Method for manufacturing a projection lens, projection lens, projection exposure system, and projection exposure method

Abstract

The invention relates to a method for manufacturing a projection lens for imaging a pattern arranged in an object plane of the projection lens onto an image plane of the projection lens, said method comprising the following steps: assembling the projection lens by arranging a plurality of optical elements in accordance with a specification in such a way that optical surfaces of the optical elements form a projection beam path through which a pattern arranged in the object plane can be imaged onto the image plane by means of the optical elements, wherein at least one manipulator of a wavefront manipulation system is integrated in order to dynamically influence the wavefront of the projection radiation in response to control signals from a control unit of the wavefront manipulation system, wherein the manipulator comprises at least one manipulator element having at least one manipulator surface arranged in the projection beam path, and comprises an actuating device, which can be controlled by control signals from the control unit, for reversibly altering the optical effect of the manipulator element; measuring the projection lens, involving spatially resolved determination of the wavefront, for the spatially resolved determination of wavefront errors, wherein the manipulator element has a starting configuration during the measurement; calculating a first configuration of the manipulator element, which first configuration is suitable for correcting the wavefront errors; defining a first operating mode of the control unit, wherein, in the first operating mode, the control unit generates first control signals that cause the actuating device to set the manipulator element to the first configuration.

Description

[0001] Method for producing a projection lens, projection lens, projection exposure apparatus and projection exposure method

[0002] The following disclosure is based on the German patent application with the file number 10 2023 115 801.5, filed on June 16, 2023. The disclosure content of this patent application is incorporated by reference into the content of the present application.

[0003] FIELD OF APPLICATION AND STATE OF THE ART

[0004] The invention relates to a method for producing a projection lens, a projection lens produced by means of the method, a projection exposure apparatus and a projection exposure method.

[0005] Microlithographic projection exposure processes are predominantly used today to manufacture semiconductor components and other finely structured parts, such as micro-electronic-mechanical systems (MEMS). These processes involve masks (reticles) or other pattern-generating devices that carry or form the pattern of a structure to be imaged, e.g. a line pattern of a layer of a semiconductor component. The pattern is positioned in a projection exposure system between an illumination system and a projection lens in the area of ​​the object plane of the projection lens and illuminated with illumination radiation provided by the illumination system. The radiation modified by the pattern passes as projection radiation through the projection lens, which images the pattern onto the substrate to be exposed, usually at a reduced scale.The surface of the substrate is positioned in the image plane of the projection lens, which is optically conjugate to the object plane. The substrate is usually coated with a radiation-sensitive layer (resist, photoresist).

[0006] Projection exposure systems with high-resolution projection lenses currently operate at wavelengths of less than 260 nm in the deep ultraviolet (DUV) or extreme ultraviolet (EUV) range, e.g., wavelengths between 6 nm and 20 nm. They typically incorporate a multitude of optical elements to accommodate sometimes conflicting requirements for correcting aberrations, even when large numerical apertures are used. Both refractive and catadioptric projection lenses used in microlithography often have ten or more transparent optical elements. EUV lithography systems attempt to use as few reflective elements as possible, e.g., four or six mirrors. For projection lenses, the total aberrations are the sum of the errors of the individual optical elements contributing to the image.Since error tolerances for individual components cannot be reduced arbitrarily, alignment of the entire system is usually required to minimize the overall system errors. Such an alignment process is very complex, for example, with high-performance projection lenses for microlithography. Without complex alignment, the required imaging performance with resolutions in the submicrometer range cannot be achieved with these complex optical systems.

[0007] An alignment process typically involves several different manipulations of lenses and / or mirrors and / or other optical elements. These include lateral displacements of the elements perpendicular to a reference axis, displacements along the reference axis to change distances, rotations, and / or tilts of elements. The alignment process is performed under the control of a suitable aberration measurement of the projection lens to verify the effects of the manipulations and derive instructions for further alignment steps.

[0008] Even after extensive adjustment, residual errors may remain that can only be eliminated with significantly increased adjustment effort or not at all. If the errors exceed the specifications for the optical system, further measures are required to improve imaging performance. One measure is the introduction of so-called "corrective aspheres" into the optical imaging system. These are often referred to by the abbreviation ICA (integrated correction asphere). By using corrective aspheres, any residual errors that may exist can be further minimized.

[0009] US Pat. No. 6,268,903 B1 (corresponding to EP 724 199 B1) describes an adjustment method for an optical imaging system for which a correction element is manufactured based on a distortion measurement. For this purpose, a correction element, which is part of the projection lens, is provided at a predetermined location in the imaging system. After measuring the distortion of the system, the topography of the surface of the correction element is calculated, which is required to eliminate the corresponding distortion component. The correction element is then removed from the projection system, and the correction surface is machined. The correction element is then reinserted.

[0010] US Patent No. 5,392,119 (see also WO 96 / 07075) describes a method for correcting aberrations in an optical imaging system. This method involves measuring at least one aberration on the imaging system, such as distortion, field curvature, spherical aberration, coma, or astigmatism. Based on the measurements, correction plates are manufactured that are individually adapted to the imaging system. Their correction surfaces serve to minimize the measured aberrations. In this way, "glasses" can be retrofitted to an imaging system. This can improve the imaging performance of existing imaging systems.

[0011] Document DE 102 58 715 A1 (corresponding to US Pat. No. 7,283,204 B2) discloses a method for manufacturing a microlithographic projection lens, in which the projection lens is measured after assembly in order to determine the wavefront in the exit pupil or a surface of the imaging system conjugated thereto with spatial resolution and, based on this, to produce a correction surface near the pupil. The surface intended as the correction surface initially remains uncoated during installation, is then processed after removal, for example, by ion beam etching, and is then coated before reinstallation.

[0012] The patent US 10,001,631 B2 describes a projection lens for EUV microlithography and a method for producing an EUV projection lens, in which one or more radiation-permeable film elements are introduced into the projection lens at a suitable point in the beam path, which can influence the local wavefront two-dimensionally in the sense of a corrective asphere by specifically controlling the thickness distribution of the individual layers of the film over the optically free area.

[0013] In addition to the intrinsic aberrations that a projection lens may exhibit due to its optical design and manufacturing, aberrations can also occur during its service life, particularly during the operation of a projection exposure system at the user's site. Such aberrations are often caused by changes in the optical elements built into the projection lens caused by the projection radiation used during use. This problem is often referred to as "lens heating." Other internal or external disturbances can also lead to a deterioration in imaging performance.These include, among other things, a possible scale error of the mask, changes in ambient air pressure, differences in the strength of the gravitational field between the location of the original lens adjustment and the location of use by the customer, changes in the refractive index and / or shape of optical elements due to material changes caused by high-energy radiation (e.g., compaction), deformations due to relaxation processes in the holding devices, the drifting of optical elements, and the like. Modern projection exposure systems for microlithography include an operating control system that allows for timely fine-tuning of imaging-relevant properties of the projection exposure system in response to environmental influences and other disturbances. For this purpose, at least one manipulator is controlled according to the current system state in order to counteract any adverse effects of a disturbance on imaging performance.The system state can be estimated or determined in another way, for example, based on measurements, a simulation and / or on the basis of calibration results.

[0014] The operating control system comprises a subsystem belonging to the projection lens in the form of a wavefront manipulation system for dynamically influencing the wavefront of the projection radiation traveling from the object plane to the image plane of the projection lens. With dynamic manipulation, the effect of the components of the wavefront manipulation system arranged in the projection beam path can be variably adjusted depending on control signals from the operating control system, allowing the wavefront of the projection radiation to be specifically modified. The optical effect of the wavefront manipulation system can be changed, for example, before or during an exposure under certain predefined circumstances or depending on the situation.

