Methods for improving the correction potential of a semiconductor technology system and semiconductor technology system

Abstract

The invention relates to a method for improving the correction potential for correcting at least one load case for a system (1, 101) for semiconductor technology with an optical module (10, 110) with an optical assembly (30, 50), wherein the optical assembly (30, 50) has at least one actuator (41.x, 61.x) for moving an optical element (31, 51) of the optical assembly (30, 50), comprising the following method steps: - Determination of a desired correction potential of the system (1,101), - Design of a correction profile of at least one optical assembly (30, 50) of the system (1,101) by designing a distance (A DS ) between a mechanical pivot point (D M ,D M1 ) and an optical center of gravity (S opt ) of the optical element (31,51). The invention further relates to a system (1, 101) for semiconductor lithography with at least one optical module (10, 110) with at least one optical assembly (30, 50), wherein the optical assembly (30, 50) has at least one actuator (41.x, 61.x) for moving an optical element (31, 51) of the optical assembly (30, 50), wherein the optical element (31, 51) has an optical center of gravity (S opt ) and wherein the optical assembly (30, 50) has a mechanical pivot point (D M ,D M1 ) exhibits, characterized in that the distance (A DS ) of the mechanical pivot point (D M ,D M1 ) and the optical center of gravity (S opt ) is designed such that the optical assembly (30, 50) has a desired correction profile.

Description

[0001] The invention relates to a method for improving the correction potential of a semiconductor technology system for at least one load case and to a semiconductor technology system, in particular a projection exposure system.

[0002] Projection exposure systems for semiconductor lithography are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on the creation of ultra-fine structures down to the nanometer range by means of a typically reduced-size image of structures onto a mask, a so-called reticulum, on a photosensitive material to be structured, such as a wafer. The minimum dimensions of the generated structures depend directly on the wavelength of the light used.

[0003] The light sources used have emission wavelengths from 100 nm to 300 nm in a range known as the DUV range. More recently, light sources with emission wavelengths in the nanometer range, for example between 1 nm and 120 nm, particularly in the 13.5 nm range, have been increasingly used. This emission wavelength range is also referred to as the EUV range.

[0004] Optical elements such as lenses, but also (especially in the EUV range) mirrors are used to illuminate the structures and in particular to image them. Their so-called optical surfaces are exposed to useful radiation, i.e., radiation used for imaging and exposure, during the normal operation of the associated system.

[0005] The optical elements are usually arranged in mounts of optical assemblies, whereby the optical elements are mounted on mounts which in turn are movable via actuators and can thus be positioned at a predetermined position.

[0006] The optical assemblies are interconnected and together form an optical module, such as a projection optic that images the structures onto the wafer, or an illumination system that provides the useful radiation in various so-called illumination settings. The illumination settings encompass the geometry of the useful radiation on the mask and the intensity of the useful radiation.

[0007] Deviations of the optical surfaces from an optimal target position and / or target shape have a massive impact on the quality of the image and thus on the quality of the manufactured components.

[0008] The deviations have various causes, such as mechanical excitation of the optical elements and / or thermally induced expansion of the optical element and / or its mounting due to the illumination settings described above. The effects of the illumination settings on the heating of the optical elements and / or their mounting are also referred to as load cases, which must be corrected using the available manipulators of the optical assemblies to ensure sufficient image quality.

[0009] For the purposes of this application, a manipulator shall be understood to be that part of an assembly with an optical element which causes a movement (translational or rotational), a change in shape or any other influence on the optical element.

[0010] The requirements for the positioning of the image on the wafer and the intensity of the light provided by the illumination system are increased with each new generation, leading to a higher heat load on the optical elements, i.e., new load cases.

[0011] Existing manipulators in the state of the art no longer have a correction profile corresponding to the desired correction potential for the new load cases.

[0012] This can have two causes. Either the required travel distance cannot be provided by the manipulator, or the optical sensitivities of the optical element are no longer suitable or no longer exhibit the correction profile corresponding to the load case. A combination of both causes can also occur. Optical sensitivity refers to the optical effect of a change in the state of an optical element on the wavefront passing through it. This change in state can, in particular, affect the position, orientation, or geometry of the optical element. The optical sensitivity is usually specified for a normalized movement of the optical element of, for example, one micrometer, and is given for each of the six degrees of freedom.

