A micromachined comb structure made of glass and a method and use pertaining thereto

Abstract

To expand the applicability of the known LIDE (laser-induced deep etching) method, a plurality of laser pulses (4) are set on a glass substrate (3), followed by a wet chemical etching step for exposing the comb-shaped structure portion (25), thereby manufacturing a micro-mechanical comb-shaped structure portion (25). At this time, it is proposed to accurately control the position of the laser pulse (4) that defines the outer contour (6) of each finger (24) of the comb-shaped structure portion (25). Thereby, it becomes possible to form very narrow fingers (24) having uniformly formed side walls (13), thereby enabling a very small gap dimension (35) and a uniform electrostatic activation portion of the comb-shaped structure portion (25). Furthermore, by controlling the phase position φ and / or the degree of side wall scalloping of the finger (24), it is possible to advantageously affect the mechanical characteristics of the comb-shaped structure portion (25) or set them as desired (see FIG. 9).

Description

Technical Field

[0001] The present invention relates to a micro-mechanical comb-shaped structure made of glass having a plurality of micro-mechanical fingers, the comb-shaped structure being displaceable within a substrate plane defined by a glass substrate, and the fingers being etched away using laser-induced deep etching (LIDE) from the glass substrate, that is, exposed by laser-induced modification of the glass substrate followed by wet chemical anisotropic etching. Thus, in other words, the present invention proposes a monolithic comb-shaped structure made of glass that is (completely / entirely) defined using the LIDE method, and the resulting glass comb-shaped structure is designed to be movable and may therefore be designed as part of a micro-electro-mechanical (MEMS) sensor or actuator.

[0002] The present invention further relates to a micro-mechanical actuator based on such a comb-shaped structure (which may in particular be designed as a stepping actuator) as well as to a method for manufacturing such a comb-shaped structure. Finally, the present invention further proposes a particular use of such a comb-shaped structure.

[0003] The LIDE method is known, for example, from European Patent No. 2964417. So far, the LIDE method has been frequently used, for example, to etch a structural part in a glass substrate forming a housing of a sensor. The present invention deals with how to expand the application of the LIDE method. In the LIDE method, using individual laser pulses, typically, a material change (modification) is (optically) introduced into the glass body throughout the thickness of the glass substrate, and this material change (modification) enables anisotropic etching of the structure optically pre-treated / exposed with the laser in the glass substrate in a subsequent wet chemical etching step, even though the etching solution originally exhibits isotropic etching characteristics. By using this technique, for example, high-quality continuous vias can be manufactured in the glass, which is of interest for hermetic building and connection technologies (AVT, or hermetic packaging).

[0004] In the case of the LIDE method, here, a pulsed laser can be used, and thus, in this case, the glass is modified along the z-direction (= the optical axis / surface normal of the glass substrate) using each laser shot (one laser pulse). Here, typically, no change in the beam profile used is applied. Thus, in the case of the LIDE method, in particular, unlike other laser-based (e.g., ablative) glass processing methods, individual small volumes (voxels) within the glass volume are not processed differently using the laser. Starting from this known prior art, the problem underlying the present invention is to expand the possible applications of the LIDE method.

[0005] Here, the present invention recognizes the following: The wet chemical etching used in the LIDE method always starts from the substrate surface and proceeds from there in the depth direction (z-direction) of the glass substrate. Here, depending on the selected process parameters (especially the material of the glass substrate, the etching solution used, and the temperature), the etching radius r in the xy plane (= substrate plane) can be more or less significantly reduced along the z-direction (i.e., perpendicular to the substrate plane), thereby enabling an edge extension having a gradient with respect to the z-axis (e.g., in the xz plane). Here, only a gradient corresponding to an etching radius r that always decreases with an increase in depth z is possible. However, the etching radius r on the substrate surface is always of the same magnitude because this etching radius r depends only on the etching solution and the total etching time, and thus, a spatially resolvable change representing a central boundary condition of the LIDE method cannot be achieved. The present invention further recognizes that the freely possible arrangement of laser pulses on the substrate surface enables extremely precise structuring of the fingers of the micro-mechanical comb-shaped structure, and thus, these fingers can be formed monolithically with advantageous micro-mechanical properties, as will be described in more detail below.

[0006] Therefore, the optical processing of the glass substrate is performed non-ablatively in the LIDE method, i.e., the desired material removal within the glass substrate is achieved for the first time during a subsequent wet chemical etching step, but not using a laser beam. Similarly, in the LIDE method, a sacrificial layer can be omitted, and the manufacture of a time-consuming mask as used in classical photolithography is also unnecessary. In other words, in the LIDE method, the laser irradiation of the glass substrate is performed masklessly for the formation of the above-mentioned modification.

[0007] Regarding the LIDE method, furthermore, the original etching step of releasing the comb-shaped structure portion may be characterized by being performed in one step, that is, being performed in the only wet chemical etching step (this can be utilized by the present invention). Similarly, "thermal annealing" as required for certain anisotropic etchable glass types can also be omitted in the LIDE method. All of these lead to very efficient manufacturing and ultimately to inexpensive manufacturing.

[0008] By using the LIDE method, furthermore, a further glass substrate incorporating the micro-mechanical glass comb-shaped structure portion according to the present invention can be processed. Therefore, for example, one notch or additional perforation holes can be formed in each further glass substrate, whereby, for example, the comb-shaped structure portion is protected from external mechanical influences while maintaining mobility and further communicates with the outside world through the perforation holes. Depending on the respective etching radius r(z) generated in various xy planes at different z-direction depths of the glass substrate, characteristic depressions can be formed on the side surfaces (in the direction of the xz or yz plane). These depressions always result in a concave shape because the etching solution etches isotropically in a specific xy plane and thus forms a convex etching front. As a result, on these side surfaces removed by wet etching, glass ribs protrude between the respective depressions and extend along the z direction like these depressions. Depending on the selected process parameters, here, not only can a swelling gradient appear in the y direction (for example, in the case of a structure extending in the x direction), but it can also appear in the x direction (for example, at the tip of such a structure).

[0009] Furthermore, it has been observed that the ribs, which would originally result in purely geometrically sharp angles, become rounded together with the increase in the etching duration, and this is thought to be due to the chemical process in the micro-region. These ribs / swellings are at a distance L corresponding to the pulse interval p from the laser spot that causes each swelling formation xis shown. Since these ribs / bulges resemble the wavy pattern that appears on the outer side of the shell, these structural parts can also be referred to as "sidewall scalloping".

[0010] In view of these aspects, according to the present invention, in order to solve the above problems, in the micro-mechanical comb-shaped structure, the features of claim 1 are assumed.

[0011] Thus, in particular, according to the present invention, in order to solve the above problems in a micro-mechanical comb-shaped structure made of glass of the type described at the beginning, during the manufacture of the fingers, the laser pulses defining the outer contour of the fingers are preferably set / assumed to be set at a constant pulse interval p on each continuous, particularly linear or curved, opposing (actual or otherwise virtual) (contour-following) tool path. Further, each of the tool paths has a maximum distance r (perpendicular) to the contour, particularly to the concave depressions of the contour, and this maximum distance r is assumed to correspond exactly to the etching radius r of the wet chemical etching step used for the exposure of the fingers.

[0012] In order to form a movable and monolithic comb-shaped structure made of glass (the fingers may be movable passively, for example, in the case of a sensor housing, or actively, in the case of an actuator housing), at least one solid joint (which couples the comb-shaped structure, particularly the individual fingers of the comb-shaped structure, in a displaceable manner and is monolithically coupled to the glass substrate) can also be defined / assumed to be defined using the LIDE method (i.e., by laser-induced modification of the glass substrate and subsequent wet chemical anisotropic etching).

[0013] Accordingly, the present invention recognizes that the LIDE method opens up entirely new possibilities for forming glass-based high-performance MEMS in a monolithic manner with the desired micro-mechanical properties. As a result, there is no longer a need to work on a second substrate made of silicon, on which the original MEMS chip / original comb-shaped structure has been formed, which has been common in many cases until now. Instead, the entire comb-shaped structure can be formed monolithically on the glass substrate in a single wet chemical etching step.

