U.S. patent application number 13/240750 was filed with the patent office on 2012-01-12 for lithographic apparatus and device manufacturing method.
This patent application is currently assigned to ASML NETHERLANDS B.V.. Invention is credited to Hans Jansen, Marco Koert Stavenga, Martinus Cornelis Maria Verhagen, Jacobus Johannus Leonardus Hendricus Verspay.
Application Number | 20120008115 13/240750 |
Document ID | / |
Family ID | 36573769 |
Filed Date | 2012-01-12 |
United States Patent
Application |
20120008115 |
Kind Code |
A1 |
Verhagen; Martinus Cornelis Maria ;
et al. |
January 12, 2012 |
LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD
Abstract
A lithographic apparatus is disclosed wherein a liquid supply
system is configured to at least partly fill a region between a
substrate and a projection system of the lithographic apparatus
with a liquid and having a liquid confinement structure fixed in a
plane substantially perpendicular to an optical axis of the
projection system and configured to cooperate with a substrate
table configured to hold the substrate in order to restrict the
liquid to a region above an upper surface of the substrate table so
that a side of the substrate to be exposed is substantially covered
in the liquid during exposure.
Inventors: |
Verhagen; Martinus Cornelis
Maria; (Valkenswaard, NL) ; Jansen; Hans;
(Eindhoven, NL) ; Stavenga; Marco Koert;
(Eindhoven, NL) ; Verspay; Jacobus Johannus Leonardus
Hendricus; (Thorn, NL) |
Assignee: |
ASML NETHERLANDS B.V.
Veldhoven
NL
|
Family ID: |
36573769 |
Appl. No.: |
13/240750 |
Filed: |
September 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12153116 |
May 14, 2008 |
8045137 |
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13240750 |
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11005221 |
Dec 7, 2004 |
7397533 |
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12153116 |
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Current U.S.
Class: |
355/30 |
Current CPC
Class: |
G03F 7/70341 20130101;
G03F 7/70808 20130101 |
Class at
Publication: |
355/30 |
International
Class: |
G03B 27/52 20060101
G03B027/52 |
Claims
1. A lithographic apparatus, comprising: a substrate table
constructed to hold a substrate to be exposed; a projection system
configured to project a patterned radiation beam onto a target
portion on a side of the substrate to be exposed; a liquid supply
system configured to at least partly fill a region between the
substrate and the projection system with a liquid; and a liquid
confinement structure fixed in a plane substantially perpendicular
to an optical axis of the projection system and configured to
cooperate with the substrate table in order to restrict the liquid
to a region above an upper surface of the substrate table so that a
side of the substrate to be exposed is substantially covered in the
liquid during exposure.
2. The apparatus according to claim 1, wherein a portion of the
liquid confinement structure extends further towards the substrate
than any part of a final element of the projection system.
3. The apparatus according to claim 1, wherein the substrate table
comprises: a substrate seat configured to hold the substrate; and a
sealing projection surrounding the substrate seat in a plane
substantially perpendicular to the optical axis and configured to
cooperate with the liquid confinement structure so as to
substantially prevent liquid from escaping from the region between
the substrate and the projection system.
4. The apparatus according to claim 3, wherein the sealing
projection comprises a gas seal configured to substantially prevent
flow of liquid through a gap between a surface of the liquid
confinement structure and the sealing projection.
5. The apparatus according to claim 4, wherein the gas seal is
arranged to produce a flow of gas within the gap that is directed
substantially towards the optical axis in such a way as to at least
partially confine the liquid.
6. The apparatus according to claim 1, wherein: the liquid
confinement structure comprises a gas seal, and the substrate table
comprises a sealing zone arranged to cooperate with the gas seal so
as to substantially prevent liquid from escaping from the region
between the substrate and the projection system.
7. A lithographic apparatus, comprising: a projection system
configured to project a patterned radiation beam onto a target
portion of a substrate; a liquid supply system configured to at
least partly fill a region between the substrate and the projection
system with a liquid; and a saturated gas supply system configured
to provide substantially saturated gas to a surface of the
substrate not covered by liquid.
8. The apparatus according to claim 7, further comprising a liquid
confinement structure fixed in a plane substantially perpendicular
to an optical axis of the projection system and configured to
contain the liquid, the liquid confinement structure comprising an
extension structure extending substantially radially with respect
to the optical axis from the liquid confinement structure.
9. The apparatus according to claim 8, wherein the extension
structure is arranged to cooperate with a vapor sealing projection,
forming part of a substrate table configured to hold the substrate,
so as to substantially contain the substantially saturated gas.
10. The apparatus according to claim 9, wherein the extension
structure and the vapor sealing projection are configured to
contain the substantially saturated gas in a region delimited by
the substrate table, the substrate, the liquid when provided to the
region, the liquid confinement structure, the extension structure
and the vapor sealing projection.
11. The apparatus according to claim 9, wherein the vapor sealing
projection comprises a gas seal configured to substantially prevent
flow of substantially saturated gas through a gap between a surface
of the extension structure and the vapor sealing projection.
12. The apparatus according to claim 7, wherein the saturated gas
supply system comprises a saturated gas preparer configured to make
substantially saturated gas from the liquid.
13. The apparatus according to claim 7, wherein the liquid supply
system is configured to supply liquid to a region covering only a
localized portion of the substrate at any one time.
14. A lithographic apparatus, comprising: a substrate table
configured to hold a substrate to be exposed; a projection system
configured to project a patterned radiation beam onto a target
portion on a side of the substrate to be exposed; a liquid supply
system configured to at least partly fill a region between the
substrate and the projection system with a liquid; a first
confinement structure fixed in a plane substantially perpendicular
to an optical axis of the projection system and configured to
cooperate with the substrate table in order to restrict the liquid
to a region above an upper surface of the substrate table; and a
second confinement structure fixed in a plane substantially
perpendicular to an optical axis of the projection system and
configured to cooperate with the substrate table in order to
restrict substantially saturated gas to a region above an upper
surface of the substrate table, wherein the first and second
confinement structures and the substrate table are arranged so that
a side of the substrate to be exposed is entirely covered with
substantially saturated gas except for an area covered with liquid
during exposure.
15. The apparatus according to claim 14, wherein the substrate
table comprises a vapor sealing projection arranged to cooperate
with the second confinement structure so as to substantially
contain the substantially saturated gas.
