIGS. 8A-8I.
[0144] FIGS. 8A-8I further illustrate another embodiment of how
four sites labeled 1-4 can be exposed using the exposure apparatus
410 as illustrated in FIG. 4 and as described above. Similar to the
embodiment illustrated in FIGS. 7A-71, in this embodiment, the box
with solid lines is the first used field 862A, the box with dashed
lines is the second used field 862B, and the slashes represent the
pattern beam. Further, the arrow again represents the direction in
which the substrate is being moved during scanning at that
particular time, with the substrate initially being moved down the
page, then left, and then up during the exposure of the four
sites.
[0145] Starting with FIG. 8A, at the beginning of the exposure of
the first site 1, the second pattern beam 836B (illustrated with
slashes) is exposing the first site 1 and there is no first pattern
beam. At this time, both the first used field 862A and the second
used field 862B are positioned over the first site 1. Further, at
this time, the substrate is being moved down the page.
[0146] Next, referring to FIG. 8B, during continuation of exposure
of the first site 1, the first used field 862A is positioned over
the second site 2, and the second used field 862B is positioned
over the first site 1. Once the first used field 862A is positioned
over the second site 2, the first pattern beam 836A (illustrated
with slashes) begins to expose the second site 2. At the same time,
the second pattern beam 836B (illustrated with slashes) is still
being generated and is still exposing the first site 1. Stated
another way, at this time both of the pattern beams 836A, 836B are
being generated, and the continuing exposure of the first site 1
coincides or overlaps with the beginning of the exposure of the
second site 2.
[0147] Subsequently, referring to FIG. 8C, both the first used
field 862A and the second used field 862B are positioned over the
second site 2. Once the second used field 862B is positioned over
the second site 2, the second pattern beam is no longer being
generated, but the first pattern beam 836A (illustrated with
slashes) is still being generated and is continuing exposure of the
second site 2.
[0148] Next, referring to FIG. 8D, only the second used field 862B
is still positioned over the second site 2, and the first used
field 862A is not positioned over any of the sites. This is the
condition after completion of the exposure of the second site 2. At
this time, neither of the pattern beams are being generated, and
the substrate is already stepping to the left.
[0149] Referring next to FIG. 8E, the second used field 862B is
positioned over the third site 3, and the first used field 862A is
not positioned over any of the sites. At this time, neither of the
pattern beams are being generated. Further, at this time, the
substrate is being moved up the page, and is finishing its stepping
motion to the left.
[0150] Next, referring to FIG. 8F, once the first used field 862A
is positioned over the third site 3, the first pattern beam 836A
(illustrated with slashes) begins to expose the third site 3. At
this time, the second used field 862B is still positioned over the
third site 3, and no second pattern beam is being generated.
[0151] Subsequently, referring to FIG. 8G, during continuation of
exposure of the third site 3, the first used field 862A is still
positioned over the third site 3, and the second used field 862B is
now positioned over the fourth site 4. Once the second used field
862B is positioned over the fourth site 4, the second pattern beam
836B (illustrated with slashes) begins to expose the fourth site 4.
At the same time, the first pattern beam 836A (illustrated with
slashes) is still being generated and is still exposing the third
site 3. Stated another way, at this time both of the pattern beams
836A, 836B are being generated, and the continuing exposure of the
third site 3 coincides or overlaps with the beginning of the
exposure of the fourth site 4.
[0152] Next, referring to FIG. 8H, both the first used field 862A
and the second used field 862B are now positioned over the fourth
site 4. Once the first used field 862A is positioned over the
fourth site 4, the first pattern beam is no longer being generated,
but the second pattern beam 836B (illustrated with slashes) is
still being generated and is continuing exposure of the fourth site
4.
[0153] Subsequently, referring to FIG. 81, only the first used
field 862A is still positioned over the fourth site 4, and the
second used field 862B is not positioned over any of the sites. At
this time, neither of the pattern beams are being generated.
[0154] In this embodiment, the system is designed so that the
exposure of the second site 2 is started prior to the exposure of
the first site 1 being fully completed.
[0155] Comparing the exposures illustrated in FIGS. 7A-7I with
exposures illustrated in FIGS. 8A-8I, the overall scanning distance
is longer for the embodiment illustrated in FIGS. 7A-7I. Therefore,
the exposure of FIG. 8A-8I is completed faster, leading to higher
overall throughput, assuming the same scan velocity for the two
cases. The B-A-A-B sequence shown in FIGS. 8A-8I achieves this
higher throughput by having time when both pattern beams are used
simultaneously. The drawbacks of this sequence are (1) that the
reticle stage acceleration must be proportional to the substrate
acceleration (e.g., in a 4.times. reduction system, the reticle
acceleration is four times the substrate acceleration), and (2) the
design of the illumination system may be more difficult compared to
what is required for the sequence shown in FIGS. 7A-7I.
[0156] FIGS. 9A-9I further illustrate another embodiment of how
four sites labeled 1-4 can be exposed using the exposure apparatus
410 as illustrated in FIG. 4 and as described above. Similar to the
embodiment illustrated in FIGS. 7A-7I and 8A-8I, in this
embodiment, the box with solid lines is the first used field 962A,
the box with dashed lines is the second used field 962B, and the
slashes represent the pattern beam. Further, the arrow again
represents the direction in which the substrate is being moved
during scanning at that particular time, with the substrate
initially being moved down the page, then left, and then up during
the exposure of the four sites.
