DE102019215226A1 - Measuring arrangement and measuring method for determining the position and / or orientation of an optical element and projection exposure apparatus - Google Patents

Abstract

The invention relates to a measuring arrangement (1) for determining the position and / or orientation of an optical element (2) having at least one sensor device (9), comprising a sensor (12) and a measuring target (7), wherein the sensor (12) is positioned at a distance from the measuring target (7) and the measuring target (7) associated with the sensor (12) is connected in a material-locking manner to the optical element (2) at a joining surface (15). The sensor (12) and the measuring target (7) are aligned with one another in such a way that a functional surface (11) of the measuring target (7) is provided between the sensor (12) and the measuring target (7) for determining an actual distance (L _IST ) Measuring beam of the sensor (12) reflected. A plane of the joining surface (15) and the functional surface (11) are aligned at least approximately orthogonally to each other.

Description

The invention relates to a measuring arrangement for determining the position and / or orientation of an optical element having at least one sensor device, comprising a sensor and a measurement target, wherein the sensor is positioned at a distance from the measurement target and the measurement target associated with the sensor has a material fit to a joining surface optical element is connected, wherein the sensor and the measurement target are aligned such that for determining an actual distance between the sensor and the measurement target, a functional surface of the measurement target reflects a measuring beam of the sensor.

The invention further relates to a measuring method for determining the position and / or orientation of an optical element having at least one sensor device, comprising a sensor and a measurement target, after which the sensor is positioned at a distance from the optical element and the measurement target associated with the sensor is bonded to a joining surface is connected to the optical element, after which the sensor and the measurement target are aligned such that for determining an actual distance between the sensor and the measurement target, a measuring beam of the sensor is reflected by a functional surface of the measurement target.

The invention also relates to a projection exposure apparatus for semiconductor lithography with an illumination system having a radiation source and an optical system which has at least one optical element.

Due to the progressive miniaturization of semiconductor circuits, the requirements for resolution and accuracy of projection exposure systems increase equally. Correspondingly high demands are placed on the optical elements used there, which, inter alia, influence the beam path within the projection exposure apparatus. In particular, the requirements for the positioning of the optical elements, for example the mirror of an EUV ("Extreme Ultra Violet") projection exposure apparatus, are now very high due to the resolution.

The currently under development EUV optics should also have a numerical aperture (NA), which makes it possible to further reduce the critical feature sizes achieved in the lithographic process. The current EUV systems are based on optics with a NA of 0.33, whereas the new optics should have a NA greater than 0.5 (also referred to as high NA).

In general, more and more optical elements require additional functional surfaces to determine mechanical reference points, as target surfaces for sensors or as attachment points for sensors.

Particularly in the case of the abovementioned high-NA mirrors of a projection exposure apparatus, the position and movement of all mirrors via sensors must be determined as accurately as possible. The sensors require exact and drift-stable reference or target surfaces (functional surfaces) on the mirror.

Due to the production-specific requirements, it is not possible or only with enormous effort to produce the reference surfaces monolithically or in one piece on the optical element, in particular an optical element of a projection exposure apparatus, in particular a mirror.

When using interferometers as sensors, these target surfaces must be able to reflect the measuring beams of the sensors. The target surfaces are usually formed by a mirror coating. Since the position of the target surfaces represent the direct reference for the mirrors, particularly high demands are placed on the drift stability, since no other correction option is available during wafer exposure.

From the prior art, for example the DE 10 2018 218 162 A1 , It is known to form the target surface (functional surface) on a carrier substrate independent of the optical element and to connect the carrier substrate to a joining surface cohesively with the optical element.

The position detection required for a control of the optical elements of a projection exposure apparatus can be carried out very accurately using interferometric sensor devices. For this purpose, optically reflective so-called "target mirrors", hereinafter also referred to in generalized form as "measurement target", are fastened to the optical elements, for example to the mirrors, and their distance from a frame structure is measured using an interferometer. Based on this distance measurement can finally be concluded that the orientation of the optical element. An exemplary interferometric measuring arrangement is known from DE 10 2019 201 146 A1 which relates to an interferometric measuring arrangement in an optical system, in particular in an optical system for microlithography.

Due to the required high accuracy, the positions and / or the orientations of the optical elements must preferably be precisely determined in all six degrees of freedom in order to avoid aberrations and concomitant impairments of the imaging result or at least reduce them to a tolerable level. Within the scope of determining the position of the optical elements of a projection exposure apparatus, accuracies of the length measurement in the picometer range can be required, for example, over a path length of one meter.

However, the known joining methods for connecting the measuring target to the optical element are associated with disadvantages. In particular, the adjuvants used, in particular an adhesive, show a drift behavior when the environmental conditions change. This drift behavior leads, for example, in the preferred joining by gluing to a drifting of the joint surface, which is above the requirements necessary for high-NA mirror.

