Method for manufacturing a micromirror element and micro-electro-mechanical system

Abstract

The invention relates to a method for producing at least one micromirror element (200) as it can be used in micro-electro-mechanical systems (100), in particular for use in semiconductor technology equipment (1), and to a micro-electro-mechanical system (100) comprising corresponding micromirror elements (200). The process includes the following steps: - Providing a flat, two-sided mirror substrate (210); - Incorporating a predetermined shape at least on the side (215) of the provided mirror substrate (210) intended to be reflective; and - Applying a reflective coating (220) at least to the side (215) of the provided mirror substrate (210) intended to be reflective.

Description

[0001] The invention relates to a method for manufacturing at least one micromirror element, such as can be used in micro-electro-mechanical systems, in particular for use in semiconductor technology equipment, and to a corresponding micro-electro-mechanical system.

[0002] In the prior art, semiconductor technology equipment refers to equipment used for the production or testing of microstructured devices or the components required for their manufacture. An example of such equipment is a projection exposure system for photolithography.

[0003] 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 reticulum) illuminated by the illumination system is projected in a reduced size onto a substrate, such as a silicon wafer, coated with a photosensitive layer and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0004] In illumination systems, particularly projection exposure systems designed for the EUV range (i.e., for exposure wavelengths from 5 nm (or possibly 2 nm) to 30 nm), but also for the DUV range with exposure wavelengths of, for example, 193 nm, two faceted mirrors are typically positioned in the beam path between the actual exposure radiation source and the mask to be illuminated. The faceted mirror closer to the exposure radiation source in the beam path is often a so-called field faceted mirror, while the other is a so-called pupil faceted mirror.

[0005] 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 faceted mirrors – in particular those of the field faceted mirror – from one or more individually electromechanically pivotable micromirrors. A corresponding method is disclosed, for example, in WO 2012 / 130768 A2.

[0006] In order to achieve a small size for 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 micro-electro-mechanical systems (MEMS).

[0007] Micro-electro-mechanical systems (MEMS) are small components that combine micromechanical structures and electronic elements on a single chip. MEMS can be manufactured using integrated circuits, similar to microchips. A MEMS essentially comprises a basic structure on which movable elements, controlled relative to the basic structure, are arranged.

[0008] In a MEMS mirror array, a multitude of small mirror elements are mounted so that they can be moved individually relative to a common base structure. At least one actuator is provided for each mirror element, allowing it to be adjusted along a predefined degree of freedom. Often, the mirror elements can be pivoted about two axes perpendicular to each other and parallel to the base. In such cases, a sufficient number of actuators are provided to allow the mirror elements to pivot independently about these axes. Sensors can also be provided for the individual mirror elements to determine their position relative to the base, thus enabling monitoring of the mirrors' alignment. 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 manufacturing a micromirror or a MEMS mirror array comprising a plurality of such micromirrors is disclosed in DE 10 2015 220 018 A1, together with further details on a possible embodiment of the micromirror.

[0010] Particularly when the reflective surfaces of individual mirror elements cannot be flat to achieve desired optical properties, but rather require a specific shape, often a curvature, it is known to appropriately curve the actual reflective surface, which is formed by a mirror plate coated with a suitable reflective layer, by introducing layer stresses into the mirror plate. While this method generally achieves the desired curvatures for optical reasons, it has been shown that the reproducibility of the curvature, in particular, is difficult to achieve with the required accuracy for the serial production of the mirror elements.

[0011] The object of the present invention is to provide a method for manufacturing at least one micromirror element and a micro-electro-mechanical system in which the challenges known from the prior art no longer occur or only occur to a lesser extent.

[0012] This problem is solved by a method according to claim 1 and a micro-electro-mechanical system according to claim 17. Advantageous further developments are the subject of the dependent claims.

[0013] Accordingly, the invention relates to a method for manufacturing at least one micromirror element for use in micro-electro-mechanical systems, in particular for semiconductor technology equipment, comprising the following steps: - Providing a flat, two-sided mirror substrate; - Implementing a predetermined shape, at least on the side of the provided mirror substrate intended to be reflective; and - Applying a reflective coating at least to the side of the provided mirror substrate intended to be reflective.

[0014] The invention further relates to a micro-electro-mechanical system, in particular for semiconductor technology equipment, comprising a micro-electro-mechanically movable element relative to a basic structure in at least one degree of freedom by at least one actuator, wherein the micro-electro-mechanically movable element comprises a micro-mirror element produced according to the invention.

[0015] First, some terms used in connection with the invention will be explained.