[0014] Here, preferably, at that time, all the laser pulses that define the outer contour of at least one (i.e., in some cases, even two) of the plurality of fingers in a specific section of the finger are present on such a (actually or virtually continuously following the contour) tool path. Each laser pulse is here directed (perpendicular to the tool path) towards each concave depression on the side wall of the finger. Thus, in this case, the contour of the finger on one side is set / pre-set solely by the laser pulses that are set / are present at a distance r from the contour, more precisely, at a distance r from the concave depression on the side wall of the finger, on the only continuous tool path. Accordingly, the characteristic side wall structure of the finger with side wall scalloping as described above occurs. Each tool path here connects adjacent laser spots and thus continuously passes through the laser spots that define the contour.

[0015] Each individual laser spot can here, in some cases, also define the contour of two directly adjacent fingers of the comb-shaped structure. This is the case when the laser spot is set in the center between two adjacent fingers. Accordingly, according to that, at the location of the laser spot, the fingers have a distance of D = 2r (on the substrate surface).

[0016] Such process guidance during manufacturing enables the design of particularly thin fingers. This allows for achieving a high filling factor, measured as the number of fingers / surfaces of the comb structure, which is advantageous for achieving an efficient electrical activation or sensor system based on the comb structure. A comb structure having fingers of this kind can be used, for example, as an electrostatic microactuator of a micromechanical linear or rotary drive.

[0017] If LIDE already defines relatively large cavities or vias within the glass substrate that are used for that purpose, then it does not matter exactly where and at what density the laser pulses are set, or at what intensity sidewall scalloping is significant. This is because these do not have a significant impact on the structure to be formed. However, these matters change dramatically when using the LIDE method to define the delicate fingers of the comb actuator as proposed by the present invention. This is because, as will be shown in more detail, in such cases, the micro-mechanical properties of the fingers are significantly affected by the relative position of the laser pulses on two opposing tool paths, as well as by the density of the laser pulses on each tool path (more or less with uniform properties). As mentioned, the laser pulses can preferably be arranged, at least extractively, on each tool path at a constant pulse interval p (for example, at least three adjacent laser pulses are set on each tool path in succession at the pulse interval p). Depending on the selected degree of sidewall scalloping, each tool path can have a minimum distance of r - t with respect to the contour, where t y is the depth of each depression within the sidewall of each finger, which is self-evident. y

[0018] Furthermore, the fingers may be envisioned as forming or having two opposing sidewalls each showing a concave depression (extending across the substrate plane, i.e., in particular in the direction of the surface normal of the substrate plane). These depressions here each exhibit a curvature with an etching radius r and / or are defined by respective convex ribs, and / or these depressions and ribs extend along the surface normal of the substrate plane. Each recess here can be assigned to a laser pulse defining the outer contour of the finger on the respective tool path. These ribs directly adjacent to each other here can have a distance L x = p, and this distance L x = p exactly corresponds to the pulse interval p of the respective laser spot. The above-mentioned ribs can typically extend in the z direction, i.e., perpendicular to the substrate plane. The same applies to the extension of the depressions themselves. Here, these ribs and depressions can also form an inclination with respect to the z-axis depending on the selected degree of anisotropy of the etching process. Each of the depressions here can be assigned to a contour (= the outer contour line of the substrate surface / upper surface of the bending structure) or to the respective laser spot existing at a distance r from the depression.

[0019] In the design of fingers with such sidewall scalloping, preferably the depressions show at least selectively, but preferably consistently, a constant / average distance L x along the entire length of each respective finger (thus L x is the average distance between two directly adjacent ribs formed on the same sidewall). This is because in this case the sidewalls can be formed uniformly, which is advantageous for a precise electrostatic activation part.

[0020] Particularly advantageously, furthermore, these ribs follow an outer virtual contour path that extends parallel to the central axis of each finger (in the case of straight fingers) or the center line (in the case of curved fingers). This is because this can minimize / may minimize the ripples of the contour path and thus the ripples of the side walls of the fingers. When using curved fingers, the center line of the finger can preferably extend with a constant curvature here, and then the same applies to the contour path to which it belongs. In contrast, in the case of straight fingers, the contour path can preferably extend linearly.

[0021] The opposing ribs formed within the opposing side walls of each finger among the plurality of fingers can be formed to exhibit an offset Δx along the extending direction of the fingers. Thus, preferably the following condition applies for this offset: L x / 4 ≦ Δx ≦ L x / 2, provided that L x is the average distance between two directly adjacent ribs among the ribs formed within the same side wall applies. In such a design, the width B(x) of the finger varies only slightly for a given degree of side wall scalloping, which is advantageous for achieving high breaking strength and high uniformity of the mechanical properties of each finger. That is, this is the first example of how the exact relative placement of the laser pulses affects the micro-mechanical properties of the fingers.

[0022] To design the sidewalls of the fingers to be as smooth as possible, weakly pronounced sidewall scalloping may be beneficial. This is because the laborious post-treatment of the fingers after wet chemical exposure can be avoided, and furthermore, the variation in the width of the fingers along their extension direction becomes smaller, resulting in a more uniform rigidity of the fingers. To achieve weakly pronounced sidewall scalloping, for the ratio of the average pulse interval p between adjacent laser pulses on one of the two tool paths and preferably the etching radius r along the entire length of each finger, the following condition: p < r, preferably p < r / 2, particularly preferably p < r / 3 is applied so that the laser pulses are set and the fingers can be etched away. This is a further example of how the density of the laser pulses on each tool path significantly changes the micro-mechanical properties of the fingers.

[0023] In such a design, it is also advantageous that the spacing between the opposing fingers of the comb structure has relatively little variation. This is because in the case of weakly pronounced sidewall scalloping, the side surfaces show only depressions of a smaller depth, and thus the spacing (gap dimension) between the fingers directly adjacent to the comb structure changes only slightly (e.g., change < 10%) along the longitudinal direction of each finger. This has an advantageous effect on the response characteristics of the comb structure. Furthermore, a uniform drift electric field can be obtained in this way, and thus a uniform stress distribution during the electrostatic activation of the comb structure can be ensured. In sensor applications, correspondingly, a uniform sensor characteristic curve (i.e., a charge shift uniformly generated as a result of the displacement of the fingers) occurs.

[0024] In such a design in general, furthermore, it is also preferable that directly adjacent laser spots (= laser pulses) have a minimum pulse interval of at least 3 μm, or rather at least 5 μm. This is because, by this means, an optical shadow effect can be avoided and a uniform etching result can be achieved, which results in the degree of sidewall scalloping being reproducible and being able to be set as desired.

[0025] Regarding the ratio between the local etching radius r of each depression and the lateral depth t y for example, the following conditions: t y / r < 0.1, preferably t y / r < 0.05 are applicable.

[0026] For such features, additionally or alternatively, regarding the ratio between the maximum width B of each finger crossing its extending direction and the lateral depth t y the following conditions: t y / B ≤ 0.1, especially t y / B ≤ 0.05 can be applied. Such parameters of the comb-shaped structure part also result in a particularly effective electrical activation or electrical sensor system based on the comb-shaped structure part. This is because the micro-mechanical properties of the fingers are improved thereby. Therefore, such a design proposes a particularly flat / slightly prominent sidewall scalloping, whereby a particularly slight variation in the width of the bending structure part, and thus a high rigidity uniformity, is achieved. Such a design may be advantageous, for example, to enable a particularly high breaking strength and thus a particularly large displacement of the bending structure part. In contrast, in the case of a sensor application, the sensitivity with which the bending structure part can capture mechanical vibrations can be increased.

[0027] Particularly weak sidewall scalloping provides advantages especially with respect to the uniformity of the mechanical properties of the comb structure when the finger width is relatively small, and thus this is associated with a correspondingly high ratio of t y / B and furthermore leads to a high energy density of the electrostatic activation section / sensor system.