During operation of a projection exposure apparatus, in particular due to temperature changes or moisture fluctuations, the adhesive may be adversely affected, as a result of which the measurement target undergoes a parasitic movement or drifts. This parasitic target movement can ultimately lead to a not insignificant error in the position determination of the optical element.

The problem of humidity fluctuations exists even in EUV projection exposure systems, the projection lens of which is exposed to a vacuum during operation, as its projection lens must be ventilated during maintenance work and subsequently vented again. During this process, the adhesive or the adhesive can absorb and / or release atmospheric moisture. The sometimes lasting several days change in humidity in the environment of the adhesive compound (s) during maintenance can eventually lead to said unwanted parasitic target movement and a subsequent measurement error.

The problem is especially in the DE 10 2018 218 162 A1 and the DE 10 2019 200 746 A1 described. In the DE 10 2018 218 162 A1 In order to avoid the problem, it is proposed to determine a measure of the relative humidity in the vicinity of the splice between the optical element and the measurement target and to deduce the change in volume of the adhesive at the splice with this measure. In the DE 10 2019 200 746 A1 however, it is proposed to use specially designed measuring targets which are able to compensate for a change in volume of the adhesive connection.

The object of the present invention is to provide a measuring arrangement for determining the position and / or the orientation of an optical element, in which measurement deviations due to movements of the measurement target are largely avoided.

It is also an object of the present invention to provide a measuring method for determining the position and / or the orientation of an optical element, in which measuring deviations due to movements of the measuring target are largely avoided.

Finally, it is also an object of the invention to provide a projection exposure apparatus for semiconductor lithography, in which the position and / or orientation of an optical element can be detected with high accuracy, in particular in order to be able to regulate the alignment of the optical element with high precision.

The object is achieved for the measuring arrangement by the features listed in claim 1. With regard to the measuring method, the object is achieved by the features of claim 8. With regard to the projection exposure apparatus, the object is achieved by the features of claim 10.

The dependent claims and the features described below relate to advantageous embodiments and variants of the invention.

The measuring arrangement according to the invention for determining the position and / or the orientation of an optical element has at least one sensor device, comprising a sensor and a measuring target. The sensor is positioned at a distance from the measurement target. The measurement target assigned to the sensor is connected in a material-locking manner to the optical element at a joining surface. The sensor and the measurement target are aligned with one another in such a way that a functional area of the measurement target reflects a measurement beam of the sensor in order to determine an actual distance between the sensor and the measurement target. According to the invention, it is provided that one plane of the joining surface and the functional surface are aligned at least approximately orthogonally to one another.

The inventors have recognized that a drift behavior or an undesired parasitic target movement, in particular due to temperature or humidity-related changes in the material connection, no longer causes any relevant measurement errors when the measurement target is so on optical element is attached, that a plane of the joining surface and the functional surface are aligned at least approximately orthogonal to each other.

The inventors have recognized that the cohesive connection between the measurement target and the optical element primarily leads to a movement of the measurement target orthogonal to the plane of the joining surface. Due to the arrangement according to the invention of the joining surface to the functional surface drifting the joining surface only leads to a lateral displacement of the functional surface, so that the drift of the joint no longer leads to measurement errors or the measurement error taking into account tolerances at least one order of magnitude smaller than before ,

According to the invention the plane of the joining surface is aligned at least approximately orthogonal to the functional surface, preferably exactly orthogonal. It should be noted that even then results in an improvement in the measurement results when a plane of the joining surface and the functional surface are aligned at an angle between 70 ° and 110 ° to each other. At an angle of 70 ° or 110 °, for example, drifting of the functional surface still leads to measurement errors, but these are lower than in the prior art.

The solution according to the invention is particularly suitable for planar functional surfaces, as is the case, for example, with interferometer target surfaces, which have high requirements for flatness.

The optical element to which the measurement target is connected can, in particular, be a lens or a mirror, preferably a projection exposure apparatus, in particular an EUV projection exposure apparatus which has, in particular, a numerical aperture greater than 0.5 (High-NA ), act. However, the invention is not limited thereto. With the solution according to the invention, in principle, the position and / or the orientation of any optical element can be determined.

The measuring arrangement can be designed in particular as an interferometer arrangement.

The cohesive connection between the measurement target and the optical element is preferably produced by an adhesive. In principle, however, it is also possible to use another cohesive connection, for example soldering or welding. This may also be dependent on the optical element to be connected to the measurement target.

It should be noted that the feature "joint surface", hereinafter also the characteristics "joint regions", are not to be understood as limiting such that a coating, ie. H. the application of a firmly adhering layer to the surface of only one of the connection partners, would be excluded. A cohesive connection to a joining surface between the measuring target and the optical element can also be produced by a coating in the sense of the invention.

