U.S. patent application number 16/008355 was filed with the patent office on 2018-10-11 for lithographic apparatus, drying device, metrology apparatus and device manufacturing method.
This patent application is currently assigned to ASML NETHERLANDS B.V.. The applicant listed for this patent is ASML NETHERLANDS B.V.. Invention is credited to Anca Mihaela ANTONEVICI, Adrianes Johannes BAETEN, Marcel BECKERS, Nicolaas Rudolf KEMPER, Anthonie KUIJPER, Joost Jeroen OTTENS, Marco POLIZZI, Michel RIEPEN, Koen STEFFENS, Nicolaas TEN KATE.
Application Number | 20180292762 16/008355 |
Document ID | / |
Family ID | 41696074 |
Filed Date | 2018-10-11 |
United States Patent
Application |
20180292762 |
Kind Code |
A1 |
KEMPER; Nicolaas Rudolf ; et
al. |
October 11, 2018 |
LITHOGRAPHIC APPARATUS, DRYING DEVICE, METROLOGY APPARATUS AND
DEVICE MANUFACTURING METHOD
Abstract
An immersion lithographic apparatus is described in which a
two-phase flow is separated into liquid-rich and gas-rich flows by
causing the liquid-rich flow to preferentially flow along a
surface.
Inventors: |
KEMPER; Nicolaas Rudolf;
(Eindhoven, NL) ; TEN KATE; Nicolaas; (Almkerk,
NL) ; OTTENS; Joost Jeroen; (Veldhoven, NL) ;
BECKERS; Marcel; (Eindhoven, NL) ; POLIZZI;
Marco; (Eindhoven, NL) ; RIEPEN; Michel;
(Veldhoven, NL) ; KUIJPER; Anthonie; (Best,
NL) ; STEFFENS; Koen; (Veldhoven, NL) ;
BAETEN; Adrianes Johannes; (Eindhoven, NL) ;
ANTONEVICI; Anca Mihaela; (Veldhoven, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASML NETHERLANDS B.V. |
Veldhoven |
|
NL |
|
|
Assignee: |
ASML NETHERLANDS B.V.
Veldhoven
NL
|
Family ID: |
41696074 |
Appl. No.: |
16/008355 |
Filed: |
June 14, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15452445 |
Mar 7, 2017 |
10018925 |
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16008355 |
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|
14498883 |
Sep 26, 2014 |
9606429 |
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15452445 |
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12543011 |
Aug 18, 2009 |
8953142 |
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14498883 |
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61136216 |
Aug 19, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 19/0021 20130101;
G03F 7/70341 20130101; G03B 27/52 20130101; G03F 7/70866
20130101 |
International
Class: |
G03F 7/20 20060101
G03F007/20; B01D 19/00 20060101 B01D019/00 |
Claims
1. A lithographic apparatus comprising: a substrate table
constructed to hold a substrate; and a fluid handling structure
arranged to remove liquid and gas in a two-phase flow from a
surface, the fluid handling structure comprising a phase separator
having a surface and arranged to separate the two-phase flow into a
first flow and a second flow, the first flow having a higher ratio
of liquid to gas than the two-phase flow and flowing along the
phase separator surface, the second flow having a higher ratio of
gas to liquid than the two-phase flow.
2. The apparatus of claim 1, wherein the phase separator comprises
a channel having first and second walls and arranged so that liquid
preferentially flows along the first wall, the first wall defining
the surface.
3. The apparatus of claim 2, wherein the phase separator further
comprises a dry chamber connected to the channel via an opening in
the second wall.
4. The apparatus of claim 2, wherein the first wall has a lower
contact angle than the second wall.
5. The apparatus of claim 2, wherein the phase separator further
comprises a wet chamber arranged so that liquid flowing along the
first wall enters the wet chamber.
6. The apparatus of claim 5, wherein the wet chamber is connected
to the channel by a slit defined by the first wall and a divider,
wherein the first wall is substantially straight between an inlet
of the channel and the wet chamber and the slit has a width
arranged so that capillary forces encourage substantially only
liquid to enter the slit.
7. The apparatus of claim 5, wherein the first wall is curved so
that at a point where the channel enters the wet chamber the first
wall is lower than the second wall.
8. The apparatus of claim 3, wherein the phase separator further
comprises a gas extraction channel separated from the wet chamber
by a gas-permeable liquidphobic membrane.
9. The apparatus of claim 8, wherein the phase separator further
comprises a liquid extraction opening defined in a wall of the wet
chamber, the liquid extraction opening being below the
gas-permeable liquidphobic membrane.
10. The apparatus of claim 8, wherein the phase separator further
comprises a drain path to allow liquid to drain from the wet
chamber to a space between the substrate and a projection system
arranged to project a patterned radiation beam onto the
substrate.
11. The apparatus of claim 1, wherein the phase separator comprises
a chamber, defined by first and second walls, and a plurality of
channels entering into the chamber through the second wall, the
channels being arranged at an angle to the second wall such that a
two-phase flow entering the chamber from a channel at least
partially separates into a liquid flow along the first wall and a
gas flow along the second wall.
12. The apparatus of claim 11, wherein the phase separator further
comprises a plurality of flow directing structures in the chamber
adjacent the openings of the channels.
13. The apparatus of claim 12, wherein the flow directing
structures have curved surfaces that define flow paths leading away
from the openings, the flow paths increasing in width away from the
openings over at least part of their length and the curved surfaces
are arranged so that the flow paths turn through at least
90.degree..
14. The apparatus of claim 1, wherein the phase separator comprises
a conduit defined by a wall and having a substantially circular
cross-section over at least a part of the length thereof and a
substantially helical structure provided on the wall.
15. The apparatus of claim 1, wherein the phase separator further
comprises a gas extraction conduit arranged within a part of a
conduit so as to define an annular gap between an outer surface of
the gas extraction conduit and an inner surface of the conduit.
16. The apparatus of claim 1, wherein the surface is in part
defined by a porous member through which liquid can be
extracted.
17. The apparatus of claim 1, wherein the phase separator further
comprises a gas supply arranged to add additional gas to the
two-phase flow.
18. The apparatus of claim 1, wherein the fluid handling structure
comprises a barrier member arranged to at least partly confine a
liquid to a space between the substrate and a projection system
arranged to project a patterned radiation beam onto the substrate,
the phase separator being contained in the barrier member.
19. A liquid-gas separator comprising: a conduit or chamber divided
into two parts by a porous plate, the first part being
substantially filled with liquid; and a current generator
configured to supply liquid to the first part and constructed and
arranged to generate a current in the liquid so as to substantially
prevent bubbles of gas remaining on a surface of the porous plate
which defines in part the first part.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/452,445 filed on Mar. 7, 2017, now allowed,
which is a continuation of U.S. patent application Ser. No.
14/498,883 filed on Sep. 26, 2014, now U.S. Pat. No. 9,606,429,
which is a continuation of U.S. patent application Ser. No.
12/543,011, filed on Aug. 18, 2009, now U.S. Pat. No. 8,953,142,
which claims priority and benefit under 35 U.S.C. .sctn. 119(e) to
U.S. Provisional Patent Application No. 61/136,216, filed on Aug.
19, 2008, the content of each of the foregoing applications is
incorporated herein in its entirety by reference.
FIELD
[0002] The present invention relates to a liquid removal device, in
particular that can be used in or in conjunction with a
lithographic apparatus or a metrology apparatus, as well as a
method for liquid removal and device manufacture.
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 and so-called scanners. In a
stepper each target portion is irradiated by exposing an entire
pattern onto the target portion at one time. In a scanner 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.
[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
liquid is desirably distilled water, although other liquids can be
used. An embodiment of the present invention will be described with
reference to liquid. However, another fluid may be suitable,
particularly a wetting fluid, an incompressible fluid and/or a
fluid with a higher refractive index than air, desirably a higher
refractive index than water. Fluids excluding gases are
particularly desirable. 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 be regarded
as increasing the effective numerical aperture (NA) of the system
and increasing the depth of focus.) Other immersion liquids have
been proposed, including water with solid particles (e.g. quartz)
suspended therein, or a liquid with a nano-particle suspension
(e.g. particles with a maximum dimension of up to 10 nm). The
suspended particles may or may not have a similar or the same
refractive index as the liquid in which they are suspended. Other
liquids which may be suitable are a hydrocarbon, such as an
aromatic, e.g. Decalin, or a fluorohydrocarbon, or an aqueous
solution.