[0028] More precisely, the fingers of the comb structure can also be released by wet chemical etching on both sides, i.e., from two opposing surfaces of the glass substrate. Therefore, the fingers can exhibit a rhombic cross-section that results especially from wet chemical etching from both sides of the glass substrate. In such a design, the maximum width B of the fingers max can be spaced apart from the surface of the glass substrate and can be present, for example, in the central plane of the glass substrate if etching is carried out simultaneously (and at the same rate) from both sides.

[0029] Depending on the material selected for the glass substrate and the other process parameters of the etching step, which also affect the anisotropy of the etching, the sides of the fingers can form respective taper angles φ with respect to the surface normal of the glass substrate. In this case, a taper angle of less than 6°, preferably less than 3°, is suitable for a high filling factor and effective activation.

[0030] A further process parameter is the selection of the pulse interval compared to the width of the individual fingers. Here, for the ratio of the minimum or maximum pulse interval p between two adjacent laser pulses or laser spots on a tool path extending parallel to the respective contour of each finger to the maximum width B of each finger measured transversely to its extension direction, the following condition: p / B < 0.5, preferably p / B < 0.3 or rather p / B < 0.2 can be applied.

[0031] The maximum width B of each finger of the comb-shaped structure can be, for example, less than 100 μm, particularly less than 50 μm.

[0032] Furthermore, the gap dimension between two directly adjacent fingers of the comb-shaped structure can be less than 50 μm, particularly less than 30 μm.

[0033] To enable electrostatic activation, the side wall of the finger can have a metallization used for forming an electrode. Such an electrode can be used to realize a capacitive sensor system using an electrostatic activation part or a comb-shaped structure part.

[0034] According to a further advantageous design aspect, each laser pulse pair / laser spot pair or each spatial phase position φ(x) from the opposing ribs on the side wall of one of the fingers along the respective extending direction of the (respective) fingers is such that at a specific activation position of the comb-shaped structure, the ribs formed on the side wall of the finger are formed flush with the corresponding ribs of the directly adjacent first finger on one side and are formed offset with respect to the corresponding ribs of the directly adjacent second finger on the opposing side. In this case, the opposing ribs of the fingers existing between the directly adjacent first finger and the second finger can exhibit an offset Δx < Lx / 4, particularly Δx = 0.

[0035] Regarding all the features described above, it is self-evident that preferably, all the fingers of the comb-shaped structure can be formed as described for each individual finger respectively.

[0036] In an extreme case, for a semi-circular depression, for the length L of the depression x the following condition: L x = p = 2r can be applied. That is, in this case, the ratio of p = 2r is selected, and sidewall scalloping will be maximally prominent. The present invention has indeed recognized here that it leads to very large ripples on the sidewalls of each finger. However, this ripple can be utilized precisely during electrostatic activation to realize a micromachanical stepping motor or a stepping actuator with a very small and accurate step width. Therefore, the present invention proposes a micromachanical stepping actuator based on a comb-shaped structure made of glass, which includes a plurality of fingers that have been etched and removed from a glass substrate using laser-induced deep etching (LIDE), that is, exposed by laser-induced modification of the glass substrate followed by wet chemical anisotropic etching. This comb-shaped structure may be designed particularly as described above. Further, the stepping actuator may preferably be electrostatically activatable (for example, using sidewall electrodes formed on the fingers).

[0037] This stepping actuator, here, the step size G of the stepping actuator is the distance L from a convex rib 9 that forms a lateral concave depression 8 on the sidewall of the finger and exhibits a curvature having an etching radius r x corresponds to (L x = G), and is excellent in this regard.

[0038] Here, in order to enable the non-linear response of the stepping actuator, in particular, regarding the ratio of the etching radius r and the lateral depth t of each depression y the following condition: t y / r > 0.1, preferably t y / r > 0.2, or rather t y / r > 0.3 may be assumed to be applied. Further, supplementary or alternative to these features, regarding the ratio of the distance L x (which is further the same as the step size G) and the etching radius r, the following condition: Lx / r > 0.5, preferably L x / r > 0.7 may be assumed to be applicable.

[0039] The design of such a comb-shaped structure part results in strongly pronounced sidewall scalloping, which in turn results in a non-uniform stress characteristic curve of the stepping actuator, which is desired for the stepping drive part. Therefore, when designing the corresponding depression specifications, a step size within the range of several micrometers can be reproducibly preset in advance. In this case, the step size can be determined by the geometric shape of the comb-shaped structure part determined using the LIDE method. Here, the degree of prominence of the sidewall scalloping determines how much the stress characteristic curve deviates from a linear characteristic curve. That is, the deeper and more prominent the concave depression, the more stepped the stress characteristic curve will be.

[0040] Such a stepping actuator based on a glass comb actuator manufactured by the LIDE method can be used, for example, to position optical components (components such as diaphragms, lenses, mirrors, etc.) or mechanical components (i.e., components as micropositioning components). This concept is particularly simplified compared to known "inchworm" actuators based on silicon technology, which require a large number of activation electrodes, especially holding electrodes, to achieve step drive. Furthermore, by utilizing the LIDE method, advantages in terms of cost are provided, especially when a long adjustment distance over several millimeters or even several centimeters is to be achieved. This is because such a microstructure with such a length dimension can be manufactured at low cost using the LIDE method.

[0041] In the above-described stepping actuator, further, each spatial phase position φ(x) from each laser spot pair or the lateral depression (11) may be assumed to be φ = 0° ± 60°, preferably φ = 0° ± 30°, particularly φ = 0° ± 5° along the respective extending directions of the fingers directly adjacent to the comb-shaped structure. In such a design, for example, at a specific activation position of the comb-shaped structure, ribs formed on the opposing sidewalls of two directly adjacent fingers are at least substantially, preferably even completely flush with each other, and preferably flush on both sides of each finger.

[0042] Moreover, by using the above-described micro-mechanical comb-shaped structure, a further micro-mechanical actuator such as a linear drive or a rotary drive can be formed. Accordingly, the present invention also proposes a micro-mechanical actuator including a comb-shaped structure according to the present invention as described above. Here, the fingers of the comb-shaped structure can have sidewall electrodes for electrostatic activation of the comb-shaped structure. Further, it is also possible to use the comb-shaped structure according to the present invention as a movable capacitive sensor element in a capacitive sensor.

[0043] In order to solve the problems described at the beginning, a method for manufacturing a micro-mechanical comb-shaped structure made of glass is also proposed. In this case, the comb-shaped structure (according to this method) can be designed with the features as described above. Therefore, the comb-shaped structure includes a plurality of micro-mechanical fingers. Here, the comb-shaped structure is displaceable within the substrate plane defined by the glass substrate. Here, the fingers are etched away from the glass substrate using laser-induced deep etching (LIDE), that is, exposed by laser-induced modification of the glass substrate followed by wet chemical anisotropic etching. The method further provides that, for the exposure of the fingers, the laser pulses defining the outer contour of the fingers are preferably set at a constant pulse interval p on two opposing tool paths that are each continuous, in particular linear or curved. Subsequently, all the fingers of the comb-shaped structure are exposed in a common wet chemical etching step, whereby each outer contour of the fingers (i.e., of each respective finger) has a maximum distance r from the respective tool path, and this maximum distance r corresponds to the etching radius r of the etching step.

[0044] Thus, in order to manufacture the comb-shaped structure portion, the laser spot can be arranged on each laser line having a respective distance r with respect to the contour of each finger r, and this distance r corresponds to the etching radius r of the wet chemical etching step. In order to manufacture the comb-shaped structure portion, for example, within the framework of the LIDE method, for this purpose, a series of laser spots may be arranged / are arranged on the laser line in order to introduce modification into the glass substrate using a laser beam. Subsequently, the region of the glass substrate modified / being modified using the laser beam in this way can be etched away / has been etched away in the subsequent wet chemical etching step. The fingers of the comb-shaped structure portion preferably have microscopic dimensions in this case, for example, with respect to the width (in the substrate plane) and / or the height (perpendicular to the substrate plane) of the bending structure portion. For example, these widths / heights can be in the sub-mm range, for example, less than about 100 μm, particularly less than 50 μm. In contrast, the length of the finger can reach from the sub-mm range to the cm range.

