Patent Description:
Various variants of pupil facet mirrors for an illumination optical unit of a projection exposure apparatus are known from <CIT>, <CIT> and the references cited therein. <CIT> discloses a method for illuminating an object field of a projection exposure system. <CIT> discloses an optical system and a multi facet mirror of a microlithographic projection exposure apparatus. <CIT> discloses an illumination system for a microlithographic projection exposure apparatus.

It is an object of the present invention to develop a pupil facet mirror of the type set forth at the outset, in such a way that its use in the illumination optical unit leads to increased flexibility of use of the illumination optical unit and, in particular, facilitates the observation of exacting illumination parameter specifications of the projection exposure apparatus.

According to the invention, this object is achieved by a pupil facet mirror comprising the features specified in Claim <NUM>.

According to the invention, it was recognized that a tilt actuator system which firstly facilitates the specification of a coarse tilt angle by way of a coarse actuator system mode of operation and secondly facilitates the specification of a fine tilt angle of the tiltable pupil facets via a fine actuator system mode of operation leads to a very flexibly utilizable pupil facet mirror. The tilt actuator system can be separated into a coarse actuator system for the coarse actuator system mode of operation and into a fine actuator system for the fine actuator system mode of operation. Such a separation of an actuator system into two sub-actuator systems with different actuator ranges and usually also different actuator accuracies is also referred to as the use of a long-range actuator (coarse actuator system) and short-range actuator (fine actuator system). The coarse actuator system can be realized by way of actuators which interact with tilt stops of the respective tiltable pupil facet. Corresponding actuators are known in conjunction with switchable field facets. The fine actuator system of the tilt actuator system for the pupil facets can be realized by way of piezo-actuators, in particular piezo-stacks. A corresponding piezo-stack actuator system is known from <CIT>.

Alternatively, such a tilt actuator system can also be realized by means of a single actuator, which can be operated both in the coarse actuator system mode of operation and in the fine actuator system mode of operation. This actuator then combines the actuator range of the coarse tilt angle adjustment in the coarse actuator system mode of operation with the actuator resolution or actuator accuracy of the fine tilt angle adjustment of the fine actuator system mode of operation.

If only a single actuator is used to implement a coarse tilt angle adjustment and a fine tilt angle adjustment, the coarse tilt angle adjustment facilitates a switch over to another illumination channel, i.e., to a guidance of illumination radiation via a different pair consisting of a field facet and a pupil facet. The fine tilt angle adjustment allows the illumination radiation to continue to be guided via the same pair consisting of a field facet and a pupil facet. Wherever reference is made to a coarse actuator system or a fine actuator system below, this also means coarse tilt angle adjustments in the coarse actuator system mode of operation and fine tilt angle adjustments in the fine actuator system mode of operation of one and the same tilt actuator system.

In particular, a pupil fill ratio of freely specifiable illumination pupils of the illumination optical unit can be minimized; i.e., it is possible to arrive at the situation where not only does illumination light fall on an object field of the projection exposure apparatus only from as few as possible, clearly defined directions but also it is also possible for the user of the projection exposure apparatus to choose these few directions such that an optimal imaging behaviour arises. The effective pupil fill ratio (PFR), which is a measure of what pupil area of an illumination pupil is covered by illumination light, represents an illumination parameter which can be specified flexibly and within exacting tolerances by way of an illumination optical unit with the pupil facet mirror according to the invention. A person skilled in the art finds details in respect of the pupil fill ratio in <CIT> and <CIT>, and in the references cited therein. Depending on the requirements placed on the illumination optical unit, a particularly small pupil fill ratio may be preferred. The object then is to use the illumination light guided over as many illumination channels as possible for illumination purposes but in the process only cover regions of the illumination pupil that are as small as possible, which in fact ensure a contrast that is as good as possible or a NILS (normalized image log slope, derivative of an aerial image intensity curve at an edge position of an imaged structure) value that is as good as possible.

In addition to a tilt displaceability, the pupil facets may also be displaceable perpendicular to the reflection surface thereof as a matter of principle. A corresponding displaceability is known from <CIT>.

The option of a dynamic actuation of the pupil facets by way of the tilt actuator system of the pupil facet mirror ensures an individual assignment solution of field facets to the pupil facets via the respective illumination channels, which respectively depends on the illumination setting to be specified. Such an illumination setting-individual solution is not possible in the case of non-actuatable pupil facets.

Tilt angle ratios according to Claim <NUM> have proven their worth for dividing the functions of, firstly, the coarse actuator system and, secondly, the fine actuator system of the tilt actuator system of the pupil facet mirror. A ratio between the maximum specifiable coarse tilt angle range and the maximum specifiable fine tilt angle range can be greater than <NUM>, can be greater than <NUM>, can be greater than <NUM>, can be greater than <NUM>, can range between <NUM> and <NUM>, can be greater than <NUM> and can also be greater than <NUM>. This ratio is regularly less than <NUM>. Absolute coarse tilt angles can lie in the region around <NUM>°, for example range between <NUM>° and <NUM>° or range between <NUM>° and <NUM>°. Absolute fine tilt angles can lie in the region around <NUM>°, by way of example range between <NUM>° and <NUM>° or range between <NUM>° and <NUM>°. The advantages of an illumination optical unit according to Claim <NUM> and an illumination system according to Claim <NUM> correspond to those which were already explained above in conjunction with the pupil facet mirror.

In addition to the two facet mirrors, the illumination optical unit can still comprise a transmission optical unit for overlaid imaging of the field facets into the object field. Such a transmission optical unit can comprise one or more mirrors for the illumination light. Alternatively, such a transmission optical unit can also be dispensed with, i.e., the downstream facet mirror in the beam path can be the last illumination light-guiding optical component of the illumination optical unit upstream of the object field.

In addition to the illumination optical unit, the illumination system can also comprise a collector for illumination light emanating from a source volume of the light source. In principle, the light source can also be part of the illumination system.

The switchable field facets of the illumination optical unit can be designed in such a way that, by way of one field facet, a plurality of pupil facets can be assigned via a respective illumination channel, for example two, three, four, five or even more pupil facets. In principle, it is possible to embody at least some of the switchable field facets in such a way that, via these, all pupil facets can be assigned to this field facet via illumination channels by means of appropriate switching positions of the field facet. In this case, each pupil facet of the pupil facet mirror can be impinged by illumination light by way of one and the same field facet depending on the switching position of the field facet.

The coarse actuator system of the tilt actuator system of the pupil facet mirror can be used to tilt pupil facets, which can be assigned to a plurality of field facets in corresponding field facet switch positions, in a manner adapted to the relative position of the respective field facet and in such a way that the illumination channel corresponding to this field facet/pupil facet assignment then leads to a field facet image that is guided into the object field. Then, a fine adjustment of this relative field facet image position relative to the object field can still be ensured by way of the fine actuator system.

Switchable pupil facets can be realized by way of the coarse actuator system, in particular analogously to the switchable field facets.

Energy sensors according to Claim <NUM> have proven their worth for monitoring the performance of the light source and the illumination optical unit.

A field intensity specification device according to Claim <NUM> allows the illumination intensity over the object field, in particular over a coordinate perpendicular to an object displacement direction or scanning direction of the object, to be adapted in its profile along this field coordinate to a specification value and, in particular, to be designed to be uniform. The illumination intensity along this field coordinate perpendicular to the scanning direction can deviate from a mean value by, for example, less than <NUM>% or else by less than <NUM>%. Alternatively, a specified field intensity curve along this field coordinate can also be set. In particular, this field intensity specification can be implemented in illumination angle-independent fashion. It is also possible to make the field intensity specification field-dependent in a targeted manner.

In principle, a field intensity specification device is known from <CIT>.

A far field sensor according to Claim <NUM> allows determination as to which field facets of the illumination optical unit are impinged with higher illumination intensity levels and which field facets are impinged with lower illumination intensity levels. Depending on this, illumination channel assignments can then be specified in order to observe certain illumination parameters within specified tolerances. As an alternative or in addition to such a far field sensor, it is possible to use a pupil measurement in the image plane, i.e., in the arrangement plane of a wafer, on which the object field is imaged. To this end, an object with a pinhole or a slot, which is also referred to as measurement fiducial, can be used in the image plane. This renders a far field reconstruction possible, optionally taking account of apodizations of the measurement fiducial and of the imaging optical unit and of the beam path of the illumination light. As an alternative or in addition thereto, an illumination of the field facets may be possible for the spatially resolved prediction of a far field of the illumination light source by virtue of said field facets being switched on the far field sensors or switched away therefrom by way of appropriate switching of the associated respective pupil facet by way of the tilt actuator system.