[0157] Starting with FIG. 9A, at the beginning of the exposure of
the first site 1, the first pattern beam 936A (illustrated with
slashes) is exposing the first site 1 and there is no second
pattern beam. At this time, the first used field 962A is positioned
over the first site 1, and the second used field 962B is not over
any of the sites 1-4.
[0158] Next, referring to FIG. 9B, after the first site 1 is
exposed, the first used field 962A is positioned over the second
site 2, and the second used field 962B is positioned over the first
site 1. At this time neither of the pattern beams is being
generated.
[0159] Subsequently, referring to FIG. 9C, once the second used
field 962B is positioned over the second site 2, the second pattern
beam 936B (illustrated with slashes) begins to expose the second
site 2, and there is no first pattern beam.
[0160] Next, referring to FIG. 9D, while the second used field 962B
is still positioned over the second site 2, the second pattern beam
936B (illustrated with slashes) continues to expose the second site
2, and there is no first pattern beam.
[0161] Subsequently, upon the completion of the exposure of the
second site 2, the substrate is moved to the left. Referring to
FIG. 9E, once the second used field 962B is positioned over the
third site 3, neither of the pattern beams is being generated.
[0162] Next, referring to FIG. 9F, once the first used field 962A
is positioned over the third site 3, the first pattern beam 736A
(illustrated with slashes) begins to expose the third site 3, and
there is no second pattern beam.
[0163] Subsequently, referring to FIG. 9G, while still exposing the
third site 3, the first used field 962A is positioned over the
third site 3, and the second used field 962B is positioned over the
fourth site 4. At this time both pattern beams 936A, 936B are being
generated.
[0164] Next, referring to FIG. 9H, with the second used field 962B
is still positioned over the fourth site 4, the second pattern beam
936B (illustrated with slashes) continues to expose the fourth site
4, and there is no first pattern beam.
[0165] Subsequently, referring to FIG. 9I, after the second used
field 962B is no longer positioned over the fourth site 4, and
there is no pattern beam being generated.
[0166] With this sequence, the first site 1 and the third site 3
are exposed with the first pattern beam 936A, and the second site 2
and the fourth site 4 are exposed with the second pattern beam
936B. This sequence provides the same throughput and scanning
distance as the sequence illustrated in FIGS. 7A-7I, and requires
some times (half as much) when both pattern beams are used
simultaneously, like the sequence in FIGS. 8A-8I. The advantage of
this sequence is that the two masks are always used for alternate
exposures, so the requirement for mask acceleration is much lower.
In other words, each of the mask stages 422A, 422B can perform its
"turn-around" acceleration during an exposure using the other mask,
412B, 412A, respectively. For future machines with very high
throughput, this advantage may make this sequence the preferred
embodiment.
[0167] It should be noted that with these designs, greater
throughput of the exposure apparatus is achieved because the number
of steps required to process the substrate is less than if the
sites are scanned along the long dimension of the sites.
[0168] FIGS. 10A-10D further illustrate one embodiment of how a
first site 1 can be exposed using the exposure apparatus 410 as
illustrated in FIG. 4 and as described above. Similar to the
embodiments illustrated above, in this embodiment, the box with
solid lines represents the first used field 1062A, the box with
dashed lines represents the second used field 1062B, and the
slashes represent the pattern beam. Further, the arrow again
represents the direction in which the substrate is being moved
during scanning at that particular time, with the substrate
initially being moved down the page, and then up during the
exposure of the first site 1. Moreover, in this embodiment, the
first site 1 is sequentially exposed to the first pattern beam
1036A and the second pattern beam 1036B.
[0169] Starting with FIG. 10A, at the beginning of the exposure of
the first site 1, the first pattern beam 1036A (illustrated with
slashes) is exposing the first site 1 and there is no second
pattern beam. At this time, the first used field 1062A is
positioned over the first site 1, and the second used field 1062B
is not positioned over any of the sites. Further, at this time, the
substrate is being moved down the page.
[0170] Next, referring to FIG. 10B, the first used field 1062A is
now positioned over a second site 2 (i.e., not over the first site
1) and the second used field 1062B is now positioned over the first
site 1, and the substrate is still being moved down the page. At
this time, neither of the pattern beams are being generated.
[0171] Subsequently, referring to FIG. 10C, the first used field
1062A is again positioned over the second site 2 (i.e., not over
the first site 1) and the second used field 1062B is positioned
over the uppermost portion of the first site 1. At this time, the
substrate is beginning to be moved back up the page. With the
second used field 1062B being positioned over the uppermost portion
of the second site 2, and the substrate being moved up the page,
the second pattern beam 1036B is being generated and the first site
1 is being exposed. Further, at this time, no first pattern beam is
being generated.
[0172] Next, referring to FIG. 10D, the first used field 1062A is
positioned over the first site 1, and the second used field 1062B
is not positioned over any of the sites. At this time, neither of
the pattern beams are being generated.
[0173] Other sequences can be utilized than that illustrated in
FIGS. 10A-10D. For example, two adjacent sites can be sequentially
scanned in one motion, then the substrate can be turned around and
the second exposure of these sites can be performed. For example,
while moving substrate in one direction along the X axis, the first
site can be exposed using the first reticle and subsequently the
second site can be exposed using second reticle (similar as
illustrated in FIGS. 9A-9D). Next, the direction of the substrate
along the X axis can be reversed, the second site can exposed using
the first reticle, and subsequently the first site can be exposed
using the second reticle. This is similar to sequence illustrated
in FIG. 9A-9I, except without the Y direction stepping motion.
