U.S. patent application number 12/882886 was filed with the patent office on 2011-01-06 for lithographic apparatus and device manufacturing method.
This patent application is currently assigned to ASML NETHERLANDS B.V.. Invention is credited to Johannes Jacobus Matheus BASELMANS, Sjoerd Nicolaas Lambertus DONDERS, Christiaan Alexander HOOGENDAM, Jeroen Johannes Sophia Maria MERTENS, Johannes Catharinus Hubertus MULKENS, Bob STREEFKERK.
Application Number | 20110001944 12/882886 |
Document ID | / |
Family ID | 35698857 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110001944 |
Kind Code |
A1 |
BASELMANS; Johannes Jacobus Matheus
; et al. |
January 6, 2011 |
LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD
Abstract
An immersion lithographic apparatus is disclosed which includes
a liquid supply system having an inlet configured to supply a
liquid to a space between a projection system of the lithographic
apparatus and a substrate and an outlet configured to remove at
least part of the liquid, the liquid supply system configured to
rotate the inlet, the outlet, or both, about an axis substantially
perpendicular to an exposure plane of the substrate.
Inventors: |
BASELMANS; Johannes Jacobus
Matheus; (Oirschot, NL) ; DONDERS; Sjoerd Nicolaas
Lambertus; ('s-Hertogenbosch, NL) ; HOOGENDAM;
Christiaan Alexander; (Veldhoven, NL) ; MERTENS;
Jeroen Johannes Sophia Maria; (Duizel, NL) ; MULKENS;
Johannes Catharinus Hubertus; (Waalre, NL) ;
STREEFKERK; Bob; (Tilburg, NL) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
ASML NETHERLANDS B.V.
Veldhoven
NL
|
Family ID: |
35698857 |
Appl. No.: |
12/882886 |
Filed: |
September 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11524262 |
Sep 21, 2006 |
7812924 |
|
|
12882886 |
|
|
|
|
11001082 |
Dec 2, 2004 |
7161654 |
|
|
11524262 |
|
|
|
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Current U.S.
Class: |
355/30 ;
355/77 |
Current CPC
Class: |
G03F 7/70341
20130101 |
Class at
Publication: |
355/30 ;
355/77 |
International
Class: |
G03B 27/52 20060101
G03B027/52; G03B 27/32 20060101 G03B027/32 |
Claims
1.-20. (canceled)
21. A lithographic apparatus, comprising: a substrate table
configured to hold a substrate; a projection system configured to
project a patterned beam of radiation onto a target portion of the
substrate; a liquid supply system comprising an inlet configured to
supply a liquid to a space between the projection system and the
substrate and an outlet configured to remove at least part of the
liquid; and a controller configured to control the inlet and/or
outlet so as to maintain a direction of flow of liquid in the space
substantially perpendicular to a direction of movement of the
substrate during movement of the substrate in the direction.
22. The apparatus of claim 21, wherein the controller is configured
to maintain the direction of flow through rotation of the inlet,
the outlet, or both.
23. The apparatus of claim 21, wherein the controller is configured
to maintain the direction of flow during projection of the
patterned beam of radiation.
24. The apparatus of claim 23, wherein the controller is further
configured to maintain a direction of flow of liquid in the space
during a stepping motion in a direction substantially parallel to
the direction of the stepping motion.
25. The apparatus of claim 21, wherein the inlet and outlet are
respectively positioned on opposite sides of an exposure field
through which the patterned beam is projected.
26. The apparatus of claim 21, wherein the outlet surrounds an
exposure field through which the patterned beam is projected.
27. The apparatus of claim 21, comprising a further outlet outward,
relative to an optical axis of the projection system, to the inlet
and/or outlet.
28. A device manufacturing method, comprising: supplying a liquid
to a space between a projection system of a lithographic apparatus
and a substrate using an inlet; removing at least part of the
liquid using an outlet; moving the substrate in a direction;
controlling the inlet and/or outlet so as to maintain a direction
of flow of liquid in the space substantially perpendicular to the
direction of movement of the substrate during the movement of the
substrate in the direction; and projecting a patterned beam of
radiation, using the projection system, through the liquid onto a
target portion of the substrate.
