U.S. patent application number 11/822672 was filed with the patent office on 2007-11-08 for exposure apparatus, exposure method, and method for producing device.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Nobutaka Magome, Hiroyuki Nagasaka.
Application Number | 20070258063 11/822672 |
Document ID | / |
Family ID | 32500881 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070258063 |
Kind Code |
A1 |
Nagasaka; Hiroyuki ; et
al. |
November 8, 2007 |
Exposure apparatus, exposure method, and method for producing
device
Abstract
In an exposure apparatus, an exposure of a substrate (P) is
carried out by filling at least a portion of the space between a
projection optical system (PL) and the substrate (P) with a liquid
(50) and projecting the image of a pattern onto the substrate (P)
via the projection optical system (PL). An optical element (60) and
a barrel (PK), which are in contact with the liquid (50) when the
substrate (P) is moved, are surface-treated for adjusting the
affinity with the liquid (50). Consequently, generation of bubbles
in the liquid between the projection optical system and the
substrate is suppressed and the liquid is always retained between
the projection optical system and the substrate, thereby creating a
good immersion state.
Inventors: |
Nagasaka; Hiroyuki;
(Kumagaya-shi, JP) ; Magome; Nobutaka;
(Kumagaya-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
NIKON CORPORATION
TOKYO
JP
|
Family ID: |
32500881 |
Appl. No.: |
11/822672 |
Filed: |
July 9, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11312477 |
Dec 21, 2005 |
|
|
|
11822672 |
Jul 9, 2007 |
|
|
|
11147373 |
Jun 8, 2005 |
|
|
|
11312477 |
Dec 21, 2005 |
|
|
|
PCT/JP03/15735 |
Dec 9, 2003 |
|
|
|
11147373 |
Jun 8, 2005 |
|
|
|
Current U.S.
Class: |
355/30 ; 355/53;
355/77 |
Current CPC
Class: |
G03F 7/709 20130101;
G03F 7/2041 20130101; G03F 7/70341 20130101 |
Class at
Publication: |
355/030 ;
355/077; 355/053 |
International
Class: |
G03B 27/42 20060101
G03B027/42 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2002 |
JP |
2002-357931 |
Claims
1. An exposure apparatus comprising: an optical member via which a
substrate is exposed to an exposure beam through a liquid; and a
liquid supply system which includes a supply opening for supplying
the liquid from the supply opening through a flow passage to a
space between the optical member and the substrate; wherein the
liquid supply system includes a liquid flow control member which is
located in the flow passage adjacent to the supply opening and by
which a flow of the liquid supplied from the supply opening is
controlled.
2. The exposure apparatus according to claim 1, wherein the liquid
flow control member rectifies the flow of the liquid.
3. The exposure apparatus according to claim 2, wherein the liquid
flow control member includes a porous member.
4. The exposure apparatus according to claim 2, wherein the liquid
flow control member forms a plurality of slits.
5. The exposure apparatus according to claim 2, wherein the liquid
flow control member is located adjacent to the supply opening.
6. The exposure apparatus according to claim 1, wherein the liquid
flow control member includes a porous member.
7. The exposure apparatus according to claim 1, wherein the liquid
flow control member forms a plurality of slits.
8. The exposure apparatus according to claim 1, wherein the
substrate is moved under the supply opening during the exposure,
and the substrate is partially covered by the liquid supplied from
the supply opening during the exposure.
9. A device manufacturing method comprising: supplying a liquid
through a flow passage to a space between a substrate and an
optical member from a supply opening; controlling a flow of the
liquid supplied from the supply opening by a liquid flow control
member located in the flow passage adjacent to the supply opening;
and exposing the substrate through the liquid supplied from the
supply opening to the space and the optical member.
10. The method according to claim 9, further comprising partially
covering the substrate with the liquid supplied from the supply
opening.
11. The method according to claim 9, wherein the liquid flow
control member rectifies the flow of the liquid.
12. The exposure apparatus according to claim 9, wherein the liquid
flow control member includes a porous member.
13. The exposure apparatus according to claim 9, wherein the liquid
flow control member forms a plurality of slits.
Description
CROSS-REFERENCE
[0001] This application is a Continuation of application Ser. No.
11/312,477 filed Dec. 21, 2005, which in turn is a Continuation of
application Ser. No. 11/147,373 filed Jun. 8, 2005, which in turn
is a Continuation Application of International Application No.
PCT/JP03/015735 which was filed on Dec. 9, 2003 claiming the
conventional priority of Japanese patent Application No.
2002-357931 filed on Dec. 10, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exposure apparatus and
an exposure method for performing the exposure with an image of a
pattern projected by a projection optical system in a state in
which at least a part of a space between the projection optical
system and a substrate is filled with a liquid. The present
invention also relates to a method for producing a device.
[0004] 2. Description of the Related Art
[0005] Semiconductor devices and liquid crystal display devices are
produced by the so-called photolithography technique in which a
pattern formed on a mask is transferred onto a photosensitive
substrate. The exposure apparatus, which is used in the
photolithography step, includes a mask stage for supporting the
mask and a substrate stage for supporting the substrate. The
pattern on the mask is transferred onto the substrate via a
projection optical system while successively moving the mask stage
and the substrate stage. In recent years, it is demanded to realize
the higher resolution of the projection optical system in order to
respond to the further advance of the higher integration of the
device pattern. As the exposure wavelength to be used is shorter,
the resolution of the projection optical system becomes higher. As
the numerical aperture of the projection optical system is larger,
the resolution of the projection optical system becomes higher.
Therefore, the exposure wavelength, which is used for the exposure
apparatus, is shortened year by year, and the numerical aperture of
the projection optical system is increased as well. The exposure
wavelength, which is dominantly used at present, is 248 nm of the
KrF excimer laser. However, the exposure wavelength of 193 nm of
the ArF excimer laser, which is shorter than the above, is also
practically used in some situations. When the exposure is
performed, the depth of focus (DOF) is also important in the same
manner as the resolution. The resolution R and the depth of focus
.delta. are represented by the following expressions respectively.
R=k.sub.1.lamda./NA (1) .delta.=.+-.k.sub.2.lamda./NA.sup.2 (2)
[0006] In the expressions, .lamda. represents the exposure
wavelength, NA represents the numerical aperture of the projection
optical system, and k.sub.1 and k.sub.2 represent the process
coefficients. According to the expressions (1) and (2), the
following fact is appreciated. That is, when the exposure
wavelength .lamda. is shortened and the numerical aperture NA is
increased in order to enhance the resolution R, then the depth of
focus .delta. is narrowed.
[0007] If the depth of focus .delta. is too narrowed, it is
difficult to match the substrate surface with respect to the image
plane of the projection optical system. It is feared that the
margin is insufficient during the exposure operation. Accordingly,
the liquid immersion method has been suggested, which is disclosed,
for example, in International Publication No. 99/49504 as a method
for substantially shortening the exposure wavelength and widening
the depth of focus. In this liquid immersion method, the space
between the lower surface of the projection optical system and the
substrate surface is filled with a liquid such as water or any
organic solvent to utilize the fact that the wavelength of the
exposure light beam in the liquid is 1/n as compared with that in
the air (n represents the refractive index of the liquid, which is
about 1.2 to 1.6 in ordinary cases) so that the resolution is
improved and the depth of focus is magnified about n times.
[0008] When the exposure is performed while making the liquid to
flow through the space between the projection optical system and
the substrate, or when the exposure is performed while moving the
substrate with respect to the projection optical system in a state
in which the space between the projection optical system and the
substrate is filled with the liquid, then there is such a
possibility that the liquid may be exfoliated from the projection
optical system and/or the substrate. An inconvenience arises such
that the pattern image, which is to be transferred to the
substrate, is deteriorated. In other cases, the pattern image is
deteriorated as well when any turbulence appears in the liquid flow
when the exposure is performed while making the liquid to flow
through the space between the projection optical system and the
substrate.
