U.S. patent application number 11/217464 was filed with the patent office on 2006-03-09 for liquid immersion optical tool, method for cleaning liquid immersion optical tool, and method for manufacturing semiconductor device.
Invention is credited to Tatsuhiko Higashiki.
Application Number | 20060050351 11/217464 |
Document ID | / |
Family ID | 35995896 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060050351 |
Kind Code |
A1 |
Higashiki; Tatsuhiko |
March 9, 2006 |
Liquid immersion optical tool, method for cleaning liquid immersion
optical tool, and method for manufacturing semiconductor device
Abstract
There is disclosed is a liquid immersion optical tool, which
comprises a light source, an optical lens system, a stage which
moves an object base on which an object is to be placed, a head
comprising a liquid immersion medium fluid supply device and a
liquid immersion medium fluid discharge device to provide a layer
of liquid immersion medium fluid between the optical lens system
and the object, a fence which limits a region of the layer of
liquid immersion medium fluid, and a cleaning device which cleans a
portion having been contacted with the liquid immersion medium
fluid by means of a cleaning solution.
Inventors: |
Higashiki; Tatsuhiko;
(Fujisawa-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
35995896 |
Appl. No.: |
11/217464 |
Filed: |
September 2, 2005 |
Current U.S.
Class: |
359/228 |
Current CPC
Class: |
G03F 7/70341 20130101;
G02B 27/0006 20130101; G03F 7/70925 20130101 |
Class at
Publication: |
359/228 |
International
Class: |
G02B 26/02 20060101
G02B026/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2004 |
JP |
2004-258676 |
Claims
1. A liquid immersion optical tool comprising: a light source; an
optical lens system; a stage which moves an object base on which an
object is to be placed; a head comprising a liquid immersion medium
fluid supply device and a liquid immersion medium fluid discharge
device to provide a layer of liquid immersion medium fluid between
the optical lens system and the object; a fence which limits a
region of the layer of liquid immersion medium fluid; and a
cleaning device which cleans a portion having been contacted with
the liquid immersion medium fluid by means of a cleaning
solution.
2. The liquid immersion optical tool according to claim 1, wherein
the portion having been contacted with the liquid immersion medium
fluid is one or more selected from the group including the optical
lens system, the fence, the object base, the stage, the head, the
liquid immersion medium fluid supply device, and the liquid
immersion medium fluid discharge device.
3. The liquid immersion optical tool according to claim 1, wherein
the cleaning device generates cavities in the cleaning
solution.
4. The liquid immersion optical tool according to claim 3, wherein
an average diameter of the cavities is equal to or smaller than 1
.mu.m.
5. The liquid immersion optical tool according to claim 1, wherein
the cleaning device has any of a cavitation jet, a venturi tube, a
Pitot tube, and a ultrasound generator, and the cavities are
generated by any of the cavitation jet, the venturi tube, the Pitot
tube, and the ultrasound generator.
6. The liquid immersion optical tool according to claim 1, wherein
the cleaning device is connected to the liquid immersion medium
fluid supply device.
7. The liquid immersion optical tool according to claim 1, wherein
the cleaning device is loaded on the stage.
8. The liquid immersion optical tool according to claim 1, wherein
the cleaning device is detachable.
9. The liquid immersion optical tool according to claim 1, wherein
the cleaning solution is one selected from the group of function
waters including ozone water, ionized water, carbonated water, and
peroxide water.
10. The liquid immersion optical tool according to claim 1, wherein
the cleaning solution is acid.
11. The liquid immersion optical tool according to claim 1, wherein
the cleaning solution is water vapor.
12. The liquid immersion optical tool according to claim 1, further
comprising a measuring mechanism which measures intensity of light
transmitting the optical lens system.
13. The liquid immersion optical tool according to claim 12,
further comprising: a computing mechanism which computes a lowered
quantity of light intensity from information on the light intensity
measured by the measuring mechanism; and a calculating mechanism
which calculates a period of cleaning by the cleaning device from
the computed lowered quantity of light intensity.
14. The liquid immersion optical tool according to claim 1, wherein
a predetermined pattern is transferred to the object by using the
optical lens system.
15. The liquid immersion optical tool according to claim 14,
wherein the predetermined pattern is a pattern of a semiconductor
element.
16. The liquid immersion optical tool according to claim 1, wherein
a surface of the object is observed or measured by using the
optical lens.