[0174] FIGS. 11A-11D further illustrate another embodiment of how a
first site 1 can be exposed using the exposure apparatus 410 as
illustrated in FIG. 4 and as described above. Similar to the
embodiments illustrated above, in this embodiment, the box with
solid lines is the first used field 1162A, the box with dashed
lines is the second used field 1162B, and the slashes represent the
pattern beam. Further, the arrow again represents the direction in
which the substrate is being moved during scanning at that
particular time, with the substrate being moved down the page
during the exposure of the first site 1. Moreover, in this
embodiment, the first site 1 is exposed to both the first pattern
beam 1136A and the second pattern beam 1136B.
[0175] Starting with FIG. 11A, at the beginning of the exposure of
the first site 1, the first pattern beam 1136A (illustrated with
slashes) is exposing the first site 1 and there is no second
pattern beam. At this time, the first used field 1162A is
positioned over the first site 1, and the second used field 1162B
is not positioned over any of the sites 1-4.
[0176] Next, referring to FIG. 11B, both the first used field 1162A
and the second used field 1162B are now positioned over the first
site 1. At this time, both of the pattern beams 1136A, 1136B
(illustrated with slashes) are being generated, and the first site
1 is simultaneously being exposed to both the first pattern beam
1136A and the second pattern beam 1136B.
[0177] Subsequently, referring to FIG. 11C, the first used field
1162A is now positioned over the second site 2 (i.e., not over the
first site 1) and the second used field 1162B is still positioned
over the first site 1. At this time, the second pattern beam 1136B
(illustrated with slashes) is exposing the first site 1 and no
first pattern beam 1136A is being generated.
[0178] Next, referring to FIG. 11D, both the first used field 1162A
and the second used field 1162B are positioned over the second site
2 (i.e., not over the first site 1). At this time, neither of the
pattern beams are being generated.
[0179] FIG. 12 is a schematic illustration of the first mask 412A,
the second mask 412B, the substrate 414, and one, non-exclusive
embodiment of an optical assembly 1220 having features of the
present invention. As noted above, the optical assembly 1220
projects and/or focuses the first pattern beam 436A and the second
pattern beam 436B onto the substrate 414.
[0180] As illustrated, the optical assembly 1220 includes (i) the
first optical inlet 421A, (ii) the second optical inlet 421B, (iii)
the optical outlet 421C, (iv) a plurality of first vertical optical
elements 1220AA that are positioned along the first inlet axis, (v)
a plurality of second vertical optical elements 1220AB that are
positioned along the second inlet axis, (vi) a plurality of first
transverse optical elements 1220AC that are positioned along a
first transverse axis between the first inlet axis and the outlet
axis, (vii) a plurality of second transverse optical elements
1220AD that are positioned along a second transverse axis between
the second inlet axis and the outlet axis, and (viii) a plurality
of third vertical optical elements 1220AE that are positioned along
the outlet axis.
[0181] During projection and/or focusing of the first pattern beam
436A from the first mask 412A onto the substrate 414, the first
pattern beam 436A is initially directed through the first optical
inlet 421A and through the plurality of first vertical optical
elements 1220AA. Subsequently, the first pattern beam 436A is
redirected toward the plurality of first transverse optical
elements 1220AC. Next, the first pattern beam 436A is redirected
toward the plurality of third vertical optical elements 1220AE. The
third vertical optical elements 1220AE then project and/or focus
the first pattern beam 436A through the optical outlet 421C and
toward the substrate 421 offset from the outlet axis.
[0182] Similarly, during projection and/or focusing of the second
pattern beam 436B from the second mask 412B onto the substrate 414,
the second pattern beam 436B is initially directed through the
second optical inlet 421B and toward the plurality of second
vertical optical elements 1220AB. Subsequently, the second pattern
beam 436B is redirected toward the plurality of second transverse
optical elements 1220AD. Next, the second pattern beam 436B is
redirected toward the plurality of third vertical optical elements
1220AE. The third vertical optical elements 1220AE then project
and/or focus the second pattern beam 436B through the optical
outlet 421C and toward the substrate 414 offset from the outlet
axis.
[0183] As illustrated in FIG. 12, the first vertical optical
elements 1220AA are substantially identical to the second vertical
optical elements 1220AB. Additionally, the first transverse optical
elements 1220AC are substantially identical to the second
transverse optical elements 1220AD. Accordingly, only the first
vertical optical elements 1220AA and the first transverse optical
elements 1220AC will be described in detail herein. Further, both
beams 436A, 436B travel through the same third vertical optical
elements 1220AE.
[0184] The first vertical optical elements 1220AA include a
plurality of individual optical elements labeled E1 through E18. In
this embodiment, the first pattern beam 436A is altered and/or
focused as it initially passes in a generally downward direction
through optical elements E1 through E13. Optical elements E1
through E13 are optical lenses that can be made from material such
as silicon dioxide (SiO.sub.2). Subsequently, the first pattern
beam 436A is reflected off optical element E14 so that it is now
directed in a generally upward direction. In one embodiment,
optical element E14 can be a spherical mirror. Next, the first
pattern beam 436A is directed through optical elements E15 through
E17. As illustrated in FIG. 10, optical elements E15 through E17
are the same as optical elements E11 through E13, with the first
pattern beam 436A passing through optical elements E11 through E13
in one direction and subsequently passing through optical elements
E15 through E17 and in the substantially opposite direction. Next,
the first pattern beam 436A is reflected transversely off optical
element E18 so that it is now redirected toward the first
transverse optical elements 1220AC. Optical element E18 can be a
mirror or other reflecting element.
