U.S. patent application number 10/237133 was filed with the patent office on 2003-02-20 for exposure apparatus and air-conditioning apparatus for use with exposure apparatus.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Murayama, Masayuki.
Application Number | 20030035087 10/237133 |
Document ID | / |
Family ID | 27524413 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030035087 |
Kind Code |
A1 |
Murayama, Masayuki |
February 20, 2003 |
Exposure apparatus and air-conditioning apparatus for use with
exposure apparatus
Abstract
Air-conditioning is effected in a chamber of an exposure
apparatus for transferring a pattern formed on a mask onto a
photosensitized substrate by exposure. The chamber houses at least
a part of the exposure apparatus. An impurity-removing filter is
provided for removing gaseous impurities from a stream of ambient
air being introduced into the chamber and/or from a gas stream
recirculating in the chamber. A pair of
impurity-concentration-measuring devices are disposed upstream and
downstream, respectively, of the filter. End-of-life of the filter
is determined based on measurements from the
impurity-concentration-measurin- g devices. Introducing the ambient
air into the chamber is stopped when the
impurity-concentration-measuring device disposed upstream of the
filter has indicated a gaseous impurity concentration above a
predetermined level. The integrity of the airtightness of the
chamber around a negative pressure area in the chamber is sensed.
When a failure in airtightness is detected, the failure is
indicated and/or the recirculation of a gas stream in the chamber
is stopped to prevent the ambient air containing impurities from
leaking into the chamber under the influence of the negative
pressure. In the exposure apparatus, among others the
photosensitized substrate and the illumination optical system are
quite sensitive to impurities, so that dehumidified gas is supplied
to the areas around them. An air-conditioning apparatus for
effecting air-conditioning to the chamber is separated from the
chamber, and an impurity-removing filter element is disposed in a
gas supply duct in the air-conditioning apparatus.
Inventors: |
Murayama, Masayuki;
(Kanagawa-ken, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW.
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
27524413 |
Appl. No.: |
10/237133 |
Filed: |
September 9, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10237133 |
Sep 9, 2002 |
|
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09266873 |
Mar 12, 1999 |
|
|
|
09266873 |
Mar 12, 1999 |
|
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08824908 |
Mar 26, 1997 |
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Current U.S.
Class: |
355/30 ; 355/53;
355/67 |
Current CPC
Class: |
G03F 7/70858 20130101;
G03F 7/70933 20130101; G03F 7/70866 20130101 |
Class at
Publication: |
355/30 ; 355/53;
355/67 |
International
Class: |
G03B 027/52 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 1996 |
JP |
72894/1996 |
Mar 28, 1996 |
JP |
73776/1996 |
Apr 3, 1996 |
JP |
81300/1996 |
Apr 9, 1996 |
JP |
86711/1996 |
Claims
What is claimed is:
1. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; an ambient
air introducing unit for introducing ambient air into said chamber;
an impurity-removing filter for removing gaseous impurities from
one of gas streams including a stream of ambient air being
introduced into said chamber and a gas stream recirculating in said
chamber; a pair of impurity-concentration-measuring devices
disposed upstream and downstream, respectively, of said
impurity-removing filter; and a filter end-of-life determination
device for determining end-of-life of said impurity-removing filter
based on measurements from said impurity-concentration-measuring
device disposed upstream of said impurity-removing filter and
measurements from said impurity-concentration-measuring device
disposed downstream of said impurity-removing filter.
2. An exposure apparatus according to claim 1, wherein: said
impurity-removing filter is arranged for removing gaseous
impurities from said stream of ambient air being introduced into
said chamber, and wherein said exposure apparatus further comprises
a control device for stopping operation of said ambient air
introducing unit when said impurity-concentration-measuring device
disposed upstream of said impurity-removing filter has indicated a
gaseous impurity concentration above a predetermined level.
3. An exposure apparatus according to claim 1, wherein: each of
said impurity-concentration-measuring devices measures
concentration of at least one of impurities including ammonium ion
(NH.sub.4.sup.+) and sulfate ion (SO.sub.4.sup.2-).
4. An exposure apparatus according to claim 1, wherein: each of
said impurity-concentration-measuring devices measures
concentration of organosilicon compounds.
5. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; an ambient
air introducing unit for introducing ambient air into said chamber;
an impurity-removing filter for removing gaseous impurities from a
stream of ambient air being introduced into said chamber; an
impurity-concentration-measuring device disposed upstream of said
ambient air introducing unit; and a control device for stopping
operation of said ambient air introducing unit when said
impurity-concentration-measuring device has indicated a gaseous
impurity concentration above a predetermined level.
6. An exposure apparatus according to claim 5, wherein: said
impurity-concentration-measuring device measures concentration of
at least one of impurities including ammonium ion (NH.sub.4.sup.+)
and sulfate ion (SO.sub.4.sup.2-).
7. An exposure apparatus according to claim 5, wherein: said
impurity-concentration-measuring device measures concentration of
organosilicon compounds.
8. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus, said
chamber having an air inlet for introducing ambient air into said
chamber; a gas-recirculating device disposed in said chamber for
producing a gas stream recirculating in said chamber while
generating a negative pressure area near said air inlet; and an
airtightness-integrity-sensing device for sensing integrity of
airtightness of said chamber around said negative pressure
area.
9. An exposure apparatus according to claim 8, further comprising:
a control device for taking, when a failure of integrity of
airtightness of said chamber is detected by means of said
airtightness-integrity-sensing device, at least one of actions
including providing an alarm of a failure of integrity of
airtightness and stopping operation of said gas-recirculating
device.
10. An exposure apparatus according to claim 8, wherein: said
airtightness-integrity-sensing device comprises a differential
pressure gauge.
11. An exposure apparatus according to claim 8, wherein: said
airtightness-integrity-sensing device comprises an anemometer
disposed in said air inlet of said chamber.
12. An exposure apparatus according to claim 8, further comprising:
a first gaseous-impurity-removing device disposed in said air inlet
of said chamber; and a second gaseous-impurity-removing device
disposed in a flow path of said gas stream recirculating in said
chamber.
13. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus, said
chamber having an air inlet for introducing ambient air into said
chamber; a gas-recirculating device disposed in said chamber for
producing a gas stream recirculating in said chamber while
generating a negative pressure area near said air inlet; an
airtightness-integrity-sensing device for sensing integrity of
airtightness of said chamber around said negative pressure area;
and a control device for taking, when a failure of integrity of
airtightness of said chamber is detected by means of said
airtightness-integrity-sensing device, at least one of actions
including providing an alarm of a failure of integrity of
airtightness and stopping operation of said gas-recirculating
device.
14. An exposure apparatus according to claim 13, wherein: said
airtightness-integrity-sensing device comprises a differential
pressure gauge.
15. An exposure apparatus according to claim 13, wherein: said
airtightness-integrity-sensing device comprises an anemometer
disposed in said air inlet of said chamber.
16. An exposure apparatus according to claim 13, further
comprising: a first gaseous-impurity-removing device disposed in
said air inlet of said chamber; and a second
gaseous-impurity-removing device disposed in a flow path of said
gas stream recirculating in said chamber.
17. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus, said
chamber having an air inlet for introducing ambient air into said
chamber; a gas-recirculating device disposed in said chamber for
producing a gas stream recirculating in said chamber while
generating a negative pressure area near said air inlet; a
differential pressure gauge for sensing integrity of airtightness
of said chamber around said negative pressure area; a control
device for taking, when a failure of integrity of airtightness of
said chamber is detected by means of said differential pressure
gauge, at least one of actions including providing an alarm of a
failure of integrity of airtightness and stopping operation of said
gas-recirculating device; a first gaseous-impurity-removing device
disposed in said air inlet of said chamber; and a second
gaseous-impurity-removing device disposed in a flow path of said
gas stream recirculating in said chamber.
18. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus, said
chamber having an air inlet for introducing ambient air into said
chamber; a gas-recirculating device disposed in said chamber for
producing a gas stream recirculating in said chamber while
generating a negative pressure area near said air inlet; an
anemometer disposed in said air inlet of said chamber for sensing
integrity of airtightness of said chamber around said negative
pressure area; a control device for taking, when a failure of
integrity of airtightness of said chamber has been detected by
means of said anemometer, at least one of actions including
providing an alarm of a failure of integrity of airtightness and
stopping operation of said gas-recirculating device; a first
gaseous-impurity-removing device disposed in said air inlet of said
chamber; and a second gaseous-impurity-removing device disposed in
a flow path of said gas stream recirculating in said chamber.
19. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; and a gas
supply device for supplying dehumidified gas to a desired area
around said exposure apparatus.
20. An exposure apparatus according to claim 19, wherein: said
dehumidified gas comprises dehumidified ambient air.
21. An exposure apparatus according to claim 19, further
comprising: a gaseous-impurity-removing filter and a dehumidifier,
wherein said dehumidified gas is generated by causing a gas stream
to pass through said gaseous-impurity-removing filter and then
through said dehumidifier.
22. An exposure apparatus according to claim 19, wherein: said
desired area around said exposure apparatus includes an area of
said illumination optical system.
23. An exposure apparatus according to claim 19, wherein: said
desired area around said exposure apparatus includes an area on and
around said photosensitized substrate.
24. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; and a gas
supply device for supplying dehumidified gas to an area of said
illumination optical system; wherein said dehumidified gas is
generated by causing a gas stream to pass through a
gaseous-impurity-removing filter and then through a
dehumidifier.
25. An exposure apparatus according to claim 24, wherein: said
dehumidified gas comprises dehumidified ambient air.
26. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; and a gas
supply device for supplying dehumidified gas to an area on and
around said photosensitized substrate; wherein said dehumidified
gas is generated by causing a gas stream to pass-through a
gaseous-impurity-removing filter and then through a
dehumidifier.
27. An exposure apparatus according to claim 26, wherein: said
dehumidified gas comprises dehumidified ambient air.
28. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; a gas
supply device for supplying dehumidified gas to an area on and
around said photosensitized substrate; and an antistatic device
provided for parts which come into contact with said
photosensitized substrate in a local atmosphere in said area to
which said dehumidified gas is supplied.
29. An exposure apparatus according to claim 28, wherein: said
dehumidified gas comprises dehumidified ambient air.
30. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; a gas
supply device for supplying dehumidified gas to an area on and
around said photosensitized substrate; and a humidity-measuring
device for measuring humidity of a local atmosphere in said area on
and around said photosensitized substrate; and a control device for
controlling said gas supply device based on humidity data from said
humidity-measuring device.
31. An exposure apparatus according to claim 30, further
comprising: a gaseous-impurity-removing filter and a dehumidifier,
wherein said dehumidified gas is generated by causing a gas stream
to pass through said gaseous-impurity-removing filter and then
through said dehumidifier.
32. An exposure apparatus according to claim 30, wherein: said
dehumidified gas comprises dehumidified ambient air.
33. An exposure apparatus according to claim 30, wherein: an
antistatic device is provided for parts which come into contact
with said photosensitized substrate in a local atmosphere in said
area to which said dehumidified gas is supplied.
34. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; a gas
supply device for supplying dehumidified gas to an area on and
around said photosensitized substrate; a sensing device for sensing
the existence of said photosensitized substrate; and a control
device for controlling said gas supply device based on sensing data
from said sensing device in order to adjust the supply of said
dehumidified gas depending on presence/absence of said
photosensitized substrate.
35. An exposure apparatus according to claim 34, further
comprising: a gaseous-impurity-removing filter and a dehumidifier,
wherein said dehumidified gas is generated by causing a gas stream
to pass through said gaseous-impurity-removing filter and then
through said dehumidifier.
36. An exposure apparatus according to claim 34, wherein: said
dehumidified gas comprises dehumidified ambient air.
37. An exposure apparatus according to claim 34, wherein: an
antistatic device is provided for parts which come into contact
with said photosensitized substrate in a local atmosphere in said
area to which said dehumidified gas is supplied.
38. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into said mask; an exposure unit for making exposure
of a photosensitized substrate in order to transfer said pattern
formed on said mask onto said photosensitized substrate; a chamber
for housing at least a part of said exposure apparatus; a gas
supply device for supplying dehumidified gas to an area on and
around said photosensitized substrate; a humidity-measuring device
for measuring humidity of a local atmosphere in said area on and
around said photosensitized substrate; a sensing device for sensing
the existence of said photosensitized substrate; and a control
device for controlling said gas supply device based on humidity
data from said humidity-measuring device and sensing data from said
sensing device in order to adjust supply of said dehumidified gas
depending on presence/absence of said photosensitized
substrate.
39. An exposure apparatus according to claim 38, further
comprising: a gaseous-impurity-removing filter and a dehumidifier,
wherein said dehumidified gas is generated by causing a gas stream
to pass through said gaseous-impurity-removing filter and then
through said dehumidifier.
40. An exposure apparatus according to claim 38, wherein: said
dehumidified gas comprises dehumidified ambient air.
41. An exposure apparatus according to claim 38, wherein: an
antistatic device is provided for parts which come into contact
with said photosensitized substrate in a local atmosphere in said
area to which said dehumidified gas is supplied.
42. An air-conditioning apparatus for removing impurities from gas,
adapted for effecting air-conditioning to a semiconductor device
factory and/or an exposure apparatus, comprising: a body housing; a
gas supply duct housed in said body housing; and an
impurity-removing filter element disposed inside said gas supply
duct.
43. An air-conditioning apparatus according to claim 42, wherein:
said impurity-removing filter element comprises a hollow
cylindrical body.
44. An air-conditioning apparatus according to claim 42, wherein:
said impurity-removing filter element comprises a bellows wall.
45. An air-conditioning apparatus according to claim 42, wherein:
said impurity-removing filter element is so supported by a support
member as to be kept out of contact with an inner wall of said gas
supply duct.
46. An air-conditioning apparatus for removing impurities from gas,
adapted for effecting air-conditioning to a semiconductor device
factory and/or an exposure apparatus, comprising: a body housing; a
gas supply duct housed in said body housing; and an
impurity-removing filter element comprising a hollow cylindrical
body and disposed inside said gas supply duct; wherein said
impurity-removing filter element is so supported by a support
member as to be kept out of contact with an inner wall of said gas
supply duct.
47. An air-conditioning apparatus for removing impurities from gas,
adapted for effecting air-conditioning to a semiconductor device
factory and/or an exposure apparatus, comprising: a body housing; a
gas supply duct housed in said body housing; and an
impurity-removing filter element comprising a bellows wall and
disposed inside said gas supply duct; wherein said
impurity-removing filter element is so supported by a support
member as to be kept out of contact with an inner wall of said gas
supply duct.
48. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into a mask; an exposure unit for making exposure of a
photosensitized substrate in order to transfer said pattern formed
on said mask onto said photosensitized substrate; a chamber for
housing at least a part of said exposure apparatus; and an
air-conditioning apparatus for effecting conditioning of gas in
said chamber, said air-conditioning apparatus being disposed
outside said chamber and comprising a body housing, a gas supply
duct housed in said body housing and an impurity-removing filter
element disposed inside said gas supply duct.
49. An exposure apparatus according to claim 48, wherein: said
impurity-removing filter element comprises a hollow cylindrical
body.
50. An exposure apparatus according to claim 48, wherein: said
impurity-removing filter element comprises a bellows wall.
51. An exposure apparatus according to claim 48, wherein: said
impurity-removing filter element is so supported by a support
member as to be kept out of contact with an inner wall of said gas
supply duct.
52. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into a mask; an exposure unit for making exposure of a
photosensitized substrate in order to transfer said pattern formed
on said mask onto said photosensitized substrate; a chamber for
housing at least a part of said exposure apparatus; and an
air-conditioning apparatus for effecting conditioning of gas in
said chamber, said air-conditioning apparatus being disposed
outside said chamber and comprising a body housing, a gas supply
duct housed in said body housing and an impurity-removing filter
element disposed inside said gas supply duct, said
impurity-removing filter element comprises a hollow cylindrical
body; wherein said impurity-removing filter element is so supported
by a support member as to be kept out of contact with an inner wall
of said gas supply duct.
53. An exposure apparatus for transferring a pattern formed on a
mask onto a photosensitized substrate by exposure, comprising: a
light source for emitting a light beam having a wavelength falling
in a range from ultraviolet to deep ultraviolet radiation; an
illumination optical system for directing said light beam from said
light source into a mask; an exposure unit for making exposure of a
photosensitized substrate in order to transfer said pattern formed
on said mask onto said photosensitized substrate; a chamber for
housing at least a part of said exposure apparatus; and an
air-conditioning apparatus for effecting conditioning of gas in
said chamber, said air-conditioning apparatus being disposed
outside said chamber and comprising a body housing, a gas supply
duct housed in said body housing and an impurity-removing filter
element disposed inside said gas supply duct, said
impurity-removing filter element comprises a bellows wall; wherein
said impurity-removing filter element is so supported by a support
member as to be kept out of contact with an inner wall of said gas
supply duct.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an exposure apparatus used
for generating fine patterns for various products including
semiconductor circuits (Ics), liquid crystal displays (LCDs) and
the like, as well as to air-conditioning apparatus for use with
such exposure apparatus. More particularly, the present invention
relates to apparatus for effecting air-conditioning of a chamber
which houses all or some of the components of an exposure apparatus
for transferring a pattern formed on a mask onto a photosensitized
substrate by exposure, including a light source, an illumination
optical system, an exposure unit and others, in order to eliminate
or minimize any harmful effects of impurities in the chamber.
[0002] A clean room used in fabrication of semiconductor devices is
provided with an air purification system for removing particulate
contaminants from the air in the room, and such air purification
system typically uses high efficiency particulate air (HEPA)
filters and/or ultra low penetration air (ULPA) filters. Various
equipment and apparatus are used in the fabrication of
semiconductor devices, among which exposure apparatus using
ultraviolet (UV) light or deep-ultraviolet (DUV) light for exposure
have been commonly used. In an exposure apparatus of this type,
gaseous impurities in the surrounding atmosphere may undergo
certain chemical and/or physical changes and form adhesive
substances that tend to adhere to the surface of glass optical
elements such as lenses and mirrors, resulting in blurring and/or
reduced transmittance of the elements. For example, ammonium ions
(NH.sub.4) and sulfur oxides (SOx), two typical, harmful gaseous
impurities, form an adhesive layer of ammonium sulfate
((NH.sub.4).sub.2SO.sub.4) on a surface of a glass optical
element.
[0003] Thus, for long-term, continuous and effective operation of
an exposure apparatus using a UV or DUV light source, it is
required that the space along the light path of the light beam from
the light source be filled with a gas having no sensitivity to UV
or DUV radiation such as nitrogen and helium, or with an
environmental gas (ambient air) having any harmful gaseous
impurities removed therefrom. A known technique used for this
purpose is to confine the space along the light path of the
exposure light beam to an airtight chamber, and fill the chamber
with a gas having no sensitivity to exposure radiation. The gas is
supplied from a suitable gas supply device such as a gas cylinder
or a gas storage tank. Another known technique used for this
purpose is to supply ambient air outside the exposure apparatus to
the illumination optical system in the exposure apparatus, after
the air has been passed through an impurity-removing filter such as
a chemical filter to remove any harmful gaseous impurities from the
air.
