MEMS micromirror unit and production thereof

Abstract

The invention relates to a method for producing a MEMS micromirror unit (100) for use in projection lighting systems (1) for photolithography, and to a MEMS micromirror unit (100) produced according to this method. The invention also relates to a system for semiconductor technology with a corresponding MEMS micromirror unit (100) and to an electronic component produced with such a system. The MEMS micromirror unit (100) comprises a MEMS mirror array assembly (110) having a MEMS mirror array structure (111) and a joining structure (115) and an interface element (120) for fixing the MEMS micromirror unit (100) on a higher-level assembly, a joining structure (125) interacting therewith in a form-fitting manner, and at least one stop surface (121, 121'). The production comprises the steps: a) measuring the position and location of the MEMS mirror array structure (111) relative to the joining structure (115); b) adjusting the relative position and / or location of the joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') in such a way that the relative position and location of the MEMS mirror array structure (111) and the at least one stop surface (121, 121'), after joining the MEMS mirror array assembly (110) and the interface element (120) via the joining structures (115, 125), corresponds to a predetermined position and location.

Description

MEMS micromirror unit and its manufacturing

[0001] The present application claims the priority of German patent application 10 2023 123 889.2, filed on September 5, 2023. The content of this German patent application is incorporated by reference into the present application text.

[0002] The invention relates to a method for producing a MEMS micromirror unit for use in semiconductor technology systems, as well as to a MEMS micromirror unit for use in semiconductor technology systems. The invention also relates to a semiconductor technology system with a corresponding MEMS micromirror unit, as well as to an electronic component produced using such a system.

[0003] In the state of the art, semiconductor technology systems refer to systems used to manufacture or test microstructured devices or the components required for them. An example of such a system is a projection exposure system for photolithography.

[0004] Photolithography is used to manufacture microstructured components, such as integrated circuits. The projection exposure system used comprises an illumination system and a projection system. The image of a mask (also called a reticle) illuminated by the illumination system is projected onto a substrate, such as a silicon wafer, coated with a light-sensitive layer and arranged in the image plane of the projection system. projected to transfer the mask structure onto the light-sensitive coating of the substrate.

[0005] In illumination systems, particularly projection exposure systems designed for the EUV range, i.e., for exposure wavelengths from 5 nm to 30 nm, two facet mirrors are typically arranged in the beam path between the actual exposure radiation source and the mask to be illuminated. These facet mirrors enable radiation homogenization, essentially similar to the principle of a honeycomb condenser. The facet mirror closest to the exposure radiation source in the beam path is often a so-called field facet mirror, while the other is a so-called pupil facet mirror.

[0006] In order to be able to produce different intensity and / or angle of incidence distributions when illuminating the mask, it is known to form the facets of at least one of the two facet mirrors—in particular those of the field facet mirror—from one or more electromechanically individually pivotable micromirrors. A corresponding method is disclosed, for example, in WO 2012 / 130768 A2.

[0007] In order to achieve a small size of the individual micromirrors, it is known to form groups of micromirrors in the form of a so-called MEMS mirror array, namely a mirror array made of microelectromechanical systems (MEMS).

[0008] In a MEMS mirror array, a multitude of small mirror elements are mounted on a common base, each individually movable. At least one actuator is provided for each mirror element, allowing the mirror element to be adjusted along a given degree of freedom. The mirror elements are often arranged at two Pivotable about axes running perpendicular to one another and parallel to the base, with sufficient actuators being provided to enable the mirror element to be pivoted independently of one another about these axes. Sensors can also be provided for the individual mirror elements, with which the position of the mirror element relative to the base can be determined in order to thus monitor the alignment of the mirrors. A particularly advantageous embodiment for the mirrors of a MEMS mirror array is described in DE 10 2015 204 874 A1.

[0009] A method for producing a micromirror or a MEMS mirror array comprising a plurality of such micromirrors is disclosed - together with further details on a possible design of the micromirror - in DE 10 2015 220 018 A1.

[0010] To form a facet mirror for a projection exposure system, several MEMS mirror arrays are mounted in a dense, planar grid arrangement on a higher-level assembly. For this purpose, the MEMS mirror arrays are designed as MEMS micromirror units (MMUs), which, in addition to the actual MEMS mirror arrays, also feature an interface element with which the units can be mounted to the higher-level assembly.

[0011] In order for the MEMS mirror arrays to be arranged with a small distance from one another for the intended purpose and to have the required precise position and alignment when inserted and fastened in the assembly, it is necessary that the individual mirror elements of a MEMS micromirror unit are positioned and aligned with high precision relative to its interface element. The invention is based on the object of creating a method for producing a MEMS micromirror unit and a MEMS micromirror unit which can meet these requirements.

[0012] This object is achieved by a method according to claim 1 and a MEMS micromirror unit according to claim 12. Advantageous further developments are the subject of the dependent claims.

[0013] Accordingly, the invention relates to a method for producing a MEMS micromirror unit for use in systems for semiconductor technology, comprising a MEMS mirror array assembly with a MEMS mirror array structure and a joining structure arranged on the side facing away from the MEMS mirror array structure, and an interface element for fastening the MEMS micromirror unit to a higher-level assembly with a joining structure that interacts positively with the joining structure of the MEMS mirror array assembly and at least one stop surface for positioning and / or aligning the MEMS micromirror unit with respect to the higher-level assembly, comprising the steps of: a) measuring the relative position and orientation of the MEMS mirror array structure to the joining structure of the MEMS mirror array assembly;b) adjusting the relative position and / or location of the joining structure of the interface element and the at least one stop surface such that the relative position and / or location of the MEMS mirror array structure and the at least one stop surface after joining the MEMS mirror array assembly and the interface element; about the joining structures corresponds to a given position and location.