17. A cleaning method in the liquid immersion optical tool
comprising a light source; an optical lens system; a stage which
moves an object base on which an object is to be placed; a head
comprising a liquid immersion medium fluid supply device and a
liquid immersion medium fluid discharge device to provide a layer
of liquid immersion medium fluid between the optical lens system
and the object; a fence which limits a region of the layer of
liquid immersion medium fluid; and a cleaning device which cleans a
portion having been contacted with the liquid immersion medium
fluid by means of a cleaning solution, wherein the portion having
been contacted with the liquid immersion medium fluid is cleaned
for a predetermined time by means of the cleaning device.
18. The cleaning method according to claim 17, wherein a rinse
process is carried out by means of a rinse solution in which no
cavities exist, after cleaning by the cleaning solution is carried
out for the predetermined time.
19. The cleaning method according to claim 18, wherein the rinse
solution is water.
20. A semiconductor device manufacturing method in which a
semiconductor device is manufactured by using a liquid immersion
exposure tool, the liquid immersion exposure tool comprising: a
light source; an optical lens system; a stage which moves an object
base on which an object is to be placed; a head comprising a liquid
immersion medium fluid supply device and a liquid immersion medium
fluid discharge device to provide a layer of liquid immersion
medium fluid between the optical lens system and the object; a
fence which limits a region of the layer of liquid immersion medium
fluid; and a cleaning device which cleans a portion having been
contacted with the liquid immersion medium fluid by means of a
cleaning solution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2004-258676,
filed Sep. 6, 2004, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a liquid immersion optical
tool, a method for cleaning the liquid immersion optical tool, and
a method for manufacturing a semiconductor device, wherein a liquid
immersion medium fluid layer is provided between an optical lens
system and an object, improving an optical performance.
[0004] 2. Description of the Related Art
[0005] A liquid immersion microscope or a liquid immersion exposure
tool and the like is used as a liquid immersion optical tool for
immersing liquid immersion medium fluid between an object and an
optical lens system, thereby improving a resolution and a depth of
focus. In a liquid immersion microscope, a liquid immersion medium
liquid such as oil or water is provided between an objective lens
of the microscope and an object, thereby improving a resolution and
a depth of focus. In a liquid immersion exposure tool for use in a
semiconductor lithography process, a liquid immersion medium fluid
is provided between a lens and a wafer, thereby making it possible
to increase NA (Numerical Aperture) and to increase a depth of
focus. This exposure tool is expected to be a main exposure tool in
manufacturing a semiconductor device in a generation following a 65
nm half pitch generation (WO 99/49504).
[0006] The lens of the liquid immersion optical tool is in contact
with liquid immersion medium fluid for a long time when the liquid
immersion optical tool is used. Thus, there is a problem that
substances generated from the tool, the object surface, and a
structure for guiding the liquid immersion medium fluid react with
each other to adhere to the lens so that the lens surface is
clouded. This clouding of the lens surface is problematic because
it degrades the resolution and the luminescence.
[0007] In addition, there is a problem that the substance or
impurities adhered to the lens or members of the tool contaminate
the object surface.
[0008] In addition, portions having been contacted with the liquid
immersion medium fluid include a liquid immersion head, an object
stage, and a liquid immersion medium fluid supply and discharge
device. There is a problem that, when the liquid immersion optical
tool is used for a long time, impurities adhere to their associated
portions, and the adhered impurities reach an object and
contaminate the object surface.
BRIEF SUMMARY OF THE INVENTION
[0009] According to a first aspect of the present invention, there
is provided a liquid immersion optical tool comprising:
[0010] a light source;
[0011] an optical lens system;
[0012] a stage which moves an object base on which an object is to
be placed;
[0013] a head comprising a liquid immersion medium fluid supply
device and a liquid immersion medium fluid discharge device to
provide a layer of liquid immersion medium fluid between the
optical lens system and the object;
[0014] a fence which limits a region of the layer of liquid
immersion medium fluid; and
[0015] a cleaning device which cleans a portion having been
contacted with the liquid immersion medium fluid by means of a
cleaning solution.
[0016] According to a second aspect of the present invention, there
is provided a cleaning method in the liquid immersion optical tool
comprising a light source; an optical lens system; a stage which
moves an object base on which an object is to be placed; a head
comprising a liquid immersion medium fluid supply device and a
liquid immersion medium fluid discharge device to provide a layer
of liquid immersion medium fluid between the optical lens system
and the object; a fence which limits a region of the layer of
liquid immersion medium fluid; and a cleaning device which cleans a
portion having been contacted with the liquid immersion medium
fluid by means of a cleaning solution,
[0017] wherein the portion having been contacted with the liquid
immersion medium fluid is cleaned for a predetermined time by means
of the cleaning device.
