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

Abstract

The present invention relates to a method for manufacturing a projection lens, the projection lens causing a pattern placed within the objective plane of the projection lens to be imaged onto the image plane of the projection lens, the method comprising: assembling a projection lens by arranging a plurality of optical elements in such a manner that the optical surfaces of the optical elements form a projection beam path, thereby causing a pattern placed within the objective plane to be imaged onto the image plane through the projection beam path by the optical elements, wherein at least one manipulator of a wavefront manipulation system is integrated to dynamically influence the wavefront of the projection radiation in response to a control signal from the control unit of the wavefront manipulation system, the manipulator having at least one manipulator surface positioned within the projection beam path The present invention comprises: a manipulator element and an actuator, the actuator being controlled by a control signal from a control unit to reversibly change the optical effect of the manipulator element; measuring a projection lens, the measurement including a spatially resolved wavefront measurement for spatially resolved wavefront error, the manipulator element having an initial shape during the measurement; calculating a first shape of the manipulator element, the first shape being suitable for correcting wavefront error; and defining a first operating mode of the control unit, in which the control unit generates a first control signal, the first control signal causing the actuator to set the manipulator element to a first shape.

Description

Technical Field

[0001] The following disclosure is based on German Patent Application Publication No. 102023115801.5, filed on June 16, 2023. The disclosure of this patent application is incorporated herein by reference.

Background Art

[0002] Field of the Application and Prior Art The present invention relates to a method for manufacturing a projection lens, a projection lens manufactured by this method, a projection exposure apparatus, and a projection exposure method.

[0003] Currently, the microlithography projection exposure method is mainly used for manufacturing semiconductor components and other micro-structured components, such as microelectromechanical systems (MEMS). Here, a mask (reticle) or other pattern generation device is used, and these pattern generation devices carry or form the pattern of the structure to be imaged, such as the line (straight line) pattern in the layer of a semiconductor component. This pattern is arranged in the region of the object plane of the projection lens between the illumination system and the projection lens in the projection exposure apparatus and is illuminated by the illumination radiation provided by the illumination system. The radiation modified by the above pattern travels through the projection lens as projection radiation, and the projection lens images the above pattern, usually reduced, onto the substrate to be exposed. The surface of the substrate is arranged in an image plane optically conjugate to the object plane in relation to the projection lens. The substrate is generally coated with a radiation-sensitive layer (resist, photoresist).

[0004] Currently, projection lithography systems with high-resolution projection lenses operate in the deep ultraviolet (DUV) or extreme ultraviolet (EUV) range at wavelengths shorter than 260 nm, for example, 6 nm to 20 nm. Typically, these projection lithography systems have a very large number of optical elements, sometimes even using large numerical apertures, to satisfy the somewhat conflicting requirements for correcting imaging aberrations. In the field of microlithography, refractive and catadioptic lenses often have more than 10 transparent optical elements. In systems for EUV lithography, efforts are made to use a minimum number of reflective elements, for example, four or six mirrors.

[0005] In projection lenses, the overall imaging error is given by the sum of the errors of the individual optical elements contributing to imaging. Since the tolerances for individual components cannot be reduced at will, system-wide adjustment is generally required to minimize the overall error in the system. For example, this adjustment process is extremely complex for high-performance microlithography projection lenses. Without complex adjustments, it is impossible to achieve the required imaging performance with submicron-level resolution within these complex optical systems.

[0006] Typically, the adjustment process involves numerous different manipulations of lens elements and / or mirrors and / or other optical elements. These manipulations include lateral displacement of elements perpendicular to the reference axis, displacement along the reference axis for the purpose of changing the spacing, rotation and / or tilting of elements. The adjustment procedure is performed under the supervision of appropriate aberration measurements of the projection lens so that the effects of the manipulations can be checked and instructions for further adjustment steps can be derived.

[0007] Even after complex adjustments, residuals (residual errors) may remain, and these residuals can only be eliminated through significantly increased adjustment costs, or in some cases, not at all through adjustments. If the error exceeds the predetermined specifications for the optical system, further measures are needed to improve imaging performance. One such measure is to introduce what is known as a "correction aspheric surface" into the optical imaging system. These correction aspheric surfaces are often also called abbreviated ICA (integrated correction asphere). Any residuals that may exist can be further minimized by using a correction aspheric surface.

[0008] U.S. Patent No. 6,268,903 (Patent Document 1) (corresponding to European Patent No. 724,199 (Patent Document 2)) describes a method for adjusting an optical imaging method, for the purpose of this method, a corrective element is manufactured based on distortion measurement. For this purpose, the corrective element, which is part of the projection lens, is provided at a predetermined position in the imaging system. After measuring the distortion of the system, the corresponding distortion The topography (overall shape diagram) of the surface of the correcting element, which is necessary to eliminate the component, is calculated. The correcting element is then removed from the projection system, and the corrected surface is processed. After that, the correcting element is reinserted.

[0009] U.S. Patent No. 5,392,119 (Patent Document 3) (see also International Publication No. 96 / 07075 (Patent Document 4)) describes a method for correcting aberrations in an optical imaging system, the method of measuring at least one imaging error, such as distortion, field curvature, spherical aberration, coma aberration, or astigmatism, on the imaging system. A correction plate, individually fitted to the imaging system, is manufactured based on the measurement, and the correction surface of this correction plate functions to minimize the measured imaging error. In this way, "glasses" can be retrospectively fabricated to fit the imaging system. This can improve the imaging performance of existing imaging systems.

[0010] German Patent Application Publication No. 10258715 (Patent Document 5) (corresponding to U.S. Patent No. 7283204 (Patent Document 6)) discloses a method for manufacturing a microlithography projection lens, wherein the projection lens is measured after assembly to measure the wavefront in the exit pupil or on the surface of the conjugate imaging system in a spatially resolved manner, and a corrective surface near the pupil is manufactured based on this. In this case, the surface provided as the corrective surface remains uncoated during the initial installation, is then treated, for example, by ion beam etching after removal, and then coated before reinstallation.

[0011] U.S. Patent No. 1,0001,631 (Patent Document 7) describes a projection lens for EUV microlithography and a method for manufacturing an EUV projection lens, wherein one or more radiation-transmitting film (thin film) elements are introduced at appropriate positions within the beam path of the projection lens, and these film elements can two-dimensionally affect the local wavefront in the sense of corrected aspheric surfaces by target-controlled distribution of the thickness of individual layers of film across an optically transparent region.

[0012] In addition to the inherent imaging errors that a projection lens may have due to its optical shape (its optical design) and manufacturing, imaging errors can also occur during use, particularly during the operation of the projection exposure apparatus by the user. Such imaging errors often result from changes in the optical elements installed within the projection lens as a result of the projection radiation used during use. This area of ​​problem is often addressed under the preceding "lens heating" section. Other internal or external disturbances can also impair imaging performance. These impairments include, among others, possible dimensional errors in the mask, changes in ambient air pressure, differences in the intensity of the gravitational field between the original lens adjustment position and the position used by the customer, changes in the refractive index and / or shape of the optical elements due to material deformation as a result of high-energy radiation (e.g., compaction), deformation due to the relaxation process within the holding device, drift of the optical elements, etc.

[0013] Modern microlithography projection lithography systems are equipped with motion control systems that enable near-instantaneous and delicate optimization of imaging-related characteristics of the projection lithography system in response to environmental influences and other disturbances. To this end, at least one manipulator is operated in a manner appropriate to the current system state to counteract the adverse effects of disturbances on imaging performance. In this case, the system state can be estimated, for example, based on measurements, simulations, and / or calibration results, or confirmed by some other means.

[0014] The motion control system comprises a subsystem belonging to the projection lens, which is in the form of a wavefront manipulation system. This wavefront manipulation system dynamically influences the wavefront of the projection radiation traveling from the objective plane of the projection lens to the image plane. In the process of dynamically influencing the wavefront, the effects of the components positioned within the projection beam path in the wavefront manipulation system can be set in a variable manner based on the control signals of the motion control system, thereby allowing the wavefront of the projection radiation to be modified in a targeted manner. The optical effects of the wavefront manipulation system can be modified, for example, in specific predetermined cases, or depending on the conditions before or during exposure.