[0014] Furthermore, the invention relates to a MEMS micromirror unit for use in systems for semiconductor technology, comprising a MEMS mirror array assembly with a MEMS mirror array structure and a joining structure arranged on the side facing away from the MEMS mirror array structure and an interface element for fastening the MEMS micromirror unit to a higher-level assembly with a joining structure that interacts positively with the joining structure of the MEMS mirror array assembly and at least one stop surface for positioning and / or aligning the MEMS micromirror unit relative to the higher-level assembly, wherein the MEMS micromirror unit is manufactured according to the invention.

[0015] The invention further relates to a system for semiconductor technology comprising at least one MEMS micromirror unit according to the invention, which is used to deflect radiation used by the system, for example, to illuminate an object. The invention also extends to an electronic component manufactured using a corresponding semiconductor technology system, wherein the component preferably has structures in the micrometer and / or nanometer range.

[0016] In the context of the present invention, "system for semiconductor technology" refers to any system that can be used to manufacture or test microstructured components or the components required therefor. In addition to projection exposure systems for photolithography, this also includes, in particular, inspection systems and metrology systems. In the case of inspection systems For masks or wafers, for example, the variability of the illumination can be increased using one or more MEMS micromirror units, which can result in higher-contrast or entirely new images of the surface of a mask or wafer, which can be advantageous for the inspection of the mask or wafer. A similar situation also applies to metrology systems with which masks, wafers, or other optical elements, such as mirrors, can be measured; increased variability in the illumination can improve the measurement results.

[0017] The invention is based on the finding that the accuracy of the position and orientation of the individual mirror elements relative to the stop surfaces of the interface element, which is required for the use of such a MEMS micromirror unit in a system for semiconductor technology and with which the position and alignment of the MEMS micromirror unit as a whole relative to the higher-level assembly is determined, cannot be achieved, or at least not easily, simply by reducing the permissible tolerances in the manufacture of the individual components of a MEMS micromirror unit and when joining the components. To counter this problem, the invention provides for the actual MEMS mirror array structure and any further elements to be combined to form a MEMS mirror array assembly which has a defined joining structure on the side facing away from the MEMS mirror array structure.If a corresponding assembly is available, the position and orientation of the MEMS mirror array structure relative to the joining structure can be precisely measured. Based on the position and orientation information resulting from this measurement, the interface element can then be adjusted in such a way that, after the MEMS mirror array assembly and interface element are joined together, the corresponding alignment at the designated joining structures can be achieved. positive-locking and thus positionally and positionally accurate interaction results in a predetermined position and orientation of the MEMS mirror array structure relative to those stop surface(s) on the interface element with which the position and orientation of the MEMS micromirror unit relative to a higher-level assembly is at least partially determined, with sufficiently high precision.

[0018] The adjustment in question of the relative position and / or location of the joining structure of the interface element and the at least one stop surface can be carried out by adjusting the joining structure of the interface element. For this purpose, the surfaces on the interface element provided for the positive locking can be suitably modified, for example by machining. In particular, the interface element in its initial state can be a blank in which the surfaces in question are not yet present or are only present in such a rudimentary manner that the surfaces ultimately required and desired for the positive locking can be produced solely by machining, for example using a CNC milling machine.

[0019] Alternatively or additionally, the adjustment of the relative position and / or location of the joining structure of the interface element and the at least one stop surface can also be carried out by adjusting at least one of the at least one stop surface, for example by machining. This also allows the position and location of the stop surfaces to be defined relative to the joining structure of the interface element and - after the MEMS mirror array assembly has been assembled - also relative to the MEMS mirror array structure. In order to enable adjustment by machining, it is preferred if the basic The areas of an interface element blank intended for stop surfaces must have sufficient excess material.

[0020] The interface element can preferably be designed in two parts. A basic element of the interface element forms the joining structure for connection to the MEMS mirror array assembly. A compensating element can be attached to this basic element in a predetermined position - for example, by suitable shaping, at least in part - which in turn forms the at least one stop surface of the interface element. An adjustment of the relative position and / or orientation of the joining structure of the interface element and the at least one stop surface can then be achieved solely by machining the compensating element.

[0021] If the compensating element has a geometrically simple shape, the machining of the compensating element required for adaptation is generally also easy. For example, the compensating element can be a compensating sleeve whose inner or outer contour - for connection to the base element or for attachment to a higher-level assembly - is fixed, while the other contour can be modified. The same naturally also applies to the end faces of the compensating sleeve, which can also represent stop surfaces. The combination of base element and compensating element in the predetermined position and / or orientation relative to one another then forms an interface element, as provided for according to the invention.It is irrelevant whether the base element and compensating element are joined together first or whether the base element is joined to the MEMS mirror array assembly in a first step and only then is the compensating element attached.

[0022] In view of the two-part design of the interface element explained above, it should also be noted that if an element comparable to the base element is connected to the MEMS mirror array assembly or formed integrally therewith, the area intended for connection to an element comparable to the compensation element is subsequently measured and, on the basis of this measurement, the element comparable to the compensation element is adapted before it is attached, that the element comparable to the base element is to be regarded as part of the MEMS mirror array assembly, and that the element comparable to the compensation element is the actual interface element.