SUMMARY OF THE INVENTION
[0009] The present invention has been made taking the foregoing
circumstances into consideration, an object of which is to provide
an exposure apparatus, an exposure method, and a method for
producing a device, in which a pattern can be transferred
accurately by arranging a liquid in a desired state when an
exposure process is performed while filling a space between a
projection optical system and a substrate with the liquid. It is
noted that parenthesized numerals or symbols affixed to respective
elements merely exemplify the elements by way of example, with
which it is not intended to limit the respective elements.
[0010] In order to achieve the object as described above, the
present invention adopts the following constructions corresponding
to FIGS. 1 to 9 as illustrated in embodiments.
[0011] According to a first aspect of the present invention, there
is provided an exposure apparatus (EX) which exposes a substrate
(P) by transferring an image of a pattern through a liquid (50)
onto the substrate, the exposure apparatus comprising:
[0012] a projection optical system (PL) which projects the image of
the pattern onto the substrate, wherein:
[0013] a portion (60, PK) of the projection optical system (PL),
which makes contact with the liquid (50), is surface-treated to
adjust affinity for the liquid (50).
[0014] In the exposure apparatus of the present invention, the
surface treatment is applied to the portion of the projection
optical system (hereinafter appropriately referred to as "liquid
contact portion") which makes contact with the liquid in order to
adjust the affinity for the liquid. Therefore, the liquid is
maintained in a desired state between the projection optical system
and the substrate. For example, if the affinity of the liquid
contact portion for the liquid is too low, any phenomenon, in which
any harmful influence is exerted on the liquid immersion exposure,
arises, for example, such that the liquid is exfoliated from the
contact portion, and/or any bubble is generated. On the other hand,
if the affinity of the liquid contact portion for the liquid is too
high, any inconvenience arises in some cases, for example, such
that the liquid is spread while causing excessive wetting with
respect to the contact portion and the liquid outflows from the
space between the projection optical system and the substrate. On
the contrary, in the case of the exposure apparatus of the present
invention, the affinity is adjusted with respect to the liquid
disposed at the liquid contact portion of the projection optical
system. Therefore, the liquid immersion state is reliably
maintained between the substrate and the projection optical system
even in the case of the full field exposure in which the substrate
stands still with respect to the exposure light beam during the
exposure as well as in the case of the scanning type exposure
apparatus in which the substrate is moved by a movable stage during
the exposure.
[0015] According to a second aspect of the present invention, there
is provided an exposure apparatus (EX) which exposes a substrate
(P) by transferring an image of a pattern through a liquid (50)
onto the substrate, the exposure apparatus comprising:
[0016] a projection optical system (PL) which projects the image of
the pattern onto the substrate, wherein:
[0017] the projection optical system (PL) has a first surface area
(AR1) which includes a surface of an optical element (60) disposed
at a tip of the projection optical system, and a second surface
area (AR2) which is disposed around the first surface area (AR1);
and
[0018] affinity of the first surface area (AR1) for the liquid (50)
is higher than affinity of the second surface area (AR2) for the
liquid (50).
[0019] According to the present invention, the affinity for the
liquid of the first surface area including the optical element
disposed at the tip of the projection optical system is made higher
than that of the second surface area disposed therearound.
Accordingly, the liquid is stably arranged on the optical path for
the exposure light beam owing to the first surface area. Further,
the liquid is not spread with the wetting to the surroundings owing
to the second surface area, and thus does not outflow to the
outside. Therefore, the liquid can be stably arranged on the
optical path for the exposure light beam even in the case of the
full field exposure in which the substrate stands still with
respect to the exposure light beam during the exposure as well as
in the case of the scanning type exposure in which the substrate is
moved with respect to the exposure light beam during the
exposure.
[0020] According to a third aspect of the present invention, there
is provided an exposure apparatus (EX) which exposes a substrate
(P) by illuminating a pattern with an exposure beam (EL) and
transferring an image of the pattern through a liquid (50) onto the
substrate (P), the exposure apparatus comprising:
[0021] a projection optical system (PL) which projects the image of
the pattern onto the substrate; and
[0022] a liquid immersion unit (1, 2) which fills, with the liquid
(50), at least a part of a space between the projection optical
system (PL) and the substrate (P), wherein:
[0023] a conditional expression (vd.rho.)/.mu..ltoreq.2,000 is
satisfied provided that d represents a thickness of the liquid
(50), v represents a velocity of a flow of the liquid (50) between
the projection optical system (PL) and the substrate (P), .rho.
represents a density of the liquid (50), and .mu. represents a
coefficient of viscosity of the liquid (50).
[0024] According to the present invention, the condition, under
which the liquid is maintained in at least the part of the space
between the projection optical system (PL) and the substrate (P),
is set so that the conditional expression described above is
satisfied. Accordingly, no turbulence arises in the liquid.
Therefore, it is possible to suppress any inconvenience which would
be otherwise caused, for example, such that the pattern image to be
projected onto the substrate is deteriorated due to the turbulence
of the liquid.
[0025] According to a fourth aspect of the present invention, there
is provided an exposure apparatus (EX) which exposes a substrate
(P) by illuminating a pattern of a mask (M) with an exposure beam
(EL) and transferring an image of the pattern through a liquid (50)
onto the substrate, the exposure apparatus comprising:
[0026] a projection optical system (PL) which projects the image of
the pattern onto the substrate; and
[0027] a liquid immersion unit (1, 2) which fills, with the liquid,
at least a part of a space between the projection optical system
(PL) and the substrate (P), wherein:
[0028] the liquid (50) flows as a laminar flow in parallel to a
scanning direction of the substrate (P).
[0029] According to the present invention, the liquid immersion
state is controlled by various methods, and thus the liquid flows
while forming the laminar flow in parallel to the scanning
direction of the substrate during the exposure. Therefore, it is
possible to avoid the deterioration of the pattern image to be
projected onto the substrate. Further, no unnecessary vibration is
generated, for example, in the projection optical system which
makes contact with the liquid as well as in the wafer and the
substrate stage which holds the wafer. The flow of the liquid can
be made into the laminar flow, for example, by controlling the
amount of supply (recovery) of the liquid by the liquid immersion
unit, adjusting the structure of the liquid supply nozzle of the
liquid immersion unit, and/or adjusting the velocity when the
substrate is moved during the exposure.
[0030] According to a fifth aspect of the present invention, there
is provided an exposure apparatus (EX) which exposes a substrate
(P) by illuminating a pattern with an exposure beam (EL) and
transferring an image of the pattern through a liquid (50) onto the
substrate, the exposure apparatus comprising:
[0031] a projection optical system (PL) which projects the image of
the pattern onto the substrate;
[0032] a liquid immersion unit (1, 2) which supplies the liquid
(50) onto only the substrate (P); and
[0033] a control unit (CONT) which controls the liquid immersion
unit (1, 2), wherein:
[0034] the control unit (CONT) controls the liquid immersion unit
(1, 2) so that the supply of the liquid (50) is stopped during the
exposure of the substrate (P).
[0035] According to the present invention, the liquid immersion
unit is controlled such that the liquid is not supplied during the
exposure for the substrate. Accordingly, the photosensitive
material, which has been applied onto the substrate, is not
damaged. It is possible to avoid the deterioration of the pattern
to be formed on the substrate. Further, the positional relationship
between the projection optical system and the substrate can be
stably maintained in a desired state.
[0036] According to a sixth aspect of the present invention, there
is provided an exposure method for exposing a substrate (P) by
projecting an image of a pattern onto the substrate by using a
projection optical system (PL), the exposure method comprising:
[0037] applying a surface treatment to a surface of the substrate
(P) before the exposure in order to adjust affinity for the liquid
(50);
[0038] filling at least a part of a space between the projection
optical system (PL) and the substrate (P) with the liquid (50);
and
[0039] projecting the image of the pattern onto the substrate (P)
through the liquid (50).
[0040] According to the present invention, the surface treatment is
applied to the surface of the substrate depending on the affinity
for the liquid before performing the liquid immersion exposure.
