Patent Description:
An illumination optical unit comprising a transmission optical unit and an illumination-predetermining facet mirror, disposed downstream thereof, is known from <CIT> and <CIT>. Illumination optical units, in which the illumination-predetermining facet mirror or a corresponding refractive component is arranged in a pupil plane, are known from <CIT>, <CIT> and <CIT>. <CIT> has disclosed a projection exposure apparatus with an anamorphic projection optical unit. <CIT> discloses a microlithographic projection exposure apparatus. <CIT> discloses a facet mirror for use in a microlithographic projection exposure apparatus and a projection exposure apparatus equipped therewith. <CIT> discloses astigmatic components for reducing a honeycomb aspect ratio in EUV illumination systems. <CIT> discloses an optical mirror having a plurality of neighboring mirror elements and a method to produce such a mirror. <CIT> discloses an optical apparatus as part of an exposure apparatus capable of illuminating an irradiation surface under a required illumination condition.

It is an object of the present invention to develop an illumination optical unit of the type set forth at the outset in such a way that this results in an exit pupil of a downstream projection optical unit for imaging the object field in an image field being filled as completely as possible. According to the invention, this object is achieved by an illumination optical unit comprising the features specified in Claim <NUM>.

What was identified is that a line-by-line and/or column-by-column arrangement of sub-pupil regions in the illumination pupil leads to the possibility of, within predetermined pupil regions, tightly filling not only the illumination pupil with the envelope deviating from the circular form but also the exit pupil of a downstream projection optical unit for imaging the object field. Integrated over an object displacement, it is possible to achieve, in particular, a completely filled pupil and, within predetermined tolerances, even a homogeneously completely filled pupil.

The envelope of the illumination pupil of the illumination optical unit is a contour within which an illumination pupil of the illumination optical unit with the maximum extent can be inscribed. The illumination pupil of the illumination optical unit with the maximum extent is the illumination pupil with which the largest illumination angle bandwidth of the illumination angle distribution in the object field is generated using the illumination optical unit. To the extent that different illumination settings with different illumination angle distributions can be generated by the illumination optical unit, the illumination pupil with the largest generable area is the illumination pupil with the maximum extent. In the case of a uniform pupil filling, such a pupil with the largest area is also referred to as a conventional illumination setting.

To the extent that the illumination optical unit includes a pupil facet mirror, the envelope of a maximum impingement region of the pupil facet mirror corresponds to the envelope of the illumination pupil. The sub-pupil regions can be present in a line-by-line and column-by-column manner in a raster arrangement. The lines of this raster arrangement can extend along one of the two dimensions spanning the illumination pupil and the columns of the raster arrangement can extend along the other of these pupil dimensions spanning the illumination pupil. The lines and columns of this raster arrangement can also be rotated, for example by <NUM> degrees, in relation to dimensions which span the illumination pupil. One of these dimensions spanning the illumination pupil extends parallel to an object displacement direction, along which an object to be illuminated during projection lithography is displaced during the projection exposure. To the extent that the illumination optical unit is used in a scanner-illumination-projection exposure apparatus, the object displacement direction is the scanning direction. The arrangement of the first transmission optical unit and of the illumination-predetermining facet mirror can be such that an illumination of the illumination pupil of the illumination optical unit, which predetermines the illumination distribution in the object field, results with an envelope deviating from a circular form.

Alternatively or additionally, the envelope of the illumination pupil, deviating from the circular form, can also be generated by a further transmission optical unit disposed downstream of the illumination-predetermining facet mirror.

An object to be illuminated is arrangeable in the object field which is illuminated by the illumination optical unit. During the projection exposure, this object is displaceable along an object displacement direction. The object field is spanned by object field coordinates x and y, wherein the y-coordinate extends parallel to the object displacement direction. An x/y-aspect ratio of the envelope of the illumination pupil with the maximum extent can be greater than <NUM> and can, in particular, be greater than <NUM>, can be greater than <NUM>, can be greater than <NUM>, can be greater than <NUM>, can be greater than <NUM> and can, for example, equal <NUM>.

The sub-pupil regions in the illumination pupil have a maximum extent in a first sub-pupil dimension and a minimum extent in a second sub-pupil dimension, wherein a ratio between the maximum extent and the minimum extent is at least <NUM>. Such an aspect ratio deviating from <NUM> of the sub-pupil regions, even in the illumination pupil, can be used for pre-compensation of an anamorphic effect of a projection optical unit, which is arranged downstream from the illumination optical unit. The aspect ratio of the sub-pupil regions can be pre-set in such a way that e.g. round sub-pupil regions then emerge in an exit pupil of the projection optical unit as a result of the subsequent anamorphic effect of this projection optical unit. The ratio between the maximum extent and the minimum extent of the sub-pupil regions can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM> and can be even larger. In particular, the sub-pupil regions can have an elliptical embodiment. The aspect ratio can either be due to the light source or can be caused by means of a transmission optical unit, for example via anamorphic imaging within the illumination optical unit. The sub-pupil dimension with the maximum extent of the sub-pupil regions can extend parallel to the pupil dimension with the maximum extent of the envelope of the illumination pupil.

An embodiment of the illumination optical unit comprising a pupil facet mirror according to Claim <NUM> has proven its worth. A field facet mirror arranged in a field plane of the illumination optical unit can be part of the first transmission optical unit. Field facets of such a field facet mirror can be subdivided into a plurality of individual mirrors, in particular into a plurality of MEMS mirrors. In the case of a pupil facet mirror embodiment of the illumination optical unit, an arrangement of the pupil facets corresponds to the arrangement of the sub-pupil regions. Correspondingly, the arrangement of the pupil facets is then present in a corresponding line-by-line and/or column-by-column manner. On their part, such pupil facets can in turn be made up of a plurality of individual mirrors, for example a plurality of MEMS mirrors. As a result, the etendue that is usable overall for a downstream projection optical unit can be optimized.

An illumination optical unit according to Claim <NUM> constitutes an alternative to the embodiment with a pupil facet mirror. This alternative embodiment, in which the illumination-predetermining facet mirror is arranged at a distance from a pupil plane of the illumination optical unit, is also known as a specular reflector.

A configuration of the illumination pupil according to Claim <NUM> allows compensation of an anamorphic effect of a downstream projection optical unit. The ratio between the maximum and the minimum extent, which corresponds to the x/y-aspect ratio of the envelope discussed above, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM>, can be at least <NUM> and can be even larger. The transmission optical unit and the illumination-predetermining facet mirror of the illumination optical unit can be arranged in such a way that the sub-pupil regions in the two pupil dimensions have the same spacing from one another. Alternatively, the transmission optical unit and the illumination-predetermining facet mirror of the illumination optical unit can be arranged in such a way that the sub-pupil regions are spaced further from one another in the pupil dimension with the maximum extent than in the pupil dimension with the minimum extent.

An offset arrangement of the sub-pupil regions according to Claim <NUM> enables further compacting of the sub-pupil regions in the illumination pupil. The sub-pupil regions of one of the lines of the arrangement can be arranged offset from one another relative to the sub-pupil regions of an adjacent line of the arrangement by half the spacing of sub-pupil regions adjacent to one another within a line. By way of example, a rotated Cartesian arrangement of the sub-pupil regions or else a hexagonal arrangement of the sub-pupil regions may then emerge, depending on the spacings of the sub-pupil regions within a column and within a line, i.e. depending on the grid constants of such a line-by-line and column-by-column arrangement.

The sub-pupil regions of adjacent lines can partly overlap one another in a direction perpendicular to the extent of the line, which further increases the compactness of the arrangement of the sub-pupil regions in the illumination pupil. A corresponding statement applies to a possible overlap of the columns.

The transmission facets according to Claim <NUM> can be embodied monolithically or as groups of individual MEMS mirrors. The transmission facets or transmission facet groups can be embodied as cylindrical optical units. This can make a contribution to a desired anamorphic image of the illumination optical unit.

An aspect ratio of the envelope of the transmission facet mirror according to Claim <NUM> can be advantageous when the transmission facet mirror is part of anamorphic imaging of the illumination optical unit. The maximum field dimension can extend parallel to the minimum pupil dimension. The minimum field dimension can extend parallel to the maximum pupil dimension.

A collector according to Claim <NUM> was found to be particularly suitable for the predetermination of an anamorphic imaging effect of the illumination optical unit. This saves an additional component of the illumination optical unit. Anamorphic imaging of such a collector can generate sub-pupil regions deviating from rotational symmetry, in particular elliptical sub-pupil regions. The collector can include a collector subunit which generates a secondary intermediate image of the light source in the beam path of the illumination light. The collector can include at least one further collector subunit which generates a further intermediate image in the pupil plane of the illumination pupil. The secondary intermediate image can be rotationally symmetric. The collector can include collector subunits or collector components which are realized by NI mirrors and/or by GI mirrors. At least one of the collector subunits can be configured as a Wolter collector unit. By way of example, Wolter optical units are described in <CIT> and in the citations specified there. The collector can also generate an intermediate image of the light source deviating from rotational symmetry as the first intermediate image. Such an intermediate image can then be imaged in the pupil plane of the illumination pupil by further components of the transmission optical unit.