29. The method of claim 28, wherein the controlling comprises
rotating the inlet, the outlet, or both, to maintain the direction
of flow.
30. The method of claim 28, wherein the controlling comprises
maintaining the direction of flow during a projection of the
patterned beam of radiation.
31. The method of claim 30, wherein the controlling further
comprises maintaining a direction of flow of liquid in the space
during a stepping motion in a direction substantially parallel to
the direction of the stepping motion.
32. The method of claim 28, wherein the controlling comprising
supplying liquid through the inlet on a side of an exposure field
through which the patterned beam is projected and removing liquid
through the outlet on an opposite side of the exposure field.
33. The method of claim 28, wherein the outlet surrounds an
exposure field through which the patterned beam is projected.
34. The method of claim 28, comprising removing liquid using a
further outlet outward, relative to an optical axis of the
projection system, to the inlet and/or outlet.
35. A device manufacturing method, comprising: supplying a liquid
to a space between a projection system of a lithographic apparatus
and a table using an inlet; removing at least part of the liquid
using an outlet; moving the table in a direction; controlling the
inlet and/or outlet so as to maintain a direction of flow of liquid
in the space substantially perpendicular to the direction of
movement of the table during the movement of the table in the
direction; and projecting a patterned beam of radiation, using the
projection system, through the liquid onto a surface on the
table.
36. The method of claim 35, wherein the controlling comprises
rotating the inlet, the outlet, or both, to maintain the direction
of flow.
37. The method of claim 35, wherein the controlling comprises
maintaining the direction of flow during projecting of the
patterned beam of radiation.
38. The method of claim 37, wherein the controlling further
comprises maintaining a direction of flow of liquid in the space
during a motion when the patterned beam is not projected in a
direction substantially parallel to the direction of the motion
when the patterned beam is not projected.
39. The method of claim 35, wherein the controlling comprising
supplying liquid through the inlet on a side of a field through
which the patterned beam is projected and removing liquid through
the outlet on an opposite side of the exposure field.
40. The method of claim 35, wherein the outlet surrounds a field
through which the patterned beam is projected.
Description
[0001] This is a continuation application of co-pending U.S. patent
application Ser. No. 11/524,262, filed Sep. 21, 2006, now allowed,
which is a continuation application of U.S. patent application Ser.
No. 11/001,082, filed Dec. 2, 2004, now U.S. Pat. No. 7,161,654,
each of the foregoing applications is incorporated by reference
herein in its entirety.
FIELD
[0002] The present invention relates to a lithographic apparatus
and a method for manufacturing a device.
BACKGROUND
[0003] A lithographic apparatus is a machine that applies a desired
pattern onto a substrate, usually onto a target portion of the
substrate. A lithographic apparatus can be used, for example, in
the manufacture of integrated circuits (ICs). In that instance, a
patterning device, which is alternatively referred to as a mask or
a reticle, may be used to generate a circuit pattern to be formed
on an individual layer of the IC. This pattern can be transferred
onto a target portion (e.g. comprising part of, one, or several
dies) on a substrate (e.g. a silicon wafer). Transfer of the
pattern is typically via imaging onto a layer of
radiation-sensitive material (resist) provided on the substrate. In
general, a single substrate will contain a network of adjacent
target portions that are successively patterned. Known lithographic
apparatus include so-called steppers, in which each target portion
is irradiated by exposing an entire pattern onto the target portion
at one time, and so-called scanners, in which each target portion
is irradiated by scanning the pattern through a radiation beam in a
given direction (the "scanning"-direction) while synchronously
scanning the substrate parallel or anti-parallel to this direction.
It is also possible to transfer the pattern from the patterning
device to the substrate by imprinting the pattern onto the
substrate.
[0004] It has been proposed to immerse the substrate in the
lithographic projection apparatus in a liquid having a relatively
high refractive index, e.g. water, so as to fill a space between
the final element of the projection system and the substrate. The
point of this is to enable imaging of smaller features since the
exposure radiation will have a shorter wavelength in the liquid.
(The effect of the liquid may also be regarded as increasing the
effective numerical aperture (NA) of the system and also increasing
the depth of focus.) Other immersion liquids have been proposed,
including water with solid particles (e.g. quartz) suspended
therein.