A relative source position sensor according to Claim <NUM> can be used to capture a movement of the source volume relative to the collector of the illumination system and compensate the latter in respect of its effect on an object field illumination by way of appropriate tilting of the pupil facets and/or the field facets at least in parts.

The advantages of a fine tilt actuator system for the switchable field facets according to Claim <NUM> correspond to those already explained above with reference to the fine actuator system for the pupil facets. Field facets displaceable by way of a fine actuator system can be used to optimize a positioning of source images on the pupil facets assigned by illumination channels.

Moreover, facet-dependent mechanical tolerances of the illumination optical unit can be at least partly compensated by way of the fine actuator system for pupil facets and/or for the field facets.

In particular, the illumination channel specification can be implemented on the basis of the respective illumination setting of the illumination system and/or can be implemented on the basis of an intensity profile of the illumination light over the field facets assigned to the illumination channels.

The advantages of a projection exposure apparatus according to Claim <NUM> correspond to those already explained above with reference to the illumination system.

The method according to Claim <NUM> allows the energy sensors of the illumination system according to Claim <NUM> to be used particularly well for monitoring illumination parameters of the illumination system. An illumination parameter relevant in this case can be an illumination light dose radiated in level with the object plane, i.e., at the level of the reticle. The dose radiated onto the energy sensors, which captures right and left sections of images of the field facets of a number of field facets that is as large as possible, can be used as an estimate for the dose of the entire object field. In particular, the energy sensors can be operated in their optimized sensitivity range. A sensitivity of jitter or drift movements of the far field over the field facet mirror in particular can be reduced by a suitable specification of the illumination channels using this adjustment method.

An adjustment method according to Claim <NUM> facilitates a precise function of the field intensity specification device of the illumination system according to Claim <NUM>. This can implement either targeted influencing of the illumination intensity, where possible independently of the illumination angle, or else implement a targeted field-dependent profile of an illumination intensity distribution over the object field.

In principle, such an adjustment method can also be used in the case of a field intensity specification device which does not have shadowing fingers that are individually displaceable by way of an actuator but, for example, has a single static field stop.

What is exploited in a method according to Claim <NUM> is that a tilt of a pupil facet by way of the fine actuator system about an axis parallel to the longitudinal axis of the shadowing finger can nevertheless lead to a change in distance between the field facet image and the free end of the shadowing finger in the case of a field facet image which has a curved profile in particular. Such a tilt regularly leads to a displacement of the field facet image perpendicular to the object displacement direction, which can be used to specify certain field-dependent illumination intensity parameters.

In particular, the parameters of EPE, ellipticity, telecentricity, NILS (normalized image log slope, derivative of an aerial image intensity curve at an edge position of an imaged structure), throughput and uniformity come into question as adjustable illumination parameters. A person skilled in the art finds details in respect of the ellipticity parameter in <CIT>. A person skilled in the art finds details in respect of the NILS parameter and in respect of the telecentricity parameter in <CIT>. The throughput parameter denotes the energy throughput of the illumination optical unit, i.e., the ratio of the entire illumination light energy downstream of the illumination optical unit to the energy upstream of the illumination optical unit. A person skilled in the art finds details in respect of the uniformity parameter in, for example, <CIT> and also <CIT>. EPE is an abbreviation for edge placement error, i.e., the deviation between the desired position of an edge in the aerial image (or final structure on the wafer) and the actual position thereof. Since the variable relates to a single edge it is very generic. By way of example, no distinction is made whether the edge offset is caused by broadening of the structure (CD error) or a simple displacement of the structure (overlay error, or telecentricity error if generated via the defocus of the wafer). A relatively current article considering EPE in the EUV range, albeit with a focus on the mask layout, is the following:
<NPL>.

An adjustment method according to Claim <NUM> allows specification of an illumination channel assignment, in such a way that specified illumination parameters can be realized. In addition to the coarse actuator-based displacement of the field facets and the pupil facets, there can still additionally be a fine actuator-based displacement of these facets for fine adjustment purposes.

Assessment functions, discussed in, e.g., <CIT>, can be included within the scope of the illumination channel assignment.

An adjustment method according to Claim <NUM> takes account of a possible source volume displacement. As a controlled method, the method can ensure automatic tracking of the facets relative to a respectively captured relative position of the source volume. Thus, this adjustment method can be designed as a real-time closed-loop control method.

The methods according to Claims <NUM> to <NUM> can also be used in any combination. After selecting an illumination setting, implemented in particular in a manner adapted to the structures of the object to be implemented, the method according to Claim <NUM> can initially be used to realize the illumination setting. The further methods according to Claims <NUM> and/or <NUM> and/or <NUM> and/or <NUM> can then optionally be used simultaneously as co-optimization in order to optimize an object illumination in respect of further parameters, for example energy sensor sensitivity, crosstalk of a field intensity specification device.

Initially, at least one of the above-explained adjustment methods can be used to produce microstructured/nanostructured components with the aid of such a projection exposure apparatus. Subsequently, a wafer is provided, to which a layer made of a light-sensitive material is partly applied. Moreover, a reticle, which has structures to be imaged, is provided. At least part of the reticle is imaged, i.e., projected, onto a region of the layer of the wafer with the aid of the projection exposure apparatus. Then, the microstructured or nanostructured component arises after developing the light-sensitive layer. This can be a semiconductor chip, in particular a memory chip.

At least one exemplary embodiment of the invention is described below on the basis of the drawing. In the drawing:.

In the following text, the essential components of a microlithographic projection exposure apparatus <NUM> are described first by way of example with reference to <FIG>. The description of the basic construction of the projection exposure apparatus <NUM> and its components should not be construed as limiting here.

An illumination system <NUM> of the projection exposure apparatus <NUM> has, besides a radiation source <NUM>, an illumination optical unit <NUM> for illuminating an object field <NUM> in an object plane <NUM>. In this case, a reticle <NUM> arranged in the object field <NUM> is exposed. The reticle <NUM> is held by a reticle holder <NUM>. The reticle holder <NUM> is displaceable by way of a reticle displacement drive <NUM>, in particular in a scanning direction.

A global Cartesian xyz-coordinate system is shown in <FIG> for explanation purposes. The x-direction extends perpendicular to the plane of the drawing. The y-direction extends horizontally, and the z-direction extends vertically. The scanning direction extends along the y-direction in <FIG>. The z-direction extends perpendicular to the object plane <NUM>.

In the subsequent figures, a local xy- or xyz-coordinate system is optionally used for elucidation purposes. The x-direction of the respective local coordinate system corresponds to that of the global coordinate system. The y- and the z-direction of the local coordinate system are tilted about this common x-direction depending on an orientation of the component to be described.

The projection exposure apparatus <NUM> comprises a projection optical unit <NUM>. The projection optical unit <NUM> serves for imaging the object field <NUM> into an image field <NUM> in an image plane <NUM>. The image plane <NUM> extends parallel to the object plane <NUM>. Alternatively, an angle between the object plane <NUM> and the image plane <NUM> that differs from <NUM>° is also possible.

A structure on the reticle <NUM> is imaged onto a light-sensitive layer of a wafer <NUM> arranged in the region of the image field <NUM> in the image plane <NUM>. The wafer <NUM> is held by a wafer holder <NUM>. The wafer holder <NUM> is displaceable in particular along the y-direction by means of a wafer displacement drive <NUM>. The displacement, firstly, of the reticle <NUM> by way of the reticle displacement drive <NUM> and, secondly, of the wafer <NUM> by way of the wafer displacement drive <NUM> can be implemented so as to be synchronized to one another.

The radiation source <NUM> is an EUV radiation source. The radiation source <NUM> emits, in particular, EUV radiation <NUM>, which is also referred to below as used radiation or illumination radiation. In particular, the used radiation has a wavelength in the range between <NUM> and <NUM>. The radiation source <NUM> can be a plasma source, for example an LPP (laser produced plasma) or GDPP (gas discharge produced plasma) source. It can also be a synchrotron-based radiation source. The radiation source <NUM> can be a free electron laser (FEL).