A further transmission optical unit according to Claim <NUM> increases the number of degrees of freedom when designing the optical components of the illumination optical unit. The further transmission optical unit can be embodied as anamorphic optical unit. Alternatively, an already non-rotationally symmetric image of the light source can be imaged by means of the further transmission optical unit. The further transmission optical unit can be embodied by a rotationally symmetric telescopic optical unit. Alternatively, the transmission optical unit can include at least one cylinder component.

The advantages of an optical system according to Claim <NUM>, an illumination system comprising an illumination optical unit according to one of the aspects discussed above and further comprising a light source, a projection exposure apparatus according to Claim <NUM>, a production method according to Claim <NUM> and a microstructured or nanostructured component, produced according to such a production method, correspond to those which were already discussed above with reference to the illumination optical unit.

Exemplary embodiments of the invention are explained in detail below on the basis of the drawing. In the latter:.

A microlithographic projection exposure apparatus <NUM>, depicted very schematically and in a meridional section in <FIG>, includes a light source <NUM> for illumination light <NUM>. The light source is an EUV light source which generates light in a wavelength range between <NUM> and <NUM>. Here, this can be an LPP (laser produced plasma) light source, a DPP (discharge produced plasma) light source or a synchrotron radiation-based light source, for example a free electron laser (FEL).

A transmission optical unit <NUM> serves to guide the illumination light <NUM> emanating from the light source <NUM>. Said transmission optical unit includes a collector <NUM>, merely depicted in <FIG> in respect of its reflective effect, and a transmission facet mirror <NUM>, which is also referred to as first facet mirror and described in more detail below. An intermediate focus 5a of the illumination light <NUM> is arranged between the collector <NUM> and the transmission facet mirror <NUM>. A numerical aperture of the illumination light <NUM> in the region of the intermediate focus 5a is e.g. NA = <NUM>. An illumination-predetermining facet mirror <NUM>, which is likewise still explained in more detail below, is disposed downstream of the transmission facet mirror <NUM> and hence downstream of the transmission optical unit <NUM>. As will likewise be explained in more detail below, the illumination-predetermining facet mirror <NUM> can be arranged in, or in the region of, a pupil plane of the illumination optical unit <NUM> in one embodiment of the illumination optical unit <NUM> and can also be arranged at a distance from the pupil plane or the pupil planes of the illumination optical unit <NUM> in a further embodiment of the illumination optical unit <NUM>.

A reticle <NUM>, which is arranged in an object plane <NUM> of a downstream projection optical unit <NUM> of the projection exposure apparatus <NUM>, is disposed downstream of the illumination-predetermining facet mirror <NUM> in the beam path of the illumination light <NUM>. The projection optical unit <NUM> and the projection optical units of the further embodiments described below respectively are a projection lens.

A Cartesian xyz-coordinate system is used below so as to simplify the illustration of positional relationships. In <FIG>, the x-direction extends perpendicular to the plane of the drawing and into the latter. In <FIG>, the y-direction extends to the right. In <FIG>, the z-direction extends downwards. Coordinate systems used in the drawing respectively have x-axes extending parallel to one another. The extent of a z-axis of these coordinate systems follows a respective main direction of the illumination light <NUM> within the respectively considered figure.

The optical components <NUM> to <NUM> are constituents of an illumination optical unit <NUM> of the projection exposure apparatus <NUM>. The illumination optical unit <NUM> is used to illuminate an object field <NUM> on the reticle <NUM> in the object plane <NUM> in a defined manner. The object field <NUM> has an arcuate or partial circle-shaped form and is delimited by two circular arcs, parallel to one another, and two straight side edges which extend in the y-direction with a length y<NUM> and which have a spacing of x<NUM> in the x-direction. The aspect ratio x<NUM>/y<NUM> is <NUM> to <NUM>. An insert in <FIG> shows a plan view (not to scale) of the object field <NUM>. An edge form 8a is arcuate. In the case of an alternative and likewise possible object field <NUM>, the edge form thereof is rectangular.

The projection optical unit <NUM> is merely indicated in part and very schematically in <FIG>. What is depicted is an object field-side numerical aperture <NUM> and an image field-side numerical aperture <NUM> of the projection optical unit <NUM>. Further optical components (not depicted in <FIG>) of the projection optical unit <NUM> for guiding the illumination light <NUM> between the optical components <NUM>, <NUM> are situated between these indicated optical components <NUM>, <NUM> of the projection optical unit <NUM>, which, for example, can be embodied as mirrors that reflect the EUV illumination light <NUM>.

The projection optical unit <NUM> images the object field <NUM> in an image field <NUM> in an image plane <NUM> on a wafer <NUM> which, like the reticle <NUM> as well, is carried by a holder not depicted in any more detail. Both the reticle holder and the wafer holder are displaceable both in the x-direction and the y-direction by means of appropriate displacement drives. In <FIG>, installation space requirements of the wafer holder are depicted at <NUM> as a rectangular box. The installation space requirements <NUM> are rectangular with an extent in the x-, y- and z-direction that is dependent on the components to be housed therein. By way of example, proceeding from the centre of the image field <NUM>, the installation space requirements <NUM> have an extent of <NUM> in the x-direction and in the y-direction. Proceeding from the image plane <NUM>, the installation space requirements <NUM> also have an extent of e.g. <NUM> in the z-direction. The illumination light <NUM> must be guided in the illumination optical unit <NUM> and in the projection optical unit <NUM> in such a way that it is in each case guided past the installation space requirements <NUM>.

The transmission facet mirror <NUM> has a plurality of transmission facets <NUM>. The transmission facet mirror <NUM> can be configured as a MEMS mirror. Of these transmission facets <NUM>, the meridional section according to <FIG> schematically shows a line with a total of nine transmission facets <NUM>, which, from left to right, are denoted by <NUM><NUM> to <NUM><NUM> in <FIG>. In actual fact, the transmission facet mirror <NUM> has a substantially larger multiplicity of transmission facets <NUM>. The transmission facets <NUM> are grouped into a plurality of transmission facet groups not depicted in any more detail.

Overall, the transmission facet mirror <NUM> has a region which is impinged by the illumination light <NUM> and can have an x/y-aspect ratio of less than <NUM>. The value y/x of this aspect ratio may be at least <NUM> or be even larger.

In one embodiment of the illumination optical unit with an illumination-predetermining facet mirror <NUM> arranged in a pupil plane, an x/y-aspect ratio of the transmission facet groups at least has the same size as the x/y-aspect ratio of the object field <NUM>. In the depicted embodiment, the x/y-aspect ratio of the transmission facet groups is greater than the x/y-aspect ratio of the object field <NUM>. The transmission facet groups have a partial circle-shaped bent group edge form which is similar to the edge form of the object field <NUM>. In respect of further details in relation to the design of the transmission facet mirror <NUM>, reference is made to <CIT>.

The transmission facet groups which are formed by grouping the transmission facets <NUM> or the monolithic facets corresponding to these facet groups can have an extent of <NUM> in the x-direction and of approximately <NUM> in the y-direction.

By way of example, each transmission facet group is arranged in <NUM> columns which are arranged offset from one another in the x-direction and respectively consist of seven lines of transmission facets <NUM> arranged adjacently in the y-direction. Each one of the transmission facets <NUM> is rectangular.

Each one of the transmission facet groups guides a portion of the illumination light <NUM> for partial or complete illumination of the object field <NUM>.

The transmission facets <NUM> are micromirrors that are switchable between at least two tilt positions. The transmission facets <NUM> can be embodied as micromirrors that are tiltable about two mutually perpendicular axes of rotation. The transmission facets <NUM> are aligned in such a way that the illumination-predetermining facet mirror <NUM> is illuminated with a predetermined edge form and a predetermined association between the transmission facets <NUM> and illumination-predetermining facets <NUM> of the illumination-predetermining facet mirror <NUM>. In respect of further details in relation to the embodiment of the illumination-predetermining facet mirror <NUM> and the projection optical unit <NUM>, reference is made to <CIT>. The illumination-predetermining facets <NUM> are micromirrors that are switchable between at least two tilt positions. The illumination-predetermining facets <NUM> can be embodied as micromirrors which are continuously and independently tiltable about two mutually perpendicular tilt axes, i.e. which can be put into a multiplicity of different tilt positions, particularly if the illumination-predetermining facet mirror <NUM> is arranged at a distance from a pupil plane of the illumination optical unit.

An example for the predetermined association between the transmission facets <NUM> and the illumination-predetermining facets <NUM> is depicted in <FIG>. The illumination-predetermining facets <NUM> respectively associated with the transmission facets <NUM><NUM> to <NUM><NUM> have an index corresponding to this association. As a result of this association, the illumination facets <NUM> are illuminated from left to right in the sequence <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>.