[0045] In this method, the anisotropy of the etching step may be selected such that the fingers are formed with a taper angle φ of at most 6°, preferably at most 3°, with respect to the surface normal of the substrate plane. Here, it is preferable that the ratio of the first etching rate of the region of the glass substrate modified using the laser beam to the second etching rate of the unmodified region of the glass substrate is selected to be greater than 15:1, preferably greater than 20:1.

[0046] Thus, the taper angle describes the gradient formed by each side wall of the finger with respect to the surface normal (z-axis) of the (xy) substrate plane.

[0047] The anisotropy of wet chemical etching, i.e., the ratio of the etching rate of the region modified using a laser beam to the etching rate of the unmodified region of the glass substrate, can be set via the etching chemistry. For example, hydrofluoric acid, or an alkaline solution such as KOH or NaOH can be used to etch the unmodified region as slowly as possible, and thus achieve a high anisotropy. Further, it is also possible to use glass types that are etched slowly, such as borofloat glass or quartz glass (fused silica).

[0048] In this method, the fingers can further be released with a rhombic cross-sectional shape by being etched using a wet chemical etching solution from two sides of the glass substrate. This can be advantageous for achieving a high aspect ratio of the fingers (this aspect ratio (= height of the finger / width) can be, for example, greater than 10:1, or rather greater than 50:1), which provides advantages for both the actuator system and the sensor system. In this case, the anisotropy of the etching step can be set, for example, such that the fingers form an internal angle of at least 170° with respect to each side wall after etching. Further, for simplified process guidance, preferably, for etching both sides of the glass substrate, substantially the same process parameters, such as the same wet chemical etching solution, preferably the concentration and / or temperature of the etching solution, are used. Thus, the etching of both sides can be performed in a single etching step.

[0049] In the case of vertical etching (however, this can only be approximately achieved even using wet chemistry because the etching solution etches the untreated glass isotropically), the side walls will extend vertically and thus exhibit an internal angle of 180°. Further, it is also obvious that laser pulses can be set from both sides of the glass substrate, i.e., on the opposing two surfaces of the glass substrate, to define the modified regions within the glass substrate to be etched away by wet chemistry.

[0050] In this method, in order to achieve weakly pronounced sidewall scalloping, preferably, for the ratio of the average pulse interval p between adjacent laser spots to the etching radius r along the entire length of each finger, the following condition: p < r, preferably p < r / 2 The laser pulses may be set and the fingers may be assumed to be etched away such that the above is applied.

[0051] As already mentioned, the respective profiles of the fingers can exhibit laterally concave depressions as a result of wet chemical etching, and these depressions each exhibit a curvature with an etching radius r on the surface of the glass substrate and are defined by the respective convex ribs. Accordingly, in this method as well, the process induction is related to the local etching radius r and the lateral depth t y of each depression, the following condition: t y / r < 0.1, preferably t y / r < 0.05 can be designed to be applied. Further, for the ratio of the maximum width B of each finger across its extension direction to the lateral depth t y additionally or supplementarily, the following condition: t y / B ≦ 0.1, especially t y / B ≦ 0.05 can be applicable.

[0052] This method may also include the deposition of a metallization part. Therefore, the metallization part used to form the electrodes of the fingers (24) can be deposited on the sidewalls of the fingers as a mask layer using a shadow mask or a spray photoresist or a stackable dry photoresist, respectively. The deposition of the metallization part on the sidewalls can preferably be carried out using physical vapor deposition (PVD), especially sputtering.

[0053] Finally, the present invention further proposes a special use of a micro-mechanical comb-shaped structure made of glass in a portable electronic device. This comb-shaped structure may also be manufactured and / or designed as described above according to the present invention. In this use, the comb-shaped structure is part of an electrostatic actuator and / or part of a capacitive sensor, and may be assumed to be used to add or maintain electrostatic holding force in an energy-efficient manner. In this case, the fingers of the comb-shaped structure can each have a length of more than 500 μm, particularly more than 1 mm.

[0054] By forming long fingers with only weak and prominent sidewall scalloping, such an electrostatic array (interdigital structure / comb-shaped structure) can be obtained, which enables quasi-static activation with minimal power consumption (based on very little leakage current), and thus enables the application of a relatively large (microscopic) holding force using voltage. For example, unlike electromagnetic activation, a relatively large operating current for maintaining such a holding force can be avoided. This is useful for both energy-saving sensor systems and actuators, and can provide advantages for portable (energy self-sufficient) devices in particular.

[0055] Furthermore, even during quasi-static activation, minimal sidewall scalloping is considered advantageous for improving the breaking strength of the micro-mechanical springs and torsion springs used in the actuator system (which can be formed as described herein). Quasi-static activation is also of great interest, for example, for the micromirrors used in 3D tracker systems. Therefore, these are also applications in which the comb-shaped structure according to the present invention can be used.

[0056] The present invention will now be described in more detail based on examples, but is not limited to these example embodiments. Further configurations of the present invention can be obtained from the following description of preferred example embodiments in conjunction with the general description, claims, and drawings. In the following description of various embodiments of the present invention, elements that are identical in function are given identical reference numerals even if there are differences in design or shape.

Brief Description of the Drawings

[0057]

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Figure 19

[0058] Figure 1 schematically shows a micromechanical microstructure 1 in the form of a finger 24 exposed from a glass substrate 3 in the form of a glass wafer using a wet chemical etching and the LIDE (Laser Induced Deep Etching) method. The drawing of Figure 1 is here a drawing from above the xy plane of a glass substrate 3 having a specific substrate thickness t in the z direction glas As can be recognized, the finger 24 is coupled to a relatively large armature structure part, one side of which is part of the glass substrate 3. This armature 36 / 37 may be stationary compared to the glass substrate 3, but otherwise may be movably supported, for example, using a micromechanical spring element 29 (see Figure 14). Thus, in the latter case, the finger 24 may be displaceable in the xy plane, for example, by a linear or rotational movement.

[0059] By using the LIDE (Laser Induced Deep Etching) method, fine glass pieces can be cut out or exposed from the glass substrate 3. For this purpose, first, a laser is used to start from a contour 6 that describes the outer boundary of the microstructure 1 to be exposed, for example, the finger 24 in Figure 1. For this purpose, it is proposed to operate a laser head that irradiates a pulsed laser beam on the respective tool paths 5a, 5b that follow the contour 6 at a specific distance (see Figure 3). However, since the laser is pulsed, the glass substrate 3 is not continuously irradiated by the laser beam, but rather individual laser pulses 4 are set as laser spots 4 at specific xy coordinates on the surface of the glass substrate 3. In this case, this laser spot 4 can have a constant geometric pulse interval p (measured in μm in the substrate plane) and / or all can be present on the above tool paths 5a, 5b. The block arrows in Figure 3 are here intended to show in which order the tool path 5 is moved and the laser spot 4 is set (see also Figure 6).

[0060] For example, when an elongated slit is to be formed in the glass substrate 3, a predetermined number of laser pulses 4 are arranged along the tool path 5 at a pulse interval p. In this case, typically, the glass substrate 3 is modified over its entire thickness using each laser pulse 5. In the subsequent wet chemical etching process, the etching solution erodes the substrate 3 in the z-direction from the upper surface. In this case, since the etching rate is isotropic in the xy-plane, a disk-shaped etching profile 7 with rotational symmetry centered on each laser spot 4 is formed on the surface (see the circles in FIGS. 4 and 6 to 8). This results in the final etching contour 6 of the microstructured portion 1 showing a distance r (=etching radius 27) from the center of the original laser spot 4 (see FIG. 3 or FIG. 6). In other words, the contour line 6 of the finger 24 in FIG. 1 etched away on the surface of the glass substrate 3 shows the maximum distance r to the tool path 5 (projected onto the substrate plane) where the laser pulses 4 are arranged.

