Capacitive pressure sensor with a self-supporting sensing structure

Abstract

The invention relates to a capacitive pressure sensor (10) for measuring a pressure quantity, comprising a layer structure (16) formed from several layers (14) stacked along a normal direction (12) and at least one sensing structure (18) comprising at least a first membrane (20) deflectable depending on the pressure quantity and a second membrane (22) deflectable depending on the pressure quantity spaced apart therefrom.a first capacitance (24) that is variable depending on the deflection of the first membrane (20) with a first counter electrode (26) and a first measuring electrode (28) coupled to the first membrane (20) and movable relative to the first counter electrode (26) while changing the first capacitance (24), and a second capacitance (30) that is variable depending on the deflection of the second membrane (22) with a second counter electrode (32) spaced apart from the first counter electrode (26) and a second measuring electrode (34) coupled to the second membrane (22) and movable relative to the second counter electrode (32) while changing the second capacitance (30), wherein the at least one sensing structure (18) is received in at least one recess (46) of the layer structure (16) and is connected to the layer structure (16) via at least one connection area (48) in a cantilevered manner.

Description

[0001] The invention relates to a capacitive pressure sensor according to the preamble of claim 1. State of the art

[0002] In DE 10 2022 213 217 A1 a micromechanical pressure sensor is described, comprising a first pressure sensor arrangement with a first diaphragm and a first capacitor with a first measuring electrode and a first counter electrode arranged on the first diaphragm and a second pressure sensor arrangement with a second diaphragm and a second capacitor with a second measuring electrode and a second counter electrode arranged on the second diaphragm. Disclosure of the invention

[0003] According to the present invention, a capacitive pressure sensor with the features of claim 1 is proposed. This reduces parasitic electrical influences on the sensing structure. For example, electrical leakage currents between the first and second capacitances can be reduced. The pressure sensor can be more robust and less sensitive to environmental influences such as water and humidity, as well as to stresses such as material stresses and electromagnetic interference. The pressure sensor can measure pressure more accurately over a wider pressure range. With the required measurement sensitivity, the pressure sensor can be designed to be more cost-effective and with a more compact design.

[0004] The pressure sensor can be a microelectromechanical pressure sensor. It can measure absolute ambient pressure or relative pressure. The pressure sensor can be mechanically and electrically connected to an ASIC chip.

[0005] The invention further relates to a sensor assembly comprising the described pressure sensor and an ASIC chip mechanically and electrically connected thereto. The pressure sensor and the ASIC chip can be mechanically and / or electrically connected to each other via a wire bonding process, flip-chip bonding, or a wafer bonding process.

[0006] The pressure value can be the ambient pressure of the pressure sensor. The ambient pressure can be a fluid pressure, in particular atmospheric pressure.

[0007] The sensing structure and / or the layer structure can have at least one reference capacitance. The reference capacitance is constant with respect to the pressure. The first and second measuring capacitances, and in particular the reference capacitance, can be electrically interconnected in a measuring bridge circuit, for example in a Wheatstone bridge circuit.

[0008] The layered structure can be arranged on a substrate, particularly silicon. The substrate can be machined by mechanical surface treatment, for example grinding and / or polishing, particularly to reduce material thickness. A multilayer metallization can be applied to the layered structure, particularly to a side of the layered structure facing away from the substrate.

[0009] The layers can consist of polysilicon, in particular doped polysilicon. The layers can contain and / or consist of at least one dielectric, in particular silicon dioxide and / or silicon nitride. The layers can have or form etch-stop structures. The layers can be electrically conductive and / or electrically insulating.

[0010] The first diaphragm can be positioned at a distance from the first measuring electrode. The second diaphragm can be positioned at a distance from the second measuring electrode. The first and second diaphragms can have at least one identical dimension and / or at least one different dimension. The first and second diaphragms can have the same or different mechanical stiffness and, with respect to the same pressure applied to the diaphragms, exhibit different deflections from a rest position.

[0011] The first and second measuring electrodes can have the same or different dimensions. The first and second counter electrodes can have the same or different dimensions. The first measuring electrode and the first counter electrode can have the same or different dimensions. The second measuring electrode and the second counter electrode can have the same or different dimensions. At least one of the membranes, measuring electrodes, and / or counter electrodes can have the same or different dimensions. The distance between the first measuring electrode and the first membrane can be the same or different from the distance between the second measuring electrode and the second membrane. The distance between the first measuring electrode and the first counter electrode can be the same or different from the distance between the second measuring electrode and the second counter electrode.The distance between the counter electrodes can be the same or different from the distance between at least one of the measuring electrodes and the associated membrane and / or at least one of the measuring electrodes and the associated counter electrode.