[0013] The correction profile of an optical assembly is determined by the change in the optical element's state caused by the manipulator and the optical sensitivity of the optical element. A correction profile can be determined for each degree of freedom. A correction profile encompasses the correction of so-called Zernike coefficients for a normalized movement of, for example, 1 µm. These coefficients are frequently used in semiconductor technology to describe wavefronts or residual errors after correction by the assemblies. The correction profiles of the individual degrees of freedom can be superimposed, depending on the degrees of freedom provided by the manipulator. In this case, the overall correction profile is determined by superimposing the correction profiles of the provided degrees of freedom.This has the disadvantage that in the case of load cases requiring correction which do not match the defined correction profile of the manipulator, imaging errors cannot be corrected.

[0014] The trivial solution of a new optical design, which is possible in principle, has the disadvantage that the development and manufacturing costs are very high and therefore it is not a preferred solution.

[0015] The object of the present invention is to provide a method for designing a system to eliminate the disadvantages of the prior art explained above. A further object of the invention is to provide a system with an improved correction profile.

[0016] This problem is solved by a method and a device having the features of the independent claims. The dependent claims relate to advantageous embodiments and variants of the invention.

[0017] An inventive method for improving the correction potential for correcting at least one load case for a semiconductor technology system with an optical module and an optical assembly, wherein the optical assembly has at least one actuator for moving an optical element of the optical assembly, comprises the following method steps: - Determining a desired correction potential for the system. - Design of a correction profile for at least one optical assembly of the system by defining a distance between a mechanical pivot point and an optical center of gravity of the optical element.

[0018] The pivot point is understood to be a point on the mechanical axis of rotation. In the following, the terms are used synonymously depending on the context.

[0019] The method enables an improvement in the correction potential of the system without changing the optical design of a projection optic, which advantageously allows existing systems to be adapted to new load cases relatively easily.

[0020] The correction potential of the entire system is comprised of the correction profiles of the optical assemblies. As explained above, a correction profile is defined by the degree of freedom provided by a manipulator and the optical sensitivity of the optical element in the direction of this degree of freedom.

[0021] In a manipulator with three actuators arranged at an angular distance of 120° around an optical element, for example, one degree of freedom can be formed in the direction of the movement of the actuators, referred to as the z-direction, and two further degrees of freedom can be formed by a rotation of the optical element about the two axes arranged perpendicular to the z-direction and orthogonal to each other (x-direction, y-direction).

[0022] The optical element can be mounted in such a way that its mechanical axis of rotation and optical center of gravity coincide. This prevents parasitic optical effects of the lens, such as parasitic decentering during rotation. Avoiding these parasitic effects thus advantageously improves the correction profile and therefore the correction potential of the optical assembly and the system.

[0023] The mechanical axis of rotation is the axis of rotation of the manipulator used by a control system, in particular the mounting of the optical element connected to the actuators. This axis typically runs through the center of the surface spanned by the mounting points of the actuators, whereby the axis of rotation can theoretically be defined almost arbitrarily in space.

[0024] The optical center of gravity is defined by the fact that the optical sensitivities act orthogonally to each other at the optical center of gravity, meaning that a rotation about an axis through the optical center of gravity or a translational movement of the optical center of gravity only causes an optical effect corresponding to the product of the rotation angle or the translational displacement and the optical sensitivities for the rotation or the displacement.

[0025] The optical effect of the optical assembly, which is also referred to as the correction profile of the optical assembly, is thus determined on the basis of the optical sensitivities in the z-direction, the rotation about an axis formed in the x-direction and in the y-direction.

[0026] In a further embodiment of the invention, the distance between the mechanical pivot point and the optical center of gravity of the optical element can be determined based on the desired correction potential of the system. In the case of the manipulator described above, the distance can be designed such that the contribution of the optical assembly to the desired correction potential of the system can be improved by superimposing a rotation of the optical element and a decentering of the optical element caused by the rotation of the manipulator and dependent on the rotation (i.e., a translational movement of the optical center of gravity in the x / y plane).