[0023] The adjustment of the relative position and / or orientation of the joining structure of the interface element and the at least one stop surface can take place in at least two, preferably three translational degrees of freedom and / or at least one, preferably two rotational degrees of freedom. Thus, an adjustment of the position can preferably take place in the direction of the base area of ​​the MEMS mirror array structure and / or perpendicular thereto. Alternatively or additionally, the inclination of the MEMS mirror array structure with respect to the interface element can also preferably be changed. In other words, the relative orientation should be influenced by rotation about two axes running parallel to the base area of ​​the MEMS mirror array structure.

[0024] The number and design of the stop surfaces on the interface element is preferably selected so that when inserted into the higher-level assembly, as few degrees of freedom as possible are available, preferably one degree of freedom (namely in particular a translational degree of freedom for inserting or removing the MEMS micromirror unit) or two degrees of freedom (additionally, for example, a Any remaining degrees of freedom (rotational degree of freedom around the first translational degree of freedom) remain immediately after insertion. Any remaining degrees of freedom can then be blocked by suitable fixation devices. Such fixation can be achieved, in particular, by force and / or form closure, e.g., by screwing.

[0025] The joining structures of the MEMS mirror array assembly and the interface element are preferably designed to be self-centering. This ensures that the relative position and / or orientation affected by the self-centering is achieved with high accuracy when joining the MEMS mirror array assembly and the interface element, which also benefits the accuracy of the relative orientation of the MEMS mirror array structure and the at least one stop surface. It is further preferred if the joining structures have a limiting stop for the degree of freedom in the direction of the self-centering axis. A high positional accuracy is then also achieved in this direction.

[0026] For example, the joining structure of the MEMS mirror array assembly can comprise a cylindrically shaped protrusion. The joining structure of the interface element can then have a corresponding cylindrical receptacle, which—as explained above—can be adapted as needed. In addition, the base surface at the free end of the protrusion and / or the surface from which the protrusion protrudes can be designed as a limit stop. The limit stop then determines the extent to which the two joining structures engage during joining.

[0027] The actual joining of the MEMS mirror array assembly and the interface element is preferably carried out by force fit or material fit.

[0028] If the joining structures are suitably designed, joining can be achieved, in particular, by shrinking. In this case, the two joining structures are manufactured to provide an interference fit, and one of the joining structures is heated for joining, temporarily changing the interference fit to a transition or clearance fit, where the joining parts can be pushed together. After cooling, the interference fit returns, resulting in a force-locking connection. If the frictional connection is to be designed to be gas-tight, inserts made of indium can be provided between the surfaces intended for forming the frictional connection.

[0029] If a material connection is to be created, it is preferable to join the MEMS mirror array assembly and the interface element by soldering. If the MEMS mirror array assembly and / or the interface element do not offer a surface made of a material suitable for soldering in the contact area between the MEMS mirror array assembly and the interface element, the MEMS mirror array assembly and / or the interface element can be provided with a coating suitable for soldering, in particular a metallic coating, in the areas in question.

[0030] In addition to the MEMS mirror array structure and the joining structure, the MEMS mirror array assembly can comprise at least one substrate with at least one application-specific integrated circuit, a rewiring element for converting the contacts of the MEMS mirror array structure into contacts, generally larger, to which control and supply cables can be plugged or soldered, and / or a spacer element, preferably for forming a cavity for accommodating electronic elements in particular. These elements can be manufactured from silicon, as is usually the case with the MEMS mirror array structure. The connections The thermal conductivity of the elements among each other is preferably good, so that heat can be dissipated at the MEMS mirror array structure by conduction via the MEMS mirror array assembly. The defined joining structure is preferably formed integrally with the element of the MEMS mirror array assembly furthest from the MEMS mirror array structure. This eliminates the need for a separate joining structure element.

[0031] Each element of the MEMS mirror array assembly as well as the connections between two adjacent elements are subject to tolerances which, in total, exceed the requirements for use in semiconductor technology equipment, but can be adequately compensated by the method according to the invention.

[0032] It is preferred if the interface element has a cylindrical or truncated cone-shaped basic shape, with at least one stop surface preferably being formed at least partially by the basic shape. A corresponding design of the interface element has proven advantageous.

[0033] For an explanation of the MEMS micromirror unit according to the invention, reference is made to the above explanations.

[0034] The verification of whether a MEMS micromirror unit has been manufactured according to the method according to the invention is possible by comparative investigations of at least two MEMS micromirror units. If two investigated, structurally identical MEMS micromirror units each have a fundamentally identical relative position and location of the MEMS mirror array structure and the at least one stop surface - i.e. within tolerances considered permissible -, however, differences beyond the usual tolerance are revealed in a contact surface influencing this position and location between two components of the MEMS micromirror units, it can be assumed that the contact surface in question was adapted according to the method according to the invention.

[0035] For an explanation of the system according to the invention for semiconductor technology, reference is made to the above explanations. The system can, in particular, be a projection exposure system for photolithography. The at least one MEMS micromirror unit is preferably arranged in the illumination system.