[0185] The first transverse optical elements 1220AC include a
plurality of individual optical elements E19 through E29. The first
pattern beam 436A is altered and/or refocused as it passes in a
generally transverse or horizontal direction through optical
elements E19 through E28. Optical elements E19 through E28 are
optical lenses that can be made from material such as silicon
dioxide (SiO.sub.2). Subsequently, the first pattern beam 436A is
reflected off optical element E29 so that it is now redirected
toward the third vertical optical elements 1120AE. In one
embodiment, optical element E29 can be a field splitting
V-mirror.
[0186] The third vertical optical elements 1220AE include a
plurality of optical elements E30 through E45. The first pattern
beam 436A is altered and/or refocused as it passes in a generally
downward direction through optical elements E30 through E45.
Optical elements E30 through E45 are optical lenses that can be
made from material such as silicon dioxide (SiO.sub.2). The first
pattern beam 436A then passes through element E46 (represented as
X's), which is a fluid, such as water, if the exposure apparatus
410 is an immersion type system, before being projected and/or
focused onto the substrate 414.
[0187] It should be noted that the design of the optical assembly
1220 illustrated in FIG. 12 contains more intermediate images than
the optical assemblies used in prior art lithography machines. It
should be noted that these intermediate images can be highly
aberrated, as is the case in this embodiment. This makes it easier
to increase the field size without increasing the diameter of the
optical elements, since the optical distance between the reticle
and the wafer is much longer than in the current state of the art
for projection optical assemblies, thanks to the folded optical
path (i.e. the physical distance between the plane containing the
reticle 412A and the plane containing the substrate 414 is
nominally the same as current state of the art). Further, the
optical assembly 1220 allows for the continuous exposure of two or
more shots per scanning motion. With this exposure pattern, the
reduction in scanning time is much greater than the increase in
stepping time, and dramatic improvements in throughput are
possible.
[0188] Table 1, as provided below, illustrates one, non-exclusive
example of a prescription for the optic elements E1 through E46 of
the optical assembly 1216 illustrated in FIG. 12. More
particularly, for each optical element E1 through E46, the charts
in Table 1 show a prescription for (i) the radius of curvature for
the front of the optical element, (ii) the radius of curvature for
the back of the optical element, (iii) the thickness of the optical
element (in the column for thickness the top number represents the
distance between that optical element and the preceding optical
element (or the mask in the case of optical element E1), and the
bottom number represents the actual thickness of that optical
element, (iv) the aperture diameter for the front of the optical
element, and (v) the aperture diameter for the back of the optical
element. The thickness of each optical element is specified along
the optical axis (e.g. the center of rotation for the element).
TABLE-US-00001 TABLE 1 APERTURE ELEMENT RADIUS OF CURVATURE
DIAMETER NUMBER FRONT BACK THICKNESS FRONT BACK MASK INF 80.0000 E1
332.3631 CX -772.3579 CX 38.0763 215.2012 217.2506 26.9220 E2
1988.1790 CX -557.1967 CX 26.6978 220.9056 221.1825 56.1372 E3
128.4263 CX A(1) 31.0843 198.8483 187.8534 26.0025 E4 98.6558 CX
321.1966 CC 45.2849 159.9568 143.6474 16.3918 E5 -454.4909 CC
-730.0124 CX 59.99325 137.4985 118.9757 59.7289 E6 -64.8711 CC
-199.1701 CX 12.5000 125.5907 190.0548 1.0877 E7 -224.3732 CC
-132.7050 CX 46.3257 196.0660 217.1116 1.0000 E8 A(2) -158.7960 CX
45.6873 245.0434 260.0687 1.0000 E9 -646.1248 CC -226.2058 CX
51.0836 289.0873 295.5915 1.0000 E10 360.6986 CX A(3) 53.3734
287.2861 282.7083 139.9997 211.4006 100.0000 E11 237.9744 CX
-1445.3266 CX 51.2169 244.1453 240.7614 174.1733 E12 A(4) 487.4478
CC 12.5000 158.1046 166.9962 58.1229 E13 -98.2161 CC -210.5104 CX
12.5000 168.7470 212.4076 24.2148 E14 -145.6557 CC -24.2148
218.4194 E15 -210.5104 CX -98.2161 CC -12.5000 209.9116 168.2949
