U.S. patent application number 12/836982 was filed with the patent office on 2010-11-04 for illumination optics for a microlithographic projection exposure apparatus.
This patent application is currently assigned to Carl Zeiss SMT AG. Invention is credited to Damian Fiolka.
Application Number | 20100277707 12/836982 |
Document ID | / |
Family ID | 41667603 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100277707 |
Kind Code |
A1 |
Fiolka; Damian |
November 4, 2010 |
ILLUMINATION OPTICS FOR A MICROLITHOGRAPHIC PROJECTION EXPOSURE
APPARATUS
Abstract
Illumination optics for a microlithographic projection exposure
apparatus is used for illumination of an object field in the object
plane with illumination light of a radiation source. The
illumination optics has an optical beam influencing element which
is divided into at least two beam influencing regions in order to
generate various illumination modes for the object field which are
independent of a light attenuation. The optical beam influencing
element is displaceable between a first beam influencing position
where a first one of the beam influencing regions is exposed to a
bundle of the illumination light, and at least another beam
influencing position where another one of the beam influencing
regions is exposed to the bundle of the illumination light. Each of
the beam influencing regions has a surface which is exposable to
illumination light and has a long and a short side length, with the
optical beam influencing element being displaceable perpendicular
to the long side length. The result is an illumination optics which
allows rapid switching between various illumination settings,
preferably within fractions of a second and substantially without
light loss.
Inventors: |
Fiolka; Damian; (Oberkochen,
DE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Carl Zeiss SMT AG
Oberkochen
DE
|
Family ID: |
41667603 |
Appl. No.: |
12/836982 |
Filed: |
July 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12536925 |
Aug 6, 2009 |
7787104 |
|
|
12836982 |
|
|
|
|
Current U.S.
Class: |
355/67 ;
355/77 |
Current CPC
Class: |
G03F 7/70108
20130101 |
Class at
Publication: |
355/67 ;
355/77 |
International
Class: |
G03B 27/54 20060101
G03B027/54; G03B 27/32 20060101 G03B027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2008 |
DE |
102008041179.5 |
Claims
1. An illumination system, comprising: an illumination optics
configured to be used in a microlithographic projection exposure
apparatus, the illumination optics comprising an optical beam
influencing element which is divided into at least first and second
beam influencing regions, the optical beam influencing element is
configured to generate different illumination modes in the object
field, the optical beam influencing element being displaceable
between first and second beam influencing positions, wherein: each
of the beam influencing regions has a long side, a short side and a
surface which is exposable to the illumination light; the optical
beam influencing element is displaceable perpendicular to the long
side of each of the beam influencing regions; when the optical beam
influencing element is in the first beam influencing position, a
first beam influencing region is exposed to a bundle of the
illumination light; when the optical beam influencing element is in
the second beam influencing position, a second beam region is
exposed to the bundle of the illumination light, the illumination
light bundle has a cross-section in a plane of the optical beam
influencing element; the cross-section of the illumination light
bundle has a longer dimension and a shorter dimension; the optical
beam influencing element is displaceable in a direction of the
shorter dimension of the cross-section of the illumination light
bundle; and a ratio between the longer dimension of the
cross-section of the illumination light bundle to the shorter
dimension of the cross-section of the light bundle cross-section is
greater than 2.
2. The illumination system of claim 1, the optical beam influencing
element is configured to generate different angular distribution of
the illumination light.
3. The illumination system of claim 1, wherein: the optical beam
influencing element comprises an optical polarisation forming
element which is divided into at least first and second
polarization forming regions configured to generate various
polarization distributions of the illumination light; the optical
polarization forming element is displaceable between first and
second polarization positions; when the optical polarization
forming element is in the first polarization position, the first
polarization forming region is exposed to the bundle of the
illumination light; and when the optical polarization forming
element is in the second polarization position, the second
polarization forming region is exposed to the bundle of the
illumination light.
4. The illumination system of claim 1, wherein the optical beam
influencing element is arranged in a field plane of the
illumination optics, and the field plane is conjugated with the
object plane.
5. The illumination system of claim 1, wherein the optical beam
influencing element is a diffractive optical element, and the beam
influencing regions are diffractive beam influencing regions.
6. The illumination system of claim 1, wherein the beam influencing
regions have different polarizing effects on the illumination
light.
7. The illumination system of claim 1, wherein at least one of the
beam influencing regions has a depolarizing effect.
8. The illumination system of claim 1, wherein the polarization
forming regions are made of optically active material.