[0015] The wavefront manipulation system comprises at least one manipulator, which has at least one manipulator element with at least one manipulator surface arranged in the projection beam path. A manipulator comprises an adjusting device for reversibly changing the optical effect of the manipulator element based on corresponding control signals from the operating control system of the projection exposure system. The optical effect can be changed, for example, by changing the surface shape of a manipulator surface and / or by changing the refractive index distribution within the manipulator element. The change can be designed such that an occurring error is at least partially compensated.

[0016] Manipulators can operate according to different principles. Examples are described in the following documents, among others: US 7112772 B2, WO 2008 / 080537 A1, WO 2022 / 074022 A1, US 2009 / 257032 A1, US 9651872 B2. TASK AND SOLUTION

[0017] The invention is based on the object of providing a resource-efficient method for manufacturing a projection lens that makes it possible to create projection lenses with excellent correction over long periods of use at a reasonable cost. In particular, a method is to be provided that allows the production of projection lenses that could previously only be brought to a sufficiently low residual error level using at least one individually machined correction asphere.

[0018] These objects are achieved by a method having the features of claim 1 and a projection lens having the features of claim 11. Furthermore, a projection exposure method and a projection exposure system are proposed. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated into the description by reference.

[0019] According to one formulation of the invention, a method for producing a projection lens is provided, which is designed to image a pattern arranged in an object plane of the projection lens into an image plane of the projection lens. The projection lens is assembled by arranging a plurality of optical elements according to a specification such that optical surfaces of the optical elements form a projection beam path, via which a pattern arranged in the object plane can be imaged into the image plane using the optical elements.

[0020] When assembling the projection lens, at least one manipulator of a wavefront manipulation system is installed, which is designed to dynamically influence the wavefront of the projection radiation in response to control signals from a control unit of the wavefront manipulation system. The term "dynamic" here means that the optical effect of the manipulator can be changed by appropriate control. Such a manipulator has at least one manipulator element with at least one manipulator surface arranged in the projection beam path, as well as an actuating device controllable by control signals from the control unit for reversibly changing the optical effect of the manipulator element. A manipulator contains one or more actuators, whose current actuating value can be changed or adjusted based on control signals from the operating control system by changing the actuating value. A change in the actuating value can, for example,cause a displacement or deformation of a manipulator element or lead to a change in the temperature distribution in the optically used area. The method comprises at least one measuring operation in which the wavefront of the projection radiation is measured with spatial resolution in order to determine any wavefront errors with spatial resolution. For this purpose, the complete wavefront can be measured near a field plane, in particular near the image plane, with spatial resolution, i.e. for many field points. The wavefront at a specific field point can be described as a phase delay plotted via two-dimensional pupil coordinates and is therefore also spatially resolved in angular space. This two-dimensional angularly resolved wavefront can be measured at many field points, i.e. with spatial resolution. This makes field-point resolved wavefront errors obtainable.

[0021] During this measurement operation, the manipulator element has a starting configuration. The starting configuration is the configuration in which the manipulator element is present during the first measurement operation, with the first measurement operation being the measurement operation that serves to determine the initial state of the projection lens after assembly. In the starting configuration, the manipulator element has a specific optical effect that is known or at least determinable.

[0022] The starting configuration can, in particular, be a neutral configuration of the manipulator element. The term "neutral configuration" refers to a configuration in which the optical effect of the manipulator element corresponds to the desired effect of the manipulator element according to the optical design of the projection lens. The neutral configuration can be described as a configuration that the manipulator element would ideally have if all optical surfaces of the projection lens, including the manipulator element, were designed exactly according to the desired configuration resulting from the optical design calculations. This case, in which the starting configuration corresponds to the neutral configuration, simplifies the further process control. It usually occurs when a new, previously never-used manipulator element is installed.

[0023] The starting configuration of the manipulator element does not have to correspond to its neutral configuration, but can deviate significantly from it. This can be the case, for example, if a manipulator element that has already been used in another projection lens and has been provided with a permanent, individual corrective asphere in order to bring that projection lens into specification is incorporated during recycling. The optical effect of this corrective asphere can then be neutralized or compensated for for use in the newly assembled projection lens. It is highly likely that the wavefront measured during the measuring operation will deviate from the ideally desired wavefront (according to specification). The measuring operation will therefore determine a wavefront error that quantitatively represents the deviation of the measured wavefront from the desired target wavefront.Such deviations from the ideal state are the rule due, among other things, to unavoidable manufacturing errors in the production of the individual optical elements as well as unavoidable errors in the assembly and adjustment of the projection lens.

[0024] The method comprises a calculation operation in which a first configuration of the manipulator element suitable for correcting the wavefront error is calculated. The first configuration usually differs significantly from the starting configuration, in which wavefront errors are still present, and specifies how the manipulator element would have to be configured to eliminate the wavefront errors detected during the measurement operation or at least to compensate them sufficiently so that the projection lens has an imaging performance within the specifications. The first configuration can differ from the starting configuration, for example, in that a manipulator surface of a manipulator element has a different topography or surface shape in the first configuration than in the starting configuration.Alternatively or additionally, the first configuration may also have a different local refractive index distribution within the manipulator element than in the start configuration.

[0025] Which property of the manipulator element is changed to correct the wavefront errors depends, among other things, on the type of manipulator. For example, if the manipulator is a mirror with a deformable mirror surface, the topography of the mirror surface acting as the manipulator surface will change between the initial configuration and the first configuration. If, on the other hand, the manipulator element is a transmissive optical element, it may be that the transition from the initial configuration to the first configuration essentially only changes the refractive index distribution within the optically used area of ​​the manipulator element.This can be the case, for example, if the manipulator is a transparent optical element which is heated and / or cooled to different degrees, either electrically or in some other way, in order to change the local refractive index distribution at different locations in the useful area. In some manipulators, both the topography of at least one manipulator surface and the refractive index distribution in the optically used area (useful area) of the manipulator element change when the control value is changed. For an understanding of this aspect of the invention, it is important that the first configuration of the manipulator element is a configuration which is individualised for the respective state of the projection lens based on the underlying measurement. The first configuration is suitable for compensating for those errors which occur precisely in this projection lens, e.g.were accumulated by previous manufacturing steps and could not be eliminated by the previous adjustment operations.

[0026] The method further comprises defining a first operating mode of the control unit. In the first operating mode, the control unit generates first control signals that cause the actuator to set the first configuration of the manipulator element. This definition step represents the creation of a recipe containing all parameter values ​​that must be set using the control unit to bring the manipulator into the first configuration and thus the imaging performance of the projection lens into specification. The recipe does not need to be implemented or realized during adjustment. The recipe is required in later usage phases.

[0027] The first operating mode can be considered a static operating mode. The manipulator operated in the first operating mode replaces the effect of conventional, individually adjusted corrective aspheres. In other words: As long as the projection lens is operated with the manipulator installed, but the manipulator is not controlled and / or is in the neutral configuration, the imaging performance of the projection lens will generally not reach the required specification for operation. This is achieved when the manipulator is controlled by the control unit according to the first operating mode, i.e., when the manipulator is activated and assumes the first configuration.

[0028] This aspect of the invention can also be described in such a way that a conventional correction asphere, which was manufactured individually for a projection lens and only effects the corresponding correction for the individual, can be replaced by a dynamically controllable manipulator which can be controlled in the first operating mode in such a way that it can replace the effect of the conventional correction asphere.

[0029] Preferably, the assembly and adjustment steps are carried out by the manufacturer of the projection lens at a manufacturing site, while use takes place by an end user at a remote location. After adjustment, the projection lens can be delivered in a not yet fully functional state, in which the manipulator is not activated and is therefore in the start-up configuration, e.g., the neutral configuration. Productive use of the projection lens then takes place after installation in a projection exposure system in a production facility at the site of use. For this purpose, the control unit is switched to the first operating mode before the start of production and generates initial control signals that cause the actuating device to set the first configuration of the manipulator element. This brings the imaging performance into specification.

