Microsensor comprising stiffening means on a membrane

Abstract

The invention relates to a microsensor (10) for measuring a measurement variable, having an edge region (14), at least one membrane (16) having a membrane surface (22) which adjoins the edge region (14), is self-supporting, is spanned by a first main axis (18) and a second main axis (20), and has a total length (26) along the first main axis (18), and which can be deflected in a normal direction (24) of the membrane surface (22) depending on the measurement variable, and stiffening means (34) connected to the membrane surface (22) which are arranged, running along the first main axis (18), at least in a first section (36) between a first edge section (38) of the edge region (14) as far as a centre (40) of the total length (26), and which have a width (52) in the direction of the second main axis (20), wherein the width (52) of the stiffening means (34) increases precisely once at least in a first direction (54) along the first main axis (18), starting from the first edge section (38) to the centre (40), and then decreases again precisely once.

Description

[0001] R.416710

[0002] - 1 -

[0003] Description

[0004] title

[0005] Microsensor with stiffening agent on a membrane

[0006] The invention relates to a microsensor according to the preamble of claim 1.

[0007] State of the art

[0008] In DE 102022 203 215 A1 a microsensor is described which has a membrane having a first and second principal axis and to which a stiffening element extending along the first principal axis is attached for damping a membrane movement.

[0009] Disclosure of the invention

[0010] According to the present invention, a microsensor with the features of claim 1 is proposed. This allows the microsensor to measure the measured quantity more sensitively. The signal-to-noise ratio when measuring the quantity by the microsensor can be increased. The microsensor can be designed to be more cost-effective and space-saving. The diaphragm deflection can be achieved over a large, planar area.

[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.416710

[0013] - 2 -

[0014] acoustic vibrations. The membrane can be deflected depending on the acoustic vibrations.

[0015] The microsensor can be a capacitive or piezoresistive microsensor. The microsensor can measure the quantity capacitively or piezoresistively.

[0016] The first and second principal axes can be angled to each other, in particular orthogonal. The first and / or second principal axis can be straight or curved.

[0017] The membrane can be round. The first principal axis can run along the circumferential direction and the second principal axis along the radial direction.

[0018] The membrane can be oval, rectangular, polygonal, square, or trapezoidal.

[0019] The total length of the membrane area can be less than, equal to, or greater than the total width of the membrane area running along the second principal axis.

[0020] The first principal axis can be perpendicular to the first boundary section. The second principal axis can be parallel to the first boundary section. The first boundary section can be straight or curved, especially round.

[0021] The membrane and the edge area can be made up of one piece or of separate components.

[0022] The stiffening means and the membrane can be constructed at least partially, preferably completely, in one piece or from separate components.

[0023] The first section can span half of the membrane area with respect to the first principal axis.

[0024] The length of the area, with respect to the first principal axis, with increasing width of the stiffening elements, may be greater than, equal to, or less than the length of the area, with respect to the first principal axis, with decreasing width of the stiffening elements. The areas with increasing and decreasing width may differ from any existing R.416710.

[0025] - 3 -

[0026] Areas of constant width relative to length along the first principal axis predominate.

[0027] Furthermore, the total width of the membrane area and / or the thickness of the membrane area running along the second principal axis can increase exactly once and decrease exactly once from the first edge section to the middle of the total length along the first principal axis.

[0028] In a preferred embodiment of the invention, it is advantageous if the stiffening means are further arranged along the first principal axis in a second section between a second edge section of the edge region opposite the first edge section, extending to the midpoint of the overall length along the first principal axis, and have a width in the direction of the second principal axis that initially increases and then decreases in a second direction along the first principal axis from the second edge section towards the midpoint. The second section can span another half of the membrane area with respect to the first principal axis. The first and second sections can span the entire membrane area with respect to the first principal axis.

[0029] In an advantageous embodiment of the invention, the stiffening means of the first and second sections are mirror-symmetrical to each other with respect to an axis of symmetry extending through the center and parallel to the second principal axis. Alternatively, the stiffening means can be asymmetrical with respect to a central axis extending through the center and parallel to the second principal axis.