[0015] The wavefront manipulation system comprises at least one manipulator, which comprises at least one manipulator element having at least one manipulator surface positioned within the projection beam path. The manipulator comprises an actuation device, which reversibly changes the optical effect of the manipulator element based on a corresponding control signal of the operation control system of the projection exposure apparatus. The optical effect can be modified, for example, by modifying the surface shape of the manipulator surface and / or by modifying the refractive index distribution within the manipulator element. This modification can be designed such that any resulting errors are at least partially compensated by the modification.

[0016] The manipulator can operate based on different principles. Examples thereof are described, inter alia, in the following documents: U.S. Patent No. 7,112,772 (Patent Document 8), International Publication No. 2008 / 080537 (Patent Document 9), International Publication No. 2022 / 074022 (Patent Document 10), U.S. Patent Application Publication No. 2009 / 257032 (Patent Document 11), U.S. Patent No. 9,651,872 (Patent Document 12).

Prior Art Documents

Patent Documents

[0017]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Patent Document 14

Patent Document 15

Patent Document 16

Patent Document 17

Patent Document 18

Summary of the Invention

Problems to be Solved by the Invention

[0018] Problems and Solutions The problem that the present invention addresses is to provide a method for manufacturing a projection lens while reducing resources, which enables the development of a projection lens having an excellent correction state over a long period of use at a reasonable cost. In particular, the intention is to provide a method that enables the manufacture of a projection lens that has hitherto been able to achieve only a sufficiently small residual level using at least one individually processed aspherical surface for correction.

Means for Solving the Problems

[0019] These problems are solved by a method having the features of claim 1 and by a projection lens having the features of claim 11. A projection exposure method and a projection exposure apparatus are also proposed. Advantageous developments are defined in the dependent claims. The language of all claims is incorporated into the description by reference.

[0020] One way in which the present invention is expressed provides a method for manufacturing a projection lens, which is designed to image a pattern placed within the objective plane of the projection lens into the image plane of the projection lens. In this regard, a projection lens is assembled by arranging a very large number of optical elements according to specifications such that the optical surfaces of the optical elements form a projection beam path, and through this projection beam path, a pattern placed within the objective plane can be imaged into the image plane using the optical elements.

[0021] The assembly of the projection lens includes the installation of at least one manipulator of a wavefront manipulation system, which is designed to dynamically affect the wavefront of the projection radiation in response to a control signal from the control unit of the wavefront manipulation system. Here, "dynamic" means that the optical effect of the manipulator can be modified by appropriate activation. Such a manipulator has at least one manipulator element and an actuator, the at least one manipulator element having at least one manipulator surface positioned in the projection beam path, and the actuator is controllable by a control signal from the control unit and functions to reversibly change the optical effect of the manipulator element. The manipulator includes one or more actuators or working members, the current operated values ​​of these actuators or working members can be changed or adjusted by a change in the operated value based on a control signal from the motion control system. A change in the operated value can result in, for example, displacement or deformation of the manipulator element, or a temperature change in the optically used region.

[0022] The above method includes at least one measurement operation in which the wavefront of the projected radiation is measured in a spatially resolved manner, and the possible wavefront error is measured in a spatially resolved manner. For this purpose, the entire wavefront can be measured in a spatially resolved manner, i.e., for a number of field of view points, near the field of view plane, particularly near the image plane. The wavefront at a particular field of view point can be described as a phase delay plotted over the entire two-dimensional pupil coordinate system, and at this point it is also spatially resolved at angular intervals. This two-dimensional angularly resolved wavefront can be measured at a number of field of view points, i.e., in spatial resolution. The wavefront error resolved to the field of view points is obtained as a result.

[0023] For this measurement operation, the manipulator element has an initial shape. In this case, the initial shape is the shape of the manipulator during the first measurement operation, and the first measurement operation serves to establish the initial state of the assembled projection lens. In the initial shape, the manipulator element has a known, or at least identifiable, specific optical effect.

[0024] In particular, the initial shape can be the neutral shape of the manipulator element. Here, "neutral shape" refers to a shape in which the optical effect of the manipulator element corresponds to the effect of the manipulator element intended by the optical design of the projection lens. The neutral shape can be described as the shape of the manipulator element when all optical surfaces of the projection lens, including the manipulator element, are materialized exactly according to the intended shape derived from the optical design calculations. Additional procedures are simplified in such cases where the initial shape corresponds to the neutral shape. Additional procedures usually exist when a new manipulator element that has never been used before is installed.

[0025] However, the initial shape of the manipulator element does not need to correspond to its neutral shape and may deviate significantly from it. For example, this could mean that, in the case of recycling, a manipulator element that has already been used in another projection lens—that is, a used manipulator element—is installed, and the manipulator element may have a permanent, separate corrective aspheric surface to ensure that the other projection lens satisfies the specifications. Therefore, the optical effect of this corrective aspheric surface can be neutralized or compensated for use in a newly assembled projection lens.

[0026] During the measurement process, the measured wavefront is very likely to deviate from the desired wavefront under ideal conditions (according to the specifications). Therefore, the measurement process establishes a wavefront error, which represents the deviation of the measured wavefront from the required target wavefront. Such deviations from the ideal state are common, particularly due to unavoidable manufacturing errors during the production of individual optical elements, and unavoidable errors during the assembly and adjustment of projection lenses.

[0027] The above method includes a calculation operation, which calculates a first shape of the manipulator element suitable for correcting wavefront errors. Typically, the first shape differs significantly from the initial shape in which wavefront errors still exist, and specifies a configuration in which the manipulator element must be made to eliminate wavefront errors established during the measurement operation, or in any case, to compensate for these wavefront errors to the extent that the imaging performance of the projection lens satisfies the specifications. For example, the first shape may differ from the initial shape in that the manipulator surface of the manipulator element has a different topography or surface shape compared to the initial shape. Alternatively, or in addition to this, the first shape may also have a different local refractive index distribution within the manipulator element than the initial shape.

[0028] The characteristics of a manipulator element modified to correct wavefront errors depend, 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 changes between the initial shape and the first shape. In contrast, if the manipulator element is a radiation-transmitting optical element, this may mean that substantially only the refractive index within the optically used region of the manipulator element changes during the transition from the initial shape to the first shape. For example, this may mean that the manipulator is a transparent optical element and is electrically and / or otherwise heated and / or cooled to different degrees to change the local refractive index distribution at different locations within the region of use. In some manipulators, as the manipulated value changes, there is a change in the topography of at least one manipulator surface of the manipulator element, and a change in the refractive index distribution within the optically used region (region of use).

[0029] To understand this aspect of the present invention, it is important here that the first shape of the manipulator element is individually tailored to each state of the projection lens based on the underlying measurements. The first shape is suitable, for example, in the case of this projection lens, for compensating for errors that have accumulated as a result of the preceding manufacturing steps and that have not been eliminated by the preceding adjustment operations.

[0030] As an additional step, the method includes defining a first operating mode of the control unit, in which the control unit generates a first control signal in the first operating mode, which facilitates the actuator setting a first shape of the manipulator element. This defining step represents the creation of a specification that includes all parameter values ​​that must be set using the control unit in order to bring the manipulator to the first shape, and therefore for the imaging performance of the projection lens to satisfy the specifications. This specification does not need to be actually performed or implemented during adjustment. This specification is required in a later stage of use.

[0031] The first operating mode can be considered a static operating mode. In this case, a manipulator operating in the first operating mode replaces the effect of conventional, individually fitted corrected aspherical surfaces. To put it another way: the imaging performance of the projection lens does not satisfy the specifications required for operation as long as the projection lens operates with a manipulator that is normally installed but installed in a neutral shape, and / or with a non-operating manipulator. This imaging performance is achieved when the manipulator is operated by the control unit in the first operating mode, that is, when the manipulator operates and takes on a first shape.

[0032] Aspects of the present invention can also be described as a conventional corrective aspheric surface, which is manufactured on an individual basis for projection lenses and provides the corresponding correction only for individual projection lenses, and can be replaced by a dynamically actuated manipulator, which in a first operating mode can be operated in a manner that can replace the conventional corrective aspheric surface.

[0033] Optionally, the assembly and adjustment steps are performed at the manufacturing site by the projection lens manufacturer, while the projection lens is used by the customer at a remote location. Following adjustment, the projection lens may be supplied in a state that is not yet fully functional, with the manipulator not yet activated and therefore in its initial shape, i.e., neutral shape. In this case, the projection lens is used productively at the location of use, within the scope of the manufacturing operation, following installation in the projection exposure apparatus. For this purpose, before initiating the manufacturing operation, the control unit is switched to a first operating mode and generates a first control signal, which facilitates the actuator setting the first shape of the manipulator element. As a result, the imaging performance satisfies the specifications.

