Glass microstructure, micro-mechanics, and associated use

Abstract

In order to extend the possible applications of the previously known LIDE (laser induced deep etching) process, according to the invention, during the production of a micromechanical microstructure (1), the position of those laser pulses (4) which define the outer contour (6) of the microstructure (1) are precisely controlled by applying a plurality of laser pulses (4) to a glass substrate (3) with a subsequent wet-chemical etching step in order to expose the microstructure (1). This makes it possible to control the spatial phase position φ of opposing laser pulses (4) or laser points (4), which are arranged on both sides of the microstructure 1 and form a laser pulse pair (18), but also the extent of so-called sidewall scalloping. By controlling the phase position φ and / or the sidewall scalloping, it is possible to influence the mechanical properties of the microstructure (1) favourably or in the desired form or to adjust them in a targeted manner (cf. figure 8).

Description

[0001] Microstructure made of glass,

[0002] Micro-mechanics and related applications

[0003] The invention relates to a glass microstructure, which can be configured in particular as a micromechanical bending structure (which can form, for example, a micromechanical spring element) or, for example, as a movable finger of a micromechanical comb structure or as a cantilever. The microstructure is etched (completely / in its entirety) from a glass substrate by means of laser-induced deep etching (LIDE), i.e., exposed by laser-induced modification of the glass substrate followed by wet-chemical anisotropic etching.

[0004] The invention further relates to a (movable) micro-mechanism having (at least) such a microstructure, a specific use of such a micro-mechanism, which can also be manufactured by means of the LIDE method, and finally to an associated manufacturing method.

[0005] The LIDE process is already known, for example, from patent EP 2964417 Bl. Until now, it has frequently been used to etch structures into glass substrates, for example, forming a sensor housing. The invention addresses how the applications of the LIDE process can be expanded.

[0006] In the LIDE process, a single laser pulse is used, typically across the entire thickness of a glass substrate, to optically introduce a material change (modification) into the glass body. This modification results in the optically pretreated / exposed structure in the glass substrate being etched anisotropically in a subsequent wet-chemical etching step, even though the etching solution actually exhibits isotropic etching properties in the glass substrate. This technique can be used, for example, to create high-quality, continuous vias in glass, which is of interest for hermetic packaging (AVT).

[0007] Pulsed lasers can be used in the LIDE process, with each laser shot (one laser pulse) modifying the glass along the z-direction (= optical axis / surface normal of the glass substrate). Typically, no changes to the beam profile used are made. In the LIDE process, therefore, no individual small volumes (voxels) within the glass volume are processed differently with the laser, as is the case with other laser-based (e.g. ablative) glass processing processes. The optical processing of the glass substrate in the LIDE process is therefore non-ablative, i.e. the desired material removal in the glass substrate is only achieved later during the wet-chemical etching step, but not by means of the laser radiation.

[0008] Based on this prior art, the invention is based on the object of expanding possible applications of the LIDE method.

[0009] The invention has recognized the following: The wet chemical etching used in the LIDE process always begins on a substrate surface and progresses from there into the depth (z-direction) of the glass substrate. Depending on the selected process parameters (in particular the material of the glass substrate, the etching solution used and the temperature), the etching radius r in the xy-plane (= substrate plane) can decrease more or less significantly along the z-direction (i.e. normal to the substrate plane), whereby edge profiles (for example in the xz-plane) can be achieved which have a slope with respect to the z-axis. In this case, only such slopes are possible which correspond to a decreasing etching radius r with increasing depth z. However, the etching radius r on the substrate surface is always the same, since it only depends on the etching solution and the total etching time, and thus cannot be changed with spatial resolution, which represents a central boundary condition of the LIDE process.

[0010] Due to the respective etching radius r (z), which is generated in different xy planes at different z depths of the glass substrate, characteristic indentations can be formed in the side surfaces (in the direction of the xz or yz plane). These indentations are always concave because the etching solution etches isotropically in a specific xy plane, thus forming a convex etch front. This creates protruding glass ribs in these wet-chemically etched side surfaces, which protrude between the respective indentations and, like the indentations, run along the z direction. Depending on the selected process parameters, the indentations can be inclined not only in the y direction (e.g., in a structure running in the x direction), but also in the x direction (e.g., at the tip of such a structure).

[0011] It was also observed that the ribs, which should actually be sharp-edged purely geometrically, become rounded with increasing etching time, which appears to be caused by chemical processes at the microscale. The ribs / bulges exhibit a distance L x , which corresponds to the pulse spacing p, from those laser points that are responsible for the formation of the respective bulge. Since the ribs / bulges appear similar to the ribs on the outside of a mussel shell, these structures can be referred to as "sidewall scalloping." Taking these aspects into account, the features of claim 1 and / or claim 2 are provided according to the invention for a mechanical microstructure to achieve the above object.

[0012] In particular, according to the invention, to achieve the object in a mechanical microstructure of the type mentioned at the outset, it can be provided that, in order to produce the microstructure, laser pulses were / are placed on two opposing tool paths in a deflection region of the microstructure (i.e., where the bending structure can move in or out of the substrate plane, or where the micromechanical finger can move relative to the substrate), which tool paths have a respective maximum distance r perpendicular to an (outer) contour (in particular to concave indentations in the contour) along a direction of travel of the microstructure. This distance r corresponds precisely to an etching radius r of a wet-chemical etching step that is / was used to expose the microstructure, wherein the etching radius r lies in a substrate plane of the glass substrate.With such an approach, the microstructure is designed monolithically (i.e. as a whole), as part of the glass substrate.

[0013] Furthermore, it is intended that the laser pulses were (or are) placed during the production of the microstructure in such a way that a respective spatial phase position <p(x) von jeweiligen Laserpulspaaren entlang einer Verlaufsrichtung der Mikrostruktur innerhalb des besagten Auslenkungsbereichs homogen eingestellt ist. Die homogene Einstellung der Phasenlage sollte dabei mindestens abschnittsweise realisiert sein, um einen signifikanten technischen Effekt zu erzielen; vorzugweise kann die Phasenlage jedoch entlang des gesamten Auslenkungsbereichs homogen eingestellt sein. Alternativ oder ergänzend zu diesen Merkmalen kann zur Lösung der Aufgabe auch vorgesehen sein, dass bei der Herstellung der Mikrostruktur (vorzugsweise alle) diejenigen Laserpulse (bzw.Laser points) that define an outer contour of the microstructure are / were placed on respective continuous (i.e., for example, straight or curved) tool paths, at least in the said deflection range of the microstructure. Each of the tool paths has a maximum distance from the contour that exactly corresponds to an etching radius r of a wet-chemical etching step that was / is used to expose the microstructure (from the glass substrate). The laser pulses on the tool path thus have a distance r to associated concave indentations in the contour. The laser pulses can preferably be placed at a constant pulse spacing p on the respective tool path, at least in sections (e.g., placing at least three adjacent laser pulses one after the other at a pulse spacing p on the respective tool path).It goes without saying that depending on the selected extent of sidewall scalloping, the respective tool path has a minimum distance of rt. y to the contour, with t y the depth of the respective indentation in the sidewall of the microstructure.

[0014] Under a phase position <p(x) kann hier insbesondere folgende räumliche Beziehung verstanden werden, die die Positionierung der Laserpunkte beziehungsweise der hieraus entstehenden (oben beschriebenen) Einbuchtungen beschreibt: <p(x) = Ax / p'x360°. Hierbei steht <p(x) für die räumliche Phasenlage an einer bestimmten x-Position entlang der Verlaufsrichtung der Mikrostruktur, Ax ist ein Versatz zwischen zwei sich gegenüberliegenden Laserpunkten entlang der Verlaufsrichtung der Mikrostruktur und p' ist ein effektiver Pulsabstand auf einer Mittelachse der Mikrostruktur (bei einer geradlinigen Mikrostruktur ist p' gleich dem geometrischen Pulsabstand p zwischen zwei direkt auf einer Werkzeugbahn benachbarten

[0015] Laser points). This will be explained in more detail using the drawings.

[0016] A homogeneous phase position can be achieved if the phase position <p(x) entlang der Verlaufsrichtung der Mikrostruktur um weniger als + / - 60°, besonders bevorzugt um weniger als + / - 30°, schwankt. Hierbei kann die mittlere Phasenlage (oder auch mittlerer Phasenwinkel cp beziehungsweise mittlerer Phasenverzug cp) unterschiedlich gewählt sein (etwa cp = 0° oder cp = 180°).

