Microsensor with anchor elements
The microsensor design with optimized anchor elements and stiffening structures addresses the challenge of uneven force distribution and stress peaks, improving robustness and deflection homogeneity.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-10-29
- Publication Date
- 2026-05-21
AI Technical Summary
Existing microsensors face challenges in optimizing force distribution during membrane deflection, leading to local stress peaks and reduced robustness, particularly in mobile electronic devices.
A microsensor design with optimized anchor elements and stiffening structures that distribute load evenly, reducing local stress peaks and enhancing membrane deflection homogeneity.
The design improves the robustness and homogeneity of membrane deflection, reducing stress concentrations and enhancing structural integrity under dynamic loads.
Smart Images
Figure EP2025081305_21052026_PF_FP_ABST
Abstract
Description
[0001] R.416709
[0002] - 1 -
[0003] Description
[0004] title
[0005] Microsensor with anchor elements
[0006] The invention relates to a microsensor according to the preamble of claim 1.
[0007] State of the art
[0008] In DE 102020213 772 A1 a microsensor with a membrane and an anchor structure is described, in the area of which a stiffening structure reinforcing the membrane is arranged.
[0009] Disclosure of the invention
[0010] According to the present invention, a microsensor with the features of claim 1 is proposed. This allows the force distribution during membrane deflection to be optimized and local stress peaks in the material to be reduced. The load acting on the membrane can be distributed more evenly. The microsensor can be made more robust. The membrane can be deflected more homogeneously.
[0011] The microsensor can be used in mobile devices, especially mobile electronic devices, preferably mobile end devices such as smartphones, tablets, AR glasses, VR glasses, or in vehicles, mobile robots and / or industrial equipment.
[0012] The microsensor can be a microelectromechanical sensor. The microsensor can be a pressure sensor for measuring a pressure quantity as the measurand. The diaphragm can be deflected depending on the measurand, especially the pressure quantity. The microsensor can be a microphone for measuring R.416709
[0013] - 2 -
[0014] acoustic vibrations. The membrane can be deflected depending on the acoustic vibrations.
[0015] The microsensor can be capacitive or piezoresistive. The microsensor can measure the quantity capacitively or piezoresistively. The capacitive microsensor can have at least one electrode on the membrane, which is movable depending on the deflection of the membrane relative to at least one counter electrode.
[0016] The membrane can be polygonal, rectangular, square, elliptical, oval, or round when viewed laterally. The membrane can be made of silicon, particularly polysilicon. The membrane can have a length and a width. The length can be equal to or greater than the width. For example, in a rectangular membrane, the length might be the dimension of one side and the width the dimension of a side perpendicular to it. In an elliptical membrane, the length might be the dimension of a major axis and the width the dimension of a minor axis.
[0017] A protective medium, in particular a protective gel, can be applied to the membrane to protect it from environmental influences and to transmit the measured quantity from the environment of the microsensor to the membrane.
[0018] In the layered structure, at least one intermediate layer, spaced in the normal direction from the membrane, can be connected to the anchor elements. The intermediate layer can be made of silicon, in particular polysilicon. An electrode connected to the membrane can be arranged within the intermediate layer.
[0019] At least one of the anchor elements can overlap the center of the membrane with respect to its length. At least one of the anchor elements can overlap the center of the membrane with respect to its width.
[0020] In a preferred embodiment of the invention, it is advantageous if the, in particular non-linear, edge contour is formed along a width or length of each anchor element facing the membrane. The anchor elements can be oriented with their length or width perpendicular to the membrane edge. R.416709
[0021] - 3 -
[0022] The anchor elements can be aligned with their length or width perpendicular to a tangent formed at the anchor element and the membrane edge.
[0023] The edge contour can form the non-linear membrane edge by mutually laterally offset individual edge contours of the adjacent anchor elements.
[0024] In a particular embodiment of the invention, it is advantageous if the end face of a single anchor element facing the membrane, and having a width or length, has a non-linear edge contour. The edge contour of the respective anchor element can be curved. At least two laterally adjacent anchor elements can each have a curved edge contour.
