Method for compensating actuator effect of actuator

Abstract

The present invention relates to a method for driving an actuator of a component (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, the method comprising a step (30) of evaluating the characteristics of the actuator, a step (31) of parameterizing an actuator model, a step (32) of implementing the actuator model in a control structure, and a step (34) of driving the actuator using the actuator model.

Description

Technical Field

[0001] This application claims the priority of German Patent Application No. 10 2022 206 038.5 filed on Jun. 15, 2022, the content of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a method for compensating the actuator effect of an actuator of a projection exposure apparatus for semiconductor lithography.

Background Art

[0003] As the demand for lithography systems, especially in the DUV or EUV region, is increasing, adaptive optical elements are becoming even more important. For example, such an element can be in the form of a deformable mirror that can be driven by an actuator in a very short period of time, for example, to compensate for wavefront aberration as a result of deformation of the optically effective surface of a mirror. The optically effective surface is the surface of the mirror on which the light used for imaging the structure of the mask onto the wafer during the normal operation of the apparatus is incident.

[0004] Electrostrictive actuators or piezoelectric actuators classified as ferroelectric solid actuators are often used as actuators. However, such actuators often exhibit undesirable effects, such as hysteresis and creep effects. This behavior of the actuator is particularly harmful when the so-called feedforward method is used to drive the actuator system. The above method is characterized in that only the actuation signal generated by the control unit is output to the actuator for the purpose of setting a desired state, such as the deflection of the actuator. The response of the system, that is, the path along which the actuator actually moves, is not considered initially in this type of control. Therefore, very strict requirements must be imposed on the model that forms the basis for the calculation and output of the control signal for the desired deflection of the actuator.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Accordingly, the present invention is based on the object of identifying a method that makes it possible to improve the accuracy of driving an actuator of a projection exposure apparatus for semiconductor lithography.

Means for Solving the Problems

[0006] This object is achieved by a method having the features of the independent patent claims. The dependent claims relate to advantageous embodiments and variants of the present invention.

[0007] The method according to the present invention for driving an actuator of an optical component of a projection exposure apparatus for semiconductor lithography includes a step of evaluating the characteristics of the actuator, a step of parameterizing an actuator model, a step of implementing the actuator model in a control structure, and a step of driving the actuator using the actuator model.

[0008] According to the present invention, as a result of considering the characteristics of the actuator by applying the actuator model when driving the actuator, it is possible to minimize the adverse effects of the above effects on the accuracy of actuator control. In particular, this can lead to an improvement in the image quality of the projection exposure apparatus, particularly the overlay performance.

[0009] In an advantageous embodiment of the present invention, a reference step is performed at a specific point in time. In this regard, the reference step is to be understood as meaning a method step in which a defined state of the system under consideration is established. In this case, the system under consideration may particularly include the model itself and its parameters, but may also include the real world, for example, the actuator.

[0010] ​Thus, for example, by means of a reference step, it becomes possible to take into account that even a model that only exists in software may be changed over a long period of time. For example, parameters set at the start of the method according to the present invention may change over several days, weeks, or years due only to the nature of the computer hardware. Thus, it may be necessary to reset these parameters intermittently.

[0011] Furthermore, it is also advantageous to intermittently bring the driven actuator into a defined deflection state. As already mentioned above, the starting point and direction of the application of the control voltage definitely influence the actual actuator deflection. Based on this, the actual deflection of the actuator can proceed along one of the two branches of the hysteresis curve. If a defined state is set by means of an appropriate setting of the actuator deflection and subsequent appropriate selection of the driving direction, it is possible to ensure that it is on the correct branch of the hysteresis curve.

[0012] The period between the exposure of the two wafers is an advantageous choice as the time of the reference step. The few milliseconds of time available here are sufficient to perform the necessary reference. In this regard, the reference itself does not necessarily have to include the resetting of the model and the control of the actuator, and of course, it is also conceivable to perform only one of the two measures.

[0013] In particular, one or more of the actuator parameters such as length change, frequency response, hysteresis, and drift are suitable for the characterization of the actuator for preparing the method according to the present invention.

[0014] In particular, the actuator can be characterized in a test environment. In this case, it is also conceivable to use an equivalent sample instead of the actuator itself for the characterization.