[0017] In other words, according to the invention, it can be provided that the laser pulses and the resulting etching radii (which result from the wet-chemical exposure of the microstructure in the glass substrate) are / were placed uniformly along two opposite side surfaces (or side walls) of the microstructure in such a way that opposite laser point pairs (and the resulting indentations) always show a homogeneous (i.e., approximately constant) offset Ax. The offset Ax can vary somewhat, for example, due to the process or the geometry of the microstructure, but should always be selected so that a homogeneous phase position <p(x) ergibt. Beispielsweise kann die Schwankung von Ax so gering sein, dass sich die Phasenlage <p(x) im Auslenkungsbereich der Mikrostruktur um weniger als + / - 60°, besonders bevorzugt um weniger als + / - 30°, ändert.

[0018] Alternatively or in addition to controlling said phase position, the invention further proposes specifically adjusting the sidewall scalloping of the microstructure in order to adjust the mechanical properties in a desired manner (high homogeneity or targeted inhomogeneity). Therefore, to achieve the object, according to the invention, with a mechanical microstructure of the type mentioned at the outset, laser pulses are placed on two opposing tool paths to produce the microstructure in a deflection range of the microstructure, which tool paths have a respective maximum distance r perpendicular to an (outer) contour (in particular to concave indentations in the contour) along a direction of travel of the microstructure, which corresponds to said etching radius r of the wet-chemical etching step.Since this etching radius r, as mentioned, lies in the substrate plane of the glass substrate, the contour after wet-chemical exposure exhibits lateral concave indentations, each curving with the etching radius r and delimited by respective convex ribs. In order to improve the homogeneity of the mechanical properties of the microstructure or to deliberately create inhomogeneity in the mechanical properties of the microstructure, it is proposed that the laser pulses were / are placed in such a way that the manifestation of sidewall scalloping of the microstructure is specifically adjusted, at least in sections, but preferably along the entire deflection range.

[0019] For example, sidewall scalloping can be described as a ratio t y / r from the local etching radius r and a respective lateral depth t yof the respective indentation. Targeted adjustment here can be understood in particular as meaning that the sidewall scalloping is either consistently weak or consistently strong across the entire deflection range.

[0020] In other words, the extent of sidewall scalloping, in particular the size of the respective lateral depth t y , thus be adjusted spatially along the direction of travel by appropriate placement of the laser pulses on the substrate plane. For example, it can be provided that to achieve consistently weak sidewall scalloping, for the respective lateral depth t y at least in sections, but preferably along the entire deflection range, the following applies: t y / r < 0.1, preferably t y / r < 0.05, where r is the etching radius. In this case, the mechanical properties of the micro- / bend structure will be very homogeneous. It can also be provided that the lateral depth t y in the deflection range fluctuates by less than 40%, in particular by less than 20% or even less than 10%.

[0021] If, however, a targeted inhomogeneity is to be created, which can be exploited, for example, by actuators or sensors, it can be provided that for the respective lateral depth t y at least in sections, but preferably along the entire deflection range, the following applies: t y / r > 0.1, preferably t y / r > 0.2, which allows for a pronounced sidewall scalloping (relative to the etch radius r). In this case, the mechanical properties of the micro- / bend structure will be inhomogeneous. Under certain circumstances, the lateral depth t yin the deflection range fluctuate by 50%, or the fluctuation is small, so that a homogeneous, strongly pronounced sidewall scalloping results, which also leads to the desired inhomogeneity.

[0022] This invention(s) can be used in particular to form glass-based MEMS (micro-electro-mechanical systems), i.e., GMEMS, which have excellent mechanical properties. A first example is a cantilever with a width of less than 50 μm or even less than 20 μm. Such narrow widths carry a high risk of spring breakage. By forming a homogeneous phase position of, for example, <p(x) = 180°+ / -30° oder sogar <p(x) = 180°+ / -15° und / oder eines nur schwach ausgeprägten und homogen eingestellten sidewall scallopings kann die Bruchfestigkeit des Federbalkens wesentlich verbessert werden. Dadurch kann eine solche Federstruktur in einem GMEMS sicher eingesetzt werden. Das Platzieren der Laserpunkte auf kontinuierlichen Werkzeugbahnen, die den besagten Maximalabstand von r zur Kontur des Biegebalkens aufweisen, stellt dabei sicher, dass sehr dünne Biegebalken reproduzierbar hergestellt werden können.This also results in advantages for the actuator / sensor technology that uses such a bending beam.

[0023] Unlike conventional MEMS based on silicon as the substrate material, GMEMS uses glass to form the micromechanical structures, or more precisely, the aforementioned micromechanical microstructure. Unlike silicon, glass is not a semiconductor, but an insulator. However, the electrical functionality of a GMEMS can be achieved by adding electrically conductive layers, such as metallic thin films, to the glass.

[0024] The invention therefore proposes not simply leaving the phase position to chance, but rather specifically adjusting the phase position in specific regions of a microstructure, namely in the region of relevant deflection of the microstructure (deflection range), and making it homogeneous, for example, with either a weak or strong phase delay. The phase delay can be considered to be maximum at a phase of cp = 180° and minimum at a phase of cp = 0°. One advantage of such a design is that the mechanical properties of the microstructure can be better controlled, as will be explained in more detail below.

[0025] To produce the microstructure, for example, the LIDE process may involve placing a series of laser pulses along a laser line to introduce a modification into the glass substrate using laser radiation. The areas of the glass substrate that are / were modified by the laser radiation can then be etched free in a subsequent wet-chemical etching step (particularly the one described above).

[0026] The microstructure can have microscopic dimensions, for example, in terms of its width (in the substrate plane) and / or height (normal to the substrate plane). For example, the width / height can be in the sub-mm range and be less than 100 μm, less than 50 μm, or even less than 20 μm (e.g., for very narrow cantilevers). The length of the microstructure, however, can range from the sub-mm range through the mm range to the cm range, since LIDE is particularly suitable for forming large GMEMS structures.

[0027] The microstructure thus created can thus have at least one microscopic dimension, such as the length and / or width and / or height (perpendicular to the substrate plane) of the microstructure. This is because the positioning accuracy of the laser pulses can be within a few micrometers, allowing very fine microstructures to be exposed wet-chemically, whereby the high anisotropy achievable with the LIDE process is also beneficial here. A microstructure designed according to the invention can, for example, exhibit an aspect ratio (height:width) of at least 10:1, at least 20:1, or even at least 50:1.

[0028] The microstructure can, for example, be designed as a self-supporting cantilever beam (spring beam) with one free-standing end. However, it can also be anchored, preferably monolithically, on both sides in the glass substrate. Depending on the application, the microstructure can be designed for both in-plane deflections (in the xy plane, which corresponds to the substrate surface) and / or for out-of-plane deflections (then in the z direction). In addition to such vibration modes, torsional vibrations of the microstructure can also be excited, either additionally or alternatively. For all such applications, the invention offers technical advantages with regard to the mechanical properties of the glass microstructure, in particular with regard to fracture strength, homogeneity of stiffness, and reduced cross-sensitivity.

[0029] A microstructure within the meaning of the invention can thus be designed as a micromechanical bending element, in particular as a micromechanical spring element, for example, as a bending beam clamped on one or both sides, but also, for example, as a membrane, as a torsion beam, or, for example, as a movable finger of a comb structure, such as a micromechanical actuator or sensor. The mobility of the finger can be achieved, for example, by suspending the finger from a micromechanical spring element (this can be designed in particular according to the invention).

[0030] It should also be noted that each laser pulse can be assigned a corresponding laser spot on the surface of the glass substrate, which corresponds to the center of the laser pulse's impact point on the glass substrate surface. The tool paths mentioned correspond to the paths along which a laser head emitting the laser pulses is guided, with the laser head typically being guided at a constant z-distance from the substrate surface.

[0031] Due to the homogeneous design of the phase position <p(x) der Mikrostruktur (in Bezug auf eine Kontur der Mikrostruktur) kann insbesondere erreicht werden, dass (i) eine Federsteifigkeit der Mikrostruktur minimiert wird und / oder dass (ii) eine Homogenität der mechanischen Eigenschaften der Mikrostruktur gezielt eingestellt (also insbesondere minimiert oder maximiert) wird und / oder dass (iii) eine Querempfindlichkeit der Mikrostruktur auf eine Störgröße gezielt eingestellt (also insbesondere minimiert oder maximiert) wird und / oder dass (iv) eine Bruchfestigkeit der Mikrostruktur erhöht wird. Mit anderen Worten lassen sich also durch die gezielte Kontrolle der Phasenlage <p(x) zahlreiche mechanische Eigenschaften der Mikrostruktur kontrollieren und optimieren .

[0032] It is understood that microstructures as described herein and the associated manufacturing processes can thus be used to achieve the four technical effects (i) - (iv) mentioned above. Low spring stiffness / high homogeneity / low cross-sensitivity / high fracture strength can be achieved through a large phase distortion and / or a low degree of sidewall scalloping. Conversely, a low phase distortion, especially with a very narrow microstructure width, and / or a highly pronounced sidewall scalloping can result in a comparatively high spring stiffness / low or poor homogeneity / high cross-sensitivity / low fracture strength of the microstructure.