-58.1229 E16 487.4478 CC A(5) -12.5000 166.3525 155.5700 -174.1733
E17 -1445.3266 CX 237.9744 CX -51.2169 252.3990 255.2359 -100.0000
DECENTER(1) E18 INF 0.0000 358.2570 230.1752 139.9999 E19 A(6)
-489.7915 CX 48.1053 269.5593 273.1352 1.0509 E20 440.2750 CX
-1319.4966 CX 42.3662 278.5086 276.5223 1.0004 E21 153.2021 CX A(7)
35.3619 249.4052 236.0525 1.0048 E22 129.8182 CX 247.8748 CC
51.0939 218.2553 199.2937 14.1804 E23 139.9820 CX 69.7240 CC
17.4815 161.4679 118.1128 56.7295 E24 -317.8201 CC -19220.6836 CX
12.5000 92.5138 103.8677 51.6277 E25 -239.6328 CC -120.1306 CX
53.8056 186.4776 208.1471 1.0000 E26 A(8) -134.3606 CX 57.5209
232.5554 249.2932 3.2068 E27 3402.1195 CX -375.2978 CX 40.6273
270.0570 271.5381 9.9100 E28 501.3345 CX -4078.3847 CX 31.4270
258.1145 253.6591 140.0003 DECENTER(2) E29 INF 0.0000 340.0505
167.4372 -119.0000 E30 -725.7800 CX 971.2181 CX -26.7346 215.7113
218.7057 -1.0000 E31 -246.2088 CX -2291.7420 CC -37.5566 227.3402
224.6272 -1.0000 E32 -240.3807 CX -491.2120 CC -27.0952 217.7132
211.0205 -1.0000 E33 -359.5177 CX A(9) -26.0330 208.1157 200.6343
-2.5888 E34 3436.6049 CC -155.1981 CC -12.5000 201.2703 181.4202
-53.9084 E35 201.2753 CC A(10) -12.5000 181.5783 206.3011 -32.1960
E36 A(11) 22055.3033 CX -18.2557 222.3822 232.1830 -5.7398 E37
-444.9630 CX 855.8885 CX -44.4071 269.0140 274.6713 -1.0250 E38
-1241.2380 CX A(12) -48.8825 285.3656 288.3814 4.0469 E39 505.0198
CC A(13) -19.5442 288.9709 293.2339 -27.7418 E40 A(14) 300.9422 CX
-54.8835 293.3251 329.7481 -1.0029 E41 -384.4074 CX 1165.4799 CX
-69.9286 356.7095 354.3822 -1.0000 347.3775 -1.0000 APERTURE STOP
313.1895 E42 -192.8071 CX -336.3459 CC -57.1654 313.1895 301.4309
-1.0015 E43 -146.6712 CX A(15) -63.7532 260.7714 240.3029 -1.2011
E44 -93.7790 CX A(16) -53.0084 174.6861 139.7743 -1.0108 E45
-64.9508 CX INF -44.5062 105.4047 44.5875 E46 INF INF -1.5000
44.5875 36.2567 SUBSTRATE INF 36.2567
[0189] In Table 1, it should be noted that (i) positive radius
indicates the center of curvature is to the right; (ii) negative
radius indicates the center of curvature is to the left; (iii)
dimensions are given in millimeters; (iv) thickness is axial
distance to next surface; and (v) image diameter is a paraxial
value, it is not a ray traced value.
[0190] Table 2, as provided below, illustrates the calculation of
aspheric constants related to the radius of curvature for certain
of the optical elements as shown in Table 1. More particularly,
aspheric constant A(1) relates to the radius of curvature for the
back of optical element E3; aspheric constant A(2) relates to the
radius of curvature for the front of optical element E8; aspheric
constant A(3) relates to the radius of curvature for the back of
optical element E10; aspheric constant A(4) relates to the radius
of curvature for the front of optical element E12; aspheric
constant A(5) relates to the radius of curvature for the back of
optical element E16; aspheric constant A(6) relates to the radius
of curvature for the front of optical element E19; aspheric
constant A(7) relates to the radius of curvature for the back of
optical element E21; aspheric constant A(8) relates to the radius
of curvature for the front of optical element E26; aspheric
constant A(9) relates to the radius of curvature for the back of
optical element E33; aspheric constant A(10) relates to the radius
of curvature for the back of optical element E35; aspheric constant
A(11) relates to the radius of curvature for the front of optical
element E36; aspheric constant A(12) relates to the radius of
curvature for the back of optical element E38; aspheric constant
A(13) relates to the radius of curvature for the back of optical
element E39; aspheric constant A(14) relates to the radius of
curvature for the front of optical element E40; aspheric constant
A(15) relates to the radius of curvature for the back of optical
element E43; and aspheric constant A(16) relates to the radius of
curvature for the back of optical element E44.
[0191] Additionally, within the formula for the aspheric constants,
Y represents the distance from the optical axis (i.e., the first
inlet axis, a first transverse axis, or the outlet axis), CURV
represents (1/radius of curvature), and K represents the conic
constant.