[0015] Alternatively, the actuator can be characterized within the projection exposure apparatus. In this case, one or more wafers can be exposed, for example, within one test run. The wafers after exposure are subsequently measured. Next, actuator parameters can also be determined from the determined image aberrations using a model suitable for the relationship between the image aberrations and the actuator characteristics.

[0016] In an advantageous variant of the invention, during the parameterization of the actuator model, at least one separate model is generated for at least one of the actuator parameters, which is subsequently superimposed on at least one further separate model.

[0017] In this regard, models that are advantageous for drift are, in particular, Padé approximation, S = a * tanh(b * U) 2 + c, P = tanh(b * U + c * P + d * P 3 ), S = a * P 2 , polynomials where S represents the actuator deflection, P represents the surface charge density, U represents the voltage, and a, b, c, d are fitting parameters.

[0018] In particular, the following models are suitable for the description of hysteresis. Bouc Wen, Prandtl - Ishlinskii, Preisach.

[0019] Models that are advantageous for the modeling of dynamics are, in particular, superimposed Pt1 functions, superimposed logarithmic functions, fractional - order differential equations are included.

[0020] The models developed as described above are subsequently implemented in a controller that can be used to drive the actuator system of the components of the projection exposure apparatus.

[0021] In particular, the following options can be selected for control purposes. Inverse model, Model-based control, Observer-based control, Subtraction of the actuator model, Machine learning control, Neural network control.

[0022] For example, the actuator can be a piezoelectric actuator and a piezoceramic actuator or a magnetostrictive actuator.

[0023] In particular, the actuator can be configured to position and / or deform the component.

[0024] The component can be an optical element, in particular a mirror, and in some cases a deformable mirror.

[0025] Exemplary embodiments and variations of the present invention will be described in more detail below with reference to the drawings.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0027] The essential components of the microlithographic projection exposure apparatus 1 will be illustratively described first with reference to FIG. 1. It should be understood here that the description of the basic structure of the projection exposure apparatus 1 and its components is non-limiting.

[0028] One embodiment of the illumination system 2 of the projection exposure apparatus 1 has an illumination optical unit 4 that illuminates the object field of view 5 of the object plane 6 in addition to the radiation source 3. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0029] The reticle 7 disposed in the object field of view 5 is illuminated. The reticle 7 is held by the reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by the reticle displacement drive 9.

[0030] In FIG. 1, an orthogonal xyz coordinate system is shown for the purpose of explanation. The x direction extends perpendicular to the plane of the figure. The y direction extends horizontally, and the z direction extends vertically. In FIG. 1, the scanning direction extends in the y direction. The z direction extends perpendicular to the object plane 6.

[0031] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to image the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, an angle other than 0° is also possible between the object plane 6 and the image plane 12.

[0032] The structure on the reticle 7 is imaged on the photosensitive layer of the wafer 13 disposed in the region of the image field 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, particularly in the y direction, by a wafer displacement drive 15. The displacement of the reticle 7 by the reticle displacement drive 9 and the displacement of the wafer 13 by the wafer displacement drive 15 can be carried out in synchronization with each other.

[0033] The radiation source 3 is an EUV radiation source. The radiation source 3 emits EUV radiation 16, which is also particularly referred to hereinafter as used radiation, illumination radiation, or illumination light. In particular, the used radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 can be a plasma source, for example, an LPP (laser-produced plasma) source or a GDPP (gas discharge plasma) source. This can also be a synchrotron-based radiation source. The radiation source 3 can be a free electron (FEL).

[0034] The illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17. The collector 17 can be a collector having one or more elliptical reflecting surfaces and / or hyperbolic reflecting surfaces. The illumination radiation 16 can be incident on at least one reflecting surface of the collector 17 at a grazing incidence (GI), that is, at an incident angle greater than 45° with respect to the direction of the normal to the mirror surface, or at a normal incidence (NI), that is, at an incident angle less than 45°. The collector 17 can be structured and / or coated, firstly, to optimize the reflectivity for the used radiation and, secondly, to suppress the extraneous light.

[0035] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focus of the intermediate focal plane 18. The intermediate focal plane 18 can represent the separation between the radiation source module including the radiation source 3 and the collector 17 and the illumination optical unit 4.