[0036] The invention will now be described by way of example using advantageous embodiments with reference to the accompanying drawings. In the drawings: Figure 1: a schematic representation of a projection exposure system for photolithography comprising MEMS micromirror units according to the invention; Figure 2a-c: a schematic representation of a first embodiment of a manufacturing method according to the invention; Figure 3 : a schematic representation of a Interface element manufactured using the method according to Figure 2a-c; Figure 4a-c: a schematic representation of a second embodiment of a manufacturing method according to the invention; and Figure 5 : a schematic representation of an alternative Starting point for a manufacturing process according to the invention similar to Figure 4a-c .

[0037] Figure 1 shows a schematic meridional section of a projection exposure system 1 for photolithography as an example of a system for semiconductor technology. The projection exposure system 1 comprises an illumination system 10 and a projection system 20.

[0038] With the help of the illumination system 10, an object field 11 in an object plane or reticle plane 12 is illuminated. The illumination system 10 comprises an exposure radiation source 13 which, in the illustrated embodiment, emits illumination radiation at least comprising useful light in the EUV range, i.e. in particular with a wavelength between 5 nm and 30 nm. The exposure radiation source 13 can be a plasma source, for example an LPP source (laser produced plasma, plasma generated with the aid of a laser) or a DPP source (gas discharge produced plasma, plasma generated by means of gas discharge). It can also be a synchrotron-based radiation source. The exposure radiation source 13 can also be a free-electron laser (FEL).

[0039] The illumination radiation emanating from the exposure radiation source 13 is first bundled in a collector 14. The collector 14 can be a collector with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 14 can be exposed to the illumination radiation at grazing incidence (Gl), i.e., at angles of incidence greater than 45°, or at normal incidence (NI), i.e., at angles of incidence less than 45°. The collector 14 can be structured and / or coated, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.

[0040] After the collector 14, the illumination radiation propagates through an intermediate focus in an intermediate focal plane 15. If the illumination system 10 is constructed in a modular design, the intermediate focal plane 15 can in principle be used for the - also structural - separation of the illumination system 10 into a radiation source module, comprising the exposure radiation source 13 and the collector 14, and the illumination optics 16 described below. With such a separation, the radiation source module and illumination optics 16 then together form a modular illumination system 10.

[0041] The illumination optics 16 comprises a deflecting mirror 17. The deflecting mirror 17 can be a flat deflecting mirror or, alternatively, a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror 17 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation from stray light of a different wavelength.

[0042] The deflecting mirror 17 deflects the radiation originating from the exposure radiation source 13 onto a first facet mirror 18. If the first facet mirror 18 is arranged—as in the present case—in a plane of the illumination optics 16 that is optically conjugated to the reticle plane 12 as a field plane, it is also referred to as a field facet mirror.

[0043] The first facet mirror 18 comprises a plurality of micromirrors 18' which can be individually pivoted about two mutually perpendicular axes for the controllable formation of facets, which are each preferably provided with an orientation sensor (not shown) for determining the Orientation of the micromirror 18'. The first facet mirror 18 is thus a microelectromechanical system (MEMS system), as described, for example, in DE 10 2008 009 600 A1.

[0044] In the beam path of the illumination optics 16, a second facet mirror 19 is arranged downstream of the first facet mirror 18, resulting in a double-faceted system, the basic principle of which is also referred to as a honeycomb condenser (fly's eye integrator). If the second facet mirror 19 - as in the illustrated embodiment - is arranged in a pupil plane of the illumination optics 16, it is also referred to as a pupil facet mirror. However, the second facet mirror 19 can also be arranged at a distance from a pupil plane of the illumination optics 16, whereby the combination of the first and the second facet mirror 18, 19 results in a specular reflector, as is the case, for example. in US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0045] The second facet mirror 19 does not necessarily have to be constructed from pivotable micromirrors, but can instead comprise individual facets formed from one or a manageable number of mirrors that are significantly larger than micromirrors, which are either fixed or can only be tilted between two defined end positions. However, as shown, it is also possible to provide the second facet mirror 19 with a microelectromechanical system having a plurality of micromirrors 19' that can each be individually pivoted about two mutually perpendicular axes, each preferably comprising an orientation sensor.

[0046] With the aid of the second facet mirror 19, the individual facets of the first facet mirror 18 are imaged into the object field 11, whereby this usually only involves an approximate image. The second facet mirror 19 can be the last beam-forming mirror or actually the last mirror for the illumination radiation in the beam path before the object field 11.

[0047] Each facet of the second facet mirror 19 is assigned to exactly one of the facets of the first facet mirror 18 to form an illumination channel for illuminating the object field 11. This can, in particular, result in illumination according to the Köhler principle.

[0048] The facets of the first facet mirror 18 are each imaged by an associated facet of the second facet mirror 19, superimposed on one another, to illuminate the object field 11. The illumination of the object field 11 is thereby as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0049] By selecting the illumination channels used, which is easily possible by suitable adjustment of the micromirrors 18' of the first facet mirror 18, the intensity distribution in the entrance pupil of the projection system 20 described below can also be adjusted. This intensity distribution is also referred to as illumination setting. In this case, it can also be advantageous not to arrange the second facet mirror 19 exactly in a plane which is optically conjugated to a pupil plane of the projection system 20. In particular, the pupil facet mirror 19 can be arranged opposite a pupil plane of the Projection system 20 may be arranged tilted, as described for example in DE 10 2017 220 586 A1.

