Micromechanical sensor with an electrically decoupled upper electrode

Abstract

The invention relates to a micromechanical sensor (10) for capacitive measurement of at least one environmental variable, having an edge region (30) of a bounded cavity (32), a diaphragm (28) which at least sectionally spans the cavity (32) and which is displaceable in a vertical direction into the cavity (32) as a function of the environmental variable, at least one measurement capacitor (12) which changes as a function of the environmental variable, the measurement capacitor having a first upper electrode (Mt) which is coupled to the diaphragm (28) and an opposite first lower electrode (Mb), at least one reference capacitor (K1, K2, K3, K4) which has a second upper electrode (Nt) and an opposite second lower electrode (Nb) which are respectively fixed relative to the edge region (30), wherein the second upper electrode (Nt) is electrically uncoupled from the diaphragm (28).

Description

Technical Field

[0001] The present invention relates to a micromechanical sensor as described in the preamble of claim 1. Background Technology

[0002] DE 10 2020 214 757 A1 describes a capacitive pressure sensor having a diaphragm adjacent to a hermetically sealed internal volume within a housing component of the pressure sensor. The diaphragm can deform when a pressure difference exists between the internal and external pressures. Measuring electrodes are mounted on the diaphragm, and the position of the measuring electrodes can be changed by the arching of the diaphragm. This change in position results in a change in the measuring capacitance formed by the measuring electrodes and their associated measuring pairs. Additionally, the sensor includes at least one unchanging reference capacitor having two reference electrodes fixed to the housing component, and the position of the reference electrodes is not changed by the arching of the diaphragm. Thus, the reference capacitance remains unaffected by diaphragm movement. Summary of the Invention

[0003] According to the present invention, a micromechanical sensor having the features of claim 1 is proposed. This reduces or prevents stray capacitance in the output potential. Environmental parameters can be detected more accurately and reliably. Measurements can be performed with greater insensitivity to external electromagnetic influences.

[0004] The sensor can be a pressure sensor. The pressure sensor can be an absolute pressure sensor, especially a barometer-type pressure sensor or a differential pressure sensor. The sensor can be a capacitive pressure sensor. The sensor can be a microelectromechanical (MEMS) sensor. The environmental parameter can be fluid pressure, especially water pressure and / or air pressure.

[0005] The diaphragm can be deflected according to the fluid pressure. The diaphragm can be received indirectly or directly on the edge region.

[0006] The cavity can be bounded by its edge region at least with respect to a direction perpendicular to the vertical. The cavity can be filled with fluid. A reference fluid pressure can exist within the cavity. The cavity can be a vacuum.

[0007] Cavities can be formed as recesses within layers or in layered structures. Edge regions can be the edges of adjacent cavities in layers or layered structures. Membranes can be integrally implemented with layers or layered structures.

[0008] The designations of the upper and lower electrodes refer to the vertical direction. The first lower electrode can be fixed relative to the edge region. The first lower electrode can be vertically opposite the first upper electrode. The vertical spacing between the first upper and lower electrodes can be varied depending on the membrane offset.

[0009] The first lower electrode and / or the second lower electrode may be disposed on a carrier element. The carrier element may form a substrate or be disposed on a substrate. An edge region may be received on the carrier element. The edge region may be securely connected to the carrier element. The carrier element may be made of silicon, polysilicon, glass, silicon nitride, or silicon dioxide.

[0010] The first and / or second lower electrode may include a conductive layer, particularly a polysilicon layer and / or a metal layer. The first and / or second electrodes may be disposed on a carrier element. An insulating layer may be disposed between the carrier element and the first and / or second lower electrode. The insulating layer may be made of silicon nitride or silicon dioxide.

[0011] The first upper electrode, the first lower electrode, the second upper electrode, and / or the second lower electrode may be arranged at least partially, preferably completely, about a direction perpendicular to the vertical direction or about two directions that are respectively perpendicular to the vertical direction and perpendicular to each other, overlapping the membrane.

[0012] In a preferred embodiment of the invention, it is advantageous that the second upper electrode is electrically decoupled from the first upper electrode. The first upper electrode and the diaphragm may have the same potential.

