U.S. patent application number 12/430633 was filed with the patent office on 2009-10-22 for method and device for replacing objective parts.
This patent application is currently assigned to Carl Zeiss SMT AG. Invention is credited to Peter Deufel, Bernhard Geuppert, Guido Limbach, Harald Woelfle.
Application Number | 20090260654 12/430633 |
Document ID | / |
Family ID | 39185783 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090260654 |
Kind Code |
A1 |
Geuppert; Bernhard ; et
al. |
October 22, 2009 |
METHOD AND DEVICE FOR REPLACING OBJECTIVE PARTS
Abstract
A method and a device for replacing objective parts, especially
of a projection or illumination objective for microlithography in
which an objective having an objective interior and objective parts
provided therein is provided. At least one objective part is
replaceably accommodated in the objective. Immediately prior to
installation in the objective, the replaceable objective part is
cleaned outside the objective interior in at least one cleaning
room sealed off from the ambient atmosphere. Immediately after
cleaning, the replaceable objective is installed in the objective
without contact with the normal ambient atmosphere.
Inventors: |
Geuppert; Bernhard; (Aalen,
DE) ; Limbach; Guido; (Aalen, DE) ; Woelfle;
Harald; (Waldkirch, DE) ; Deufel; Peter;
(Koenigsbronn, DE) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Carl Zeiss SMT AG
Oberkochen
DE
|
Family ID: |
39185783 |
Appl. No.: |
12/430633 |
Filed: |
April 27, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2007/061563 |
Oct 26, 2007 |
|
|
|
12430633 |
|
|
|
|
Current U.S.
Class: |
134/1.1 ; 134/1;
134/21; 134/59; 134/6; 359/507 |
Current CPC
Class: |
G03F 7/70808 20130101;
G03F 7/70925 20130101; G03F 7/70975 20130101; B08B 3/12 20130101;
B23P 6/00 20130101; G03F 7/70833 20130101; B08B 7/0035 20130101;
G03F 7/70916 20130101; G03F 7/70825 20130101; Y10T 29/49723
20150115 |
Class at
Publication: |
134/1.1 ;
359/507; 134/1; 134/6; 134/21; 134/59 |
International
Class: |
G02B 7/14 20060101
G02B007/14; B08B 3/12 20060101 B08B003/12; B08B 7/00 20060101
B08B007/00; B08B 1/00 20060101 B08B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2006 |
DE |
DE102006050835.1 |
Claims
1. Method for replacing objective parts comprising: providing an
objective having an objective interior and objective parts provided
therein, at least one objective part being replaceably accommodated
in the objective, cleaning the replaceable objective part outside
the objective interior in at least one cleaning room sealed off
from the ambient atmosphere and, immediately after the cleaning,
installing the replaceable objective part in the objective without
contact with the ambient atmosphere.
2. Method in accordance with claim 1, wherein the objective part is
selected from the group consisting essentially of optical lenses,
mirrors, mirror elements, filters, diaphragms, membranes and other
elements inside the objective interior.
3. Method in accordance with claim 1, wherein the cleaning room
sealed off from the ambient atmosphere has a cleaning atmosphere
differing from the ambient atmosphere.
4. Method in accordance with claim 3, wherein the cleaning
atmosphere is selected from the group consisting essentially of
vacuum, dry air, nitrogen, dry nitrogen, argon, oxygen, helium,
hydrogen, at least one inert gas, at least one noble gas and
combinations thereof.
5. Method in accordance with claim 1, wherein the cleaning room
sealed off from the ambient atmosphere is provided in local
proximity to the objective interior, and further comprising moving
the replaceable objective part, through at least one of a
geometrically simple and a temporally short movement, from the
cleaning room into the objective interior.
6. Method in accordance with claim 1, wherein the cleaning room is
detachably coupled to the objective interior so as to be
gastight.
7. Method in accordance with claim 1, further comprising providing
at least one further cleaning room, the cleaning rooms being
respectively connected to each other, and passing the replaceable
objective part through the cleaning rooms in succession.
8. Method in accordance with claim 1, wherein the cleaning in the
cleaning room comprises at least one of: cleaning by irradiation
with electromagnetic waves, ultraviolet irradiation, plasma
cleaning, oxygen plasma cleaning, hydrogen plasma cleaning,
evaporation, gas cleaning, liquid cleaning, ultrasonic cleaning,
dipping in at least one bath, mechanical cleaning, and wiping.
9. Method in accordance with claim 1, wherein the cleaning in the
cleaning room comprises at least one of elimination of particles,
elimination of hydrocarbons, elimination of water monolayers and
combinations thereof in an order as listed here.
10. Method in accordance with claim 9, wherein the elimination of
particles comprises at least one of utilizing an ultrasonic bath,
utilizing a dipping bath in an optics-cleaning mixture, and
wiping.
11. Method in accordance with claim 9, wherein the elimination of
hydrocarbons comprises at least one of utilizing irradiation,
utilizing irradiation with broadband ultraviolet light, gas
flushing, gas flushing with dry nitrogen, gas flushing with dry
nitrogen and a low quantity of admixed oxygen, gas flushing with
dry nitrogen and a low quantity of admixed dry air, plasma
cleaning, and plasma cleaning with an oxygen plasma excited by
microwave energy in vacuum conditions with simultaneous suction of
the cleaning room.
12. Method in accordance with claim 9, wherein the elimination of
water monolayers comprises at least one of evaporation, heating
with an infrared lamp, heating with a heating wire, plasma
cleaning, flushing with dry nitrogen, flushing with dry air, and
flushing with helium.
13. Method in accordance with claim 1, further comprising providing
a magazine for replaceable objective parts.
14. Method in accordance with claim 13, wherein the magazine
facilitates clean storage and rapid replacement of objective parts
via the cleaning room.
15. Method in accordance with claim 1, wherein the replaceable
objective part is a part of an optical system for one of
ultraviolet and extreme ultraviolet lithography.
16. Method in accordance with claim 1, further comprising
completely removing the objective part from the objective
interior.
17. Method in accordance with claim 1, further comprising bringing
the objective part from a position spaced apart from the objective
interior into the objective interior.
18. Method in accordance with claim 1, wherein the objective is an
objective of a projection or illumination objective for
microlithography.
