Projection exposure apparatus and method for designing components of projection exposure apparatus

Abstract

The invention relates to a component (30) of a projection exposure apparatus (1, 101) for semiconductor lithography, the component (30) comprising an optical element (31) and an actuator (32, 35, 39.x, 43, 50), the optical element (31) and the actuator (32, 35, 39.x, 43, 50) being frictionally connected to one another, the actuator (32, 35, 39.x, 43, 50) being configured to at least locally deform the optical element (31). According to the invention, the actuator (32, 35, 39.x, 43, 50) is embodied in such a way as to minimize the influence on the imaging quality of stiffness losses in a perimeter defining the actuator (32, 35, 39.x, 43, 50). The invention further relates to a method for designing a component (30) of a projection exposure apparatus (1, 101) having an optical element (31) and actuators (32, 35, 39.x, 43, 50) in order to minimize the effects of parasitic deformations on the imaging quality of the projection exposure apparatus (1, 101) in the event of deformations of the optical element (31) caused by the actuators (32, 35, 39.x, 43, 50), comprising the steps of designing the actuators (32, 35, 39.x, 43, 50) and determining whether the actuators (32, 35, 39.x, 43, 50) are capable of deforming the optical element (31) or the optical element (31) by actuation or by the actuators (32, 35, 39.x, 43, 50). The method includes the steps of: determining parasitic deformations of an optical element (31) caused by differences in the thermal expansion coefficients of the elements (32, 35, 39.x, 43, 50); determining parasitic aberrations based on the parasitic deformations, taking into account the summation effect of scanning exposures used in a projection exposure apparatus (1, 101); optimizing an actuator (32, 35, 39.x, 43, 50) based on the determined parasitic aberrations; and repeating at least some of the previous process steps (61, 62, 63, 64) until the value of the parasitic aberrations falls below a predetermined value.

Description

Technical Field

[0001] This application claims the priority of German Patent Application No. 10 2021 205 368.8 filed on May 27, 2021, the content of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a component of a projection exposure apparatus for semiconductor lithography and a method for designing the component, in particular for minimizing the adverse effects of parasitic deformations caused by actuators on the imaging quality of the projection exposure apparatus.

Background Art

[0003] In a projection exposure apparatus for semiconductor lithography, an optical element such as a lens element and / or a mirror is used to image a lithography mask, also known as a reticle, for example a phase mask, onto a semiconductor substrate, also known as a wafer.

[0004] In particular, in order to achieve high resolution of the lithography optical unit, EUV light having a wavelength in the region of, for example, 1 nm to 120 nm, particularly 13.5 nm, has also been used in recent years compared to conventional systems having typical wavelengths of 365 nm, 248 nm, or 193 nm.

[0005] Among the optical elements used in that case, there are those that are particularly mechanically operated for improving imaging quality and correcting disturbances occurring during operation, and it is necessary to distinguish between a pure shift of the optical element and a deformation of the optical element.

[0006] In the case of a deformable mirror, for example, an actuator in the form of an actuator matrix is adhesively connected or joined to the back side of the mirror to create a mechanical connection for the desired deformation.

[0007] An actuator matrix embodied in the form of a quadrilateral plate and including a plurality of interconnected actuator pads is known from the prior art. The individual actuator pads are usually quadrilateral or triangular and include holes that are usually arranged at the corners or sides of the actuator pads. These have the function of being able to bring the actuator pads into contact with a controller. A physical loss of rigidity in the combination of the actuator and the optical element occurs around the entire circumference of the actuator, that is, at the outer edge of the plate of the actuator matrix and around the holes, and this loss results in parasitic deformation of the surrounding area during operation or due to, for example, a difference in thermal expansion based on a difference in the coefficient of thermal expansion. This has an adverse effect on the imaging quality of the projection exposure apparatus.

[0008] Due to the scanning operation mode of today's lithography systems, that is, the movement of the phase mask under the illumination slit and the movement of the wafer in the opposite direction, the aberration caused by the above parasitic deformation can accumulate along the scanning direction, making the adverse effect even more prominent.

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a component that eliminates the above-mentioned drawbacks of the prior art. Another further object of the present invention consists of specifying a method for designing the above-mentioned component.

Means for Solving the Problems

[0010] This object is achieved by a component and a method having the features of the independent claims. The dependent claims relate to advantageous developments and variants of the present invention.

