MEMS device, assembly comprising the MEMS device, and method of operating the MEMS device

Patent metadata

Field	Value
Publication number	US-11770659-B2
Application number	US-202017753031-A
Country	US
Kind code	B2
Filing date	Jul 28, 2020
Priority date	Aug 16, 2019
Publication date	Sep 26, 2023
Grant date	Sep 26, 2023

Abstract

Proposed is a MEMS device comprising a layer stack having at least one second layer formed between a first layer and a third layer. A cavity is formed in the second layer. The MEMS device further comprises two laterally deflectable elements arranged laterally spaced apart in the cavity. Each of the two laterally deflectable elements comprises a respective end connected to a side wall of the cavity. Additionally, the MEMS device comprises a connecting element connected to the two laterally deflectable elements to couple the movement of the two laterally deflectable elements. A plurality of first fingers are arranged discretely spaced between the two laterally deflectable elements on the side wall of the cavity. Further, a plurality of second fingers are arranged discretely spaced between the two laterally deflectable elements on the connecting element. The plurality of second fingers interdigitate with the plurality of first fingers. Further, the plurality of second fingers are laterally displaceable relative to the plurality of first fingers upon deformation of the two laterally deflectable elements such that the plurality of first fingers and the plurality of second fingers define a plurality of volume variable sub-cavities within the cavity. Each of the plurality of sub-cavities is in contact with an ambient fluid of the MEMS device via a respective opening. In case of adjacent sub-cavities of the plurality of sub-cavities, the respective opening of one sub-cavity of the adjacent sub-cavities is formed in a different layer of the first layer, the second layer and the third layer than the opening of the other sub-cavity of the adjacent sub-cavities.

First claim

The invention claimed is:

1. A MEMS device, comprising:
a layer stack having at least one second layer formed between a first layer and a third layer, wherein a cavity is formed in the second layer;
two laterally deflectable elements arranged laterally spaced apart in the cavity, each of the two laterally deflectable elements comprising a respective end connected to a side wall of the cavity;
a connecting element connected to the two laterally deflectable elements to couple the movement of the two laterally deflectable elements;
a plurality of first fingers arranged discretely spaced between the two laterally deflectable elements on the side wall of the cavity;
a plurality of second fingers arranged discretely spaced between the two laterally deflectable elements on the connecting element and interdigitating with the plurality of first fingers, the plurality of second fingers being laterally displaceable relative to the plurality of first fingers upon deformation of the two laterally deflectable elements such that the plurality of first fingers and the plurality of second fingers define a plurality of volume variable sub-cavities within the cavity,
wherein each of the plurality of sub-cavities is in contact with an ambient fluid of the MEMS device via a respective opening, and wherein, in case of adjacent sub-cavities of the plurality of sub-cavities, the respective opening of one sub-cavity of the adjacent sub-cavities is formed in a different layer of the first layer, the second layer and the third layer than the opening of the other sub-cavity of the adjacent sub-cavities.

2. The MEMS device of claim 1 , wherein the opening of the one sub-cavity of the adjacent sub-cavities is formed in the second layer and the opening of the other sub-cavity of the adjacent sub-cavities is formed in the first layer or the second layer.

3. The MEMS device of claim 1 , wherein the opening of the one sub-cavity of the adjacent sub-cavities is formed in the first layer and the opening of the other sub-cavity of the adjacent sub-cavities is formed in the third layer.

4. The MEMS device of claim 1 , wherein the connecting element is connected to the two laterally deflectable elements via a respective flexible element, the flexible element exhibiting a lower stiffness than the connecting element and the two laterally deflectable elements.

5. The MEMS device of claim 1 , wherein a cross-section of each of the plurality of first fingers decreases from an end of the respective first finger connected to the side wall of the cavity toward a free end of the respective first finger.

6. The MEMS device of claim 1 , wherein a cross-section of each of the plurality of second fingers decreases from an end of the respective second finger connected to the connecting element toward a free end of the respective second finger.

7. The MEMS device of claim 1 , wherein the plurality of first fingers and the plurality of second fingers overlap along their longitudinal extent by at least 65%.