19. Cleaning device for at least one replaceable objective part,
comprising: a cleaning device for cleaning the replaceable
objective part, a cleaning room for accommodating the replaceable
objective part during the cleaning, and a connecting part for
gastight connection to an objective housing.
20. Cleaning device in accordance with claim 19, further comprising
at least one connecting element for gastight connection of at least
one of a transport channel and at least one further cleaning
device.
21. Cleaning device in accordance with claim 20, wherein the
connecting part and the connecting element are at least one of
identical to and compatible with each other.
22. Cleaning device in accordance with claim 19, further comprising
a transport channel comprising the connecting part for gastight
connection to the objective housing.
23. Cleaning device in accordance with claim 19, wherein the
connecting part comprises a device mechanically decoupling the
connecting part from the objective housing.
24. Cleaning device in accordance with claim 22, wherein the
connecting part comprises a device mechanically decoupling the
connecting part from the objective housing.
25. Cleaning device in accordance with claim 23, wherein the
mechanical decoupling device comprises at least one of an air
bearing, an elastic bearing and a bellows.
26. Cleaning device in accordance with claim 24, wherein the
mechanical decoupling device comprises at least one of an air
bearing, an elastic bearing and a bellows.
27. Cleaning device in accordance with claim 19, wherein the
cleaning room is either sealed gastight or provided with excess
pressure, and wherein at least one sealing element comprising at
least one of an elastic element and a leaky seal with the excess
pressure is provided for at least one of the connecting part, an
inlet opening for the objective part and a connecting element to
either a transport channel or a further cleaning device.
28. Cleaning device in accordance with claim 19, further comprising
a handling device configured and arranged to move the replaceable
objective part in the cleaning device.
29. Cleaning device in accordance with claim 28, wherein the
handling device is configured and arranged to move the objective
part between the cleaning device and the objective housing.
30. Cleaning device in accordance with claim 28, wherein the
handling device comprises kinematic parts at least partially
arranged within the housing of at least one of the cleaning room
and a transport channel interposed between the cleaning device and
the objective housing.
31. Cleaning device in accordance with claim 28, wherein the
handling device comprises a linear motor.
32. Cleaning device in accordance with claim 28, wherein the
handling device is mechanically decoupled from a housing of at
least one of the cleaning room and a transport channel interposed
between the cleaning device and the objective housing.
33. Cleaning device in accordance with claim 19, further comprising
at least one of a gas supply, a gas evacuator, a pump, and a vacuum
pump.
34. Cleaning device in accordance with claim 19, wherein the
cleaning device comprises at least one of an irradiation device
utilizing electromagnetic waves, an irradiation devices utilizing
ultraviolet radiation, a plasma cleaning device, a microwave plasma
device, an evaporator, an infrared lamp, a heating wire, a
gas-flushing device, a liquid-flushing device, an ultrasonic
cleaner, a dipping bath, a mechanical cleaning device, and a wiping
device.
35. Cleaning device in accordance with claim 19, further comprising
a magazine for replaceable objective parts, connected to the
cleaning room such that the objective part is transferred between
the cleaning room and the magazine.
36. Cleaning device in accordance with claim 19, wherein the
connecting part comprises a quick-coupling mechanism for rapid
connection to and disconnection from the objective housing.
37. Objective for at least one of a projection device or an
illumination device for microlithography, comprising: an objective
housing that houses at least one replaceable objective part
wherein, in the region of the replaceable objective part, the
objective housing comprises at least one coupling element for
coupling a cleaning device, the cleaning device comprising a
cleaning room for accommodating and cleaning the replaceable
objective part and a connecting part for gastight connection to the
objective housing.
38. Objective in accordance with claim 37, wherein the objective is
an optical system configured for use with ultraviolet or extreme
ultraviolet light.
39. Objective in accordance with claim 37, further comprising at
least one additional housing arranged at least partially inside the
objective housing, the objective housing and the additional housing
each having a respective opening for accessing a respective
replaceable objective part.
40. Objective in accordance with claim 39, further comprising a
vacuum-tight transport channel between the objective housing and
the additional housing.
41. System comprising: at least one cleaning device, and at least
one objective comprising an objective housing, in which at least
one replaceable objective part is housed, wherein, in the region of
the replaceable objective part, the objective housing comprises at
least one coupling element for coupling the cleaning device, and
wherein the cleaning device comprises a cleaning room for
accommodating and cleaning the replaceable objective part and a
connecting part for gastight connection to the objective housing.
Description
[0001] This is a Continuation of International Application
PCT/EP2007/061563, with an international filing date of Oct. 26,
2007, which was published under PCT Article 21(2) in German, and
the complete disclosure of which, including amendments, is
incorporated into this application by reference.
FIELD OF AND BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method and a device for
replacing objective parts, especially of a projection or
illumination objective for microlithography.
[0003] Modern lenses in lithography increasingly have replaceable
or exchangeable elements, such as replaceable or exchangeable
lenses, filters, diaphragms and the like. US 2006/0176460 A1
describes, for example, an EUV (extreme ultraviolet) lithography
system having optical elements, such as mirrors and the like, which
are individually selectable for use, wherein the optical elements
are not replaced, in the sense of being moved into and out of the
objective, but rather are exchanged only in the form of a rotatable
turret. However, this imposes a very high space requirement.
[0004] WO 2006/069755 A1 describes, in contrast, a replaceable
optical element of an objective module of a lithography system,
which can be completely removed from the objective, wherein a
proposal is made to avoid contamination of the objective room by
providing a load-lock chamber.
[0005] When parts located in the highly clean, gas-flushed or
evacuated objective interior are replaced, there is a problem that
the process of replacement can introduce impurities into the
objective. In addition to contamination via the gas room during the
replacement, contaminants adhering to the replaceable components
can be introduced into the objective, said contaminants
subsequently capable of leading to a deterioration of the objective
characteristics. Possible contaminants in this context are
particularly hydrocarbons, water deposits and other particles.
[0006] The hydrocarbons, which are mostly present in the form of
monolayers on the surface of the replacement parts, mostly do not
become detached until irradiation with the objective light used for
imaging, for example, UV laser light. Accordingly, unless further
cleaning takes place, this means that hydrocarbons are present in
the objective and can then enter into chemical reactions at
undesirable regions, and so lead to deposits on the optical
elements. As a result, the imaging properties of the objective are
impaired.