[0033] Alternatively or in addition to the features described above, the object can also be achieved by means of a microstructure according to independent claim 2. Thus, in order to achieve the object, it can be provided in particular that a respective spatial phase position <p(x) von jeweiligen Laserpulspaaren entlang einer Verlaufsrichtung der Mikrostruktur innerhalb des Auslenkungsbereichs <p(x) = 180° + / - 60°, vorzugsweise <p(x)= 180° + / -30°, beträgt. Bei solchen Ausgestaltungen besteht also ein großer räumlicher Phasenverzug cp. Bei einer solchen Ausgestaltung ist es zudem vorzuziehen, wenn für eine maximale Breite B der Mikrostruktur innerhalb des gesamten Auslenkungsbereichs gilt: B < 200 μm, insbesondere B < 100 gm oder sogar B < 50 gm oder B < 20 gm. Denn durch solche Merkmale können Mikrostrukturen gefertigt beziehungsweise erhalten werden, die ein sehr gutes mechanisches Ansprechen zeigen und die trotz ihrer mikroskopischen Größe eine hohe Bruchfestigkeit aufweisen.

[0034] Since both the pulse spacing p and the etching radius r are limited for technical and process cost reasons, a phase angle of approximately 180° allows for the production of softer and more homogeneous micromechanical springs with higher reproducibility. This means lower deflection forces are required, less space is required, or the fill factor is increased, and the lower peaks of mechanical stress during deflection result in higher fracture strength.

[0035] Such a phase position can thus, especially in combination with mild sidewall scalloping, lead to excellent homogeneity of the mechanical properties of the microstructure, which is relevant, for example, for micro-actuator or micro-sensor applications. For example, certain desired characteristics of the micro-actuator can be specifically tuned, i.e., the electrostatic response of the microstructure can be favorably influenced. This allows for improved actuation and / or sensor performance of a GMEMS compared to microstructures in which the sidewall scalloping and / or phase are not specifically tuned.

[0036] In order to realize such advantages, it can further be provided that in order to achieve a slightly pronounced sidewall scalloping, the laser pulses are / were set and the microstructure was / is etched free in such a way that the ratio of an average pulse spacing p between adjacent laser pulses on one of the two tool paths (i.e. placed on the same tool path) and the etching radius r, preferably in the entire deflection range, applies: p < r. Preferably, the following can even apply: p < r / 2. It should be emphasized here that the extent of the micro-scalloping only depends on the ratio p / r, but not on the selected spatial phase position, which is determined by the offset Ax.

[0037] In the extreme case, with semicircular indentations, the length L x of a respective indentation in the side wall of the microstructure apply: L x= 2r = p. Then the following would apply: p / r = 2:1 or p = D = 2r with D being the etching diameter at the substrate surface.

[0038] In general, and especially in such configurations, it is also preferable if directly adjacent laser pulses have a minimum pulse spacing of at least 3.0 μm or even at least 5.0 μm (on the respective tool path). This allows optical shadowing effects to be avoided and a homogeneous etching result to be achieved, which ensures that the extent of the sidewall scalloping is reproducible and can therefore be specifically adjusted during the production of the microstructure. On the other hand, for minimal sidewall scalloping, it is advantageous if the pulse spacing p remains below 10.0 μm, in particular below 7.0 μm, at least in the deflection range of the microstructure.

[0039] As already mentioned, the contour of the microstructure (in the area of ​​the sidewalls) typically exhibits lateral concave indentations after wet-chemical exposure. These indentations each exhibit a curvature with the etching radius r and are delimited by respective convex ribs. It can now be provided that a ratio of the local etching radius r and a lateral depth t y of the respective indentations applies: t y / r < 0.1. Preferably, t y / r < 0.05 or even t y / r < 0.03. Here, the depth t y measured transversely to the direction of the microstructure.

[0040] In addition or alternatively to these features just described, a ratio of the maximum width B of the microstructure transverse to the direction of travel and the lateral depth t y the respective indentation applies: t y / B < 0.1, especially t y / B < 0.05. Such configurations also define a very weak sidewall scalloping.

[0041] Such indentations delimited by (more or less pronounced and / or more or less rounded) ribs can, as mentioned, be subsumed under the term "sidewall scalloping", since the ribs structure the side surfaces of the etched microstructure, similar to a mussel shell, but on a microscopic scale. The two designs described above thus result in a particularly flat / less pronounced sidewall scalloping, whereby a particularly small fluctuation in the width of the microstructure and thus a high homogeneity of stiffness is achieved.It should be noted that the area moment of inertia for deflections in the substrate plane depends cubically on the width (for out-of-plane deflections, however, the area moment of inertia increases linearly with the width and cubically with the height / thickness of the microstructure). Thus, with pronounced sidewall scalloping, the local area moment of inertia can fluctuate considerably along the longitudinal axis of the microstructure. Adjacent ribs can be separated by a distance L. x which corresponds exactly to the pulse spacing p of the corresponding laser pulses.

[0042] The ribs in question can typically run in the z-direction, i.e., normal to the substrate plane. The same applies to the course of the indentations themselves. In this case, the ribs as well as the indentations can form an inclination to the z-axis (especially at a taper angle <p), je nach dem gewählten Grad der Anisotropie des verwendeten nasschemischen Ätzprozesses .

[0043] Each of the indentations in the respective sidewall of the microstructure can generally be assigned to a corresponding laser pulse located at a distance r from the contour (= outer outline in the substrate surface / on the top side of the microstructure). The corresponding laser pulse or laser spot (= point of impact of the laser pulse on the glass substrate surface) is responsible for the formation of this indentation because the etching front emanates isotropically from the laser spot.

[0044] A microstructure design with low sidewall scalloping and comparatively large phase distortion <p(x) kann vorteilhaft sein, etwa um eine besonders hohe Bruchfestigkeit und damit besonders große Auslenkungen der Mikrostruktur zu ermöglichen. Denn bei wenig ausgeprägtem sidewall scalloping werden insbesondere lokale Spitzen der mechanischen Belastung vermieden, weil das Flächenträgheitsmoment homogener ausgestaltet ist. Bei sensorischen Anwendungen kann hingegen (aus denselben Gründen) die Sensitivität erhöht werden, mit dem die Mikrostruktur mechanische Schwingungen erfassen kann.

[0045] A particularly weak sidewall scalloping will bring advantages for the homogeneity of the mechanical properties of a microstructure, especially if its width is comparatively small, which then leads to a correspondingly high ratio of t y / B leads, for a given t yThis becomes particularly relevant when the maximum width B of the microstructure (transverse to the direction of travel) is less than 100 μm or even 50 μm.

[0046] Another way to describe the phase delay between opposing laser pulses or laser spots is to specify a step angle a, which a respective laser pulse pair forms in the deflection range of the microstructure 1 with respect to the direction of travel. The step angle a can, for example, be more than 2.5°, in particular more than 5°, or even more than 7°, or even more than 9°, depending on the width of the microstructure.

[0047] In particular, the following applies to the step angle a: a = arctan (Ax / Dy) where Ax is the offset of the laser pulses forming the laser pulse pair to each other along the direction of travel and Dy is the distance between the two opposing laser pulses (or the associated tool paths) transverse to the direction of travel. The step angle a decreases with decreasing width B and increasing offset Ax / increasing phase delay. <p(x) zu.

[0048] For example, if the offset between the laser points is Ax = p / 2 = 5 μm with a pulse spacing of p = 10 μm, then <p(x)= Ax / p'x360°= 180° und wird ferner ein Ätzdurchmesser D = 2r = 20 μm verwendet, so kann bei einer Federbreite von B = 10 μm der Abstand D y between the tool paths, for example D y « 30 μm. This results in a step angle of a « arctan (Ax / Dy) = arctan (5 / 30) = 9.5°.

[0049] A further embodiment provides that for a ratio of a (particularly minimum or maximum) pulse spacing p between two (directly) adjacent laser pulses on one of the two tool paths and a maximum width B of the microstructure transverse to the direction of travel, the following applies: p / B < 1.0, preferably p / B < 0.75 or even p / B < 0.5. For high aspect ratios (e.g. t / B > 40) and / or very small spring widths (B < 20 μm), the following can even be provided for the microstructure: p / B < 0.4, preferably p / B < 0.3. The pulse spacing p used can be based on the distance L x between two adjacent indentations in the sidewall of the microstructure created by wet chemical etching.

[0050] In such configurations, the maximum width of the microstructure can be less than 50 μm, in particular less than 20 μm. For example, a minimum pulse spacing of p min= 5 μm and a maximum / nominal width of 10 μm of a microstructure used as a micromechanical spring, a ratio of p / B = 0.5 can be set.

