This application claims the benefit of German Application No. 102017103195.2, filed on Feb. 16, 2017, which application is hereby incorporated herein by reference in its entirety.
Various embodiments relate generally to a microelectromechanical microphone and to a method for producing a microelectromechanical microphone.
Microelectromechanical microphones have acquired great importance in modern communication. During the production of microelectromechanical microphones, a major challenge consists in producing their components with a well-defined shape and arranging them in a well-defined manner relative to one another. A major problem here results from intrinsic mechanical stresses to which the microphone components are subjected and which can lead to a deformation of said components, which in turn makes it more difficult to effect a well-defined relative positioning of the components of a microelectromechanical microphone.
Such stresses may have intrinsic causes and be attributable to thermal and mechanical loads during the production process. Alternatively or additionally, such stresses may arise only as a result of the coupling of different components, for example as a result of the coupling of a plurality of components having mutually different coefficients of thermal expansion.
In order to produce a microelectromechanical microphone having reproducible properties, it is therefore necessary to compensate for the mechanical stresses to which the components of said microphone are subjected.
In accordance with various embodiments, a microelectromechanical microphone is provided which can comprise: a reference electrode, a first membrane arranged on a first side of the reference electrode and displaceable by sound to be detected, and a second membrane arranged on a second side of the reference electrode, said second side being situated opposite the first side of the reference electrode, and displaceable by sound to be detected. A region of one from the first and second membranes that is displaceable by sound relative to the reference electrode, independently of said region's position relative to the reference electrode, can comprise a planar section and also an undulatory section adjoining the planar section and arranged in a region of overlap of the one membrane with the other from the first and second membranes.
In accordance with various embodiments, a method for producing a microelectromechanical microphone includes forming a first membrane, and forming a reference electrode on the first membrane. Forming the first membrane includes producing a first negative mold for the first membrane, wherein the first negative mold for the first membrane includes a first section complementary to a planar section of a region of the first membrane that is displaceable by sound, and a second section complementary to an undulatory section of the region of the first membrane that is displaceable by sound, wherein producing the first negative mold includes depositing a membrane material onto the first negative mold to form the first membrane, and removing the first negative mold, wherein the first membrane is exposed when removing the first negative mold.
Various embodiments will be described in greater detail below by reference to the accompanying drawings, in which:
The term “exemplary” is used here to mean “serving as an example, as an exemplar or for illustration”. Any embodiment or configuration described here as “exemplary” should not necessarily be understood as preferred or advantageous vis-à-vis other embodiments or configurations.
The term “planar” denotes the geometry of a component or of a component section which has a significantly larger extent in a first direction and in a second direction, orthogonal to the first direction, compared with a third direction (thickness direction), orthogonal to the first and second directions.
In the drawings, identical reference signs refer to the same parts in the different views. The drawings serve primarily to illustrate the essential principles of the present disclosure and are therefore not necessarily true to scale.
A region 103 of the first membrane 104 that is displaceable relative to the reference electrode 102, independently of said region's position relative to the reference electrode 102, can comprise a planar section 108 and also an undulatory (e.g. grooved) section 110 adjoining the planar section 108 and arranged in a region of overlap of the first membrane 104 with the second membrane 106. A region 105 of the second membrane 106 that is displaceable relative to the reference electrode 102, independently of said region's position relative to the reference electrode 102, can also comprise a planar section 112 and also an undulatory (e.g. grooved) section 114 adjoining the planar section 112 and arranged in a region of overlap of the second membrane 106 with the first membrane 104. That means, in particular, that the first and second membranes 104, 106, in a respective neutral position in which they are not deflected, can comprise the planar section 108 and 112, respectively, and also the undulatory section 110 and 114, respectively. The region 103, 105 of the first and second membranes 104, 106, respectively, that is displaceable by sound relative to the reference electrode 102 can be a region which is not in permanent physical contact with another structural part.
The first and second membranes 104, 106 in a respective edge region 104r and 106r, can be secured to a holder 116, for example by interposition of respective supporting elements 107a-c. The region 103, 105 of the first and second membranes 104, 106, respectively, that is displaceable by sound can be in particular a region of the first and second membranes 104, 106, respectively, that is different from the respective edge regions 104r, 106r.