[0027] In particular, the mechanical axis of rotation of a manipulator can be adjusted by a control device for controlling the actuators of the optical assembly. This adjustment can shift the mechanical axis of rotation, which, as explained above, usually runs through the center of the surface spanned by the actuators, away from the center.

[0028] This causes a decentering of the center point of the optical element mount during rotation by the manipulator, and consequently also a decentering of the optical element connected to the mount, independent of the distance in the z-direction between the mechanical pivot point and the optical center of gravity.

[0029] An example with a mechanical pivot point located at one of the attachment points of the mount to the actuators is given in the Fig. 3D explained. The decentering caused by the adjustment of the mechanical axis of rotation and the decentering caused by the fixed distance between the mechanical axis of rotation and the optical center of gravity can therefore be additively superimposed. This means the decentering can both compensate for and reinforce each other.

[0030] In another embodiment, the mechanical axis of rotation of the optical assembly can be defined as an adjustable parameter of the control device. This has the advantage that the correction profile of the optical assembly, and thus of the optical module, can be changed during operation. While the distance in the z-direction between the optical center of gravity and the mechanical axis of rotation is defined once during development, the decentering can be changed relatively easily during operation by adjusting the control parameters of the optical assembly by setting the mechanical axis of rotation of the mount.

[0031] In particular, the mechanical pivot point can be selected depending on a load case acting on the system. The load cases typically occurring in projection exposure systems are known, and can therefore be used as a basis for designing the spacing and / or setting the control parameters. Several load cases can also serve as the basis for the design, with the correction profiles of the individual components being designed such that an acceptable correction potential of the system can be achieved for all considered load cases.

[0032] Furthermore, the mechanical pivot point can also be adjusted to compensate for nonlinearities, especially at larger deflections, depending on the deflection from a zero position of the manipulator. These dependencies can be provided, for example, via a table, a database, in-situ simulations, or machine learning.

[0033] In a further embodiment of the invention, the distance can be configured such that the resulting parasitic movements within the assembly caused by the distance can be reduced. This also reduces the parasitic optical effects for each optical assembly and thus advantageously improves the correction potential of the system, as explained above.

[0034] Furthermore, the distance can be configured in such a way as to reduce the parasitic optical effect within the assembly caused by the distance and the optical sensitivity of the optical element. In this case, for example, a decentering effect can be set by the defined distance, which can advantageously compensate for an optical effect that is parasitic for the desired correction profile and is caused by the defined optical sensitivities during rotation.

[0035] Furthermore, the distance can be designed in such a way that the parasitic optical effect of the optical module, caused by the distance and the optical sensitivities, can be reduced. In this case, the focus is not on a single component of the optical module, such as a projection optic in a system designed as a projection exposure unit, but rather on the correction potential of the optical module generated by the superposition of the individual optical effects or correction profiles of the optical components.

[0036] In another embodiment, the distance can be designed such that the imaging errors of the system can be reduced. In this case, in addition to the optical module comprising the optical assemblies, other components, such as the mask and / or the wafer, are taken into account when designing the distance, so that the imaging error of the system can be advantageously reduced.

[0037] In a further embodiment of the invention, the distance can be configured such that the resulting movement within the optical assembly generated by the distance can be increased. This can be an alternative to the approach already described above, which involves designing the distance to reduce parasitic errors. This involves deliberately increasing the distance to increase the decentering of the optical element during rotation. In conjunction with the optical sensitivities of the moving optical element, this can advantageously lead to an increase in the optical effect and thus to an improved correction profile.

[0038] In particular, the distance can be designed such that the resulting optical effect within the assembly, generated by the distance and the optical sensitivity of the optical element, can be increased. The same principles apply here as explained above for minimization.

[0039] Furthermore, the distance can be configured in such a way that the resulting optical effect of the optical module, generated by the distance and the optical sensitivities, can be increased. As explained above, in this case the focus is on the correction profile of the optical module, such as a projection lens.