[0034] To ensure that the manipulator can quickly and easily satisfy its intended use at the point of use, it is preferable to prepare to store a first operational data record representing a first operating mode in a data memory accessible to the control unit. In this case, the contents of the memory can be easily read within the range in which the projection lens is operated at the point of use, and thus the control unit can operate the manipulator in a manner in which the first shape is set. Thus, the correction specifications determined within the range of measurement operation can be made available at the point of use, either as software or in the form of data, and can be set at the point of use without new measurements of the lens.

[0035] The substantial advantage of this concept lies in the fact that the manipulator remains a dynamically operable manipulator, allowing for the adoption of additional functions during and even after the operation time of the projection lens. According to the development, the control device is prepared to operate in multiple operating modes, which include, in addition to the first operating mode—optionally, progressing from the first operating mode—at least one second operating mode, in which the manipulator element has a second shape having different optical effects than the first shape. In contrast to conventional corrected aspherical surfaces, here, dynamic components of the manipulator are used to compensate for possible components of wavefront errors that occur during operation. Thus, the manipulator can be reconfigured within the projection lens to operate in the second shape, which is suitable for recovering any corrections that may have been lost throughout the entire period of use, or for avoiding situations where the projection lens fails to meet specifications during operation, for example, due to thermal effects (thermal influences). Therefore, the manipulator can perform a dual function, specifically, as a replacement for conventional corrective aspherical surfaces when a first shape is set, and as a dynamically operable corrective means for wavefront errors that arise in the second shape due to operational reasons.

[0036] Typically, adjusting microlithography lenses is a relatively complex and time-consuming process because there are a great many degrees of freedom that improve imaging performance, but also a great many that degrade it. To provide sufficient freedom for correction, it is preferable to install at least one additional manipulator in addition to the manipulator mentioned above. In this case, a suitable shape for the additional manipulator must also be found. In this case, the adjustment is preferably an iterative process, in which the adjustment is performed in a way that limits costs as much as possible in terms of time and that the adjustment process systematically converges to a sufficiently corrected state.

[0037] In this case, it has been found that the effect of operating the manipulator to set the first shape, along with the effect of the (one or more) additional manipulators that are actually implemented, can be taken into account by simulation during adjustment without actually operating the manipulator. In this case, the first shape of the manipulator can be similarly compensated for residuals when setting other manipulators by applying multiple mirror modifications within separate adjustment loops, and this is done until a first shape is found that is suitable for adequately compensating for all residuals of the projection lens, including residuals arising from other manipulators.

[0038] Even though extremely small manufacturing tolerances can be observed in the manufacture of projection lenses these days, each projection lens has a distinct set of wavefront aberrations, and this distinct set of wavefront aberrations can be substantially compensated for by individually fabricated corrective aspherical surfaces. However, in this case, conventional corrective aspherical surfaces are only useful in a single projection lens and, after being used in a single projection lens, are either completely unusable or, in some cases, can only be used for other purposes after complex reprocessing. In contrast, a preferred example is to provide a manipulator that is removed from a projection lens after its service life has elapsed and is then used as a manipulator element in another projection lens. In this case as well, the scope of the first adjustment may again include determining a first shape, in which the manipulator element can function as a substitute for a corrective aspherical surface, thereby the first shape generally differs significantly from the set in other projection lenses.

[0039] Therefore, regardless of the possibility of individualizing the optical effect for a particular projection lens, the manipulator according to this proposal can still be reused in other projection lenses after use in that projection lens. Such "recycling" allows for significant resource savings and substantial cost reductions without any loss of the desired optical correction effect.

[0040] Compared to the conventional concept of corrected aspherical surfaces, this novel concept also offers the advantage of optimizing the optical properties of the manipulator element. In some conventional methods, the surface of the optical element considered as the corrective surface was uncoated during the initial installation. The above measurements were performed on the uncoated manipulator surface. Subsequently, the manipulator element was removed again, and the corrective surface was treated by ion beam etching to modify the surface shape so that the desired corrective effect would occur. After that, the manipulator element, which was already mounted in its mount, was reinstalled. Thus, the coating process was applied to the manipulator element that was already held by its mount.

[0041] In a preferred example of the method proposed herein, the manipulator surface is coated with an optical functional layer before being placed in the projection lens. The coating operation can be performed before the manipulator element is placed in its mount. This facilitates logistics, in particular.

[0042] In another aspect of the present invention, a projection lens of the type described in the introduction is provided, in which, in the absence of a control signal, the manipulator element of the manipulator has an initial shape, particularly a neutral shape, and the projected radiation has a wavefront error during operation when the manipulator element has a neutral shape or other initial shape as its initial shape. The unique aspect is that, in this case, a first operation data record representing a first operation mode is stored in a data memory accessible to the control unit, and the control unit generates a first control signal in the first operation mode, which facilitates the actuator setting a first shape of the manipulator element suitable for correcting the wavefront error.

[0043] Therefore, initially, that is, especially when the manipulator is not yet operating, the projection lens cannot yet provide the imaging performance specified by the specifications. However, during operation, the user can ensure that the projection lens satisfies the specifications by switching the control unit to a first operating mode, which converts the manipulator in such a way that the manipulator elements are designed in a first shape such that the wavefront error is corrected to at least a degree that satisfies the specifications overall.

[0044] Therefore, the results of measurement operations performed within the adjustment range are transferred to the manipulator element by software for later use. Thus, during additional operation of the projection lens, the manipulator element may also take on at least one second shape to additionally compensate for wavefront error components that still occur during operation, the second shape deviating from the first shape.

[0045] The present invention also relates to a projection exposure apparatus, which comprises such projection lenses and / or is configured to perform the above-described projection exposure method.

[0046] The advantages of the embodiments of the present invention can be utilized not only in the new or initial manufacture of projection lenses, but also in relation to the repair or restoration of projection lenses, for example, when maintenance or repair is required after long-term use. As already stated above, the types of manipulators described herein can be used, in particular, as a substitute for conventional corrective asphericals, specifically because a first shape is set on the manipulator, and the first shape can realize the effect of the conventional corrective aspherical being replaced. "Conventional corrective aspherical" within the scope of this application can be, for example, an aspherical curved surface of a lens element or mirror, the surface shape of which functions to partially or completely compensate in a targeted manner for aberration components of the optical system caused by manufacturing errors. Typically, a corrective aspherical is a corrective aspherical that is fitted to the projection lens on an individual basis, is substantially fixed in terms of effect, and is used to correct residual aberrations that remain after adjustment.

[0047] At that time, numerous projection lenses existed, and in these projection lenses, at least one of the optical elements was configured as a corrective element to two-dimensionally influence a local wavefront in a region located within the projection beam path, in the style of a fixed corrective aspherical surface individually adapted to the projection lens. For example, in optical design, a corrective aspherical surface provided on an optical element can be fabricated by ion beam treatment and / or some other method to locally treat the optical surface of the element to different degrees to achieve the desired corrective effect. For example, such a corrective aspherical surface can be formed on a transparent planar plate, but optionally on the surface of a planar or curved lens element, and these lens element surfaces may have a spherical or rotationally symmetric shape before the corrective aspherical surface is fabricated, and may no longer have a rotationally symmetric shape after the introduction of the corrective aspherical surface.

[0048] If, after prolonged use of a projection lens, it is possible that the projection lens may no longer meet specifications within a foreseeable period due to reasons such as the effects of degradation induced by radiation, this can be corrected by repair. For this purpose, according to the method proposed herein, in order to repair the projection lens, an assembly comprising a corrective element having a (conventional) corrective aspheric surface is removed from the projection lens and a replacement assembly is installed in its place. In this case, the replacement assembly comprises a manipulator of the type described herein, the manipulator element having an initial shape, particularly a neutral shape, and during operation in the initial shape of the manipulator element, the initial shape introduces a wavefront error to the projection radiation. In this regard, the repair includes the step of storing a first operating data record representing a first operating mode in a data memory accessible to the control unit of the projection lens. The control unit is configured to generate a first control signal in the first operating mode, the control signal facilitates the actuator of the manipulator setting a first shape of the manipulator element, in which the manipulator element has an optical effect substantially in which the corrective aspheric surface is removed. This allows us to replace conventional corrected aspherical surfaces, whose optical effects are fixed based on the principle, with corrected aspherical surfaces that have the same or substantially the same optical effects, which are created by operating a manipulator.