The joining surface can be provided, for example, by virtue of the fact that the optical element and the measuring target each have a flat or flat joining region, which are connected to one another in a material-locking manner in order to form a joining surface. Due to the flat or flat joining areas then the joining surface is flat.

A particularly preferred embodiment of the joining surface is shown below.

According to the invention, it can be provided that the optical element for forming the joining surface has an at least approximately spherical or at least approximately conical joining region and / or that the measuring target has an at least approximately spherically shaped joining region or an at least approximately conically shaped joining region to form the joining surface.

The formation of the joining surface such that the optical element or the Messtarget have an at least approximately spherical shaped or an at least approximately conical joining region, and the other connection partner adapted thereto, preferably also at least approximately spherically shaped or at least approximately conical joining area has, allows a particularly advantageous adjustment of the measurement target on the optical element. Thus, it is also advantageously possible to set the functional area of the measurement target to the mirror surface of the mirror.

The formation of a spherical joining region is particularly advantageous for adjusting the angle at which the measuring target is mounted on the optical element.

It may be provided within the scope of the invention that the joining regions are spherical or cone-shaped. However, it may already be sufficient if the joining regions are at least approximately spherical or at least approximately conical. In particular, it can be provided that the measuring target and / or the optical element has a spherical or conical region, wherein a portion the spherical or conical region is flattened or flat and this section forms the respective joining region.

Instead of an at least approximately spherical or at least approximately conical joining region, any other curved contour or a curved course of the joining region can be provided such that an adjustment of the measuring target on the optical element is possible in order to vary the alignment of the joining surface.

It is advantageous if the joining surface is circular, preferably annular, is formed. It can be provided one, two or more circular or annular joining surfaces. Furthermore, the joining surface can also be formed by ring segments, in particular circular ring segments.

With a symmetry of the joining surface, homogeneous changes in the joining surface, for example a swelling of the adhesive, only lead to a displacement orthogonal to the joining surface.

It should be noted that, in the case of a joining surface which is curved in itself, in particular which is at least approximately spherically or at least approximately conically shaped, a uniform (theoretical) plane of the joining surface is determined by the plane of the joining surface being orthogonal to a central axis of the joining surface Joining surface is aligned. The central axis of the joining surface thus runs parallel to the functional surface in an alignment according to the invention of the joining surface. That is, a drift of, for example, an adhesive used in the joint surface causes the functional surface to move parallel to the central axis of the joint surface.

According to the invention, it can be provided that the measurement target lies directly against the optical element at a contact surface.

The inventors have recognized that it can be of advantage if the measurement target lies directly against the optical element at a contact surface. A hard contact between the measurement target and the optical element results in a preferred maximum stiffness of the connection. It is advantageous if the contact surface is at least approximately spherically shaped and / or at least approximately conical, so that the functional surface can be adjusted in terms of their orientation to the optical element or to the joining surface. In particular, in the case of an EUV projection exposure apparatus, a hard or rigid connection of the measurement target to the mirror is advantageous from the perspective of mirror dynamics.

In the context of the invention, the feature that the measurement target lies directly against the optical element at a contact surface is to be understood as meaning that no adjuvant, ie. H. For example, no adhesive is present, but the Messtarget and the optical element directly touch.

According to the invention, it can further be provided that the contact surface on which the measurement target rests directly on the optical element is circular, preferably annular.

A circular, preferably annular, design of the contact surface has been found to be particularly suitable, in particular if the joining surface is formed accordingly. The contact surface can also be provided by ring segments, in particular circular ring segments.

It is advantageous if the contact surface adjoins the joining surface. It has been shown that it is advantageous to fix the direct contact (contact surface) between the measuring target and the optical element by means of a material-locking joining process. It is particularly advantageous if the cohesive connection takes place directly next to the contact surface. As a result, the deformation effect of the cohesive joining method on the optical element and the measurement target is minimized.

According to the invention, it can further be provided that the contact surface and the joining surface are designed and arranged such that the contact surface is formed at least partially within the joining surface.

It has proven to be advantageous to arrange the contact surface and the joining surface in such a way that the joining surface comprises the contact surface as far as possible. It may be advantageous in that, if the contact surface is annular or formed by corresponding ring segments, adjacent to the inner radius and / or to the outer radius of the annular surface of the contact surface is formed, preferably also annular or formed by ring segments joining surface. In particular, the inner joining surface, which has a smaller radius than the outer joining surface, may optionally also be circular. The joining surface may be formed on one side or on both sides of the hard contact surface. A symmetrical arrangement of the joining surface may be suitable in a special way.

It is advantageous if a measurement by the measuring arrangement during operation of the wafer, preferably continuously during operation of the wafer. Alternatively or additionally, it can also be provided that a measurement is performed by the measuring arrangement during setup of the optical element, in particular a projection exposure apparatus, and / or the measurement is carried out for adjusting the optical element, in particular a projection exposure apparatus.

