DE102022205227A1 - Optical device, method for determining an actual deformation, method for setting a target deformation and lithography system - Google Patents

Abstract

The invention relates to an optical device (1), in particular for a lithography system (100, 200), comprising: - an optical element (2) with an optical surface (3), and - one or more actuators (4) for a deformation of the optical element ( 2), and- a back plate (5) for supporting the at least one actuator (4), wherein the at least one actuator (4) is arranged between the optical element (2) and the back plate (5), wherein- a deformation measuring device (6 ) is provided for determining the deformation of the optical surface (3) having at least one measuring unit (7), wherein - the back plate (5) has a lower rigidity than the optical element (2) to be deformed, and - the deformation measuring device (6) set up is to measure a deformation of the back plate (5) and/or the at least one actuator (4).

Description

The invention relates to an optical device, in particular for a lithography system, comprising an optical element with an optical surface, and one or more actuators for a deformation of the optical element, and a back plate for supporting the at least one actuator, the at least one actuator between the optical Element and the back plate is arranged.

The invention also relates to a method for determining an actual deformation of an optical surface of an optical element, in particular an optical element of a lithography system.

The invention also relates to a method for setting a target deformation of an optical surface of an optical element, in particular an optical element of a lithography system.

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

Optical elements for guiding and shaping radiation in projection exposure systems are known from the prior art. In the known optical elements, a surface of the optical element guides and shapes the light waves incident on the optical element. Precise control of the shape of the surface is therefore of particular advantage in order to form an exact wavefront with the desired properties.

Lithography systems are known from the prior art which use ultraviolet radiation, in particular DUV (deep ultraviolet) and/or EUV (extreme ultraviolet) light, in order to produce microlithographic structures with the greatest precision. In this case, the light from a radiation source is directed via a number of mirrors to a wafer to be exposed. An arrangement, a position and a shape of the mirror make a decisive contribution to the quality of the exposure.

For example, in order to further increase the number of transistors on a chip, it is necessary to further develop existing lithography systems.

Various systems for actuating deformable mirrors are also described in the prior art.

It is known from the prior art to integrate optical elements in optical devices which have actuators for generating force in order to specifically shape the optical surface which interacts with the light waves. To improve the steering and/or shaping of the radiation from a radiation source, it is known to attach actuators to mirrors, which shape the surface of the mirrors with as many degrees of freedom as possible, in particular with the aim of creating a free-form surface

According to the prior art, an effect of the actuators on the optical surface is predicted, for example on the basis of modelling. However, influences not taken into account in the modeling can weaken the predictive power of the model.

Systems known from the prior art for the deformation of optical elements use a regulation for the deformation of the optical surface and for the setting of a target deformation. For this purpose, the deformation is detected by a sensor and sent to the actuators in a coded form as an electrical signal within a control system. In the context of lithography systems, it is not possible according to the prior art to integrate a sensor with a sufficiently high measurement performance into the lithography system or the optical element. For this reason, optical devices of this type are operated within an open control chain or in a feed-forward mode, at least during specific time windows.

A disadvantage of optical devices according to the prior art is that, in order to meet the constantly increasing requirements for increasing precision, it is crucial to adhere to the target deformation as precisely as possible, while the measures known for this purpose for the exact setting of the target deformation are inadequate, in particular because the actual deformation cannot be determined precisely enough.

The present invention is based on the object of creating an optical device which avoids the disadvantages of the prior art, in particular enabling precise shaping or precise setting of a target deformation of an optical surface.

According to the invention, this object is achieved by an optical device having the features specified in claim 1 .

The present invention is also based on the object of providing a method for determining an actual deformation of an optical surface, which has the disadvantages of the prior art Technology avoids, in particular, enables a precise and reliable measurement of an actual deformation of the optical surface.

This object is achieved by a method having the features specified in claim 17 .

The present invention is also based on the object of creating a method for setting a target deformation of an optical surface which avoids the disadvantages of the prior art, in particular precise and reliable shaping or precise setting of a target deformation of the optical surface allows.

This object is achieved by a method having the features specified in claim 24.

The present invention is also based on the object of creating a lithography system which avoids the disadvantages of the prior art, in particular enabling the formation of precisely shaped wavefronts of a radiation.

According to the invention, this object is achieved by a lithography system having the features specified in claim 25.

The optical device according to the invention, in particular for a lithography system, comprises an optical element with an optical surface, and one or more actuators for a deformation of the optical element, and a back plate for supporting the at least one actuator, the at least one actuator between the optical element and the back plate is arranged. According to the invention, a deformation measuring device for determining the deformation of the optical surface is provided, having at least one measuring unit, the back plate having a lower rigidity than the optical element to be deformed. According to the invention, the deformation measuring device is set up to measure a deformation of the back plate and/or of the at least one actuator.

The optical device according to the invention has the advantage that the deformation measuring device enables the actual deformation of the optical surface to be determined by measurement. Due to the fact that the back plate has a lower rigidity than the optical element to be deformed, increased deformations can occur on various components of the optical device compared to the optical surface, which can be detected with high precision by the deformation measuring device.

As a result, the desired shape of the optical surface can be controlled and adjusted by the at least one actuator in a particularly reliable manner, since the deformation of the optical surface can be adjusted via feedback control.

The feature that the at least one actuator is arranged between the optical element and the back plate includes both arrangements in which the at least one actuator is arranged directly on the optical element and / or the back plate, as well as arrangements in which between the at least further intermediate elements or intermediate layers are arranged in an actuator and the optical element and/or the back plate.

The optical surface of the optical element is preferably light-reflecting, preferably EUV light-reflecting and/or DUV light-reflecting.

If the surface is designed to be light-reflecting, in particular EUV light-reflecting, this enables the optical device to be used as a deformable mirror. The optical element is preferably a mirror, in particular a mirror of a projection exposure system. Alternatively or additionally, it can be provided that the optical surface is transparent and designed as part of a deformable lens.

Furthermore, the optical element can be a lens, in particular a lens of a DUV projection exposure system.

Provision can be made for the at least one actuator to be in the form of an electrostrictive actuator. A design as an electrostrictive actuator has the advantage that electrostrictive actuators have a very low tendency to drift and a low tendency to hysteresis.

Provision can be made for the at least one actuator to be a ferroelectric actuator, in particular a piezo actuator.

It can be provided that the optical device has a plurality of actuators for a deformation of the optical surface, each of the plurality of actuators preferably being able to be controlled individually.

By controlling each individual actuator, it is possible to adjust profiles of the optical surface and/or the optical element, in particular a mirror, in a targeted manner and thus optimize the optical device or the lithography system into which the optical device is integrated in the best possible way correct and/or carry out desired wavefront manipulations.

A deformation of the back plate is advantageously accessible to a measurement by the deformation measuring device, since the back plate undergoes greater deformation due to its lower rigidity when the optical element is deformed by means of the at least one actuator. Accordingly, compared to the optical element, the back plate shows an increased deformation and can therefore act as a deformation intensifier.

Provision can be made for the optical element to have a carrier element on which the optical surface is arranged and/or formed.

It can advantageously be provided that the at least one actuator is connected to the optical element, in particular the carrier element, and/or the back plate by a force-transmitting connection, in particular a material connection. In particular, it can be provided that the at least one actuator is connected to the optical element, in particular the carrier element, and/or the back plate by a connecting layer, preferably having an adhesive.

It can be provided that the optical surface is formed on the carrier element, for example by a coating and/or structuring.

Provision can be made for the optical surface to have a multi-layer system, in particular a molybdenum-silicon multi-layer system.

In order to ensure a force transmission between the at least one actuator and the optical element, in particular the carrier element of the optical element, these can be connected with a connecting layer. This has the advantage that the at least one actuator and the optical element can be manufactured separately and can only be assembled when the optical device is produced. The connecting layer, which connects the at least one actuator to the optical element, is preferably formed from an adhesive or has an adhesive. In this case, the use of an adhesive enables great flexibility in the assembly of the optical device.

The at least one actuator can preferably be arranged on a rear side of the optical element which is remote from the optical surface.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one actuator for deforming the optical surface is arranged in such a way that a first effective area, preferably a first end of the actuator, acts on the optical element and a second effective area, preferably a second end of the actuator acts on the back plate.

If the at least one actuator is arranged between the back plate and the optical element in such a way that it acts on the optical element on one side and on the back plate on the other side, an advantageously high force can be applied to deform the optical surface on the optical item to be exercised.

It can be provided that the at least one actuator is arranged in such a way that its direction of action or direction of force runs at least approximately perpendicular to the optical surface or the optical element and/or the back plate. This results in a particularly good exertion of force and a particularly advantageous deformation effect of the at least one actuator.

In particular, it can be provided that the optical device is a deformable mirror that acts normal to the surface.

In an advantageous development of the optical device according to the invention, it can be provided that the optical element and the back plate are designed in such a way that a deflection of the actuator in order to deform the optical surface leads to a deformation of a surface of the back plate that is at least double, preferably corresponds to at least three times, more preferably at least four times, even more preferably at least five times, very preferably at least six times, in particular at least eight times the deformation of the optical surface.

Matching the mechanical properties of the back plate to those of the optical element has the advantage that the deformation of the back plate, which is to be expected during normal operation of the optical device, can be designed in such a way that the deformation of the back plate and/or the at least one actuator are large enough to achieve high measurement accuracy and at the same time are small enough so that the precision of the optical device is not impaired by parts that are highly mobile and widely deflecting or severely deformed.

