System and Method for a Perpendicular Electrode Transducer

• US 20170142525A1
• Filed: 11/13/2015
• Published: 05/18/2017
• Est. Priority Date: 11/13/2015
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Dehe, Alfons, Glacer, Christoph
• Granted Patent: US 10,104,478 B2
• Time in Patent Office: Days
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 2201/013 Etching
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2207/00 Details of diaphragms or cones for electromechanical transducers or their suspension covered by H04R7/00 but not provided for in H04R7/00 or in H04R2307/00
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• 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 31/003 for diaphragms or their outer suspension
• CPC Class Codes: H04R 7/122 comprising a plurality of sections or layers

Abstract

According to an embodiment, a method of operating a microelectromechanical systems (MEMS) transducer that has a membrane includes transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes using the first pair of electrostatic drive electrodes. The first pair of electrostatic drive electrodes is formed on the membrane extending in an out-of-plane direction and form a variable capacitance between the first pair of electrostatic drive electrodes.

Claims

1. A method of operating a microelectromechanical systems (MEMS) transducer having a membrane, the method comprising:

transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes using the first pair of electrostatic drive electrodes, wherein the first pair of electrostatic drive electrodes are formed on the membrane extending in an out-of-plane direction and forming a variable capacitance between the first pair of electrostatic drive electrodes.

2. The method of claim 1, wherein transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes comprises:

generating an electrostatic force between the first pair of electrostatic drive electrodes by applying a voltage to the first pair of electrostatic drive electrodes;

generating a force on the membrane at the first pair of electrostatic drive electrodes by moving the first pair of electrostatic drive electrodes based on the electrostatic force; and

deflecting the membrane based on the force.

3. The method of claim 2, wherein transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes further comprises generating an acoustic signal by deflecting the membrane.

4. The method of claim 1, wherein transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes comprises:

deflecting the membrane; and

generating a voltage signal at the first pair of electrostatic drive electrodes based on deflecting the membrane.

5. The method of claim 4, wherein transducing between out-of-plane deflection of the membrane and voltage on a first pair of electrostatic drive electrodes further comprises determining an acoustic signal incident on the membrane based on the voltage signal.

6. A microelectromechanical systems (MEMS) transducer comprising:

a deflectable membrane; and

a first electrode pair on the deflectable membrane, the first electrode pair having a variable capacitance and comprising a first movable electrode and a second movable electrode, wherein

the first movable electrode and the second movable electrode have a variable separation distance and are movable in relation to each other, and

the variable capacitance depends on the variable separation distance.

7. The MEMS transducer of claim 6, further comprising

a second electrode pair on the deflectable membrane, the second electrode pair having a variable capacitance and comprising a third movable electrode and a fourth movable electrode, wherein

the third movable electrode and the fourth movable electrode have a variable separation distance and are movable in relation to each other, and

the variable capacitance depends on the variable separation distance of the third movable electrode and the fourth movable electrode;

and

wherein the first electrode pair is on a bottom surface of the deflectable membrane facing downwards and the second electrode pair is on a top surface of the deflectable membrane facing upwards.

8. The MEMS transducer of claim 6, wherein the first electrode pair is configured to adjust the variable separation distance based in deflection of the deflectable membrane.

9. The MEMS transducer of claim 8, further comprising an interface circuit electrically coupled to the first electrode pair and configured to generate an electrical signal representative of an acoustic signal incident on the deflectable membrane based on changes in the variable separation distance.

10. The MEMS transducer of claim 6, wherein the deflectable membrane comprises a layer stress that is configured to deflect the deflectable membrane in a first direction from a neutral position during an unbiased state.

11. The MEMS transducer of claim 6, further comprising an interface circuit electrically coupled to the first electrode pair and configured to:

generate an electrostatic force between the first electrode pair by applying a voltage to the first electrode pair;

generate a force on the deflectable membrane at the first electrode pair by adjusting the variable separation distance based on the electrostatic force; and

deflect the deflectable membrane based on the force.

12. The MEMS transducer of claim 6, wherein the first electrode pair comprises a plurality of electrode pairs formed on the deflectable membrane, each electrode pair of the plurality of electrode pairs having a respective variable capacitance and comprising a first respective movable electrode and a second respective movable electrode, wherein

the first respective movable electrode and the second respective movable electrode have a respective variable separation distance and are movable in relation to each other, and

the respective variable capacitance depends on the respective variable separation distance.

13. The MEMS transducer of claim 6, further comprising an electrically insulating material that electrically insulates the first movable electrode from the second movable electrode.

14. The MEMS transducer of claim 13, wherein the electrically insulating material is silicon nitride.

15. The MEMS transducer of claim 6, further comprising a substrate comprising a cavity, wherein the deflectable membrane is supported by the substrate and the first electrode pair overlies the cavity.