[0025] In a particular embodiment of the invention, it is advantageous if the anchoring elements completely surround the membrane in a plane having the normal direction as its normal, and if the majority of the anchoring elements form a boundary contour that creates a nonlinear membrane edge. In this case, all anchoring elements that completely surround the membrane with respect to the plane can form a boundary contour that creates a nonlinear membrane edge.
[0026] In a preferred embodiment of the invention, the anchor elements fully surround the membrane in a plane having the normal direction as its normal, and the majority of the anchor elements are aligned with their respective lengths parallel to the membrane edge adjacent to the respective anchor elements. In this respect, all anchor elements that fully surround the membrane with respect to the plane can be aligned with their respective lengths parallel to the membrane edge adjacent to the respective anchor elements.
[0027] In a preferred embodiment of the invention, it is advantageous if the anchor elements are laterally offset from one another along the membrane edge. Further anchor elements can be arranged laterally offset from the anchor elements forming the membrane edge in a direction away from the membrane edge. R.416709
[0028] - 4 -
[0029] A preferred embodiment of the invention is advantageous in which stiffening elements are attached to the membrane to stiffen any deflection of the membrane. The individual stiffening elements can be beam-shaped.
[0030] In a particular embodiment of the invention, it is advantageous if the stiffening elements are arranged extending along the membrane in a first lateral direction and have a changing dimension in a second lateral direction perpendicular to the first lateral direction. The first direction can span the length of the membrane.
[0031] In an advantageous embodiment of the invention, the anchor elements in a second layer offset in the normal direction to the first layer have a smaller width and / or length than those in the first layer. This allows the material stresses in the layer structure to be laterally relieved and reduces local stress peaks that are aligned in the normal direction to each other.
[0032] In a preferred embodiment of the invention, a cover layer is applied to the membrane in the normal direction above the membrane and opposite the first layer with respect to the membrane. This cover layer overlaps the membrane laterally towards the center of the membrane. The lateral overlap can have an overlap length that is at least ten times, preferably twenty times, greater than the thickness of the cover layer. The overlap length can be equal to or less than one-third of the lateral distance between the anchor elements and stiffening elements on the membrane.
[0033] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations.
[0034] Character description
[0035] The invention is described in detail below with reference to the illustrations. Specifically, the illustrations show: R.416709
[0036] - 5 -
[0037] Figure 1: A cross-section of a microsensor in a special embodiment of the invention.
[0038] Figure 2: A top view of a microsensor in another special embodiment of the invention.
[0039] Figure 3: A top view of a microsensor in another special embodiment of the invention.
[0040] Figure 4: A top view of a microsensor in another special embodiment of the invention.
[0041] Figure 5: A cross-section of a microsensor in a further special embodiment of the invention.
[0042] Figure 6: A cross-section of a microsensor in a further special embodiment of the invention.
[0043] Figure 1 shows a cross-section of a microsensor in a specific embodiment of the invention. The microsensor 10 is, for example, a microelectromechanical pressure sensor 12 for the capacitive measurement of a measured quantity, preferably a pressure quantity. The microsensor 10 comprises a boundary region 14, which surrounds a free region 16 and is formed by several individual anchor elements 18. The anchor elements 18 each extend with a width 20 and a length greater than the width 20 through a layer structure 24 built up in the normal direction 22.
[0044] The microsensor 10 comprises a membrane 26, which is cantilevered to the anchor elements 18 with a uniform membrane thickness 28 and can be deflected in the normal direction 22, depending on the measured quantity, here the pressure quantity, starting from a membrane edge 32 formed by the connection 30 and along the connection 30 to the anchor elements 18, into the free area 16. The membrane 26 is part of a membrane layer 34, which is made, for example, of silicon. In the normal direction 22 below the membrane layer 34, a first layer 36 of the layer structure 24 is arranged, in which connection elements 38 connected to the membrane 26 are implemented. Adjacent to this first layer 36 in the normal direction 22 is an upper electrode layer 40, which is made, for example, of polysilicon and in which a [missing information] is located.