The indices <NUM>, <NUM> and <NUM> of the facets <NUM>, <NUM> are associated with three illumination channels VI, VIII and III, which illuminate three object field points <NUM>, <NUM>, <NUM>, which are numbered from left to right in <FIG>, from a first illumination direction. The indices <NUM>, <NUM> and <NUM> of the facets <NUM>, <NUM> are associated with three further illumination channels IV, I, VII, which illuminate the three object field points <NUM> to <NUM> from a second illumination direction. The indices <NUM>, <NUM> and <NUM> of the facets <NUM>, <NUM> are associated with three further illumination channels V, II, IX, which illuminate the three object field points <NUM> to <NUM> from a third illumination direction.

The illumination directions which are assigned to.

are identical in each case. Therefore, the transmission facets <NUM> are assigned to the illumination-predetermining facets <NUM> in such a way that a telecentric illumination of the object field <NUM> results in the illumination example depicted by way of a figure.

The object field <NUM> is illuminated by the transmission facet mirror <NUM> and the illumination-predetermining facet mirror <NUM> in the style of a specular reflector. The principle of the specular reflector is known from <CIT>.

The projection optical unit <NUM> has an object/image offset dOIS of <NUM>. The latter is defined as the distance of a centre point of the object field <NUM> from an intersection point of a normal on the centre point of the image field <NUM> through the object plane <NUM>. The projection exposure apparatus <NUM> with the projection optical unit <NUM> has an intermediate focus/image offset D of <NUM>. The intermediate focus/image offset D is defined as the distance of the centre point of the image field <NUM> from an intersection point of a normal of the intermediate focus 5a on the image plane <NUM>. The projection exposure apparatus <NUM> with the projection optical unit <NUM> has an illumination light beam/image offset E of <NUM>. The illumination light beam/image offset E is defined as the distance of the centre point of the image field <NUM> from an intersection region of the illumination light beam <NUM> through the image plane <NUM>.

The projection optical unit <NUM> has an entry pupil with an envelope deviating from a circular form. Simultaneously, the projection optical unit <NUM> is embodied as an anamorphic optical unit such that this entry pupil is transferred to an image field-side exit pupil, the envelope of which is rotationally symmetric. A pupil plane, in which the exit pupil of the projection optical unit <NUM> lies, is indicated schematically in Figure <NUM> at 29a.

An example for such a rotationally symmetric, i.e., in particular, circular, envelope <NUM> of the exit pupil of the projection optical unit <NUM> is depicted in <FIG>. Within this envelope <NUM>, the illumination light <NUM> can be guided as imaging light in the projection optical unit <NUM>. Sub-pupil regions <NUM>, within which the illumination light <NUM> is guided, are depicted. That is to say, the sub-pupil regions <NUM> represent illumination channels of the illumination optical unit <NUM>. The sub-pupil regions <NUM> are grouped to form poles <NUM> in the style of a quadrupole illumination setting for exposing the wafer <NUM>. The poles <NUM> according to <FIG> have an approximately circular sector-shaped form and respectively cover a circumferential angle of approximately <NUM>°. The individual poles <NUM> of this quadrupole illumination setting emerge as envelope of raster-like arranged groups of the sub-pupil regions <NUM>. Within these groups, the sub-pupil regions <NUM> are arranged in a line-by-line and column-by-column manner.

<FIG> shows an arrangement of the sub-pupil regions <NUM> in an illumination pupil of the illumination optical unit <NUM>, which further down along the beam path of the illumination light <NUM> leads to the arrangement of the sub-pupil regions <NUM> according to <FIG>.

A pupil plane, in which the illumination pupil of the illumination optical unit lies, is indicated schematically in <FIG>. This illumination pupil plane <NUM> is at a distance from an arrangement plane of the illumination-predetermining facet mirror <NUM> in the embodiment according to <FIG>.

In an alternative illumination optical unit, the illumination pupil plane <NUM> coincides with the arrangement plane of the illumination-predetermining facet mirror. In this case, the illumination-predetermining facet mirror <NUM> is a pupil facet mirror. In this case, the illumination-predetermining facets <NUM> are embodied as pupil facets. Here, this can relate to monolithic pupil facets or else to mirror groups subdivided into a plurality of micromirrors. Such a pupil facet mirror as part of an illumination optical unit is known from e.g. <CIT>, <CIT> and <CIT>.

The illumination pupil according to <FIG> is generated by a variant of the illumination optical unit <NUM>, in which the illumination-predetermining facet mirror <NUM> is embodied as a pupil facet mirror.

The illumination pupil of the illumination optical unit <NUM> according to <FIG> is adapted to the entry pupil of the projection optical unit <NUM> and, in accordance with this adaptation, has an envelope <NUM> which deviates from a circular form.

The envelope <NUM> of the illumination pupil of the illumination optical unit <NUM> is a contour within which an illumination pupil of the illumination optical unit <NUM> with the maximum extent can be inscribed. The illumination pupil of the illumination optical unit <NUM> with the maximum extent is the illumination pupil with which a largest illumination angle bandwidth of the illumination angle distribution in the object field <NUM> is generated using the illumination optical unit <NUM>. To the extent that different illumination settings with different illumination angle distributions can be generated by the illumination optical unit <NUM>, the illumination pupil with the largest generable area is the illumination pupil with the maximum extent. In the case of a uniform pupil filling, such a pupil with the largest area is also referred to as a conventional illumination setting.

In the embodiment according to <FIG>, the envelope <NUM> has an elliptical form. In accordance with this adaptation, the poles <NUM> are also compressed in the y-direction compared to the form in the exit pupil according to <FIG>. In the illumination pupil according to <FIG>, the sub-pupil regions <NUM> are circular and emerge as images of the light source <NUM>. In the case of a light source <NUM> with a rotationally symmetric used-light emission surface, this accordingly results in the circular form of the sub-pupil regions <NUM> in the illumination pupil of the illumination optical unit <NUM> in the case of non-anamorphic imaging.

The anamorphic projection optical unit <NUM> leads to the sub-pupil regions <NUM> being elliptically distorted in the exit pupil of the projection optical unit and having a greater extent in the y-direction than in the x-direction, as depicted in <FIG>.

The envelope <NUM> of the illumination pupil has a maximum extent A in a first pupil dimension, namely in the x-direction, and has a minimum extent B in a second pupil dimension, namely in the y-direction. The ratio of extent A/B, i.e. an x/y-aspect ratio, of the envelope <NUM> corresponds to the ratio of the anamorphic imaging scales of the projection optical unit. In the projection optical unit <NUM>, these imaging scales are a reduced imaging scale βy of <NUM>/<NUM> in the yz-plane and a reduced imaging scale βx of <NUM>/<NUM> in the xz-plane. What emerges is βx/βy = A/B = <NUM>. Other ratios in the range between <NUM> and <NUM>, in particular in the range between <NUM> and <NUM>, are also possible.

The arrangement of the sub-pupil regions <NUM> within the illumination pupil according to <FIG> is such that the sub-pupil regions <NUM> are spaced further from one another in the pupil dimension with the maximum extent A than in the pupil dimension with the minimum extent B. This distance ratio adapts within the exit pupil of the projection optical unit <NUM> to a ratio of approximately <NUM>:<NUM> (cf.

The arrangement of the sub-pupil regions <NUM> in the illumination pupil is a raster arrangement with lines Z and columns S. The distance between adjacent lines Zi, Zj in this case approximately corresponds to the extent of the sub-pupil regions <NUM>. The distance between adjacent columns is a multiple of the extent of the individual sub-pupil regions <NUM>.

The sub-pupil regions <NUM> of adjacent lines Zi, Zj are arranged offset from one another by half a line spacing aij of adjacent sub-pupil regions <NUM>.

<FIG> show an alternative arrangement of sub-pupil regions <NUM>, firstly in the exit pupil of the projection optical unit <NUM> (cf. <FIG>) and secondly in the illumination pupil of the illumination optical unit <NUM> (cf. <FIG>) which is adapted to the entry pupil of the projection optical unit <NUM>. Components and structure elements and also functions which correspond to those already explained above in relation to <FIG> are appropriately denoted by the same reference signs and are not discussed again in detail. This also applies to the subsequent pairs of figures, which respectively show arrangements of sub-pupil regions <NUM>, firstly in the exit pupil of the projection optical unit <NUM> and secondly in the illumination pupil of the illumination optical unit <NUM> which is adapted to the entry pupil of the projection optical unit <NUM>.

The arrangement of the sub-pupil regions <NUM> according to <FIG> is also generated by an illumination optical unit with an illumination-predetermining facet mirror embodied as a pupil facet mirror. The pupil facets according to <FIG> are rectangular. The aspect ratio of the edge lengths corresponds to the ratio of the imaging scales of the projection lens.