[0005] Submersing the substrate or substrate and substrate table in
a bath of liquid (see, for example, U.S. Pat. No. 4,509,852) 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] In an immersion apparatus, immersion liquid is handled by a
fluid handling system or apparatus. In an embodiment the fluid
handling system may supply immersion fluid and therefore be a fluid
supply system. In an embodiment the fluid handling system may
confine fluid and thereby be a fluid confinement system. If the
confined fluid is a liquid, the fluid confinement system may have a
liquid confinement structure. In an embodiment the fluid handling
system may provide a barrier to fluid and thereby be a barrier
member. In an embodiment the fluid handling system may create or
use a flow of fluid (such as gas), for example to help in handling
liquid such as to confine liquid for example as a contactless gas
seal. In an embodiment, immersion liquid may be used as the
immersion fluid. In that case, the fluid handling system may be a
liquid handling system.
[0007] One of the arrangements proposed is for a liquid handling
system, such as a liquid supply system. The liquid supply system is
to provide liquid on only a localized area of the substrate and in
between the final element of the projection system and the
substrate using a liquid confinement structure (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. As illustrated in FIGS. 2 and 3, liquid is supplied by at
least one inlet onto the substrate, desirably along the direction
of movement of the substrate relative to the final element, Liquid
is removed by at least one outlet 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 and is taken up
on the other side of the element by outlet 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.
Note that the direction of flow of the liquid is shown by arrows in
FIGS. 2 and 3.
[0008] A further immersion lithography solution with a localized
liquid supply system is shown in FIG. 4. Liquid is supplied by two
groove inlets on either side of the projection system PS and is
removed by a plurality of discrete outlets arranged radially
outwardly of the inlets The inlets and 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 on one side of
the projection system PS and removed by a plurality of discrete
outlets on the other side of the projection system PS, causing a
flow of a thin film of liquid between the projection system PS and
the substrate W. The choice of which combination of inlet and
outlets to use can depend on the direction of movement of the
substrate W (the other combination of inlet and outlets being
inactive). Note that the direction of flow of fluid and of the
substrate W is shown by arrows in FIG. 4.
[0009] In European patent application publication no. EP 1420300
and United States patent application publication no. US
2004-0136494, 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.
[0010] PCT patent application publication WO 2005/064405 discloses
an all wet arrangement in which the immersion liquid is unconfined.
In such a system substantially the whole top surface of the
substrate is covered in liquid. This may be advantageous because
then the substantially whole top surface of the substrate is
exposed to the substantially same conditions. This has an advantage
for temperature control and processing of the substrate. In WO
2005/064405, a liquid supply system provides liquid to the gap
between the final element of the projection system and the
substrate. The liquid between the final element of the projection
system and the substrate during exposure is optical liquid. That
liquid is allowed to leak over the remainder of the substrate. A
barrier at the edge of a substrate table prevents the liquid from
escaping so that it can be removed from the top surface of the
substrate table in a controlled way. The meniscus of the liquid
defining the extent of the immersion liquid is remote from the
projection system. Although such a system improves temperature
control and processing of the substrate, evaporation of the
immersion liquid may still occur. One way of helping to alleviate
that problem is described in United States patent application
publication no. US 2006-0119809 in which a cover member is provided
which covers the substrate W in all positions. The cover member is
arranged to have immersion liquid extending between it and the top
surface of the substrate and/or substrate table which holds the
substrate.
SUMMARY
[0011] In an immersion lithography apparatus, a two-phase flow
(that is a flow of mixed liquid and gas) often arise. A two-phase
flow can range from a flow in which there are droplets of liquid in
a majority gas flow, to bubbles of gas in a majority liquid flow.
Two-phase flow covers all possibilities in between except where the
gas is dissolved in the liquid or the gas and the liquid are
separate and flow side by side in an orderly manner. For example,
in a localized immersion system using a gas flow and liquid
extraction to stabilize the meniscus of the immersion liquid, a
substantial amount of liquid is swept up and extracted with the gas
of the stabilizing gas flow. A two-phase flow may cause a problem.
Evaporation of the immersion liquid into the gas, if non-saturated,
can cause localized cooling. Two-phase flow is often unsteady,
with, for example, a large volume of liquid interspersed with the
gas. Such unsteady flow can cause vibration due to the irregular
movements of a large volume of liquid and due to variation in the
pressure in the extraction channel. Also, designing a pump and
pipework to cope with gas, liquid and variable mixtures of gas and
liquid adds complication and expense.
[0012] It is desirable, for example, to provide an improved
apparatus by which two-phase flow can be stabilized and/or at least
substantially separated into liquid and gas flows, and desirably
substantially minimized.
[0013] According to an aspect of the invention, there is provided a
lithographic apparatus comprising a substrate table constructed to
hold a substrate, and a fluid handling structure arranged to remove
liquid and gas in a two-phase flow from a surface of the substrate
table, or of a substrate held by the substrate table, or both the
substrate table and the substrate. The fluid handling structure
comprises a phase separator having a surface and arranged to
separate the two-phase flow into a first flow and a second flow.
The first flow has a higher ratio of liquid to gas than the
two-phase flow and flows along the surface. The second flow has a
higher ratio of gas to liquid than the two-phase flow.
[0014] According to an aspect of the invention, there is provided a
fluid handling structure configured to remove liquid and gas in a
two-phase flow from a surface. The fluid handling structure
comprises a phase separator having a surface and arranged to
separate the two-phase flow into a first flow and a second flow.
The first flow has a higher ratio of liquid to gas than the
two-phase flow and flows along the surface. The second flow has a
higher ratio of gas to liquid than the two-phase flow. In an
embodiment, a drying device comprises the fluid handling structure.
In an embodiment, an immersion metrology device comprises the fluid
handling structure.
[0015] According to an aspect of the invention, there is provided a
device manufacturing method comprising projecting an image of a
pattern onto a substrate through a liquid confined to a space
adjacent the substrate. The method further comprises removing
liquid from the substrate in a two-phase flow with gas, and
separating the two-phase flow into a first flow and a second flow.
The first flow has a higher ratio of liquid to gas than the
two-phase flow and flows along a surface. The second flow has a
higher ratio of gas to liquid than the two-phase flow.
[0016] According to an aspect of the invention, there is provided a
liquid-gas separator comprising a conduit or chamber divided into
two parts by a porous plate, the first part being substantially
filled with liquid. The separator further comprises a current
generator configured to supply liquid to the first part and
constructed and arranged to generate a current in the liquid so as
to substantially prevent bubbles of gas remaining on a surface of
the porous plate which defines in part the first part. In an
embodiment, a lithographic apparatus or a metrology device having
an immersion system comprises the separator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] 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:
[0018] FIG. 1 depicts a lithographic apparatus according to an
embodiment of the invention;
[0019] FIGS. 2 and 3 depict a fluid handling structure for use in a
lithographic projection apparatus;
[0020] FIG. 4 depicts a further fluid handling structure for use in
a lithographic projection apparatus;
[0021] FIG. 5 depicts parts of a substrate stage in an embodiment
of the invention, including a structure to handle fluid in order to
control a localized area of immersion liquid on a substrate held on
a substrate table and a liquid removal device to remove liquid from
the substrate;
[0022] FIG. 6 depicts other arrangements in the substrate stage of
a lithographic apparatus including a liquid removal device
according to an embodiment of the present invention;
[0023] FIG. 7 depicts, in cross-section, a barrier member forming
part of the fluid handling structure of FIG. 5;
[0024] FIG. 8 depicts, in cross-section, an arrangement in a
barrier member forming part of a fluid handling structure according
an embodiment of the invention;
[0025] FIG. 9 depicts, in cross-section, a two-phase extraction
arrangement in a barrier member forming part of a fluid handling
structure according to a further embodiment of the invention;
[0026] FIG. 10 depicts, in cross-section, a two-phase extraction
arrangement in a barrier member forming part of a fluid handling
structure according to a further embodiment of the invention;
[0027] FIG. 11 depicts, in cross-section, a two-phase extraction
arrangement in a barrier member forming part of a fluid handling
structure according to a further embodiment of the invention;
[0028] FIG. 12 depicts, in perspective and partly cut-away, a
two-phase extraction arrangement in a barrier member forming part
of a fluid handling structure according to a further embodiment of
the invention;
[0029] FIG. 13 depicts, in perspective and partly cut-away, a
two-phase extraction arrangement in a barrier member forming part
of a fluid handling structure according to a further embodiment of
the invention;
[0030] FIG. 14 depicts, in cross-section, a two-phase flow in an
ordinary cylindrical tube;
[0031] FIG. 15 depicts, in cross-section, a two-phase flow in a
cylindrical tube usable in an embodiment of the invention;
[0032] FIG. 16 depicts, in cross-section, a two-phase flow in
another cylindrical tube usable in an embodiment of the
invention;
[0033] FIG. 17 depicts in perspective a further cylindrical tube
usable in an embodiment of the invention;
[0034] FIG. 18 depicts in perspective a further cylindrical tube
usable in an embodiment of the invention;
[0035] FIG. 19 depicts in perspective a further cylindrical tube
usable in an embodiment of the invention;
[0036] FIG. 20 depicts in perspective a further cylindrical tube
usable in an embodiment of the invention; and
[0037] FIGS. 21A to 21D depict a liquid-gas separator usable in an
embodiment of the invention.