[0030] In an advantageous embodiment of the invention, the center is spaced apart from the first edge section by a total distance with respect to the first principal axis, and the maximum width of the stiffening means is present at a distance from the first edge section with respect to the first principal axis greater than 30%, preferably greater than 40%, and specifically greater than 50%, of the total distance. A distance between the first or second edge section and the center with respect to the first principal axis can be subdivided into three, in particular equally sized, sub-sections, and the maximum width of the stiffening means of the first or second section can be at least R.416710

[0031] - 4 -

[0032] lie section by section in the middle sub-area and / or the area facing the center in relation to the first principal axis.

[0033] In an advantageous embodiment of the invention, the stiffening means extend from the first edge section in the first direction, beginning with a first width and a second width. The second width can be located, in particular, in the middle with respect to the first principal axis.

[0034] In a preferred embodiment of the invention, it is advantageous if the first width is the minimum width of the stiffening means of the entire first section. This allows the stiffness of the membrane surface adjacent to the first edge section to be reduced, thereby concentrating the deflection of the membrane surface in the edge region.

[0035] In a preferred embodiment of the invention, the second width is greater than the first width. This allows the stiffness of the membrane surface to be higher in the central region than in the area facing the edge, resulting in a large-area, plane-parallel deflection.

[0036] In an advantageous embodiment of the invention, the stiffening means are each subdivided into several individual stiffening elements, each having a width and a length relative to the first principal axis and being spaced apart relative to the first principal axis. The stiffening elements can be spaced apart from the first edge region by a distance relative to the first principal axis. This distance can be greater than the average or maximum distance between the stiffening elements. The stiffening elements can have the same or different lengths relative to each other. The length of the stiffening elements can vary from the first edge region to the center, in particular increasing and decreasing at least once.

[0037] The stiffening means in the first and / or second section may be subdivided into spaced-apart individual stiffening elements with respect to the first principal axis. R.416710

[0038] - 5 -

[0039] In a particular embodiment of the invention, it is advantageous if the minimum width of the stiffening elements is at least three times greater than the mean and / or maximum length of the stiffening elements. At least one stiffening element may have a length that differs from that of the other connecting elements. This connecting element may be located closest to the center with respect to the first principal axis or extend beyond the center.

[0040] In a particular embodiment of the invention, it is advantageous if at least two stiffening elements are connected to each other in the direction of the first principal axis. The stiffening elements can be connected to each other by at least one connecting element running parallel to the principal axis.

[0041] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations.

[0042] Character description

[0043] The invention is described in detail below with reference to the illustrations. These show, in detail:

[0044] Figure 1: A cross-section of a microsensor in a special embodiment of the invention.

[0045] Figures 2 to 7: A top view of a membrane of a microsensor, each in a specific embodiment of the invention.

[0046] Figure 8: A deflection curve of a membrane of a microsensor in another special embodiment of the invention.

[0047] Figure 1 shows a cross-section of a microsensor in a special embodiment of the invention. The microsensor 10 is, for example, a pressure sensor 12 for measuring a pressure quantity and comprises an edge region 14 and a membrane 16 with a cantilevered section adjoining the edge region 14 and defined by a first principal axis 18 and a second principal axis 20. R.416710

[0048] - 6 -

[0049] The membrane surface 22 is stretched and can be deflected in a normal direction 24 depending on the pressure. The membrane surface 22 has a total length 26 along the first principal axis 18.

[0050] The membrane 16 is constructed as a single unit with the edge region 14, for example made of silicon. Support structures 28 are incorporated in the edge region 14, thereby increasing the free volume 30 in the unsupported area 32 below the membrane surface 22.

[0051] The microsensor 10 further comprises stiffening means 34 connected to the membrane 16, which are integrally formed with the membrane 16 and are arranged along the first principal axis 18 in a first section 36 between a first edge section 38 of the edge region 14 to a center 40 of the total length 26 and in a second section 42 between a second edge section 44 of the edge region 14 opposite the first edge section 38 with respect to the first principal axis 18 to the center 40 of the membrane surface 22.