TABLE-US-00002 TABLE 2 ASPHERIC CONSTANTS Z = ( CURV ) Y 2 1 + ( 1
- ( 1 + K ) ( CURV ) 2 Y 2 ) 1 / 2 + ( A ) Y 4 + ( B ) Y 6 + ( C )
Y 8 + ( D ) Y 10 + ( E ) Y 12 + ( F ) Y 14 + ( G ) Y 16 + ( H ) Y
18 + ( J ) Y 20 ##EQU00002## K A B C D ASPHERIC CURV E F G H J A(1)
0.00521230 0.000000 7.36515E-08 5.65704E-12 -1.19986E-15
3.47493E-20 1.94010E-24 -2.67446E-28 0.00000E+00 0.00000E+00
0.00000E+00 A(2) -0.00474024 0.000000 1.94442E-08 7.19217E-13
-4.39422E-17 -8.49737E-22 1.08518E-25 -2.62326E-30 0.00000E+00
0.00000E+00 0.00000E+00 A(3) -0.00181913 0.000000 1.97669E-08
-2.81921E-14 -2.03611E-18 3.92721E-23 8.64464E-29 -2.01755E-32
0.00000E+00 0.00000E+00 0.00000E+00 A(4) -0.00943927 0.000000
4.03091E-07 -1.84915E-11 -3.06102E-16 -5.60022E-20 9.77410E-24
-1.64771E-27 0.00000E+00 0.00000E+00 0.00000E+00 A(5) -0.00943927
0.000000 1.22035E-07 1.75899E-12 -8.89537E-18 2.56518E-20
-1.72833E-24 2.12380E-28 0.00000E+00 0.00000E+00 0.00000E+00 A(6)
0.00250445 0.000000 -2.24797E-08 -1.71809E-14 4.18962E-18
-1.25992E-22 1.93598E-27 -1.52571E-32 0.00000E+00 0.00000E+00
0.00000E+00 A(7) 0.00598617 0.000000 -1.78129E-08 -1.34754E-12
-9.63168E-18 -5.96286E-22 8.22593E-26 -3.07075E-30 0.00000E+00
0.00000E+00 0.00000E+00 A(8) -0.00402385 0.000000 -5.66102E-08
4.94563E-13 -2.86196E-17 -1.14660E-21 6.70516E-26 -1.34290E-30
0.00000E+00 0.00000E+00 0.00000E+00 A(9) 0.00043217 0.000000
-4.01551E-08 7.98475E-13 -8.77129E-17 -1.03388E-21 5.28663E-25
-4.41691E-29 6.99988E-34 0.00000E+00 0.00000E+00 A(10) -0.00708334
0.000000 1.59565E-07 -5.12216E-12 3.09234E-16 -1.36558E-20
6.81623E-25 -9.67188E-30 -7.26516E-35 0.00000E+00 0.00000E+00 A(11)
-0.00159664 0.000000 8.79056E-08 -4.58660E-12 1.44100E-16
-1.79547E-20 4.80695E-25 -2.72623E-29 1.93370E-33 0.00000E+00
0.00000E+00 A(12) 0.00262213 0.000000 1.87932E-08 7.71419E-13
-1.47309E-16 3.46140E-21 1.30616E-25 -1.07939E-29 1.84542E-34
0.00000E+00 0.00000E+00 A(13) 0.00317050 0.000000 -2.49489E-08
-8.47598E-13 1.17616E-16 -3.41773E-21 -1.01449E-25 8.58972E-30
-1.27042E-34 0.00000E+00 0.00000E+00 A(14) 0.00395847 0.000000
6.54729E-09 3.01118E-13 1.06282E-17 -1.83601E-21 1.35202E-25
-5.49884E-30 9.45241E-35 0.00000E+00 0.00000E+00 A(15) -0.00373059
0.000000 2.81186E-08 -3.40496E-12 1.73002E-16 -4.39804E-21
-1.60826E-25 1.48359E-29 -3.52669E-34 0.00000E+00 0.00000E+00 A(16)
-0.00548781 0.000000 -1.89752E-07 -2.61284E-13 -1.75568E-15
2.78432E-20 2.85207E-23 -8.14237E-27 5.98295E-31 0.00000E+00
0.00000E+00
[0192] Table 3, as provided below, illustrates the decentering
information as it relates to optical elements E18 and E29 (i.e.,
certain of the mirror elements). Table 3 further provides
additional system characteristics for the optical assembly
1120.
TABLE-US-00003 TABLE 3 DECENTERING CONSTANTS DECENTER X Y Z ALPHA
BETA GAMMA D (1) 0.0000 0.0000 0.0000 -45.0000 0.0000 0.0000 (BEND)
D (2) 0.0000 0.0000 0.0000 -45.0000 0.0000 0.0000 (BEND) A decenter
defines a new coordinate system (displaced and/or rotated) in which
subsequent surfaces are defined. Surfaces following a decenter are
aligned on the local mechanical axis (z-axis) of the new coordinate
system. The new mechanical axis remains in use until changed by
another decenter. The order in which displacements and tilts are
applied on a given surface is specified using different decenter
types and these generate different new coordinate systems; those
used here are explained below. Alpha, beta, and gamma are in
degrees. DECENTERING CONSTANT KEY: TYPE TRAILING CODE ORDER OF
APPLICATION DECENTER DISPLACE (X, Y, Z) TILT (ALPHA, BETA, GAMMA)
REFRACT AT SURFACE THICKNESS TO NEXT SURFACE DECENTER & BEND
BEND DECENTER (X, Y, Z, ALPHA, BETA, GAMMA) REFLECT AT SURFACE BEND
(ALPHA, BETA, GAMMA) THICKNESS TO NEXT SURFACE REFERENCE WAVELENGTH
= 193.3 NM SPECTRAL REGION = 193.3-193.3 NM This is non-symmetric
system. If elements with power are decentered or tilted, the first
order properties are probably inadequate in describing the system
characteristics. INFINITE CONJUGATES EFL = 8645.9595 BFL =
2159.9899 FFL = 23989.7701 F/NO = 0.0000 AT USED CONJUGATES
REDUCTION = -0.2500 FINITE F/NO = -0.3704 OBJECT DIST = 80.0000
TOTAL TRACK = 763.7529 IMAGE DIST = -1.5000 OAL = 685.2529 PARAXIAL
IMAGE HT = 18.1250 IMAGE DIST = -1.5000 SEMI-FIELD ANGLE = 0.0000
ENTR PUPIL DIAMETER = 0.717E+10 DISTANCE = 0.100E+11 EXIT PUPIL
DIAMETER = 4314.9615 DISTANCE = 2159.9951 NOTES FFL is measured
from the first surface BFL is measured from the last surface
[0193] It should be noted that the projection optical assembly 1216
provided herein is uniquely designed so that a plurality of
intermediate images are directed at the field splitting V-mirror
E-29 inside the projection optical assembly 1216. Stated in another
fashion, with the present design, the field splitting V-mirror E-29
is positioned away from the image plane of the optical assembly
1216. As used herein, the term "image plane" shall mean the plane
in which an image produced by the optical assembly is formed. With
the present design, the image plane of the optical assembly 1216 is
located at the substrate. Thus, in FIG. 12, elements E-30 through
E-46 separate the field splitting V-mirror E-29 from the image
plane. With the present design, many aberrated images are
transmitted through elements E-30-E-46. The aberrated images give
the optical designer much more flexibility in balancing aberrations
before and after the V-mirror E-29. This also enables the larger
field size for scanning along the short dimension of the site (X
axis scan), without a larger and more complicated optical
design.