[0050] In the arrangement of the components of the illumination optics 16 shown in Figure 1, the second facet mirror 19 is arranged in a surface conjugated to the entrance pupil of the projection system 20. Deflecting mirror 17 and the two facet mirrors 18, 19 are tilted both relative to the object plane 12 and relative to each other.

[0051] In an alternative, not shown embodiment of the illumination optics 16, a transmission optics comprising one or more mirrors can be provided in the beam path between the second facet mirror 19 and the object field 11. The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GL mirrors, gracing incidence mirrors). With an additional transmission optics, in particular, different positions of the entrance pupil for the tangential and for the sagittal beam path of the projection system 20 described below can be taken into account.

[0052] Alternatively, it is possible to dispense with the deflection mirror 17 shown in Figure 1, for which purpose the facet mirrors 18, 19 are then to be suitably arranged opposite the radiation source 13 and the collector 14.

[0053] With the help of the projection system 20, the object field 11 in the reticle plane 12 is transferred to the image field 21 in the image plane 22.

[0054] The projection system 20 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0055] In the example shown in Figure 1, the projection system 20 comprises six mirrors Mx to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation, thus making the projection system 20 shown a doubly obscured optics. The projection system 20 has an image-side numerical aperture that is greater than 0.3 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0056] The reflection surfaces of the mirrors M ± can be designed as freeform surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors M ± but can also be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. The mirrors Mi, like the mirrors of the illumination optics 16, can have highly reflective coatings for the illumination radiation. These reflective coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0057] The projection system 20 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 11 and a y-coordinate of the center of the image field 21. This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 12 and the image plane 22.

[0058] The projection system 20 can in particular be anamorphic, ie it has in particular different image scales ß x , ß y in the x- and y-direction. The two magnifications ß x , ß y of the pro ection system 20 are preferably (ß x , ß y ) = (+ / - 0.25, / + - 0.125). A magnification ß of 0.25 corresponds to a reduction in the ratio 4:1, while a magnification ß of 0.125 results in a reduction in the ratio 8:1. A positive sign for the magnification ß means an image without image inversion, a negative sign an image with image inversion.

[0059] Other magnifications are also possible, including identical and absolutely identical magnifications ß x , ß y in x and y directions are possible.

[0060] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 11 and the image field 21 can be the same or different, depending on the design of the projection system 20. Examples of projection systems 20 with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1.

[0061] The projection system 20 can, in particular, have a homocentric entrance pupil. This can be accessible. But it can also be inaccessible.

[0062] A reticle 30 (also called a mask) arranged in the object field 11 is illuminated by the illumination system 10 and transferred to the image plane 21 by the projection system 20. The reticle 30 is held by a reticle holder 31. The reticle holder 31 can be displaced, in particular in a scanning direction, via a reticle displacement drive 32. In the illustrated embodiment, the scanning direction is in the y-direction.

[0063] A structure on the reticle 30 is imaged onto a light-sensitive layer of a wafer 35 arranged in the region of the image field 21 in the image plane 22. The wafer 35 is held by a wafer holder 36. The wafer holder 36 can be displaced, in particular along the y-direction, via a wafer displacement drive 37. The displacement of the reticle 30, on the one hand, via the reticle displacement drive 32, and the displacement of the wafer 35, on the other hand, via the wafer displacement drive 37, can be synchronized with one another.

[0064] The projection exposure system 1 shown in Figure 1 or its illumination system 10, the above description of which essentially reflects known prior art, is characterized in that the first and / or second facet mirror 18, 19 is each composed of a plurality of MEMS micromirror units 100 according to the invention (cf. Figures 2 to 4), wherein the MEMS micromirror units 100 each comprise a plurality of micromirrors 18', 19'. The individual MEMS micromirror units 100 are fastened to a higher-level assembly in order to jointly form the facet mirrors 18, 19 sketched in Figure 1. In addition to the mechanical fastening, any necessary connection of the individual MEMS micromirror units 100, for example to control electronics and / or cooling circuits, is also carried out via the higher-level assembly.

[0065] Figures 2a-c schematically show a first exemplary embodiment of a MEMS micromirror unit 100 according to the invention, as can be used in Figure 1, and in particular the method according to the invention for its production.

[0066] The structure of the MEMS micromirror unit 100 is first explained in more detail using Figure 2c.

[0067] The MEMS micromirror unit 100 comprises a MEMS mirror array assembly 110 and an interface element 120 permanently connected thereto.

[0068] Part of the MEMS mirror array assembly 110 is the actual MEMS mirror array structure 111 comprising a plurality of micromirrors 18', 19'. In the illustrated embodiment, 12x12 = 144 micromirrors 18', 19' are arranged in a grid pattern in a common plane 111'. The MEMS mirror array structure 111 also includes all actuators and sensors required for the individual pivoting of each of the micromirrors 18', 19', as described above.

[0069] The MEMS mirror array structure 111 is arranged on a rewiring element 113 made of a multilayer ceramic with metallic rewiring levels between the individual ceramic layers, e.g., a high-temperature multilayer ceramic ("High Temperature Cofired Ceramic", HTCC), wherein a substrate 112, also based on silicon, with application-specific integrated circuits is provided between the rewiring element 113 and the MEMS mirror array structure 111. The rewiring substrate 113 converts the electrical contacts of the MEMS mirror array structure 111 and the application-specific integrated circuits intended for operation into electrical contacts to which, for example, electrical control and supply lines can be connected.Also, the rewiring substrate 113 provides structural integrity to the MEMS mirror array structure 111 and the application-specific integrated circuit substrate 112, which supports the MEMS mirror array structure. 111 and the substrate 112 may not have sufficient properties on their own.