9. The illumination system of claim 3, wherein the polarization
forming regions are transmissive, and the polarization forming
regions have different thicknesses.
10. The illumination system of claim 1, wherein the optical beam
influencing element is linearly displaceable in a driven
manner.
11. The illumination system of claim 1, wherein the optical beam
influencing element is displaceable about a pivot axis in a driven
manner.
12. The illumination system of claim 11, wherein the beam forming
regions are arranged about the pivot axis in the form of sector
portions when seen in the peripheral direction.
13. An apparatus, comprising the illumination system of claim 1;
and a projection optics configured to image the object field
disposed in the object plane into an image field in an image plane,
wherein the apparatus is a projection exposure apparatus.
14. The apparatus of claim 13, wherein the beam forming regions are
rectangular, and a displacement direction extends parallel to the
short side of the beam influencing regions.
15. The apparatus of claim 13, further comprising a reticle holder
and a wafer holder, wherein the reticle holder and the wafer holder
are configured to be synchronously displaceable perpendicular to a
beam direction of the illumination light in a displacement
direction during projection exposure.
16. A method, comprising: using a projection exposure apparatus to
produce microstructured components, wherein the projection exposure
apparatus comprises: the illumination system of claim 1; and a
projection optics configured to image the object field disposed in
the object plane into an image field in an image plane.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/536,925, filed Aug. 6, 2009, which claims priority under 35
U.S.C. .sctn.119 to German Patent Application DE 10 2008 041 179.5,
filed Aug. 12, 2008. The contents of these applications are
incorporated herein by reference in their entirety.
FIELD
[0002] The disclosure relates to an illumination optics for a
microlithographic projection exposure apparatus. The disclosure
further relates to an optical beam influencing element for use in
an illumination optics of this type, an illumination system
comprising an illumination optics of this type, a projection
exposure apparatus comprising an illumination system of this type,
a production method for a microstructured or nanostructured
component using a projection exposure apparatus of this type and a
component produced according to this production method.
BACKGROUND
[0003] An illumination optics for a microlithographic projection
exposure apparatus is disclosed in US 2006/0072095 A1, in US
2007/0211231 A1, in US 2007/0058151 A1 and in US 2006/0158624
A1.
[0004] As far as the microlithographic production of semiconductor
components and other finely structured components is concerned, the
performance of projection exposure apparatuses is essentially
determined by the imaging properties of the projection objectives.
Moreover, the image quality, the process flexibility, the wafer
throughput that is achievable using the apparatus, and other
performance features are essentially determined by properties of
the illumination system, i.e., the illumination optics and the
radiation source, disposed upstream of the projection objective.
The illumination optics should be capable of preparing the light of
a primary light source such as a laser at the highest possible
efficiency so as to generate the most uniform possible intensity
distribution in an object or illumination field of the illumination
system. Furthermore, the illumination system should be able to
generate various modes of illumination so as to optimize the
illumination in terms of the structures of the individual
templates, in other words masks or reticles, to be imaged.
Conventional setting possibilities include various conventional
illumination settings having different degrees of coherence as well
as annular field illuminations and dipole or quadrupole
illumination. Non-conventional illumination settings for generating
an oblique illumination may for instance be employed to achieve an
increased depth of field using two-beam interference or an
increased resolution capability. The generation of various
illumination modes for the object field using the at least two beam
influencing regions of the optical beam influencing element may be
independent of a light attenuation. This is achievable by a
diffractive, refractive or reflective generation in the beam
influencing regions.
[0005] Rapid modifications of the illumination setting allowing a
mask in the object field to be exposed to two different
illumination settings in short intervals may be desired to perform
multiple patternings. The possibilities of conventional
illumination optical systems comprising variably adjustable pupil
forming devices are limited in this regard, in particular if the
masses of the displaceable optical components need to travel
relatively long travel distances in order to switch between
different illumination settings. When exchangeable pupil filters
are used, this may result in light losses.
SUMMARY
[0006] In certain aspects, illumination optics are provided for a
microlithographic projection exposure apparatus which enables rapid
switching between various illumination settings to be carried out
preferably within fractions of a second and substantially without
light loss.