[0018] According to a third aspect of the present invention, there
is provided a semiconductor device manufacturing method in which a
semiconductor device is manufactured by using a liquid immersion
exposure tool, the liquid immersion exposure tool comprising:
[0019] a light source;
[0020] an optical lens system;
[0021] a stage which moves an object base on which an object is to
be placed;
[0022] a head comprising a liquid immersion medium fluid supply
device and a liquid immersion medium fluid discharge device to
provide a layer of liquid immersion medium fluid between the
optical lens system and the object;
[0023] a fence which limits a region of the layer of liquid
immersion medium fluid; and
[0024] a cleaning device which cleans a portion having been
contacted with the liquid immersion medium fluid by means of a
cleaning solution.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0025] FIG. 1 is a view showing a configuration of a liquid
immersion exposure tool according to a first embodiment of the
present invention;
[0026] FIG. 2 is a view showing an example of a cleaning device
according to the first embodiment of the present invention;
[0027] FIG. 3 is a view showing another example of the cleaning
device according to the first embodiment of the present
invention;
[0028] FIG. 4 is a view showing another example of the cleaning
device according to the first embodiment of the present
invention;
[0029] FIG. 5 is a view showing a configuration of a liquid
immersion exposure tool according to a second embodiment of the
present invention; and
[0030] FIG. 6 is a view showing a configuration of a liquid
immersion exposure tool according to a third embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings.
First Embodiment
[0032] FIG. 1 is a view showing an outline configuration of a
liquid immersion exposure tool according to a first embodiment of
the present invention. A reticle stage 31 is provided under a
lighting optical system (light source) 20. A reticle 32 which is a
photo mask is placed on the reticle stage 31. The reticle stage 31
is movable in parallel to an object base 37 (i.e., in a horizontal
direction in the exposure tool). A projection lens system (optical
lens system) 33 is provided under the reticle stage 31. The object
base 37 is provided under the projection lens system 33. A
semiconductor substrate 10 is placed on the object base 37. The
heights of the surface of the semiconductor substrate 10 and part
of the object base 37 near the semiconductor substrate 10 are
almost equal to each other. The object base 37 is movable together
with a stage 34 and the semiconductor substrate 10 in the parallel
direction and the orthogonal direction to the reticle stage 31
(i.e., horizontal and vertical directions in the exposure tool).
The stage 34 can be inclined with respect to the horizontal
plane.
[0033] A fence 35 is mounted at the lower part of the projection
lens system 33. A liquid immersion medium fluid supply and
discharge mechanism is provided at the side of the projection lens
system 33. The supply and discharge mechanism comprises a pair of
liquid immersion medium fluid supply and discharge devices 36 which
supply liquid immersion medium fluid into the fence 35, and
discharge the liquid immersion medium fluid from the fence 35. A
structure of the liquid immersion medium fluid supply and discharge
mechanism is not limited to this structure. When one of the pair of
liquid immersion medium fluid supply and discharge devices 36
functions as a liquid immersion medium supply device, the other
liquid immersion medium fluid supply and discharge device functions
as a liquid immersion medium discharge device. That is, the pair of
liquid immersion medium fluid supply and discharge devices 36
functions complementarily with respect to the supply and discharge
of the liquid immersion medium fluid. During exposure, a space
between the substrate 10 and the projection lens system 33
surrounded by the fence 35 is filled with a layer of liquid
immersion medium fluid, for example, water, supplied from one of
the liquid immersion medium fluid supply and discharge devices 36.
Light of exposure emitted from a light source 20 reaches the
semiconductor substrate 10 placed on the object base 37 via a mask
pattern (i.e., a semiconductor element pattern) of the reticle 32,
the projection lens system 33 and the liquid immersion medium fluid
layer. In this manner, an image of the mask pattern of the reticle
32 is projected on a photo resist film provided on the
semiconductor substrate 10 so that a latent image is formed on the
photo resist film. A structure formed of the fence 35 and the pair
of the light immersion medium fluid supply and discharge devices 36
is called a head.
[0034] A pair of cleaning devices 38 are connected to a pair of the
liquid immersion medium fluid supply and discharge devices 36 in
order to defog the projection lens system 33 and remove impurities
adhered at the time of exposure. The pair of the cleaning devices
38 complementarily supply a cleaning solution into the fence 35 via
the pair of the liquid immersion medium fluid supply and discharge
devices 36. After exposure, the cleaning solution is supplied into
the fence 35, whereby parts or portions having been contacted with
the liquid immersion medium fluid supplied from the liquid
immersion medium fluid supply device 36 are cleaned.