It can be provided within the scope of the invention exactly one sensor device which has exactly one sensor and exactly one sensor associated Messtarget. However, it is also possible to provide a plurality of sensor devices, for example two sensor devices, three sensor devices, four sensor devices, five sensor devices, six sensor devices or even more sensor devices each having a sensor and a respective measurement target assigned to the sensor. Preferably, exactly six sensor devices are provided in order to preferably be able to detect the orientation or the position and / or the orientation of the optical element in all six degrees of freedom. An advantageous number of sensor devices can also result from the geometry of the optical element and / or the overall system.

The sensor of the sensor device can be arranged on a frame structure adjacent to the optical element. The frame structure may preferably partially or completely surround the optical element. The frame structure may be a so-called "sensor frame" which can serve for the defined arrangement of various sensors of a projection exposure apparatus, in particular for the arrangement of sensors for detecting orientations of optical elements of a projection optics or a so-called "projection optical assembly" (POB).

The sensors of the sensor device are preferably arranged on the frame structure, in particular on the sensor frame.

A control device can be provided which calculates the position and / or the orientation of the optical element on the basis of the at least one detected actual distance of the at least one sensor device.

The control device can be designed as a microprocessor. Instead of a microprocessor, any further device for implementing the control device can be provided, for example one or more arrangements of discrete electrical components on a printed circuit board, a programmable logic controller (PLC), an application-specific integrated circuit (ASIC) or another programmable circuit, for example a Field Programmable Gate Array (FPGA), a Programmable Logic Array (PLA), and / or a commercially available computer.

In an advantageous embodiment of the invention can be provided that the at least one sensor device is designed as an interferometric sensor device, which is used as a sensor interferometer, which is aligned to detect the actual distance to an optically reflective measurement target.

The measurement can thus be carried out preferably interferometrically.

It should be mentioned that the invention can in principle also be suitable for improving the measuring accuracy of differently designed sensor devices, in which an optically, electronically or tactually detectable measuring target is attached to the optical element in a material-locking manner, in particular by means of an adhesive connection.

In particular, for use within a projection exposure apparatus, however, an interferometric measurement or an interferometric measurement method has proven to be particularly suitable.

The invention also relates to a measuring method for determining the position and / or orientation of an optical element having at least one sensor device, comprising a sensor and a measurement target, after which the sensor is positioned at a distance from the optical element and the measurement target associated with the sensor is bonded to a joining surface is connected to the optical element, after which the sensor and the measurement target are aligned such that for determining an actual distance between the sensor and the measurement target, a measuring beam of the sensor is reflected by a functional surface of the measurement target, characterized in that the measurement target such is connected to the optical element, that a plane of the joining surface and the functional surface are aligned at least approximately orthogonal to each other.

It is advantageous if in the context of the measuring method according to the invention, the joining surface is designed such that the joining surface has at least approximately a spherical geometry. The "plane" of the joining surface resulting from the spherical geometry of the joining surface and its orientation relative to the functional surface can be determined in such a way as has already been explained with regard to the measuring arrangement according to the invention.

The measuring method according to the invention for determining the position and / or the orientation An optical element has been found to be particularly suitable, since thereby the functional surface is arranged on the measurement target such that it extends perpendicular to the joining surface. That is, a vertical displacement of the joint surface, for example by the swelling of an adhesive, leads to a merely lateral displacement of the functional surface, whereby a drift of the joint surface has no relevant effect on the measurement result.

The measuring method according to the invention can be carried out during the operation of the entire installation, for example a projection exposure installation, and / or during the initial installation and / or during the maintenance of the installation.

The invention further relates to a projection exposure apparatus for semiconductor lithography with an illumination system having a radiation source and an optical system which has at least one optical element, and having a measuring arrangement according to the preceding and following statements.

The hitherto existing problem that a drift or a parasitic movement of the measurement target, in particular of interferometer targets or optically reflective measurement targets, due to temperature or humidity changes of the adhesive leads to a measurement error that is no longer acceptable, in particular for high-NA POBs, is achieved by the measuring arrangement according to the invention or the inventive method.

The invention is particularly suitable for use with a deep ultra violet (DUV) microlithographic projection exposure apparatus, and more particularly for use with a microlithographic EUV projection exposure apparatus. One possible use of the invention also relates to immersion lithography.

Features which have been described in connection with the measuring method according to the invention are of course also advantageous for the measuring arrangement and the projection exposure apparatus - and vice versa. Furthermore, advantages which have already been mentioned in connection with the measuring method according to the invention can also be understood in relation to the measuring arrangement and the projection exposure apparatus - and vice versa.

It should be noted that the cited as prior art documents DE 10 2019 201 146 A1 . DE 10 2018 218 162 A1 and DE 10 2019 200 746 A1 may contain additional features and developments, which can also be implemented advantageously in the context of the present invention or combined with the present invention. The content of said documents is therefore incorporated by reference into the present specification.