[0016] In a micro-electromechanical system, a "micromirror element" is the element of a micro-electromechanically adjustable micromirror that forms the actual reflective mirror surface. The micromirror element comprises at least the structural element that forms the surface in question. However, particularly on the side facing away from the reflective mirror surface, other elements, such as connecting elements or elements required for the formation of actuators and / or sensors in the final application within a micro-electromechanical system, may be molded onto the micromirror element.

[0017] A "reflective coating" is a coating that reflects radiation at the wavelength of the radiation incident upon the micromirror element during its subsequent proper use. Since radiation at wavelengths for which structural elements made of known materials are typically not reflective or only insufficiently reflective is used, particularly in semiconductor technology systems, it is known to achieve or ensure sufficient reflection through a suitable coating. The reflective coating can be adapted to the wavelength expected for the intended application and, for example, reflect radiation in the EUV range with a wavelength of 13.5 nm.

[0018] A surface is considered "irreversibly shaped" if, after the shaping process is complete, it retains its formed shape permanently. In particular, this means that neither an elastic recovery of any part of the structure forming the surface occurs, nor can the surface be returned to its flat original state by simple measures such as applying a force and / or changing the temperature.

[0019] A coating is considered "curable" if the strength of a material—especially its hardness and toughness—can be increased by suitable measures tailored to the material, such as irradiation with UV light or temporary heating. It is also possible for a material to cure "spontaneously" under normal environmental conditions, for example, by drying.

[0020] In contrast to the prior art method of creating a curved micromirror by suitablely introducing layer stresses into the structure of the micromirror itself, the inventive method starts with a planar mirror substrate that is flat on both sides in order to create one or more micromirror elements with an arbitrarily shaped mirror surface – i.e., the surface intended for reflection and, in particular, suitably coated. Specifically, the invention does not rely on stresses statically introduced into a micromirror, which are intended to permanently hold the micromirror in a stress state that produces the desired curvature, but in which the release of internal stresses, e.g., due to temperature fluctuations, leads to deviations from the desired curvature.By ensuring that the initially provided planar mirror substrate is flat on both sides, a stress-free or at least extremely low-stress substrate can be used with regard to internal stresses, in which the problems described from the prior art practically do not arise.

[0021] Starting with a suitable flat mirror substrate, a predetermined shape is then applied, at least on the side of the provided mirror substrate intended to reflect light. Depending on the application method, the shape of the intended reflective side of the provided mirror substrate may also appear on the other side of the mirror substrate, usually as a negative image. However, it is also possible that the side of the mirror substrate not intended to reflect light remains flat.

[0022] To ensure the reflection of at least one micromirror element, a reflective coating is applied to at least the side of the mirror substrate intended to reflect light. As already mentioned, the coating must be reflective to the incident radiation expected when using the micromirror element.

[0023] Depending on how the intended shape is created, it is generally possible to apply the reflective coating before or after the desired shape is created. However, to avoid damaging the reflective coating during the creation of the intended shape, it is preferable to apply the reflective coating only after the shape has been created.

[0024] To achieve the specified shape, at least on the side of the provided mirror substrate intended to be reflective, it is possible to irreversibly shape the relevant side of the mirror substrate in order to achieve the specified shape.

[0025] The surface to be shaped can be formed by plastically deforming the mirror substrate or a coating applied to it, preferably a curable one. This shaping can be achieved, in particular, by imprinting a negative die of the desired shape. Specifically, the desired shape is created by pressing in a suitable die. The force required for this imprinting depends on the desired shape and the material properties of the mirror substrate or the coating applied to it. In the case of a curable coating, the desired shape can generally be pressed in with manageable force before the final curing, and subsequent curing ensures that the imprinted shape is permanently and irreversibly retained.

[0026] Alternatively, the irreversible shaping can be achieved through a subtractive machining process. In other words, excess material is selectively removed to achieve the desired shape.

[0027] Although other processing methods using suitable tools may be conceivable, it is preferred to achieve the desired predefined shape by spatially resolved ablation of the provided mirror substrate or a coating applied to it. In this context, "spatially resolved ablation" means that for every point in the plane of the initial surface of the mirror substrate or a coating applied to it, the required material removal is determined by the predefined shape and is selectively removed. It is particularly preferred to use grayscale lithography for this purpose. Grayscale lithography is known for the production of 3D structures on surfaces.Put simply, the desired structure is formed onto the surface to be shaped using a lacquer, and then the lacquer is removed by etching until no lacquer remains; in areas with no or only a thin lacquer layer, the material underneath the lacquer is also removed, thus transferring the initial shape of the lacquer into the underlying material.

[0028] Alternatively, irreversible shaping can be achieved through an additive manufacturing process. For this, material can be applied to the mirror substrate in such a targeted manner that the desired shape is achieved on the mirror substrate after the application process is complete.