[0007] Similar considerations apply to monolayers of water, which
are also present on replacement parts that are exposed to the
ambient atmosphere. In the normally extremely dry environment
within the objective, the water monolayers desorb or evaporate and
are then also in the objective, as a result of which ozone, which
is highly reactive, can form due to UV light. The water molecules,
too, can then enter into reactions, for example, with hydrocarbons
that are also present in the objective interior or with other
components in the objective interior, such that, due to the
monolayers of water as well, deposits can form on the surfaces of
the optical elements, especially salts. To prevent imaging damage,
US 2006/0001854 A1 accordingly proposes the provision of optical
elements having several usable areas in the objective, such that,
following contamination of one area, a different, clean area can be
moved into the beam, while the contaminated area can be
cleaned.
[0008] JP 11288870 A proposes exchanging contaminated areas and
subsequent cleaning of the contaminated areas for a protective
device between the projection objective and the wafer of a
lithography system.
[0009] A further problem of replaceable components of the optical
system of a lithography system is that particles adhering to the
replacement parts can become detached from the replacement parts
and precipitate on the surfaces of the optical elements, a fact
which also impairs the imaging properties.
[0010] These problems have so far been counteracted by cleaning the
replaced objective parts or the objective interior with cleaning
gas for an adequate length of time. As a result, the desorbed or
evaporated water monolayers or the hydrocarbons or residual parts
thereof which have been transferred into the gas phase during
illumination are driven out of the objective, such that the
corresponding negative deposits are avoided.
[0011] However, this approach has the disadvantage that, first, the
contaminants are introduced into the objective interior and there
is a risk that, on account of the subsequent cleaning, said
contaminants are not completely removed from the objective
interior, such that, for example, a device according to US
2006/0001854 A1 is required. Furthermore, this approach means that
the objective is inoperable for a long period because, during this
time, cleaning takes place after the corresponding parts of the
objective have been replaced.
[0012] Accordingly, the proposed solution was to avoid
contamination of replaceable objective parts by preventing the
parts for installation into the objective from being exposed to the
ambient atmosphere after production and cleaning. This means,
however, that the entire transport chain from storage to transport
right into the objective must be carried out in a correspondingly
clean atmosphere, a fact which represents considerable outlay.
Moreover, there is a risk that, in storage, tiny amounts of
contaminants in the sealed atmosphere around the replaceable
objective part will in turn lead to deposits.
OBJECTS AND SUMMARY OF THE INVENTION
[0013] It is therefore an object of the present invention to
provide a method and a device to replace objective parts for the
purpose of largely avoiding introduction of contaminants into the
objective interior, wherein the replacement is to be conducted in
an effective and easy way. Especially, rapid replacement of
objective parts with short downtimes for the objective is to be
made possible while the problems of the prior art are avoided.
[0014] The above-mentioned objects are achieved, in whole or in
part by methods, cleaning devices, objectives and systems as
disclosed and claimed herein. Advantageous embodiments are also
disclosed and claimed in particular through dependent claims.
[0015] The present invention proceeds from the insight that the
introduction of contaminants into the objective interior can be
effectively prevented during objective parts replacement by
cleaning the replaceable objective part outside the objective
interior immediately prior to installation into the objective and
immediately installing it in the objective after the cleaning and
without contact with the normal ambient atmosphere. Instead of
downstream cleaning of optical elements which become contaminated
by contaminants present in the objective, as is proposed in US
2006/0001854 A1, the approach of the present invention is
pre-emptive avoidance of contamination. The immediate installation
of the replaceable objective part in the objective immediately
after cleaning, without further contact with the normal ambient
atmosphere, has the advantage of minimising the effort of handling
the cleaned objective part under exclusion of the normal ambient
atmosphere, and also prevents contaminant deposits from recurring
on the replaceable objective part after cleaning. Similarly,
immediate installation directly after cleaning means that only as
much time is available until commencement of transfer into the
objective as is necessary for the stages of the transfer process,
or, that less time remains than is required for appreciable
deposition of contaminants. Essentially, therefore, the immediate
installation proceeds without any time delay directly after
cleaning of the replaceable objective part. However, in isolated
cases, short intermediate storage times ranging from a few minutes
to several hours are possible. In normal circumstances, however,
installation of the replaceable objective part is commenced or
completed less than 30 minutes, preferably less than 15 minutes,
especially from a few minutes to several seconds after
cleaning.
[0016] The replaceable objective parts can be all parts present in
an objective or optical system, particularly optical lenses,
mirrors, mirror elements, filters, diaphragms, membranes and the
like.
[0017] By replaceable is particularly understood that the
corresponding objective part can be removed completely from the
objective interior, i.e. completely leaves a housing that seals the
objective interior. Accordingly, replaceable objective parts differ
from merely exchangeable objective parts in that, in the removed
state, they are completely separate from the objective or can be
simply separated from it.
[0018] By objective is understood any optical system, even where no
object is imaged onto an image plane, for example, illumination
systems of microlithography systems. The corresponding objectives
or optical systems can be operated at all kinds of wavelengths,
especially the wavelengths used for microlithography in the range
of 248 nm, 193 nm, 157 nm as well as in the extreme ultraviolet
light range of wavelengths less than 30 nm, especially in the range
of 13 nm and 13.5 nm. Generally, the invention can be realized for
optical systems that use all kinds of wavelengths.
[0019] Cleaning of the replaceable objective part takes place in a
sealed cleaning room to ensure that defined cleaning can take
place. Preferably, the cleaning room has a cleaning atmosphere
different from that of the ambient atmosphere, such that precisely
the contaminants in the ambient atmosphere, such as water,
hydrocarbons and particles can be removed effectively from the
objective part to be cleaned. The cleaning atmosphere can be formed
by vacuum, dry air, nitrogen, dry nitrogen, argon, oxygen, helium,
hydrogen, general inert gases or noble gases and combinations
thereof.
[0020] The cleaning atmosphere can also be different from the
atmosphere in the objective interior, with, however, the atmosphere
in the objective interior also capable of being formed by inert
gases or noble gases, nitrogen, dry nitrogen and combinations
thereof and vacuum.
