U.S. patent application number 16/460159 was filed with the patent office on 2019-10-24 for lithographic 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 Johannes Jacobus Matheus BASELMANS, Herman BOOM, Richard Joseph BRULS, Marcel Mathijs Theodore Marie DIERICHS, Sjoerd Nicolaas Lambertus DONDERS, Christiaan Alexander HOOGENDAM, Hans JANSEN, Erik Roelof LOOPSTRA, Jeroen Johannes Sophia Maria MERTENS, Johannes Catharinus Hubertus MULKENS, Timotheus Franciscus SENGERS, Ronald Walther Jeanne SEVERIJNS, Sergei SHULEPOV, Bob STREEFKERK.
Application Number | 20190324374 16/460159 |
Document ID | / |
Family ID | 34702361 |
Filed Date | 2019-10-24 |
![](/patent/app/20190324374/US20190324374A1-20191024-D00000.png)
![](/patent/app/20190324374/US20190324374A1-20191024-D00001.png)
![](/patent/app/20190324374/US20190324374A1-20191024-D00002.png)
![](/patent/app/20190324374/US20190324374A1-20191024-D00003.png)
![](/patent/app/20190324374/US20190324374A1-20191024-D00004.png)
![](/patent/app/20190324374/US20190324374A1-20191024-D00005.png)
![](/patent/app/20190324374/US20190324374A1-20191024-M00001.png)
United States Patent
Application |
20190324374 |
Kind Code |
A1 |
STREEFKERK; Bob ; et
al. |
October 24, 2019 |
LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD
Abstract
An immersion lithographic projection apparatus is disclosed in
which liquid is provided between a projection system of the
apparatus and a substrate. The use of both liquidphobic and
liquidphilic layers on various elements of the apparatus is
provided to help prevent formation of bubbles in the liquid and to
help reduce residue on the elements after being in contact with the
liquid.
Inventors: |
STREEFKERK; Bob; (Tilburg,
NL) ; BASELMANS; Johannes Jacobus Matheus; (Oirschot,
NL) ; BRULS; Richard Joseph; (Eindhoven, NL) ;
DIERICHS; Marcel Mathijs Theodore Marie; (Venlo, NL)
; DONDERS; Sjoerd Nicolaas Lambertus; (Vught, NL)
; HOOGENDAM; Christiaan Alexander; (Veldhoven, NL)
; JANSEN; Hans; (Eindhoven, NL) ; LOOPSTRA; Erik
Roelof; (Eindhoven, NL) ; MERTENS; Jeroen Johannes
Sophia Maria; (Duizel, NL) ; MULKENS; Johannes
Catharinus Hubertus; (Waalre, NL) ; SEVERIJNS; Ronald
Walther Jeanne; (Veldhoven, NL) ; SHULEPOV;
Sergei; (Eindhoven, NL) ; BOOM; Herman;
(Eindhoven, NL) ; SENGERS; Timotheus Franciscus;
('s-I-Iertogenbosch, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASML NETHERLANDS B.V. |
Veldhoven |
|
NL |
|
|
Assignee: |
ASML NETHERLANDS B.V.
Veldhoven
NL
|
Family ID: |
34702361 |
Appl. No.: |
16/460159 |
Filed: |
July 2, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15918575 |
Mar 12, 2018 |
10345712 |
|
|
16460159 |
|
|
|
|
14839633 |
Aug 28, 2015 |
9952515 |
|
|
15918575 |
|
|
|
|
14266591 |
Apr 30, 2014 |
9134623 |
|
|
14839633 |
|
|
|
|
14107734 |
Dec 16, 2013 |
9134622 |
|
|
14266591 |
|
|
|
|
13186991 |
Jul 20, 2011 |
8634056 |
|
|
14107734 |
|
|
|
|
12411952 |
Mar 26, 2009 |
8547519 |
|
|
13186991 |
|
|
|
|
10986178 |
Nov 12, 2004 |
7528929 |
|
|
12411952 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/70341 20130101;
G03F 7/70958 20130101; G03F 7/2041 20130101; G03F 7/70908
20130101 |
International
Class: |
G03F 7/20 20060101
G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2003 |
EP |
03257195.2 |
Aug 3, 2004 |
EP |
04254659.8 |
Claims
1. A lithographic apparatus, comprising: a substrate table
constructed to hold a substrate; a projection system configured to
project a patterned radiation beam onto a target portion of the
substrate; and a liquid supply system configured to at least partly
fill a space between the projection system and the substrate with a
liquid, wherein the liquid has a contact angle of (a) less than
60.degree. with the projection system, or the liquid supply system,
or both, or (b) less than 80.degree. with a surface of the
substrate, or (c) both (a) and (b).
2. The apparatus according to claim 1, wherein the liquid includes
an additive configured to reduce surface tension of the liquid.
3. The apparatus according to claim 2, wherein the additive is a
surfactant, or a soap, or a salt, or any combination of the
foregoing.
4. The apparatus according to claim 1, wherein surface tension
between the liquid and (i) the substrate, or (ii) the projection
system, or (iii) the liquid supply system, or (iv) any combination
of (i)-(iii), is greater than between the liquid and air.
5. The apparatus according to claim 1, wherein the liquid has a
contact angle of less than 60.degree. with a surface of the
projection system and the liquid supply system and a contact angle
of greater than 90.degree. with a (i) surface of the substrate, or
(ii) the substrate table, or (iii) a substrate table mounted
sensor, or (iv) any combination of (i)-(iii).
6. The apparatus according to claim 1, wherein the surface with
which the liquid has a contact angle of less than 60.degree.
comprises a glass, a glass ceramic, a metal oxide or a metal.
7. The apparatus according to claim 6, wherein the surface has been
surface treated.
8. The apparatus according to claim 6, wherein the surface has a
coating or a polymer.
9. The apparatus according to claim 1, wherein an inlet and outlet
of the liquid supply system, or a part of the projection system not
being a final element of the projection system, or both, have a
surface with which the liquid has a contact angle of greater than
90.degree..
10. The apparatus according to claim 9, wherein the surface with
which the liquid has a contact angle of greater than 90.degree. is
a surface with which the liquid has a contact angle of greater than
100.degree., 110.degree. or 120.degree..
11. A lithographic apparatus, comprising: a substrate table
constructed to hold a substrate; a projection system configured to
project a patterned radiation beam onto a target portion of the
substrate; and a liquid supply system configured to at least partly
fill a space between the projection system and (a) the substrate,
or (b) a sensor, or (c) a shutter member, or (d) any combination of
(a)-(c), with a liquid, wherein the liquid has a contact angle of
greater than 90.degree. with a surface of (e) the substrate, or (f)
the sensor, or (g) the shutter member, or (h) the projection
system, or (i) any combination of (e)-(h), which surface is (j)
alignable with an optical axis of the apparatus, or (k) a surface
of the projection system, or (l) substantially all of a top surface
of the substrate table, or (m) any combination of (j)-(l).
12. The apparatus according to claim 11, wherein the liquid has a
contact angle of greater than 90.degree. with surfaces of both the
substrate and the projection system.
13. The apparatus according to claim 12, wherein the liquid supply
system comprises a plurality of gas inlets configured to confine
the liquid to a localized area of the substrate and the plurality
of gas inlets are positioned around the optical axis of the
apparatus and are configured to direct gas in a direction with at
least a component towards the optical axis.