The holder 116 can be produced for example from a semiconductor material, for example crystalline silicon. The supporting elements 107a-c can be formed from an electrically insulating material, for example SiOx or/and SixNy. As indicated in
The first membrane 104, the second membrane 106 and the reference electrode 102 can have diameters of less than 1 mm, optionally less than 750 μm, and further optionally less than 100 μm.
The first membrane 104, the second membrane 106 and the reference electrode 102 can be produced at least in sections or even completely from an electrically conductive material, such as, for instance, from a polycrystalline semiconductor material, for example silicon, or from a metal.
An electrically conductive material can be a material having an electrical conductivity of more than 10 S/m, e.g. more than 102 S/m or more than 104 S/m or even more than 106 S/m. An electrically insulating material can be a material having an electrical conductivity of less than 10-2 S/m, e.g. less than 10-5 S/m or even less than 10-7 S/m.
The microphone 100 can be read for example capacitively by a control unit C for example by a first electrical signal, which represents a change—caused by sound—in a first capacitance between the reference electrode 102 and the first membrane 104, or/and for example by a second electrical signal, which represents a change—caused by sound—in a second capacitance between the reference electrode 102 and the second membrane 106, being determined or read out by the control unit C. For this purpose, by way of example, a reference voltage can be applied to the reference electrode 102 and respective operating voltages that are different from the reference voltage can be applied to the first and second membranes 104, 106 by the control unit C and an electric current caused by the change in the first and second capacitances can be measured by the control unit C and the sound pressure can be determined from said electric current. A change in the first or/and in the second capacitance is caused by a displacement of the first and/or second membrane 104, 106 relative to the reference electrode 102.
The first and second membranes 104, 106 can be electrically insulated from one another, optionally in each of their positions relative to the reference electrode 102. This configuration affords the possibility of applying mutually different electrical operating voltages to the membranes 104, 106 and of reading out a first electrical signal, characterizing a change in a first capacitance between the first membrane 104 and the reference electrode 102, separately from a second electrical signal, characterizing a change in a second capacitance between the second membrane 106 and the reference electrode 102. In this configuration, the reference voltage applied to the reference electrode 102 constitutes a common reference voltage for both membranes 104, 106. The reference electrode 102 here can be formed completely from an electrically conductive material. In one exemplary embodiment, the operating voltages to be applied to the membranes 104, 106 can have the same magnitude, but opposite signs, in relation to the reference voltage. As a result, the first and second electrical signals can be combined with one another, for instance subtracted from one another or added together, in order for example to reduce or eliminate common noise contributions. As a result, a differential measurement scheme can be realized, as a result of which a precise measurement of properties of the sound to be detected, such as the sound pressure, for instance, is made possible.
In the case of this construction, the sensitivity of the microphone 100 can be influenced by parasitic capacitances which can be caused for example by parts of the membranes 104, 106 which are not displaceable relative to the reference electrode 102, for instance the edge regions 104r, 106r of the first and second membranes 104, 106, respectively. These parts of the membranes 104, 106 do not yield a useful signal contribution since they are not displaceable relative to the reference electrode 102, but they yield a contribution to the total capacitance if, for instance, the first and second membranes 104, 106 are formed completely from an electrically conductive material and the respective edge regions 104r, 106r therefore also define a capacitor.
In order to reduce the parasitic capacitance caused by said parts of the first or/and second membrane 104, 106, as shown in
As shown in
As indicated in
As can likewise be seen in
By providing an insulation section 111a, 113a on a side of the undulatory section 110 of the first membrane 104 and of the undulatory section 114 of the second membrane 106, respectively, that faces away from a securing section 104r, 106r, it is possible to reduce an influencing of an electric field between the membranes 104, 106 by the respective undulatory sections 110, 114, for instance by reading out only electrical signals from the dynamic sections 104a, 106a of the regions 103, 106 displaceable by sound for the purpose of sound detection.
