Sound transducer with interdigitated first and second sets of comb fingers

Patent metadata

Field	Value
Publication number	US-9402137-B2
Application number	US-201113295749-A
Country	US
Kind code	B2
Filing date	Nov 14, 2011
Priority date	Nov 14, 2011
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A sound transducer includes a substrate with a cavity with extending from a first surface of the substrate, a body at least partially covering the cavity and being connected to the substrate by at least one resilient hinge, a first set of comb fingers mounted to the substrate, and a second set of comb fingers mounted to the body. The first set of comb fingers and the second set of comb fingers are interdigitated and configured to create an electrostatic force driving the body in a direction perpendicular to the first surface of the substrate. The body and the at least one resilient hinge are configured for a resonant or a near-resonant excitation by the electrostatic force.

First claim

What is claimed is:

1. A sound transducer comprising:
a substrate having a first surface and a second surface, the first surface defining a first plane, the substrate having a cavity with an interior peripheral edge, the cavity extending from the first surface;
a body having an exterior peripheral edge, the body being parallel to the first plane and at least partially covering the cavity, the body being connected to the substrate by at least one resilient hinge;
a first set of comb fingers mounted to the substrate, the first set of comb fingers being connected to a first electrical connection; and
a second set of comb fingers mounted to the body and extending past the exterior peripheral edge of the body, the second set of comb fingers being connected to a second electrical connection that is isolated from the first electrical connection,
wherein the first set of comb fingers and the second set of comb fingers are interdigitated and configured to create an electrostatic force driving the body in a direction perpendicular to the first plane,
wherein the body and the at least one resilient hinge are configured for a resonant or a near-resonant excitation by the electrostatic force,
wherein the body and the at least one resilient hinge form a resonating structure, and
wherein the first set of comb fingers and the second set of comb fingers are configured to drive the resonating structure, during an operation of the sound transducer, in a substantially permanent resonant or near-resonant excitation and to amplitude-modulate a resulting oscillation of the body at or near a resonant frequency of the resonating structure with a control signal that is based on an electrical input signal to be transduced by the sound transducer.

2. The sound transducer according to claim 1 , wherein, at a rest position of the body, the first set of comb fingers and the second set of comb fingers are displaced with respect to each other, and wherein a displacement between the first set of comb fingers and the second set of comb fingers is less or equal to 10% of a maximum amplitude of an operative displacement of the body in the direction perpendicular to the first plane.

3. The sound transducer according to claim 1 , wherein, at a rest position of the body, the first set of comb fingers and the second set of comb fingers are offset with respect to each other in the direction perpendicular to the first plane by an offset less or equal to 10% of a maximum amplitude of an operative displacement of the body in the direction perpendicular to the first plane.

4. The sound transducer according to claim 1 , wherein the first set of comb fingers and the second set of comb fingers have different extensions in the direction perpendicular to the first plane.

5. The sound transducer according to claim 1 , further comprising a film of a material having an intrinsic stress different from an intrinsic stress of a body material and a hinge material, the film being located at or in at least one of the body and the at least one resilient hinge such that, due to an intrinsic stress difference, the first set of comb fingers and the second set of comb fingers are displaced with respect to each other in the direction perpendicular to the first plane.

6. The sound transducer according to claim 1 , wherein the body and the at least one resilient hinge are monolithically integrated with the substrate.

7. The sound transducer according to claim 1 , wherein the body has a lateral extension parallel to the first plane between 200 μm and 1000 μm, and a thickness in the direction perpendicular to the first plane between 5 μm and 70 μm.

8. The sound transducer according to claim 1 , wherein the body and the at least one resilient hinge form a resonating structure having a resonating frequency between 40 kHz and 400 kHz.

9. The sound transducer according to claim 1 , further comprising a Helmholtz resonator.

10. A sound transducer comprising:
a substrate having a first surface and a second surface, the first surface defining a first plane, the substrate having a cavity with an interior peripheral edge, the cavity extending from the first surface;
a body having an exterior peripheral edge, the body being parallel to the first plane and at least partially covering the cavity, the body being connected to the substrate by at least one resilient hinge;
a first set of comb fingers mounted to the substrate, the first set of comb fingers being connected to a first electrical connection; and
a second set of comb fingers mounted to the body and extending past the exterior peripheral edge of the body, the second set of comb fingers being connected to a second electrical connection that is isolated from the first electrical connection,
wherein the first set of comb fingers and the second set of comb fingers are interdigitated and configured to create an electrostatic force driving the body in a direction perpendicular to the first plane,
wherein the body and the at least one resilient hinge are configured for a resonant or a near-resonant excitation by the electrostatic force,
wherein the first set of comb fingers and the second set of comb fingers form an in-plane comb drive structure,
wherein the body and the at least one resilient hinge form a resonating structure, and
wherein the first set of comb fingers and the second set of comb fingers are configured to drive the resonating structure, during an operation of the sound transducer, in a substantially permanent resonant or near-resonant excitation and to amplitude-modulate a resulting oscillation of the body at or near a resonant frequency of the resonating structure with a control signal that is based on an electrical input signal to be transduced by the sound transducer.

11. The sound transducer according to claim 1 , wherein the substrate has a further cavity with a further interior peripheral edge, the further cavity extending between the first surface and the second surface, and wherein the sound transducer further comprises a further body having a further exterior peripheral edge, the further body being parallel to the first plane and at least partially blocking the further cavity, the further body connected to the substrate by further resilient hinges.

12. The sound transducer according to claim 11 , wherein the cavity and the body form a first sound transducing device and the further cavity and the further body form a second sound transducing device, the first and second sound transducing devices being interconnected with a polysilicon routing or a metal routing.

13. The sound transducer according to claim 11 , wherein the cavity and the body form a first sound transducing device and the further cavity and the further body form a second sound transducing device, the first and second sound transducing devices being electrically isolated by deep trenches in the substrate.

14. The sound transducer according to claim 1 , wherein a part of the substrate is electrically isolated by means of at least one of a pn-junction, a buried oxide isolation layer, or dielectric layer.

15. The sound transducer according to claim 1 , further comprising an anti-stiction structure at least at one of the first set of comb fingers and the second set of comb fingers, the anti-stiction structure configured to prevent a stiction of the interdigitated comb fingers.

16. The sound transducer according to claim 1 , wherein the first set of comb fingers and the second set of comb fingers maintain a minimum relative spacing as the body moves.

17. An array of sound transducers, the array comprising:
a substrate

Assignees

• Hsu Shu-Ting
• Dehe Alfons
• Infineon Technologies Ag

Inventors

• Hsu Shu-Ting
• Dehe Alfons

Classifications

• H04R1/02

  Casings; Cabinets {; Supports therefor;} Mountings therein (H04R1/28 takes precedence {; attachments for microphones H04R1/08; mounting of transducers in earpieces H04R1/1075}) · CPC title

• H04R9/048

  of the ribbon type · CPC title

• H04R19/005 Primary

  using semiconductor materials · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• H04R19/013

  for loudspeakers · CPC title