[0013] A preferred configuration of the invention is advantageous, in which a first upper electrode has a first input potential and a second upper electrode has a second input potential. An input voltage can be applied between the first and second input potentials. The input voltage can be a pre-defined power supply voltage, particularly an AC voltage, a pulse voltage (e.g., a rectangular wave voltage), or a DC voltage.

[0014] A preferred configuration of the invention is advantageous in which the first lower electrode and the second lower electrode are electrically connected to each other and have the same potential. This suppresses stray capacitance between the lower electrodes of the measuring capacitor and the reference capacitor.

[0015] In a particular configuration of the invention, it is advantageous that the potentials of the first and second lower electrodes constitute the output potential. The first and second input potentials can shield the output potential from external electromagnetic influences. The output potential can form an output voltage with a reference potential, particularly a ground potential. The output voltage can be correlated with environmental parameters via diaphragm offset and changes in the spacing of the measuring capacitors.

[0016] The output potential can form an output voltage relative to a reference potential, especially a ground potential.

[0017] In a particular embodiment of the invention, it is advantageous that the measuring capacitor and the reference capacitor are electrically connected in series. An output potential can be applied between the measuring capacitor and the reference capacitor. An input voltage can be applied across both the measuring capacitor and the reference capacitor. Thus, a bridge circuit, for example, having two measuring capacitors and two reference capacitors, can be implemented through such a further configuration.

[0018] A preferred configuration of the invention is advantageous in which the second upper electrode of the reference capacitor is received on one side and has a suspended region extending from the receiving point. The second upper electrode of the reference capacitor can be received by at least one support member. The support member can be oriented toward or away from the first upper electrode with respect to the suspended region.

[0019] In an advantageous embodiment of the invention, the first upper electrode, the first lower electrode, the second upper electrode, and the second lower electrode are arranged entirely within the cavity. The electrical connections of the first lower electrode, the second upper electrode, and / or the second lower electrode can be guided at least partially below the edge region, away from the cavity. The electrical connections can be implemented at least partially as buried conductor layers.

[0020] A preferred configuration of the invention is advantageous in which the first lower electrode is completely surrounded by the potential of the second lower electrode of a separate reference capacitor. The separate reference capacitor may have a second upper electrode having the same potential as the second lower electrode of the reference capacitor.

[0021] In a particular embodiment of the invention, it is advantageous that the first lower electrode is electrically connected via the second upper electrode of another reference capacitor. The potential at the first lower electrode can be applied via the second upper electrode of the other reference capacitor. The potential of the first lower electrode can be applied spatially across the second lower electrode of the other reference capacitor via the second upper electrode of the other reference capacitor. The first lower electrode, the second upper electrode of the other reference capacitor, and the second lower electrode of the reference capacitor can be electrically connected to each other and have the same potential.

[0022] Other advantages and advantageous configurations of the invention are derived from the description and figures. Attached Figure Description

[0023] The present invention will now be described in detail with reference to the accompanying drawings. The drawings show in detail: Figure 1 : A top view of a micromechanical sensor in a particular embodiment of the present invention.

[0024] Figure 2 :along Figure 1 The cross-section of AA in the diagram.

[0025] Figure 3 :along Figure 1 The cross-section of BB in the diagram.

[0026] Figures 4 to 7 Top views of the upper and lower electrodes of the micromechanical sensor in another particular embodiment of the present invention.

[0027] Figure 8 : A top view of the upper electrode of a micromechanical sensor in another particular embodiment of the present invention.

[0028] Figure 9 : A top view of a micromechanical sensor in another particular embodiment of the present invention.

[0029] Figure 10 :along Figure 9 The cross-section of AA in the diagram.

[0030] Figure 11 : A top view of a micromechanical sensor in another particular embodiment of the present invention. Detailed Implementation

[0031] Figure 1 A top view of a micromechanical sensor according to a particular embodiment of the invention is shown. The micromechanical sensor 10 is preferably a capacitive pressure sensor for capacitively measuring at least one environmental parameter, preferably a fluid pressure as environmental pressure on a diaphragm that can be offset in the vertical direction according to the environmental parameter. The diaphragm of the sensor and the edge region receiving the diaphragm are hidden here.