The illumination radiation <NUM> emerging from the radiation source <NUM> is focused by a collector <NUM>. The collector <NUM> can be a collector with one or with a plurality of ellipsoidal and/or hyperboloid reflection surfaces. The at least one reflection surface of the collector <NUM> can be impinged upon by illumination radiation <NUM> with grazing incidence (GI), i.e., at angles of incidence of greater than <NUM>°, or with normal incidence (NI), i.e., at angles of incidence of less than <NUM>°. The collector <NUM> can be structured and/or coated, firstly, for optimizing its reflectivity for the used radiation and, secondly, for suppressing extraneous light.

The illumination radiation <NUM> propagates through an intermediate focus in an intermediate focal plane <NUM> downstream of the collector <NUM>. The intermediate focal plane <NUM> can represent a separation between a radiation source module, having the radiation source <NUM> and the collector <NUM>, and the illumination optical unit <NUM>.

The illumination optical unit <NUM> comprises a deflection mirror <NUM> and, arranged downstream thereof in the beam path, a first facet mirror <NUM>. The deflection mirror <NUM> can be a plane deflection mirror or, alternatively, a mirror with a beam-influencing effect going beyond a pure deflection effect. As an alternative or in addition thereto, the mirror <NUM> can be embodied as a spectral filter separating a used wavelength of the illumination radiation <NUM> from extraneous light having a wavelength that deviates therefrom. If the first facet mirror <NUM> is arranged in a plane of the illumination optical unit <NUM> that is optically conjugate to the object plane <NUM> as a field plane, said facet mirror is also referred to as a field facet mirror. The first facet mirror <NUM> comprises a multiplicity of individual first facets <NUM>, which are also referred to as field facets below. Some of these facets <NUM> are shown in <FIG> only by way of example.

The first facets <NUM> can be embodied as macroscopic facets, in particular as rectangular facets or as facets with an arcuate edge contour or an edge contour of part of a circle. The first facets <NUM> can be embodied as plane facets or, alternatively, as convexly or concavely curved facets.

As is known from <CIT>, for example, the first facets <NUM> themselves can also each be composed of a multiplicity of individual mirrors, in particular a multiplicity of micromirrors. The first facet mirror <NUM> can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to <CIT>.

The illumination radiation <NUM> travels horizontally, i.e., along the y-direction, between the collector <NUM> and the deflection mirror <NUM>.

In the beam path of the illumination optical unit <NUM>, a second facet mirror <NUM> is arranged downstream of the first facet mirror <NUM>. If the second facet mirror <NUM> is arranged in or in the vicinity of a pupil plane of the illumination optical unit <NUM>, it is also referred to as a pupil facet mirror. The second facet mirror <NUM> can also be arranged at a distance from a pupil plane of the illumination optical unit <NUM>. In this case, the combination of the first facet mirror <NUM> and the second facet mirror <NUM> is also referred to as a specular reflector. Specular reflectors are known from <CIT>, <CIT> and <CIT>.

The second facet mirror <NUM> comprises a plurality of second facets <NUM>. In the case of a pupil facet mirror, the second facets <NUM> are also referred to as pupil facets.

The second facets <NUM> can likewise be macroscopic facets, which can, for example, have a round, rectangular or hexagonal boundary, or alternatively be facets composed of micromirrors. In this regard, reference is also made to <CIT>.

The second facets <NUM> can have plane or, alternatively, convexly or concavely curved reflection surfaces.

The illumination optical unit <NUM> consequently forms a double-faceted system. This basic principle is also referred to as a fly's eye integrator or honeycomb condenser.

It can be advantageous to arrange the second facet mirror <NUM> not exactly within a plane that is optically conjugate to a pupil plane of the projection optical unit <NUM>.

The individual first facets <NUM> are imaged into the object field <NUM> with the aid of the second facet mirror <NUM>. The second facet mirror <NUM> is the last beam-shaping mirror or, in fact, the last mirror for the illumination radiation <NUM> in the beam path upstream of the object field <NUM>.

In a further embodiment of the illumination optical unit <NUM> (not illustrated), a transmission optical unit contributing in particular to the imaging of the first facets <NUM> into the object field <NUM> can be arranged in the beam path between the second facet mirror <NUM> and the object field <NUM>. The transmission optical unit can have exactly one mirror or, alternatively, two or more mirrors, which are arranged in succession in the beam path of the illumination optical unit <NUM>. The transmission optical unit can in particular comprise one or two normal-incidence mirrors (NI mirrors) and/or one or two grazing-incidence mirrors (GI mirrors).

In the embodiment shown in <FIG>, the illumination optical unit <NUM> has exactly three mirrors downstream of the collector <NUM>, specifically the deflection mirror <NUM>, the field facet mirror <NUM> and the pupil facet mirror <NUM>.

The deflection mirror <NUM> can also be dispensed with in a further embodiment of the illumination optical unit <NUM>, and the illumination optical unit <NUM> can then have exactly two mirrors downstream of the collector <NUM>, specifically the first facet mirror <NUM> and the second facet mirror <NUM>.

As a rule, the imaging of the first facets <NUM> into the object plane <NUM> by means of the second facets <NUM> or using the second facets <NUM> and a transmission optical unit is only approximate imaging.

The projection optical unit <NUM> comprises a plurality of mirrors Mi, which are numbered in accordance with their arrangement in the beam path of the projection exposure apparatus <NUM>.

In the example illustrated in <FIG>, the projection optical unit <NUM> comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are likewise possible. The penultimate mirror M5 and the last mirror M6 each have a through opening for the illumination radiation <NUM>. The projection optical unit <NUM> is a double-obscured optical unit. The projection optical unit <NUM> has an image-side numerical aperture that is greater than <NUM> and can also be greater than <NUM> and, for example, be <NUM> or <NUM>.

Reflection surfaces of the mirrors Mi can be embodied as free-form surfaces without an axis of rotational symmetry. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface form. Just like the mirrors of the illumination optical unit <NUM>, the mirrors Mi can have highly reflective coatings for the illumination radiation <NUM>. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optical unit <NUM> has a large object-image offset in the y-direction between a y-coordinate of a centre of the object field <NUM> and a y-coordinate of the centre of the image field <NUM>. In the y-direction, said object-image offset can be approximately the same size as a z-distance between the object plane <NUM> and the image plane <NUM>.

In particular, the projection optical unit <NUM> can have an anamorphic design. In particular, it has different imaging scales βx, βy in the x- and y-directions. The two imaging scales Bx, βy of the projection optical unit <NUM> preferably lie at (Bx, βy) = (+/- <NUM>, +/- <NUM>). A positive imaging scale β means imaging without image erection. A negative sign for the imaging scale β means imaging with image erection.

Consequently, the projection optical unit <NUM> leads to a reduction with a ratio of <NUM>:<NUM> in the x-direction, i.e., in a direction perpendicular to the scanning direction.

The projection optical unit <NUM> leads to a reduction of <NUM>:<NUM> in the y-direction, i.e., in the scanning direction.

Other imaging scales are likewise possible. Imaging scales with the same sign and the same absolute value in the x- and y-directions are also possible, for example with absolute values of <NUM> or <NUM>.

The number of intermediate image planes in the x- and in the y-direction in the beam path between the object field <NUM> and the image field <NUM> can be the same or, depending on the embodiment of the projection optical unit <NUM>, can be different. Examples of projection optical units with different numbers of such intermediate images in the x- and y-directions are known from <CIT>.

In each case one of the pupil facets <NUM> is assigned to exactly one of the field facets <NUM> for forming in each case an illumination channel for illuminating the object field <NUM>. In particular, this can produce illumination according to the Köhler principle. An illumination region of an arrangement plane of the field facets <NUM>, which is also referred to as the far field, is decomposed into a multiplicity of object fields <NUM> with the aid of the field facets <NUM>. The field facets <NUM> produce a plurality of images of the intermediate focus on the pupil facets <NUM> respectively assigned thereto.

The field facets <NUM> are imaged, in each case by way of an assigned pupil facet <NUM>, onto the reticle <NUM> in a manner such that they are overlaid on one another for the purposes of illuminating the object field <NUM>. The illumination of the object field <NUM> is in particular as homogeneous as possible. It preferably has a uniformity error of less than <NUM>%. Field uniformity can be attained by overlaying different illumination channels.