In addition, it should be noted that terms such as "comprising", "having" or "having" do not preclude other features or steps. Further, terms such as "on" or "that" indicating a singular number of steps or features do not exclude a plurality of features or steps - and vice versa.

Embodiments of the invention will be described in more detail with reference to the drawing.

The figures each show preferred embodiments in which individual features of the present invention are illustrated in combination with each other. Features of an exemplary embodiment can also be implemented independently of the other features of the same exemplary embodiment and can accordingly be readily connected by a person skilled in the art to further meaningful combinations and sub-combinations with features of other exemplary embodiments.

In the figures, functionally identical elements are provided with the same reference numerals.

• 1 eine EUV-Projektionsbelichtungsanlage;
• 2 eine DUV-Projektionsbelichtungsanlage;
• 3 eine immersionslithographische Projektionsbelichtungsanlage;
• 4 eine erfindungsgemäße Messanordnung mit einem optischen Element, zwei beispielhaften Sensoreinrichtungen und einer Steuereinrichtung;
• 5 einen Spiegel einer EUV-Projektionsbelichtungsanlage mit sechs über jeweilige Klebstoffverbindungen mit dem Spiegel verbundenen Messtargets für eine jeweilige interferometrische Sensoreinrichtung;
• 6 einen Ausschnitt auf eine Sensoreinrichtung mit einem Sensor und einem Messtarget, wobei eine Fügefläche und eine Funktionsfläche - zum Vergleich mit der erfindungsgemäßen Lösung - nach dem Stand der Technik ausgerichtet sind;
• 7 einen Ausschnitt auf eine Sensoreinrichtung, beispielsweise eine Sensoreinrichtung gemäß 4, wobei eine Fügefläche und eine Funktionsfläche erfindungsgemäße orthogonal zueinander ausgerichtet sind und wobei die Fügefläche als ebene Fläche ausgebildet ist;
• 8 einen Ausschnitt auf eine Sensoreinrichtung, beispielsweise eine Sensoreinrichtung gemäß 4, wobei eine Fügefläche und eine Funktionsfläche erfindungsgemäß orthogonal zueinander ausgerichtet sind und wobei die Fügefläche ringförmig ausgebildet ist und das Messstarget und das optische Element sphärisch ausgebildete Fügebereiche aufweisen;
• 9 eine Darstellung gemäß 8, in der eine resultierende Ebene der sphärischen Fügefläche und die Ausrichtung zur Funktionsfläche des Messtargets eingezeichnet sind;
• 10 eine Schnittdarstellung durch ein Messtarget und ein optisches Element im Bereich der Fügefläche und der Kontaktfläche; und
• 11 eine prinzipmäßige Ansicht auf eine entsprechend 10 ausgebildete Fügefläche, die zwei kreisringförmige Flächen aufweist, mit einer dazwischen angeordneten, ebenfalls kreisringförmig ausgebildeten Kontaktfläche.

They show schematically:

• 1 an EUV projection exposure system;
• 2 a DUV projection exposure machine;
• 3 an immersion lithographic projection exposure apparatus;
• 4 a measuring arrangement according to the invention with an optical element, two exemplary sensor devices and a control device;
• 5 a mirror of an EUV projection exposure apparatus having six measurement targets connected to the mirror via respective adhesive bonds for a respective interferometric sensor device;
• 6 a detail of a sensor device with a sensor and a Messtarget, wherein a joining surface and a functional surface - for comparison with the inventive solution - are aligned according to the prior art;
• 7 a section on a sensor device, for example, a sensor device according to 4 wherein a joining surface and a functional surface according to the invention are aligned orthogonal to each other and wherein the joining surface is formed as a flat surface;
• 8th a section on a sensor device, for example, a sensor device according to 4 wherein a joining surface and a functional surface according to the invention are aligned orthogonal to each other and wherein the joining surface is annular and the measuring target and the optical element have spherically formed joining regions;
• 9 a representation according to 8th in which a resulting plane of the spherical joining surface and the orientation to the functional surface of the measuring target are plotted;
• 10 a sectional view through a measuring target and an optical element in the region of the joining surface and the contact surface; and
• 11 a principle view on a corresponding 10 trained joining surface having two annular surfaces, with an interposed, also annular contact surface formed.

1 shows an example of the basic structure of an EUV projection exposure system 400 for semiconductor lithography, to which the invention may find application. A lighting system 401 the projection exposure system 400 points next to a radiation source 402 an optic 403 for illuminating an object field 404 in an object plane 405 on. Illuminated is a in the object field 404 arranged reticle 406 that of a schematically represented Retikelhalter 407 is held. A merely schematically illustrated projection optics 408 serves to represent the object field 404 in a picture field 409 in an image plane 410 , A structure is shown on the reticle 406 on a photosensitive layer in the area of the image field 409 in the picture plane 410 arranged wafers 411 , by a wafer holder also shown in detail 412 is held.