16. The apparatus according to claim 15, wherein the second
confinement structure and the vapor sealing projection are
configured to contain the substantially saturated gas in a region
delimited by the substrate table, the substrate, the liquid when
provided to the region, the first confinement structure, the second
confinement structure and the vapor sealing projection.
17. The apparatus according to claim 15, wherein the vapor sealing
projection comprises a gas seal configured to substantially prevent
flow of substantially saturated gas through a gap between a surface
of the second confinement structure and the vapor sealing
projection.
18. The apparatus according to claim 14, wherein the liquid supply
system is configured to supply liquid to a region covering only a
localized portion of the substrate at any one time.
19. The apparatus according to claim 14, further comprising a
saturated gas supply system configured to provide substantially
saturated gas to a surface of the substrate not covered by
liquid.
20. A lithographic apparatus, comprising: a substrate table
configured to hold a substrate to be exposed; a projection system
configured to project a patterned radiation beam onto a target
portion of a substrate; a liquid supply system configured to at
least partly fill a region between the substrate and the projection
system with a liquid; a saturated gas supply system configured to
provide substantially saturated gas to a surface of the substrate
not covered by liquid; a first confinement structure fixed in a
plane substantially perpendicular to an optical axis of the
projection system and configured to contain the liquid; and a
second confinement structure fixed in a plane substantially
perpendicular to an optical axis of the projection system and
configured to cooperate with the substrate table in order to
restrict substantially saturated gas to a region above an upper
surface of the substrate table, wherein the first and second
confinement structures and the substrate table are arranged so that
aside of the substrate to be exposed is entirely covered with
substantially saturated gas except for an area covered with liquid
during exposure.
21.-42. (canceled)
Description
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 12/153,116, filed May 14, 2008, now allowed,
which is a divisional of U.S. patent application Ser. No.
11/005,221, filed Dec. 7, 2004, now U.S. Pat. No. 7,397,533, the
contents of each of the foregoing applications is incorporated
herein in its entirety by reference.
FIELD
[0002] The present invention relates to a lithographic apparatus
and a method for manufacturing a device.
BACKGROUND
[0003] A lithographic apparatus is a machine that applies a desired
pattern onto a substrate, usually onto a target portion of the
substrate. A lithographic apparatus can be used, for example, in
the manufacture of integrated circuits (ICs). In that instance, a
patterning device, which is alternatively referred to as a mask or
a reticle, may be used to generate a circuit pattern to be formed
on an individual layer of the IC. This pattern can be transferred
onto a target portion (e.g. comprising part of, one, or several
dies) on a substrate (e.g. a silicon wafer). Transfer of the
pattern is typically via imaging onto a layer of
radiation-sensitive material (resist) provided on the substrate. In
general, a single substrate will contain a network of adjacent
target portions that are successively patterned. Known lithographic
apparatus include so-called steppers, in which each target portion
is irradiated by exposing an entire pattern onto the target portion
at one time, and so-called scanners, in which each target portion
is irradiated by scanning the pattern through a radiation beam in a
given direction (the "scanning"-direction) while synchronously
scanning the substrate parallel or anti-parallel to this direction.
It is also possible to transfer the pattern from the patterning
device to the substrate by imprinting the pattern onto the
substrate
[0004] It has been proposed to immerse the substrate in the
lithographic projection apparatus in a liquid having a relatively
high refractive index, e.g. water, so as to fill a space between
the final element of the projection system and the substrate. The
point of this is to enable imaging of smaller features since the
exposure radiation will have a shorter wavelength in the liquid.
(The effect of the liquid may also be regarded as increasing the
effective NA of the system and also increasing the depth of focus.)
Other immersion liquids have been proposed, including water with
solid particles (e.g. quartz) suspended therein.
[0005] However, submersing the substrate or substrate and substrate
table in a bath of liquid (see, for example, U.S. Pat. No.
4,509,852, hereby incorporated in its entirety by reference) means
that there is a large body of liquid that must be accelerated
during a scanning exposure. This requires additional or more
powerful motors and turbulence in the liquid may lead to
undesirable and unpredictable effects.
[0006] One of the solutions proposed is for a liquid supply system
to provide liquid on only a localized area of the substrate and in
between the final element of the projection system and the
substrate (the substrate generally has a larger surface area than
the final element of the projection system). One way which has been
proposed to arrange for this is disclosed in PCT patent application
publication no. WO 99/49504, hereby incorporated in its entirety by
reference. As illustrated in FIGS. 2 and 3, liquid is supplied by
at least one inlet IN onto the substrate, preferably along the
direction of movement of the substrate relative to the final
element, and is removed by at least one outlet OUT after having
passed under the projection system. That is, as the substrate is
scanned beneath the element in a -X direction, liquid is supplied
at the +X side of the element and taken up at the -X side. FIG. 2
shows the arrangement schematically in which liquid is supplied via
inlet IN and is taken up on the other side of the element by outlet
OUT which is connected to a low pressure source. In the
illustration of FIG. 2 the liquid is supplied along the direction
of movement of the substrate relative to the final element, though
this does not need to be the case. Various orientations and numbers
of in- and out-lets positioned around the final element are
possible; one example is illustrated in FIG. 3 in which four sets
of an inlet with an outlet on either side are provided in a regular
pattern around the final element.
[0007] U.S. Pat. No. 6,788,477 discloses an immersion lithography
system in which the substrate is entirely covered by immersion
liquid during exposure. The liquid supply system for providing the
immersion liquid is provided in a "fluid-containing wafer stage",
which moves relative to the projection system. The wafer stage
disclosed includes a cover that helps to protect the fluid from the
atmospheric environment.
SUMMARY
[0008] A possible disadvantage of an immersion lithographic system
as disclosed in U.S. Pat. No. 6,788,477 is the supply of liquid to
a liquid containment system that moves during exposure. For this
reason, for example, an immersion lithographic system may comprise
a liquid supply system that is fixed relative to the projection
system, a substantially sealed volume of liquid being moved over
the substrate surface during exposure. However, liquid residue may
be left behind on the substrate with such a system due to, for
example, a leaky seal. Evaporation of such liquid, and cooling of
the substrate caused by such evaporation, may reduce the quality of
the image formed on the substrate.
[0009] Accordingly, it would be advantageous, for example, to
reduce the extent of imaging defects attributable to immersion
liquid.