By providing an insulation section 111b, 113b on a side of the undulatory section 110 of the first membrane 104 and of the undulatory section 114 of the second membrane 106, respectively, that faces a securing section 104r, 106r, it is possible to reduce or prevent mechanical loads on the dynamic sections 104a, 106a of the first and of the second membrane 104, 106, respectively, said mechanical loads resulting from mechanical stresses in the insulation sections 111b, 113b, by virtue of the undulatory sections 110 and 114, as a result of which it is possible in turn to provide for a defined electric field between the first and second membranes 104, 106.
The insulation sections 111a, 111b, 113a, 113b can be formed from an electrically insulating material, for example from an oxide, such as SiOx, for instance, or a nitride, for instance SixNy.
In the case of the microphone 100′ shown in
Even though this is not shown in
reading out a first electrical signal from the microphone 100, 100′, which characterizes a sound-governed displacement of the first membrane 104, 104′ relative to the reference electrode 102, 102′ (12),
reading out a second electrical signal from the microphone 100, 100′, which characterizes a sound-governed displacement of the second membrane 106, 106′ relative to the reference electrode 102, 102′ (14), and
adding the first and second electrical signals or/and subtracting a first electrical signal from the second electrical signal or subtracting the second electrical signal from the first electrical signal in order to determine properties of the sound by which the first membrane 104, 104′ and the second membrane 106, 106′ are displaceable (16).
Reading out the first and second electrical signals can be carried out for example by the control units C and C′ shown in
For the description of common features of the microphones 100 and 100′, reference is made below only to the microphone 100, while reference is made to the microphone 100′ only to elucidate differences between the microphones 100 and 100′.
For a precise measurement of sound properties, a reproducible displacement of the first or/and of the second membrane 104, 106 relative to the reference electrode 102 is necessary in order that an unambiguous relationship exists between a position of the first or/and the second membrane 104, 106 relative to the reference electrode 102 and a specific sound pressure. Such a relationship can be adversely affected by deformations of the first or/and of the second membrane 104, 106 relative to the reference electrode 102 which are not attributable to sound to be detected. As mentioned initially, said deformations can be caused by thermal or mechanical loads during the production of the first or/and of the second membrane 104, 106 or by thermal deformations during operation of the microphone 100. Thermally governed deformations of the first or/and of the second membrane 104, 106 during the operation of the microphone 100 can be caused for example by mutually different coefficients of thermal expansion of the first or/and of the second membrane 104, 106, on the one hand, and of the holder 116 or/and of the supporting elements 107a-c, on the other hand.
By means of the undulatory sections 110, 114 of the first and second membranes 104, 106, respectively, deformations of the first and second membranes 104, 106, respectively, which are caused by such mechanical stresses can be compensated for since the respectively undulatory sections no, 114 can act as spring elements, as a result of which they can compensate for said stresses. As a result, an unambiguous relationship exists between a position of the first and second membranes 104, 106 relative to the reference electrode 102 and a specific sound pressure, as a result of which a precise measurement of a sound pressure becomes possible.
By virtue of the fact that the undulatory section 110 of the first membrane 104 is provided in a region of the first membrane 104 that overlaps the second membrane 106 and that the undulatory section 114 of the second membrane 106 is provided in a region of the second membrane 106 that overlaps the first membrane 104, it is possible to ensure that it is possible to compensate for mechanical stresses in the membranes 104, 106 by virtue of the respective undulatory sections 110, 114 independently of the respective other membrane 104, 106. As a result, mechanical stresses in the membranes 104, 106 can be compensated for more precisely in comparison for example with a microphone in which the membranes are connected by a common connection section to a holder which comprises a spring element embodied as an undulatory section.