[0021] The cleaning room sealed off from the ambient atmosphere can
be provided in such local proximity to the objective interior or
arranged there such that a geometrically simple replacement
movement for the objective part or a temporally and/or locally
particularly short replacement movement is possible. This has the
advantage of keeping the handling effort for the cleaned objective
part low.
[0022] By geometrically simple movement can be understood a linear
movement or a swivelling or rotational movement of the replacement
part or generally a movement which can be effected with simple
transport.
[0023] A short temporal movement corresponds to the above-defined
immediate arrangement in the objective directly after cleaning and
corresponds to the definitions specified there.
[0024] In an advantageous embodiment of the invention, the cleaning
room is detachably coupled to the objective interior so as to be
gastight, such that, advantageously, a direct connection is
possible between the cleaning room and objective interior, at least
during installation and removal of the replaceable objective
part.
[0025] The detachable coupling of the cleaning room particularly
ensures that the effort for handling the cleaned replacement part
is kept low. Moreover, the detachable arrangement can permit
flexible use of the cleaning device containing the cleaning room.
This can be coupled to the corresponding coupling point of the
objective housing only in the event of a necessary replacement,
without there being any need for a permanent stationary
arrangement, although this is of course conceivable. Thus, for
example, a service technician can bring a required replacement part
and the mobile cleaning device to the location of the objective to
arrange the cleaning device at the objective there, to remove the
old part from the objective and to install in the objective the new
replacement part after cleaning in the cleaning device. This
ensures a high degree of flexibility and versatility.
[0026] The cleaning device can have a magazine for replaceable
objective parts or can interact with this. This allows different
filters, diaphragms, lenses, mirrors, prisms and the like to be
used in the objective, without causing major downtimes. By means of
the combination of a cleaning device with a magazine for
replaceable objective parts, such as filters, diaphragms, lenses,
mirrors, prisms and the like, a replacement of objective parts can
be effected between two process stages of objective use, such that
the imaging properties of the objective can be coordinated with the
successive process steps of the objective use, without causing
major downtimes of the objective. In the magazine, the replaceable
objective parts can be stored in the same atmosphere that prevails
in the cleaning room or in a separate atmosphere, which largely
avoids contamination during storage in the magazine. Nevertheless,
additional cleaning can take place through introduction via the
cleaning room. Moreover, during the periods in which no replacement
takes place, the objective parts stored in the magazine can undergo
cleaning by repeated movement into the cleaning room.
[0027] According to a further advantageous embodiment of the
invention, several cleaning devices or cleaning rooms can be
provided or be attachable to the objective or to each other. This
enables different cleaning methods and stages to be executed.
[0028] Thus, for cleaning removable objective parts, different
cleaning processes can be used, which preferably can comprise
cleaning by irradiation with electromagnetic waves, especially
ultraviolet radiation, plasma cleaning, especially hydrogen or
oxygen plasma cleaning, evaporation, gas cleaning, liquid cleaning,
ultrasonic cleaning, dipping baths, mechanical cleaning, especially
wiping and the like, and combinations thereof.
[0029] These methods serve to eliminate particles, hydrocarbons and
water monolayers. The cleaning method can relate to the elimination
of one or more of these contaminants, more precisely through a
combination of several or all of the method steps for the purpose
of eliminating these contaminants. Where several cleaning steps are
combined, it is advantageous to eliminate particles first, then
hydrocarbons and then water monolayers. Especially, the elimination
of water monolayers after the removal of hydrocarbons is
advantageous because, during the elimination of the hydrocarbons,
for example, by irradiation with ultraviolet light (UV
irradiation), the presence of a certain quantity of water molecules
is advantageous. The presence of water accelerates the elimination
of hydrocarbons since free-radicals are produced from water
molecules during irradiation.
[0030] For the elimination of particles, the use of ultrasonic
baths, dipping baths with optics-cleaning mixtures and mechanical
wiping of the surface of the objective parts to be replaced is
possible. The applicable optics-cleaning mixtures are generally
known to a person skilled in the art of optics, with corresponding
mixtures of alcohols and the like being used that are absolutely
residue-free.
[0031] For the elimination of hydrocarbons, irradiation of the
replaceable objective part with electromagnetic radiation,
preferably ultraviolet light, is suitable, with a cleaning flow
capable of being adjusted simultaneously in the cleaning room of
the cleaning device in order that hydrocarbons transferred to the
gas phase or residues thereof may be flushed from the cleaning
room. To this end, dry nitrogen with a low oxygen proportion, dry
air or other gas mixtures containing oxygen are suitable. Removal
of hydrocarbons may also be effected by plasma cleaning, with both
low pressure plasma under vacuum conditions (.about.0.1 bar) as
well as a plasma at atmospheric pressure being possible.
Especially, oxygen and hydrogen make suitable gases for the
low-pressure plasma, but other gases such as argon can be used
also. A particularly advantageous method for generating the plasma
consists in excitement by microwaves, for which purpose a
corresponding microwave head in a corresponding cleaning device may
be simply provided. By the aforementioned vacuum is meant a
technical vacuum which can be generated by corresponding extraction
devices, such as pumps.
[0032] Elimination of water monolayers may be effected by
evaporative heating of the replaceable objective part in addition
to using plasma cleaning and here especially of plasma cleaning in
a vacuum. Heating may be effected by an infrared lamp or a heating
wire. Moreover, the removal of water monolayers can be achieved by
cleaning for a sufficiently long period with cleaning gas, for
example dry nitrogen or dry air and helium. This cleaning is
rendered advantageous by the present invention in that the
objective does not have to be decommissioned during cleaning of the
replacement part and thus sufficiently long cleaning times are
facilitated. This is particularly true if the cleaning device is
designed such that, during the replacement process at least, both
the old replaceable objective part as well as the new replaceable
objective part may be accommodated in the cleaning device, such
that, as it were, the objective parts can be exchanged on the
fly.
[0033] A cleaning device according to the present invention
includes a cleaning room for accommodating and cleaning the
replaceable objective part and a connecting part for gastight
connection to an objective housing. The cleaning device can be
detachably connected to an objective, especially an illumination or
projection objective for microlithography.