DETAILED DESCRIPTION
[0038] FIG. 1 schematically depicts a lithographic apparatus
according to one embodiment of the invention. The apparatus
comprises:
[0039] an illumination system (illuminator) IL configured to
condition a radiation beam B (e.g. UV radiation or DUV
radiation);
[0040] 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;
[0041] 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
[0042] a projection system (e.g. a refractive projection lens
system) PS 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.
[0043] 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.
[0044] The support structure MT holds the patterning device. The
support structure MT 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 MT can use mechanical, vacuum,
electrostatic or other clamping techniques to hold the patterning
device. The support structure MT may be a frame or a table, for
example, which may be fixed or movable as required. The support
structure MT 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."
[0045] 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.
[0046] 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.
[0047] 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".
[0048] 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).
[0049] The lithographic apparatus may be of a type having two (dual
stage) or more substrate tables (and/or two or more patterning
device tables). 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.
[0050] 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
mirrors 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.
[0051] 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.
[0052] The radiation beam B is incident on the patterning device
(e.g., mask) MA, which is held on the support structure (e.g., mask
table) MT, and is patterned by the patterning device. Having
traversed the patterning device MA, the radiation beam B passes
through the projection system PS, 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 shod-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. A fluid handling
structure IH, which is described further below, controls a
localized area of immersion liquid between the projection system PS
and the substrate W.
[0053] 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 PS. 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.
[0054] Combinations and/or variations on the above described modes
of use or entirely different modes of use may be employed
additionally or in the alternative.
[0055] An embodiment of the present invention relates to an
immersion lithographic apparatus. FIG. 5 depicts schematically, in
plan, a fluid handling arrangement relative to a substrate stage in
more detail. In particular, a fluid handling structure 12 is
provided to supply and control immersion liquid flow in the
lithographic apparatus. In an embodiment, the fluid handling
structure is provided to supply and confine an immersion liquid to
a space between the final element of the projections system PS (not
shown in this figure) and the substrate W and/or substrate table.
(Note that reference to the substrate herein includes references to
the substrate table in the alterative or as an addition, unless
stated to the contrary). This structure includes a liquid removal
device 100 and is described further below. During the course of a
series of exposures and measurements carried out on a substrate W,
the substrate table WT is moved relative to the projection system
PS and fluid handling structure 12 at high speeds and with high
accelerations. At various times, e.g. when exposing an edge die on
the substrate and when making measurements using a sensor provided
in sensor block FID, the edge of the substrate may pass under the
localized body of immersion liquid 11. This, and large
accelerations or changes in direction of the substrate table WT,
can cause a droplet or film to break away from the body of
immersion liquid 11. A droplet can be left behind on the substrate,
substrate table and/or sensor FID. A droplet left on the substrate
can cause problems, as discussed above. The droplet may cause
localized cooling and hence distortion of the substrate. A droplet
may deposit dissolved or suspended contaminants and/or by
attracting contaminants from the environment. Therefore, the liquid
removal system 100 according to an embodiment of the invention is
intended to minimize the creation of droplets left on the substrate
by stabilizing the meniscus of the body of immersion liquid.
[0056] An additional liquid removal device 200 according to an
embodiment of the invention may be provided to remove any liquid
left on the substrate W. The liquid removal device 200 may be fixed
in position relative to the projection system so that the normal
movement of the substrate table under the projection system during
a series of exposures sweeps the substrate under it. The liquid
removal device 200 may be provided with its own positioner. The
liquid removal device 200 may be used when the fluid handling
structure 12 does not have a liquid removal system 100 according to
an embodiment of the invention. For example the fluid handling
structure 12 may be of one of the types fluid handling structures
depicted in FIGS. 2 to 4 and described above. Or it may be a type
which uses a gas knife to confine the immersion liquid, e.g. as
disclosed in United States patent application publication no. US
2004-0207824, incorporated herein by reference.
[0057] A liquid removal device according to an embodiment of the
invention may alternatively or in addition be placed at other
positions in a lithographic apparatus. For example, as shown in
FIG. 6, a liquid removal device 300 may be positioned between an
exposure station, at which a substrate is exposed on substrate
table WTa, and a measurement station at which measurements are
taken of, for example, a substrate on substrate table WTb. A
measurement taken at the measurement station may be a height map of
the substrate using a level sensor LS. A substrates may be loaded
onto and off a substrate table at the measurement station. Liquid
removal device 300 may be sufficiently large and suitably
positioned so that the whole of the substrate is swept as the
substrate table passes beneath it when transferring between
stations, A liquid removal device 400 may be positioned at the
measurement station to dry the substrate in conjunction with the
taking of measurements. The liquid removal device 400 may be
provided with its own positioning system. The liquid removal device
may be located outside a lithographic device, for example in the
track. There it would have the same features as any of the liquid
removal devices 200, 300, 400 herein described.
[0058] Another arrangement which has been proposed is to provide a
fluid handling system having a barrier member. Such an arrangement
is illustrated in FIG. 7. In an embodiment, a seal is formed
between the barrier member and the surface of the substrate. In an
embodiment, the seal is a contactless seal such as a gas seal. The
seal may confine the immersion liquid and so create a meniscus.
Thus, near the seal is a meniscus of the immersion liquid. As
exposure light passes through the confined immersion liquid it may
be considered optical liquid.
[0059] The fluid handling structure is schematically depicted in
FIG. 7. It forms part of a localized immersion system. The fluid
handling structure is arranged to control, in particular to supply
and to confine, immersion liquid to a space between the final
element of the projection system PS and the substrate W. The main
part of the fluid handling structure is a barrier member 12, which
extends along at least a part of a boundary of the space between
the final element of the projection system and the substrate. The
barrier member 12 is, in use, 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).
[0060] The barrier member 12 is a structure which may at least
partly contain liquid in the space 11 between a final element of
the projection system PS and the substrate W. Immersion liquid is
provided via liquid supply conduit 14, i.e. it is an inlet, and
fills the space between the substrate surface and the final element
of the projection system. The space is at least partly delimited by
the barrier member 12 positioned below and surrounding the final
element of the projection system PS. Liquid may be supplied to or
removed from the space via inlet-outlet 13. The barrier member 12
may extend a little above the final element of the projection
system. The liquid level may rise above the final element so that a
buffer of liquid is provided. The barrier member 12 has an inner
periphery that at the upper end, in an embodiment, 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 may
closely conform to the shape of the image field IF, e.g.,
rectangular, though this need not be the case.
[0061] The liquid 11 in the space is prevented from spilling out
over the whole of the surface of the substrate by liquid extraction
conduit 15, forming part of liquid removal device 100. Liquid
extraction conduit 15 is in fluid communication with a plurality of
orifices. The orifices form liquid openings which are disposed
around the space occupied by the immersion liquid. The shape and
arrangement of these orifices serves to control and in particular
stabilize the meniscus 16 of the immersion liquid 11 so as to
reduce or minimize droplets breaking away from or bubbles entering
the immersion liquid. While a plurality of orifices or openings are
referred to herein, the plurality of orifices or openings may be a
singular orifice or opening, which may be annular.
[0062] In an embodiment of the invention, the openings of the
liquid removal device are conveniently defined by a plate that
covers the lower surface of the barrier member 12 and has an
appropriately shaped aperture or apertures. In an embodiment, the
openings may be individual nozzles. The openings each may be
co-planar with or protrude from the lower surface of the barrier
member.
[0063] In localized immersion systems, liquid is only provided to a
localized area of the substrate. The space 11 filled by liquid,
i.e. the reservoir, is smaller in plan than the top surface of the
substrate. The reservoir remains substantially stationary relative
to the projection system PS while the substrate W moves underneath
it. Another category of immersion system is the bath type
arrangement in which the whole of the substrate W and optionally
part of the substrate table WT is submersed in a bath of liquid. A
further category is an all wet solution in which the liquid is
unconfined. In this arrangement the whole top surface of the
substrate and optionally all or part of the substrate table is
covered in a thin film of immersion liquid. Any of the liquid
supply devices of FIGS. 2 to 5 can be used in such a system;
however, their sealing features are not present, are not activated,
are not as efficient as normal or are otherwise ineffective to seal
liquid to only the localized area. Other arrangements are possible
and, as will be clear from the description below, an embodiment of
the present invention may be implemented in any type of liquid
supply system.
[0064] In an immersion lithography apparatus, substantial
quantities of the immersion liquid are often extracted from the
vicinity of the substrate. In doing so, it is common that gas, e.g.
air from the environment, is extracted with the immersion liquid.