[0007] In certain aspect, the invention features an illumination
optics for a microlithographic projection exposure apparatus for
the exposure of an object field disposed in an object plane to
illumination light of a radiation source, [0008] with the
illumination optics comprising an optical beam influencing element
which is divided into at least two beam influencing regions for the
generation of various illumination modes for the object field
independently of a light attenuation; [0009] with the optical beam
influencing element being displaceable between [0010] a first beam
influencing position where a first one of the beam influencing
regions is exposed to a bundle of the illumination light; [0011] at
least another beam influencing position where another one of the
beam influencing regions is exposed to the bundle of the
illumination light, [0012] with each of the beam influencing
regions comprising a surface which is exposable to illumination
light and has a long and a short side length, with the optical beam
influencing element being displaceable perpendicular to the long
side length.
[0013] Embodiments of the beam influencing element include several
beam influencing regions, with one of the various beam influencing
regions being selectable for exposure to the illumination light
bundle by displacing the beam influencing element. As the beam
influencing regions generate various illumination modes for the
object field, this allows one to switch between the illumination
modes. The beam influencing regions have a beam influencing effect
which is independent of a light attenuation. Examples of such a
beam influencing effect which is independent of the attenuation of
the illumination light include a reflective, a refractive or a
diffractive effect. The beam influencing regions can therefore not
be regarded as filters for the illumination light. The beam
influencing element may comprise two beam influencing regions or
even more than two beam influencing regions such as three, four,
five, eight, ten or even more beam influencing regions. As the
surface of the beam influencing regions is in each case designed
such as to comprise a long and a short side length, a short travel
distance is achievable by displacing the beam influencing element
perpendicular to the long side length, which in turn results in
short switching times. An aspect ratio between the long and the
short side length may be greater than 1.5, greater than 2, greater
than 3, greater than 4, greater than 5 or even greater than 8 or
10.
[0014] The optical beam influencing element may comprise an optical
beam forming element which is divided into at least two beam
forming regions for the generation of various beam angle
distributions of the illumination light, [0015] with the beam
forming element being displaceable between [0016] a first beam
forming position where a first one of the beam forming regions is
exposed to the bundle of the illumination light; [0017] at least
another beam forming position where another one of the beam forming
regions is exposed to the bundle of the illumination light.
[0018] Alternatively, the optical beam influencing element may
comprise an optical polarisation forming element which is divided
into at least two polarization forming regions for the generation
of various polarization distributions of the illumination light,
[0019] with the optical polarization forming element being
displaceable between [0020] a first polarization position where a
first one of the polarization forming regions is exposed to the
bundle of the illumination light; [0021] at least another
polarization position where another one of the polarization forming
regions is exposed to the bundle of the illumination light.
[0022] Beam influencing elements of this type allow illumination
settings to be defined selectively. This may be useful to carry out
demanding exposure tasks such as defined multiple patternings of
one and the same object structure.
[0023] The optical beam influencing element may be arranged in a
field plane of the illumination optics, the field plane being
conjugated to the object plane. In an arrangement of this type, the
beam influencing element only influences the illumination angle.
Alternatively, the beam influencing element may also be arranged
adjacent to or at a distance from a field plane which is conjugated
to the object plane. The beam influencing element is then not only
able to influence illumination parameters across the object field
but also the shape of the object field; in this case, the main
focus may be on influencing the intensity distribution across the
object field. Furthermore, the beam influencing element may be
arranged in a pupil plane which is optically conjugated to a pupil
plane of a projection optics of a projection exposure apparatus,
said projection optics being arranged downstream of the
illumination optics. In this case, the optical beam influencing
element is only able to influence an illumination angle
distribution. Finally, the beam influencing element may also be
arranged adjacent to or at a distance from such a pupil plane. In
this case, the beam influencing element is again able to influence
illumination parameters across the object field as well as the
shape of the object field and the intensity distribution across the
object field; the main focus is then on influencing the
illumination angles.
[0024] The optical beam influencing element may be a diffractive
optical element, with the beam influencing regions being configured
as diffractive beam influencing regions. Using beam influencing
regions of this type, a beam can be influenced in a defined manner
in such a way as to allow even complicated illumination settings
such as multipole settings to be performed.
[0025] The beam influencing regions may have a different polarizing
effect on the illumination light such that the resolution in
particular object geometries to be imaged can be improved even
more. A polarizing beam influencing region may be configured as a
diffractive optical element. Polarizing diffractive optical
elements are disclosed in US 2007/0058151 A1 and in US 2006/0158624
A1.
[0026] At least one of the beam influencing regions may have a
depolarizing effect. This may avoid a preferred direction which may
be undesirable in particular exposure tasks. A depolarizing beam
influencing region is disclosed in U.S. Pat. No. 6,466,303 B1.
