Optical device

A device including an imaging optical unit (9) imaging an object field (5) in an image field (10), a structured mask (7), arranged in the region of the object field (5) via reticle holder (8) displaceable in a reticle scanning direction (21), and a sensor apparatus (25), arranged in the region of the image field (10) via a substrate holder (13) displaceable in a substrate scanning direction (22). The mask (7) has at least one measurement structure (27; 33) to be imaged on the sensor apparatus (25), wherein the sensor apparatus (25) includes at least one line sensor (28) with a multiplicity of sensor elements (29), and affords the possibility of testing the imaging optical unit (9) during the displacement of the substrate holder (13) for exposing a substrate (12) arranged on the substrate holder.

FIELD OF AND BACKGROUND OF THE INVENTION

The invention relates to an optical device and a method for testing an imaging optical unit. The invention furthermore relates to a projection exposure apparatus, a method for producing a microstructured or nanostructured component and a component produced according to this method.

Generic modules and/or methods have been disclosed in the prior art, for example in U.S. Pat. No. 7,298,498 B2, DE 101 09 929 A1 and US 2008/0130012 A1.

OBJECTS AND SUMMARY OF THE INVENTION

One object of the invention is to optimize an optical device with an imaging optical unit in respect of testing the imaging optical unit.

According to a primary aspect of the invention, a sensor apparatus is arranged with at least one line sensor on a substrate holder in the region of the image field. Hence, this is a scanner-integrated measurement arrangement. In the process, the sensor apparatus is embodied such that it affords the possibility of testing the imaging optical unit during a scanning movement, more particularly during a uniform scanning movement, of the substrate holder. The imaging optical unit can more particularly be tested during an overscan method, during which the substrate holder is moved on, more particularly uniformly moved on, after the actual exposure of a substrate arranged on the former. Accordingly, the imaging optical unit can also be tested before the actual exposure of the substrate.

As a result of using a line sensor and the arrangement according to the invention of same, a test of the imaging optical unit is made possible, even at high scanning speeds. Hence the device according to the invention enables a test of the imaging optical unit with minimal expenditure of time. Moreover, tremors and vibrations are avoided as a result of the possibility of a uniformly continued scanning movement.

The line sensor can more particularly have a substantially one-dimensional embodiment, i.e. the sensor elements thereof can be uniquely characterized by their position in the direction of the orientation of the line sensor. Such line sensors can have image-recording frequencies in the kilohertz range and thus enable a test of the imaging optical unit with the aforementioned advantages.

The sensor apparatus can be designed such that all sensor elements of the sensor apparatus are used for the measurement. This ensures a high read-out frequency since there is no need to distinguish between used and unused sensor elements during the read out.

According to a preferred embodiment, the device comprises at least two line sensors. In particular, these can be arranged parallel or perpendicular to one another. In particular, the line sensors are embodied as separate, spatially separated components. This enables separate, parallel evaluation of the signals from the individual line sensors. This further reduces the expenditure of time required for testing the imaging optical unit. A greater number of line sensors are also possible. In particular, provision can be made for the device to comprise at least three, more particularly at least four, more particularly at least six line sensors. In particular, it can respectively have at least two, more particularly at least three, more particularly at least four, more particularly at least six line sensors per light channel. This further improves the test of the imaging optical unit. A spatially-resolved or field-resolved test of the imaging optical unit is improved by a multiplicity of line sensors. Moreover, this improves a component-resolved test of the imaging optical unit.

The sensor apparatus preferably comprises at least one interferometer. This is preferably a shearing interferometer, more particularly a lateral-shearing interferometer (LSI), a point-diffraction interferometer (PDI) or a line-diffraction interferometer (LDI). Such an embodiment of the sensor apparatus affords the possibility of measuring phase and amplitude of incident waves. In the case of a shearing interferometer, the latter is preferably arranged such that the shearing direction is respectively parallel to the row direction of the associated line sensor. The sensor apparatus preferably comprises a plurality of sets with respectively at least one, more particularly at least two, more particularly at least three shearing gratings, the shearing gratings from different sets having different orientations, more particularly being arranged perpendicular to one another. Within one set, the shearing gratings are preferably arranged respectively displaced with respect to one another in the shearing direction. A lateral phase offset arises as a result of the displacement, and so measurements at different phases are possible parallel in time. Arranging shearing gratings with different orientations makes it also possible, within a single measuring process, to determine e.g. astigmatism in addition to carrying out defocus determination.