[0049] A repair kit for repairing projection lenses comprises a combination of hardware and software components. The hardware component includes a replacement assembly having a manipulator that can be operated by a control unit. The software component includes a first operation data record, which should be stored in a data memory accessible to the control unit, enabling the control unit to adopt a first operation mode, which then results in a manipulator set in a manner having the effect of a conventional fixed corrected aspherical surface, and the manipulator itself is usable in an appropriate manner. The data of the first operation data record can be determined by computer calculation and / or based on measurement.

[0050] The advantage over conventional solutions lies, in principle, in the fact that these repair kits can be reused repeatedly. In other words, these repair kits are, in a sense, universally applicable because the combination of hardware and software components can replace conventional fixed compensating aspherical surfaces that are designed differently. The individualization here is achieved not by the fixed physical properties of the compensating element, but by its proper operation.

[0051] Such repair measures can be applied to projection lenses configured in different ways. For example, a projection lens may already be equipped with a dynamically usable manipulator for a wavefront manipulation system. The manipulator element may be, for example, a transparent lens element or a transparent plate, and may be fitted with a separately manufactured corrective aspheric surface to satisfy the specifications of the projection lens within the scope of the initial manufacture. In this case, the assembly already having the corrective element comprises the manipulator element and an actuator that reversibly changes the optical effect of the manipulator element. Such manipulators may require maintenance or repair, and may be fitted with a conventional corrective aspheric surface to satisfy the specifications of the projection lens, and therefore can be removed on-site at the user of the projection lens and replaced with a structurally equivalent manipulator without a corrective aspheric surface (or a structurally equivalent or compatible manipulator with another corrective aspheric surface), ensuring that the projection lens again satisfies the specifications with respect to wavefront errors through appropriate operation according to the desired concept.

[0052] Conventional, non-operable corrective elements having corrective aspherical surfaces can also be replaced with manipulators of the type described herein, which are operable in a first operating mode. For example, after initial manufacturing, the projection lens may have a transparent planar plate optically positioned near the pupil. This planar plate having a corrective aspherical surface can be replaced with a manipulator having a planar plate-shaped manipulator element described herein, and the effect of the corrective aspherical surface can then be set in a software-controlled manner.

[0053] Within the scope of the repair, it is also possible to leave the conventional corrective element having a positive aspherical surface that no longer provides the desired corrective effect within the projection lens, and to install the type of manipulator described herein in a position optically conjugate to the position of the corrective element that no longer functions adequately. In this case, a corrective effect can be established that at least approximately corrects the errors that have occurred in between.

[0054] This invention also discloses a novel concept for recycling optical components for wavefront correction within projection lenses. As already mentioned, a projection lens already in use may be equipped with a dynamically usable manipulator for a wavefront manipulation system. The manipulator element of this manipulator is equipped with a separately manufactured corrective aspheric surface to satisfy the imaging performance in the projection lens in which the manipulator is installed. As long as this manipulator is functional in principle, it can be optionally used in other projection lenses. Therefore, such manipulators are suitable for recycling. For example, a still-functional manipulator of this type can be removed from its previous installation environment in a projection lens (first projection lens) and reused in another projection lens (second projection lens). This other projection lens (second projection lens) may be, for example, a repaired projection lens equipped with a structurally identical or compatible dynamically usable manipulator whose manipulator element is not equipped with a separately manufactured corrective aspheric surface. The recycled manipulator (a manipulator with a corrective aspheric surface individually fitted to the old projection lens) can then be used as a manipulator in another projection lens (a second projection lens), for example, in the projection lens being repaired. In this case, this projection lens (the second projection lens) has wavefront errors in its original shape, and these wavefront errors originate from the corrective aspheric surface (which does not fit the new projection lens). In this case, this original shape deviates significantly from the neutral shape.

[0055] However, the undesirable influence of the corrective aspheric surface (which does not fit the second projection lens) can be taken into account in the calculation of the manipulator's first operating mode. This manipulator can be operated in the first operating mode, which firstly compensates for the influence of the (improperly fitted) corrective aspheric surface, and secondly compensates for aberration components arising in connection with the assembly of the projection lens being repaired. This is therefore relevant when the initial shape during the measurement operation does not correspond to the neutral shape of the manipulator.

[0056] If the projection lens to be repaired is equipped with a dynamically operable manipulator on which a corrective aspherical surface, fitted to the projection lens, is provided on a separate base, a similar recycling procedure for the dynamically operable manipulator is also possible.

[0057] Additional advantages and aspects of the present invention are evident from the claims and from the following description of preferred exemplary embodiments of the invention, which will be described below with reference to the drawings. [Brief explanation of the drawing]

[0058] [Figure 1] This figure shows a microlithography projection exposure apparatus according to a preferred embodiment of the present invention. [Figure 2] This is a schematic plan view of a preferred embodiment of a transparent manipulator integrating a thin heating conductor. [Figure 3] Figures 3A, 3B, and 3C are three sub-diagrams, each illustrating a different configuration of the manipulator and its optical effect on wavefront error. [Figure 4] Figures 4A and 4B are schematic diagrams of two-dimensional heating profiles using a conventional method. [Figure 5] Figures 5A and 5B show heating profiles according to a preferred embodiment, where Figure 5A shows a first embodiment and Figure 5B shows a second embodiment deviating from the first embodiment. [Figure 6] Figures 6A, 6B, and 6C illustrate two different scenarios for repairing the projection lens. [Modes for carrying out the invention]

[0059] Detailed description of preferred embodiments Figure 1 shows an example of a WSC (Wide-Screen Microlithography) system, which can be used in the manufacturing of semiconductor components and other microstructure components. It operates with light or electromagnetic radiation from the deep ultraviolet (DUV) range to achieve a resolution down to the micron fraction. An ArF (argon fluoride) excimer laser with an operating wavelength of approximately 193 nm (λ) functions as the primary radiation source or light source (LS). Other UV (ultraviolet) laser sources are also possible, such as a 157 nm F2 (fluorine) laser or a KrF (krypton fluoride) excimer laser with an operating wavelength of 248 nm.

[0060] At the exit surface ES, the illumination system ILL, positioned downstream of the light source LS, generates a broadly defined, sharply defined, and nearly uniformly illuminated field of view, which meets the telecentricity (parallel light) requirements of the projection lens PO positioned downstream in the optical path. The illumination system ILL has a device for setting different illumination modes (illumination settings), and can switch, for example, between conventional on-axis illumination and off-axis illumination with different degrees of coherence.

[0061] The optical component that receives light from the light source LS and shapes the illumination radiation from this light is part of the projection exposure apparatus, and this illumination radiation is directed towards the illumination field located within the exit surface ES or reticle M.

[0062] Downstream of the illumination system is a device RS, which holds and operates the mask M (reticle) in such a way that the pattern placed on the reticle is located within the area of ​​the objective plane OS of the projection lens PO, where the objective plane OS coincides with the exit plane ES of the illumination system and is also referred to here as the reticle plane OS. For the purpose of scanner operation, the mask is movable using a scanning drive (driver) parallel to this plane and perpendicular to the optical axis OA (z direction) in the scanning direction (y direction). The device RS includes an integrated lift device and an integrated tilt device, the lift device displacing the mask linearly in the z direction relative to the objective plane, i.e., perpendicular to the objective plane, and the tilt device tilting the mask about a tilt axis extending in the x direction.

[0063] Downstream of the reticle surface OS is a projection lens PO, which functions as a reduction lens, reducing the magnification of the image of the pattern placed on the mask M, for example, to a reduction ratio of 1:4 (|β|=0.25) or 1:5 (|β|=0.20), and projecting it onto the photoresist coated substrate W, with the photosensitive substrate surface SS of the substrate W located within the region of the image plane IS of the projection lens PO.

[0064] The substrate to be exposed is typically a semiconductor wafer, which is held by the apparatus WS, which is equipped with a scanner drive, and the scanner drive moves the wafer in the scanning direction (y direction) perpendicular to the optical axis OA in synchronization with the reticle M. The apparatus WS further comprises a lifting device and a tilting device, the lifting device displaces the substrate linearly in the z direction with respect to the image plane, and the tilting device tilts the substrate about a tilting axis extending in the x direction.