[0011] A component of a projection exposure apparatus for semiconductor lithography according to the present invention includes an optical element and an actuator. The optical element and the actuator are mutually force-fittinglyConnected, the actuator is configured to at least locally deform the optical element. According to the present invention, the actuator is embodied so as to minimize the influence of the loss of rigidity in the periphery defining the actuator on the imaging quality. Between the actuator and an optical element such as a mirror force-fitting with each other The connection can be realized by an adhesive connection or bonding, or by a detachable connection such as a screw connection.

[0012] In a first embodiment of the present invention, the actuator can be embodied in the form of an actuator matrix including at least two actuator pads. The actuator matrix usually includes 9 to 30 actuator pads.

[0013] In particular, the cumulative length of the peripheral portion of the actuator extending on an axis parallel to the scanning direction used in the projection exposure apparatus can be minimized. In the scanning exposure method used in the projection exposure apparatus, in this case, some of the optical effects of disturbances extending perpendicular to the scanning direction such as parasitic deformation are averaged and minimized by the scanning operation, which has an advantageous effect.

[0014] Furthermore, the outer periphery of the actuator is oriented at least partially inclined with respect to the scanning direction. As a result, it is advantageous that the total due to the scanning operation of the portion extending in the scanning direction of the periphery is minimized.

[0015] In particular, the actuator includes a peripheral contour that meanders with respect to the scanning direction. The contour can be realized, for example, by the actuator pads being hexagonal and arranging the actuator pads in a row shape by shifting them by half the width of the actuator pads, and the protrusions of the actuator pads protruding into the recesses of adjacent pads.

[0016] Furthermore, the linear peripheral structure of the actuator can be oriented at an angle with respect to the scanning direction. This has the advantage that there are no parts on the periphery defining the actuator that are aligned with the scanning direction. However, it is necessary to consider the structural influence that the inclination of the actuator may have on the deformation effect of the actuator with respect to the optically effective surface.

[0017] In particular, the contact holes of the actuator pads formed in the actuator matrix can be designed to reduce the cumulative length of the edge portions of the holes extending on an axis parallel to the scanning direction used in the projection exposure apparatus.

[0018] This can be achieved, for example, by minimizing the area of at least some of the holes, as a result of which the total cumulative length of the edges of all the holes is reduced. The holes can be formed at corners, sides, within the effective surface of the actuator pads, or a combination of these parts. The size of the holes is determined by the space required for contact.

[0019] Furthermore, the holes can be arranged such that the number of holes arranged on an axis extending parallel to the scanning direction is minimized. In this way, the parasitic aberration accumulated by the scanning movement is minimized. The number of holes positioned on the axis can be reduced, for example, by the advantageous arrangement of the holes with respect to the actuator pads as described above.

[0020] In yet another embodiment of the present invention, the actuator pads can have a geometric shape such as triangular, rectangular, or hexagonal. In addition to the geometric shape of the actuator pads, the number of rows and columns of the actuator matrix formed by the actuator pads can also be freely selected, so, for example, a matrix of 3 rows and 3 columns to 5 rows and 5 columns or more is conceivable. The number of rows and columns does not have to be the same, and thus a matrix of 4 rows and 6 columns can also be formed.

[0021] In yet another embodiment of the present invention, the actuator can have a separately controllable portion for correcting stiffness loss. Thereby, it becomes possible to consider the stiffness of the entire system consisting of the actuator pads and the mirror material that vary in the region of the intermediate space by correspondingly changing the control of the above portion, so that unwanted movement / deformation is suppressed and possible resulting image errors are avoided.

[0022] In particular, the above portion is formed as a peripheral actuator pad of the actuator pads arranged in the peripheral region of the actuator matrix, is controllable independently of the second region of the actuator pads formed as partial actuator pads, and can be configured to correct parasitic deformation caused by stiffness loss. Since the peripheral actuator pads enhance the deformation effect in the periphery compared to the non-divided actuator pads, the stiffness loss can be compensated.

[0023] A method according to the present invention for designing components of a projection exposure apparatus to minimize the effect of parasitic deformation on the imaging quality of a projection exposure apparatus having an optical element and an actuator when deformation of the optical element is caused by the actuator is a step of designing an actuator, a step of determining parasitic deformation of the optical element caused by actuation or by the difference in the thermal expansion coefficients of the optical element and the actuator, a step of determining parasitic aberration based on the parasitic deformation in consideration of the total effect of the scanning exposure used in the projection exposure apparatus, a step of optimizing the actuator based on the determined parasitic aberration, a step of repeating at least some of the previous process steps until the value of the parasitic aberration falls below a predetermined value and includes.