As indicated in
In the exemplary microphone 100 shown in
The undulatory section 110 of the first membrane 104 or/and the undulatory section 114 of the second membrane 106 can each comprise at least one hollow projection 110-1, 110-2 or/and 114-1, 114-2, respectively, protruding from the respective planar section 108 or/and 112. In the exemplary microphone 100 shown in
The configuration of the undulatory sections 110, 114 having hollow projections 110-1, 110-2, 114-1, 114-2, in particular having a rectangular cross section, constitutes a construction that is simple overall. Moreover, mechanical stresses occurring in the plane of the planar sections 108 and 112, respectively, can be taken up effectively as a result. The opposite arrangement of the respective hollow projections 110-1, 110-2 and 114-1, 114-2 makes it possible to compensate for stresses in the first and second membranes 104, 106 in a similar manner, such that it is thereby possible to ensure a symmetrical arrangement of the first and second membranes 104, 106 relative to the reference electrode 102.
As furthermore shown in
As likewise shown in
In the case of the exemplary microphone 100 shown in
Alternatively, anti-stick projections may be provided only on the respective sides of the first and second membranes 104, 106 that face the reference electrode 102. In such a configuration, anti-stick projections on the reference electrode 102 can be entirely dispensed with.
The exemplary microphone 100 shown in
At least one spacer 122, a plurality of the spacers 122 or even all the spacers 122 can be produced at least in sections, optionally completely, from an electrically insulating material, for instance from SiOx or SixNy. This configuration is suitable for example if the first and second membranes 104, 106 are electrically insulated from one another. In this case, provision can also be made for forming at least one spacer 122, a plurality of the spacers 122 or even all spacers 122 from a combination of an electrically insulating material with an electrically conductive material, for instance a metal or a polycrystalline semiconductor material, e.g. polycrystalline silicon, as a result of which the capacitive coupling between the first and second membranes 104, 106 is able to be reduced, which coupling may otherwise be problematic since the first and second membranes 104, 106 may be at different electrical potentials.
At least one of the spacers 122, optionally a plurality of the spacers 122, further optionally all spacers 122, can be in permanent physical contact with the first or/and the second membrane 104, 106. As a result, the distance between the first and second membranes 104, 106 can be kept constant independently of whether stresses occurring in the first or the second membrane 104, 106 lead to a tensile or compressive loading.
In one exemplary embodiment, for example in the case of the microphone 100′ shown in
As shown in
In order not to adversely affect the displaceability of the membranes 104, 106, provision can be made, as indicated in
The diameter of a spacer 122 can be approximately 1 to 5 μm. The diameter of a through opening 124 can be larger by 10% to 100%, optionally by 25% to 75%, further optionally by 40% to 60%, than the diameter of a spacer 122 extending through the relevant through opening 124. The above designations may apply, of course, to a plurality of through openings 124 or even to all through openings 124 and the spacers 122 extending through them. These diameters make it possible to limit an air flow through the through openings 124 in the case of a displacement of the membranes 104, 106, which can in turn limit the noise contributions caused by the air flow.
The noise contributions caused by an air flow through the through openings 124 can additionally be reduced by a gas pressure that is lower than the normal pressure (approximately 1013 mbar) being present in a space S defined between the first and second membranes 104, 106, in which space the reference electrode 102 is arranged. The gas pressure in the space S can be less than 100 mbar, optionally less than 50 mbar, further optionally less than 10 mbar. Such a gas pressure additionally makes it possible to reduce the resistance caused by gas, for instance air, in the space S, said resistance counteracting a movement of the membranes 104, 106.
Further exemplary microelectromechanical microphones will be described below by reference to
The exemplary microphone 200 shown in
The exemplary microphone 300 shown in
The exemplary microphone 400 shown in
The microphone 500 shown in
The exemplary microphone 600 in accordance with
The exemplary microphone 700 in accordance with
The exemplary microphone 800 shown in
It goes without saying that the hollow projections 810-1 and 814-1, respectively, need not face in the same direction, but rather can be varied with regard to their orientation in a manner similar to the configurations in accordance with
Virtually no limits are imposed on the concrete configuration of a cross section of a hollow projection. They can be realized with a multiplicity of further cross sections in order to satisfy concrete requirements. A further exemplary microphone 900 is shown in
The hollow projection 910-1 of the first membrane 904 can comprise a first section 910a, which extends substantially orthogonally to a planar section 908 of a region 903 of the first membrane 904 that is displaceable by sound, and a second section 910b adjacent to the first section 910a and having a substantially elliptic or circular cross section.