[0005] However, submersing the substrate or substrate and substrate
table in a bath of liquid (see for example United States patent
U.S. Pat. No. 4,509,852, hereby incorporated in its entirety by
reference) means that there is a large body of liquid that must be
accelerated during a scanning exposure. This requires additional or
more powerful motors and turbulence in the liquid may lead to
undesirable and unpredictable effects.
[0006] One of the solutions proposed is for a liquid supply system
to provide liquid on only a localized area of the substrate and in
between the final element of the projection system and the
substrate (the substrate generally has a larger surface area than
the final element of the projection system). One way which has been
proposed to arrange for this is disclosed in PCT patent application
no. WO 99/49504, hereby incorporated in its entirety by reference.
As illustrated in FIGS. 2 and 3, liquid is supplied by at least one
inlet IN onto the substrate, preferably along the direction of
movement of the substrate relative to the final element, and is
removed by at least one outlet OUT after having passed under the
projection system. That is, as the substrate is scanned beneath the
element in a -X direction, liquid is supplied at the +X side of the
element and taken up at the -X side. FIG. 2 shows the arrangement
schematically in which liquid is supplied via inlet IN and is taken
up on the other side of the element by outlet OUT which is
connected to a low pressure source. In the illustration of FIG. 2
the liquid is supplied along the direction of movement of the
substrate relative to the final element, though this does not need
to be the case. Various orientations and numbers of in- and
out-lets positioned around the final element are possible, one
example is illustrated in FIG. 3 in which four sets of an inlet
with an outlet on either side are provided in a regular pattern
around the final element.
SUMMARY
[0007] It would be advantageous, for example, to provide a
lithographic apparatus having a liquid supply system wherein a
substrate may be moved in different directions without having to
switch a flow direction of the liquid between the projection system
of the lithographic apparatus and a substrate.
[0008] According to an aspect of the invention, there is provided a
lithographic apparatus, comprising:
[0009] a substrate table configured to hold a substrate;
[0010] a projection system configured to project a patterned beam
onto a target portion of the substrate; and
[0011] a liquid supply system comprising an inlet configured to
supply a liquid to a space between the projection system and the
substrate and an outlet configured to remove at least part of the
liquid, the liquid supply system configured to rotate the inlet,
the outlet, or both, about an axis substantially perpendicular to
an exposure plane of the substrate.
[0012] According to an aspect of the invention, there is provided a
lithographic apparatus, comprising:
[0013] a substrate table configured to hold a substrate;
[0014] a projection system configured to project a patterned beam
onto a target portion of the substrate; and
[0015] a liquid supply system comprising an inlet configured to
supply a liquid to a space between the projection system and the
substrate and an outlet configured to remove at least part of the
liquid, the liquid supply system configured to rotate the inlet and
outlet in tandem about an axis substantially parallel to an optical
axis of the projection system in accordance with a change in
movement of the substrate.
[0016] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0017] supplying a liquid to a space between a projection system of
a lithographic apparatus and a substrate;
[0018] rotating an inlet configured to supply the liquid to the
space, an outlet configured to remove the liquid, or both, about an
axis substantially perpendicular to an exposure plane of the
substrate; and
[0019] projecting a patterned beam of radiation, using the
projection system, through the liquid onto a target portion of the
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] 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:
[0021] FIG. 1 depicts a lithographic apparatus according to an
embodiment of the invention;
[0022] FIGS. 2 and 3 depict a liquid supply system for use in a
lithographic projection apparatus;
[0023] FIG. 4 depicts another liquid supply system for use in a
lithographic projection apparatus;
[0024] FIG. 5 depicts another liquid supply system for use in a
lithographic projection apparatus;
[0025] FIG. 6 depicts a top view of a liquid supply system
according to an embodiment of the invention;
[0026] FIG. 7 depicts a side view of the liquid supply system of
FIG. 6;
[0027] FIGS. 8a to 8c depict various rotations of a liquid
confinement structure according to an embodiment of the invention;
and
[0028] FIG. 9 depicts a side view of a liquid supply system
according to another embodiment of the invention.