The illumination of the entrance pupil of the projection optical unit <NUM> can be geometrically defined by an arrangement of the pupil facets. The intensity distribution in the entrance pupil of the projection optical unit <NUM> can be set by selecting the illumination channels, in particular the subset of pupil facets, which guide light. This intensity distribution is also referred to as illumination setting.

A likewise preferred pupil uniformity in the region of sections of an illumination pupil of the illumination optical unit <NUM> that are illuminated in a defined manner can be achieved by a redistribution of the illumination channels.

Further aspects and details of the illumination of the object field <NUM> and, in particular, of the entrance pupil of the projection optical unit <NUM> are described below.

In particular, the projection optical unit <NUM> can comprise a homocentric entrance pupil. The latter can be accessible. It can also be inaccessible.

The entrance pupil of the projection optical unit <NUM> cannot be illuminated regularly with the pupil facet mirror <NUM> in an exact manner. In the case of imaging the projection optical unit <NUM> in which the centre of the pupil facet mirror <NUM> is telecentrically imaged onto the wafer <NUM>, the aperture rays often do not intersect at a single point. However, it is possible to find a surface in which the spacing of the aperture rays, determined in pairwise fashion, is minimal. This area represents the entrance pupil or an area in real space that is conjugate thereto. In particular, this area has a finite curvature.

The projection optical unit <NUM> might have different positions of the entrance pupil for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optical unit, should be provided between the second facet mirror <NUM> and the reticle <NUM>. With the aid of said optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the arrangement of the components of the illumination optical unit <NUM> illustrated in <FIG>, the pupil facet mirror <NUM> is arranged in a surface conjugate to the entrance pupil of the projection optical unit <NUM>. The field facet mirror <NUM> is arranged so as to be tilted with respect to the object plane <NUM>. The first facet mirror <NUM> is arranged so as to be tilted with respect to an arrangement plane defined by the deflection mirror <NUM>.

The first facet mirror <NUM> is arranged so as to be tilted with respect to an arrangement plane defined by the second facet mirror <NUM>.

<FIG> schematically shows a section of an illumination channel <NUM> of the illumination optical unit <NUM>, which is also referred to as an illumination channel. A schematic beam path of the illumination channel <NUM> is illustrated between one of the field facets <NUM> of the field facet mirror <NUM> and an image <NUM> of this field facet <NUM> in the object plane <NUM>. The illumination channel <NUM> is specified by way of the field facet <NUM> and the associated pupil facet <NUM> of the pupil facet mirror <NUM> of the illumination optical unit <NUM>. In the embodiment illustrated in <FIG>, the field facet <NUM> is illustrated with an arcuate edge of its reflection surface and the pupil facet <NUM> is illustrated with a hexagonal edge of its reflection surface. Other edge shapes of the field facets <NUM> are also possible, for example rectangles. An x/y-aspect ratio of the field facets <NUM> is in the region of <NUM>:<NUM>, but it can also adopt other values ranging between <NUM>:<NUM> and <NUM>:<NUM>, for example. The pupil facets <NUM> can also have different edge shapes for their reflection surfaces, for example circles, rectangles or squares.

The illumination light <NUM> is guided via the field facet <NUM> and the pupil facet <NUM> to the object field in the object plane <NUM> of the projection exposure apparatus <NUM>, not illustrated in <FIG>, by means of the illumination channel <NUM>. The field facet images <NUM> generated by way of the various illumination channels <NUM> assigned to the various facets <NUM>, <NUM>, are imaged, in a manner overlaid on one another, into the object field via the pupil facets <NUM> of the pupil facet mirror <NUM>.

The field facets <NUM> are embodied to be switchable between different tilt positions such that illumination channels <NUM> with a plurality of different pupil facets <NUM> that are selectable by way of the respective switching position of the field facet <NUM> can be specified by way of one and the same field facet <NUM>. This can be used to specify various illumination settings.

The pupil facets <NUM> each have a tiltable embodiment. Each of the tiltable pupil facets <NUM> interacts with a tilt actuator system <NUM>, which is illustrated schematically in <FIG>.

This tilt actuator system <NUM> of the pupil facet <NUM> or the pupil facet mirror <NUM> has a coarse actuator system or a coarse actuator system mode of operation <NUM> for specifying a coarse tilt angle of the tiltable pupil facet <NUM>. This coarse tilt angle is the result of an illumination channel assignment of the tiltable pupil facet <NUM> to the field facet <NUM> and ensures the overlaid imaging of the field facet images <NUM> in the object field <NUM>.

Furthermore, the tilt actuator system <NUM> comprises a fine actuator system or a fine actuator system mode of operation <NUM> for specifying a fine tilt angle of the tiltable pupil facet <NUM>. The fine tilt angle serves to specify a precise relative position of the field facet image <NUM> of the illumination channel <NUM> of the tiltable pupil facet <NUM> relative to the object field and thus facilitates a fine displacement of the field facet image <NUM> in the object plane <NUM>.

The image <NUM> of the field facet <NUM> in the object plane <NUM> is regularly smaller than the object field <NUM> in the scan direction y. A fine displacement of the image <NUM> of the field facet <NUM> in the y-direction therefore typically leads to the image <NUM> still lying within the object field <NUM> in the y-direction. The image <NUM> of the field facet <NUM> in the object plane <NUM> is regularly larger than the object field <NUM> orthogonal to the scan direction y, i.e., along the x-coordinate. What suitable stops in or in front of the projection optical unit <NUM> achieve is that the region of the object plane <NUM> which is imaged into the image plane <NUM> is restricted to the width of the object field <NUM> or the width of the image field <NUM> in the x-direction. A fine displacement of the image <NUM> of the field facet <NUM> in the x-direction therefore typically leads to the image still illuminating the entire object field <NUM> in the x-direction. Thus, fine displacements of the image <NUM> of the field facet <NUM> change the illumination of the object field <NUM> without changing the fact of the illumination as such. This can be used according to the invention as described below.

The coarse actuator system <NUM> can be realized by means of actuators respectively assigned to the pupil facets <NUM>, said actuators interacting with stops for specifying a respective coarse tilt position. In this case, use can be made of actuators which are already known from the prior art in the context of switchable field facets.

The fine actuator system <NUM> of the respective pupil facet <NUM> can be realized by way of piezo-actuators, in particular piezo-stacks. Such piezo-actuators are also known from the prior art.

As an alternative to realizing, firstly, the coarse actuator system <NUM> and, secondly, the fine actuator system <NUM> by way of separate actuators, a coarse actuator system and a fine actuator system of the tilt actuator system <NUM> can also be realized by, firstly, a coarse actuator system mode of operation and, secondly, a fine actuator system mode of operation of one and the same actuator system.

A tilt of the respective pupil facet <NUM>, firstly about an axis parallel to the x-axis and secondly about an axis parallel to the y-axis, is possible by way of the fine actuator system. Additionally, a displacement of the respective pupil facet <NUM> along the z-direction can be facilitated by way of the coarse actuator system <NUM> and/or the fine actuator system <NUM>.

A maximum coarse tilt angle range specifiable by the coarse actuator system <NUM> can be greater than a maximum fine tilt angle range specifiable by the fine actuator system <NUM> by at least a factor of <NUM>.

In principle, all pupil facets <NUM> of the pupil facet mirrors <NUM> can have a tiltable design in the style of the pupil facet <NUM> described above in conjunction with <FIG>. A plurality of types of pupil facets <NUM> are present in alternative embodiments of the pupil facet mirror <NUM>, specifically pupil facets <NUM> which have a tilt actuator system <NUM> in the style of the pupil facet <NUM> illustrated in <FIG> and at least one further type of pupil facet with a simpler variant of the tilt actuator system or without any tilt actuator system.

An illumination light intensity can vary over the field facet image <NUM> and can have different values, in each case integrated over the respective y-coordinate of the field facet image <NUM>, for example depending on the x-dimension. By way of example, the illumination channel <NUM> in the section of the field facet image <NUM> on the right in <FIG> can carry less intensity than in the mid and left section in <FIG>.