[0027] The polarization forming regions may consist of optically
active material. Said material may be an optical rotator or a
birefringent optical material. If the polarization forming regions
are made of optically active material, this ensures a precisely
adjustable polarization.
[0028] The polarization forming elements may be transmissive and
made of material of different thickness. The respective polarizing
effect of the polarization forming region is in each case definable
by selecting the respective thickness.
[0029] The optical beam influencing element may be linearly
displaceable in a driven manner and/or displaceable about a pivot
axis in a driven manner, wherein in the latter case, the beam
forming regions may be arranged about the pivot axis in the form of
sector portions when seen in the peripheral direction. Such
displacement arrangements of the beam influencing element can be
implemented with comparatively little construction effort.
[0030] The advantages of an optical beam influencing element for
use in an illumination optics correspond to those which have
already been explained above with reference to the illumination
optics.
[0031] The advantages of an illumination system including an
illumination optics and a radiation source correspond to those of
the illumination optics. The radiation source may be a DUV source
or an EUV source.
[0032] The forming effect of the illumination system may be such
that the illumination light bundle is spanned in the plane of the
optical beam influencing element by a longer and a shorter bundle
cross-section dimension, with the optical beam influencing element
being displaceable in the direction of the shorter bundle
cross-section dimension. The ratio of the longer to the shorter
bundle cross-section dimension may be greater than 2. The beam
influencing regions of the optical beam influencing element may
have an extension in the direction of the shorter beam
cross-section dimension which exceeds the shorter beam
cross-section dimension by no more than 10%. These embodiments
ensure particularly short switching times of the beam influencing
element when modifying the illumination settings, thus allowing for
switching times in the range of milliseconds.
[0033] A projection exposure apparatus including an illumination
system includes a projection optics for imaging the object field in
the object plane into an image field in an image plane, a reticle
holder for holding a reticle, which is provided which structures to
be imaged, in the object field, and a wafer holder for holding a
wafer in the image field, with preferably the reticle holder and
the wafer holder being displaceable synchronously with each other
in a displacement direction perpendicular to the beam direction of
the illumination light during projection exposure. The advantages
of a projection exposure apparatus of this type correspond to those
which have already been explained above with reference to the
components.
[0034] The beam forming regions may be rectangular, with the
displacement direction of the reticle holder or the wafer holder,
respectively, being substantially parallel to the long side lengths
of the in particular rectangular beam influencing regions. This
ensures a defined illumination of the individual object field
points during projection exposure.
[0035] The advantages of a method for the production of structured
components, the method comprising the following steps: [0036]
providing a wafer which is at least partially provided with a layer
of a light-sensitive material; [0037] providing a reticle which
comprises structures to be imaged; [0038] providing a projection
exposure apparatus; [0039] projecting at least a part of the
reticle onto a region of the layer on the wafer using the
projection exposure apparatus, and the advantages of a component
produced according to this method correspond to those which have
been explained above with reference to the illumination optics and
the projection exposure apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Embodiments of the disclosure will hereinafter be explained
in more detail by means of the drawing in which
[0041] FIG. 1 is a highly diagrammatic meridional section through
optical main components of a projection exposure apparatus for
microlithography;
[0042] FIG. 2 is a highly diagrammatic view of an embodiment of a
modular illumination system for the projection exposure apparatus
according to FIG. 1, with optical components inside the modules
being exposed;
[0043] FIG. 3 is a plan view of a beam influencing element
comprising several beam influencing regions for the generation of
various illumination modes for an object field of the projection
exposure apparatus;
[0044] FIG. 4 is a cutout of the beam influencing element according
to FIG. 3 comprising two beam influencing regions, with far field
distributions generated by these two beam influencing regions also
being shown diagrammatically;
[0045] FIG. 5 is another view similar to FIG. 4 of two beam
influencing regions of a beam influencing element, with the beam
influencing effects thereof, including a polarization influencing
effect, also being shown diagrammatically;
[0046] FIG. 6 is a view similar to FIG. 2 of a cutout of a beam
influencing element comprising an optical beam forming element and
an optical polarization forming element; and
[0047] FIG. 7 is a plan view of another embodiment of an optical
beam influencing element.
DETAILED DESCRIPTION
[0048] FIG. 1 is a diagrammatic meridional section through the
optical main groups of a projection exposure apparatus 1. The
optical main groups are refractive optical elements in this
diagrammatic illustration. The optical main groups may however just
as well be diffractive or reflective components or combinations or
sub combinations of refractive/diffractive/reflective assemblies of
optical elements.