The hollow projection 914-1 of the second membrane 906 can comprise a first section 914a, which extends substantially orthogonally to a planar section 912 of a region 905 of the second membrane 906 that is displaceable by sound, and a second section 914a adjacent to the first section 914a and having a substantially rectangular cross section. As shown in
Even though this is not shown in
One exemplary method for producing a membrane of a microelectromechanical microphone in accordance with
The starting point of the method may be providing a substrate 1000, for instance a substrate composed of a semiconductor material, such as crystalline silicon, for instance. Onto said substrate, as indicated in
Afterward, as shown in
An opening 1008 can then be formed in the sacrificial layer 1002, which opening exposes an edge region of the membrane material layer 1004 that delimits the through opening or cutout 1006 in the membrane material layer 1004 (
A further sacrificial layer can then be deposited onto the web-shaped section 1004′ and also onto the sacrificial layer 1002 (
As shown in
Afterward, as shown in
Like the membranes described above by reference to
One exemplary method for producing a microelectromechanical microphone having a similar construction to the microphone 900 shown in
The starting point of the method, as shown in
As shown in
Afterward, as shown in
In principle, a membrane material layer could then be applied on the protective layer 2004, in order to form a membrane having an undulatory section embodied as a hollow projection, for which the first cavity 2008 can serve as a negative mold. A hollow projection formed thereby would have a cross section having a substantially rectangular shape.
Alternatively, as shown in
Afterward, as shown in
A first membrane material layer 2014 can then be applied (
By removing a part of the substrate 2000 and the sacrificial layer 2002, it is possible for the first membrane 2014 to be exposed. This will be shown and described in detail later.
As shown in
The membrane sacrificial layer 2020 can additionally serve as a support for forming a reference electrode 2022. The latter can be formed by depositing a layer composed of an electrically conductive material, for instance composed of a metal or a polycrystalline semiconductor material, e.g. silicon (
Afterward, as shown in
Afterward, as shown in
Openings 2030 can then be formed in the reference electrode sacrificial layer 2024, which openings expose an edge region of the second membrane material layer 2026 that delimits the through opening 2028 (
The second membrane material layer 2026 can subsequently be structured, as shown in
Afterward, as shown in
Even though this is not shown explicitly in the figures, the method can furthermore comprise forming at least one through opening in the reference electrode 2022 and also a spacer extending through the through opening in the reference electrode 2022. The spacer can be connected to the first membrane 2014 or/and the second membrane 2026.
forming a first membrane (3002),
forming a membrane sacrificial layer on the first membrane (3004),
forming a reference electrode on the membrane sacrificial layer (3006),
forming a reference electrode sacrificial layer on the reference electrode (3008),
forming a second membrane on the reference electrode sacrificial layer (3010), and
removing a part of the membrane sacrificial layer and a part of the reference electrode sacrificial layer (3012).
forming a negative mold for the first or/and the second membrane, wherein the negative mold comprises a first section, which is complementary to a planar section of a region of the first or/and of the second membrane that is displaceable by sound, and also a second section, which is complementary to an undulatory section of the region of the first or/and of the second membrane that is displaceable by sound (3002-2),
depositing a membrane material onto the negative mold and in the process forming a membrane (3002-4), and
removing the negative mold and in the process exposing the membrane (3002-6).
Numerous exemplary microelectromechanical microphones are described below.
Example 1 is a microelectromechanical microphone which can comprise: a reference electrode, a first membrane arranged on a first side of the reference electrode and displaceable by sound to be detected, and a second membrane arranged on a second side of the reference electrode, said second side being situated opposite the first side of the reference electrode, and displaceable by sound to be detected. A region of one from the first and second membranes that is displaceable by sound relative to the reference electrode, independently of said region's position relative to the reference electrode, can comprise a planar section and also an undulatory section adjoining the planar section and arranged in a region of overlap of the one membrane with the other from the first and second membranes.