Accordingly, the liquid can be maintained on the substrate in a
state preferable for the liquid immersion exposure. For example, if
the affinity for the liquid is too low, any inconvenience arises,
for example, such that the liquid is exfoliated from the surface of
the substrate, and/or any bubble is generated. On the other hand,
if the affinity for the liquid is too high, any inconvenience
arises in some cases, for example, such that the liquid is spread
excessively while causing wetting on the substrate. On the
contrary, when the appropriate surface treatment is applied to the
substrate surface in consideration of the affinity for the liquid
as in the exposure method of the present invention, then the liquid
can be maintained in a desired state on the substrate, and it is
possible to appropriately perform the recovery and the removal of
the liquid on the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows a schematic arrangement illustrating an
embodiment of the exposure apparatus of the present invention.
[0042] FIG. 2 shows an exemplary arrangement of supply nozzles and
recovery nozzles.
[0043] FIG. 3 shows an exemplary arrangement of supply nozzles and
recovery nozzles.
[0044] FIG. 4 schematically illustrates areas in which a projection
optical system and a substrate are surface-treated.
[0045] FIGS. 5A to 5C schematically illustrates situations in which
the liquid flows between a substrate and a projection optical
system which are not surface-treated.
[0046] FIGS. 6A to 6C schematically illustrates situations in which
the liquid flows between a substrate and a projection optical
system which are surface-treated.
[0047] FIG. 7 illustrates another embodiment of the present
invention.
[0048] FIGS. 8A and 8B show other embodiments of supply
nozzles.
[0049] FIG. 9 shows a cover glass provided over a substrate.
[0050] FIG. 10 shows a flow chart illustrating exemplary steps for
producing a semiconductor device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0051] An explanation will be made below about the exposure
apparatus and the method for producing the device according to the
present invention with reference to the drawings. However, the
present invention is not limited thereto. FIG. 1 shows a schematic
arrangement illustrating an embodiment of the exposure apparatus of
the present invention.
[0052] With reference to FIG. 1, an exposure apparatus EX includes
a mask stage MST which supports a mask M, a substrate stage PST
which supports a substrate P, an illumination optical system IL
which illuminates, with an exposure light beam EL, the mask M
supported by the mask stage MST, a projection optical system PL
which performs projection exposure for the substrate P supported by
the substrate stage PST with an image of a pattern of the mask M
illuminated with the exposure light beam EL, and a control unit
CONT which collectively controls the overall operation of the
exposure apparatus EX.
[0053] The embodiment of the present invention will now be
explained as exemplified by a case of the use of the scanning type
exposure apparatus (so-called scanning stepper) as the exposure
apparatus EX in which the substrate P is exposed with the pattern
formed on the mask M while synchronously moving the mask M and the
substrate P in mutually different directions (opposite directions)
in the scanning directions. In the following explanation, the Z
axis direction is the direction which is coincident with the
optical axis AX of the projection optical system PL, the X axis
direction is the synchronous movement direction (scanning
direction) for the mask M and the substrate P in the plane
perpendicular to the Z axis direction, and the Y axis direction is
the direction (non-scanning direction) perpendicular to the Z axis
direction and the Y axis direction. The directions about the X
axis, the Y axis, and the Z axis are designated as .theta.X,
.theta.Y, and .theta.Z directions respectively. The term
"substrate" referred to herein includes those obtained by applying
a resist on a semiconductor wafer, and the term "mask" includes a
reticle formed with a device pattern to be subjected to the
reduction projection onto the substrate.
[0054] The illumination optical system IL is used so that the mask
M, which is supported on the mask stage MST, is illuminated with
the exposure light beam EL. The illumination optical system IL
includes, for example, an exposure light source, an optical
integrator which uniformizes the illuminance of the light flux
radiated from the exposure light source, a condenser lens which
collects the exposure light beam EL supplied from the optical
integrator, a relay lens system, and a variable field diaphragm
which sets the illumination area on the mask M illuminated with the
exposure light beam EL to be slit-shaped. The predetermined
illumination area on the mask M is illuminated with the exposure
light beam EL having a uniform illuminance distribution by the
illumination optical system IL. Those usable as the exposure light
beam EL radiated from the illumination optical system IL include,
for example, emission lines (g-ray, h-ray, i-ray) in the
ultraviolet region radiated, for example, from a mercury lamp, far
ultraviolet light beams (DUV light beams) such as the KrF excimer
laser beam (wavelength: 248 nm), and vacuum ultraviolet light beams
(VUV light beams) such as the ArF excimer laser beam (wavelength:
193 nm) and the F.sub.2 laser beam (wavelength: 157 nm). In this
embodiment, the ArF excimer laser beam is used.
[0055] The mask stage MST supports the mask M. The mask stage MST
is two-dimensionally movable in the plane perpendicular to the
optical axis AX of the projection optical system PL, i.e., in the
XY plane, and it is finely rotatable in the OZ direction. The mask
stage MST is driven by a mask stage-driving unit MSTD such as a
linear motor. The mask stage-driving unit MSTD is controlled by the
control unit CONT. The position in the two-dimensional direction
and the angle of rotation of the mask M on the mask stage MST are
measured in real-time by a laser interferometer. The result of the
measurement is outputted to the control unit CONT. The control unit
CONT drives the mask stage-driving unit MSTD on the basis of the
result of the measurement obtained by the laser interferometer to
thereby position the mask M supported on the mask stage MST.
[0056] The projection optical system PL projects the pattern on the
mask M onto the substrate P at a predetermined projection
magnification .beta. to perform the exposure. The projection
optical system PL includes a plurality of optical elements
(lenses). The optical elements are supported by a barrel PK formed
of a metal member, for example, stainless steel (SUS 403). In this
embodiment, the projection optical system PL is a reduction system
having the projection magnification .beta. which is, for example,
1/4 or 1/5. The projection optical system PL may be any one of the
1.times. magnification system and the magnifying system. The plane
parallel plate (optical element) 60, which is formed of a glass
member such as quartz and calcium fluoride (fluorite), is provided
at the tip section 7 on the side of the substrate P of the
projection optical system PL of this embodiment. The optical
element 60 is provided detachably (exchangeably) with respect to
the barrel PK. The tip section 7 of the projection optical system
PL includes the optical element 60 and a part of the barrel
(holding member) PK for holding the same.
[0057] The substrate stage PST supports the substrate P. The
substrate stage PST includes a Z stage 51 which holds the substrate
P by the aid of a substrate holder, an XY stage 52 which supports
the Z stage 51, and a base 53 which supports the XY stage 52. The
substrate stage PST is driven by a substrate stage-driving unit
PSTD such as a linear motor. The substrate stage-driving unit PSTD
is controlled by the control unit CONT. When the Z stage 51 is
driven, the substrate P, which is held on the Z stage 51, is
subjected to the control of the position (focus position) in the Z
axis direction and the positions in the .theta.X and .theta.Y
directions. When the XY stage 52 is driven, the substrate P is
subjected to the control of the position in the XY directions
(position in the directions substantially parallel to the image
plane of the projection optical system PL). That is, the Z stage 51
controls the focus position and the angle of inclination of the
substrate P so that the surface of the substrate P is adjusted to
match the image plane of the projection optical system PL in the
auto-focus manner and the auto-leveling manner. The XY stage 52
positions the substrate P in the X axis direction and the Y axis
direction. It goes without saying that the Z stage and the XY stage
may be provided as an integrated body.
[0058] A movement mirror 54, which is movable together with the
substrate stage PST with respect to the projection optical system
PL, is provided on the substrate stage PST (Z stage 51). A laser
interferometer 55 is provided at a position opposed to the movement
mirror 54. The angle of rotation and the position in the
two-dimensional direction of the substrate P on the substrate stage
PST are measured in real-time by the laser interferometer 55. The
result of the measurement is outputted to the control unit CONT.
The control unit CONT drives the substrate stage-driving unit PSTD
on the basis of the result of the measurement of the laser
interferometer 55 to thereby position the substrate P supported on
the substrate stage PST.