[0004] Chemical filters can remove, unlike HEPA and ULPA filters,
gaseous impurities from the environmental gas. Various chemical
filters are commonly used, including those using fibrous or
granulate activated carbon, those utilizing ion exchange reaction
provided by various ion exchange resins, and those using fibrous
activated carbon with some sort of agent added. Examples of
chemical filters utilizing an ion exchange reaction are products
bearing a trademark "EPIX" available from Ebara Corporation in
Japan. Examples of chemical filters using fibrous activated carbon
with some sort of agent added are products bearing a trademark
"CLEAN SORB" available from Kondo Kogyo Co, Ltd. in Japan.
[0005] Various resists are used in photolithographic process in
order to form patterns on a substrate, among which chemically
sensitized resists have become common recently. In general,
chemically sensitized resists consist of a resin, a photosensitive
acid generator (PAG), and either a dissolution promotor (for
positive resists) or a cross-linking agent (for negative resists).
When exposed to exposure radiation, the photosensitive acid
generator generates an acid. During the post-exposure baking
process, the acid acts as a catalyst. In the case of a positive
resist, the catalyst increases the activity of the dissolution
promotor to break cross-links between the polymer molecules. In the
case of a negative resist, the catalyst increases the activity of
the cross-linking agent to form cross-links between the polymer
molecules. In both cases, a pattern is formed with the aid of the
catalyst during the following development process, in which a
positive resist using a dissolution promotor forms positive
patterns while a negative resist using a cross-linking agent forms
negative patterns on the substrate. Examples of the positive
chemically amplified resists are products bearing a trademark
"FH-EX1" available from Fuji-Hunt Corporation. Examples of negative
chemically amplified resists are products bearing a trademark "XP"
available from Shipray Corporation.
[0006] When a chemically sensitized resist is used, some basic
gaseous impurities (ammonia and amines, for example) in the local
atmosphere around the substrate and acid generated from the
photosensitive acid generator may cause a neutralization reaction
during the time interval between exposure to post-exposure baking,
resulting in reduced sensitivity. Further, in the case of a
positive resist this also results in the formation of a
dissolution-resistant surface layer, which may affect the pattern
transfer process. A commonly used technique used to avoid the
adverse effects of such gaseous impurities is to fill the process
atmosphere for the sequence of processes from the application
process of chemically sensitized resist on a substrate (or from the
exposure process of a substrate applied with chemically amplified
resist) to post-exposure baking with a clean gas containing no
impurities.
[0007] More specifically, where this technique is used to avoid
adverse effects of gaseous impurities, a chamber is used to house
the entire exposure apparatus or at least a critical part thereof.
The chamber has an air inlet through which ambient air is
introduced into the chamber. The air inlet is provided with a
gaseous-impurity-removing device, such as a chemical filter, for
preventing any gaseous impurities from entering the chamber. In
addition, the chamber is provided with a second chemical filter for
removing any gaseous impurities from a gas stream recirculating in
the chamber.
[0008] However, the above prior art technique suffers from several
problems as described below. First, a problem arises relating to
the filters used. Chemical filters are commonly used as
gaseous-impurity-removing devices. The impurity removal efficiency
of a chemical filter, however, tends to gradually decrease as more
gaseous impurities are caught and removed by the filter. The rate
of decrease in the impurity removal efficiency depends on several
factors including the concentrations of the gaseous impurities
contained in the environmental gas in which the chemical filter is
used, as well as the humidity of the environmental gas. An even
rate of operation of the semiconductor device factory equipped with
an exposure apparatus may cause significant changes in the
concentrations of the gaseous impurities in the environmental air
of the exposure apparatus.
[0009] An impurity-removing filter element has to be replaced when
its impurity removal efficiency has dropped below a minimum
acceptable level. Typically, the life of a filter element is
defined as the point of time when its impurity removal efficiency
has decreased to a predetermined threshold level. However, the rate
of degradation of a filter element depends on environmental
conditions as described above, and impurity concentrations in
different environments of respective filter elements are quite
different from each other, so that it is difficult to predict with
precision when a particular filter element has reached the end of
its effective life.
[0010] In order to determine the impurity removal efficiency of a
filter element used with an exposure apparatus, it is required to
set a gas-concentration-measuring device on the exposure apparatus
for measurement at regular intervals. However, this may result in
an increase in the nonworking time of the exposure apparatus
because of the necessary time for setting and removal of the
gas-concentration-measuring device on and away from the exposure
apparatus as well as of the time for the concentration measurement
itself. Further, where a plurality of exposure apparatus are
disposed in a single clean room, the impurity concentration in the
environment of one exposure apparatus may be quite different from
that of another exposure apparatus, resulting in different rates of
degradation of the filter elements used with them. Therefore, for
the plurality of exposure apparatus, the impurity concentrations
have to be measured individually, which results in a troublesome
measurement work and may often result in a reduced
productivity.
[0011] In addition, for an exposure apparatus using a chemical
filter for introducing ambient air into the apparatus through the
filter, if an abrupt and significant increase occurs in the gaseous
impurity concentration in the ambient air outside the apparatus,
then the chemical filter may not completely remove gaseous
impurities from the air stream being introduced in the apparatus,
resulting in possible contamination inside the apparatus and/or the
formation of a dissolution-resistant layer on the surface of the
chemically sensitized resist layer on the substrate being processed
in the apparatus.
[0012] The above prior art technique also suffers from another
problem relating to the integrity of the airtightness of the
chamber which houses the entire exposure apparatus or a part
thereof. The chamber is provided with an gas-delivering fan for
producing a gas stream recirculating in the chamber, with the
result that a negative pressure area is generated in the chamber
upstream of the gas-delivering fan. Further, the chamber has an air
inlet through which the ambient air is introduced into the chamber
by means of suction produced by the negative pressure area near the
air inlet. The chamber has a wall composed of panels, which joined
to each other in such a way as to ensure airtightness of the
chamber. In particular, such a portion of the chamber wall that is
around the negative pressure area must be kept airtight, and the
panels constituting that wall portion are typically joined with
each other with appropriate sealant (silicone sealant, for example)
applied to the joints between the panels. The airtightness is
required because all the air introduced into the chamber must pass
through the air inlet, i.e., no air must not be allowed to leak
into the chamber through any other path such as a defect in a joint
between two panels.
[0013] However,the airtightness of the chamber may be lost due to
degradation or a failure of the sealant applied to the joints
between the panels, such as chipping and cracking of the sealant.
If the sealant suffers from such chips and/or cracks that are very
small or hidden behind some other components of the exposure
apparatus, the operator of the apparatus can not locate such
defects in the sealant. This may allow leakage of ambient air
containing impurities into the chamber, resulting in accelerated
degradation of the gaseous-impurity-removing filter used in the
chamber and/or contamination inside the chamber.
[0014] It is also known that a problem arises due to moisture
contained in the gas in the chamber, as follows. Most of the amount
of impurities contained in the ambient air is adsorbed on the
surface of dust and water particulates floating in the ambient air.
The ambient air in a building of a typical semiconductor device
factory as well as the gas in the local atmosphere in the chamber
of an exposure apparatus equipped in such factory has relatively
large particles already removed therefrom by some sort of
particulate filters such as ULPA filters. On the other hand, the
humidity of such ambient air or gas is maintained at a level
typically in the range of 30 to 50%. Any humidity level in this
range allows the existence of water particulates floating in the
air or gas, to which ions and other impurities are adsorbed,
resulting in possible contamination inside the exposure
apparatus.
[0015] Hexamethyldisilazane (HMDS), which is commonly used in
semiconductor processes, tends to react with moisture in air or gas
to undergo hydrolysis into trimethylsilanol and ammonia, as
follows. 1
[0016] HMDS+moisture.fwdarw.trimethylsilanol+ammonia
[0017] The resultant ammonia may react with the acid generated by
PAG in the resist, which reaction affects the image formation
properties of the resist. It is also known that some sort of
amines, such as NMP, can affect the image formation properties of
resists. In addition, it is very likely that various other matters
which may react with moisture in air or gas to form harmful
impurities are used in semiconductor processes.
[0018] Further, even moisture in ambient air itself may affect the
image formation properties of resists. However, no special
consideration has been given to humidity so far.
[0019] It is also noted in this relation that the complete removal
or elimination of the moisture from the air in a semiconductor
device factory or from the gas in the exposure apparatus equipped
in the factory tends to cause a static discharge problem which may
affect the exposure apparatus.
[0020] Often, either helium gas or nitrogen gas generated by
vaporization of liquid nitrogen is used as a dry gas to be filled
in the exposure apparatus. In such a case, because the exposure
apparatus has to be continuously supplied with the dry gas in order
to keep the inside of the apparatus filled with the gas,
considerable consumption of the supplied gas arises, resulting in a
large expenditure and even in a possible decrease in oxygen
concentration in the environmental air in the factory, which may
put workers at risk in the factory.
[0021] A further known problem arises in relation to the chemical
filter elements which have to be housed in respective boxes and
disposed at various places, such as inside the exposure apparatus,
around the apparatus and/or in the flow path of the supplied gas.
This problem is described with reference to FIG. 26 of the
accompanying drawings.
[0022] FIG. 26 is a schematic representation showing a typical
prior art exposure apparatus. The exposure apparatus has an
exposure unit comprising a light source 200, a first mirror 201a,
an illumination optical system 202, a second mirror 201b, a
projection lens 203 and an XY-stage 204. The exposure unit serves
to transfer a pattern formed on the reticle 205 onto a
photosensitized substrate 207 placed on the XY-stage 204. The
exposure unit is housed in a chamber 208.
