System and Method for a MEMS Transducer

• US 20150125003A1
• Filed: 11/06/2013
• Published: 05/07/2015
• Est. Priority Date: 11/06/2013
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Wiesbauer, Andreas, Mandl, Christian, Fueldner, Marc, Hsu, Shu-Ting
• Granted Patent: US 10,589,987 B2
• Time in Patent Office: Days
• US Class Current: 381/111
• 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 2203/0315 Cavities
• 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: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00388 Etch mask forming
• CPC Class Codes: B81C 1/00523 Etching material
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2924/15151 the die mounting substrate comprising an aperture, e.g. for underfilling, outgassing, window type wire connections
• CPC Class Codes: H01L 2924/16152 Cap comprising a cavity for hosting the device, e.g. U-shaped cap
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• 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

Abstract

An embodiment as described herein includes a microelectromechanical system (MEMS) with a first MEMS transducer element, a second MEMS transducer element, and a semiconductor substrate. The first and second MEMS transducer elements are disposed at a top surface of the semiconductor substrate and the semiconductor substrate includes a shared cavity acoustically coupled to the first and second MEMS transducer elements.

Claims

1. A microelectromechanical system (MEMS) comprising:

a first MEMS transducer element;

a second MEMS transducer element; and

a semiconductor substrate comprising a shared cavity, wherein the first MEMS transducer element and the second MEMS transducer element are disposed at a top surface of the semiconductor substrate and are acoustically coupled to the shared cavity.

2. The MEMS of claim 1, further comprising:

an amplifier having input terminals coupled to the first and second MEMS transducer elements, and having output terminals configured to provide a differential output signal; and

a bias generator coupled to the first and second MEMS transducer elements.

3. The MEMS of claim 2, wherein the bias generator comprises:

a first bias generator coupled to the first MEMS transducer element and configured to provide a first bias voltage; and

a second bias generator coupled to the second MEMS transducer element and configured to provide a second bias voltage.

4. The MEMS of claim 2, wherein the amplifier and the bias generator are disposed on an integrated circuit (IC) and are electrically coupled to the first and second MEMS transducer elements.

5. The MEMS of claim 2, wherein the amplifier and the bias generator are integrated on the substrate.

6. The MEMS of claim 1, wherein the first MEMS transducer element comprises a plurality of first MEMS transducer elements and the second MEMS transducer element comprises a plurality of second MEMS transducer elements.

7. The MEMS of claim 1, further comprising a single sound port coupled to the shared cavity.

8. A microelectromechanical system (MEMS) comprising:

a first MEMS transducer element disposed at a top surface of a first semiconductor substrate overlying a first cavity within the first semiconductor substrate;

a second MEMS transducer element disposed at a top surface of a second semiconductor substrate overlying a second cavity within the second semiconductor substrate;

a third substrate comprising a shared cavity, wherein the first substrate and the second substrate are disposed on the third substrate, at least a portion of the first cavity and a portion of the second cavity overly the shared cavity, and the third substrate is different from the first semiconductor substrate and the second semiconductor substrate; and

a fourth substrate comprising a sound port, wherein the third substrate is disposed on the fourth substrate, at least a portion of the shared cavity overlies the sound port, and the fourth substrate is different from the first semiconductor substrate, the second semiconductor substrate and the third substrate.

9. The MEMS of claim 8, wherein the third substrate comprises a carrier chip.

10. The MEMS of claim 8, wherein the fourth substrate comprises a printed circuit board (PCB).

11. The MEMS of claim 8, wherein the shared cavity is wider than the sound port.

12. The MEMS of claim 8, wherein the first substrate and the second substrate are a same substrate.

13. The MEMS of claim 8, further comprising:

an amplifier having input terminals coupled to the first and second MEMS transducer elements, and having output terminals configured to provide a differential output signal; and

a bias generator coupled to the first and second MEMS transducer elements.

14. The MEMS of claim 8, wherein the first MEMS transducer element comprises a plurality of first MEMS transducer elements and the second MEMS transducer element comprises a plurality of second MEMS transducer elements.

15. A method of operating an acoustic transducer system, comprising:

receiving an acoustic signal via a shared sound port using a first transducer element and a second transducer element;

generating a first differential signal at outputs of the first and second transducer elements; and

amplifying the first differential signal with an amplifier.

