MEMS microphone

• US 9,029,963 B2
• Filed: 09/24/2013
• Issued: 05/12/2015
• Est. Priority Date: 09/25/2012
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Sand 9, Inc. (Analog Devices, Inc.)
• Inventors: Sparks, Andrew, Borkowski, Todd M.
• Primary Examiner(s): Coleman, William D
• Application Number:
  US14/034,986
• Publication Number:
  US 20140084395A1
• Time in Patent Office: 595 Days
• Field of Search: 257/419, 438/53, 381/113, 381/175
• US Class Current: 257/416
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• 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: B81C 2201/0191 Transfer of a layer from a carrier wafer to a device wafer
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025
• CPC Class Codes: H04R 17/02 Microphones
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 7/04 Plane diaphragms

Abstract

Mechanical resonating structures, as well as related devices and methods of manufacture. The mechanical resonating structures can be microphones, each including a diaphragm and a piezoelectric stack. The diaphragm can have one or more openings formed therethrough to enable the determination of an acoustic pressure being applied to the diaphragm through signals emitted by the piezoelectric stack.

Claims

1. A method, comprising:

obtaining a first wafer;

forming vias and a cavity in the first wafer;

bonding a silicon-on-insulator (SOI) wafer to the first wafer;

removing material from at least one of the SOI wafer and the first wafer to create a released diaphragm;

depositing a piezoelectric stack in proximity to the released diaphragm;

etching diaphragm holes in the released diaphragm to create a micro-electro-mechanical-systems (MEMS) wafer;

bonding the MEMS wafer to an integrated circuit wafer; and

exposing the MEMS wafer to an ambient environment.

2. The method of claim 1, wherein the exposing of the MEMS wafer includes at least one of grinding, polishing, and reactive ion etching the MEMS wafer.

3. The method of claim 1, comprising forming one or more support structures on the diaphragm.

4. A microphone, comprising:

a substrate;

a diaphragm disposed over an opening in the substrate, wherein the diaphragm includes one or more openings therein; and

a piezoelectric stack in proximity to the one or more openings in the diaphragm,

wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm,

wherein the microphone does not include a backplate, and

wherein the diaphragm has variable thickness.

5. The microphone of claim 4, wherein the piezoelectric stack is a ring that surrounds the one or more openings in the diaphragm.

6. The microphone of claim 4, wherein the microphone is connected with an integrated circuit to form one of a top port wafer-level chip-scale package (WLCSP) configuration and a bottom port WLCSP configuration.

7. The microphone of claim 4, wherein the one or more openings in the diaphragm are circular openings.

8. The microphone of claim 4, wherein the diaphragm comprises one of silicon (Si), silicon dioxide (SiO₂), silicon nitride (SiN), silicon carbide (SiC), or combinations thereof.

9. The microphone of claim 4, wherein the one or more openings in the diaphragm are disposed in a symmetrical pattern.

10. A microphone, comprising:

a substrate;

a diaphragm disposed over an opening in the substrate, wherein the diaphragm includes one or more openings therein; and

a piezoelectric stack in proximity to the one or more openings in the diaphragm,

wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm,

wherein the microphone does not include a backplate, and

wherein the one or more openings in the diaphragm define a plurality of cantilevers in the diaphragm.

11. A microphone, comprising:

a substrate;

a diaphragm disposed over an opening in the substrate, wherein the diaphragm includes one or more openings therein; and

a piezoelectric stack in proximity to the one or more openings in the diaphragm,

wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm,

wherein the microphone does not include a backplate, and

wherein the one or more openings in the diaphragm are non-circular openings.

12. A microphone, comprising:

a substrate;

a diaphragm disposed over an opening in the substrate, wherein the diaphragm includes one or more openings therein; and

a piezoelectric stack in proximity to the one or more openings in the diaphragm,

wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm,

wherein the microphone does not include a backplate, and

wherein the one or more openings in the diaphragm are disposed in an asymmetrical pattern.

13. A microphone, comprising:

a substrate;

a diaphragm disposed over an opening in the substrate, wherein the diaphragm includes one or more openings therein; and

a piezoelectric stack in proximity to the one or more openings in the diaphragm,

wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm,

wherein the microphone does not include a backplate, and

wherein the piezoelectric stack comprises a first metal layer and a piezoelectric layer, wherein the piezoelectric layer comprises one of aluminum nitride (AlN), zinc oxide (ZnO), cadmium sulfide (CdS), quartz, lead titanate (PbTiO₃), lead zirconate titanate (PZT), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), rand combinations thereof, and wherein the first metal layer comprises one of aluminum (Al), molybdenum (Mo), titanium (Ti), chromium (Cr), ruthenium (Ru), gold (Au), platinum (Pt), AlSiCu, and combinations thereof.

14. The microphone of claim 13, wherein the piezoelectric stack further comprises a second metal layer, wherein the second metal layer comprises one of aluminum (Al), molybdenum (Mo), titanium (Ti), chromium (Cr), ruthenium (Ru), gold (Au), platinum (Pt), AlSiCu, and combinations thereof.