[0052] The stiffening means 34 are in the first and second sections 36, 42 each subdivided into several individual stiffening elements 46 spaced apart with respect to the first principal axis 18, which are formed in one piece with the membrane 16 on a bottom side of the membrane surface 22 with respect to the normal direction 24.

[0053] Figures 2 to 7 show a top view of a membrane of a microsensor, each in a specific embodiment of the invention. Figure 2 illustrates a top view in the normal direction 24 of the membrane surface 22 with the associated stiffening means 34. The stiffening means 34 comprise several stiffening elements 46 spaced apart from one another with respect to the first principal axis 18, which are preferably arranged on a side of the membrane surface 22 facing away from the measured quantity with respect to the normal direction 24.

[0054] The membrane surface 22 has a total length 26 extending along the first principal axis 18, which is greater than a total width 50 extending along the second principal axis 20. The stiffening elements 46 have a width 52 in the direction of the second principal axis 20, which initially rises and then falls again in a first direction 54 along the first principal axis 18 from the first edge section 38 to the center 40. (Further R.416710)

[0055] - 7 -

[0056] The stiffening means 34 exhibit a width 52 that increases in a second direction 56 along the first principal axis 18, extending from the second edge section 44 to the center 40, and then decreases again. The stiffening means 34 of the first and second sections 36, 42 are mirror-symmetrical to each other with respect to an axis of symmetry 58, which extends parallel to the second principal axis 20 through the center 40.

[0057] A total distance 60 between the first edge section 38 and the center 40 with respect to the first principal axis 18 can be subdivided into, specifically, three equally sized sub-areas 62, and the maximum width 64 of the stiffening elements 46 of the first section 36 lies section by section in the middle sub-area 62.1 and in the sub-area 62.2 facing the center 40. Due to the mirror-symmetric arrangement, the maximum width 64 of the stiffening elements 46 of the second section 42 lies in the sub-area 62.3, which is middle with respect to the second section 42, and in the sub-area 62.4 facing the center 40. The maximum width 64 of the stiffening elements 64 is present when the distance from the first edge section with respect to the first principal axis is greater than 50% of the total distance.

[0058] The stiffening means 34 begin at the first section 36 along the first direction 54 starting from the first edge section 38 with a first width 66 and end at a second width 68, wherein the first width 66 is the smallest width 52 of the entire first section 36 and the second width 68 is larger than the first width 66.

[0059] The stiffening elements 46 have a length 70 with respect to the first principal axis 18, wherein in the first and second sections 36, 42 the minimum width 72 of the stiffening elements 46 is at least three times greater than the maximum length 74 of the stiffening elements 46.

[0060] In Figure 3, the stiffening elements 46 are designed as in Figure 2; however, the length 70 of the stiffening elements 46 is variable. While all stiffening elements 46 have the same length 70, a longer stiffening element 76 is arranged in the middle 40 of the membrane surface 22, which in turn has a variable width 52 along its length 70. The minimum width 52 of this stiffening element 76 is at the middle 40 of the total length 26. The longer stiffening element 76 results in a larger R.416710

[0061] - 8 -

[0062] Resistance to bending of the membrane surface 22 and thus to a deflection of the membrane surface 22 that is as parallel to the plane as possible.

[0063] Figure 4 shows stiffening elements 46 as in Figure 1, however, several stiffening elements 46 are connected to each other in a central area 78 of the total length 26 in the direction of the first principal axis 18 by a connecting element 80 running parallel to the first principal axis 18.

[0064] Figure 5 shows a membrane surface 22 as shown in Figure 3, however the longer stiffening element 76 is extended even further in the first and second directions 54, 56.

[0065] In Figure 6, the stiffening elements 46 are designed as in Figure 4, while in contrast, further stiffening elements 82 are connected to each other by the connecting element 80.

[0066] The stiffening elements 46 in Figure 7 are designed as in Figure 2, but divided with respect to the second principal axis 20.

[0067] Figure 8 shows a deflection profile of a membrane of a microsensor in a further specific embodiment of the invention. The deflection profile 84 is shown in comparison with a standard deflection profile 86 of a membrane with conventional stiffening means, in particular as described in the prior art above. The membrane surface exhibits a greater deflection at the edges of the first edge section 38 and the second edge section 44.