[0035] In a step and scan type exposure tool, all of the patterns
on a photo mask are not collectively transferred to a resist
laminate film. Only a pattern portion of the entire pattern of the
photo mask, which is smaller than the entire pattern of the photo
mask, is collectively transferred. The pattern portion is a slit
shape predetermined area called an exposure field. Exposure is
carried out in a state in which the photo mask and the substrate
are moved at a rate according to a magnification of the projection
optical system, whereby the photo mask and substrate are scanned by
light ray to project the entire pattern of the photo mask onto the
resist laminate film. The term "exposure field" may mean the
predetermined area of the slit shape on the substrate plane which
is optically conjugate with the pattern side on the photo mask.
[0036] A photo mask movement distance is greater than a substrate
movement distance. Thus, in general, the number of photo mask
movements is reduced in order to reduce an exposure process time.
Therefore, it is general that relative movement directions of the
photo mask and substrate are opposite to each other between the
unit exposure regions in which the exposure sequence is
continuous.
[0037] The relative movement directions (scan directions) of the
photo mask and substrate are changed depending on the unit exposure
regions. Therefore, the supply/discharge functions of the pair of
the liquid immersion medium fluid supply and discharge devices 36
are complementarily changed to be supply/discharge according to the
scan direction so that an orientation of the liquid immersion
medium fluid flow is changed. In addition, it is possible that one
of the cleaning devices 38 is operated according to the scan
direction so that a cleaning solution may be supplied from the one
cleaning device 38 into the fence 35 via the corresponding liquid
immersion medium fluid supply and discharge device 36, and the
liquid immersion medium fluid supply and discharge device 36
connected to the other inactive cleaning device 38 is operated so
that the cleaning solution after used may be discharged from the
fence 35 by means of the other liquid immersion medium fluid supply
and discharge device 36.
[0038] A pattern region on the photo mask may be restricted by
means of a diaphragm called a mask blind. A region of a resist film
on which a latent image corresponding to the mask pattern on the
photo mask is to be formed (unit exposure region) may be called an
exposure shot.
[0039] Now, cleaning after exposure will be described. Function
water such as ozone water, ionized water, carbonated water, or
peroxide water is used as a cleaning solution. Alternatively, acid
is used as a cleaning solution. However, when acid is used as a
cleaning solution, the lens surface is corroded so that the lens
performance may change. Thus, it is preferable that function water
be used as a cleaning solution. In addition, cleaning may be
carried out by using water vapor.
[0040] The cleaning solution is supplied into the fence 35 in a
state in which cavities are provided. It is preferable that the
cavities be micro-cavities whose average in diameter is 1 .mu.m or
less. The micro-cavities have long service life, and are unlikely
to disappear before they reach the top of the substrate.
[0041] An ultrasound wave, a water jet, or a cavitation jet can be
used in order to generate cavities in a cleaning solution. For
example, cavities are generated in the cleaning solution by means
of a cavitation jet nozzle shown in FIG. 2 or a venturi tube shown
in FIG. 3. In FIG. 2, reference numeral 41 denotes a high pressure
water nozzle from which a high pressure cleaning solution flows;
reference numeral 42 denotes a low pressure nozzle from which a low
pressure cleaning solution flows; and reference numeral 43 denotes
a mixing portion. In FIG. 3, reference numeral 44 denotes a low
speed flow section, and reference numeral 45 denotes a high speed
flow section.
[0042] The cavitation jet nozzle of FIG. 2 is disclosed in detail
in transactions of Japanese Machinery Society (Edition B), Volume
67, Issue 653 (2001-1), pp. 88, Transaction No. 00 to 0620. In
general, cavitation jet cleaning is a cleaning method efficiently
utilizing a physical force from which there occurs a cavitation
phenomenon usually desired to be avoided in fluid engineering. If a
pressure lower than a saturated vapor pressure is generated in
fluid, cavities occur. The cavities are destroyed if the pressure
in the fluid is returned to a pressure higher than the saturated
vapor pressure, and at this time, a high pressure is momentarily
generated.
[0043] The cavitation jet shown in FIG. 2 is designed so that a
speed difference in water flow occurs on a boundary between the
high speed water discharged from the high pressure nozzle 41 and
the low speed water discharged from the low pressure nozzle 42.
[0044] The venturi tube 38 of FIG. 3 can be used as a device for
generating cavities. When a fluid passes from a nozzle 44 having a
large aperture via a nozzle 45 having a small aperture, cavities
occur in the fluid, since the speed of the fluid changes from a low
speed at the nozzle 44 to a high speed at the nozzle 45.