The sensors for reading out the sensor signals preferably have a clock frequency of at least 1 kHz. More particularly, the clock frequency is at least 2 kHz, more particularly at least 3 kHz, more particularly at least 5 kHz, more particularly at least 10 kHz, more particularly at least 25 kHz. The time required for a measurement is reduced as a result of such a high clock frequency. This affords the possibility of recording the shearograms during a scanning movement with a uniformly continued scanning speed.

The measurement structure of the mask preferably has a diffraction structure with at least two diffraction directions. In particular, it can have a cross, chequerboard or triangular structure. The measurement mask is more particularly embodied as a coherence-forming mask. The structure of the measurement mask and the embodiment and orientation of the shearing gratings are preferably matched to one another. By using a measurement mask embodied thus, it is possible, in a targeted fashion, to produce test beams for testing the imaging optical unit.

The reticle holder and the substrate holder can preferably be displaced in a synchronized fashion. In particular, they can be displaced in such a synchronized fashion that the association between a point on the measurement mask and the point on the sensor apparatus in the image plane is maintained during the scan. In other words, the image of the measurement mask remains stationary on the respectively associated sensor element or the associated sensor elements. In particular, the scanning speeds of the reticle holder and the substrate holder have the same ratio as the imaging scale of the imaging optical unit. However, in principle it is also possible to displace the substrate holder with a scanning speed that deviates therefrom. More particularly, provision can be made for the reticle holder to be arranged in a stationary fashion and for only the substrate holder with the sensor apparatus to be displaced. This is more particularly provided for scanning a so-called aerial image. In the process, the sensor apparatus scans an image being created in the image plane in a stationary fashion.

The measurement structure is preferably embodied such that a plurality of channels are formed for the channel-resolved test of the imaging optical unit. These channels are also referred to as measurement channels. They are arranged distributed over the image field. More particularly, at least 2, more particularly at least 3, more particularly at least 6, more particularly at least 12, more particularly at least 20, more particularly at least 30 channels are arranged in the image field. This is particularly advantageous for a field- and/or component-resolved test of the imaging optical unit. The spatial association of the individual measurement channels with respect to one another is preferably fixed. This enables a tomographic evaluation of the measurement results, more particularly a component-resolved deduction of so-called lens-heating effects.

A specific region of the sensor apparatus with a multiplicity of sensor elements is preferably associated with each of the channels. At least two line sensors are preferably associated with each channel. In this case, each line sensor advantageously has at least three sensor elements. Hence at least six sensor elements are associated with each channel.

Moreover, the invention is based on a further object of improving a method for testing an imaging optical unit. Advantages associated with this method substantially correspond to those described above.

In particular, provision can be made that the mask to be arranged in the object plane first has structures for producing a microstructured or nanostructured component and secondly has measurement structures for testing the imaging optical unit.

Provision is made for the substrate holder, more particularly the sensor apparatus, to be displaced with a constant speed, more particularly uniformly, in the substrate scanning direction for imaging the imaging structures and the measurement structures. The substrate holder is advantageously displaced uniformly, i.e. with constant scanning speed, while the whole mask is imaged first on the substrate and secondly on the sensor apparatus. This first affords a particularly efficient method for testing the imaging optical unit, and secondly tremors are avoided as a result of the uniform displacement.

The scanning speed is preferably set to at least 100 mm/s. More particularly, it is at least 200 mm/s, more particularly at least 350 mm/s, more particularly at least 500 mm/s.

The substrate holder is preferably displaced synchronized with the reticle holder. In this case, the ratio of the scanning speeds of the reticle holder and the substrate holder preferably corresponds precisely to the imaging ratio of the imaging optical unit. This enables a fixed association between the points on the mask and the points on the wafer or the sensor apparatus.

T radiation used to image the object field in the image field is split into beams. To this end, provision is made, in particular, for an illumination optical unit with a field and pupil facet mirror. The individual rays of a test beam are spaced apart in angular space. This affords the possibility of uniquely associating a test beam with each ray registered by the sensor apparatus. A suitable evaluation of the sensor data thus enables a component-resolved test of the imaging optical unit.

Moreover, the invention is based on objects of developing a projection exposure apparatus, a method for producing a microstructured or nanostructured component and such a component.