[0049] Each of the Figures is provided with a Cartesian xyz
coordinate system so as to facilitate the description of positional
relationships. The x-axis of FIG. 1 extends perpendicular to and
into the drawing plane. The y-axis of FIG. 1 extends upwards. The
z-axis of FIG. 1 extends to the right and parallel to an optical
axis 2 of the projection exposure apparatus 1. As shown in Figures
yet to be described, the optical axis 2 can optionally be folded
once or several times.
[0050] The projection exposure apparatus 1 comprises a radiation
source 3 which generates useful light in the form of a bundle 4 of
illumination or imaging rays. The useful light 4 has a wavelength
in the deep ultraviolet range (DUV), for instance in the range
between 100 and 200 nm. Alternatively, the useful light may also
have a wavelength in the EUV range, in particular in the range
between 5 and 30 nm.
[0051] An illumination optics 5 of the projection exposure
apparatus 1 transmits the useful light 4 from the radiation source
3 to an object plane 6 of the projection exposure apparatus 1. In
the object plane 6 is arranged an object in the form of a reticle 7
to be imaged using the projection exposure apparatus 1. The reticle
7 is outlined by dashed lines in FIG. 1. The reticle 7 is held by a
reticle holder (not shown) of the projection exposure apparatus 1.
An object field, which is for example rectangular, is illuminated
in the object plane 6.
[0052] The illumination optics 5 and the radiation source 3 are
together also referred to as illumination system of the projection
exposure apparatus 1.
[0053] The first optical main group of the illumination optics 5 is
a pupil forming optics 8. Said pupil forming optics 8 serves to
generate a defined intensity distribution of the useful light 4 in
a downstream pupil plane 9 of the illumination optics 5. The pupil
forming optics 8 images the radiation source 3 in a plurality of
secondary light sources. The pupil forming optics 8 may
additionally also have a field forming effect. As will be explained
below, the pupil forming optics 8 may be equipped with a
diffractive optical element. Alternatively or in addition thereto,
the pupil forming optics 8 may also be equipped with pupil-forming
optical elements in the form of facet elements or honeycomb
elements. The pupil plane 9 is optically conjugated to another
pupil plane 10 of a projection objective 11 of the projection
exposure apparatus 1, the projection objective 11 being arranged
downstream of the illumination optics 5 between the object plane 6
and an image plane 12.
[0054] In the image plane 12 is arranged a wafer 13 which is
outlined by dashed lines in FIG. 1. Using the projection objective
11, the object field in the object plane 7 is imaged into an image
field on the wafer 13 in the image plane 12. The wafer 13 is held
by a wafer holder of the projection exposure apparatus 1, the wafer
holder not being shown in the drawing.
[0055] During projection exposure, the reticle 7 and the wafer 13
are scanned synchronously with each other in the y-direction. A
so-called stepper operation of the projection exposure apparatus 1
is conceivable as well where the reticle 7 and the wafer 13 are
gradually displaced synchronously with each other in the
y-direction between two exposures. The y-direction is therefore an
object displacement direction of the projection exposure apparatus
1.
[0056] Downstream of the pupil plane 9 that is arranged behind the
pupil forming optics 8 is disposed another optical main group of
the illumination optics 5 in the form of a field lens group 14. The
field lens group 14 has an object-field forming effect. The field
lens group 14 may be additionally be provided with a diffractive
field forming element. A microlens array may be part of the field
lens group 14 as well. Behind the field lens group 14 is arranged
an intermediate image plane 15 which is conjugated to the object
plane 6. In the intermediate image plane 15 is disposed a diaphragm
16 which defines an edge boundary of the object field to be
illuminated in the object plane 6. The diaphragm 16 is also
referred to as REMA diaphragm (reticle masking system for masking
the reticle 7).
[0057] The intermediate image plane 15 is imaged into the object
plane 6 using an objective group 17 which is also referred to as
REMA lens group. The objective group 17 is another optical main
group of the illumination optics 5. In the objective group 17 is
arranged another pupil plane 18 of the illumination optics 5.