[0032] The micromechanical sensor 10 includes a measuring capacitor 12 that varies according to environmental parameters. This measuring capacitor has a first upper electrode Mt and an opposing first lower electrode Mb, which is drawn in dashed lines. The first upper electrode is composed of a plurality of electrode elements 14 and is coupled to a diaphragm. The first lower electrode is fixed with respect to an edge region. Therefore, the first upper electrode Mt can move relative to the first lower electrode Mb according to environmental parameters, and the measuring capacitor 12 can vary according to environmental parameters.

[0033] In addition, a total of four reference capacitors are arranged, each having a second upper electrode Nt fixed relative to the edge region and a corresponding second lower electrode Nb. The second upper electrode Nt of the reference capacitor is also composed of multiple individual electrode elements 14, which are fixed vertically spaced from the second lower electrode Nb via a support 16. The first upper electrode Mt is mechanically decoupled from the second upper electrode Nt, and the second upper electrode Nt is mechanically decoupled from the diaphragm.

[0034] Here, the first lower electrode Mb and the second lower electrode Nb are respectively implemented in a flat manner.

[0035] The second upper electrode Nt of the first reference capacitor K1 and the second upper electrode Nt of the second reference capacitor K2, which is opposite to the first reference capacitor K1 in the first direction R1, are fixed on one side by a support member 16 and have a suspended region 18 extending from the support member 16. The support member 16 faces the first upper electrode Nt with respect to the suspended region 18. The second upper electrode Nt of the third reference capacitor K3 and the second upper electrode Nt of the fourth reference capacitor K4, which is opposite to the third reference capacitor K3 in the second direction R2 perpendicular to the first direction R1, are fixed on both sides by the support member 16.

[0036] A first input potential P1 is applied to the first upper electrode Mt, and especially to the diaphragm. A second input potential P2 is applied to the second upper electrode Nt of the first and second reference capacitors K1 and K2, forming an input voltage with the first input potential P1. The second input potential P2 is applied through the electrode element 14 of the second reference capacitor K2, which extends outward along the first direction R1 and forms a contact area 20. Here, the support 16 is conductive and transmits the second input potential P2 to the first conductor line L1 (shown here in dashed lines) arranged vertically below the second upper electrode Nt, which extends along the second direction R2, and the conductor line L1 transmits the input potential P2 to the second lower electrode Nb of the third and fourth reference capacitors K3 and K4, on which the second input potential P2 is also applied. The second conductor line L2 (shown here in dashed lines) is arranged opposite to the first conductor line L1 about the first direction R1. The support 16 of the second reference capacitor K2 is electrically connected to the second conductor line L2.

[0037] An output potential PA exists on the second upper electrode Nt of the third and fourth reference capacitors K3 and K4, on the second lower electrode Nb of the first and second reference capacitors K1 and K2, and on the first lower electrode Mb of the measuring capacitor 12. The output potential PA is applied through the contact area 22, shown here in dashed lines, to which the third conductor line L3 is electrically connected. The third conductor line L3 connects to the second lower electrode Nb of the first and second reference capacitors K1 and K2. The first portion 24 of the support 16 of the second upper electrode Nt of the third reference capacitor K3 is electrically connected to the third conductor line L3. The third conductor line L3 transmits the output potential PA to the second lower electrode Nb of the first and second reference capacitors K1 and K2. A fourth conductor line L4 is arranged opposite to the third conductor line L3 about the second direction R2 and is also connected to the second lower electrode Nb of the first and second reference capacitors K1 and K2. The first portion 24 of the support 16 of the second upper electrode Nt of the fourth reference capacitor K4 is electrically connected to the fourth conductor line L4.

[0038] The first conductor line, the second conductor line, the third conductor line, and the fourth conductor line L1, L2, L3, and L4 are all arranged entirely within the cavity 32.

[0039] The second portion 26 of the support 16 for the second upper electrode Nt of the third reference capacitor K3 is electrically connected to the first lower electrode Mb. The second portion 26 of the support 16 for the second upper electrode Nt of the fourth reference capacitor K4 is also electrically connected to the first lower electrode Mb. Thus, the output potential PA is transmitted from the contact region 22 via the first portion 24 of the support 16 for the second upper electrode Nt of the third reference capacitor K3 to the second upper electrode Nt of the third reference capacitor K3, and via the second portion 26 of the support 16 for the second upper electrode Nt of the third reference capacitor K3 to the first lower electrode Mb, thereby bridging the second lower electrode Nb of the third reference capacitor K3.