[0029] The application of material can be carried out directly onto the mirror substrate, e.g., with spatial resolution. Alternatively, it is also possible to first create a coating element by filling a negative mold with the desired shape, which then has the desired shape on one side and is subsequently attached to the mirror substrate. The side of the coating element intended for attachment to the mirror substrate is preferably flat. Attachment can be achieved, for example, by bonding.

[0030] Alternatively, a cavity can be temporarily created on one side of the mirror substrate using a suitable mold or a suitably shaped membrane, which is then filled with a suitable filler material. If the filler material has sufficient dimensional stability, the mold or membrane can be removed; however, the membrane can also remain permanently on the mirror substrate. The filler material is preferably curable, and the curing can occur completely or partially while the cavity is still formed by the mold or a membrane that may be removed later.

[0031] Irreversible deformation can also be achieved by permanently bonding the mirror substrate to a support structure, whereby the mirror substrate is deformed by bending. For this purpose, the support structure has, for example, multiple connection points not lying in a single plane, to which the mirror substrate is permanently attached, e.g., by bonding. With sufficient stiffness and a suitable design of the support structure, the mirror substrate, and especially its reflective side (which typically faces away from the support structure), acquires the desired shape. In addition to providing the support structure, it is also possible to selectively weaken the mirror substrate in certain areas in order to achieve the desired shape, particularly on the reflective side, after bonding it to the support structure.

[0032] Instead of irreversibly shaping the reflective side of the provided mirror substrate, reversible reshaping of the mirror substrate, or at least of the relevant side, is also possible. This reversible reshaping of the mirror substrate can be initially set, for example, using clamping elements, and then permanently maintained. However, for achieving a predetermined shape through reshaping, it is also sufficient, according to the present invention, to provide the mirror substrate with an actively controllable element that is only activated during the final use of the micromirror element, in order to achieve the desired reshaping of the mirror substrate, or of the reflective side of the mirror substrate, in situ. Depending on the design of the actively controllable element, monitoring and / or adjustment during the use of the micromirror element can also be performed.

[0033] It is preferred that an actively controllable layer be applied to the mirror substrate to impart a predetermined shape, which, when appropriately controlled, causes a reversible deformation of the mirror substrate. The active layer can preferably be thermally, piezoelectrically, or inductively adjustable. The desired shape can be achieved by targeted, and optionally spatially resolved, changes in temperature, an applied voltage, or an alternating magnetic field. Instead of an actively controllable layer, an actively controllable structure can also be provided.

[0034] Alternatively, a membrane can be arranged on the reflective side of the provided mirror substrate, and this membrane can be selectively deformed by means of at least one actuator arranged on the mirror substrate. For example, a membrane can be stretched between several points, at least one of which can be adjusted, e.g., piezoelectrically.

[0035] In the inventive method for producing at least one micromirror element for use in micro-electro-mechanical systems, it is preferred if several micromirror elements are manufactured from a common mirror substrate, wherein the common mirror substrate is separated into individual micromirror elements during the production of the micromirror elements or after being introduced into a micro-electro-mechanical system.

[0036] The specified shape for the reflective side of the provided mirror substrate can be any freeform shape where the correspondingly shaped surface no longer lies exclusively in a plane. In particular, the shape can include a curvature, such that the radiation incident in the region of curvature is focused and / or dispersed. The shape in this region can be spherical or aspherical. If the surface of a micromirror is concave-spherical, it is a concave mirror with a concave reflective surface in the form of a spherical surface with a constant radius of curvature in all directions.

[0037] The micro-electro-mechanical system is characterized in that at least one electro-mechanically movable element comprises a micromirror element produced according to the invention. In particular, the micro-electro-mechanical system can be a MEMS mirror array in which the individual micromirrors are produced using the method according to the invention.

[0038] The invention will now be described by way of example with reference to advantageous embodiments and the accompanying drawings. These show: Fig. 1: a schematic representation of a projection exposure system for photolithography comprising a micro-electro-mechanical system according to the invention; Fig. 2: a schematic representation of the micro-electro-mechanical system according to the invention made of Fig. 1; and Fig. 3-9: Schematic representation of various manufacturing processes for micromirror elements made of Fig. 2.

[0039] In Fig. Figure 1 shows a projection exposure system 1 for photolithography as an example of a system for semiconductor technology in a schematic meridional section. The projection exposure system 1 comprises an illumination system 10 and a projection system 20.

[0040] The illumination system 10 illuminates an object field 11 in an object plane or reticulum plane 12. The illumination system 10 comprises an illumination radiation source 13, which, in the illustrated embodiment, emits illumination radiation comprising at least useful light in the EUV range, i.e., in particular with a wavelength between 5 nm and 30 nm. The illumination radiation source 13 can be a plasma source, for example, an LPP source (laser-produced plasma) or a DPP source (gas-discharge-produced plasma). It can also be a synchrotron-based radiation source. The illumination radiation source 13 can also be a free-electron laser (FEL).

[0041] The illumination radiation emanating from the light source 13 is first focused in a collector 14. The collector 14 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 14 can be illuminated at grazing incidence (GI), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 14 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0042] After the collector 14, the illumination radiation propagates through an intermediate focus in an intermediate focal plane 15. If the illumination system 10 is to be constructed in a modular manner, the intermediate focal plane 15 can, in principle, be used for the separation – including 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 the illumination optics 16 then together form a modularly constructed illumination system 10.

[0043] The illumination optics 16 include a deflecting mirror 17. The deflecting mirror 17 can be a flat 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 17 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation from stray light of a different wavelength.

[0044] The deflecting mirror 17 deflects the radiation from the illumination radiation source 13 onto a first faceted mirror 18. If the first faceted mirror 18 is arranged – as in the present case – in a plane of the illumination optics 16 that is optically conjugate to the reticular plane 12 as a field plane, it is also referred to as a field faceted mirror.

[0045] The first faceted mirror 18 comprises a plurality of micromirrors 18' that can be individually pivoted about two mutually perpendicular axes for the controllable formation of facets, each preferably equipped with an orientation sensor (not shown) for determining the orientation of the micromirror 18'. The first faceted mirror 18 is thus a microelectromechanical system (MEMS system), as described, for example, in DE 10 2008 009 600 A1.

[0046] In the beam path of the illumination optics 16, a second faceted mirror 19 is arranged downstream of the first faceted mirror 18, resulting in a double-faceted system, the basic principle of which is also known as a honeycomb condenser (fly's eye integrator). If the second faceted mirror 19 is arranged in a pupil plane of the illumination optics 16 – as in the illustrated embodiment – ​​it is also referred to as a pupil faceted mirror. However, the second faceted mirror 19 can also be arranged at a distance from a pupil plane of the illumination optics 16, in which case the combination of the first and second faceted mirrors 18, 19 results in a specular reflector, as described, for example, in US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0047] The second faceted mirror 19 need not 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, and which are either fixed or tiltable only between two defined end positions. However, as shown, it is also possible to provide the second faceted mirror 19 with a microelectromechanical system comprising a plurality of micromirrors 19' that are individually pivotable about two axes perpendicular to each other, each preferably including an orientation sensor.

[0048] With the aid of the second faceted mirror 19, the individual facets of the first faceted mirror 18 are projected onto the object field 11, although this is regularly only an approximate projection. The second faceted mirror 19 can be the last beam-shaping or even the last mirror for the illumination radiation in the beam path before the object field 11.

[0049] Each of the facets of the second faceted mirror 19 is assigned to exactly one of the facets of the first faceted mirror 18 to form an illumination channel for illuminating the object field 11. This can result in illumination according to Köhler's principle.

[0050] The facets of the first faceted mirror 18 are each superimposed by a corresponding facet of the second faceted mirror 19 to illuminate the object field 11. The illumination of the object field 11 is as homogeneous as possible. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0051] By selecting the illumination channels ultimately used, which is easily achieved by appropriately adjusting the micromirrors 18' of the first faceted 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 the illumination setting. Furthermore, it can be advantageous not to arrange the second faceted mirror 19 exactly in a plane that is optically conjugate to a pupil plane of the projection system 20. In particular, the pupil faceted mirror 19 can be tilted relative to a pupil plane of the projection system 20, as described, for example, in DE 10 2017 220 586 A1.

[0052] During the Fig. In the arrangement of the components of the illumination optics 16 shown in Figure 1, the second faceted mirror 19 is arranged in a surface conjugate to the entrance pupil of the projection system 20. Deflection mirror 17 and the two faceted mirrors 18, 19 are arranged at an angle both to the object plane 12 and to each other.

[0053] In an alternative embodiment of the illumination optics 16, not shown, a transmission optic comprising one or more mirrors can be provided in the beam path between the second faceted mirror 19 and the object field 11. 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). With an additional transmission optic, different positions of the entrance pupil for the tangential and sagittal beam paths of the projection system 20 described below can be accommodated.

[0054] Alternatively, it is possible that on the in Fig. The deflecting mirror 17 shown in Figure 1 is dispensed with, for which the faceted mirrors 18, 19 are then to be arranged appropriately opposite the radiation source 13 and the collector 14.

[0055] Using the projection system 20, the object field 11 in the reticulum plane 12 is transferred to the image field 21 in the image plane 22.

[0056] The projection system 20 comprises a plurality of mirrors M. i , which are numbered according to their arrangement in the beam path of the projection exposure system 1. Regarding the mirrors M i These are optical elements 25.

[0057] In the Fig. In the example shown, the projection system 20 comprises six mirrors M1 to M6 as optical elements 25. Alternatives with four, eight, ten, twelve or another number of mirrors M iare also possible. The penultimate mirror M5 and the last mirror M6 each have a passage for the illumination radiation, making the depicted projection system 20 a doubly obscured optic. 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.

[0058] The reflective surfaces of the mirrors M i can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors M can be i but can also be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflecting surface shape. The mirrors M iLike the mirrors of the lighting optics 16, they 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.

[0059] The projection system 20 has a large object-image offset in the y-direction between a y-coordinate of the 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.

[0060] The projection system 20 can in particular be anamorphic, i.e. it has in particular different image scales β x , β y in the x and y directions. The two image scales β x , β y of the projection system 20 are preferably located at (β x , βy ) - (+ / - 0.25, / +- 0.125). A magnification β of 0.25 corresponds to a reduction in the ratio of 4:1, while a magnification β of 0.125 results in a reduction in the ratio of 8:1. A positive sign for the magnification β indicates a magnification without image inversion, a negative sign indicates a magnification with image inversion.

[0061] Other magnification ratios are also possible. Magnification ratios with the same sign and those with the same absolute value β are also possible. x , β y In the x and y directions, adjustments are possible.

[0062] 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.

[0063] Projection system 20 can, in particular, have a homocentric entrance pupil. This may be accessible. However, it may also be inaccessible.

[0064] A reticle 30 (also called a mask) arranged in the object field 11 is exposed by the lighting 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 moved, particularly in a scanning direction, by means of a reticle displacement drive 32. In the illustrated embodiment, the scanning direction is in the y-direction.

[0065] The reticle 30 can have an aspect ratio between 1:1 and 1:3, preferably between 1:1 and 1:2, and particularly preferably 1:1 or 1:2. The reticle 30 can be substantially rectangular and is preferably 5 to 7 inches (12.70 to 17.78 cm) long and wide, more preferably 6 inches (15.24 cm) long and wide. Alternatively, the reticle 30 can be 5 to 7 inches (12.70 to 17.78 cm) long and 10 to 14 inches (25.40 to 35.56 cm) wide, and is preferably 6 inches (15.24 cm) long and 12 inches (30.48 cm) wide.

[0066] A structure on the reticulum 30 is imaged onto a photosensitive layer of a wafer 35 located in the image plane 22 within the image field 21. The wafer 35 is held by a wafer holder 36. The wafer holder 36 can be displaced, particularly along the y-direction, via a wafer transfer drive 37. The displacement of the reticulum 30 via the reticulum transfer drive 32 and of the wafer 35 via the wafer transfer drive 37 can be synchronized.

[0067] The in Fig. The projection exposure system 1 shown in Figure 1, or its projection system 20, the above description of which essentially reflects known prior art, is characterized in that the first and second faceted mirrors 18, 19 are MEMS mirror arrays comprising a micro-electro-mechanical system 100 according to the invention, of which one micro-electro-mechanical system 100 is shown by way of example in Fig. Figure 2 is shown schematically. It is also possible that only one of the two faceted mirrors 18, 19 comprises a MEMS mirror array.

[0068] Fig. Figure 2 shows a sectional view through a part of a micro-electro-mechanical system 100. The micro-electro-mechanical system 100 comprises a basic structure 101 on which a plurality of elements 103 are arranged to be movable, namely pivotable about two degrees of freedom. Actuators 102 are provided for the individual movement of each of the elements 103, namely for pivoting about the two degrees of freedom, so that each of the elements 103 is a micro-electro-mechanical movable element 103.

[0069] Element 103 comprises a flat base plate 104, which serves as the connection to the base structure 101 and on which parts of the actuators 102 are also arranged. A micromirror 200 is arranged on the upper surface of the base plate 104 of each micro-electro-mechanically movable element 103.

[0070] The micromirror 200 comprises a planar mirror substrate 210, which—as explained below—is initially flat on both sides during the manufacturing process. A reflective coating 220 is applied to the side 215 of the mirror substrate 210 that is intended to be reflective and faces away from the base plate 104 in the operating state. This side 215 also has a shape that is predetermined such that the micromirror 200 exhibits the desired optical properties within the micro-electro-mechanical system 100. In the illustrated embodiment, the side 215 of the micromirror 200 is concave-spherically shaped.

[0071] In Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 shows various manufacturing processes used to produce micromirrors 200, as described in Fig. The micromirrors shown in Figure 2 can be manufactured. The design of the micromirrors 200 can certainly differ from that shown in Figure 2. Fig. The embodiment shown in Figure 2 is rejected. However, the essential point initially is only that the reflective side of the mirror substrate 210 has the specified shape at the end of the manufacturing process or that it can be produced directly. Any necessary adjustments to the elements 103 (see Figure 2) are not required. Fig. 2) the attachment of the respective micromirrors 210 to it is within the scope of professional expertise.

[0072] In some of the manufacturing processes described below, the application of the reflective coating 220 (see below) is required. Fig. 2) not shown, at least not graphically. In these manufacturing processes, this coating 220 can be applied in various process steps. For the sake of clarity, the representation of the reflective coating 220 has been omitted, at least in the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 waived.

[0073] In some of the manufacturing processes - without this being explained separately below - several micromirrors 200 are first formed on the basis of a common mirror substrate 210, before the micromirrors 200 are then appropriately separated at the end of the manufacturing process.

[0074] In Fig. Figure 3 shows a first manufacturing process according to the invention in two variants. On the left side of the Fig. 3 is the method without, on the right side with an additional coating 211 on the mirror substrate 210.

[0075] In the initial state ( Fig. 3a) A planar mirror substrate 210 is provided, which is flat on both sides, especially on the side 215 to be shipped with a mold. In the embodiment shown on the right, the side 215 in question is coated with a coating 211 made of a material that is inherently dimensionally stable but still plastically deformable with minimal force. The coating 211 can be cured, for example by UV irradiation, which gives the coating 211 high stiffness.

[0076] To achieve the desired, predetermined shape shown on page 215, a negative die 300 of the predetermined shape is provided. In the illustrated embodiment, the die 300 comprises the negative mold for a plurality of micromirrors 200.

[0077] The negative stamp 300 is used to transfer the shape directly into the mirror substrate 210 (see below). Fig. 3b, left) or into the coating 211 located on the mirror substrate 210 (see Fig. 3b, right). The force required for irreversible shaping is generally very high during the direct plastic deformation of the mirror substrate 210, but can be reduced somewhat by temporarily increasing the temperature of the mirror substrate 210. The required force is generally more manageable during the plastic deformation of the coating 211, since the final stiffness of the material to be formed before the coating 211 cures is lower than the desired or required stiffness in the cured state.

[0078] Once the plastic and therefore irreversible deformation of the mirror substrate 210 or the coating 211 is complete, the negative stamp 300 can be removed (see Fig. 3c). The coating 211 is then cured, e.g. by irradiation with UV light. It is also conceivable to cure the coating 211 while the negative die 300 is still in contact with it (cf. Fig. 3b, right). In this case, it is only necessary to ensure that the energy required for curing can be supplied to the coating 211. If the coating 211 cures by heat, it may be sufficient to heat the negative die 300. If curing only occurs when the coating 211 is exposed to radiation of a specific wavelength, e.g., UV radiation, the negative die 300 can be designed to be transparent to this radiation.

[0079] Finally, the mirror substrate 210 and, if applicable, the coating 211 on it are separated to create micromirror elements 200 which can be arranged on micro-electro-mechanically movable elements 103 of a micro-electro-mechanical system 100 (see Fig. 2) The reflective coating 220 can, in principle, be applied to any of the in Fig. The reflective coating is applied in the 3 process steps shown. However, it is preferred that the reflective coating be applied after the removal of the negative stamp 300 ( Fig. 3c) and a possible hardening process ( Fig. 3d), but before singulation ( Fig. 3e) is applied.

[0080] In Fig. Figure 4 shows another manufacturing process for a micromirror element 200, in which the desired shape for the reflective side 215 is also irreversibly introduced.

[0081] Starting again from a flat, two-sided mirror substrate 210 (see Fig. 4a), a three-dimensional lacquer layer 310 is applied to the side 215 intended to be reflective by photolithographic means according to the known gray tone lithography process, the shape of which corresponds to the ultimately desired shape (cf. Fig. 4b). Subsequently, an etching process is carried out (see Fig. 4c) the previously applied lacquer layer 310 is removed from the mirror substrate 210, whereby the shape of the lacquer layer 310 is transferred to the mirror substrate 210 (cf. Fig. 4d). This involves a spatially resolved ablation of the mirror substrate 210, thus a subtractive processing of the mirror substrate 210. In other possible methods, spatially resolved ablation is achieved, for example, by a shadow mask or active control. Finally, the mirror substrate 210 is isolated (see Fig. 4d). The reflective coating 220 can be applied to the mirror substrate 210, in particular before or after singulation.