The radiation source 402 can EUV radiation 413 , in particular in the range between 5 nanometers and 30 nanometers, emit. For controlling the radiation path of the EUV radiation 413 become optically differently formed and mechanically adjustable optical elements 415 . 416 . 418 . 419 . 420 used. The optical elements are at the in 1 illustrated EUV projection exposure system 400 designed as adjustable mirrors in suitable and subsequently only exemplary embodiments.

The with the radiation source 402 generated EUV radiation 413 is by means of one in the radiation source 402 integrated collector so aligned that the EUV radiation 413 in the area of an intermediate focus level 414 undergoes an intermediate focus before the EUV radiation 413 on a field facet mirror 415 meets. After the field facet mirror 415 becomes the EUV radiation 413 from a pupil facet mirror 416 reflected. With the aid of the pupil facet mirror 416 and an optical assembly 417 with mirrors 418 . 419 . 420 become field facets of the field facet mirror 415 in the object field 404 displayed.

In 2 is an exemplary DUV projection exposure system 100 shown. The projection exposure machine 100 has a lighting system 103 , a reticle day 104 said device for receiving and exact positioning of a reticle 105 through which the later structures on a wafer 102 be determined, a wafer holder 106 for holding, moving and exact positioning of the wafer 102 and an imaging device, namely a projection lens 107 , with several optical elements 108 that about versions 109 in a lens housing 140 of the projection lens 107 are held up.

The optical elements 108 can be considered single refractive, diffractive and / or reflective optical elements 108 , such as As lenses, mirrors, prisms, end plates and the like may be formed.

The basic operating principle of the projection exposure system 100 Provides that in the reticle 105 introduced structures on the wafer 102 be imaged.

The lighting system 103 represents one for the picture of the reticle 105 on the wafer 102 required projection beam 111 in the form of electromagnetic radiation ready. The source of this radiation may be a laser, a plasma source or the like. The radiation is in the lighting system 103 via optical elements shaped so that the projection beam 111 when hitting the reticle 105 has the desired properties in terms of diameter, polarization, wavefront shape and the like.

By means of the projection beam 111 becomes a picture of the reticle 105 generated and from the projection lens 107 correspondingly reduced to the wafer 102 transfer. This can be the reticle 105 and the wafer 102 be moved synchronously, so that practically continuously during a so-called scanning areas of the reticle 105 on corresponding areas of the wafer 102 be imaged.

In 3 is a third projection exposure machine 200 in training as an immersion lithographic DUV projection exposure system exemplified. For further background of such a projection exposure system 200 for example, on the WO 2005/069055 A2 referred to, the contents of which are incorporated by reference into the present specification; on the exact functioning is therefore not discussed in detail at this point.

Is recognizable, comparable to the DUV projection exposure system 100 according to 2 , a reticle day 104 through which the later structures on the wafer 102 standing on the wafer holder 106 or wafer table is arranged to be determined. The projection exposure machine 200 of the 3 also has several optical elements, in particular lenses 108 and mirrors 201 , on.

The use of the invention is not for use in projection exposure equipment 100 . 200 . 400 limited, especially not on projection exposure equipment 100 . 200 . 400 with the described structure. The measuring arrangement according to the invention and the measuring method according to the invention are basically suitable for determining the orientation or the position and / or the orientation of any optical elements.

In a particularly advantageous manner, the invention is suitable for EUV projection exposure systems, in particular for the projection optical assemblies (POB) used there, in particular with a numerical aperture (NA) greater than 0.5.

The following figures illustrate the invention by way of example only and highly schematic.

4 shows a measuring arrangement according to the invention 1 for determining the position and / or the orientation of an optical element 2 , The optical element 2 is preferably as an optical element 2 a projection exposure system 100 . 200 . 400 designed for semiconductor lithography. The optical element 2 is formed in the embodiment as a mirror of an EUV projection exposure system and comprises a substrate 3 and a reflective coating 4 for reflection of EUV radiation 413 is trained. An example is a tilt axis 6 shown to the the optical element 2 for controlling the beam path of the EUV radiation 413 can be tilted.

On the optical element 2 are exemplary two measuring targets 7 firmly attached. In the embodiment, the connection is an adhesive connection 8th intended. The measurement targets 7 are part of a respective sensor device 9 , which is formed in the embodiment - purely by way of example - as an interferometric sensor device. The measurement targets 7 each have a carrier substrate 10 as well as an optically reflective functional surface 11 on. The sensor device 9 each has a respective measurement target 7 associated sensor 12 (In the embodiment, an interferometer). The sensor 12 is the measurement target 7 the sensor device 9 assigned and sends out a measuring radiation (shown in dashed lines), of the respective measurement target 7 reflected and to the sensor 12 is thrown back. The sensor 12 allows an actual distance L _actual to the assigned measurement target 7 to detect in an optical way.

