Microelectromechanical microphone with differential capacitive sensing

Patent metadata

Field	Value
Publication number	US-10123131-B2
Application number	US-201514733560-A
Country	US
Kind code	B2
Filing date	Jun 8, 2015
Priority date	Jun 8, 2015
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

Microelectromechanical microphones include structures that permit differential capacitive sensing. In certain structures, a movable plate is disposed between a rigid plate and a substrate. A first capacitor is formed between the movable plate and the substrate and a second capacitor is formed between the movable plate and the rigid plate. Respective bias voltages can be applied to the rigid plate and the substrate, and a differential capacitive signal can be probed in response to displacement of the movable plate caused by a pressure wave. The movable plate and the rigid plate are mechanically coupled to first and second portions of the substrate, respectively. A dielectric member mechanically couples the movable plate and the rigid plate, thus providing mechanical stability.

First claim

What is claimed is:

1. A microelectromechanical microphone system, comprising:
a substrate that defines an opening configured to receive an acoustic wave;
a movable diaphragm having a first portion mechanically coupled to the substrate and a second portion that is flexibly coupled to the first portion, wherein the movable diaphragm and the substrate form a first capacitor having a first capacitance based on a displacement of the movable diaphragm caused by the acoustic wave; and
a backplate mechanically coupled to the movable diaphragm via one or more dielectric members, each of the one or more dielectric members extends between a surface of the backplate and a surface of the movable diaphragm, wherein the backplate and the movable diaphragm form a second capacitor having a second capacitance based on the displacement of the movable diaphragm, and wherein the first capacitor is measured on a first side of the movable diaphragm and the second capacitor is measured on a second side of the movable diaphragm, the first side being opposite the second side.

2. The microelectromechanical microphone system of claim 1 , wherein the movable diaphragm defines openings.

3. The microelectromechanical microphone system of claim 1 , wherein a surface of the first portion is in contact with a dielectric layer overlaying the substrate.

4. The microelectromechanical microphone system of claim 1 , wherein each of the one or more dielectric members comprises a semiconductor oxide.

5. The microelectromechanical microphone system of claim 1 , wherein the substrate comprises a semiconductor.

6. The microelectromechanical microphone system of claim 1 , wherein the diaphragm comprises polycrystalline silicon or a doped semiconductor.

7. The microelectromechanical microphone system of claim 1 , wherein the backplate comprises silicon, germanium, a semiconductor from group III, a semiconductor from group V, a semiconductor from group II, a semiconductor from group VI, silicon oxide, polycrystalline silicon, or a combination thereof.

8. A device, comprising:
a microelectromechanical microphone including:
a substrate that defines an opening configured to receive an acoustic wave;
a movable diaphragm having a first portion mechanically coupled to the substrate and a second portion that is flexibly coupled to the first portion, wherein the movable diaphragm and the substrate form a first capacitor having a first capacitance based on a displacement of the movable diaphragm caused by the acoustic wave; and
a backplate mechanically coupled to the movable diaphragm via one or more dielectric members, each of the one or more dielectric members extends between a surface of the backplate to a surface of the movable diaphragm, wherein the backplate and the movable diaphragm form a second capacitor having a second capacitance based on the displacement of the movable diaphragm, and wherein the first capacitor is measured on a first side of the movable diaphragm and the second capacitor is measured on a second side of the movable diaphragm, the first side being opposite the second side; and

a circuit coupled to the microelectromechanical microphone and configured to receive a first signal indicative of the first capacitance and a second signal indicative of the second capacitance, the circuit is further configured to generate a third signal indicative of a difference between the first capacitance and the second capacitance, the third signal is representative of an amplitude of the acoustic wave.

9. The device of claim 8 , wherein the movable diaphragm defines openings, and wherein a surface of the first portion is in contact with a dielectric layer overlaying the substrate.

10. The device of claim 8 , wherein the circuit is further configured to apply a first bias voltage to the backplate and a second bias voltage to the substrate, and wherein the circuit is further configured to apply a ground reference voltage to the movable diaphragm.

11. The device of claim 8 , further comprising a housing comprising the microelectromechanical microphone and the circuit.

12. The device of claim 11 , wherein the microelectromechanical microphone and the circuit are formed on a single die.

13. The device of claim 11 , wherein the microelectromechanical microphone is formed on a first die and the circuit is formed on a second die, and wherein the first die and the second are electrically coupled.

Assignees

• Invensense Inc

Inventors

• Liu Fang
• Daneman Michael
• Chen Thomas

Classifications

• H04R19/04 Primary

  Microphones (H04R19/01 takes precedence) · CPC title

• H04R31/00

  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 title

• H04R19/005

  using semiconductor materials · CPC title