In example 2, the subject matter of example 1 can optionally furthermore comprise the fact that a region of the first membrane that is displaceable by sound relative to the reference electrode comprises a planar section and also an undulatory section adjoining the planar section and arranged in a region of overlap with the second membrane, and that a region of the second membrane that is displaceable by sound relative to the reference electrode comprises a planar section and also an undulatory section adjoining the planar section and arranged in a region of overlap with the first membrane.
In example 3, the subject matter of example 1 can optionally furthermore comprise the fact that a region of only a single one from the first and second membranes that is displaceable by sound relative to the reference electrode comprises an undulatory section, and a region of the other from the first and second membranes that is displaceable by sound relative to the reference electrode is embodied as substantially completely planar.
In example 4, the subject matter of any of examples 1 to 3 can optionally furthermore comprise the fact that the undulatory section is delimited by the planar section on all sides.
In example 5, the subject matter of any of examples 1 to 4 can optionally furthermore comprise the fact that the undulatory section has a ring-segment-like or ring-shaped configuration.
In example 6, the subject matter of any of examples 1 to 5 can optionally furthermore comprise the fact that the undulatory section comprises a hollow projection protruding from the planar section, which protrudes from the planar section in a direction facing toward the reference electrode or in a direction facing away from the reference electrode. The undulatory section can optionally comprise a plurality of hollow projections protruding from the planar section, which protrude in a direction facing toward the reference electrode or/and in a direction facing away from the reference electrode.
In example 7, the subject matter of example 6 can optionally furthermore comprise the fact that the hollow projection or the hollow projections has or have at least in sections a rectangular, optionally square, cross section or/and an elliptic, optionally circular, cross section or/and an angular cross section.
In example 8, the subject matter of any of examples 1 to 7 can optionally furthermore comprise the fact that the first membrane comprises at least one membrane anti-stick projection facing the reference electrode, optionally a plurality of membrane anti-stick projections facing the reference electrode, or/and that the second membrane comprises at least one membrane anti-stick projection facing the reference electrode, optionally a plurality of membrane anti-stick projections facing the reference electrode.
In example 9, the subject matter of either of examples 6 and 7 and of example 8 can optionally furthermore comprise the fact that at least one membrane anti-stick projection is provided on a hollow projection protruding in the direction of the reference electrode.
In example 10, the subject matter of any of examples 1 to 9 can optionally furthermore comprise the fact that the reference electrode comprises at least one electrode anti-stick projection protruding toward the first membrane or/and at least one electrode anti-stick projection protruding toward the second membrane.
In example 11, the subject matter of any of examples 1 to 10 can optionally furthermore comprise at least one spacer which is arranged between the first and second membranes and which is configured to maintain a predefined distance between the first and second membranes, wherein the reference electrode comprises at least one through opening through which at least one spacer extends.
In example 12, the subject matter of example 11 can optionally furthermore comprise the fact that at least one spacer is permanently, optionally integrally, connected to the first or/and the second membrane.
In example 13, the subject matter of examples 2 and 12 can optionally furthermore comprise the fact that at least one spacer is connected to the planar section of the region of the first membrane that is displaceable by sound, and to the planar section of the region of the second membrane that is displaceable by sound.
In example 14, the subject matter of examples 6 and 13 can optionally furthermore comprise the fact that the undulatory section of the region of the first membrane that is displaceable by sound comprises a plurality of hollow projections, wherein at least one spacer is connected to a part of the planar section of the region of the first membrane that is displaceable by sound between two hollow projections or/and that the undulatory section of the region of the second membrane that is displaceable by sound comprises a plurality of hollow projections, wherein at least one spacer is connected to a part of the planar section of the region of the second membrane that is displaceable by sound between two hollow projections.
In example 15, the subject matter of examples 2 and 12 can optionally furthermore comprise the fact that at least one spacer is connected to the undulatory section of the region of the first membrane that is displaceable by sound or/and to the undulatory section of the region of the second membrane that is displaceable by sound.
In example 16, the subject matter of any of examples 11 to 15 can optionally furthermore comprise the fact that at least one spacer extends without contact through a through opening in at least one position of the first or/and of the second membrane, optionally in all positions of the first or/and of the second membrane.