<FIG> furthermore shows two energy sensors <NUM>, <NUM> which are arranged separately from one another and which measure illumination energy of the illumination light <NUM> in the object plane <NUM> at two sensor locations, the object field <NUM> being arranged therebetween. A left edge <NUM>l and a right edge <NUM>r of the object field arranged between the two energy sensors <NUM>, <NUM> are schematically indicated in <FIG>.

It is also possible to provide a greater number of such energy sensors around the object field <NUM>. In particular, the energy sensors can facilitate a spatially resolved energy measurement around the object field, wherein use can be made of more than two energy sensors, for example four energy sensors, five energy sensors, eight energy sensors, ten energy sensors or even more of such energy sensors.

Each of the switchable field facets <NUM> has a tilt actuator system <NUM> which, in addition to a switch actuator system <NUM> for specifying the respective switch position, comprises a fine tilt actuator system <NUM> corresponding to the fine actuator system <NUM> of the tiltable pupil facets <NUM>. The fine tilt actuator system <NUM> of the respective field facet <NUM> serves to specify a fine tilt angle of the field facet <NUM> for the purposes of specifying a relative position of the illumination channel <NUM> relative to the pupil facet <NUM> assigned to the field facet <NUM> by way of this illumination channel <NUM>.

A tilt of the respective field facet <NUM>, firstly about an axis parallel to the x-axis and secondly about an axis parallel to the y-axis, is possible by way of the fine tilt actuator system <NUM>. Additionally, a displacement of the field facet <NUM> along the z-direction can be facilitated by way of the fine actuator system <NUM>.

The guidance of the illumination channel <NUM> by the respective field facet <NUM> can be such that a source image <NUM> of the light source or radiation source <NUM> is located in the vicinity of an impingement location of the pupil facet <NUM> of the illumination channel <NUM>.

In the current setting illustrated in <FIG>, the fine tilt actuator system <NUM> of the field facets <NUM> is set such that the source image <NUM> is located centrally on the pupil facet <NUM>. The fine actuator system <NUM> of the pupil facet <NUM> is set in turn such that the right section of the field facet image <NUM> completely covers the energy sensor <NUM> to the right in <FIG>, and so the energy sensor <NUM> stably measures a measure for the energy transported in the illumination channel <NUM>. A right edge of the field facet image <NUM> in <FIG> in this case is located beyond the energy sensor <NUM> so that slight jitter movements of the field facet image <NUM> or slight drifts in the field facet image <NUM> do not lead to the right section of the field facet image <NUM> in <FIG> only still incompletely covering the energy sensor <NUM>.

Typically, there is a systematic intensity profile of the illumination light <NUM> across the width (x-direction) of the respective field facet <NUM>, said intensity profile being different for different field facets <NUM>. This also applies accordingly to the intensity profile of the field facet image <NUM>. If the intensity of the field facet image <NUM> is lower at the right edge than the mean over the entire field facet image, the right energy sensor <NUM> systematically underestimates the contribution of the field facet <NUM> to the illumination of the object field <NUM>. Analogously, the contribution of the field facet <NUM> can also be systematically overestimated by the right energy sensor <NUM> in the case of an opposite intensity profile.

<FIG> likewise shows the illumination channel <NUM> according to <FIG> with the associated components in an illustration similar to <FIG>. In contrast to <FIG>, the fine actuator system <NUM> of the pupil facet mirror <NUM> has been adjusted in the current setting according to <FIG> so that the field facet image <NUM> has been displaced to the left energy sensor <NUM> in <FIG> in the negative x-direction of <FIG>. While only the right energy sensor <NUM> of <FIG> is impinged by the field facet image <NUM> in the current setting according to <FIG>, only the left energy sensor <NUM> of <FIG>, i.e., the other of the two energy sensors <NUM>, <NUM>, is impinged by the field facet image <NUM> in the current setting according to <FIG>. To this end, the pupil facet <NUM> is tilted about an axis parallel to the y-axis by way of the fine actuator system <NUM>.

This fine actuator-based adjustment of the pupil facet <NUM> can be used in a method for setting or adjusting the facet mirrors <NUM>, <NUM> of the illumination optical unit <NUM> of the illumination system <NUM>. In this case, the illumination channels <NUM> of the illumination optical unit <NUM> which should impinge a first of the two energy sensors <NUM>, <NUM>, for example the energy sensor <NUM>, are specified in an initial step. Furthermore, those illumination channels <NUM> which should impinge a second of the two energy sensors <NUM>, <NUM>, for example the energy sensor <NUM>, are specified. In an alternative configuration of this adjustment method, numbers of the illumination channels <NUM> of the illumination optical unit which should respectively impinge the first energy sensor, i.e., for example the left energy sensor <NUM>, and respectively impinge the second energy sensor, i.e., for example the right energy sensor <NUM>, can be specified. Subsequently, the respective fine actuator system <NUM> of the tilt actuator systems <NUM> of the pupil facets <NUM> which are assigned to the respective illumination channels <NUM> is set such that the specified energy sensors <NUM>, <NUM> are impinged by the illumination channels <NUM>.

By way of example, this makes it possible to ensure that, given a specified illumination setting, a desired energy distribution of an illumination of the object field from different directions is observed without unwanted systematic errors arising.

If there is an intensity gradient across the field facet image <NUM>, one of the two energy sensors <NUM>, <NUM> will systematically underestimate the contribution of the field facet <NUM> to the illumination of the object field <NUM> while the other will systematically overestimate the contribution. As a result of the described fine control, it is possible to switch between the two energy sensors <NUM>, <NUM> in such a way that these systematic effects of the individual illumination channels are cancelled when averaged over the field facet mirror <NUM>.

Particularly if an illumination light intensity within the field facet image <NUM> near the left energy sensor <NUM> in <FIG> deviates from the intensity near the right energy sensor <NUM> in <FIG>, for example on account of an intensity gradient within the illumination of the field facets <NUM>, the energy sensor <NUM> or <NUM> which is suitable in respect of its sensitivity can be selected for such an illumination channel <NUM> by specifying the fine tilt angle. As a result of this, it is possible in particular to reduce a far field tilt sensitivity of the illumination optical unit <NUM> in respect of a dose measured by the energy sensors <NUM>, <NUM>, leading to a stabilisation of the illumination optical unit <NUM> in the case of such a far field tilt.

An assignment of the energy sensors <NUM> and <NUM>, which are impinged via the illumination channels <NUM> of the respective pupil facets <NUM>, can be adapted on the basis of the respective illumination setting and can also be adapted on the basis of, for example, a change in a far field intensity profile ascertained by calibration measurement or simulation. Such an adaptation can be implemented within the scope of an automated method.

<FIG> shows the effect of relative mechanical position tolerances, firstly, of the field facet <NUM> and, secondly, of the pupil facet <NUM> of the associated illumination channel <NUM> on a relative position of the field facet image <NUM> in an representation which is firstly schematic and secondly exaggerated in terms of the tolerances. Components and functions corresponding to those which were already explained above with reference to <FIG> have the same reference signs and are not discussed in detail again.

The effect of corresponding manufacturing tolerances is illustrated in <FIG> on the basis of possible target positions on account of these manufacturing tolerances, firstly of a top left corner <NUM><NUM> and secondly of a top right corner <NUM><NUM> of the field facet image <NUM>. On account of the mechanical tolerances, these corners <NUM><NUM>, <NUM><NUM> could be located within a region which is schematically indicated in each case by way of a circular tolerance line <NUM><NUM>, <NUM><NUM>. By specifying corresponding fine tilt angles by way of the fine actuator system <NUM> of the pupil facet <NUM> on the one hand and the fine tilt actuator system <NUM> of the field facet <NUM> on the other hand, it is possible to compensate these tolerances in accordance with the tolerance lines <NUM><NUM>, <NUM><NUM>. With the aid of a closed-loop position control, which facilitates an accurate determination of the relative position of the respective field facet image <NUM>, for example relative to the two energy sensors <NUM>, <NUM>, it is possible to specify travels for adjustment movements <NUM> in the x-direction and <NUM> in the y-direction such that the corners <NUM><NUM> and <NUM><NUM> come to rest in the centre of the respective tolerance lines <NUM><NUM>, <NUM><NUM> after an adjustment has been implemented, as visualized in <FIG>. A positioning of the respective source image <NUM> on the pupil facet <NUM> can also be optimized in this way.