This occurs in particular in localized fluid handling systems that
use liquid extraction to pin the meniscus of the localized
immersion liquid. When liquid and gas are extracted together in a
two-phase flow, vibrations can be caused due to irregular flows
that occur and/or because of fluctuations in the pressure at the
extraction points due to that irregular flow. It is therefore
desirable to separate the liquid and gas phases of a two-phase flow
at least partially, and desirably as much as possible. Complete
separation is often not necessary since a small proportion of gas
in a liquid flow or a small proportion of liquid in a gas flow
tends not to cause such undesired vibrations. Undesirable
vibrations are avoided if the two-phase flow is homogeneous on the
scale of the conduit, for example a "bubbly flow" of small bubbles
in liquid or a "misty flow" of small droplets in gas. Partial
separation is also desirable as it tends to reduce the amount of
evaporation of the liquid. This in turn reduces the undesirable
localized cooling caused by evaporation.
[0065] Therefore, an embodiment of the present invention provides a
lithographic apparatus comprising a substrate table and a fluid
handling structure. The substrate table is constructed to hold a
substrate. The fluid handling structure is arranged to remove
liquid and gas in a two-phase flow from a surface of the substrate
table and/or a substrate held by the substrate table. The fluid
handling structure comprises a phase separator having a surface and
arranged to separate the two-phase flow into a first flow and a
second flow, the first flow having a higher ratio of liquid to gas
than the two-phase flow and flowing along the surface, the second
flow having a higher ratio of gas to liquid than the two-phase
flow.
[0066] By causing a high liquid content flow (also referred to as a
liquid-rich flow) to flow along the surface, the two phases of the
mixed two-phase flow can be separated sufficiently to reduce
undesirable vibrations and uneven flow. The liquid can be
encouraged to flow desirably along the surface by any one or
combination of means as discussed below.
[0067] In an embodiment, the phase separator comprises a channel
having first and second walls and arranged so that liquid
preferentially flows along the first wall, the first wall defining
the surface. The shape of the channel is designed to encourage the
liquid to flow along the first wall, e.g. by providing a change in
direction such that centrifugal force directs the liquid onto the
first wall. Alternatively or in addition, the shape of the channel
may be such as to cause cyclonic flow, directing the liquid
outwardly to the wall. Another possibility is that the shape of the
channel slows the two-phase flow sufficiently that the liquid
separates out by or with the assistance of gravity.
[0068] In an embodiment, the first wall is more liquidphilic than
the second wall. By liquidphilic it is meant that the liquid has a
contact angle to the liquidphilic surface that is less than
90.degree., desirably less than 75.degree., 50.degree., or
25.degree.. The surface may be made liquidphilic by any suitable
surface treatment, for example a coating or by a surface relief, or
may be liquidphilic by virtue of the material from which it is
made. A surface relief may be a regular pattern or irregular
roughness.
[0069] In an embodiment, the phase separator further comprises a
wet chamber arranged so that liquid flowing along the first wall
enters the wet chamber. In this way, the separation achieved at the
surface can be fixed, by directing the liquid-rich flow into a
chamber from which it can be removed separately from the gas-rich
flow. It is desirable that the path of the liquid-rich flow is
straight and/or tends downwardly.
[0070] In an embodiment, the wet chamber is connected to the
channel by a slit defined by the first wall and a divider. The
width of the slit can be defined by the divider so as to
substantially ensure that the slit is substantially filled by the
liquid-rich flow at a flow rate expected in use of the apparatus
and thereby gas is kept out of the wet chamber. Also, the slit
width can be chosen so that capillary forces encourage
substantially only liquid to enter the slit.
[0071] In an embodiment, the phase separator comprises a dry
chamber connected to the channel via an opening in the second wall.
The gas can then be extracted from the dry chamber, substantially
without liquid.
[0072] In an embodiment, the first wall is curved so that at a
point where the channel enters the wet chamber the first wall is
lower than the second wall. With this arrangement, gravity assists
flow of the liquid and separation from the gas. Also, the first
wall can be configured to form a dam that substantially prevents
flow of the liquid back out of the wet chamber.
[0073] In an embodiment, the phase separator comprises a gas
extraction channel separated from the wet chamber by a
gas-permeable liquidphobic membrane. The liquidphobic membrane
substantially prevents liquid entering the gas extraction channel.
A suitable material for the membrane depends on the immersion
liquid used. If the immersion liquid is water, a hydrophobic
membrane such as a porous fluoropolymer membrane, in particular a
thermo-mechanically expanded polytetrafluoroethylene (PTFE) and
other fluoropolymer product sold under the "Gore-Tex" trademark,
may be used.
[0074] In such an embodiment, the phase separator may comprise a
liquid extraction conduit projecting into the wet chamber and
having an opening below the gas-permeable liquidphobic membrane.
The position of the liquid extraction conduit can be set so that
substantially only liquid is extracted and separation of the liquid
and gas in the wet chamber is encouraged.
[0075] In an embodiment, the phase separator comprises a drain
path. The drain path allows liquid to drain from the wet chamber to
a space between the substrate and a final element of a projection
system arranged to project a patterned radiation beam onto the
substrate. With this arrangement the immersion liquid can be
directly recycled into the path of the projection beam, reducing
the flow of liquid into and out of the fluid handling system.
[0076] In an embodiment, the phase separator comprises a chamber,
defined by first and second walls, and a plurality of channels
entering into the chamber through the second wall. The channels are
arranged at an angle to the second wall such that a two-phase flow
entering the chamber from a channel at least partially separates
into a liquid flow along the first wall and a gas flow along the
second wall. In such an embodiment, the direction of one or more
channels and the shape of the chamber are each designed to
encourage separation of the liquid and gas. For example, one of the
channels may be configured such that the two-phase flow makes a
sharp change of direction on encountering the first wall, thereby
encouraging the liquid to flow along it.
[0077] In an embodiment, the phase separator further comprises a
plurality of flow directing structures in the chamber adjacent the
openings of the channels. The flow directing structures can have
curved surfaces that define flow paths leading away from the
openings, the flow paths flaring away from the openings over at
least part of their length. The curved surfaces can be arranged so
that the flow paths turn through at least 90.degree., desirable
180.degree.. In this way the flow paths can ensure a suitable flow
of the two-phase mixture to ensure that cyclonic and/or centrifugal
forces cause the liquid to separate and desirably follow the first
wall.
[0078] In an embodiment, the phase separator comprises a conduit
having a liquidphilic surface, for example provided by a
liquidphilic coating provided thereon and/or a liquidphilic surface
relief provided thereon. As mentioned above, by liquidphilic it is
meant that the liquid has a contact angle to the liquidphilic
surface that is less than 90.degree., desirably less than
75.degree., 50.degree., or 25.degree..
[0079] In an embodiment, the phase separator comprises a conduit
defined by a wall and having a substantially circular cross-section
over at least a part of the length thereof and a substantially
helical structure provided on the wall. The substantially helical
structure can be a substantially helical groove in the wall and/or
a substantially helical wire mounted on the wall. The groove and/or
the wire can be provided with a liquidphilic coating. Such a
helical structure promotes establishment and maintenance of a
separated flow in which the liquid desirably flows along the
surface of the conduit and the gas flows down the middle of the
conduit. This may reduce turbulence and hence vibration.
[0080] In an embodiment, the conduit is in part defined by a wall
in the form of a porous member, for example a porous plate such as
a microsieve through which liquid can be extracted. Microsieves are
described further below and in US patent application publication
no. 2006/0038968, which document is hereby incorporated in its
entirety by reference. In an embodiment, the phase separator
further comprises a gas extraction conduit arranged within a part
of the conduit so as to define an annular gap between an outer
surface of the gas extraction conduit and an inner surface of the
conduit. These arrangements enable the liquid and gas flows
established around the outside and middle of the conduit to be
directed into separate channels, effectively fixing the
separation.
[0081] In an embodiment, the fluid handling structure comprises a
barrier member arranged to at least partly confine a liquid to a
space between the substrate and a final element of a projection
system. The projection system is arranged to project a patterned
radiation beam onto the substrate. The phase separator is contained
in the barrier member. By providing the separator in the barrier
member, separation of the two phases can be effected as close as
possible to the point(s) where the two-phase flow is taken up. In
this way, the occurrence of vibration may be minimized as much as
possible.
[0082] An embodiment of the present invention also provides a fluid
handling structure configured to remove liquid and gas in a
two-phase flow from a surface. The fluid handling structure
comprises a phase separator having a surface and arranged to
separate the two-phase flow into a first flow and a second flow.
The first flow has a higher ratio of liquid to gas than the
two-phase flow and flows along the surface. The second flow has a
higher ratio of gas to liquid than the two-phase flow.