In an advantageous development of the optical device according to the invention, it can be provided that the deformation of the optical surface and/or the back plate is a deflection and/or a stretching.

A deformation of the optical surface and/or the back plate can be expressed, for example, in a deflection from a rest position and/or in an elongation.

Depending on how the deformation of the back plate and/or the optical element manifests itself, different measurement techniques can be used.

In an advantageous development of the optical device according to the invention, it can be provided that the back plate has a lower thickness than the optical element, preferably has a thickness that is less than half, preferably less than a third, particularly preferably less than a quarter of the thickness of the optical element corresponds.

If the back plate is less thick, that is to say less thick, than the optical element, then the back plate can be made less rigid than the optical element in a particularly simple manner.

Furthermore, a smaller thickness of the back plate compared to the optical element enables the optical device to be designed in a space-efficient manner.

If the back plate has a thickness that corresponds to less than half but more than one fifth of the thickness of the optical element, then advantageous values for a deformation amplification of the back plate compared to the optical element can be achieved in a particularly reliable manner.

Furthermore, the strengths or thicknesses of the back plate described above have proven to be favorable in comparison to the optical element in order to give the back plate that rigidity which it can advantageously have for mechanically supporting the actuators when they act against the optical element.

In an advantageous development of the optical device according to the invention, it can be provided that the back plate and the optical element are made of the same material, in particular the same material.

Forming the back plate and the optical element from an identical or at least approximately the same material has the advantage that it is easier to adjust the rigidity of the back plate compared to the optical element on the basis of geometric considerations.

It is also advantageous that when the back plate and the optical element are formed from an identical or at least approximately the same material, homogeneous heating does not lead to lateral tensioning of the components relative to one another.

It can be provided that the back plate and/or the optical element is at least partially made of borosilicate glass and/or aluminum and/or copper and/or preferably amorphous silicon and/or quartz glass and/or titanium silicate glass or SiO ₂ -TiO ₂ glass are formed.

The back plate and the optical element are preferably formed from the aforementioned materials.

It can be provided that, in particular to achieve a desired rigidity, the back plate is designed in the form of strips and/or in the form of a net.

Provision can be made for the back plate to have webs and/or internal cavities in order to achieve a desired rigidity.

It is thus also possible to influence the rigidity of the back plate geometrically.

It can be provided that, in particular to achieve anisotropic rigidity, the backing plate is made thinner and/or thicker in strips, so that the rigidity is higher along the strips than across the strips.

It can be provided that, in particular to achieve a reliable supporting effect of the back plate, the back plate is made thicker in regions that are mechanically heavily stressed when the optical surface is deformed than in those regions that are less severely stressed when the optical element is deformed are mechanically stressed.

In an advantageous development of the optical device according to the invention, it can also be provided that the back plate and the optical element are made of different materials, with the back plate preferably being made of a material which has a low has greater rigidity than the material from which the optical element is formed.

If the back plate and the optical element are made of different materials, materials with special elastic and/or physical properties can be used to form the back plate, for example, which result in greater deformation than the optical element.

If the back plate is made of a less rigid material than the optical element, then, for example, a back plate can be made thicker than in an embodiment with a stiffer material. As a result, an edge fiber spacing can advantageously be large in order to generate a strong measurement signal through high mechanical signal amplification.

It can be provided that a reduction in rigidity and/or an increase in deformation is set and/or influenced by a structural design of the back plate, such as cavities, preferably inner cavities.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit is arranged in and/or on the back plate.

If the at least one measuring unit is arranged in or on the back plate, a deformation, ie in particular a deflection or a stretching of the back plate, can be detected particularly easily and directly.

In a further advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit is arranged in and/or on the at least one actuator.

If the at least one measuring unit is arranged in or on the at least one actuator, a deflection and/or expansion of the at least one actuator, which is increased due to the configuration of the back plate according to the invention, can be measured in a particularly simple and reliable manner.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit is arranged on a reference element at a distance from the back plate.

If the at least one measuring unit is arranged on the preferably stationary reference element, a deflection of the back plate from a rest position relative to the reference element or to the at least one measuring unit can be determined in a particularly simple manner.

In a further advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit is arranged between the back plate and the optical element.

If the at least one measuring unit, like the at least one actuator, is arranged between the back plate and the optical element, in particular the carrier element, the at least one measuring unit can detect the effective range of the at least one actuator and the distance between the optical element and the back plate in a particularly simple manner measure way.

Provision can be made for the at least one measuring unit to be arranged between the back plate and the optical element and at a distance from the at least one actuator. As a result, the measurement precision can be prevented from being influenced by sources of interference, such as heat and/or electric fields, emanating from the at least one actuator.

Provision can be made for the measuring unit to be arranged and/or designed to be distributed over a number of components and regions of the optical device. Furthermore, a mixture of measuring units placed in different ways can be provided.

For example, a measuring unit can be arranged partly on the back plate and partly on the at least one actuator. Several measuring units can also be provided, with at least one measuring unit being arranged on the back plate and at least one measuring unit being arranged on the at least one actuator and at least one measuring unit being arranged on the optical element.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit has at least one optical waveguide, preferably an optical fiber.

If the at least one measuring unit has an optical waveguide, an expansion of the back plate and/or the at least one actuator can be measured particularly well, since a mechanical coupling between the optical waveguide and the back plate and/or the actuator causes a deformation of the back plate and/or the actuator the optical waveguide is also deformed. In this way it can be achieved that the deformation of the optical surface correlates with an optically detected signal. In particular, an optical path length in the optical waveguide can change, which can be measured exactly using suitable measurement technology.

An optical fiber represents a particularly reliable and simple type of optical waveguide.

Provision can be made for the at least one optical waveguide to be formed in the back plate and/or the at least one actuator by means of femtosecond laser writing.

In this case, the waveguide can be a component of the back plate and/or of the actuator and can be produced, for example, by writing with a femtosecond laser.

In particular, it can be provided that the at least one optical waveguide is formed by femtosecond laser writing in a glass made of a silica glass and/or a fused silica glass and/or a titanium silicate glass or SiO ₂ -TiO ₂ glass and/or a back plate formed from borosilicate glass.

Provision can be made for the optical fiber to be integrated into the back plate. In particular, it can be provided that the optical fiber is placed in a groove in the back plate and glued in this. This achieves a particularly good mechanical coupling between the optical fiber and the backing plate.

It can advantageously be provided that the measuring unit is at least partially arranged, preferably inserted, in the optional connection layer between the actuator and the back plate.

An at least partial arrangement of the measuring unit on the connection layer has the advantage that the strains and distortions of both the at least one actuator and the optical element can be detected by means of the measuring unit or the deformation measuring device. A further advantage is that no modifications have to be made to the at least one actuator and/or the optical element and/or the back plate for the arrangement of the measuring unit.

An arrangement of the measuring unit in the connecting layer is particularly advantageous if the measuring unit can be inserted into this, preferably completely. This is the case, for example, when the measuring unit has an optical fiber with a fiber Bragg grating, while the connecting layer is made of an adhesive. In this case, the optical fiber with the fiber Bragg grating can be placed in the connection layer and preferably cast around with the adhesive, so that the formation of the connection layer is not impaired by the adhesive through the optical fiber of the measuring unit.

It is particularly advantageous here if the measuring unit is arranged in the connecting layer in such a way that mechanical coupling of the measuring unit to the at least one actuator and/or the optical element and/or the back plate is made possible. For example, this can be made possible by the fact that when the connecting layer is formed by an adhesive, the adhesive also glues the optical fiber of the measuring unit, resulting in a mechanical coupling between the measuring unit, the connecting layer, the back plate and the at least one actuator.

In particular, it can be provided that the measuring unit is arranged in parts both in the back plate and in the at least one actuator as well as in the at least one connection layer.

If the optical waveguide has a fiber Bragg grating, then the optically detected signal, which correlates with the deformation of the optical surface, is, for example, a reflected frequency of the fiber Bragg grating.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one measuring unit has at least one distance sensor, preferably an interferometer.

Preferably in the case in which the at least one measuring unit is arranged on the reference element and/or between the optical element and the back plate, a distance sensor is advantageous as part of the at least one measuring unit, since a measurement of the deflection of the back plate and/or the at least one actuator from a rest position can thereby be measured in a particularly simple manner.

Interferometers are reliable and accurate distance sensors.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one distance sensor is arranged at a distance from the back plate in such a way that that the distance between the distance sensor and the back plate corresponds to a preferred working distance of the distance sensor in the case of a substantially, in particular average, expected deflection of the back plate.

If the distance sensor has a preferred working area, in particular a working area with a particularly high resolution, it is advantageous if the at least one distance sensor is arranged at a distance from a target area arranged on the back plate in such a way that the most common or normally in an operation Optical device expected distance between the target area and the distance sensor, is within the working area.

In this way it can be ensured that the distance sensors work with the greatest precision for most of the deformations that occur during the operation of a projection exposure system and/or optical device.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one waveguide has one or more fiber Bragg gratings with respective grating interference spectra.

Fiber Bragg gratings are particularly suitable for determining strains, even on the smallest scales.

Provision can be made for the at least one waveguide, in particular the at least one optical fiber, to have a plurality of fiber Bragg gratings, preferably running in a loop shape, and passing through the effective ranges of a plurality of actuators.