[0040] In addition, the distance can be designed in such a way as to improve the optical imaging quality of the system.

[0041] A semiconductor lithography system according to the invention comprises at least one optical module with at least one optical assembly. The optical assembly has at least one actuator for moving an optical element of the optical assembly, wherein the optical element has an optical center of gravity. Furthermore, the optical assembly has a mechanical pivot point and is characterized in that the distance between the mechanical pivot point and the optical center of gravity is configured such that the optical assembly exhibits a desired correction profile.

[0042] In particular, the optical assembly can have at least two adjustable rotational degrees of freedom.

[0043] Furthermore, the rotational degrees of freedom can be orthogonal to each other.

[0044] In another embodiment of the invention, the system can be designed as a projection exposure system.

[0045] Exemplary embodiments and variants of the invention are explained in more detail below with reference to the drawing. The drawing shows Fig. 1. Schematic representation in meridional section of a projection exposure system for EUV projection lithography, Fig. 2 schematically in meridional section a projection exposure system for DUV projection lithography, Fig. 3a-d a first and second embodiment of the invention, Fig. 4 a diagram to illustrate the effect of the invention, and Fig. 5 a flowchart for a method according to the invention.

[0046] The following will first refer to the Fig. 1. The essential components of a projection exposure system 1 for microlithography are described as an example. The description of the basic structure of the projection exposure system 1 and its components is not intended to be restrictive.

[0047] One embodiment of a lighting system 2 of the projection exposure system 1 has, in addition to a radiation source 3, a lighting optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the lighting system. In this case, the lighting system does not include the light source 3.

[0048] A reticule 7 located in the object field 5 is illuminated. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in one scanning direction, via a reticule displacement drive 9.

[0049] In the Fig. Figure 1 shows a Cartesian xyz coordinate system for illustrative purposes. The x-direction runs perpendicular to the plane of the drawing. The y-direction runs horizontally, and the z-direction runs vertically. The scan direction runs in the Fig. 1 along the y-direction. The z-direction runs perpendicular to the object plane. 6.

[0050] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 is parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0051] A structure on the reticulum 7 is imaged onto a photosensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved, particularly along the y-direction, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0052] Radiation source 3 is an EUV radiation source. Specifically, radiation source 3 emits EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has a wavelength in the range between 5 nm and 30 nm. Radiation source 3 can be a plasma source, for example, an LPP source (laser-produced plasma) or a DPP source (gas-discharged produced plasma). It can also be a synchrotron-based radiation source. Radiation source 3 can be a free-electron laser (FEL).

[0053] The illumination radiation 16 emanating from the radiation source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated with the illumination radiation 16 at grazing incidence (GI), i.e., with angles of incidence greater than 45° relative to the normal direction of the mirror surface, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0054] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the radiation source 3 and the collector 17, and the illumination optics 4.

[0055] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam shape beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which are also referred to as field facets in the following. Of these facets 21, the following are in the Fig. 1 only some examples are shown.

[0056] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0057] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 can themselves each be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0058] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction.

[0059] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0060] The second facet mirror 22 comprises 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.

[0061] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0062] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0063] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (Fly's Eye Integrator).

[0064] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the pupil faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0065] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping, or indeed the last, mirror for the illumination radiation 16 in the beam path before the object field 5.

[0066] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can in particular comprise one or two mirrors for normal incidence (NI mirrors) and / or one or two mirrors for grazing incidence (GI mirrors).

[0067] The lighting optics 4, in the version shown in the Fig. Figure 1 shows exactly three mirrors after the collector 17, namely the deflecting mirror 19, the field facet mirror 20 and the pupil facet mirror 22.

[0068] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0069] The mapping of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate mapping.

[0070] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0071] In the Fig. In the example shown, the projection optics 10 comprise six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 are a double-obscured optic. The projection optics 10 have an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0072] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0073] The projection optics 10 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0074] The projection optics 10 can be anamorphic. In particular, they have different magnifications βx, βy in the x and y directions. The two magnifications βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive magnification β indicates a projection without image inversion. A negative magnification β indicates a projection with image inversion.