[0051] As a technical effect, it should be taken into account that the smaller the pulse spacing p is chosen and thus the smaller p / B is, the weaker the micro-scalloping will be and the more homogeneous the mechanical properties of the microstructure will be.

[0052] Alternatively or in addition to all the features described so far, the object can also be achieved by means of a microstructure according to independent claim 7. Thus, in order to achieve the object, it can be provided in particular that a respective spatial phase position <p(x) von jeweiligen Laserpulspaaren entlang einer Verlaufsrichtung der Mikrostruktur innerhalb des Auslenkungsbereichs der Mikrostruktur cp = 0° + / - 60°, vorzugsweise cp = 0° + / -30°, beträgt. Bei einer solchen Ausgestaltung kann ferner vorgesehen sein, dass für eine maximale Breite B der Mikrostruktur innerhalb des gesamten Auslenkungsbereichs gilt: B < 100 μm, insbesondere B < 50 μm oder sogar B < 20 gm.

[0053] Such a phase position with only a very small phase delay cp can lead to a comparatively large inhomogeneity in the mechanical properties of the microstructure, especially in combination with pronounced sidewall scalloping. Even if this appears unfavorable at first glance, advantageous effects can arise from such inhomogeneity, as will be explained in more detail. For example, certain desired characteristics of the micro-actuator can be specifically adjusted, i.e., the electrostatic response of the microstructure can be favorably influenced. This makes it possible to achieve improved or qualitatively different actuation compared to previously known microstructures, especially those that do not exhibit sidewall scalloping and / or such a spatial phase distribution.

[0054] Therefore, in particular with very low homogeneous phase delay cp, in order to achieve a strongly pronounced sidewall scalloping, the laser pulses can also be set and the microstructure etched free in such a way that the ratio of an average pulse spacing p between adjacent laser pulses on one of the two tool paths and the etching radius r, preferably in the entire deflection range, is: p > r or even p > 1.2 r.

[0055] In the extreme case, with semicircular indentations (= maximum pronounced sidewall scalloping), the length L x an indentation in the direction of travel applies: L x= 2r = D = p, i.e. then the following would apply: p = 2r (p is then maximally large). If the pulse spacing p is reduced starting from this maximum, the extent of the sidewall scalloping decreases continuously. For values ​​p > 1.0 r or even p > 1.20 r, however, the sidewall scalloping will still be comparatively pronounced. Such pronounced sidewall scalloping, especially in conjunction with the previously explained phase position around 0°, can lead to interesting mechanical properties of the microstructure that can be exploited technically, particularly for novel microactuators or microsensors.

[0056] A pronounced sidewall scalloping can alternatively be achieved by the following design or process parameters. For example, the contour of the microstructure (as already explained) can be designed to exhibit lateral concave indentations, each curving with the etching radius r and defined by convex ribs. Furthermore, a ratio of the etching radius r to a lateral depth t can be determined. y The following applies to the respective indentations: t y / r > 0.1, especially t y / r > 0.2 or even t y / r > 0.3 (see Tables 4 and 5).

[0057] In order to achieve a small phase delay, it can further be provided (additionally or alternatively) that the previously described step angle a is comparatively small. For example, the step angle a can be at most 4.0°, in particular at most 3.0°, preferably at most 2.0°. With such small step angles, which can be achieved by appropriate placement of the laser pulses (used for etching the microstructure), a small phase delay <p(x) für einen gegebenen Ätzradius r resultieren, der seinerseits bei einer bestimmten Substratdicke und gewählten Materialien (Glassubstrat, Ätzlösung) weitgehend vorgegeben ist.

[0058] Furthermore, according to a further embodiment, it can be provided that a ratio of a, in particular minimum or maximum, pulse spacing p between two adjacent laser pulses on one of the two tool paths and a maximum width B of the microstructure transverse to the direction of travel applies: p / B > 0.5, preferably p / B > 0.75 or p / B > 1.0 or even p / B > 1.5. In this case, in particular the maximum width of the microstructure can be less than 100 μm, in particular less than 50 μm or even less than 20 μm. As a technical effect, it should be taken into account that the larger the pulse spacing p is selected and thus the larger p / B is, the more pronounced the micro-scalloping will be and the more inhomogeneous the mechanical properties of the microstructure will be. This inhomogeneity can be of technical interest for novel actuator and sensor mechanisms.For example, for a minimum pulse spacing p of at least 10 μm and a maximum / nominal width B of 10 μm of a microstructure used as a spring, a ratio of p / B = 1.0 can be achieved.

[0059] As already mentioned, the phase position cp (x) of a laser pulse pair can be defined in particular as cp (x) = 360° Ax / p with Ax the offset of the two laser pulses of the laser point pair in the direction of the microstructure and p the pulse spacing of two adjacent laser pulses on one of the tool paths.

[0060] The invention can be advantageously applied, for example, to micromechanical microstructures characterized by the fact that the opposing tool paths run approximately or strictly parallel to each other. However, microstructure designs according to the invention are also possible if the opposing tool paths enclose an angle or, for example, follow a respective curve. In the first two cases, the direction of the microstructure can follow a straight line; in the latter case, however, it can follow a curve. In such cases, the phase position may also change locally.By appropriately positioning the laser points and selecting the pulse spacing and the etching radius r (which is essentially determined by the substrate material, the etching time and the etching liquid used), homogeneous phase positions can be set or formed, at least in sections, along the direction of the microstructure - either with a large or small phase position, depending on the task.

[0061] To ensure reproducible processing / production of the microstructure, it can be provided, in particular, that a minimum pulse spacing of 3 μm and / or a maximum pulse spacing of 15 μm, in particular 10 μm, is maintained during the production of the microstructure in the deflection range. Compliance with this requirement can be determined, for example, from the severity of the sidewall scalloping, since—as already mentioned—the spacing of the ribs of the sidewall scalloping corresponds precisely to the pulse spacing of the corresponding laser pulses responsible for the respective sidewall etching that created the ribs.

[0062] For example, it may be appropriate to select a pulse spacing in the range of 2-8 μm, preferably in the range of 3-5 μm, especially if only slight sidewall scalloping is to be achieved. Such values ​​are possible for substrate thicknesses between 100 μm and 500 μm. However, if the sidewall scalloping is to be more pronounced, it may be appropriate to select a pulse spacing such that p > 7 μm, especially p > 10 μm, applies.

[0063] The invention can be used particularly advantageously in a micromechanical device. This device can comprise at least one microstructure according to the invention or a plurality of microstructures according to the invention, for example, configured as the fingers of a comb actuator or comb sensor.

[0064] The invention further proposes a specific application or use of a microstructure according to the invention or of such a micromechanics. Thus, to achieve the object, the use of a micromechanical microstructure made of glass produced by laser-induced deep etching (LIDE) is proposed, in particular, as part of a micromechanical actuator and / or as part of a micromechanical sensor and / or as part of a micromechanical support structure, preferably using electrostatic actuation or a capacitive sensor principle. In this case, the microstructure can be configured as explained above, in particular according to one of claims 1 to 7, i.e. in particular with a comparatively large phase angle and / or with specifically adjusted, in particular slightly pronounced, sidewall scalloping.In such a use, the targeted adjustment of the phase position <p(x) und / oder die gezielte Ausprägung eines sidewall scalloping der Mikrostruktur dazu genutzt werden, um die Homogenität der mechanischen Eigenschaften der Mikrostruktur zu verbessern, wie zuvor bereits im Detail erläutert wurde. Die Mikrostrukturen können dabei Federelemente der Aktorik / Sensorik ausbilden oder beispielsweise die Finger einer mikromechanischen Kammstruktur. Dies ist beispielsweise sowohl für lineare aber auch rotative Mikroaktorik relevant.

[0065] In addition, it is also possible to use a micromechanical microstructure produced by LIDE as part of a micromechanical actuator and / or as part of a micromechanical sensor, preferably using an electrostatic actuation or a capacitive

[0066] sensor principle, and thereby the phase position <p(x) und / oder die Ausprägung eines sidewall scalloping der Mikrostruktur gezielt einzustellen, um eine Inhomogenität der mechanischen Eigenschaften der Mikrostruktur zu erzeugen, die sensorisch oder aktuatorisch nutzbar ist beziehungsweise ausgenutzt wird. Eine solche Mikrostruktur aus Glas mit vorzugsweise geringem Phasenverzug und / oder mit ausgeprägtem sidewall scalloping kann insbesondere zur Realisation eines mikromechanischen Schrittmotors eingesetzt werden. Hierbei kann die Schrittweite des Motors gerade der (lokalen) Periode des sidewall scalloping entsprechen.

[0067] Finally, to achieve the aforementioned objective, a method for producing a micromechanical microstructure made of glass using LIDE is proposed. In this method, laser pulses are placed in a deflection range of the microstructure on two opposing tool paths, as previously described in greater detail with reference to the microstructure according to the invention. As mentioned, the laser pulses or associated laser spots have

[0068] (already in the layout) a respective distance r to a contour (more precisely to respective associated concave indentations) of the microstructure, which corresponds to an etching radius r of a later wet-chemical etching step. This etching step is used to expose the microstructure in the glass substrate and thus enable mobility of the microstructure, either in the plane of the glass substrate or normal to it. The process can now be characterized by the fact that the laser pulses are set on the respective laser line in such a way that (i) a homogeneous distribution of the spatial phase position <p(x) und / oder (ii) ein homogenes Ausmaß eines sidewall scalloping (welches wie zuvor beschrieben angelegt und definiert werden kann) entlang einer Verlaufsrichtung der Mikrostruktur ergibt, was ja zuvor bereits mit Bezug auf die Mikrostruktur im Detail erläutert wurde.In this case, the laser pulses / laser points can be set in such a way that a microstructure as described above, in particular according to one of claims 1 to 14, is wet-chemically etched free.

[0069] Homogeneous distribution of the phase position can be understood here in particular as meaning that (in particular independent of the course of the microstructure) the phase position <p(x) im gesamten Auslenkungsbereich nicht mehr als + / - 60°, vorzugsweise weniger als + / -30° um einen mittleren Phasenwert <p0schwankt. Unter homogener Einstellung des sidewall scalloping kann hingegen insbesondere verstanden werden, dass beispielsweise die erwähnte laterale Tiefe t y The deflection range should not fluctuate by more than + / - 30%, preferably less than + / - 20%, or even by no more than + / - 10% around a mean lateral depth to. Depending on the desired microstructure properties, the ratio to / r can be more or less large.

[0070] The invention will now be described in more detail using exemplary embodiments, but is not limited to these embodiments. Further developments of the invention can be derived from the following description of a preferred embodiment in conjunction with the general description, the claims, and the drawings. In the following description of various embodiments of the invention, elements that correspond in function are given the same reference numerals, even if they have different designs or shapes.

[0071] It shows:

[0072] Fig. 1 shows a first example of a micromechanical microstructure in glass designed according to the invention, Fig. 2 shows a further example of a microstructure according to the invention,

[0073] Fig. 3 shows another example of a microstructure according to the invention,

[0074] Fig. 4 is a detailed and schematic view of the outer contour of a partial section of a microstructure designed according to the invention,

[0075] Fig. 5 shows a graph showing the width B (x) of a bending beam designed according to the invention as a function of the x-position for three cases of differently designed phase positions <p(x) zeigt,

[0076] Fig. 6 is a further schematic illustration of a partial section of a microstructure according to the invention,

[0077] Fig. 7 shows an example of a microstructure according to the invention showing a curve shape in the x-substrate plane,

[0078] Fig. 8 is a further schematic plan view similar to Figures 1-3, of a microstructure according to the invention, illustrating numerous design and process parameters,

[0079] Fig. 9 shows another example of a microstructure according to the invention, in which the outer contour lines run at an angle to each other,

[0080] Fig. 10 is a cross-sectional view of a microstructure according to the invention with a medium taper angle,

[0081] Fig. 11 is a cross-sectional view of a microstructure according to the invention with a larger taper angle, Fig. 12 is a further cross-sectional view of a microstructure according to the invention with an extremely small taper angle,

[0082] Fig. 13 is a scanning electron microscope (SEM) image of a micromechanical comb structure having microstructures in the form of fingers designed according to the invention and

[0083] Fig. 14 is a scanning electron microscope (SEM) image of a microstructure designed according to the invention in the form of a thin cantilever.

[0084] Figure 1 schematically shows a micromechanical microstructure 1 in the form of a cantilever 16, exposed using the LIDE (laser-induced deep etching) process, which was exposed from a glass substrate 3 in the form of a glass wafer by means of wet-chemical etching. The view in Figure 1 is a top view of the xy plane of the glass substrate 3, which has a specific substrate thickness t. gias i n z-direction. As can be seen, the spring beam 16 is connected on one side to the bulk of the glass substrate 3, where it forms a solid-state joint 17 or a one-sided mechanical suspension. The spring beam 16 can be deflected in principle in the xy-plane but also out of the plane in the z-direction.

[0085] Using the LIDE (laser induced deep etching) process, it is possible to cut out or expose fine pieces of glass from a glass substrate 3. Similar to using a jigsaw, a contour 6 can be traced with the help of a laser, which describes the outer boundary of the microstructure 1 to be exposed. For this purpose, the invention proposes that a laser head, which emits the pulsed laser beam, is moved along an associated tool path 5a, 5b that follows the contour 6 at a specific distance (cf. Figure 3). However, since the laser is pulsed, the glass substrate 3 is not continuously illuminated by the laser beam, but rather individual laser pulses 4 are placed at specific xy coordinates on the surface of the glass substrate 3 as laser spots 4. The laser spots 4 can have a constant geometric pulse spacing p (measured in μm in the substrate plane) and / or can all lie on the said tool path 5a, 5b.The block arrows in Figure 3 are intended to indicate the order in which the tool paths 5 are traversed and the laser points 4 are set (see also Figure 6).

[0086] If, for example, an elongated slit is to be created in the glass substrate 3, a certain number of laser pulses 4 are placed along a tool path 5, each at a pulse spacing p, whereby the glass substrate 3 is typically modified across its entire thickness with each laser pulse 5. In the subsequent wet-chemical etching process, the etching solution eats into the substrate 3 from the surface in the z-direction, whereby the etching speed is isotropic in the xy plane, so that a circular disk-shaped etching profile 7 with rotational symmetry around a respective laser spot 4 is created on the surface (cf. the circles in Figures 4 and 6 to 8). This has the result that the finally etched contour 6 of the microstructure 1 shows a distance r (= etching radius 27) from the center of the original laser spot 4 (cf. Fig. 3 or Figure 6).In other words, the etched contour line 6 on the surface of the glass substrate 3 shows a maximum distance r from the tool path 5 (projected onto the substrate plane) on which the laser pulses 4 were placed. In other words, each of the laser pulses 4 on the tool path 5 has a distance r from the respective corresponding indentation 8, which is created due to the etching radius 27 starting from the respective laser pulse 4.

[0087] Due to the etching radii r, concave indentations 8 are created in the respective sidewall 13 of the microstructure 1, each exhibiting a curvature with the etching radius r 27 and delimited by respective convex ribs 9, whereby these ribs 9 and the indentations 8 run along the z-direction (cf. Figures 1-3 as well as 4 and 6-9). These structures created in the respective sidewall 13 during the wet-chemical exposure of the microstructure 1 are referred to as sidewall scalloping, since the indentations 8 and the ribs 9 located between them form a structure similar to that on the inside of a mussel shell.

[0088] Depending on the selected process parameters and thus the degree of anisotropy of the wet-chemical etching, the etching radius 27 r in the xy-plane along the z-direction (ie normal to the substrate plane) can decrease more or less, whereby (for example in the xz-plane) courses of the side walls 13 of the microstructure 1 can be achieved, which have a slope or a taper angle with respect to the z-axis, as illustrated in Figures 10-12. However, on the substrate surface, the etching radius 27 r is always the same size, starting from each laser point 4. Furthermore, only those bevels are possible that correspond to a decreasing etching radius 27 r with increasing depth z. This results from the fact that the wet-chemical etching always begins on the substrate surface and progresses from there into the substrate depth. However, it is possible to start this process either on one side (Figure 12) or on both sides (cf. Figures 10 and 11) from both substrate surfaces, so that correspondingly symmetrical bevels are then produced, each of which runs towards a centrally arranged plane 21 (which lies parallel to the xy plane) (in the z-direction).

[0089] As indicated in Figure 11, which shows a cross-section through a microstructure 1 according to the invention (where the direction of travel 2 of the microstructure 1 runs in the direction of view of the drawing), a single laser spot 4 may be sufficient to define a slit with a width 2r between a microstructure 1 and the substrate 3, wherein the etching solution then forms an etching radius 27r on both sides of the surface of the glass substrate 3, starting from the laser spot 4 (for example, as in Figure 11 in the positive and negative y-direction). The maximum width B 15 of the microstructure 1 measured on the surface of the glass substrate 3 (measured transversely to the direction of travel 2, i.e. in the y-direction in Figure 11) may deviate considerably from the width B M , which shows the microstructure 1 in the illustrated central plane 21 of the substrate 3, depending on the selected taper angle

[0090] As Figure 12 illustrates, laser spots 4 can also be placed next to each other at a very close pulse spacing p, so that the resulting etching radii r overlap (see also Figure 8). If the anisotropy of the laser-induced wet-chemical etching is chosen to be very high, almost vertical sidewalls 13 can be defined, as shown in Figure 12.