By running the optical fiber in a loop, several effective areas of several actuators can be covered by a single optical fiber.

To this end, it is advantageous if the optical fiber is dimensioned and set up in such a way that a fiber Bragg grating comes to lie in a majority, preferably in each, of the effective areas. Due to a loop-shaped course, the effective areas to be measured can each be addressed individually without the optical fiber crossing over itself.

Furthermore, it can be provided that several fiber Bragg gratings are arranged in one and the same effective range of an actuator. In this case, the fiber Bragg gratings can be oriented differently, for example, and/or can be arranged in different areas of the effective range. As a result, a deformation, in particular an expansion, of the effective area in three-dimensional space can be precisely detected in a particularly advantageous manner.

Provision can also be made for the waveguides to intersect, in particular also in different planes.

Alternatively, it can be provided that the optical fiber has only one fiber Bragg grating, runs in a loop and passes through the effective ranges of a number of actuators.

Provision can be made for the effective ranges to at least partially overlap with the measurement ranges explained later or to coincide with them.

Provision can advantageously be made for the at least one waveguide to have a plurality of fiber Bragg gratings, with the grating interference spectra of the individual fiber Bragg gratings being designed to be distinguishable.

A back-reflected spectral range and/or a spectral range of the incision in the radiation spectrum of an individual fiber Bragg grating and thus an expansion of an individual fiber Bragg grating is thus separated from the expansions of the other effective ranges of the other fiber Bragg gratings of the at least one waveguide distinguishable. As a result, a number of effective areas can be monitored synchronously with the evaluation of only one reflection and/or transmission spectrum

At least one spectrometer device can advantageously be provided for determining and/or characterizing the grating interference spectra.

The at least one grating interference spectrum can be examined in whole or in part by means of a spectrometer device.

It can be provided that several fiber Bragg gratings are present and the radiated radiation has a spectrum that includes all reflection frequencies of all fiber Bragg gratings and/or that a spectral resolution range of the spectrometer device includes all grating interference spectra of all fiber Bragg gratings includes.

In particular, it can be provided that the spectrometer device is set up to measure reflected radiation within the fiber bandwidths of the fiber Bragg grating and/or transmitted fiber spectra with incisions within the fiber to determine and/or analyze the bandwidth of the fiber Bragg grating. Accordingly, the spectrometer device does not have to be set up to resolve the complete fiber interference spectrum in the full spectral width, but the spectrometer device can be limited to determining and/or characterizing particularly characteristic areas of the fiber interference spectra.

Provision can advantageously be made for the at least one spectrometer device to be set up to detect a direct frequency shift.

Direct detection of the frequency shift or wavelength shift of the reflected radiation and/or the notch in the transmitted radiation spectrum has the advantage that a particularly fast and reliable analysis of the grating interference spectra is made possible by limiting it to such a relevant part of the spectrum.

Provision can be made for the at least one measuring unit to have a Mach-Zehnder interferometer.

It can also be provided that the measuring device works according to the principle of a log-in amplifier and records the logged frequency.

If the at least one measuring unit has a Mach-Zehnder interferometer, the deformations of the back plate can be determined by measuring a transit time difference in several arms of the interferometer.

Provision can be made for the at least one measuring unit to be arranged at least partially between the actuators. Due to the low rigidity, in particular the thin embodiment of the back plate, the at least one actuator expands significantly more than without a thin back plate, preferably by a factor of 10 more than without a thin back plate. As a result, the measuring unit can use a measuring range that is 10 times larger. An attachment between the actuators is therefore advantageous.

In an advantageous development of the optical device according to the invention, it can be provided that the at least one optical waveguide is polarization-maintaining.

The measurement signal (e.g. reflected frequency of the fiber Bragg grating) generally depends both on the strain condition of the fiber (in the case of fiber Bragg sensors in particular on the change in the grating constant of the optical grating) and on the temperature.

The invention enables the state of strain to be detected and correlated with the deformation of the optical surface. The influences of strain and temperature on the measurement signal (e.g. reflected frequency of the fiber Bragg grating) can be separated by means of a polarization-maintaining fiber. A temperature-compensated strain value can thus be used to control the actuators. Furthermore, the information about the temperature field can be made available for further regulations and can be used here, for example, to improve pilot control values for the actuator system or to improve temperature regulation or form the basis for it. Alternatively, the temperature of the measuring points can also be detected by other temperature sensors, which can be based, for example, on the temperature dependence of electrical resistances.

This enables an even more accurate and precise control of the deformation or the precise shaping of the optical surface, since the various factors influencing the shaping of the optical surface can be addressed and/or eliminated separately.

A separation of temperature-induced influences is of particular advantage, since one of the greatest disruptive factors when operating the optical device can be temperature fluctuations on the optical surface, in particular when used in EUV lithography systems. In particular, the temperature of the optical surface or of the optical element can be changed between 20° C. and 40° C. during operation.

The optical device according to the invention is also suitable for use in deformable mirrors in fields of technology other than semiconductor lithography, in particular in space applications and in a military field.

The invention also relates to a method for determining an actual deformation with the features mentioned in claim 17 .

In the method according to the invention for determining an actual deformation of an optical surface of an optical element, in particular an optical element of a lithography system, at least one actuator is arranged between the optical element and a backing plate, which acts on the optical element and deforms the optical surface supported on the back plate. An actual deformation of the optical surface is determined in that at least one actual deformation of at least one Measuring range is measured in or on the back plate and / or in and / or on the at least one actuator. In this case, the back plate and the optical element are designed in such a way that the back plate is more strongly deformed by the at least one actuator than the optical surface.

The method according to the invention has the advantage that a metrological control of an actual deformation of the optical surface is made possible by the deformation measuring device provided. The method according to the invention for determining the actual deformation thus enables a more precise and reliable deformation of the optical surface than systems according to the prior art, which do not allow the actual deformation of the optical surface to be measured.

This is particularly advantageous when using the actuators for the deformation or for bringing about the deformation, since their effect on the exact shaping of the optical surface in the prior art is based on a pure modeling. With the method according to the invention, the modeling can be supplemented and/or replaced by empirical measurement of the actual deformation.

Recording the deformation of the back plate has the advantage that the sensitive optical surface on the front side of the optical element, which is designed with the highest degree of precision for shaping the wave fronts, is not disturbed by further measurement technology.

An elongation of the actuators can be described in a first approximation by the formula (1). Here, M describes an electrostrictive coefficient, which leads to a strain S when an electric field E is applied. As can be seen from formula (1), the electrostrictive coefficient M depends on the temperature ϑ of the actuator. Furthermore, the expansion S of the actuator is dependent on its stiffness s and an applied mechanical stress T. Furthermore, a thermal component of the expansion results from multiplying the thermal expansion coefficient CTE by the difference between the temperature θ and an initial temperature θ ₀ . $$S\left(E,\vartheta \right)=M\left(\vartheta \right)\cdot {\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="DE102022205227A1\_0004.png,DE102022205227A1\_0005.png"\; state="\{\{state\}\}">E</figure-callout>}}^2+s\cdot T+CTE\cdot \left(\vartheta -{\vartheta }_0\right)$$

For high-precision and constant regulation of a position of the at least one actuator, it is advantageous if both a loss of expansion of the at least one actuator based on the electrostrictive effect and the thermal expansion are corrected using the method according to the invention. For this purpose it can be provided that the at least one actuator uses more than 80% of its working distance for self-correction of thermal expansions or thermal effects.

Accordingly, it is advantageous if a highly precise positioning or deformation of the optical surface is made possible by modeling and calibrating an electrostrictive and thermal hysteresis and a drift of the actuator in addition to a temperature calibration.

Furthermore, there is no need to model the temperature dependency of the actuator system if it is in a control circuit or is controlled by a control circuit, in particular a feedback control.

Modeling with regard to the at least one actuator can contribute to an improvement in pilot control or operation in an open control chain. One of the main advantages of the invention can be seen in the elimination of the need for modeling for the actuator.

Provision can advantageously be made for the actual deformation, in particular an actual deflection, to be determined in one or more measurement areas in at least one connection layer connecting the at least one actuator to the back plate.

The determination or determination of the actual deformation in the connecting layer has the advantage that the at least one measuring area can be arranged particularly easily in the connecting layer, in particular if the connecting layer is made of an adhesive material. As a result, a relative position of the at least one actuator and the back plate can remain almost unchanged.

Furthermore, if the connecting layer is in the form of an adhesive, the adhesive can bring about an advantageously high mechanical coupling between the at least one actuator, the measuring area and the back plate.

The adhesive can also be designed as a different material connection.

Provision can advantageously be made for the actual deformation, in particular an actual deflection, to be determined synchronously in a number of measurement areas.

The actual deformation of the optical surface can be determined by a synchronous determination of several actual deformations in several measuring areas can be determined at least approximately completely. A narrow grid of measurement areas results in dense sampling of the actual deformation of the optical surface.

Provision can be made for the actual elongation to be determined in a number of measurement areas in rapid chronological order. In particular, the measurement ranges can be read out using a multiplex method.

In an advantageous development of the method according to the invention, it can be provided that each location on the optical surface is assigned at least one, preferably exactly one, measurement area in such a way that the actual deformation of the optical surface at the location from the actual deformation, in particular an actual -Deflection in which at least one measuring range can be clearly determined.