[0012] With identical geometric and mechanical design of the first and second diaphragms, and by providing two equally sized measuring capacitances with equally sized electrode areas, the maximum measurement sensitivity of the pressure sensor for a given pressure range can be doubled. The first diaphragm can be electrically and / or mechanically coupled to the first measuring electrode. The second diaphragm can be electrically and / or mechanically coupled to the second measuring electrode. The first diaphragm can be electrically decoupled from the first measuring electrode. The second diaphragm can be electrically decoupled from the second measuring electrode.

[0013] The recess can be connected to a pressure sensor environment via at least one access channel, and in particular at least one additional lateral channel connecting at least the access channel and the recess, for transmitting the pressure value from the sensor environment to the recess. The geometric shape and / or position of the access channel and / or the lateral channel can be arbitrarily selected. The access channel and / or the lateral channel can include shielding means, i.e., means and / or structures that act as a barrier against particles and / or liquids from the sensor environment towards the recess.

[0014] At least one sensing structure can be accommodated in one or more recesses of the layer structure and cantilevered to the layer structure via the connection area or several such connection areas. Multiple such sensing structures can also be provided. Some or all of the sensing structures can have the same or different pressure measuring ranges.

[0015] The sensing structure or structures, the recess or recesses and / or the attachment area or attachment areas can have any shape, any surface, any cross-section and / or any cross-sectional area.

[0016] In a preferred embodiment of the invention, it is advantageous if the first and second membranes have a common electrical potential. The first and second measuring electrodes can have a common or different electrical potential. The first and second membranes can have separate electrical potentials. The first and / or second membranes can have a common electrical potential.

[0017] In a preferred embodiment of the invention, the first membrane and / or the second membrane, on the one hand, and at least one wall of the layer structure bounding the recess, on the other hand, have a common electrical potential. The first and second membranes, as well as at least the majority of the walls bounding the recess, can have a common electrical potential.

[0018] In a particular embodiment of the invention, it is advantageous if the first membrane and the first measuring electrode have a common electrical potential. A connection mechanically linking the first membrane to the first measuring electrode can be electrically conductive.

[0019] In a preferred embodiment of the invention, the second membrane and the second measuring electrode are provided to have a common electrical potential. A connection mechanically linking the second membrane to the second measuring electrode can be electrically conductive.

[0020] In a preferred embodiment of the invention, it is advantageous if the first counter electrode and the second counter electrode are mechanically connected to each other, at least partially, without forming an intervening gap. The first and second counter electrodes can be mechanically connected over their entire surface and, at the same time, be electrically conductive or electrically decoupled from each other. This increases the mechanical stability of the assembly consisting of the first and second counter electrodes. The first and second counter electrodes can be mechanically coupled to each other via at least one spacer structure, forming the at least one gap. The at least one spacer structure can comprise a spacer rib. The at least one spacer structure can be electrically conductive or insulating.

[0021] The first and second counter electrodes can be arranged directly adjacent to each other with respect to the normal direction, in particular without the interposition of further components.

[0022] In a preferred embodiment of the invention, it is advantageous if the first counter electrode and the second counter electrode have separate electrical potentials. The first and second counter electrodes can be mechanically connected but electrically isolated from each other.

[0023] In a particular embodiment of the invention, it is advantageous if the sensing structure is elastically connected to the layer structure in at least one connection area via at least one spring suspension. The sensing structure can be elastically and freely attached to the layer structure via the spring suspension. The spring suspension can have any shape, cross-section, and / or cross-sectional area.

[0024] In a particular embodiment of the invention, it is advantageous if the sensing structure is electrically connected to at least one bond pad on the surface of the layer structure via at least one connection area. One or more electrical connections can extend across the connection area. If the sensing structure is connected to the layer structure via several connection areas, the sensing structure can be electrically connected to the bond pad(s) via all or only some of the connection areas.

[0025] In a particular embodiment of the invention, it is advantageous if, with respect to the normal direction, the first membrane, the first measuring electrode, the first counter electrode, the second counter electrode, the second measuring electrode, and the second membrane are arranged one above the other, particularly directly, and especially without the interposition of at least one further component. The first and second membranes can be arranged on opposite sides of the sensing structure with respect to the normal direction and form part of the boundary surface of the sensing structure. The first membrane, the first measuring electrode, the first counter electrode, the second counter electrode, the second measuring electrode, and the second membrane can be arranged laterally, i.e., in a plane that has the normal direction as its normal, at least partially, particularly mainly, preferably completely, overlapping.This allows the sensing structure to have the smallest possible lateral surface area for a given measuring capacity.

[0026] The first counter electrode can be positioned between the second counter electrode and the first membrane with respect to the normal direction, and / or the second counter electrode can be positioned between the first counter electrode and the second membrane with respect to the normal direction. The first measuring electrode can be positioned between the first counter electrode and the first membrane with respect to the normal direction, and / or the second measuring electrode can be positioned between the second counter electrode and the second membrane.