[0036] The illumination optical unit 4 includes a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a planar deflection mirror or a mirror having a beam influence effect exceeding a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be embodied in the form of a spectral filter that separates the used light wavelength of the illumination radiation 16 from extraneous light of a wavelength deviating therefrom. When the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which are also referred to as field facets hereinafter. FIG. 1 shows only some of the facets 21 as an example.

[0037] The first facet 21 can be embodied in the form of a macroscopic facet, particularly in the form of a rectangular facet, or in the form of a facet having an arcuate or partial circular peripheral contour. The first facet 21 can be embodied as a planar facet or as a convexly or concavely curved facet.

[0038] As known, for example, from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of a plurality of individual mirrors, particularly a plurality of micromirrors. The first facet mirror 20 can be embodied particularly as a microelectromechanical system (MEMS system). For details, reference is made to German Patent Application Publication No. 10 2008 009 600.

[0039] The illumination radiation 16 travels horizontally, i.e., in the y direction, between the collector 17 and the deflection mirror 19.

[0040] In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. When the second facet mirror 22 is arranged on the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US Patent Application Publication No. 2006 / 0132747, European Patent No. 1 614 008, and US Patent No. 6,573,978.

[0041] The second facet mirror 22 includes a plurality of second facets 23. In the case of a pupil facet mirror, the second facet 23 is also referred to as a pupil facet.

[0042] Similarly, the second facet 23 can be a macroscopic facet that can have a boundary such as circular, rectangular, or hexagonal, or a facet composed of micromirrors. In this regard, reference is also made to German Patent Application Publication No. 10 2008 009 600.

[0043] The second facet 23 can have a planar reflecting surface or a reflecting surface that is curved convexly or concavely.

[0044] Therefore, the illumination optical unit 4 forms a double-facet system. This basic principle is also referred to as a fly-eye condenser (fly-eye integrator).

[0045] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 can be arranged to be inclined with respect to the pupil plane of the projection optical unit 10, as described, for example, in German Patent Application Publication No. 10 2017 220 586.

[0046] Using the second facet mirror 22, the individual first facets 21 are imaged onto the object field of view 5. The second facet mirror 22 is the last beam shaping mirror or the actual final mirror for the illumination radiation 16 in the beam path in front of the object field of view 5.

[0047] In yet another embodiment (not shown) of the illumination optical unit 4, a transfer optical unit that particularly contributes to the imaging of the first facet 21 onto the object field of view 5 can be arranged in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit can have exactly one mirror, or two or more mirrors arranged one after the other in the beam path of the illumination optical unit 4. The transfer optical unit can particularly include one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0048] In the embodiment shown in FIG. 1, the illumination optical unit 4 has exactly three mirrors downstream of the collector 17, specifically the deflection mirror 19, the field facet mirror 20, and the pupil facet mirror 22.

[0049] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 can also be omitted, so that in that case the illumination optical unit 4 can have exactly two mirrors behind the collector 17, specifically the first facet mirror 20 and the second facet mirror 22.

[0050] The imaging of the first facet 21 onto the object plane 6 by the second facet 23, or using the second facet 23 and the transfer optical unit, is generally only an approximate imaging.

[0051] The projection optical unit 10 includes a plurality of mirrors Mi, which are sequentially numbered according to their arrangement in the beam path of the projection exposure apparatus 1.

[0052] In the example shown in FIG. 1, the projection optical unit 10 includes six mirrors M1 to M6. Replacements with four, eight, ten, twelve, or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the final mirror M6 each have a passage aperture for the illumination radiation 16. The projection optical unit 10 is a double shielding optical unit. The projection optical unit 10 has a numerical aperture on the image side that is greater than 0.5, may be greater than 0.6, and can be, for example, 0.7 or 0.75.

[0053] The reflecting surface of the mirror Mi can be embodied as a free-form surface without an axis of rotational symmetry. Alternatively, the reflecting surface of the mirror Mi can be designed as an aspherical surface with exactly one axis of rotational symmetry of the reflecting surface shape. Similar to the mirrors of the illumination optical unit 4, the mirror Mi can include a high-reflection coating for the illumination radiation 16. These coatings can be designed in particular as multilayer coatings having alternating layers of molybdenum and silicon.