A variant of a quadrupole illumination setting, which differs from the setting according to <FIG> in the form of the envelope of the poles <NUM>, is present in the exit pupil of the projection optical unit <NUM>. The poles <NUM> according to <FIG> have an approximately square form, wherein a radially outer boundary of the poles <NUM> follows the form of the envelope <NUM>.

In the arrangement according to <FIG>, the sub-pupil regions <NUM> are arranged in the form of a rectangular raster. A line spacing of this sub-pupil region arrangement approximately corresponds to the extent of the sub-pupil regions <NUM> in the illumination pupil according to <FIG>. A column spacing is a multiple thereof.

<FIG> show arrangements of sub-pupil regions <NUM>, firstly in the exit pupil of the projection optical unit <NUM> (<FIG>) and secondly in the illumination pupil of the illumination optical unit <NUM> (<FIG>), in the case of a quadrupole illumination setting which, in principle, corresponds to the one according to <FIG>. This arrangement of the sub-pupil regions <NUM> according to <FIG> is generated by an illumination-predetermining facet mirror <NUM> which is not arranged in a pupil plane. An overlap of the illumination channels emerges in the pupil plane, and so the sub-pupil regions <NUM> merge into one another in the y-direction. Then, a line spacing of the sub-pupil regions <NUM> in the y-direction is less than the extent of individual sub-pupil regions <NUM>. The column spacing of the sub-pupil regions is approximately the same size as the extent of the sub-pupil regions in the x-direction. The facets <NUM> of the illumination-predetermining facet mirror <NUM> are rectangular in <FIG>, like the pupil facets from <FIG>. The aspect ratio of the edge lengths corresponds to the ratio of the imaging scales of the projection lens.

<FIG> show a further arrangement variant of the sub-pupil regions <NUM> in the case of a further quadrupole illumination setting. In contrast to the setting according to <FIG>, the poles <NUM> in the setting according to <FIG> are delimited in the form of cut-off circular sectors, and so a quadrupole illumination emerges with a larger minimum illumination angle compared to <FIG>.

In the illumination pupil (cf. <FIG>), the sub-pupil regions <NUM> are arranged with the spacings of adjacent lines Zi, Zj, which correspond to the spacing of adjacent columns Si, Sj. Once again, the sub-pupil regions <NUM> of adjacent lines Zi, Zj are respectively arranged offset from one another by half a spacing aij of adjacent sub-pupil regions <NUM> within one line. The sub-pupil regions <NUM> can be arranged in a hexagonal grid. The facets <NUM> of the illumination-predetermining facet mirror <NUM> are round or hexagonal in this case, adapted to the form of the plasma, i.e. to the form of the light source <NUM>.

<FIG> show a further arrangement of the sub-pupil regions <NUM>, which corresponds to the one according to <FIG>, wherein the distances between adjacent columns of the sub-pupil region arrangement are reduced. The poles <NUM> have an approximately square edge contour in the exit pupil of the projection optical unit <NUM>.

<FIG> show an arrangement of the sub-pupil regions <NUM>, otherwise corresponding to the arrangement according to <FIG>, wherein, in this case, the sub-pupil regions <NUM> of one of the lines of the raster arrangement are arranged offset from one another relative to the sub-pupil regions of an adjacent line of the raster arrangement by half a spacing aij of sub-pupil regions <NUM> adjacent to one another within a line. This results in a very dense packing of the sub-pupil regions, even in the exit pupil, after the compression in the y-direction as a result of the anamorphic imaging effect of the projection optical unit <NUM> (cf.

The facets <NUM> of the illumination-predetermining facet mirror <NUM> are not embodied as monolithic or macroscopic facets and can be approximated by groups of micromirrors. In this case, a line-by-line or column-by-column displacement of these virtual facets is not possible if the micromirrors are respectively combined on subunits. A displacement as described above then fails due to gaps which are present as a result of transitions between the subunits since the virtual facets cannot extend beyond the subunits. Particularly for this technical implementation of the facets <NUM> of the illumination-predetermining facet mirror <NUM>, it is advantageous for these subunits, and hence also for the arrangement of the virtual facets <NUM>, to be undertaken on a Cartesian grid which is rotated in relation to the main axes of the illumination pupil without a rotationally symmetric edge, e.g. an elliptical illumination pupil. In relation to the coordinates x and y of the pupils perpendicular and parallel to the scanning direction, this corresponds to an offset from one another of the sub-pupil regions of one of the columns Si of the arrangement relative to the sub-pupil regions <NUM> of an adjacent column Sj of the arrangement by a half spacing bij of sub-pupil regions <NUM> adjacent to one another within a column. As a result, an effect virtually identical to the above-described displacement can be generated in the exit pupil. This is depicted in <FIG>.

These figures show a variant of an illumination of, firstly, the exit pupil of the projection optical unit <NUM> (<FIG>) and, secondly, of the associated illumination pupil of the illumination optical unit <NUM> (<FIG>), respectively for an illumination setting with a pupil filled in the most complementary manner possible. The illustration in <FIG> in principle corresponds to the pupil illustrations of e.g. <FIG>.

<FIG> shows the arrangement of the virtual illumination-predetermining facets <NUM> in accordance with the arrangement of the sub-pupil regions <NUM> as this is based on an arrangement for the illumination optical unit <NUM> with the illumination-predetermining facet mirror <NUM> arranged in the illumination pupil. The illumination-predetermining facets <NUM> are rotated by <NUM>° in relation to a Cartesian xy-grid.

<FIG> shows the effect emerging after the anamorphic imaging onto the arrangement of the sub-pupil regions <NUM> in the exit pupil of the projection optical unit <NUM>. The Cartesian-rotated arrangement of the round sub-pupil regions <NUM> in the illumination pupil becomes an approximately hexagonal arrangement of elliptical sub-pupil regions <NUM> in the exit pupil.

<FIG> show an arrangement of the sub-pupil regions <NUM>, otherwise corresponding to <FIG>, with the difference that the sub-pupil regions <NUM> in the illumination pupil (cf. <FIG>) respectively have a form deviating from the circular form, namely having a maximum extent in a first sub-pupil dimension - the x-direction in <FIG> - and a minimum extent in a second sub-pupil dimension - the y-direction in <FIG>.

The sub-pupil regions <NUM> are elliptical with an axis ratio of <NUM>, wherein the major axis of the ellipse extends parallel to the x-direction and the minor axis extends parallel to the y-direction.

The elliptical sub-pupil regions <NUM> in the illumination pupil according to <FIG> emerge, for example, as images of a corresponding elliptical light source <NUM>. The orientation of the sub-pupil regions <NUM> that are elliptical in the illumination pupil is selected in such a way that round sub-pupil regions <NUM> emerge in the exit pupil of the projection optical unit <NUM> as a result of the anamorphic effect of the projection optical unit <NUM>.

Alternatively, sub-pupil regions which are elliptical in the manner of <FIG> can also emerge via anamorphic imaging of an e.g. rotationally symmetric light source <NUM>.

<FIG> shows an example for a collector <NUM>, which can be used in place of the collector <NUM> according to <FIG> and, together with the first facet mirror <NUM>, forms the transmission optical unit <NUM> for guiding the illumination light to the pupil plane <NUM>. Components which correspond to those already explained above in relation to <FIG>, and in particular in relation to <FIG> and <FIG>, are denoted by the same reference signs and are not discussed again in detail.

The transmission optical unit <NUM> comprising the collector <NUM> has an anamorphic effect such that elliptical sub-pupil regions <NUM> in the style of <FIG> are generated in the illumination pupil in the pupil plane <NUM>. The first facet mirror <NUM> is depicted schematically in transmission in <FIG>. It is clear that the optical effect of the first facet mirror <NUM> is achieved correspondingly in reflection.

The collector <NUM> includes a first ellipsoid mirror <NUM> in the beam path of the illumination light <NUM>, which ellipsoid mirror is rotationally symmetric in relation to a central optical axis OA of the collector <NUM>.

The ellipsoid mirror <NUM> transfers the used light emission from the source <NUM> to the intermediate focus 5a. Consequently, the ellipsoid mirror <NUM> is a first collector subunit which generates a secondary intermediate image of the light source <NUM> in the beam path of the illumination light <NUM>. In the embodiment according to <FIG>, the intermediate image 5a has the symmetry of the light source <NUM>. To the extent that the light source <NUM> is rotationally symmetric, this also applies to the intermediate image 5a.

In the beam path of the illumination light <NUM>, the ellipsoid mirror <NUM> is followed by another collector subunit <NUM>, which is embodied as nested collector and, in terms of its function, in any case in terms of its main planes, corresponds to a Wolter collector. <FIG> depicts, using dashed lines, a beam path in the yz-section, i.e. in the plane corresponding to the meridional section according to <FIG>. The beam path of the illumination light <NUM> in the xz-section perpendicular thereto is shown in <FIG> using dash-dotted lines.

The collector subunit <NUM> is subdivided into hyperbolic shells <NUM> with a reflection surface profile rotationally symmetric in relation to the optical axis OA and into elliptical shells <NUM>.