[0059] In this embodiment, the liquid immersion method is applied
in order that the resolution is improved by substantially
shortening the exposure wavelength and the depth of focus is
substantially widened. Therefore, the space between the surface of
the substrate P and the tip section 7 of the projection optical
system PL is filled with the predetermined liquid 50 at least
during the period in which the image of the pattern on the mask M
is transferred onto the substrate P. As described above, the
optical element 60 and the part of the barrel PK are arranged at
the tip section 7 of the projection optical system PL. The liquid
50 makes contact with the optical element (glass member) 60 and the
barrel (metal member) PK. In this embodiment, pure water is used
for the liquid 50. The exposure light beam EL, which is not limited
to only the ArF excimer laser beam, can be transmitted through pure
water, even when the exposure light beam EL is, for example, the
emission line (g-ray, h-ray, i-ray) in the ultraviolet region
radiated, for example, from a mercury lamp or the far ultraviolet
light beam (DUV light beam) such as the KrF excimer laser beam
(wavelength: 248 nm).
[0060] The exposure apparatus EX includes a liquid supply unit
(liquid immersion unit, supply unit) 1 which supplies the
predetermined liquid 50 to a space 56 between the substrate P and
the tip section 7 of the projection optical system PL, and a liquid
recovery unit (liquid immersion unit, recovery unit) 2 which
recovers the liquid 50 from the space 56. The liquid supply unit 1
is provided to allow the liquid 50 to flow in parallel to the
scanning direction of the substrate P to at least a part of the
space between the projection optical system PL and the substrate P.
The liquid supply unit 1 includes, for example, a tank for
accommodating the liquid 50, and a pressurizing pump. One end of a
supply tube 3 is connected to the liquid supply unit 1. Supply
nozzles 4 are connected to the other end of the supply tube 3. The
liquid supply unit 1 supplies the liquid 50 to the space 56 through
the supply tube 3 and the supply nozzles 4.
[0061] The liquid recovery unit 2 includes, for example, a suction
pump, and a tank for accommodating the recovered liquid 50. One end
of a recovery tube 6 is connected to the liquid recovery unit 2.
Recovery nozzles 5 are connected to the other end of the recovery
tube 6. The liquid recovery unit 2 recovers the liquid 50 from the
space 56 through the recovery nozzles 5 and the recovery tube 6.
When the space 56 is filled with the liquid 50, then the control
unit CONT drives the liquid supply unit 1 so that the liquid 50,
which is in a predetermined amount per unit time, is supplied to
the space 56 through the supply tube 3 and the supply nozzles 4,
and the control unit CONT drives the liquid recovery unit 2 so that
the liquid 50, which is in a predetermined amount per unit time, is
recovered from the space 56 through the recovery nozzles 5 and the
recovery tube 6. Accordingly, the liquid 50 is retained in the
space 56 between the substrate P and the tip section 7 of the
projection optical system PL.
[0062] During the scanning exposure, a pattern image of a part of
the mask M is projected onto the rectangular projection area
disposed just under an end surface 60A. The mask M is moved at the
velocity V in the -X direction (or in the +X direction) with
respect to the projection optical system PL, in synchronization
with which the substrate P is moved at the velocity .beta.V (.beta.
is the projection magnification) in the +X direction (or in the -X
direction) by the aid of the XY stage 52. After the completion of
the exposure for one shot area, the next shot area is moved to the
scanning start position in accordance with the stepping of the
substrate P. The exposure process is successively performed
thereafter for each of the shot areas in the step-and-scan manner.
This embodiment is designed so that the liquid 50 is allowed to
flow in the same direction as the movement direction of the
substrate in parallel to the movement direction of the substrate
P.
[0063] FIG. 2 shows the positional relationship among the tip
section 7 of the projection optical system PL, the supply nozzles 4
(4A to 4C) for supplying the liquid 50 in the X axis direction, and
the recovery nozzles 5 (5(a), 5(b)) for recovering the liquid 50.
In FIG. 2, the tip section 7 (end surface 60A of the optical
element 60) has a rectangular shape which is long in the Y axis
direction. The three supply nozzles 4A to 4C are arranged on the
side in the +X direction, and the two recovery nozzles 5(a), 5(b)
are arranged on the side in the -X direction so that the tip
section 7 of the projection optical system PL is interposed thereby
in the X axis direction. The supply nozzles 4A to 4C are connected
to the liquid supply unit 1 through the supply tube 3, and the
recovery nozzles 5(a), 5(b) are connected to the liquid recovery
unit 2 through the recovery tube 4. Further, the supply nozzles
8(a) to 8C and the recovery nozzles 9A, 9B are arranged at
positions obtained by rotating, by substantially 180.degree., the
positions of the supply nozzles 4A to 4C and the recovery nozzles
5(a), 5(b) about the center of the tip section 7. The supply
nozzles 4A to 4C and the recovery nozzles 9A, 9B are alternately
arranged in the Y axis direction. The supply nozzles 8(a) to 8C and
the recovery nozzles 5(a), 5(b) are alternately arranged in the Y
axis direction. The supply nozzles 8(a) to 8C are connected to the
liquid supply unit 1 through the supply tube 10. The recovery
nozzles 9A, 9B are connected to the liquid recovery unit 2 through
the recovery tube 11. The liquid is supplied from the nozzles so
that no gas portion is formed between the projection optical system
PL and the substrate P.
[0064] As shown in FIG. 3, the supply nozzles 31, 32 and the
recovery nozzles 33, 34 may be also provided on the both sides in
the Y direction with the tip section 7 intervening therebetween.
The supply nozzles and the recovery nozzles can be used to stably
supply the liquid 50 to the space between the projection optical
system PL and the substrate P even during the movement of the
substrate P in the non-scanning direction (Y axis direction) when
the stepping movement is performed.
[0065] The shape of the nozzle is not specifically limited. For
example, two pairs of the nozzles may be used to supply or recover
the liquid 50 for the long side of the tip section 7. In this
arrangement, the supply nozzles and the recovery nozzles may be
arranged while being aligned vertically in order that the liquid 50
can be supplied and recovered in any one of the directions of the
+X direction and the -X direction.
[0066] FIG. 4 shows a magnified view illustrating those disposed in
the vicinity of the tip section 7 of the projection optical system
PL. As shown in FIG. 4, the surface treatment, which depends on the
affinity for the liquid 50, is applied to the tip section 7 of the
projection optical system PL. The tip section 7 is a portion to
make contact with the liquid 50 when the substrate P is moved in
the scanning direction (X axis direction) in order to perform the
scanning exposure. The tip section 7 includes a lower surface 7A of
the projection optical system PL which includes the lower surface
60A of the optical element 60 and a part of the lower surface of
the barrel PK, and a side surface 7B'of a part of the barrel PK
which is adjacent to the lower surface 7A. In this embodiment, the
liquid 50 is water. Therefore, the surface treatment, which is in
conformity with the affinity for water, is applied to the tip
section 7.
[0067] The surface treatment, which is applied to the tip section 7
of the projection optical system PL, is performed in mutually
different manners for a first surface area AR1 which includes the
surface (lower surface) 60A of the optical element 60 and the part
of the lower surface of the barrel PK, and for a second surface
area AR2 which is disposed around the first surface area AR1 and
which includes the remaining area of the lower surface of the
barrel PK and the side surface of the barrel PK. Specifically, the
surface treatment is applied to the first and second surface areas
AR1, AR2 respectively so that the affinity of the first surface
area AR1 for the liquid (water) 50 is higher than the affinity of
the second surface area AR2 for the liquid (water) 50. In this
embodiment, a lyophilic or liquid-attracting treatment (hydrophilic
or water-attracting treatment) to give the lyophilicity or
liquid-attracting property is applied to the first surface area AR1
including the optical element 60, and a lyophobic or
liquid-repelling treatment (hydrophobic or water-repelling
treatment) to give the lyophobicity or liquid-repelling property is
applied to the second surface area AR2. The lyophilic or
liquid-attracting treatment refers to a treatment to increase the
affinity for the liquid. The lyophobic or liquid-repelling
treatment refers to a treatment to decrease the affinity for the
liquid.