[0061] Based on the etching radius r, concave depressions 8 are formed in each side wall 13 of the finger 24 here (see FIGS. 1 to 3). These depressions 8 each exhibit a curvature with an etching radius r27 and are defined by respective convex ribs 9. In this case, not only these ribs 9 but also the depressions 8 extend along the z-direction (see FIGS. 1 to 3, FIGS. 4, FIGS. 6, and FIGS. 11 to 13). These structures within each side wall 13 that occur during the wet chemical exposure of the finger 24 are referred to as side wall scalloping. This is because these depressions 8 and the intervening ribs 9 form a structure similar to the inside of a mussel shell.

[0062] Depending on the selected process parameters and thus the degree of anisotropy of the wet chemical etching, here the etching radius 27r in the xy plane can be more or less significantly reduced along the z direction (i.e., perpendicular to the substrate plane), whereby (for example, in the xz plane) the extension of the side wall 13 of the finger 24 having a gradient with respect to the z-axis or forming a taper angle φ, as shown in FIGS. 11 to 13, can be achieved. Thus, even in the case of FIG. 12, a taper angle occurs and moreover it occurs over the entire height of the finger 24, but this taper angle is very weak and not very significant. However, on the substrate surface, the etching radius 27r always starts from each laser spot 4 and is of the same size. Furthermore, only a gradient corresponding to the etching radius 27r that decreases with the increase in depth z is always possible. This results from the fact that the wet chemical etching always starts from the substrate surface and proceeds from there into the deep part of the substrate. Of course, this process can start from one side (FIG. 13) or, if not, from both sides of both substrate surfaces (see FIGS. 11 and 12), and thus, in the latter case, corresponding symmetric gradients occur, and these gradients extend in the direction towards a plane 21 (parallel to the xy plane) arranged centrally (in the z direction) (see FIG. 12).

[0063] As shown in FIG. 12 showing the cross-section of the finger 24 of the comb-shaped structure 25 according to the present invention (here the extension direction 2 of the microstructure 1 / finger 24 extends in the field-of-view direction with respect to the drawing), already each laser spot 4 can be sufficient to define a slit having a width 2r between the finger 24 and an adjacent finger 24 or the bulk of the glass substrate 3. In this case, the etching solution then starts from the laser spot 4 and forms an etching radius 27r on both sides at the surface of the glass substrate 3 (for example, as in the positive and negative y directions in FIG. 12). At this time, the maximum width B15 of the finger 24 measured at the surface of the glass substrate 3 (in the direction across the extension direction 2, that is, in the y direction in FIG. 12) is, depending on the selected taper angle φ22, the maximum width B shown by the microstructure 1 in the illustrated central plane 21 of the substrate 3Max may deviate significantly from

[0064] However, as shown in FIG. 12, since the laser spots 4 can also be set adjacent to each other with a very narrow pulse interval p, the resulting etching radii r will thus overlap (see also FIG. 8 for this). When the anisotropy of the laser-induced wet chemical etching is very highly selected, as shown in FIG. 13, the substantially vertical side walls 13 of the fingers 24 of the comb-shaped structure 25 can be defined (where the taper angle 22 is very slightly prominent).

[0065] FIG. 8 shows in detail how the finger 24 of FIG. 3 was manufactured. As recognized based on the circles showing the disc-shaped etching profiles 7 each having an etching diameter D = 2r, the entire series of laser pulses 4 is arranged on two opposing tool paths 5a and 5b. Since the etching front 7 propagates isotropically within the xy substrate plane, each laser pulse 4 has a distance r to the final outer contour 6 of the finger 24, which exactly corresponds to the etching radius 27r of the wet chemical etching step used for the exposure of the finger 24. As shown in FIG. 3, the two laser pulses 4 present on the opposing tool paths 5a and 5b can be integrated into a laser pulse pair 18. As shown in FIGS. 1 - 3 and FIG. 8, the two laser pulses 4 of each laser pulse pair 18 can show an offset Δx with respect to the extending direction 2 of the finger 24 (corresponding to the x-axis in these figures), and this offset Δx can exist, for example, between Δx = 0 and Δx = p / 2 when using a constant pulse interval p.

[0066] Depending on the extent of this offset Δx, a spatial phase position φ(x) or a spatial phase distortion φ(x) occurs between the respective laser spots 4 of the laser spot pair 18. In the example of FIG. 1, the offset Δx = 0, and therefore, there, the laser spots 4 of each laser spot pair 18 are arranged in the same phase (φ = 0°) with respect to the extending direction 2. In contrast, in the example of FIG. 3, the phase difference is maximum (φ = 180°). This is because the offset Δx is Δx = p / 2 there, where p is the pulse interval, that is, the distance between two directly adjacent laser spots arranged on the same tool path (for example, 5b) (see FIG. 8 for this).

[0067] In contrast, the ratio p / r of the pulse interval p to the etching radius r determines how strongly pronounced the depressions 8 of the sidewall scalloping are. The distance L between the ribs 9 along the x-axis x is exactly the pulse interval L here x = p (see FIG. 8). Further, in detail, the lateral depth t y 14 for each depression 8 measured across the extending direction 2, that is, in the y-axis direction in FIG. 8, can be determined.

[0068] In FIG. 8, further, it is shown that two tool paths 5a, 5b have a distance Dy10. This distance and the selected offset Δx determine here the step angle α formed by the two laser spots 4 of each laser spot pair 18 with respect to the extending direction 2. In this case, the following condition: α = arctan(Δx / D y ) applies. In contrast, the spatial phase position φ(x) is determined as φ = 360°Δx / p. In this case, since the offset Δx can vary depending on the x-coordinate of the laser pulse pair 18, the phase position φ(x) can also basically vary along the extending direction 2.

[0069] FIGS. 4 and 6 show, for example, the ratio t yIt is shown how the degree of sidewall scalloping that can be read from / r affects the uniformity of the width B(x) of the finger 24 and, consequently, the mechanical properties. The three curves in the graph of FIG. 5 show how the width B(x) varies along the extending direction 2 having the x coordinate (and further how the maximum width B15 is assumed at various x locations in this case), in detail, for the three phase positions of 0° / 90° / 180° shown in FIGS. 1 to 3. As shown by the horizontal broken line in FIG. 5, here, three fingers 24 having the same average width B are compared. Also, the degree of sidewall scalloping (t y measured in / r) is similarly selected to be of the same magnitude. In the graph of FIG. 5, it is recognized that the variation of the width B(x) is maximum at the spatial phase of φ = 0°.

[0070] On the other hand, at the spatial phase position of φ = 180°, the finger 24 shows the minimum variation in the width B(x). Therefore, at the phase position of φ = 180°, not only does an advantage regarding higher breaking strength occur, but also the spring stiffness of the microstructured portion 1 manufactured in this way can be significantly reduced in the case of the same average width B. This is because this spring stiffness depends cubically on the width B (due to the displacement of the microstructured portion in the substrate plane). This is applied, for example, in the micro-mechanical spring element 29 shown in FIG. 7, which is part of the electrostatic actuator 33 (based on the comb-shaped structure portion 25 according to the present invention) shown in FIG. 14. On the other hand, at the phase position of φ = 0°, the local spring stiffness is likely to vary significantly because the variation of the spring width B becomes cubic, which may cause a peak in mechanical stress, which may cause the spring 29 to break.

[0071] Therefore, as shown in FIG. 3, the glass micro - mechanical finger 24, which exhibits a phase position φ(x) of 180° and relatively weakly pronounced side - wall scalloping, is suitable for use as part of a micro - mechanical actuator 33 or sensor. This is because this microstructure 1 has, on the one hand, a breaking strength and, on the other hand, uniform mechanical properties. Based on the variation of these properties, such a microstructure 1 can be used to realize a particularly high - quality electrostatic actuator / sensor system.