[0054] The projection optical unit 10 has a large object-image offset in the y direction between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y direction can be approximately the same magnitude as the z distance between the object plane 6 and the image plane 12.

[0055] In particular, the projection optical unit 10 can have an anamorphic embodiment. In particular, this has different imaging scales βx, βy in the x and y directions. The two imaging scales βx, βy of the projection optical unit 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0056] As a result, the projection optical unit 10 reduces its size in the x direction, i.e., in a direction perpendicular to the scanning direction, by a ratio of 4:1.

[0057] The projection optical unit 10 reduces the size by a factor of 8 in the y direction, i.e., the scanning direction.

[0058] Other imaging scales are similarly possible. Imaging scales with the same sign and the same absolute value, for example, an absolute value of 0.125 or 0.25, are also possible in the x and y directions.

[0059] The number of intermediate image planes in the x and y directions in the beam path between the object field 5 and the image field 11 may be the same or may be different depending on the design of the projection optical unit 10. An example of a projection optical unit in which the number of such intermediate images in the x and y directions is different is known from US Patent Application Publication No. 2018 / 0074303.

[0060] Each of the pupil facets 23 is assigned to exactly one of the field facets 21 to form an illumination channel for illuminating the object field 5. In particular, illumination according to the Köhler principle can thereby be obtained. The far field is decomposed into a plurality of object fields 5 using the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus for the pupil facets 23 assigned thereto.

[0061] By means of the respectively assigned pupil facets 23, the field facets 21 are imaged onto the reticle 7 overlappingly to illuminate the object field 5. The illumination of the object field 5 is particularly uniform as much as possible. The uniformity error is preferably less than 2%. By overlapping different illumination channels, field uniformity can be obtained.

[0062] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. By selecting a light-guiding illumination channel, in particular a subset of the pupil facets, the intensity distribution at the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as the illumination setting.

[0063] Similarly favorable pupil uniformity in the defined illumination portion region of the illumination pupil of the illumination optical unit 4 can be achieved by redistribution of the illumination channels.

[0064] Further aspects and details of the illumination of the object field of view 5, in particular of the entrance pupil of the projection optical unit 10, will be explained below.

[0065] The projection optical unit 10 can in particular have a concentric entrance pupil. This can be made accessible. This can also be made inaccessible.

[0066] The entrance pupil of the projection optical unit 10 generally cannot be accurately illuminated using the pupil facet mirror 22. In the case of imaging of the projection optical unit 10 that images the center of the pupil facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a surface where the distance determined for a pair of aperture rays is minimized. This surface represents the entrance pupil or the surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0067] The projection optical unit 10 may have different entrance pupil positions in the tangential beam path and the sagittal beam path. In this case, imaging elements, in particular optical components of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. Using this optical element, the difference in the positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0068] In the arrangement of the components of the illumination optical unit 4 shown in FIG. 1, the pupil facet mirror 22 is arranged on a surface conjugate to the entrance pupil of the projection optical unit 10. The field facet mirror 20 is arranged to be inclined with respect to the object plane 6. The first facet mirror 20 is arranged to be inclined with respect to the arrangement plane defined by the deflection mirror 19.

[0069] The first facet mirror 20 is arranged to be inclined with respect to the arrangement plane defined by the second facet mirror 22.

[0070] FIG. 2 schematically shows a meridian cross section of yet another projection exposure apparatus 101 for DUV projection lithography to which the present invention can similarly be applied.

[0071] The structure and imaging principle of the projection exposure apparatus 101 are equivalent to the configuration and procedure described in FIG. 1. The same components are denoted by reference numerals increased by 100 from those in FIG. 1, that is, the reference numerals in FIG. 2 start from 101.

[0072] Unlike the EUV projection exposure apparatus 1 described in FIG. 1, since the wavelength of the DUV radiation 116 used as the light to be used is in the range of 100 nm to 300 nm, particularly as large as about 193 nm, refractive, diffractive, and / or reflective optical elements 117 such as lens elements, mirrors, prisms, end plates, etc. can be used for imaging or illumination in the DUV projection exposure apparatus 101. In this case, the projection exposure apparatus 101 essentially includes an illumination system 102, a reticle holder 108 that houses and accurately positions a reticle 107 provided with a structure for determining the subsequent structure on the wafer 113, a wafer holder 114 that holds, moves, and accurately positions the wafer 113, and a projection lens 110 having a plurality of optical elements 117, and the optical elements 117 are held by mounts 118 in a lens housing 119 of the projection lens 110.