[0083] The fluid handling structure may be used in a drying device
(which may also be referred to as a dryer) or an immersion
metrology device for example. The dryer may be part of a bath type
or all wet immersion system, as described above, where immersion
liquid is not confined to a portion of the substrate, but may flow
over substantially all of the surface of the substrate. In the
dryer, the droplet remover removes liquid present on the surface of
a substrate. In an embodiment the drying may occur after exposure
of the substrate is complete and before the substrate leaves the
lithographic apparatus for processing elsewhere, for example, at a
track for development, coating, baking and etching. In an
embodiment the drying occurs after exposure in a separate unit
outside the lithography apparatus. The drying may occur after
measurement in a metrology system where immersion liquid is used to
replicate an immersion environment.
[0084] To operate the dryer, the dryer may be passed over a
substrate that has been removed from the immersion system and/or
the substrate may be passed under the dryer. In an embodiment, the
dryer is used with respect to the substrate once immersion liquid
has been drained from the immersion system and/or the liquid supply
to the immersion system has stopped. The liquid covering the
substrate may break from a film to form many droplets. As the dryer
is used with respect to the substrate surface, liquid present on
the substrate is removed, drying the surface.
[0085] An embodiment of the invention provides a device
manufacturing method in which an image of a pattern is projected
onto a substrate through an immersion liquid confined to a space
adjacent the substrate, and liquid is removed from the substrate in
a two-phase flow with gas. The two-phase flow is separated into a
first flow and a second flow, the first flow having a higher ratio
of liquid to gas than the two-phase flow and flowing along a
surface, the second flow having a higher ratio of gas to liquid
than the two-phase flow. The steps of projecting and removing can
be carried out simultaneously or the step of removing can be
carried out after the step of projecting has been carried out.
[0086] FIG. 8 is a cross-section of a part of a barrier member 12a
of a fluid handling structure according to an embodiment of the
present invention. The barrier member 12a assists in confining an
immersion liquid 11 to a space between the final element of the
projection system PS and the substrate W. Although only one side of
the barrier member 12a is shown, it can be arranged to surround
completely the localized immersion liquid 11, for example being in
the form of an annulus. Also, although shown as having a vertical
inner wall with a step, the inner wall may have other shapes, for
example slanted as shown in FIG. 7, and in particular may conform
to the contour of the lower part of the projection system PS.
[0087] As shown in FIG. 8, there is a narrow gap between the lower
surface of barrier member 12a and substrate W through which the
immersion liquid can escape. In an embodiment this gap may be made
as narrow and as long as possible to reduce or minimize the escape
of immersion liquid. Any liquid that does escape is extracted via
opening 121. Opening 121 is connected to an underpressure and draws
in fluid, e.g. immersion liquid 11 as well as gas, e.g. air, from
the local environment. Opening 121 may be a continuous slit
extending completely around the localized area of immersion liquid
11 or a series of smaller slits together substantially surrounding
the localized immersion liquid 11. For structural reasons, the
opening 121 may be bridged at certain points by small
connectors.
[0088] Opening 121 is defined by first wall 122 and second wall
123. First wall 122 is on the side of the region of immersion
liquid 11. Immersion liquid 11 will tend to flow up that wall 122.
The preferential flow of liquid 11 along first wall 122 can be
encouraged by making first wall 122 have a smaller contact angle,
e.g. smaller than 90 degrees (e.g., substantially smaller than 90
degrees), than second wall 123, e.g. by providing a coating or
surface relief on first wall 122 or by selecting the material from
which wall 122 is made. Similarly, second wall 123 can be made of a
selected material, coated or treated to have a higher contact angle
to the liquid 11. The preferential flow of immersion liquid 11
along wall 122 begins the separation of the liquid and gas entering
opening 121. This separation can be fixed, or conserved, by
directing the high liquid content and high gas content portions of
the flow into respective different chambers.
[0089] This can be achieved in the embodiment of FIG. 8 by divider
124 which is positioned adjacent and substantially parallel to
first wall 122 so as to define a channel, e.g. a capillary 125.
Liquid 11 flowing up wall 122 enters channel 125 and then wet
chamber 126. The width of channel 125, as well as the surface
coating thereon if desired, encourages liquid to enter but not gas.
In an embodiment, the width of channel 125 is in the range of from
0.5 mm to 3 mm, desirably 1 mm to 2 mm. The gas, which is more
easily diverted, enters dry chamber 127 via a gap between divider
124 and second wall 123. Divider 124 does not need to be vertical:
it can be oriented at other a different angle. Divider 124 can be
formed by a microsieve (described further below) or a liquid-phobic
porous membrane (described further below) to effect further
separation by allowing movement of gas or liquid substantially only
in one direction between the chambers. The end of divider 124 is
shown as tapering in FIG. 8 however this end can instead be flat or
rounded. If tapered or rounded, the tapering or rounding can be
provided on either or both sides of the divider 124.
[0090] Wet chamber 126 and dry chamber 127 are connected to
respective sources of under pressure, e.g. vacuum pumps (now
shown). The sources extract the liquid-rich and gas-rich flows from
the wet and dry chambers respectively and also provide the
underpressure that draws the mixed two-phase flow into slit 121 in
the first place. It is to be noted that the flow into wet chamber
126 and extracted therefrom may include some gas bubbles and
similarly the flow of gas into dry chamber 127 and extracted
therefrom may include some liquid droplets. It is not necessary
that the separation of liquid and gas be perfect at this stage but
sufficient separation to reduce the occurrence of uneven flow that
may result in vibrations and/or reduce evaporation is
desirable.
[0091] A barrier member 12b according to an further embodiment of
the present invention is shown in FIG. 9. As previously mentioned,
barrier member 12b assists in confining an immersion liquid 11 to a
space between a final element of projection system PS and substrate
W. Some immersion liquid can leak through the gap between barrier
member 12b and substrate W. Again the immersion liquid 11 and gas
from the environment are drawn up into slit 121. Slit 121 is
defined by wall 122a and 123a which are each configured to
encourage separation of the two-phase flow entering slit 121 into a
liquid-rich flow along first wall 122a and a gas-rich flow along
wall 123a. In this embodiment, walls 122a and 123a are desirably
curved so that slit 121 turns from being vertical at its entrance
to being substantially horizontal or angled downwards at a point
where it meets separation chamber 128. At this point first wall
122a forms the lower side of slit 121. Thus, gravity assists in
keeping the liquid-rich flow along first wall 122a. As the
liquid-rich and gas-rich flows enter separation chamber 128, the
liquid and gas naturally tend to separate with the liquid occupying
the lower part of the separation chamber 128. Desirably first wall
122a has a lower contact angle to the liquid 11 than second wall
123a. This can be achieved in the same ways as detailed above.
[0092] A liquid extraction opening is provided by liquid extraction
conduit 130 which, in an embodiment, projects from the upper part
of separation chamber 128 into the lower part and is connected to
an under pressure (not shown) so as to extract liquid from the
lower part of separation chamber 128. The level of the opening of
the liquid extraction conduit 130 can be set so as to control the
level of liquid in the separation chamber 128. Depending upon the
level of liquid in the chamber 128, some gas may also be extracted.
This can be reduced or minimized by providing a microsieve. A
microsieve is a porous member. In an embodiment the microsieve may
comprise a thin plate that has a large number of small holes
through it. By suitable control of the underpressure above the
microsieve, the size of the holes, and the liquid to be extracted,
it can be arranged that substantially only liquid passes through
the microsieve. The microsieve is desirably formed of a material
having a contact angle to the immersion liquid of less than
90.degree., e.g. substantially less than 90.degree.. By control of
the underpressure above the microsieve and by ensuring that there
is always liquid above the microsieve it is possible to prevent gas
being extracted through the microsieve. Further details of such
microsieves are given in United States patent application
publication no. US 2006/0038968 A1 incorporated by reference in its
entirety. Suitable microsieves are made by Stork Veco B.V. of the
Netherlands.
[0093] To extract gas from the separation chamber 128, a gas
extraction conduit 131 is provided in the upper surface of the
chamber 128. The entrance to the gas extraction conduit 131 may be
covered with a porous liquidphobic membrane 132, such as a
thermally expanded fluoropolymer membrane. Suitable membranes are
commercially available, e.g. under the trademark GORE-TEX.RTM.. If
all the gas is extracted from the separation chamber through the
membrane 132, the remainder of the fluid in the separation chamber
is liquid and there may be no need for the above mentioned
microsieve. If the separation chamber 128 is of suitable size and
shape, the microsieve and porous liquidphobic membrane can be
dispensed with and separation effected by positioning the liquid
extraction opening in the bottom of the chamber 128 and the gas
extraction opening part in the top of the chamber 128.