DETAILED DESCRIPTION
[0029] FIG. 1 schematically depicts a lithographic apparatus
according to one embodiment of the invention. The apparatus
comprises: [0030] an illumination system (illuminator) IL
configured to condition a radiation beam PB (e.g. UV radiation or
DUV radiation); [0031] 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; [0032] 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
[0033] a projection system (e.g. a refractive projection lens
system) PL configured to project a pattern imparted to the
radiation beam PB by patterning device MA onto a target portion C
(e.g. comprising one or more dies) of the substrate W.
[0034] 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.
[0035] The support structure supports, i.e. bears the weight of,
the patterning device. It holds the patterning device in a manner
that depends on the orientation of the patterning device, the
design of the lithographic apparatus, and other conditions, such as
for example whether or not the patterning device is held in a
vacuum environment. The support structure can use mechanical,
vacuum, electrostatic or other clamping techniques to hold the
patterning device. The support structure may be a frame or a table,
for example, which may be fixed or movable as required. The support
structure may ensure that the patterning device is at a desired
position, for example with respect to the projection system. Any
use of the terms "reticle" or "mask" herein may be considered
synonymous with the more general term "patterning device."
[0036] 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.
[0037] 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.
[0038] 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".
[0039] 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).
[0040] The lithographic apparatus may be of a type having two (dual
stage) or more substrate tables (and/or two or more mask 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.
[0041] 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.
[0042] 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.
[0043] The radiation beam PB 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 mask MA, the radiation beam PB passes through the
projection system PL, which focuses the beam onto a target portion
C of the substrate W. A liquid confinement structure IH, which is
described further below, supplies immersion liquid to a space
between the final element of the projection system PL and the
substrate W.
[0044] 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 PB. Similarly, the first positioner PM and another
position sensor (which is not explicitly depicted in FIG. 1) can be
used to accurately position the mask MA with respect to the path of
the radiation beam PB, e.g. after mechanical retrieval from a mask
library, or during a scan. In general, movement of the mask table
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 mask table
MT may be connected to a short-stroke actuator only, or may be
fixed. Mask MA and substrate W may be aligned using mask 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 mask MA,
the mask alignment marks may be located between the dies.
[0045] The depicted apparatus could be used in at least one of the
following modes: [0046] 1. In step mode, the mask table 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. [0047] 2. In scan
mode, the mask table 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 mask table MT may be determined by the (de-)magnification and
image reversal characteristics of the projection system. 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. [0048] 3. In another mode, the mask table 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.
[0049] Combinations and/or variations on the above described modes
of use or entirely different modes of use may also be employed.
[0050] A further immersion lithography solution with a localized
liquid supply system is shown in FIG. 4. Liquid is supplied by two
groove inlets IN on either side of the projection system PL and is
removed by a plurality of discrete outlets OUT arranged radially
outwardly of the inlets IN. The inlets IN and OUT can be arranged
in a liquid confinement structure, such as plate with a hole in its
center, through which the projection beam is projected. Liquid is
supplied by one groove inlet IN on one side of the projection
system and removed by a plurality of discrete outlets OUT on the
other side of the projection system, causing a flow of a thin film
of liquid between the projection system and the substrate. The
choice of which combination of inlet IN and outlets OUT to use can
depend on the direction of movement of the substrate (the other
combination of inlet IN and outlets OUT being inactive).
[0051] Another immersion lithography solution with a localized
liquid supply system solution which has been proposed is to provide
the liquid supply system with a liquid confinement structure which
extends along at least a part of a boundary of the space between
the final element of the projection system and the substrate table.
Such a solution is schematically illustrated in FIG. 5. The liquid
confinement structure is substantially stationary relative to the
projection system in the X-Y plane though there may be some
relative movement in the Z direction (in the direction of the
optical axis). A seal is formed between the liquid confinement
structure and the surface of the substrate.
[0052] Referring to FIG. 5, reservoir 10 forms a contactless seal
to the substrate around the image field of the projection system so
that liquid is confined to fill a space between the substrate
surface and the final element of the projection system. The
reservoir is formed by a liquid confinement structure 12 positioned
below and surrounding the final element of the projection system
PL. Liquid is brought into the space below the projection system
and within the liquid confinement structure. The liquid confinement
structure extends a little above the final element of the
projection system and the liquid level rises above the final
element so that a buffer of liquid is provided. The liquid
confinement structure 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 closely conforms to the shape of the
image field, e.g., rectangular though this need not be the
case.
