TW202246841A - Optical assembly and method for the production thereof, method for deforming an optical element, and projection exposure apparatus - Google Patents

Abstract

The invention relates to an optical assembly (1) comprising an optical element (2) with an optically active front side (3) and a back side (4) facing away from the front side (3). The optical assembly (1) comprises a plurality of electrostatic actuators (5) arranged distributed along the back side (4) of the optical element (2). Each actuator (5) comprises an electrode pair of two spaced apart electrodes (6, 7), each actuator (5) being configured and mechanically coupled to the back side (4) of the optical element (2) so that an electrostatic force which is generated by means of an electrical control voltage (U1...n) between the electrodes (6, 7) of the electrode pair and which serves to deform the optical element (2) is transferred to the optical element (2). Provision is made for a dielectric (8) to be arranged between the electrodes (6, 7) of the electrode pair.

Description

Optical component and method for its manufacture, method for anamorphic optical element, and projection exposure apparatus

The present invention relates to an optical component comprising an optical element having an optically active front side and a back side away from the front side, and a plurality of electrostatic actuators distributed along the back side of the optical element.

The invention relates more to a method for deforming an optical element by means of a plurality of electrostatic actuators, and to a computer program product having code means for implementing such a method.

The invention relates more to a method for producing an optical component comprising an optical element having an optically active front side and a back side remote from the front side and electrostatic actuators.

The invention further relates to a lithographic projection exposure apparatus comprising an illumination system having a radiation source, an illumination optics unit and a projection optics unit. [Related patent reference]

The present invention claims priority from German patent application DE 10 2021 202 769.5 filed on March 22, 2021, the entire content of which is hereby incorporated by reference and constitutes a part of this specification.

Projection exposure units or lithography units are used to produce highly accurate integrated circuits. Here, the light of the radiation source is directed to the wafer to be exposed by means of optical elements such as mirrors and/or lens elements. In this case, the configuration, position and shape of the optical elements have a decisive influence on the quality of the exposure.

Due to the continuous miniaturization of semiconductor circuits, there are more and more stringent requirements on the resolution and accuracy of projection exposure devices. Correspondingly, stringent requirements are imposed especially on its optics and the actuation of the optics.

In order to increase the imaging accuracy of a projection exposure apparatus, experience has taught us to correct imaging aberrations within the projection exposure apparatus by performing targeted deformations of the optical elements by means of actuatable components. For this purpose, ferroelectric actuators are usually fixed on the optical elements, which facilitate actuation based on piezoelectric or electrostrictive principles. By actuating each individual actuator, a target profile of an optical element such as a mirror can ultimately be set, thereby correcting the optical system.

Known actuation systems often require closed-loop operation and therefore require continuous detection of the actually implemented deformations in order to be able to operate with sufficient precision. However, it is not always possible to use sensors with sufficiently high metrological accuracy, especially in lithography. For this reason, known actuation systems generally have a feed-forward operation. For this, comprehensive system modeling is required for sufficient accuracy, which in turn requires an in-depth system understanding of the effects of individual actuators on the optical elements. All unaccounted for disturbances and all non-ideal situations directly affect the achievable performance of the actuation system.

In this case, changes in temperature can represent one of the most important disturbance variables. For example, the temperature of the optical elements within the projection exposure apparatus can range between 20°C and 40°C. Other issues in system modeling involve inherent non-reproducibility of actuators such as creep, hysteresis, thermal hysteresis, behavioral changes, and/or thermal expansion coefficient changes.

To facilitate highly accurate positioning or deformation of optical components, electrostriction and thermal hysteresis as well as actuator drift need to be modeled and calibrated in addition to temperature calibration. This is even possible only with very large metrological costs and very comprehensive metrology equipment.

By switching to electrostatic based actuators, the problems of inherent irreproducibility of the actuator's materials (such as hysteresis and creep) and significant temperature dependence can be avoided. The dynamic effect of an electrostatic actuator is based on the electric field force acting between two adjacent electrodes. For example, in generic US 7,692,838 B2 it is proposed to use electrostatic actuators to deform mirrors.

However, a problem with deforming optical elements by means of electrostatic actuators is that the dynamic effects are relatively limited compared to conventional actuators, eg ferroelectric actuators. For example, to increase the dynamic effect, US 7,692,838 B2 proposes the use of complex nanolaminated films.

DE 10 2016 209 847 A1 also considers the use of electrostatic actuators for deforming the mirror. To increase the dynamic effect, it is proposed to use comb electrodes with meshing comb teeth.

However, the methods proposed in US 7,692,838 B2 and DE 10 2016 209 847 A1 for increasing the dynamic effect of the electrostatic actuator to deform the mirror are relatively complicated. Furthermore, it was surprisingly found that even with the measures proposed in the aforementioned documents, the force of the electrostatic actuator itself is often insufficient, in particular insufficient to deform the optical elements in the projection exposure apparatus.

In view of the known prior art, it is an object of the present invention to provide an optical assembly that facilitates deformation of optical elements with high accuracy and high dynamics.

The invention is also based on the object of providing a method for deforming an optical element which facilitates deforming the optical element with high accuracy and high dynamics. Finally, another object of the invention is to provide an advantageous computer program product for carrying out the above method.

Furthermore, it is an object of the present invention to provide a method for producing optical components by which improved optical components for deforming optical elements can be produced.

Finally, another object of the present invention is to provide a lithographic projection exposure apparatus comprising at least one optical assembly having an optical element deformable by means of at least one electrostatic actuator for correcting with high accuracy Imaging aberrations.

By means of the corresponding claim independent item, the objects directed to an optical component, a deformation method, a computer program product, a method for manufacturing an optical component, and a projection exposure device are achieved. The dependent claims and the features described below relate to advantageous embodiments and variants of the invention.

An optical assembly is provided that includes an optical element having an optically active front side and a back side remote from the front side.

The backside of the optical element may optionally also have an optically active form, eg if the optical element is in the form of a lens element. However, the back side is preferably not optically active or at least not used to influence the beam path from the radiation source.

The optically active front side of the optical element is preferably in the form of a mirror surface, in particular for reflecting or influencing the beam path of DUV ("deep ultraviolet") or EUV ("extreme ultraviolet") radiation.

The rear side of the optical element can extend in a plane-parallel manner or at least substantially in a plane-parallel manner with respect to the front side, in particular in the undeformed basic state of the optical element. However, this is not mandatory within the scope of the present invention. The front side and/or the back side can also have an arcuate form, in particular concave or convex.

According to the invention, the optical assembly comprises a plurality of electrostatic actuators distributed along the backside of the optical element. Each electrostatic actuator has an electrode pair consisting of two spaced apart electrodes.

The electrodes preferably have a flat form, but may also have arched, stepped, and/or comb-shaped structures. Planar electrodes are preferably provided, for example in the form of plates, films or vapor-deposited layers. For example, the thickness of a single electrode may be 0.01 μm to 500 μm, preferably 0.01 μm to 100 μm, more preferably 0.01 μm to 10 μm.