[0070] A spacer element 114 is firmly connected to the rewiring element 113, which together with the rewiring element 113 forms an internal cavity (not shown) in which, for example, further integrated circuits, but also connections of control and supply lines for the MEMS mirror array structure 111 can be arranged. Cooling lines can also be routed in the cavity in order to dissipate heat, in particular from the MEMS mirror array structure 111. The MEMS mirror array structure 111, the substrate 112 with the application-specific integrated circuits, the rewiring element 113 and the spacer element 114 are to be designed and connected in a heat-conducting manner so that heat generated at the MEMS mirror array structure 111 can be conducted to the cavity and there into any cooling lines that may be present.

[0071] A joining structure 115 is formed integrally with the spacer element 114, the element of the MEMS mirror array assembly 110 furthest away from the MEMS mirror array structure 111. The joining structure 115 is designed as a cylindrically shaped projection 116, with the surface 117 of the spacer element 114 from which the projection 116 protrudes serving as a limit stop. Provided in the cylindrical projection 116 are feedthroughs 118 through which supply and control lines can be guided into the cavity formed by the spacer element 114 and the rewiring element 113.

[0072] At the joining structure 115 of the MEMS mirror array assembly 110, the interface element 120 is attached. The rotationally symmetrical interface element 120 is Figures are basically shown only in section to illustrate its interior and the interaction with the MEMS mirror array assembly 110.

[0073] The interface element 120, made of metal, has a substantially truncated cone shape. The outer surface of the truncated cone region of the interface element 120 serves as a stop surface 121, with which the MEMS micromirror unit 100 can be inserted in a conical receptacle of a higher-level assembly with a positive fit. After insertion into such a conical receptacle, the MEMS micromirror unit 100 retains one degree of freedom, namely a rotational degree of freedom about the longitudinal axis 122 of the interface element 120. In order to fix the MEMS micromirror unit 100 in a conical receptacle, a threaded area 123 is provided at the free end of the interface element 120, with which the interface element 120 can be clamped in the receptacle in such a way that a force connection is created on the stop surface 121, with which the two degrees of freedom mentioned are also prevented.

[0074] At the end opposite the threaded portion 123, the interface element 120 has a joining structure 125 that corresponds to the joining structure 115 on the MEMS mirror array assembly 110. The joining structure 125 comprises a cylindrical receptacle 126 that is adapted to the cylindrical projection 116 to an oversize, and a limit stop 127 that rests against the limit stop 117 when the MEMS micromirror unit 110 is assembled. To connect the interface element 120 and the MEMS mirror array assembly 110, the former is heated and then shrunk onto the cylindrical projection 116 of the MEMS mirror array assembly 110. The joining structures 117, 127 are self-centering. namely, around the axis of the cylindrical projection 116. If the two limit stops 117, 127 are in contact, the degree of freedom in the direction of the axis of the cylindrical projection 116 is also limited, and only the angular position of the interface element 120 relative to the MEMS mirror array assembly 110 around the longitudinal axis 122 of the interface element 120 remains undetermined. However, this angular position can also be specified and precisely maintained by suitable markings on the interface element 120 and the MEMS mirror array assembly 110.

[0075] The interface element 120 is hollow so that supply and control lines can be easily passed through.

[0076] In order for the MEMS micromirror unit 100 to be used as part of a facet mirror 18, 19 in a projection exposure system for photolithography, particularly in EUV projection exposure systems, the position and orientation of the individual micromirrors 18', 19' relative to the stop surface 121 on the interface element must correspond to the corresponding specifications within a narrow tolerance range. For example, for some projection exposure systems, the position of the micromirrors 18', 19' in the plane 111' may only deviate by a maximum of 10 pm from a position specification relative to the stop surface 121. The angle of inclination of the plane 111' relative to the stop surface 121 should, for example, deviate from the target by a maximum of 0.2°.

[0077] In order to achieve these specifications in the MEMS micromirror unit 100 shown in Figure 2c, the unit is manufactured using a method according to the invention, as outlined in Figures 2a-c.

[0078] In the initial state for the method according to the invention, shown in Figure 2a, the MEMS mirror array assembly 110 is already complete, i.e., the individual elements 111-114 are already completely assembled. The interface element 120 is present as a blank 120', in which, among other things, the stop surface 121 is already completely manufactured, but the joining area 125 still has some excess material.

[0079] In the first step of the method (Figure 2a), the position and orientation of the MEMS mirror array structure 111 relative to the joining structure 115 of the MEMS mirror array assembly 110 are measured with high precision. The position and orientation thus determined takes into account all deviations from the ideal assembly that occur during the manufacture and joining of the individual elements 111-114 of the MEMS mirror array assembly 110.

[0080] Subsequently, based on the measurement of the MEMS mirror array assembly 110, it is determined how the joining structure 125 on the interface element 120 is to be designed so that the desired location and position of the MEMS mirror array structure 111 relative to the stop surface 121 is precisely achieved as soon as the MEMS mirror array assembly 110 and the interface element 120 are properly joined together.

[0081] In Figure 2b, the correspondingly determined shape for the joining structure 125 of the interface element 120 on the blank 120' is shown in dashed lines on the left side. Based on the thus determined shape, the blank 120' can be machined—for example, with a CNC milling machine—to produce an interface element 120 with the desired shape.