[0024] Parasitic deformation can be determined on the optically effective surface of an optical element, for example, by FEM simulation or using optical measurement techniques. Parasitic aberration can be determined by simulation based on parasitic deformation or by measurement at the component level or for the entire system, i.e., in a projection exposure apparatus.

[0025] Furthermore, parasitic deformation can be corrected using at least a part of the movement amount of the actuator. This self-correction has the advantage that, as is known, the errors can be compensated at the sites where the errors occur.

[0026] Furthermore, when determining the parasitic aberration that occurs, further other means for optimizing the imaging quality existing in the projection exposure apparatus can be considered.

[0027] In particular, the above means can be embodied in the form of a manipulator for positioning or deforming further optical elements of the projection exposure apparatus. Usually, substantially all optical elements of the projection exposure apparatus are operable, and thus many additional correction means are available.

[0028] Furthermore, one means can be embodied in the form of an algorithm based on simulation for predicting the imaging quality considering a plurality of influencing parameters and determining the movement amount of the manipulator required therefor.

[0029] Exemplary embodiments and modifications of the present invention will be described in more detail below with reference to the drawings.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 4a

Figure 4b

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0031] The essential components of the microlithographic projection exposure apparatus 1 will first be described as an example with reference to FIG. 1. It should be understood that the description of the basic structure of the projection exposure apparatus 1 and its components is not limited here.

[0032] One embodiment of the illumination system 2 of the projection exposure apparatus 1 has an illumination optical unit 4 that illuminates the object field 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 separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0033] The reticle 7 disposed in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable particularly in the scanning direction by a reticle displacement drive 9.

[0034] For the sake of explanation, an orthogonal xyz coordinate system is shown in FIG. 1. 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 along the y direction. The z direction extends perpendicular to the object plane 6.

[0035] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to form an image of the object field 5 on the image field 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.

[0036] 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 along the y direction by a wafer displacement drive 15. On the one hand, the displacement of the reticle 7 by the reticle displacement drive 9 and, on the other hand, the displacement of the wafer 13 by the wafer displacement drive 15 can be performed in synchronization with each other.

[0037] The radiation source 3 is an EUV radiation source. The radiation source 3 particularly emits EUV radiation 16, also 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 laser (FEL).

[0038] 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°, or at a normal incidence (NI), that is, at an incident angle less than 45°. The collector 17 can be structured and / or coated in order to optimize the reflectivity for the used radiation first and to suppress the extraneous light second.

[0039] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focus of the intermediate focus plane 18. The intermediate focus plane 18 can represent the separation between the radiation source module having the radiation source 3 and the collector 17 and the illumination optical unit 4.

[0040] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a plane deflection mirror or a mirror with a beam-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be in the form of a spectral filter which separates the used optical wavelength of the illumination radiation 16 from extraneous light of wavelengths deviating therefrom. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 which is optically conjugate with the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, also referred to as field facets in the following. FIG. 1 shows only some of said facets 21 by way of example.

[0041] The first facet 21 may be in the form of a macroscopic facet, in particular a rectangular facet or a facet having an arcuate or part-circular peripheral contour. The first facet 21 may be in the form of a planar facet or a convexly or concavely curved facet.

[0042] The first facet 21 itself can also consist of a number of individual mirrors, in particular a number of micromirrors, as is known, for example, from DE 10 2008 009 600. The first facet mirror 20 can in particular be formed as a microelectromechanical system (MEMS system). See DE 10 2008 009 600 for further information.

[0043] Between the collector 17 and the deflection mirror 19, the illumination radiation 16 travels horizontally, ie along the y direction.

[0044] 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.

[0045] The second facet mirror 22 includes a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0046] Similarly, the second facets 23 can also be macroscopic facets having a surrounding such as circular, rectangular, or hexagonal, or facets composed of micromirrors. In this regard, reference is also made to German Patent Application Publication No. 10 2008 009 600.

[0047] The second facets 23 can have a planar reflecting surface, or a reflecting surface curved convexly or concavely.

[0048] As a result, 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).