[0030] In order to be able to quickly and easily adjust the manipulator to the specifications at its point of use, it is preferably provided that a first operating data set representing the first operating mode is stored in a data memory accessible to the control unit. During commissioning of the projection lens at the point of use, the memory contents can then be easily retrieved, allowing the control unit to control the manipulator to set the initial configuration. The correction recipe determined during the measurement operation is thus made available as software or in the form of data at the point of use and can be adjusted there without re-measuring the lens.

[0031] A key advantage of this concept is that the manipulator remains dynamically controllable and can assume additional functions during the operating time of the projection lens or even later. According to a further development, the control device is operable in multiple operating modes, wherein in addition to the first operating mode - and possibly based thereon - at least one second operating mode can be set, in which the manipulator element has a second configuration that has a different optical effect than the first configuration. In contrast to a conventional corrective asphere, the dynamic component of the manipulator is used here to compensate for any wavefront errors that may occur during operation.The manipulator can thus be reconfigured within the projection lens to operate with a second configuration suitable for restoring any correction state that may have been lost over its service life, or for preventing the projection lens from becoming out of specification during operation, for example due to thermal effects. The manipulator can thus perform a dual function: when set to the first configuration, as a replacement for a conventional correction asphere, and in a second configuration, as a dynamically controllable correction means for wavefront errors that occur during operation. The adjustment of projection lenses for microlithography is generally a relatively complex, time-consuming process, as there are many degrees of freedom that can improve imaging performance, but also degrade it.To provide sufficient degrees of correction freedom, at least one additional manipulator is preferably installed in addition to the manipulator. Suitable configurations must then also be found for this. Adjustment is preferably an iterative process, in which the time required is kept to a minimum and the adjustment is carried out in such a way that the adjustment process systematically converges to a sufficient correction state.

[0032] It has proven useful to simulate the effect of controlling the manipulator to set the first configuration during adjustment, without actually controlling the manipulator, while the effects of the other manipulators (one or more) are actually implemented. The first configuration of the manipulator can change slightly several times within the individual adjustment loops to compensate for residual errors in the adjustment of other manipulators until a first configuration is found that is suitable for adequately compensating all residual errors of the projection lens, including those originating from other manipulators.

[0033] Even though extremely tight manufacturing tolerances can now be maintained in the production of projection lenses, each projection lens has its own unique set of wavefront aberrations, which can then be compensated for by a custom-made corrective asphere. However, a conventional corrective asphere is only useful in a single projection lens and, after use, is either not usable at all or can only be used for other purposes after extensive reconditioning. In contrast, preferred embodiments provide for the manipulator to be removed from the projection lens after its service life has expired and, after removal, used as a manipulator element in another projection lens.There, too, a first configuration can be determined during the initial adjustment in which the manipulator element can act as a replacement for a correction asphere, whereby this first configuration usually differs significantly from the one that was set in the other projection lens.

[0034] Manipulators according to this proposal can therefore be reused as manipulators in other projection lenses, even after a period of use in that projection lens, despite the possibility of customizing the optical effect for that projection lens. This type of "recycling" can conserve resources to a considerable extent and achieve significant cost savings without any loss of the desired optical correction effect.

[0035] The new concept also offers advantages over the conventional correction asphere concept with regard to optimizing the optical properties of the manipulator element. In some conventional processes, the surface of an optical element intended as the correction surface initially remained uncoated during installation. Measurements were performed with the manipulator surface uncoated. The manipulator element was then removed, and the correction surface was machined using ion beam etching to modify the surface shape to achieve the desired correction effect. The manipulator element, already mounted in its mount, was then reinstalled. The coating process was thus performed on a manipulator element that was already mounted in its mount.

[0036] In preferred embodiments of the method proposed in this application, however, the manipulator surface is coated with an optical functional layer before installation into the projection lens. The coating operation can be performed before the manipulator element is installed in its mount. This can simplify logistics, among other things.

[0037] According to another aspect of the invention, a projection lens of the type mentioned in the introduction is provided, in which the manipulator element of the manipulator has a starting configuration, in particular a neutral configuration, in the absence of control signals, and the projection radiation has wavefront errors during operation when the manipulator element has the neutral configuration or another starting configuration as its starting configuration. A special feature is that a first operating data record representing a first operating mode is stored in a data memory accessible to the control unit, and that the control unit is configured to generate first control signals in the first operating mode, which cause the actuating device to set a first configuration of the manipulator element suitable for correcting the wavefront errors.

[0038] The projection lens is therefore initially unable to provide the imaging performance specified in the specifications, particularly when the manipulator is not yet activated. However, the user can bring the projection lens into specification during commissioning by switching the control unit to the first operating mode, which results in the manipulator being adjusted so that the manipulator element is designed according to a first configuration such that the wavefront error is corrected at least to the extent that the specification is met.

[0039] The result of the measurement operation performed during the adjustment is transferred to the manipulator element via software for later use. During further operation of the projection lens, the manipulator element can then assume at least one second configuration that differs from the first configuration in order to additionally compensate for wavefront errors that may occur during operation.

[0040] The invention also relates to a projection exposure apparatus which is equipped with such a projection lens and / or is configured to carry out the projection exposure method.

[0041] Advantages of aspects of the invention can be used not only in the new manufacture or initial manufacture of projection lenses, but also in the context of a repair or restoration of a projection lens which, for example, requires maintenance or repair after prolonged use. As already mentioned above, a manipulator of the type described here can be used, among other things, as a replacement for a conventional corrective asphere, namely by setting an initial configuration on the manipulator via which the effect of the conventional corrective asphere to be replaced can be achieved. A "conventional corrective asphere" within the meaning of this application can, for example, be an aspherically curved surface of a lens or a mirror whose surface shape is specifically used to partially or completely compensate for aberration components of an optical system caused by manufacturing defects.The correction asphere is usually a correction asphere that is individually adapted to the projection lens and whose effect is essentially unchangeable, with the help of which residual aberrations remaining after adjustment can be corrected.

[0042] Today, many projection lenses exist in which at least one of the optical elements is configured as a correction element to influence the local wavefront two-dimensionally in a region located in the projection beam path, in the manner of such a fixed correction asphere individually adapted for the projection lens. For example, a corrective asphere can be created on an optical element provided in the optical design by locally machining an optical surface of this element to varying degrees using ion beam machining and / or other means in order to achieve the desired corrective effect.Such corrective aspheres can be formed, for example, on transparent plane plates, but possibly also on flat or curved lens surfaces, which can have a spherical or rotationally symmetrical aspherical shape before the corrective asphere is created and a no longer rotationally symmetrical shape after the corrective asphere is introduced.

[0043] If, after prolonged use of the projection lens, there is reason to fear that the projection lens will soon deteriorate beyond its specifications, for example due to radiation-induced degradation effects or the like, a repair can provide a remedy. According to a method proposed here for repairing a projection lens, an assembly comprising the correction element with the (conventional) corrective asphere is removed from the projection lens, and a replacement assembly is installed in place of the assembly comprising the correction element. The replacement assembly comprises a manipulator of the type described here, the manipulator element of which has a starting configuration, in particular a neutral configuration, which results in the projection radiation exhibiting a wavefront error in the starting configuration of the manipulator element during operation.The repair includes a step in which a first operating data set representing a first operating mode is stored in a data memory accessible to the control unit of the projection lens. The control unit is configured to generate first control signals in the first operating mode, which cause the actuating device of the manipulator to set a first configuration of the manipulator element, in which the manipulator element essentially has the optical effect of the removed correction asphere. This allows a conventional correction asphere, whose optical effect is essentially unchangeable, to be replaced by a correction asphere of identical or nearly identical optical effect generated by controlling the manipulator.