[0082] The interface element 120 prepared in this way can then be joined to the MEMS mirror array assembly 110, as already described, so that a MEMS micromirror unit 100 is present in which specifications for the location and position of the MEMS mirror array structure 111 relative to the stop surface 121 are maintained with the required accuracy.

[0083] In the embodiment shown in Figures 2a-c, practically no position and location deviations need to be compensated for solely for illustration purposes, which is why the determined and ultimately implemented shape of the joining structures 125 of the interface element 120 appears symmetrical. In order to clarify that larger position and location deviations can also be compensated for in the embodiment according to Figures 2a-c, a shape for the joining structure 125, which was determined for a MEMS mirror array assembly 110 (not shown), is shown in dashed lines in Figure 3, with which shape, in addition to a not insignificant position deviation between the MEMS mirror array structure 111 and the joining structure 115 of the (not shown) MEMS mirror array assembly 110 in three degrees of freedom (namely in the plane 111' (cf. Figure 2a) and perpendicular thereto), a location deviation by two rotational degrees of freedom (namely by two in the plane 111' (cf.Figure 2a ) lying axes of rotation) is compensated.

[0084] Figures 4a-c show a second exemplary embodiment of a method according to the invention and a second exemplary embodiment of a MEMS micromirror unit 100 according to the invention. The exemplary embodiment is largely similar to that of Figures 2a-c, so reference is made to the explanations therein, and only the differences between the two exemplary embodiments will be discussed below.

[0085] In the embodiment shown in Figures 4a-c, the interface element 120 is divided into two parts. Thus, the interface element 120 comprises a base element 128 (which is essentially shown only in section) and a compensating element 129, which is separate from it in the initial state (see Figure 4a).

[0086] The base element 128 has a cylindrical basic shape, at one end of which a joining structure 125 is provided which, in the initial state (Figure 4a), is already completely adapted to the joining structure 116 of the MEMS mirror array assembly 110, i.e., can be force-fitted simply by shrinking. At the other end, a threaded area 123 is provided, which enables fixation in a higher-level assembly.

[0087] The compensating element 129 is designed as a compensating sleeve, the outer surface of which is intended as the later stop surface 121 and the inner radius of which is, however, smaller than the relevant outer radius of the base element 128.

[0088] After measuring the MEMS mirror array assembly 110 analogously to Figure 2a, a target shape for the compensating element 129 is then determined, with which, after proper assembly of base element 128 and compensating element 129 to form interface element 120, as well as joining interface element 120 to the MEMS mirror array assembly 110, the MEMS micromirror unit 100 shown in Figure 4c is obtained, in which two stop surfaces 121, 121' are present, which can interact with a suitable receptacle of a higher-level assembly in such a way as to ensure a predetermined location and position of the MEMS mirror array structure 111 relative to the higher-level assembly.

[0089] On the left-hand side of Figure 4b, the compensating element 129 is shown as a blank 129', with the determined target shape already shown in dashed lines. As can be seen, in order to achieve the target shape, only the inner contour and the end faces of the compensating element 129 need to be machined. In particular, the outer circumferential surface provided as a stop surface 121 does not need to be machined and can be used, for example, to clamp the blank 129 in a CNC milling machine and / or an adjusting lathe. The finished machined compensating element 129 is shown on the right-hand side of Figure 4b.

[0090] To complete the MEMS micromirror unit 100, as shown in Figure 4c, the compensating element 129 is first attached to the base element 128 by material bond, namely by soldering or thermal joining, to create a shrink fit between the two metal elements 128, 129. Maintaining the correct angular position of the compensating element 129 relative to the base element 128 can be ensured by suitable markings on the two elements 128, 129. The interface element 120 thus assembled is then firmly connected to the MEMS mirror array assembly 111 by shrinking it onto the joining structure 115, wherein the correct angular position can again be ensured by suitable markings.

[0091] Figure 5 shows a third embodiment of a method according to the invention which largely corresponds to the second embodiment shown in Figures 4a-c, for which reason reference is made to the above explanations.

[0092] Figure 5 shows only the initial state for the method according to the invention, comparable to Figures 2a and 4a. The base element 129 assigned to the interface element 120 in the embodiment according to Figure 4a is now already connected to the spacer element 114 in the initial state and is thus part of the MEMS mirror array assembly 110. The base element 129 subsequently forms the joining structure 115 of the MEMS mirror array assembly 110, the relative position and orientation of which with respect to the MEMS mirror array structure 111 can be measured. As an alternative to the separate formation of the base element 129 shown in Figure 5, it can be formed integrally with the spacer element 114.

[0093] The only interface element 120 then used is the compensating element 129, which in Figure 4a only forms a part of the interface element 120. In the exemplary embodiment shown, the inner diameter of the interface element 120 is adapted to the cylindrical shape of the base element 129 for a clearance or transition fit. However, the outer diameter is significantly larger than the receptacle of the higher-level assembly provided for the MEMS micromirror unit 100, so that suitable stop surfaces 121, 121', as shown by way of example in Figure 4c, can be created to compensate for any location and position errors by suitable machining depending on the measurement carried out. Figure 5 therefore shows a blank 120' of the interface element 120 ora blank 129 ' of the compensating element 129 is shown. Unlike the manufacturing process shown in Figure 4b, in the blank 129 ', 120 ', however, only the outer contour is changed, but not the inner contour, in order to arrive at the desired compensating element 129 or interface element 120.