[0027] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations. Character description

[0028] The invention is described in detail below with reference to the illustrations. These show, in detail: Fig. 1: A cross-section of a capacitive pressure sensor in a special embodiment of the invention. Fig. 2 to 4: A cross-section of a capacitive pressure sensor during successive manufacturing steps. Fig. 5: A cross-section of a capacitive pressure sensor in a further special embodiment of the invention. Fig. 6: A cross-section of each alternative spring suspension at the pressure sensor made of Fig. 5. Fig. Figures 7 to 14: A cross-section of a capacitive pressure sensor in each of a further specific embodiment of the invention.

[0029] Fig. Figure 1 shows a cross-section of a capacitive pressure sensor in a specific embodiment of the invention. The capacitive pressure sensor 10 comprises a layered structure 16 formed from several layers 14 stacked along a normal direction 12. The layers 14 can be formed at least partially from polysilicon and / or at least partially from a dielectric, for example silicon dioxide, silicon nitride, or silicon-rich nitride. The pressure sensor 10 comprises at least one sensing structure 18 with a first diaphragm 20 that can be deflected depending on the pressure magnitude and a second diaphragm 22 located directly opposite it and also deflectable depending on the pressure magnitude. To measure different pressure ranges, the first and second diaphragms 20, 22 can, for example, have different mechanical stiffnesses, on which the deflection at a given pressure magnitude depends.

[0030] Furthermore, the sensing structure 18 comprises a first capacitance 24, which is variable depending on the deflection of the first membrane 20, with a first counter electrode 26, and a first measuring electrode 28, which is mechanically and electrically coupled to the first membrane 20 and movable relative to the first counter electrode 26, thereby changing the first capacitance 24. The sensing structure 18 further comprises a second capacitance 30, which is variable depending on the deflection of the second membrane 22, with a second counter electrode 32 spaced apart from the first counter electrode 26, and a second measuring electrode 34, which is mechanically and electrically coupled to the second membrane 22 and movable relative to the second counter electrode 32, thereby changing the second capacitance 30.

[0031] The first membrane 20 is spaced apart from the first measuring electrode 28 and mechanically and electrically connected to it via coupling bridges 36. The second membrane 22 is also spaced apart from the second measuring electrode 34 and mechanically and electrically connected to it via further coupling bridges 38. The first counter electrode 26 and the second counter electrode 32 are spaced apart from each other and mechanically coupled to each other via spacers 40, in this case spacer structures, forming a free space 42. The spacers 40 comprise, in particular, spacer bridges 44 made of electrically non-conductive SiRiN, a modified silicon nitride with a higher silicon content. Alternatively, the first counter electrode 26 and the second counter electrode 32 can be mechanically connected to each other, at least partially, by spacer bridges 44 made of electrically conductive polysilicon.

[0032] With respect to the normal direction 12, the first diaphragm 20, the first measuring electrode 28, the first counter electrode 26, the second counter electrode 32, the second measuring electrode 34, and the second diaphragm 22 are arranged directly above one another. With respect to the normal direction 12, the first counter electrode 26 is arranged between the second counter electrode 32 and the first diaphragm 20, and the second counter electrode 32 is arranged between the first counter electrode 26 and the second diaphragm 22. With respect to the normal direction, the first measuring electrode 28 is arranged between the first counter electrode 26 and the first diaphragm 20, and the second measuring electrode 34 is arranged between the second counter electrode 32 and the second diaphragm 22.

[0033] The sensing structure 18 is accommodated in a recess 46 of the layer structure 16 and cantilevered to the layer structure 16 via at least one connection area 48. This allows, for example, influences from the assembly and connection technology, in particular mechanical material stresses of the layer structure 16, to be largely decoupled from the sensing structure 18. The influence of the material stresses in the layer structure 16 on the measurement of the pressure can thus be reduced. The recess 46 is bounded with respect to the normal direction 12 above the sensing structure 18, that is, on the side of the recess 46 facing away from the membrane 20, by a cover layer 50 of the layer structure 16 and perpendicular to this by a wall 52 extending over several layers 14 of the layer structure 16. Optionally or alternatively, the provision of a cover layer, at least in the area of ​​the sensing structure 18, can be omitted.

[0034] The first measuring electrode 28, the first counter electrode 26, the second measuring electrode 34, and the second counter electrode 32 are contained in a gas-tightly sealed inner region 56 of the sensing structure 18, formed by the first membrane 20, the second membrane 22, and the side walls 54 connecting the first and second membranes 20 and 22. The first membrane 20, the second membrane 22, and the side walls 54 thus form a boundary surface 58 of the sensing structure 18 with respect to the recess 46.