[0082] In the manufacturing process according to Fig. 5 is first placed into a provided negative mold 320 with the desired shape ( Fig. 5a), into which a coating material 211 is introduced and cured if necessary ( Fig. 5b). At the latest after the coating material 211 has fully cured and any planarization of the free surface, a flat, planar mirror substrate 210 is provided and bonded to the coating 210, which is still in the negative mold 320, in a materially bonded manner ( Fig. 5c). A separate adhesive can be used for this purpose. However, it is also possible that the coating material 211, if it is brought into contact with the mirror substrate 210 before it has fully cured, will form a metallurgical bond with the mirror substrate 210 during further curing.

[0083] The negative form 320 is then removed ( Fig. 5d) and the mirror substrate 210 with the coating 211 attached to it is separated to obtain the desired micromirrors 200. To remove the negative mold 320 without damage, release and / or non-stick layers (not shown) can be provided between the mold 320 and the coating material. The reflective coating 220 can be applied, in particular, after removal of the negative mold 320, whereby it should be noted that, unlike the illustration in Fig. 5 the removal of the mold can also take place before the coating 211 is bonded to the mirror substrate 210.

[0084] In the manufacturing process according to Fig. 6 is based on a flat, planar mirror substrate 210 on both sides ( Fig. 6a), by appropriately stretching a membrane 330 a cavity 331 is created, the wall of which on the side facing away from the mirror substrate 210 has the desired shape ( Fig. 6b). Instead of a membrane 330, a negative mold similar to the one made of can also be used. Fig. 5 to create the cavity 331.

[0085] The cavity 331 is then filled with a suitable curable material 212 ( Fig. 6c). Should the membrane 330 remain permanently on the mirror substrate 210 ( Fig. 6d, e, left side in each case), the material 212 can be cured immediately ( Fig. 6c, left) and then the mirror substrate 210 is separated to create individual micromirror elements 200 ( Fig. 6d, left). In this case, the membrane 330 can be directly coated with a reflective coating 220 (in Fig. 6 (not shown) or the membrane 330 itself forms the reflective coating. Alternatively, the membrane 330 can be provided with a suitable reflective coating 220 (in ) at any point in the process shown. Fig. 6 (not shown) are provided.

[0086] Should the membrane 330 be removed after additive processing of the mirror substrate 210? Is this preferably done after the material 212 has completely hardened? Fig. 6d, right). In this case, only after removal of the membrane can 330 be used, but possibly before isolation into individual micromirrors 200 ( Fig. 6e, right) the reflective coating 220 can be applied effectively.

[0087] In the manufacturing process according to Fig. In addition to the flat, two-sided mirror substrate 210, a support structure 340 is provided. The support structure 240 has a plurality of support points 341 designed for permanent connection with the mirror substrate 210 ( Fig. 7a).

[0088] The mirror substrate 340 is then connected to the support structure 340 in such a way that it is materially bonded to each of the support points 341 ( Fig. 7b). With a suitable arrangement and design of the individual support points 341, a deformation of the mirror substrate 210 can then occur which corresponds to the specified shape. In order to avoid damage during the application of the mirror substrate 210 to the support structure 340, the reflective coating 220 is preferably applied only after a complete bond has formed between the mirror substrate 210 and the support structure 340 ( Fig. 7c).

[0089] In the manufacturing process according to Fig. 8 The specified shape is only introduced indirectly, namely by creating the possibility of a reversible transformation during the later use of the micromirror element 200.

[0090] Starting from a double-sided flat mirror substrate 210, in addition to the reflective coating 220, an actively controllable layer 350 is provided ( Fig. 8a), which, when appropriately controlled, causes a reversible deformation of the mirror substrate 210 and the reflective coating 220 arranged on it ( Fig. 8b). By appropriate design and control of the actively controllable layer 350, a predetermined shape can be achieved, whereby the control can even include a control loop in order to achieve the predetermined shape permanently and precisely.

[0091] The actively controllable layer 350 can be arranged on the side of the mirror substrate 210 facing away from the reflective coating 220 (see figure). Fig. 8, left). However, it is also possible to place the actively controllable layer 350 between the mirror substrate 210 and the reflective coating 220 (cf. Fig. 8, right).

[0092] The actively controllable layer 350 can be controlled electrically or thermally. In particular, spatially resolved control can also be provided, with which the shaping of the mirror substrate 210 can be controlled locally.

[0093] comparable to Fig. 8 is in the manufacturing process according to Fig. 9. Subsequent modification of the shape of the side of the provided mirror substrate 210 intended to be reflective is possible. In the embodiment shown, the side in question is shaped according to... Fig. 9 formed by appropriately attaching a membrane 360 ​​to the flat, planar mirror substrate 210 on both sides, wherein the membrane 360 ​​already has the specified shape in its initial state.