[0034] It is also advantageous for the cleaning device to have
further connection possibilities for, for example, a transport
channel and/or one or more further cleaning devices, such that the
previously described use of several cleaning rooms or cleaning
devices and the application of different cleaning steps, especially
in succession, is possible. The provision of a transport channel,
especially a transport channel which can be arranged at the
cleaning room, is advantageous because that increases the
versatility of the cleaning device.
[0035] This is further boosted by forming both the connecting part
of the cleaning device for the gastight connection to the objective
housing and the connecting element for the gastight connection of a
transport channel and one or more further cleaning devices so that
they are identical and/or compatible with each other.
[0036] In order to prevent vibrations caused by cleaning or
handling of the replaceable objective part in the cleaning device
from being transmitted into the objective, it is advantageous for
the connecting element to the gastight connection of a transport
channel and/or cleaning devices as well as the connecting part for
the cleaning room or the cleaning device to the objective housing
to have a device for the purpose of mechanical decoupling combined
with maintenance of the sealing effect, such as a gas bearing with
leaky seal with excess pressure or corresponding elastic elements,
such as a bellows.
[0037] The cleaning room of the cleaning device can preferably be
sealed gastight, with the exception of a gas inlet and gas outlet
for the cleaning flow, in order that penetration by contaminants
may be avoided. To this end, sealing elements are provided at the
inlet openings for the objective part to be cleaned and/or at the
connecting parts or elements. Sealing elements can be formed by the
commonly known sealing elements in the form of elastic elements or
gap seals, so-called leaky seals, in which excess pressure ensures
that no contaminants can penetrate from the outside through the gap
present.
[0038] The cleaning device can have a handling device, by means of
which the replaceable objective part can be moved either only in
the cleaning device or both in the cleaning device and for the
purpose of movement into and out of the objective. Alternatively,
the handling device for the replaceable objective part can also be
integrated at the objective.
[0039] The kinematic parts of the handling device may be partially
or completely arranged within the housing of the cleaning room or
the transport channel. By kinematic parts is understood all movable
parts. This means, for example, that only inherently non-movable
control or operating elements are provided outside the cleaning
room or the cleaning device or at the outside of the cleaning
device. For example, this is the case if all parts, such as motor,
transmissions and the like are provided inside the cleaning device
and only the electrical power supply and control unit are
outside.
[0040] It is also conceivable for the drive of the handling device
to be provided outside the cleaning device, although in that event
a gastight or vacuum-tight through-guide for a movable part, such
as a rod, can be provided. To avoid this, a non-contact drive, for
example, utilizing magnetic forces, can also be provided.
Especially, the handling device can comprise a linear motor.
[0041] Like the connecting parts or connecting elements, the
handling device can also be arranged so as to be mechanically
decoupled from the housing of the cleaning room and/or a transport
channel, for which purpose an air bearing can be used. Basically,
all kinds of handling devices can find application.
[0042] The cleaning device comprises all means, devices and
equipment needed for implementing the aforementioned method, for
example, arrangements for introducing and extracting gas, or
corresponding elements for connecting such arrangements, such as
pumps, vacuum pumps, gas supply devices and the like, as well as
corresponding cleaning devices, such as UV lamps, plasma
generators, such as microwave heads, evaporators, IR lamps, heating
wires, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Further advantages, characteristics and features of the
present invention are apparent from the following detailed
description of embodiments using the enclosed drawings. The
drawings show in purely schematic form in
[0044] FIG. 1 a cross-section of a part of an objective with docked
cleaning device and a handling device;
[0045] FIG. 2 a cross-section of a part of an objective with a
further docked cleaning device;
[0046] FIG. 3 a cross-section of a part of an objective with a
third embodiment of a docked cleaning device;
[0047] FIG. 4 a cross-section of a part of an objective with docked
transport channel as well as a fourth embodiment of a cleaning
device;
[0048] FIG. 5 a cross-section of an EUV projection objective with
docked cleaning device;
[0049] FIG. 6 a partial view of a further EUV optics similar to
that in FIG. 5; and
[0050] FIG. 7 a partial view of a third EUV optics similar to that
in FIG. 5.
PREFERRED EMBODIMENTS
[0051] FIG. 1 is a purely schematic cross-section of a part of an
objective 10, which has an objective housing 18, which surrounds
the objective interior 14. In the objective interior 14 are
arranged optical elements in the form of lenses 11, 12, 13.
[0052] Reference number 15 and corresponding dashed-lines indicate
the position of a replaceable objective part 16, which can also be
a lens or a filter or a diaphragm element.
[0053] The replaceable objective part 16, in accordance with the
representation in FIG. 1, is accommodated in the cleaning room of
the cleaning device 20, which is coupled or docked to the objective
housing 18 in the area of position 15 of the replaceable objective
part 16.
[0054] To this end, the cleaning device 20 has a connecting part
21, which interacts with an objective housing opening 17 in such a
way that a gastight connection is created between objective
interior 14 and the cleaning room of the cleaning device 20.
[0055] The cleaning device 20 is detachably arranged at the
objective housing 18. In order that the objective housing opening
17 may be sealed gastight when the cleaning device is not arranged,
an objective housing closure 19 is provided, which can be executed
as a flap or slide. Sealing of the objective housing closure can be
effected by generally known sealing elements, such as elastic
elements or a so-called leaky seal, that is, a seal in which excess
pressure prevents penetration by foreign substances.
[0056] The objective housing closure 19 is formed such that it can
also be sealed when the cleaning device 20 is docked, in order that
foreign substances may be prevented from gaining access to the
objective interior 14 during cleaning in the cleaning device 20.
The closure 19 opens only for transferring the replaceable
objective part 16 in and out. Given sufficiently high gas flow from
the objective into the cleaning device 20, the closure 19 can
remain open during cleaning, since foreign substances are thereby
prevented from gaining access to the objective interior 14.
[0057] The connecting part 21 is mechanically decoupled from the
objective housing 18. This means that little or no vibrations which
arise at or in the cleaning device 20 can be transmitted to the
objective housing 18 and thus to the objective 10. Mechanical
decoupling can proceed by appropriately designing the bearing of
the cleaning device 20 at the objective housing 18. As an example
of this, reference is made to the use of corresponding elastic
elements, such as bellows arrangements or the use of air
bearings.