[0045] In addition, a Pitot tube of FIG. 4 can be used as a device
for generating cavities. In FIG. 4, reference numeral 46 denotes a
high pressure nozzle, and reference numeral 47 denotes a low
pressure nozzle.
[0046] During cleaning, a cleaning solution containing cavities is
supplied from the cleaning device 38 into the fence 35, while the
stage 34 on which the semiconductor substrate 10 is placed is moved
and accordingly the semiconductor substrate 10 is moved. Cleaning
is carried out while moving the semiconductor substrate 10, thereby
making it possible to clean parts or portions having been contacted
with the liquid immersion medium fluid used during exposure. The
parts or portions having been contacted with the liquid immersion
medium fluid include the projection lens system 33, the fence 35,
the object base 37, the stage 34, and the liquid immersion medium
fluid supply and discharge devices 36.
[0047] Now, a cleaning period will be described. For example, after
exposure has been carried out for a predetermined time, a cleaning
process is carried out. In one option, a measuring instrument for
measuring intensity of light transmitting the projection lens
system 33 (exposure light wavelength is preferable) is provided at
the liquid immersion exposure tool, and the light intensity is
measured by means of the measuring instrument after exposure has
started so that a cleaning process may be carried out when the
measured light intensity becomes smaller than a preset value. In
another option, in addition to the above-described measuring
mechanism, there are further provided: a computing mechanism for
computing a lowered quantity of light intensity from information on
the light intensity measured by the measuring mechanism; and a
calculating mechanism for calculating a cleaning period from the
computed lowered quantity of light intensity, for carrying out the
cleaning process in a computed cleaning period.
[0048] In addition, after the cleaning process has been carried
out, a rinse process may be carried out by using a rinse solution
in which no cavities exist. By supplying the rinse solution, the
cleaning solution which remains in the liquid immersion exposure
tool can be removed. Water is used as a rinse solution. For
example, by supplying water as a rinse solution from the liquid
immersion medium fluid supply and discharge device 36, the inside
of the liquid immersion exposure tool is rinsed, thereby removing
the cleaning solution which remains in the liquid immersion
exposure tool.
[0049] A cleaning process is carried out by the above-described
cleaning device, thereby making it possible to remove the
cloudiness of the lens and to recover the resolution and
luminescence. In addition, the substance or impurities adhered to
the lens or members of the tool during exposure can be removed, and
an object surface can be restricted from being contaminated.
[0050] In addition, the liquid immersion exposure tool comprises a
cleaning device, thereby making it possible to facilitate a
cleaning process and to reduce a maintenance time. By reducing the
maintenance time, an equipment operation time is enhanced, and a
manufacturing cost of a manufactured semiconductor element can be
reduced.
Second Embodiment
[0051] The present embodiment shows an example which is different
from that of the liquid immersion exposure tool shown in FIG. 1.
FIG. 5 is a view showing a liquid immersion exposure tool according
to a second embodiment of the present invention. The same elements
are designated by the same reference numerals. A duplicate
description is omitted here.
[0052] In the liquid immersion exposure tool shown in FIG. 5, a
cleaning device 58 is provided to be opposed to a substrate face of
the projection lens system 33. The cleaning device 58 is detachable
from the liquid immersion exposure tool.
Third Embodiment
[0053] The present embodiment shows another example which is
different from that of the liquid immersion exposure tool shown in
FIG. 1. FIG. 6 is a view showing a liquid immersion exposure tool
according to a third embodiment of the present invention. The same
elements are designated by the same reference numerals. A duplicate
description is omitted here.
[0054] In the liquid immersion exposure tool shown in FIG. 6, a
cleaning device 68 is provided at the back surface of the stage 34,
and the cleaning device 68 moves together with the stage 34.
[0055] According to the above-described embodiments, an optical
lens system and a liquid immersion medium fluid discharge device or
the like configuring the liquid immersion exposure tool can be
cleaned, and the cloudiness of the optical lens system can be
prevented. In addition, the impurities reaching an object surface
are reduced, thereby making it possible to prevent contamination on
the object surface.
[0056] While the above embodiments have described examples of the
liquid immersion exposure tool, the above-described cleaning device
is provided at a liquid immersion type microscope for observing a
surface of an object, and a cleaning process may be carried out.
Further, the above-described cleaning device is provided at a
liquid immersion type measuring instrument for measuring a surface
of an object, and a cleaning process may be carried out. That is,
the above-described cleaning device is provided at any liquid
immersion type equipment, and a cleaning process may be carried
out.
[0057] In addition, while, in the above embodiments, water has been
used as a liquid immersion medium fluid used during liquid
immersion, a liquid immersion medium fluid other than water may be
used.
[0058] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *