MEMS micromirror unit with temperature control function
Patent Information
- Application Number
- PCT/EP2026/056727
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-12
- Filing Date
- 2026-03-11
- Publication Date
- 2026-09-17
Smart Images
Figure EP2026056727_17092026_PF_FP_ABST
Abstract
Description
[0001] 11.03.2026 / BR
[0002] MEMS micromirror unit with temperature control
[0003]
[0001] The present patent application takes priority over the German patent application filed on March 12, 2025.
[0004] DE 10 2025 109 462.4 is claimed, which is referenced and whose content is fully incorporated here (“incorporation by reference”).
[0005]
[0002] The invention relates to a micromirror unit designed as a micro-electro-mechanical system (MEMS) for use in semiconductor technology equipment and to a semiconductor technology equipment.
[0006]
[0003] 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 production. An example of such equipment is a projection exposure system for photolithography for the production of microstructured devices, such as integrated circuits.
[0007]
[0004] The projection exposure system used in photolithography comprises an illumination system and a projection system. The image of a mask (also referred to as a reticulum) illuminated by the illumination system is projected in a reduced size by means of the projection system onto a substrate, for example a silicon wafer, coated with a photosensitive layer and arranged in the image plane of the projection system, in order to transfer the mask structure onto the photosensitive coating of the substrate.
[0008]
[0005] 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 generally arranged 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, and the other is a so-called pupil faceted mirror.
[0009]
[0006] In order 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.
[0010]
[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 micro-electro-mechanical systems (MEMS).
[0011]
[0008] Micro-electro-mechanical systems (MEMS) are small components that combine micromechanical structures and electronic elements in a single chip. MEMS can be manufactured using integrated circuits, similar to microchips. A MEMS essentially comprises a basic structure on which movable elements are arranged that can be controlled relative to the basic structure.
[0012]
[0009] In a MEMS mirror array, a plurality of small mirror elements are each individually movable relative to a common base structure. At least one actuator is provided for each mirror element, allowing it to be adjusted along a predetermined degree of freedom. Frequently, the mirror elements are pivotable about two axes perpendicular to each other and parallel to the base, and sufficient actuators are provided to allow the mirror element 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 mirror alignment. A particularly advantageous embodiment for the mirrors of a MEMS mirror array is described in DE 10 2015 204 874 A1.
[0013]
[0010] A method for producing a micromirror or a MEMS mirror array comprising a plurality of such micromirrors is disclosed - together with further details of a possible embodiment of the micromirror - in DE 10 2015 220 018 Al .
[0014]
[0011] To achieve the required precision in setting a desired intensity and angle of incidence distribution, it is necessary to be able to precisely adjust the orientation of the individual micromirrors. In addition to the microelectromechanical drive required for pivoting the mirror, the micromirrors also include a tilt sensor with which the orientation of the micromirror in two spatial directions can be read and verified. The angular position of a micromirror is then achieved by a control system in which the orientation achieved by the microelectromechanical drive is monitored by the tilt angle sensor, and the drive is readjusted as needed to achieve the desired orientation.
[0015]
[0012] It has been shown that after heat has been introduced into a MEMS mirror array, the individual micromirrors do not precisely achieve the desired reflection properties of the MEMS mirror array, despite proper alignment by the actuators and monitoring by the tilt sensors.
[0016]
[0013] The object of the present invention is to provide a MEMS micromirror unit for use in semiconductor technology systems and a semiconductor technology system comprising such a micromirror unit in which the problems known from the prior art no longer occur or only occur to a reduced extent.
[0017]
[0014] This problem is solved by a MEMS micromirror unit according to claim 1 and by a system for semiconductor technology according to claim 8. Advantageous further developments are the subject of the dependent claims.
[0018]
[0015] Accordingly, the invention relates to a MEMS micromirror unit for use in semiconductor technology systems comprising a plurality of micromirrors which are pivotable relative to a base structure by means of microelectromechanical actuators, each with at least one tilt sensor for determining the orientation of the micromirror, wherein the micromirrors (120) are designed to reflect a working radiation (90) directed towards the MEMS micromirror unit (100), and wherein several heat source elements, controllable with respect to their heat emission, are arranged on the base structure and are controlled by a control unit in such a way that a predetermined heat distribution in the base structure results, wherein at least one controllable heat source element is a driver circuit provided for controlling the microelectromechanical actuators of the pivotable micromirrors.
[0019]
[0016] The invention also relates to a system for semiconductor technology comprising a MEMS micro-mirror unit according to the invention for deflecting a working radiation used by the system.
[0020]
[0017] First, some terms used in connection with the invention are explained.
[0021]
[0018] The “working radiation” is radiation of a specific wavelength or wavelength range used in the semiconductor technology system to perform the task associated with the beam path that passes over the MEMS micromirror unit. If the semiconductor technology system is a projection exposure system for photolithography or even just its illumination system, the working radiation corresponds to the exposure radiation, the wavelength of which can be, for example, 13.5 nm for EUV or 193 nm for DUV systems. The micromirrors are generally designed for the highest possible reflectivity for the working radiation and are, for example, appropriately coated for this purpose.
[0022]
[0019] The “basic structure” of the MEMS micromirror unit is the structure on which the individual micromirrors are each individually and movably mounted. Components or parts thereof can be arranged and attached to the basic structure. In addition to at least parts of the actuators and / or tilt sensors, parts of the control and monitoring circuits as well as various supply lines can also be arranged.
[0023]
[0020] The invention recognizes that, in particular, inhomogeneous heat input into the basic structure of a MEMS micromirror unit can cause it to deform in a complex manner, which can also change the starting point from which the actuators and tilt sensors align each micromirror individually. The heat input into the individual micromirrors and – at least indirectly through heat conduction – the underlying basic structure results, on the one hand, from the operating radiation incident on a MEMS micromirror, whereby this heat input can also be inhomogeneous across a MEMS mirror array, depending on the desired intensity and / or angle of incidence distribution for illuminating the mask.In addition, the actuators intended for adjusting the individual micromirrors, as well as the circuits required for operating the actuators, also emit heat, which can also vary according to the desired intensity and / or angle of incidence distribution.
[0024]
[0021] Since it appears hardly possible to capture the complex deformation of the basic structure with sufficient accuracy, especially under changing heat inputs, the invention proposes to introduce additional heat into a MEMS micromirror unit, and in particular its basic structure, by selectively emitting heat from heat source elements controllable by a control unit provided for this purpose, such that at least a predetermined heat distribution in the basic structure results. Even with such a heat distribution, the basic structure may deform; however, since it is a predetermined heat distribution, the deformation is predictable and can subsequently be suitably taken into account when aligning the individual micromirrors.
[0025]
[0022] It is preferred if the specified heat distribution is homogeneous, meaning that the heat is distributed as evenly as possible across the basic structure of a MEMS micromirror unit, or that a uniform temperature is established throughout the basic structure. A homogeneous heat distribution often reduces or even completely avoids deformations of the basic structure that affect the alignment of the micromirrors. Other deformations of the basic structure that are unavoidable due to the heat input are generally well predictable and can be appropriately taken into account when controlling the individual micromirrors.
[0026]
[0023] Since - as already mentioned - part of the heat input into a MEMS micromirror unit comes from the waste heat of the circuits provided there, components already present in the MEMS micromirror unit can be used as heat source elements that can be controlled with respect to their heat output.
[0027]
[0024] It is thus provided that at least one controllable heat source element is a driver circuit intended for controlling the microelectromechanical actuators of the pivotable micromirrors. The actuators in MEMS micromirror units are often based on the utilization of field effects, whereby a driver circuit is required to generate the necessary fields, the power consumption of which and consequently also its heat dissipation can often be changed, at least within certain limits, which ultimately have no influence on the orientation of the micromirror (but, for example, only on the speed at which the orientation is assumed).
[0028]
[0025] If, for example, electrostatic effects are used to adjust micromirrors in the actuators, the driver circuit is variable with respect to the input voltage in such a way that a change in the voltage has practically no effect on the final orientation of a micromirror adjusted by it, for which the current is the determining factor. The power consumption and thus also the heat dissipated by the driver circuit can therefore be controlled quite simply via the input voltage. In such an embodiment, but also in other driver circuits, it is preferred if the input voltage of the driver circuit is variably adjustable. The actuators or circuits required for this are well known from the prior art.
[0029]
[0026] In addition, at least one other electronic element with variable power consumption can be provided as a controllable heat source element. The electronic elements are preferably already provided on the basic structure for other reasons, e.g., for monitoring and / or controlling the micromirrors. An electronic element is considered to have variable power consumption if it can be switched on and off at least temporarily. For example, an electronic element that only needs to be switched on periodically for its actual function, but is otherwise generally switched off, can be operated solely for the purpose of heat generation at times that are not otherwise required.
[0030]
[0027] It is of course also possible that at least one controllable heat source element is an electrically operated element designed for heat generation. Such elements can be arranged during the manufacture of a MEMS micromirror unit, particularly in the area of the basic structure.
[0031]
[0028] The control of the heat source elements can be model-based, i.e., the control unit receives information about the incident working radiation on the MEMS micromirror unit as well as the operation of the various electrically operated elements of the MEMS micromirror unit and determines the spatially distributed heat input into the basic structure from this. On this basis, the required additional heat input from the heat source elements controllable by the control unit can then be determined, with which the desired heat distribution within the basic structure can be achieved.
[0032]
[0029] However, it is preferred if at least one temperature sensor connected to the control unit is provided and the control unit is configured to control the controllable heat source elements in such a way that the temperature at the temperature sensor is set to the temperature specified by the given heat distribution as closely as possible. By providing corresponding feedback of the temperature to the control unit, it is possible to check, in a model-based control system, whether the heat input initiated by the control unit leads to the expected temperature at the temperature sensor or whether any necessary readjustment is required. If a plurality of temperature sensors are provided, it is also possible and often sufficient to carry out the control without a complex model.If the relative position of temperature sensors and controllable heat source elements is stored in the control unit, the control unit can, based solely on measured temperatures and the heat distribution specified for the basic structure, control the individual heat source elements in such a way that the desired heat distribution is achieved as quickly as possible.
[0033]
[0030] It is preferred that in the MEMS micromirror unit the ratio of micromirrors to temperature sensors is at least 25:1, 16:1, or 9:1, wherein one temperature sensor is assigned to each group of adjacent micromirrors corresponding to the ratio and is arranged in close proximity to them. In other words, each group of 9, 16, or 25 micromirrors should be assigned one temperature sensor, which should then also be arranged adjacent to the respective group of micromirrors. With such a ratio of micromirrors to temperature sensors, a plurality of temperature sensors are distributed so closely across the basic structure of the MEMS micromirror unit that the desired heat distribution can be achieved with suitable control by the control unit, even without complex heat distribution models.The provision of further temperature sensors, especially in areas not directly related to specific (groups of) micromirrors, is of course still possible.
[0034]
[0031] The system according to the invention for the semiconductor industry can, in particular, be a projection exposure system for photolithography. The at least one MEMS micromirror unit is generally arranged in the area of the illumination system. With the operating radiations regularly used in such systems, e.g., with a wavelength of 13.5 nm (EUV range) or 193 nm (DUV range), the effects addressed by the invention regularly occur and can negatively affect the exposure and thus the image quality beyond an acceptable level.
[0035]
[0032] The invention will now be described by way of example with reference to advantageous embodiments and the accompanying drawings. The drawings show:
[0036] Figure 1: a schematic representation of a projection exposure system for photolithography;
[0037] Figure 2a, b: schematic representations of a first embodiment of a MEMS micromirror unit according to the invention in a partial section; and
[0038] Figure 3: Schematic representations of a second embodiment of a MEMS micromirror unit according to the invention in a partial section.
[0033] 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.
[0039]
[0034] An object field 11 in an object plane or reticulum plane 12 is illuminated by means of the illumination system 10. The illumination system 10 comprises an exposure 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 exposure 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 exposure radiation source 13 can also be a free-electron laser (FEL).
[0040]
[0035] 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 with the radiation at grazing incidence (Gl ), 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, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.
[0036] 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 design, 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.
[0041]
[0037] The illumination optics 16 comprise a deflecting mirror 17. The deflecting mirror 17 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam shape in addition to the pure 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.
[0042]
[0038] The deflecting mirror 17 deflects the radiation originating 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.
[0043]
[0039] The first faceted mirror 18 comprises a plurality of micromirrors 18' that can be individually pivoted about two axes perpendicular to each other for the controllable formation of facets, each of which is 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), such as is also used, for example, in the
[0044] DE 10 2008 009 600 Al is described.
[0045]
[0040] 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 referred to 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 the second faceted mirrors 18, 19 results in a specular reflector, as is used, for example, in the
[0046] US 2006 / 0132747 Al, EP 1 614 008 Bl and US 6,573,978 are described.
[0047]
[0041] 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 comprising an orientation sensor.
[0048]
[0042] With the aid of the second faceted mirror 19, the individual facets of the first faceted mirror 18 are imaged into the object field 11, whereby this is regularly only an approximate image. 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]
[0043] 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]
[0044] The facets of the first faceted mirror 18 are each superimposed on an associated 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 has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.
[0051]
[0045] 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 arranged tilted relative to a pupil plane of the projection system 20, as described, for example, in DE 10 2017 220 586 A1.
[0046] 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 each tilted relative to the object plane 12 and relative to each other.
[0052]
[0047] 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 (Gl 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 taken into account.
[0053]
[0048] Alternatively, it is possible to dispense with the deflecting mirror 17 shown in Figure 1, for which the faceted mirrors 18 , 19 are to be arranged appropriately opposite the radiation source 13 and the collector 14.
[0054]
[0049] 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.
[0055]
[0050] The projection system 20 comprises a plurality of mirrors M for this purpose. ± , which are numbered according to their arrangement in the beam path of the projection exposure system 1. Regarding the mirrors M ± These are optical elements 25.
[0051] In the example shown in Figure 1, the projection system 20 comprises six mirrors M x up to M6 as optical elements 25. Alternatives with four, eight, ten, twelve or another number of mirrors M ±are 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.
[0056]
[0052] The reflective surfaces of the mirrors M ± can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors M can be ± but can also be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflecting surface shape. The mirrors M ±They can, just like the mirrors of the lighting optics, have 16 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]
[0053] 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]
[0054] The projection system 20 can in particular be anamorphic, i.e. it has in particular different image scales β x , ß y in the x and y directions. The two image scales ß x , ß y of the projection system 20 are preferably located at ( ß x, ß y ) = ( + / - 0.25, / + - 0.125) . A scale factor β of 0.25 corresponds to a reduction in the ratio 4:1, while a scale factor β of 0.125 results in a reduction in the ratio 8:1. A positive sign for the scale factor β indicates a transformation without image inversion, a negative sign indicates a transformation with image inversion.
[0059]
[0055] Other magnification scales are also possible. Magnification scales with the same sign and those with the same absolute value are also possible. x , ß y in the x and y directions are possible.
[0060]
[0056] 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 the
[0061] US 2018 / 0074303 Al .
[0062]
[0057] The projection system 20 can in particular have a homocentric entrance pupil. This can be accessible. However, it can also be inaccessible.
[0063]
[0058] A reticle 30 (also called a mask) arranged in the object field 11 is exposed 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 moved, in particular in a scanning direction, by means of a reticle displacement drive 32. In the illustrated embodiment, the scanning direction is in the y-direction.
[0064]
[0059] The reticule 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 reticule 30 can be essentially 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 reticule 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.
[0065]
[0060] A structure on the reticulum 30 is imaged onto a photosensitive layer of a wafer 35 arranged 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, in particular 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 with each other.
[0066]
[0061] 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 micromirrors 18', 19' of the faceted mirrors 18, 19 are each part of a MEMS micromirror unit 100. A portion of the micromirrors 18', 19' of the faceted mirrors 18, 19 are each assigned to a MEMS micromirror unit 100, wherein the totality of the micromirrors 18', 19' of the respective faceted mirrors 18, 19 is obtained by several MEMS micromirror units 100 arranged side by side.
[0067]
[0062] Figures 2 to 4 show MEMS micromirror units 100 in a schematic partial section.
[0068]
[0063] The MEMS micromirror unit 100 comprises a basic structure 110 with a base plate 111 on which a plurality of micromirrors 120 are arranged to be movable, namely pivotable about two degrees of freedom. The micromirrors 120 are provided with a reflective coating 122 on the side 121 facing away from the base plate 111.
[0069]
[0064] Actuators 130 are provided for the individual movement of each of the micromirrors 120, namely for pivoting about the two degrees of freedom. The actuators 130 are designed as two rotating interlocking electrode combs 131, one of which is fixedly connected to the respective micromirror 120, the other fixedly connected to the base plate 111. By selectively applying a voltage to a portion of the electrodes of the electrode combs 131, the respective micromirror 120 can be pivoted, thus making each of the micromirrors 120 a micro-electro-mechanical movable element.