[0010] According to an embodiment of the invention, there is
provided a lithographic apparatus, comprising:
[0011] a substrate table constructed to hold a substrate to be
exposed;
[0012] a projection system configured to project a patterned
radiation beam onto a target portion on a side of the substrate to
be exposed;
[0013] a liquid supply system configured to at least partly fill a
region between the substrate and the projection system with a
liquid; and
[0014] a liquid confinement structure fixed in a plane
substantially perpendicular to an optical axis of the projection
system and configured to cooperate with the substrate table in
order to restrict the liquid to a region above an upper surface of
the substrate table so that a side of the substrate to be exposed
is substantially covered in the liquid during exposure.
[0015] According to a further aspect of the invention, there is
provided a lithographic apparatus, comprising:
[0016] a projection system configured to project a patterned
radiation beam onto a target portion of a substrate;
[0017] a liquid supply system configured to at least partly fill a
region between the substrate and the projection system with a
liquid; and
[0018] a saturated gas supply system configured to provide
substantially saturated gas to a surface of the substrate not
covered by liquid.
[0019] According to a further aspect of the invention, there is
provided a lithographic apparatus, comprising:
[0020] a substrate table configured to hold a substrate to be
exposed;
[0021] a projection system configured to project a patterned
radiation beam onto a target portion on a side of the substrate to
be exposed;
[0022] a liquid supply system configured to at least partly fill a
region between the substrate and the projection system with a
liquid;
[0023] a first confinement structure fixed in a plane substantially
perpendicular to an optical axis of the projection system and
configured to cooperate with the substrate table in order to
restrict the liquid to a region above an upper surface of the
substrate table; and
[0024] a second confinement structure fixed in a plane
substantially perpendicular to an optical axis of the projection
system and configured to cooperate with the substrate table in
order to restrict substantially saturated gas to a region above an
upper surface of the substrate table,
[0025] wherein the first and second confinement structures and the
substrate table are arranged so that a side of the substrate to be
exposed is entirely covered with substantially saturated gas except
for an area covered with liquid during exposure.
[0026] According to a further aspect of the invention, there is
provided a lithographic apparatus, comprising:
[0027] a substrate table configured to hold a substrate to be
exposed;
[0028] a projection system configured to project a patterned
radiation beam onto a target portion of a substrate;
[0029] a liquid supply system configured to at least partly fill a
region between the substrate and the projection system with a
liquid;
[0030] a saturated gas supply system configured to provide
substantially saturated gas to a surface of the substrate not
covered by liquid;
[0031] a first confinement structure fixed in a plane substantially
perpendicular to an optical axis of the projection system and
configured to contain the liquid; and
[0032] a second confinement structure fixed in a plane
substantially perpendicular to an optical axis of the projection
system and configured to cooperate with the substrate table in
order to restrict substantially saturated gas to a region above an
upper surface of the substrate table,
[0033] wherein the first and second confinement structures and the
substrate table are arranged so that a side of the substrate to be
exposed is entirely covered with substantially saturated gas except
for an area covered with liquid during exposure.
[0034] According to further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0035] using a liquid confinement structure, that is fixed in a
plane substantially perpendicular to an optical axis of a
projection system of a lithographic apparatus and arranged to
cooperate with a substrate table of the lithographic apparatus
holding a substrate, to restrict a liquid to a region above an
upper surface of the substrate table and to maintain a side of the
substrate to be exposed entirely immersed in the liquid; and
[0036] projecting a patterned radiation beam through the liquid
onto a target portion of the substrate using the projection
system.
[0037] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0038] at least partly filling a region between a projection system
of a lithographic apparatus and a substrate with a liquid;
[0039] providing a substantially saturated gas to a surface of the
substrate not covered by liquid; and
[0040] projecting a patterned radiation beam through the liquid
onto a target portion of the substrate using the projection
system.
[0041] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0042] restricting a liquid to a region above an upper surface of a
substrate table of a lithographic apparatus holding a substrate
using a first confinement structure that is fixed in a plane
substantially perpendicular to an optical axis of a projection
system of a lithographic apparatus and arranged to cooperate with
the substrate table;
[0043] restricting substantially saturated gas to a region above an
upper surface of the substrate table using a second confinement
structure that is fixed in a plane substantially perpendicular to
the optical axis and arranged to cooperate with the substrate
table; and
[0044] projecting a patterned radiation beam through the liquid
onto a target portion of the substrate using the projection
system,
[0045] wherein the first and second liquid confinement structures
and the substrate table are arranged so that a side of the
substrate to be exposed is entirely covered with the substantially
saturated gas except for an area covered in the liquid during
exposure.
[0046] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0047] restricting a liquid to a region between a projection system
of a lithographic apparatus and a substrate held on a substrate
table of the lithographic apparatus using a first confinement
structure that is fixed in a plane substantially perpendicular to
an optical axis of the projection system;
[0048] supplying a substantially saturated gas to a surface of the
substrate not covered by liquid;
[0049] restricting substantially saturated gas to a region above an
upper surface of the substrate table using a second confinement
structure that is fixed in a plane substantially perpendicular to
the optical axis and arranged to cooperate with the substrate
table; and
[0050] projecting a patterned radiation beam through the liquid
onto a target portion of the substrate using the projection
system,
[0051] wherein the first and second confinement structures and the
substrate table are arranged so that a side of the substrate to be
exposed is entirely covered with the substantially saturated gas
except for an area covered in the liquid during exposure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying schematic
drawings in which corresponding reference symbols indicate
corresponding parts, and in which:
[0053] FIG. 1 depicts a lithographic apparatus according to an
embodiment of the invention;
[0054] FIGS. 2 and 3 depict a liquid supply system for use in a
lithographic projection apparatus;
[0055] FIG. 4 depicts another liquid supply system for use in a
lithographic projection apparatus;
[0056] FIG. 5 depicts an extended liquid confinement structure
arranged to cooperate with a substrate table comprising a sealing
zone according to an embodiment of the invention;
[0057] FIG. 6A depicts an extended liquid confinement structure
configured to interact with a substrate table comprising a sealing
projection according to an embodiment of the invention;
[0058] FIG. 6B shows a magnified view of the sealing projection of
FIG. 6A in the case where a gas seal is used to contain the
immersion liquid; and
[0059] FIGS. 7A and 7B depict a non-extended liquid confinement
structure configured to operate in combination with a gas seal
extension structure according to an embodiment of the
invention.
DETAILED DESCRIPTION
[0060] FIG. 1 schematically depicts a lithographic apparatus
according to an embodiment of the invention. The apparatus
comprises:
[0061] an illumination system (illuminator) IL configured to
condition a radiation beam B (e.g. UV radiation or DUV
radiation).