[0044] A repair kit for repairing a projection lens comprises a combination of hardware and software components. The hardware components include the replacement assembly with the manipulator, which can be controlled via the control unit. The software components include the first operating data set, which is stored in the data memory accessible to the control unit and enables the control unit to enter the first operating mode, which then results in the manipulator, which can be used variably, being adjusted to exhibit the effect of the conventional, fixed correction asphere. The data of the first operating data set can be determined mathematically and / or based on measurements. One advantage over the conventional solution is that such a repair kit can, in principle, be used multiple times.In other words, such a repair kit is, to a certain extent, universally applicable, since the combination of hardware and software components is capable of replacing conventional, fixed correction aspheres of various designs. Customization here is not based on a fixed physical property of the correction element, but is achieved through appropriate control.

[0045] Such repair measures can be performed on projection lenses of different designs. For example, a projection lens may already have a dynamically usable manipulator of a wavefront manipulation system, whose manipulator element, for example, a transparent lens or a transparent plate, is provided with a custom-made correction asphere to achieve the projection lens' specifications during initial production. In this case, the assembly containing the correction element already includes a manipulator element and adjustment devices for reversibly changing the optical effect of the manipulator element.Such a manipulator that has become in need of maintenance or repair and that was equipped with a conventional correction asphere to achieve the specification of the projection lens can thus be removed on-site at the user of the projection lens and replaced with an identical manipulator without a correction asphere (or an identical or compatible manipulator with a different correction asphere) in order to then bring the projection lens back into specification with regard to the wavefront errors by means of suitable control according to the described concept.

[0046] It is also possible to replace a conventional, non-manipulable correction element with a corrective asphere with a manipulator of the type described here that can be controlled in the first operating mode. For example, a projection lens can have a transparent plane plate in optical proximity to a pupil plane after initial production. This plane plate with a corrective asphere can be replaced by a manipulator described here with a plane plate-like manipulator element, whereby the effect of the corrective asphere can then be adjusted via software.

[0047] During a repair, it is also possible to leave a conventional correction element with a corrective asphere, which no longer provides the desired corrective effect, in the projection lens and install a manipulator of the type described here at a location that is optically conjugated to the position of the no longer adequately functioning correction element. This allows a corrective effect to be set that at least approximately corrects the error that has occurred in the meantime.

[0048] The present application also discloses novel concepts for recycling optical components for wavefront correction in projection lenses. As already mentioned, a projection lens already in use may include a dynamically usable manipulator of a wavefront manipulation system, whose manipulator element is provided with a custom-made correction asphere to achieve the imaging specification in the projection lens in which it is installed. As long as this manipulator is fundamentally functional, it can also be used in other projection lenses. Such manipulators are therefore suitable for recycling.For example, a still-functional manipulator of this type can be removed from an old installation environment of the projection lens in which it was previously used (first projection lens) and reused in another projection lens (second projection lens). This other projection lens (second projection lens) can, for example, be a projection lens that needs to be repaired and has an identical or compatible dynamically usable manipulator whose manipulator element does not include a custom-made correction asphere. The recycled manipulator (the one with the correction asphere customized to an old projection lens) can now be used as a manipulator in the other projection lens (second projection lens), e.g., in a projection lens that needs to be repaired.This projection lens (the second projection lens) will then exhibit wavefront errors in the initial configuration, which are due to the correction asphere (which is not compatible with the new projection lens). This initial configuration will deviate significantly from a neutral configuration.

[0049] However, the undesirable effect of the correction asphere (which is not adapted to the second projection lens) can be taken into account when calculating the manipulator's first operating mode. The manipulator can be operated in a first operating mode that, on the one hand, compensates for the effect of the (inappropriate) correction asphere and, on the other hand, also compensates for the aberration components that arise during the assembly of the repaired projection lens. This is therefore a case in which the starting configuration for the measurement operation does not correspond to the neutral configuration of the manipulator.

[0050] An analogous procedure for recycling a dynamically usable manipulator is also possible if a dynamic manipulator is installed in the projection lens to be repaired, which was provided with a correction asphere individually adapted to this projection lens.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Further advantages and aspects of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures.

[0053] Fig. 1 shows a microlithography projection exposure apparatus according to an embodiment of the invention;

[0054] Fig. 2 shows a schematic plan view of an embodiment of a transparent manipulator with integrated thin heating conductors;

[0055] Fig. 3 shows in the three sub-figures 3A, 3B and 3C different configurations of the manipulator and its corresponding optical effect on the wavefront error;

[0056] Figs. 4A and 4B show schematic representations of two-dimensional heating profiles according to a conventional method;

[0057] Figs. 5A and 5B show heating profiles according to an embodiment, wherein Fig. 5A shows the first configuration and Fig. 5B shows a second configuration differing therefrom;

[0058] Fig. 6A, 6B and 6C illustrate two different scenarios for repairing a projection lens.

[0059] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] Fig. 1 shows an example of a microlithography projection exposure system (WSC), which can be used in the production of semiconductor devices and other finely structured components. It uses light or electromagnetic radiation from the deep ultraviolet (DUV) range to achieve resolutions down to fractions of a micrometer. The primary radiation source or light source (LS) is an ArF excimer laser with an operating wavelength X of approximately 193 nm. Other UV laser light sources, such as F2 lasers with a 157 nm operating wavelength or KrF excimer lasers with a 248 nm operating wavelength, are also possible.

[0061] An illumination system ILL, located downstream of the light source LS, generates a large, sharply defined, and essentially homogeneously illuminated illumination field at its exit surface ES, which is adapted to the telecentricity requirements of the projection lens PO located downstream in the light path. The illumination system ILL has features for setting different illumination modes (illumination settings) and can, for example, switch between conventional on-axis illumination with varying degrees of coherence and off-axis illumination.

[0062] The optical components that receive the light from the light source LS and form illumination radiation from the light, which is directed onto the illumination field located in the exit plane ES or onto the reticle M, belong to the illumination system ILL of the projection exposure system.

[0063] Behind the illumination system, a device RS is arranged for holding and manipulating the mask M (reticle) such that the pattern arranged on the reticle lies in the area of ​​the object plane OS of the projection lens PO, which coincides with the exit plane ES of the illumination system and is also referred to here as the reticle plane OS. The mask can be moved parallel to this plane for scanner operation in a scanning direction (y-direction) perpendicular to the optical axis OA (z-direction) with the aid of a scanning drive. The device RS comprises an integrated lifting device for moving the mask linearly with respect to the object plane in the z-direction, i.e. perpendicular to the object plane, as well as an integrated tilting device for tilting the mask about a tilt axis running in the x-direction.

[0064] Behind the reticle plane OS follows the projection objective PO, which acts as a reduction objective and projects an image of the pattern arranged on the mask M in a reduced scale, for example in a scale of 1:4 (| ß | = 0.25) or 1:5 (| ß | = 0.20), onto a substrate W coated with a photoresist layer, the light-sensitive substrate surface SS of which lies in the area of ​​the image plane IS of the projection objective PO.

[0065] The substrate to be exposed, which in the example is a semiconductor wafer W, is held by a device WS comprising a scanner drive for moving the wafer synchronously with the reticle M perpendicular to the optical axis OA in a scanning direction (y-direction). The device WS further comprises a lifting device for moving the substrate linearly in the z-direction with respect to the image plane, as well as a tilting device for tilting the substrate about a tilt axis running in the x-direction.

[0066] The device WS, which is also referred to as “wafer stage”, and the device RS, which is also referred to as “reticle stage”, are components of a scanner device which is controlled via a scan control device which, in the embodiment, is integrated into the central control device CU of the projection exposure system.

[0067] The illumination field generated by the ILL illumination system defines the effective object field OF used for projection exposure. In the example, this field is rectangular, with a height A* measured parallel to the scan direction (y-direction) and a width B* > A* measured perpendicular to it (in the x-direction). The aspect ratio AR = B* / A* is typically between 2 and 10, especially between 3 and 6.