Further features and details of the invention emerge from the description of exemplary embodiments on the basis of the drawings. In detail:

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1schematically shows the components of a projection exposure apparatus1for microlithography. In addition to a radiation source3, an illumination system2of the projection exposure apparatus1comprises an illumination optical unit4for exposing an object field5in an object plane6. A reticle, which is also referred to as mask7below, arranged in the object field5and held by a reticle holder8(merely illustrated in sections), is exposed in this case.

A projection lens9serves to image the object field5in an image field10in an image plane11. In general, the projection lens9is also referred to as imaging optical unit. A structure on the mask7is imaged on a light-sensitive layer of a wafer12, which is held by a wafer holder13and arranged in the region of the image field10in the image plane11. In general, the wafer12is also referred to as substrate to be exposed and the wafer holder13is also referred to as substrate holder. The chemical change of the light-sensitive layer on the wafer12during the exposure is also referred to as lithographic step.

The radiation source3emits radiation14with a wavelength λ<193 nm. In particular, an argon fluoride (ArF) excimer laser with a wavelength of λ=193 nm or an F2laser with a wavelength of λ=157 nm can be used as radiation source3. As an alternative to this, the radiation source3can be a plasma source, for example a GDPP source or an LPP source. A radiation source based on a synchrotron can also be used as a radiation source3. The radiation source3can, in particular, be an EUV radiation source. The wavelength of such an EUV radiation source3is in the range between 5 nm and 30 nm, more particularly in the range between 10 nm and 20 nm, e.g. at 13.5 nm in a vacuum. A person skilled in the art finds information in respect of such a radiation source in e.g. U.S. Pat. No. 6,859,515 B2. The EUV radiation14is also referred to as illumination light or imaging light.

A collector19is provided for bundling the radiation14from the radiation source3.

The illumination optical unit4comprises a multiplicity of optical elements. In this case, these optical elements can be designed to be refractive or reflective. Combinations of refractive and reflective optical elements are also possible. For EUV radiation14with a wavelength λ<193 nm, the illumination optical unit4and the projection optical unit9more particularly comprise only reflective components. The illumination optical unit4comprises a field facet mirror15with a multiplicity of field facets16. The field facet mirror15is arranged in a plane of the illumination optical unit4that is optically conjugate to the object plane6. The EUV radiation14is reflected to a pupil facet mirror17of the illumination optical unit4by the field facet mirror15. The pupil facet mirror17has a multiplicity of pupil facets18. The field facets16of the field facet mirror15are imaged in the object field5with the aid of the pupil facet mirror17.

There is precisely one pupil facet18on the pupil facet mirror17associated with each field facet16on the field facet mirror15. A light channel20is formed between respectively one field facet16and a pupil facet18. As a result of the facet mirrors15,17, the imaging light14is split into beams with a predetermined incident angle distribution.

In principle, it is possible to embody the field facet mirror15and/or the pupil facet mirror17such that the field facets16and/or the pupil facets18can be pivoted. This affords the possibility of a variable association between the field facets16and the pupil facets18. In particular, this affords the possibility of illumination settings with different illumination angle distributions. This is advantageous, in particular, for testing the projection optical unit9.

FIG. 2schematically shows a meridional section of the components of the projection exposure apparatus1as perFIG. 1. Here, the ray path of the radiation14in the illumination optical unit4and the projection optical unit9is illustrated schematically.

The reticle holder8can be displaced in a controlled fashion such that, during the projection exposure, the structured mask7can be displaced in the object plane6along a displacement direction. Accordingly, the wafer holder13can be displaced in a controlled fashion such that the wafer12can be displaced in the image plane11along a displacement direction. As a result, the mask7and the wafer12can be scanned through the object field5and through the image field10, respectively. The displacement direction of the mask7is also referred to as the reticle scanning direction21below. The displacement direction of the wafer12is also referred to as the substrate scanning direction22below. The mask7and the wafer12can preferably be displaced synchronously along the scanning directions21,22. Here, the ratio of the scanning speeds preferably precisely corresponds to the imaging ratio of the projection optical unit9.

To simplify the illustration, a Cartesian xyz-coordinate system has been drawn in the figures. InFIGS. 1 and 2, the x-direction runs perpendicular to the plane of the drawing and into the latter. The y-direction precisely corresponds to the scanning directions21,22. The z-direction is parallel to the profile of an optical axis23of the projection optical unit9.