[0062] a support structure (e.g. a mask table) MT constructed to
support a patterning device (e.g. a mask) MA and connected to a
first positioner PM configured to accurately position the
patterning device in accordance with certain parameters;
[0063] a substrate table (e.g. a wafer table) WT constructed to
hold a substrate (e.g. a resist-coated wafer) W and connected to a
second positioner PW configured to accurately position the
substrate in accordance with certain parameters; and
[0064] a projection system (e.g. a refractive projection lens
system) PL configured to project a pattern imparted to the
radiation beam B by patterning device MA onto a target portion C
(e.g. comprising one or more dies) of the substrate W.
[0065] The illumination system may include various types of optical
components, such as refractive, reflective, magnetic,
electromagnetic, electrostatic or other types of optical
components, or any combination thereof, for directing, shaping, or
controlling radiation.
[0066] The support structure holds the patterning device in a
manner that depends on the orientation of the patterning device,
the design of the lithographic apparatus, and other conditions,
such as for example whether or not the patterning device is held in
a vacuum environment. The support structure can use mechanical,
vacuum, electrostatic or other clamping techniques to hold the
patterning device. The support structure may be a frame or a table,
for example, which may be fixed or movable as required. The support
structure may ensure that the patterning device is at a desired
position, for example with respect to the projection system. Any
use of the terms "reticle" or "mask" herein may be considered
synonymous with the more general term "patterning device."
[0067] The term "patterning device" used herein should be broadly
interpreted as referring to any device that can be used to impart a
radiation beam with a pattern in its cross-section such as to
create a pattern in a target portion of the substrate. It should be
noted that the pattern imparted to the radiation beam may not
exactly correspond to the desired pattern in the target portion of
the substrate, for example if the pattern includes phase-shifting
features or so called assist features. Generally, the pattern
imparted to the radiation beam will correspond to a particular
functional layer in a device being created in the target portion,
such as an integrated circuit.
[0068] The patterning device may be transmissive or reflective.
Examples of patterning devices include masks, programmable mirror
arrays, and programmable LCD panels. Masks are well known in
lithography, and include mask types such as binary, alternating
phase-shift, and attenuated phase-shift, as well as various hybrid
mask types. An example of a programmable mirror array employs a
matrix arrangement of small mirrors, each of which can be
individually tilted so as to reflect an incoming radiation beam in
different directions. The tilted mirrors impart a pattern in a
radiation beam which is reflected by the mirror matrix.
[0069] The term "projection system" used herein should be broadly
interpreted as encompassing any type of projection system,
including refractive, reflective, catadioptric, magnetic,
electromagnetic and electrostatic optical systems, or any
combination thereof, as appropriate for the exposure radiation
being used, or for other factors such as the use of an immersion
liquid or the use of a vacuum. Any use of the term "projection
lens" herein may be considered as synonymous with the more general
term "projection system".
[0070] As here depicted, the apparatus is of a transmissive type
(e.g. employing a transmissive mask). Alternatively, the apparatus
may be of a reflective type (e.g. employing a programmable mirror
array of a type as referred to above, or employing a reflective
mask).
[0071] The lithographic apparatus may be of a type having two (dual
stage) or more substrate tables (and/or two or more patterning
device support structures). In such "multiple stage" machines, the
additional tables may be used in parallel, or preparatory steps may
be carried out on one or more tables while one or more other tables
are being used for exposure.
[0072] Referring to FIG. 1, the illuminator IL receives a radiation
beam from a radiation source SO. The source and the lithographic
apparatus may be separate entities, for example when the source is
an excimer laser. In such cases, the source is not considered to
form part of the lithographic apparatus and the radiation beam is
passed from the source SO to the illuminator IL with the aid of a
beam delivery system BD comprising, for example, suitable directing
minors and/or a beam expander. In other cases the source may be an
integral part of the lithographic apparatus, for example when the
source is a mercury lamp. The source SO and the illuminator IL,
together with the beam delivery system BD if required, may be
referred to as a radiation system.
[0073] The illuminator IL may comprise an adjuster AD for adjusting
the angular intensity distribution of the radiation beam.
Generally, at least the outer and/or inner radial extent (commonly
referred to as .sigma.-outer and .sigma.-inner, respectively) of
the intensity distribution in a pupil plane of the illuminator can
be adjusted. In addition, the illuminator IL may comprise various
other components, such as an integrator IN and a condenser CO. The
illuminator may be used to condition the radiation beam, to have a
desired uniformity and intensity distribution in its
cross-section.
[0074] The radiation beam B is incident on the patterning device
(e.g., mask MA), which is held on the support structure MT (e.g.,
mask table), and is patterned by the patterning device. Having
traversed the patterning device MA, the radiation beam B passes
through the projection system PL, which focuses the beam onto a
target portion C of the substrate W. With the aid of the second
positioner PW and position sensor IF (e.g. an interferometric
device, linear encoder or capacitive sensor), the substrate table
WT can be moved accurately, e.g. so as to position different target
portions C in the path of the radiation beam B. Similarly, the
first positioner PM and another position sensor (which is not
explicitly depicted in FIG. 1) can be used to accurately position
the patterning device MA with respect to the path of the radiation
beam B, e.g. after mechanical retrieval from a mask library, or
during a scan. In general, movement of the support structure MT may
be realized with the aid of a long-stroke module (coarse
positioning) and a short-stroke module (fine positioning), which
form part of the first positioner PM. Similarly, movement of the
substrate table WT may be realized using a long-stroke module and a
short-stroke module, which form part of the second positioner PW.
In the case of a stepper (as opposed to a scanner) the support
structure MT may be connected to a short-stroke actuator only, or
may be fixed. Patterning device MA and substrate W may be aligned
using patterning device alignment marks M1, M2 and substrate
alignment marks P1, P2. Although the substrate alignment marks as
illustrated occupy dedicated target portions, they may be located
in spaces between target portions (these are known as scribe-lane
alignment marks). Similarly, in situations in which more than one
die is provided on the patterning device MA, the patterning device
alignment marks may be located between the dies.
