Microelectromechanical microphone

1. A microelectromechanical microphone, comprising:

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,

wherein a region of the first membrane that is displaceable by sound relative to the reference electrode comprises a planar section and an undulatory section adjoining the planar section, wherein the planar section and the undulatory section of the first membrane is arranged opposite from the reference electrode and the second membrane, and wherein a distance between the undulatory section and the reference electrode varies according to a topology of the undulatory section, and

wherein the first membrane comprises a dynamic section contained at least partly 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 the second membrane comprises a dynamic section contained at least partly in its region displaceable by sound, said dynamic section being electrically insulated from a remaining region of the second membrane by an insulation section.

2. The microelectromechanical microphone as claimed in claim 1 ,

wherein a region of the second membrane that is displaceable by sound relative to the reference electrode comprises a planar section and an undulatory section adjoining the planar section, wherein the planar section and the undulatory section of the second membrane is arranged opposite from the reference electrode and the first membrane.

3. The microelectromechanical microphone as claimed in claim 1 , wherein only the first membrane comprises the planar and undulatory sections.

4. The microelectromechanical microphone as claimed in claim 1 , wherein the undulatory section is delimited by the planar section on all sides.

5. The microelectromechanical microphone as claimed in claim 1 , wherein 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.

6. The microelectromechanical microphone as claimed in claim 1 , further comprising at least one spacer arranged between the first and second membranes and 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, and wherein at least one spacer is permanently and integrally connected to the first membrane or/and the second membrane.

7. The microelectromechanical microphone as claimed in claim 6 , wherein the at least one spacer is formed from an electrically insulating material.

8. The microelectromechanical microphone as claimed in claim 6 , wherein the at least one spacer is formed from an electrically conductive material.

9. The microelectromechanical microphone as claimed in claim 1 , wherein the first and second membranes are electrically insulated from one another.

10. The microelectromechanical microphone as claimed in claim 1 , wherein the first and second membranes are electrically connected to one another.

11. The microelectromechanical microphone as claimed in claim 1 , wherein the first and second membranes are electrically connected to one another by at least one spacer.

12. The microelectromechanical microphone as claimed in claim 1 , wherein the reference electrode is formed completely from an electrically conductive material.

13. The microelectromechanical microphone as claimed in claim 1 , wherein 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.

14. The microelectromechanical microphone as claimed in claim 1 , further comprising a holder to which the first membrane or/and the second membrane or/and the reference electrode is/are secured.

15. The microelectromechanical microphone as claimed in claim 14 , wherein the remaining region of the first membrane comprises a securing section connected to the holder, or/and wherein the remaining region of the second membrane comprises a securing section connected to the holder.

16. The microelectromechanical microphone as claimed in claim 15 ,

wherein the insulation section of the first membrane is arranged at least partly 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

wherein the insulation section of the second membrane is arranged at least partly 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.

17. A method for operating a microelectromechanical microphone comprising 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, wherein a region of o the first membrane that is displaceable by sound relative to the reference electrode comprises a planar section and an undulatory section adjoining the planar section, wherein the planar section and the undulatory section of the first membrane is arranged opposite from the reference electrode and the second membrane, and wherein a distance between the undulatory sections and the reference electrode vary according to a topology of the undulatory sections, wherein the first membrane comprises a dynamic section contained at least partly 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 the second membrane comprises a dynamic section contained at least partly in its region displaceable by sound, said dynamic section being electrically insulated from a remaining region of the second membrane by an insulation section, the method 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; and

combining the first and second electrical signals in order to determine properties of the sound by which the first and second membranes are displaceable.

18. The method as claimed in claim 17 , wherein combining the first and second electrical signals comprises adding or subtracting the first and second electrical signals.

19. A method for producing a microelectromechanical microphone, the method comprising:

forming a first membrane, and

forming a reference electrode on the first membrane,

wherein forming the first membrane comprises

producing a first negative mold for the first membrane, wherein the first negative mold for the first membrane comprises 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 comprises depositing a membrane material onto the first negative mold to form the first membrane,

removing the first negative mold, wherein the first membrane is exposed when removing the first negative mold,

forming a second membrane on the reference electrode, wherein forming the second membrane comprises

producing a second negative mold for the second membrane, wherein the second negative mold for the second membrane comprises a first section complementary to a planar section of a region of the second membrane that is displaceable by sound, and a second section complementary to an undulatory section of the region of the second membrane that is displaceable by sound, wherein producing the second negative mold comprises depositing the membrane material onto the second negative mold and to form the second membrane, and

removing the second negative mold, wherein the second membrane is exposed when removing the second negative mold,

wherein the planar section of the first membrane is adjacent to the undulatory section of the first membrane, the planar section of the second membrane is adjacent to the undulatory section of the second membrane, the planar section and the undulatory sections of the first membrane are arranged opposite from the reference electrode and the second membrane, and the planar section and the undulatory sections of the second membrane are arranged opposite from the reference electrode and the first membrane, and

wherein the first membrane comprises a dynamic section contained at least partly 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 the second membrane comprises a dynamic section contained at least partly in its region displaceable by sound, said dynamic section being electrically insulated from a remaining region of the second membrane by an insulation section.

20. The method as claimed in claim 19 , wherein the second section of the first negative mold or the second negative mold comprises a projection or a cutout.

21. The method as claimed in claim 20 , wherein the second section of the first negative mold of the second negative mold comprises the cutout, and the method further comprises producing the cutout, producing the cutout comprising:

forming a first cavity in a substrate,

depositing a protective layer onto walls of the first cavity,

forming an opening in the protective layer to expose 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.

22. The method as claimed in claim 21 , wherein the membrane material is deposited into the cutout as a layer that covers inner walls of the cutout and that defines a hollow space accessible from outside the substrate.

23. The method as claimed in claim 20 , wherein the second section comprises the projection, wherein regions of the projection are formed after producing the sections of the first membrane or the second membrane.

24. The method as claimed in claim 23 , further comprising:

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 first membrane material layer and also into the through opening formed in the first 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.