MEMS Acoustic Transducer, MEMS Microphone, MEMS Microspeaker, Array of Speakers and Method for Manufacturing an Acoustic Transducer

• US 20140270271A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Dehe, Alfons, Ruhl, Guenther
• Granted Patent: US 9,516,428 B2
• Time in Patent Office: Days
• US Class Current: 381/174
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 23/00 Transducers other than those covered by groups H04R9/00 - H04R21/00 diaphragms for transducers of the distributed-mode type H04R7/045
• CPC Class Codes: H04R 2307/023 Diaphragms comprising ceramic-like materials, e.g. pure ceramic, glass, boride, nitride, carbide, mica and carbon materials
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182
• CPC Class Codes: H04R 31/006 Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003
• CPC Class Codes: H04R 7/04 Plane diaphragms

Abstract

A MEMS acoustic transducer includes a substrate having a cavity therethrough, and a conductive back plate unit including a plurality of conductive perforated back plate portions which extend over the substrate cavity. A dielectric spacer arranged on the back plate unit between adjacent conductive perforated back plate portions, and one or more graphene membranes are supported by the dielectric spacer and extend over the conductive perforated back plate portions.

Claims

1. A MEMS acoustic transducer, comprising:

a substrate having a cavity therethrough;

a conductive back plate unit including a plurality of conductive perforated back plate portions which extend over the substrate cavity;

a dielectric spacer arranged on the back plate unit between adjacent conductive perforated back plate portions; and

one or more graphene membranes supported by the dielectric spacer and extending over the conductive perforated back plate portion.

2. The MEMS acoustic transducer of claim 1, wherein the back plate unit comprises an array structure including a plurality of adjacent cells, each cell including a conductive perforated back plate portion, and wherein the dielectric spacer comprises discrete posts or continuous ribs arrayed between the adjacent cells of the array structure and around the array structure.

3. The MEMS acoustic transducer of claim 2, wherein the array structure comprises a honeycomb structure.

4. The MEMS acoustic transducer of claim 3, wherein the cells of the honeycomb structure comprise a diameter of about 50 μ

m, and wherein the number of cells is selected so as to obtain the honeycomb structure with a diameter of about 1 mm.

5. The MEMS acoustic transducer of claim 1, wherein the graphene membrane is arranged between the substrate and the conductive back plate unit.

6. The MEMS acoustic transducer of claim 1, wherein the conductive back plate unit is arranged between the substrate and the graphene membrane.

7. The MEMS acoustic transducer of claim 6, comprising a further conductive back plate unit including a plurality of conductive perforated back plate portions and arranged such that the graphene membrane is sandwiched between the conductive back plate units.

8. The MEMS acoustic transducer of claim 7, wherein the back plate units are arranged such that the respective perforated back plate portions are registered with each other.

9. The MEMS acoustic transducer of claim 7, comprising a further dielectric spacer arranged between the further back plate unit and the graphene membrane.

10. The MEMS acoustic transducer of claim 1, comprising a first electrode arranged in contact with the conductive back plate unit, and a second electrode arranged in contact with the graphene membrane.

11. The MEMS acoustic transducer of claim 1, wherein the graphene membrane comprises a single layer graphene, a multilayer graphene, a chemically functionalized single layer graphene or combinations thereof.

12. The MEMS acoustic transducer of claim 1, comprising:

a single graphene membrane, or

a plurality of graphene membranes, wherein a graphene membrane extends over one or more of the conductive perforated back plate portions, and wherein the plurality of graphene membranes are connected to each other.

13. The MEMS acoustic transducer of claim 1, wherein the acoustic transducer is configured as a microphone or a microspeaker.

14. A MEMS microphone, comprising:

a substrate having a cavity;

a conductive back plate unit comprising a plurality of adjacent cells, each cell including a perforated back plate;

a dielectric spacer arranged on the back plate unit between the adjacent cells;

a graphene membrane supported by the dielectric spacer and extending over the cells of the back plate unit;

a first electrode arranged in contact with the conductive back plate unit; and

a second electrode arranged in contact with the graphene membrane.

15. The MEMS microphone of claim 14, wherein the cells of the conductive back plate unit comprise a rounded perimeter, or a polygonal shape.

16. The MEMS microphone of claim 14, wherein each of the cells of the back plate unit comprises a hexagonal shaped back plate, wherein the back plate comprises an outer hexagonal shaped frame and an inner hexagonal shaped frame, and wherein the outer frame and the inner frame are connected by a plurality of bars connected with each other at a center of the back plate, each bar extending from the center via one corner of the inner frame to one corner of the outer frame.

17. The MEMS microphone of claim 16, wherein the outer frame has a horizontal thickness that is greater than a horizontal thickness of the inner frame, and wherein the respective bars are tapered in the direction from the outer frame towards the center.