The two electrodes of a common electrode pair can each be formed in one piece, but can alternatively have a multi-part embodiment. Therefore, when "an" electrode is referred to within the scope of the present description, this may in principle relate to a single electrode or may relate to a group of a plurality of individual electrodes which together form an electrode. Therefore, it is not excluded that a single actuator has more than two separate electrodes. Furthermore, a single actuator may also comprise a plurality of electrode pairs, each electrode pair being made of two spaced apart electrodes. This is not necessarily important within the scope of the invention; for the sake of simplicity, the invention is described hereinafter primarily on the basis of an actuator comprising exactly one electrode pair consisting of exactly two spaced apart electrodes. However, this should not be construed as limiting.

According to the invention, each actuator is configured and mechanically coupled to the backside of the optical element such that the electrostatic force generated by the electrically controlled voltage between the electrodes of the electrode pair and used to deform the optical element is transferred to the optical element. element.

Where applicable, the optical assembly can have exactly one actuator for targeted deformation of the optical element. However, the optical assembly preferably has a plurality of actuators; particularly preferably, the optical assembly comprises at least two actuators, at least 10 actuators, at least 50 actuators, at least 100 actuators, at least 500 actuators, at least 1000 actuators, at least 5000 actuators, or at least 10000 actuators for targeted deformation of the optical element. Particularly preferably, however, the optical assembly has significantly more actuators.

The actuators are preferably in each case equally spaced from the immediately adjacent actuators or evenly distributed on the rear side of the optical element.

Due to the action of the actuator, the optical element may be elastically deformable or at least substantially reversibly deformable. The deformation of the optical element is preferably carried out without hysteresis.

In particular, "deformation" is understood to mean a deformation of the material of the optical element, as a result of which, for example, a cross-sectional change of the length of the material of the optical element or a deformation of the cross-sectional surface of the optical element may be caused.

As a result of using electrostatic actuators, positioning accuracy problems caused by inherent actuator non-reproducibility can be reduced or completely avoided, since dynamic effects are determined only by the electric field forces between the electrodes of the electrode pair.

It is preferable to provide the smallest possible distance between the electrodes of an electrode pair, since an electrostatic drive or actuator produces the largest dynamic effect for a small plate spacing. However, the maximum possible electrostatic force may be limited by the breakdown voltage above which statically occurring ionization causes an ionization burst between the two electrodes. It is known that the breakdown voltage can be described by Paschen's law and can be determined accordingly for the individual actuator.

According to the invention, a dielectric is arranged between the electrodes of the electrode pair.

Preferably a solid or liquid dielectric is provided, although a gaseous dielectric may also be provided (but preferably no air or hydrogen).

In a further development of the invention, it can in particular be provided that the dielectric strength of the dielectric is greater than that of air.

As a result of the use of dielectrics, especially solid or liquid dielectrics, it is possible to increase the dielectric strength of the actuator and, in the case of a correspondingly high dielectric constant, also the force of the actuator . As an example, the inventors have realized that when using air as the dielectric, the maximum force between the electrodes of an electrode pair is only 3 V/μm for an electrode area of 100 mm ² and is therefore only about 0.004 N. Since it is proposed to use a dielectric, preferably other than air, between the electrodes of the electrode pair, this force can be increased sufficiently to facilitate the deformation of the optical element in practice.

It may be provided that the dielectric completely fills the space between the electrodes of the electrode pair. However, it can also be provided that the dielectric medium only partially fills the space between the electrodes of the electrode pair, eg is arranged centrally between the electrodes of the electrode pair and is spaced apart from one or both electrodes. It can also be provided that one or both electrodes of an electrode pair are covered by a dielectric, for example in the form of a dielectric coating, in particular an insulating layer, in order to increase the dielectric strength of the actuator.

Preferably, the prescribed dielectric has a dielectric constant greater than 1.0 (or greater than vacuum), preferably greater than air, particularly greater than 2, particularly preferably greater than 5. The permittivity, very particularly preferably has a permittivity greater than 10, more preferably has a permittivity greater than 50, for example has a permittivity greater than 100 or greater.

Especially when a solid dielectric is provided, the dielectric is preferably compressible to facilitate a change in the distance between the electrodes of the electrode pair upon action of the actuator.

In an advantageous development of the invention, it can be provided that one of the electrodes of the electrode pair is designed as a control electrode, to which a control voltage can be applied. The other electrode is preferably designed as a reference electrode, to which a reference potential can also be applied.

The reference electrode is preferably implemented as a ground electrode. The reference potential is preferably ground potential.

In particular, it can be provided that the reference potential can be applied together to the reference electrode of the actuator and to a reference electrode of at least one further actuator, preferably all actuators.

The contact actuator can be significantly simplified by combining the reference electrodes or by common contacting of all reference electrodes.

According to a development of the invention it can be provided that one of the electrodes of the pair of electrodes is mechanically coupled to the backside of the optical element and the other electrode is mechanically coupled to a reference body spaced apart from the backside of the optical element.

Preferably, the control electrode is mechanically coupled to the reference body, and the reference electrode is mechanically coupled to the backside of the optical element. This simplifies the accessibility of the control electrodes for driving purposes or for control voltage applications.

In particular, the reference body may be part of an optical body, a mount for an optical element, a mounting frame for an optical element (eg of an optical unit or a test bench), or a housing part for an optical element. In general, the reference body is statically coupled to surrounding components.

Preferably, the electrodes are adhesively connected to the optical element, in particular to the backside of the optical element. In principle, the electrodes can be connected to the optical element in any desired manner, for example in a press-fit or interlocking manner. In particular, however, adhesive connections, for example by adhesively bonding the electrodes to the optical element or by vapor-depositing the electrodes on the optical element, have been found to be particularly suitable. Integral embodiments of electrodes with optical elements may also be provided, for example using additive manufacturing techniques. The same fixation technique can be provided to fix the other electrode to the reference body.

According to a further development of the invention, the electrodes coupled to the optical element can be fixed directly on the optical element.

This allows deformations to be introduced into the optical element in a particularly targeted manner. However, this does not allow the introduction of global modes into optical elements, even though this might be envisaged for various applications.

For this reason, it can be provided in an alternative development of the invention that the electrodes coupled to the optical element are indirectly connected to the optical element via an intermediate element spaced apart from the rear side of the optical element.

Fixing techniques already described in the context of fixing the electrodes to the optical element may be provided for fixing the electrodes to the intermediate element and/or for connecting the intermediate element to the optical element.

Thus, the intermediate element can be used as a balance plate, allowing the introduction of global modes into the optical element, or enabling more "long-wavelength" deformation of the optical element. The deformation of the actuator can thus initially have a direct effect on the intermediate element and then be transmitted via the intermediate element to the optical element.

Depending on the application, a person skilled in the art may or may not provide the intermediate element, and may also change the thickness and elasticity or material properties of the intermediate element if required.

In a further development of the invention it can be provided that the intermediate element is fastened to the optical element via spacer elements and/or spacer struts, wherein the spacer elements and/or spacer struts are distributed along the rear side of the optical element.

Fixing techniques already described in the context of fixing electrodes to optical elements may be provided for fixing spacer elements/spacer struts to optical elements and/or intermediate elements.

The influence of the actuator on the optical element via the intermediate element can be optimally set by using spacer elements and/or spacer struts, for example by varying the geometry of the spacer elements or spacer struts and/or the material of the spacer elements or spacer struts characteristic.

For example, provision may be made for the respective spacing element and/or spacing strut to be arranged centrally or centrally (relative to the electrode surface) with respect to the electrode of the corresponding actuator.