[0070]
[0065] Similar to the actuators 130, tilt sensors 140 are provided, which are also designed as interlocking electrode combs 141, one of which is fixedly connected to the respective micromirror 120 and the other fixedly connected to the base plate 111. When a micromirror 120 is tilted, the capacitance changes at least between some of the electrodes of the electrode combs 141. The capacitance or its change can be detected and the orientation of the respective micromirror 120 can be determined from this.
[0071]
[0066] Immediately adjacent to the base plate 111, on which the micromirrors 120 are arranged, the basic structure 110 comprises a first layer of application-specific integrated circuits 112 (ASICs). Each of these application-specific integrated circuits 112 includes a plurality of driver circuits 113 for the actuators 130; monitoring circuits (not shown) are also provided with which the tilt sensors 140 can be read out. A sufficient number of driver circuits 113 and monitoring circuits are provided to operate a total of nine grid-arranged micromirrors 120. Furthermore, each application-specific integrated circuit 112 includes a temperature sensor 114. The dimensions of the application-specific integrated circuit 112 essentially correspond to the combined dimensions of the nine micromirrors 120 controlled by the circuit 112.
[0072]
[0067] The base plate 111 and the application-specific integrated circuits 112 are arranged on the front side of a carrier plate 115, which is crucial for the structural integrity of the base structure 110 and thus of the MEMS micro-mirror unit 100.
[0073]
[0068] On the back of the carrier plate 115, further application-specific integrated circuits 116 are provided, which, however, unlike the application-specific integrated circuits 112 on the front, do not extend tile-like over the entire carrier plate 115, but are arranged in a distributed manner.
[0074]
[0069] In the embodiment shown in Figure 2, one of the application-specific integrated circuits 116 on the back of the carrier plate 115 comprises a control unit 200. The control unit 200 is configured to control the power consumption of the driver circuits 113 independently of the control provided for the alignment of the individual micromirrors 120 (not shown). Since the actuators 130 operate on the basis of electrostatic effects, meaning that the alignment of the individual micromirrors 120 is primarily controlled by the current, the control unit 200 can control the power consumption via the voltage. The power consumption of the driver circuits 113 corresponds directly to the heat dissipation by the driver circuit 113.
[0070] The control unit 200 is designed to control the power consumption of the driver circuit 113 in such a way that it can be considered as a heat source element and a fundamentally homogeneous heat distribution results in the basic structure 110. To achieve this, the control unit 200 receives, in addition to the temperature sensors 115 already present for other reasons from the various application-specific integrated circuits 112, basic information about the operating state of the individual driver circuits 113 as well as other electrically operated components or circuits of the MEMS micromirror unit 100 and the spatial resolution of the operating radiation 90 incident on the MEMS micromirror unit 100.Based on these input variables, the control unit 200 regulates the power consumption of the individual driver circuits 113 in such a way that the heat introduced into the MEMS micromirror unit 100 and thus also the basic structure 110 by the working radiation 90, the heat emitted by electrical components or circuits that are at least momentarily active for the operation of the MEMS micromirror unit 100, and the heat emitted by the driver circuit 113 controlled with respect to power consumption result in an essentially homogeneous heat distribution in the basic structure 110.If such a homogeneous heat distribution exists, the changes in the arrangement and / or orientation of the individual micromirrors 120 resulting from thermal expansion can be predicted with sufficient precision and thus appropriately taken into account when controlling the MEMS micromirror unit 100 and the elements of a semiconductor technology system located upstream and / or downstream of the operating radiation in the beam path. The homogeneity of the heat distribution can be monitored using the temperature sensors 115 already present for other purposes.