[0035] The sensing structure 18 is electrically connected to structures of the layered assembly 16 via conductive traces over the cantilevered connection area 48. The first membrane 20, the first measuring electrode 28, the second membrane 22, the second measuring electrode 34, the cover layer 50, at least partial areas of the polysilicon layers 60, the wall 52 of the layered assembly 16 adjacent to the recess 46, the side walls 54, and / or a substrate 84 preferably have a common electrical potential. This allows for an improvement, for example, in the EMC behavior of the sensing structure 18 and the first and second capacitors 24, 30, and better protects the pressure measurement from electrical influences in the vicinity of the sensing structure 18.Outside the connection area 48, a trench structure 62 is constructed between the sensing structure 18 and the layer structure 16, which decouples the sensing structure 18 from the layer structure 16 and enables the cantilevered connection.

[0036] The first counter electrode 26 is connected via a first electrical connection 64 in the layer structure 16 to a first electrical interface 66, for example a first bond pad 68, on the surface 70 of the pressure sensor 10, and the second counter electrode 32 is connected via a second electrical connection 72 in the layer structure 16 to a second electrical interface 74, for example a second bond pad 76, on the surface 70.

[0037] The common electrical potential of the first membrane 20, the first measuring electrode 28, the second membrane 22, the second measuring electrode 34, the partial areas of the applied layers 60 made of polysilicon, the cover layer 50, the wall 52 of the layer structure 16 adjacent to the recess, the side walls 54 and / or the substrate 84 is electrically connected to the surface 70 via a further electrical interface 78, for example a further bond pad 80.

[0038] The electrical insulation between the first counter electrode 26 on the one hand and the layer structure 16 and the side walls 54 on the other hand, as well as the electrical insulation between the second counter electrode 32 on the one hand and the layer structure 16 and the side walls 54 on the other hand, is made possible by insulating areas 82, in particular made of SiRiN.

[0039] Outside the area containing the sensing structure 18, the layer structure 16 is applied directly to the substrate 84, particularly silicon, at least partially and / or preferably over its entire surface. Within the area containing the sensing structure 18, an etch stop layer, preferably made of silicon dioxide, is located between the layer structure 16 and the substrate 84. The etching process through the substrate 84, which creates the free area 86 extending the recess 46, is stopped on this etch stop layer. In a subsequent process step, the etch stop layer is removed, as already implemented here. Ambient pressure from the pressure sensor 10 can be transmitted to the sensing structure 18 via the extended free area 86 of the recess 46.

[0040] Fig. Figures 2 to 4 show a cross-section of a capacitive pressure sensor 10, each during successive manufacturing steps. Fig. 2 is the pressure sensor 10 in a manufacturing step for the production of the in Fig. The pressure sensor 10 shown in Figure 1 is shown. The free areas 87a, 87b were created, for example, by removing sacrificial layer material, in particular silicon dioxide. Etch stop structures 88 made of silicon dioxide and / or SiRiN and / or further etch stop structures 94 made of silicon and / or further etch stop structures 96 made of SiRiN can be used. The etch stop structures 88 can prevent uncontrolled etching progress into the top layer 50 during the production of trench structures, which are defined by an etch stop layer 90 and introduced into the layer structure 16 starting from the etch stop layer 90 and moving towards the top layer 50.The further etch stop structures 94 made of silicon, preferably polysilicon, and the further etch stop structures 96 made of SiRiN can be provided within the layer structure 16 to protect areas of sacrificial layer material from etching and / or to connect areas mechanically and electrically conductively and / or electrically non-conductively.

[0041] The etch stop structures 88 can, for example, consist of a layer sequence comprising a layer 91 of SiRiN and a layer 92 of silicon dioxide, wherein SiRiN can prevent etching of the silicon dioxide layer 92 during sacrificial layer etching to form the free areas 87a, 87b, and silicon dioxide serves as an etch stop layer 90 for the trench etching process used to expose the sensing structure 18, forming the trench structure (not yet described here) through the layer structure 16. Alternatively, the free areas 87a, 87b can also be created only after the trench structure has been produced by removing sacrificial layer material, in particular silicon dioxide.

[0042] The defined removal of sacrificial layers can be achieved using etch access points (not shown here) through the cover layer 50 and using optional predefined channel structures within the layer structure 16, which also includes the cover layer 50. The etch access points can be located within and / or outside a region of the sensing structure 18, passing through the cover layer 50, and can be sealed after the sacrificial layers have been removed. The sealing of the etch access points can be achieved by depositing at least one sealing layer 93, wherein the at least one sealing layer 93 and any further optionally provided sealing layers can be electrically conductive and / or electrically non-conductive.Alternatively, the etching accesses can also be closed by melting silicon using a laser, whereby, for example, any gas and / or gas mixture and / or a particularly low cavity internal pressure independent of the closing process can be generated in the free areas 87a, 87b.