[0040] Furthermore, the output potential PA is transmitted via the third conductor line L3 to the second lower electrode Nb of the first reference capacitor K1 and the second lower electrode Nb of the second reference capacitor K2, and from there to the fourth conductor line L4. The output potential PA is transmitted from the fourth conductor line L4 to the second upper electrode Nt of the fourth reference capacitor K4 via the first portion 24 of the support 16 of the second upper electrode Nt of the fourth reference capacitor K4, and via the second portion 26 of the support 16 of the second upper electrode Nt of the fourth reference capacitor K4 to the first lower electrode Mb, thus bridging the second lower electrode Nb of the fourth reference capacitor K4.

[0041] The second upper electrode Nt of each of the first reference capacitor, second reference capacitor, third reference capacitor and fourth reference capacitor K1, K2, K3 and K4 is electrically decoupled from the first upper electrode Mt and the diaphragm 28, respectively.

[0042] The measuring capacitor 12 and the reference capacitor having individual reference capacitors K1, K2, K3, K4 can be electrically connected in series by the configuration shown and illustrated, having: an output potential PA as an abgriff between the measuring capacitor 12 and the reference capacitors, while a first input potential P1 is applied on one side of the measuring capacitor 12 and a second input potential P2 is applied on the other side of the reference capacitors, and thus an input voltage is applied across the measuring capacitor 12 and the reference capacitors.

[0043] Figure 2 It shows along Figure 1The cross-section of AA in the figure. The first upper electrode Mt is composed of a plurality of electrode elements 14 connected to the diaphragm 28. The diaphragm 28 is received on the edge region 30 and spans the cavity 32 defined by the edge region 30. The diaphragm 28 can be deflected from the outside into the cavity 32 according to environmental parameters, and thus the first upper electrode Mt measuring the capacitance 12 moves relative to the fixed first lower electrode Mb, which is arranged on the carrier element 34, in particular on a silicon substrate having an insulating layer.

[0044] The first upper electrode Mt, the first lower electrode Mb, the second upper electrode Nt of the third reference capacitor and the fourth reference capacitors K3 and K4, and the second lower electrode Nb of the third reference capacitor and the fourth reference capacitors K3 and K4 are all arranged within the cavity 32. The first lower electrode Mb and the second lower electrode Nb of the third reference capacitor and the fourth reference capacitors K3 and K4 are arranged on the carrier element 34. The first upper electrode Mt is spaced apart from the first lower electrode Mb in the vertical direction Rv, and the second upper electrode Nt of the third reference capacitor K3 is spaced apart from the second lower electrode Nb of the third reference capacitor K3, and the corresponding situation applies to the fourth reference capacitor K4.

[0045] The first lower electrode Mb is fully implemented and is electrically connected to the second upper electrode Nt of the third and fourth reference capacitors K3 and K4 via support member 16. The first lower electrode Mb is electrically isolated from the second lower electrode Nb of the third and fourth reference capacitors K3 and K4. The contact area 22 applies the output potential PA to the second upper electrode Nt of the third reference capacitor K3 via the first portion 24 of support member 16. The output potential PA is applied to the first lower electrode Mb via the second portion 26 of support member 16.

[0046] Figure 3 It shows along Figure 1 The cross-section of BB in the cavity. The first upper electrode Mt and the first lower electrode Mb of the measuring capacitor 12, the second upper electrode Nt of the first reference capacitor K1 and the second upper electrode Nt of the second reference capacitor K2, and the second lower electrode Nb of the first reference capacitor K1 and the second lower electrode Nb of the second reference capacitor K2 are completely arranged within the cavity 32.

[0047] The second lower electrode Nb of the first reference capacitor K1 is disposed on the carrier element 34. The second upper electrode Nt of the first reference capacitor K1 is electrically connected via the buried layer 35. Except for the electrical connection in the contact area 20, the second upper electrode Nt of the first reference capacitor K1 and the second upper electrode Nt of the second reference capacitor K2 are respectively received on one side of the carrier element 34 via the support member 16 and are spaced apart from the carrier element in the vertical direction Rv.