[0058] The cleaning device 20 in the embodiment of FIG. 1 has a UV
lamp 23, for example in the form of a mercury vapour lamp or
Xerodex (xenon) lamp with broadband wavelength spectrum or in the
form of an, in particular, pulsed UV laser having a correspondingly
narrow (monochromatic) wavelength spectrum.
[0059] The cleaning device 20 is designed such that the replaceable
objective part 16 for cleaning can be arranged in the irradiation
region of the UV lamp 23, such that hydrocarbons on the objective
part 16 can be eliminated by irradiation with UV light. In order
that hydrocarbons transferred to the gas phase or part of the
hydrocarbons may be removed from the cleaning room, the housing of
the cleaning device 20 has a gas inlet opening 24 and a gas outlet
opening 25. Connected to the gas inlet opening 24 is a gas supply
with which a corresponding supply of cleaning gas can be introduced
into the cleaning device 20. Candidate cleaning gases are dry
nitrogen, dry air or helium. Dry nitrogen is especially preferred
for projection or illumination objectives in microlithography,
since such objectives typically already have a supply device for
dry nitrogen, which device also can be used for the cleaning device
20.
[0060] The gas outlet 25 is connected to corresponding pump devices
(not shown), which facilitate particularly good removal of the
gaseous medium contained in the cleaning device 20. By means of the
cleaning flow, the hydrocarbons or residues thereof transferred to
the gas phase by the ultraviolet irradiation are removed from the
cleaning room of the cleaning device 20.
[0061] The cleaning device 20 furthermore has a closing device 22,
which, like the objective housing closure 19 can be realised by a
flap or a slide and corresponding seals.
[0062] A replaceable objective part 16 for introduction into the
position 15 of the objective interior 14 can be introduced into the
cleaning device 20 from outside via the closing device 22.
[0063] To this end, a handling device 30 is available, which has a
gripper 31, with which the replaceable objective part 16 can be
gripped or accommodated. Also provided is a drive 34, for example
in the form of an electric motor or in the form of a manual drive,
which, via a transmission 33, can set the gripper 31 in linear
motion in accordance with the double-headed arrow shown. With this,
the replaceable objective part 16 can be introduced into the
cleaning device 20 or removed from it.
[0064] In the embodiment shown in FIG. 1, the handling device 30
can be used for moving or transporting the replaceable objective
part 16 within the cleaning device 20 or for transporting the
replaceable objective part 16 from the cleaning device 20 into the
objective interior 14 or, conversely, from the position 15 of the
replaceable objective 16 in the objective interior 14 into the
cleaning device 20. To this end is provided closure element 32,
which, in the case of an opened closing device 22 of the cleaning
device 20, is provided at the corresponding opening in order to
seal it gastight. The gripper 31 is, for example, connected by a
rod 35, which is guided through a gastight through-guide through
the closure element 32, to the transmission 33, such that, in the
event that the cleaning device 20 is closed, handling of the
replaceable objective part 16 is possible.
[0065] Replacement of the replaceable objective part 16 proceeds in
the following manner:
[0066] Where the replaceable objective part 16 at position 15 in
the objective room 14 is to be replaced, the cleaning device 20 is
docked by the connecting part 21 to the objective housing 18 in the
region of the objective housing opening 17. In the cleaning device
20, the cleaning gas flow is then adjusted via the gas inlet 24 and
the gas outlet 25 and the cleaning room, in order that the ambient
air contained in the cleaning device 20 may be flushed out. Then,
the objective housing closure 19 is opened and, by means of the
handling device 30, which is connected gastight to the cleaning
device 20 by the closure element 32, the replaceable objective part
16 is gripped by means of the gripper 31 and moved in the direction
of the cleaning device. To this end, drive 34 is actuated, such
that the gripper 31 is retracted in the direction of the cleaning
device 20 via the transmission 33.
[0067] Once the replaceable objective part 16 is inside the
cleaning device 20, the objective housing closure 19 can be closed
again and the replaceable objective part 16 removed from the
cleaning device 20 via the closing device 22.
[0068] Now a further or appropriately prepared replaceable
objective part 16 can be reintroduced into the objective 10 in the
opposite direction. To this end, the objective part 16 located at
the gripper 31 is introduced into the cleaning device 20 in such a
way that it comes to lie in the position shown in FIG. 1. The
closure element 32 of the handling device 30 seals the opening of
the closing device 22 of the cleaning device 20 gastight.
[0069] Then, cleaning can begin, with the UV lamp 23 being switched
on in order that the hydrocarbons, which are located on the surface
of the objective part 16, may be evaporated or decomposed. The
hydrocarbons or hydrocarbon fractions transferred thereby into the
gas phase are discharged from the cleaning device 20 through the
gas outlet 25 by the cleaning gas introduced through gas inlet 24.
Candidate cleaning gas is nitrogen, dry air or helium or other
inert gases or noble gases.
[0070] Since the decomposition of the hydrocarbons is supported by
the presence of a certain quantity of water molecules, i.e. a
concentration of water in the ppm range, it is also possible to use
cleaning gas which is not especially dry and/or to commence
cleaning immediately after the introduction of the replaceable
objective part 16. In the further sequence, water is also removed
by the cleaning gas.
[0071] After cleaning has taken place, the objective housing
closure 19 is opened either under maintenance of the cleaning flow
or after closure of the gas inlet 24 and the gas outlet 25, in
order that the cleaned objective part 16 may be transferred to its
position 15 in the objective interior 14 by means of the handling
device 30. As soon as the objective part 16 is in its place in the
objective 10, the objective housing closure 19 can be closed again
and the cleaning device 20 removed from the objective housing.
[0072] By virtue of the described method using the cleaning device
20, it is no longer necessary on one hand to provide additional
load-lock devices during removal of replaceable objective parts 16
since the cleaning device 20 can take on the load-lock function. In
addition, the cleaning device 20 and the cleaning of the objective
part 16 immediately prior to its introduction avoids laborious
cleaning within the objective.