[0045] - 6 -
[0046] Membrane 26 is connected to electrode 42 via the connecting elements 38 and is movable by deflection of the membrane 26. Furthermore, an upper reference electrode 44, laterally offset from electrode 42, is provided in the upper electrode layer 40. This upper reference electrode 44 is independent of the deflection of the membrane 26 and is rigid. A second layer 46 is provided in the normal direction 22 below the upper electrode layer 40, in which support structures 48 for the upper reference electrode 44 are provided. Adjacent to the second layer 46 in the normal direction 22 is a lower electrode layer 50, in which a lower reference electrode 52 and a counter electrode 54, laterally offset from and laterally overlapping with electrode 42, are provided.
[0047] The anchor elements 18 have a uniform width 20 and uniform length in the normal direction 22 completely along the first layer 36 of the layer structure 24 adjacent to the membrane 26 in the normal direction 22, as well as in the second layer 46 and in the lower electrode layer 50.
[0048] Figure 2 shows a top view of a microsensor in a further specific embodiment of the invention. The individual anchor elements 18 are arranged offset from one another in a first lateral direction 56 perpendicular to the normal direction 22 and in a second lateral direction 58 perpendicular to this. The membrane 26 is connected to the anchor elements 18, thereby forming a membrane edge 32 by the connection 30 and along the connection 30 of the membrane 26 to the anchor elements 18, from which the membrane 26 can be deflected into the free area 16 depending on the measured quantity, in particular the pressure quantity.
[0049] The anchor elements 18 extend through the layered structure with a width 20 and a length 60, where the length 60 is greater than the width 20. The anchor elements 18 are offset from one another along the membrane edge 32 and completely surround the membrane 26 in a plane with the normal direction 22 as its normal. All anchor elements 18 are aligned with their respective lengths 60 parallel to the membrane edge 32 adjacent to the respective anchor elements 18. This allows the material stresses to be distributed more evenly when the membrane 26 is deflected and reduces local stress peaks in the material. R.416709
[0050] - 7 -
[0051] The anchor elements 18 are offset from one another along the membrane edge 32 and additionally offset from one another in a respective lateral direction 62', 62" away from the membrane edge 32 and arranged parallel to one another. The first anchor elements 64, which form the membrane edge 32 along a membrane length L, are oriented perpendicularly to the second anchor elements 66, which form the membrane edge 32 along a membrane width B. The lateral direction 62' in which the first anchor elements 64 are offset from one another is thus perpendicular to the lateral direction 62" in which the second anchor elements 66 are offset from one another. The laterally offset first anchor elements 64 can have different lengths 60. Likewise, the second anchor elements 66 can have different lengths 60. Similarly, the width 20 of the first anchor elements 64 can be of different dimensions.Likewise, the width 20 of the second anchor elements 66 can be different.
[0052] Figure 3 shows a top view of a microsensor in a further specific embodiment of the invention. The anchor elements 18 form an edge contour 68, which creates a fully nonlinear membrane edge 32 of an elliptical membrane 26. The edge contour 68 is formed here, in particular, along a width 20 of each anchor element 18 facing the membrane 26. At least some of the individual anchor elements 18 have an end face 70 facing the membrane 26 and having a width 20, with a nonlinear edge contour 68. This allows the material stress to be distributed more evenly along the membrane edge 32. The structural integrity of the membrane 26, especially under dynamic loads, can be improved. The material stresses can be distributed away from a center 72 of the membrane edge 32 along the membrane length L towards corner regions 74 of the membrane edge 32.
[0053] The first anchor elements 64, which form the membrane edge 32 along the membrane length L, are oriented perpendicularly to the second anchor elements 66, which form the membrane edge 32 along a membrane width B as a dimension of the secondary axis. The lateral direction 62' in which the first anchor elements 64 are offset from each other is thus perpendicular to the lateral direction 62", in which the second anchor elements 18 are offset. R.416709
[0054] - 8 -
[0055] Figure 4 shows a top view of a microsensor in a further specific embodiment of the invention. The structure of the microsensor 10 is similar to that of Figure 2, however, the membrane 26 has beam-shaped stiffening elements 76 for stiffening any deflection of the membrane 26. The stiffening elements 76 are arranged extending along the membrane 26 in a first lateral direction 78 spanning the membrane length, wherein the stiffening elements 76 have a changing dimension 82 in a second lateral direction 80 perpendicular to the first lateral direction 78.