[0094] FIG. 10 shows a further barrier member 12c that is a
variation of the barrier member 12b shown in FIG. 9. In barrier
member 12c, opening 121, formed by first and second walls 122a,
123a, is configured similarly to opening 121 in barrier member 12b
of FIG. 9. Again, it feeds the separating flows into separation
chamber 128 where the liquid content separates out at the bottom.
Rather than being extracted via extraction conduit 130, an outlet
133 is provided near the bottom of the separation chamber 128
opening into a channel 134 that leads back to the space between the
projection system PS and substrate W. This arrangement allows the
immersion liquid to be recycled directly back to the space between
the projection system and the substrate. This can reduce the
consumption of the immersion liquid and also the volume of liquid
flowing to and from the fluid handling structure. As in the
structure of FIG. 9, gas is extracted from separation chamber 128
through gas extraction conduit 131 whose entrance may be covered by
optional porous liquidphobic membrane 132. Also shown in FIG. 10 is
a controlled leak 135 that provides a fluid communication between
the local environment and the upper part of the slit 121 and/or
separation chamber 128. This controlled leak 135 includes a flow
restrictor and may be used to control the underpressure in slit 121
and separation chamber 128. Such a controlled leak 135 may also be
employed in other embodiments of the invention.
[0095] In the embodiments described with reference to FIGS. 9 and
10, a substantially horizontal microsieve (as described above) may
be used to divide the separation chamber into two parts and to
substantially prevent gas entering into the lower, liquid-filled
part. In the embodiment described with reference to FIG. 10, gas
and liquid extraction conduits similar to conduits 131 and 133
shown in FIG. 9 can be provided to control the liquid level in
chamber 128.
[0096] A further barrier member 121 according to an embodiment of
the invention is shown in FIG. 11. In this embodiment, immersion
liquid 11 that passes along the gap between the barrier member 121
and the substrate W is drawn into opening 121 along with gas from
the surroundings and so forms a two-phase flow in conduit 129.
Additional gas is supplied from gas source 136 to increase the
amount of gas in the two-phase flow which then enters conduit 137.
This, and the resulting increased flow rate, encourages the
two-phase flow to separate out in conduit 137. In conduit 137, the
liquid flows in around the outside 138 of the conduit while the gas
flows mainly down the center 139. The inner surface of conduit 137
can be modified to encourage this as described below with reference
to FIGS. 14 to 17. In an embodiment, conduit 137 is wider than
conduit 129.
[0097] Arrangements to divert the separated flows as described
below with reference to FIGS. 19 and 20 can also be used. The
additional gas supplied from gas supply 136 need not be the same as
the gas taken up through opening 121. The additional gas can be
taken from the surroundings of the apparatus by a pump or can be a
pressurized gas supply. Such an additional gas supply can be used
in other embodiments of the invention if desired.
[0098] A barrier member according to a further embodiment of the
invention is shown in FIG. 12 in a partially-cut away perspective
view. Shown in the Figure is the lower plate 140 of the barrier
member 12d, Lower plate 140 is provided with a ring of small
through-holes 141 through which the immersion liquid is supplied to
the space between the projection system PS and the substrate W and
a set of extraction ports 142 (only one directly visible in the
Figure). A two-phase fluid flow comprising liquid flowing
underneath the bottom plate 140 and gas from the local environment
is extracted through the extraction ports 142. The extraction ports
142 lead to vertical channels 143 through the body of the barrier
member 12d. At their tops, the channels 143 open into a generally
horizontal separation chamber 144. Between adjacent conduits 143,
flow guiding structures 145 are provided. The flow guiding
structures have curved surfaces. With curved surfaces the flow
guiding structures 145 are generally semi-circular or semi-oval in
plan. They are spaced apart so that passageways with diverging or
widening walls are defined between the top ends of the conduit 143
and the main part of the separation chamber 144. The passageways
widen with an increase in the distance from the top ends of the
conduit 143. Omitted from FIG. 12 is an upper surface in which may
be defined openings for the exit of liquid and gas from the
separation chamber 144. The upper surface may be an upper plate of
the barrier member 12b. The upper plate may close the separation
chamber 144. The openings in the upper surface define openings of
liquid and gas extraction channels. In an embodiment, a single
opening in the upper plate may be used. In this case the liquid and
gas are arranged to flow separately in a single channel.
[0099] In use, the two-phase flow from the gap between the barrier
member 12d and the substrate W flows up channels 143. The flow then
undergoes a sharp change of direction to flow horizontally into the
separation chamber 144. This sharp change of direction causes the
liquid to preferentially flow along a surface of the separation
chamber, such as the underside of the upper plate which closes the
upper side of the separation chamber 144. The liquid flow thus
separates from the mixed two-phase flow. The liquid flow leaves the
remaining fluid, i.e. the gas, to flow as a gas flow.
[0100] Flow guiding structures 145 initially confine the flow
exiting the channels 143. The flow guiding structures 145 guide the
two-phase flow away from the channels 143. As the passageways
between the flow guiding structures widen with increasing distance
from the channel 143, the surface area of the passageways
increases. With increasing passageway surface area, more of the
liquid is drawn to flow along the surface of the separation chamber
144. The flow guiding structures 145 in effect allow the two-phase
flow to spread out as it moves towards the center of the separation
chamber 144. Thus with increasing distance from the channel 143 the
separation of the phases in the two-phase flow improves.
[0101] The flow guiding structures 145 may guide the gas and liquid
flows (i.e. separated two-phase flow) to an opening. The two-phase
flow leaves the separation chamber as a separated two-phase flow,
or as separated flows of liquid and gas. Note that the opening
through which the fluid exits the separation chamber 144 is
desirably located in the upper surface. The opening may be defined
in a surface of the chamber, for example in a non-limiting list: a
lower surface of the chamber, a side surface defining a side of the
chamber or a surface of the flow guiding structure 145.
[0102] FIG. 13 is a partially cut-away perspective view of another
barrier member 12e according to an embodiment of the invention.
Note that the features shown in FIG. 13 are enlarged compared to
those shown in FIG. 12. The barrier member 12e of FIG. 13 differs
from barrier member 12d of FIG. 12 in the shape and configuration
of the flow guiding structures 145, which are labeled as flow
guiding structures 146.
[0103] In FIG. 13, flow guiding structures 146 have, in plan, a
projection on either side of an opening of the top of conduit 143.
Each projection may be a lobe with a curved surface. In plan, the
flow guiding structure 146 may be bilobed, with a recess between
the lobes. The opening of the conduit may be located between the
lobes and may be in the recess. The adjoining, or inner, walls of
each lobe of the bilobed structure may meet to define a wall
defining in part the opening to the conduit 143. The outer wall
146b of the lobes of each bilobed structure define the remaining
shape of the flow guiding structure. The outer wall of the lobes
may converge to form a third lobe directed away from the bilobed
structure. The outer wall of the lobes near the third lobe may be a
converging or tapering part of the flow guiding structure. In an
embodiment the flow guiding structure may be described as
heart-shaped. The conduit 143 may open into the recess, which may
be a cusp 146a of the heart-shape
[0104] A wall 147 of the separation chamber 144 opposing the lobes
are shaped to correspond with the lobes. The shape of the wall
defines a recess. Each recess is shaped (e.g., curved) away from
the corresponding flow guiding structure 146. Adjoining recesses
meet, in plan, at a point. The point may be an edge. A point may be
opposed to the opening of a conduit 143, i.e. the wall of the flow
guiding structure, between two lobes.
[0105] In use of the apparatus, the two-phase flow from conduit 143
is directed along passageway 148. The passageway 148 is defined by
a lobe of flow guiding structure 146 and a corresponding recess in
the wall of the separation chamber. The passageway may be curved.
The two phase flow may follow a curved path along passageway 148.
In the passageway 148, the two-phase flow may separate as it
changes direction. The two-phase flow may start to separate at this
stage. The curved path of the two-phase flow changes direction
which in an embodiment may be by substantially 180 degrees. The two
phase fluid may then flow towards the main part of the separation
chamber 144, and may be towards the tapering part.
[0106] The sharp change of direction on exit of the flow channel
143 combines with a cyclonic effect generated by the movement of
the flow through passageway 148 to cause the two-phase flow to
start to separate (or in an embodiment separate) the two-phase
fluid flow into separated flows of liquid and gas. As the two-phase
fluid flows along the passage between adjacent flow guiding
structures 146, the phases of the two-phase flow may continue to
separate. Towards the tapering part 146c, the walls of a passage
between the adjacent flow guiding structures 146 diverge. The
passage widens. The surface area over which the two-phase flow
flows increases to allow the fluid to spread out. As the phases of
the fluid have started to separate into liquid and gas, the
increase in surface area may encourage the separation to increase.