If the deformation of each location on the optical surface can be clearly measured from the measurement of the measurement area and/or if there is a biactive imaging relationship between the measurement areas and each location on the optical surface, this simplifies the method for determining the actual deformation, since the Measurement of the entirety of the measurement areas, the actual deformation of the surface can be clearly reconstructed.

In an advantageous development of the method according to the invention, it can be provided that an actual deformation of the measuring area is caused which is at least twice, preferably at least three times, more preferably at least four times, even more preferably at least six times, very preferably at least eight times, in particular at least ten times larger is as the actual deformation of the location on the optical surface associated with the measurement area.

The advantage of the method according to the invention is that the measurement signal is mechanically amplified and the measurement signal can thus be shifted in the direction of the required measurement accuracy.

The advantage of this is that the improved measurement accuracy achieved in this way enables closed-loop control of the deformation of the optical surface, which significantly reduces the control requirements.

In this way, for example, a drift can be measured during a day, which significantly reduces the requirements for the creep properties and/or the drift properties of the at least one actuator.

Provision can be made to implement a full closed loop or regulated operation. A closed loop can be advantageous, particularly in the case of strong mechanical amplification and high measurement accuracy. An implementation of a closed loop can have the advantageous consequence, for example, that all types of piezoceramics and/or actuators can be used that have not previously belonged to the favored actuator types due to excessive hysteresis.

In this way, inexpensive actuators can be used, as a result of which the method according to the invention contributes, for example, to economical operation of a projection exposure system.

In an advantageous development of the method according to the invention, it can be provided that a waveguide, preferably an optical fiber, with a fiber Bragg grating is arranged in such a way that in at least one of the fiber Bragg gratings at least one grating interference spectrum is generated by the actual deformation, in particular an actual elongation of the at least one measurement area is influenced.

By integrating an optical fiber, in particular a fiber Bragg grating, in a preferably thin back plate of a deformable mirror, the above-described mechanical deformation amplification can be measured particularly easily, since the back plate experiences greater expansion than the optical element.

It can be provided that, as an alternative or in addition to thinning the back plate, a material with significantly less rigidity is used to form the back plate.

Provision can be made for a plurality of sensors, in particular fiber Bragg gratings, to be accommodated in a single optical waveguide and the deformation at a plurality of measurement areas is thus read out by means of an optical waveguide.

It is of particular advantage if the grating interference spectra of the fiber Bragg gratings arranged in the plurality of measurement areas can be distinguished from one another. This facilitates a synchronous determination of the fiber interference spectra and thus of the actual deformations. In particular, a single optical fiber with multiple fiber Bragg gratings can be used to monitor and control multiple measurement areas.

In an advantageous development of the method according to the invention, it can be provided that a measurement radiation is coupled into the waveguide.

The use of optical methods enables the deformation to be determined with high precision. In particular, optical measuring methods, in particular the measuring radiation, generate few interference signals during operation of the projection exposure system.

Provision can be made for the waveguide, in particular the fiber Bragg grating, to be arranged directly on the at least one actuator. Since the at least one actuator is also subject to high deformation due to the low rigidity of the back plate, it is also possible to measure the greater deformation on the at least one actuator.

In an advantageous development of the method according to the invention, it can be provided that the actual deformation of the at least one measuring area, in particular an actual deflection of the at least one measuring area, is determined from a distance between the measuring area and at least one distance sensor.

Within the scope of the invention, a measurement area is to be understood as meaning a geographic location and/or an area surrounding the geographic location in and/or on the optical device at which the measurement is taken.

The determination of the actual deflection of the at least one measuring area represents a further implementation variant of the method according to the invention, in which case the deflection of the thin back plate can also be detected using other sensor variants.

In an advantageous development of the method according to the invention, it can be provided that the distance is determined interferometrically and/or capacitively.

Capacitive and/or interferometric sensors have the advantage that they can easily provide high-precision distance information.

Provision can advantageously be made for the actual deformation of the optical surface to be determined in the lithography system and/or during operation of the lithography system and/or during reflection of a radiation through the optical surface, in particular in a time range of a wafer exposure.

The method is particularly advantageous when it is used to monitor the actual deformation of the optical surface in a lithography system, since optical surfaces, particularly in the case of deformable mirrors, in lithography systems must meet special requirements for a precise formation of the surface shape.

It is particularly advantageous if the actual deformation of the optical surface is determined by the method during operation of such a mirror formed by the optical surface, in particular in the lithography system. During a reflection of a radiation that is actually taking place, in particular an EUV radiation, the optical surface is exposed to an increased energy deposition and thus to an increased risk of foreseen and uncontrolled expansions. In order to completely fulfill the task of guiding and shaping the reflected light during the operation of the optical surface during a reflection, it is therefore particularly advantageous to check or determine the actual deformation of the optical surface.

Furthermore, a variation of the shape of the optical surface over an exposure time can also be desired in order to enable increasing flexibility of lithography systems or projection exposure systems. Furthermore, a throughput and an imaging quality can be increased as a result.

The invention also relates to a method for setting a desired deformation with the features mentioned in claim 24.

In the method according to the invention for setting a target deformation of an optical surface of an optical element, in particular an optical element of a lithography system, an actual deformation of the optical surface is determined using the method according to the invention for determining an actual deformation or one of its preferred embodiments.

It can be provided that the actual deformation is set by at least one actuator.

It can be provided that the at least one actuator is arranged between the optical element and a back plate and the optical element is deformed by the action of the at least one actuator, which is supported against the back plate.

By means of the deformation of the optical surface measured by the measuring method the actuator can preferably be controlled and regulated in a closed loop.

Because the back plate is deformed more than the optical element, and thus experiences an increase in deformation, the actual deformation of the optical surface can be determined particularly precisely and the control of the at least one actuator can be supplied with particularly precise information about the actual deformation.

The target deformation of the optical surface can thus be adjusted in a targeted manner to the measured or determined actual deformation or in a controlled manner, taking into account the actual data.

The invention also relates to a lithography system having the features specified in claim 25.

The lithography system according to the invention, in particular a projection exposure system for semiconductor lithography with an illumination system having at least one radiation source and optics, which has at least one optical element, comprises at least one optics device according to the invention or one of its preferred embodiments. At least one of the optical elements is an optical element of the optical device according to the invention. Alternatively or additionally, at least one of the optical elements has an optical surface whose deformation is measured using a method according to the invention for determining the actual deformation and/or is deformed using a method according to the invention for setting the actual deformation.

Features that were described in connection with one of the objects of the invention, namely given by the optical device according to the invention, the method according to the invention for determining the actual deformation, the method according to the invention for setting the target deformation or the lithography system according to the invention, are also for the other objects of the invention can be advantageously implemented. Likewise, advantages that were mentioned in connection with one of the objects of the invention can also be understood in relation to the other objects of the invention.

In addition, it should be noted that terms such as "comprising", "having" or "with" do not exclude any other features or steps. Furthermore, terms such as "a" or "that" which indicate a singular number of steps or features do not exclude a plurality of features or steps - and vice versa.

In a puristic embodiment of the invention, however, it can also be provided that the features introduced in the invention with the terms “comprising”, “having” or “with” are listed exhaustively. Accordingly, one or more listings of features may be considered complete within the scope of the invention, e.g. considered for each claim. The invention can consist exclusively of the features mentioned in claim 1, for example.

It should be mentioned that designations such as “first” or “second” etc. are primarily used for reasons of distinguishing the respective device or method features and are not necessarily intended to indicate that features are mutually dependent or related to one another.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing.

The figures each show preferred exemplary embodiments in which individual features of the present invention are shown in combination with one another. Features of an exemplary embodiment can also be implemented separately from the other features of the same exemplary embodiment and can accordingly easily be combined with features of other exemplary embodiments by a person skilled in the art to form further meaningful combinations and sub-combinations.

Elements with the same function are provided with the same reference symbols in the figures.

• 1 eine EUV-Projektionsbelichtungsanlage im Meridionalschnitt;
• 2 eine DUV-Projektionsbelichtungsanlage;
• 3 eine schematische Darstellung einer möglichen Ausführungsform der erfindungsgemäßen Optikvorrichtung;
• 4 eine schematische Darstellung einer weiteren möglichen Ausführungsform der erfindungsgemäßen Optikvorrichtung;
• 5 eine schematische Darstellung einer weiteren möglichen Ausführungsform der erfindungsgemäßen Optikvorrichtung;
• 6 eine schematische Darstellung einer weiteren möglichen Ausführungsform der erfindungsgemäßen Optikvorrichtung;
• 7 eine schematische Darstellung der Optikvorrichtung nach 6 in einem deformierten Zustand;
• 8 eine schematische Darstellung einer weiteren möglichen Ausführungsform der erfindungsgemäßen Optikvorrichtung;
• 9 eine schematische Darstellung der Optikvorrichtung nach 8 in einem deformierten Zustand;
• 10 eine blockdiagrammartige Darstellung einer möglichen Ausführungsform des erfindungsgemäßen Verfahrens zur Ermittlung einer Ist-Deformation;
• 11 eine blockdiagrammartige Darstellung einer möglichen Ausführungsform des erfindungsgemäßen Verfahrens zur Einstellung einer Soll-Deformation;
• 12 eine schematische Darstellung möglicher Dehnungsverläufe eines elektrostriktiven Effekts bei verschiedenen Temperaturen;
• 13 eine schematische Darstellung eines möglichen Verlaufs einer thermischen Dehnung eines elektrostriktiven Aktuators;
• 14 eine schematische Darstellung einer möglichen Driftkurve eines elektrostriktiven Aktuators;
• 15 eine schematische Darstellung eines Gitterinterferenzspektrums; und
• 16 eine blockdiagrammartige Darstellung einer weiteren möglichen Ausführungsform des erfindungsgemäßen Verfahrens zur Ermittlung einer Ist-Deformation.