14. The apparatus according to claim 12, wherein the liquid supply
system comprises a plurality of gas inlets configured to confine
the liquid to a localized area of the substrate and the plurality
of gas inlets are not oriented directly towards the optical axis of
the apparatus so as to create a flow of gas in a circular pattern
around the optical axis.
15. The apparatus according to claim 11, wherein the liquid has a
contact angle of greater than 90.degree. with the surface of (i)
the substrate, or (ii) the substrate table, or (iii) the sensor, or
(iv) the shutter member, or (v) any combination of (i)-(iv), and
the liquid has a contact angle of less than 60.degree. with a
surface of the projection system, or the liquid supply system, or
both.
16. The apparatus according to claim 11, wherein the surface with
which the liquid has a contact angle of greater than 90.degree.
comprises elevations and depressions, wherein the distance between
elevations ranges from 5 to 200 .mu.m and the height of the
elevations from 5 to 100 .mu.m and wherein at least the elevations
are made of a liquidphobic polymer or a material made durably
liquidphobic.
17. The apparatus according to claim 11, wherein the surface with
which the liquid has a contact angle of greater than 90.degree. is
a polymer.
18. The apparatus according to claim 11, wherein an inlet and
outlet of the liquid supply system, a part of the projection system
not being a final element of the projection system, or both, has a
surface with which the liquid has a contact angle of greater than
90.degree..
19. The apparatus according to claim 11, wherein the surface with
which the liquid has a contact angle of greater than 90.degree. is
a surface with which the liquid has a contact angle of greater than
100.degree., 110.degree. or 120.degree..
20. A device manufacturing method, comprising projecting a
patterned beam of radiation through a liquid onto a target portion
of a substrate, a surface of the substrate comprising a topcoat
insoluble in the liquid and having a contact angle with the liquid
of less than 80.degree..
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/918,575, filed Mar. 12, 2018, now allowed,
which is a continuation of U.S. patent application Ser. No.
14/839,633, filed Aug. 28, 2015, now U.S. Pat. No. 9,952,515, which
is a continuation of U.S. patent application Ser. No. 14/266,591,
filed Apr. 30, 2014, now U.S. Pat. No. 9,134,623, which is a
continuation of U.S. patent application Ser. No. 14/107,734, filed
Dec. 16, 2013, now U.S. Pat. No. 9,134,622, which is a continuation
of U.S. patent application Ser. No. 13/186,991, filed Jul. 20,
2011, now U.S. Pat. No. 8,634,056, which is a continuation of U.S.
patent application Ser. No. 12/411,952, filed Mar. 26, 2009, now
U.S. Pat. No. 8,547,519, which is a continuation of U.S. patent
application Ser. No. 10/986,178, filed Nov. 12, 2004, now U.S.
Patent No. 7,528,929, which claims priority to European patent
application EP 03257195.2, filed Nov. 14, 2003 and European patent
application EP 04254659.8, filed Aug. 3, 2004, the entire contents
of each of the foregoing applications herein fully incorporated by
reference.
FIELD
[0002] The present invention relates to a lithographic apparatus
and a device manufacturing method.
BACKGROUND
[0003] A lithographic apparatus is a machine that applies a desired
pattern onto a target portion of a substrate. Lithographic
apparatus can be used, for example, in the manufacture of
integrated circuits (ICs). In that circumstance, a patterning
device, such as a mask, may be used to generate a circuit pattern
corresponding to an individual layer of the IC, and this pattern
can be imaged onto a target portion (e.g. comprising part of, one
or several dies) on a substrate (e.g. a silicon wafer) that has a
layer of radiation-sensitive material (resist). In general, a
single substrate will contain a network of adjacent target portions
that are successively exposed. Known lithographic apparatus include
so-called steppers, in which each target portion is irradiated by
exposing an entire pattern onto the target portion in one go, and
so-called scanners, in which each target portion is irradiated by
scanning the pattern through the projection 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
point of this is to enable imaging of smaller features since the
exposure radiation will have a shorter wavelength in the liquid.
(The effect of the liquid may also be regarded as increasing the
effective NA of the system and also increasing the depth of
focus.)
[0005] However, submersing the substrate or substrate and substrate
table in a bath of liquid (see, for example, U.S. Pat. No.
4,509,852, hereby incorporated in its entirety by reference) means
that there is a large body of liquid that must be accelerated
during a scanning exposure. This requires additional or more
powerful motors and turbulence in the liquid may lead to
undesirable and unpredictable effects.
[0006] One of the solutions proposed is for a liquid supply system
to provide liquid on only a localized area of the substrate and in
between the final element of the projection system and the
substrate (the substrate generally has a larger surface area than
the final element of the projection system). One way which has been
proposed to arrange for this is disclosed in PCT patent application
WO 99/49504, hereby incorporated in its entirety by reference. As
illustrated in FIGS. 2 and 3, liquid is supplied by at least one
inlet IN onto the substrate, preferably along the direction of
movement of the substrate relative to the final element, and is
removed by at least one outlet OUT after having passed under the
projection system. That is, as the substrate is scanned beneath the
element in a -X direction, liquid is supplied at the +X side of the
element and taken up at the -X side. FIG. 2 shows the arrangement
schematically in which liquid is supplied via inlet IN and is taken
up on the other side of the element by outlet OUT which is
connected to a low pressure source. In the illustration of FIG. 2
the liquid is supplied along the direction of movement of the
substrate relative to the final element, though this does not need
to be the case. Various orientations and numbers of in- and
out-lets positioned around the final element are possible, one
example is illustrated in FIG. 3 in which four sets of an inlet
with an outlet on either side are provided in a regular pattern
around the final element.
[0007] A problem with having various components of the lithographic
projection apparatus (e.g., the projection system, the substrate,
the substrate table, etc.) in contact with immersion liquid is that
once the liquid supply system has moved to another component or the
liquid is removed, liquid residue may remain behind which may lead
to liquid contamination of other components within the lithographic
apparatus. Furthermore, the movement of liquid relative to surfaces
of various components in the lithographic apparatus may generate
bubbles within the immersion liquid which may be deleterious to the
optical performance of the apparatus. Further, in some immersion
lithography apparatus, leakage of liquid between the liquid supply
system and the substrate, especially during scanning movement, may
occur.
SUMMARY
[0008] Accordingly, it would be advantageous, for example, to
address contamination by, bubbles in and/or leakage of immersion
liquid in an immersion lithographic apparatus
[0009] According to an aspect of the invention, there is provided a
lithographic apparatus, comprising:
[0010] an illuminator configured to condition a radiation beam;
[0011] a support constructed to hold a patterning device, the
patterning device configured to impart the radiation beam with a
pattern in its cross-section to form a patterned radiation
beam;
[0012] a substrate table constructed to hold a substrate;
[0013] a projection system configured to project the patterned
radiation beam onto a target portion of the substrate; and
[0014] a liquid supply system configured to at least partly fill a
space between the projection system and the substrate with a
liquid,
[0015] wherein the liquid has a contact angle of (a) less than
60.degree. with the projection system, or the liquid supply system,
or both, or (b) less than 80.degree. with a surface of the
substrate, or (c) both (a) and (b).
[0016] If an immersion liquid has a contact angle of less than
60.degree. with a surface, during relative movement of the
immersion liquid and the surface, the formation of bubbles in the
immersion liquid may be less likely. Thus, if the immersion liquid
is based on water, the surface should be hydrophilic. A way that
the immersion liquid has a contact angle of less than 60.degree.
with the substrate is to include in the immersion liquid an
additive configured to reduce the surface tension of the immersion
liquid. For the types of material which the substrate, final
element and liquid supply system are made of, an additive such as a
surfactant or soap is well suited. In an embodiment, it is
advantageous to have the surface tension between the immersion
liquid and the substrate, final element and/or liquid supply system
greater than between the immersion liquid and air. This is likely
to prevent bubble formation due to relative movement of the
immersion liquid to the surface.
[0017] An advantageous arrangement for reducing leakage is to have
the immersion liquid have a contact angle of less than 60.degree.
with a surface of the final element and the liquid supply system
and a contact angle greater than 90.degree. with a surface of the
substrate and/or substrate table and/or a substrate table mounted
sensor. In this arrangement, the immersion liquid "sticks" to the
final element and liquid supply system and slides easily over the
element below the liquid supply system which is moving relative to
the liquid supply system. Thus, leakage from the liquid supply
system between the liquid supply system and the element beneath the
liquid supply system may be reduced.
[0018] Examples of surfaces with which the immersion liquid has a
contact angle of less than 60.degree. include glass, a glass
ceramic, a metal oxide or a metal. The surfaces may be provided by
a surface treatment which is optionally a coating or a polymer.
[0019] According to an aspect of the invention, there is provided a
lithographic apparatus, comprising:
[0020] an illuminator configured to condition a radiation beam;
[0021] a support constructed to hold a patterning device, the
patterning device configured to impart the radiation beam with a
pattern in its cross-section to form a patterned radiation
beam;
[0022] a substrate table constructed to hold a substrate;
[0023] a projection system configured to project the patterned
radiation beam onto a target portion of the substrate; and
[0024] a liquid supply system configured to at least partly fill a
space between the projection system and (a) the substrate, or (b) a
sensor, or (c) a shutter member, or (d) any combination of (a)-(c),
with a liquid,
[0025] wherein the liquid has a contact angle of greater than
90.degree. with a surface of (e) the substrate, or (f) the sensor,
or (g) the shutter member, or (h) the projection system, or (i) any
combination of (e)-(h), which surface is (j) alignable with an
optical axis of the apparatus, or (k) a surface of the projection
system, or (l) substantially all of a top surface of the substrate
table, or (m) any combination of (j)-(l).
[0026] Having a contact angle greater than 90.degree. helps to
reject the immersion liquid from the surface so that it is an easy
task to leave the surface dry without any immersion liquid residue
remaining on the surface. If the surface is a surface of a shutter
member, this is also advantageous because it means that the shutter
member can be easily removed (i.e. with less force) from the liquid
supply system as surface tension between the liquid supply system
and the shutter member is unlikely to develop to hold the shutter
member to the liquid supply system.
[0027] If the immersion liquid has a contact angle of greater than
90.degree. with surfaces of both the substrate and the projection
system, this may form a system which can advantageously be used by
the liquid supply system to confine the liquid to only a localized
area of the substrate. With this system, the immersion liquid may
be held in place in the localized area by a plurality of gas inlets
to confine the immersion liquid to the localized area of the
substrate. This may be achieved by simply having a gas pressure
around a periphery of the localized area to hold the immersion
liquid in place. It would be advantageous, for example, that the
plurality of gas inlets are positioned around the optical axis of
the apparatus and are for directing gas in a direction with at
least a component towards the optical axis. It may be advantageous
that the gas inlets do not face directly towards the optical axis
of the apparatus but rather create a flow of gas in a circular
pattern around the optical axis. In an embodiment, gas is blown in
a plane substantially parallel to a top surface of the
substrate.
[0028] A way of ensuring that immersion liquid has a contact angle
of greater than 90.degree. with the surface is to provide a surface
that comprises elevations and depressions, wherein the distance
between elevations ranges from 5 to 200 .mu.m and the height of the
elevations from 5 to 100 .mu.m and wherein at least the elevations
are made of a liquidphobic polymer or a material made durably
liquidphobic.
[0029] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0030] providing a liquid to a space between a projection system of
a lithographic projection apparatus and a substrate, the liquid
having a contact angle of (a) less than 60.degree. with the
projection system, or a liquid supply system used to provide the
liquid, or both, or (b) less than 80.degree. with a surface of the
substrate, or (c) both (a) and (b); and
[0031] projecting a patterned beam of radiation through the liquid
using the projection system onto a target portion of the
substrate.
[0032] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising:
[0033] providing a liquid to a space between a projection system of
a lithographic projection apparatus and (a) a substrate, or (b) a
sensor, or (c) a shutter member, or (d) any combination of (a)-(c),
with a liquid, the liquid having a contact angle of greater than
90.degree. with a surface of (e) the substrate, or (f) the sensor,
or (g) the shutter member, or (h) the projection system, or (i) any
combination of (e)-(h), which surface is (j) alignable with an
optical axis of the lithographic projection apparatus, or (k) a
surface of the projection system, or (l) substantially all of a top
surface of a substrate table holding the substrate, or (m) any
combination of (j)-(l); and
[0034] projecting a patterned beam of radiation using the
projection system through the liquid onto a target portion of the
substrate.
[0035] According to a further aspect of the invention, there is
provided a device manufacturing method, comprising projecting a
patterned beam of radiation through a liquid onto a target portion
of a substrate, a surface of the substrate comprising a topcoat
insoluble in the liquid and having a contact angle with the liquid
of less than 80.degree..
[0036] According to a further aspect of the invention, there is
provided a substrate for use in immersion lithography, the
substrate having a resist provided on a surface thereof and a
topcoat provided on the surface of the resist, the topcoat having a
contact angle to the liquid of less than 80.degree..
[0037] According to a further aspect of the invention, there is
provided a use of a topcoat having a contact angle of less than
80.degree. to a liquid used in immersion lithography to prevent
bubbles sticking to a resist layer or a resist stack provided on a
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] 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:
[0039] FIG. 1 depicts a lithographic apparatus according to an
embodiment of the invention;
[0040] FIG. 2 illustrates, in cross section, a liquid supply system
which may be used with one or more embodiments of the present
invention;
[0041] FIG. 3 illustrates, in plan, the liquid supply system of
FIG. 2;
[0042] FIG. 4 illustrates, in cross section, an alternative liquid
supply system according to an embodiment of the present
invention;
[0043] FIG. 5 illustrates, in cross section, a liquid supply system
similar to that of FIG. 4 with further modifications according to
an embodiment of the present invention;
[0044] FIG. 6 illustrates a substrate table mounted sensor
according to an embodiment of the present invention;
[0045] FIG. 7 illustrates a liquid supply system and a shutter
member, in cross section, according to an embodiment of the present
invention;
[0046] FIG. 8 illustrates a further liquid supply system according
to an embodiment of the present invention;
[0047] FIG. 9 illustrates schematically in projection an element of
the liquid supply system of FIG. 8; and
[0048] FIG. 10 illustrates in cross-section a topcoat applied to a
substrate according to an embodiment of the invention.