[0075] The depicted apparatus could be used in at least one of the
following modes:
1. In step mode, the support structure MT and the substrate table
WT are kept essentially stationary, while an entire pattern
imparted to the radiation beam is projected onto a target portion C
at one time (i.e. a single static exposure). The substrate table WT
is then shifted in the X and/or Y direction so that a different
target portion C can be exposed. In step mode, the maximum size of
the exposure field limits the size of the target portion C imaged
in a single static exposure. 2. In scan mode, the support structure
MT and the substrate table WT are scanned synchronously while a
pattern imparted to the radiation beam is projected onto a target
portion C (i.e. a single dynamic exposure). The velocity and
direction of the substrate table WT relative to the support
structure MT may be determined by the (de-)magnification and image
reversal characteristics of the projection system PL. In scan mode,
the maximum size of the exposure field limits the width (in the
non-scanning direction) of the target portion in a single dynamic
exposure, whereas the length of the scanning motion determines the
height (in the scanning direction) of the target portion. 3. In
another mode, the support structure MT is kept essentially
stationary holding a programmable patterning device, and the
substrate table WT is moved or scanned while a pattern imparted to
the radiation beam is projected onto a target portion C. In this
mode, generally a pulsed radiation source is employed and the
programmable patterning device is updated as required after each
movement of the substrate table WT or in between successive
radiation pulses during a scan. This mode of operation can be
readily applied to maskless lithography that utilizes programmable
patterning device, such as a programmable mirror array of a type as
referred to above.
[0076] Combinations and/or variations on the above described modes
of use or entirely different modes of use may also be employed.
[0077] A further immersion lithography solution with a localized
liquid supply system is shown in FIG. 4. Liquid is supplied by two
groove inlets IN on either side of the projection system PL and is
removed by a plurality of discrete outlets OUT arranged radially
outwardly of the inlets IN. The inlets IN and OUT can be arranged
in a plate with a hole in its center and through which the
projection beam is projected. Liquid is supplied by one groove
inlet IN on one side of the projection system PL and removed by a
plurality of discrete outlets OUT on the other side of the
projection system PL, causing a flow of a thin film of liquid
between the projection system PL and the substrate W. The choice of
which combination of inlet IN and outlets OUT to use can depend on
the direction of movement of the substrate W (the other combination
of inlet IN and outlets OUT being inactive).
[0078] Another immersion lithography solution with a localized
liquid supply system solution which has been proposed is to provide
the liquid supply system with a liquid confinement structure which
extends along at least a part of a boundary of the space between
the final element of the projection system and the substrate table.
The liquid confinement structure is substantially stationary
relative to the projection system in the XY plane though there may
be some relative movement in the Z direction (in the direction of
the optical axis). A seal is formed between the liquid confinement
structure and the surface of the substrate. In an embodiment, the
seal is a contactless seal such as a gas seal. Such a system with a
gas seal is disclosed in U.S. patent application Ser. No.
10/705,783, hereby incorporated in its entirety by reference.
[0079] Using the localized liquid supply system having a liquid
confinement structure described above as an example, the liquid
confinement structure is used to contain a liquid film in a region
between a portion of the substrate W to be exposed and the
projection system PL. After exposure of a particular target region
or "die" on the substrate, the substrate table WT is moved relative
to the projection system PL and a portion of the substrate W that
was previously immersed in immersion liquid is exposed to the
atmosphere around the liquid confinement structure. The area of the
substrate W wetted by the liquid is generally larger than the
surface area of each of the dies exposed. The practical effect of
this is that some dies are exposed that comprise at least a portion
that has been wetted and dried before. This effect may also arise
in the other localized liquid supply systems, such as those
described herein. Although steps may be taken to reduce the level
of contaminants in the immersion liquid, and to minimize the amount
of liquid left behind after the liquid confinement structure has
passed, it is likely that some contamination will remain and some
immersion liquid will be left on the substrate. Contaminants left
behind as the liquid evaporates may cause errors when the target
region concerned comes to be exposed to the patterned radiation
beam. In addition, overlay and other errors may be caused by
cooling caused by evaporation of the residue liquid.
[0080] According to an embodiment of the present invention,
evaporation of immersion liquid from the substrate may be stemmed
while target portions or dies on the substrate are being exposed.
In this way, contaminants that may be present in the immersion
liquid remain suspended within the liquid during exposure rather
than being concentrated at the level of the top surface of the
substrate. In other words, the contaminants remain generally out of
focus and therefore have a more limited effect on the quality of
the image formed on the substrate. Furthermore, heat loss from
evaporation during exposure may be reduced (or entirely avoided)
because of the reduction (or complete prevention) of evaporation
during this period. This may reduce imaging errors caused by
contaminants on the substrate surface as well as those caused by
thermal shrinkage without necessarily having to resort to complex
and expensive methods of reducing the level of contamination in the
immersion liquid (which may never be possible to such an extent
that the effect of contaminants would be entirely negligible) or
arranging for removal of immersion liquid from the substrate as the
liquid confinement structure moves past (which again may not be
possible without expense and without risking side effects that may
be damaging in other ways to the image printed to the
substrate)
[0081] FIG. 5 illustrates an embodiment of the invention wherein a
reservoir of immersion liquid 25 is formed by a liquid confinement
structure 12 positioned below and surrounding the final element of
a projection system PL. Liquid is brought into the space below the
projection system and within the liquid confinement structure 12 by
a liquid supply system 18. The liquid confinement structure 12
extends a little above the final element of the projection system
PL and the liquid level rises above the final element so that a
buffer of liquid is provided. The liquid confinement structure 12
has an inner periphery that at the upper end preferably closely
conforms to the shape of the projection system or the final element
thereof and may, e.g., be round. At the bottom, the inner periphery
closely conforms to the shape of the image field, e.g., rectangular
though this need not be the case.
[0082] According to this embodiment, the liquid is confined in the
reservoir 25 by a gas seal 16 between the bottom of the liquid
confinement structure 12 and a sealing zone 40, surrounding a
substrate seat 60, defining where a substrate will be held on the
substrate table WT during exposure. The sealing zone 40 is arranged
to be wide enough that the gas seal 16 is always positioned
directly over a portion of it for all positions of the substrate
table WT relative to the liquid confinement structure 12 and
projection system PL during exposure of the substrate W. Therefore,
the interface maintained by the liquid confinement structure 16
between the liquid and the gas surrounding the liquid confinement
structure 12 is kept within the sealing zone 40. The gas seal is
formed by gas, e.g. air, synthetic air, N.sub.2 or an inert gas,
provided under pressure via inlet 15 to the gap between liquid
confinement structure 12 and substrate W and extracted via outlet
14. The overpressure on the gas inlet 15, vacuum level on the
outlet 14 and geometry of the gap are arranged so that there is a
high-velocity gas flow inwards that confines the liquid. In an
embodiment, the gas seal may simply be the gas outlet 14 drawing
liquid and gas from an area surrounding the liquid confinement
structure 12.