[0023] The air in the chamber 208 is temperature-controlled by an
air-conditioning apparatus 220, and delivered through an
impurity-removing unit including a chemical filter 209 and a
particulate filter 210 such as a HEPA filter. The filters 209 and
210 have respective filter boxes in which filter elements are
housed. The filters 209 and 210 are disposed one after the other
along the flow path of the air stream passing therethrough. The air
stream flows out of the impurity-removing unit into the local
atmosphere around the exposure unit, and then passes through a
return path 211 and again is temperature-controlled by the
air-conditioning apparatus 220 so as to recirculate in the chamber
208. The air-conditioning apparatus 220 includes components such as
a temperature regulator 221 and a gas-delivering fan 222, which are
connected through ducts 223a and 223b with the chamber 208. The
return path 211 is upstream of the air-conditioning apparatus 220
and defines therein a negative pressure area with respect to the
ambient air pressure outside the chamber 208. During the operation
of the exposure apparatus, certain amounts of air repetitively leak
out of the chamber from the local atmosphere around the exposure
unit, and the corresponding amounts of air are repetitivey drawn
into the chamber 208 through an air inlet 212 and an
impurity-removing filter element 213 under the infuluence of the
negative pressure in the above mentioned area.
[0024] As shown, an gaseous-impurity-removing filter, such as a
chemical filter, comprises a filter element and a filter box for
housing the filter element. The filter box is bulky and requires a
relatively large installation space. In the case where an filter
boxe is disposed in the exposure apparatus, the space in the
apparatus available for other purposes is reduced and/or the
exposure apparatus must have the larger volume for the filter
box.
SUMMARY OF THE INVENTION
[0025] In view of the foregoing, it is a first object of the
present invention to provide an exposure apparatus, in which
end-of-life of a chemical filter element used in the exposure
apparatus may be determined with precision, maintenance services
such as replacement and/or cleaning of the chemical filter element
may be performed in good time, and impurities in ambient air may be
effectively prevented from entering the apparatus even when the
impurity concentration in ambient air in the environment of the
apparatus has made an abrupt and significant increase during the
operation of the apparatus.
[0026] It is a second object of the present invention to provide an
exposure apparatus with a chamber, in which any failure of the
integrity of the airtightness of the chamber (which may be caused
by some defect or another) will never lead to a leakage of the
ambient air into the chamber through such defect, which could
otherwise result in an inconvenience increase in the gaseous
impurity concentration in the chamber.
[0027] It is a third object of the present invention to provide an
exposure apparatus, in which a portion of the apparatus that is
sensitive to impurities in ambient air may be placed in a local
atmosphere of dehumidified air.
[0028] It is a fourth object of the present invention to
miniaturize an exposure apparatus by minimizing the space occupied
by impurity-removing filter(s) used.
[0029] According to a first embodiment of the present invention for
achieving the first object described above, there is provided an
exposure apparatus for transferring a pattern formed on a mask onto
a photosensitized substrate by exposure, comprising: a light source
for emitting a light beam having a wavelength falling in a range
from ultraviolet to deep ultraviolet radiation; an illumination
optical system for directing the light beam from the light source
into the mask; an exposure unit for making exposure of a
photosensitized substrate in order to transfer the pattern formed
on the mask onto the photosensitized substrate; a chamber for
housing at least a part of the exposure apparatus; an ambient air
introducing unit for introducing ambient air into the chamber; an
impurity-removing filter for removing gaseous impurities from one
of the gas streams including a stream of ambient air being
introduced into the chamber and a gas stream recirculating in the
chamber; a pair of impurity-concentration-measuring devices
disposed upstream and downstream, respectively, of the
impurity-removing filter; and a filter end-of-life determination
device for determining end-of-life of the impurity-removing filter
based on measurements from the impurity-concentration-measuring
device disposed upstream of the impurity-removing filter and
measurements from the impurity-concentration-measuring device
disposed downstream of the impurity-removing filter.
[0030] In the exposure apparatus according to the first embodiment
of the present invention for achieving the first object described
above, the impurity-removing filter may be preferably arranged for
removing gaseous impurities from the stream of ambient air being
introduced into the chamber, and wherein the exposure apparatus may
preferably further comprise a control device for stopping operation
of the ambient air introducing unit when the
impurity-concentration-measuring device disposed upstream of the
impurity-removing filter has indicated a gaseous impurity
concentration above a predetermined level.
[0031] According to a second embodiment of the present invention
for achieving the first object described above, there is provided
an exposure apparatus for transferring a pattern formed on a mask
onto a photosensitized substrate by exposure, comprising: a light
source for emitting a light beam having a wavelength falling in a
range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing the light beam from the
light source into the mask; an exposure unit for making exposure of
a photosensitized substrate in order to transfer the pattern formed
on the mask onto the photosensitized substrate; a chamber for
housing at least a part of the exposure apparatus; an ambient air
introducing unit for introducing ambient air into the chamber; an
impurity-removing filter for removing gaseous impurities from a
stream of ambient air being introduced into the chamber; an
impurity-concentration-measuring device disposed upstream of the
ambient air introducing unit; and a control device for stopping
operation of the ambient air introducing unit when the
impurity-concentration-measuring device has indicated a gaseous
impurity concentration above a predetermined level.
[0032] In the first and second embodiments of the present invention
for achieving the first object described above, the
impurity-concentration-me- asuring device may measure
concentrations of at least one of impurities including ammonium ion
(NH.sub.4.sup.+) and sulfate ion (SO.sub.4.sup.2-), or may measure
concentration of organosilicon compounds, such as siloxanes.
[0033] According to a third embodiment of the present invention for
achieving the second object described above, there is provided an
exposure apparatus for transferring a pattern formed on a mask onto
a photosensitized substrate by exposure, comprising: a light source
for emitting a light beam having a wavelength falling in a range
from ultraviolet to deep ultraviolet radiations; an illumination
optical system for directing the light beam from the light source
into the mask; an exposure unit for making exposure of a
photosensitized substrate in order to transfer the pattern formed
on the mask onto the photosensitized substrate; a chamber for
housing at least a part of the exposure apparatus, the chamber
having an air inlet for introducing ambient air into the chamber; a
gas-recirculating device disposed in the chamber for producing a
gas stream recirculating in the chamber while generating a negative
pressure area near the air inlet; and an airtightness-integrity--
sensing device for sensing integrity of airtightness of the chamber
around the negative pressure area.
[0034] In the exposure apparatus according to the third embodiment
of the present invention for achieving the second object described
above, it may be preferable that the exposure apparatus further
comprises a control device for taking, when a failure of integrity
of airtightness of the chamber is detected by means of the
airtightness-integrity-sensing device, at least one of actions
including providing an alarm of a failure of integrity of
airtightness and stopping operation of the gas-recirculating
device.
[0035] This may effectively prevent an accelerated degradation of
any impurity-removing filter disposed in the chamber.
[0036] Further, in the exposure apparatus according to the third
embodiment of the present invention for achieving the second object
described above, the airtightness-integrity-sensing device may
comprise a differential pressure gauge or an anemometer, the
anemometer may be disposed in the air inlet of the chamber. Both of
the differential pressure gauge and the anemometer may be used in
parallel. If a failure or defect occurs in the sealant used for the
chamber, the ambient air leaks into the chamber through the defect,
resulting in the corresponding change in the flow rate of the air
stream being introduced through the air inlet into the chamber.
Thus, the integrity of the airtightness of the chamber may be
administrated by sensing the change in the flow rate.
[0037] It is preferable that a first gaseous-impurity-removing
device is disposed in the air inlet of the chamber and a second
gaseous-impurity-removing device is disposed in a flow path of the
gas stream recirculating in the chamber. Each of the
gaseous-impurity-removin- g devices may comprise a chemical filter.
Chemical filters can remove, unlike HEPA and ULPA filters, gaseous
impurities from the environmental gas. Various chemical filters are
commonly used including those using fibrous or granulate activated
carbon, those utilizing ion exchange reaction provided by various
ion exchange resins, those using fibrous activated carbon with some
sort of agent added. Examples of the chemical filters utilizing ion
exchange reaction are the products having a trademark "EPIX"
available from Ebara Corporation in Japan. Examples of the chemical
filters using fibrous activated carbon with some sort of agent
added are the products bearing a trademark "CLEAN SORB" available
from Kondo Kogyo Co, Ltd. in Japan.
[0038] This arrangement may be also used to make an inspection of
the sealing work of the chamber at the completion of the chamber,
and in particular an inspection of the sealant applied to the
joints between panels constituting the chamber wall.
[0039] According to a fourth embodiment of the present invention
for achieving the third object described above, there is provided
an exposure apparatus for transferring a pattern formed on a mask
onto a photosensitized substrate by exposure, comprising: a light
source for emitting a light beam having a wavelength falling in a
range from ultraviolet to deep ultraviolet radiations; an
illumination optical system for directing the light beam from the
light source into the mask; an exposure unit for making exposure of
a photosensitized substrate in order to transfer the pattern formed
on the mask onto the photosensitized substrate; a chamber for
housing at least a part of the exposure apparatus; and a gas supply
device for supplying dehumidified gas to a desired area around the
exposure apparatus.
[0040] However, when the moisture in an semiconductor device
factory or in an exposure apparatus is completely eliminated,
electrostatic discharges are likely to occur. Semiconductor devices
are subject to failures caused by electrostatic discharge, such as
destruction of the chips and functional failures of circuits in the
chips, so that any electrostatic charge may result in a reduced
yield of the semiconductor devices. On the other hand, filing all
the area in the apparatus all the time with some sort of dry gas is
very costly.
[0041] Therefore, in this embodiment, it is preferable that only
the local atmosphere around the photosensitized substrate and/or
the local atmosphere around the illumination optical system are/is
filled with the dehumidified gas. Further, the dehumidified gas may
preferably comprise dehumidified ambient air. One typical method of
dehumidifying the ambient air is to cool an amount of the ambient
air to a very low temperature about -30 to -40.degree. C. so as to
freeze any moisture in the air into ice and remove from the air. A
sensing device for sensing the existence of the photosensitized
substrate may be provided and the supply of the dehumidified gas
may be controlled depending on presence/absence of the
photosensitized substrate. The dehumidified gas may be generated by
causing a gas stream to pass through a gaseous-impurity-removing
filter and then through a dehumidifier. In the case where a
plurality of exposure apparatuses are equipped in a factory, the
dehumidifier for generating the dehumidified gas may comprise a
plurality of dehumidifying unit each provided for one of the
exposure apparatuses, or may comprise a single dehumidifying unit
common to all the exposure apparatuses for generating the
dehumidified air and distributing it to them.