DETAILED DESCRIPTION
[0049] FIG. 1 schematically depicts a lithographic apparatus
according to a particular embodiment of the invention. The
apparatus comprises: [0050] an illumination system (illuminator) IL
for providing a projection beam PB of radiation (e.g. UV
radiation). [0051] a first support structure (e.g. a mask table) MT
for supporting a patterning device (e.g. a mask) MA and connected
to first positioner PM for accurately positioning the patterning
device with respect to item PL; [0052] a substrate table (e.g. a
wafer table) WT for holding a substrate (e.g. a resist-coated
wafer) W and connected to second positioner PW for accurately
positioning the substrate with respect to item PL; and [0053] a
projection system (e.g. a refractive projection lens) PL for
imaging a pattern imparted to the projection beam PB by the
patterning device MA onto a target portion C (e.g. comprising one
or more dies) of the substrate W.
[0054] 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).
[0055] The illuminator IL receives a beam of radiation 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 integral part of
the 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.
[0056] The illuminator IL may comprise adjusting means AM for
adjusting the angular intensity distribution of the 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 generally comprises
various other components, such as an integrator IN and a condenser
CO. The illuminator provides a conditioned beam of radiation,
referred to as the projection beam PB, having a desired uniformity
and intensity distribution in its cross-section.
[0057] The projection beam PB is incident on the mask MA, which is
held on the mask table MT. Having traversed the mask MA, the
projection beam PB passes through the lens PL, which focuses the
beam onto a target portion C of the substrate W. With the aid of
the second positioner PW and position sensor IF (e.g. an
interferometric device), the substrate table WT can be moved
accurately, e.g. so as to position different target portions C in
the path of the 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 beam PB, e.g. after mechanical retrieval from a
mask library, or during a scan. In general, movement of the object
tables MT and WT will be realized with the aid of a long-stroke
module (coarse positioning) and a short-stroke module (fine
positioning), which form part of the positioners PM and PW.
However, 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.
[0058] The depicted apparatus can be used in the following
preferred modes:
[0059] 1. In step mode, the mask table MT and the substrate table
WT are kept essentially stationary, while an entire pattern
imparted to the projection beam is projected onto a target portion
C in one go (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.
[0060] 2. In scan mode, the mask table MT and the substrate table
WT are scanned synchronously while a pattern imparted to the
projection 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 is determined by the
(de-)magnification and image reversal characteristics of the
projection system PL. In scan mode, the maximum size of the
exposure field limits the width (in the non-scanning direction) of
the target portion in a single dynamic exposure, whereas the length
of the scanning motion determines the height (in the scanning
direction) of the target portion.
[0061] 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 projection 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 a
programmable patterning device, such as a programmable mirror array
of a type as referred to above.
[0062] Combinations and/or variations on the above described modes
of use or entirely different modes of use may also be employed.
[0063] Another immersion lithography solution with a localized
liquid supply system solution which has been proposed is to provide
the liquid supply system with a liquid confinement structure which
extends along at least a part of a boundary of the space between
the final element of the projection system and the substrate table.
The liquid confinement structure is substantially stationary
relative to the projection system in the XY plane though there may
be some relative movement in the Z direction (in the direction of
the optical axis). A seal is formed between the liquid confinement
structure and the surface of the substrate. In an embodiment, the
seal is a contactless seal such as a gas seal. Such a system with a
gas seal is disclosed in U.S. patent application Ser. No.
10/705,783, hereby incorporated in its entirety by reference.
[0064] FIG. 4 illustrates a liquid supply system which is similar
to that of FIGS. 2 and 3 in that it provides liquid to only a
localized area of the substrate W in a space between the substrate
W and a final element of the projection system PL. The liquid
touches both the substrate and final element and is continuously
present between the two. The liquid supply system of FIG. 4
comprises a seal member 10 which extends around the outer
circumference of a final element of the projection system PL. The
seal member 10 has a seal device 15, which is in an embodiment a
contactless seal device, which forms a seal between the bottom of
the seal member 10 and the top surface of the substrate W. Thus,
liquid 5 is confined between the substrate W, the seal member 10
and the projection system PL. The seal device 15 may be a gas seal
which has a gas inlet and a gas outlet such as described in U.S.
patent application Ser. No. 10/705,783. A liquid inlet 18 provides
the liquid 5 between the projection system PL and the substrate W.
A similar liquid supply system in which there is no seal device 15
is possible in which the liquid is contained by capillary forces
between the bottom of the seal member 10 which is fixed to the
projection system and the substrate W. In an embodiment, the free
working distance (i.e. the distance between the bottom of the final
element of the projection system and the top surface of the
substrate W) is of the order of 3 mm.+-.0.2 or 0.1 mm but can be as
low as 1mm.
[0065] If a localized area liquid supply system as described above
is used, it has been proposed to use a shutter member which is
positionable on a side of the liquid supply system opposite the
projection system such that the immersion liquid can be confined in
the liquid supply system and between the projection system and the
shutter member. This allows the liquid supply system to keep liquid
under the projection system during, for example, a substrate swap.
Such a system is disclosed in United States patent application U.S.
Ser. No. 10/705,785, hereby incorporated in its entirety by
reference.
[0066] Also, there is an advantage in using imaging sensors on the
substrate table under the same conditions as the substrate itself
will be imaged. The sensors are used to ensure that the substrate
can be correctly positioned relative to the projection beam. These
sensors include a transmission image sensor (TIS) which is a sensor
that is used the measure the position at substrate level of a
projected aerial image of a mark pattern at the reticle (mask)
level. Typically the projected image at substrate level is a line
pattern with a line width similar to the projection beam
wavelength. The TIS measures these patterns by using a transmissive
pattern with a photo detector underneath. The sensor data is used
to measure the position of the mask with respect to the position of
the substrate table in up to 6 degrees of freedom. The
magnification and scaling of the projected mask are also measured
by using 4 points on the mask. As the sensor must also be capable
of measuring the pattern positions and influences of all
illumination settings (sigma, projection system numerical aperture,
all masks (binary, phase shift, etc.)), a small line width is used.
Furthermore, the sensor is also used to measure/monitor the optical
performance of the lithographic projection apparatus. Different
measurements are implemented for measuring pupil shapes, and
aberrations such as coma, spherical aberration, astigmatism and
field curvature. For these measurements, different illumination
settings are used in combination with different projected images.
Another such sensor may be a projection system interferometer
integrated in the lithographic apparatus (ILIAS). The ILIAS is an
interferometric wavefront measurement system that performs (static)
measurements on projection system aberrations (up to Zernicke 36),
as needed, for system setup and calibration as well as for pupil
measurements. The ILIAS may be used for monitoring and
recalibration of the lithographic apparatus on a regular basis
depending on the apparatus needs. A further sensor may be a dose
(or spot) sensor. All of these sensors are used at substrate level
and as such are positioned on the substrate table. In order to
avoid the need to perform complex predictions about how an
immersion liquid will affect the projection beam, it is desirable
to illuminate the sensor(s) under the same conditions as the
substrate is to be imaged i.e. with the immersion liquid in place
between the projection system and the sensor.