[0068] The surface treatment is performed depending on the polarity
of the liquid 50. In this embodiment, the liquid 50 is water having
large polarity. Therefore, the hydrophilic treatment, which is to
be applied to the first surface area AR1 including the optical
element 60, is performed by forming a thin film with a substance
such as alcohol having a molecular structure of large polarity.
Accordingly, the hydrophilicity is given to the first surface area
AR1. Alternatively, for example, an O.sub.2 plasma treatment, in
which the plasma treatment is performed by using oxygen (O.sub.2)
as a treatment gas, is applied to the barrel PK and the lower
surface 60A of the optical element 60 in the first surface area
AR1. Accordingly, oxygen molecules (or oxygen atoms), which have
strong polarity, are gathered on the surface, and thus it is
possible to give the hydrophilicity. As described above, when water
is used as the liquid 50, it is desirable to perform the treatment
for arranging, on the surface, those having the molecular structure
with the large polarity such as the OH group in the first surface
area AR1. The first surface area AR1 includes the optical element
60 as a glass member and the barrel PK as a metal member.
Therefore, when the hydrophilic treatment is performed, it is
possible to perform different surface treatments, for example, such
that thin films are formed with different substances for the glass
member and the metal member respectively. Of course, the same
surface treatment may be applied to the glass member and the metal
member in the first surface area AR1 respectively. When the thin
film is formed, it is possible to use techniques including, for
example, the application and the vapor deposition.
[0069] On the other hand, the water-repelling treatment is applied
to the second surface area AR2 including the surface of the barrel
PK. The water-repelling treatment, which is to be applied to the
second surface area AR2, is performed by forming a thin film with a
substance having a molecular structure of small polarity including,
for example, fluorine. Accordingly, the water-repelling property is
given to the second surface area AR2. Alternatively, the
water-repelling property can be given by applying a CF.sub.4 plasma
treatment in which the plasma treatment is performed by using
carbon tetrafluoride (CF.sub.4) as a treatment gas. It is also
possible to use techniques including, for example, the application
and the vapor deposition when the thin film is formed in the second
surface area AR2.
[0070] In this embodiment, the surface treatment is also applied to
the surface of the substrate P in conformity with the affinity for
the liquid 50. In this case, the hydrophilic or water-attracting
treatment is applied to the surface of the substrate P. As for the
hydrophilic treatment for the substrate P, the lyophilicity is
given to the surface of the substrate P, for example, by forming a
thin film with a substance such as alcohol having a molecular
structure of large polarity as described above. When the surface of
the substrate P is surface-treated by applying alcohol or the like,
it is desirable to provide a washing step of washing the applied
film in the step after the exposure and before the subsequent
application of the photosensitive material, for example, before
transporting the substrate to a developer/coater.
[0071] When the affinity of the first surface area AR1 for the
liquid 50 is higher than the affinity of the second surface area
AR2 for the liquid 50, the liquid 50 is stably retained in the
first surface area AR1.
[0072] In this embodiment, the thin film, which is to be used for
the surface treatment, is formed of a material which is insoluble
in the liquid 50. The thin film, which is formed on the optical
element 60, is to be arranged on the optical path for the exposure
light beam EL. Therefore, the thin film is formed of a material
through which the exposure light beam EL is transmissive. The film
thickness is set to such an extent that the exposure light beam EL
is transmissive therethrough as well.
[0073] Next, an explanation will be made about the operation for
exposing the substrate P with the pattern of the mask M by using
the exposure apparatus EX described above.
[0074] When the mask M is loaded on the mask stage MST, and the
substrate P is loaded on the substrate stage PST, then the control
unit CONT drives the liquid supply unit 1 to start the liquid
supply operation to the space 56. The liquid supply unit 1 supplies
the liquid 50 to the space 56 along with the direction of movement
of the substrate P. For example, when the scanning exposure is
performed by moving the substrate P in the scanning direction (-X
direction) indicated by the arrow Xa (see FIG. 2), the liquid 50 is
supplied and recovered with the liquid supply unit 1 and the liquid
recovery unit 2 by using the supply tube 3, the supply nozzles 4A
to 4C, the recovery tube 4, and the recovery nozzles 5(a), 5(b).
That is, when the substrate P is moved in the -X direction, then
the liquid 50 is supplied to the space between the projection
optical system PL and the substrate P from the liquid supply unit 1
through the supply tube 3 and the supply nozzles 4 (4A to 4C), and
the liquid 50 is recovered to the liquid recovery unit 2 through
the recovery nozzles 5 (5(a), 5(b)) and the recovery tube 6. The
liquid 50 flows in the -X direction so that the space between the
lens 60 and the substrate P is filled therewith. On the other hand,
when the scanning exposure is performed by moving the substrate P
in the scanning direction (+X direction) indicated by an arrow Xb,
then the liquid 50 is supplied and recovered with the liquid supply
unit 1 and the liquid recovery unit 2 by using the supply tube 10,
the supply nozzles 8(a) to 8C, the recovery tube 11, and the
recovery nozzles 9A, 9B. That is, when the substrate P is moved in
the +X direction, then the liquid 50 is supplied from the liquid
supply unit 1 to the space between the projection optical system PL
and the substrate P through the supply tube 10 and the supply
nozzles 8 (8(a) to 8C), and the liquid 50 is recovered to the
liquid recovery unit 2 through the recovery nozzles 9 (9A, 9B) and
the recovery tube 11. The liquid 50 flows in the +X direction so
that the space between the lens 60 and the substrate P is filled
therewith. As described above, the control unit CONT makes the
liquid 50 to flow in accordance with the movement direction of the
substrate P by using the liquid supply unit 1 and the liquid
recovery unit 2. In this arrangement, for example, the liquid 50,
which is supplied from the liquid supply unit 1 through the supply
nozzles 4, flows so that the liquid 50 is attracted and introduced
into the space 56 in accordance with the movement of the substrate
P in the -X direction. Therefore, even when the supply energy of
the liquid supply unit 1 is small, the liquid 50 can be supplied to
the space 56 with ease. When the direction, in which the liquid 50
is made to flow, is switched depending on the scanning direction,
then it is possible to fill the space between the substrate P and
the tip surface 7 of the lens 60 with the liquid 50, and it is
possible to obtain the high resolution and the wide depth of focus,
even when the substrate P is scanned in any one of the +X direction
and the -X direction.
[0075] In view of the above, it is now assumed that the surface
treatment is not applied to the projection optical system PL and
the substrate P. FIG. 5 schematically shows the flow of the liquid
50 in a state in which the surface treatment is not applied. In
this case, it is assumed that the surface of the projection optical
system PL and the surface of the substrate P have low affinities
for the liquid 50.
[0076] FIG. 5A shows a state in which the substrate stage PST is
stopped. The liquid 50 is supplied from the supply nozzles 4, and
the liquid 50 is recovered by the recovery nozzles 5. In this
situation, the affinity is low between the liquid 50 and the
substrate P, and hence the contact angle .theta. is large. FIG. 5B
shows a state in which the substrate P starts the movement in the X
axis direction by the aid of the substrate stage PST. The liquid 50
is deformed as if the liquid 50 is pulled by the moving substrate
P. The liquid 50 tends to be separated from the surface of the
substrate P, because the affinity is low between the liquid 50 and
the substrate P. FIG. 5C shows a state in which the movement
velocity of the substrate P on the substrate stage PST is further
increased. An exfoliation area (bubble) H1 is formed between the
substrate P and the liquid 50, and an exfoliation area H2 is also
formed between the optical element 60 and the liquid 50. When the
exfoliation areas H1, H2 are formed on the optical path for the
exposure light beam EL, the pattern of the mask M is not
transferred correctly to the substrate P.
[0077] FIG. 6 schematically shows the flow of the liquid 50 in a
state in which the tip section 7 of the projection optical system
PL and the surface of the substrate P are surface-treated as
explained with reference to FIG. 4.
[0078] FIG. 6A shows a situation in which the substrate stage PST
is stopped. The contact angle .theta. is small, because the
affinity is enhanced between the liquid 50 and the substrate P by
applying the surface treatment. FIG. 6B shows a state in which the
substrate P starts the movement in the X axis direction by the aid
of the substrate stage PST. Even when the substrate P is moved, the
liquid 50 is not pulled excessively by the substrate P, because the
affinity is high between the liquid 50 and the substrate P.