[0072] However, for example, a phase position of φ = 0° as shown in FIG. 1 can also be associated with interesting mechanical properties that can be technically beneficially utilized in the comb - shaped actuator 33, especially when the side - wall scalloping is just strongly pronounced. For example, (as shown for the case of φ = 0° in FIG. 5) a high variation in the width B of the finger 24 can be associated with a strong non - linear response behavior of the respective comb - shaped structure 25 / the respective actuator 33 that can be utilized, for example, in a stepping motor / stepping actuator.

[0073] However, as can be well recognized in FIGS. 1 - 3, there, the respective spatial phase position φ(x) of each laser - pulse pair 18 is set uniformly along the extending direction 2 of the finger 24. In this case, the phase position in FIG. 1 is φ = 0°, the phase position in FIG. 2 is φ = 90°, and the phase position in FIG. 3 is φ = 180°. Based on the straight - line course of the finger 24, the phase position φ(x) varies only within the frame of the accuracy with which the laser spot 4 can be placed on the glass substrate 3 here.

[0074] As shown in FIG. 6, for the case of the straight - line course of the finger 24, the effective pulse interval p'=p exactly corresponds to the geometric pulse interval p between two directly adjacent laser spots 4 on the tool path 5.

[0075] FIG. 7 shows an example of a spring element 29 designed according to the present invention, which, together with the comb-shaped structure 25 according to the present invention, can be used in particular to support the movable armature 36 of the comb-shaped structure 25 (which supports part of the finger 24) so as to be displaceable (i.e., rotatable as shown in FIG. 14 for example, or linearly shiftable in the substrate plane 28 in a similar manner). The spring element 29 shows a curved path 2, which can be well confirmed based on the center line 19. Even with such a design, each laser spot pair 18 can be observed. Note that an effective pulse interval p’≠p can deviate from the geometric pulse interval p as shown in FIG. 7. Nevertheless, even with such a path of the microstructure 1, each spatial phase position φ can be set uniformly. In the example of FIG. 7, the phase positions vary slightly (by about + / -30°) around an average phase position of about φ = 180°.

[0076] FIGS. 9 and 10 show perspective views from above of one scanning electron microscope (REM) image each of the micromechanical comb-shaped structure 25 according to the present invention (FIG. 9) or of an individual finger 24 of such a comb-shaped structure 25 (FIG. 10). Based not only on the detailed view of FIG. 9 but also in FIG. 10, the depressions 8 and the ribs 9 existing between them and each extending in the z direction, i.e., crossing the substrate plane 28, can be well recognized. In the finger 24 of FIG. 10, the depressions 8 / ribs 9 are each formed with a uniformly set phase position of about φ = 150°. The left fingers 24 of the comb-shaped structure 25 in FIG. 9 are here movable in their respective longitudinal directions (= extending directions 2). This is because these fingers 24 are arranged on the movably supported armature 36. Thereby, the left fingers 24 can move more or less deeply into the intervening space formed between the right fingers 24 arranged on the stationary armature 37 (see block arrows).

[0077] FIG. 14 shows an example of how the comb-shaped structure 25 according to the present invention can be released within the glass substrate 3 using the LIDE method. The black surfaces here mark the regions of the glass substrate 3 that have been modified using a laser and subsequently etched away in a subsequent etching step. In contrast, the bright structures mark the glass structures that remain after etching.

[0078] To enable electrostatic activation of the comb-shaped structure 25, the sidewall metallization 30 is deposited onto the comb-shaped structure 25, more precisely onto the sidewalls 13 of the fingers 24, using a shadow mask that has likewise been manufactured using the LIDE method. The black regions in FIG. 15 here show the openings of the shadow mask and thus the regions of the glass substrate 3 that are to be metallized.

[0079] As a result of this, the comb-shaped structure 25 in FIG. 16 that realizes the electrostatic rotary drive unit / actuator 33 includes a stationary armature 37 that forms a plurality of first stationary fingers 24a, and a second armature 36 that is movably supported and forms a plurality of second movable fingers 24b. The movable second fingers 24b are here arranged in the intervening space of each of the stationary first fingers 24a. Therefore, these fingers 24a, 24b form an interdigital structure. The movable fingers 24b, in this case the armature 36, are suspended from the glass substrate 3 via micro-mechanical spring elements 29 (shown in the detailed view of FIG. 7). This spring element 29 forms a coil spring, and this coil spring enables the rotation of the fingers 24b / armature 36 around the rotation spot existing at the center of the helix. Thereby, the arm 31 that supports the end piece 32 can be rotated using the electrostatic actuator 33. For this purpose, the arm 31 is non-rotatably coupled to the armature 36 (the arm 31 and the armature 36 are formed monolithically). The end piece 32 could be designed, for example, as an optical mirror for deflecting light, or as an electromechanical switch, for example. However, if, for example, the comb-shaped structure 25 shown in FIG. 16 is more or less strongly damped at different air pressures for the movement of the arm 31, it could also be used as part of a pressure sensor. Therefore, this can be sensorially evaluated.

[0080] It is self-evident that a micro-mechanical comb-shaped structure 25 as shown in FIG. 16 can of course also be used as an electrostatic sensor, for example, to electrically capture and measure the rotational movement of the arm 31. This is because when the arm moves and as a result the movement of the fingers 24b occurs, the capacitance of the interdigital structure of the comb-shaped structure 25 changes, and this can be electrically evaluated. Furthermore, an electrostatic linear drive unit or a stepping actuator provided with the comb-shaped structure 25 according to the present invention can also be realized.

[0081] Figures 17 and 18 show how the sidewall scalloping, i.e., the recesses 8 in the sidewalls 13 of the fingers 24, can be set as desired in order to enable as uniform an activation as possible. In both cases, the respective spatial phase positions φ(x) of the opposing ribs 9 in the sidewalls 13a, 13b of the central movable finger 24b of the comb-like structure 25 are such that, in the currently illustrated activation position, the ribs 9 formed within the sidewalls 13a, 13b of the central finger 24b are flush with the corresponding ribs 9 of the directly adjacent first stationary finger 24a on the upper side (in the figure), and are formed offset with respect to the corresponding ribs 9 of the directly adjacent second stationary finger 24c on the opposing lower side. Each central finger 24b has a length L x / 2 between the two ribs 9 and moves 1 / 2 to the right, the situation is exactly reversed. This is because at that time, an offset occurs with respect to the ribs of the finger 24a, while the lower rib 9 is aligned with the rib 9 of the finger 24c.

[0082] On the other hand, when a stepwise activation is targeted, at a specific activation position, the ribs of each finger can be aligned with the ribs of the respective directly adjacent fingers on both sides. Furthermore, at that time, particularly prominent sidewall scalloping may be advantageous in order to enable the desired non-linear activation.

[0083] Finally, to clarify the present invention again, refer to FIG. 19 which shows the design of the fingers 24 of the comb structure 25 different from the previous examples according to the present invention in the upper half: As can be seen, the upper contour 6a that approximately follows the wavy course highlighted by the thick line is defined by the laser pulses 4 from the two tool paths 5a and 5c. In this case, only the laser pulse 4 of the tool path 5a shows the maximum distance r (= etching radius 27) from the concave depression 8 on the side wall 13 of the finger 24. In contrast, the distance between the depression 8 and the laser pulse 4 of the tool path 5c is slightly larger than the etching radius 27. On the other hand, the lower contour 6b shows a limiting case: The laser pulse 4 on the lowermost tool path 5d is used for the exposure of the intervening space between the fingers 24, but this does not define the contour 6b. Because it is set to the minimum distance of t y =r-(r 2 +p 2 / 4) 1 / 2 (= the lateral depth of the depression 8, which geometrically results from the pulse interval p and the etching radius r). Therefore, the lower contour 6b is defined solely by the laser pulse 4 of the tool path 5b as proposed by the present invention, and the laser pulse 4 is set to the distance r with respect to the concave depression 8 of the lower contour 6b respectively. Therefore, all the laser pulses 4 that determine the lower contour 6b in the illustrated cross-section are present on the individual continuous tool paths 5b. Accordingly, only the lower contour 6b shows the characteristic side wall scalloping with convex (and tapered) ribs 9 between the depressions 8.