[0067] To aid in keeping the immersion liquid within the liquid
supply system, it can help to make any surfaces which slide under
the liquid supply system such as the substrate W, substrate table
WT, shutter member, one or more sensors, etc., such that immersion
liquid has a contact angle of greater than 90.degree., 100.degree.,
110.degree. or 120.degree. with the surface. The contact angle of a
liquid to a surface is measured as the angle between the surface
and the tangent plane of the liquid lying on that surface at a
location where the interface of the liquid with the outside
environment, for example air, is in contact with the surface.
[0068] The surface of the substrate will generally be a topcoat or
a resist coating or the substrate material itself. In an
embodiment, all of the top surface of the substrate table which
comes in contact with immersion liquid has this property. Thus, the
immersion liquid flows over those surfaces easily.
[0069] The surfaces of the liquid supply system and, in an
embodiment, the final element 20 of the projection system PL or any
other surfaces of the projection system in contact with immersion
liquid are such that the immersion liquid makes a contact angle
with those surfaces of less than 60.degree., less than 50.degree.,
less than 40.degree., less than 30.degree., less than 25.degree.,
less than 20.degree., less than 15.degree., or less than
10.degree.. Thus, the immersion liquid `sticks` to those surfaces
and so loss of immersion liquid is reduced.
[0070] There are exceptions to the above general described
desiderata. For instance, it may be advantageous to provide a
surface 22 of the projection system which is not the final element
and is above the liquid supply system, substantially parallel with
the substrate W (e.g., an annulus in shape), to have a surface with
which the immersion liquid makes a contact angle of 90.degree. or
more, 100.degree. or more, 110.degree. or more, or 120.degree. or
more. This can help in the extraction of liquid through extraction
port 19. The one or more inlets and outlets of gas seal device 15
may also benefit from such a property. In contrast, the inner parts
of the bottom surface of the seal member 10, radially inwardly of
the seal device 15, may benefit from having a surface roughness
increasing treatment applied to make the immersion liquid have a
smaller contact angle with that area than with other areas.
[0071] When the substrate W is moved relative to the projection
system PL (indicated by arrow 50), friction between the immersion
liquid 5 and the substrate W may cause pressure to build up in the
liquid and the level 7 of immersion liquid 5 to rise on one side
and the level 9 to fall on the other side. This is the result of a
pressure gradient introduced into the immersion liquid 5 and may
result in gas being drawn into the exposing area of the liquid
under the projection system.
[0072] It is possible to reduce the likelihood of gas being drawn
into the exposing area as well as reducing the likelihood of
formation of bubbles in the immersion liquid 5 in general, by
providing surfaces of the substrate W, as well as the seal member
10 and the projection system PL, such that the immersion liquid 5
has a contact angle of less than 60.degree., less than 50.degree.,
less than 40.degree., less than 30.degree., less than 25.degree.,
less than 20.degree., less than 15.degree. or less than 10.degree.
with the surfaces (liquidphilic). This ensures that the surfaces
are wetted and if the immersion liquid 5 is based on water, the
surfaces are hydrophilic. The surfaces concerned are the top
surface 40 of the substrate W which is the surface to be imaged,
the outer surface 20 of the final element of the projection system
PL, in particular the bottom surface, and the inner surfaces of the
seal member 10 which confine the immersion liquid 5 to the
localized area.
[0073] The use of such surfaces (which may of course be coatings)
means that the surface tension between the immersion liquid and the
surfaces is larger than the surface tension between the immersion
liquid and the surrounding environment (e.g. air). The effect is to
optimize the removal of all gas bubbles from the surfaces.
[0074] One way of ensuring the desired contact angle is to lower
the surface tension as much as possible in the immersion liquid. If
the immersion liquid is substantially water (as is in the case of
193 nm wavelength projection beam), the surface tension may
conveniently be lowered by adding a surfactant or soap to the
immersion liquid, provided this has no adverse effects (e.g. loss
of 193 nm transmission). Thus, the risk of enclosing gas in the
immersion liquid is vastly reduced. Other factors, such as degree
of roughness of the surface can also be used to improve the
liquidphilic quality of a material.
[0075] An embodiment illustrated in FIG. 5 is the same as the
embodiment described above with respect to FIG. 4 except as
described below. In FIG. 5, the seal member 10 comprises layers
which have different interactions with the immersion liquid 5. A
first layer 100 comprises a material with which the immersion
liquid 5 has a contact angle of less than 60.degree., less than
50.degree., less than 40.degree., less than 30.degree., less than
25.degree., less than 20.degree., less than 15.degree. or less than
10.degree. as described above. This ensures good wetting of that
layer 100 by the immersion liquid 5 and reduces the likelihood of
bubbles forming on that layer 100. The layer 100 is on an underside
of the seal member 10 facing the substrate W and is placed closer
to the optical axis of the apparatus than the seal device 15. On
the other side of the seal device 15 is a second layer 110 with
which the immersion liquid has a contact angle of greater than
90.degree., greater than 100.degree., greater than 110.degree. or
greater than 120.degree. (liquid-phobic). This second layer 110
which is also on the bottom surface of the seal member 10 facing
the substrate W has the effect of repelling immersion liquid 5 and
thereby helps in ensuring the efficiency of the seal device 15.
[0076] Embodiments illustrated in FIGS. 6 and 7 respectively are
the same as the embodiment described above in relation to FIG. 4
and describe certain aspects of that embodiment in more detail.
[0077] The embodiment of FIG. 6 relates to through the projection
system sensors 200 which are mounted on the substrate table WT and
are imaged through the immersion liquid 5. The embodiment of FIG. 7
relates to a shutter member 300 which may be of either type (i.e.
may be a separate member or may be part of the substrate table WT)
described in U.S. patent application Ser. No. 10/705,785, hereby
incorporated in its entirety by reference.
[0078] Both embodiments make use of a surface which comes into
contact with the immersion liquid 5 with which the immersion liquid
has a contact angle of greater than 90.degree., greater than
100.degree., greater than 110.degree., or greater than 120.degree..
The use of such a surface ensures that when the sensor 200 or
shutter member 300 is moved away from the liquid supply system,
residue of immersion liquid on the sensor 200 or shutter member 300
is unlikely.
[0079] In more detail, FIG. 6 illustrates a sensor 200, which may
be any of the kinds previously described, and comprises a detector
element 210, a transmissive sensor grating 222 and an absorption
element 220. The absorption element 220 is used to enhance the
sensor contrast and thus the overall sensor performance.
[0080] The transmissive sensor grating 222 is used for convolution
of the projected aerial image of a corresponding pattern at reticle
(mask) level (4 or 5 times larger than the pattern on the sensor).
The convolution of the transmissive sensor grating 222 with the
projected aerial image of the pattern at reticle level will provide
an intensity profile depending on the position of the transmission
sensor grating 222 at substrate level. With the intensity data at
different substrate table positions, the position and shape of the
aerial image can be calculated.
[0081] The sensor detector element 210 transforms the radiation
that is transmitted to the open area of the grating into an
electrical signal. The purpose of the absorption element 220 is to
absorb part of the energy of the projection beam by providing areas
of different absorption characteristics so that the sensor can
achieve sufficient contrast. In an embodiment, the absorption
element 220 is made of at least one metal layer such as aluminum
and/or chromium (or alloys thereof) but may be made of layers of
any metals.