The projection optical unit9comprises a multiplicity of projection mirrors24i. InFIG. 2, the projection optical unit9has been illustrated with six projection mirrors241,242,243,244,245and246. In general, the projection optical unit9in particular comprises at least three, more particularly at least five, projection mirrors24i. In particular, it can also have at least six, seven or eight projection mirrors24i.

FIG. 3once again schematically illustrates the projection optical unit9and, more particularly, the details of the arrangement of the mask7on the reticle holder8and the details of the arrangement of the wafer12and also a sensor apparatus25, also referred to as detection unit or detector apparatus. The mask7is arranged in the region of the object plane6, more particularly in the region of the object field5, by means of the reticle holder8such that it can be displaced in the reticle scanning direction21. It can be embodied as transmissive mask or as reflective mask. Accordingly, the substrate12and, more particularly, the sensor apparatus25are arranged in the region of the image plane11, more particularly in the region of the image field10, by means of the substrate holder13such that they can be displaced in the substrate scanning direction22.

The substrate holder13and the reticle holder8can in particular be displaced with respect to one another in a synchronized fashion. More particularly, they can be displaced synchronized with respect to one another such that the association between a point on the mask7and a point on the substrate12or the sensor apparatus25is maintained during a scan, i.e. during the displacement. This is achieved by virtue of the fact that the ratio of the scanning speeds precisely corresponds to the imaging ratio of the projection optical unit9. Here, this mode of operation is referred to as a field point scan. In principle, it is also possible for the reticle holder8or, more particularly, the substrate holder13to be displaced with a scanning speed that deviates therefrom. Provision can be made, in particular, for a so-called aerial image scan, for the reticle holder8to be stopped at least from time to time, i.e. for the latter to be arranged in a stationary fashion. During this method of operation, the mask7can fixedly select specific field points at which, in a respectively stationary fashion, an image is created in the image plane11. This image can be scanned by means of the sensor apparatus25by displacing the substrate holder13in the substrate scanning direction22. Moreover, in principle, a mode of operation is feasible which is situated between the two described above, i.e. between the unchanging assignment of points on the mask7to points on the substrate12during the field point scan on the one hand and the stationary arrangement of the mask7during the aerial image scan on the other hand.

In the following text, a first embodiment of the mask7is described in more detail with reference toFIG. 4a. The mask7has structures to be imaged on the substrate12. These structures comprise the actual imaging structure26for exposing the wafer12, more particularly the light-sensitive coating of the wafer12, and at least one measurement structure27to be imaged on the sensor apparatus25. In general, both the actual imaging structure26and the measurement structure27form structures to be imaged.

The measurement structure27is advantageously arranged adjacent to the imaging structure26. In particular, it is arranged adjacent to the imaging structure26in the reticle scanning direction21. However, in principle, it is also feasible to arrange the measurement structure27adjacent to the imaging structure26in a direction perpendicular to the reticle scanning direction21.

According to the invention, provision is made to arrange both the imaging structure26and the measurement structure27on the mask7. However, in principle, it would also be feasible to embody the measurement structure27and the imaging structure26as separate masks7. In this case, the masks7are arranged adjacent to one another, more particularly adjacent to one another in the reticle scanning direction21, on the reticle holder8. The mask7with the measurement structure27is more particularly fixedly arranged on the reticle holder8. It is securely connected to the reticle holder8. The mask7with the measurement structure27and/or the mask7with the imaging structure26are advantageously interchangeable in this case. In particular, they can be interchanged independently of one another.

In the following text, the region of the mask7with the measurement structure27, i.e. the measurement structure27, is described in more detail. The measurement structure27is designed as diffraction structure. In particular, it is embodied as diffraction structure with at least two diffraction directions. By way of example, as illustrated inFIG. 4a, it can be embodied as chequerboard structure. It can also be embodied as a cross structure or triangle structure. In particular, the measurement structure27is designed as coherence-forming mask. It can be embodied as a perforated mask or as a reflective mask. It preferably forms origins of coherent waves of the imaging radiation14.