[0075] The projection optics 10 thus lead to a reduction in the x-direction, that is, in the direction perpendicular to the scan direction, in a ratio of 4:1.

[0076] The projection optics 10 lead to a reduction of 8:1 in the y-direction, that is, in the scan direction.

[0077] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute values ​​in the x and y directions, for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0078] 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 can be the same or, depending on the design of the projection optics 10, different. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1.

[0079] Each pupil facet 23 is assigned to exactly one of the field facets 21 to form an illumination channel for illuminating the object field 5. This can result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 by means of the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 assigned to each of them.

[0080] The field facets 21 are each superimposed on the reticulum 7 by an associated pupil facet 23 to illuminate the object field 5. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0081] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by the arrangement of the pupil facets. By selecting the illumination channels, in particular the subset of pupil facets that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting.

[0082] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0083] Further aspects and details of the illumination of the object field 5 and, in particular, the entrance pupil of the projection optics 10 are described below.

[0084] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0085] The entrance pupil of the projection optics 10 cannot always be illuminated exactly by the pupil facet mirror 22. When the projection optics 10 image 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, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0086] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0087] During the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the pupil facet mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The field facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19.

[0088] The first faceted mirror 20 is arranged at an angle to an arrangement plane defined by the second faceted mirror 22.

[0089] Fig. Figure 2 schematically shows in meridional section another projection exposure system 101 for DUV projection lithography, in which the invention can also be applied.

[0090] The design of the projection exposure system 101 and the principle of the imaging process are comparable to that in Fig. The structure and procedure described in section 1 are identical. The components are 100 times larger than the others. Fig. 1 raised reference numeral denotes the reference numerals in Fig. So, 2 starts with 101.

[0091] Unlike one such as in Fig. Due to the longer wavelength of the DUV radiation 116 used as useful light in the range of 100 nm to 300 nm, in particular of 193 nm, refractive, diffractive and / or reflective optical elements 117, such as lenses, mirrors, prisms, end plates and the like, can be used in the DUV projection exposure system 101 for imaging or illumination in the DUV projection exposure system 101 for imaging or illumination.The projection exposure system 101 essentially comprises a lighting system 102, a reticule holder 108 for receiving and precisely positioning a reticule 107 provided with a structure, by which the subsequent structures on a wafer 113 are determined, a wafer holder 114 for holding, moving and precisely positioning this wafer 113 and a projection lens 110, with several optical elements 117, which are held in a lens housing 119 of the projection lens 110 via mounts 118.

[0092] The illumination system 102 provides DUV radiation 116 required for imaging the reticulum 107 on the wafer 113. A laser, a plasma source, or the like can be used as the source for this radiation 116. In the illumination system 102, the radiation 116 is shaped by optical elements such that, upon striking the reticulum 107, the DUV radiation 116 exhibits the desired properties with respect to diameter, polarization, wavefront shape, and the like.

[0093] The construction of the following projection optics 101 with the lens housing 119 differs in principle from that in, except for the additional use of refractive optical elements 117 such as lenses, prisms, end plates. Fig. The structure described in section 1 is therefore not described further.

[0094] Fig. Figure 3a shows a top view of an optical assembly 30 with an optical element designed as a lens 31, as shown in the Fig. The optical assembly 30 comprises a manipulator 40 with three actuators 41.1, 41.2, 41.3 arranged at an angular interval of 120° around the circumference of the lens. This arrangement enables movement of the lens 31 in the direction of the z-axis, which is oriented perpendicular to the drawing plane, and rotation about the x-axis or y-axis.

[0095] Furthermore, lens 31 has an optical center of gravity S opt , which can also be referred to as the neutral point of lens 31. At the optical centroid, the optical sensitivities act orthogonally to each other. Thus, if lens 31 is rotated about an axis running in the xy-plane through the optical centroid S optWhen rotated, only a contribution of the rotation angle times the optical sensitivity of the rotation about the axis of rotation is generated, but no contribution through a decentering of the lens 31.