In <FIG>, tilt axes x<NUM>, y<NUM> for the actuator-based tilt are indicated firstly for the field facet <NUM> and secondly for the pupil facet <NUM>.

In this way, it is possible in particular to ensure exact and reproducible positioning of the respective field facet image <NUM> relative to the relative position of the energy sensors <NUM>, <NUM>, improving the stability and reproducibility of the measurement by way of the energy sensors <NUM>, <NUM>.

<FIG> shows, once again schematically, the effects of an adjustment of the fine actuator system <NUM> of the associated pupil facet <NUM> on the relative position of a respective field facet image <NUM> in the object field <NUM>. Components and functions corresponding to those which were already explained above with reference to <FIG> are denoted by the same reference signs and are not discussed in detail again.

<FIG> illustrates not only the relative position in the object field <NUM> of the field facet image <NUM> which belongs to the illumination channel <NUM> of the illustrated pupil facet <NUM>, but also the relative position of further field facet images <NUM> and <NUM> which belong to other illumination channels <NUM> and accordingly to other pupil facets <NUM> not illustrated here.

The field facet images <NUM>, <NUM>, <NUM> are all arcuate, i.e., have a similar shape to one another. The field facet images <NUM>, <NUM>, <NUM> differ from one another in respect of the arc orientation and in respect of their x-extent and, not evident from <FIG>, also in respect of their y-extent.

These orientation and/or size differences emerge firstly from different imaging effects of the field facets <NUM> and pupil facets <NUM> which are assigned to the respective illumination channels <NUM> and secondly also from the different spatial profiles of the respective illumination channels <NUM> on their path from the respective field facets <NUM> to the respective field facet image <NUM>, <NUM> and <NUM>. A corresponding different orientation can also arise from a different x-offset of the respective position specification of one of the field facet images <NUM>, <NUM>, <NUM> by way of the specification of the fine tilt angle.

The illustrated pupil facet <NUM> is shown with two exaggerated tilt positions, which differ by a tilt angle δy. The tilt of the pupil facet <NUM> through the tilt angle δy leads to a displacement of a relative y-position of the field facet image <NUM> relative to the object field <NUM>, as illustrated in <FIG> by a double-headed arrow Δy.

A tilt of the pupil facet <NUM> about a tilt axis δx lying in the plane of the drawing of <FIG>, which is possible as an alternative or in addition thereto, accordingly leads to a displacement of the field facet image <NUM> in the x-direction.

Furthermore, <FIG> illustrates a shadowing finger <NUM> of a field intensity specification device <NUM> that is otherwise illustrated schematically. The latter is arranged in the region of the field plane of the projection exposure apparatus <NUM>, for example in the region of the object plane <NUM>. In fact, the field intensity specification device <NUM> comprises a plurality of shadowing fingers <NUM>, only one of which is illustrated in <FIG>. The shadowing fingers <NUM> have a longitudinal extent in the y-direction and are displaceable independently of one another by way of an actuator in the y-direction by means of a displacement actuator system <NUM>. As a result of this displacement in the y-direction, the shadowing fingers <NUM> can be inserted into the illumination channels <NUM>, specifically into the field facet images <NUM>, <NUM>, <NUM>, from the side, for example from below in <FIG>. In this way, it is optionally possible to partly shadow the field facet images <NUM>, <NUM>, <NUM> closest to the respective shadowing finger <NUM> and hence the associated illumination channels <NUM>. This shadowing acts individually at the location of the respective shadowing finger <NUM>, i.e., in the region of the respective x-field coordinate. Corresponding field intensity specification devices <NUM> are known from the prior art.

For a given shadowing finger <NUM>, a relative position relation of the field facet image positions in the region of the x-coordinate of this shadowing finger <NUM> can be influenced by way of the fine actuator systems <NUM> of the pupil facets <NUM> assigned to the field facet images <NUM>, <NUM>, <NUM> by way of the respective illumination channels <NUM>. By way of example, this relative position relation can be chosen in such a way that all edge regions of the field facet images <NUM>, <NUM>, <NUM> facing the shadowing finger <NUM> are overlaid on one another in the region of the x-field coordinate of the shadowing finger <NUM>.

To this end and according to <FIG>, proceeding from the relative position of the field facet images <NUM>, <NUM>, <NUM>, the field facet image <NUM> must be displaced by a longer path in the negative y-direction than the field facet image <NUM> so that an edge region overlay at the location of an edge region <NUM> of the field facet image <NUM> is obtained. If the shadowing finger <NUM> is then inserted into the object field <NUM> in the positive y-direction, it simultaneously shadows all three field facet images <NUM>, <NUM>, <NUM> in the edge region <NUM>. This leads to the illumination channels <NUM> assigned to these field facet images <NUM>, <NUM>, <NUM> being shadowed in the same way, reducing the illumination intensity from the direction of these illumination channels <NUM> in the same way.

This is visualized using the example of a quadrupole illumination setting, likewise in <FIG>. This quadrupole illumination setting is illustrated in a pupil plane <NUM> of the projection optical unit <NUM>, which is spaced apart from the object plane <NUM> along the beam path of the illumination radiation <NUM>, which is therefore shown purely schematically in the plane of the drawing in <FIG>.

The quadrupole illumination setting has four individual poles Q1, Q2, Q3 and Q4, which in turn are subdivided into sub-pupil regions which are arranged in the form of a hexagonal grid in the illustrated embodiment.

Sub-pupil regions <NUM>SP, <NUM>SP and <NUM>SP, which are assigned to the illumination channels <NUM> of the field facet images <NUM>, <NUM>, <NUM>, are emphasized by circles in this quadrupole setting.

The sub-pupil region <NUM>SP is located at the left lower edge of the pole Q3. The sub-pupil region <NUM>SP is located in the mid section of the pole Q2. The sub-pupil region <NUM>SP is located in the lower right section of the pole Q1. In the aforementioned alignment of the three field facet images <NUM>, <NUM>, <NUM> such that these overlap in the edge region <NUM>, there is uniform shadowing of the illumination from the direction of the three sub-pupil regions <NUM>SP, <NUM>SP and <NUM>SP in this edge region <NUM> when the shadowing finger <NUM> is inserted. Accordingly, it is also possible to achieve overlays of other desired combinations of field facet images assigned to the illumination channels <NUM> by way of respective fine actuator-based adjustment of the pupil facets <NUM> and, accordingly, the displacement of the field facet images in the x- and/or y-direction.

In this way, it is possible for example to achieve a point-symmetric effect of shadowing of the illumination channels <NUM> in the pupil of the illumination optical unit <NUM>.

As an alternative or in addition thereto, it is possible to initially specify a relative position of the respective shadowing finger <NUM> of the field intensity specification device <NUM> and it is then possible, for example on the basis of measurement or simulation results, to specify a displacement of the respective field facet images relative to this initially specified relative position of the shadowing finger <NUM> such that this yields a desired shadowing effect in the associated x-field coordinate, as seen over the illumination setting.

An unwanted distribution of an intensity reduction between different illumination channels <NUM> during the shadowing finger correction, which is also referred to as crosstalk, for example a pronounced telecentricity deviation (y-axis asymmetry), can then be reduced or entirely avoided.

In particular, use can be made of the following method for adjusting at least one of the facet mirrors <NUM>, <NUM>, in particular for adjusting the pupil facet mirror <NUM>:
Initially, the position of the shadowing finger <NUM> of the field intensity specification device <NUM> is selected and specified by way of the displacement actuator system <NUM>. Then, at least one illumination channel <NUM> is selected and the fine actuator system <NUM> of the tilt actuator system of the associated pupil facet <NUM> is set such that a specified relative position is reached between a free end <NUM> of the shadowing finger <NUM> and an edge (edge region <NUM>) of the illumination channel <NUM> facing this free end.

In this adjustment method, it is possible in particular to also use the displacement of the field facet images, for example the field facet image <NUM>, in the x-direction. This is elucidated in greater detail below with reference to <FIG>:
In turn, <FIG> shows the field facet image <NUM> in an initial relative position relative to the object field <NUM>, which is specified by way of a scanning slot stop <NUM>. Moreover, an upper edge boundary <NUM> of a field stop <NUM> which is a constituent part of the field intensity specification device <NUM> is indicated in <FIG>.