18. A MEMS microspeaker, comprising:

a conductive substrate comprising a plurality of cavities formed in a front side of the substrate; and

one or more graphene membranes extending over the plurality of cavities and supported in an electrically isolated manner by the substrate and by the substrate portions around the cavities.

19. The MEMS microspeaker of claim 18, wherein the cavities extend from the front side of the substrate to a backside of the substrate.

20. The MEMS microspeaker of claim 18, wherein the cavities comprise cavity walls that extend perpendicular or inclined with respect to the front side and a backside the substrate through the substrate.

21. The MEMS microspeaker of claim 18, wherein an opening of the cavities at the front side has a dimension different from a dimension of an opening at a backside.

22. The MEMS microspeaker of claim 18, wherein the cavities comprise a step-shaped or a V-shaped cross section.

23. The MEMS microspeaker of claim 18, comprising:

a first electrode arranged in contact with the substrate; and

a second electrode arranged in contact with the graphene membrane.

24. The MEMS microspeaker of claim 23, comprising a signal generator coupled between the first electrode and the second electrode.

25. The MEMS microspeaker of claim 18, comprising a plate comprising a plurality of openings and arranged electrically insulated from the graphene membrane such that the graphene membrane is sandwiched between the substrate and the plate.

26. The MEMS microspeaker of claim 25, comprising:

a first electrode arranged in contact with the graphene membrane;

a second electrode arranged in contact with the substrate;

a third electrode arranged in contact with the plate;

an AC signal generator coupled between the second and third electrodes; and

a DC signal generator coupled between the first electrode and the AC signal generator.

27. The MEMS microspeaker of claim 18, comprising:

a single graphene membrane, or

a plurality of graphene membranes, wherein a graphene membrane extends over one or more of the cavities, and wherein the plurality of graphene membranes are connected to each other.

28. A MEMS microspeaker, comprising:

a substrate having a plurality of cavities extending from a front side of the substrate to a backside of the substrate;

a plurality of dielectric spacers arranged on the front side of the substrate;

a graphene membrane extending over the cavities, wherein the graphene membrane is supported by the dielectric spacers arranged on the substrate portions around the cavities;

a first electrode arranged in contact with the substrate;

a second electrode arranged in contact with the graphene membrane; and

a signal generator coupled between the first and second electrodes.

29. An array of speakers, comprising:

a substrate comprising a plurality of cavities formed in a front side of the substrate; and

a plurality of microspeakers, each microspeaker comprising one or more graphene membranes extending over one or more of the plurality of cavities and supported in an electrically isolated manner by the substrate and by the substrate portions around the cavities.

30. The array of claim 29, wherein the graphene membranes of the respective microspeakers are independent driven membranes.

31. A method for manufacturing an acoustic transducer, the method comprising:

depositing a graphene membrane on a substrate; and

fabricating one or more MEMS structures.

32. The method of claim 31, wherein depositing the graphene membrane on the substrate comprises depositing the graphene membrane on a metal layer formed on a surface of the substrate, or depositing the graphene membrane at a metal-dielectric interface formed by a metal layer and a dielectric layer on the surface of the substrate.

33. The method of claim 32, wherein

depositing the graphene membrane on the substrate comprises:

forming a graphene layer on the substrate, and

fabricating one or more MEMS structures comprises;

forming a sacrificial layer on the graphene layer,

forming a conductive layer on the sacrificial layer,

pattering the conductive layer for defining a back plate unit having a perforated back plate portion,

pattering the sacrificial layer, the graphene layer, and the metal layer,

etching the substrate from a substrate back side for removing a portion of the substrate and the metal layer for exposing a first surface of a portion of the graphene layer, and

etching through the perforated back plate portion of the back plate unit for removing a portion of the sacrificial layer for exposing a second surface of the portion of the graphene layer.

34. The method of claim 32, wherein

depositing the graphene membrane on the substrate comprises:

forming a graphene layer on the substrate, and

fabricating one or more MEMS structures comprises;

pattering the graphene layer, and the metal layer, and

etching the substrate from a substrate back side for removing a portion of the substrate and the metal layer for forming a plurality of cavities exposing a first surface of respective portions of the graphene layer.

35. The method of claim 34, further comprising:

providing a further substrate having an insulating layer formed on a first surface thereof and a plurality of cavities extending from a second surface of the substrate through the substrate and through the insulating layer, and

arranging the further substrate on the graphene layer with the insulating layer between the graphene layer and the further substrate, wherein the cavities in the substrate and the cavities in the further substrate are registered with each other.

36. The method of claim 31, wherein the acoustic transducer comprises one or more microphones or one or more micro speakers.