These elliptical shells are respectively depicted in the yz-section (cf. shell section <NUM>y in <FIG>) and in the xz-section (cf. shell section <NUM>x in <FIG>). Thus, a yz-section would only cut the shell sections <NUM>y and an xz-section would only cut the shell sections <NUM>x. The respective elliptical shells <NUM>, which are linked to one another in their continuous extent about the optical axis, are provided with the same superscript index, e.g. the index "<NUM>", in <FIG>. The shell sections <NUM>x<NUM> and <NUM>y<NUM> are conical sections with different radii of curvature and different conical constants, which continuously merge into one another along the circumferential direction about the optical axis. In this way, a total of eight elliptical shells <NUM>, arranged nested in one another, of the collector subunit <NUM> emerge.

A deflecting reflecting effect, i.e., abstractly, a refractive power, of the elliptical shells <NUM>xi is greater than the deflecting reflecting effect of the respectively associated shell <NUM>yi. What emerges are the beam paths of the illumination light <NUM> between the collector subunit <NUM> and the first facet mirror <NUM>, as depicted in <FIG>, wherein the rays of the illumination light <NUM> reflected by the elliptical shells <NUM>x propagate convergently to one another and the rays of the illumination light <NUM> reflected by the elliptical shells <NUM>y propagate parallel to one another.

In the yz-plane, the transmission facets <NUM> of the first facet mirror <NUM> have an imaging effect and, together with the elliptical shells <NUM>y, generate a further image of the light source <NUM> in the yz-plane. This image is generated in the pupil plane <NUM>. Then, a sub-pupil range <NUM> is generated in the pupil plane <NUM> for each illuminating channel or illumination channel. In the xz-plane, the transmission facets of the first facet mirror <NUM> do not have an imaging effect, and so the illumination light <NUM> is reflected in the xz-plane by the transmission facets <NUM> as it would be by a plane mirror; in the schematic transmission illustration according to <FIG>, this does not lead to a change in direction of the dash-dotted rays, propagating in the xz-direction, of the illumination light <NUM>. Consequently, it remains in the case of the imaging effect of the elliptical shells <NUM>x, which likewise image the intermediate image 5a in the pupil plane <NUM>.

Overall, the transmission facets <NUM> of the first facet mirror <NUM> of the arrangement according to <FIG> are embodied as cylindrical mirrors which have a concave curvature in the yz-plane. Since the first facet mirror <NUM> is illuminated over an illumination region, the y-extent of which is greater than the x-extent thereof, images of the light source are generated in the pupil plane <NUM>, that is to say sub-pupil regions, the y-extent of which is smaller than the x-extent thereof, as depicted in, for example, <FIG>.

<FIG> shows a further embodiment of the projection exposure apparatus <NUM>. In place of the projection optical unit <NUM>, which is depicted in the meridional section with six mirrors M1 to M6 therein, use can be made of an embodiment of an anamorphic projection optical unit, as is described in e.g. <CIT>.

In the beam path downstream of the light source <NUM>, the illumination optical unit <NUM> of the projection exposure apparatus <NUM> according to <FIG> includes a collector <NUM> and a downstream transmission mirror <NUM>, which both form an anamorphic optical unit, which generate an elliptical intermediate image in the intermediate focus 5a from the source <NUM> which is rotationally symmetric in this embodiment. Here, the beam path from the collector <NUM> to the first facet mirror <NUM> in the yz-plane is depicted by a full line and the beam path from the collector <NUM> to the first facet mirror <NUM> in the xz-plane is depicted by a dashed line.

The optical effect of the transmission-optical components <NUM>, <NUM> is such that the intermediate image in the intermediate focus 5a is not rotationally symmetric and has a greater extent in the x-direction than in the y-direction. The intermediate image in the intermediate focus 5a can be elliptical. Then, an illumination pupil with sub-pupil regions <NUM> with an x/y-aspect ratio corresponding to this intermediate image is generated by way of the first facet mirror <NUM> and the illumination-predetermining facet mirror <NUM>. This can also be used to generate an arrangement of the sub-pupil regions <NUM> in the illumination pupil in accordance with the arrangement according to e.g. <FIG>. In the illumination optical unit <NUM> according to <FIG>, the transmission facets <NUM> of the first facet mirror <NUM> do not require a rotationally asymmetrical refractive power or any refractive power substantially deviating from rotational symmetry. Since the transmission facets <NUM> of the first facet mirror <NUM> are not impinged perpendicularly by the illumination light <NUM>, it may be advantageous to embody these facets <NUM> in a toric or elliptical manner.

In the exemplary embodiment according to <FIG>, the transmission mirror <NUM> is depicted as an NI mirror, i.e. as a mirror which is impinged by the illumination light <NUM> with angles of incidence between <NUM>° and <NUM>°. Alternatively, the transmission mirror <NUM> can also be embodied as a grazing incidence mirror (GI mirror), i.e. as a mirror which is impinged by the illumination light <NUM> with angles of incidence in the range between <NUM>° and <NUM>°.

Conversely, the mirror of the collector subunit <NUM> described above in the context of <FIG>, in particular the elliptical shells <NUM>, can be embodied as an NI mirror.

The illumination optical unit <NUM> according to <FIG> includes a total of three NI mirror components downstream of the collector <NUM>, namely the transmission mirror <NUM>, the first facet mirror <NUM> and the illumination-predetermining facet mirror <NUM>. What this requires is that, unlike the illumination optical units explained above, the light source <NUM> in the illumination optical unit <NUM> according to <FIG> is arranged on the same side of the image plane <NUM> as the projection optical unit <NUM>.

Below, a further embodiment of an illumination optical unit <NUM> for the projection exposure apparatus <NUM> is described on the basis of <FIG> and <FIG>. Components which correspond to those already explained above in relation to <FIG>, and in particular in relation to <FIG>, are denoted by the same reference signs and are not discussed again in detail.

Proceeding from the light source <NUM>, the illumination optical unit <NUM> according to <FIG> includes a rotationally symmetric collector <NUM>, the function of which corresponds to that of the collector <NUM> in the embodiment according to <FIG>, and, downstream thereof, the first facet mirror <NUM> and the illumination-predetermining facet mirror <NUM>. The image of the light source <NUM> in the intermediate focus 5a is rotationally symmetric. Using the transmission facet mirror <NUM> and the illumination-predetermining facet mirror <NUM>, an illumination pupil with an envelope deviating from the circular form in accordance with the embodiments explained above is generated. In the illumination optical unit <NUM> according to <FIG>, the illumination-predetermining facet mirror <NUM> is arranged in a pupil plane conjugate to the pupil plane <NUM>. The extent of the illumination-predetermining facet mirror <NUM>, which then acts as a pupil facet mirror, is twice as large in the x-direction as it is in the y-direction.

A further transmission optical unit <NUM> with two transmission mirrors <NUM>, <NUM> is arranged between the illumination-predetermining facet mirror <NUM> and the object field <NUM>. The transmission optical unit <NUM> firstly images the transmission facet groups of the transmission facet mirror <NUM> on the object field <NUM> together with the illumination-predetermining facet mirror <NUM> and secondly images the pupil plane 32a on the entry pupil of the projection optical unit <NUM>, which is arranged in the pupil plane <NUM>. This pupil plane <NUM> can be disposed upstream of the object field <NUM>, that is to say between the second transmission mirror <NUM> and the object field <NUM>, in the beam path of the illumination light <NUM> or downstream of the object field <NUM> in the beam path of the imaging light, which was reflected by the reticle <NUM>. Both variants are indicated schematically in <FIG>. Thus, the transmission optical unit <NUM> images the pupil plane 32a on the entry pupil plane <NUM> of the projection optical unit <NUM>, in which one of the illumination pupils then is generated as a superposition of sub-pupil regions <NUM>, as already explained above in the discussion relating to the various arrangement variants of the sub-pupil regions <NUM>.

Certain pairs of imaging scales, which are elucidated in the diagram of <FIG>, can be realized for this combined field and pupil imaging, in which the transmission optical unit <NUM> is involved. What is plotted in each case is the imaging scale β as a function of a focal length f of the pupil facets of the pupil facet mirror <NUM>. The two upper branches βZP and βZF denote the dependence of the imaging scale of the pupil imaging (βZP) and the field imaging (βZF) in the case where the transmission optical unit <NUM> generates an intermediate image. The two lower branches βP and βF denote the case, which is discussed in more detail below and realized in the projection optical unit <NUM> according to <FIG>, in which the transmission optical unit <NUM> does not generate an intermediate image. Here, βP denotes the imaging scale of the pupil imaging and βF denotes the imaging scale of the field imaging.