[0083] FIGS. 6A and 6B illustrate an embodiment of the invention
that is analogous to that depicted in FIG. 5 but which does not
require an extended substrate table WT to accommodate a sealing
zone 40 or similar. Instead, the substrate table WT is provided
with a sealing projection 50, which is arranged to surround a
substrate seat 60. The sealing projection 50 is arranged to contain
liquid within a region between the substrate table WT, the liquid
confinement structure 12 and a final element of the projection
system PL in such a way that substantially the whole substrate W is
covered in liquid during exposure of each target area. As before,
the substrate table WT can move relative to the liquid confinement
structure 12 and the projection system PL with a seal being
provided between a lower surface of the liquid confinement
structure 12 and the sealing projection 50, for example a
contactless seal such as a gas seal as described above, at the tip
52 of the sealing projection 50. FIG. 6B shows an enlarged view of
the region around a tip 52 of the sealing projection 50. According
to the embodiment shown, the sealing projection 50 comprises a gas
seal 55 with a gas inlet 15 and a gas outlet 14, the gas seal 55
being arranged to operate in the same, or analogous, way as the gas
seal 16 discussed above with reference to FIG. 5. In an embodiment,
the gas seal 55 may simply be the gas outlet 14 drawing liquid and
gas from an area surrounding the liquid confinement structure 12
and/or substrate table WT.
[0084] An advantage of providing the gas seal 55 as part of the
substrate table WT, as depicted in FIGS. 6A and 6B, rather than the
liquid confinement structure 12 is that the substrate table WT
could be made more compact. On the other hand, an advantage of the
embodiment depicted in FIG. 5, where the gas seal is provided in
the liquid confinement structure 12, is that the apparatus needed
to realize the gas supply and exhaust system associated with the
gas seal could be provided more easily in a stationary system such
as the liquid confinement structure 12, and with less risk of
mechanical or thermal side effects influencing the imaging process,
than in a moving system such as the substrate table WT.
[0085] FIGS. 7A and 7B illustrate an embodiment of the invention
wherein a region of liquid is maintained between the substrate W
and the final element of the projection system PL and is radially
constrained by a gas seal 16 in a liquid confinement structure 12.
A gaseous region 76 substantially saturated with a vapor 75 of the
liquid 25 (or other liquid) is maintained outside of the gas seal
16 in such a way that each target area on the face of the substrate
W is immersed either in the liquid 25 or the substantially
saturated gas 75 for the whole period from exposure of a first
target portion on the substrate W to exposure of the final target
portion on substrate W. In order to achieve this effect, the liquid
confinement structure 12 is provided with an extension structure
70, which is fixed with respect to the liquid confinement structure
12 and extends radially. The substrate table WT is provided with a
vapor sealing projection 80 which surrounds a substrate seat 60 of
the substrate table WT. The vapor sealing projection 80 is arranged
to cooperate with the extension structure 70 in such a way that the
substrate table WT can move with respect to the projection system
PL in order to expose different portions of the substrate W while
at the same time preventing substantially saturated gas from
escaping from the region between the gas seal 16, extension
structure 70 and vapor sealing projection 80. FIG. 7B shows a
magnified view of a cross section of the liquid confinement
structure 12, showing the gas seal 16 with an inlet 15 and an
outlet 14 operating according to the principle described above with
reference to FIG. 5, and a vapor duct 17, which acts to maintain
the substantially saturated gas composition and pressure within a
desired range. This may be implemented via a single duct 17 where a
flow of substantially saturated gas isn't necessary. In order to
control one or more properties of the substantially saturated gas
above the substrate W, the duct 17 may be connected to a saturated
gas reservoir 90, which may contain one or more components to
control one or more properties of the vapor supplied to the region
76, including, for example, a temperature sensor 98 coupled with a
temperature controller 92, a pressure sensor 100 coupled with a
pressure controller 94, and/or a composition sensor 102 coupled
with a composition controller 96. The composition controller 102
may include a liquid vapor source and sink, which may exchange, for
example, liquid with the liquid supply system 18 via duct 110. More
generally, a saturated gas preparer may be provided to make
substantially saturated gas from the immersion liquid using any
presently known or future devices and/or methods of creating
saturated gas.
[0086] According to the arrangement shown, liquid remaining on the
substrate W after the liquid confinement structure 12 has passed by
will remain in liquid form because of the substantially saturated
gas maintained above the substrate W. The lack of evaporation means
that substrate shrinkage problems as well as accumulation of
contaminants at the substrate surface may be avoided. The vapor
sealing projection 80 may operate in an analogous fashion to the
sealing projection illustrated in FIGS. 6A and 6B by using a gas
seal as described above. The embodiment of FIGS. 7A and 7B has an
advantage of reducing the volume of immersion liquid maintained in
the region of the substrate W (which may be advantageous, for
example, from the point of view of maintaining liquid purity). It
also may avoid the situation where the gas seal 16 overlaps the
edge of the substrate W where gaps can exist that may disrupt the
operation of the gas seal 16 and therefore the stability of the
liquid confinement structure 12. In addition, it may be
advantageous to avoid having to provide means to cope with liquid
seeping into the region behind the substrate W.
[0087] In European Patent Application No. 03257072.3, the idea of a
twin or dual stage immersion lithography apparatus is disclosed.
Such an apparatus is provided with two tables for supporting a
substrate. Leveling measurements are carried out with a table at a
first position, without immersion liquid, and exposure is carried
out with a table at a second position, where immersion liquid is
present. Alternatively, the apparatus has only one table.
[0088] In an embodiment, there is provided a lithographic
apparatus, comprising: a substrate table constructed to hold a
substrate to be exposed; a projection system configured to project
a patterned radiation beam onto a target portion on a side of the
substrate to be exposed; a liquid supply system configured to at
least partly fill a region between the substrate and the projection
system with a liquid; and a liquid confinement structure fixed in a
plane substantially perpendicular to an optical axis of the
projection system and configured to cooperate with the substrate
table in order to restrict the liquid to a region above an upper
surface of the substrate table so that a side of the substrate to
be exposed is substantially covered in the liquid during
exposure.
