MEMS device, assembly comprising the MEMS device, and methods for operating the MEMS device

Patent metadata

Field	Value
Publication number	US-12240749-B2
Application number	US-201917755934-A
Country	US
Kind code	B2
Filing date	Nov 13, 2019
Priority date	Nov 13, 2019
Publication date	Mar 4, 2025
Grant date	Mar 4, 2025

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. At least one first cavity is formed in the second layer. The MEMS device further comprises a laterally deflectable member having an end connected to a sidewall of the first cavity and a free end. Further, the MEMS device includes a passive element rigidly tethered to the free end of the laterally deflectable element to follow movement of the laterally deflectable element. The laterally deflectable element and the passive element divide the first cavity into a first sub-cavity and a second sub-cavity. The first sub-cavity is in contact with an ambient fluid of the MEMS device via at least a first opening. Further, the second subcavity is in contact with the ambient fluid of the MEMS device via at least a second opening. The at least one first opening is formed in a different layer of the first layer and the third layer than the at least one second opening.

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 at least one first cavity is formed in the second layer;
a laterally deflectable element having an end connected to a side wall of the first cavity and a free end; and
a passive element rigidly connected to the free end of the laterally deflectable element in order to follow a movement of the laterally deflectable element;
wherein the laterally deflectable element and the passive element divide the first cavity into a first sub-cavity and a second sub-cavity,
wherein the first sub-cavity is in contact with an ambient fluid of the MEMS device via at least one first opening,
wherein the second sub-cavity is in contact with the ambient fluid of the MEMS device via at least one second opening, and
wherein the at least one first opening is formed in another layer of the first layer and the third layer than the at least one second opening.

2. The MEMS device of claim 1 , wherein a stiffness of the passive element is greater than or equal to a stiffness of the laterally deflectable element.

3. The MEMS device of claim 1 , wherein an extension of the passive element along a thickness direction of the second layer is equal to an extension of the laterally deflectable element along the thickness direction of the second layer.

4. The MEMS device of claim 1 , wherein an extension of the passive element along a thickness direction of the second layer is at least partially less than an extension of the laterally deflectable element along the thickness direction of the second layer.

5. The MEMS device of claim 1 , wherein a cross-section of the passive element along its lengthwise extension is smaller than a cross-section of the laterally deflectable element along its lengthwise extension.

6. The MEMS device of claim 1 , wherein a cross-section of the passive element decreases from an end of the passive element connected to the laterally deflectable element toward a free end of the passive element.

7. The MEMS device of claim 1 , wherein at least one hollow space is formed in the passive element.

8. The MEMS device of claim 1 , wherein a ratio of a lengthwise extension of the passive element to its lateral extension is greater than 10:1.

9. The MEMS device of claim 1 , wherein a lengthwise extension of the passive element is between 20% and 160% of a lengthwise extension of the laterally deflectable element.

10. The MEMS device of claim 1 , wherein the first cavity is bounded by two further side walls, wherein the laterally deflectable element extends along its lengthwise extension between the two further side walls, and wherein respective courses of the further side walls are adapted at least partially to an outer contour of the laterally deflectable element.

11. The MEMS device of claim 1 , wherein a separating wall is further formed in the first cavity, which, together with the laterally deflectable element and the passive element, divides the first cavity into the first sub-cavity and the second sub-cavity, wherein a gap is formed between the separating wall and a free end of the passive element in order to enable movement of the passive element relative to the separating wall.

12. The MEMS device of claim 1 , wherein the first sub-cavity is in contact with the ambient fluid of the MEMS device via two first openings, wherein one of the two first openings is arranged in an area of the first sub-cavity in which the laterally deflectable element extends, and wherein the other one of the two first openings is arranged in an area of the first sub-cavity different therefrom.

13. The MEMS device of claim 1 , wherein the laterally deflectable element is configured to laterally deform upon application of a first potential such that the laterally deflectable element and the passive element move relative to side walls of the first cavity in order to alternately decrease and increase a volume of the first sub-cavity and conversely alternately increase and/or decrease a volume of the second sub-cavity to influence the ambient fluid.

14. The MEMS device of claim 1 , wherein the laterally deflectable element and the passive element may move laterally relative to side walls of the first cavity in order to adjust volumes of the first sub-cavity and the second sub-cavity depending on the ambient fluid, and wherein the laterally deflectable element is configured to output a second potential upon lateral deformation due to an external force application by the displacement of the laterally deflectable element and the passive element relative to the side walls of the first cavity.

15. The MEMS device of claim 1 , wherein the laterally deflectable element comprises a first electrode layer and a second electrode layer between which a non-conducting 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 external force application.

16. The MEMS device of claim 1 , further comprising:
a second cavity formed in the second layer;
a further laterally deflectable element having an end connected to a side wall of the second cavity and a free end;
a further passive element rigidly connected to the free end of the further laterally deflectable element in order to follow a movement of the further laterally deflectable element;
wherein the further laterally deflectable element and the further passive element divide the second cavity into a third sub-cavity and a fourth sub-cavity,
wherein the third sub-cavity is in contact with the ambient fluid of the MEMS device via at least one third opening,
wherein the fourth sub-cavity is in contact with the ambient fluid of the MEMS device via at least one fourth opening, and
wherein the at least one third opening is formed in another layer of the first layer and the third layer than the at least one fourth opening.

17. The MEMS device of claim 16 , wherein the side wall of the first cavity and the side wall of the second cavity are opposite each other, the first cavity and the second cavity being adjacent to each other, such that the first cavity and the second cavity are each bounded by a common further side wall extending along a lengthwise extension of the laterally deflectable element and along a lengthwise extension of the further laterally deflectable element.

18. The MEMS device of claim 17 , wherein the at least one second opening and the at least one fourth opening are formed in the same layer of the first layer and the third layer and form a contiguous opening.

19. An assembly, comprising:
at least one MEMS device according to claim 1 ; and
a control circuit configured to provide at least a first potential for the laterally deflectable element of the at least one MEMS device in order to operate the laterally deflectable element as an actuator to influence the ambient fluid; and/or
a measurement circuit configured to measure at least a second potential of the laterally deflectable element in order to operate the laterally deflectable element as a sensor for the ambient fluid.

20. A method for operating a MEMS device according to claim 1 , the method comprising:
laterally deforming the laterally deflectable element in a first direction by applying a potential in order

Assignees

• Fraunhofer Ges Forschung

Inventors

• Kaiser Bert

Classifications

• B81C1/00158

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• B81B2201/032

  Bimorph and unimorph actuators, e.g. piezo and thermo · CPC title

• B81B2201/0257

  Microphones or microspeakers · CPC title

• B81B2203/051

  Translation according to an axis parallel to the substrate · CPC title

• B81B2201/036

  Micropumps · CPC title