[0049] 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, as described in German Patent Application Publication No. 10 2017 220 586, the pupil facet mirror 22 can be arranged to be inclined with respect to the pupil plane of the projection optical unit 10.

[0050] Using the second facet mirror 22, each first facet 21 is 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 upstream of the object field of view 5.

[0051] 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 another 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).

[0052] 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.

[0053] In yet another embodiment of the illumination optical unit 4, since the deflection mirror 19 is not necessary, the illumination optical unit 4 can have exactly two mirrors downstream of the collector 17 in that case, specifically the first facet mirror 20 and the second facet mirror 22.

[0054] 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 usually only an approximate imaging.

[0055] The projection optical unit 10 includes a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure apparatus 1.

[0056] 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.

[0057] The reflecting surface of the mirror Mi can be embodied as a freeform 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 have 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.

[0058] 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. In the y direction, this object-image offset can be approximately the same size as the z distance between the object plane 6 and the image plane 12.

[0059] In particular, the projection optical unit 10 can have an anamorphic form. 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.

[0060] As a result, the projection optical unit 10 reduces its size in the x direction, that is, in the direction perpendicular to the scanning direction, by a ratio of 4:1.

[0061] The projection optical unit 10 reduces the size by a factor of 8 in the y direction, i.e., the scanning direction.

[0062] 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, in the x and y directions are also possible.

[0063] 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 embodiment of the projection optical unit 10. An example of a projection optical unit 10 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.

[0064] 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 be obtained in this way. 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 on the pupil facets 23 assigned to them.

[0065] By means of the respectively assigned pupil facets 23, the field facets 21 are imaged onto the reticle 7 overlapping for the purpose of illuminating 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.

[0066] 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 in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as the illumination setting.

[0067] 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.

[0068] 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.

[0069] In particular, the projection optical unit 10 can have a concentric entrance pupil. This can be made accessible. This can also be made inaccessible.

[0070] The entrance pupil of the projection optical unit 10 usually 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 obtained for a pair of aperture rays is minimized. This surface represents the entrance pupil or a real space surface conjugate thereto. In particular, this surface has a finite curvature.

[0071] The projection optical unit 10 may have different positions of the entrance pupil in the tangential beam path and the sagittal beam path. In this case, imaging elements, in particular the optical component parts 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.

[0072] 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 surface 6. The first facet mirror 20 is arranged to be inclined with respect to the arrangement surface defined by the deflection mirror 19.

[0073] The first facet mirror 20 is arranged to be inclined with respect to the arrangement surface defined by the second facet mirror 22.

[0074] Figure 2 schematically shows in a meridional cross section another projection exposure apparatus 101 for DUV projection lithography that can similarly use the present invention.

[0075] The configuration and imaging principle of the projection exposure apparatus 101 are equivalent to the configuration and procedure described in FIG. 1. The same component parts are denoted by reference numerals increased by 100 from FIG. 1, that is, the reference numerals in FIG. 2 start from 101.

[0076] Unlike the EUV projection exposure apparatus 1 described in FIG. 1, since the DUV radiation 116 used as the light to be used has a large wavelength in the range of 100 nm to 300 nm, particularly 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 substantially includes an illumination system 102, a reticle holder 108 that houses and accurately positions a reticle 107 provided with a structure that determines 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. The optical elements 117 are held by a mount 118 in a lens housing 119 of the projection lens 110.

[0077] The illumination system 102 supplies the DUV radiation 116 necessary for imaging the reticle 107 on the wafer 113. A laser, a plasma source, etc. can be used as the source of this radiation 116. The radiation 116 is shaped by optical elements in the illumination system 102 so that the DUV radiation 116 has desired characteristics regarding diameter, polarization, wavefront shape, etc. when incident on the reticle 107.

[0078] In addition to additionally using refractive optical elements 117 such as lens elements, prisms, end plates, etc., the configuration of the downstream projection optical unit 110 having a lens housing 119 is not different in principle from the configuration described in FIG. 1, and thus will not be described in more detail.