The illumination optical unit <NUM> according to <FIG> is dimensioned in such a way that, in combination with a focal length of the pupil facets in the region of <NUM>, an imaging scale βP of -<NUM> for the pupil imaging and of approximately - <NUM> for the field imaging is realized. The first transmission mirror <NUM> has a focal length of approximately -<NUM> and the second transmission mirror <NUM> has, in absolute terms, a slightly smaller focal length of approximately <NUM>. A used region of the pupil facet mirror <NUM>, on which the illumination light <NUM> impinges, has an extent of approximately <NUM> in the x-direction and an extent of approximately <NUM> in the y-direction.

<FIG> shows a further embodiment of the illumination optical unit <NUM>, for use in the projection exposure apparatus <NUM>. Components and structure elements and also functions which correspond to those already explained above in relation to <FIG> are appropriately denoted by the same reference signs and are not discussed again in detail.

In the illumination optical unit <NUM> according to <FIG>, the illumination-predetermining facet mirror <NUM>, which in turn is embodied as a pupil facet mirror <NUM>, is round, i.e. it has an xy-aspect ratio of <NUM>. The transmission optical unit <NUM> downstream of the pupil facet mirror <NUM> is embodied as an anamorphic optical unit and generates the illumination pupil of the illumination optical unit <NUM> with an envelope <NUM> deviating from the circular form from the pupil still present with a rotationally symmetric envelope in the pupil plane 32a, as already explained above in the context of the various sub-pupil region arrangements.

The anamorphic transmission optical unit <NUM> according to <FIG> is in turn embodied with two transmission mirrors which, in the sequence of the impingement thereof by the illumination light <NUM>, are denoted by the reference numerals <NUM> and <NUM>. Together with the focal lengths of the pupil facets of the pupil facet mirror <NUM> of approximately <NUM> and <NUM>, this transmission optical unit <NUM> generates imaging scales βF of approximately -<NUM> in the xy-plane and <NUM> in the yz-plane. Simultaneously, the transmission optical unit <NUM> images the round pupil facet mirror in the xz-plane and in the yz-plane with the imaging scales of -<NUM> and -<NUM> respectively, and thus provides the desired elliptical entry pupil.

The focal lengths f of the transmission mirrors <NUM>, <NUM> are -<NUM> and <NUM> in the xz-plane and -<NUM> and <NUM> in the yz-plane.

In the illumination optical unit <NUM> according to <FIG>, an impinged-upon region on the pupil facet mirror <NUM> has an overall radius of <NUM>. The diameter of the impinged-upon region on the pupil facet mirror <NUM> is therefore significantly smaller than the maximum extent of the impinged-upon region in the pupil facet mirror <NUM> according to <FIG>. This results in smaller switching angles for the transmission facets <NUM>. This simplifies the technological implementation of these facets <NUM>.

The transmission facet groups, into which the transmission facets <NUM> are grouped, or the monolithic facets corresponding to these facet groups have an extent of <NUM> in the x-direction and <NUM> in the y-direction in the illumination optical unit <NUM> according to <FIG>.

<FIG> shows a further embodiment of the illumination optical unit <NUM>, which otherwise corresponds to <FIG>, comprising a different design of a transmission optical unit <NUM>, which otherwise corresponds to the transmission optical unit <NUM> according to <FIG>. The transmission mirrors <NUM>, <NUM> of the transmission optical unit <NUM> are matched to the focal lengths of the pupil facets of the pupil facet mirror <NUM> of approximately <NUM> and <NUM>, respectively, and once again image field and pupil without intermediate image. This results in imaging scales βP for the pupil imaging of -<NUM> and -<NUM>, respectively, and imaging scales βF for the field imaging of -<NUM> and -<NUM>, respectively.

The pupil facet mirror <NUM> is also round in the illumination optical unit <NUM> according to <FIG>, wherein the impinged-upon region of the pupil facet mirror <NUM> has a radius of <NUM>.

The transmission facet groups which are formed by grouping the transmission facets <NUM> or the monolithic field facets corresponding to these have a dimension of <NUM> in the x-direction and of slightly less than <NUM> in the y-direction.

A transmission optical unit disposed downstream of the illumination-predetermining facet mirror <NUM> can also be used to reduce necessary switching angles for the transmission facets <NUM>, particularly if said illumination-predetermining facet mirror is not arranged in a pupil plane, i.e. if it is embodied as a specular reflector.

<FIG> shows a yz-section through a portion of the illumination optical unit <NUM> between the illumination-predetermining facet mirror <NUM> and a pupil plane <NUM>, disposed downstream of the reticle <NUM> in this case in the beam path of the illumination light <NUM>, in which the illumination pupil is generated.

What is depicted is a construction of the beam path of the illumination light <NUM>, once again in a schematic transmission lens section comparable to <FIG> explained above.

An extent of the sub-pupil ranges <NUM> within the illumination pupil emerges from the following relationship: <MAT>.

Δk is a measure for the variation of the illumination angle and therefore a measure for the extent of the respective sub-pupil region <NUM> belonging to the respectively considered illumination channel. Here, l denotes the extent of the object field <NUM> in the respectively considered dimension x or y. zEP describes a distance between the illumination pupil and the object plane <NUM> in the z-direction, i.e. along the beam path of the illumination light <NUM>. This distance in the yz-plane may differ from that in the xz-plane. zSR describes the distance of the illumination-predetermining facet mirror <NUM> from the object plane <NUM> in the z-direction.

If the above equation is considered in the yz-plane, i.e. in the plane containing the object displacement direction y, l represents the scanning length (object field dimension in the scanning direction). Then Δk quantifies a length of the sub-pupil regions <NUM>, which emerges in an integrated manner during the scanning process in the y-direction. As a result of the scanning process, the respective sub-pupil range <NUM> is therefore deformed in a rod-shaped manner along the scanning direction, which is why the sub-pupil regions <NUM> are also referred to as rods.

What can be achieved in the case of the anamorphic projection optical unit <NUM> in a scan-integrated manner is that the illumination pupil is completely filled by the sub-pupil regions <NUM>, either overall or within the predetermined illumination poles (cf. poles <NUM>, e.g. in <FIG>), that is to say that, in a scan-integrated manner, a point on the reticle <NUM> is impinged with illumination light from every illumination direction within the illumination pupil or within the predetermined poles. A homogeneously completely filled pupil can be obtained in a scan-integrated manner within predetermined tolerances by means of appropriate matching of the distance conditions for zSR and zEP with the scanning geometry of the projection exposure apparatus.

A cylindrical mirror <NUM>, which represents a transmission optical unit disposed downstream of the illumination-predetermining facet mirror <NUM>, is arranged between the illumination-predetermining facet mirror <NUM> and the reticle <NUM>. The cylindrical mirror <NUM> only has an imaging effect in the xz-plane, as a result of which, as depicted in <FIG>, this results in a virtual enlargement of the illumination-predetermining facet mirror <NUM>. A virtual, magnified image of the illumination-predetermining facet mirror <NUM> is shown in <FIG> at <NUM>. Thus, as a result of the cylindrical mirror <NUM>, there is a size reduction of the illumination-predetermining facet mirror <NUM> in respect of its x-extent, as indicated in <FIG> by means of a double-headed arrow <NUM>. As a result, the necessary switching angles of the transmission facets <NUM> are reduced. Once again, elliptical sub-pupil regions <NUM> emerge in the illumination pupil plane due to the different imaging effects of the illumination optical unit according to <FIG> in, firstly, the yz-plane and, secondly, in the xz-plane. These are then converted into round sub-pupil regions <NUM> in the exit pupil of the projection optical unit <NUM>, as already explained above for example in the context of <FIG>.

The pupil plane <NUM> need not have the same z-coordinate in the xz-plane as in the yz-plane. This is also indicated in <FIG>, where a distance between the reticle <NUM> and the pupil plane <NUM> is greater in <FIG> than in <FIG>.

As an alternative to the reduction in the tilt angle requirements of the transmission facets <NUM> described in <FIG>, an aspect ratio of the illumination-predetermining facet mirror <NUM> requiring larger switching angles of the facets <NUM> can be accounted for by transmission facets <NUM> that comprise two tilt axes which are designed for differently large switching angles and accuracies. By way of example, these anisotropic tilt angle characteristics can be realized by spring hinges with different stiffness, positioning motors with different positioning forces or anisotropic damping.

<FIG> shows a variant of the projection exposure apparatus <NUM> comprising an exemplary embodiment of the projection optical unit <NUM> comprising such a cylindrical mirror <NUM>. Proceeding from the collector <NUM>, the projection optical unit <NUM> according to <FIG> once again includes an odd number of reflecting components, namely the transmission facet mirror <NUM>, the illumination-predetermining facet mirror <NUM> and the cylindrical mirror <NUM>. Therefore, in a manner comparable to the illumination optical unit according to <FIG>, the light source is also arranged on the same side of the image plane <NUM> as the projection optical unit <NUM> in the illumination optical unit according to <FIG>.

<FIG> show further variants of illuminations of, firstly, the illumination pupil of the illumination optical unit <NUM> and, secondly, of the exit pupil of the projection optical unit <NUM>, respectively for an illumination setting with a pupil that is filled as completely as possible. The illustrations in <FIG> in principle correspond to the pupil illustrations of <FIG>.