Show it:

• 1 an EUV projection exposure system in the meridional section;
• 2 a DUV projection exposure system;
• 3 a schematic representation of a possible embodiment of the optical device according to the invention;
• 4 a schematic representation of a further possible embodiment of the optical device according to the invention;
• 5 a schematic representation of a further possible embodiment of the optical device according to the invention;
• 6 a schematic representation of a further possible embodiment of the optical device according to the invention;
• 7 a schematic representation of the optical device 6 in a deformed state;
• 8th a schematic representation of a further possible embodiment of the optical device according to the invention;
• 9 a schematic representation of the optical device 8th in a deformed state;
• 10 a block diagram representation of a possible embodiment of the method according to the invention for determining an actual deformation;
• 11 a block diagram representation of a possible embodiment of the method according to the invention for setting a target deformation;
• 12 a schematic representation of possible strain curves of an electrostrictive effect at different temperatures;
• 13 a schematic representation of a possible course of a thermal expansion of an electrostrictive actuator;
• 14 a schematic representation of a possible drift curve of an electrostrictive actuator;
• 15 a schematic representation of a grating interference spectrum; and
• 16 a block diagram representation of a further possible embodiment of the method according to the invention for determining an actual deformation.

The following are first with reference to 1 the essential components of an EUV projection exposure system 100 for microlithography are described as an example of a lithography system. The description of the basic structure of the EUV projection exposure system 100 and its components should not be understood as limiting here.

In addition to a radiation source 102 , an illumination system 101 of the EUV projection exposure system 100 has illumination optics 103 for illuminating an object field 104 in an object plane 105 . In this case, a reticle 106 arranged in the object field 104 is exposed. The reticle 106 is held by a reticle holder 107 . The reticle holder 107 can be displaced via a reticle displacement drive 108, in particular in a scanning direction.

In 1 a Cartesian xyz coordinate system is drawn in for explanation. The x-direction runs perpendicularly into the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scan direction is in 1 along the y-direction. The z-direction runs perpendicular to the object plane 105.

The EUV projection exposure system 100 includes projection optics 109. The projection optics 109 are used to image the object field 104 in an image field 110 in an image plane 111. The image plane 111 runs parallel to the object plane 105. Alternatively, there is also an angle other than 0° between the object plane 105 and the image plane 111 is possible.

A structure on the reticle 106 is imaged onto a light-sensitive layer of a wafer 112 arranged in the region of the image field 110 in the image plane 111. The wafer 112 is held by a wafer holder 113. The wafer holder 113 can be displaced via a wafer displacement drive 114, in particular along the y-direction. The displacement of the reticle 106 via the reticle displacement drive 108 on the one hand and the wafer 112 on the other hand via the wafer displacement drive 114 can be synchronized with one another.

The radiation source 102 is an EUV radiation source. The radiation source 102 emits in particular EUV radiation 115, which is also referred to below as useful radiation or illumination radiation. The useful radiation 115 has, in particular, a wavelength in the range between 5 nm and 30 nm a DPP (Gas Discharged Produced Plasma) source. It can also be a synchrotron-based radiation source. The radiation source 102 can be a free-electron laser (FEL).

The illumination radiation 115 emanating from the radiation source 102 is bundled by a collector 116 . The collector 116 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 116 can in grazing incidence ("Grazing Incidence", GI), i.e. with angles of incidence greater than 45 °, or in normal incidence ("Normal Incidence", NI), i.e. with incidence angles (to the surface normal) smaller than 45°, are acted upon by the illumination radiation 115. The collector 116 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation 115 and on the other hand to suppress stray light.

After the collector 116, the illumination radiation 115 propagates through an intermediate focus in an intermediate focal plane 117. The intermediate focal plane 117 can represent a separation between a radiation source module, comprising the radiation source 102 and the collector 116, and the illumination optics 103.

The illumination optics 103 includes a deflection mirror 118 and a first facet mirror 119 downstream of this in the beam path. The deflection mirror 118 can be a planar deflection mirror or alternatively a mirror with an effect that influences the bundle beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 118 can be designed as a spectral filter, which separates a useful light wavelength of the illumination radiation 115 from stray light of a different wavelength. If the first facet mirror 119 is arranged in a plane of the illumination optics 103 which is optically conjugate to the object plane 105 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 119 includes a multiplicity of individual first facets 120, which are also referred to below as field facets. Of these facets 120 are in the 1 only a few shown as examples.

The first facets 120 can be embodied as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or part-circular edge contour. The first facets 120 can be embodied as planar facets or alternatively as convexly or concavely curved facets.

Like for example from the DE 10 2008 009 600 A1 is known, the first facets 120 themselves can each also be composed of a multiplicity of individual mirrors, in particular a multiplicity of micromirrors. The first facet mirror 119 can be embodied in particular as a microelectromechanical system (MEMS system). For details refer to the DE 10 2008 009 600 A1 referred.

The illumination radiation 115 runs horizontally between the collector 116 and the deflection mirror 118, ie along the y-direction.

A second facet mirror 121 is arranged downstream of the first facet mirror 119 in the beam path of the illumination optics 103. If the second facet mirror 121 is arranged in a pupil plane of the illumination optics 103, it is also referred to as a pupil facet mirror. The second facet mirror 121 can also be arranged at a distance from a pupil plane of the illumination optics 103 . In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also referred to as a specular reflector. Specular reflectors are known from US 2006/0132747 A1 , the EP 1 614 008 B1 and the U.S. 6,573,978 .

The second facet mirror 121 includes a plurality of second facets 122. In the case of a pupil facet mirror, the second facets 122 are also referred to as pupil facets.

The second facets 122 can also be macroscopic facets, which can have round, rectangular or hexagonal borders, for example, or alternatively facets composed of micromirrors. In this regard, also on the DE 10 2008 009 600 A1 referred.

The second facets 122 can have plane or alternatively convexly or concavely curved reflection surfaces.

The illumination optics 103 thus forms a double-faceted system. This basic principle is also known as the "Fly's Eye Integrator".

It can be advantageous not to arrange the second facet mirror 121 exactly in a plane which is optically conjugate to a pupil plane of the projection optics 109 .

The individual first facets 120 are imaged in the object field 104 with the aid of the second facet mirror 121 . The second facet mirror 121 is the last beam-forming mirror or actually the last mirror for the illumination radiation 115 in the beam path in front of the object field 104.

In a further embodiment of the illumination optics 103 that is not shown, transmission optics can be arranged in the beam path between the second facet mirror 121 and the object field 104 , which particularly contribute to the imaging of the first facets 120 in the object field 104 . The transmission optics can have exactly one mirror, but alternatively also have two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 103 . The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirror, "normal incidence" mirror) and/or one or two mirrors for grazing incidence (GI mirror, "gracing incidence" mirror).

The illumination optics 103 has the version in which 1 is shown, after the collector 116 exactly three mirrors, namely the deflection mirror 118, the field facet mirror 119 and the pupil facet mirror 121.

In a further embodiment of the illumination optics 103, the deflection mirror 118 can also be omitted, so that the illumination optics 103 can then have exactly two mirrors downstream of the collector 116, namely the first facet mirror 119 and the second facet mirror 121.

The imaging of the first facets 120 by means of the second facets 122 or with the second facets 122 and transmission optics in the object plane 105 is generally only an approximate imaging.

The projection optics 109 includes a plurality of mirrors Mi, which are numbered consecutively according to their arrangement in the beam path of the EUV projection exposure system 100 .

At the in the 1 example shown, the projection optics 109 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 115. The projection optics 109 are doubly obscured optics. The projection optics 109 has an image-side numerical aperture which is greater than 0.5 and which can also be greater than 0.6 and which can be 0.7 or 0.75, for example.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without an axis of rotational symmetry. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. Just like the mirrors of the illumination optics 103, the mirrors Mi can have highly reflective coatings for the illumination radiation 115. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 109 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 104 and a y-coordinate of the center of the image field 110. This object-image offset in the y-direction can be something like this be as large as a z-distance between the object plane 105 and the image plane 111.

The projection optics 109 can in particular be anamorphic. In particular, it has different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 109 are preferably at (βx, βy)=(+/−0.25, +/-0.125). A positive image scale β means an image without image reversal. A negative sign for the imaging scale β means imaging with image inversion.

The projection optics 109 thus leads to a reduction in the ratio 4:1 in the x-direction, ie in the direction perpendicular to the scanning direction.

The projection optics 109 lead to a reduction of 8:1 in the y-direction, ie in the scanning direction.

Other imaging scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x-direction and in the y-direction in the beam path between the object field 104 and the image field 110 can be the same or, depending on the design of the projection optics 109, can be different. Examples of projection optics with different numbers of such intermediate images in the x and y directions are known from U.S. 2018/0074303 A1 .

In each case one of the pupil facets 122 is assigned to precisely one of the field facets 120 in order to form a respective illumination channel for illuminating the object field 104 . In this way, in particular, lighting can result according to Köhler's principle. The far field is broken down into a large number of object fields 104 with the aid of the field facets 120 . The field facets 120 generate a plurality of images of the intermediate focus on the pupil facets 122 respectively assigned to them.