[0089] In an embodiment, a portion of the liquid confinement
structure extends further towards the substrate than any part of a
final element of the projection system. In an embodiment, the
substrate table comprises: a substrate seat configured to hold the
substrate; and a sealing projection surrounding the substrate seat
in a plane substantially perpendicular to the optical axis and
configured to cooperate with the liquid confinement structure so as
to substantially prevent liquid from escaping from the region
between the substrate and the projection system. In an embodiment,
the sealing projection comprises a gas seal configured to
substantially prevent flow of liquid through a gap between a
surface of the liquid confinement structure and the sealing
projection. In an embodiment, the gas seal is arranged to produce a
flow of gas within the gap that is directed substantially towards
the optical axis in such a way as to at least partially confine the
liquid. In an embodiment, the liquid confinement structure
comprises a gas seal, and the substrate table comprises a sealing
zone arranged to cooperate with the gas seal so as to substantially
prevent liquid from escaping from the region between the substrate
and the projection system.
[0090] In an embodiment, there is provided a lithographic
apparatus, comprising: a projection system configured to project a
patterned radiation beam onto a target portion of a substrate; a
liquid supply system configured to at least partly fill a region
between the substrate and the projection system with a liquid; and
a saturated gas supply system configured to provide substantially
saturated gas to a surface of the substrate not covered by
liquid.
[0091] In an embodiment, the apparatus further comprises a liquid
confinement structure fixed in a plane substantially perpendicular
to an optical axis of the projection system and configured to
contain the liquid, the liquid confinement structure comprising an
extension structure extending substantially radially with respect
to the optical axis from the liquid confinement structure. In an
embodiment, the extension structure is arranged to cooperate with a
vapor sealing projection, forming part of a substrate table
configured to hold the substrate, so as to substantially contain
the substantially saturated gas. In an embodiment, the extension
structure and the vapor sealing projection are configured to
contain the substantially saturated gas in a region delimited by
the substrate table, the substrate, the liquid when provided to the
region, the liquid confinement structure, the extension structure
and the vapor sealing projection. In an embodiment, the vapor
sealing projection comprises a gas seal configured to substantially
prevent flow of substantially saturated gas through a gap between a
surface of the extension structure and the vapor sealing
projection. In an embodiment, the saturated gas supply system
comprises a saturated gas preparer configured to make substantially
saturated gas from the liquid. In an embodiment, the liquid supply
system is configured to supply liquid to a region covering only a
localized portion of the substrate at any one time.
[0092] In an embodiment, there is provided a lithographic
apparatus, comprising: a substrate table configured to hold a
substrate to be exposed; a projection system configured to project
a patterned radiation beam onto a target portion on a side of the
substrate to be exposed; a liquid supply system configured to at
least partly fill a region between the substrate and the projection
system with a liquid; a first confinement structure fixed in a
plane substantially perpendicular to an optical axis of the
projection system and configured to cooperate with the substrate
table in order to restrict the liquid to a region above an upper
surface of the substrate table; and a second confinement structure
fixed in a plane substantially perpendicular to an optical axis of
the projection system and configured to cooperate with the
substrate table in order to restrict substantially saturated gas to
a region above an upper surface of the substrate table, wherein the
first and second confinement structures and the substrate table are
arranged so that a side of the substrate to be exposed is entirely
covered with substantially saturated gas except for an area covered
with liquid during exposure.
[0093] In an embodiment, the substrate table comprises a vapor
sealing projection arranged to cooperate with the second
confinement structure so as to substantially contain the
substantially saturated gas. In an embodiment, the second
confinement structure and the vapor sealing projection are
configured to contain the substantially saturated gas in a region
delimited by the substrate table, the substrate, the liquid when
provided to the region, the first confinement structure, the second
confinement structure and the vapor sealing projection. In an
embodiment, the vapor sealing projection comprises a gas seal
configured to substantially prevent flow of substantially saturated
gas through a gap between a surface of the second confinement
structure and the vapor sealing projection. In an embodiment, the
liquid supply system is configured to supply liquid to a region
covering only a localized portion of the substrate at any one time.
In an embodiment, the apparatus further comprises a saturated gas
supply system configured to provide substantially saturated gas to
a surface of the substrate not covered by liquid.
[0094] In an embodiment, there is provided a lithographic
apparatus, comprising: a substrate table configured to hold a
substrate to be exposed; a projection system configured to project
a patterned radiation beam onto a target portion of a substrate; a
liquid supply system configured to at least partly fill a region
between the substrate and the projection system with a liquid; a
saturated gas supply system configured to provide substantially
saturated gas to a surface of the substrate not covered by liquid;
a first confinement structure fixed in a plane substantially
perpendicular to an optical axis of the projection system and
configured to contain the liquid; and a second confinement
structure fixed in a plane substantially perpendicular to an
optical axis of the projection system and configured to cooperate
with the substrate table in order to restrict substantially
saturated gas to a region above an upper surface of the substrate
table, wherein the first and second confinement structures and the
substrate table are arranged so that a side of the substrate to be
exposed is entirely covered with substantially saturated gas except
for an area covered with liquid during exposure.
[0095] In an embodiment, the substrate table comprises a vapor
sealing projection arranged to cooperate with the second
confinement structure so as to substantially contain the
substantially saturated gas. In an embodiment, the vapor sealing
projection comprises a gas seal configured to substantially prevent
flow of substantially saturated gas through a gap between a surface
of the second confinement structure and the vapor sealing
projection.
[0096] In an embodiment, there is provided a device manufacturing
method, comprising: using a liquid confinement structure, that is
fixed in a plane substantially perpendicular to an optical axis of
a projection system of a lithographic apparatus and arranged to
cooperate with a substrate table of the lithographic apparatus
holding a substrate, to restrict a liquid to a region above an
upper surface of the substrate table and to maintain a side of the
substrate to be exposed entirely immersed in the liquid; and
projecting a patterned radiation beam through the liquid onto a
target portion of the substrate using the projection system.
[0097] In an embodiment, the method further comprises substantially
preventing the liquid from escaping from a region between the
substrate and the projection system using a sealing projection
surrounding the substrate in a plane substantially perpendicular to
the optical axis and configured to cooperate with the liquid
confinement structure. In an embodiment, the method comprises
substantially preventing flow of liquid through a gap between a
surface of the liquid confinement structure and the sealing
projection using a gas seal. In an embodiment, the method further
comprises substantially preventing liquid from escaping from a
region between the substrate and the projection system using a gas
seal of the liquid confinement structure cooperating with a sealing
zone of the substrate table.