[0071] In the section of the MEMS micromirror unit 100 shown in Figure 2a, only one of the micromirrors 120 is exposed to operating radiation 90, whereby, despite reflection by the reflective coating 122, a portion of the operating radiation 90 is absorbed as heat.A portion of the operating radiation 90 can also bypass the micromirror 120 in question and directly strike the base structure 110, which also results in heat input. To achieve the most homogeneous heat distribution possible in the base structure 110, the control unit 200 controls the driver circuits 113 of those micromirrors 120 that are not exposed to the operating radiation 90, such that they absorb electrical power and consequently also emit heat. It is irrelevant whether the micromirrors 120 not exposed to operating radiation 90 remain in the position shown in Figure 2a or whether their orientation changes. The power consumption of the driver circuit 113 is controlled in any case such that the resulting heat input essentially corresponds to that caused by the operating radiation 90 and the circuits 113 activated for the micromirror 120 exposed to operating radiation 90.As a result, a substantially homogeneous heat input occurs over the entire surface of the basic structure 110, which in turn results in a homogeneous heat distribution that can be read via the temperature sensors 115.
[0075]
[0072] Figure 2b again shows the embodiment from Figure 2a, but with more micromirrors 120 exposed to working radiation 90. At the same time, the micromirrors 120 exposed to working radiation 90 are tilted so that the driver circuits 113 responsible for this tilt emit heat. To achieve a homogeneous heat distribution, the remaining micromirrors 120 are also entangled accordingly, with the power consumption of the driver circuits 113 being increased by a higher voltage so that a substantially homogeneous heat input occurs over the surface of the base structure 110.
[0076]
[0073] In the embodiment according to Figure 3, not only the driver circuits 113 (cf. Figure 2; not shown in Figure 3) are used as heat source elements. In addition, electrical elements 117, whose on and off states are variable within certain limits, and elements 118 explicitly designed for heat generation are used as heat source elements. Both the electrical elements 117 and the elements 118 designed for heat generation are operated by the control unit 200, which in this embodiment is integrated into the application-specific integrated circuits 112 on the front of the carrier plate 114, analogously to the control strategies explained in connection with Figure 2. Here, too, the goal is a homogeneous heat distribution in the basic structure 110.In order to monitor the submission and compliance with this heat distribution, the MEMS micromirror unit 100 according to Figure 3 additionally includes temperature sensors 119 on the carrier plate 114 provided for this purpose.
Claims
Patent claims 1. MEMS micromirror unit (100) for use in semiconductor technology equipment comprising a plurality of micromirrors (120) pivotable relative to a base structure (110) by microelectromechanical actuators (130), each with at least one tilt sensor (140) for determining the orientation of the micromirror (120), wherein the micromirrors (120) are designed to reflect a working radiation (90) directed towards the MEMS micromirror unit (100), characterized by the fact that Several heat source elements, controllable with respect to their heat emission, are arranged on the basic structure (110) and controlled by a control unit (200) in such a way that essentially a predetermined heat distribution results in the basic structure (110), wherein at least one controllable heat source element is a driver circuit (113) provided for controlling the microelectromechanical actuators (130) of the pivotable micromirrors (120).
2. MEMS micromirror unit according to claim 1, characterized by the fact that The specified heat distribution is a homogeneous heat distribution.
3. MEMS micromirror unit according to one of the preceding claims, characterized by the fact that the input voltage of the driver circuit ( 113) is variably adjustable.
4. MEMS micromirror unit according to one of the preceding claims, characterized in that at least one controllable heat source element is an electronic element variable with respect to power consumption ( 117 ).
5. MEMS micromirror unit according to one of the preceding claims, characterized by the fact that at least one controllable heat source element is an electrically operated element designed for heat generation ( 118 ).
6. MEMS micromirror unit according to one of the preceding claims, characterized by the fact that at least one temperature sensor ( 115, 119) connected to the control unit is provided and the control unit is designed to control the controllable heat source elements in such a way that the temperature at the temperature sensor ( 115, 119) is as close as possible to the specified temperature resulting from the specified heat distribution.
7. MEMS micromirror unit according to one of the preceding claims, characterized by the fact that In the MEMS micromirror unit (100), the ratio of micromirrors (120) and temperature sensors (115, 119) is at least 25 : 1, 16 : 1 or 9 : 1, wherein each temperature sensor (115, 119) is assigned to a number of adjacent micromirrors (120) corresponding to the ratio and is arranged in close proximity to them.
8. Semiconductor technology system comprising a MEMS micromirror unit ( 100) according to any of the foregoing claims for deflecting working radiation ( 90) used by the system.
9. System according to claim 8, characterized by the fact that the system for semiconductor technology 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 ).