The field facets 120 are each imaged onto the reticle 106 by an associated pupil facet 122 in a superimposed manner in order to illuminate the object field 104 . In particular, the illumination of the object field 104 is as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

The illumination of the entrance pupil of the projection optics 109 can be geometrically defined by an arrangement of the pupil facets. The intensity distribution in the entrance pupil of the projection optics 109 can be set by selecting the illumination channels, in particular the subset of the pupil facets that guide light. This intensity distribution is also referred to as an illumination setting.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 103 can be achieved by redistributing the illumination channels.

Further aspects and details of the illumination of the object field 104 and in particular the entrance pupil of the projection optics 109 are described below.

The projection optics 109 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 109 cannot regularly be illuminated exactly with the pupil facet mirror 121 . When imaging the projection optics 109, which telecentrically images the center of the pupil facet mirror 121 onto the wafer 112, the aperture rays often do not intersect at a single point. However, a surface can be found in which the distance between the aperture rays, which is determined in pairs, is minimal. This surface represents the entrance pupil or a surface conjugate to it in position space. In particular, this surface shows a finite curvature.

The projection optics 109 may have different positions of the entrance pupil for the tangential and for the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 121 and the reticle 106 . With the help of this optical component, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

At the in the 1 In the arrangement of the components of the illumination optics 103 shown, the pupil facet mirror 121 is arranged in a surface conjugate to the entrance pupil of the projection optics 109 . The first field facet mirror 119 is arranged tilted to the object plane 105 . The first facet mirror 119 is tilted relative to an arrangement plane that is defined by the deflection mirror 118 .

The first facet mirror 119 is tilted relative to an arrangement plane that is defined by the second facet mirror 121 .

In 2 an exemplary DUV projection exposure system 200 is shown. The DUV projection exposure system 200 has an illumination system 201, a device known as a reticle stage 202 for receiving and precisely positioning a reticle 203, by means of which the later structures on a wafer 204 are determined, a wafer holder 205 for holding, moving and precisely positioning the wafer 204 and an imaging device, namely projection optics 206, with a plurality of optical elements, in particular lenses 207, which are held in an objective housing 209 of the projection optics 206 via mounts 208.

As an alternative or in addition to the lenses 207 shown, various refractive, diffractive and/or reflective optical elements, including mirrors, prisms, end plates and the like, can be provided.

The basic functional principle of the DUV projection exposure system 200 provides that the structures introduced into the reticle 203 are imaged onto the wafer 204 .

The illumination system 201 provides a projection beam 210 in the form of electromagnetic radiation that is required for imaging the reticle 203 onto the wafer 204 . A laser, a plasma source or the like can be used as the source for this radiation. The radiation is shaped in the illumination system 201 via optical elements in such a way that the projection beam 210 has the desired properties in terms of diameter, polarization, shape of the wave front and the like when it strikes the reticle 203 .

An image of the reticle 203 is generated by means of the projection beam 210 and transmitted to the wafer 204 in a correspondingly reduced size by the projection optics 206 . The reticle 203 and the wafer 204 can be moved synchronously, so that areas of the reticle 203 are imaged onto corresponding areas of the wafer 204 practically continuously during a so-called scanning process.

Optionally, an air gap between the last lens 207 and the wafer 204 can be replaced by a liquid medium that has a refractive index greater than 1.0. The liquid medium can be, for example, ultrapure water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

The use of the invention is not limited to use in projection exposure systems 100, 200, in particular not with the structure described. The invention is suitable for any lithography system, but in particular for projection exposure systems with the structure described. The invention is suitable also for EUV projection exposure systems, which have a lower image-side numerical aperture than those associated with 1 is described, and have no obscured mirror M5 and / or M6. In particular, the invention is also suitable for EUV projection exposure systems which have an image-side numerical aperture of 0.25 to 0.5, preferably 0.3 to 0.4, particularly preferably 0.33. Furthermore, the invention and the following exemplary embodiments are not to be understood as being restricted to a specific design. The following figures represent the invention only by way of example and in a highly schematic manner.

3 shows a schematic representation of a possible embodiment of an optical device 1, in particular for a lithography system 100, 200.

The optical device 1 comprises an optical element 2 with an optical surface 3 and one or more actuators 4 for a deformation of the optical element 2 and a back plate 5 for supporting the at least one actuator 4. Here, the at least one actuator 4, in the exemplary embodiment, a plurality on actuators 4, arranged between the optical element 2 and the back plate 5.

In the optical device 1, a deformation measuring device 6 for determining the deformation of the optical surface 3 is provided, having at least one measuring unit 7, in the exemplary embodiment a plurality of measuring units 7. The back plate 5 has a lower rigidity than the optical element 2 to be deformed.

The optical element 2 is preferably an optical element 116, 118, 119, 120, 121, 122, Mi, 207 of the lithography system 100,200.

In the illustrated exemplary embodiments, the optical device 1 has an optical element 2 , an optical surface 3 , a number of actuators 4 and a number of measuring units 7 . A measuring unit 7 is preferably provided for each actuator 4 and/or a measuring unit 7 is assigned to each actuator 4 .

in the in 3 illustrated embodiment, the deformation measuring device 6 is preferably set up to measure a deformation of the back plate 5 .

Furthermore, in the in 3 illustrated embodiment, the optical element 2 preferably a carrier element 8, on which the optical surface 3 is arranged or formed. The carrier element 8 is preferably a glass body.

in the in 3 In the exemplary embodiment shown, the at least one actuator 4 for deforming the optical surface 3 is preferably arranged in such a way that a first effective area 9, preferably a first end of the actuator 4, acts on the optical element 2 and a second effective area 10, preferably a second end of the actuator 4, acting on the back plate 5.

in the in 3 In the exemplary embodiment illustrated, the optical element 2 and the back plate 5 are preferably designed in such a way that a deflection of the actuator 4 in order to deform the optical surface 3 leads to a deformation of a surface 11 of the back plate 5 which is at least twice, preferably at least three times , more preferably at least four times, even more preferably at least six times, very particularly preferably at least eight times, in particular at least ten times, the deformation of the optical surface 3 corresponds.

in the in 3 illustrated embodiment of the optical device 1 is preferably the deformation of the optical surface 3 and the back plate 5 both a deflection and a strain.

Depending on the type of embodiment of the optical surface 3 and the back plate 5, the deformation can preferably also be in the form of just a deflection or just an elongation.

Furthermore, preferably in the in 3 illustrated embodiment, the back plate 5 has a lower strength or thickness than the optical element 2. In particular, the back plate 5 has a thickness that is less than half, preferably less than a third, particularly preferably at least less than a quarter, the thickness of the optical element 2 corresponds.

At the in 3 illustrated embodiment, the back plate 5 and the optical element 2 are preferably made of different materials, the back plate 5 preferably being made of a material which has a lower rigidity than the material from which the optical element 2 is made. The different materials are in 3 symbolized by different hatching.

Alternatively it can be provided that the back plate 5 and the optical element 2 are formed from the same materials. This represents in particular This represents a particularly preferred embodiment with regard to the minimization of thermal stresses between the optical element 2 and the back plate 5. In this way, for example, a CTE mismatch problem can be avoided.

At the in 3 The exemplary embodiment of the optics device 1 illustrated is the at least one measuring unit 7 preferably arranged on the back plate 5, preferably attached.

Alternatively or additionally, it can be provided that the measuring unit 7 is arranged or attached in the back plate 5 .

in the in 3 The exemplary embodiment of the optical device 1 illustrated has the at least one measuring unit 7, preferably at least one optical waveguide 12, preferably an optical fiber 13.

Furthermore, a measurement radiation 19 is preferably coupled into the optical fiber, which 3 is symbolized by a double arrow.

The at least one waveguide 12 has in the in 3 illustrated embodiment preferably several fiber Bragg gratings 14 with respective grating interference spectra 15 (see 15 ) on.

Alternatively, it can be provided that the at least one waveguide 12 has only one fiber Bragg grating 14 .

in the in 3 illustrated embodiment, the deformation measuring device 6 preferably detects the actual deformation in at least one measuring area 18 (see also 10 )

in the in 3 At least one spectrometer device 23 for determining and/or characterizing the grating interference spectra 15 is preferably provided. The spectrometer device 23 can be part of the deformation measuring device 6 .

Furthermore, in the in 3 illustrated embodiment, a control device 24 is present and preferably set up to set the target deformation by a closed control loop. In this case, the actual deformation serves as a feedback signal for the activation and/or regulation of the at least one actuator 4 . Active compounds are in 3 represented by dashed lines.

The at least one optical waveguide 12 is in the in 3 illustrated embodiment is preferably formed polarization-maintaining.

The following are based on the 4 until 9 further exemplary embodiments of the optical device 1 are explained. With regard to the reference numerals and the possible configurations is on the 3 referred.

4 shows a schematic representation of a further possible embodiment of the optical device 1.

in the in 4 In the exemplary embodiment shown, both the back plate 5 and the optical element 2 are in a deformed state due to the action of the actuators 4 .

in the in 4 illustrated embodiment, the back plate 5 is preferably formed from the same, in particular the same material as the optical element 2, in particular like the carrier element 8.

5 shows a schematic representation of a further possible embodiment of the optical device 1.

At the in 5 In the illustrated exemplary embodiment of the optical device 1, the at least one measuring unit 7 is preferably arranged on the at least one actuator 4.