An in 4 dashed line indicated control device 13 Finally, it calculates the position and / or the orientation of the optical element 2 on the basis of the detected actual distances L _{IST of} the respective sensor devices 9 ,

In the exemplary embodiment, it is (optionally) provided that the sensors 12 at one of the optical element 2 adjacent frame structure 14 are arranged.

In 5 is an example of an optical element 2 or a mirror of a projection exposure apparatus 100 . 200 . 400 shown in perspective. Preferably, in the context of the measuring method according to the invention, the position and / or the orientation of the optical element 2 be recorded in all six degrees of freedom. In this regard, it may be advantageous to have multiple sensor devices 9 consisting of one sensor each 12 and one to the sensor 12 assigned measurement target 7 to use, preferably six sensor devices 9 , In the 5 are exemplary six measuring targets 7 on the optical element 2 positioned.

Like from the 5 to 11 is apparent, is the respective measurement target 7 at a joint surface 15 cohesively, in the embodiment by means of the adhesive connection 8th , with the optical element 2 connected.

The basic principle of determining the position or orientation of the optical element 2 using the at least one sensor device 9 is in 6 illustrated by the prior art. The sensor 12 or the interferometer is preferably direct, ie without an adhesive connection 8th , at the optical element 2 adjacent frame structure 14 arranged and thus detects its actual distance L _IST to its associated measurement target 7 , The detected actual distance L _IST can finally be used to determine the orientation of the optical element 2 be used. The problem with this type of measurement is that a parasitic movement (drift) of the measurement target 7 towards the associated sensor 12 can lead to a measurement error ΔL _IST . Thus, for example, a moisture or temperature-induced stretching of the adhesive or the adhesive connection 8th the measured actual distance L _{IS is changed} by the measuring error ΔL _actual , in the exemplary embodiment shorten, and thus to an inaccurate or incorrectly detected alignment of the optical element 2 to lead.

According to the invention is now, as in the 4 and 5 and in particular the 7 to 11 shown, provided that a plane of the joining surface 15 and the functional area 11 of the measurement target 7 are aligned at least approximately orthogonal to each other.

As in particular from a synopsis of 6 with the 7 can be removed, now leads, for example, moisture-related or temperature-induced stretching of the adhesive connection 8th if the joining surface 15 and the functional area 11 , as in 7 are positioned at an angle of 90 ° to each other, only or substantially only to a lateral displacement of the functional surface 11 , Especially with flat functional surfaces 11 , as with interferometer target surfaces, is the drift of the mating surface 15 thus no longer relevant for the measurement result.

In the in 7 The embodiment shown is the joining surface 15 just trained, so that the newly formed joining surface 15 directly the plane of the joining surface according to the invention 15 that is orthogonal to the functional area 11 or the level of the functional area 11 is formed represents. In the 8th to 11 For this purpose, an alternative embodiment is shown. The plane of the joining surface 15 is in this case by a curved in itself, in particular a spherical or at least approximately spherical or a conical or at least approximately conical joining surface 15 provided. This will be explained below.

In the in the 8th to 11 illustrated embodiment has both the optical element 2 as well as the measurement target 7 for the formation of the joining surface 15 an at least approximately spherical shaped joining area 16 on. The joining areas 16 can in that in the 8th to 11 illustrated embodiment, in principle, at least approximately conical or otherwise curved.

The formation of such joining areas 16 , in particular the formation of spherically shaped joining areas 16 , allows a particularly advantageous adjustment of the measurement target 7 on the optical element 2 , Ie. the measurement target 7 can on the optical element 2 be set so that the plane of the joining surface 15 is oriented such that the plane of the joint surface 15 at least approximately orthogonal to the functional surface 11 , preferably exactly orthogonal, is aligned.

Deriving from the orientation of the joining surface 15 resulting level of joining surface 15 and their orthogonal alignment to the functional surface 11 is in 9 through the horizontal through the joining surface 15 symbolizing progressing bars.

The joining surface 15 is in the in the 8th to 11 illustrated embodiment circular, preferably annular, formed. An education of the joining surface 15 as in the 10 and 11 will be shown in more detail below, is suitable in a special way.

The determination of the plane of the joining surface 15 in the sense of the invention takes place in the in the 8th to 11 illustrated embodiment, as shown in the 9 is shown. After the joining surface 15 itself is not flat, but, for example, spherical shaped, resulting in a resulting plane of the joint surface 15 in that first a central axis 17 the joint surface 15 is determined. The plane of the joining surface 15 is orthogonal to the central axis 17 like this 9 is shown. By aligning the joining surfaces 15 on the spherically shaped joining areas 16 results in the orientation and the course of the central axis 17 and thus also the orientation of the plane of the joining surface 15 which is chosen such that it is at least approximately orthogonal to the functional surface 11 is aligned. The central axis 17 is in the 8th to 11 shown in principle.