[0091] Figure 8 illustrates in detail how the microstructure 1 of Figure 3 was manufactured. As can be seen from the circles, which each illustrate the circular disk-shaped etching profile 7 with the etching diameter D = 2r, a whole series of laser pulses 4 were placed on two opposite tool paths 5a and 5b in the deflection region 12 of the microstructure 1. Since the etching front 7 propagates isotropically in the xy substrate plane, the laser pulses 4 each have a distance r from the final outer contour 6 of the microstructure 1, which exactly corresponds to the etching radius 27r of the wet-chemical etching step used to expose the microstructure 1. As Figure 3 shows, two laser pulses 4, which lie on the opposite tool paths 5a and 5b, can be combined to form a laser pulse pair 18.As Figures 1-3 and 8 show, the two laser pulses 4 of a respective laser pulse pair 18 can show an offset Ax with respect to the direction of travel 2 of the microstructure 1, which in these figures corresponds to the x-axis, which can, for example, be between Ax = 0 and Ax = p / 2 when using a constant pulse spacing p.

[0092] Depending on the extent of this offset Ax, a spatial phase position results <p(x) bzw. ein räumlicher Phasenverzug <p(x) zwischen den jeweiligen Laserpunkten 4 eines Laserpunktpaares 18. Beim Beispiel der Figur 1 beträgt der Versatz Ax = 0 und somit sind dort die Laserpunkte 4 des jeweiligen Laserpunktpaares 18 gerade in Phase (cp = 0°) angeordnet in Bezug auf die Verlaufsrichtung 2. Beim Beispiel der Figur 3 ist der Phasenunterschied hingegen maximal (cp = 180°), denn der Versatz Ax beträgt dort Ax = p / 2, mit p dem Pulsabstand, also dem Abstand zwischen zwei direkt benachbarten Laserpunkten, die auf derselben Werkzeugbahn (z.B. 5b) platziert sind - vgl. dazu Figur 8.

[0093] The ratio p / r of pulse spacing p and etching radius 27 r, however, determines how pronounced the indentations 8 of the sidewall scalloping are. The distance between the ribs 9 along the x-axis L x corresponds exactly to the pulse interval L x= p - see Figure 8. In addition, for each indentation 9 a lateral depth t y 14, measured transversely to the direction of travel 2, i.e. in the y-direction in Figure 8. In Figures 1-3, for example, it can be seen that - regardless of the selected phase position - the sidewall scalloping along the outer contour 6 in the deflection area 12 of the microstructure 1 is only weakly pronounced, which can be seen from the small ratio t y / r. This also applies to the microstructure shown in Figure 7, because there too, despite the curved path, the laser pulses 4 are set such that the sidewall scalloping is consistently weak along the entire deflection range 12, so that this microstructure will exhibit homogeneous mechanical properties.

[0094] In Figure 4 or in Figure 9, however, the sidewall scalloping is (in each case) much more pronounced, that is, the lateral depth t y14 is selected to be larger in relation to the etching radius r. Such pronounced sidewall scalloping alone leads to an inhomogeneity in the mechanical properties of the bent structure 1, because, for example, the width B along the x-axis fluctuates more strongly along the direction x of the microstructure 1, as can be clearly seen in Figure 5. This fluctuation and thus the inhomogeneity will be greater for a given extent of sidewall scalloping, the smaller the phase position is selected (compare, for example, the course of the mean width B at 0° and at 180° phase).

[0095] In both cases of Figures 1-3 and 4+9, however, it can be seen that the extent of the sidewall scalloping is set homogeneously in the entire deflection range 12, because the respective fluctuation of the lateral depth t y 14 is chosen to be very low, due to suitable placement of the laser points 4.

[0096] It can therefore be stated that the laser points 4 in the inventive approach do not follow a predetermined grid, but are defined or specifically positioned based on the outer contour 6 of the desired microstructure 1 (i.e., based on design or geometry parameters of the microstructure 1) in order to achieve the desired phase position and / or the desired sidewall scalloping. This distinguishes this process from, for example, DEEP-RIE (deep reactive ion etching), which has long been used in the structuring of silicon, where the formation of ribs is merely predetermined by dry etching process parameters, but is not specifically set / specified based on a structural design.

[0097] Figure 8 also illustrates that the two tool paths 5a and 5b have a distance D y10. This distance and the selected offset Ax determine the step angle a, which two laser points 4 of a respective laser point pair 18 form with respect to the direction of travel 2, where a = arctan (Ax / D y ). The spatial phase position <p(x) bestimmt sich hingegen zu cp = 360° Ax / p, wobei der Versatz Ax abhängig von der x-Koordinate des Laserpulspaars 18 variieren kann, sodass auch die Phasenlage <p(x) entlang der Verlaufsrichtung 2 grundsätzlich schwanken kann.

[0098] Figures 4 and 6 illustrate how the extent of sidewall scalloping, which can be measured, for example, by the ratio t y / r, affects the homogeneity of the width B(x) of the microstructure 1 and thus also the mechanical properties. The three curves of the graph in Figure 5 illustrate how the width B(x) changes along the direction 2 with the x-coordinate (and in each case assumes a maximum width B 15 ) for the three cases of a phase position of 0° / 90° / 180°, which were illustrated in Figures 1-3. As the horizontal dashed line in Figure 5 shows, three microstructures 1 were compared, each having the same average width B. The extent of sidewall scalloping (measured in t y / r) was also chosen to be the same size. It can be seen in the graph of Figure 5 that for a spatial phase of <p=0° die Schwankung der Breite B(x) am größten ist.

[0099] With a spatial phase position of <p=180° zeigt die Mikrostruktur 1 hingegen die geringste Schwankung der Breite B(x). Bei einer Phasenlagen von <p=180° ergeben sich somit nicht nur Vorteile hinsichtlich einer höheren Bruchfestigkeit, sondern es kann, bei gleicher mittlerer Breite B, auch die Federsteifigkeit der Mikrostruktur 1 signifikant reduziert werden, da diese (für Auslenkungen der Mikrostruktur in der Substratebene) kubisch von der Breite B abhängt. Bei einer Phasenlage von <p=0° wird die lokale Federsteifigkeit somit erheblich schwanken, da die Schwankungen der Federbreite B mit dritter Potenz eingehen, wodurch Spitzen der mechanischen Spannung entstehen können, die einen Bruch der Feder verursachen können.

[0100] A micromechanical microstructure 1 made of glass as illustrated in Figure 3, which has a phase position <p(x) von 180° und ein vergleichsweise schwach ausgeprägtes sidewall scalloping zeigt, ist daher hervorragend geeignet, um als Teil eines mikromechanischen Aktuators oder Sensors verwendet zu werden, da diese Mikrostruktur 1 einerseits weich / sensitiv ist, aber andererseits homogene mechanische Eigenschaften, insbesondere eine gute Bruchfestigkeit zeigt. Aufgrund der dieser Eigenschaften lässt sich mit einer solchen Mikrostruktur 1 insbesondere eine hoch qualitative elektrostatische Aktuierung / Sensorik realisieren.

[0101] But also, for example, a phase position of <p=0°, wie in Figur 1 gezeigt, kann, insbesondere dann, wenn das sidewall scalloping gerade stark ausgeprägt ist, zu interessanten mechanischen Eigenschaften führen, die sich gewinnbringend technisch ausnutzen lassen. Beispielsweise kann eine hohe Inhomogenität der mechanischen Eigenschaften der Mikrostruktur 1, verursacht beispielsweise durch eine hohe Schwankung der Breite B (wie für den Fall <p=0° in Figur 5 illustriert), zu einem starken nicht-linearen Ansprechverhalten der Mikrostruktur 1 bei elektrostatischer Aktuierung führen, die sich beispielsweise in einem Schrittmotor ausnutzen lässt.

[0102] As can be clearly seen in Figures 1-3, however, the respective spatial phase position <p(x) der jeweiligen Laserpulspaare 18 entlang der Verlaufsrichtung 2 der Mikrostruktur 1 innerhalb des gesamten Auslenkungsbereichs 12 homogen eingestellt, wobei die Phasenlage in Figur 1 <p=0°, in Figur 2 <p=90° und in Figur 3 <p=180° beträgt. Aufgrund des jeweils gradlinigen Verlaufs der Mikrostruktur 1 schwankt die Phasenlage <p(x) dabei nur im Rahmen der Genauigkeit, mit der die Laserpunkte 4 auf dem Glas-Substrat 3 platziert werden können.

[0103] As Figure 6 illustrates, for a straight line of the microstructure 1, the effective pulse spacing p'=p corresponds exactly to the geometric pulse spacing p between two laser points 4 directly adjacent on a tool path 5.