[0042] In order to avoid any electrostatic discharge, it is
preferable that an antistatic device is provided for such parts
that are likely to accumulate electrostatic charge by friction,
such as the parts which come into contact with the photosensitized
substrate in a local atmosphere in the area to which the
dehumidified gas is supplied. The antistatic device may be a device
for grounding such parts.
[0043] In this arrangement, only selected area(s) will undergo
dehumidification, so that the dehumidification can be effectively
performed and the reduction in nonuniformity among the resist
images and the reduction in the contamination of the optical
elements can be achieved because any contamination by the
impurities conveyed by water particulates or by the moisture itself
is eliminated.
[0044] Further, in the case where purified dehumidified gas is
generated by causing a gas stream to pass through a
gaseous-impurity-removing filter and then through a dehumidifier,
any contamination of the apparatus may be reduced more effectively.
Chemical filters be used as the gaseous-impurity-removing filter,
and it can remove, unlike HEPA and ULPA filters, gaseous impurities
from the environmental gas. Various chemical filters are commonly
used including those using fibrous or granulate activated carbon,
those utilizing ion exchange reaction provided by various ion
exchange resins, those using fibrous activated carbon with some
sort of agent added. Examples of the chemical filters utilizing ion
exchange reaction are products bearing a trademark "EPIX" available
from Ebara Corporation in Japan. Examples of the chemical filters
using fibrous activated carbon with some sort of agent added are
products bearing a trademark "CLEAN SORB" available from Kondo
Kogyo Co, Ltd. in Japan. Gaseous impurities to be removed by the
chemical filter include SO.sub.4.sup.2-, NH.sub.4.sup.+,
organosilicom compounds, trimethylsilanol, N-methyl-2-pyrrolidon
and others.
[0045] In addition, the supplied dehumidified gas may typically
comprise dehumidified ambient air, with the result that a possible
leakage of the dehumidified gas into a factory room will never risk
the workers in the room. This also provides an advantage that the
use of such dehumidified gas is less costly than the use of
nitrogen or helium gas.
[0046] According to a fifth embodiment of the present invention for
achieving the fourth object described above, there is provided an
air-conditioning apparatus for removing impurities from gas,
adapted for effecting air-conditioning to a semiconductor device
factory and/or an exposure apparatus, comprising: a body housing; a
gas supply duct housed in the body housing; and an
impurity-removing filter element disposed inside the gas supply
duct.
[0047] According to a sixth embodiment of the present invention for
achieving the fourth object described above, there is provided an
exposure apparatus for transferring a pattern formed on a mask onto
a photosensitized substrate by exposure, comprising: a light source
for emitting a light beam having a wavelength falling in a range
from ultraviolet to deep ultraviolet radiations; an illumination
optical system for directing the light beam from the light source
into a mask; an exposure unit for exposing a photosensitized
substrate in order to transfer the pattern formed on the mask onto
the photosensitized substrate; a chamber for housing at least a
part of the exposure apparatus; and an air-conditioning apparatus
for effecting conditioning of gas in the chamber, said
air-conditioning apparatus being disposed outside the chamber and
comprising a body housing, a gas supply duct housed in the body
housing and an impurity-removing filter element disposed inside the
gas supply duct.
[0048] The impurity-removing filter element may comprise a hollow
cylindrical body or may comprise a bellows wall. Further, the
impurity-removing filter element may be so supported by a support
member as to be kept out of contact with an inner wall of the gas
supply duct. The duct is bendable with the impurity-removing filter
element contained therein. A filter element having a hollow
cylindrical body has a relatively large filtering surface area and
is effective to reduce the pressure loss across the filter
element.
[0049] The impurity-removing filter element may be a
gaseous-impurity-removing element, or may be a combined filter
element comprising a gaseous-impurity-removing filter element and a
particulate filter element. Further, the gaseous-impurity-removing
filter element may comprise a chemical filter using some sort of
ion exchange resin, or a chemical filter using fibrous activated
carbon with some sort of agent added, for removing gaseous
impurities such as ammonia, basic amines, sulfate ion,
N-methyl-2-pyrrolidon, trimethylsilanol and others. The particulate
filter may comprise a HEPA filter or an ULPA filter.
[0050] According to this embodiment, an impurity-removing filter
element may be disposed in an air-conditioning apparatus at a space
inside an existing duct, occupying no other space which may be
utilized for other purposes. An air-conditioning apparatus
according to this embodiment may be used with an exposure apparatus
or with a clean room.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] The above and other objects, features and advantages of the
present invention will be apparent from the following detailed
description of preferred embodiments thereof, reference being made
to the accompanying drawings, in which:
[0052] FIG. 1 is a schematic representation of an optical system
for an exposure apparatus showing a first embodiment of the present
invention;
[0053] FIG. 2 is a schematic representation of an exemplified
exposure apparatus showing the first embodiment of the present
invention;
[0054] FIG. 3 is a flow chart illustrating an sequence of
operations of the exposure apparatus shown in FIG. 2;
[0055] FIG. 4 is a flow chart illustrating another sequence of
operations of the exposure apparatus shown in FIG. 2;
[0056] FIG. 5 is a schematic representation of an exemplified
exposure apparatus showing a third embodiment of the present
invention;
[0057] FIG. 6 is a flow chart illustrating a sequence of operations
of the exposure apparatus shown in FIG. 5;
[0058] FIG. 7 is a schematic representation of an optical system
for an exposure apparatus showing a fourth embodiment of the
present invention;
[0059] FIG. 8 is a schematic representation of an exemplified
exposure apparatus showing the fourth embodiment of the present
invention;
[0060] FIG. 9 is a flow-chart illustrating a sequence of operation
of the exposure apparatus shown in FIG. 8;
[0061] FIG. 10 is a schematic representation of another exemplified
exposure apparatus showing the fourth embodiment of the present
invention;
[0062] FIG. 11 is a flow chart illustrating a sequence of
operations of the exposure apparatus shown in FIG. 10;
[0063] FIG. 12 is a flow chart illustrating another sequence of
operations of the exposure apparatus shown in FIG. 10;
[0064] FIG. 13 is a schematic representation of an exemplified
impurity-removing filter provided at an air inlet of an exposure
apparatus showing the fourth embodiment of the present
invention;
[0065] FIG. 14 is a schematic representation of a further
exemplified exposure apparatus showing the fourth embodiment of the
present invention;
[0066] FIG. 15 is a schematic representation of an exemplified
air-conditioning apparatus showing a fifth embodiment of the
present invention;
[0067] FIG. 16 is a perspective view, partially broken away, of a
duct showing an exemplified filter element disposed in the
duct;
[0068] FIG. 17 is a longitudinal sectional view of the duct showing
the filter element shown in FIG. 16;
[0069] FIG. 18 is a longitudinal sectional view of a duct showing
another exemplified filter element and an associated baffle plate
in the duct;
[0070] FIG. 19 is a longitudinal sectional view of a duct showing a
further exemplified filter element in the duct;
[0071] FIG. 20 is a longitudinal sectional view of a duct showing a
yet further exemplified filter element in the duct;
[0072] FIG. 21 is a cross sectional view of the duct and the filter
element shown in FIG. 20;
[0073] FIG. 22 is a longitudinal sectional view of a duct showing a
still further exemplified filter element in the duct;
[0074] FIG. 23 is a perspective view, partially broken away, of a
duct showing a still further exemplified filter element in the
duct;
[0075] FIG. 24 is a perspective view, partially broken away, of a
duct showing a still further exemplified filter element in the
duct;
[0076] FIG. 25 is a plot illustrating the change of the impurity
removal efficiency of a chemical filter with time; and
[0077] FIG. 26 is a schematic representation showing a typical
prior art exposure apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0078] The above and other objects, features and advantages of the
present invention will be apparent from the following detailed
description of preferred embodiments thereof.
[0079] The present invention will be now described in more detail
with reference to preferred embodiments.
[0080] Referring now to FIGS. 1 and 2, an exposure apparatus
according to a first embodiment of the present invention is
described, which is useful for achieving the first object of the
present invention described above.
[0081] FIG. 1 is a schematic representation showing an exemplified
exposure apparatus. A DUV light source 1, which may be an excimer
laser or a mercury lamp, emits a light beam. The light beam is
reflected by a first mirror 2a into an illumination optical system
3 which comprises an illuminance equalizer (which may be an optical
integrator (a fly-eye lens, for example) or a condenser lens),
various lenses and mirrors. The illumination optical system 3
shapes the received light beam into an illumination light beam
having uniform illuminance over its entire cross section. The
illumination light beam exits the illumination optical system 3 and
is again reflected by a second mirror 2b into a reticle 4. The
reticle 4 has a pattern formed thereon and is illuminated uniformly
by the illumination light beam. The pattern on the reticle 4 is
projected through a projection lens 5 onto a photosensitized
substrate 6, and an image of the pattern is formed on and
transferred to the substrate 6. The substrate 6 may be, typically,
a wafer having a layer of resist formed thereon, and thus we call
it "wafer" hereinafter. The wafer 6 is carried on a
two-dimensionally movable XY-stage 7. Before undergoing the
exposure process the wafer 6 is located at the waiting location,
and after having undergone an exposure process the wafer 6 is again
returned to the waiting location 8.