[0058] FIG. 2 is a partially more detailed view of an embodiment of
the illumination optics 5. First of all, the pupil forming optics 8
includes a beam expansion optics which is configured as a Galilei
telescope comprising lenses 19, 20. A typical expansion factor of
this expansion optics 19, 20 is between 2 and 5. Behind the
expansion optics 19, 20, the useful light 4 impinges upon a row
array 21 of diffractive optical elements (DOEs) 22. The array 21 is
an optical beam influencing element, with the individual DOEs 22
forming beam influencing regions of the beam influencing element 21
for generating various illumination modes for the object field. In
front of the array 21, the useful light 4 is polarized in a
direction that is linearly parallel to the drawing plane of FIG. 2
(p-pol). The DOE 22, which is currently passed through by light in
the arrangement according to FIG. 2, causes the polarization of the
useful light 4 to be rotated. Behind the array 21, the useful light
4 is polarized in a direction that is linearly perpendicular to the
drawing plane of FIG. 2 (s-pol).
[0059] FIG. 3 shows a current illumination mode of the beam
influencing element 21. There are eight beam influencing regions 22
in FIG. 3 which are arranged next to one another in the
x-direction, with the third beam influencing region 22 to the left
being exposed to the bundle 4 of useful radiation. The beam
influencing regions 22 comprise in each case one surface that is
exposable to the bundle 4 of illumination radiation, the surface
comprising a long side length which extends in the y-direction and
a short side length which extends in the x-direction. The beam
influencing regions 22 are directly adjacent to each other in the
x-direction. The beam influencing regions 22 are rectangular and
have a y/x aspect ratio of approximately 5.5 in the illustrated
embodiment. Other aspect ratios, for instance in the range between
2 and 10, are conceivable as well. The bundle 4 of illumination
radiation is also rectangular in the plane of the beam influencing
element 21 and is spanned by a longer bundle cross-section
dimension extending in the y-direction and a shorter bundle
cross-section dimension extending in the x-direction. The ratio of
the longer bundle cross-section dimension to the shorter bundle
cross-section dimension is approximately 8 in the illustrated
embodiment. Other aspect ratios which may be greater than 5 or
greater than 2 are conceivable as well. Exactly one of the DOEs 22,
in other words exactly one beam influencing region, is exposed to
the bundle 4 of useful radiation.
[0060] Due to their DOE design, the beam influencing regions 22
have a beam influencing effect which is independent of an
attenuation of the bundle 4 of useful radiation. The bundle 4 of
useful radiation is therefore influenced by the beam influencing
element 21 in such a way that no filtering of the bundle 4 of
useful radiation occurs. The DOEs 22 are outlined as transmissive
DOEs in FIG. 2. Alternatively, the DOEs 22 may also be designed as
reflective DOEs.
[0061] The beam influencing element 21 may be arranged in a field
plane of the illumination optics 5 which is optically conjugated to
the object plane 6. Alternatively, the beam influencing element 21
may also be arranged in an intermediate plane between a field plane
conjugated to the object plane and a pupil plane of the
illumination optics 5.
[0062] The beam influencing regions 22 of the beam influencing
element 21 have an extension x.sub.0 in the x-direction which
exceeds the shorter bundle cross-section dimension x.sub.B of the
bundle 4 of useful radiation in the plane of the beam influencing
element 21 by no more than 10%. Provided that the beam influencing
element 21 is adjusted correctly, this ensures that the bundle 4 of
useful radiation is able to impinge upon exactly one of the beam
influencing regions 22, thus preventing portions of the useful
light 4 from impinging upon the directly adjacent beam influencing
regions 22 in an unwanted manner.
[0063] The beam influencing element 21 is displaceable in a
switching direction 23 which extends parallel to the x-direction. A
length of a switching displacement with an absolute value of
x.sub.0 causes an adjacent one of the beam influencing regions 22
to be exposed to the bundle 4 of useful radiation instead of the
beam influencing region 22 exposed thereto in FIG. 3. At a given
shorter bundle cross-section dimension x.sub.B, the length ratio
between the dimensions x.sub.0 and x.sub.B ensures that modifying
the exposure of the beam influencing regions 22 only requires a
short switching travel of the beam influencing element 21 in the
switching direction 23.
[0064] For displacement in the switching direction 23, the beam
influencing element 21 is mechanically connected to a driven
retaining element 24 which is diagrammatically shown in FIGS. 2 and
3. A drive motor of the retaining element 24 is connected with a
central control device 26 of the projection exposure apparatus 1
via a signal line 25 (cf. FIG. 3).