[0048] Figures 4 to 7Top views of the upper and lower electrodes of a micromechanical sensor according to another particular embodiment of the invention are shown. Figure 4 a) shows the upper electrode with a support, in Figure 4 b) shows the source Figure 1 The lower electrode of the micromechanical sensor 10. For example... Figure 4 As shown in b), the first lower electrode Mb is completely surrounded by the second input potential P2. With respect to the first direction R1, it is surrounded by the first and second conductor lines L1 and L2, and with respect to the second direction R2, it is surrounded by the second lower electrodes Nb of the third and fourth reference capacitors K3 and K4, respectively. The second lower electrodes Nb of the first reference capacitor K1 and the second lower electrodes Nb of the second reference capacitor K2 are electrically connected to each other through the third and fourth conductor lines L3 and L4 and have the same potential as the first lower electrode Mb, which is the output potential PA. The second lower electrodes Nb of the third reference capacitor K3 and the fourth reference capacitor K4, as well as the third and fourth conductor lines L3 and L4, have the second input potential P2.

[0049] like Figure 4 As shown in a), the first lower electrode Mb is electrically connected to the second upper electrode Nt of the third reference capacitor K3. Figure 4 b) on the contact area 22 shown.

[0050] Figure 5 The construction of is different from the following Figure 4 The construction is the same. For example, Figure 5 As shown in b), the first lower electrode Mb is directly and flatly connected to the second lower electrodes Nb of the first and second reference capacitors K1 and K2, respectively. The first and second conductor lines L1 and L2 therefore extend at the edge. A second input potential P2 is applied to the first conductor line L1 via the contact region 20, and also to the second lower electrode Nb of the third reference capacitor K3 and the fourth reference capacitor K4 via this conductor line.

[0051] like Figure 5 As shown in a), the second upper electrode Nt of the third and fourth reference capacitors K3 and K4 is increased at the expense of the area of ​​the second upper electrode Nt of the first and second reference capacitors K1 and K2. The support 16 for the second upper electrode Nt of the first reference capacitor K1 and... Figure 5 b) The first conductor line L1 on the edge side is electrically connected, and the support 16 of the second upper electrode Nt of the second reference capacitor K2 is connected to Figure 5 The second conductor line L2 on the edge side shown in b) is electrically connected.

[0052] Figure 6 The construction of is different from the following Figure 4 The construction is the same. For example, Figure 6 As shown in a), the second upper electrodes Nt of the first reference capacitor, second reference capacitor, third reference capacitor, and fourth reference capacitors K1, K2, K3, and K4 have the same potential, which is the output potential PA in this case. The second input potential P2 is applied at the height of the second upper electrode Nt of the first reference capacitor K1 via the contact area 20 and via the support member 16. For this purpose, a notch is formed in the second upper electrode Nt of the first reference capacitor K1.

[0053] like Figure 6 As shown in b), the output potential PA is applied to the first conductor line L1 and the second conductor line L2 via the third conductor line L3 through the contact area 22, thus giving these conductor lines the output potential PA. Furthermore, the first and second conductor lines L1 and L2 are electrically connected to a fourth conductor line L4, which also has the output potential PA. The first, second, third, and fourth conductor lines L1, L2, L3, and L4 surround the second lower electrode Nb of the first, second, third, and fourth reference capacitors K1, K2, K3, and K4 on their edge sides.

[0054] like Figure 6 As shown in a), the support 16 for the second upper electrode Nt of the first reference capacitor and the second reference capacitors K1 and K2 is arranged on the edge side, and is connected to the support 16 for the second upper electrode Nt of the first reference capacitor and the second reference capacitors K1 and K2. Figure 6 The first conductor line and the second conductor lines L1 and L2 shown in b) are electrically connected.

[0055] Figure 7 The construction of is different from the following Figure 6 The construction is the same. For example, Figure 7 As shown in a), the support 16 for the second upper electrode Nt of the first reference capacitor and the second reference capacitors K1 and K2 is arranged on the inner side, and is connected to the support 16 for the second upper electrode Nt of the first reference capacitor and the second reference capacitors K1 and K2. Figure 7 The first lower electrode Mb is electrically connected as shown in b).

[0056] like Figure 7 As shown in b), the first and second conductor lines are no longer needed, and the second lower electrode Nb of the first and second reference capacitors K1 and K2 is arranged on the edge side. The second input potential P2 is applied directly to the second lower electrode Nb of the first reference capacitor K1 via the contact area 20.