<FIG> shows an embodiment with elliptical sub-pupil regions <NUM> in the exit pupil of the projection optical unit <NUM> having a circular envelope <NUM>. The sub-pupil regions <NUM> are elliptical with an x/y-aspect ratio of approximately <NUM>/<NUM>. The associated illumination pupil (cf. <FIG>) has an envelope <NUM> with an x/y-aspect ratio of <NUM> and round sub-pupil regions <NUM>. The region impinged overall in the illumination pupil is elliptical.

In the exit pupil (<FIG>), a raster arrangement of the sub-pupil regions <NUM> is present with the same grid constant in the x- and y-direction.

<FIG> correspond to <FIG> with the difference that a packing density of the sub-pupil regions <NUM>, firstly in the exit pupil of the projection optical unit <NUM> and secondly in an illumination pupil of the illumination optical unit <NUM>, is increased.

<FIG> show an arrangement of the sub-pupil regions <NUM>, wherein, in turn, the sub-pupil regions <NUM> of one of the columns of the raster arrangement are arranged offset from one another relative to the sub-pupil regions of an adjacent column of the raster arrangement by half a spacing of sub-pupil regions <NUM> adjacent to one another within a column. Additionally, the sub-pupil regions <NUM> of adjacent lines overlap since the spacing between adjacent lines is smaller than the y-extent of the sub-pupil regions <NUM>. This results in reduced breaking of the symmetry of the arrangement of the illumination sub-pupils in the exit pupil of the lens and, as result thereof, in a smaller directional dependence of the imaging properties of the projection exposure apparatus (cf.

<FIG> show sub-pupil region arrangements corresponding to those of <FIG>, wherein, unlike in <FIG>, the illumination-predetermining facet mirror <NUM> is not arranged in a pupil plane, but rather at a distance therefrom. This once again results in a confluence of the sub-pupil regions <NUM> in the y-dimension.

<FIG> show the situation of the arrangement of the sub-pupil regions when using an illumination-predetermining setting mirror arranged at a distance from the pupil plane, wherein the sub-pupil regions <NUM> are arranged firstly in an offset manner and secondly in a densely packed manner, comparable to <FIG>. This results in practically complete filling of the exit pupil of the projection optical unit <NUM>, without unimpinged regions.

<FIG> show, once again comparable to <FIG>, the situation with elliptical sub-pupil regions in the illumination pupil (cf. <FIG>) and round resultant sub-pupil regions <NUM> in the exit pupil of the projection optical unit <NUM> as a result of the anamorphic effect of the projection optical unit <NUM>.

<FIG> and <FIG> show the optical design of a further embodiment of a projection optical unit <NUM>, which can be used in the projection exposure apparatus <NUM> in place of the projection optical unit <NUM>. What is depicted in <FIG> and <FIG> is, in each case, the beam path of three individual rays, which emanate from the object field points spaced apart in the y-direction in <FIG> and <FIG>. What is depicted are chief rays <NUM>, i.e. individual rays which pass through the centre of a pupil in a pupil plane of the projection optical unit <NUM>, and in each case an upper and lower coma ray <NUM> of these object field points. <FIG> shows a meridional section of the projection optical unit <NUM>. <FIG> shows a sagittal view of the projection optical unit <NUM>.

Proceeding from the object field <NUM>, the chief rays <NUM> include an angle CRAO of <NUM>° with a normal of the object plane <NUM>.

The object plane <NUM> lies parallel to the image plane <NUM>.

The projection optical unit <NUM> has an image-side numerical aperture of <NUM>.

The projection optical unit <NUM> according to <FIG> has a total of eight mirrors which, in the sequence of the beam path of the individual rays <NUM> emanating from the object field <NUM>, are numbered M1 to M8 in sequence. Such an imaging optical unit can also have a different number of mirrors, for example four mirrors or six mirrors.

On the object side, the projection optical unit <NUM> is embodied as anamorphic optical unit. In the yz-section according to <FIG>, the projection optical unit <NUM> has a reducing imaging scale βy of <NUM>/<NUM>. In the xz-plane perpendicular thereto (cf. <FIG>), the projection optical unit <NUM> has a reducing imaging scale βx of <NUM>/<NUM>.

In combination with a rotationally symmetric exit pupil, these different imaging scales βx, βy lead to an object-side numerical aperture being half the size in the yz-plane compared to the xz-plane, as emerges immediately from comparison between <FIG> and <FIG>. As a result of this, an advantageously small chief ray angle CRAO of <NUM>° is obtained in the yz-plane.

Advantages of an anamorphic projection lens connected herewith are also discussed in <CIT>.

The anamorphic effect of the projection optical unit <NUM> is distributed to all optical surfaces of the mirrors M1 to M8.

<FIG> and <FIG> depict the calculated reflection surfaces of the mirrors M1 to M8. As can be seen from the illustration according to <FIG> and <FIG>, only a portion of these calculated reflection surfaces is used. Only this actually used region of the reflection surfaces is in fact present in the real mirrors M1 to M8. These used reflection surfaces are carried by mirror bodies in a known manner.

In the projection optical unit <NUM>, the mirrors M1, M4, M7 and M8 are embodied as mirrors for normal incidence, that is to say as mirrors on which the imaging light <NUM> is incident with an angle of incidence that is smaller than <NUM>°. Thus, the projection optical unit <NUM> has a total of four mirrors M1, M4, M7 and M8 for normal incidence.

The mirrors M2, M3, M5 and M6 are mirrors for grazing incidence of the illumination light <NUM>, that is to say mirrors on which the illumination light <NUM> is incident with angles of incidence which are greater than <NUM>°. A typical angle of incidence of the individual rays <NUM> of the imaging light <NUM> on the mirrors M2, M3 and M5, M6 for grazing incidence lies in the region of <NUM>°. Overall, the projection optical unit <NUM> comprises exactly four mirrors M2, M3, M5 and M6 for grazing incidence.

The mirrors M2 and M3 form a mirror pair arranged directly in succession in the beam path of the imaging light <NUM>. The mirrors M5 and M6 also form a mirror pair arranged directly in succession in the beam path of the imaging light <NUM>.

The mirror pairs M2, M3 on the one hand and M5, M6 on the other hand reflect the imaging light <NUM> in such a way that the angles of reflection of the individual rays on the respective mirrors M2, M3 or M5, M6 of these two mirror pairs add up. Thus, the respective second mirror M3 and M6 of the respective mirror pair M2, M3 and M5, M6 amplifies a deflecting effect which the respective first mirror M2, M5 exerts on the respective individual ray. This arrangement of the mirrors of the mirror pairs M2, M3 and M5, M6, respectively, corresponds to that described in <CIT> for an illumination optical unit.

The mirrors M2, M3, M5 and M6 for grazing incidence in each case have very large absolute values for the radius, i.e. have a relatively small deviation from a plane surface. These mirrors M2, M3, M5 and M6 for grazing incidence therefore have practically no refractive power, i.e. practically no overall beam-forming effect like a concave or convex mirror, but contribute to specific and, in particular, to local aberration correction.

The mirrors M1 to M8 carry a coating optimizing the reflectivity of the mirrors M1 to M8 for the imaging light <NUM>. This can be a ruthenium coating, a molybdenum coating or a molybdenum coating with an uppermost layer made of ruthenium. In the mirrors M2, M3, M5 and M6 for grazing incidence, use can be made of a coating with e.g. a ply made of molybdenum or ruthenium. These highly reflecting layers, in particular of mirrors M1, M4, M7 and M8 for normal incidence, can be embodied as multi-ply layers, wherein successive layers can be manufactured from different materials. Use can also be made of alternating material layers. A typical multi-ply layer can comprise <NUM> bi-plies made of in each case a layer of molybdenum and a layer of silicon.

The mirror M8, i.e. the last mirror in the imaging beam path in front of the image field <NUM>, has a passage opening <NUM> for the imaging light <NUM>, which is reflected from the antepenultimate mirror M6 to the penultimate mirror M7, to pass through. The mirror M8 is used in a reflective manner around the passage opening <NUM>. All other mirrors M1 to M7 do not include a passage opening and are used in a reflective manner in a continuous region without gaps.

The mirrors M1 to M8 are embodied as free-form surfaces which cannot be described by a rotationally symmetric function. Other embodiments of the projection optical unit <NUM>, in which at least one of the mirrors M1 to M8 is embodied as a rotationally symmetric asphere, are also possible. It is also possible for all mirrors M1 to M8 to be embodied as such aspheres.

A free-form surface can be described by the following free-form surface equation (equation <NUM>): <MAT>.

The following applies to the parameters of this equation (<NUM>):
ZPH is the sag of the free-form surface at the point x, y, where x<NUM> + y<NUM> = r<NUM>. Here, r is the distance from the reference axis of the free-form surface equation (x = <NUM>; y = <NUM>).