The measurement structure27comprises a plurality of partial structures for each measurement channel. In particular, the partial structures have an identical design. The arrangement of the partial structures of the mask7is matched to the embodiment of the sensor apparatus25, which will still be described in more detail below. In particular, the measurement structure27comprises at least two, more particularly at least three, more particularly at least four, more particularly at least five, preferably at least six partial structures. Here, the partial structures are preferably, at least in part, arranged in one or more rows.

WhileFIG. 4ashows the design of the mask7, more particularly of the measurement structure27, for a single-channel embodiment,FIG. 4billustrates, in an exemplary fashion, a multi-channel embodiment of the measurement structures27of the mask7. According to the exemplary embodiment illustrated inFIG. 4b, the mask7comprises four measurement structures271,272,273and274, which respectively comprise six partial structures in accordance with the embodiment illustrated inFIG. 4a. The four measurement structures271 . . . 4are arranged distributed over the object field5perpendicular to the reticle scanning direction21. Here, each measurement structure271 . . . 4forms one measurement channel. Hence the measurement structures271 . . . 4enable a channel-resolved test of the projection optical unit9. It is self-evident that the mask7may also comprise a different number of measurement structures27i. In particular, the mask7can comprise at least two, more particularly at least three, more particularly at least four, more particularly at least six, more particularly at least eight, twelve, twenty, thirty or more measurement structures27.

In respect of further details of the measurement structures27, reference is made to DE 101 09 929 A1.

In the following text, a first exemplary embodiment of the sensor apparatus25is described with reference toFIG. 5a. The sensor apparatus25as perFIG. 5acorresponds to the single-channel mask7with the measurement structure27as perFIG. 4a. Accordingly, the sensor apparatus25as perFIG. 5bcorresponds to the multi-channel embodiment of the mask7as perFIG. 4b. The measurement structure27of the mask7is imaged in the image field10by means of the projection optical unit9. Here, inFIG. 5a, the point of the image of the individual partial structures is respectively denoted in an exemplary fashion by a dashed line.

The sensor apparatus25respectively comprises a plurality of line sensors28for each measurement channel. In general, it comprises at least one line sensor28, more particularly at least two, more particularly at least three, more particularly at least four, more particularly at least six line sensors28. The line sensors28respectively comprise a multiplicity of sensor elements29. The line sensors28are respectively, in a pair-wise fashion, arranged parallel or perpendicular to one another. Each of the partial structures of a measurement structure27respectively is associated with at least one part, more particularly a separate part, of a line sensor28. This means that the line sensors28are designed and arranged such that a uniquely determined, separate part of a line sensor28, on which the image of the respective partial structure is imaged during the test of the projection optical unit9, is provided for each of the partial structures of a measurement structure27.

The line sensors28more particularly are fast line sensors. They have a clock frequency of at least 1 kHz. The clock frequency of the line sensors28, more particularly of the sensor elements29, is preferably at least 2 kHz, more particularly at least 3 kHz, more particularly at least 5 kHz, more particularly at least 10 kHz, more particularly at least 25 kHz. By way of example, the line sensors28are embodied as diode rows. They afford the possibility of measuring a field point, and hence of testing the projection optical unit9, in a very short time, more particularly in less than 1 ms, more particularly in less than 0.5 ms, more particularly in less than 0.33 ms, more particularly in less than 0.2 ms, more particularly in less than 0.1 ms.

Here, the time available for obtaining a measurement value emerges from the diameter of the isoplanatic patch, i.e. the field region in the image field10within which the aberrations are considered unchanged, the maximum aberrations, the required measurement accuracy and the scanning speed of the substrate holder13. In the present case, it is of the order of at most one millisecond.

Hence, the sensor apparatus25is embodied in particular such that it enables a test of the projection optical unit9during the displacement of the substrate holder13for exposing the substrate12arranged on the latter. In particular, this is also understood to mean that the projection optical unit9is tested before and/or subsequent to the actual exposure of the light-sensitive layer on the substrate12, with the substrate holder13being displaced with a uniformly continued scanning speed in the substrate scanning direction22.

The sensor apparatus25moreover comprises at least one interferometric apparatus. According to the exemplary embodiment illustrated inFIG. 5a, the interferometric apparatus comprises a multiplicity of shearing gratings30. In the embodiment embodied inFIG. 5a, provision is made for two sets of respectively three shearing gratings30, with the shearing gratings30of one set respectively having the same orientation. The shearing gratings30of different sets have different orientations. They are, in particular, arranged rotated by 90° with respect to one another. The orientations of the shearing gratings preferably precisely correspond to the substrate scanning direction22and the direction perpendicular thereto. This affords the possibility of obtaining deflections of the wave front in two directions. The shearing gratings30of one set are respectively arranged displaced relative to one another in the shearing direction. This generates a phase shift required for evaluating the shearogram phase step. This avoids a shift of the shearing gratings for evaluating the phase step.