[0056] Figure 5 shows a cross-section of a microsensor in a further specific embodiment of the invention. The microsensor 10 is constructed as in Figure 1, except that, in the normal direction 22 above the membrane 26 and the first layer 36 opposite the membrane 26, a cover layer 84 is applied to the membrane 26, overlapping the membrane 26 laterally by an overlap length D. This reduces the material stress at the membrane edge 32 when the membrane 26 is deflected.
[0057] Figure 6 shows a cross-section of a microsensor in a further specific embodiment of the invention. The microsensor 10 in Figure 6 is similar to that in Figure 1; however, the anchor elements 18 in the second layer 46, which is offset in the normal direction 22 to the first layer 36, have a smaller width 86 than the width 20 in the first layer 36. This allows the material stresses in the layer structure 24 to be laterally relieved and reduces local stress peaks of the material stresses that are aligned with each other in the normal direction 22.
Claims
R.416709 - 9 - Patent claims 1. Microsensor (10) for measuring a measurand, comprising a boundary region (14) surrounding a free region (16) formed by several individual anchor elements (18) which are laterally offset to each other perpendicular to a normal direction (22) and each extend with a width (20) and a length (60) greater than the width (20) through a layer structure (24) built up in the normal direction (22), at least one membrane (26) which is freely connected to the anchor elements (18) with a uniform membrane thickness (28) and which is deflectable in the normal direction (22) depending on the measured quantity starting from a membrane edge (32) formed by the connection (30) and along the connection (30) to the anchor elements (18) into the free region (16), wherein the individual anchor elements (18) have a uniform width (20) and uniform length (60) in the normal direction (22) completely along at least one first layer (36) of the layer structure (24) adjacent to the membrane (26) in the normal direction (22), characterized by the fact that the anchor elements (18) with their respective length (60) are aligned parallel to the membrane edge (32) adjacent to the anchor elements (18) and / or form a boundary contour (68) forming a non-linear membrane edge (32) at least on a boundary section of the membrane edge (32).
2. Microsensor (10) according to claim 1, characterized in that the edge contour (68) is formed along a width (20) or length (60) of each of the anchor elements (18) facing the membrane (26).
3. Microsensor (10) according to claim 1 or 2, characterized in that the area facing the membrane (26) and the width (20) or length (60) R.416709 - 10 - The end face (70) of a single anchor element (18) has a non-linear edge contour (68).
4. Microsensor (10) according to one of the preceding claims, characterized in that the anchoring elements (18) completely surround the membrane (26) in a plane having the normal direction (22) as the normal and the majority of the anchoring elements (18) form a boundary contour (68) forming a non-linear membrane edge (32).
5. Microsensor (10) according to one of the preceding claims, characterized in that the anchoring elements (18) completely surround the membrane (26) in a plane having the normal direction (22) as the normal and the majority of the anchoring elements (18) are aligned with their respective length (60) parallel to the membrane edge (32) adjacent to the respective anchoring elements (18).
6. Microsensor (10) according to one of the preceding claims, characterized in that the anchor elements (18) are laterally offset from each other along the membrane edge (32).
7. Microsensor (10) according to one of the preceding claims, characterized in that stiffening elements (76) are attached to the membrane (26) to stiffen a deflection of the membrane (26).
8. Microsensor (10) according to claim 7, characterized in that the stiffening elements (76) are arranged extending in a first lateral direction (78) along the membrane (26) and have a changing dimension (82) in a second lateral direction (80) perpendicular to the first lateral direction (78).
9. Microsensor (10) according to one of the preceding claims, characterized in that the anchor elements (18) in a second layer (46) offset in the normal direction (22) to the first layer (36) have a smaller width (86) and / or length than in the first layer (36). R.416709 - 11 - 10. Microsensor (10) according to one of the preceding claims, characterized in that a cover layer (84) is applied to the membrane (26) in the normal direction (22) above the membrane (26) and opposite the first layer (36) in relation to the membrane (26), which laterally overlaps the membrane (26).