[0068] In the example case, the projection lens PO is a catadioptric projection lens that can have a single concave mirror or two concave mirrors.

[0069] The effective object field lies at a distance in the y-direction from the optical axis (off-axis field). The effective image field in the image area IS, which is optically conjugated to the effective object field, is also an off-axis field and has the same shape and the same aspect ratio between height B and width A as the effective object field. The absolute field size is reduced by the image scale ß of the projection lens, i.e., A = I ß IA* and B = | ß | B*.

[0070] It is also possible to use a dioptric projection lens, then an object field centered on the optical axis can be used.

[0071] If the projection lens is designed and operated as an immersion lens, the light passes through a thin layer of immersion liquid located between the exit surface of the projection lens and the image plane IS. In immersion mode, image-side numerical apertures of NA > 1 are possible. A dry lens configuration is also possible, in which case the image-side numerical aperture is limited to values ​​of NA < 1.

[0072] The projection exposure system (WSC) features an operating control system configured to perform timely fine-tuning of imaging-relevant properties of the projection exposure system in response to environmental influences and other disturbances and / or based on stored control data. For this purpose, the operating control system has a plurality of manipulators that allow targeted intervention in the projection behavior of the projection exposure system. An actively controllable manipulator contains one or more control elements (or one or more actuators) whose current control value can be changed based on control signals from the operating control system by making defined control value changes.

[0073] The projection lens or the projection exposure system is equipped, among other things, with a wavefront manipulation system WFM, which is configured to controllably change the wavefront of the projection radiation running from the object plane OS to the image plane IS in the sense that the optical effect of the wavefront manipulation system can be variably adjusted via control signals of an operating control system.

[0074] The wavefront manipulation system of the exemplary embodiment comprises a manipulator MAN comprising a manipulator element ME, which is arranged in the immediate vicinity of the object plane of the projection lens in the projection beam path. The manipulator element is essentially transparent to the wavelength used and has an entrance-side manipulator surface MS1 and an exit-side manipulator surface MS2, through which the projection beam path passes. The optical effect of the manipulator element on the passing projection radiation can be reversibly changed using an adjusting device DR.

[0075] Alternatively or additionally, a manipulator element can be arranged, for example, in a pupil plane or in its optical proximity. The projection lens has several additional manipulators, which are not shown in detail here.

[0076] Fig. 2 shows a schematic plan view of an embodiment of a manipulator MAN. In this embodiment, the manipulator MAN is designed to variably influence the wavefront of the passing projection radiation with high spatial resolution in the radial and azimuthal directions within its useful optical area traversed by the projection radiation. For this purpose, the manipulator has a manipulator element ME in the form of a plane-parallel plate made of material transparent to the projection radiation, in which different two-dimensional temperature profiles can be set across the optically utilized area in such a way that locally warmer zones can be created alongside locally colder zones. For this purpose, devices are provided that allow specific amounts of heat to be specifically supplied to any point in the traversable area in order to generate an uneven temperature profile.The heating device works against the effect of a cooling device, which supports the cooling process.

[0077] The manipulator works similarly to a heated rear window. Conductor tracks EL (see Fig. 3A) made of an electrically conductive material, which as a heating conductor material has a certain electrical resistance, run on and / or in the manipulator element ME. The conductor tracks are relatively thin (e.g., less than 50 pm wide) and, in the example, run like a square grid, electrically insulated from one another with mutual spacing in the x-direction and y-direction. The optical effect of the manipulator element can thus be influenced in a spatially resolved manner by appropriately selectively controlling the conductor tracks by sending a heating current required for heating through a conductor track. The temperature dependence of the optical refractive index of the transparent material of the manipulator element is utilized.By controlling the temperature in the individual areas, the optical path length between the entrance-side manipulator surface MS1 (entrance surface) and the exit-side manipulator surface MS2 (exit surface) can be varied. For a given geometry of the manipulator element, the phase change caused by the passing light is approximately proportional to the temperature change.

[0078] If the manipulator element is not controlled, i.e., the conductor tracks are de-energized and there is no active cooling of the manipulator element, a passing wavefront is practically unchanged, since the optical path length for the radiation is essentially the same at all locations in the useful optical range. However, if a temperature distribution with different warm zones is generated by applying current to corresponding conductor tracks, an optical wavefront passing through the manipulator element experiences a wavefront deformation that correlates with the set temperature profile. Conversely, a deformed wavefront can be corrected by a suitable inverse temperature profile. Electrically controllable manipulators that operate according to this principle are disclosed, for example, in WO 2008 / 034636 A2 (corresponding, for example, to US Pat. No. 8,891,172 B2). The disclosure content of these documents is incorporated into the description by reference.

[0079] During production, the projection lens PO is first assembled. The numerous optical elements required to construct the projection beam path, which are held individually or in groups in mounts, are assembled according to the design specifications to create the projection beam path. The MAN manipulator is also installed during this process. After the initial assembly, the imaging performance of the projection lens is usually still far from the imaging performance required by the specifications.

[0080] Then, a first adjustment loop is run through, in which some or all optical elements whose position can still be adjusted in the installed state are modified in their rigid-body degrees of freedom in such a way as to improve imaging performance. For this purpose, optical elements, such as lenses and / or mirrors, can be moved, rotated, or tilted, for example, perpendicular to the reference axis (optical axis) and / or parallel to it. This initial adjustment process is performed under the control of an aberration measurement to verify the effects of the changes to the manipulators and to derive instructions for further manipulations.

[0081] During these initial adjustment steps, the manipulator MAN is not controlled, so that a homogeneous refractive index is present within the plane plate across the entire useful cross-section. During this phase, the manipulator therefore only has the optical effect of a transparent plane plate, which here corresponds to the optical effect intended for this optical element according to the underlying optical design. This special starting configuration of the manipulator element is also referred to in this application as the "neutral configuration" because the manipulator element exerts its desired effect according to the optical design. In this state of the projection lens, the wavefront of the projection radiation determined by measurement will deviate from the desired wavefront according to the specification; thus, a wavefront error exists.

[0082] A first configuration of the manipulator element is then calculated, which is characterized by the fact that the wavefront error would be compensated or corrected if the manipulator element was in the first configuration. In the example case of the manipulator element that can be heated to varying degrees locally, the first configuration would correspond to a specific local distribution of the refractive index of the manipulator element in the optically used cross-section, or to a corresponding two-dimensional temperature profile or heating profile. If the manipulator element were then placed in the first configuration after the measurement, the detected wavefront error would be more or less completely compensated.

[0083] Experience has shown that a single adjustment loop of this kind is usually not sufficient to reliably bring the projection lens into specification. The adjustment process is therefore generally iterative, involving multiple adjustment loops, with individual or all manipulator elements being adjusted between each adjustment loop. During the adjustment, the effect of controlling the manipulator of the wavefront manipulation system is preferably only considered in simulation, without actually controlling the manipulator, while the adjustments are actually implemented on the other manipulators. The adjustment loops are then run through in such a way that the adjustment process converges such that the imaging performance is brought as close to the specification performance as is possible through adjustments to the other manipulators.

[0084] Once this state is reached, further measurements are taken to determine what the first configuration of the manipulator MAN or the manipulator element must look like to correct the remaining residual aberrations. Based on this, a first operating mode of the control unit is defined. In the first operating mode, the control unit generates initial control signals that cause the actuator to set the first configuration of the manipulator element. The first operating mode thus uses a recipe to control the manipulator so that it assumes the first configuration and thus corrects the residual aberrations.