[0065] The device WS is also called the "wafer stage," and the device RS is also called the "reticle stage." These devices constitute part of the scanner device, which is controlled by a scan control device, and in this embodiment, the scan control device is integrated into the central control device CU of the projection exposure apparatus.

[0066] The illumination field of view generated by the illumination system (ILL) defines the effective objective field of view (OF) used during projection exposure. In a typical case, the objective field of view (OF) is rectangular, with a height A measured parallel to the scanning direction (y-direction). * It has a width B measured perpendicular to the scanning direction (in the x-direction). * >A * It has. Generally, the aspect ratio AR = B * / A * The range is between 2 and 10, especially between 3 and 6.

[0067] In typical cases, the projection lens PO is a catadioptric projection lens and comprises a single concave mirror or two concave mirrors.

[0068] The effective objective field of view is located adjacent to the optical axis but at a distance in the y-direction (off-axis field of view). The effective exposure region within the image plane IS is optically conjugate to the effective objective field of view, is also an off-axis field of view, has the same shape as the effective objective field of view, and has the same aspect ratio of height B to width A, i.e., A = |β|A * and B=|β|B * That is the case.

[0069] A dioptric projection lens can also be used; in this case, an objective field of view centered on the optical axis can be used.

[0070] When a projection lens is designed and operates as an immersion lens, radiation passes through a thin layer of immersion liquid during the operation of the projection lens, and this thin layer is located between the exit surface of the projection lens and the image plane IS. An image-side numerical aperture NA > 1 is possible during immersion operation. A dry lens configuration is also possible; in this case, the image-side numerical aperture is limited to a value NA < 1.

[0071] The WSC projection lithography system is equipped with a motion control system configured to initiate near-instantaneous fine-tuning of image-related characteristics of the projection lithography system in response to environmental influences and other disturbances and / or based on stored control data. For this purpose, the motion control system is equipped with a very large number of manipulators, which enable targeted intervention in the projection operation of the projection lithography system. An actively actuated manipulator includes one or more actuating elements (or one or more actuators), whose current operating value can be changed based on a control signal from the motion control system by initiating a change in a defined operating value.

[0072] The projection lens or projection exposure apparatus is equipped in particular with a wavefront manipulation system (WFM), which is configured to modify the wavefront of the projection radiation traveling from the objective plane (OS) to the image plane (IS) in a controllable manner, meaning that the optical effect of the wavefront manipulation system can be variably adjusted by a control signal from the operation control system.

[0073] For this purpose, a wavefront control system in a preferred embodiment comprises a manipulator MAN, which comprises a manipulator element ME, the manipulator element ME positioned in the projection beam path, immediately adjacent to the objective plane of the projection lens. The manipulator element is substantially transparent to the wavelength being used and comprises an inlet manipulator surface MS1 and an outlet manipulator surface MS2, through which the projection beam path is guided. The optical effect of the manipulator element on the passing projection radiation can be reversibly changed using an actuator device DR.

[0074] Alternatively, or in addition to the above, the manipulator element can be positioned, for example, on or near the pupil. The projection lens also comprises several additional manipulators, which will not be described in detail here.

[0075] Figure 2 shows a plan view of a preferred embodiment of the manipulator MAN. In this preferred embodiment, the manipulator MAN is designed to vary with high spatial resolution in the radial and azimuth directions of the wavefront of the projected radiation passing through it, within the optically used region. For this purpose, the manipulator comprises a manipulator element ME in the form of a parallel-plane plate, which is made of a material transparent to the projected radiation, and can set different two-dimensional temperature profiles across the entire optically used surface in such a way that locally hotter zones are generated next to locally colder zones. For this purpose, a device is provided that allows a specific amount of heat to be supplied in a targeted manner to each point within the radiatively transparent region, thereby generating a non-uniform temperature profile. In this case, the heating device acts in opposition to the operation of a cooling device that supports the cooling process.

[0076] The manipulator operates in a manner similar to that of a heated rear window. Conductor tracks EL (see Figure 3A) made of conductive material have a certain degree of electrical resistance as a heating conductor material and extend along and / or within the manipulator element ME. The conductor tracks are relatively thin (e.g., less than 50 μm wide) and, if suitable, extend like a square grid with pitch (spacing) in the x and y directions, insulating each other. As a result, the optical effects of the manipulator element can be influenced in a spatially resolved manner by the appropriate selective operation of the conductor tracks, through which the heating current required for heating is delivered. Here, the temperature dependence of the refractive index of light of the transparent material of the manipulator element is utilized. By controlling the temperature within individual regions, the optical path length between the inlet-side manipulator surface MS1 (inlet surface) and the outlet-side manipulator surface MS2 (outlet surface) can be changed. In this case, the phase change occurring in the transmitted light is approximately proportional to the temperature change for a given geometric shape of the manipulator element.

[0077] When the conductor track is uncurrented and therefore inoperable, and there is no active cooling of the manipulator element, the wavefront that passes through the manipulator element remains substantially unchanged because the optical path length of the radiation is approximately the same at all locations in the optically used region. In contrast, when a temperature distribution with different temperature zones is generated by supplying current to the corresponding conductor track, wavefront deformation occurs in the wavefront of the light passing through the manipulator element, and this wavefront deformation correlates with the set temperature profile. Conversely, the deformed wavefront can be corrected by an appropriate inverse temperature profile. For example, an electrically actuated manipulator operating on this principle is disclosed in International Publication No. 2008 / 034636 (Patent Document 13) (corresponding, for example, to U.S. Patent No. 8891172 (Patent Document 14)). The disclosures of these documents are incorporated herein by reference.

[0078] When a projection lens (PO) is manufactured, it is initially assembled from a very large number of optical elements. These optical elements are necessary for the configuration of the projection beam path and are held in a mount either on individual bases or in groups, assembled according to structural specifications in a way that produces the projection beam path. The manipulator (MAN) is also installed during this process. After the initial assembly, the imaging performance of the projection lens is generally still far from the imaging performance required by the specifications.

[0079] Next, some or all of the optical elements, which can still be changed in their installed position, are modified in terms of their rigid degrees of freedom to perform the initial adjustment loop and improve imaging performance. For this purpose, the optical elements, i.e., lens elements and / or mirrors, can be displaced, rotated, or tilted, for example, along the reference axis (optical axis) and / or in the lateral direction parallel thereto. The initial adjustment process is performed by monitoring with aberration measurements to check the effect of the changes on the manipulator and derive additional operation commands for the manipulator.

[0080] During these initial adjustment steps, the manipulator MAN is not in operation, and therefore a uniform refractive index exists across the entire cross-section used within the planar plate. Thus, during this stage, the manipulator only has the effect of a transparent planar plate, in this case corresponding to the optical effect brought to this optical element by the underlying optical design. This initial shape of the manipulator element is also referred to in this application as the "neutral shape" because the manipulator element exhibits the effect intended by the optical design. In this state of the projection lens, the wavefront of the projected radiation, as confirmed by measurement, deviates from the wavefront required by the specifications; that is, a wavefront error exists.

[0081] The calculation of the first shape of the manipulator element follows, and the first shape is distinguished in that, if the manipulator element were to exist in the first shape, wavefront errors would be compensated or corrected. Thus, in the preferred case of a manipulator element that can be heated to locally different degrees, the first shape corresponds to a specific local distribution of refractive index in the optically used cross section or in the corresponding two-dimensional temperature profile or heating profile. Thus, if the manipulator element were brought to the first shape after the above measurement, the observed wavefront errors would be almost completely compensated.

[0082] Experience has shown that a single such adjustment loop is usually insufficient to guarantee that the projection lens will reliably meet the specifications. Therefore, the adjustment process is typically iterative, with multiple adjustment loops being run through, and individual manipulator elements, or all manipulator elements, still changing between individual adjustment loops. Depending on preference, the effect of activating the manipulators of the wavefront manipulation system may be taken into account only by simulation during adjustment, while the manipulators are not actually activated, and the adjustment is actually achieved by other manipulators. Thus, the adjustment loops are run through so that they converge in a way that brings the imaging performance as close as possible to the specified performance through the settings for the other manipulators.

[0083] Once this state is reached, the properties of the first shape of the manipulator MAN or manipulator element, required to correct the remaining residual aberrations, are determined by further measurements. The first operating mode of the control unit is defined based on these properties. In the first operating mode, the control unit generates a first control signal, which facilitates the actuator device setting the first shape of the manipulator element. Thus, the first operating mode uses instructions to actuate the manipulator, causing it to adopt the first shape and thus correct the residual aberrations.

