DIFFERENTIAL MICROPHONE WITH SEALED BACKSIDE CAVITIES AND DIAPHRAGMS COUPLED TO A ROCKING STRUCTURE THEREBY PROVIDING RESISTANCE TO DEFLECTION UNDER ATMOSPHERIC PRESSURE AND PROVIDING A DIRECTIONAL RESPONSE TO SOUND PRESSURE

• US 20120257778A1
• Filed: 04/06/2012
• Published: 10/11/2012
• Est. Priority Date: 04/08/2011
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Hall, Neal A., Kuntzman, Michael Louis, Kirk, Karen Denise
• Granted Patent: US 8,989,411 B2
• Time in Patent Office: Days
• US Class Current: 381/356
• 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

Abstract

A vacuum sealed directional microphone and methods for fabricating said vacuum sealed directional microphone. A vacuum sealed directional microphone includes a rocking structure coupled to two vacuum sealed diaphragms which are responsible for collecting incoming sound and deforming under sound pressure. The rocking structure'"'"'s resistance to bending aids in reducing the deflection of each diaphragm under large atmospheric pressure. Furthermore, the rocking structure exhibits little resistance about its pivot thereby enabling it to freely rotate in response to small pressure gradients characteristic of sound. The backside cavities of such a device can be fabricated without the use of the deep reactive ion etch step thereby allowing such a microphone to be fabricated with a CMOS compatible process.

Claims

1. A microphone comprising:

a first and a second diaphragm, wherein said first and second diaphragms form a top layer of a first and a second backside sealed cavity; and

a rocking structure coupled to said first and second diaphragms, wherein said rocking structure rotates on a pivot, wherein said rocking structure is placed external to said first and second backside sealed cavities.

2. The microphone as recited in claim 1, wherein said first and second backside sealed cavities comprise a first and a second electrode, respectively.

3. The microphone as recited in claim 2, wherein said first and second diaphragms are electrically conductive, wherein parallel plate capacitors are formed between said first and second diaphragms and said first and second electrodes, respectively.

4. The microphone as recited in claim 2, wherein an electrostatic charge is placed on said first and second diaphragms and an electrostatic charge of a same type is placed on said first and second electrodes.

5. The microphone as recited in claim 1, wherein said first and second backside sealed cavities comprise a plurality of electrodes thereby forming a plurality of capacitors between said first and second diaphragms and said plurality of electrodes.

6. The microphone as recited in claim 5, wherein a portion of said plurality of capacitors are used for sensing, wherein a portion of said plurality of capacitors are used for electrostatic actuation.

7. The microphone as recited in claim 1, wherein said first and second backside sealed cavities are vacuum sealed.

8. The microphone as recited in claim 1, wherein said rocking structure turns into motion when pressure arrives from a horizontal direction.

9. The microphone as recited in claim 1, wherein said first and second diaphragms are repulsed upwards by use of magnetic forces.

10. The microphone as recited in claim 9, wherein current is run through said first and second diaphragms thereby creating a magnetic field.

11. A microphone comprising:

a diaphragm, wherein said diaphragm forms a top layer of a backside sealed cavity;

a rocking structure coupled to said diaphragm, wherein said rocking structure rotates on a pivot, wherein said rocking structure is placed internal in said backside sealed cavity.

12. The microphone as recited in claim 11, wherein said backside sealed cavity comprises a first electrode and a second electrode.

13. The microphone as recited in claim 12, wherein said first and second electrodes are positioned beneath said rocking structure.

14. The microphone as recited in claim 12, wherein said rocking structure is electrically conductive, wherein parallel plate capacitors are formed between said rocking structure and said first and second electrodes.

15. The microphone as recited in claim 12, wherein an electrostatic charge is placed on said diaphragm and an electrostatic charge of a same type is placed on said first and second electrodes.

16. The microphone as recited in claim 11, wherein said backside sealed cavity comprises a plurality of electrodes thereby forming a plurality of capacitors between said rocking structure and said plurality of electrodes.

17. The microphone as recited in claim 16, wherein a portion of said plurality of capacitors are used for sensing, wherein a portion of said plurality of capacitors are used for electrostatic actuation.

18. The microphone as recited in claim 11, wherein said backside sealed cavity is vacuum sealed.

19. The microphone as recited in claim 11, wherein said rocking structure turns into motion when pressure arrives from a horizontal direction.

20. The microphone as recited in claim 11, wherein said diaphragm is repulsed upwards by use of magnetic forces.

21. The microphone as recited in claim 20, wherein current is run through said diaphragm thereby creating a magnetic field.

22. The microphone as recited in claim 11, wherein a plurality of posts extend from a top surface of said microphone to a substrate of said microphone.

23. The microphone as recited in claim 22, wherein said posts protrude through holes in said rocking structure.

24. A method for fabricating a microphone, the method comprising:

depositing and patterning a first structural layer to form a first and a second electrode on a substrate;

depositing and patterning a first sacrificial layer onto said patterned first structural layer;

performing a dimpled cut in said first sacrificial layer used to create a pivot, wherein said dimpled cut etches said first sacrificial layer in a manner that leaves a portion of said first sacrificial layer on said substrate;

depositing and patterning a second structural layer on said patterned first sacrificial layer to form a first and a second diaphragm, said pivot and a bottom layer of a rocking structure; and

depositing and patterning additional structural layers to form other layers of said rocking structure.

25. The method as recited in claim 24 further comprising:

depositing and patterning a third structural layer to form posts on top of said first and second diaphragms.

26. The method as recited in claim 24 further comprising:

depositing and patterning additional sacrificial layers.

27. The method as recited in claim 26 further comprising:

performing a release etch to remove remaining portions of said first sacrificial layer and said additional sacrificial layers.

28. A method for fabricating a microphone, the method comprising:

depositing and patterning a first structural layer to form a first and a second electrode on a substrate and a bottom layer of post structures;

depositing and patterning a first sacrificial layer onto said patterned first structural layer;

performing a dimpled cut in said first sacrificial layer used to create a pivot, wherein said dimpled cut etches said first sacrificial layer in a manner that leaves a portion of said first sacrificial layer on said substrate;

depositing and patterning a second structural layer on said patterned first sacrificial layer to form said pivot and a bottom layer of a rocking structure; and

depositing and patterning additional structural layers to form other layers of said rocking structure.

29. The method as recited in claim 28 further comprising:

depositing and patterning additional sacrificial layers as well as depositing and patterning said additional structural layers to form post structures.

30. The method as recited in claim 29 further comprising:

performing a release etch to remove remaining portions of said first sacrificial layer and said additional sacrificial layers.

31. The method as recited in claim 28 further comprising:

forming a lip underneath an etch release hole to catch sealant as said sealant is applied to a top structural layer of said microphone.