[0073] The illumination system 102 supplies the DUV radiation 116 necessary for imaging the reticle 107 onto the wafer 113. A laser, a plasma source, or the like can be used as a source for this radiation 116. The radiation 116 is shaped by optical elements in the illumination system 102 such that the DUV radiation 116 has desired characteristics regarding diameter, polarization, wavefront shape, etc. when incident on the reticle 107.

[0074] In addition to using additional refractive optical elements 117 such as lens elements, prisms, end plates, etc., the configuration of the downstream projection optical unit 110 having the lens housing 119 is basically the same as the configuration described in FIG. 1, and thus will not be described in further detail.

[0075] The devices shown in FIGS. 1 and 2 each accommodate a plurality of components that can be positioned or deformed by an actuator. Therefore, the characteristics of the actuator used for this purpose directly affect the performance of the illustrated device.

[0076] FIG. 3 schematically shows the behavior of the mechanical strain of the actuator when the voltage is returned to the minimum voltage, in this example 0V, after applying the voltage until the maximum voltage is reached, and this behavior is known per se. The occurrence of hysteresis is easily distinguishable from the figure. In other words, the mechanical strain of the actuator corresponding to the corresponding voltage value in the case of voltage drop does not correspond to the mechanical strain of the actuator in the case of voltage rise. In principle, it is difficult to explain the root causes from a physical point of view, and these effects can essentially only be modeled macroscopically.

[0077] Furthermore, as shown in FIG. 4, a normal actuator also has a certain degree of drift behavior in addition to the above-mentioned hysteresis effect. In other words, even when a rectangular voltage signal is applied, the desired deflection of the actuator does not occur instantaneously but occurs with a specific time profile.

[0078] The above effects are particularly advantageous when the actuator has to achieve a large deflection in a relatively short period of time. This situation will be explained based on FIG. 5. The drift in the direction of the target deflection of this actuator during the first exposure of the adjacent region after the exemplary actuator has deflected over a relatively large distance of movement is easily distinguishable in this figure. In these first regions, it can be assumed that only insufficient imaging results can be obtained.

[0079] The operating mode of the model will be exemplarily described below based on FIGS. 6 and 7.

[0080] In this case, in the diagram shown in Fig. 6, the deflection of the actuator is qualitatively plotted against the voltage applied to the actuator. In this case, the actual deflection is represented by a dashed line, while the curve generated based on the model is represented by a dotted curve. It is easily distinguishable in this diagram that there is initially a slight deviation between the two curves.

[0081] The quality and operating mode of the model can only be identified when performing an examination of the differences as shown in Fig. 7. The solid curve in Fig. 7 shows the result obtained by subtracting the curve that occurs when using a model that does not consider the above effects from the curve generated based on a complete model, that is, particularly considering hysteresis and drift. As a result, a diagram that clearly identifies the influence of the above effects is obtained. As already described, the solid curve is based only on model-based calculations.

[0082] The second graph shown in Fig. 7 is obtained by subtracting the measured value of the deflection of the target actuator from the ideal curve, that is, the curve that would result from the model when the effects are omitted. It is clearly distinguishable in this diagram that there is a high degree of correspondence between the two displays, and conclusions regarding the quality of the model used can be drawn.

[0083] The diagrams shown in Figs. 8a - d show various deformation forms for implementing the model.

[0084] First, Fig. 8a visualizes the subtraction method. This method is essentially based on first assuming a specific target value of deflection, for example, 40 pm. Subsequently, using the model, the simulated deflection resulting from assuming the above target value is obtained. For example, if the model supplies a value of 38 pm at this time, the difference between the two values, that is, 2 pm, is added to the target value, and this forms the basis for the actual control to obtain the desired deflection.

[0085] Fig. 8b shows the inversion method. In this case, for a reversible model, the output and input are swapped and incorporated into the controller.