The shearing gratings30are in each case arranged at a distance from one another. Here, respectively two adjacent shearing gratings30are arranged at a distance from one another which is at least so large that the shearograms respectively generated by the shearing gratings30are without overlap in the evaluation region. The shearograms generated by the individual shearing gratings30of a test channel are more particularly incident on pair-wise different regions of the line sensors28.

To the extent that provision is made for a use of the sensor apparatus25in the case of an immersion scanner, the shearing gratings30are provided with an image grating protective layer in order to increase the duration of their service life. In respect of details, reference is made to WO 2005/119368 A2.

In the case of applications of the sensor apparatus25in EUV projection exposure apparatuses, the line sensor28more particularly comprises sensor elements29that are sensitive in the EUV spectral range. Alternatively, or in addition thereto, the sensor row28can be provided with a quantum conversion layer. In respect of details of the quantum conversion layer, reference is made to DE 102 53 874 A1.

The device according to the invention for testing the projection optical unit9, comprising the mask7with the measurement structures27and the sensor apparatus25, thus, in principle, is suitable for both projection exposure apparatuses in the form of an immersion scanner and for EUV projection exposure apparatuses.

The shearing gratings30are arranged in the region of the image plane11. In particular, they are arranged so close to the image plane11that the image of each of the partial structures of the measurement structure27of each of the measurement channels is respectively incident on precisely one specific shearing grating30. The mask7, more particularly the measurement structures27, and the sensor apparatus25, more particularly the interferometric apparatus thereof, are therefore matched to one another such that a plurality of measurement channels are formed for the channel-resolved test of the projection optical unit9. A specific region of the sensor apparatus25with at least one line sensor28, more particularly at least two line sensors28, is associated with each channel.

Each of the channels of the sensor apparatus25preferably comprises at least three shearing gratings, displaced relative to one another in the shearing direction. Each of the channels preferably respectively comprises at least two sets with respectively at least three shearing gratings30, displaced relative to one another in the shearing direction, with the shearing gratings30of different sets having different orientations. The shearing gratings30of one set respectively have the same orientation. They are arranged respectively displaced relative to one another in the shearing direction.

According to the embodiment illustrated inFIG. 5b, the sensor apparatus25has a multi-channel, more particularly four-channel, design. Here, the design of each channel corresponds to those described above with reference toFIG. 5a. The channels are arranged distributed over the image field10, i.e. over the scanner slit. In particular, provision is made for arranging at least three separate channels in the image field10. A multiplicity of channels is preferably arranged distributed over the image field10, more particularly in a uniform fashion. In particular, the number of channels is at least three, more particularly at least four, more particularly at least six, more particularly at least twelve, more particularly at least twenty, more particularly at least thirty.

A multi-channel embodiment affords the possibility of establishing a field-dependent tilt of the wave front. It is possible to determine a distortion therefrom. In respect of details for determining a field-dependent tilt of the wave front, reference is made to DE 101 09 929 A1.

FIG. 5cshows an alternative embodiment, in which the shearing gratings30of the sensor apparatus25are arranged in an L-shape. This L-shaped arrangement affords the possibility of providing a single line sensor28for respectively three shearing gratings30of a given orientation. In this embodiment, all shearing gratings30with a predetermined orientation are respectively arranged offset with respect to one another in the shearing direction only. Since each shearing grating produces all shearing in a specific spatial direction—the shearing direction—this arrangement affords the possibility of covering and detecting the shearograms of all of these shearing gratings30using a single line sensor28, which in each case is arranged precisely in this shearing direction.

The embodiment according to the invention affords the possibility of a field-resolved measurement of wave-front aberrations in the pupil. Moreover, it is possible to determine the irradiation strength distribution in the pupil. In particular, the device according to the invention affords the possibility of a component-resolved test of the projection optical unit9. It is possible to measure component-resolved faults, more particularly so-called lens-heating effects. Here, the fact that is exploited, in particular, is that a predetermined illumination setting with a predetermined angular distribution of the imaging radiation14is used to illuminate the mask7, more particularly the measurement structures27. More particularly, the fact is exploited that the imaging radiation14used to image the mask7on the sensor apparatus25is split into beams by the facet mirrors15,17.