The measuring unit 7 can preferably have an optical fiber 13 with a fiber Bragg grating 14, it being possible for the fiber Bragg grating 14 to be attached to the side of the at least one actuator 4.

In an alternative embodiment that is not shown, it can be provided that the at least one measuring unit 7 is arranged in the at least one actuator 4 .

Furthermore, in the in 5 illustrated embodiment, the at least one measuring unit 7 is preferably arranged between the back plate 5 and the carrier element 8 or the optical element 2 .

6 shows a schematic representation of a further possible embodiment of the optical device 1.

The at least one measuring unit 7 is in 6 illustrated embodiment spaced from the back plate 5 preferably on a, preferably stationary, reference element 16 is arranged.

The at least one measuring unit 7 has in 6 illustrated embodiment preferably at least one distance sensor 17. in the in 6 illustrated embodiment, the distance sensor 17 is preferably an interferometer. Alternatively or additionally, sensors can be provided which are based on a capacitive mode of operation.

7 1 shows the optical device 1 6 in a deflected state.

The distance sensors 17 are preferably arranged in such a way that they can particularly reliably detect the increased deflection of the back plate 5 due to the deflection increase.

In an embodiment that is not shown, provision can be made for the optical element 2 and/or the back plate 5 to be arranged in a mount.

With regard to the other reference symbols is on 3 refer.

8th shows a schematic representation of a further possible embodiment of the optical device 1.

in the in 8th In the illustrated embodiment, the distance sensors 17 of the measuring unit 7 are arranged between the back plate 5 and the optical element 2 , preferably between the back plate 5 and the carrier element 8 of the optical element 2 .

in the in 8th In the exemplary embodiment illustrated, the at least one actuator 4 is arranged at a distance from the distance sensors 17 .

The at least one distance sensor 17 is also in the in 8th illustrated embodiment is preferably arranged at a distance from the back plate 5 in such a way that a distance between the distance sensor 17 and the back plate 5 corresponds to a preferred working distance of the at least one distance sensor 17 when the back plate 5 is essentially expected to be deflected.

The distance sensor 17 can be mechanically connected to the carrier element 8 , preferably it can be mechanically connected to the back plate 5 . It can also be held in a separate holding device.

9 1 shows the optical device 1 8th in a deformed or deflected state.

10 shows a block diagram representation of a possible embodiment of the method according to the invention for determining an actual deformation of the optical surface 3.

In the method for determining an actual deformation of the optical surface 3 of the optical element 2, in particular an optical element 2 of a lithography system 100, 200, at least one actuator 4 is arranged between the optical element 2 and a back plate 5. In an action block 50 the at least one actuator 4 acts on the optical element 2 to deform the optical surface 3 and is supported on the back plate 5 in the process. At least one actual deformation of at least one measuring area 18 in and/or on the back plate 5 and/or in and/or on the at least one actuator 4 is measured in a measuring block 51 . An actual deformation of the optical surface 3 is determined in a determination block 52 from the actual deformation of the at least one measurement area 18 determined in the measurement block 51 .

The back plate 5 and the optical element 2 are designed in such a way that in a reinforcement block 53 the back plate 5 is deformed by the at least one actuator 4 more than the optical surface 3.

As part of the measuring block 51 and/or the determination block 52, it can preferably be provided that at least one, preferably exactly one, measuring area 18 is assigned to each location on the optical surface 3 in such a way that the actual deformation of the optical surface 3 at the location the actual deformation, in particular the actual deflection in the at least one measuring area 18 can be clearly determined.

As part of the reinforcement block 53, it can preferably be provided that an actual deformation of the measuring region 18 is effected which is at least twice, preferably at least three times, more preferably at least four times, even more preferably at least six times, very preferably at least eight times, in particular at least ten times larger is the actual deformation of the location on the optical surface 3 assigned to the measurement area 18.

A waveguide block 54 can preferably be provided, in which the waveguide 12, preferably the optical fiber 13, is arranged with the fiber Bragg grating 14 in such a way that in at least one of the fiber Bragg gratings 14 at least one grating interference spectrum 15 (see 15 ) is influenced by the actual deformation, in particular an actual elongation of the at least one measuring area 18 .

Within the framework of the measurement block 51 it can preferably be provided that the measurement radiation 19 is coupled into the waveguide 12 .

As part of measuring block 51, it can preferably be provided that the actual deformation of the at least one measuring area 18, in particular the actual deflection, of the at least one measuring area 18 is determined from a distance between measuring area 18 and at least one distance sensor 17.

In the context of the measuring block 51, it can also be provided that the distance is preferably determined interferometrically and/or capacitively.

11 shows a block diagram representation of a method for setting a target deformation.

In the method for setting the target deformation of the optical surface 3 of the optical element 2, in particular an optical element 2 of the lithography system 100, 200, the actual deformation of the optical surface 3 is in an input block 70 with the associated 10 described method or one of its embodiments determined. In an output block 71, the at least one actuator 4 is subjected to a control signal in such a way that the optical surface assumes a desired deformation.

In particular, it can be provided that the input block 70 and the output block 71 are connected via a closed control loop.

The optical device 1, as in connection with 3 until 9 described, as well as the two in connection with the 10 and 11 described methods are particularly suitable for use in a lithography system, in particular a projection exposure system 100, 200 for semiconductor lithography, but especially for the mirrors M1 to M6 of the EUV projection exposure system 100.

The mirrors M1 to M6 represent the optical element 2 of the optical device 1.

12 shows a schematic representation of various expansion curves of the at least one actuator 4.

An elongation of the actuator 4 and/or an elongation of the effective range of the actuator 4 is plotted on a vertical elongation axis 20 .

On a horizontal axis 21 is in 12 the field strength of an applied electric field. In the diagram in 12 four expansion curves are shown, which correspond to different temperatures of the actuator 4. All four strain curves show hysteresis.

In this case, the expansion curve with the lowest profile corresponds to the highest temperature, while the expansion curve with the highest profile corresponds to the lowest temperature of the actuator 4 .

In the 12 The expansion curves of the actuator 4 shown reflect the behavior of the actuator 4 according to the formula (1). A hysteresis of the actuator 4 can be seen here and is in a range of <1% in the example shown.

13 shows a schematic representation of an expansion curve of the actuator 4 under temperature change. The expansion of the actuator 4 is again plotted on the expansion axis 20 , while the temperature of the actuator 4 is plotted on the horizontal axis 21 . A hysteresis of the expansion curve can be seen when running through a temperature cycle.

The expansion of the actuator 4 with the change in temperature compared to that at the origin of the in 13 The normal temperature arranged in the diagram shown is determined in particular by the thermal expansion coefficient CTE (see formula (1)). At the in 13 The expansion curve shown shows a thermal hysteresis of the expansion. The effects of the hysteresis may not be reproducible here.

14 shows a schematic representation of a drift curve of the actuator 4. The elongation of the actuator 4 is plotted on the elongation axis 20, while a time course is plotted on the horizontal axis 21. At the origin, i.e. at the beginning of the time measurement, the actuator 4 is in an initial position or initial stretch and receives a jump signal at a signal instant 62, preferably in the form of an applied voltage, a target position 61 (in 14 shown as a dashed line), that is to say a target elongation, in order to set a target deformation on the optical surface 3 . In the course of time, the actuator 4 approaches the desired position 61 or the desired elongation or drifts towards it.

Furthermore, the in 14 shown drift depending on the respective jump height of the actuator 4.

The in the 12 , 13 and 14 properties of the at least one Aktua shown Tors 4 may be undesirable when used in the optics device 1 and may be corrected by the features of the optics device.

15 shows a schematic representation of the grating interference spectrum 15. The wavelength is plotted on the horizontal axis 21. The measured grating interference spectrum 15 of a back-reflected measuring radiation 19 is plotted in a solid line on an intensity axis 22 . An input spectrum of the irradiated measurement radiation 19 is plotted in a dashed line.
16 shows a block diagram representation of a further possible embodiment of the method for setting a target deformation.

in the in 16 In the exemplary embodiment shown, a setpoint value block 55 is provided, in which a setpoint value for a deformation of the surface 3 is specified.

In a control block 56, the setpoint specification from the setpoint block 55 is forwarded to the action block 50 in the form of a control signal. Active connections between individual blocks are in 16 represented by arrows. Control paths 56a are described by arrows with solid lines.

In the rule block 56, in 16 illustrated embodiment results of a modeling block 57 fed. in the in 16 illustrated embodiment, this information flow is represented by a modeling input path 57a in the form of a dashed arrow.

A deformation of the optical surface 3 is brought about in a deformation block 58 by the action block 50 .

The mechanically amplified translation of the deformation of the optical surface 3 on the back plate 5 is also effected in the reinforcement block 53 by the action block 50 .

The mechanically amplified deformation is measured in a measuring block 59 .

The collection of measurement data regarding the mechanically amplified deformation from the reinforcement block 53 within the measurement block 59 can be carried out in 16 illustrated embodiment along at least three paths.

In a first possible embodiment, it can be provided that data or measured values are recorded in the measuring block 59 by means of the waveguide 12, which is 16 is also symbolized as a block. In a second possible embodiment, it can be provided that in the measurement block 59 data about the mechanically amplified deformation from the amplification block 53 is recorded by means of preferably capacitively and/or interferometrically acting distance sensors 17 . The distance sensor 17 is in the 16 illustrated embodiment also symbolized as a block.