The two-phase flow may be extracted through openings of extraction
channels defined in an upper surface, for example in the upper
plate (not shown) of the barrier member 12e. The two-phase flow may
be extracted through a single opening as a flow in which the phases
flow separately.
[0107] In an embodiment of the invention, it may be necessary to
transport a two-phase flow through a conduit which may be
substantially circular in cross-section. In order to help prevent
uneven mixed two-phase flow, which may cause vibrations, it is
desirable to separate the liquid and gas within the conduit which
may be circular. In an embodiment of the invention, the liquid
content of the two-phase flow is encouraged to adopt an annular
flow (i.e. annular two-phase flow) in an axial direction of the
conduit, radially outwardly from the gaseous flow. That is the
liquid may flow along the outside inner surface of the conduit
while the gas flows substantially along the middle of the conduit.
This can be achieved with an appropriate coating and/or structure
in or on the inner surface of the conduit.
[0108] FIG. 14 is a cross-sectional view of a circular
cross-section conduit having no particular surface treatment. There
is a relatively high contact angle between the liquid 11 and the
wall of the conduit 150. Under the influence of gravity (if
sufficiently stronger relative to the forces applied to the fluid
to cause it to flow through the conduit) the liquid tends to flow
along the bottom of the conduit 150. The liquid may accumulate into
larger bodies filling the entire cross-section of the conduit. Such
a cross-sectional blockage disrupts the smooth flow of the fluid,
resulting in uneven flow, which may be referred to as plug-slug
flow. In an embodiment of the invention, shown in FIG. 15, a
liquidphilic coating 151 is on the interior wall of the conduit 150
(i.e. a surface portion which may be treated which has a reduced
contact angle relative to the surrounding surface). This reduces
the contact angle between the liquid 11 and the wall of the conduit
150 (i.e. at the surface portion). The liquid is caused to spread
out over the interior surface of the conduit 150, for example the
bottom of the conduit 150, into a liquid layer. The liquid layer
reduces the tendency for the liquid 11 to form into a slug filling
a cross-sectional portion of the conduit. Vibration caused by the
flow may be reduced.
[0109] In an embodiment, shown in FIG. 16, liquidphilic surface
relief pattern 152 is formed on the interior wall of the conduit
150. As well as encouraging the liquid 11 to spread out more widely
on the part of the conduit 11, this pattern 152 forms one or more
pathways along which a small stream of liquid can flow, again
reducing the tendency of the liquid 11 to form a slug.
[0110] In an embodiment, a liquidphobic (increased contact angle)
surface relief pattern may achieve a similar outcome. The
patterning (whether liquidphobic or liquidphilic) may be formed by
a coating of material on the conduit, a surface relief of the
conduit, a physical structure such as a projection or groove, or a
combination of any of these features. The patterning may have a
coiled pattern. The patterning may be applied to an untreated
surface, so that where the patterning is not applied, an adjustment
or change to the contact angle of the surface does not occur. In an
embodiment the effective surface is between patterned features. In
an embodiment the entire surface of the conduit may be a surface
with adjusted contact angle; liquidphobic and liquidphilic
patterning may be present in combination.
[0111] In an embodiment of the invention, a helical structure may
be formed on the inside of the conduit 150. This helical structure
can take one or a combination of forms. For example, as shown in
FIG. 17, a helical groove 153 can be formed on the interior wall of
the conduit 150, similarly to rifling in a gun barrel. As shown in
FIG. 18, a helical projection 154, e.g. wire, can be located
substantially on the interior surface of the conduit. (In the case
of wire, the wire can be inserted into the conduit). The projection
154 may be made of, or coated with, a liquidphilic material.
Alternatively or additionally, not illustrated, the helical ridge
(i.e. projection) is located on the interior wall of the coating.
In each case, the helical structure encourages the liquid 11 to
flow in an annulus against the interior wall of the conduit 150.
The depth or height of the groove, coil or ridge, its pitch and
number of starts can be selected based on the expected flow rates
of liquid and gas in the two-phase flow. In an example, a 6 mm
(internal diameter) hose was provided with an internal spring of
stainless steel wire of diameter 0.5 mm having a pitch of 6 mm.+-.2
mm. This arrangement may be effective in providing smooth flow at a
water ratio of about 1:250. In an embodiment the pitch of the
helical structure is greater than 50% of the diameter of the
conduit. In an embodiment the pitch of the helical structure is
substantially equal to or greater than the diameter of the
conduit.
[0112] Having separated the two-phase flow within conduit 150 into
annular flow or (where the two-phase flow is supplied as annular
flow) maintaining the annular flow, it is desirable to fix or
conserve that separation by diverting the liquid and gas into
separate conduits. Two-phase annular flow may be supplied from a
fluid handling structure shown in and described with reference to
FIGS. 12 and 13. So conduit 150 may be connected to openings though
which fluid exits separation chamber 144.
[0113] Two arrangements to help achieve fixation of the phase flow
separation are shown in FIGS. 19 and 20. In FIG. 19, a part 155 of
the wall of the conduit 150 is formed of a microsieve as described
above. As mentioned above, a microsieve may be a thin metal plate
having a large number of small holes formed therein, the size of
the holes being determined so that desirably only liquid passes
through, especially if the space on the other side of the sieve is
filled with liquid. In this way, the liquid can be extracted from
conduit 150 while the gas continues to flow down conduit 150. In
FIG. 20, a smaller tube 156 is inserted into the center of conduit
150 so that the gas flowing down the middle of conduit 150 enters
the smaller tube 156 and can therefore be separated from the liquid
which preferentially flows around the interior wall of the conduit
150. This arrangement can of course be combined with the microsieve
arrangement of FIG. 19.
[0114] FIGS. 21A-D relate to a problem, and a solution therefor,
that can occur with the use of a microsieve to separate liquid and
gas, as described with reference to FIGS. 8 and 9. FIG. 21A shows a
conventional situation in which a microsieve 161 is used to
separate or remove liquid 11 from gas in a volume such as chamber
160. Chamber 160 is, for example, connected to a gap defined
between the surface of a substrate table and the surface of a
substrate (commonly known as a substrate bubble extraction system)
or adjacent a restricted space, such as the underside of a fluid
handing structure 12. The microsieve 161 separates chamber 160 from
a volume e.g. an extraction conduit 164. The extraction conduit 164
is filled with liquid. Through the extraction conduit 164, liquid
extracted through the microsieve 161 may be removed. If an
underpressure is applied to the extraction conduit 164 so as to
withdraw the liquid 11 through the microsieve 161 but no additional
liquid enters the chamber 160, a situation as shown in FIGS. 21B, C
can arise. What happens is that a bubble 162 may begin to develop
on the surface of the microsieve 161 within the extraction conduit
164 as the underpressure in the extraction conduit 164 increases.
Once that bubble has formed, the surface tension effect that
normally prevents gas passing through the microsieve 161 ceases to
operate locally and the bubble 162 may quickly expand to form a gas
layer 163 adjacent the microsieve 161 within the extraction conduit
164, as shown in FIG. 21C. In this situation, additional liquid
entering the chamber 160 can become trapped within the chamber 160.
Gas instead of liquid may enter the extraction conduit 164.
[0115] According to an embodiment of the invention, a solution is
to provide a current within the liquid 11 in the conduit 164. The
current may flow in a direction with a component which is
perpendicular to the plane of microsieve 161, for example in the
surface of the microsieve in which defines in part the conduit 164.
Desirably, the current may be substantially perpendicular to the
plane of the microsieve 161. This current may be achieved by
supplying additional liquid in one part of the extraction conduit
164 and extracting it in another part or simply by setting up a
recirculating flow of the liquid within the extraction conduit 164.
The flow within the liquid 11 causes a bubble 162 to detach from
the microsieve 161 before it can expand. The surface tension effect
limiting the passing of gas through the microsieve is maintained.
This arrangement can result in small bubbles entering into the
liquid in the extraction conduit 164 through the microsieve 161.
However this is generally less undesirable than formation of a
complete gas layer below the microsieve 161.
[0116] The embodiments described above provide various different
arrangements for at least partially separating two-phase flow into
separate flows: one with a relatively high liquid content
(liquid-rich), one with a relatively low liquid content (gas-rich).
Complete separation into liquid and gas flows is not necessary;
sufficient separation to reduce vibration and/or evaporative
cooling is desirable. Separation may occur in a single chamber or
conduit. Subsequently such separation can be substantially fixed by
directing the separate flows into separate chambers or
conduits.
[0117] Separation of a two-phase flow can occur in stages. The
liquid-rich and/or gas rich flows generated by any of the
embodiments described above may be provided as input(s) to a
separator or separator(s) of any of the other embodiments, or to
another similar stage. In this way increasingly complete separation
can be achieved. In particular, an output of separation as
described with reference to any of FIGS. 8 to 13 may be conveyed
and/or further separated by an arrangement as described with
reference to any of FIGS. 15 to 21D.