FIG. 6once again illustrates the geometry of the image field10in an exemplary fashion. The image field10can have a curved design, more particularly the shape of an annular section. In particular, the dimension of the short side thereof is approximately 2 mm. In particular, the dimension of the longer side is approximately 26 mm. It is self-evident that other dimensions are likewise possible. InFIG. 6, an arrangement of twelve measurement channels is illustrated in an exemplary fashion. Here, each of the measurement channels comprises an arrangement of shearing gratings30and line sensors28as perFIGS. 5aand 5c, which are not illustrated inFIG. 6. Moreover, an aperture31for each measurement channel is respectively illustrated schematically inFIG. 6.

Moreover, a dimension of the isoplanatic patch32, i.e. the region of the image field10within which the aberrations are considered unchanged, is illustrated schematically inFIG. 6.

In the following text, a further exemplary embodiment of the invention will be described with reference toFIGS. 7 to 7c. The exemplary embodiment substantially corresponds to the embodiments described above, and so reference is hereby made to the description thereof. As an alternative to the above-described shearing interferometer, provision is made for a so-called point diffraction interferometer (PDI) in this embodiment. As an alternative to this, a line diffraction interferometer (LDI) is also possible. These interferometers also afford the possibility of testing the projection optical unit9in a single pass-through. In this embodiment, the mask7comprises measurement structures27which are embodied in a perforated mask34in the form of so-called pinholes33. The perforated mask34is followed by a shearing grating35in the direction of the optical axis23. The combination of perforated mask34and shearing grating35serves to generate spherical waves361,362, which run at a slight tilt to one another and are illustrated inFIG. 7in an exemplary fashion.

In this embodiment, the sensor apparatus25comprises a pinhole/pinhole-diaphragm mask37arranged in the region of the image plane11. For each pinhole33of the perforated mask34, the pinhole/pinhole-diaphragm mask37has an associated pair of a pinhole38and a pinhole diaphragm39. The pinholes38and pinhole diaphragms39of each pair are respectively arranged at a distance from one another. The distances between associated pinholes38and pinhole diaphragms39can differ from channel to channel. In order to enable a tomographic evaluation of the measurement results, provision can be made for calibrating the PDI.

The pinholes38are arranged such that the pinhole38of the pinhole/pinhole-diaphragm mask37is arranged precisely at the point of the focus of the image of a pinhole33of the perforated mask34. It is more particularly arranged at the point of the zero-order maximum of the diffraction pattern of a pinhole33of the perforated mask34generated by the shearing grating35. Accordingly, the pinhole diaphragm39is respectively arranged at the point of a higher-order maximum, more particularly, for example, at the point of the first-order maximum, of the diffraction pattern of a pinhole33of the perforated mask34generated by the shearing grating35.

The pinholes38of the pinhole/pinhole-diaphragm mask37in turn form origins of spherical waves. The pinhole diaphragms39have a clear opening that is so large that a higher-order maximum of the diffraction pattern, more particularly the first-order maximum of this diffraction pattern, generated by the shearing grating35can pass through said opening, substantially without diffraction effects. Hence, the sensor elements29of the line sensors28respectively register part of an interference pattern between a spherical wave originating from the pinhole38and the wave front passing through the pinhole diaphragm39. This interference pattern contains information from which it is possible to deduce aberrations in the projection optical unit9.

FIG. 7cschematically illustrates the arrangement of the line sensors28with the sensor elements29relative to the pinhole/pinhole-diaphragm mask37. In particular, the line sensors28are respectively arranged across, preferably perpendicular to, the substrate scanning direction22. Here, in particular, a field-point scan is provided as method of operation. In principle, there may also be an aerial image scan or an operating mode situated between these two.