[0043] Fig. Figure 3 shows one of the manufacturing steps. Fig. In a subsequent manufacturing step, for example, after the deposition of the sealing layer 93 onto the cover layer 50, trenches 100 are introduced into the sealing layer 93 and the cover layer 50, starting from the top surface of the sealing layer 93, for the electrical insulation of via structures. The trenches 100 can terminate at an etch stop structure 102 consisting of a layer of silicon dioxide. Furthermore, preferably, a further layer 104 made of a different material is provided on the side of the etch stop structure 102 facing the substrate 84. This layer can act as a stop layer and / or as a moisture barrier, such as SiRiN. Preferably, the etch stop structure 88 and the etch stop structure 102 can have the same layer structure.

[0044] After the trenches 100 have been created, a further layer structure 106 can be applied to the sealing layer 93, which serves at least partially to create the first and second electrical connections 64, 72, the first electrical interface 66, the second electrical interface 74 and / or the further electrical interface 78. The trenches 100 intended for electrical insulation can be completely sealed, at least superficially, with at least one dielectric layer 107 of the further layer structure 106, and the structures serving at least partially to create the first and / or second electrical connections 64, 72, the first electrical interface 66, the second electrical interface 74 and / or the further electrical interface 78 can be electrically insulated from one another.After the production of at least the first and / or second electrical connection 64, 72 and / or the first, second and / or further electrical interface 66, 74, 78, at least one further layer 108 can subsequently be deposited on at least the dielectric layer 107 and act as a moisture barrier. By structuring the further layer 108, electrical contact can be established at least at the first and / or second electrical connection 64, 72 and / or the first, second and / or further electrical interface 66, 74, 78.

[0045] Alternatively, prior to the deposition of the sealing layer 93, trenches 100 can be introduced, starting from the top of the cover layer 50 and passing through it. These trenches serve at least partially to create the first and second electrical connections 64, 72, the first electrical interface 66, the second electrical interface 74, and / or the further electrical interface 78, and / or as etching access points for removing sacrificial layers. During subsequent sacrificial layer etching, a layer of silicon dioxide can also be removed in the area of ​​an etch stop structure 102. By depositing at least one electrically non-conductive sealing layer 93, the trenches 100 intended for electrical insulation can be completely sealed, at least superficially.

[0046] In Fig. 4 is a step in the manufacturing process from Fig. Figure 3 shows a further manufacturing step in which a free area 86 is introduced into a region of the substrate 84 spanning the sensing structure 18, starting from the side of the substrate 84 facing away from the sensing structure 18. The etching process for creating the free area 86 in the substrate 84 stops here at the etch stop layer 90 made of silicon dioxide, which is provided at least in the region of the sensing structure 18 and arranged between the layer structure 16 and the side of the substrate 84 facing the layer structure 16. In areas where the etch stop layer 90 has been removed, a trenching process implemented for introducing the free area 86 can be continued, and at least one trench structure 62 can be introduced into the layer structure 16 of the pressure sensor 10 on the front side of the substrate 84, stopping at the optional etch stop structures 88 on / in the top layer 50 of the layer structure 16.This allows the sensing structure 18 of the pressure sensor 10 to be self-supporting and stress-decoupled from the surrounding layer structure 16 and / or the substrate 84, for example, from material stresses introduced into the layer structure 16 and acting on the pressure sensor 10 by means of a mounting and connection technique. Following the trenching process, the etch stop layer 90 is removed (not shown here), as is the optional removal of the etch stop layer 91 and, if necessary, the removal of any sacrificial layer of silicon dioxide that has not yet been removed from the recess 46.

[0047] Fig. Figure 5 shows a cross-section of a capacitive pressure sensor 10 in a further specific embodiment of the invention. The pressure sensor 10 is similar to the one shown in Figure 5. Fig. 1 except for the following essential differences. The sensing structure 18 is elastically connected to the layer structure 16 via at least one spring suspension 110 of the at least one connection area 48 in a self-supporting manner.

[0048] This can lead to even better decoupling of material stresses introduced into the sensing structure 18 from the layer structure 16. The spring suspension 110 is formed at least partially from the layers 14 of the layer structure 16.

[0049] The spring suspension 110, for example, has a rectangular cross-section with walls 53 arranged around a cavity 111, consisting of layers 14 of the polysilicon layer structure 16 and the first and / or second electrical connection 64, 72 arranged therein for electrical contacting the at least first counter electrode 26 and / or the second counter electrode 32. However, the cross-section of the spring suspension 110 is not limited to a rectangular shape, but can have any geometric shape and cross-sectional area. Likewise, the geometric dimensions of the spring suspension 110 can be chosen and implemented arbitrarily.