[0079] Figure 3a shows a component 30 known from the prior art, which includes a mirror 31 and two actuators in the form of an actuator matrix 32. The actuator matrix 32 is arranged side by side on the back side of the mirror 31, which is positioned on the opposite side of the optically effective surface (not shown) of the mirror 31. Each actuator matrix 32 has a plurality of square actuator pads 33 arranged in a matrix, and has holes at its corners for contacting the actuator pads 33 with a controller (not shown). The plate-shaped actuator matrix 32 is rectangular, and two of the four circumferences of the actuator matrix 32 extend in the scanning direction indicated by the thick arrow in Fig. 3a. The holes 34 between the actuator pads 33 are respectively positioned one behind the other on an axis (indicated by a dashed line) extending parallel to the scanning direction. The resulting parasitic deformation accumulates in the scanning direction and causes aberration. In principle, the actuator matrix 32 can also have a curved shape. The number of actuator matrices 32 arranged on the mirror 31 can be freely selected, that is, three, four, or more actuator matrices 32 can be formed on the mirror 31. Similarly, the number of rows and columns of the actuator matrix 32 can also be freely selected. Therefore, in addition to the embodiment described in Fig. 3a having two actuator matrices 32 with four rows and three columns, the component 30 can also include three actuator matrices 32 with five rows and five columns, or four matrices 32 with four rows and five columns, or any other combination on the mirror 31. The number of actuator matrices 32 and matrices here mainly varies according to the use and productivity of the actuator matrix 32.

[0080] Figure 3b shows a diagram of the parasitic aberration that accumulates during the scanning operation. These are caused by parasitic deformations due to the peripheral effect of the actuator matrix 32 based on the loss of rigidity. The dot density used in the figure here corresponds to the wavefront deviation in the positive or negative direction. The aberration arranged in the scanning direction indicated by the thick arrow in Fig. 3b can be clearly visually recognized in the form of a region of the same dot density extending in the scanning direction.

[0081] Figure 4a shows a component 30 according to the invention, comprising a mirror 31 and two actuators in the form of an actuator matrix 35 arranged side by side. Each actuator matrix 35 has hexagonal actuator pads 36, which also have holes 38 at the corners for contacting the actuator pads 36 with a controller (not shown). The holes 38 are elliptical, and the major axes of the holes 38 are aligned perpendicular to the scanning direction. The actuator pads 36 are arranged in rows 37 perpendicular to the scanning direction indicated by the thick arrows in Figure 4a. The rows 37 are also offset from each other by half the width of each actuator pad and arranged alternately, perpendicular to the scanning direction. This results in a peripheral contour that meanders with respect to the scanning direction around the actuator matrix 35 positioned parallel to the scanning direction. Thus, it is advantageous that parasitic deformations caused by the peripheral contour due to rigidity loss are averaged by the scanning operation, and the resulting aberration is thereby minimized. In addition to the adaptation of the peripheral contour to the scanning direction, the minor axis of the elliptical holes 38 for contacting the actuator pads 36 is smaller than the diameter of the holes shown in Figure 3a, so that the cumulative length of the edge portions of the holes 38 extending parallel to the scanning direction is reduced. Furthermore, a plurality of on-axis holes 38 shown by dashed lines in Figure 4a are arranged parallel to the scanning direction due to the hexagonal shape of the actuator pads 36, so that the parasitic cumulative error per axis is reduced. As a result, it is advantageous that the amplitude of the aberration is minimized. In order to keep the distance between adjacent actuator matrices 35 as small as possible, the actuator matrices 35 are arranged in an intermeshing manner. Thus, the deformation effect of the actuator pads 36 at the abutting edges of two adjacent actuator matrices 35 is equivalent to that of the actuator matrix 32 described in Figure 3a known from the prior art. As already explained with respect to Figure 3a, the actuator matrix 32 can also have a curved shape in principle. Furthermore, the number of actuator matrices 32 arranged on the mirror 31 can be freely selected, i.e., three, four, or more actuator matrices 32 can be formed on the mirror 31. Similarly, the number of rows and columns of the actuator matrix 32 can also be freely selected.Thus, in addition to the embodiment described in FIG. 4a where the component 30 has two actuator matrices 32 of 4 rows and 3 columns, the mirror 31 can also include three actuator matrices 32 of 5 rows and 5 columns, or four matrices 32 of 4 rows and 5 columns, or any other combination. The number of actuator matrices 32 and the matrix will mainly vary here according to the use and productivity of the actuator matrix 32.