FIG. 8illustrates, in an exemplary fashion, two possible arrangements of the sensor apparatus25on the substrate holder13relative to the wafer12. Here, the image field10and three line sensors28, arranged in an exemplary fashion, are respectively illustrated in place of the sensor apparatus25. In particular, the sensor apparatus25is arranged in front of the wafer12in the substrate scanning direction22. What this achieves is that the projection optical unit9is tested before the wafer12is exposed. The corresponding result can preferably already be taken into account when exposing the wafer12. As an alternative to this, it is also possible to arrange the sensor apparatus25behind the wafer12in the substrate scanning direction22. Moreover, the sensor apparatus25can also be arranged offset to the wafer12in a direction perpendicular to the substrate scanning direction22. A so-called overscan is provided for testing the projection optical unit9. This means that regions arranged adjacent to the wafer12are exposed. Here, the wafer holder13is preferably displaced with a uniformly continued scanning speed in the substrate scanning direction22.

According to the exemplary embodiment illustrated inFIG. 9, the sensor apparatus25can also comprise a plurality of line sensors28, which are arranged on mutually opposite sides of the wafer12, i.e. in front of and behind the wafer12, in respect of the substrate scanning direction22.

In order to test the projection optical unit9during the exposure of the light-sensitive coating of a wafer12, the mask7with the structures26,27to be imaged is arranged in the object plane6of the projection optical unit9. The wafer12and the sensor apparatus25are accordingly arranged in the region of the image plane11of the projection optical unit9by means of the substrate holder13. The imaging structures26of the mask7are imaged on the wafer12, more particularly on the light-sensitive coating thereof, as a result of suitably displacing the reticle holder8and/or the substrate holder13and illuminating the mask7. The measurement structures27and33of the mask7are correspondingly imaged on the sensor apparatus25. The measurements can more particularly be undertaken in an integrating fashion, i.e. during a displacement of the sensor apparatus25in the image field10. More particularly, provision can be made for in each case establishing one measurement value when scanning the isoplanatic patch. The result is an integrated, more particularly a scanner-slit integrated, and/or field-resolved measurement of the wave-front aberration.

The projection optical unit9is more particularly tested during a single pass therethrough.

The intensity and/or phase distribution detected by the sensor apparatus25can be subject to further online and/or offline processing. In respect of details of the further processing of the data measured by the sensor apparatus25, reference is made to DE 10 2010 062 763.1.

According to the invention, provision is made for the mask7with the imaging structures26and the measurement structures27for exposing the wafer12to be displaced by means of the reticle holder8, at least in the reticle scanning direction21. The substrate holder13with the wafer12and the sensor apparatus25is correspondingly displaced in the substrate scanning direction22. The reticle holder8and the substrate holder13can more particularly be displaced with respect to one another in a synchronized fashion. The ratio of the scanning speeds of the reticle holder8and the substrate holder13precisely corresponds to the imaging ratio of the projection optical unit9.

In particular, the scanning speed of the substrate holder13is at least 100 mm/s, more particularly at least 200 mm/s, more particularly at least 350 mm/s, more particularly at least 500 mm/s.

When imaging the imaging structures26and the measurement structures27of the mask7on the wafer12and the sensor apparatus25, respectively, the substrate holder13is displaced with a constant scanning speed vscanin the substrate scanning direction22. Hence, the method according to the invention enables a field-resolved wave-front measurement technique, more particularly a lens-heating measurement technique, at scanning speed.

For the purpose of a component-resolved test of the projection optical unit9, it is possible, in particular, to exploit the fact that the radiation14used to image the object field5in the image field10is split into separate radiation channels, more particularly into radiation beams with a specific radiation angular distribution, by means of the two facet mirrors15,17.

The method according to the invention affords the possibility of testing the projection optical unit9during a continuously continued scan of the substrate holder13.

When the projection exposure apparatus1is used, the mask7and the wafer12, which carries a coating that is light-sensitive to the illumination light14, are provided. Subsequently, at least one section of the imaging structure26of the mask7is projected onto the wafer12with the aid of the projection exposure apparatus1. The reticle holder8and/or the substrate holder13can be displaced in the scanning direction21,22parallel to the object plane6and parallel to the image plane11, respectively, while the imaging structure26of the mask7is projected onto the wafer12. The mask7and the wafer12can preferably be displaced synchronously with respect to one another. The test of the projection optical unit9with the aid of imaging the measurement structures27on the sensor apparatus25as per the above-described method can take place before, while or after the wafer12is exposed. Finally, the light-sensitive layer on the wafer12that was exposed to the illumination light14is developed. This is how a microstructured or nanostructured component, more particularly a semiconductor chip, is produced.