ACOUSTIC GALVANIC ISOLATION DEVICE

• US 20160183007A1
• Filed: 09/10/2015
• Published: 06/23/2016
• Est. Priority Date: 12/17/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV), Université François Rabelais de Tours
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV), Université François Rabelais de Tours
• Inventors: Ngo, Sophie, Certon, Dominique, Alquier, Daniel
• Granted Patent: US 9,820,056 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H04R 19/00 Electrostatic transducers

Abstract

An acoustic galvanic isolation device includes a substrate capable of transmitting an acoustic wave. A first network of vibrating membrane electroacoustic transducers is arranged on a first surface of the substrate. A second network of vibrating membrane electroacoustic transducers is arranged on a second opposite surface of the substrate. An effective thickness of the substrate exhibits a gradient between the first and second surfaces with respect to propagating the acoustic wave.

Claims

1. An acoustic galvanic isolation device, comprising:

a substrate configured for transmitting an acoustic wave;

a first network of vibrating membrane electroacoustic transducers arranged on a first surface of the substrate; and

a second network of vibrating membrane electroacoustic transducers arranged on a second surface of the substrate opposite the first surface;

wherein the substrate has an effective thickness gradient between the first and second surfaces.

2. The device of claim 1, wherein the substrate includes a non-porous silicon portion and a porous silicon portion, wherein the first and second surfaces are planar and parallel to each other, and wherein an interface between the non-porous silicon portion and the porous silicon portion is non-planar.

3. The device of claim 2, wherein a thickness of the non-porous silicon portion defining the non-planar interface varies in discrete steps.

4. The device of claim 2, wherein the interface between the non-porous silicon portion and the porous silicon portion is concave.

5. The device of claim 1, wherein the substrate is made of a single material.

6. The device of claim 5, wherein a thickness of the single material of the substrate varies in discrete steps.

7. The device of claim 5, wherein at least one of the first and second surfaces is concave.

8. The device of claim 1, wherein the substrate includes a non-porous silicon portion and a plurality of porous silicon areas arranged at a periphery of the substrate and extending from the first surface to the second surface.

9. The device of claim 1, wherein the acoustic wave has a frequency in a range from a high frequency f_max to a low frequency f_min, and the substrate has a maximum effective thickness L_max and a minimum effective thickness L_min selected to be such that:

10. The device of claim 1, further comprising means capable of modifying the biasing of the transducers to adapt the resonance frequency of the transducers to the frequency of the acoustic wave.

11. The device of claim 1, wherein the substrate includes a non-porous silicon portion and a plurality of porous silicon areas arranged in the first surface, each porous silicon area associated with at least one transducer and each porous silicon area having a different depth extending into the substrate from the first surface.

12. An acoustic galvanic isolation device, comprising:

a substrate configured for transmitting an acoustic wave;

a first network of vibrating membrane electroacoustic transducers arranged along a lateral dimension on a first surface of the substrate; and

a second network of vibrating membrane electroacoustic transducers arranged along the lateral dimension on a second surface of the substrate opposite the first surface;

wherein an effective thickness for acoustic propagation between the first surface and second surface varies along the lateral dimension.

13. The device of claim 12, wherein the effective thickness varies in discrete steps along the lateral dimension.

14. The device of claim 13, wherein the first surface is a stepped surface.

15. The device of claim 13, wherein the first and second surfaces are planar and parallel to each other, the substrate comprises a non-porous silicon portion and a porous silicon portion in contact with each other at an interface that is stepped along the lateral dimension.

16. The device of claim 13, wherein the first and second surfaces are planar and parallel to each other, the substrate comprises a non-porous silicon portion and a plurality of porous silicon regions formed in the first surface, separated from each other and having different depths along the lateral dimension.

17. The device of claim 12, wherein the effective thickness varies continuously along the lateral dimension.

18. The device of claim 17, wherein the first surface is a continuously curved concave surface along the lateral dimension.

19. The device of claim 17, wherein the first and second surfaces are planar and parallel to each other, the substrate comprises a non-porous silicon portion and a porous silicon portion in contact with each other at an interface that has a continuously curved concave shape along the lateral dimension.

20. The device of claim 12, wherein the substrate includes a non-porous silicon portion and a plurality of porous silicon areas arranged at a periphery of the substrate and extending from the first surface to the second surface.