The edge boundary <NUM> can be formed by a plurality of free ends of shadowing fingers in the style of the free ends <NUM> of the shadowing finger <NUM> which were explained above in conjunction with <FIG> and which are inserted into the object field <NUM> from above at the various x-field coordinates in <FIG>. In <FIG>, these shadowing fingers <NUM> are indicated for a section of the field stop <NUM>. An x-extent of the field facet image <NUM> is greater on both sides of the object field <NUM> than an x-extent of the object field <NUM>. Corresponding x-protrusion regions <NUM>l to the left of the object field <NUM> in <FIG> and <NUM>r to the right of the object field <NUM> in <FIG> can be used firstly for impinging energy sensors in the style of the energy sensors <NUM>, <NUM> of <FIG> but secondly also yield an x-displacement degree of freedom of the field facet image <NUM> relative to the object field <NUM>.

<FIG> shows, in an illustration otherwise corresponding to <FIG>, the relative position of the field facet image <NUM> after a fine actuator-based tilt of the associated pupil facet <NUM> about an axis parallel to the y-axis. This fine-actuator based tilt leads to displacement of the field facet image <NUM> relative to the object field <NUM> in the negative x-direction. On account of the x-extent of the field facet image <NUM> being significantly greater than the x-extent of the object field <NUM>, the field facet image <NUM> still covers the entire x-extent of the object field <NUM>. On account of the arcuate form of the field facet image <NUM> there is approximately sickle-section-shaped shadowing <NUM> of the field facet image <NUM> by the field stop <NUM> since the relative position of the edge boundary <NUM> of the field stop <NUM> of the field intensity specification device <NUM> is unchanged in comparison with <FIG>. This shadowing acts approximately over a complete left half of the x-extent of the object field <NUM> and increases toward the left side, i.e., toward the left edge section <NUM>l, from the centre of the object field <NUM>. Field-dependent shadowing of the associated illumination channel arises in respect of the edge boundary of the field facet image <NUM>. To the extent that the field facet image <NUM> is illuminated with a homogeneous intensity distribution by the illumination light <NUM>, greater shadowing from the direction of this illumination channel <NUM> arises for small x-coordinates of the object field <NUM> (left region of the object field <NUM>) than for larger x-coordinates.

As a result of an additional tilt of the pupil facet <NUM> about an axis parallel to the x-axis, the field facet image <NUM> can be moved further in the direction of the field stop <NUM> of the field intensity specification device <NUM> in the y-direction such that the field facet image is shadowed by the field stop at each x-coordinate. A change in the tilt of the pupil facet <NUM> about an axis parallel to the y-axis, i.e., a displacement of the field facet image <NUM> in the x-direction, then leads to a change in the shadowing by the field stop <NUM>, which is approximately linear with the x-coordinate. Hence, a change in the tilt of the pupil facet <NUM> about an axis parallel to the y-axis leads to a change in the scan-integrated illumination of the object field, with the change being approximately linear to the x-coordinate. In contrast to a single lone application of the field intensity specification device <NUM>, this can specify a different intensity change profile for each illumination channel <NUM>k (and hence for the associated region in the illumination pupil).

The x-coordinate-dependent shadowing <NUM> of the field facet image <NUM>, which is attained by the x-displacement of the arcuate field facet image <NUM>, can be used for desired field dependencies of an angle-dependent illumination intensity distribution of the respective illumination setting. As an alternative or in addition thereto, other inhomogeneities in such a field distribution present can be corrected and/or compensated by field dependencies introduced in such targeted fashion. When setting the fine actuator system <NUM>, which is explained above with reference to <FIG>, the associated pupil facet <NUM> is tilted about a y-axis, i.e., about an axis which is arranged parallel to the longitudinal axis of the respective shadowing fingers <NUM>. Accordingly, a displacement of the field facet image <NUM> perpendicular to this longitudinal axis arises.

The effect of the coarse actuator system <NUM> of the tilt actuator system <NUM> of the pupil facets <NUM> on the one hand and the switching actuator system <NUM> of the field facets <NUM> on the other hand is explained below on the basis of <FIG>. In particular, the tilt actuator system <NUM> can be used to optimize a pupil fill ratio or a NILS value.

<FIG> schematically shows the field facet mirror <NUM> and the pupil facet mirror <NUM> of the illumination optical unit <NUM>. Two illumination channels <NUM><NUM>, <NUM><NUM> with field facets <NUM><NUM>, <NUM><NUM> and pupil facets <NUM><NUM> and <NUM><NUM> assigned thereto are emphasized. In the switch configuration of the field facets <NUM><NUM> and <NUM><NUM> according to <FIG>, the pupil facet <NUM><NUM> is assigned to the field facet <NUM><NUM> via the illumination channel <NUM><NUM> and the pupil facet <NUM><NUM> is assigned to the field facet <NUM><NUM> via the illumination channel <NUM><NUM>. Angles of incidence α1, α2 of chief rays of the illumination light <NUM> on the pupil facets <NUM><NUM> and <NUM><NUM> in the switch configuration according to <FIG> are visualized in <FIG>.

<FIG> shows an alternative switch configuration of the field facets <NUM><NUM>, <NUM><NUM>, which was obtained by switching these two field facets <NUM><NUM>, <NUM><NUM> by means of the switching actuator system <NUM>. Now, the pupil facet <NUM><NUM> is assigned to the field facet <NUM><NUM> via the illumination channel <NUM><NUM> and the pupil facet <NUM><NUM> is assigned to the field facet <NUM><NUM> via the illumination channel <NUM><NUM>. Thus, in comparison with <FIG>, there has been a change in the assignment of the pupil facets <NUM><NUM>, <NUM><NUM> to the field facets <NUM><NUM>, <NUM><NUM>. The two field facets <NUM><NUM>, <NUM><NUM> have accordingly switched between the pupil facets <NUM><NUM>, <NUM><NUM>.

<FIG> elucidate the angles of incidence β1, β2 on the pupil facets <NUM><NUM>, <NUM><NUM> in the switch configuration according to <FIG>. These angles of incidence β1, β2 and, in particular, reflected directions of the illumination light <NUM> differ in the case of the respective pupil facets <NUM><NUM>, <NUM><NUM> when the two switch configurations according to <FIG> and <FIG> are compared. So that the field facet images respectively assigned to the illumination channels <NUM><NUM>, <NUM><NUM> are overlaid as desired in the object field <NUM>, it is therefore necessary to tilt the pupil facets <NUM><NUM>, <NUM><NUM> in order to bring about the desired reflected direction of the illumination light <NUM>. This tilt is implemented by means of the coarse actuator system <NUM> of the pupil facets <NUM><NUM>, <NUM><NUM>.

The change in the assignment of the field facets <NUM><NUM>, <NUM><NUM> to the pupil facets <NUM><NUM>, <NUM><NUM> can be used, for example, when different integrated illumination light intensity levels are transported via the field facets <NUM><NUM>, <NUM><NUM> on account of a corresponding far field distribution of the illumination light over the field facet mirror <NUM>. By way of example, should the field facet <NUM><NUM> be impinged with a higher intensity level than the field facet <NUM><NUM> in the impingement situation of the field facet mirror <NUM> according to <FIG> and if this intensity ratio is precisely inverted in the impingement situation of the field facet mirror <NUM> according to <FIG>, this inversion of the intensity impingement can be exactly compensated by the assignment change on account of the different switch configurations of <FIG> and <FIG>.

The illumination system <NUM> can comprise a far field sensor <NUM>, illustrated schematically in <FIG>, for a spatially resolved far field measurement of an illumination intensity level of the radiation source or light source <NUM> of the illumination system <NUM>. The far field sensor <NUM> can be configured as a plurality of energy sensors which, for example, are attached around the field facet mirror <NUM>. As an alternative or in addition thereto, individual sensors of the far field sensor <NUM> can be housed in sections of the field facet mirror <NUM> not used in terms of occupancy by field facets <NUM>. A far field measurement over a further alternative embodiment of the far field sensor <NUM> can be implemented, for example, by way of a thermal imaging camera which captures the entire field facet mirror <NUM> impinged by the illumination light <NUM>.