[0053] The liquid is confined in the reservoir by a gas seal 16
between the bottom of the liquid confinement structure and the
surface of the substrate W. The gas seal is formed by gas, e.g.
air, synthetic air, N.sub.2 or an inert gas, provided under
pressure via inlet 15 to the gap between liquid confinement
structure 12 and substrate and extracted via first outlet 14. The
overpressure on the inlet 15, vacuum level on the first outlet 14
and geometry of the gap are arranged so that there is a
high-velocity gas flow inwards that confines the liquid. Such a
system is disclosed in United States patent application no. U.S.
Ser. No. 10/705,783, hereby incorporated in its entirety by
reference.
[0054] In the liquid confinement structure of FIG. 5, liquid may
supplied to and/or removed from the space between the projection
system and the substrate /substrate table by port 13. In an
embodiment, port 13 comprises a pair of inlets 13 (for example, on
opposite sides of an exposure field) which supply liquid to the
space. The liquid supplied by the inlet(s) 13 may be removed by
outlet 14 which surrounds a periphery of the exposure field (as
used herein, exposure field includes not only an area through which
the projection beam passes but additionally or alternatively may
include an area through which measurement, by for a measurement
radiation beam, may be taken). Due to the outlet 14, liquid is
confined to the space and within the exposure field irrespective of
the direction of movement of the substrate/substrate table. A
liquid flow may be established and/or maintained in the space
through appropriate configuration of inlet(s) 13 and outlet 14.
However, where only seal 16 is used, liquid supplied by inlet(s) to
the space and within the exposure field may only just be maintained
therein without a liquid flow in the space.
[0055] In an embodiment, port 13 comprises an inlet and an outlet
(for example, on opposite sides of an exposure field). The seal 16,
which surrounds an exposure field, confines the liquid to the space
and within the exposure field without a need for a liquid outlet.
Where a flow of liquid through the space is desired, the
inlet/outlet 13 may be appropriately configured to establish and/or
maintain the flow.
[0056] In an embodiment, the port 13 extends around a periphery of
an exposure field and thus provides a rotationally symmetric liquid
inlet. Where port 13 only includes an inlet, outlet 14 may be
provided around a periphery of an exposure field to contain liquid
therein during movement of the substrate/substrate table in any
direction. Additionally or alternatively, seal 16 provided around a
periphery of an exposure field may contain liquid in the exposure
field during movement of the substrate/substrate table in any
direction. And, where port 13 further includes an outlet and a
liquid flow is established between the inlet and outlet of port 13,
seal 16 provided around a periphery of an exposure field may
contain liquid in the exposure field during movement of the
substrate/substrate table in any direction.
[0057] Thus, with the liquid supply system of FIG. 5, liquid is
confined to the space between the projection system and the
substrate/substrate table and within the exposure field without the
need for turning off or on particular inlet(s) and/or outlet(s) or
without depending on a direction of movement of the
substrate/substrate table.
[0058] Referring to FIGS. 6 and 7, a top view and a side view,
respectively, of a liquid supply system according to an embodiment
of the invention are schematically depicted. The liquid supply
system comprises a liquid confinement structure 20 configured to at
least partially confine a liquid to a space 22 between the
projection system and the substrate W and/or substrate table WT.
The liquid confinement structure 20 comprises an inlet 24
configured to supply liquid to the space and an outlet 26
configured to remove the liquid. The substrate/substrate table
moves relative to the liquid confinement structure (and the
projection system) in an X-Y plane substantially parallel to a
plane of the liquid confinement structure. In FIGS. 6 and 7, arrows
28 (e.g., in the X direction) depict one example of this movement,
although as will be apparent the substrate/substrate table may move
in other directions (including rotations)
[0059] The liquid confinement structure is connected to a base or
the ground (not shown) via a frame 30. In an embodiment, the
projection system is connected to a different frame (not shown)
from the liquid confinement structure so that the projection system
and the liquid confinement structure are mechanically isolated such
that transmission of vibrations and forces between the projection
system and the liquid confinement structure is minimized or
reduced. The different frame for the projection system may also be
connected to the base or ground or may connected to, but isolated
from, the frame for the liquid confinement structure. The liquid
confinement structure is substantially stationary in the X and Y
directions and may move in the Z direction. In FIG. 6, a top
portion of the projection system (seen, for example, in FIG. 7) is
omitted so the liquid confinement structure can be clearly
seen.