8. The MEMS device of claim 1 , wherein the plurality of first fingers and the plurality of second fingers overlap along a thickness direction of the second layer by at least 80%.

9. The MEMS device of claim 1 , wherein a ratio of a lateral extent of a finger of the plurality of first fingers to its longitudinal extent is greater than a ratio of a lateral extent of a finger of the plurality of second fingers to its longitudinal extent.

10. The MEMS device of claim 1 , wherein the respective lateral distance between the plurality of first fingers is 100 μm or less.

11. The MEMS device of claim 1 , wherein a ratio of an extent of the plurality of first fingers and/or an extent of the plurality of second fingers along a thickness direction of the second layer to an extent of the two laterally deflectable elements along the thickness direction of the second layer is between 10% and 100%.

12. The MEMS device of claim 1 , wherein an extent of the plurality of first fingers, the plurality of second fingers, and the two laterally deflectable elements along a thickness direction of the second layer is between 10 μm and 750 μm.

13. The MEMS device of claim 1 , wherein the two laterally deflectable elements are configured to deform laterally upon application of a first potential such that the plurality of second fingers shift laterally with respect to the plurality of first fingers to alternately decrease and increase a volume of the one sub-cavity of the adjacent sub-cavities and, . . . conversely, alternately increase and decrease a volume of the other sub-cavity of the adjacent sub-cavities to influence the ambient fluid.

14. The MEMS device of claim 1 , wherein the plurality of second fingers are laterally displaceable relative to the plurality of first fingers in order to adjust volumes of the adjacent sub-cavities depending on the ambient fluid by lateral deformation of the two laterally deflectable elements, and wherein the two laterally deflectable elements are configured to output a respective second potential in case of lateral deformation due to the external force exerted by the displacement of the plurality of second fingers.

15. The MEMS device of claim 1 , wherein at least one of the two laterally deflectable elements comprises a first electrode layer and a second electrode layer between which a non-conductive layer is formed, wherein the laterally deflectable element is configured to:
laterally deform upon application of a first voltage signal to the first electrode layer and the second electrode layer; and/or
generate a second voltage signal at the first electrode layer and the second electrode layer upon lateral deformation due to an application of an external force.

16. The MEMS device of claim 1 , wherein each of the two laterally deflectable elements further comprises a free end, and wherein the connecting element is connected to the free ends of the two laterally deflectable elements.

17. The MEMS device of claim 1 , wherein each of the two laterally deflectable elements comprises a respective further end connected to a further sidewall of the cavity, the sidewall and the further sidewall being opposite to each other.

18. The MEMS device of claim 1 , further comprising:
two further laterally deflectable elements arranged laterally spaced apart in the cavity, each of the two further laterally deflectable elements comprising a respective end connected to a further side wall of the cavity, and wherein the connecting element is connected to the two further laterally deflectable elements;
a plurality of third fingers arranged discretely spaced between the two further laterally deflectable elements on the further side wall of the cavity;
a plurality of fourth fingers arranged discretely spaced between the two further laterally deflectable elements on the connecting element and interdigitating with the plurality of third fingers, the plurality of fourth fingers being laterally displaceable relative to the plurality of third fingers such that the plurality of third fingers and the plurality of fourth fingers define a further plurality of volume variable sub-cavities within the cavity,
wherein each of the further plurality of sub-cavities is in contact with the ambient fluid via a respective opening, and wherein, in case of adjacent sub-cavities of the further plurality of sub-cavities, the opening of one sub-cavity of the adjacent sub-cavities is formed in a different layer of the first layer, the second layer and the third layer than the opening of the other sub-cavity of the adjacent sub-cavities.

Assignees

• Fraunhofer Ges Forschung

Inventors

• Kaiser Bert
• Monsalve Guaracao Jorge Mario
• Conrad Holger

Classifications

• H04R19/00 Primary

  Electrostatic transducers · CPC title

• B81B3/007

  For controlling stiffness, e.g. ribs · CPC title

• H04R3/00

  Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) · CPC title

• B81B2201/0257

  Microphones or microspeakers · CPC title

• B81B2203/0136

  Comb structures · CPC title