[0104] Figure 7 shows a further example of a microstructure 1 designed according to the invention, although this one has a curved profile 2, which can be clearly seen from the center line 19. Even with such a configuration, respective laser point pairs 18 can be observed. However, the effective pulse spacing p' V p can, as illustrated in Figure 7, deviate from the geometric pulse spacing p. Nevertheless, even with such a profile of the microstructure 1, the respective spatial phase position cp can be set homogeneously. In the example of Figure 7, the phase position fluctuates, at least in sections, slightly (by approximately + / - 30°) around an average phase position of approximately cp = 180°. Figure 9 shows a further example of a microstructure 1 according to the invention. There, too, respective laser pulses 4 are arranged at a constant pulse spacing p on two opposing tool paths 5a and 5b, which, however, enclose an angle.Accordingly, the outer contour 6 of the microstructure 1 exhibits a wedge-shaped profile in the xy plane. In this example, too, a spatial phase position cp can be determined for each laser pulse pair 18 with respect to the center line 19 shown. At least in some sections, the phase position cp is set homogeneously in this example and therefore fluctuates only slightly around an average value.

[0105] Figures 13 and 14 each show a scanning electron microscope (SEM) image in an oblique view from above of respective microstructures 1, which are formed according to the invention with a homogeneously adjusted phase position cp. The indentations 8 and the intervening ribs 9, which each run in the z-direction, i.e., transversely to the substrate plane 28, are clearly visible, particularly in the detailed view of Figure 13, but also in Figure 14. Figure 14 shows a micromechanical spring element in the form of a thin bending structure 23, while the microstructures 1 of Figure 13 are designed as respective fingers 24 of an electrostatic comb actuator 25. The left-hand fingers 24 are movable in their respective longitudinal direction (= direction of extension 2), since these fingers 24 are movably suspended from a main body of the glass substrate 3 by means of micromechanical spring elements 29 (not shown in Figure 13).

[0106] Below, some exemplary design and process parameters of microstructures 1 designed according to the invention are listed in tabular form for different substrate thicknesses and substrate materials, namely: A) Examples of microstructures according to the invention with low sidewall scalloping p / B

[0107] B) Examples of inventive microstructures with pronounced sidewall scalloping

[0108] Tab. 4: Substrate material: Mempax BF33

[0109] Substrate thickness [μm] 500 400 300 200 100

[0110] Etching diameter (D=2r) [μm] 25 20 20 15 15 Pulse spacing (p) [μm] 10 10 10 10 10 Feather width (B) [μm] 10 10 10 10 10 Scalloping depth (t y ) [μm] 1.04 1.34 1.34 1.91 1.91 Taper (0) [°] 1.5 1.5 1.5 1.5 1.5 p / r 0.80 1.00 1.00 1.33 1.33 ty / r 0.08 0.13 0.13 0.25 0.25 ty / B 0.10 0.13 0.13 0.19 0.19 p / B 1 1 1 1 1

[0111] Tab. 5: Substrate material: AF32 (= glass substrate with low thermal expansion coefficient, which is similar to that of a

[0112] silicon wafer)

[0113] Substrate thickness [μm] 500 400 300 200 100

[0114] Etching diameter (D=2r) [μm] 65 55 40 30 20 Pulse spacing (p) [μm] 15 15 15 15 15 Feather width (B) [μm] 10 10 10 10 10 Scalloping depth (t y ) [μm] 0.88 1.04 1.46 2.01 3.39 Taper (0) [°] 6 6 6 6 6 p / r 0.46 0.55 0.75 1.00 1.50 ty / r 0.03 0.04 0.07 0.13 0.34 ty / B 0.09 0.10 0.15 0.20 0.34 p / B 1.5 1.5 1.5 1.5 1.5 Tab. 6: Substrate material: Fused Silica

[0115] Substrate thickness [μm] 500

[0116] Etching diameter (D=2r) [μm] 20 Pulse spacing (p) [μm] 5

[0117] Spring width (B) [μm] 10

[0118] Scalloping depth (t y ) [μm] 0.32

[0119] Taper (0) [°] 0.5 p / r 0.5 ty / r 0.03 ty / B 0.03 p / B 0.5

[0120] As can be seen from the numerical values, the etching diameters D=2r in these examples are in the range of a few μm; typically, r < 50 μm or even r < 20 μm or even r < 10 μm can apply. The ratio of etching diameter D=2r to substrate thickness t is typically at least: D / t < 1:5 = 0.2; for very large substrate thicknesses (tk 400 μm), D / t < 1:20 = 0.05 can even apply. The specified taper angle 022 describes the inclination of the sidewall surfaces 13 of the microstructure 1 to the z-axis (= surface normal of the substrate) - compare Figures 10-12.

[0121] In the example in Table 6, an aspect ratio (= substrate thickness : feather width) of the microstructure of 1 out of 100 is achieved. The sidewall scalloping is still very weak with a ratio t y / r = 0.03. This demonstrates that LIDE can be used to produce highly homogeneous spring structures with enormous aspect ratios, which are ideally suited for micromechanics.

[0122] In the examples in Table 4, the extent of sidewall scalloping increases with decreasing substrate thickness. For a substrate thickness of 100 μm, approximately t y / B = 19% and t y / r > 20%. For the same substrate thickness of 100 μm, the ratio of lateral depth t in Table 5 is y the indentation 8 and maximum width B 15 of the microstructure 1 even reach 34%. Accordingly, in these examples, distinct indentations 8 and ribs 9 are formed in the side walls 13 of the microstructure 1.

[0123] In summary, in order to expand the application possibilities of the previously known LIDE (laser induced deep etching) method, it is proposed to precisely control the position of the laser pulses 4, which define the outer contour 6 of the microstructure 1, during the production of a micromechanical microstructure 1 by applying a plurality of laser pulses 4 on a glass substrate 3, followed by a wet-chemical etching step to expose the microstructure 1. This makes it possible, on the one hand, to control a spatial phase position cp of opposing laser pulses 4 or laser spots 4, which are arranged on both sides of the microstructure 1 and form a respective laser pulse pair 18, and also to control the extent of so-called sidewall scalloping. By controlling the phase position cp and / or the sidewall scalloping, it is possible to favorably influence or specifically adjust the mechanical properties of the microstructure 1 in the desired form (cf.Figure 8), which can be used advantageously for actuators or sensors.

[0124] List of reference symbols

[0125] 1 Microstructure (can be used particularly as micromechanical

[0126] Bending structure or designed as a movable finger)

[0127] 2 Direction of travel (from 1)

[0128] 3 Glass substrate

[0129] 4 laser pulse (the point of impact on 3 defines a

[0130] Laser point with xy coordinates on the surface of 3)

[0131] 5 Tool path (along which the laser head is guided and on which the laser pulses are set)

[0132] 6 Contour (of 1, in particular outer boundary of 1 in the substrate surface / on the top side of 1)

[0133] 7 Etching profile (in the xy plane, caused by 4)

[0134] 8 (concave) indentation (in side wall of 1)

[0135] 9 (convex) rib (in side wall of 1)

[0136] 10 tool path distance (or local y-distance between 4)

[0137] 11 modified areas (in 3)

[0138] 12 deflection range (of 1)

[0139] 13 Side wall or side wall surface (of 1)

[0140] 14 lateral depth (of 14)

[0141] 15 (maximum) width (from 1 across to 2)

[0142] 16 spring beams

[0143] 17 Solid joint

[0144] 18 laser pulse pairs

[0145] 19 Center axis or center line (of 1)

[0146] 20 (wet-chemical) etched area

[0147] 21 Middle Level (of 3)

[0148] 22 taper angle 0

[0149] 23 Bending structure (e.g. designed as a micromechanical spring element)

[0150] 24 movable fingers (out of 25)

[0151] 25 micromechanical comb structure

[0152] 26 surface normals (of 3 = z-axis)