[0094] The interface element 120 can then be plugged onto the MEMS mirror array assembly 110 and connected in the correct angular position, which is ensured by suitable markings, to the base element 129 forming the joining structure 115, in particular by soldering.

[0095] At the conclusion of the above-outlined manufacturing method according to the invention, starting from the MEMS mirror array assembly 110 and the interface element 120 according to Figure 5, a MEMS micromirror unit 100 is obtained, as shown in Figure 4c.

Claims

Patent claims 1. Method for manufacturing a MEMS micromirror device (100) for use in systems for semiconductor technology, comprising a MEMS mirror array assembly (110) with a MEMS mirror array structure (111) and a joining structure (115) arranged on the side facing away from the MEMS mirror array structure (111), and an interface element (120) for fastening the MEMS micromirror unit (100) to a higher-level assembly with a joining structure (125) that interacts positively with the joining structure (115) of the MEMS mirror array assembly (110) and at least one stop surface (121, 121') for positioning and / or aligning the MEMS micromirror unit (110) with respect to the higher-level assembly, comprising the steps of: a) measuring the relative position and orientation of the MEMS mirror array structure (111) to the joining structure (115) of the MEMS mirror array assembly (110) ;b) adjusting the relative position and / or location of the joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') such that the relative position and / or location of the MEMS mirror array structure (111) and the at least one stop surface (121, 121') after joining the MEMS mirror array assembly (110) and the interface element; (120) via the joining structures (115, 125) corresponds to a predetermined position and location.

2. Method according to claim 1, characterized in that the adjustment of the relative position and / or location of the Joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') is carried out by adapting the joining structure (125) of the interface element (120).

3. Method according to claim 1 or 2, characterized in that Adapting the relative position and / or location of the joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') is carried out by adapting the at least one stop surface (121, 121').

4. The method according to claim 3, characterized in that the interface element (120) is designed in two parts, wherein a base element (128) has the joining structure (125) for connection to the MEMS mirror array assembly (110) and a compensating element (129) which can be fastened to the base element (128) in a predetermined location and position forms the at least one stop surface (121, 121'), wherein the adaptation of the relative position and / or location of the joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') takes place by machining the compensating element (129) before it is fastened to the base element (128).

5. Method according to one of the preceding claims, characterized in that the adjustment of the relative position and / or location of the joining structure (125) of the interface element (120) and the at least one stop surface (121, 121') takes place in at least two, preferably three translational degrees of freedom and / or at least one, preferably two rotational degrees of freedom.

6. Method according to one of the preceding claims, characterized in that the number and design of the stop surfaces (121, 121') on the interface element (120) is selected such that, when inserted into the higher-level assembly, at most two degrees of freedom remain, which can preferably be blocked by suitable fixing means.

7. Method according to one of the preceding claims, characterized in that the joining structures (115, 125) of the MEMS mirror array assembly (110) and the interface element (120) are designed to be self-centering, wherein the joining structures (115, 125) preferably have a limit stop for the degree of freedom in the direction of the self-centering axis.

8. Method according to one of the preceding claims, characterized in that the joining structure (115) of the MEMS mirror array assembly (110) comprises a cylindrically shaped projection (116), the base surface of which at the free end of the projection (116) and / or the surface (117) from which the projection (116) protrudes is preferably designed as a limit stop.

9. Method according to one of the preceding claims, characterized in that MEMS mirror array assembly (110) and interface element (120) are joined to the joining structures (115, 125) by force fit, preferably by shrinkage, or by material fit, preferably by soldering.

10. Method according to one of the preceding claims, characterized in that the MEMS mirror array assembly (11) comprises, in addition to the MEMS mirror array structure (111) and the joining structure (115), a substrate (112) with at least one application-specific integrated circuit, a rewiring element (113) and / or a spacer element (114), wherein the defined joining structure (115) is preferably formed integrally with the element (111-114) of the MEMS mirror array assembly (110) that is furthest away from the MEMS mirror array structure (110).

11. Method according to one of the preceding claims, characterized in that the interface element (120) has a cylindrical or frustoconical basic shape, wherein at least one stop surface (121, 121') is preferably formed at least partially by the basic shape.

12. MEMS micromirror unit (100) for use in systems for semiconductor technology, comprising a MEMS mirror array assembly (110) with a MEMS mirror array structure (111) and a joining structure (115) arranged on the side facing away from the MEMS mirror array structure (111), and an interface element (120) for fastening the MEMS micromirror unit (100) to a higher-level assembly with a joining structure (125) that interacts positively with the joining structure (115) of the MEMS mirror array assembly (110), and at least one stop surface (121, 121') for positioning and / or aligning the MEMS micromirror unit (100) relative to the superordinate assembly, characterized in that the MEMS micromirror unit (100) is manufactured according to one of the preceding claims.

13. A system for semiconductor technology comprising at least one MEMS micromirror unit (100) according to claim 12 for deflecting radiation used by the system.

14. System according to claim 13, characterized in that the system is a projection exposure system (1) for photolithography, wherein the at least one MEMS micromirror unit (100) is preferably arranged in the illumination system (10).

15. Electronic component, characterized in that the component is manufactured using a semiconductor technology system according to claim 14, wherein the component preferably has structures in the micrometer and / or nanometer range.

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