[0068] The deflection profile 84 has two inflection points 88 from the first edge section 38 to the center 40, which allow for a deflection that is as parallel to the plane as possible along the total length 26. In a first region 90 along the first principal axis 18 between the first edge section 38 and the first inflection point 92, a high first bending moment 94 and thus a steep slope in the deflection profile 84 result from the low stiffness of the stiffening elements, in particular from their smaller width. In an adjacent second region 96 up to the second inflection point 98, a contrasting second bending moment 100 is generated by a widening of the stiffening elements, which is counteracted by a further R.416710

[0069] - 9 -

[0070] The opposing third bending moment 102 in a subsequent third area 104 including the center 40 counteracts this. This makes it possible to achieve a deflection that is as parallel as possible along the total length 26 compared to the standard deflection pattern 86.

[0071] Figures 3 to 7 show the three areas divided by the inflection points along the first principal axis, in which the first, second and third bending moment acts.

Claims

R.416710 - 10 - Patent claims 1. Microsensor (10) for measuring a measurand, comprising a marginal area (14), at least one membrane (16) with a freely supporting membrane surface (22) adjoining the edge region (14) and spanned by a first principal axis (18) and a second principal axis (20) and having a total length (26) along the first principal axis (18), which is deflectable in a normal direction (24) of the membrane surface (22) depending on the measured quantity and stiffening means (34) connected to the membrane surface (22), which are arranged at least in a first section (36) between a first edge section (38) of the edge region (14) to a midpoint (40) of the total length (26) extending along the first principal axis (18) and which have a width (52) in the direction of the second principal axis (20), characterized by the fact that the width (52) of the stiffening means (34) rises exactly once in at least a first direction (54) along the first principal axis (18) starting from the first edge section (38) to the center (40) and then falls exactly once again.

2. Microsensor (10) according to claim 1, characterized in that the stiffening means (34) are further arranged along the first principal axis (18) in a second section (42) between a second edge section (44) of the edge region (14) opposite the first edge section (38) extending to the center (40) of the total length (26) along the first principal axis (18) and have a width (52) in the direction of the second principal axis (20) which initially rises and then falls again in a second direction (56) along the first principal axis (18) starting from the second edge section (44) to the center (40). R.416710 - 11 - 3. Microsensor (10) according to claim 2, characterized in that the stiffening means (34) of the first and second sections (36, 42) are mirror-symmetric to each other with respect to an axis of symmetry (58) extending through the center (40) and parallel to the second principal axis (20).

4. Microsensor (10) according to one of the preceding claims, characterized in that the center (40) is spaced a total distance away from the first principal axis (18) and the first edge section (38) is spaced a total distance away and the maximum width (64) of the stiffening means is present at a distance from the first edge section (38) with respect to the first principal axis greater than 30%, preferably greater than 40%, specifically greater than 50%, of the total distance.

5. Microsensor (10) according to one of the preceding claims, characterized in that the stiffening means (34) starting from the first edge section (38) in the first direction (54) begin with a first width (66) at the first section (36) and end with a second width (68).

6. Microsensor (10) according to claim 5, characterized in that the first width (66) is the minimum width (72) of the stiffening means (34) of the entire first section (36).

7. Microsensor (10) according to claim 5 or 6, characterized in that the second width (68) is larger than the first width (66).

8. Microsensor (10) according to one of the preceding claims, characterized in that the stiffening means (34) are each divided into several individual stiffening elements (46, 76) having a width (52) and a length (70) with respect to the first principal axis (18) and spaced apart with respect to the first principal axis (18).

9. Microsensor (10) according to claim 8, characterized in that the minimum width (72) of the stiffening elements (46, 76) is at least three times greater than the maximum length (74) of the stiffening elements (46, 76). R.416710 - 12 - 10. Microsensor (10) according to claim 8 or 9, characterized in that at least two stiffening elements (46, 76) are connected to each other in the direction of the first principal axis (18).

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