In example 17, the subject matter of any of examples 11 to 16 can optionally comprise a plurality of spacers between the first and second membranes.
In example 18, the subject matter of any of examples 11 to 17 can optionally furthermore comprise the fact that at least one spacer, optionally a plurality of spacers, further optionally each spacer, at least in sections, optionally completely, is formed from an electrically insulating material.
In example 19, the subject matter of any of examples 11 to 18 can optionally furthermore comprise the fact that at least one spacer, optionally a plurality of spacers, further optionally each spacer, at least in sections, optionally completely, is formed from an electrically conductive material.
In example 20, the subject matter of any of examples 17 to 19 can optionally furthermore comprise the fact that the reference electrode comprises a plurality of through openings through which a respective spacer extends.
In example 21, the subject matter of any of examples 1 to 20 can optionally furthermore comprise the fact that the first and second membranes are electrically insulated from one another, optionally are electrically insulated from one another in each of their positions relative to the reference electrode.
In example 22, the subject matter of any of examples 1 to 20 can optionally furthermore comprise the fact that the first and second membranes are electrically connected to one another, optionally are electrically connected to one another in each of their positions relative to the reference electrode.
In example 23, the subject matter of examples 19 and 22 can optionally furthermore comprise the fact that the first and second membranes are electrically connected to one another by at least one spacer, optionally by a plurality of spacers, further optionally by all spacers.
In example 24, the subject matter of any of examples 1 to 23 can optionally furthermore comprise the fact that the reference electrode is formed completely from an electrically conductive material.
In example 25, the subject matter of any of examples 1 to 23 can optionally furthermore comprise the fact that the reference electrode comprises: an electrically conductive first reference electrode layer facing the first membrane, an electrically conductive second reference electrode layer facing the second membrane, and an electrically insulating third reference electrode layer arranged between the first and second reference electrode layers and configured to electrically insulate the first reference electrode layer from the second reference electrode layer.
In example 26, the subject matter of any of examples 1 to 25 can optionally furthermore comprise the fact that the first membrane comprises a dynamic section contained at least partly, optionally completely, in its region displaceable by sound, said dynamic section being electrically insulated from a remaining region of the first membrane by an insulation section, or/and that the second membrane comprises a dynamic section contained at least partly, optionally completely, in its region displaceable by sound, said dynamic section being electrically insulated from a remaining region of the second membrane by an insulation section.
In example 27, the subject matter of any of examples 1 to 26 can optionally furthermore comprise a holder to which the first membrane or/and the second membrane or/and the reference electrode is/are secured.
In example 28, the subject matter of examples 26 and 27 can optionally furthermore comprise the fact that the remaining region of the first membrane comprises a securing section connected to the holder, or/and that the remaining region of the second membrane comprises a securing section connected to the holder.
In example 29, the subject matter of example 28 can optionally furthermore comprise the fact that the insulation section of the first membrane is provided at least partly, optionally completely, on a side of the undulatory section of the first membrane that faces the securing section of the first membrane or/and on a side of said undulatory section that faces away from the securing section of the first membrane, or/and that the insulation section of the second membrane is arranged at least partly, optionally completely, on a side of the undulatory section of the second membrane that faces the securing section of the second membrane or/and on a side of said undulatory section that faces away from the securing section of the second membrane.
In example 30, the subject matter of any of examples 1 to 29 can optionally furthermore comprise the fact that a gas pressure that is lower than the normal pressure is present in a space defined between the first and second membranes, in which space the reference electrode is arranged.
Example 31 is a method for operating a microelectromechanical microphone according to any of examples 1 to 30, comprising: reading out a first electrical signal from the microphone, which characterizes a sound-governed displacement of the first membrane relative to the reference electrode, reading out a second electrical signal from the microphone, which characterizes a sound-governed displacement of the second membrane relative to the reference electrode, combining the first and second electrical signals in order to determine properties of the sound by which the first and second membranes are displaceable.