[0060] In an embodiment, like the liquid supply system in FIGS. 2,
3 and 4, the movement of the substrate W/substrate table WT
facilitates confinement and distribution of the liquid in the space
and within an exposure field. In particular, liquid is supplied by
the inlet to the space at one side of the exposure field and
movement of the substrate/substrate table facilitates distribution
of the liquid in the exposure field and to the outlet on an
opposite side of the exposure field. Thus, the projection system
and the liquid confinement structure provide confinement for a top
of the space, the substrate/substrate table provide confinement for
a bottom of the space, and the inlet and outlet on opposite sides
of an exposure field in combination with movement of the
substrate/substrate table in a direction from the inlet to the
outlet provide distribution and confinement laterally within the
space. The combination of the movement of the substrate/substrate
table and positioning of the inlet and outlet on opposite sides of
the exposure field facilitates to establish and maintain a flow of
a thin film of liquid in the space. The arrows 32 (e.g., extending
in the X direction) depict an example of the flow of the liquid in
the space although as will be apparent the flow of liquid may move
in other directions (including rotations) depending on the
positioning of the inlet and outlet and the movement of the
substrate/substrate table.
[0061] In the supply systems of FIGS. 2, 3 and 4, where there is a
change in direction of movement of the substrate/substrate table,
confinement and distribution of the liquid in the space and within
an exposure field is facilitated by activating/deactivating one or
more particular inlet and outlets on or outside a periphery of the
exposure field. For example, in the case of FIGS. 2, 3 and 4, a
first inlet IN on one side of the exposure field supplies liquid to
the space and a first outlet OUT on another side of the exposure
field when the substrate/substrate table moves in a first direction
from the first inlet IN towards the second outlet OUT. Where the
substrate/substrate table moves in a second direction 180.degree.
to the first direction, a second inlet IN and a second outlet OUT
are activated and the first inlet IN and second outlet OUT are
deactivated. The second inlet IN is positioned at a position
opposite to the first inlet IN (adjacent the first outlet OUT) and
the second outlet OUT is positioned at a position opposite to the
first outlet OUT (adjacent the first inlet IN). Thus, in this
configuration, the second direction of the substrate/substrate
table is from the second inlet IN towards the second outlet OUT. In
an embodiment, the first inlet IN may be switched into the second
outlet OUT, for example, by switching from a liquid source to a low
pressure source, and the first outlet OUT may be switched into the
second inlet IN, for example, by switching from a low pressure
source to a liquid supply. Inlets and outlets may also be provided
for movements of the substrate/substrate table in other directions
(see, for example, FIG. 3). Thus, the liquid supply systems of
FIGS. 2, 3 and 4 employ a non-rotationally symmetric liquid inlet
and outlet system leading to the switching of liquid inlet and
outlet positions on or outside the periphery of the exposure field
depending on substrate/substrate table movement (e.g., in a scan
direction) through activation/deactivation of one or more liquid
inlets and outlets.
[0062] In an embodiment, switching of liquid inlet and outlet
positions through activation/deactivation of one or more liquid
inlets and outlets may be avoided where one or more inlets and/or
outlets are rotated around an axis substantially perpendicular to
an exposure plane of the substrate, e.g., the Z axis or an optical
axis of the projection system. Referring to FIGS. 6 and 7, one or
more motors 34 rotate the liquid confinement structure, comprising
the inlet and outlet, relative to the frame and about the axis,
thus moving both the inlet and outlet in tandem. The curved arrows
38 show how the liquid confinement structure rotates. A controller
40 controls the motor(s) based upon a direction of movement of the
substrate/substrate table. In particular, the controller controls
the motor(s) so that the liquid confinement structure is positioned
so that a direction from the inlet to the outlet is substantially
parallel and in the same direction as the movement of the
substrate/substrate table. In this way, the inlet and outlet need
not be activated/deactivated as the liquid confinement structure
rotates with a change in the movement of the substrate/substrate
table to keep the liquid confined in the space between the
projection system and the substrate/substrate table and the flow of
liquid in the space in the same direction as the movement of the
substrate/substrate table. With appropriate rotation of the inlet
and outlet, the movement of the substrate/substrate table may
automatically transport the liquid from the inlet to the outlet in
all directions of movement of the substrate/substrate table. The
controller may operated in a feed-forward or feedback manner.