In the free-form surface equation (<NUM>), C<NUM>, C<NUM>, C<NUM>. denote the coefficients of the free-form surface series expansion in powers of x and y.

In the case of a conical base area, cx, cy is a constant corresponding to the vertex curvature of a corresponding asphere. Thus, cx = <NUM>/Rx and cy = <NUM>/Ry applies. kx and ky each correspond to a conical constant of a corresponding asphere. Thus, equation (<NUM>) describes a bi-conical free-form surface.

An alternative possible free-form surface can be generated from a rotationally symmetric reference surface. Such free-form surfaces for reflection surfaces of the mirrors of projection optical units of microlithographic projection exposure apparatuses are known from <CIT>.

Alternatively, free-form surfaces can also be described with the aid of two-dimensional spline surfaces. Examples for this are Bezier curves or non-uniform rational basis splines (NURBS). By way of example, two-dimensional spline surfaces can be described by a grid of points in an xy-plane and associated z-values, or by these points and the gradients associated therewith. Depending on the respective type of the spline surface, the complete surface is obtained by interpolation between the grid points using e.g. polynomials or functions which have specific properties in respect of the continuity and the differentiability thereof. Examples for this are analytical functions.

The optical design data of the reflection surfaces of the mirrors M1 to M8 of the projection optical unit <NUM> can be gathered from the following tables. These optical design data in each case proceed from the image plane <NUM>, i.e. describe the respective projection optical unit in the reverse propagation direction of the imaging light <NUM> between the image plane <NUM> and the object plane <NUM>.

The first one of these tables specifies a vertex radius (radius = R = Ry) for the optical surfaces of the optical components.

The second table specifies, for the mirrors M1 to M8 in mm, the conical constants kx and ky, the vertex radius Rx possibly deviating from the value R (= Ry) and the free-form surface coefficients Cn.

The third table still specifies the magnitude along which the respective mirror, proceeding from a reference surface, was decentred (DCY) in the y-direction, and displaced (DCZ) and tilted (TLA, TLC) in the z-direction. This corresponds to a parallel displacement and a tilt when carrying out the free-form surface design method. Here, a displacement is carried out in the y-direction and in the z-direction in mm, and tilting is carried out about the x-axis and about the z-axis. Here, the tilt angle is specified in degrees. Decentring is carried out first, followed by tilting. The reference surface during decentring is in each case the first surface of the specified optical design data. Decentring in the y-direction and in the z-direction is also specified for the object field <NUM>.

The fourth table still specifies the transmission data of the mirrors M8 to M1, namely the reflectivity thereof for the angle of incidence of an illumination light ray incident centrally on the respective mirror. The overall transmission is specified as a proportional factor remaining from an incident intensity after reflection at all mirrors in the projection optical unit.

An overall reflectivity of the projection optical unit <NUM> is <NUM>%.

The axes of rotation symmetry of the aspherical mirrors are generally tilted with respect to a normal of the image plane <NUM>, as is made clear by the tilt values in the tables.

The object field <NUM> has an x-extent of two times <NUM> and a y-extent of <NUM>. The projection optical unit <NUM> is optimized for an operating wavelength of the illumination light <NUM> of <NUM>.

The projection optical unit <NUM> has exactly eight mirrors M1 to M8. The mirrors M2 and M3 on the one hand, and M5, M6 on the other hand are embodied as mirrors for grazing incidence and are arranged in each case as a mirror pair directly behind one another in the imaging beam path. The projection optical unit <NUM> has exactly four mirrors for grazing incidence, namely the mirrors M2, M3, M5 and M6. The mirrors M1, M4, M7 and M8 are embodied as mirrors for normal incidence.

In the projection optical unit <NUM>, a stop <NUM> is arranged in the beam path between the mirrors M1 and M2, near the grazing incidence on the mirror M2. The stop <NUM> is arranged between the mirrors M1 and M2 in the region of a first pupil plane in the beam path of the illumination or imaging light <NUM>. This first pupil plane <NUM> is tilted relative to the chief ray <NUM> of a central field point, i.e. it includes an angle ≠ <NUM>° with this chief ray. The whole beam of the imaging light <NUM> is accessible from all sides between the mirrors M1 and M2 in the region of this first pupil plane, and so the stop <NUM> embodied as an aperture stop is arranged here. Alternatively or additionally, a stop can be arranged directly on the surface of the mirror M2.

In the xz-plane (cf. <FIG>), an entry pupil of the projection optical unit <NUM> lies <NUM> in front of the object field <NUM> in the beam path of the illumination light. In the yz-plane, the entry pupil lies <NUM> downstream of the object field <NUM> in the imaging beam path of the projection optical unit <NUM>. An extent of the chief rays <NUM> emanating from the object field <NUM> is therefore convergent both in the meridional section according to <FIG> and in the view according to <FIG>.

In the xz-section (cf. <FIG>), the stop <NUM> can lie at a position displaced in the z-direction compared to its position in the yz-section.

A z-distance between the object field <NUM> and the image field <NUM>, i.e. a structural length of the projection optical unit <NUM>, is approximately <NUM>.

An object/image offset (dOIS), i.e. a y-spacing between a central object field point and a central image field point, is approximately <NUM>.

A free working distance between the mirror M7 and the image field <NUM> is <NUM>.

In the projection optical unit <NUM>, an RMS value for the wavefront aberration is at most <NUM> mλ and, on average, <NUM> mλ.

A maximum distortion value is at most <NUM> in the x-direction and at most <NUM> in the y-direction. A telecentricity value in the x-direction is at most <NUM> mrad on the image field side and a telecentricity value in the y-direction is at most <NUM> mrad on the image field side.

Further mirror data of the projection optical unit <NUM> emerge from the following table.

There is an intermediate image 53a in the beam path in the region of a reflection on the mirror M5 in the yz-plane (<FIG>) and in the imaging beam path region between the mirrors M6 and M7 in the xz-plane (<FIG>).

A further pupil plane of the projection optical unit <NUM> is arranged in the region of the reflection of the imaging light <NUM> on the mirrors M7 and M8.

Aperture stops in the region of the mirrors M7 and M8 can be arranged distributed for the x-dimension, on the one hand, and for the y-dimension, on the other hand, at two positions in the imaging beam path, for example there can be an aperture stop for primarily providing a restriction along the y-dimension on the mirror M8 and an aperture stop for primarily providing a restriction along the x-dimension on the mirror M7.

The mirror M8 is obscured and comprises a passage opening <NUM> for the passage of the illumination light <NUM> in the imaging beam path between the mirrors M6 and M7. Less than <NUM>% of the numerical aperture of the projection optical unit <NUM> is obscured as a result of the passage opening <NUM>. Thus, in a system pupil of the projection optical unit <NUM>, a surface which is not illuminated due to the obscuration is less than <NUM><NUM> of the surface of the overall system pupil. The non-illuminated surface within the system pupil can have a different extent in the x-direction than in the y-direction. Moreover, this surface in the system pupil which cannot be illuminated can be decentred in the x-direction and/or in the y-direction in relation to a centre of the system pupil.

Only the last mirror M8 in the imaging beam path includes a passage opening <NUM> for the imaging light <NUM>. All other mirrors M1 to M7 have a continuous reflection surface. The reflection surface of the mirror M8 is used around the passage opening <NUM> thereof.

The mirrors M1, M3, M4, M6 and M8 have negative values for the radius, i.e. are, in principle, concave mirrors. The other mirrors M2, M5 and M7 have positive values for the radius, i.e. are, in principle, convex mirrors. The mirrors M2, M3, M5 and M6 for grazing incidence have very large radii and only constitute small deviations from plane reflection surfaces.

Claim 1:
Illumination optical unit (<NUM>) for projection lithography for illuminating an object field (<NUM>),
- comprising a first transmission optical unit (<NUM>) for guiding illumination light (<NUM>) emanating from a light source (<NUM>),
- comprising an illumination-predetermining facet mirror (<NUM>) which is disposed downstream of the first transmission optical unit (<NUM>) and comprises a multiplicity of illumination-predetermining facets (<NUM>), said facet mirror generating a predetermined illumination of the object field (<NUM>) by means of an arrangement of illuminated illumination-predetermining facets (<NUM>),
- comprising an arrangement of the illumination optical unit (<NUM>) in such a way that this results in an illumination, with an envelope (<NUM>) deviating from a circular form, of an illumination pupil having a maximum extent of the illumination optical unit (<NUM>), which predetermines an illumination angle distribution in the object field (<NUM>),
- wherein the illumination pupil is subdivided into a plurality of sub-pupil regions (<NUM>), which are present arranged in a line-by-line (Z) and/or column-by-column (S) manner,
- wherein the sub-pupil regions (<NUM>) in the illumination pupil have a maximum extent in a first sub-pupil dimension (x) and a minimum extent in a second sub-pupil dimension (y), wherein a ratio between the maximum extent and the minimum extent is at least <NUM>.