[0057] Figure 8 A top view of the upper electrode of a micromechanical sensor according to another particular embodiment of the invention is shown. This construction differs from the following: Figure 5The construction is the same as in the first reference capacitor 12. The first upper electrode Mt extends towards the edge along the first direction R1, and occupies its space there at the expense of the length of the second upper electrode Nt of the first reference capacitor and the second reference capacitors K1 and K2. As a result, the area of ​​the first upper electrode Mt of the measuring capacitor 12 can be increased.

[0058] Figure 9 A top view of a micromechanical sensor in another particular embodiment of the invention is shown. Figure 9 The construction of the same type differs from the following: Figure 5 The construction is the same. The second upper electrode Nt of the first reference capacitor K1 and the second upper electrode Nt of the second reference capacitor K2 are partially recessed to support the device 36. The support device is used to form a stop element for the maximum displacement of the limiting diaphragm, where the diaphragm and the edge region are hidden.

[0059] Figure 10 Show along Figure 9 The cross-section of AA in the diagram. The support device 36 includes a support element 38 on the diaphragm 28, which can be stopped against a vertically opposite support surface 40 on the carrier element 34. The support surface 40 is preferably grounded or has the same potential as the diaphragm 28. The support element 38 can reinforce the diaphragm 28.

[0060] Figure 11 A top view of a micromechanical sensor in another particular embodiment of the invention is shown. Figure 11 The construction of the same type differs from the following: Figure 6 The construction is the same. The second upper electrode Nt of the first reference capacitor K1 and the second upper electrode Nt of the second reference capacitor K2 are partially recessed to support the device 36. The support device is used to form a stop element for the maximum displacement of the limiting diaphragm, where the diaphragm and the edge region are hidden.

Claims

1. A micromechanical sensor (10) for capacitive measurement of at least one environmental parameter, comprising: The edge region (30) of the boundary cavity (32). A diaphragm (28) that spans at least a section of the cavity (32), the diaphragm being vertically offset into the cavity (32) according to the environmental parameters. At least one measuring capacitor (12) that changes according to the environmental parameters, the measuring capacitor having a first upper electrode (Mt) coupled to the diaphragm (28) and a corresponding first lower electrode (Mb). At least one reference capacitor (K1, K2, K3, K4) has a second upper electrode (Nt) and a corresponding second lower electrode (Nb) fixed relative to the edge region (30). Its features are, The second upper electrode (Nt) is electrically decoupled from the membrane (28).

2. The micromechanical sensor according to claim 1, characterized in that, The second upper electrode (Nt) is electrically decoupled from the first upper electrode (Mt).

3. The micromechanical sensor (10) according to claim 1 or 2, characterized in that, The first upper electrode (Mt) has a first input potential (P1), and the second upper electrode (Nt) has a second input potential (P2).

4. The micromechanical sensor (10) according to any one of the preceding claims, characterized in that, The first lower electrode (Mb) and the second lower electrode (Nb) are electrically connected to each other and have the same potential.

5. The micromechanical sensor (10) according to claim 4, characterized in that, The potentials of the first lower electrode and the second lower electrode (Mb, Nb) are the output potentials (PA).

6. The micromechanical sensor (10) according to any one of the preceding claims, characterized in that, The measuring capacitor (12) and the reference capacitors (K1, K2, K3, K4) are connected in series.

7. The micromechanical sensor (10) according to any one of the preceding claims, characterized in that, The second upper electrode (Nt) of the reference capacitors (K1, K2, K3, K4) is received on one side and has a suspended region (18) extending outward from the receiving point.

8. The micromechanical sensor (10) according to any one of the preceding claims, characterized in that, The first upper electrode (Mt), the first lower electrode (Mb), the second upper electrode (Nt), and the second lower electrode (Nb) are completely arranged within the cavity (32).

9. The micromechanical sensor (10) according to any one of the preceding claims, characterized in that, The first lower electrode (Mb) is completely surrounded by the potential of the second lower electrode (Nb) of the other reference capacitors (K1, K2, K3, K4).

10. The micromechanical sensor (10) according to claim 9, characterized in that, The first lower electrode (Mb) is electrically connected via the second upper electrode (Nt) of the other reference capacitors (K1, K2, K3, K4).

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