[0086] Figure 8c shows a model-based closed-loop control method. In this case, the planned actuation signal is first used as the starting value of the model, and subsequently a specific movement distance is obtained. The movement distance simulated by the model is then supplied to the loop controller, which compares the desired model with the model thus obtained and then uses the model again to adjust the actuation signal until the desired movement distance is obtained. As soon as this state is achieved, the actuator is driven using the actuation signal thus obtained.

[0087] Figure 8d shows a combination of the deformation modes described based on Figures 8b and 8c. Naturally, different combinations are also possible.

[0088] The effect of the method according to the present invention will be explained once again based on Figure 9. Here, the time-dependent overlay error of the structure generated after the deflection of the actuator is plotted. Here, each individual exposure procedure is visualized using dots in the case of correction and dashed lines in the case of no correction. It is clear from the figure that in the case of no correction, there is a large error for each first exposure procedure of a group of exposure procedures. As already described above, this is due to the fact that after a large displacement of the actuator, the first in the group has not yet reached the desired end position. In contrast, in the case of correction (indicated by dots), practically no deviation can be identified.

[0089] Figure 10 schematically shows the method procedure according to the present invention again in a flowchart.

[0090] The following steps are illustrated. Step 30 of evaluating the characteristics of the actuator, Step 31 of parameterizing the actuator model, Step 32 of implementing the actuator model in the control structure, Step 34 of driving the actuator using the actuator model, and The above-mentioned reference step 33.

[0091] It is obvious that the schematic diagram shown in FIG. 10 is merely illustrative. In particular, reference 33, while being an advantageous step, is optional.

Explanation of Reference Signs

[0092] 1 Projection Exposure Device 2 Illumination System 3 Radiation Source 4 Illumination Optical Unit 5 Object Field of View 6 Object Plane 7 Reticle 8 Reticle Holder 9 Reticle Displacement Drive 10 Projection Optical Unit 11 Image Field of View 12 Image Plane 13 Wafer 14 Wafer Holder 15 Wafer Displacement Drive 16 EUV Radiation 17 Collector 18 Intermediate Focus Plane 19 Deflection Mirror 20 Facet Mirror 21 Facet 22 Facet Mirror 23 Facet 30 Method Step of "Evaluating the Characteristics of the Actuator" 31 Method Step of "Parameterizing the Actuator Model" 32 Method Step of "Implementing the Model" 33 Method Step of "Referring to" 34 Method Step of "Driving" 101 Projection Exposure Device 102 Illumination System 107 Reticle 108 Reticle Holder 110 Projection Optical Unit 113 Wafer 114 Wafer Holder 116 DUV Radiation 117 Optical Element 118 Mount 119 Lens housing Mirrors M1 to M6

Claims

1. A method for driving an actuator of an optical component (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, comprising: a step (30) of evaluating the characteristics of the actuator; a step (31) of parameterizing an actuator model; a step (32) of implementing the actuator model in a control structure; a step (34) of driving the actuator using the actuator model, wherein the step (30) of evaluating the characteristics of the actuator is a method executed within the projection exposure apparatus (1, 101).

2. The method according to claim 1, wherein a reference step (33) is performed at a specific time point.

3. The method according to claim 2, wherein the reference step (33) includes resetting model parameters.

4. The method according to claim 2 or 3, wherein the reference step (33) includes moving towards a specified actuator position.

5. The method according to any one of claims 2 to 4, wherein the time at which the reference step (33) is performed is between the exposures of two wafers.

6. The method according to any one of claims 1 to 5, wherein the evaluation of the characteristics (30) of the actuator includes detecting one or more of length change, frequency response, hysteresis, and drift, which are actuator parameters.

7. The method according to any one of claims 1 to 6, wherein during the parameterization (31) of the actuator model, at least one separate model is generated for at least one of the actuator parameters, and this is subsequently superimposed on at least one further separate model.

8. The method according to any one of claims 1 to 7, wherein the actuator is an electrostrictive actuator, a piezoelectric actuator, or a magnetostrictive actuator.

9. The method according to any one of claims 1 to 8, wherein the actuator is configured to position the component (Mx, 117).

10. The method according to any one of claims 1 to 9, wherein the actuator is configured to deform the component (Mx, 117).

11. The method according to any one of claims 1 to 10, The component is an optical element (Mx, 117). **Claim 12** In the method according to claim 11, The component is a mirror (Mx).

Images