Further, the liquid 50 is not exfoliated from the first surface
area AR1, because the affinity of the first surface area AR1 of the
projection optical system PL is also high with respect to the
liquid 50. In this situation, the circumference of the first
surface area AR1 is surrounded by the second surface area AR2 which
has the low affinity for the liquid 50. Therefore, the liquid 50 in
the space 56 does not outflow to the outside, and the liquid 50 is
stably arranged in the space 56. FIG. 6C shows a state in which the
movement velocity of the substrate P on the substrate stage PST is
further increased. Even when the movement velocity of the substrate
P is increased, no exfoliation occurs between the liquid 50 and the
projection optical system PL and the substrate P, because the
surface treatment is applied to the projection optical system PL
and the substrate P.
[0079] As explained above, the surface treatment, which is in
conformity with the affinity for the liquid 50, is applied to the
surface of the substrate P and the tip section 7 of the projection
optical system PL as the portions to make contact with the liquid
50 during the exposure process based on the liquid immersion
method. Accordingly, it is possible to suppress the occurrence of
inconveniences including, for example, the exfoliation of the
liquid 50 and the generation of the bubble, and it is possible to
stably arrange the liquid 50 between the projection optical system
PL and the substrate P. Therefore, it is possible to maintain a
satisfactory pattern transfer accuracy.
[0080] The surface treatment, which depends on the affinity for the
liquid 50, may be applied to only any one of the tip section 7 of
the projection optical system PL and the surface of the substrate
P.
[0081] The foregoing embodiment has been explained such that the
surface 60A of the optical element 60 and the part of the lower
surface of the barrel (holding member) PK are designated as the
first surface area AR1, and the surface treatment is applied to the
first surface area AR1 so that the affinity for the liquid 50 is
enhanced. That is, the explanation has been made assuming that the
boundary between the lyophilic or liquid-attracting treatment area
and the lyophobic or liquid-repelling treatment area exists on the
lower surface of the barrel PK. However, the boundary may be set on
the surface of the optical element 60. That is, it is also
allowable that the liquid-attracting treatment is applied to a part
of the area of the optical element 60 (at least an area through
which the exposure light beam passes), and the liquid-repelling
treatment is applied to the remaining area. Of course, it is also
allowable that the boundary between the liquid-attracting treatment
area and the liquid-repelling treatment area may be coincident with
the boundary between the optical element 60 and the barrel PK. That
is, it is also allowable that the liquid-attracting treatment is
applied to only the optical element 60. Further, there is no
limitation to the setting of the boundary on the lower surface 7A
of the projection optical system PL. All of the lower surface 7A of
the projection optical system PL may be subjected to the
liquid-attracting treatment.
[0082] Further, when the surface treatment is performed, it is also
possible to allow the lyophilicity (lyophobicity) to have a
distribution. In other words, the surface treatment can be
performed such that the contact angle of the liquid has mutually
different values for a plurality of areas on the surface subjected
to the surface treatment. Alternatively, lyophilic areas and
lyophobic areas may be appropriately arranged in a divided
manner.
[0083] The thin film, which is to be used for the surface
treatment, may be a single layer film or a film composed of a
plurality of layers. As for the material for forming the film, it
is possible to use arbitrary materials provided that the material
exhibits desired performance, including, for example, metals, metal
compounds, and organic matters.
[0084] For example, the thin film formation and the plasma
treatment are effective for the surface treatment for the optical
element 60 and the substrate P. However, in relation to the surface
treatment for the barrel PK as the metal member, it is possible to
adjust the affinity for the liquid by any physical technique
including, for example, the rough surface treatment for the surface
of the barrel PK.
[0085] In the embodiment described above, the surface of the
substrate P is made lyophilic (subjected to the liquid-attracting
treatment) while giving much weight to the stable retention of the
liquid between the projection optical system PL and the substrate
P. However, when much weight is given to the recovery and the
removal of the liquid from the surface of the substrate P, the
surface of the substrate P may be made lyophobic (subjected to the
liquid-repelling treatment).
[0086] In the embodiment described above, the surface treatment,
which is in conformity with the affinity for the liquid 50, is
applied to the tip section 7 of the projection optical system PL
and the surface of the substrate P. However, it is also allowable
that any liquid, which is in conformity with the affinity for at
least one of the tip section 7 of the projection optical system PL
and the surface of the substrate P, is supplied from the liquid
supply unit 1.
[0087] As described above, pure water is used as the liquid 50 in
this embodiment. Pure water is advantageous in that pure water is
available in a large amount with ease, for example, in the
semiconductor production factory, and pure water exerts no harmful
influence, for example, on the optical element (lens) and the
photoresist on the substrate P. Further, pure water exerts no
harmful influence on the environment, and the content of impurity
is extremely low. Therefore, it is also expected to obtain the
function to wash the surface of the substrate P and the surface of
the optical element provided at the tip surface of the projection
optical system PL.
[0088] It is approved that the refractive index n of pure water
(water) with respect to the exposure light beam EL having a
wavelength of about 193 nm is approximately in an extent of 1.44 to
1.47. When the ArF excimer laser beam (wavelength: 193 nm) is used
as the light source of the exposure light beam EL, then the
wavelength is shortened on the substrate P by 1/n, i.e., to about
131 to 134 nm, and a high resolution is obtained. Further, the
depth of focus is magnified about n times, i.e., about 1.44 to 1.47
times as compared with the value obtained in the air. Therefore,
when it is enough to secure an approximately equivalent depth of
focus as compared with the case of the use in the air, it is
possible to further increase the numerical aperture of the
projection optical system PL. Also in this viewpoint, the
resolution is improved.
[0089] In this embodiment, the plane parallel plate is attached as
the optical element 60 to the tip of the projection optical system
PL. However, the optical element, which is attached to the tip of
the projection optical system PL, may be an optical plate which is
usable to adjust the optical characteristics of the projection
optical system PL, for example, the aberration (for example,
spherical aberration and comatic aberration), or the optical
element may be a lens. On the other hand, when the optical element,
which makes contact with the liquid 50, is the plane parallel plate
which is cheaper than the lens, it is enough that the plane
parallel plate is merely exchanged immediately before supplying the
liquid 50 even when any substance (for example, any silicon-based
organic matter), which deteriorates the transmittance of the
projection optical system PL, the illuminance of the exposure light
beam EL on the substrate P, and the uniformity of the illuminance
distribution, is adhered to the plane parallel plate, for example,
during the transport, the assembling, and/or the adjustment of the
exposure apparatus EX. An advantage is obtained such that the
exchange cost is lowered as compared with the case in which the
optical element to make contact with the liquid 50 is the lens.
That is, the surface of the optical element to make contact with
the liquid 50 is dirtied, for example, due to the adhesion of
scattered particles generated from the resist by being irradiated
with the exposure light beam EL or any impurity contained in the
liquid 50. Therefore, it is necessary to periodically exchange the
optical element. However, when the optical element is the cheap
plane parallel plate, then the cost of the exchange part is low as
compared with the lens, and it is possible to shorten the time
required for the exchange. Thus, it is possible to suppress the
increase in the maintenance cost (running cost) and the decrease in
the throughput.
[0090] When the pressure, which is generated by the flow of the
liquid 50, is large between the substrate P and the optical element
disposed at the tip of the projection optical system PL, it is also
allowable that the optical element is tightly fixed so that the
optical element is not moved by the pressure, rather than allowing
the optical element to be exchangeable.
[0091] The liquid 50 is water in the embodiment described above.
