MEMS process and device

Patent metadata

Field	Value
Publication number	US-9756430-B2
Application number	US-201615148375-A
Country	US
Kind code	B2
Filing date	May 6, 2016
Priority date	Aug 17, 2007
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A method of fabricating a micro-electrical-mechanical system (MEMS) transducer comprises the steps of forming a membrane on a substrate, and forming a back-volume in the substrate. The step of forming a back-volume in the substrate comprises the steps of forming a first back-volume portion and a second back-volume portion, the first back-volume portion being separated from the second back-volume portion by a step in a sidewall of the back-volume. The cross-sectional area of the second back-volume portion can be made greater than the cross-sectional area of the membrane, thereby enabling the back-volume to be increased without being constrained by the cross-sectional area of the membrane. The back-volume may comprise a third back-volume portion. The third back-volume portion enables the effective diameter of the membrane to be formed more accurately.

First claim

What is claimed is:

1. A MEMS transducer comprising:
a substrate;
at least one membrane formed relative to a first side of the substrate;
a back volume formed relative to a second side of the substrate;
wherein the back volume comprises a first, second and third back-volume portions.

2. A MEMS transducer as claimed in claim 1 , wherein the first and/or third back-volume portion is separated from the second back-volume portion by a discontinuity in a sidewall of the substrate.

3. A MEMS transducer as claimed in claim 2 , wherein the discontinuity comprises a step in the sidewall of the back volume that separates the first and/or third back volume portions.

4. A MEMS transducer as claimed in claim 3 , wherein the step comprises a discontinuity in the cross-sectional area of the back volume in a plane parallel to the substrate.

5. A MEMS transducer as claimed in claim 2 , wherein the discontinuity comprises a discontinuity in the rate of change of cross-sectional area of the back volume in a plane parallel to the substrate.

6. A MEMS transducer as claimed in claim 3 , wherein the step is curved.

7. A MEMS transducer as claimed in claim 1 , wherein the first and third back-volume portions meet the second back-volume portion in a plane parallel to the substrate.

8. A MEMS transducer as claimed in claim 1 , wherein the second back-volume portion has a greater cross-sectional area than the first and third back-volume portions.

9. A MEMS transducer as claimed in claim 1 , wherein the cross-sectional area of the second back-volume portion is greater than the cross-sectional area of the membrane.

10. A MEMS transducer as claimed in claim 1 , wherein the first and third back-volume portions are separated from the second back-volume portion by a discontinuity in a sidewall of the substrate, and wherein the discontinuity comprises a discontinuity in the cross-sectional area of the back-volume going from the first and third back-volume portions to the second back-volume portion.

11. A MEMS transducer as claimed in claim 1 , wherein the back volume is formed by openings in the substrate, and wherein the shape of the openings may be one or more of: circular, square and rectangular.

12. A MEMS transducer as claimed in claim 1 , wherein at least one of said back-volume portions has a square or rectangular cross-section, and at least one of the back-volume portions has a circular cross-section.

13. A MEMS transducer as claimed in claim 1 , wherein the back-volume comprises more than three back-volume portions.

14. A MEMS transducer as claimed in claim 1 , wherein the third back-volume is directly beneath the membrane.

15. A MEMS transducer as claimed in claim 1 , wherein the third back-volume portion is directly beneath the membrane, the first and third back-volume portions being separated from the second back-volume portion by a discontinuity in a sidewall of the substrate, and wherein the discontinuity comprises a discontinuity in the cross-sectional area of the back-volume going from the first and third back-volume portions to the second back-volume portion.

16. A MEMS transducer comprising:
a substrate;
at least one membrane formed relative to a first side of the substrate;
a back volume formed relative to a second side of the substrate;
wherein the back volume comprises a first, second and third back-volume portions, the first and third back-volume portions meeting the second back-volume portion in a plane parallel to the substrate and wherein the second back-volume portion has a greater cross-sectional area than the first and third back-volume portions.

17. A communications device comprising a MEMS transducer as claimed in claim 1 .

18. A package comprising a MEMS transducer as claimed in claim 1 .

19. A package as claimed in claim 18 , wherein the package comprises a lid.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Traynor Anthony Bernard
• Laming Richard Ian
• Hoekstra Tsjerk H

Classifications

• 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

• B81B3/0021 Primary

  Transducers for transforming electrical into mechanical energy or vice versa (dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00) · CPC title

• B81B3/0094

  Constitution or structural means for improving or controlling physical properties not provided for in B81B3/0067 - B81B3/0091 · CPC title

• B81B2201/0235

  Accelerometers · CPC title

• B81B2201/0264

  Pressure sensors · CPC title