[0082] Compared with the diagram of the parasitic aberration described in FIG. 3b, FIG. 4b shows a significant reduction in the parasitic aberration accumulated by the scanning operation, which can be recognized firstly by the reduction in the average absolute value of the point density and secondly by the shift of the profile of the region of the same point density, and thus the same aberration, from the scanning direction.

[0083] FIGS. 5a to 5f show still other alternative embodiments of the actuator matrices 39.1, 39.2, 39.3, 39.4, 39.5, 39.6 with different geometric shapes of the actuator pads 40.1, 40.2, 40.3, 40.4, 40.5, 40.6 and different arrangements of the holes 41.1, 41.2, 41.3, 41.4, 41.5, 41.6 for contact. Different combinations of the geometric shapes of the actuator pads 40.1, 40.2, 40.3, 40.4, 40.5, 40.6 and the shapes and arrangements of the holes 41.1, 41.2, 41.3, 41.4, 41.5, 41.6 are shown in the following table. The scanning direction is illustrated by the arrow.

[0084]

Table 1

[0085] FIG. 6 shows yet another embodiment of the present invention showing a component 30 having a mirror 31 and an actuator matrix 43. As already described above, the parasitic deformation caused by the loss of rigidity in the peripheral region of the actuator matrix 43 is minimized by the scanning operation if the peripheral length of the actuator matrix 43 on an axis aligned parallel to the scanning direction is minimized. In the exemplary embodiment shown in FIG. 6, by making the actuator matrix 43 trapezoidal, since the entire circumference is not aligned parallel to the scanning direction, it is advantageous that the parasitic aberration caused by the parasitic deformation in the peripheral region can be substantially completely avoided or significantly averaged by the scanning operation.

[0086] FIG. 7 shows a detailed view of a component 30 having a mirror 31 and actuator pads 51 arranged around an actuator embodied in the form of an actuator matrix 50. The actuator pads 51 are divided into partial actuator pads 52 and peripheral actuator pads 53, which can be controlled independently of each other via respective lines 54, 55. This has the advantage that the deformation of the optically effective surface 56 caused by the peripheral actuator pads 53 shown by solid lines in FIG. 7 is larger in the peripheral region than the deformation caused by the undivided actuator pads shown by dashed lines in FIG. 7. The parasitic deformation caused by the loss of rigidity in the peripheral region of the actuator matrix 50 is thereby at least partially compensated, so that it is advantageous that the parasitic aberration is minimized.

[0087] FIG. 8 shows a possible way of designing a component 30 of a projection exposure apparatus 1, 101 to minimize the effect of parasitic deformation on the imaging quality of the projection exposure apparatus 1, 101 having an optical element 31 and actuators 32, 35, 39.x, 43, 50 when the optical element 31 is deformed by the actuators 32, 35, 39.x, 43, 50.

[0088] In a first method step 61, the actuators 32, 35, 39.x, 43, 50 are designed.

[0089] In the second method step 62, parasitic deformation of the optical element 31 caused by actuation or by the difference in the coefficients of thermal expansion between the optical element 31 and the actuators 32, 35, 39.x, 43, 50 is determined.

[0090] In the third method step 63, parasitic aberrations are determined based on the parasitic deformation, taking into account the overall effect of the scanning exposure used in the projection exposure apparatus.

[0091] In the fourth method step 64, the actuators are optimized based on the determined parasitic aberrations. In this case, in particular, the shape and arrangement of the individual actuator pads and holes can be changed.

[0092] In the fifth step 65, at least some of the previous process steps are repeated until the value of the parasitic aberration falls below a predetermined value.

Explanation of Signs

[0093] 1 Projection exposure apparatus 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 18 Intermediate focal plane 19 Deformable mirror 20 Facet mirror 21 Facet 22 Facet mirror 23 Facet 30 Component 31 Mirror 32 Actuator matrix 33 Actuator Pad 34 Hole 35 Actuator Matrix 36 Actuator Pad 37 Row 38 Hole 39.1 - 39.6 Actuator Matrix 40.1 - 40.6 Actuator Pad 41.1 - 41.6 Hole 42 Electrode 43 Actuator Matrix 50 Actuator Matrix 51 Actuator Pad 52 Partial Actuator Pad 53 Peripheral Actuator Pad 54 Line 55 Line 56 Optically Active Surface 61 Method Step 1 62 Method Step 2 63 Method Step 3 64 Method Step 4 65 Method Step 5 101 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