However, the liquid 50 may be any liquid other than water. For
example, when the light source of the exposure light beam EL is the
F.sub.2 laser, the F.sub.2 laser beam is not transmitted through
water. Therefore, in this case, those preferably usable as the
liquid 50 may include, for example, fluorine-based oil
(fluorine-based liquid) and perfluoropolyether (PFPE) through which
the F.sub.2 laser beam is transmissive. In this case, the surface
of the substrate P and the portion of the projection optical system
PL to make contact with the liquid 50 are subjected to the
liquid-attracting treatment by forming the thin film, for example,
with a substance having a molecular structure of small polarity
including fluorine. Alternatively, other than the above, it is also
possible to use, as the liquid 50, those (for example, cedar oil)
which have the transmittance with respect to the exposure light
beam EL, which have the refractive index as high as possible, and
which are stable against the photoresist applied to the surface of
the substrate P and the projection optical system PL. Also in this
case, the surface treatment is performed depending on the polarity
of the liquid 50 to be used.
[0092] Next, an explanation will be made with reference to FIG. 7
about a second embodiment of the present invention.
[0093] An exposure apparatus EX of this embodiment is designed such
that the following conditional expression is satisfied provided
that d represents a thickness of the liquid 50 between the lower
surface 7A of the projection optical system PL and the surface of
the substrate P (in this case, the spacing distance between the
projection optical system PL and the substrate P), v represents a
velocity of a flow of the liquid 50 between the projection optical
system PL and the substrate P, .rho. represents a density of the
liquid 50, and .mu. represents a coefficient of viscosity of the
liquid 50: (vd.rho.)/.mu..ltoreq.2,000 (3)
[0094] Accordingly, the liquid 50 flows as a laminar flow in the
space 56. As for the liquid 50, it is also assumed that a plurality
of different flow velocities v exist depending on the position in
the liquid. However, it is enough that the maximum velocity
V.sub.max thereof satisfies the expression (3).
[0095] The control unit CONT adjusts at least one of the amount of
supply of the liquid per unit time to the space 56 by the aid of
the liquid supply unit 1 and the amount of recovery of the liquid
per unit time from the space 56 by the aid of the liquid recovery
unit 2 so that the conditional expression (3) is satisfied.
Accordingly, the velocity v of the liquid 50 to flow through the
space 56 is determined, and it is possible to satisfy the
conditional expression (3). When the conditional expression (3) is
satisfied, the liquid 50 flows through the space 56 while forming
the laminar flow.
[0096] Alternatively, the control unit CONT can also satisfy the
conditional expression (3) by adjusting the movement velocity in
the scanning direction of the substrate P by the substrate stage
PST. That is, the velocity v of the liquid 50 flowing through the
space 56 is also determined by the movement velocity of the
substrate P in some cases. That is, there is such a possibility
that the liquid 50 on the substrate P may flow such that the liquid
50 is pulled by the substrate P in accordance with the movement of
the substrate P. In this case, the conditional expression (3) can
be satisfied by adjusting the movement velocity of the substrate P.
For example, when the substrate P and the liquid 50 flow or move at
approximately identical velocities with respect to the projection
optical system PL, it is appropriate that the movement velocity of
the substrate P may be regarded as the velocity v of the liquid 50
to satisfy the conditional expression (3). Also in this case, the
liquid 50 flows through the space 56 while forming the laminar
flow. Further, in this case, it is not necessarily indispensable to
operate the liquid supply unit 1 and the liquid recovery unit 2
during the exposure for the substrate P. The flow of the liquid 50
can be made to be the laminar flow by adjusting only the movement
velocity of the substrate P.
[0097] In order to satisfy the conditional expression (3), the
thickness d of the liquid 50 (i.e., the spacing distance between
the projection optical system PL and the substrate P) may be
previously set as a designed value for the exposure apparatus, and
the velocity v may be determined on the basis of this value.
Alternatively, the velocity v may be previously set as a designed
value, and the thickness (distance) d may be determined on the
basis of this value.
[0098] In order that the liquid 50 flows while forming the laminar
flow in the space 56, for example, slits may be provided at
openings of the supply nozzles 4 connected to the liquid supply
unit 1 as shown in FIG. 8A, or porous members are provided at
openings of the supply nozzles 4 as shown in FIG. 8B. Accordingly,
the liquid 50 can be rectified to flow in the laminar flow
state.
[0099] When the liquid 50 flows as the laminar flow, it is possible
to suppress inconveniences such as the vibration and the change in
the refractive index which would be otherwise caused by the
fluctuation of the pressure. Thus, it is possible to maintain a
satisfactory pattern transfer accuracy. Further, when the surface
treatment is applied to the surface of the substrate P and the
portion of the projection optical system PL to make contact with
the liquid 50, and the exposure apparatus EX is set so that the
conditional expression (3) is satisfied to perform the exposure
process, then the liquid 50 in the space 56 is established to be in
a more satisfactory state in which no influence is exerted on the
pattern transfer accuracy.
[0100] In the embodiment described above, the exposure apparatus is
adopted, in which the space between the projection optical system
PL and the substrate P is locally filled with the liquid. However,
the present invention is also applicable to a liquid immersion
exposure apparatus in which a stage holding a substrate as an
exposure objective is moved in a liquid bath, and a liquid
immersion exposure apparatus in which a liquid pool having a
predetermined depth is formed on a stage and a substrate is held
therein. The structure and the exposure operation of the liquid
immersion exposure apparatus in which the stage holding the
substrate as the exposure objective is moved in the liquid bath are
disclosed, for example, in Japanese Patent Application Laid-open
No. 6-124873, content of which is incorporated herein by reference
within a range of permission of the domestic laws and ordinances of
the state designated or selected in this international application.
The structure and the exposure operation of the liquid immersion
exposure apparatus in which the liquid pool having the
predetermined depth is formed on the stage and the substrate is
held therein are disclosed, for example, in Japanese Patent
Application Laid-open No. 10-303114 and U.S. Pat. No. 5,825,043,
contents of which are incorporated herein by reference within a
range of permission of the domestic laws and ordinances of the
state designated or selected in this international application.
[0101] In the embodiment described above, the liquid supply unit 1
and the liquid recovery unit 2 are used to continue the supply and
the recovery of the liquid 50 during the exposure for the substrate
P as well. However, it is also allowable to stop the supply and the
recovery of the liquid 50 by the liquid supply unit 1 and the
liquid recovery unit 2 during the exposure for the substrate P.
That is, a small amount of the liquid 50 is supplied by the liquid
supply unit 1 onto the substrate P to such an extent that the
liquid immersion portion, which has a thickness of not more than
the working distance of the projection optical system PL (about 0.5
to 1.0 mm), is formed between the substrate P and the tip section 7
of the projection optical system PL, or to such an extent that a
thin liquid film is formed on the entire surface of the substrate P
before the start of the exposure for the substrate P. The tip
section 7 of the projection optical system PL and the substrate P
are made to tightly contact with each other by the aid of the
liquid 50. The spacing distance between the tip section 7 of the
projection optical system PL and the substrate P is not more than
several mm. Therefore, even when the substrate P is moved without
supplying and recovering the liquid by using the liquid supply unit
1 and the liquid recovery unit 2 during the exposure for the
substrate P, it is possible to continuously retain the liquid 50
between the projection optical system PL and the substrate P owing
to the surface tension of the liquid 50. The resist (photosensitive
film), which is disposed on the substrate P, is not damaged by the
supply of the liquid from the liquid supply unit 1 as well. In this
case, when a coating for repelling the liquid 50 (water-repelling
coating when the liquid is water) is applied with a predetermined
width to the circumferential edge of the substrate P, it is
possible to avoid the outflow of the liquid 50 from the substrate
P. It goes without saying that the conditional expression (3) is
satisfied to generate no turbulence in the liquid 50 when the
substrate P is moved.
[0102] In the embodiment described above, the liquid (50) is
supplied on the substrate stage PST. However, the liquid may be
supplied onto the substrate P before the substrate P is imported
onto the substrate stage PST. In this case, when the liquid, which
is supplied to a part or all of the surface of the substrate P, has
a thickness of about 0.5 to 1.0 mm, then the substrate P can be
imported to the substrate stage PST and the substrate P can be
exported from the substrate stage PST while placing the liquid on
the substrate P by the surface tension. Also in this case, when a
liquid-repelling coating having a predetermined width is applied to
the circumferential edge of the substrate P, it is possible to
enhance the retaining force for the liquid on the substrate P. When
the substrate P is imported to the substrate stage PST and the
substrate P is exported from the substrate stage PST while
retaining the liquid on the substrate P as described above, it is
possible to omit the mechanism for supplying and recovering the
liquid on the substrate stage PST.