16. The method of claim 15, further comprising generating a second differential signal at an output of the amplifier.

17. The method of claim 15, wherein receiving the acoustic signal further comprises receiving the acoustic signal through a single cavity formed in a substrate and acoustically coupled to the shared sound port, wherein the first and second transducer elements are formed on the substrate over the cavity.

18. The method of claim 15, wherein generating the first differential signal at the first and second transducer elements comprises generating a first signal from the first transducer element and generating a second signal from the second transducer element, wherein the second signal is antiphase to the first signal.

19. A method of fabricating a transducer system, comprising:

forming a first microelectromechanical system (MEMS) microphone and a second MEMS microphone on a top surface of a semiconductor substrate;

applying a first etch mask on a bottom surface of the semiconductor substrate, the first etch mask comprising a first opening aligned with the MEMS microphones;

applying a second etch mask on a bottom surface of the semiconductor substrate, the second etch mask comprising second and third openings aligned with and corresponding to the first MEMS microphone and the second MEMS microphone;

etching a portion of the semiconductor substrate according to the second mask from the bottom surface of the semiconductor substrate and stopping the etching before bottom sides of the first and second MEMS microphones are exposed; and

removing the second mask and etching a portion of the semiconductor substrate according to the first etch mask until the bottom sides of the first and second MEMS microphones are exposed.

20. A transducer system comprising:

a first mechanically rigid backplate;

a first deflectable diaphragm adjacent to the first backplate and configured to be electrically coupled to a first bias voltage;

a second mechanically rigid backplate;

a second deflectable diaphragm adjacent to the second backplate and configured to be electrically coupled to a second bias voltage; and

an amplifier having input terminals electrically coupled to the first and second mechanically rigid backplates.

21. The transducer system of claim 20, wherein the amplifier has output terminals configured to provide a differential output signal.

22. The transducer system of claim 21, wherein the amplifier comprises a differential amplifier.

23. The transducer system of claim 20, further comprising a bias voltage generator configured to generate the first bias voltage and the second bias voltage.

24. The transducer system of claim 23, wherein the first bias voltage is different from the second bias voltage.

25. The transducer system of claim 23, wherein the amplifier and the bias voltage generator are disposed on an integrated circuit (IC).

26. The transducer system of claim 20, wherein the first mechanically rigid backplate and the first deflectable diaphragm comprise a plurality of first mechanically rigid backplates and a plurality of first deflectable diaphragms, and wherein the second mechanically rigid backplate and the second deflectable diaphragm comprise a plurality of second mechanically rigid backplates and a plurality of second deflectable diaphragms.

27. The transducer system of claim 20, wherein the first and second mechanically rigid backplates comprise a double backplate microelectromechanical system (MEMS) microphone, and wherein the first and second deflectable diaphragms comprise a single diaphragm of the double backplate MEMS microphone.

28. The transducer system of claim 20, wherein the amplifier comprises a first single ended amplifier and a second single ended amplifier, wherein the first single ended amplifier has a first gain of a substantially equal magnitude and opposite sign as a second gain of the second single ended amplifier.

29. A microelectromechanical system (MEMS) comprising:

a board comprising a first cavity disposed above a second cavity, the first cavity being larger than the second cavity; and

a MEMS transducer disposed at a top surface of the board adjacent the first cavity, the MEMS transducer comprising;

a semiconductor substrate,

a first MEMS transducer element disposed at a top surface of the semiconductor substrate overlying a third cavity formed in the semiconductor substrate, and

a second MEMS transducer element disposed at the top surface of the semiconductor substrate overlying a fourth cavity formed in the semiconductor substrate, wherein the first, second, third, and fourth cavities are all acoustically coupled.

30. The MEMS of claim 29, wherein the board comprises a first layer comprising the first cavity and a second layer comprising the second cavity.

31. The MEMS of claim 29, wherein the first and second MEMS transducer elements comprise a double backplate MEMS microphone.

32. The MEMS of claim 29, wherein the first cavity is wider than the second cavity.

33. The MEMS of claim 29, wherein the board comprises a printed circuit board (PCB).

34. The MEMS of claim 29, wherein the board comprises a ceramic substrate.