[0050] Along the normal direction 12, at least one dielectric layer 14a of the layer structure 16, for example made of silicon dioxide, is arranged above and below the cavity 111 between the cavity 111 and the walls 53 of the spring suspension 110. This layer at least partially delimits the cavity 111 in the normal direction 12. Between the dielectric layer 14a, which at least partially delimits the cavity 111, and the cavity 111 itself, a further dielectric layer 14b of the layer structure 16, for example made of SiRiN, is arranged as a protective layer. This layer protects the layer 14a, which at least partially delimits the cavity 111, from etching during the production of the cavity 111. Within the cavity 111, at least one conductor track structure consisting of polysilicon of the layer structure 16 is arranged on the side of the further dielectric layer 14b facing the cavity 111, spaced apart and electrically insulated from the walls 53 of the spring suspension 110.

[0051] Fig. Figure 6 shows a cross-section of one alternative spring suspension of the pressure sensor. Fig. 5. As in Fig. As shown in Figure 6 a), the spring suspension 110 can have different configurations with respect to the arrangement and material of the layers 14 of the layer structure 16 of the spring suspension 110. Within the layer structure 16, the layers 14 can, for example, be made of polysilicon and further layers 14b of a dielectric, here in particular SiRiN.

[0052] In Fig. 6 a) In the spring suspension 110, an additional dielectric layer is removed, creating cavities 113 at least between the further layer 14b and the walls 53 of the spring suspension 110. A further layer 14b, which carries the first and / or second electrical connection 64, 72 designed as a conductor structure, is at least partially connected to the walls 53 of the spring suspension 110.

[0053] In Fig. 6 b) in the spring suspension 110, a dielectric layer is replaced by additional reinforcements 116 made of silicon.

[0054] In Fig. 6 c) In the spring suspension 110, a recess 118 is provided in the direction of the cavity 111, starting from at least one surface of the spring suspension 110 which is perpendicular to the normal direction 12.

[0055] In Fig. 6 d) the spring suspension 110 does not have all layers of the layer structure 16, which in particular with respect to the normal direction 12 results in a spring suspension 110 with a smaller cross-sectional area, here a lower height with respect to the normal direction 12, than the spring suspension made of Fig. 6 a), b), c) is implemented. By adjusting at least one lateral dimension of the spring suspension 110 perpendicular to the normal direction 12 relative to the spring suspension in Fig. 6 a), b), c) a spring suspension 110 with a more elastic or flexible mechanical connection of the sensing area can be implemented.

[0056] In Fig. 6 e) In the spring suspension 110, at least one additional support 122 is arranged between the first and second electrical connections 64, 72, which are arranged directly opposite each other in the cavity 111 and are designed as a conductor track structure, and which mechanically connects the conductor tracks of the first and second electrical connections 64, 72 at least in certain areas and is preferably electrically non-conductive.

[0057] Alternatively, the cavity 111 can be at least partially filled with a dielectric layer of the layer structure.

[0058] Fig. Figures 7 to 14 show a cross-section of a capacitive pressure sensor, each in a further specific embodiment of the invention. Fig. 7 shows a pressure sensor 10, which is from Fig. 5, except for the following essential differences. Pressure access to the sensing structure 18 is provided via at least one access channel 124 in the layer structure 16, which has an opening 123. This access channel extends from the front face of the pressure sensor 10, which has a first electrical interface 66, a second electrical interface 74, and / or a further electrical interface 78, towards the substrate 84 and preferably terminates on a layer 126 of silicon dioxide within the layer structure 16. Alternatively, and not shown here, the access channel 124 can open directly into the recess 46 surrounding the sensing structure 18. The at least one access channel 124 can have any shape and / or any geometric dimensions and / or be arranged at least partially surrounding the contour of the sensing structure 18 and / or at a distance from the sensing structure 18.

[0059] The at least one access channel 124 is circumferentially bounded, at least partially, by lateral etched polysilicon boundaries, arranged laterally spaced from the recess 46 in a plane having the normal direction 12 as its normal, and connected to the recess 46 via lateral channels 128. The lateral channels 128 can be formed at least between two adjacent polysilicon layers 14 or, alternatively (not shown here), at least between two structures within a polysilicon layer 14, and comprise shielding elements 130, in particular consisting of the material of the layers 14, for example, polysilicon and / or SiRiN, which act as a barrier against particles and / or liquids, for example, water. The integration of the access channel 124 into the layer structure 16 can be accomplished in various ways.This example shows that the access channel 124 was introduced into the layer structure 16 in a final manufacturing step, after all sacrificial layers of silicon dioxide in the area of ​​the recess 46 and in the area of ​​the access channel 124 had already been removed. Optionally, the access channel 124 can be introduced into the layer structure 16, and starting from the access channel 124, the sacrificial layers of silicon dioxide in the lateral channels 128 and in the recess 46 surrounding the sensing structure 18 can be removed.