[0084] To illustrate this procedure, Figure 3 shows different configurations of the manipulator and their effects in three sub-figures 3A, 3B, and 3C, respectively. At the top of each sub-figure is a schematic cross-section of a transparent parallel-plane manipulator element ME, with a conductor track EL extending inside it. Below this are respective figures schematically showing the selected wavefront error WF (e.g., distortion) as a function of the position on the x-axis corresponding to the shape of the manipulator element.

[0085] In the situation shown in Figure 3A, the entire conductor track EL is current-free; this is represented by a uniformly small dot. This shape corresponds to the neutral shape KONF-0 of the manipulator element. This figure shows the spatial profile of the wavefront error WF after adjustment is complete, in the case where the manipulator is in this neutral shape KONF-0.

[0086] In the principle of this manipulator, another possibility for setting a neutral shape is that power is already supplied to the conductor track, but the resulting heating effect is compensated for by appropriate cooling, so that the manipulator is already operating, but nevertheless the optical effect of the manipulator element corresponds to a non-operating passive mode (without heating and cooling). Thus, this kind of neutral shape is an active switch-on operation, in which the cooling power and its opposite heating maintain equilibrium in all spatial zones, and thus the temperature is constant across the entire glass plate that functions as the manipulator element. Incidentally, this does not mean that the power (or current) of the electric heating is the same for all zones. For details of such calibration, refer to German Patent Application Publication No. 102013225381 (Patent Document 15).

[0087] Figure 3B shows a manipulator element in the first shape, KONF-1, which is adopted when the control unit CU is switched to the first operating mode. In the illustrated shape, the manipulator element is heated to locally different degrees by supplying current to the conductor tracks at different degrees (corresponding to conductor track symbols of different thicknesses), and thus a non-uniform temperature profile is produced across the entire surface used. Preferably, this is calculated in a way that significantly compensates for the wavefront errors that still exist in the situation of Figure 3A, and thus the wavefront errors approach zero across the entire cross-section used. Thus, in this first operating mode, the manipulator MAN produces the effect achieved by individually manufactured corrected aspherical surfaces in conventional methods.

[0088] However, a major advantage of this novel procedure is that this compensation effect is generated using a dynamically variable manipulator MAN, and the range of settings for the manipulator MAN, starting from this first shape, also provides the possibility of compensating for further wavefront errors that may occur during further operation of the projection exposure apparatus by correspondingly adapted modified temperature profiles. The upper part of Figure 3C schematically shows how the heating current is supplied to the conductive track to an otherwise non-uniform degree in the second shape KONF-2, which deviates from the shapes in Figures 3A and 3B, and so that wavefront errors that occur later during operation are corrected to such an extent that this ensures a substantially error-free image with a wavefront error of 0 or near 0.

[0089] Adjustments, including assembly and measurement assistance, are generally performed by the projection lens manufacturer.

[0090] Therefore, typically, the adjustment causes the projection lens to produce a shape with unacceptable wave errors, as long as the installed manipulator element is in its neutral shape (without operation by the control unit). According to the method proposed here, in the case of the above adjustment, a spatially resolvable, operable thermal manipulator MAN with an installed and activated heating profile is used for wavefront optimization in the same way. Therefore, the temperature profile associated with the first shape KONF-1 does not actually need to be generated.

[0091] However, the first operational data record is stored in a data memory accessible to the control unit (CU), and this operational data record represents the first operating mode. Therefore, the CU can use the specifications in the data record as a basis to set the manipulator element to a first shape, which is suitable for reducing the wavefront error of the assembled projection lens to a degree that the imaging performance satisfies the specifications (see Figure 3B). Thus, the delivered product achieves guaranteed performance by incorporating the heating profile set when the projection lens enters operation. In other words: each projection lens is delivered with its individual heating profile, which remains constant over a long period and, unlike the neutral profile (neutral shape), corresponds to the first shape of the manipulator element. Initially, when the manipulator operates in the first operating mode, the projection lens merely satisfies the above specifications.

[0092] This procedure can replace the conventional procedure, which involved generating at least one (invariant) corrective aspheric surface based on measurements at the manufacturer, then installing it to ensure that the projection lens met the specifications before shipment. Therefore, when performing surface treatment on the manipulator surface, the corresponding manufacturing costs can be omitted. Omitting the processing step for manufacturing individually fitted corrective aspheric surfaces results in a significant reduction in throughput time (processing capacity per unit of time) for generating the corrective effect.

[0093] An additional advantage is that this process allows the use of a variably adjustable manipulator MAN, which, when installed, is not yet individualized for a specific projection lens and, with the appropriate operating profile, simply adopts a first shape that, in terms of its effect, corresponds to the effect of a conventional corrective aspheric lens.

[0094] It is advantageous that the manipulator retains its variability, and therefore, the manipulator can also be used to correct additional wavefront aberrations that may occur later in the lifespan of the projection lens, for example, due to "lens heating" (see, for example, Figure 3C). For continuous production, all manipulators of the same type installed here actually have the same neutral shape during the delivery state of the system. In this case, the correction effect is achieved using a manipulator that operates only by operation according to instructions determined during measurement to set the first shape.

[0095] This concept significantly increases the effective lifespan of the projection lens available to the end user. If the installed manipulator requires maintenance or repair, it can be removed from the projection lens at the user's site and replaced with a variable manipulator of the same configuration, which, like the replaced manipulator, of course exists in its neutral shape when not in operation. A suitable heating profile to compensate for the current wavefront error can then be set purely by appropriate operation by the control unit. Thus, for on-site repair measures, any desired manipulator of the same configuration can be used as a replacement part.

[0096] To further illustrate the essential differences between the conventional method with a installed manipulator and the method proposed in this application, Figures 4A and 4B show schematic diagrams of two-dimensional heating profiles of the conventional method, and Figures 5A and 5B show heating profiles of preferred embodiments of the method presented in this application. All figures show a two-dimensional representation of the manipulator element, where the local temperature T (in arbitrary units) is represented at a grayscale level. In Figure 4A, the intermediate gray areas correspond to the reference temperature, and the darker areas correspond to the lower deviation in local temperature. These deviations are typically on the order of a fraction of a Kelvin.

[0097] Traditionally, a dynamic manipulator was installed and used solely to correct wavefront aberrations that occurred during operation. Therefore, in its unmodified state, the manipulator had a neutral shape with a uniform temperature across its entire operating area; consequently, its optical effect across the entire cross-section was equivalent to the optical effect of a flat plate (Figure 4A). To correct residual aberrations remaining after adjustment, a specially fitted corrective aspherical surface was manufactured and installed. During use of the projection exposure system at the end customer's site, the manipulator was activated only when necessary to correct imaging errors by modifying the local heating profile (see Figure 4B).

[0098] In the adjustment method presented herein, the manipulator is already used as an adjustment means during commissioning to achieve the specified imaging performance. For this purpose, the heating profile is simulated and designed so that, in combination with the previous adjustment means, specifications applicable to commissioning are achieved. This heating profile is made available to the end customer through corresponding data recordings stored in memory accessible to the control unit, and these values ​​can be read out for generating the first operating mode. This means that, typically, the heating profile of the manipulator no longer corresponds to a neutral profile at the time of purchase by the customer, but a spatially non-uniform temperature distribution (due to the first shape) already exists with a corresponding effect on the wavefront (Figure 5A). In this case, this effect corresponds to the effect of a conventional corrected aspherical surface. However, during operation at the end customer's site, imaging errors can be corrected by modifying the heating profile using the manipulator as before (Figure 5B). Thus, the operation of the manipulator in specific operating conditions can be considered in two stages. In this case, the actual heating profile that is set is the sum of the heating profile used during trial operation (Figure 5A) and the operating profile used to correct wavefront errors that occur as a result of operation at the customer's site.

[0099] Additional aspects and advantages of the present invention, as well as optional uses, will be described with reference to Figures 6A, 6B, and 6C. An advantage of the present invention is that it can also be used for the repair or maintenance of projection lenses, which are expected to fail to meet required specifications for a much longer period after prolonged use.