[0103] The embodiment described above is constructed such that the
space between the projection optical system PL and the surface of
the substrate P is filled with the liquid 50. However, for example,
as shown in FIG. 9, the space may be filled with the liquid 50 in a
state in which a cover glass 65, which is composed of a plane
parallel plate, is attached to the surface of the substrate P. In
this arrangement, the cover glass 65 is supported over the Z stage
51 by the aid of a support member 66. The space 57, which is formed
by the cover glass 65, the support member 66, and the Z stage 51,
is a substantially tightly closed or sealed space. The liquid 50
and the substrate P are arranged in the space 57. The cover glass
65 is composed of a material through which the exposure light beam
EL is transmissive. The liquid 50 is supplied to and recovered from
a space 56' between the surface of the cover glass 65 and the
projection optical system PL by using the liquid supply unit 1 and
the liquid recovery unit 2. The setting is made such that the
conditional expression (3) described above is satisfied in the
space 56' provided that d represents the spacing distance between
the surface of the cover glass 65 and the tip section 7 of the
projection optical system PL.
[0104] The surface treatment, which is in conformity with the
affinity for the liquid 50, can be also applied to the surface
(upper surface) of the cover glass 65. It is desirable that the
liquid-attracting treatment is applied to the surface of the cover
glass 65. Therefore, when the liquid 50 is water, a thin film is
formed with a substance having a molecular structure of large
polarity on the surface of the cover glass 65.
[0105] The substrate P, which is usable in the respective
embodiments described above, is not limited to the semiconductor
wafer for producing the semiconductor device. Those applicable
include, for example, the glass substrate for the display device,
the ceramic wafer for the thin film magnetic head, and the master
plate (synthetic quartz, silicon wafer) for the mask or the reticle
to be used for the exposure apparatus.
[0106] As for the exposure apparatus EX, the present invention is
also applicable to the scanning type exposure apparatus (scanning
stepper) based on the step-and-scan system for performing the
scanning exposure for the pattern of the mask M by synchronously
moving the mask M and the substrate P as well as the projection
exposure apparatus (stepper) based on the step-and-repeat system
for performing the full field exposure for the pattern of the mask
M in a state in which the mask M and the substrate P are made to
stand still, while successively step-moving the substrate P. The
present invention is also applicable to the exposure apparatus
based on the step-and-stitch system in which at least two patterns
are partially overlaid and transferred on the substrate P.
[0107] The present invention is also applicable to a twin-stage
type exposure apparatus. The structure and the exposure operation
of the twin-stage type exposure apparatus are disclosed, for
example, in Japanese Patent Application Laid-open Nos. 10-163099
and 10-214783 (corresponding to U.S. Pat. Nos. 6,341,007,
6,400,441, 6,549,269, and 6,590,634), Published Japanese
Translation of PCT International Publication for Patent Application
No. 2000-505958 (corresponding to U.S. Pat. No. 5,969,441), and
U.S. Pat. No. 6,208,407, contents of which are incorporated herein
by reference within a range of permission of the domestic laws and
ordinances of the state designated or selected in this
international application.
[0108] As for the type of the exposure apparatus EX, the present
invention is not limited to the exposure apparatus for the
semiconductor production apparatus for exposing the substrate P
with the semiconductor device pattern. The present invention is
also widely applicable, for example, to the exposure apparatus for
producing the liquid crystal display device or for producing the
display as well as the exposure apparatus for producing, for
example, the thin film magnetic head, the image pickup device
(CCD), the reticle, or the mask.
[0109] When the linear motor is used for the substrate stage PST
and/or the mask stage MST, it is allowable to use any one of those
of the air floating type based on the use of the air bearing and
those of the magnetic floating type based on the use of the
Lorentz's force or the reactance force. Each of the stages PST, MST
may be either of the type in which the movement is effected along
the guide or of the guideless type in which no guide is provided.
An example of the use of the linear motor for the stage is
disclosed in U.S. Pat. Nos. 5,623,853 and 5,528,118, contents of
which are incorporated herein by reference respectively within a
range of permission of the domestic laws and ordinances of the
state designated or selected in this international application.
[0110] As for the driving mechanism for each of the stages PST,
MST, it is also allowable to use a plane motor in which a magnet
unit provided with two-dimensionally arranged magnets and an
armature unit provided with two-dimensionally arranged coils are
opposed to one another, and each of the stages PST, MST is driven
by the electromagnetic force. In this arrangement, any one of the
magnet unit and the armature unit is connected to the stage PST,
MST, and the other of the magnet unit and the armature unit is
provided on the side of the movable surface of the stage PST,
MST.
[0111] The reaction force, which is generated in accordance with
the movement of the substrate stage PST, may be mechanically
released to the floor (ground) by using a frame member so that the
reaction force is not transmitted to the projection optical system
PL. The method for handling the reaction force is disclosed in
detail, for example, in U.S. Pat. No. 5,528,118 (Japanese Patent
Application Laid-open No. 8-166475), contents of which are
incorporated herein by reference within a range of permission of
the domestic laws and ordinances of the state designated or
selected in this international application.
[0112] The reaction force, which is generated in accordance with
the movement of the mask stage MST, may be mechanically released to
the floor (ground) by using a frame member so that the reaction
force is not transmitted to the projection optical system PL. The
method for handling the reaction force is disclosed in detail, for
example, in U.S. Pat. No. 5,874,820 (Japanese Patent Application
Laid-open No. 8-330224), contents of which are incorporated herein
by reference within a range of permission of the domestic laws and
ordinances of the state designated or selected in this
international application.
[0113] As described above, the exposure apparatus EX according to
the embodiment of the present invention is produced by assembling
the various subsystems including the respective constitutive
elements as defined in claims so that the predetermined mechanical
accuracy, the electric accuracy, and the optical accuracy are
maintained. In order to secure the various accuracies, those
performed before and after the assembling include the adjustment
for achieving the optical accuracy for the various optical systems,
the adjustment for achieving the mechanical accuracy for the
various mechanical systems, and the adjustment for achieving the
electric accuracy for the various electric systems. The steps of
assembling the various subsystems into the exposure apparatus
include, for example, the mechanical connection, the wiring
connection of the electric circuits, and the piping connection of
the air pressure circuits in correlation with the various
subsystems. It goes without saying that the steps of assembling the
respective individual subsystems are performed before performing
the steps of assembling the various subsystems into the exposure
apparatus. When the steps of assembling the various subsystems into
the exposure apparatus are completed, the overall adjustment is
performed to secure the various accuracies as the entire exposure
apparatus. It is desirable that the exposure apparatus is produced
in a clean room in which, for example, the temperature and the
cleanness are managed.
[0114] As shown in FIG. 10, the microdevice such as the
semiconductor device is produced by performing, for example, a step
201 of designing the function and the performance of the
microdevice, a step 202 of manufacturing a mask (reticle) based on
the designing step, a step 203 of producing a substrate as a base
material for the device, an exposure process step 204 of exposing
the substrate with a pattern of the mask by using the exposure
apparatus EX of the embodiment described above, a step 205 of
assembling the device (including a dicing step, a bonding step, and
a packaging step), and an inspection step 206. The exposure process
step 204 includes a step of performing the surface treatment for
the substrate in order to adjust the hydrophilicity for the
substrate and the liquid before the exposure.
[0115] According to the present invention, it is possible to
suppress the exfoliation of the liquid, the generation of the
bubble, or the occurrence of the turbulence, and it is possible to
maintain the liquid in a desired state between the projection
optical system and the substrate in the liquid immersion exposure.
Accordingly, the pattern can be transferred correctly with a wide
depth of focus. Therefore, the present invention is extremely
useful for the exposure based on the use of the short wavelength
light source such as ArF. It is possible to produce a highly
integrated device having desired performance.
* * * * *