16. The MEMS transducer of claim 15, wherein the deflectable membrane is circular and fixed to a support structure on the substrate around a circumference of the deflectable membrane.

17. The MEMS transducer of claim 16, wherein the first movable electrode and the second movable electrode are formed in concentric circles.

18. The MEMS transducer of claim 15, wherein the deflectable membrane is rectangular and fixed to a support structure on the substrate along one edge of the deflectable membrane.

19. The MEMS transducer of claim 18, wherein the first movable electrode and the second movable electrode are formed in parallel lines.

20. The MEMS transducer of claim 6, wherein

the deflectable membrane extends in a first plane and has a first layer thickness,

the first movable electrode is formed on the deflectable membrane extending a first distance perpendicular to the first plane,

the second movable electrode is formed on the deflectable membrane extending the first distance perpendicular to the first plane, and

the first distance is greater than the first layer thickness.

21. The MEMS transducer of claim 20, wherein the first layer thickness is less than or equal to 1 micron and the first distance is greater than or equal to 1 micron and less than or equal to 25 microns.

22. A microelectromechanical systems (MEMS) transducer comprising:

a corrugated membrane; and

a first concentric electrode pair in contact with the corrugated membrane and comprising a first circular electrode and a second circular electrode formed concentrically and having a variable capacitance that varies with separation distance between the first circular electrode and the second circular electrode.

23. The MEMS transducer of claim 22, further comprising a second concentric electrode pair in contact with the corrugated membrane and comprising a third circular electrode and a fourth circular electrode formed concentrically and having a variable capacitance that varies with separation distance between the third circular electrode and the fourth circular electrode;

and

wherein the first concentric electrode pair is on a bottom surface of the corrugated membrane facing downwards and the second concentric electrode pair is on a top surface of the corrugated membrane facing upwards.

24. The MEMS transducer of claim 22, further comprising:

a substrate comprising a cavity, wherein the corrugated membrane overlies the cavity.

25. The MEMS transducer of claim 24, wherein the corrugated membrane is circular and fixed at a circumference to a support structure on the substrate.

26. The MEMS transducer of claim 22, wherein the first concentric electrode pair comprises a plurality of concentric electrode pairs in contact with the corrugated membrane, each concentric electrode pair of the plurality of concentric electrode pairs comprising a first respective circular electrode and a second respective circular electrode formed concentrically and having a respective variable capacitance that varies with respective separation distance between the first respective circular electrode and the second respective circular electrode.

27. The MEMS transducer of claim 26, wherein the corrugated membrane comprises a plurality of corrugations and a concentric electrode pair of the plurality of concentric electrode pairs is formed in each corrugation of the plurality of corrugations.

28. The MEMS transducer of claim 22, wherein the corrugated membrane has a layer thickness that is less than or equal to 1 micron and the first concentric electrode pair extends away from the corrugated membrane a distance greater than or equal to 1 micron and less than or equal to 25 microns.

29. The MEMS transducer of claim 22, further comprising an electrically insulating material connected to the first circular electrode and the second circular electrode, wherein the electrically insulating material insulates the first circular electrode from the second circular electrode.

30. The MEMS transducer of claim 22, wherein the corrugated membrane and the first concentric electrode pair are formed of polysilicon.

31. The MEMS transducer of claim 22, wherein the corrugated membrane comprises a layer stress that is configured to deflect the corrugated membrane in a first direction from a neutral position without application of an external force.

32. A method of forming a microelectromechanical systems (MEMS) transducer, the method comprising:

forming trenches in a substrate;

forming an electrode layer in the trenches and over and in contact with the substrate;

patterning a first electrode and a second electrode in the electrode layer, wherein the first electrode and the second electrode are formed in the trenches;

forming an insulation layer between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the insulation layer form a membrane;

forming a first conductive line contacting the first electrode;

forming a second conductive line contacting the second electrode; and

etching a cavity in the substrate below the first electrode and the second electrode.

33. The method of claim 32, further comprising forming a corrugation patterning element at the substrate before forming the electrode layer.

34. The method of claim 32, further comprising:

forming an etch mask in the trenches before forming the electrode layer; and

etching the etch mask to release the membrane after etching the cavity in the substrate.

35. The method of claim 32, wherein forming the insulation layer comprises:

forming a first insulation layer along sidewalls and bottom surfaces in the trenches before forming the electrode layer; and

forming a second insulation layer on the first electrode and the second electrode after patterning the first electrode and the second electrode in the electrode layer.

36. The method of claim 32, wherein forming the electrode layer and forming the insulation layer comprises forming a layer stress that causes a deflection of the electrode layer and the insulation layer after a release etch.