In an advantageous development of the invention, it can be provided that the reference body is fixed to the optical element or the intermediate element via bearing units and/or bearing struts distributed along the rear side of the optical element.

The fixing techniques already described in the context of fixing the electrodes to the optical element can be provided for fixing the bearing unit/bearing strut to the optical element and/or the intermediate element and/or the reference body.

Preferably, the electrodes of each actuator are arranged between each bearing unit and/or bearing strut. Favorable force distribution can be promoted in this way.

In a further development of the invention it can be provided that the spacer unit or the spacer strut is offset from the bearing unit or the bearing strut along the rear side of the optical element.

In this way, the optical element can be deformed to a large extent without being restricted by the fact that the optical element is carried on the reference body.

In an advantageous development of the invention it can be provided that the electrodes coupled to the optical element run parallel to the rear side of the optical element.

In principle, however, electrode configurations deviating from the parallel range with respect to the rear side of the optical element can also be provided. However, parallel ranges have been found to be particularly suitable and also relatively easy to implement from a technical point of view.

In an advantageous development of the invention, an electrode coupled to the optical element, preferably a control electrode, can be arranged on the side wall of the cutout extending from the back side into the optical element.

Optionally, it may additionally be provided that an electrode coupled to the reference body, preferably a reference electrode, is arranged on a protrusion extending from the reference body into the cutout of the optical element. Alternatively, electrodes coupled to the reference body may also form the protrusion itself.

Preferably, the electrodes of the electrode pair are arranged orthogonally or at least substantially orthogonally in their basic state with respect to the backside and/or frontside of the optical element when extending into or through the cutout.

In particular, the cutouts may be grooves with a small width, for example grooves with a width of a few micrometers.

In the described manner, when a control voltage is applied, forces can be generated within the cutout and thus deformation within the optical element, which in turn can lead to deformation of the optically active front side of the optical element. In this way, it is also possible to introduce global deformations into the optical elements.

In an advantageous development of the invention it can be provided that the two electrodes of the electrode pair are mechanically coupled to the optical element and are arranged for this purpose on opposite side walls of the cutout extending from the rear side into the optical element.

In particular, two electrodes can be vapor deposited or adhesively bonded to two opposing side walls.

In a development of the invention, provision can be made for the dielectric medium to be a liquid medium.

The liquid medium may preferably be distilled water or formamide. In principle, however, any desired dielectric medium can be provided, in particular those with a high dielectric strength and/or a high dielectric constant.

The use of liquid media as dielectric was found to be particularly suitable.

When combining different dielectrics, especially different liquid media, it should be noted that the overall breakdown voltage can be determined by which dielectric layer first reaches the corresponding critical potential difference or field strength.

If a gaseous dielectric is provided, it may for example be sulfur hexafluoride (SF ₆ ).

High vacuum may also be advantageously suitable.

According to a development of the invention, it may be provided that a fluid connection is formed between pairs of electrodes of adjacent actuators in order to facilitate the exchange of liquid medium between the actuators.

In the case of incompressible liquid media, this ensures that they can flow out of the gap between the electrodes in case of actuation to facilitate the movement of the actuator.

In particular, the fluid connections between the actuators may be cutouts, holes etc. in the bearing unit and/or the bearing strut, which preferably extend between the respective actuators.

According to this refinement, it may be provided that the optical assembly has at least one balancing vessel fluidly connected to one, a plurality of the actuators, or all of the actuators to facilitate expansion of the liquid medium into the balancing vessel.

In particular, the balancing container can be a balancing bellows which can be stretched elastically depending on the amount of fluid medium received.

The balancing container in particular ensures that the optical components are not deformed by thermal expansion of the dielectric. The balancing container, in particular the balancing bellows, is able to receive excess liquid when the liquid medium thermally expands or when the gap between the electrodes of the common electrode pair shrinks due to actuation.

In order to prevent crosstalk between actuators, it may be advantageous to provide a separate balancing container for each actuator or for each individual group of actuators.

According to a refinement, it can also be provided that the optical assembly has at least one inlet and at least one outlet for the liquid medium, which are fluidically connected to the actuator, so that the liquid medium can flush the electrode pairs of the actuator.

Furthermore, turbines, such as pumps, may optionally be provided to facilitate the passage of liquid media.

In particular, the inflow port can be connected to an external liquid supply. In this case, the balancing container can optionally be omitted.

In an advantageous development of the invention, it can be provided that the electrodes of the electrode pair are arranged to extend parallel to one another.

Alternatively, however, it can also be provided that the electrodes of an electrode pair are arranged at an angle to one another. However, this is not optimal.

In an advantageous development of the invention, it can be provided that the actuators are distributed in a grid along the rear side of the optical element.

Due to the grid-like distribution of the actuators, different deformation profiles can be set. Preferably, the actuators are distributed and arranged between the above-mentioned bearing units and/or bearing struts.

For example, the actuators may be configured as quadrilateral segments. Furthermore, the configuration of individual longitudinal grooves in only one spatial direction can be selected. Arrangements in the form of triangles or any other grid-like arrangement may also be provided.

According to a development of the invention, the optical assembly can comprise a control device for generating a control voltage for the actuator for deforming the optical element in a targeted manner.

The control means may be in the form of a microprocessor. Any additional means for implementing the control means may be provided in place of the microprocessor, such as one or more configurations of discrete electronic components on a printed circuit board, a programmable logic controller (PLC), an application specific integrated circuit (ASIC) , or any other programmable circuit, such as a Field Programmable Gate Array (FPGA), Programmable Logic Array (PLA), and/or a commercial computer.

According to a development of the invention, provision can be made for the control device to be configured to use the actuator as a sensor unit for recording the actual state of the deformation by exciting it with a control voltage in a frequency range which is not important for the deformation operation.

Optionally, the actuator can thus also be used as a sensor unit, since the current actual state of deformation is derived from the electrical behavior of the two electrodes of a common electrode pair. Driving using a control voltage for operation as a sensor unit can be realized in the radio frequency range, for example of the order of a few megahertz. Since the driving when used as an actuator is generally realized within a bandwidth of the order of a few hundred hertz, there is generally no mutual interference in this case, so the operations of the actuator and the sensor can be performed in parallel.

The invention relates more to a method of deforming an optical element by means of a plurality of electrostatic actuators, each electrostatic actuator having an electrode pair consisting of two spaced apart electrodes. A control voltage is applied between the electrodes of the electrode pair to generate an electrostatic force that is transmitted from the actuator to the optical element to deform the optical element. In addition, a dielectric is disposed between the electrodes of the electrode pair. Preferably, a solid or liquid dielectric is provided. However, gaseous dielectrics or high vacuum are also available.

The use of the electrostatic actuators described above may be particularly advantageous, since in the case of electrostatic actuators the force or extension is not produced by properties of the material itself, as in the otherwise conventional case of piezoelectric or electrostrictive actuators , but based on charge attraction. Consequently, the forces generated during actuation are more predictable and facilitate modeling.

Since electrostatic actuators have only very small non-reproducibility and their dynamic effect can be significantly increased due to the proposed use of a dielectric between the electrodes of an electrode pair, it is possible to make optical The elements are deformed to provide a high accuracy system.

By applying a control voltage or reference potential to the electrodes, a tensile or compressive force can be selectively generated between the electrodes involved. Preferably tension generation is provided.