[0085] To illustrate this approach, Fig. 3 shows three sub-figures (3A, 3B, and 3C) showing different configurations of the manipulator and their optical effects. In each sub-figure, a schematic cross-section through the transparent, plane-parallel manipulator element ME with the conductor tracks EL running through it is shown at the top. Below each sub-figure is a diagram with a schematic representation of a selected wavefront error WF (e.g., distortion) as a function of the location on the x-axis for the corresponding configuration of the manipulator element.

[0086] In the situation shown in Fig. 3A, all conductor tracks EL are de-energized, which is represented by the uniformly small dot size. This configuration corresponds to a neutral configuration (CONF-O) of the manipulator element. The diagram shows the spatial variation of the wavefront error WF after completion of the adjustment in the situation where the manipulator is in this neutral configuration (CONF-O). A significant spatially dependent wavefront error WF is present.

[0087] Another option for setting the neutral configuration with this manipulator principle is to already apply electrical power to the conductor tracks, but to compensate for the resulting heating with appropriate cooling, so that although the manipulator is already activated, the optical effect of the manipulator element nevertheless corresponds to that of the non-activated, passive mode (without heating and cooling). This type of neutral configuration is therefore operation in the active, switched-on state, in which the cooling power and counter-heating are spatially balanced in all zones, so that the temperature across the glass plate serving as the manipulator element is constant. This does not necessarily mean that the electrical heating power (or current) is the same for all zones. For details of such calibrations, please refer to DE 102013225 381 A1.

[0088] Fig. 3B shows the manipulator element in its first configuration KONF-1, which is assumed when the control unit CU is switched to the first operating mode. In the configuration shown, the manipulator element ME is heated to different local intensities by applying current to the conductor tracks (corresponding to conductor track symbols of different thicknesses), resulting in an uneven temperature profile across the usable area. In the example case, this is calculated such that the wavefront error still present in the situation shown in Fig. 3A is largely compensated and thus lies close to zero across the entire usable cross-section. In this first operating mode, the manipulator MAN thus exerts the effect that was achieved in conventional methods using individually manufactured corrective aspheres.

[0089] A major advantage of the novel approach, however, is that this compensating effect is generated with a dynamically variable manipulator (MAN), whose adjustment range, based on this first configuration, also offers the possibility of compensating for any further wavefront errors that may arise during subsequent operation of the projection exposure system by means of a correspondingly adapted, modified temperature profile. The upper part of Fig. 30 schematically shows how, in a second configuration (KONF-2), the conductor tracks are subjected to uneven heating current in a different way than in the configuration in Figs. 3A and 3B. This corrects the wavefront errors that arise later during operation to such an extent that virtually error-free imaging with wavefront errors at or near zero is ensured.

[0090] The assembly and measurement-assisted adjustment usually take place at the manufacturer of the projection lens.

[0091] The adjustment will then typically result in a configuration in which the projection lens exhibits an intolerable wavefront error as long as the built-in manipulator element is in its neutral configuration (without control by the control unit). According to the adjustment procedure proposed here, the built-in, spatially controlled, thermal manipulator MAN with a controlled heating profile is used for simulating wavefront optimization. The temperature profile associated with the first configuration KONF-1 therefore does not need to be actually generated.

[0092] However, a first operating data set is stored in a data memory accessible to the control unit CU. This first operating data set represents the first operating mode and thus enables the control unit, based on the information in the data set, to set the manipulator element to the first configuration suitable for reducing the wavefront error of the assembled projection lens to such an extent that the imaging performance is within specifications (see Fig. 3B). A heating profile is therefore supplied, which is adjusted when the projection lens is commissioned in order to achieve the promised performance. In other words: For each projection lens, an individual, temporally constant heating profile is supplied upon delivery. This heating profile differs from the neutral profile (neutral configuration) and corresponds to the first configuration of the manipulator element.Only when the manipulator is controlled in the first operating mode is the projection lens initially in specification.

[0093] This approach can replace the conventional procedure, whereby at least one (fixed) correction asphere is created based on the manufacturer's measurements, which is then installed to bring the projection lens into specification before delivery. The corresponding manufacturing effort for surface finishing on the manipulator surface can thus be eliminated. By eliminating the machining step for producing individually adapted correction aspheres, the lead times for generating the corrective effect are significantly reduced.

[0094] A further advantage is that a variably adjustable manipulator MAN can be used for this process, which is not yet individualized to the specific projection lens during installation and which only assumes an initial configuration through a corresponding control profile, which corresponds in terms of its effect to the effect of a conventional correction asphere.

[0095] Advantageously, the manipulator retains its variability, allowing it to be used to compensate for additional wave aberrations that may occur later during the projection lens's lifetime, e.g., due to lens heating (see, for example, Fig. 30). For series production, it is important that all installed manipulators of the same type have the same de facto neutral configuration upon delivery of the system. The corrective effect is then achieved with the activated manipulator only by controlling it according to the recipe determined during measurement for setting the initial configuration.

[0096] This concept significantly increases the service life of the projection lenses available to the end user. Should an installed manipulator require maintenance or repair, it can be removed from the projection lens on-site and replaced with an identically constructed variable manipulator, which, like the replaced manipulator, is in its neutral configuration without control. Simply by appropriate control via the control unit, the heating profile can then be set to compensate for the currently present wavefront errors. Thus, any manipulator of the same design can be used as a replacement part for a repair in the field.

[0097] In order to further illustrate the key differences between conventional methods with built-in manipulators and the method proposed by this application, Figs. 4A and 4B show schematic representations of two-dimensional heating profiles according to a conventional method, and Figs. 5A and 5B show the heating profiles according to an embodiment of the method presented in this application. All figures show a two-dimensional representation of a manipulator element in which the local temperatures T (in arbitrary units, au) are represented in grayscale. The neutral gray in Fig. 4A corresponds to a reference temperature, lighter grayscale corresponds to upward deviations of the local temperature, and darker areas correspond to downward deviations of the local temperature. The deviations are usually in the range of fractions of a Kelvin.

[0098] Traditionally, a built-in dynamic manipulator was used only to compensate for wavefront aberrations that only occurred during operation. Accordingly, the manipulator was delivered in its neutral configuration with a uniform temperature across the entire usable range, so that the optical effect across the cross-section corresponded to that of a plane plate (Fig. 4A). To correct any residual aberrations remaining after alignment, a specially adapted correction asphere was manufactured and installed. During operation of the projection exposure system at the end customer's site, the manipulator was controlled as needed to correct imaging errors by changing the local heating profile (see Fig. 4B). In the alignment procedure presented here, the manipulator is used as an adjustment tool for commissioning to achieve the imaging performance according to the specifications.For this purpose, a heating profile is simulated that is designed such that, in combination with the existing adjustment tools, the specification applicable for commissioning is achieved. This heating profile is made available to the end customer by storing a corresponding data set in a memory accessible to the control unit, and these values ​​can be retrieved to generate the first operating mode. This means that the heating profile of the manipulator usually no longer corresponds to a neutral profile upon acceptance by the customer, but that a locally uneven temperature distribution (according to an initial configuration) with a corresponding effect on the wavefront is already present (Fig. 5A). This effect corresponds to the effect of the conventional correction asphere. During operation at the end customer, however, the manipulator can then also be used as before to correct imaging errors by changing the heating profile (Fig. 5B).The control of the manipulator in a specific situation during operation can thus be considered two-stage. The actually set heating profile is the sum of the heating profile during commissioning (Fig. 5A) and the control profile at the customer's site to compensate for the wavefront error that occurred during operation.

[0099] Further aspects, advantages, and possible uses of the invention are explained with reference to Figs. 6A, 6B, and 6C. The advantages of the invention can also be used for the repair or maintenance of projection lenses that, after extended use, are likely to no longer meet the required specifications for a longer period of time.