[0082] FIG. 2 is a schematic representation showing a first
embodiment according to the present invention. The exposure
apparatus of FIG. 1 is confined in the chamber 9, the inside of
which is maintained at a fixed temperature by means of an
air-conditioning apparatus 10. The ambient air outside the chamber
9 may be introduced into the chamber 9 through an air inlet by
means of a first gas-delivering fan 12, and the gas in the local
atmosphere in the chamber 9 is recirculated by means of a second
gas-delivering fan 11. The air inlet is provided with an
impurity-removing unit 13a for removing impurities from the air
stream being introduced into the chamber 9 through the air inlet. A
second impurity-removing unit 13b is provided in the chamber 9 for
removing impurities from the gas stream recirculating in the
chamber 9. The chamber 9 of FIG. 1 houses the entire exposure
apparatus; however, instead of the chamber 9 a modified chamber may
be used which houses only a part of the exposure apparatus, such as
the illumination optical system 3 only.
[0083] Each of the impurity-removing units 13a and 13b includes an
impurity-removing filter for removing gaseous impurities, which may
be any suitable one of chemical filters such as those using fibrous
or granular activated carbon, those utilizing the ion-exchange
reaction of some sort of ion-exchange resin and those using fibrous
activated carbon with some sort of agent added, or may be a filter
utilizing the electrostatic adsorption wherein a gas stream is
directed to flow between positive and negative electrodes such that
any gaseous impurities are adsorbed to the electrodes and removed
from the gas stream.
[0084] For example, products bearing a trademark "CLEAN SORB"
available from Kondo Kogyo Co, Ltd. in Japan include a
basic-gas-removing chemical filter which may be used for removing
various basic gasses such as ammonia, and a sulfur-gas-removing
chemical filter which may be used for removing sulfur dioxide gas
(SO.sub.2). If either ammonia or sulfur oxides (SO.sub.x) can be
completely removed or eliminated from the gas in the chamber 9, the
glass optical elements used in the chamber 9 will be free from
being blurred by the formation of a deposit layer of ammonium
sulfate ((NH.sub.4).sub.2SO.sub.4) or the like on their surfaces.
Further, an activated carbon filter may be used to remove
organosilicon such as siloxanes and silanoles, so that the glass
optical elements will be free from being blurred by the formation
of a deposit layer of silicon dioxide and the like on their
surfaces.
[0085] Two gaseous impurity-concentration-measuring devices 14a and
14b are used, one disposed at a position upstream of the first
impurity-removing unit 13a (that is, disposed in the ambient air in
the environment of the exposure apparatus) and the other at a
position downstream of the first impurity-removing unit 13a. There
are provided additional two gaseous
impurity-concentration-measuring devices 14c and 14d disposed at
position upstream and downstream, respectively, of the second
impurity-removing unit 13b. The measurements obtained through the
impurity-concentration-measuring units 14a, 14b, 14c and 14d are
sent to an arithmetic operation unit 15, which uses the received
measurements to calculate the impurity removal efficiency of the
gaseous-impurity-removin- g filters used in the impurity-removing
units 13a and 13b in order to determine end-of-life of each filter
elements used therein.
[0086] The impurity-concentration-measuring devices 14a-14d may be
of any known type. For example, a measurement device may be used
which includes a crystal resonator having a synthetic bilayer
membrane (which is similar to a lipid molecular membrane) formed
thereon, and the amount of impurities adsorbed on the membrane
causes the corresponding change in the resonance frequency of the
crystal resonator and thus can be detected electrically. If it is
desired to measure individual concentrations of different
impurities, a plurality of such measurement devices may be used.
Alternatively, the gas may be sampled at the
concentration-measuring points and analyzed by means of the gas
chromatography or the spectrophotometry in order to determine
individual impurity concentrations in the gas.
[0087] Next, we will describe the method of determining end-of-life
of an impurity-removing filter. In general, the impurity removal
efficiency of an impurity-removing filter will decreases with time
as the removed impurities are accumulated more in the filter, as
shown by the curve in FIG. 25. The arithmetic operation unit 15
makes calculations to determine the current impurity removal
efficiency of each of the impurity-removing unit 13a and 13b based
on the following the equation.
[0088] 1 impurityremoval efficiency(%) = ( 1 - downstreamgaseous
impurity concentration upstreamgaseous impurity concentration )
.times. 100
[0089] That is, the difference between the gaseous impurity
concentration measured at the measuring point downstream of that
impurity-removing unit (i.e., the gaseous impurity concentration in
the gas stream after having passed through the filter) and the
gaseous impurity concentration measured at the measuring point
upstream of the unit (i.e., the gaseous impurity concentration in
the gas stream just before passing through the filter) is
calculated, and then the difference is divided by the gaseous
impurity concentration measured at the measuring point upstream of
the unit.
[0090] Then, the end-of-life of the impurity-removing unit is
defined as the point of time when the impurity removal efficiency
decrease to a predetermined level, such as 90%. The arithmetic
operation unit 15 calculates the impurity removal efficiency of
each of the impurity-removing units 13a and 13b, either
continuously or iteratively at regular intervals, from the
measurements obtained through the impurity-concentration-measuring
devices, and when the impurity removal efficiency has decreased to
a level near 90%, such as 91% level, it causes the control panel to
display an indication of the decrease of the impurity removal
efficiency of the corresponding gaseous impurity-removing device
13a or 13b (See flow chart in FIG. 3). The operator of the
apparatus is taught by the indication that the end-of-life of that
gaseous impurity-removing device is coming soon. The indication may
be, in addition to the visual indication by the display, a sound
alarm such as a buzzer note, a synthetic voice warning, and
others.
[0091] Additional impurity-concentration-measuring devices 14e, 14f
and 14g may be provided at those positions which are not related to
the impurity-removing devices 13a and 13b but are subject to
possible contamination by the impurities, such as positions near
the XY-stage 6, near the wafer waiting location 8, within the
illumination optical system 3 and others.
[0092] End-of-life of the impurity-removing devices 13a and 13b may
be determined in another way. That is, the impurity concentration
measurements are performed at the positions near those parts of the
exposure apparatus which are likely to be contaminated, and the
end-of-life of the impurity-removing devices 13a and 13b is
determined when one of the measured impurity concentrations has
reached a predetermined level. In this case, an indication may be
made when one of the measured impurity concentrations has reached
or are reaching the predetermined level, so that the operator can
recognize from the indication that it is to replace the
gaseous-impurity-removing filter elements. Further, the apparatus
may be stopped when the measured impurity concentration(s) has/have
exceeded the end-of-life level, so as to prevent contamination
inside the apparatus.
[0093] A further additional impurity-concentration-measuring device
may be provided outside the chamber 9 to measure the impurity
concentration in the environmental air of the chamber 9, so that
any abnormally abrupt increase in the impurity concentration in the
air surrounding the apparatus may be detected as one of the
abnormalities in the apparatus environment. Although ambient air is
introduced into the chamber through the impurity-removing device,
an abnormally high level of gaseous impurity concentration in the
ambient air, which may be caused for some reason or another, may
result in the contamination inside the apparatus. Thus, it is
preferable to stop the operation of the gas-delivering fan 12 used
for introducing the ambient air into the chamber 9, so as to stop
air introduction to prevent the contamination inside the apparatus
(see flow chart in FIG. 4). In the arrangement of FIG. 1, the
impurity-concentration-measuring device 14a, which is disposed at
the position upstream of the impurity-removing device 13a, may be
used as the ambient air impurity-concentration-measuring
device.
[0094] As described above, in the above exposure apparatus,
impurity-concentration-measuring devices are used to measure the
impurity concentrations in the gas inside the apparatus and in the
ambient air, so that the end-of-life of the impurity-removing
filter may be administrated in an appropriate manner. Further, the
impurity concentrations in the ambient air outside the apparatus
may be monitored, so that quick and appropriate actions may be
taken against any abnormalities occurring in the environment of the
exposure apparatus.
[0095] Referring next to FIG. 5, we will describe an exposure
apparatus according to another embodiment of the present invention,
which is useful to achieve the second object of the present
invention described above.
[0096] FIG. 5 is a schematic representation showing the exposure
apparatus of the embodiment having the exposure unit of FIG. 1
confined in a chamber. A wafer waiting location is defined at an
appropriate position but is not shown.
[0097] The air within the chamber 9 is temperature-controlled by an
air-conditioning apparatus 10 disposed in the chamber 9, and then
delivered by a gas-delivering fan 11 to pass through an
impurity-removing device 20 including a chemical filter and a
particulate filter to be the atmosphere of the exposure unit.
Because of the pressure increase caused by the gas-delivering fan
11, the atmosphere surrounding the exposure unit is maintained at a
pressure level greater than the air pressure level outside the
chamber 9. Thus, any failure in an air tight seal at an edge of a
door or between panels surrounding the atmosphere of the exposure
unit would only result in leakage out of the chamber 9, and no
ambient air, which generally contains dusts and gaseous impurities,
is sucked in and allowed to leak into the chamber 9. The air
supplied from the impurity-removing device 20 to the local
atmosphere around the exposure unit then flows through a return
passage 21 into the air-conditioning apparatus 10, and then again
temperature-controlled by the air-conditioning apparatus 10 and
delivered by the gas-delivering fan 11, so as to recirculate within
the chamber 9.
[0098] Because the gas-delivering fan 11 delivers air at a
considerable flow rate, the pressure in the space upstream of the
gas-delivering fan 11 is maintained to be a negative pressure with
respect to the air pressure outside the chamber 9. This negative
pressure serves to draw the ambient air into the chamber 9 through
the air inlet 22, so that air is supplied from the outside of the
chamber 9 at the same rate as the air in the space surrounding the
exposure unit escapes out of the chamber 9. The air inlet 22 is
provided with an impurity-removing filter 23 including a
gaseous-impurity-removing filter element and a particulate filter
element, and the ambient air is introduced into the chamber 9
through the impurity-removing filter 23.