[0098] In an embodiment, there is provided a device manufacturing
method, comprising: at least partly filling a region between a
projection system of a lithographic apparatus and a substrate with
a liquid; providing a substantially saturated gas to a surface of
the substrate not covered by liquid; and projecting a patterned
radiation beam through the liquid onto a target portion of the
substrate using the projection system.
[0099] In an embodiment, the method further comprises containing
the liquid using a liquid confinement structure fixed in a plane
substantially perpendicular to an optical axis of the projection
system, the liquid confinement structure comprising an extension
structure extending substantially radially with respect to the
optical axis from the liquid confinement structure. In an
embodiment, the method comprises substantially containing the
substantially saturated gas using the extension structure in
cooperation with a vapor sealing projection forming part of a
substrate table holding the substrate. In an embodiment, the method
comprises containing the substantially saturated gas in a region
delimited by the substrate table, the substrate, the liquid when
provided to the region, the liquid confinement structure, the
extension structure and the vapor sealing projection. In an
embodiment, the method comprises substantially preventing flow of
substantially saturated gas through a gap between a surface of the
extension structure and the vapor sealing projection using a gas
seal. In an embodiment, the method further comprises making the
substantially saturated gas from the liquid. In an embodiment, the
liquid covers only a localized portion of the substrate at any one
time.
[0100] In an embodiment, there is provided a device manufacturing
method, comprising: restricting a liquid to a region above an upper
surface of a substrate table of a lithographic apparatus holding a
substrate using a first confinement structure that is fixed in a
plane substantially perpendicular to an optical axis of a
projection system of a lithographic apparatus and arranged to
cooperate with the substrate table; restricting substantially
saturated gas to a region above an upper surface of the substrate
table using a second confinement structure that is fixed in a plane
substantially perpendicular to the optical axis and arranged to
cooperate with the substrate table; and projecting a patterned
radiation beam through the liquid onto a target portion of the
substrate using the projection system, wherein the first and second
confinement structures and the substrate table are arranged so that
a side of the substrate to be exposed is entirely covered with the
substantially saturated gas except for an area covered in the
liquid during exposure.
[0101] In an embodiment, the method comprises substantially
containing the substantially saturated gas using a vapor sealing
projection of the substrate table in cooperation with the second
confinement structure. In an embodiment, the method comprises
substantially containing the substantially saturated gas in a
region delimited by the substrate table, the substrate, the liquid
when provided to the region, the first confinement structure, the
second confinement structure and the vapor sealing projection. In
an embodiment, the method comprising substantially preventing flow
of substantially saturated gas through a gap between a surface of
the second confinement structure and the vapor sealing projection
using a gas seal. In an embodiment, the liquid covers only a
localized portion of the substrate at any one time. In an
embodiment, the method further comprises providing a substantially
saturated gas to a surface of the substrate not covered by
liquid.
[0102] In an embodiment, there is provided a device manufacturing
method, comprising: restricting a liquid to a region between a
projection system of a lithographic apparatus and a substrate held
on a substrate table of the lithographic apparatus using a first
confinement structure that is fixed in a plane substantially
perpendicular to an optical axis of the projection system;
supplying a substantially saturated gas to a surface of the
substrate not covered by liquid; restricting substantially
saturated gas to a region above an upper surface of the substrate
table using a second confinement structure that is fixed in a plane
substantially perpendicular to the optical axis and arranged to
cooperate with the substrate table; and projecting a patterned
radiation beam through the liquid onto a target portion of the
substrate using the projection system, wherein the first and second
confinement structures and the substrate table are arranged so that
a side of the substrate to be exposed is entirely covered with the
substantially saturated gas except for an area covered in the
liquid during exposure.
[0103] In an embodiment, the method comprises substantially
containing the substantially saturated gas using a vapor sealing
projection of the substrate table in cooperation with the second
confinement structure. In an embodiment, the method comprises
substantially preventing flow of substantially saturated gas
through a gap between a surface of the second confinement structure
and the vapor sealing projection using a gas seal.
[0104] Although specific reference may be made in this text to the
use of lithographic apparatus in the manufacture of ICs, it should
be understood that the lithographic apparatus described herein may
have other applications, such as the manufacture of integrated
optical systems, guidance and detection patterns for magnetic
domain memories, flat-panel displays, liquid-crystal displays
(LCDs), thin-film magnetic heads, etc. The skilled artisan will
appreciate that, in the context of such alternative applications,
any use of the terms "wafer" or "die" herein may be considered as
synonymous with the more general terms "substrate" or "target
portion", respectively. The substrate referred to herein may be
processed, before or after exposure, in for example a track (a tool
that typically applies a layer of resist to a substrate and
develops the exposed resist), a metrology tool and/or an inspection
tool. Where applicable, the disclosure herein may be applied to
such and other substrate processing tools. Further, the substrate
may be processed more than once, for example in order to create a
multi-layer IC, so that the term substrate used herein may also
refer to a substrate that already contains multiple processed
layers.
[0105] The terms "radiation" and "beam" used herein encompass all
types of electromagnetic radiation, including ultraviolet (UV)
radiation (e.g. having a wavelength of or about 365, 248, 193, 157
or 126 nm).
[0106] The term "lens", where the context allows, may refer to any
one or combination of various types of optical components,
including refractive and reflective optical components.
[0107] While specific embodiments of the invention have been
described above, it will be appreciated that the invention may be
practiced otherwise than as described. For example, the invention
may take the form of a computer program containing one or more
sequences of machine-readable instructions describing a method as
disclosed above, or a data storage medium (e.g. semiconductor
memory, magnetic or optical disk) having such a computer program
stored therein.
[0108] One or more embodiments of the present invention may be
applied to any immersion lithography apparatus, in particular, but
not exclusively, to those types mentioned above. A liquid supply
system is any mechanism that provides a liquid to a space between
the projection system and the substrate and/or substrate table. It
may comprise any combination of one or more structures, one or more
liquid inlets, one or more gas inlets, one or more gas outlets,
and/or one or more liquid outlets, the combination providing and
confining the liquid to the space. In an embodiment, a surface of
the space may be limited to a portion of the substrate and/or
substrate table, a surface of the space may completely cover a
surface of the substrate and/or substrate table, or the space may
envelop the substrate and/or substrate table.
[0109] The descriptions above are intended to be illustrative, not
limiting. Thus, it will be apparent to one skilled in the art that
modifications may be made to the invention as described without
departing from the scope of the claims set out below.
* * * * *