The invention also relates to a computer program product with program code means for, when a program is executed on a control device, in particular of the above-mentioned optical assembly, to execute, according to the explanations given above and below, to make the optical element deformation method.

In particular, the invention is suitable for use in a projection exposure apparatus as will be mentioned hereinafter, or in general, in lithography optics. In principle, however, the invention is applicable to any desired application in which optical elements are to be deformed, in particular also in aerospace and astronomy, and in military applications.

The invention also relates to a method for producing an optical assembly comprising an optical element having an optically active front side and a back side remote from the front side and a plurality of electrostatic actuators each having a electrode pairs. The actuator is mechanically coupled to the backside of the optical element such that the electrostatic force generated by the electrical control voltage between the electrodes of the electrode pair and used to deform the optical element can be transmitted to the optical element. Furthermore, provision is made to introduce a dielectric between the electrodes of the electrode pair. Preferably, a solid or liquid dielectric is provided. However, gaseous dielectrics or high vacuum are also available.

The technique described in DE 10 2016 209 847 A1 for establishing a mechanical connection between optical elements, reference bodies, intermediate elements, spacer elements/spacer struts, bearing units/bearing struts, and/or electrodes can be advantageously used in current scope of the claimed invention. The disclosure content of DE 10 2016 209 847 A1 is fully integrated into this description by this reference.

In particular, it may be provided that the individual elements of the optics are connected to each other by means of silicate or direct bonding, or alternatively by adhesive connections, welded connections or the like, especially with regard to bearing units/bearing struts and optical elements and/or reference connections between bodies.

Applying electrodes on the optical element, the reference body, and/or the intermediate element can be achieved, for example, by vapor deposition of a conductive layer. Other techniques for applying the electrodes are also available. In principle, any bonding, interlocking, and/or press-fit connection technology is possible.

The invention also relates to a lithographic projection exposure apparatus comprising an illumination system having a radiation source, an illumination optics unit, and a projection optics unit. The illumination optics unit and/or the projection optics unit comprise at least one optical component according to the explanations given above and below.

The invention is particularly suitable for correcting the imaging aberration of the projection exposure device by the deformation of the optical elements of the optical assembly.

The invention is applicable, inter alia, to lithographic DUV projection exposure devices, but in particular to EUV projection exposure devices. One possible use of the invention also relates to immersion lithography.

In combination with the features described in one of the objects of the invention, in particular the features given by the optical component, the method for deforming an optical element, the computer program product, the method for producing an optical component and the projection exposure apparatus, for other aspects of the invention The objective is also achievable advantageously. Likewise, advantages specified in combination with one of the objects of the invention are also to be understood in combination with the other objects of the invention.

Furthermore, references to terms such as "comprising", "having" or "with" do not exclude other features or steps. Furthermore, terms denoting a single step or feature, such as "a" or "the", do not exclude a plurality of features or steps, and vice versa.

However, in purely specific embodiments of the invention it may also be provided that features introduced in the invention using the terms "comprising", "having" or "with" are listed in an exhaustive manner . Thus, within the scope of the present invention, one or more feature lists may be considered complete, for example when each claim item is considered separately. For example, the present invention may consist entirely of the features specified in claim 1.

Labels such as "first" or "second" are primarily used to distinguish various device and method features and do not necessarily indicate that these features need to be related to each other or to each other.

In addition, it should be emphasized that the currently described values and parameters also include ±10% or less, preferably ±5% or less, more preferably ±1% or less, And very particularly preferred are deviations or variations of ±0.1% or less, as long as these deviations are not excluded when implementing the invention in practice. The ranges specified by the start and end values also include all numbers and fractions contained within the respective specified ranges, in particular the start and end values and the respective average values.

The present invention also relates to the optical assembly of claim 1, comprising an optical element and at least one electrostatic actuator having at least two spaced apart electrodes, wherein the actuator is configured and mechanically coupled to the optical element such that upon actuation The electrostatic force generated between the electrodes of the device is transferred to the optical element for deforming and/or aligning and/or positioning the optical element. The further features of claim 1 and the dependent claims as well as the features described in the present description relate to advantageous specific embodiments and variants of this optical assembly.

Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

The drawings show preferred exemplary embodiments in each case, in which individual features of the invention are explained in combination with one another. The features of an exemplary embodiment can also be implemented independently of other features of the same exemplary embodiment, and those skilled in the art can easily make corresponding combinations to combine with other exemplary embodiments. Features form further convenience combinations and subcombinations.

Referring to FIG. 1 , basic components of a lithography EUV projection exposure apparatus 100 will be briefly described below by way of example. The description here of the basic structure of the EUV projection exposure apparatus 100 and its components should not be interpreted restrictively.

The illumination system 101 of the EUV projection exposure apparatus 100 comprises, in addition to the radiation source 102 , an illumination optics unit 103 for illuminating an object field 104 in an object plane 105 . Here, exposure is performed on a mask 106 arranged in the object field 104 . The mask 106 is held by a mask holder 107 . The mask holder 107 can be displaced by a mask displacement drive 108, in particular in the scanning direction.

In Figure 1, a Cartesian xyz coordinate system is depicted to aid in explanation. The x direction is perpendicular to the drawing plane. The y direction runs horizontally and the z direction runs vertically. In Figure 1, the scan direction runs along the y-direction. The z direction is perpendicular to the object plane 105 .

The EUV projection exposure apparatus 100 includes a projection optical unit 109 . The projection optics unit 109 is used to image the object field 104 into an image field 110 in an image plane 111 . The image plane 111 is parallel to the object plane 105 . Alternatively, the angle between the object plane 105 and the image plane 111 may also be different from 0°.

The structures on the mask 106 are imaged onto the photosensitive layer of the wafer 112 , which are arranged in the region of the image field 110 in the image plane 111 . Wafer 112 is held by wafer holder 113 . The wafer holder 113 is displaceable by means of a wafer displacement drive 114, in particular in the y-direction. The mask 106 is displaced by the mask displacement driver 108 on the one hand, and the wafer 112 is displaced by the wafer displacement driver 114 on the other hand, which can be performed in a synchronous manner with each other.

The radiation source 102 is an EUV radiation source. In particular, the radiation source 102 emits EUV radiation 115 , which is also referred to below as use radiation or illumination radiation. In particular, the radiation 115 used has a wavelength in the range between 5 nm and 30 nm. The radiation source 102 may be a plasma source, such as an LPP source ("laser produced plasma") or a GDPP source ("gas discharge produced plasma"). It can also be a synchrotron-based radiation source. The radiation source 102 may be a free electron laser (FEL).

The illuminating radiation 115 emerging from the radiation source 102 is focused by a collector 116 . Light collector 116 may be a light collector having one or more elliptical and/or hyperbolic reflective surfaces. At least one reflective surface of the collector 116 may be struck by the illumination radiation 115 at grazing incidence (GI), ie, an angle of incidence greater than 45°, or at normal incidence (NI), ie, an angle of incidence less than 45°. The light collector 116 may be structured and/or coated, firstly to optimize its reflectivity for the use radiation 115 and secondly to suppress extraneous light.

Downstream of the light collector 116 , the illuminating radiation 115 propagates through an intermediate focal point in an intermediate focal plane 117 . The intermediate focal plane 117 may represent the separation between the radiation source module with the radiation source 102 and the light collector 116 and the illumination optics unit 103 .