In the case of a facet mirror adjustment method using such a far field sensor <NUM>, a far field of the light source <NUM> of the illumination system <NUM> is initially measured in spatially resolved fashion by the far field sensor <NUM>. This measurement can be implemented at the location of the field facet mirror <NUM>, although this is not mandatory. Subsequently, an illumination channel assignment of firstly the field facets <NUM> and secondly the pupil facets <NUM> assigned thereto via the respective illumination channels <NUM> is undertaken, in such a way that a specified intensity illumination of the object field <NUM> from the direction of the pupil facets <NUM> arises when the far field measurement result is used as a basis. Finally, the field facets <NUM> switched by the switch actuator system <NUM> and the coarse actuator system <NUM> of the tilt actuator system <NUM> of the pupil facets <NUM> are set in such a way that the selected illumination channel assignment arises. To finely adjust the relative illumination channel positions, it is possible also to use the fine actuator system <NUM> of the tilt actuator system <NUM> and the fine tilt actuator system <NUM>, as explained in exemplary fashion above. Beyond a simple pairwise change of two relative illumination channel positions, an adjustment of a plurality of relative illumination channel positions can also be attained accordingly for the purposes of improving selected illumination parameters.

<FIG> shows a further application of the actuator-based displacement of the field facets <NUM> on one hand and the pupil facets <NUM> on the other hand. Component parts and functions which were already explained above on the basis of <FIG> have the same reference signs and are not discussed again in detail.

<FIG> schematically shows the beam path of an illumination channel <NUM> between a source volume <NUM>, for example a plasma volume, and the object field <NUM>. The EUV radiation <NUM> emanating from the source volume <NUM> is initially collected by the collector <NUM>, which is a collector mirror with an ellipsoid shape in the embodiment according to <FIG>.

<FIG> illustrates the field facet <NUM> of the field facet mirror <NUM> assigned to the illumination channel <NUM> and the pupil facet <NUM> of the pupil facet mirror <NUM> assigned to the illumination channel <NUM> in exaggerated fashion.

In the embodiment according to <FIG>, the illumination system <NUM> furthermore comprises a relative source position sensor <NUM> for determining a relative spatial position of the source volume <NUM> relative to the collector <NUM>.

In particular, the relative source position sensor <NUM> captures jitter movements and/or drift movements of the source volume <NUM>, visualized in <FIG> by a double-headed arrow <NUM>. These movements <NUM> of the source volume <NUM> lead to a corresponding displacement of the source image <NUM> on the pupil facet <NUM>, which is visualized in <FIG> by a double-headed arrow <NUM>.

The displacement of the source image <NUM> on the pupil facet <NUM> leads to a change in direction of the chief ray <NUM> of the illumination light <NUM>, which is guided in the illumination channel <NUM>, relative to a normal n on the reflection surface of the pupil facet <NUM> in the region of the source image <NUM>. As a matter of principle, this leads to a displacement of the field facet image <NUM> relative to the object field <NUM> along the y-direction, which is visualized by a double-headed arrow <NUM> in <FIG>. To compensate for this displacement <NUM>, the angle relation between the normal n and the direction of the chief ray <NUM> is updated by way of the fine actuator system <NUM> of the pupil facet <NUM> such that the location of the field facet image <NUM> relative to the object field <NUM> is maintained independently of the displacement <NUM> of the source image <NUM>.

Thus, overall, a method for adjusting the facet mirrors <NUM>, <NUM> can be carried out by means of the relative source position sensor <NUM>, in which method the relative position of the source volume <NUM> relative to the collector <NUM> is initially measured with the aid of the relative source position sensor <NUM>.

By way of example, the relative source position sensor <NUM> can be realized as a camera which captures the source volume <NUM> in imaging fashion. A plurality of such cameras can also be used such that the relative position of the source volume <NUM> in space can be captured. In particular, this capture can be implemented in real-time and with a high time resolution such that the relative source position sensor <NUM> can be part of a real-time closed-loop controlled updating method.

Subsequently, the fine actuator system <NUM> of the tilt actuator system <NUM> of the respective pupil facet <NUM> is firstly set in such a way that, on the basis of the relative source position measurement result, a specified position of the assigned illumination channel <NUM> on the object plane <NUM> is reached.

Below, estimates relating to the orders of magnitude of, firstly, the coarse tilt angle range which must be specified by way of the coarse actuator system mode of operation of the tilt actuator system <NUM> and, secondly, the fine tilt angle range which must be specified by way of the fine actuator system mode of operation of the tilt actuator system <NUM> are made on the basis of <FIG>.

<FIG> schematically illustrates a row of field facets <NUM><NUM> to <NUM>N of the field facets <NUM>i (i=<NUM>, <NUM>,. N) of the field facet mirror <NUM>, which specify a maximum diameter DF of the far field of the light source <NUM> in the arrangement region of the field facet mirror <NUM>.

Shown is the extreme situation where, firstly, the field facet <NUM><NUM> in the region of the left-hand side of the far field is assigned (Z1) to a pupil facet and, secondly, the field facet <NUM>N on the right-hand side of the far field is assigned (Z2) to the same pupil facet <NUM>. On account of the diameter DF of the far field, an angle α arises here between the illumination channels of the assignments Z1, Z2, which must be compensated in the coarse actuator system mode of operation of the tilt actuator system <NUM> of the pupil facet <NUM>.

<FIG> shows a tilt angle β of the pupil facet <NUM>, which is spanned by two possible positions of a facet image in the object field <NUM>. The field facet image <NUM> is indicated in the object field <NUM> in <FIG>. Under the assumption that the images of the field facets <NUM>i have a similar size to the field facets themselves and if the field facet image <NUM> is intended to be displaced by a fraction VR by the fine actuator system <NUM>, it is possible to derive the ratio. Here, for simplification, the assumption is made that a distance d between an arrangement plane of the field facet mirror <NUM> and the pupil facet <NUM> on the one hand and a distance between the pupil facet <NUM> and the object plane <NUM> on the other hand are approximately the same size.

Thus, a maximum coarse tilt angle range to be specified is typically greater than a maximum fine tilt angle range to be specified by a factor of <NUM> to <NUM>.

During the projection exposure, the reticle <NUM> and the wafer <NUM>, which bears a coating that is light-sensitive to the EUV illumination light <NUM>, are provided. Subsequently, at least one portion of the reticle <NUM> is projected onto the wafer <NUM> with the aid of the projection exposure apparatus <NUM>. Finally, the light-sensitive layer on the wafer <NUM> that has been exposed with the EUV illumination light <NUM> is developed. A microstructured or nanostructured component, for example a semiconductor chip, is produced in this way.

Claim 1:
Pupil facet mirror (<NUM>) for an illumination optical unit (<NUM>) of a projection exposure apparatus (<NUM>),
- wherein, in addition to the pupil facet mirror (<NUM>), the illumination optical unit (<NUM>) comprises a field facet mirror (<NUM>) with a plurality of switchable field facets (<NUM>),
- wherein an illumination channel (<NUM>) is specified by means of one respective field facet (<NUM>) of the field facet mirror (<NUM>) and one respective pupil facet (<NUM>) of the pupil facet mirror (<NUM>), illumination light (<NUM>) being guided by means of said illumination channel to an object field (<NUM>) in an object plane (<NUM>) of the projection exposure apparatus (<NUM>) via the field facet (<NUM>) and the pupil facet (<NUM>), with images (<NUM>, <NUM>, <NUM>) of the field facets (<NUM>) being imaged in overlaid fashion into the object field (<NUM>) via the pupil facets (<NUM>),
- wherein a plurality of tiltable pupil facets (<NUM>) belong to the pupil facets (<NUM>) of the pupil facet mirror (<NUM>),
- wherein each of the tiltable pupil facets (<NUM>) interacts with a tilt actuator system (<NUM>) of the pupil facet mirror (<NUM>), said tilt actuator system comprising:
-- a coarse actuator system mode of operation (<NUM>) for specifying a coarse tilt angle of the tiltable pupil facet (<NUM>) as a result of an illumination channel assignment of this tiltable pupil facet (<NUM>) to a field facet (<NUM>),
-- a fine actuator system mode of operation (<NUM>) for specifying a fine tilt angle of the tiltable pupil facet (<NUM>) for specifying a relative position of the field facet image (<NUM>, <NUM>, <NUM>) of the illumination channel (<NUM>) of the tiltable pupil facet (<NUM>) relative to the object field (<NUM>).