[0065] FIG. 4 shows the beam influencing effect of a first
embodiment of the beam influencing regions 22. The Figure shows a
slightly enlarged view of two selected beam influencing regions 22a
and 22b of the beam influencing element 21. The beam influencing
regions 22a, 22b only have a beam forming effect, in other words
they do not influence the polarization of the incident bundle 4 of
useful radiation.
[0066] Apart from the two beam influencing regions 22a, 22b, FIG. 4
also shows the beam influencing effect of far field distributions
characterizing these two beam influencing regions 22a, 22b. The
beam influencing region 22a shown on the left of FIG. 4 generates a
far field distribution 27a in the form of a y-dipole. When the beam
influencing region 22a is exposed to the bundle 4 of useful
radiation, a corresponding y-dipole illumination of the reticle 7
is generated in the object plane 6.
[0067] The beam influencing region 22b shown on the right of FIG. 4
generates a far field distribution 27b in the form of an x-dipole.
When the beam influencing region 22b is exposed to the bundle 4 of
useful radiation, this results in a corresponding x-dipole
illumination of the reticle 7 in the object plane 6.
[0068] Alternatively or in addition thereto, the beam influencing
element 21 may also comprise polarization forming regions whose
rectangular extension in the plane of the beam influencing element
21 is identical to that of the beam influencing regions 22. FIG. 5
is an illustration similar to FIG. 4 of such polarization forming
regions 28, shown by the example of two polarization forming
regions 28a and 28b. The illumination forming effect of the
polarization forming regions 28a, 28b corresponds to that of the
beam influencing regions 22a and 22b. The illumination forming
effect of the polarization forming region 28a is such that a
y-dipole 27a is generated while the illumination forming effect of
the polarization forming region 28b is such that an x-dipole 27b is
generated. In addition thereto, the polarization forming region
shown 28a on the left of FIG. 5 generates a polarization x.sub.pol
of the useful light 4 in the x-direction while the polarization
forming region 28b generates a polarization y.sub.pol of the useful
light 4 in the y-direction.
[0069] The polarization forming regions 28 may be made of optically
active material, for instance in the form of an optical rotator or
of a birefringent optical material. In order to generate different
polarizing effects, the polarization forming regions 28a, 28b may
consist of the same material while having a different thickness
when seen in the beam direction of the useful light 4. This applies
if the polarization forming regions 28 are designed as regions
which are transmissive of the useful light 4. In this case,
advantage can be taken of a linear or a circular birefringence.
[0070] Corresponding polarization forming regions 28 may also have
a depolarizing effect, in other words they may influence incident
polarized useful light 4 in such a way that said useful light 4
will be depolarized behind the polarization forming regions 28.
[0071] Downstream of the beam influencing element 21, the useful
light 4 propagates through a lens 29 (cf. FIG. 2) and a zoom axicon
30 which allows illumination angles defined by the beam influencing
element 21 to be continuously fine-tuned in the object field. The
optical components 19, 20, 21, 20 and 30 are components of the
pupil forming optics 8 of the illumination optics 5. Behind the
zoom axicon 30, the useful light 4 is reflected by a 90.degree.
mirror 31 before passing through a raster element 32 in the form of
a honeycomb condenser. The optical components 29 to 32 are combined
in a zoom axicon module 33.
[0072] Behind the raster element 32, the useful light 4 passes
through a field lens 34 which is a part of an input coupling module
35 of the illumination optics 5. The optical components 32 and 34
are parts of the field lens group 14 of the illumination optics
5.
[0073] The REMA diaphragm 16 is arranged behind the input coupling
module 35. Arranged downstream of said REMA diaphragm 16 is another
90.degree. mirror 36 behind which is arranged the objective group
17 of which two lenses 37, 38 are shown. The optical components 16,
36, 37 and 38 are parts of a REMA module 39 of the illumination
optics 5.
[0074] During operation of the projection exposure apparatus 1
comprising the illumination optics 5, the reticle 7 may be
subjected to double patterning. To this end, the impingement of a
first beam influencing region 22 of the beam influencing element 21
is first determined by corresponding actuation of the drive motor
of the retaining element 24 using the control device 26. The
reticle 7 is then exposed to the correspondingly formed bundle 4 of
illumination radiation. The beam influencing element 21 is then
displaced in the switching direction 23 by the drive motor of the
retaining element 24 via a switching command of the control device
in such a way that a second selected beam forming region 22 of the
beam forming element 21 is now exposed to the bundle 4 of
illumination radiation, with the bundle 4 of illumination radiation
being formed correspondingly in this process. The already
illuminated portion of the reticle 7 in the object field of the
object plane 6 is then illuminated for a second time. The second
selected beam forming region 22 is generally a beam forming region
that is directly adjacent to the beam forming region 22 that was
first illuminated. It is generally conceivable to skip one beam
influencing region 22 or several beam influencing regions 22 when
displacing the beam influencing element 21. These two exposures in
which illumination is carried out using bundles 4 of illumination
radiation with correspondingly different illumination angle
distributions may take place in rapid succession, with the beam
influencing element 21 being rapidly switched from one position to
the other, for example.