[0194] Additionally, in the embodiment illustrated in FIG. 12, the
projection optical assembly 1216 is a Catadioptric design that
includes one or more lenses and one or more curved mirrors. In this
embodiment, the projection optical assembly 1216 includes at least
one concave mirror (e.g. E14 for each optical path), for the
purposes of field curvature correction over the large field size of
33 mm. It is conceivable that the projection optical assembly 1216
can be designed with more than one curved mirror per optical
path.
[0195] Further with the projection optical assembly 1216 provided
herein, the fold mirror E18 allows light to be incident on, and
reflected from, the concave mirror E14 without obscuration. The
fold direction is in the short direction of the field (e.g. 5 mm at
the wafer), and it is close to a second intermediate image (FIG. 12
illustrates the rays coming to a focus right next to E18, as they
do next to E29). This facilitates the folding arrangement at E18,
in the same way that it does at the V-mirror E29.
[0196] Additionally, it should be noted that the projection optical
assembly 1216 illustrated and described herein is a 4.times.
reduction system that reduces the size of the projected image
between elements E1 and E45. Alternatively, the projection optical
assembly 1216 can be designed to be a 1.times. system, a
magnification system, or a reduction system that is greater than or
less than 4.times..
[0197] FIG. 13 is a simplified perspective view that includes, a
first mask 1312A, a second mask 1312B, a third mask 1312C, a fourth
mask 1312D, and another embodiment of an optical assembly 1320. In
this embodiment, the optical assembly 1320 projects and/or focuses
a first pattern beam 1336A from the first mask 1312A, a second
pattern beam 1336B from the second mask 1312B, a third pattern beam
1336C from the third mask 1312C, and a fourth pattern beam 1336D
from the fourth mask 1312D onto the substrate 1414 (illustrated in
FIG. 14).
[0198] In this embodiment, the masks 1312A-1312D can be
individually positioned and individually illuminated, and the
substrate can be positioned with components that somewhat similar
to those described above and illustrated in FIG. 4. As provided
herein, the mask patterns from the four masks 1312A-1312D can be
sequentially transferred to the substrate 414 while the substrate
14 is being moved along the X axis (e.g. the scanning along the
short dimension of the site) to provide further improvements in the
throughput of the system.
[0199] One embodiment of a four mask exposure apparatus is
disclosed in concurrently filed application Ser. No. ______,
entitled "Optical Imaging System and Method for Imaging Up to Four
Reticles to a Single Imaging Location" (PAO1041-00/045004/Oremland
Ref. No. 6162.118US), which is assigned to the assignee of the
present invention, and is incorporated by reference herein.
[0200] The design of the optical assembly 1320 can be varied
depending on the requirements of the exposure apparatus. As
illustrated, the optical assembly 1320 is substantially similar to
the optical assembly 1220 illustrated in FIG. 12. For example, the
design, positioning and orientation of optical elements E6 through
E46 (the immersion fluid is not shown in FIG. 13) is substantially
repeated in this embodiment. Accordingly, a detailed description
that portion of the optical assembly 1320 will not be repeated
herein. However, the optical assembly 1320, as illustrated in the
embodiment shown in FIG. 13, includes (i) optical elements E1
through E5, which are positioned substantially between the first
mask 1312A and optical element E6 and are oriented substantially
transversely relative to optical element E6, (ii) optical elements
E1' through E5', which are positioned substantially between the
second mask 1312B and optical element E6 and are oriented
substantially transversely relative to optical element E6, (iii)
optical elements E1'' through E5'', which are positioned
substantially between the third mask 1312C and optical element E6''
and are oriented substantially transversely relative to optical
element E6'', and (iv) optical elements E1''' through E5''', which
are positioned substantially between the fourth mask 1312D and
optical element E6'' and are oriented substantially transversely
relative to optical element E6''.