[0100] In the schematically illustrated embodiment of Figs. 6A and 6B, the projection lens was brought into specification during original production after completion of the adjustment in solid degrees of freedom using a custom-made correction asphere CAS. For this purpose, a flat plate PP intended for this purpose in the design was provided with a correction asphere CAS on its entrance side (or exit side) based on wavefront measurements using ion beam etching with location-dependently varying material removal. This corrective asphere CAS made it possible to correct the residual aberrations at the time of production. The upper part of Fig. 6A shows the resulting correction element CE, on whose entrance surface the correction asphere CAS was created. The exit side retained its flat original shape. The lower part of the figure shows the resulting wavefront error at that time with a solid line, which is close to zero across the entire field.During operation, the aberration level slowly increased until it reached close to the specification limit (dashed line). In the example case, the projection lens is repaired or brought back into specification by removing the assembly containing the correction element CE from the projection lens and replacing it with a replacement assembly REP equipped with a manipulator element ME that can be heated to varying degrees locally, of the type described in connection with Figs. 2 and 3. The manipulator element ME contains thin conductor tracks EL that can be energized with heating current to adjust the current to a desired refractive index distribution across the cross-section used. The replacement assembly REP, which contains this manipulator element, also includes the associated adjusting devices DR.These hardware components are part of a repair kit (KIT), which, in addition to the hardware component, also includes customized software components. In the example, this includes an initial operating data record, which is stored in a memory (SP) of the control unit (CU).

[0101] Based on the initial operating data, the adjustment device DR, which acts on the manipulator element, can be operated such that the manipulator element ME has essentially the same optical effect as the removed correction element CE with a fixed correction asphere CAS. Additionally, a correction profile can be electronically applied, which also compensates for the residual errors that have built up over time, so that when the manipulator element ME is controlled in the initial operating mode, the residual aberrations again reach a tolerable level with only minor fluctuations across the field. Fig. 6B thus schematically illustrates the hardware and software components of a repair kit that can be used to restore the degraded projection lens to specification.

[0102] A different scenario is explained by comparing Figs. 6C and 6A. In this alternative initial situation (shown by dashed lines), the correction element originally installed in the projection lens, which was provided with a permanent correction asphere CAS, is itself a correction element that can be manipulated via control commands from the control unit using appropriate adjustment devices, i.e., a manipulator element ME. In the example in Fig. 6C, this is a transparent plate in which heating conductors EL are incorporated, via which a selectable heating profile and thus a desired refractive index distribution can be set across the used cross-section (see, for example, Figs. 2 and 3).Such a manipulator can perform a dual function during initial production, not only by preserving the potential for subsequent dynamic wavefront manipulation, but also by compensating for residual aberrations remaining after adjustment by means of a corrective asphere created on a surface of the manipulator element. This makes it possible, for example, to replace an optical element requiring repair or maintenance that is equipped with a conventional corrective asphere in order to bring the projection lens into its original specification. This optical element is replaced by a manipulator of the type described here with a first operating mode that takes over the effect of this corrective asphere and can also dynamically correct effects that may arise during operation.The operating data for setting the first operating mode can be calculated based on the known performance data of the originally installed corrective asphere without further measurement. Alternatively, the first operating data can be calculated based on a field-resolved wavefront measurement of the lens to be repaired and the newly installed manipulator in neutral configuration. The first operating mode can then also take other aging effects of the lens into account.

[0103] In more general terms, a manipulator requiring repair or maintenance, with or without a permanent correction asphere, can be replaced by a manipulator of the new type, which is operated in the first operating mode in order to bring the projection lens into specification.

[0104] Repair scenarios are also conceivable that require the replacement of other optical elements requiring maintenance or repair, i.e., optical elements that do not have a corrective asphere. For example, a manipulator with a conventional corrective asphere or a manipulator with a first operating state can be installed. According to this scenario, replacing the other optical elements results in wavefront errors that were previously only possible by replacing the corrective asphere on a manipulator and thus the entire manipulator. It is now possible to configure the installed manipulator for the first time or to reconfigure it so that an initial operating state is adopted that adequately corrects the residual aberrations present after the replacement.

[0105] This application also discloses concepts for recycling still-functional manipulators that have already been in use in a projection lens for a certain period of time and can now be used in another projection lens, for example, in a projection lens that needs to be repaired. For an explanation, reference is first made to Fig. 6C. This shows a dynamically controllable manipulator element ME with built-in heating elements EL, which, during its first use in a first projection lens, was provided with a correction asphere CAS that was individually tailored to this projection lens. The manipulator element has a "prehistory," so to speak. Just like the manipulator element in Fig. 6B, the manipulator element is suitable for being dynamically controlled by means of a control unit via appropriate actuating devices (not shown in Fig. 6C). This functionality can also be used in recycling scenarios.One scenario involves removing such a still-functional manipulator, which had a conventional correction asphere and had previously been operated conventionally without using the invention, from an old projection lens and reusing the manipulator in a projection lens to be repaired, which, for example, was operated with a corresponding manipulator that lacked a corrective asphere. The newly installed, previously used, and now recycled manipulator can now be operated in an initial operating state that, on the one hand, compensates for the effect of the CAS correction asphere (which is unsuitable for the projection lens to be repaired) and, on the other hand, compensates for the residual aberrations that arise after the initial assembly of the repaired projection lens.Furthermore, the adjustment range of the manipulator is sufficient to dynamically compensate for any aberrations that may occur during operation of the repaired projection lens. Accordingly, such a recycled, used manipulator element with a history can also be used to replace another manipulator element equipped with a different correction asphere in a projection lens to be repaired (or in a newly manufactured projection lens).

[0106] Some aspects of the new concept were explained using the example of a manipulator MAN, which has a manipulator element ME that is transparent to the radiation to be influenced and, by setting different non-uniform temperature profiles in the useful area, exerts a location-dependent effect on the wavefront of the passing radiation. Numerous manipulators that operate according to other principles can be used analogously within the framework of embodiments of the invention. For example, at least one manipulator with an optically transparent manipulator element can be used, which can be deformed locally to varying degrees in response to control signals. Examples of this are described, for example, in US Pat. No. 9,651,872 B2 or US Pat. No. 1,061,206 B2.DE 10 2020 212 742 A1 (corresponding to WO 2022 / 074022 A1) describes manipulators that use a dielectric medium connected to electrodes to change the shape of an optical surface. The manipulator element can be a mirror with a deformable mirror surface configured to reflect EUV radiation. The EUV radiation can, for example, have wavelengths in the range from 6 nm to 20 nm, in particular approximately 13.5 nm or 6.8 nm. DE 198 24 030 A1 discloses a catadioptric projection lens with a specifically deformable concave mirror for correcting wavefront errors.

[0107] In the example, the manipulator is positioned optically close to the object plane, i.e., in optical proximity to a field plane. This allows for different correction effects of varying strengths to be achieved for different field points. A similar approach would be possible with a positioning close to another field plane, e.g., near a real intermediate image. Alternatively or additionally, a manipulator can also be positioned in or near a pupil plane, so that location-dependent, different changes in angular space affect the projection radiation. A positioning in an intermediate region between the field plane and the pupil plane is also possible.

Claims

Patent claims 1. Method for producing a projection lens for imaging a pattern arranged in an object plane of the projection lens into an image plane of the projection lens, comprising the following steps: Assembling the projection lens by arranging a plurality of optical elements according to a specification such that optical surfaces of the optical elements form a projection beam path via which a pattern arranged in the object plane can be imaged into the image plane by means of the optical elements, wherein at least one manipulator of a wavefront manipulation system is installed for dynamically influencing the wavefront of the projection radiation in response to control signals from a control unit of the wavefront manipulation system, wherein the manipulator comprises at least one manipulator element with at least one manipulator surface arranged in the projection beam path and an actuating device controllable by control signals from the control unit for reversibly changing the optical effect of the manipulator element; Measuring the projection lens with spatially resolved determination of the wavefront for spatially resolved determination of wavefront errors, wherein the manipulator element has a starting configuration during the measurement; Calculating a first configuration of the manipulator element suitable for correcting the wavefront errors; Defining a first operating mode of the control unit, wherein in the first operating mode the control unit generates first control signals which cause the actuating device to set the first configuration of the manipulator element.