[0073] This advantage is increased especially if the cleaning
device 20 is designed such that two objective elements 16 and 16'
can be accommodated in it. In this case, the new objective part 16
can then be cleaned in the cleaning device 20 for a certain period
of time, while the old objective part 16' is still located in the
objective 10, such that this can be operated further during
cleaning of the new objective part 16. Once cleaning of the new
objective part 16 is complete, the old objective part 16' is first
removed from the objective 10, stored temporarily in the cleaning
device 20, as shown in FIG. 1, and the new objective part 16 is
introduced into the objective 10. Then, the old objective part 16'
can be removed from the cleaning device 20 or the entire cleaning
device removed from the objective housing 18. In this way,
particularly short replacement times can be realized.
[0074] This applies even more if removal of the one objective part
from the objective and the introduction of the other objective part
16 into the objective 10 occur in a common process step, i.e. the
same handling device is used to move the one objective part 16'
from the objective 10 and to introduce the other objective part 16
into the objective at the same time, such as on a turntable or the
like.
[0075] It can prove advantageous in this connection for a magazine
to be provided at the cleaning device, in which magazine
replaceable objective parts 16, 16' can be stored. Although such a
device is not explicitly depicted in the attached drawings, it can
however be easily realized by an attached gastight room, in which
the same atmosphere exists as in the cleaning room or a special
atmosphere which is particularly suitable for clean storage of the
objective parts.
[0076] FIG. 2 shows a further embodiment of an inventive cleaning
device 126 interacting with an inventive objective 110, with,
again, a purely schematic cross-sectional view being shown.
[0077] The embodiment of FIG. 2 corresponds in large part to that
of FIG. 1, such that similar or identical components having the
same reference symbols have had their numbers increased by 100. A
repeat description of the corresponding components is therefore
unnecessary. The description of FIG. 2 is therefore limited only to
differences in the embodiment.
[0078] The embodiment of FIG. 2 differs from that of FIG. 1
essentially in that, instead of a UV lamp 23, a microwave head 123
is used to generate a plasma. By means of the microwave head 123, a
plasma can be excited in the cleaning room, said plasma being used
to clean the surface of the replaceable objective part 116.
[0079] To excite the plasma, a vacuum is generated in the cleaning
room of the cleaning device 120, said vacuum being generated by
corresponding suction or pump devices (not shown), which are
connected to the outlet 125. Since no additional gas needs to be
introduced in the case of the cleaning device 120, there is no need
for a gas inlet 24 of the kind shown in FIG. 1. However, for the
purpose of generating a plasma, a gas atmosphere, such as hydrogen,
oxygen or argon atmosphere may be adjusted, too, for which purpose
then only a corresponding gas inlet (not shown) with corresponding
gas supply would need to be provided.
[0080] The cleaning device 120 serves especially to remove the
water monolayers. Removal of the water is promoted by the creation
of a vacuum, since in that event a fraction of the water monolayers
on the replaceable objective part 116 is removed by
evaporation.
[0081] Once a stable vacuum has been established, the plasma
excited by the microwave head 123 effects removal of the water
monolayers from the surface of the objective part 116, which are
then removed by the vacuum suction.
[0082] The cleaning device 120 can also be combined with the
cleaning device 20, with, for example, the cleaning device 20
capable of being connected to the closing device 122, such that a
replaceable objective part 116, on being introduced into the
objective 110, is first cleaned of hydrocarbons in the cleaning
device 20 and freed of the water monolayers in a further step in
the cleaning device 120.
[0083] The embodiment of FIG. 2 differs furthermore from the
embodiment of FIG. 1 in that the objective housing closure 119 of
the objective 110 is arranged such that, when the cleaning device
120 is docked, it is arranged outside of it and can no longer be
closed. Instead, the connecting part 121 of the cleaning device 120
has an additional connecting part closure 150, with which the
cleaning room of the cleaning device 120 can be separated from the
objective interior 114 during the cleaning process.
[0084] FIG. 3 shows a further embodiment of an inventive objective
and a cleaning device 220 interacting with it. Again, as in
embodiment 2, similar or identical components are provided with
identical reference symbols, with, in turn, the reference numbers
being 200 higher than in FIGS. 1 and 100 higher than the reference
numbers of FIG. 2. Here, too, an additional description of
components already discussed is eschewed.
[0085] FIG. 3 shows in addition to FIGS. 1 and 2 sealing elements
227 in the region where the cleaning device 220 is connected to the
objective housing 218. In the simplest case, these may be O-rings
or other tensioned elastic elements, such as metal seals, that
guarantee a gastight seal. Alternatively, a leaky seal may be
chosen if, by means of corresponding excess pressure in the
objective 210 or the cleaning device 220, it is ensured that no
foreign substances can gain entry into the objective 210 or the
cleaning device 220.
[0086] Further, FIG. 3 shows that the handling device 230 can also
be fully accommodated in the cleaning device 220, such that
elaborate gastight through-guides for movable parts can be
eschewed. Rather, with such a simple embodiment, it is necessary
only to guide the electrical connecting cable gastight through the
housing of the cleaning device 220 in order, for example, that an
electric power supply for the drive 234 of the handling device 230
may be ensured.
[0087] In this embodiment, an additional closing device 22 or 122,
as in the embodiments of FIGS. 1 and 2, can be eschewed because
accommodation and release of the replaceable objective part 216 in
the removed state from the objective can be effected through the
opening of the connecting part 221.
[0088] To prevent generation of particles by the drive 234 and any
transmission provided for the handling device 230 or to avoid the
need to provide gastight through-guides for movable parts, such as
the rod 35 of the handling device 30, a contactless, externally
driven handling device (not shown) may also be provided, which
functions, for example, by magnetic forces. An example of this
would be a linear motor.
[0089] FIG. 4 shows a fourth embodiment of a cleaning device 320 in
cooperation with an objective 310, also in a schematic
cross-section like the previous depictions of FIGS. 1 to 3.
[0090] Here, again, identical or similar components have identical
reference numbers, but have been increased by 300 relative to FIG.
1, by 200 relative to FIG. 2 and by 100 relative to FIG. 3.
Accordingly, here, too, an additional description of components
already described is eschewed, and only additional components and
parts are described in detail.
[0091] FIG. 4 shows a transport channel 340 as a component of the
cleaning device 320, which channel, however, can be separated from
the actual cleaning room 328, in which cleaning room the dashed
lines represent the position of the replaceable objective part 316
during cleaning.
[0092] In the embodiment shown in FIG. 4, the transport channel 340
accommodates the handling device 330. However, the transport
channel 340 can also be designed so as not to have a handling
device.