A direct arrow between the blocks 53 and 59 also contains further possible measurement methods for detecting the mechanically amplified deformation from the reinforcement block 53 in the measurement block 59 .

The actually present actual deformation of the optical surface 3 is determined within the scope of the determination block 52 . For this purpose, measured values from the measuring block 59 flow into the determination block 52 . Furthermore, data or information from a further modeling block 57 optionally flows into the determination block 52, in which a functional relationship between the measured values from the measuring block 59 and the actually present actual deformation of the optical surface 3 is modeled.

Furthermore, information from a calibration block 60 optionally flows into the determination block 52, in which the surface deformation or the actual deformation of the optical surface 3 is recorded directly, i. H. is not detected by the mechanically amplified deformation of the back plate 5.

In the calibration block 60, a functional relationship between the measured mechanically amplified actual deformation of the back plate 5 and the actually existing actual deformation of the optical surface 3 is accordingly determined or established. The calibration block 60 is connected to the determination block 52 in the in 16 illustrated embodiment connected via a calibration path 60a, which is shown as a dotted line.

In particular, in connection with 16 described embodiment of the method for setting a target deformation partially or entirely within the scope of the input block 70 and / or the output block 71 in 11 described embodiment of the method for setting a target deformation flow.

Reference List

1

optics device

2

optical element

3

optical surface

4

actuator

5

backplate

6

deformation measuring device

7

unit of measure

8th

carrier element

9

first effective range

10

second effective area

11

backplate surface

12

waveguide

13

optical fiber

14

Fiber Bragg Grating

15

grating interference spectrum

16

reference element

17

distance sensor

18

measuring range

19

measuring radiation

20

strain axis

21

horizontal axis

22

intensity axis

23

spectrometer setup

24

control device

50

effect block

51

measuring block

52

investigation block

53

reinforcement block

54

waveguide block

55

setpoint block

56

rule block

56a

control path

57

modeling block

57a

modeling input path

58

deformation block

59

measuring block

60

calibration block

61

target position

62

signal time

70

input block

71

output block

100

EUV projection exposure system

101

lighting system

102

radiation source

103

lighting optics

104

object field

105

object level

106

reticle

107

reticle holder

108

reticle displacement drive

109

projection optics

110

image field

111

picture plane

112

wafers

113

wafer holder

114

Wafer displacement drive

115

EUV / useful / illumination radiation

116

collector

117

intermediate focal plane

118

deflection mirror

119

first facet mirror / field facet mirror

120

first facets / field facets

121

second facet mirror / pupil facet mirror

122

second facets / pupil facets

200

DUV projection exposure system

201

lighting system

202

reticle stage

203

reticle

204

wafers

205

wafer holder

206

projection optics

207

lens

208

version

209

lens body

210

projection beam

wed

Mirror

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• DE 102008009600 A1 [0193, 0197]
• US 2006/0132747 A1 [0195]
• EP 1614008 B1 [0195]
• US6573978 [0195]
• US 2018/0074303 A1 [0214]

Claims (25)

Optical device (1), in particular for a lithography system (100, 200), comprising: - an optical element (2) with an optical surface (3), and - One or more actuators (4) for a deformation of the optical element (2), and - A back plate (5) for supporting the at least one actuator (4), wherein the at least one actuator (4) is arranged between the optical element (2) and the back plate (5), wherein - A deformation measuring device (6) for determining the deformation of the optical surface (3) having at least one measuring unit (7) is provided, wherein - the back plate (5) has a lower rigidity than the optical element (2) to be deformed, and - The deformation measuring device (6) is set up to measure a deformation of the back plate (5) and/or the at least one actuator (4). Optical device (1) after claim 1 , characterized in that the at least one actuator (4) for deforming the optical surface (3) is arranged in such a way that a first effective region (9), preferably a first end of the actuator (4) acts on the optical element (2) and a second active area (10), preferably a second end of the actuator (4), acts on the back plate (5). Optical device (1) according to one of Claims 1 or 2 , characterized in that the optical element (2) and the back plate (5) are designed such that a deflection of the actuator (4) to deform the optical surface (3) to a deformation of a surface (11) of the back plate (5) which corresponds to at least twice, preferably at least three times, more preferably at least four times, even more preferably at least six times, very preferably at least eight times, in particular at least ten times the deformation of the optical surface (3). Optical device (1) according to one of Claims 1 until 3 , characterized in that the deformation of the optical surface (3) and/or the back plate (5) is a deflection and/or a stretching. Optical device (1) according to one of Claims 1 until 4 , characterized in that the back plate (5) has a lower thickness than the optical element (2), preferably has a thickness which is less than half, preferably less than a third, particularly preferably less than a quarter of the thickness of the optical element (2) corresponds. Optical device (1) according to one of Claims 1 until 5 , characterized in that the back plate (5) and the optical element (2) are formed from the same material, in particular the same material. Optical device (1) according to one of Claims 1 until 6 , characterized in that the back plate (5) and the optical element (2) are formed from different materials, the back plate (5) preferably being formed from a material which has a lower rigidity than the material from which the optical element ( 2) is trained. Optical device (1) according to one of Claims 1 until 7 , characterized in that the at least one measuring unit (7) is arranged in and/or on the back plate (5). Optical device (1) according to one of Claims 1 until 8th , characterized in that the at least one measuring unit (7) is arranged in and/or on the at least one actuator (4). Optical device (1) according to one of Claims 1 until 9 , characterized in that the at least one measuring unit (7) is arranged at a distance from the back plate (5) on a reference element (16). Optical device (1) according to one of Claims 1 until 10 , characterized in that the at least one measuring unit (7) is arranged between the back plate (5) and the optical element (2). Optical device (1) according to one of Claims 1 until 11 , characterized in that the at least one measuring unit (7) has at least one optical waveguide (12), preferably an optical fiber (13). Optical device (1) according to one of Claims 1 until 12 , characterized in that the at least one measuring unit (7) has at least one distance sensor (17), preferably an interferometer. Optical device (1) after Claim 13 , characterized in that the at least one distance sensor (17) is arranged at a distance from the back plate (5) in such a way that the distance between the distance sensor (17) and the back plate (5) when the back plate (5) is essentially to be expected to deflect corresponds to a preferred working distance of the distance sensor (17). Optical device (1) according to one of Claims 12 until 14 , characterized in that the at least one waveguide (12) has one or more fiber Bragg gratings (14) with respective grating interference spectra (15). Optical device (1) according to one of Claims 12 until 14 , characterized in that the at least one optical waveguide (12) is polarization-maintaining. Method for determining an actual deformation of an optical surface (3) of an optical element (2), in particular an optical element (2) of a lithography system (100,200), with at least one actuator between the optical element (2) and a back plate (5). (4) is arranged, which acts on the optical element (2) to deform the optical surface (3) and is thereby supported on the back plate (5), after which - An actual deformation of the optical surface (3) is determined in that at least one actual deformation of at least one measuring area (18) in and/or on the back plate (5) and/or in and/or on the at least one actuator ( 4) is measured, where - the back plate (5) and the optical element (2) are designed in such a way that the back plate (5) is deformed more strongly by the at least one actuator (4) than the optical surface (3). procedure after Claim 17 , characterized in that each location on the optical surface (3) is assigned at least one, preferably exactly one, measurement area (18) in such a way that the actual deformation of the optical surface (3) at the location from the actual deformation, in particular an actual deflection in which at least one measuring range (18) can be clearly determined. procedure after Claim 17 or 18 , characterized in that an actual deformation of the measuring area (18) is brought about which is at least twice, preferably at least three times, more preferably at least four times, even more preferably at least six times, very preferably at least eight times, in particular at least ten times greater than the actual - Deformation of the measuring area (18) associated location on the optical surface (3). Procedure according to one of claims 17 until 19 , characterized in that a waveguide (12), preferably an optical fiber (13), with a fiber Bragg grating (14) is arranged such that in at least one of the fiber Bragg gratings (14) at least one grating interference spectrum ( 15) is influenced by the actual deformation, in particular an actual elongation, of the at least one measuring area (18). procedure after claim 19 , characterized in that a measuring radiation (19) is coupled into the waveguide (12). Procedure according to one of claims 17 until 21 , characterized in that the actual deformation of the at least one measuring area (18), in particular an actual deflection of the at least one measuring area (18), is determined from a distance between the measuring area (18) and at least one distance sensor (17). procedure after Claim 22 , characterized in that the distance is determined interferometrically and/or capacitively. Method for setting a target deformation of an optical surface (3) of an optical element (2), in particular an optical element (2) of a lithography system (100,200), after which an actual deformation of the optical surface (3) with a method according to one of claims 17 until 23 is determined. Lithography system, in particular projection exposure system (100, 200) for semiconductor lithography, with an illumination system (101, 201) with a radiation source (102) and an optical system (103, 109, 206) which has at least one optical element (116, 118, 119, 120, 121, 122, Mi, 207), characterized in that at least one optical device (1) according to one of Claims 1 until 16 is provided, wherein at least one of the optical elements (116, 118, 119, 120, 121, 122, Mi, 207) is an optical element (2) of the at least one optical device (1) and/or at least one of the optical elements (116, 118, 119, 120, 121, 122, Mi, 207) has an optical surface (3) which, with a method for determining according to one of claims 17 until 23 is measured and/or with a method for adjustment according to Claim 24 is deformed.

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