The illumination optics unit 103 comprises a deflection mirror 118 and a first facet mirror 119 arranged downstream thereof in the beam path. The deflecting mirror 118 may be a flat deflecting mirror or a mirror having a beam-influencing effect beyond a purely deflecting effect. Alternatively or additionally, the deflection mirror 118 may be in the form of a spectral filter which separates the use light wavelengths of the illumination radiation 115 from extraneous light whose wavelengths deviate therefrom. If the first facet mirror 119 is arranged in a plane of the illumination optics unit 103 which is optically conjugate to the object plane 105 as the field plane, it is also called a field facet mirror. The first facet mirror 119 comprises a plurality of individual first facets 120, which are also referred to as field facets in the following. Only a few of these facets 120 are shown in FIG. 1 by way of example.

The first facet 120 may be in the form of a macroscopic facet, in particular a rectangular facet or a facet with an arcuate or partially circular peripheral contour. The first facet 120 may be in the form of a flat facet, or may be a convex or concave curved facet.

It is known, for example, from DE 10 2008 009 600 A1 that the first facet 120 itself can also be formed in each case from a plurality of individual mirrors, in particular from a plurality of micromirrors. The first facet mirror 119 may especially be formed as a micro-electro-mechanical system (MEMS system). Details can be found in DE 10 2008 009 600 A1.

Between the light collector 116 and the deflecting mirror 118, the illuminating radiation 115 travels horizontally, ie in the y-direction.

The second facet mirror 121 is arranged downstream of the first facet mirror 119 in the beam path of the illumination optics unit 103 . If the second facet mirror 121 is arranged in the pupil plane of the illumination optical unit 103 , it is also referred to as a pupil facet mirror. The second facet mirror 121 may also be arranged at a distance from the pupil plane of the illumination optical unit 103 . In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also called a specular reflector. Specular reflectors are known from US 2006/0132747 A1, EP 1 614 008 B1 and US 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 facet 122 is also referred to as a pupil facet.

The second facet 122 can also be a macro facet, which can have, for example, a circular, rectangular, or hexagonal periphery, or it can be a facet composed of micromirrors. In this respect, reference is likewise made to DE 10 2008 009 600 A1.

The second facet 122 may have a flat surface, or may be a convexly or concavely curved reflective surface.

The illumination optics unit 103 thus forms a two-facet system. This basic principle is also known as the fly's eye integrator.

It may be advantageous to arrange the second facet mirror 121 imprecisely in a plane optically conjugate to the pupil plane of the projection optical unit 109 .

With the aid of the second facet mirror 121 , the respective first facets 120 are imaged into the object field 104 . The second facet mirror 121 is the last beam shaping mirror, or actually the last mirror for the illumination radiation 115 in the beam path upstream of the object field 104 .

In another specific embodiment (not shown) of the illumination optical unit 103, a transfer optical unit that is particularly helpful for imaging the first facet 120 into the object field 104 can be arranged between the second facet mirror 121 and the object field 104. 104 in the beam path between. The transfer optics unit can have exactly one mirror, or can have two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics unit 103 . In particular, the transfer optical unit may comprise one or two mirrors for normal incidence (NI mirror, "normal incidence" mirror) and/or one or two mirrors for grazing incidence (GI reflector mirrors, "grazing incidence" mirrors).

In the particular embodiment shown in FIG. 1 , the illumination optics unit 103 comprises exactly three mirrors downstream of the collector 116 , in particular a deflection mirror 118 , a field facet mirror 119 , and a pupil facet mirror 121 .

In another specific embodiment of the illumination optics unit 103 the deflection mirror 118 can also be omitted, so that the illumination optics unit 103 can have exactly two mirrors downstream of the light collector 116, in particular the first facet mirror 119 and The second facet mirror 121 .

In general, imaging the first facet 120 into the object plane 105 through the second facet 122 or using the second facet 122 and a transfer optic is only approximate imaging.

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

In the example shown in FIG. 1, the projection optical unit 109 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the last mirror M6 each have a through hole for the illumination radiation 115 . The projection optical unit 109 is a double shielding optical unit. The image-side numerical aperture of the projection optical unit 109 is greater than 0.5, and may also be greater than 0.6, such as 0.7 or 0.75.

The reflective surface of the mirror Mi can be embodied as a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of the mirror Mi can be designed as an aspheric surface with exactly one axis of rotational symmetry of the shape of the reflective surface. Like the mirror of the illumination optics unit 103 , the mirror Mi may have a highly reflective coating 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 unit 109 has a large object-image offset in the y-direction between the y-coordinate of the center of the object field 104 and the y-coordinate of the center of the image field 110 . In the y-direction, this object-image offset may have approximately the same magnitude as the z-distance between object plane 105 and image plane 111 .

In particular, the projection optics unit 109 may have a deformed form. In particular, it has different imaging scales βx, βy in the x and y directions. The two imaging ratios βx and βy of the projection optical unit 109 are preferably (βx, βy) = (+/-0.25, +/-0.125). A positive imaging ratio β means imaging without image inversion. A negative imaging scale β indicates imaging with image inversion.

Therefore, the projection optical unit 109 is reduced in size at a ratio of 4:1 in the x direction (ie, the direction perpendicular to the scanning direction).

The projection optics unit 109 results in a size reduction of 8:1 in the y-direction, ie in the scan direction.

Other imaging scales are also possible. Imaging scales with the same sign and the same absolute value in the x-direction and in the y-direction are also possible, for example with an absolute value of 0.125 or 0.25.

In the beam path between object field 104 and image field 110 , the number of intermediate image planes in x-direction and y-direction may be the same, or may be different depending on the specific embodiment of projection optics unit 109 . An example of a projection optics unit with a different number of such intermediate images in the x-direction and in the y-direction is known from US 2018/0074303 A1.

In each case exactly one of the pupil facets 122 is assigned to one of the field facets 120 for forming an illumination channel for illuminating the object field 104 in each case. In particular, this can produce illumination according to the Kohler principle. With the aid of field facets 120 , the far field is decomposed into object fields 104 . The field facets 120 produce a plurality of images of intermediate focus on the pupil facets 122 respectively assigned thereto.

With the respectively assigned pupil facets 122 , the field facets 120 are imaged superimposed on one another on the mask 106 for illuminating the object field 104 . In particular, the illumination of object field 104 is as uniform as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by covering different illumination channels.

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

A likewise better pupil homogeneity in subregions of the illumination pupil of the illumination optics unit 103 illuminated in a defined manner can be achieved by redistribution of the illumination channels.

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

In particular, projection optics unit 109 may have a concentric entrance pupil. A concentric entrance pupil is accessible. It may also be inaccessible.

The entrance pupil of the projection optics unit 109 cannot be properly illuminated using the pupil facet mirror 121 on a regular basis. In the case of the imaging projection optics 109 (which telecentrically images the pupil facet mirror 121 onto the wafer 112), the aperture rays generally do not intersect at one point. However, it is possible to find the region where the distance of the pairwise determined aperture rays becomes smallest. This region represents the entrance pupil or the region in real space conjugated to it. In particular, this region has finite curvature.

The projection optics unit 109 may have different entrance pupil positions for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical part of the transfer optical unit, should be provided between the second facet mirror 121 and the mask 106 . With the assistance of this optic, different relative positions of the tangential and sagittal entrance pupils can be taken into account.