[0099] The embodiment of FIG. 5 includes a differential pressure
gauge 24 between the negative pressure area in the chamber 9 and
the outside of the chamber 9 for measuring the pressure difference
between them. Further, it includes an anemometer 25 disposed near
the air inlet 22 for measuring the speed of the stream of the
ambient air flowing through the air inlet 22 into the chamber 9,
from which the flow rate of the air stream may be determined. The
outputs from the differential pressure gauge 24 and from the
anemometer 25 are supplied to the control unit 26.
[0100] If a failure such as a breakage has occurred in the sealant
used to seal the joints between the panels of the chamber wall
defining the negative pressure area in the chamber 9, then an
opening may be formed in the sealant by such breakage and the
ambient air may be drawn into the chamber through the opening under
the influence of the negative pressure. This leakage of air into
the chamber through the chamber wall results in the pressure
increase in the negative pressure area, which in turn causes the
decrease in the flow rate of the air stream flowing into the
chamber through the air inlet 22. The control device 26 monitors
the flow rate and the pressure difference between the negative
pressure area and the outside of the chamber, so that when a change
or changes are detected in at least one of these factors the
control unit 26 outputs a signal to an alarm unit 27 so as to
indicate the abnormality to the operator of the apparatus.
Alternatively, upon detection of an abnormality, the control unit
26 may stop the operation of the fan 11 so as to cause the negative
pressure area to disappear and prevent the leakage of air into the
chamber through the sealant breakage (see flow chart in FIG.
6).
[0101] In the arrangement of the embodiment of FIG. 5, the chamber
houses the entire exposure unit. A modification may be made wherein
only a part of the exposure unit is confined in the chamber and
some of the components of the exposure unit such as a light source
1 and a power supply (not shown), which generally produce a
considerable amount of heat, are disposed outside the chamber
9.
[0102] As clearly understood from the above, the integrity of the
airtightness of the chamber is continuously monitored and any
impurities are prevented from entering into the chamber, so that
any contamination inside the apparatus and degradation of impurity
filters, which could otherwise occur due to a failure of the
integrity of airtightness of the chamber, are effectively
prevented.
[0103] Referring next to FIGS. 7 to 14, we will describe an
exposure apparatus according to a further embodiment of the present
invention, which is useful to achieve the third object of the
present invention described above.
[0104] FIG. 7 is a schematic representation showing an exposure
apparatus. The exposure apparatus includes a light source 30 for
emitting deep ultraviolet light, which may be an excimer laser or a
mercury lamp. The light emitted from the light source 30 passes
through various lenses 32a-32c while being reflected by mirrors
31a-31c, which lenses 32a-32c and mirrors 31a-31c together
constitute an illumination optical system, so that the light is
shaped by means of the illumination optical system into a uniform
illuminance light beam. The uniform illuminance light beam exiting
the illumination optical system illuminates, with a uniform
illuminance, a reticle 34 having a pattern formed thereon. The
pattern on the reticle 34 is projected through a projection lens 35
onto the photosensitized substrate 36, so that an image of the
pattern is formed on and transferred to the substrate 36. The
photosensitized substrate 36 may be a wafer with a layer of resist
formed on its surface, so that we call it "wafer" hereinafter. The
wafer 36 is carried on a two-dimensionally movable XY-stage 38.
Before exposure the wafer 36 is placed at a wafer waiting location
40, and after exposure the wafer 36 is again returned to the wafer
waiting location 40. Conveyance of the wafer between the wafer
waiting location 40 and the wafer holder 37 on the stage 38 is made
by means of a wafer conveyor 41.
[0105] FIG. 8 is a schematic representation showing a fourth
embodiment of the present invention as applied to the exposure
apparatus shown in FIG. 7.
[0106] Each wafer 36 being transferred into the exposure apparatus
is first placed at the wafer waiting location 40, and thence
conveyed by the wafer conveyor 41 onto the stage 38 and held
thereon. Then, an image of the reticle pattern is projected through
the projection lens 35 onto the wafer 36.
[0107] A dry air blower 42 is disposed above the wafer conveyance
path between the wafer waiting location 40 and the stage 38. The
dry air blower 42 may comprise one or more pipes having a
downwardly facing pipe wall portion perforated to form therein a
lot of tiny holes, or alternatively may comprise a rectangular duct
having a bottom in which a lot of tiny holes or small slits are
formed. The ambient air is drawn by an gas-delivering fan 43 and
delivered to a dehumidifier 44 which dehumidify the air to a
humidity of a few percent. The dehumidified air is then downwardly
blown by the dry air blower 42 at a flow rate which is sufficient
to fill the space providing atmosphere for the wafer. In the
embodiment of FIG. 8, a single dry air blower 42 is used to cover
all of the wafer waiting location 40, the wafer conveyor 41 and the
stage 38. Alternatively, individual dry air blowers may be used
each to cover one of the wafer waiting location 40, the wafer
conveyor 41 and the stage 38. The direction of the air stream blown
out of the dry air blower 42 may be any of the directions which may
be used to fill the space providing atmosphere for the wafer.
[0108] Electrostatic discharges are likely to occur in the
atmosphere composed of dehumidified air, and may arise a problem
that an electrostatic discharge through a wafer may destroy the
devices formed on the wafer or cause functional failures of some
circuits in the devices. In view of this, all the components which
may contact with the wafer, such as a wafer case 45, the wafer
conveyor 41 and the wafer holder 37, as well as some of the movable
components, are made of conductive material such as metals and
grounded so as to avoid any electrostatic charges.
[0109] A hygrometer (or humidity-measuring device) 47 is disposed
in the wafer process atmosphere in order to continuously monitor
the humidity in that atmosphere. The control device 48 send a
signal to the alarm unit 49 when an increase in the humidity is
detected by the hygrometer 47, so that the operator of the
apparatus may recognize the humidity increase in the wafer process
atmosphere. An additional hygrometer (or humidity-measuring device)
50 may be disposed near the air entrance opening of the
gas-delivering fan 43. The control device 48 monitors the humidity
in the ambient air based on the output of the hygrometer 50 in
order to control the dehumidifying power of the dehumidifier 44
such that the humidity of the wafer process atmosphere may be
maintained at a constant level irrespective of the humidity of the
ambient air (see flow chart of FIG. 9).
[0110] FIG. 10 is a schematic representation showing another
exemplified exposure apparatus according to the fourth embodiment
of the present invention.
[0111] In the arrangement shown in FIG. 10, the wafer waiting
location 40 and the space for the wafer conveyor 41 are
individually housed in respective chambers 51a and 51b which are
filled with dry air dehumidified to a humidity of a few percent. As
with the embodiment of FIG. 8, the ambient air is drawn by an
gas-delivering fan 43 and delivered to a dehumidifier 42 which
dehumidify the air so as to provide the dry air. Three shutters
52a, 52b and 52c are provided between the chamber 51a and the
outside, between the chambers 51a and 51b and between the chamber
51b and the outside, respectively. The shutters 52a-52c open
individually by means of respective shutter actuators 53a-53c only
when a wafer enters or exits any of the chambers 51a and 51b. At
other times, the shutters 52a-52c are kept closed. Because of the
division of the entire space into two individual blocks defined by
the chambers 51a and 51b, each chamber has the smaller volume and
thus may be ventilated with the dry air in an efficient manner. In
addition, the pressure in each chamber is maintained at a pressure
a little greater than the ambient air pressure, such that the
moisture in the ambient air is prevented from entering the chamber.
Because the stage 36, which is surrounded by many movable parts, is
difficult to house in a chamber, a dry air blower 54 is used which
is disposed above the stage 38 and serves to blow the dehumidified,
dry air into the atmosphere for the wafer 36 placed on the stage
8.
[0112] Wafer detectors 55a, 55b and 55c are provided for
determining as to whether a wafer 36 exists at the wafer waiting
location 40, on the wafer conveyor 41 and on the stage 38,
respectively. Further, dry air is distributed to the wafer waiting
location 40, the wafer conveyor 41 and the stage 38 through
respective air pipes provided with respective control valves 57a,
57b and 57c. The control device 56 monitors the outputs of the
detector 55a-55c in order to determine any area(s) in which no
wafer exists, and controls the flow rate of dry air to be supplied
to such area(s) by throttling or closing the corresponding control
valve(s) (see flow chart of FIG. 11). This control of dry air
depending on presence/absence of wafer contributes to the reduction
of the running cost in the case where the dry air is supplied from
a steel cylinder or a storage tank.
[0113] As with the embodiment of FIG. 8, the embodiment of FIG. 10
may include hygrometers disposed in the wafer process atmosphere in
order to provide the humidity control of that atmosphere (see flow
chart of FIG. 12).
[0114] An impurity-removing filter may be preferably disposed at
the air inlet of the dehumidifier 42. As shown in FIG. 13, the
impurity-removing filter may preferably comprise a combination of a
chemical filter 60 and a particulate filter 61 such as a HEPA
filter, an ULPA filter or the like. Gaseous impurities to be
removed by the chemical filter 60 include SO.sub.4.sup.2-,
NH.sub.4.sup.+, organosilicon compounds, trimethylsilanol,
N-methyl-2-pyrrolidon and others.
[0115] FIG. 14 is a schematic representation showing a further
exemplified exposure apparatus according to the fourth embodiment
of the present invention.
[0116] In the arrangement shown in FIG. 14, the atmosphere
surrounding an illumination optical system is confined in a housing
62 and dehumidified air is supplied to the confined atmosphere
through a supply pipe 63. It is not necessarily required to house
the entire illumination optical system in the housing 62. Only such
a part of the illumination optical system may be housed in the
housing 62 that is highly subject to contamination and/or is likely
to provide considerable degradation in optical performance when
contaminated.
[0117] As is clearly understood from the above, dehumidified air
containing little water, which otherwise could be a carrier of
contaminants or could be itself comprise a contaminant, is supplied
to such areas of the apparatus that otherwise could be subject to
considerable contamination. In this manner, any contamination
inside the apparatus may be lowered and the longer maintenance
intervals may be allowed. Further, according to the invention, the
supplied dehumidified air is produced by removing water from the
ambient air resulting in lower cost, and the control of the flow
rate of the supplied dehumidified air supplied can prevent waist of
the supplied dehumidified air, resulting in a lower cost for
maintenance of the apparatus.