[0084] Hereinafter, some exemplary design parameters and process parameters of the fingers 24 of the comb-shaped structure 25 designed according to the present invention will be listed in tabular form for different substrate thicknesses and substrate materials.

[0085] A) Example of a finger according to the present invention having slight side wall scalloping [Table 1]

Table 2

Table 3

[0086] B) Example of a finger according to the invention having significant sidewall scalloping

Table 4

Table 5

Table 6

[0087] As can be recognized from these numerical values, in these examples, the etching diameter D = 2r varies in the range of several μm and typically the following conditions: r ≦ 50 μm, or rather r ≦ 20 μm, or rather r ≦ 10 μm can be applied. Here, for the ratio of the etching diameter D = 2r to the substrate thickness t, typically at least the following condition: D / t ≦ 1:5 = 0.2 is applied, and in the case of a very large substrate thickness (t ≧ 400 μm), the following condition: D / t ≦ 1:20 = 0.05 can even be applied. The presented taper angle φ22 describes the inclination of the sidewall surface 13 of the finger 24 with respect to the z-axis (= the normal 26 of the surface of the substrate 3) (see FIGS. 11 to 13 for this).

[0088] In the example of Table 6, the aspect ratio of the finger 24 (= substrate thickness: spring width) reaches 100. This sidewall scalloping is still very weakly significant here, and the ratio is t y / r = 0.03. This indicates that by using LIDE, it is possible to manufacture fingers 24 with a very uniform and high aspect ratio, which are particularly suitable for the micro - mechanical comb - shaped structure 25. In the example of Table 4, the degree of side - wall scalloping increases with the decrease in substrate thickness. For a substrate thickness of 100 μm, for example, the following conditions: t y / B = 19% and t y / r>20% are applied. For the same substrate thickness of 100 μm, in Table 5, the ratio of the lateral depth t y of the depression 8 to the maximum width B15 of the finger 24 is up to 34%. Accordingly, in these examples, distinct depressions 8 or ribs 9 are formed on the side walls 13 of the microstructure 1. This type of finger 24 would be suitable for use in a stepping actuator.

[0089] In summary, in order to expand the applicability of the known LIDE (laser - induced deep etching) method, when manufacturing the micro - mechanical comb - shaped structure 25, by setting a plurality of laser pulses 4 on the glass substrate 3 and then using a wet - chemical etching step to expose the comb - shaped structure 25, it is proposed to accurately control the position of the laser pulses 4 that define the outer contour 6 of each finger 24 of the comb - shaped structure 25. This makes it possible to form very narrow fingers 24 with uniformly formed side walls 13, thereby enabling a very small gap dimension 35 and uniform electrostatic activation of the comb - shaped structure 25. Furthermore, by controlling the phase position φ and / or the degree of side - wall scalloping of the fingers 24, it is possible to favorably influence the mechanical properties or set them as desired (see Figure 9).

Explanation of Reference Numerals

[0090] 1 Microstructure, particularly a bending structure 2 Extension direction of (1) 3 Glass substrate 4 laser pulses (the incident spot on 3 defines a laser spot having xy coordinates on the surface of 3) 5 tool paths (along which the laser head is guided and on which laser pulses are set up) 6 contour (of 1, particularly of the outer boundary line of 1 within the substrate surface / on the upper surface of 1) 7 etching profile (in the xy plane caused by 4) 8 (concave) depression (within the side wall of 24) 9 (convex) rib (within the side wall of 24) 10 tool path distance (or local y - direction distance between 4) 11 modified region (within 3) 12 offset region (of 1) 13 side wall or side wall surface (of 1) 14 lateral depth (of 14) 15 (maximum) width (of 1 across 2) 16 spring beam 17 solid joint 18 laser pulse pair 19 central axis or center line (of 1) 20 (wet chemical) etched - away region 21 central plane (of 3) 22 taper angle φ 23 bending structure (designed, for example, as a micro - mechanical spring element) 24 movable finger (of 25) 25 micro - mechanical comb - shaped structure 26 surface normal (of 3 = z - axis) 27 etching radius 28 substrate plane (of 3 = xy plane) 29 micro - mechanical spring element 30 metallization (particularly of 13) 31 movable arm 32 end piece (of 31 activated by 25) 33 electrostatic activation part / electrostatic actuator 34 inner angle (of 13) 35 Gap dimension 36 Movable armature 37 Stationary armature

Claims

1. A micro - mechanical comb - shaped structure part (25) made of glass, comprising: - a plurality of micro - mechanical fingers (24); - the comb - shaped structure part (25) is displaceable within a substrate plane (28) defined by a glass substrate (3); - the fingers (24) are exposed from the glass substrate (3) by laser - induced modification of the glass substrate (3) followed by wet chemical anisotropic etching; - during the manufacture of the fingers (24), laser pulses (4) defining the outer contour (6) of the fingers (24) are preferably set at a constant pulse interval p on respective continuous, in particular linear or curved, opposing tool paths (5a, 5b); - each of the tool paths (5a, 5b) has a maximum distance r from the contour (6), and the maximum distance r corresponds exactly to the etching radius (27) r of the wet chemical etching step used for the exposure of the fingers (24), a micro - mechanical comb - shaped structure part (25) made of glass.

2. At least one solid joint (17) that monolithically bonds the comb - shaped structure part (25) to the glass substrate (3) is exposed by laser - induced modification of the glass substrate (3) followed by wet chemical anisotropic etching in order to enable displaceability, the micro - mechanical comb - shaped structure part (25) made of glass according to Claim 1.

3. Each of the fingers (24) has two opposing side walls (13a, 13b) each showing a concave depression (8), - the concave depressions (8) each show a curvature with an etching radius r and are each defined by a respective convex rib (9); - Preferably, the recess (8) is at least extractively, but preferably at a constant average distance L along the entire length of each finger (24). ｘ is shown, - in particular, the ribs (9) each follow an outer virtual contour path (36) extending parallel to the central axis (19) or center line (19) of the respective finger (24); - in particular, thereby minimizing the ripple of the contour path (36), the micro - mechanical comb - shaped structure part (25) made of glass according to Claim 1 or 2.

4. Opposing ribs (9) formed within the opposing side walls (13a, 13b / 13c, 13) of each of the fingers (24) show an offset Δx along the extension direction (2) of the fingers (24), and for the offset Δx, the following condition: L ｘ L / 4 ≤ Δx ≤ L ｘ / 2, provided that the above L ｘ is the average distance between two directly adjacent ribs (9) among the ribs (9) formed within the same side wall (13a / 13b). The micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 3, to which [the following conditions] are applied.

5. For achieving weakly prominent sidewall scalloping, regarding the ratio of the average pulse interval p between adjacent laser pulses (4) on one of the two tool paths (5a or 5b), and preferably the etching radius (27) r along the entire length of each finger (24), the following condition: p < r, preferably p < r / 2, particularly preferably p < r / 3 The laser pulses (4) are set and the fingers (24) are etched away so that [the following conditions] are applied, for the micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 4.

6. The ratio of the local etching radius (27) r of each of the depressions (8) to the lateral depth t ｙ (14) satisfies the following condition: t ｙ / r < 0.1, preferably t ｙ / r < 0.05 [The following conditions] are applied, - Preferably, for the ratio of the maximum width B(15) of each of the fingers(24) crossing the extending direction(2) to the depth t ｙ (14) in the transverse direction, the following conditions are additionally or alternatively satisfied: t ｙ / B ≤ 0.1, particularly t ｙ / B ≤ 0.05 The micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 5, to which [the following conditions] are applied.