[0153] 27 Etching radius 28 Substrate plane

[0154] 29 gap

Claims

Claims Microstructure (1) made of glass, in particular designed as - a movable finger (24) of a micromechanical comb structure (25) or - as a micromechanical bending structure (1), in particular as a cantilever, - wherein the microstructure (1) was exposed from a glass substrate (3) by laser-induced modification of the glass substrate (3) and subsequent wet-chemical anisotropic etching, characterized in that - that for the production of the microstructure (1) in a deflection region (12) of the microstructure (1) laser pulses (4) were placed on two opposing tool paths (5a, 5b) which have a respective maximum distance r perpendicular to a contour (6) of the microstructure (1), which corresponds to an etching radius (27) r of a wet-chemical etching step, wherein the etching radius (27) r lies in a substrate plane (28) of the glass substrate (3), - that the laser pulses (4) were placed in such a way that a respective spatial phase position <p(x) von jeweiligen Laserpulspaaren (18) entlang einer Verlaufsrichtung (2) der Mikrostruktur (1) innerhalb des Auslenkungsbereichs (12) mindestens abschnittsweise, - preferably however along the entire deflection range (12), is set homogeneously, wherein the spatial phase position cp (x) of a laser pulse pair (18) is defined as cp (x) = 360° Ax / p with Ax the offset of the two laser pulses (4) of the laser pulse pair (18) in the direction of travel (2) and p the pulse spacing of two adjacent laser pulses (4) on one of the tool paths (5a or 5b), - preferably so that the phase position <p(x) entlang der Verlaufsrichtung (2) um weniger als + / - 60°, besonders bevorzugt um weniger als + / - 30°, schwankt. Microstructure (1) made of glass, in particular according to the preamble of claim 1 or according to claim 1, wherein the microstructure (1) was exposed from a glass substrate (3) by laser-induced modification of the glass substrate (3) and subsequent wet-chemical anisotropic etching, characterized in that - that for the production of the microstructure (1) in a deflection region (12) of the microstructure (1) laser pulses (4) were placed on two opposing tool paths (5a, 5b), which have a respective maximum distance r perpendicular to a contour (6) along a direction (2) of the microstructure (1), which corresponds to an etching radius (27) r of the wet-chemical etching step, wherein the etching radius (27) r lies in a substrate plane (28) of the glass substrate (3) and wherein the contour (6) after the wet-chemical exposure shows lateral concave indentations (8), which each show a curvature with the etching radius (27) r and which are delimited by respective convex ribs (9), and - that the laser pulses (4) were placed in such a way that the manifestation of a sidewall scalloping of the microstructure (1) was specifically adjusted in order to improve the homogeneity of the mechanical properties of the microstructure (1) or to specifically create an inhomogeneity of the mechanical properties of the microstructure (1), - where sidewall scalloping is defined as a ratio t y / r from the local etching radius (27) r and a respective lateral depth t y (14) of the respective indentation (8). Microstructure (1) according to one of the preceding claims, wherein the respective spatial phase position <p(x) der jeweiligen Laserpulspaare (18) entlang der Direction (2) of the microstructure (1) within the deflection range (12) <p(x) = 180° + / - 60°, vorzugsweise <p(x) = 180° + / -30°, beträgt, - preferably wherein for a maximum width B (15) of the microstructure (1) within the entire deflection range (12) the following applies: B < 100 μm, in particular B < 50 μm, preferably B < 20 μm. Microstructure (1) according to one of the preceding claims, wherein in order to achieve a slightly pronounced sidewall scalloping the laser pulses (4) were set and the microstructure (1) was etched free in such a way that for a ratio of an average pulse spacing p between adjacent laser pulses (4) on one of the two tool paths (5) and the etching radius (27) r, preferably in the entire deflection range (12), the following applies: p < r, preferably p < r / 2. Micromechanical microstructure (1) according to one of the preceding claims, wherein the contour (6) shows lateral concave indentations (8), each of which shows a curvature with the etching radius (27) r and which are delimited by respective convex ribs (9), and - where for a ratio of the local etching radius (27) r and a lateral depth t y (14) of the respective indentations (8) applies: t y / r < 0.1, preferably t y / r < 0.

05. - preferably wherein additionally or alternatively for the ratio of maximum width B (15) of the microstructure transverse to the direction of extension (2) and the lateral depth t y (14) applies: t y / B < 0.1, especially t y / B < 0.

05. Micromechanical microstructure (1) according to one of the preceding claims, wherein a respective step angle a, which a respective laser pulse pair (18) in Deflection range (12) with respect to the direction of travel (2) is at least 2.5°, - in particular where the step angle a is: a = arctan (Ax / D y ) with Ax the offset of the laser pulses (4) forming the laser pulse pair (18) to each other in the direction of travel (2) and D ythe distance between the two opposing laser pulses (4) transverse to the direction of travel (2). Micromechanical microstructure (1) according to one of the preceding claims, wherein a ratio of a, in particular minimum or maximum, pulse spacing p between two adjacent laser pulses (4) on one of the two tool paths (5) and a maximum width B (17) of the microstructure (1) transverse to the direction (2) applies: p / B < 0.5, preferably p / B < 0.3, - in particular, wherein the maximum width (17) of the microstructure (1) is less than 50 μm, in particular less than 20 μm. Micromechanical microstructure (1) according to the preamble of claim 1, in particular according to claim 1 and / or according to claim 2, characterized in - that a respective spatial phase position <p(x) von jeweiligen Laserpulspaaren (18) entlang einer Verlaufsrichtung (2) der Mikrostruktur (1) innerhalb des Auslenkungsbereichs (12) <p(x) = 0° + / - 60°, vorzugsweise <p(x) = 0° + / -30°, beträgt, - preferably, wherein the maximum width B (15) of the microstructure (1) within the entire deflection range (12) is: B < 100 μm, in particular B < 50 μm, preferably B < 20 μm. Micromechanical microstructure (1) according to one of the preceding claims, wherein, to achieve a strongly pronounced sidewall scalloping, the laser pulses (4) were set and the microstructure (1) was etched free in such a way that for a ratio of an average pulse spacing p between adjacent laser pulses (4) on one of the two tool paths (5) and the etching radius (27) r, preferably in the entire deflection range (12), the following applies: p / r > 1:2, and thus p > r, preferably p > 1.20 r. Micromechanical microstructure (1) according to one of the preceding claims, wherein the contour (6) has lateral concave indentations (8), each of which has a curvature with the etching radius (27) r and which are delimited by respective convex ribs (9), and - where for a ratio of the etching radius (27) r (15) and a lateral depth t y (14) of the respective indentations (8) applies: t y / r > 0.1, preferably t y / r > 0.

2. Micromechanical microstructure (1) according to one of claims 8 to 10, wherein a respective step angle a, which a respective laser pulse pair (18) in the deflection region (12) with respect to the direction of travel (2) is at most 4.0°, preferably at most 2.0°. Micromechanical microstructure (1) according to one of claims 8 to 11, wherein a ratio of a, in particular minimum or maximum, pulse spacing p between two adjacent laser pulses (4) on one of the two tool paths (5) and a maximum width B (17) of the microstructure (1) transverse to the direction (2) applies: p / B > 0.5, preferably p / B > 1.0, - in particular wherein the maximum width (17) of the microstructure (1) is less than 100 μm, in particular less than 50 μm. Micromechanical microstructure (1) according to one of the preceding claims, wherein the opposing tool paths (5a or 5b) - run approximately or strictly parallel to each other or - enclose an angle or - follow a respective curve. Micromechanical microstructure (1) according to one of the preceding claims, wherein during the manufacture of the microstructure (1) in the deflection region (12) - a minimum pulse spacing of 3 μm and / or - a maximum pulse spacing of 15 μm was maintained on the respective tool path (5a or 5b). Micro-mechanics, in particular designed as micro-actuators and / or micro-sensors, which - at least one microstructure (1) according to one of claims 1 to 7 and / or - at least one microstructure (1) according to one of claims 8 to 14. Use of a micromechanical microstructure (1) made of glass produced by laser-induced deep etching (LIDE), in particular according to one of claims 1 to 7, - as part of a micromechanical actuator and / or as part of a micromechanical sensor and / or as part of a micromechanical support structure, - where the phase position <p(x) und oder die ausprägung eines sidewall scalloping der mikrostruktur (1) gezielt eingestellt ist, um homogenität mechanischen eigenschaften zu verbessern.Use of a micromechanical microstructure (1) made of glass according to one of claims 8 to 14, produced by means of laser induced deep etching (LIDE), - as part of a micromechanical actuator and / or as part of a micromechanical sensor, - where the phase position <p(x) und oder die ausprägung eines sidewall scalloping der mikrostruktur (1) gezielt eingestellt ist, um eine inhomogenität mechanischen eigenschaften zu erzeugen, sensorisch aktuatorisch ausgenutzt wird. verfahren zur herstellung einer mikromechanischen aus glas mittels laser induced deep etching(LIDE), wherein for this purpose laser pulses (4) are placed in a deflection region (12) of the microstructure (1) on two opposing tool paths (5) which have a respective distance r to a contour (6) of the microstructure (1) which corresponds to an etching radius (27) r of a subsequent wet-chemical etching step, characterized in that - that the laser pulses (4) on the respective laser line (5) be set so that - a homogeneous distribution of the spatial phase position cp(x) and / or - a homogeneous extent of sidewall scalloping along a direction (2) of the microstructure (1) results, - in particular wherein the laser pulses (4) are set such that a microstructure (1) according to one of claims 1 to 14 can be wet-chemically etched free.

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