[0096] In addition, the manipulator 40 causes a rotation around a pivot point D. M , which lies on a mechanical axis of rotation of the manipulator. If the two points S lie opt , D M on top of each other, during a rotation around the pivot point D M the optical effect depends solely on the angle of rotation and the optical sensitivity of the lens during rotation around the optical center of mass S opt causes.

[0097] Fig. Figure 3b shows the optical assembly 30 in a schematic side view. The lens 31 is represented by a single line; the directions of movement of the actuators 41.1, 41.2, and 41.3 are each indicated by a double arrow. Furthermore, as shown in the Fig. 3a, the optical center of gravity S opt or the pivot point D M of the manipulator 40.

[0098] Fig. Figure 3c shows an optical assembly 50, which belongs to the one described in the Fig. The assembly 30 shown in 3b is similarly designed, wherein, where appropriate, corresponding elements are arranged opposite the Fig. 3b are designated by 20 increased reference marks.

[0099] The structure of assembly 50 differs from that of assembly 30 in that the optical center of gravity S opt and the mechanical pivot point D M They do not lie on top of each other, but are shifted relative to each other in the z-direction. The optical element 51 is connected to a receptacle 62 of the manipulator 60, which rests on the connection points 63.1, 63.2, 63.3 of the actuators 61.1, 61.2, 61.3, whereby the connecting elements are not shown for the sake of clarity.

[0100] The one in Fig. The already rotated position of the mount 62, and thus of the lens 51, shown in Figure 3c, is achieved by a first variant of the control of the manipulator 60 by a control device not shown. In this process, the mount 62 is rotated about the mechanical pivot point D. M rotates. The distance A DS between the optical center of gravity S opt and the mechanical pivot point D M This causes an additional decentering D during rotation. R1 of lens 51. The center point M opt the lens 51, which is rotated with the optical center of gravity S opt The two layers, lying on top of each other, shift due to the decentering D. R1 into a position D M1 This has the advantage that the optical effect of the optical assembly 50 consists of the component of the rotation of the lens 51 and an additional component from the decentering D. R1The lens 51 is composed of a value multiplied by the optical sensitivity of lens 51 for decentering. As explained above, this reduces a parasitic optical effect or increases a desired optical effect.

[0101] Fig. 3d again shows the optical assembly 50 and serves to explain a second variant of the control of the manipulator 60.

[0102] In this case, the rotation-free initial state, shown with dashed lines, is depicted, as is an intermediate state, represented by dashed-dotted lines, which will be explained in more detail below. The final rotated state is as shown in the Fig. 3c is represented by solid lines. To distinguish the different states, the reference symbols for the recording are 62, 62', 62'' and for the lens 51, 51', 51'' in the Fig. In 3D, starting from the non-rotating state, there are no, one, or two lines. Actuators 61.1, 61.2, 61.3 and connection points 63.1, 63.2, 63.3, on the other hand, are only shown where relevant for clarity.

[0103] In step A, which in the Fig. As represented in 3D by an arrow A, the recording 62 and the lens 51 connected to it are rotated around the pivot point D. M1 of the manipulator 60 rotates, with the pivot point D M1 is located at the connection point 63.3 of the actuator 61.3. This rotation causes a decentering D. RM of the center point M A the recording 62' of the manipulator 60 to a position M' A of the center point. In the figure, the decentering is somewhat exaggerated for representational reasons. This decentering D RM The signal is transmitted via the connection not shown from the sensor 62' to the lens 51', thus shifting the center point M optof the lens 51' by a decentering D R2 to position M opt2 shifts. The decentering D R2 This therefore includes, in addition to the one from the Fig. 3c known by distance A DS caused decentering D R1 a further proportion due to the altered pivot point D M1 decentering caused by manipulator 60.

[0104] In a second step B, which is in the Fig. In 3d, represented by an arrow B, the displacement of the center point M' caused by the rotation around the recording point 63.1 is shown. A The deviation of the recording 62' in the z-direction is compensated by a process of all three actuators 61.1, 61.2, 61.3 in the positive z-direction, so that the center point M'' A The 62'' recording in the z-direction has the same height as the center point M. A before rotation.