In example 32, the subject matter of example 31 can optionally furthermore comprise the fact that the first electrical signal is an electrical voltage or an electric current or/and that the second electrical signal is an electrical voltage or an electric current.
In example 33, the subject matter of example 31 or 32 can optionally furthermore comprise the fact that combining the first and second electrical signals comprises: adding the first and second electrical signals or/and subtracting the first electrical signal from the second electrical signal or subtracting the second electrical signal from the first electrical signal.
Example 34 is a method for producing a microelectromechanical microphone according to any of examples 1 to 30. The method can comprise: producing a first membrane, producing a reference electrode on the first membrane, and producing a second membrane on the reference electrode. Producing the first or/and the second membrane can comprise: producing a negative mold for the first or/and the second membrane, wherein the negative mold comprises a first section complementary to a planar section of a region of the first or/and of the second membrane that is displaceable by sound, and also a second section complementary to an undulatory section of the region of the first or/and of the second membrane that is displaceable by sound, depositing a membrane material onto the negative mold and in the process forming the first or the second membrane, and removing the negative mold and in the process exposing the first or the second membrane.
In example 35, the subject matter of example 34 can optionally furthermore comprise the fact that the second section of the negative mold comprises a projection or/and a cutout.
In example 36, the subject matter of example 35 can optionally furthermore comprise the fact that the second section of the negative mold comprises a cutout or is embodied as a cutout. Producing the cutout can comprise: forming a first cavity in a substrate, depositing a protective layer onto the walls of the first cavity, forming an opening in the protective layer and in the process exposing the substrate, forming a second cavity, connected to the first cavity, in the substrate through the opening in the protective layer, and removing the protective layer.
In example 37, the subject matter of example 36 can optionally furthermore comprise the fact that the membrane material is deposited into the cutout as a layer which covers the inner walls of the cutout and which defines a hollow space accessible from outside the substrate.
In example 38, the subject matter of any of examples 35 to 37 can optionally furthermore comprise the fact that the second section comprises a projection or is embodied as a projection. Regions of the projection can be formed after the process of producing sections of the first and/or the second membrane.
In example 39, the subject matter of example 38 can optionally furthermore comprise: depositing a first membrane material layer onto a first sacrificial layer, forming a through opening in the first membrane material layer, depositing a second sacrificial layer onto the membrane material layer and also into the through opening formed in the membrane material layer, forming an opening in the second sacrificial layer, which exposes an edge region of the first membrane material layer that delimits the through opening in the first membrane material layer, and depositing a second membrane material layer onto the second sacrificial layer and also into the opening formed in the second sacrificial layer.
In example 40, the subject matter of example 39 can optionally furthermore comprise: structuring the second membrane material layer and in the process forming a web-shaped section composed of membrane material which is connected to the first membrane material layer via the opening formed in the second sacrificial layer, depositing a third sacrificial layer onto the web and also onto the second sacrificial layer, forming an opening in the third sacrificial layer or in the second and third sacrificial layers, which opening exposes an edge region of the web, and depositing a third membrane material layer onto the third sacrificial layer and also into the opening formed in the third sacrificial layer or in the second and third sacrificial layers.
In example 41, the subject matter of example 40 can optionally furthermore comprise the fact that removing the negative mold comprises removing the first to third sacrificial layers.
In example 42, the subject matter of any of examples 34 to 41 can optionally furthermore comprise: forming a membrane sacrificial layer on the first membrane, wherein the reference electrode is formed on the membrane sacrificial layer.
In example 43, the subject matter of any of examples 34 to 42 can optionally furthermore comprise: forming a reference electrode sacrificial layer on the reference electrode, wherein the second membrane is formed on the reference electrode sacrificial layer.
In example 44, the subject matter of any of examples 34 to 43 can optionally furthermore comprise: forming at least one through opening in the reference electrode and forming a spacer extending through the through opening between the first and second membranes, wherein optionally the spacer is connected to the first or/and the second membrane.
Number | Date | Country | Kind |
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10 2017 103 195 | Feb 2017 | DE | national |
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Number | Date | Country | |
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20180234774 A1 | Aug 2018 | US |