In the configuration of components of the illumination optical unit 103 shown in FIG. 1 , the pupil facet mirror 121 is arranged in a region conjugate to the entrance pupil of the projection optical unit 109 . The field facet mirror 119 is arranged in an oblique manner with respect to the object plane 105 . The first facet mirror 119 is arranged in an oblique manner with respect to the arrangement plane defined by the deflection mirror 118 .

The first facet mirror 119 is arranged in an oblique manner with respect to the arrangement plane defined by the second facet mirror 121 .

FIG. 2 shows an exemplary DUV projection exposure apparatus 200 . The DUV projection exposure device 200 includes: an illumination system 201; a device called a mask table 202, which is used to receive and precisely position a mask 203, and the subsequent structure on the wafer 204 is determined by the mask 23; for holding, the wafer holder 205 for moving and precisely positioning the wafer 204; In the lens housing 209 of the projection optical unit 206 .

As an alternative or in addition to the shown lens element 207, various refractive, diffractive and/or reflective optical elements may be provided, in particular mirrors, prisms, termination plates or the like.

The basic functional principle of the DUV projection exposure apparatus 200 enables the imaging of structures introduced into the mask 203 onto the wafer 204 .

Illumination system 201 provides projected beam 210 in the form of electromagnetic radiation, which is required to image mask 203 on wafer 204 . Lasers, plasma sources, etc. can be used as sources of this radiation. The radiation is shaped in the illumination system 201 by means of optical elements such that the projection beam 210 has desired properties with respect to diameter, polarization, wavefront shape, etc. when it is incident on the mask 203 .

The image of mask 203 is generated by projection beam 210 and transferred from projection optics unit 206 to wafer 204 in a suitably reduced form. In this case, the mask 203 and the wafer 204 can be moved synchronously, so that areas of the mask 203 are imaged almost continuously onto corresponding areas of the wafer 204 during a so-called scanning procedure.

The air gap between the last lens element 207 and the wafer 204 can optionally be replaced by a liquid medium with a refractive index greater than 1.0. For example, the liquid medium can be high purity water. This setup is also known as immersion lithography and has increased optical lithography resolution.

The use of the invention is not restricted to use in projection exposure apparatuses 100 , 200 , in particular not to the described structures. Neither should the invention and the following exemplary embodiments be construed as limited to a particular design. The following drawings show the invention by way of example and highly schematic only.

Target deformations of the optical elements 118, 119, 120, 121, 122, Mi, 207 of a projection exposure apparatus (eg projection exposure apparatus 100, 200) may be particularly suitable for correcting their imaging aberrations. This is the starting point of the present invention.

3 to 13 show in an exemplary and very schematic manner various exemplary specific embodiments of the optical assembly 1 according to the invention. The optical assembly 1 facilitates targeted deformation of the optical element 2 , in particular for correcting imaging aberrations in the projection exposure apparatus 100 , 200 . The optical element 2 to be deformed can in particular be arranged in the illumination optics unit 103 and/or the projection optics unit 109 , 206 of the projection exposure apparatus 100 , 200 .

In the exemplary embodiment, the optical element 2 is represented as a mirror in an exemplary manner; however, this should not be construed as limiting. The optical element 2 has an optically active front side 3 and a back side 4 remote from the front side 3 . When impinging on the optical element 2 , the illuminating radiation 115 or the projection beam 210 is influenced in a defined manner by the optically active front side 3 , in particular to guide the beam path.

First, it is intended to describe a first exemplary embodiment of the proposed optical assembly 1 based on FIGS. 3 and 4 .

The optical assembly 1 includes a plurality of electrostatic actuators 5 distributed along the backside 4 of the optical element 2 . In particular, the actuators 5 can be distributed in a grid-like manner along the rear side 4 of the optical element 2 , as can be seen particularly clearly on the basis of FIG. 4 . Each actuator 5 has an electrode pair consisting of two spaced apart electrodes 6,7.

Preferably, the electrodes 6, 7 of the common electrode pair are arranged to extend parallel to each other (in their non-deflected state), as shown in all exemplary embodiments. In principle, however, configurations inclined with respect to each other can also be provided.

Each actuator 5 is configured and mechanically coupled to the backside 4 of the optical element 2 such that it is generated by an electrical control voltage U1 _...n between the electrodes 6, 7 of the electrode pair and is used to deform the optical element 2 The electrostatic force is transferred to the optical element 2. For illustration purposes, FIG. 3 and subsequent FIGS. 5 to 7 show in each case one of the actuators 5 in a deflected state and thus the optical element 2 in a partially deformed state.

For a sufficiently high dynamic effect and to increase the dielectric strength between the electrodes 6, 7, a solid or liquid dielectric 8 is arranged between the electrodes 6, 7 of the electrode pair. Optionally, a gaseous dielectric 8 may also be provided, but preferably a gaseous dielectric 8 other than air. In the exemplary embodiment of FIG. 3 , a solid medium is provided as dielectric 8 , which is shaded in FIG. 4 for illustration. Instead, liquid media are provided in the exemplary embodiments that follow.

Preferably, the solid medium according to the exemplary embodiment of FIGS. 3 and 4 is deformable to facilitate reducing the distance between the electrodes 6 , 7 in the deflected state of the actuator 5 . Alternatively, however, it is also possible for the dielectric 8 not to completely fill the interspace between the electrodes 6 , 7 . For example, it is possible to arrange the dielectric 8 only on one of the two electrodes 6 , 7 or to coat the electrodes 6 , 7 with an insulating layer of the dielectric 8 . In this way, the dielectric strength and force of the actuator 5 can be increased.

In the exemplary embodiment, one of the electrodes of the electrode pair is designed as a control electrode 6 , to which the control voltage U _{1 . . . n} is applied. The other electrode is in the form of a reference electrode 7 to which a common reference potential GND can be applied together as well as to further reference electrodes 7 of other actuators 5 .

In the exemplary embodiment of FIGS. 3 to 8 and 13 , one of the electrodes 6 , 7 , preferably the reference electrode 7 as shown, is mechanically coupled to the backside 4 of the optical element 2 . A further electrode 6 , 7 , preferably a control electrode 6 as shown, is mechanically coupled to a reference body 9 , which is spaced apart from the backside 4 of the optical element 2 .

For example, the reference body 9 can be a mount of the optical element 2 , a fixing frame of the optical element 2 , or even the optical element 2 itself.

In the exemplary embodiment of FIGS. 3 to 7 , the reference body 9 is fixed to the optical element 2 by means of longitudinal struts 10 (see also FIG. 4 in particular) distributed along the back side 4 of the optical element 2 . Each actuator 5 is arranged between each bearing strut 10 . In the exemplary embodiment of FIGS. 3 to 8 , the actuators 5 are arranged parallel to the back side 4 of the optical element 2 .

A control device 11 , shown with dashed lines in FIG. 3 , can be provided for generating control voltages U _{1 . . . n} for the actuators 5 . The control device 11 can be configured to deform the optical element 2 in a targeted manner.

However, the control device 11 can also be configured to use the actuator 5 as a sensor unit by being excited with the control voltage U _{1 . . . n} in a frequency range that is not important for the deformation operation. In this way it is possible to capture the actual state of deformation of the optical element 2, for example in a higher frequency band. The method described above and below for deforming the optical element 2 can be implemented as a computer program product with program code means on the control device 11 .