[0105] This results in the same z-position and rotation for lens 51'' as in the Fig. 3c described embodiment, wherein the lens 51'' is connected by the other pivot point D M1 of the manipulator 60 a greater decentering D R2 exhibits the decentering D R2 of the lens center M'' opt In the final position of the lens, 51'' is, compared to the one in the Fig. 3c achieved decentering M opt1 lens 51, which is also included for comparison in the Fig. The 3D representation is larger.

[0106] The one in Fig. The 3D-explained variant of the control has the advantage that, with constant rotation and z-position in the Fig. The 3D version shows an enlarged decentering D R2 and thereby achieves a greater optical effect. Depending on the selection of the pivot point D. M or D M1 can the distance A DScaused decentering D R2 can be further enlarged, but also reduced in size.

[0107] In principle, the type of control can therefore be used as a further possibility for setting the optical correction profile of an optical assembly 50. This has the advantage that, in addition to the distance A, which is only set once, DS and whose effect on the optical correction profile is complemented by a second parameter, adjustable during use of the system, for setting the correction profile. This can, for example, be selected depending on the load case, as explained above.

[0108] Fig. Figure 4 shows a possible qualitative change in a residual error of various so-called Zernike coefficients, which are commonly used to represent wavefronts in semiconductor technology. The residual errors are the errors remaining after correction of parasitic imaging errors caused by a predefined load case in a system designed as a projection exposure unit for semiconductor technology. The correction utilizes all available optical components for correcting image errors, including those in the Fig. 3a to Fig. 3D explained assemblies 30 and 50.

[0109] The nine bars each representing the average residual error shown at the beginning of the diagram and the individual Zernike coefficients represent the result for optical assemblies 50 with different spacings A DS in the Fig. In example 4, the distance A is shown. DSThe value for the middle bar is 0, and from there it increases by 5 mm in the negative (to the left) or positive (to the right) direction. Due to the different distances from the optical center of gravity S opt to mechanical pivot point D M Different correction profiles result from the optical assembly 50, leading to different residual errors. The effects vary for different Zernike coefficients, which can have various causes that are not discussed further in the present application, as they are irrelevant to the invention. For example, the apparent outlier of the penultimate line from the left in the Zernike Z5 / 6 could also have been caused by an artifact of the algorithm used for the qualitative simulation. Fig. 4 is intended to merely represent a qualitative and possible effect of the distance on the residual errors, which are clearly visible in all Zernike coefficients.

[0110] Assuming small movements, the effect of adjusting the distance A can be DS assumed to be linear, whereby in the case of larger distances non-linearities will occur in the correction profile, which are also partly reflected in the Fig. The 4 residual errors shown are recognizable.

[0111] Fig. Figure 5 shows a flowchart of a method for improving the correction potential for correcting at least one load case for a system 1, 101 for semiconductor technology with an optical module 10, 110 with an optical assembly 30, 50, wherein the optical assembly 30, 50 has at least one actuator 41.x,61.x for moving an optical element 31, 51 of the optical assembly 30, 50.

[0112] In a first procedural step 71, a desired correction potential for Annex 1, 101 is determined,

[0113] In a second process step 72, a correction profile of at least one optical assembly 30, 50 of Annex 1, 101 is created by adjusting the distance A DS between a mechanical pivot point D M , D M1 and an optical focus S opt of the optical element 31, 51 of the assembly 30, 50 designed. Reference symbol list 1 Projection exposure system 2 Lighting system 3. Radiation source 4 Lighting optics 5 object field 6 Object level 7 reticles 8 label holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 wafer transfer drive 16 EUV radiation 17 Collector 18 Intermediate focus plane 19 deflecting mirrors 20 faceted mirrors 21 facets 22 faceted mirrors 23 facets 30 Optical assembly 31 Optical element 40 Manipulator 41.1-41.3 Actuator 50 Optical assembly 51 Optical element 60 Manipulator 61.1-61.3 Actuator 62nd recording 63.1-63.3 Connection points actuator to receiver 101 Projection exposure system 102 Lighting system 107 reticles 108 label holders 110 Projection optics 113 wafers 114 wafer holders 116 DUV radiation 117 optical element 118 versions 119 lens bodies M1-M6 mirrors S opt Optical focal point optical element D M , DM1 Pivot point manipulator (Rot-x, Rot-y) A DS Distance optical center of gravity pivot point manipulator D R1 , D R2 Decentering of an optical element through rotation D RM Decentering image manipulator M A ,M' A ,M'' A Center point shot M opt , M' opt , M'' opt , M opt1 Center point of optical element (Index = Position) A, B Movement states Recording QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2008 009 600 A1 [0057, 0061] US 2006 / 0132747 A1