[0060] In Fig. 8 shows a pressure sensor 10, which is from Fig. 5, except for the following essential differences. The access channel 124 in the layer structure 16 is created starting from the back side 132 of the substrate 84 facing away from the layer structure 16. The sacrificial layers of silicon dioxide were previously removed from the recess 46 and in the area of ​​the access channel 124.

[0061] Alternatively, starting from the access channel 124 introduced into the layer structure 16 from the back side 132 of the substrate 84, the sacrificial layers of silicon dioxide in the lateral channels 128 and in the recess 46 surrounding the sensing structure 18 can be removed.

[0062] Alternatively or in addition to the ones in the Fig. 7 and Fig. In addition to the shielding means 130 shown in Figure 8 and arranged at least between two adjacent layers 14 of polysilicon, further shielding means can also be arranged as a barrier within the at least one access channel 124.

[0063] Fig. 9 shows the pressure sensor 10 from Fig. 8, but additionally with solder balls 134 arranged on the first bond pad 68, the second bond pad 76 and the further bond pad 80. The solder balls 134 enable flip-chip mounting, whereby the pressure sensor 10 can be mechanically and electrically connected to corresponding bond pads, for example on an ASIC chip. Alternatively, an electrical connection to the first bond pad 68, the second bond pad 76 and the further bond pad 80 of the pressure sensor 10 can also be made via a wire bonding process.

[0064] In Fig. 10 is the one in Fig. Figure 9 shows a pressure sensor 10 attached to an ASIC chip 135 by a flip-chip connection 136. Before or after making the connection between the pressure sensor 10 and the ASIC chip 135, an underfill can be provided and the sensor assembly 138 can be encased by potting, for example using film-assisted molding, in such a way that pressure access via the access channel 124 into the recess 46 is enabled.

[0065] Alternatively, and not shown, a substrate containing pressure sensors can be mechanically and electrically connected to a substrate containing at least one ASIC chip by applying a wafer bonding process, and optionally, self-contained cavities can be formed between the facing surfaces of the connected substrates, which may contribute to a volume expansion of the recess 46 and / or the interior 56. The substrates containing pressure sensors and / or ASIC chips can, for example, be silicon wafers.

[0066] In Fig. 11 shows a pressure sensor 10, which is from Fig. 8 is similar except for the following essential differences. The first and second counter electrodes 26, 32 are connected to each other, at least partially, and in particular over their entire surface, either mechanically and electrically, or non-conductively. This further increases the mechanical stability of the composite of the first and second counter electrodes 26, 32.

[0067] To prevent an electrical short circuit between the first measuring electrode 28 and / or the second measuring electrode 34 and the first counter electrode 26 and / or the second counter electrode 32 in the event of an overload, electrically non-conductive stop structures 144 are arranged on the first counter electrode 26 and / or on the second counter electrode 32 and / or on the first measuring electrode 28 and / or on the second measuring electrode 34. The stop structures 144 can also be made electrically conductive or omitted if it can be ensured that an electrical short circuit between the first and second measuring electrodes 28, 34 and the first and second counter electrodes 26, 32 has no negative impact on an electrical evaluation circuit. To minimize the mechanical stress on the components in the event of an overload, the stop structures 144 can preferably be arranged in the area of ​​the coupling webs 36, 38.

[0068] The pressure sensor 10 in Fig. 12 is similar to the one from Fig. 8 except for the following essential differences. The first and second counter electrodes 26, 32 are mechanically and electrically connected to each other via spacers 140, in particular made of polysilicon.

[0069] The pressure sensor 10 in Fig. 13 is similar to the one from Fig. 8 except for the following essential differences. The first and second counter electrodes 26, 32 are mechanically and electrically conductive or electrically non-conductively connected to each other exclusively via edge-side spacer webs 142 arranged laterally outside of the first and second membranes 20, 22 and preferably in the area of ​​a membrane clamping of the first and second membranes 20, 22. This allows the second measuring electrode 34 attached to the second membrane 22 to bear against the second counter electrode 32 when a limit pressure of the pressure quantity is exceeded, without exerting a force on the first counter electrode 26, which, together with the first membrane 20 and the first measuring electrode 28 attached to it, may be used, for example, to measure a higher pressure range of the pressure quantity.