Like from the 8th to 11 is recognizable, leads a drift of the joining surface 15 even with a design of the joining surface 15 according to the 8th to 11 because the plane of the joining surface 15 orthogonal to the plane of the functional area 11 is aligned, only to a lateral displacement of the functional surface 11 , reducing the drift of the joint surface 15 or the adhesive connection 8th has no or no relevant effect on the measurement result.

A particularly preferred compound of the measurement target 7 with the optical element 2 is in the 10 and 11 shown. It is provided that the measurement target 7 at a contact surface 18 directly on the optical element 2 is applied. Under an immediate concern of the measurement target 7 on the optical element 2 is understood to mean that a firm or hard contact is provided, ie that no adjuvant, in particular no adhesive, between the surface of the Messtargets 7 and the facing surface of the optical element 2 is available. This results in a maximum rigidity of the connection.

The fixation of the contact surface 18 is in the in the 10 and 11 illustrated embodiment, characterized in that the joining surface 15 right next to the contact area 18 is positioned to the deformation effect of the joining surface 15 on the optical element 2 and the measurement target 7 to minimize.

The contact surface 18 at which the measurement target 7 directly on the optical element 2 is present, is preferably formed annular. It is particularly preferred, as in the 10 and 11 shown when the contact surface 18 and the joining surface 15 are formed and arranged such that the contact surface 18 at least partially within the joining area 15 is trained. For this purpose, it is preferably provided that the joining surface 15 has two annular surfaces, between which the likewise annular contact surface 18 is arranged.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102018218162 A1 [0010, 0016, 0067]
• DE 102019201146 A1 [0011, 0067]
• DE 102019200746 A1 [0016, 0067]
• WO 2005/069055 A2 [0081]

Claims (10)

Measuring arrangement (1) for determining the position and / or the orientation of an optical element (2) with at least one sensor device (9), comprising a sensor (12) and a measuring target (7), wherein the sensor (12) of the measuring target ( 7) is positioned at a distance, and the measurement target (7) associated with the sensor (12) is bonded to the optical element (2) on a joining surface (15), whereby the sensor (12) and the measuring target (7) are aligned with one another in that, to determine an actual distance (L _IST ) between the sensor (12) and the measurement target (7), a functional surface (11) of the measuring target (7) reflects a measuring beam of the sensor (12), characterized in that one plane of the Joining surface (15) and the functional surface (11) are aligned at least approximately orthogonal to each other. Measuring arrangement (1) according to Claim 1 , characterized in that the optical element (2) for forming the joining surface (15) has an at least approximately spherically shaped or an at least approximately conical joining region (16) and / or that the measuring target (7) for forming the joining surface (15) Having at least approximately spherically shaped joining region (16) or an at least approximately conically shaped joining region (16). Measuring arrangement (1) according to Claim 1 or 2 , characterized in that the joining surface (15) is circular, preferably annular, is formed. Measuring arrangement (1) according to one of Claims 1 to 3 , characterized in that the measurement target (7) bears against a contact surface (18) directly on the optical element (2). Measuring arrangement (1) according to Claim 4 , characterized in that the contact surface (18) on which the measuring target (7) bears directly on the optical element (2), circular, preferably annular, is formed. Measuring arrangement (1) according to Claim 4 or 5 , characterized in that the contact surface (18) adjacent to the joining surface (15). Measuring arrangement (1) according to Claim 4 . 5 or 6 , characterized in that the contact surface (18) and the joining surface (15) are formed and arranged such that the contact surface (18) is at least partially formed within the joining surface (15). Measuring method for determining the position and / or orientation of an optical element (2) with at least one sensor device (9), comprising a sensor (12) and a measuring target (7), after which the sensor (12) is separated from the optical element (2). is positioned at a distance, and the measurement target (7) associated with the sensor (12) is adhesively bonded to the optical element (2) at a joining surface (15), after which the sensor (12) and the measuring target (7) are aligned with one another such that for determining an actual distance (L _IST ) between the sensor (12) and the measuring target (7), a measuring beam of the sensor (12) is reflected by a functional surface (11) of the measuring target (7), characterized in that the measuring target ( 7) is connected to the optical element (2) such that one plane of the joining surface (15) and the functional surface (11) are aligned at least approximately orthogonally to one another. Measuring method according to Claim 8 , characterized in that the joining surface (15) is designed such that the joining surface (15) has at least approximately a spherical geometry. A projection exposure apparatus (100, 400, 400) for semiconductor lithography comprising an illumination system (103, 401) having a radiation source (402) and an optic (107, 403, 408) comprising at least one optical element (415, 414, 419, 420, 48, 201) and a measuring arrangement (1) according to any one of Claims 1 to 7 for determining the position and / or orientation of the optical element (415, 416, 418, 419, 420, 208, 201).

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