[0059] EP 1 614 008 B1

[0059] US 6,573,978

[0059] DE 10 2017 220 586 A1

[0064] US 2018 / 0074303 A1

[0078]

Claims

[1] Method for improving the correction potential for correcting at least one load case for a system (1,101) for semiconductor technology with an optical module (10,110) with an optical assembly (30, 50), wherein the optical assembly (30, 50) has at least one actuator (41.x,61.x) for moving an optical element (31,51) of the optical assembly (30, 50) comprising the following method steps: - Determination of a desired correction potential of the system (1,101), - Design of a correction profile of at least one optical assembly (30, 50) of the system (1,101) by designing a distance (A DS ) between a mechanical pivot point (D M , D M1 ) and an optical center of gravity (S opt ) of the optical element (31,51). [2] Method according to claim 1, characterized by , that the distance (A DS ) between a mechanical pivot point (D M ,DM1 ) and the optical center of gravity (S opt ) of the optical element (31,51) is determined based on the desired correction potential. [3] Method according to claim 1 or 2, characterized by , that the mechanical pivot point (D M , D M1 ) an optical assembly (30, 50) is set by a control device for controlling actuators (41.x,61.x) of the optical assembly (30, 50). [4] Method according to one of claim 3, characterized by , that the mechanical pivot point (D M , D M1 ) of the optical assembly (30, 50) is defined as an adjustable parameter of the control device during operation. [5] Method according to any of the preceding claims, characterized by , that the mechanical pivot point (D M ,D M1 ) is selected depending on a load case acting in the plant. [6] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) generated resulting parasitic movements within the assembly (30, 50) are reduced. [7] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) and the optical sensitivity of the optical element (31,51) reduces the parasitic optical effect generated within the assembly (30, 50). [8] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) and the parasitic optical effect of the optical module (10,110) generated by the optical sensitivities is reduced. [9] Method according to any of the preceding claims, characterized by, that the distance (A DS ) is designed in such a way that the imaging errors of the system (1,101) are reduced. [10] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) and the optical sensitivity of the optical element (31,51) increases the resulting optical effect within the assembly (30, 50). [11] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) and the optical sensitivity of the optical element (31,51) increases the resulting optical effect within the assembly (30, 50). [12] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS) and the resulting optical effect of the optical modulus (10,110) is increased by the optical sensitivities. [13] Method according to any of the preceding claims, characterized by , that the distance (A DS ) is designed in such a way that the distance (A) DS ) and the optical sensitivity improves the resulting optical imaging quality of the system (1,101). [14] System (1,101) for semiconductor lithography with at least one optical module (10,110) with at least one optical assembly (30, 50), wherein the optical assembly (30, 50) has at least one actuator (41.x,61.x) for moving an optical element (31,51) of the optical assembly (30, 50), wherein the optical element (31,51) has an optical center of gravity (S opt ) and wherein the optical assembly (30, 50) has a mechanical pivot point (D M ,D M1 ) shows, characterized by , that the distance (A DS) of the mechanical pivot point (D M ,D M1 ) and the optical center of gravity (S opt ) is designed such that the optical assembly (30, 50) has a desired correction profile. [15] Plant (1,101) according to claim 14, characterized by , that the optical assembly (30, 50) has at least two adjustable rotational degrees of freedom. [16] Plant (1,101) according to claim 15, characterized by that the rotational degrees of freedom are orthogonal to each other. [17] Plant (1,101) according to one of claims 14 to 16, characterized by , that the system is designed as a projection exposure system (1,101).

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