[0201] Additionally, the optical assembly 1320 further includes a
first switching mirror 1384A that is positioned substantially
between optical elements E5 and E6 and between optical elements E5'
and E6, and a second switching mirror 1384B that is positioned
substantially between optical elements E5'' and E6'' and between
optical elements E5''' and E6'' on the opposite side of the optical
assembly 1320. The first switching mirror 1384A enables the optical
assembly 1320 to selectively, alternatively and/or sequentially
project and/or focus the first pattern beam 1336A from the first
mask 1312A onto the substrate 414, and the second pattern beam
1336B from the second mask 1312B onto the substrate 414. Similarly,
the second switching mirror 1384B enables the optical assembly 1320
to selectively, alternatively and/or sequentially project and/or
focus the third pattern beam 1336C from the third mask 1312C onto
the substrate 414, and the fourth pattern beam 1336D from the
fourth mask 1312D onto the substrate 414.
[0202] The process of the optical assembly 1320 projecting and/or
focusing the first pattern beam 1336A from the first mask 1312A
onto the substrate 414 is substantially similar to the projecting
and/or focusing of the second pattern beam 1336B from the second
mask 1312B, the third pattern beam 1336C from the third mask 1312C,
and/or the fourth pattern beam 1336D from the fourth mask 1312D
onto the substrate 414.
[0203] FIG. 14 is a simplified top view of one non-exclusive
embodiment of a substrate 1414 that was exposed utilizing the four
mask design and the optical assembly 1320 illustrated in FIG. 13.
The design of the substrate 1414 is similar to the substrate 414
described above and illustrated in FIG. 5A. However, in FIG. 14,
the sequence in which the sites 1415 are exposed is different.
[0204] In this embodiment, the substrate 1414 is again labeled "1"
through "32" (one through thirty-two). In this example, the labels
"1" through "32" represent one non-exclusive embodiment of the
sequence in which mask patterns from each of the first mask 1312A,
the second mask 1312B, the third mask 1312C and the fourth mask
1312D (illustrated In FIG. 13) can be transferred to the sites 1415
on the substrate 1414.
[0205] Moreover, FIG. 14 includes an exposure pattern 1452A
(illustrated with a dashed line) which further illustrates the
order in which the mask patterns are transferred to sites 1415. In
this example, the exposure pattern 1452A comprises a plurality of
scanning operations 1452B and a plurality of stepping operations
1452C, wherein the scanning operations 1452B and the stepping
operations 1452C alternate so that the exposure proceeds in a
scan-step-scan-step-scan fashion. In this embodiment, the scanning
1452B occurs as the substrate 1414 is moved along a scan axis 1458
(the X axis), and the stepping 1452C occurs as the substrate 1414
is moved along a step axis 1460 (the Y axis).
[0206] It should be noted that in this embodiment, the sites are
scanned along the short dimension of the sites. This allows for
greater throughput of the exposure apparatus because there are
fewer steps of the substrate 1414 required during the exposure of
the substrate 1414.
[0207] In this embodiment, because four individual masks 1312A,
1312B, 1312C, 1312D are utilized, four adjacent sites 1415 (e.g. 1,
2, 3 and 4) can be scanned sequentially while moving the substrate
1414 at a constant velocity along the scan axis 1458. As a result
thereof, the substrate 1414 does not have to be stepped and
reversed in direction between the exposures of adjacent sites 1415.
Instead, for the embodiment illustrated in FIG. 13, the substrate
1414 is only stepped between the exposure of sets of four adjacent
sites 1415 aligned on the scan axis 1458. Stated in another
fashion, with the present design, there is one stepping motion for
every four sites 1415 scanned. This results in fewer steps and
significantly improved throughput from the exposure apparatus 410
(illustrated in FIG. 4).
[0208] It should be noted that in this example, the site 1415 that
is exposed first and the order in which the sites 1415 are exposed
can be different than that illustrated in FIG. 14. Further, the
site 1415 that is first exposed can be located away from the edge
of the substrate 1414.
[0209] Semiconductor devices can be fabricated using the above
described systems, by the process shown generally in FIG. 15A. In
step 1501 the device's function and performance characteristics are
designed. Next, in step 1502, a mask (reticle) having a pattern is
designed according to the previous designing step, and in a
parallel step 1503 a wafer is made from a silicon material. The
mask pattern designed in step 1502 is exposed onto the wafer from
step 1503 in step 1504 by a photolithography system described
hereinabove in accordance with the present invention. In step 1505,
the semiconductor device is assembled (including the dicing
process, bonding process and packaging process), finally, the
device is then inspected in step 1506.
[0210] FIG. 15B illustrates a detailed flowchart example of the
above-mentioned step 1504 in the case of fabricating semiconductor
devices. In FIG. 15B, in step 1511 (oxidation step), the wafer
surface is oxidized. In step 1512 (CVD step), an insulation film is
formed on the wafer surface. In step 1513 (electrode formation
step), electrodes are formed on the wafer by vapor deposition. In
step 1514 (ion implantation step), ions are implanted in the wafer.
The above mentioned steps 1511-1514 form the preprocessing steps
for wafers during wafer processing, and selection is made at each
step according to processing requirements.
[0211] 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 1515 (photoresist formation step), photoresist is
applied to a wafer. Next, in step 1516 (exposure step), the
above-mentioned exposure device is used to transfer the circuit
pattern of a mask (reticle) to a wafer. Then in step 1517
(developing step), the exposed wafer is developed, and in step 1518
(etching step), parts other than residual photoresist (exposed
material surface) are removed by etching. In step 1518 (photoresist
removal step), unnecessary photoresist remaining after etching is
removed. Multiple circuit patterns are formed by repetition of
these preprocessing and post-processing steps.
[0212] It is to be understood that the exposure apparatuses 10
disclosed herein 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.
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