[0118] An embodiment of the present invention may be applied to any
two-phase flow. In an immersion lithographic apparatus, particular
sources of two-phase flows to which an embodiment of the invention
may be used to separate include: a dryer; a droplet or film removal
device; and/or a bubble extraction device (e.g., to extract liquid
and gas from gaps between or below a substrate, a sensor or a
closing disk and the substrate table or between a substrate table
and a swap bridge or a measurement stage, or a gap between a
barrier member and a substrate or substrate table, or a gutter on a
substrate table).
[0119] It may be desirable to effect separation of a two-phase flow
as close to its source as possible. Thus, the phase separation
according to an embodiment of the invention may be incorporated in
a barrier member, a substrate table, an extraction conduit, a swap
bridge or a measurement stage.
[0120] In an embodiment of the invention, the effectiveness of the
separation can sometimes be improved by control of flow rates and
pressures in various parts of the apparatus. Such control may be
effected by a suitable control system connected to sources of
underpressure, sources of liquid and/or gas, and controllable
valves, for example. The control system may be embodied in
software, hardware or a combination of software and hardware. A
control system may be responsive to servos and or control systems
of other parts of the apparatus so as to anticipate or respond to
conditions and actions of other parts of the apparatus that might
affect the two-phase flow.
[0121] In an aspect, there is provided a lithographic apparatus
comprising a substrate table constructed to hold a substrate, and a
fluid handling structure arranged to remove liquid and gas in a
two-phase flow from a surface of the substrate table, or of a
substrate held by the substrate table, or both the substrate table
and the substrate, the fluid handling structure comprising a phase
separator having a surface and arranged to separate the two-phase
flow into a first flow and a second flow, the first flow having a
higher ratio of liquid to gas than the two-phase flow and flowing
along the surface, the second flow having a higher ratio of gas to
liquid than the two-phase flow. Optionally, the phase separator
comprises a channel having first and second walls and arranged so
that liquid preferentially flows along the first wall, the first
wall defining the surface. Optionally, the first wall has a lower
contact angle than the second wall. Optionally, the phase separator
further comprises a wet chamber arranged so that liquid flowing
along the first wall enters the wet chamber. Optionally, the wet
chamber is connected to the channel by a slit defined by the first
wall and a divider. Optionally, the first wall is substantially
straight between an inlet of the channel and the wet chamber.
Optionally, the slit has a width arranged so that capillary forces
encourage substantially only liquid to enter the slit, desirably
the slit width is in the range of from 0.5 mm to 3 mm, desirably
from in the range of from 1 mm to 2 mm. Optionally, the first wall
is curved so that at a point where the channel enters the wet
chamber the first wall is lower than the second wall. Optionally,
the phase separator further comprises a gas extraction channel
separated from the wet chamber by a gas-permeable liquidphobic
membrane. Optionally, the phase separator further comprises a
liquid extraction opening defined in a wall of the wet chamber, the
liquid extraction opening being below the gas-permeable
liquidphobic membrane. Optionally, the phase separator further
comprises a drain path to allow liquid to drain from the wet
chamber to a space between the substrate and a projection system
arranged to project a patterned radiation beam onto the substrate.
Optionally, the phase separator further comprises a dry chamber
connected to the channel via an opening in the second wall.
Optionally, the phase separator comprises a chamber, defined by
first and second walls, and a plurality of channels entering into
the chamber through the second wall, the channels being arranged at
an angle to the second wall such that a two-phase flow entering the
chamber from a channel at least partially separates into a liquid
flow along the first wall and a gas flow along the second wall.
Optionally, the phase separator further comprises a plurality of
flow directing structures in the chamber adjacent the openings of
the channels. Optionally, the flow directing structures have curved
surfaces that define flow paths leading away from the openings, the
flow paths increasing in width away from the openings over at least
part of their length. Optionally, the curved surfaces are arranged
so that the flow paths turn through at least 90.degree., desirably
180.degree.. Optionally, the phase separator comprises a
liquidphilic surface, desirably the liquidphilic surface is in a
conduit. Optionally, the liquidphilic surface is a liquidphilic
coating. Optionally, the liquidphilic surface has a liquidphilic
surface relief provided thereon. Optionally, the phase separator
comprises a conduit defined by a wall and having a substantially
circular cross-section over at least a part of the length thereof
and a substantially helical structure provided on the wall.
Optionally, the substantially helical structure is a substantially
helical groove in the wall, or a substantially helical wire mounted
on the wall, or a contact angle surface patterning which is
helical, or any combination selected therefrom. Optionally, the
substantially helical structure has a liquidphilic coating.
Optionally, the phase separator further comprises a gas extraction
conduit arranged within a part of a conduit so as to define an
annular gap between an outer surface of the gas extraction conduit
and an inner surface of the conduit. Optionally, the surface is in
part defined by a porous member, desirably a plate, through which
liquid can be extracted. Optionally, the phase separator further
comprises a gas supply arranged to add additional gas to the
two-phase flow. Optionally, the fluid handling structure comprises
a barrier member arranged to at least partly confine a liquid to a
space between the substrate and a projection system arranged to
project a patterned radiation beam onto the substrate, the phase
separator being contained in the barrier member.
[0122] In an aspect, there is provided a fluid handling structure
configured to remove liquid and gas in a two-phase flow from a
surface, the fluid handling structure comprising a phase separator
having a surface and arranged to separate the two-phase flow into a
first flow and a second flow, the first flow having a higher ratio
of liquid to gas than the two-phase flow and flowing along the
surface, the second flow having a higher ratio of gas to liquid
than the two-phase flow.
[0123] In an aspect, there is provided a drying device comprising
the above fluid handling structure.
[0124] In an aspect, there is provided an immersion metrology
device comprising the above fluid handling structure.
[0125] In an aspect, there is provided a device manufacturing
method comprising projecting an image of a pattern onto a substrate
through a liquid confined to a space adjacent the substrate,
removing liquid from the substrate in a two-phase flow with gas,
and separating the two-phase flow into a first flow and a second
flow, the first flow having a higher ratio of liquid to gas than
the two-phase flow and flowing along a surface, the second flow
having a higher ratio of gas to liquid than the two-phase flow.
Optionally, the projecting and removing are carried out
simultaneously. Optionally, the removing is carried out after the
projecting has been carried out.
[0126] In an aspect, there is provided a liquid-gas separator
comprising a conduit or chamber divided into two parts by a porous
plate, the first part being substantially filled with liquid, and a
current generator configured to supply liquid to the first part and
constructed and arranged to generate a current in the liquid so as
to substantially prevent bubbles of gas remaining on a surface of
the porous plate which defines in part the first part.
[0127] In an aspect, there is provided an apparatus having an
immersion system with the above separator, wherein the apparatus is
a lithographic apparatus or a metrology device.
[0128] 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.
[0129] 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).
[0130] 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.
[0131] 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 embodiments
of 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. Further, the machine readable
instruction may be embodied in two or more computer programs. The
two or more computer programs may be stored on one or more
different memories and/or data storage media.
[0132] The controllers described above may have any suitable
configuration for receiving, processing, and sending signals. For
example, each controller may include one or more processors for
executing the computer programs that include machine-readable
instructions for the methods described above. The controllers may
include data storage medium for storing such computer programs,
and/or hardware to receive such medium.
[0133] One or more embodiments of the invention may be applied to
any immersion lithography apparatus, in particular, but not
exclusively, those types mentioned above and whether the immersion
liquid is provided in the form of a bath, only on a localized
surface area of the substrate, or is unconfined. In an unconfined
arrangement, the immersion liquid may flow over the surface of the
substrate and/or substrate table so that substantially the entire
uncovered surface of the substrate table and/or substrate is
wetted. In such an unconfined immersion system, the liquid supply
system may not confine the immersion liquid or it may provide a
proportion of immersion liquid confinement, but not substantially
complete confinement of the immersion liquid.
[0134] A liquid supply system as contemplated herein should be
broadly construed. In certain embodiments, it may be a mechanism or
combination of structures that provides a liquid to a space between
the projection system and the substrate and/or substrate table. It
may comprise a combination of one or more structures, one or more
liquid outlets, one or more gas outlets, one or more fluid outlets
for two-phase flow, one or more gas inlets, and/or one or more
liquid inlets that provide liquid to the space. In an embodiment, a
surface of the space may be a portion of the substrate and/or
substrate table, or 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. The liquid supply
system may optionally further include one or more elements to
control the position, quantity, quality, shape, flow rate or any
other features of the liquid.
[0135] It should be noted that the term "gas knife" should not be
taken as requiring that a specific gas is necessarily used, any gas
or mixture of gases may be used.
[0136] 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.
* * * * *