[0094] At the in Fig. In the embodiment shown on the left, the membrane 360 ​​is supported at one point by an actuator element 361, which can act on the membrane 360 ​​in at least one degree of freedom. For example, the actuator element 361 could be a piezoelectric element, which allows the distance between the membrane 360 ​​and the mirror substrate 210 to be changed at precisely this point.

[0095] In the version on the right in Fig. 9. The membrane 360 ​​itself can be influenced by electric and / or magnetic fields. The corresponding fields can be generated separately from the micromirror element 200 and enable targeted deformation of the membrane 360.

[0096] In the design variants according to Fig. 9 the membrane 360 ​​itself can form a reflective coating 220 of the mirror substrate 210 or can be provided with a suitable coating 220. 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] WO 2012 / 130768 A2

[0005] DE 10 2015 204 874 A1

[0008] DE 10 2015 220 018 A1

[0009] DE 10 2008 009 600 A1

[0045] US 2006 / 0132747 A1

[0046] EP 1 614 008 B1

[0046] US 6,573,978

[0046] DE 10 2017 220 586 A1

[0051] US 2018 / 0074303 A1

[0062]

Claims

[1] Method for producing at least one micromirror element (200) for use in micro-electro-mechanical systems (100), in particular for semiconductor technology equipment (1), comprising the steps: - Providing a planar mirror substrate (210); - Incorporating a predetermined shape at least on the side (215) of the provided mirror substrate (210) intended to be reflective; and - Applying a reflective coating (220) at least to the side (215) of the provided mirror substrate (210) intended to be reflective. [2] Method according to claim 1, characterized by that the provided mirror substrate (210) is flat on both sides. [3] Method according to claim 1 or 2, characterized by , that the reflective coating (220) is applied after the specified shape has been introduced. [4] Method according to any one of claims 1 to 3, characterized by, that the side (215) of the provided mirror substrate (210) intended to be reflective is irreversibly shaped in order to achieve the specified shape. [5] Method according to claim 4, characterized by , that the irreversible shaping of the side (215) to be provided with a shaping is achieved by plastic deformation of the mirror substrate (210) or a coating (211) arranged thereon, preferably curable. [6] Method according to claim 5, characterized by that the shaping is carried out by imprinting a negative die (300) of the predetermined shape into the provided mirror substrate (210) or a coating (211) applied to the mirror substrate (210), preferably curable. [7] Method according to claim 4, characterized by that the irreversible shaping is achieved through a subtractive processing method. [8] Method according to claim 7, characterized by, that the desired predetermined shape is achieved by spatially resolved removal of the provided mirror substrate (210) or a coating (310) applied thereto, preferably using grey tone lithography. [9] Method according to claim 4, characterized by that the irreversible deformation is achieved through an additive machining process. [10] Method according to claim 9, characterized by , that a coating (211) is created by filling a negative mold (320) of the specified shape and subsequently attaching the coating (211) thus formed to the mirror substrate (210). [11] Method according to claim 9, characterized by , that on one side of the mirror substrate (210) a cavity (331) is created at least temporarily by a suitable shape or a suitable shaped membrane (330), which is then filled with a filling material (212), preferably curable. [12] Method according to claim 4, characterized by , that the irreversible transformation is achieved by permanently connecting the mirror substrate (210) with a support structure (340), whereby the mirror substrate (210) is deformed by bending. [13] Method according to claim 1 or 2, characterized by , that at least the side (215) of the provided mirror substrate (210) intended to be reflective is reversibly transformed. [14] Method according to claim 13, characterized by , that an actively controllable layer (350) or structure is applied to the mirror substrate (210), which, when the actively controllable layer (350) or structure is appropriately controlled, introduces a reversible deformation of the mirror substrate (210). [15] Method according to claim 14, characterized by , that the actively controllable layer (350) is thermally, piezoelectrically or inductively adjustable. [16] Method according to claim 13, characterized by, that on the side (215) of the mirror substrate (210) provided as reflective a membrane (360) is arranged which can be selectively deformed by means of at least one actuator (361) arranged on the mirror substrate (210). [17] Micro-electro-mechanical system (100), in particular for semiconductor technology equipment, comprising an element (103) that is micro-electro-mechanically movable relative to a basic structure (101) in at least one degree of freedom by at least one actuator (102), characterized by , that the micro-electro-mechanically movable element (103) comprises a micro-mirror element (200) manufactured according to one of claims 1 to 16. [18] Micro-electro-mechanical system according to claim 17, characterized by, that the micro-electro-mechanical system (100) is a MEMS mirror array with a plurality of micro-mirror elements (200) movable relative to the basic structure (101) by at least one, preferably two, preferably rotational, degrees of freedom manufactured according to one of claims 1 to 16.

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