[0063] In an embodiment, the liquid supply system is configured to
rotate the inlet, the outlet, or both, about an axis substantially
perpendicular to an exposure plane of the substrate. While the
liquid supply system may be able to provide all these rotating
functions, in embodiments, the liquid supply system may provide
rotation of only the inlet (without the ability to rotate the
outlet) or rotation of only the outlet (without the ability to
rotate the inlet) or rotation of both the inlet or outlet. In other
words, a liquid supply system need not be able to provide all these
rotation capabilities but rather may provide only one type of
rotation capability.
[0064] Referring to FIGS. 8a to 8c, the liquid confinement
structure is shown schematically at different rotations to explain
the operation of the liquid supply system according to an
embodiment of the invention. In this example, however, the liquid
confinement structure is connected to the projection system (or a
frame supporting the projection system) without the use of a frame
as depicted in FIGS. 4 and 5. In this case, one or more motors (not
shown) move the liquid confinement structure relative to the
projection system about an axis substantially parallel to the
optical axis of the projection system. Transmission of vibrations
and/or forces between the liquid confinement structure and the
projection system may be reduced or avoided through the use of an
isolator or a damping mechanism. The rotation of this exemplary
liquid confinement structure is substantially similar to the
rotation of the exemplary liquid confinement structure in FIGS. 4
and 5.
[0065] Referring to FIG. 8a, the liquid confinement structure is
positioned so that a direction from the inlet to the outlet of the
liquid confinement structure (represented by arrows) is
substantially parallel to and in the same direction as the movement
of the substrate/substrate table (represented by arrow). In FIG.
8a, the movement of the substrate/substrate table is in a scanning
direction. When the movement of the substrate/substrate table
changes to, for example, a stepping direction as shown in FIG. 8b,
the liquid confinement structure is rotated about 90 degrees in the
clockwise direction so that the direction from the inlet to the
outlet of the liquid confinement structure (represented by arrows)
is substantially parallel to and in the same direction as the
movement of the substrate/substrate table (represented by arrow).
When the movement of the substrate/substrate table changes again
to, for example, a scanning direction again (although having an
opposite sign to the scanning direction in FIG. 8a) as shown in
FIG. 8c, the liquid confinement structure is rotated about 90
degrees further in the clockwise direction so that the direction
from the inlet to the outlet of the liquid confinement structure
(represented by arrows) is substantially parallel to and in the
same direction as the movement of the substrate/substrate table
(represented by arrow). If the movement of the substrate/substrate
table changed again to, for example, a stepping direction such as
shown in FIG. 8b, the liquid confinement structure need only be
rotated about 90 degrees in the counterclockwise direction so that
the direction from the inlet to the outlet of the liquid
confinement structure (represented by arrows) is substantially
parallel to and in the same direction as the movement of the
substrate/substrate table (represented by arrow). Thus, while the
one or more inlets and/or outlets may be rotated to any angle in an
embodiment (e.g., 0 to 360 degrees), the one or more inlets and/or
outlets may be rotated only within the range from 0 to 200
degrees.
[0066] In an embodiment, the one or more inlets and/or outlets may
be rotated only to positions where the direction from the inlet to
the outlet of the liquid confinement structure is substantially
parallel to and in the same direction as the scanning movement of
the substrate/substrate table. In this case, only a limited number
of rotations may be needed.
[0067] In an embodiment, instead of the liquid confinement
structure being rotated, an individual inlet and/or outlet or a
group of inlets and/or outlets may rotated within the liquid
confinement structure itself. For example, where an outlet is
provided around a periphery of an exposure field, it may be
advantageous simply to rotate one or more inlets around all or a
part of the periphery of the exposure field.