It is preferably provided that the dielectric medium 8 is a liquid medium, especially distilled water or formamide. For example, FIG. 5 shows a corresponding embodiment. In order to facilitate the liquid medium exchange between the actuators 5 , in the exemplary embodiments of FIGS. 5 to 13 , corresponding fluid connections are established between pairs of electrodes of adjacent actuators 5 . In the exemplary embodiment of FIGS. 5 to 8 , the fluid connection between the actuators 5 is achieved by means of corresponding holes 12 through bearing struts 10 arranged between the actuators 5 . An inflow port 13 and an outflow port 14 for a liquid medium may be provided, which are fluidly connected to the actuator 5 such that the electrode pairs of the actuator 5 are flushed with the liquid medium, as shown in FIG. 5 . To this end, a turbine, such as a pump (not shown), can optionally also be provided.

However, in particularly preferred embodiments a closed system is provided, as shown in the following exemplary embodiments. In this case, expansion possibilities may preferably be provided for the liquid medium, in particular in order to facilitate thermally induced expansion and/or displacement of the dielectric medium 8 in the event of deflection of the actuator 5 . In this regard, by way of example, a balancing container 15 may be provided which is fluidly connected to one of the actuators 5 to facilitate the expansion of a liquid medium (via a network of fluid connections) into the balancing container 15 . The balancing bellows are shown in an exemplary manner in the figure. In order to facilitate the separation of the actuators 5 from each other, it is possible to provide a plurality of balancing containers 15, such as the balancing container 15 shown in FIG. 7 for each actuator 5 .

In the exemplary embodiments shown in FIGS. 3 to 7 , one of the electrodes 6 , 7 of the electrode pair, in the present case the corresponding reference electrode 7 , is in each case fixed directly to the optical element 2 . This can facilitate localized or short wavelength deformation of the optical element 2, as shown. However, to the extent that global deformation or longer wavelength deformation is required, the electrodes 6, 7 coupled to the optical element 2 (in particular the reference electrode 7) can be arranged to pass through an intermediate element spaced from the backside 4 of the optical element 2 16 to connect indirectly to the optical element 2. This is shown based on FIG. 8 .

In this case, reference body 9 can be fixed via bearing struts 10 to intermediate element 16 which itself is secured to optical element 2 via spacer struts 17 distributed along back side 4 of optical element 2 . The bearing strut 10 and the spacer strut 17 can be arranged offset along the rear side 4 of the optical element 2 , the spacing strut 17 being arranged as centrally as possible on the optical element 2 below the actuator surface or electrode surface. In this way, the optical element 2 can be influenced particularly advantageously.

As can be seen from the exemplary deflection in FIG. 8 , the intermediate element 16 can cause a certain degree of decoupling between the individual actuators 5 and the optical element 2 , as a result of which global deformation or long wavelength deformation of the optical element 2 is possible. This may be advantageous for some applications.

9 to 12 show alternative embodiments of the optical assembly 1 . Figure 9 shows the optical assembly 1 in the non-deflected state of the actuator 5, and Figure 10 shows the optical assembly with the deflected actuator 5, which is purely exemplary and only to be understood as a schematic diagram.

11 and 12 show possible grid configurations for the distribution of the actuators 5 along the backside 4 of the optical element 2 . The variants shown in Figures 9 to 12 are particularly suitable for rectangular distribution configurations (see Figure 11) or linear configurations (see Figure 12).

In Figures 9 to 13, the dielectric 8 has been masked to simplify the drawing. Again preferably a liquid medium is provided. In the exemplary embodiment of FIGS. 9 to 13 , the fluid connection between the actuators 5 is provided by an appropriate spacing of the reference bodies 9 and the channels 18 formed thereby. A common balancing container 15 is provided as an example only.

As presented on the basis of FIGS. 9 and 10 , the two electrodes 6 , 7 of the electrode pair can also be mechanically coupled to the optical element 2 . To this end, the electrodes 6 , 7 can in particular be arranged on opposite side walls of a cutout 19 , eg a groove, starting from the back side 4 of the optical element 2 . For example, the sidewalls may be (fully or partially) coated with a dielectric. When a suitable electrical control voltage U ₁ . Relatively long wavelengths or global deformations can also be achieved in this way, in a manner similar to the exemplary embodiment in FIG. 8 with the intermediate element 16 .

FIG. 13 shows another exemplary embodiment of the optical assembly 1 . The electrode 7 is again coupled to the optical element 2 and for this purpose is arranged on the side wall of the cutout 19 extending from the back side 4 into the optical element 2 . In contrast, the electrode 6 coupled to the reference body 9 is arranged on (or forms the protrusion 20 itself) a protrusion 20 extending from the reference body 9 to the cutout 19 of the optical element 2 . This also advantageously allows introducing forces directly into the optical element 2 in a manner similar to that described for the exemplary embodiment based on FIGS. 9 and 10 . In addition to the channel 18 between the actuators 5, a hole 12 may be provided in the protrusion 20 to provide a fluid connection.

Optionally, the force of the individual actuators 5 can be further increased in the exemplary embodiment of Figure 13, as shown, if two electrode pairs are provided instead of one electrode pair, the corresponding control electrodes 6 are electrically connected to each other. _{n, which can have the same control voltage U 1} . In this way, the effective electrode area can be doubled.

Naturally, it is also possible to provide a structure in which the reference electrode 7 protrudes from the reference body 9 into the cutout 19 .

Finally, it should be pointed out that the specific exemplary embodiments shown can in principle always be combined with one another, as long as this is not excluded from a technical point of view. Furthermore, further specific embodiments of the actuator 5 and alignment/configuration of the electrodes 6, 7 of the electrode pair may be provided. In particular, the geometric relationships and proportions shown are purely schematic and exemplary and should not be construed as true to scale.

Another option for increasing the electrostatic force is also possible in the teething of the electrodes 6 , 7 of a common electrode pair and/or in dividing the individual electrodes 6 , 7 between a plurality of individual electrodes.

1: Optical assembly 2: Optical element 3: Front side 4: Back side 5: Actuator 6: Electrode 7: Electrode 8: Dielectric 9: Reference body 10: Bearing strut 11: Control device 12: Hole 13: Inflow port 14: Outflow port 15: Balance container 16: Intermediate element 17: Spacer strut 18: Channel 19: Cutout 20: Protrusion 100: EUV projection exposure device 101: Illumination system 102: Radiation source 103: Illumination optics unit 104: Object field 105 : object plane 106: mask 107: mask holder 108: mask displacement driver 109: projection optical unit 110: image field 111: image plane 112: wafer 113: wafer holder 114: wafer displacement driver 115: Illumination radiation 116: Collector 117: Intermediate focal plane 118: Deflecting mirror 119: First facet mirror 120: First facet mirror 121: Second facet mirror 122: Second facet 200: Projection exposure device 201: illumination system 202: mask table 203: mask 204: wafer 205: wafer holder 206: projection optical unit 207: lens element 208: mount 209: lens housing 210: projection beam M1-M6: reflection Mirror U ₁ -U _n : Control Voltage

In the figures, functionally identical elements have the same reference symbols. The schematic diagram is:

Figure 1 shows a longitudinal section of an EUV projection exposure device;

Figure 2 shows a DUV projection exposure device;

Figure 3 shows a transverse cross-sectional view of an optical assembly having an optical element, a reference body and a plurality of electrostatic actuators, wherein a solid dielectric is disposed between the reference body and the optical element;

Figure 4 shows an excerpt from the cross-sectional view along cutting line IV in Figure 3, used to represent the grid-like configuration of the actuators along the backside of the optical element;

Figure 5 shows a transverse cross-sectional view of an optical assembly according to another exemplary embodiment, with inflow and outflow ports for the liquid dielectric and fluid connections between the actuators;

Figure 6 shows a transverse cross-sectional view of an optical assembly having a fluidic connection between a balancing container for liquid dielectric and the actuator according to another exemplary embodiment;

Figure 7 shows a transverse cross-sectional view of an optical assembly according to yet another exemplary embodiment, with fluid connections between a plurality of balancing containers for liquid dielectrics and actuators;

8 shows a transverse cross-sectional view of an optical assembly according to another exemplary embodiment, with a balancing container for a liquid dielectric, a fluid connection between the actuator, and a configuration between the actuator and the optical element. intermediate elements between

Figure 9 shows a side view of an optical assembly according to another exemplary embodiment, wherein electrodes are disposed within cutouts on the backside of the optical element, in a non-deflected state of the actuator;

Figure 10 shows the optical assembly of Figure 9 in the deflected state of the actuator;

Figure 11 shows an example of a grid configuration of the actuators of the optical assembly according to Figure 9;

Figure 12 shows an example of another grid configuration of the actuator of the optical assembly according to Figure 9; and

Figure 13 shows a side view of an optical assembly according to another exemplary embodiment, wherein electrodes are disposed within cutouts on the back side of the optical element.

1: Optical components

2: Optical components

3: front side

4: dorsal side

5: Actuator

6: Electrode

7: Electrode

8: Dielectric

9: Reference body

10: Bearing strut

11: Control device

115: Illumination radiation

210: Projection Beam

U ₁ -U _n : Control voltage

Claims (26)

An optical assembly comprising an optical element having an optically active front side and a back side remote from the front side, and a plurality of electrostatic actuators distributed along the back side of the optical element, each actuator comprising two spacers An electrode pair of open electrodes, each actuator configured and mechanically coupled to the backside of the optical element such that an electrically controlled voltage across the electrodes of the electrode pair generates an electrostatic force, which uses For deforming the optical element and being transferred to the optical element, it is characterized in that a dielectric is arranged between the electrodes of the electrode pair. The optical component as claimed in claim 1, wherein the dielectric is a solid or liquid dielectric. The optical component as claimed in claim 1 or 2 is characterized in that a dielectric constant of the dielectric is greater than that of vacuum, preferably greater than that of air. The optical component according to any one of claims 1 to 3, wherein a dielectric strength of the dielectric is greater than that of air. The optical component as described in any one of claims 1 to 4, wherein one of the electrodes of the electrode pair is designed as a control electrode, the control voltage can be applied to the control electrode, and in addition An electrode is designed as a reference electrode, to which a common reference potential can be applied together and to the reference electrode of at least one further actuator. An optical component as claimed in any one of claims 1 to 5, wherein one of the electrodes of the electrode pair is mechanically coupled to the backside of the optical element, and the other electrode is mechanically coupled to a reference body spaced from the backside of the optical element. The optical component as claimed in claim 6, wherein the electrode coupled to the optical element is fixed directly to the optical element. The optical component of claim 6, wherein the electrode coupled to the optical element is indirectly connected to the optical element via an intermediate element spaced apart from the backside of the optical element. The optical component as claimed in item 8, characterized in that the intermediate element is fixed to the optical element by a plurality of spacer elements and/or a plurality of spacer struts, and the spacer elements and/or the spacer struts are along the optical element The dorsal distribution configuration of this. The optical component according to any one of claims 6 to 9, characterized in that the reference body is fixed to the optical element or the intermediate element by a plurality of bearing units and/or a plurality of bearing posts, the bearing units And/or the bearing struts are distributed along the back side of the optical element. The optical component as claimed in claim 9 and 10 is characterized in that the spacer units or the spacer struts deviate from the bearing units or the bearing struts along the back side of the optical element. Optical component according to any one of claims 6 to 11, characterized in that the electrode coupled to the optical element extends parallel to the back side of the optical element. The optical component as claimed in any one of claims 6 to 11, wherein the electrode coupled to the optical element is disposed on a side wall of a cutout extending from the back side into the optical element, the electrode Coupled to the reference body, the reference body is disposed on a protrusion extending from the reference body into the cutout of the optical element. Optical component according to any one of claims 1 to 5, characterized in that the two electrodes of the pair of electrodes are mechanically coupled to the optical element and are arranged for this purpose in extending from the back side into the optical element on opposite sides of a cutout. The optical component according to any one of claims 1 to 14, characterized in that the dielectric medium is a liquid medium, preferably distilled water or formamide. The optical component according to claim 15, wherein a fluid connection is formed between the electrode pairs of adjacent actuators to facilitate the exchange of the liquid medium between the actuators. The optical assembly as claimed in claim 15 or 16, wherein at least one balancing container is fluidly connected to one of the actuators, a plurality of the actuators, or all of the actuators , to facilitate the expansion of the liquid medium into the equilibrium vessel. Optical assembly according to any one of claims 15 to 17, characterized in that at least one inlet and at least one outlet for the liquid medium are fluidly connected to the actuators so that the liquid medium can be flushed the electrode pairs of the actuators. The optical component according to any one of claims 1 to 18, characterized in that the electrodes of the electrode pair are arranged to extend parallel to each other. The optical component according to any one of claims 1 to 19, characterized in that the actuators are distributed in a grid along the back side of the optical element. Optical component according to any one of claims 1 to 20, characterized in that a control device is used to generate control voltages for the actuators to deform the optical element in a targeted manner. Optical assembly as claimed in claim 21, characterized in that the control means is configured to use the actuators as multiple sensing devices by exciting with the control voltage in a frequency range not important for deformation operation device unit to record an actual state of deformation. A method for deforming an optical element by means of a plurality of electrostatic actuators each having an electrode pair of two spaced apart electrodes, according to which method a control voltage is applied to the electrode pair between the electrodes of the pair to generate an electrostatic force transferred from the actuator to the optical element to deform the optical element, characterized in that a dielectric is arranged between the electrodes of the pair of electrodes . A computer program product having program code means for implementing a method for deforming an optical element according to claim 23 when the program is executed on a control device. A method for manufacturing an optical assembly comprising an optical element having an optically active front side and a back side remote from the front side and a plurality of electrostatic actuators each comprising two spaced apart electrodes A pair of electrodes, the actuators are mechanically coupled to the backside of the optical element according to the invention, such that an electrically controlled voltage across the electrodes of the pair generates an electrostatic force for The optical element is deformed and can be transferred to the optical element, characterized in that a dielectric is introduced between the electrodes of the electrode pair. A lithographic projection exposure device comprising an illumination system, the illumination system comprising a radiation source, an illumination optical unit, and a projection optical unit, wherein the illumination optical unit and/or the projection optical unit comprise claims 1 to 22 The at least one optical component described in any one of.

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