[0082] In FIG. 6, the final element of the projection system PL is
depicted as lens 230. In this embodiment, an immersion liquid 5,
such as water, is present between the final element 230 of the
projection system and the sensor 200. The top surface of the sensor
200 is provided with a coating 240 with which the immersion liquid
5 has a contact angle of more than 90.degree., more than
100.degree., more than 110.degree., or more than 120.degree..
[0083] The coating 240 serves one or more purposes. It enables easy
removal of immersion liquid and/or prevents immersion liquid
residue from remaining on the sensor. This means that measurements
may also be performed using the sensor in gas (e.g. air), without
the immersion liquid. The presence of immersion liquid residue
could result in faulty measurements. A further effect of the
coating layer 240 is to isolate the metal of the absorption element
220 from the immersion liquid 5 to avoid possible corrosion of the
metal of the absorption element 220, for example by a galvanic
reaction between metal layers forming the absorption element
220.
[0084] FIG. 7 illustrates an embodiment of a shutter member 300
(also termed a cover plate, closing plate, edge seal member, gap
seal member or intermediary plate). The shutter member 300 may be a
surface other than a substrate surface, perhaps an upper surface of
the substrate table WT which is substantially co-planar with the
upper surface of the substrate W and is closely adjacent to the
edge of the substrate W. The area of the shutter member 300 is
large enough so that if the substrate table WT is moved such that
the projection system PL and seal member 10 are positioned over the
shutter member 300, the shutter member blocks the entire aperture
of the seal member 10 to prevent liquid escaping through the
aperture. In this position, the substrate W can be removed from the
substrate table WT using usual substrate handling equipment.
[0085] In the embodiment illustrated in FIG. 7, it is possible for
the substrate table WT to be moved completely away from the
projection system PL and the seal member 10 and for the substrate W
to be removed from the substrate table WT and a new substrate to be
placed on the substrate table WT.
[0086] In FIG. 7, the shutter member 300 is in the form of a plate
with a primary cross sectional area larger than that of the
localized area or aperture in the seal member 10. The shape of the
shutter member 300 may be any shape so long as it covers the
aperture. The shutter member 300 is not a substrate and is moveable
relative to both the substrate table WT and the seal member 10 and
may be attached to the seal member 10 by any means such as magnets
360 illustrated in FIG. 7.
[0087] After exposure of the substrate W the substrate table WT is
moved so that the shutter member 300 is positioned under the
aperture of the seal member 10. Once positioned under the
projection system PL, the shutter member 300 is attached to the
bottom of the seal member 10 to cover the aperture. The attachment
method may be, for example, by a vacuum source. The substrate table
WT may then be moved out of the way to a place where the substrate
W may be exchanged. In FIG. 7, the shutter member 300 is attached
to the substrate table WT by a magnet 370 when not attached to the
seal member 10 but, if made of a non-magnetic material, may be
attached by a vacuum source, for example.
[0088] The surface of the shutter member 300 which comes into
contact with the immersion liquid 5 is such that the immersion
liquid 5 has a contact angle of greater than 90.degree., greater
than 100.degree., greater than 110.degree. or greater than
120.degree. with it. Thus, as with embodiment described in relation
to FIG. 6, when the substrate table moves and the shutter member
300 is left behind, the seal device 15 on the seal member 10 can
ensure that little, if any, immersion liquid 5 is left behind.
Furthermore, significantly less force will be required to remove
the shutter member 300 from the seal member 10 if the surface of
the seal member is as described above, i.e., it rejects the
immersion liquid. If the immersion liquid is water, the surface
should be hydrophobic.
[0089] An embodiment illustrated in FIGS. 8 and 9 is the same as
the embodiment described in reference to FIG. 4 except as described
below.
[0090] In this embodiment, a different type of liquid confinement
system is illustrated. The final element of the projection system
PL and the top surface of the substrate W are made of a material
with which the immersion liquid 5 has a contact angle of greater
than 90.degree., greater than 100.degree., greater than
110.degree., or greater than 120.degree..
[0091] The immersion liquid 5 is held in place by pressurized gas
on the surface of the liquid not in contact with the substrate W or
the projection system PL. The pressurized gas is provided through
inlets 400 in a seal member 10 which surrounds the immersion liquid
5. A plurality of inlets 400 are provided and they may be of any
configuration which is effective to maintain the immersion liquid 5
in place.
[0092] It will be appreciated that FIG. 8 is schematic and that in
fact the distance between the projection system PL and the
substrate W is of the order of a few microns to a few mm so that
the pressure of gas on the immersion liquid 5 required to keep the
immersion liquid in place is low.
[0093] As can be seen in FIG. 8, the seal member 10 may comprise
several sets of gas inlets 400 which are at different levels above
the substrate W. However, this need not be the case and, as in FIG.
9, only one level of gas inlets 400 may be provided.
[0094] Different pressures of gas can be provided through
individual inlets 400 to ensure that the immersion liquid 5 is in
the correct position.
[0095] The seal member 10 may be attached to the projection system
PL. The pressure of gas through inlets 400 may be controlled in a
feedforward or feedback manner depending upon the measurement of
the position of the immersion liquid 5. When the substrate W moves
relative to the projection system PL forces will be generated
within the immersion liquid 5 and based on measurement or
prediction of this, the pressure of gas flowing through each of the
gas inlets 400 can be adjusted accordingly, e.g., pressure on one
side may be raised above the pressure on other sides.
[0096] As can be seen from FIG. 9, the gas inlets 400 are, in an
embodiment, in a direction such that the gas is projected in a
direction with a component towards the optical axis of the
apparatus. The direction lies in a plane substantially parallel to
the upper surface of the substrate W though is not directed exactly
towards the optical axis. It is desirable to create a gas flow
which swirls around the immersion liquid 5 and this is done by
angling the direction of the gas inlets 400 away from the optical
axis. It will be appreciated that other configurations of gas
inlets may be used.
Surfaces and Immersion Liquids
[0097] When a projection beam wavelength of 193 nm is used, the
immersion liquid is likely to be substantially water. On untreated
glass, water has a contact angle of about 70.degree., on untreated
aluminum or stainless steel, the contact angle is about 80.degree..
The contact angle is the angle through the liquid. Embodiments
described herein apply equally to other types of immersion
liquid.
[0098] In one or more embodiments, surfaces which are liquid-phobic
(contact angle greater than 90.degree.) or hydrophobic (if the
immersion liquid is water) are used. These surfaces are generally
made of polymers such as Teflon, polyethylene, polypropylene,
polyacetal, fluoro-alkyl-silanes, wax or diamond like carbon.
[0099] One particularly effective surface which results in a high
contact angle between most liquids and surfaces has been described
in PCT patent application WO 96/04123, hereby incorporated in its
entirety by reference. This surface, termed a `lotus surface`, is
particularly suited to any of the embodiments described above which
require a large contact angle between immersion liquid and a
surface (hydrophobic surface) and comprises a surface structure
consisting of elevations and depressions, where the distance
between the elevations ranges from 5 to 200 microns and the height
of the elevations ranges from 5 to 100 microns. At least the
elevations are made of liquidphobic polymers or materials made
durably liquidphobic and the elevations cannot be taken off by
liquid (e.g., water) or by liquid with detergents.