[0070] This ensures that the second diaphragm 22, intended for the lower pressure range, is reliably protected from damage in the event of an overload, while still allowing for the measurement of higher pressure values. To prevent an electrical short circuit between the first measuring electrode 28 and / or the second measuring electrode 34 and the first counter electrode 26 and / or the second counter electrode 32 in the event of an overload, electrically non-conductive stop structures 144 are arranged on the first counter electrode 26 and / or the second counter electrode 32 and / or on the first measuring electrode 28 and / or the second measuring electrode 34. Alternatively, the stop structures 144 can be made electrically conductive or omitted if it is ensured that an electrical short circuit between the first and second measuring electrodes 28, 34 and the first and second counter electrodes 26, 32 has no negative impact on an electrical evaluation circuit.

[0071] Furthermore, sacrificial layers made of silicon dioxide in the sensing structure 18 can be removed before the application of the sealing layer 93. The necessary etching access within the sensing structure 18 is sealed after the sacrificial layer etching by at least one layer 146, which has a low etch rate compared to an etching medium used to remove the sacrificial layer in the recess 46, such as SiRiN. A seal with multiple sealing layers is also conceivable, wherein a layer 146 with the lowest possible etch rate compared to an etching medium used to remove the sacrificial layer in the recess 46 is preferably provided between the sacrificial layer in the recess 46 and further sealing layers. For example, when using a sacrificial layer made of silicon dioxide, the layer 146 protecting the further sealing layers from etching can consist of SiRiN.

[0072] The pressure sensor 10 in Fig. 14 is similar to the one from Fig.8 except for the following essential differences. The first and second membranes 20, 22 are electrically decoupled from each other by an insulating layer 148 and can have different electrical potentials. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 213 217 A1

[0002]

Claims

[1] Capacitive pressure sensor (10) for measuring a pressure quantity, comprising a layer structure (16) formed from several layers (14) stacked along a normal direction (12) and at least one sensing structure (18) comprising at least a first membrane (20) which can be deflected depending on the pressure quantity and a second membrane (22) which can be deflected depending on the pressure quantity, spaced apart from it.a first capacitance (24) that is variable depending on the deflection of the first membrane (20) with a first counter electrode (26) and a first measuring electrode (28) coupled to the first membrane (20) and movable relative to the first counter electrode (26) while changing the first capacitance (24), and a second capacitance (30) that is variable depending on the deflection of the second membrane (22) with a second counter electrode (32) spaced apart from the first counter electrode (26) and a second measuring electrode (34) coupled to the second membrane (22) and movable relative to the second counter electrode (32) while changing the second capacitance (30). characterized by , that at least one sensing structure (18) is received in at least one recess (46) of the layer structure (16) and is connected to the layer structure (16) in a self-supporting manner via at least one connection area (48). [2] Capacitive pressure sensor (10) according to claim 1, characterized by, that the first and second membranes (20, 22) have a common electrical potential. [3] Capacitive pressure sensor (10) according to claim 1 or 2, characterized by , that the first membrane (20) and / or the second membrane (22) on the one hand, and at least one wall (52) of the layer structure (16) limiting the recess (46) on the other hand, have a common electrical potential. [4] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the first membrane (20) and the first measuring electrode (28) have a common electrical potential. [5] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the second membrane (22) and the second measuring electrode (34) have a common electrical potential. [6] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by, that the first counter electrode (26) and the second counter electrode (32) are mechanically firmly connected to each other at least in certain areas without forming an intermediate free space (42). [7] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the first counter electrode (26) and the second counter electrode (32) have separate electrical potentials. [8] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the sensing structure (18) is elastically connected to the layer structure (16) in the at least one connection area (48) via at least one spring suspension (110) in a self-supporting manner. [9] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the sensing structure (18) is electrically connected via the connection area (48) to at least one bond pad (68, 76, 80) on the surface of the layer structure (16). [10] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by , that the first counter electrode (26) is arranged between the second counter electrode (32) and the first membrane (20) and the second counter electrode (32) is arranged between the first counter electrode (26) and the second membrane (22), wherein the first measuring electrode (28) is arranged between the first counter electrode (26) and the first membrane (20) and the second measuring electrode (34) is arranged between the second counter electrode (32) and the second membrane (22). [11] Capacitive pressure sensor (10) according to claim 10, characterized by , that with respect to the normal direction (12) the first membrane (20), the first measuring electrode (28), the first counter electrode (26), the second counter electrode (32), the second measuring electrode (34) and the second membrane (22) are arranged directly on top of each other. [12] Capacitive pressure sensor (10) according to any one of the preceding claims, characterized by, that the recess (46) is connected via an access channel (124) having at least one opening (123) to a sensor environment of the pressure sensor (10) for the transmission of the pressure quantity from the sensor environment to the recess (46). [13] Capacitive pressure sensor (10) according to claim 12, characterized by , that the access channel (124) and / or at least one channel (128) connecting the access channel (124) and the recess (46) is shielding means (130) acts as a barrier against particles and / or liquids from the sensor environment towards the recess (46).

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