Pre-collapsed capacitive micro-machined transducer cell with annular-shaped collapsed region

1. A pre-collapsed capacitive micro-machined transducer cell comprising:

a substrate comprising a first electrode,

a membrane comprising a second electrode,

an outer region including a support where the membrane is mounted to the substrate,

an inner region surrounded by the outer region,

wherein the membrane is collapsed to the substrate in an annular-shaped first collapsed region located within the inner region to form an annular-shaped cavity between the membrane and the substrate which surrounds the annular-shaped first collapsed region, wherein a height of the annular-shaped cavity continuously decreases from the support to the annular-shaped first collapsed region; and

wherein the second electrode is located above the annular-shaped cavity to provide a transduction region surrounding the annular-shaped first collapsed region.

2. The cell of claim 1 , wherein the second electrode is located at least in close proximity to the annular-shaped first collapsed region.

3. The cell of claim 1 , wherein the second electrode and/or the first electrode have/has an annular shape.

4. The cell of claim 1 , wherein the annular-shaped first collapsed region is located centered around the center of the cell or membrane.

5. The cell of claim 1 , wherein the membrane is further collapsed to the substrate in a second collapsed region located within the inner region.

6. The cell of claim 5 , wherein the second collapsed region is located in a center region or in the center of the cell or membrane.

7. The cell of claim 1 , wherein the membrane has a built-in stress in the inner region, wherein the built-in stress is controlled through stoichiometry of the membrane, use of a multilayer membrane, or combinations thereof.

8. The cell of claim 1 , the membrane further comprising a third electrode located in the first collapsed region.

9. The cell of claim 8 , wherein the second electrode and/or the third electrode have/has at least one opening, and wherein a connector to the fourth electrode and/or the second electrode are/is located in the opening.

10. The cell of claim 1 , wherein the membrane is permanently collapsed.

11. The cell of claim 1 , wherein the membrane is collapsed only during operation of the cell.

12. The cell of claim 1 , further comprising a second collapsed region located within the inner region and a third electrode located within the second collapsed region.

13. The cell of claim 1 , wherein the transduction region surrounding the annular-shaped first collapsed region is a first transduction region, and wherein the cell further comprises another electrode located over a second cavity surrounded by the annular-shaped first collapsed region to provide a second transduction region inside the inner region.

14. A method of manufacturing a pre-collapsed capacitive micro-machined transducer cell, the method comprising:

providing a substrate comprising a first electrode,

providing a membrane comprising a second electrode, wherein the cell has an outer region including a support where the membrane is mounted to the substrate, and an inner region surrounded by the outer region, and

collapsing the membrane to the substrate in a annular-shaped first collapsed region located within the inner region to form an annular-shaped cavity between the membrane and the substrate, wherein the annular-shaped cavity surrounds the annular-shaped first collapsed region, and wherein a height of the annular-shaped cavity continuously decreases from the support to the annular-shaped first collapsed region,

wherein the providing a membrane comprising a second electrode includes locating the second electrode above the annular-shaped cavity to

provide transduction region surrounding the annular-shaped first collapsed region.

15. The method of claim 14 , the membrane further comprising a third electrode located in the annular-shaped first collapsed region,

wherein collapsing the membrane to the substrate comprises applying a voltage between the first electrode and the third electrode.

16. The method of claim 14 , wherein the transduction region surrounding annular-shaped the first collapsed region is a first transduction region, the method further comprising providing another electrode over a second cavity surrounded by the annular-shaped first collapsed region to provide a second transduction region inside the inner region.