[0075] FIG. 6 shows another embodiment of a beam influencing
element 40. Said beam influencing element 40 not only has a beam
forming element 41 comprising beam forming regions 22 corresponding
to those that have been explained above with reference to FIGS. 3
and 4 but also a polarization forming element comprising
polarization forming regions 43a and 43b. The polarization forming
regions 43 are beam forming regions as well and have only a
polarizing but no beam forming effect. The polarization forming
region 43b shown on the right of FIG. 6 rotates the polarization of
the incident useful light 4 through 90.degree.. The situation is
shown where p-polarized useful light 4, i.e. incident useful light
4 which is parallel to the drawing plane of FIG. 6, is s-polarized,
i.e. in the direction perpendicular to the drawing plane of FIG. 6,
after passing through the polarization forming region 43b. The
polarization forming region 43a has for example a depolarizing
effect, causing p-polarized incident useful light 4 to be
depolarized when passing through the polarization forming region
43a, with the result that a depolarized illumination of the object
field is achieved in the object plane 6.
[0076] The polarization forming element 42 and the beam forming
element 41 are arranged one behind the other in the beam direction
(z-direction) of the bundle 4 of illumination radiation. The
distance between these two elements 42, 41 may amount to several
millimetres. Alternatively, the two elements 42, 41 may be arranged
at positions in the illumination optics 5 which are at a greater
distance from each other.
[0077] The beam forming element 41 on the one hand and the
polarization forming element 42 on the other are displaceable in
switching directions 23.sub.f and 23.sub.p independently of each
other, said switching directions 23.sub.f, 23.sub.p extending
parallel to the x-direction. To this end are provided respective
retaining elements 24.sub.f and 24.sub.p whose drives are signally
connected with the control device 26 in a manner not shown.
[0078] The beam influencing element 40 allows for independent
setting of the illumination angle in the object plane 6 on the one
hand and of the illumination polarizations in the object plane 6 on
the other.
[0079] The drive of the retaining element 24.sub.p also allows the
polarization forming element 42 to be moved out of the beam path of
the useful light 4 entirely, with the result that a non-polarizing
effect is achieved.
[0080] FIG. 7 shows another embodiment of a beam influencing
element 44. Components which correspond to those that have already
been explained above with reference to FIGS. 1 to 6 are denoted by
the same reference numerals and are not discussed in detail
again.
[0081] Instead of rectangular beam influencing regions 22, beam
influencing regions 45 of the beam influencing element 44 have the
shape of sector portions which are arranged about a pivot axis 46
of the beam influencing element 44 when seen in the peripheral
direction. A switching direction 47 of the beam influencing element
44 extends about the pivot axis 36 in the peripheral direction as
well. The beam influencing regions 45 have a beam influencing
effect as described above with reference to the various embodiments
of the beam influencing regions 22, 28 and 43 according to FIGS. 2
to 6.
[0082] The beam influencing element 44 is drivable, via a retaining
element (not shown), about the pivot axis 46 using a drive
motor.
[0083] Said retaining element is again signally connected with the
control device 26 of the projection exposure apparatus 1.
[0084] The control device 26 again permits actuated switching
between the beam influencing regions 45 as described above with
reference to the embodiments according to FIGS. 2 to 6.
[0085] The above described embodiments of the beam influencing
elements are provided with diffractive beam influencing regions.
Reflective or refractive beam influencing regions may be provided
alternatively or in addition to the diffractive beam influencing
regions as well. Alternatively or in addition to beam influencing
regions of this type, it is finally conceivable as well to provide
beam influencing regions such as gray filters for useful light 4
which attenuate the useful light 4. The exposable surface of the
refractive, reflective or filtering beam influencing regions may be
dimensioned such as explained above with reference to the
embodiments, in other words they may in particular comprise a long
and a short side length, with the optical beam influencing element
comprising said beam influencing regions then being displaceable
perpendicular to said long side length as well.
[0086] Other embodiments are in the following claims.
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