[0100] In one or more embodiments, liquidphilic surfaces (contact
angle less than 60.degree.) or hydrophilic (if the immersion liquid
is water) are used. These surfaces can be provided by a metal oxide
(e.g. on the surface of a metal) or a glass (such as quartz or
Zerodur). Surfaces should be highly cleaned of foreign matter if
provided with such a surface treatment.
[0101] Thus, the type of surface needed can be provided by the
material of the element itself, with a surface treatment if
necessary, and/or by a coating on a surface of the element. For
example, the substrate table WT is typically made of a structural
glass or glass ceramic such as Zerodur. A coating of a polymer or a
lotus surface treatment could be applied to make the surface
liquidphobic. Another example might be a liquid supply system made
of a polymer (e.g. Teflon) which is coated or has a surface
treatment to make it liquidphilic or made of a metal (e.g.
stainless steel) surface treated (e.g. highly cleaned and polished)
to make it liquidphilic.
[0102] Another way to influence (reduce) the contact angle of the
immersion liquid with the surface, is to add a surfactant to the
immersion liquid. Adding a surfactant has the effect to reduce the
surface tension, .gamma., of the liquid so that the bubble radius,
R, of a stable bubble, which is given by:
R = 4 .gamma. .DELTA. P ##EQU00001##
where .DELTA.P is the pressure difference across the interface, is
reduced. Furthermore, the surface spreading coefficient S is also
affected by the surface tension so that the contact angle of the
liquid on a surface can be decreased by the addition of surfactants
without changing the surface properties.
[0103] Surfactants might be organic or inorganic salts (whose ions
disrupt the liquid molecules). The surfactants can be of any type
(e.g. anionic, cationic, zwitterionic and non ionic) and added at a
concentration which is effective to produce the desired result
(usually below the critical micelle concentration).
[0104] Evaporation of the immersion liquid from the surface of the
substrate may cause an unacceptable temperature drop of the
substrate. It may therefore be advantageous to use one or more
further additions to the immersion liquid to change the vapor
pressure of the liquid to reduce evaporation.
Topcoat
[0105] In an embodiment, referring to FIG. 10, a topcoat is applied
to the substrate, on top of the resist, to prevent gas (e.g., air)
bubbles sticking to the surface of the resist or the resist stack.
Bubbles on the resist during exposure may result in defects due to
defocus and/or distortion of the printed image, reducing yield.
According to an embodiment, the top coat is liquidphilic (i.e.,
hydrophilic if the immersion liquid is water based) and has a
contact angle less than 80.degree., e.g. in the range of from 65 to
75.degree.. Using surfaces with contact angles of 65.degree. and
72.degree., the number of bubble defects per substrate may be
reduced to less than 10, compared to about 500 with a hydrophobic
topcoat or a resist with no topcoat, under the same conditions. The
use of a liquidphilic topcoat is not believed to prevent formation
of bubbles but instead prevents them from attaching to the
substrate where they may cause defects. Bubbles that are prevented
from attaching to the resist can be removed from the immersion
liquid to prevent imaging defects being caused.
[0106] Topcoats are known in dry lithography and are used to
protect the resist from gas borne contaminants and have been
proposed for use in immersion lithography. However, in order to
make the topcoat insoluble in the immersion liquid (e.g., water), a
fluorinated polymer is added. A fluorinated polymer makes the
topcoat liquidphobic, e.g. with a contact angle of about
118.degree.. According to this embodiment, the amount of additive
in the topcoat, especially fluorinated polymer, is selected to
provide the desired degree of liquidphilicity.
[0107] The topcoat should also be applied using a solvent that is
incompatible with the resist solvent, which is commonly propylene
glycol monomethyl ether acetate (PGMEA) or ethyl lactate, sometimes
with a co-solvent of methyl ethyl ketone (MEK), and is desirably
easily soluble in the resist developer, which may be a weak (0.262
normal) alkaline solution of tetra-methyl ammonium hydroxide
(TMAH). The topcoat should also be stable under intense irradiation
with radiation of the exposure wavelength to be used, e.g. 248, 193
or 157 nm.
[0108] In an embodiment, there is provided a lithographic
apparatus, comprising: an illuminator configured to condition a
radiation beam; a support constructed to hold a patterning device,
the patterning device configured to impart the radiation beam with
a pattern in its cross-section to form a patterned radiation beam;
a substrate table constructed to hold a substrate; a projection
system configured to project the patterned radiation beam onto a
target portion of the substrate; and a liquid supply system
configured to at least partly fill a space between the projection
system and the substrate with a liquid, wherein the liquid has a
contact angle of (a) less than 60.degree. with the projection
system, or the liquid supply system, or both, or (b) less than
80.degree. with a surface of the substrate, or (c) both (a) and
(b).
[0109] In an embodiment, the liquid includes an additive configured
to reduce surface tension of the liquid. In an embodiment, the
additive is a surfactant, or a soap, or a salt, or any combination
of the foregoing. In an embodiment, surface tension between the
liquid and (i) the substrate, or (ii) the projection system, or
(iii) the liquid supply system, or (iv) any combination of
(i)-(iii), is greater than between the liquid and air. In an
embodiment, the liquid has a contact angle of less than 60.degree.
with a surface of the projection system and the liquid supply
system and a contact angle of greater than 90.degree. with a (i)
surface of the substrate, or (ii) the substrate table, or (iii) a
substrate table mounted sensor, or (iv) any combination of
(i)-(iii). In an embodiment, the surface with which the liquid has
a contact angle of less than 60.degree. comprises a glass, a glass
ceramic, a metal oxide or a metal. In an embodiment, the surface
has been surface treated. In an embodiment,n the surface has a
coating or a polymer. In an embodiment, the liquid has a contact
angle of less than 75.degree. with the surface of the substrate. In
an embodiment, the liquid has a contact angle of less than
70.degree. with the surface of the substrate. In an embodiment, the
liquid has a contact angle of less than 65.degree. with the surface
of the substrate. In an embodiment, the liquid has a contact angle
of less than 60.degree. with the surface of the substrate. In an
embodiment, an inlet and outlet of the liquid supply system, or a
part of the projection system not being a final element of the
projection system, or both, have a surface with which the liquid
has a contact angle of greater than 90.degree.. In an embodiment,
the surface with which the liquid has a contact angle of greater
than 90.degree. is a surface with which the liquid has a contact
angle of greater than 100.degree., 110.degree. or 120.degree.. In
an embodiment, the surface with which the liquid has a contact
angle of less than 60.degree., is a surface with which the liquid
has a contact angle of less than 50.degree., 40.degree.,
30.degree., 25.degree. or 20.degree..
[0110] In an embodiment, there is provided a lithographic
apparatus, comprising: an illuminator configured to condition a
radiation beam; a support constructed to hold a patterning device,
the patterning device configured to impart the radiation beam with
a pattern in its cross-section to form a patterned radiation beam;
a substrate table constructed to hold a substrate; a projection
system configured to project the patterned radiation beam onto a
target portion of the substrate; and a liquid supply system
configured to at least partly fill a space between the projection
system and (a) the substrate, or (b) a sensor, or (c) a shutter
member, or (d) any combination of (a)-(c), with a liquid, wherein
the liquid has a contact angle of greater than 90.degree. with a
surface of (e) the substrate, or (f) the sensor, or (g) the shutter
member, or (h) the projection system, or (i) any combination of
(e)-(h), which surface is (j) alignable with an optical axis of the
apparatus, or (k) a surface of the projection system, or (l)
substantially all of a top surface of the substrate table, or (m)
any combination of (j)-(l).