Claims

1. A projection exposure apparatus (1, 101) comprising a projection objective lens (10, 110) including a component (30), wherein the component (30) includes an optical element (31) and actuators (32, 35, 39.x, 43, 50), and the optical element (31) and the actuators (32, 35, 39.x, 43, 50) are connected so as to be fixed to each other by a mating force, and the actuators (32, 35, 39.x, 43, 50) are configured to at least locally deform the optical element (31). In the projection exposure apparatus (1, 101), the actuator is in the form of an actuator matrix (32, 35, 39.x, 43, 50) including at least two interconnected actuator pads (33, 36, 40.x, 51), the actuators (32, 35, 39.x, 43, 50) are embodied such that the peripheral contour of the actuator (35) meanders with respect to the scanning direction, or the peripheral contour of the actuator (39.x) is formed by shifting the actuator pads (40.x) into a row shape, or the linear peripheral structure of the actuator (43) is oriented at an angle with respect to the scanning direction. A projection exposure apparatus characterized by this.

2. In the projection exposure apparatus (1, 101) according to Claim 1, the contact holes (34, 38, 41.x) of the actuator pads (33, 36, 40.x, 51) formed in the actuator matrix (32, 35, 39.x, 43, 50) are designed to reduce the cumulative length of the edge portions of the holes (34, 38, 41.x) extending on an axis parallel to the scanning direction used in the projection exposure apparatus (1, 101). A projection exposure apparatus characterized by this.

3. In the projection exposure apparatus (1, 101) according to Claim 2, at least some of the areas of the holes (34, 38, 41.x) are minimized. A projection exposure apparatus characterized by this.

4. In the projection exposure apparatus (1, 101) according to Claim 2, the holes (34, 38, 41.x) are arranged to reduce the number of the holes (34, 38, 41.x) arranged on an axis extending parallel to the scanning direction. A projection exposure apparatus characterized by this.

5. In the projection exposure apparatus (1, 101) according to Claim 1, The projection exposure apparatus is characterized in that the actuator pads (33, 36, 40.x, 51) have a triangular, rectangular, or hexagonal geometric shape.

6. In the projection exposure apparatus (1, 101) according to claim 1, the actuator (50) has a separately controllable part (53) for correcting rigidity loss, and the projection exposure apparatus is characterized thereby.

7. In the projection exposure apparatus (1, 101) according to claim 6, the part is formed as a peripheral actuator pad (53) of an actuator pad (51) arranged in a peripheral region of an actuator matrix (50), is controllable independently of a second region of the actuator pad (51) formed as a partial actuator pad (52), and is configured to correct parasitic deformation caused by rigidity loss, and the projection exposure apparatus is characterized thereby.

8. A method for designing a component (30) of a projection exposure apparatus (1, 101) having an optical element (31) and actuators (32, 35, 39.x, 43, 50) to minimize the effect of parasitic deformation on the imaging quality of the projection exposure apparatus (1, 101) when deformation of the optical element (31) is caused by the actuators (32, 35, 39.x, 43, 50), the method comprising: designing the actuators (32, 35, 39.x, 43, 50); determining parasitic deformation of the optical element (31) caused by actuation or by a difference in the thermal expansion coefficients of the optical element (31) and the actuators (32, 35, 39.x, 43, 50); determining parasitic aberration based on the parasitic deformation in consideration of the overall effect of the scanning exposure used in the projection exposure apparatus (1, 101); optimizing the actuators (32, 35, 39.x, 43, 50) based on the determined parasitic aberration; and repeating at least some of the previous process steps (61, 62, 63, 64) until the value of the parasitic aberration falls below a predetermined value. The method includes the above steps.

9. In the method according to claim 8, the method is characterized in that parasitic deformation is corrected using at least a part of the movement amount of the actuators (32, 35, 39.x, 43, 50).

10. In the method according to claim 8 or 9, A method for determining parasitic aberration, characterized by considering still other means for optimizing the imaging quality present in the projection exposure apparatus (1, 101). **Claim 11** In the method according to claim 10, the means is embodied in the form of a manipulator for positioning or deforming further optical elements of the projection exposure apparatus (1, 101), characterized by the method. **Claim 12** In the method according to claim 10, characterized by embodying one means in the form of an algorithm based on a simulation for predicting the imaging quality considering a plurality of influencing parameters and determining the amount of movement of the manipulator required therefor.

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