[0100] In the preferred embodiments schematically illustrated in Figures 6A and 6B, the original manufacturing ensures that the projection lens satisfies specifications after the adjustment of the rigid body degrees of freedom is completed by a separately manufactured corrective aspherical CAS. For this purpose, the corrective aspherical CAS is provided on the inlet (or outlet) surface of a planar plate PP prepared for this purpose during the design phase by position-dependent material removal by ion beam etching based on wavefront measurements, and this corrective aspherical surface allows for correction of residual aberrations during manufacturing. In Figure 6A, the upper sub-view shows the resulting manufactured corrective element CE, with the corrective aspherical CAS manufactured on its inlet surface. The outlet side retains its flat initial shape. The lower sub-view, indicated by a solid line, shows the resulting wavefront error during manufacturing, which is close to zero across the entire field of view. Throughout the entire operation, the aberration level slowly increases to near the specification limit (dashed line).

[0101] Preferably, the projection lens is repaired or maintained to again satisfy the specifications by removing the assembly containing the correcting element CE from the projection lens and installing a replacement assembly REP in its place. The replacement assembly REP comprises a manipulator element ME, which can be heated locally to different degrees and is of the type described in relation to Figures 2 and 3. The manipulator element ME includes a thin conductive track EL to which a heating current can be supplied, and this supply is variable to such an extent that a desired refractive index distribution is set over the entire cross-section used. The replacement assembly REP containing this manipulator element also comprises an associated actuator DR. These hardware components are part of a repair kit KIT, which also comprises adapted software components in addition to these hardware components. Preferably, this software component includes a first operation data record, which is stored in the memory SP of the control unit CU.

[0102] The actuator DR acting on the manipulator element can, based on first operating data, cause the manipulator element to operate in a manner that has the same optical effect as the removed corrector element CE, which has an invariant corrector aspherical CAS. In addition, the correction profile can be applied electronically, and this electronic application also corrects residuals that increase over time, so that the residual aberrations again have an acceptable level with only small fluctuations across the entire field of view when the manipulator element ME operates in the first operating mode. Accordingly, Figure 6B schematically shows the hardware and software components of the repair kit, which can be used to ensure that the degraded projection lens again satisfies the specifications.

[0103] Different scenarios are described based on a combination of Figures 6C and 6A. (Shown by dashed lines) In the initial state of this alternative, a corrective element originally installed within the projection lens, provided with a permanent corrective aspherical surface CAS, is itself a corrective element that can be operated by an appropriate actuator based on control commands from the control unit; that is, this corrective element is a manipulator element ME. In the example of Figure 6C, this corrective element is a transparent plate, within which a heating conductor EL is embedded, and using the heating conductor EL, a selectable heating profile, and therefore a desired refractive index distribution, can be set over the entire cross-section used (see, for example, Figures 2 and 3). Within the scope of the initial manufacture, such a manipulator can perform a dual function not only by preserving the possibility of later dynamic wavefront manipulation, but also by additionally compensating for residual aberrations that exist after the adjustment of the manipulator element by the corrective aspherical surface generated on the surface of the manipulator element.

[0104] Accordingly, for example, an optical element requiring repair or maintenance can be replaced, which is provided with a conventional corrective aspheric surface to ensure that the projection lens satisfies the specifications. In this regard, the optical element can be replaced with a manipulator of the type described herein, which has a first operating mode that employs the effect of this corrective aspheric surface and, in addition, can dynamically compensate for any effects that may arise from the operation. The operating data for setting the first operating mode can, in this case, be calculated without additional measurements based on known effect data of the originally installed corrective aspheric surface. Alternatively, the first operating data can be calculated based on point-resolved wavefront measurements in a neutral shape for the lens being repaired and for the newly installed manipulator. In this case, the first operating mode may also take into account other aging effects of the lens.

[0105] More generally, a manipulator with or without permanent aspheric correction that requires repair or maintenance can be replaced with a new type of manipulator, and the new type of manipulator can be operated in a first operating mode to ensure that the projection lens meets the specifications.

[0106] A repair scenario is also conceivable that requires the replacement of other optical elements that need maintenance or repair, namely optical elements without corrective aspheric surfaces. For example, a manipulator with a conventional corrective aspheric surface, or a manipulator with a first operating state, can be installed. In this scenario, the replacement of other optical elements would introduce wavefront errors that previously could only be achieved by replacing the corrective aspheric surface on the manipulator, and therefore the entire manipulator. Now, for the first time, it becomes possible to configure or reconfigure the installed manipulator so that it has a first operating state, which corrects any residual aberrations present after replacement to a sufficiently good degree.

[0107] The present invention also discloses the concept of recycling still-functioning manipulators, which have already been used 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 being repaired. For illustrative purposes, we first refer to Figure 6C. Figure 6C shows a dynamically actuated manipulator element ME incorporating a heating conductor EL, which is provided with a corrective aspherical CAS, which is individually fitted to the first projection lens during its initial use in the aforementioned projection lens. In other words, this manipulator element has a "history". Just like the manipulator element in Figure 6B, this manipulator element is suitable for being dynamically actuated by a corresponding actuating element using a control unit (not shown in Figure 6C). This functionality can also be used in the recycling scenario. One scenario involves removing these still-functioning manipulators from the old projection lens and reusing them in the projection lens being repaired, where these manipulators have conventional corrective aspheric surfaces and have previously operated conventionally without using the present invention, and the projection lens being repaired has, for example, operated with a corresponding, but without, corrective aspheric surface manipulator. The newly installed, previously used, and now recycled manipulator can now be operated in a first operating state, which first compensates for the effect of the corrective aspheric surface CAS (which is not suitable for the projection lens being repaired) (which is suitable for the previous projection lens), but also compensates for residual aberrations that may enter after the initial assembly of the projection lens being repaired. Furthermore, the range of motion of this manipulator is also sufficient to dynamically compensate for any aberration components that may occur during the operation of the projection lens being repaired. Therefore, these recycled used manipulator elements with a history can also be used to replace other manipulator elements with different corrective aspherical surfaces within a repaired projection lens (or a newly manufactured projection lens).

[0108] Several aspects of the novel concept have been described based on the example of a manipulator MAN. The manipulator MAN has a manipulator element ME that is transparent to the radiation being affected and has a spatially dependent effect on the wavefront of the transmitted radiation by setting different non-uniform temperature profiles within the region of use. Within the scope of preferred embodiments of the present invention, a great many manipulators operating according to other principles can be used similarly. Thus, for example, at least one manipulator can be used that has an optically transparent manipulator element that can be deformed to locally different degrees in response to a control signal. An example of this is described in Patent Document 12 or U.S. Patent No. 10061206 (Patent Document 16), for example, German Patent Application Publication No. 102020212742 (Patent Document 17) (corresponding to Patent Document 10) describes a manipulator that uses a dielectric medium to change the shape of an optical surface connected to an electrode. The above manipulator element may be a mirror having a deformable mirror surface, which is configured to reflect EUV radiation. For example, EUV radiation can have wavelengths ranging from 6 nm to 20 nm, particularly around 13.5 nm or 6.8 nm. German Patent Application Publication No. 19824939 (Patent Document 18) discloses a catadioptic projection lens having a concave mirror that can be deformed in a targeted manner to correct wavefront errors.

[0109] In preferred cases, the manipulator is positioned optically near the objective plane, i.e., optically near the field of view. As a result, correction effects of different intensities can be achieved for different points in the field of view. In the case of positioning near other field of view planes, for example, in the case of an intermediate image of a real image, something similar is possible. Alternatively, or in addition to this, the manipulator can also be positioned in or near the pupil plane, so that different changes in a space-dependent manner have an effect on the projected radiation at angular intervals. Positioning in an intermediate region between the field of view plane and the pupil plane is also possible.

Claims

1. A method for manufacturing a projection lens, wherein the projection lens is a method for forming an image of a pattern placed within the objective plane of the projection lens within the image plane of the projection lens, The step of assembling the projection lens is to arrange a plurality of optical elements in accordance with the specifications, such that the optical surfaces of the optical elements form a projection beam path, and the pattern placed in the objective plane is imaged into the image plane by the optical elements through the projection beam path, At least one manipulator of a wavefront manipulation system is installed to dynamically influence the wavefront of the projected radiation in response to a control signal from the control unit of the wavefront manipulation system. The aforementioned manipulator is, At least one manipulator element having at least one manipulator surface arranged within the projection beam path, The device comprises an actuator that is controllable by a control signal from the control unit and functions to reversibly change the optical effect of the manipulator element, A step of measuring the projection lens by spatially resolved measurement of the wavefront for spatially resolved measurement of wavefront error, comprising the step of the manipulator element having an initial shape during the measurement, A step of calculating a first shape of the manipulator element, wherein the first shape is suitable for correcting the wavefront error, A step of defining a first operating mode of the control unit, wherein the control unit generates a first control signal in the first operating mode, and the first control signal facilitates the actuator setting the first shape of the manipulator element. A method that includes this.