[0118] Referring next to FIGS. 15 to 24, an air-conditioning
apparatus according to a still further embodiment of the present
invention will be described, which is useful to achieve the fourth
object of the present invention described above.
[0119] FIG. 15 is a schematic representation showing a exemplified
application of the present invention to an air-conditioning
apparatus for an exposure apparatus. The exposure apparatus has an
exposure unit housed in a chamber 70 to which the air-conditioning
apparatus 85 is connected. A DUV light source 71 is provided, which
may be an excimer laser or a mercury lamp. The light source 71
emits a light beam which is reflected by a first mirror 72a into an
illumination optical system 73. The illumination optical system 73
comprises an illuminance equalizer, which may be an optical
integrator (a fly-eye lens, for example) or a condenser lens. The
illumination optical system 73 further comprises various lenses and
mirrors. The light beam is shaped by the illumination optical
system 73 into an illumination light beam having uniform
illuminance distribution over its entire cross section. The
illumination light beam having the uniform illuminance distribution
exits the illumination optical system 73 and again reflected by a
second mirror 72b into a reticle 74. The reticle 74 has a pattern
formed thereon and is illuminated uniformly by the illumination
light beam. The pattern on the reticle 74 is projected through a
projection lens 75 onto a photosensitized substrate 76 and an image
of the pattern is formed on and transferred to the substrate 76.
The substrate 76 may be, typically, a wafer having a layer of
resist formed thereon, and thus we call it "wafer" hereinafter. The
wafer 76 is carried on a two-dimensionally movable XY-stage 77.
[0120] The air inside the chamber 70 is temperature-controlled by
the air-conditioning apparatus 85 which comprises a heater/cooler
86 and an gas-delivering fan 87 and connected with the chamber 70
through air ducts 88a and 88b. An air stream passes through the
space around the exposure unit into a return passage 78 and then
undergoes temperature-control by the air-conditioning apparatus 85
and enter again into the chamber 70 for recirculation.
[0121] The pressure in the return passage 78, which is upstream of
the air-conditioning apparatus 85, is a negative pressure with
respect to the air pressure outside the chamber 70. This negative
pressure serves to draw the ambient air into the chamber 70 through
an air inlet 79, so that air is supplied from the outside of the
chamber 70 at the same rate as the leakage air out of the chamber
70 escapes from the space around the exposure unit. The air inlet
79 is provided with an impurity-removing filter unit 80, through
which the ambient air is introduced into the chamber 70.
[0122] In this exemplified arrangement, a chemical filter element,
which serves to remove gaseous impurities from the air
recirculating in the chamber 70, is disposed in a duct 88b of the
air-conditioning apparatus 85. As the result, only a particulate
filter 81 has to be disposed in the chamber 70 and the chemical
filter occupies none of the space inside the chamber, which may be
effectively used for other purposes.
[0123] Next, we will describe various manners of disposing of a
chemical filter element in a duct with reference to FIGS. 16 to
24.
[0124] FIG. 16 is a perspective view of the duct, partially broken
away, showing the chemical filter element disposed in the duct, and
FIG. 17 is a longitudinal cross section of the duct. As shown, the
duct 88b for supplying gas to the chamber 70 houses a chemical
filter element 89, which comprises a hollow cylindrical body with
its upper end closed by a top plate 91. The duct 88b has an inner
flange 90 serving as a partition wall, to which the lower end of
the chemical filter element 89 is fixedly connected. The partition
wall (inner flange) 90 extends between the lower edge of the
chemical filter element 89 and the inner wall of the duct 88b in
order to ensure that all the gas flowing through the duct 88b
necessarily passes through the chemical filter 89. Alternatively,
the partition wall 90 itself may be made of the same chemical
filter material as the chemical filter element 89. The gas flowing
in the duct 88b passes through the cylindrical wall of the chemical
filter 89 from the outside to the inside, during which any gaseous
impurities are removed from the gas. The part of the duct 88b which
supports and houses the chemical filter element 89 therein is
separated and detachable from the remaining part of the duct 88b,
and when the chemical filter element 89 needs to be replaced with a
new one, that part of the duct and the chemical filter element
therein are together replaced.
[0125] The top plate 91 of the chemical filter element 89 extends
perpendicular to the direction of the arriving gas stream impinging
against the top plate 91. Therefore if the top plate 91 were made
of the same chemical filter material as the cylindrical wall of the
chemical filter element 89, it would suffer from earlier
degradation than the cylindrical wall because the gas passing
through such top plate would have a much larger flow rate per unit
of area than the gas passing through the cylindrical wall, which is
apparently inconvenient. In view of this, the top plate 91 may be
preferably made of one of materials allowing little outgassing,
such as a piece of stainless steel sheet processed by
electropolishing or of any fluororesin.
[0126] Nevertheless, in the case where the top plate 91 is made of
the same chemical filter material as the cylindrical body of the
chemical filter element 89, it may be preferable that a baffle
plate 92 is disposed upstream of the top plate as shown in FIG. 18.
The baffle plate 92 may be made of a stainless steel sheet
processed by electropolishing or of any suitable fluororesin. The
baffle plate 92 causes the gas stream to diverge so as to reduce
the flow rate per unit of area of the gas passing through the top
plate 91, so that the earlier degradation of the chemical filter
material forming the top plate may be effectively prevented.
[0127] As shown in FIG. 19, the hollow cylindrical chemical filter
element 89 may be disposed in the duct 88b upside down with respect
to the disposition of FIGS. 16 to 18. In such case, the gas flowing
in the duct 88b passes through the cylindrical wall of the chemical
filter element 89 from the inside to the outside. If the top plate
91 is made of the same chemical filter material as the cylindrical
wall of the chemical filter element, the flow rate per unit of the
gas passing through the top plate 91 is much greater than that of
the gas passing through the cylindrical wall, resulting in the
earlier degradation of the top plate 91. Thus, it may be preferable
that the top plate 91 is made of a gas-nonpermeable material.
[0128] If a part of a filter element for removing gaseous
impurities happens to come into contact with the inner wall of the
duct in which it is disposed, that part of the filter element would
lose its gas-permeability fully or partially. Even a partial loss
of the gas-permeability of a filter element may cause an increase
in the pressure loss across the filter element and a decrease in
the effective area of the filter element, resulting in a shorter
operational life of the filter element. Further, any increase in
the pressure loss causes the corresponding increase in the load
imposed on the gas-delivering fan, which may result in an
insufficient supply of gas. It is necessary therefore to keep the
filter element out of contact with the inner wall of the duct.
[0129] FIGS. 20 and 21 show an exemplified arrangement for keeping
a chemical filter element out of contact with a duct. FIG. 20 is a
longitudinal section of the duct and FIG. 21 is its cross section.
In this arrangement, a cylindrical chemical filter element 96 has a
top plate 95 made of a suitable gas-permeable material and fixed to
an annular partition wall formed as an inner flange of a duct 88b.
The filter element 96 is connected, at a plurality of positions
along the length of the element, with the inner wall of the duct
88b through corresponding sets of support members (wire spokes, for
example) 98. The support members 98 define the space between the
outer surface of the filter element 96 and the inner wall of the
duct 88b. Thus, when the duct 88b is bent, the chemical filter
element 96 in the duct 88b is also bent with the space between the
outer surface of the filter element 96 and the inner wall of the
duct 88b being kept substantially unchanged, so that the filter
element 96 is kept out of contact with the inner wall of the duct
88b even when the latter is bent.
[0130] FIG. 22 shows another exemplified arrangement using a
different chemical filter element. In this arrangement, the
chemical filter element 100 comprises a bellows wall and a top
plate 101 made of a suitable gas-permeable material. The bellows
wall is longitudinally extendable and contractible. The filter
element 100 is connected, at a plurality of positions along the
length of the element, with the inner wall of the duct 88b through
corresponding sets of support members (wire spokes, for example)
102. The bellows wall provides a larger surface area and a greater
bendability of the element than a simple cylindrical wall for the
same size of filter element. This results in a high bendability of
the duct 88b housing the filter element 100, which in turn allow
less restricted layout of the duct 88b utilizing a free space in
the apparatus which is generally very tight. The larger surface
area of the filter element may provide the smaller pressure loss
and the longer operational life.
[0131] FIG. 23 shows a further exemplified chemical filter element.
The chemical filter element 110 has a serrated side wall and a top
wall 111. The serrated side wall provides a larger operational area
for a given size of element, which in turn provides the higher
filter efficiency, the smaller pressure loss and the longer
operational life of the element. The top plate 111 may be made of a
piece of electoropolished stainless steel sheet or a fluororesin
plate.
[0132] Not only chemical filter elements having a generally
cylindrical shape but also chemical filter elements of various
shapes may be used. For example, a chemical filter element having a
box-like shape as shown in FIG. 24, as well as polygon shaped
filter element may be used.
[0133] The duct may house not only a chemical filter element but
also a particulate filter element together with a chemical filter
element. In such case, the particulate filter element occupies no
space in the chamber for the exposure apparatus, so that the space
may be effectively used for other purposes. Air-conditioning
apparatus according to the present invention may be used not for
the exposure apparatus but also for the building having a clean
room.
[0134] As is clearly understood from the foregoing, the disclosed
air-conditioning apparatus allows the impurity-removing filter
element to be installed in the duct, such that it occupies no space
outside the duct. Thus, the space in the exposure apparatus as well
as the space in the clean room in which the exposure apparatus is
equipped may be effectively used for other purposes.
[0135] The present invention is not limited to the embodiments
described above, but may be embodied in various other forms and
arrangements without departing from the spirit and the scope of the
present invention.
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