7. The finger (24) shows a rhombic cross-section resulting from wet chemical etching from both sides of the glass substrate (3), and in particular, the maximum width B of the finger (24) ｍａｘ is a micro-mechanical comb-shaped structure portion (25) made of glass according to any one of claims 1 to 6, which is spaced apart from the surface of the glass substrate (3) and preferably exists in the central plane (21) of the glass substrate (3).

8. The side surfaces (13) of the fingers (24) form respective taper angles φ (22) with respect to the surface normal (26) of the glass substrate (3), and the taper angle φ (22) is less than 6°, preferably less than 3°, for the micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 7.

9. Regarding the ratio of, particularly the minimum or maximum pulse interval p between two adjacent laser pulses (4) on the tool path (5) extending parallel to the respective contour (6) of each finger (24), and the maximum width B (15) of each finger (24) across its extending direction (2), the following condition: p / B < 0.5, preferably p / B < 0.3 [The following conditions] are applied, - In particular, the maximum width B (15) of each finger (24) is less than 100 μm, particularly less than 50 μm, and / or the gap dimension (36) between two directly adjacent fingers (24) is less than 50 μm, particularly less than 30 μm, for the micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 8.

10. The side walls (13) of the fingers (24) have a metallization part (30), and the metallization part (30) is the electrode of the finger (24), - In particular, a micromachined comb-shaped structure part (25) made of glass according to any one of claims 1 to 9, which is used to form an electrostatic activation part (33) or an electrode for realizing a capacitive sensor system by using the comb-shaped structure part (25).

11. Each laser pulse pair (18) or each spatial phase position φ(x) from the opposing rib (9) on the side walls (13a, 13b) of one of the fingers (24b) along the respective extending direction (23) of the fingers (24b) is - At a specific activation position of the comb-shaped structure part (25), the rib (9) formed on the side walls (13a, 13b) of the finger (24b) is - On one side, formed flush with the corresponding rib (9) of the directly adjacent first finger (24a), - On the opposite side, formed offset with respect to the corresponding rib (9) of the directly adjacent second finger (24c), selected, - In particular, the opposing ribs (9) of the finger (24b) present between the directly adjacent first finger (24a) and the second finger (24c) have an offset Δx < L ｘ / 4, in particular Δx = 0, of the glass micro - mechanical comb - shaped structure (25) according to any one of claims 1 to 10.

12. A micromachined actuator including the comb-shaped structure part (25) according to any one of claims 1 to 11, - Preferably, the fingers (24) of the comb-shaped structure part (25) have side wall electrodes for electrostatic activation of the comb-shaped structure part (25), the micromachined actuator.

13. Based on a comb-shaped structure part (25) made of glass, particularly according to any one of claims 1 to 11, having a plurality of fingers (24) exposed from a glass substrate (3) by laser-induced modification of the glass substrate (3) and subsequent wet chemical anisotropic etching, - The step size G of the stepping actuator corresponds to the distance L from a convex rib (9) that defines a laterally concave depression (8) formed in the side wall (13) of the finger (24) and having a curvature with an etching radius (27) r ｘ (L ｘ = G), - Preferably, for the ratio of the etching radius (27) r to the lateral depth t ｙ (14) of each of the depressions (8), the following condition: t ｙ / r > 0.1, preferably t ｙ / r > 0.2 is applied, and / or - the distance L ｘ = G and the etching radius r, the following condition for the ratio: L ｘ / r > 0.5, preferably L ｘ / r > 0.7 is applied, characterized by a micromachined stepping actuator.

14. Each spatial phase position φ(x) from each laser spot pair (18) or the lateral depression (8) is φ = 0° ± 60°, preferably φ = 0° ± 30°, particularly φ = 0° ± 5° along the respective extending direction (2) of the directly adjacent fingers (24) of the comb-shaped structure part (25). - In particular, thereby, at a specific activation position of the comb-shaped structure part (25), ribs (9) formed on the opposing side walls (13) of two directly adjacent fingers (24) are at least substantially, preferably completely, flush with each other. The stepping actuator according to claim 13.

15. A method for manufacturing a micro-mechanical comb-shaped structure part (25) made of glass according to any one of claims 1 to 11, in particular, The comb-shaped structure part (25) is - including a plurality of micro-mechanical fingers (24), - the comb-shaped structure part (25) is displaceable within a substrate plane (28) defined by a glass substrate (3), - the fingers (24) made of the glass substrate (3) are exposed by laser-induced modification of the glass substrate (3) followed by wet chemical anisotropic etching, - for the exposure of the fingers (24), laser pulses (4) defining the outer contour (6) of the fingers (24) are set on respective continuous, in particular linear or curved, opposing tool paths (5a, 5b), preferably at a constant pulse interval p, - subsequently, all fingers (24) of the comb-shaped structure part (25) are exposed in a common wet chemical etching step, whereby each outer contour (6) of the fingers (24) has a maximum distance r from the respective tool path (5a, 5b), and the maximum distance r corresponds to the etching radius (27) r of the etching step. The method.

16. - the anisotropy of the etching step is selected such that the fingers (24) are formed with a taper angle φ (22) of at most 6°, preferably at most 3°, with respect to the surface normal (26) of the substrate plane (28), - preferably, the ratio of the first etching rate of the region (11) of the glass substrate (3) modified using a laser beam to the second etching rate of the unmodified region of the glass substrate (3) is selected to be greater than 15:

1. The method according to claim 15.

17. The fingers (24) are etched using a wet chemical etching solution from two sides of the glass substrate (3), thereby being released with a rhombic cross-sectional shape. - The anisotropy of the etching step is set such that the fingers (24) form an inner angle (34) of at least 170° with respect to the respective side walls (13) after etching. - Preferably, the same wet chemical etching solution, preferably with substantially the same process parameters such as, for example, the concentration and / or temperature of the etching solution, is used to etch both sides of the glass substrate (3). - Particularly preferably, the etching of both sides is carried out in a single etching step, according to the method of claim 15 or 16.

18. To achieve weakly pronounced sidewall scalloping, preferably, for the ratio of the average pulse interval p between adjacent laser pulses (4) to the etching radius r along the entire length of each finger (24), the following condition: p < r, preferably p < r / 2 is applied, the laser pulses (4) are set, and the fingers (24) are etched away, according to the method of any one of claims 15 to 17.

19. The respective profile (6) of the fingers (24) shows a lateral concave depression (8), and the depression (8) shows a curvature having an etching radius r on the surface of the glass substrate (3) and is defined by respective convex ribs (9). - The ratio between the local etching radius (27) r and the lateral depth t ｙ (14) of each depression (8) satisfies the following condition: t ｙ / r < 0.1, preferably, t ｙ / r < 0.05 is applied, - Preferably, additionally or alternatively, the ratio between the maximum width B(15) of each finger (24) transverse to its longitudinal direction (2) and the transverse depth t ｙ (14) satisfies the following condition: t ｙ / B ≤ 0.1, particularly t ｙ / B ≤ 0.05 is applied, according to the method of any one of claims 15 to 18.

20. The metallization (30) used to form the electrodes of the fingers (24) is - a shadow mask or - a spray photoresist or - a stackable dry photoresist is used and deposited as a mask layer on the side walls (13) of the fingers (24). - Preferably deposited using physical vapor deposition (PVD), particularly sputtering, according to the method of any one of claims 15 to 19.

21. Use of a micromachined comb structure (25) made of glass in a portable electronic device, - The comb structure (25) is formed as described in any one of claims 1 to 11. - As part of an electrostatic actuator (33) and / or as part of a capacitance sensor, the electrostatic holding force is added or maintained in an energy-saving manner. - In particular, the use of a micromachined comb-shaped structure (25) made of glass in a portable electronic device, wherein the fingers (24) of the comb-shaped structure (25) have respective lengths of more than 100 µm, in particular more than 300 µm.

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