[0093] The cleaning channel 340 has a connecting element 341,
which, corresponding to connecting parts 21, 121 and 221, can be
connected to the objective housing 318.
[0094] Moreover, the transport channel 340 has a corresponding
connecting element 343 for connection to the cleaning room 328.
[0095] Corresponding sealing elements for providing a gastight
connection are provided at connecting elements 341 and 343.
[0096] Furthermore, the transport channel 340 also has a gas inlet
342 and a gas outlet 344 to enable flushing of the transport
channel 340, too.
[0097] The embodiment of FIG. 4 differs furthermore from all
previous embodiments in that the gas inlet 324 and the gas outlet
325 are arranged on the same side of the housing of the cleaning
room 328 or the cleaning device 320, in contrast to the previous
examples in which gas inlet 24, 224 and gas outlet 25, 225 are
provided on opposite sides of the housing, more precisely
diametrically opposite each other, in order that gas exchange may
be maximized by the cleaning flow.
[0098] Furthermore, FIG. 4 shows that the housing of the cleaning
room 328 has wheels 329, which schematically are intended to convey
that the cleaning device 320 can have a transport mechanism for
facilitating and executing in a defined manner the movement of the
cleaning device 320, especially during docking and undocking to the
objective housing. Apart from wheels, sliding elements in
conjunction with rails and the like are conceivable.
[0099] FIG. 5 shows the application of the present invention in an
EUV projection objective 410. This exemplifies that the present
invention can be flexibly used in all kinds of optical systems,
such as illumination systems or projection optics, which work at
different wavelength ranges, in microlithography.
[0100] The EUV projection objective 410 has a vacuum vessel 418,
which is shown only in purely schematic form. In the vacuum vessel
418 are arranged the reticle 401 with the structures to be imaged
as well as the mirrors M1 to M6, said mirrors imaging the light
coming from an illumination system IL (not shown) and reflected at
reticle 401 onto a wafer (substrate) 403, which is located on a
wafer stage (substrate holder) 402. As a result, the structure of
the reticle 401 is imaged in reduced form onto a photosensitive
layer on the wafer 403.
[0101] The vacuum vessel 418 has a vacuum vessel opening 417, which
comprises a vacuum vessel closure 419, such that the vacuum vessel
opening 417 can be sealed vacuum-tight in order that the vacuum in
the vacuum vessel 418 may be maintained.
[0102] In order that an objective part, namely the mirror M4, may
be replaced, a cleaning device 420 can be docked vacuum-tight to
the vacuum vessel 418, such that, after opening of the vacuum
vessel closure 419, inside the cleaning device 420 and in the
objective interior of the vacuum vessel 418 a vacuum can be
maintained.
[0103] The cleaning device 420 is merely shown in schematic form
and can be formed according to the embodiments of the examples in
FIGS. 1 to 4. Thus, the mirror M4 can be replaced via the cleaning
device 420 in accordance with the preceding examples. Instead of
the mirror M4, further objective parts can be provided for
replacement, especially diaphragms for the mirrors M1 to M6.
Especially, the cleaning device can be used with a
diaphragm-changing system, as described in US 2007/0053076 A1.
Correspondingly, US 2007/0053076 A1 is hereby incorporated into the
present application by reference in its entirety. The cleaning
device can, in the case of US 2007/0053076 A1, be provided in
combination with the diaphragm magazine, more precisely for the
purpose of cleaning prior to introduction into the magazine and/or
during transfer from the magazine into the optical arrangement.
Furthermore, parts of diaphragm-changing system of US 2007/0053076
A1 can be integrated into the cleaning device, such as the
magazine, or conversely, the cleaning device into the
diaphragm-changing system, such as cleaning devices in the magazine
or a diaphragm-transport path.
[0104] In FIG. 5, the EUV projection optics 410 are shown only with
a vacuum vessel 418. However, the EUV optics can comprise further
housing parts (not shown), which surround individual elements, such
as mirrors, or the light path, in order that a different
atmosphere, such as a different vacuum state, may be adjusted in
surrounded regions. Such a design of an optical arrangement is
described in PCT/EP2007/008113, which is hereby incorporated into
the present application by reference in its entirety. The cleaning
device described in the present application or the corresponding
method for replacing objective parts can also be used for such
optical configurations.
[0105] The cleaning device can in this regard be provided at the
outer vacuum vessel 418, as shown in FIG. 5, while only a
corresponding replacement opening is to be provided in an inner
housing part. This is shown schematically in FIG. 6. FIG. 6 shows a
detail of the vacuum vessel wall 418, at which is provided a vacuum
vessel opening 417 for the replacement of corresponding optics
parts. The vacuum vessel opening 417 can be sealed vacuum-tight
with the vacuum vessel closure 419. For the purpose of replacing a
corresponding objective or optics part, the cleaning device 420, as
described exemplarily in FIGS. 1 to 4, is flanged to the vacuum
vessel wall 418. Provided on the left side of the vacuum vessel
wall 418, i.e. inside the vacuum vessel, is a further housing 430,
in which one or more components of the optical arrangement can be
accommodated in order that atmospheric conditions different from
those of the external vacuum vessel may be adjusted. For the
replacement of an appropriate optics or objective part, a housing
opening 431 is provided, which also can accordingly be sealed
vacuum-tight via a housing closure 432. For the replacement of an
optics part, only the closures 432 and 419 now need to be opened so
that that an optics part can be transferred from the housing 430
into the cleaning device 420 and vice versa.
[0106] FIG. 7 shows a further embodiment in which, provided between
the housing opening 431 and the vacuum vessel opening 417, is a
transport channel 433 in order that the part to be replaced may be
transferred from the housing 430 into the cleaning device 420
direct or vice versa, without coming into contact with the interior
of the external vacuum vessel.
[0107] Although the present invention has been described in detail
in relation to the embodiments presented, the person skilled in the
art will appreciate that the invention is not restricted to these
embodiments, but rather that modifications, especially in the form
of combinations of individual components or omission of certain
individual items, can be realized without departing from the
subject matter of the invention. The applicant seeks, therefore, to
cover all such changes and modifications as fall within the spirit
and scope of the invention, as defined by the appended claims, and
equivalents thereof.
* * * * *