2. The method according to claim 1, characterized in that, during the measurement of the projection lens, the manipulator element has a neutral shape as its initial shape, and in the neutral shape, the optical effect of the manipulator element corresponds to the target effect of the manipulator element due to the optical design of the projection lens.

3. The method according to claim 1 or 2, characterized in that the installation of the projection lens in the projection exposure apparatus is followed by the use of the projection lens in the manufacturing work at the location where the projection lens is used, and the switching of the control unit to the first operating mode at the location where the operation device is used to generate the first control signal that facilitates the setting of the first shape of the manipulator element precedes the start of the manufacturing work.

4. The steps include storing the first operation data record representing the first operation mode in a data memory accessible to the control unit, The method according to any one of claims 1 to 3, comprising the step of reading the first operation data record from the data memory and setting a first operation mode of the control unit, wherein in the first operation mode, the control unit generates a first control signal that facilitates the actuator setting the first shape of the manipulator element.

5. The method according to any one of claims 1 to 4, wherein the control unit is capable of operating in multiple operating modes, and in addition to the first operating mode, at least one second operating mode can be set, and in the second operating mode, the manipulator element has an optical effect different from the first shape.

6. The method according to any one of claims 1 to 5, characterized in that, in addition to the manipulator, at least one additional manipulator is provided, preferably a plurality of manipulators are provided.

7. During the adjustment, the effect of operating the manipulator to set the first shape without actually operating the manipulator is taken into consideration by simulation, along with the effect of actually implementing the at least one additional manipulator, and / or The method according to any one of claims 1 to 6, characterized in that the adjustment operation is performed iteratively in the form of multiple adjustment loops until the first shape is found, and the first shape is suitable for sufficiently correcting all residual aberrations of the projection lens, including residual aberrations generated from other manipulators.

8. The manipulator is equipped with a mirror having a deformable mirror surface, or The method according to any one of claims 1 to 7, wherein the manipulator element is a transparent optical element, preferably a transparent optical element whose local refractive index distribution changes when different positions within the usage area are heated and / or cooled electrically or by other means to different degrees.

9. The method according to any one of claims 1 to 8, characterized in that the manipulator surface is coated with an optical functional layer before being placed in the projection lens.

10. The method according to any one of claims 1 to 9, characterized in that the manipulator is removed from the projection lens and, after removal, used as a manipulator in another projection lens.

11. A projection lens that forms an image of a pattern placed within the objective plane (OS) of the projection lens (PO) within the image plane (IS) of the projection lens, wherein the projection lens is Multiple optical elements, A wavefront manipulation system (WFM) comprising at least one manipulator (MAN), The optical element is arranged such that its optical surface forms a projection beam path, and the pattern placed within the objective plane can be imaged into the image plane through the projection beam path by the optical element. The manipulator dynamically influences the wavefront of the projected radiation in response to a control signal from the control unit (CU) of the wavefront manipulation system. The aforementioned manipulator is, A manipulator element (ME) having at least one manipulator surface (MS1, MS2) arranged within the projection beam path, The system comprises an actuator (DR) that is controllable by a control signal from the control unit and functions to reversibly change the optical effect of the manipulator element, The manipulator element has an initial shape (KONF-0), and the projected radiation is in the initial shape of the manipulator element, in a projection lens having a wavefront error during operation. A first operation data record representing the first operation mode is stored in a data memory accessible to the control unit (CU). The projection lens is characterized in that the control unit is configured to generate a first control signal in the first operating mode, the first operating signal facilitates the actuator setting a first shape (KONF-1) of the manipulator element, and the first shape is suitable for correcting the wavefront error.

12. The manipulator is equipped with a mirror having a deformable mirror surface, or The projection lens according to claim 11, characterized in that the manipulator element is a transparent optical element, preferably a transparent optical element capable of changing the local refractive index distribution by electrically or otherwise heating and / or cooling different positions within the usage area to different degrees.

13. A projection exposure method for exposing a radiosensitive substrate with at least one image of a mask pattern, The steps include: preparing a pattern between the illumination system and the projection lens of a projection exposure apparatus, such that the pattern is positioned within the area of ​​the objective plane of the projection lens; The steps include: holding the substrate such that the radiation-sensitive surface of the substrate is positioned within the region of the image plane of the projection lens which is optically conjugate to the objective plane; The steps include illuminating the illumination region of the mask with illumination radiation provided by the illumination system, A step of projecting a portion of the pattern located within the illumination region onto an exposure region on the substrate using the projection lens, wherein all rays of the projection radiation contributing to the generation of the image within the exposure region form a projection beam path; The steps include: influencing the wavefront of the projection radiation traveling from the objective plane to the image plane by operating a manipulator comprising at least one manipulator element having at least one manipulator surface arranged in the projection beam path, and a first actuator that reversibly changes the optical effect of the manipulator element; In a projection exposure method including, The manipulator element has an initial shape without a control signal, and the projected radiation has a wavefront error during operation of the manipulator element in its initial shape. A first operation data record representing the first operation mode is stored in a data memory accessible to the control unit. A projection exposure method wherein the control unit switches to the first operating mode and generates a first control signal based solely on the first operation data recording, the first control signal facilitates the actuator setting the first shape of the manipulator element, and the first shape is suitable for correcting the wavefront error.

14. The projection exposure method according to claim 13, using the projection lens according to claim 11 or 12.

15. A projection exposure apparatus for exposing a radiosensitive substrate located in the image plane region of a projection lens with at least one image of a mask pattern located in the objective plane region of the projection lens, A light source (LS) that emits light at the operating wavelength, An illumination system (ILL) that receives light from the light source and forms illumination radiation directed towards the pattern on the mask, The mask comprises a projection lens for imaging the pattern of the mask onto the radiation-sensitive substrate, A projection exposure apparatus in which the projection lens is configured as the projection lens described in claim 11 or 12.

16. A method for repairing a projection lens having multiple optical elements, wherein the optical elements are arranged in accordance with specifications such that the optical surfaces of the optical elements form a projection beam path and a pattern placed in the objective plane is imaged by the optical elements through the projection beam path into the image plane of the projection lens, and at least one of the optical elements acts as a corrective element, in the form of a fixed corrective aspherical surface individually adapted to the projection lens, thereby two-dimensionally influencing a local wavefront located in the projection beam path, wherein the method is: The steps include removing the assembly equipped with the correction element, The steps include installing a replacement assembly in place of the assembly having the correction element, The exchange assembly comprises a manipulator for a wavefront manipulation system, which dynamically influences the wavefront of projected radiation in response to a control signal from the control unit of the wavefront manipulation system. The manipulator comprises at least one manipulator element having at least one manipulator surface arranged within the projection beam path, and an actuator that is controllable by a control signal from the control unit and functions to reversibly change the optical effect of the manipulator element. The manipulator element has an initial shape, and the projected radiation has a wavefront error during operation of the manipulator element in its initial shape. A first operation data record representing the first operation mode is stored in a data memory accessible to the control unit. The control unit is configured to generate a first control signal in the first operating mode, the first control signal facilitates the actuator setting a first shape of the manipulator element, and in the first shape, the manipulator element substantially has the optical effect of the removed corrector element.

17. The correction element having the fixed correction aspherical surface is formed as the manipulator element of the manipulator having the actuator, the actuator is controllable by a control signal from the control unit, and functions to reversibly change the optical effect of the manipulator element, or The method according to claim 16, characterized in that the correction element having a fixed correction aspherical surface is an unoperable correction element having a correction aspherical surface.

18. A repair kit for repairing a projection lens, comprising a combination of hardware and software components, The hardware component comprises a replacement assembly having a manipulator controllable by a control unit, The software component includes a first operational data record stored in a data memory accessible to the control unit of the projection lens, the first operational data record enabling the control unit to have a first operational mode, the first operational mode resulting in the manipulator of the installed replacement assembly being set in a manner that has approximately or exactly the effect of the fixed corrective aspheric lens being replaced.

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