[0068] While one or more motors were described above to rotate the
liquid confinement structure or the one or more inlets and/or
outlets, almost any movement mechanism may be used. The motor(s)
may be one or more linear motors or one or more mechanical
actuators. The frame and/or liquid confinement structure may
comprise a track to guide the rotation of the one or more inlets
and/or outlets or the liquid confinement structure. One or more
appropriate bearings may be provided.
[0069] Rotation of one or more of the inlets and/or outlets has an
advantage of avoiding activating/deactivating one or more inlets
and/or outlets. Such activation/deactivation may have deleterious
effects to the liquid quality. For example, valves in the liquid
supply system may be contaminated and so introduce contamination in
the liquid when liquid inlet and outlet positions are switched
through activation/deactivation of one or more inlets and/or
outlets. Changing the direction of or stopping the flow of liquid
through particle filters and/or de-bubblers may cause introduction
of contamination and/or bubbles when switching liquid inlet and
outlet positions through activation/deactivation of one or more
inlets and/or outlets. Further, where a liquid supply system has a
single liquid inlet and a single liquid outlet or an inlet/outlet
combination at each of two opposing positions (such as for example
as shown in FIG. 4), rotation may help to avoid or reduce liquid
leakage in certain substrate/substrate table movement directions,
for example, in a direction perpendicular to the line between the
single liquid inlet and the single liquid outlet or perpendicular
to the line between the inlet/outlet combinations at opposing
positions. Further, rotation may help to avoid or reduce
deleterious vibrations in the lithographic apparatus caused by
activation/deactivation of one or more inlets and/or outlets.
[0070] In an embodiment, the inlet, the outlet, or both may be
rotated so as to maintain the flow of liquid in a direction
substantially perpendicular to a direction of movement of the
substrate. To maintain the liquid in the exposure field, a seal or
outlet is provided around the periphery of the exposure field to
contain or remove liquid as movement of the substrate perpendicular
to the direction of the flow of the liquid in the exposure field
may draw the liquid out of the exposure field (as distinct from a
flow of liquid in the same direction as a direction of movement of
the substrate in which case surface tension could keep the liquid
substantially in the exposure field) and out to portions of the
apparatus where liquid is undesirable. Referring to FIG. 9, the
liquid supply system of this embodiment is substantially the same
as shown in FIG. 7 except that an outlet 42 is provided around a
periphery of the exposure field to remove liquid that may escape
from the exposure field. Depending on the configuration of the
liquid supply system, the flow of liquid and/or the movement of the
substrate, the outlet 42 need not fully surround the exposure
field.
[0071] In an embodiment, the inlet, the outlet, or both may rotated
so as to maintain the flow of liquid, at different times or points,
in a direction substantially perpendicular to a direction of
movement of the substrate or in a direction substantially parallel
to a direction of movement of the substrate.
[0072] In a twin or dual stage immersion lithography apparatus, two
tables are provided for respectively 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 and moves
between separate leveling and exposure positions.
[0073] 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.
[0074] 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).
[0075] 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.
[0076] 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, where
applicable, 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.
[0077] One or more embodiments of the present invention may be
applied to any immersion lithography apparatus, in particular, but
not exclusively, those types mentioned above. A liquid supply
system is any mechanism that provides a liquid to a space between
the projection system and the substrate and/or substrate table. It
may comprise any combination of one or more structures, one or more
liquid inlets, one or more gas inlets, one or more gas outlets,
and/or one or more liquid outlets, the combination providing and
confining the liquid to the space. In an embodiment, a surface of
the space may be limited to a portion of the substrate and/or
substrate table, a surface of the space may completely cover a
surface of the substrate and/or substrate table, or the space may
envelop the substrate and/or substrate table.
[0078] The immersion liquid used in the apparatus may have
different compositions, according to the desired properties and the
wavelength of exposure radiation used. For an exposure wavelength
of 193 nm, ultra pure water or water-based compositions may be used
and for this reason the immersion liquid is sometimes referred to
as water and water-related terms such as hydrophilic, hydrophobic,
humidity, etc. may be used.
[0079] 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.
* * * * *