2. Method according to claim 1, characterized in that the manipulator element has a neutral configuration as a starting configuration when measuring the projection lens, in which an optical effect of the manipulator element corresponds to a desired effect of the manipulator element according to an optical design of the projection lens.

3. Method according to claim 1 or 2, characterized by use of the projection lens after installation in a projection exposure system in a production operation at a place of use, wherein before the start of the production operation the control unit at the place of use is switched to the first operating mode and generates first control signals which cause the actuating device to set the first configuration of the manipulator element.

4. Method according to claim 1, 2 or 3, characterized by: Storing a first operating data record representing the first operating mode in a data memory accessible to the control unit; Retrieving the first operating data set from the data memory to set a first operating mode of the control unit, wherein the control unit generates first control signals in the first operating mode which cause the actuating device to set the first configuration of the manipulator element.

5. Method according to one of the preceding claims, characterized in that the control device can be operated in several operating modes, wherein in addition to the first operating mode at least one second operating mode can be set, in which the manipulator element has a second configuration which has a different optical effect than in the first configuration.

6. Method according to one of the preceding claims, characterized in that in addition to the manipulator at least one further manipulator is installed, preferably several further manipulators being installed.

7. Method according to one of the preceding claims, characterized in that the effect of a control of the manipulator for setting the first configuration is taken into account in a simulation during the adjustment without controlling the manipulator, wherein effects of the at least one further manipulator are actually implemented and / or that the adjustment operation is carried out iteratively in several adjustment loops until a first configuration is found which is suitable for adequately compensating all residual errors of the projection lens, including those originating from other manipulators.

8. Method according to one of the preceding claims, characterized in that the manipulator has a mirror with a deformable mirror surface or that the manipulator element is a transparent optical element, in particular a transparent optical element which is heated and / or cooled to different degrees electrically or in another way in order to change the local refractive index distribution at different locations of the useful area.

9. Method according to one of the preceding claims, characterized in that a manipulator surface is coated with an optical functional layer before installation in the projection lens.

10. Method according to one of the preceding claims, characterized in that the manipulator is removed from the projection lens and, after removal, is used as a manipulator in another projection lens.

11. Projection lens (PO) for imaging a pattern arranged in an object plane (OS) of the projection lens into an image plane (IS) of the projection lens, comprising: a plurality of optical elements arranged in such a way that optical surfaces of the optical elements form a projection beam path in such a way that a pattern arranged in the object plane can be imaged into the image plane by means of the optical elements, at least one manipulator (MAN) of a wavefront manipulation system (WFM) for dynamically influencing the wavefront of the projection radiation in response to control signals from a control unit (Oll) of the wavefront manipulation system, wherein the manipulator has at least one manipulator element (ME) with at least one manipulator surface (MS1) arranged in the projection beam path.MS2) and an adjusting device (DR) controllable by control signals from the control unit for reversibly changing the optical effect of the manipulator element; wherein the manipulator element has a starting configuration (KONF-O) and the projection radiation has wavefront errors in the starting configuration of the manipulator element during operation; characterized in that a first operating data set is stored in a data memory accessible to the control unit (CU), which represents a first operating mode, and the control unit is configured to generate first control signals in the first operating mode, which cause the adjusting device to set a first configuration (KONF-1) of the manipulator element suitable for correcting the wavefront errors.

12. Projection lens according to claim 11, characterized in that the manipulator has a mirror with a deformable mirror surface or that the manipulator element is a transparent optical element, in particular a transparent optical element which can be heated and / or cooled to different degrees electrically or in another way in order to change the local refractive index distribution at different locations of the useful area.

13. Projection exposure method for exposing a radiation-sensitive substrate with at least one image of a pattern of a mask, comprising the following steps: Providing a pattern between an illumination system and a projection lens of a projection exposure apparatus such that the pattern is arranged in the region of the object plane of the projection lens; Holding the substrate such that a radiation-sensitive surface of the substrate is arranged in the region of an image plane of the projection lens that is optically conjugated to the object plane; Illuminating an illumination region of the mask with illumination radiation provided by the illumination system; Projecting a part of the pattern lying in the illumination area onto an image field on the substrate with the aid of the projection lens, whereby all rays of the projection radiation contributing to the image formation in the image field form a projection beam path, Influencing the wavefront of the projection radiation extending from the object plane to the image plane by controlling a manipulator having at least one manipulator element with at least one manipulator surface arranged in the projection beam path and a first adjusting device for reversibly changing an optical effect of the manipulator element; characterized in that the manipulator element has a starting configuration in the absence of control signals, and the projection radiation exhibits wavefront errors in the starting configuration of the manipulator element during operation;a first operating data set is stored in a data memory accessible to the control unit, said first operating data set representing a first operating mode, and the control unit switches to a first operating mode exclusively based on the first operating data set and generates first control signals that cause the actuating device to set a first configuration of the manipulator element suitable for correcting the wavefront errors; 14. A projection exposure method according to claim 13, wherein a projection lens according to claim 11 or 12 is used.

15. Projection exposure system for exposing a radiation-sensitive substrate arranged in the region of an image surface of a projection lens with at least one image of a pattern of a mask arranged in the region of an object surface of the projection lens, comprising: a light source (LS) for emitting light of a working wavelength; an illumination system (ILL) for receiving the light from the light source and for shaping illumination radiation directed onto the pattern of the mask; and a projection lens (PO) for imaging the structure of the mask onto a light-sensitive substrate; wherein the projection lens is configured according to claim 11 or 12.

16. Method for repairing a projection lens with a plurality of optical elements which are arranged according to a specification such that optical surfaces of the optical elements form a projection beam path via which a pattern arranged in the object plane can be imaged into the image plane by means of the optical elements, wherein at least one of the optical elements is configured as a correction element to influence the local wavefront two-dimensionally in a region lying in the projection beam path in the manner of an unchangeable correction asphere individually adapted for the projection lens, the method comprising the following steps: removing an assembly having the correction element; Installing a replacement assembly instead of the assembly having the correction element, wherein the replacement assembly comprises a manipulator of a wavefront manipulation system for dynamically influencing the wavefront of the projection radiation in response to control signals from a control unit of the wavefront manipulation system, wherein the manipulator comprises at least one manipulator element with at least one manipulator surface arranged in the projection beam path and an actuating device controllable by control signals from the control unit for reversibly changing the optical effect of the manipulator element; wherein the manipulator element has a starting configuration and the projection radiation has wavefront errors in the starting configuration of the manipulator element during operation;a first operating data record is stored in a data memory accessible to the control unit, said first operating data record representing a first operating mode, and the control unit is configured to generate first control signals in the first operating mode, which cause the actuating device to set a first configuration of the manipulator element, in which the manipulator element essentially has the optical effect of the removed correction asphere; 17. Method according to claim 16, characterized in that the correction element having the unchangeable correction asphere is designed as a manipulator element of a manipulator which comprises an adjusting device controllable by control signals of the control unit for reversibly changing the optical effect of the manipulator element or that the correction element having the unchangeable correction asphere is a non-manipulable correction element with correction asphere.

18. A repair kit for repairing a projection lens, comprising a combination of hardware components and software components, wherein the hardware components comprise a replacement assembly with a manipulator that is controllable via a control unit; the software components comprise a first operating data set to be stored in a data memory accessible to the control unit of the projection lens, which enables the control unit to assume a first operating mode, which results in the manipulator of the installed replacement assembly being adjusted such that it has approximately or exactly the effect of a fixed correction asphere to be replaced.

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