[0111] In an embodiment, the liquid has a contact angle of greater
than 90.degree. with surfaces of both the substrate and the
projection system. In an embodiment, the liquid supply system
comprises a plurality of gas inlets configured to confine the
liquid to a localized area of the substrate. In an embodiment, the
plurality of gas inlets are positioned around the optical axis of
the apparatus and are configured to direct gas in a direction with
at least a component towards the optical axis. In an embodiment,
the direction is in a plane substantially parallel to a top surface
of the substrate. In an embodiment, the plurality of gas inlets are
not oriented directly towards the optical axis of the apparatus so
as to create a flow of gas in a circular pattern around the optical
axis. In an embodiment, the liquid has a contact angle of greater
than 90.degree. with the surface of (i) the substrate, or (ii) the
substrate table, or (iii) the sensor, or (iv) the shutter member,
or (v) any combination of (i)-(iv), and the liquid has a contact
angle of less than 60.degree. with a surface of the projection
system, or the liquid supply system, or both. In an embodiment, the
surface with which the liquid has a contact angle of greater than
90.degree. comprises elevations and depressions, wherein the
distance between elevations ranges from 5 to 200 .mu.m and the
height of the elevations from 5 to 100 .mu.m and wherein at least
the elevations are made of a liquidphobic polymer or a material
made durably liquidphobic. In an embodiment, the surface with which
the liquid has a contact angle of greater than 90.degree. is a
polymer. In an embodiment, an inlet and outlet of the liquid supply
system, a part of the projection system not being a final element
of the projection system, or both, has a surface with which the
liquid has a contact angle of greater than 90.degree.. In an
embodiment, the surface with which the liquid has a contact angle
of greater than 90.degree. is a surface with which the liquid has a
contact angle of greater than 100.degree., 110.degree. or
120.degree.. In an embodiment, the surface with which the liquid
has a contact angle of less than 60.degree., is a surface with
which the liquid has a contact angle of less than 50.degree.,
40.degree., 30.degree., 25.degree. or 20.degree..
[0112] In an embodiment, there is provide a device manufacturing
method, comprising: providing a liquid to a space between a
projection system of a lithographic projection apparatus and a
substrate, the liquid having a contact angle of (a) less than
60.degree. with the projection system, or a liquid supply system
used to provide the liquid, or both, or (b) less than 80.degree.
with a surface of the substrate, or (c) both (a) and (b); and
projecting a patterned beam of radiation through the liquid using
the projection system onto a target portion of the substrate.
[0113] In an embodiment, the liquid has a contact angle of less
than 75.degree., 70.degree., 65.degree. or 60.degree. with the
surface of the substrate.
[0114] In an embodiment, there is provided a device manufacturing
method, comprising: providing a liquid to a space between a
projection system of a lithographic projection apparatus and (a) a
substrate, or (b) a sensor, or (c) a shutter member, or (d) any
combination of (a)-(c), with a liquid, the liquid having a contact
angle of greater than 90.degree. with a surface of (e) the
substrate, or (f) the sensor, or (g) the shutter member, or (h) the
projection system, or (i) any combination of (e)-(h), which surface
is (j) alignable with an optical axis of the lithographic
projection apparatus, or (k) a surface of the projection system, or
(l) substantially all of a top surface of a substrate table holding
the substrate, or (m) any combination of (j)-(l); and projecting a
patterned beam of radiation using the projection system through the
liquid onto a target portion of the substrate.
[0115] In an embodiment, there is provided a device manufacturing
method, comprising projecting a patterned beam of radiation through
a liquid onto a target portion of a substrate, a surface of the
substrate comprising a topcoat insoluble in the liquid and having a
contact angle with the liquid of less than 80.degree..
[0116] In an embodiment, the topcoat has a contact angle in the
range of from 65 to 75.degree.. In an embodiment, the topcoat
comprises a fluorinated polymer in an amount sufficient to provide
the contact angle. In an embodiment, the substrate has a resist
provided on a surface thereof and the topcoat is provided on the
surface of the resist.
[0117] In an embodiment, there is provided a substrate for use in
immersion lithography, the substrate having a resist provided on a
surface thereof and a topcoat provided on the surface of the
resist, the topcoat having a contact angle to the liquid of less
than 80.degree..
[0118] In an embodiment, the topcoat has a contact angle in the
range of 65 to 75.degree.. In an embodiment, the topcoat comprises
a fluorinated polymer in an amount sufficient to provide the
contact angle.
[0119] In an embodiment, there is provided use of a topcoat having
a contact angle of less than 80.degree. to a liquid used in
immersion lithography to prevent bubbles sticking to a resist layer
or a resist stack provided on a substrate.
[0120] In an embodiment, the topcoat has a contact angle in the
range of 65 to 75.degree.. In an embodiment, the topcoat comprises
a fluorinated polymer in an amount sufficient to provide the
contact angle.
[0121] 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, 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) or
a metrology or 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.
[0122] The terms "radiation" and "beam" used herein encompass all
types of electromagnetic radiation, including ultraviolet (UV)
radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126
nm).
[0123] The term "patterning device" used herein should be broadly
interpreted as referring to any device that can be used to impart a
projection 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 projection beam may not
exactly correspond to the desired pattern in the target portion of
the substrate. Generally, the pattern imparted to the projection
beam will correspond to a particular functional layer in a device
being created in the target portion, such as an integrated
circuit.
[0124] A 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; in this manner, the reflected beam is
patterned. In each example of a patterning device, the support
structure may be a frame or table, for example, which may be fixed
or movable as required and which 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".
[0125] The term "projection system" used herein should be broadly
interpreted as encompassing various types of projection system,
including refractive optical systems, reflective optical systems,
and catadioptric optical systems, as appropriate for example for
the exposure radiation being used, or for other factors such as the
use of an immersion fluid or the use of a vacuum. Any use of the
term "lens" herein may be considered as synonymous with the more
general term "projection system".
[0126] The illumination system may also encompass various types of
optical components, including refractive, reflective, and
catadioptric optical components for directing, shaping, or
controlling the projection beam of radiation, and such components
may also be referred to below, collectively or singularly, as a
"lens".
[0127] 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.
[0128] One or more embodiments of the present invention may be
applied to any immersion lithography apparatus, in particular, but
not exclusively, to those types mentioned above. A liquid supply
system is any mechanism that provides a liquid to a space between
the projection system and the substrate and/or substrate table. It
may comprise any combination of one or more structures, one or more
liquid inlets, one or more gas inlets, one or more gas outlets,
and/or one or more liquid outlets, the combination providing and
confining the liquid to the space. In an embodiment, a surface of
the space may be limited to a portion of the substrate and/or
substrate table, a surface of the space may completely cover a
surface of the substrate and/or substrate table, or the space may
envelop the substrate and/or substrate table.
[0129] While specific embodiments of the invention have been
described above, it will be appreciated that the invention may be
practiced otherwise than as described. The description is not
intended to limit the invention.
* * * * *