Semiconductor devices with cavities and methods for fabricating semiconductor devices with cavities

1. A method for fabricating a semiconductor device with a cavity, the method comprising:

providing a substrate terminating at an uppermost surface;

forming a sacrificial structure in and/or over the substrate;

forming a device structure overlying a lower portion of the sacrificial structure, overlying the uppermost surface of the substrate, and underlying an upper portion of the sacrificial structure;

depositing a permeable layer over the sacrificial structure, the device structure and the substrate, wherein the permeable material has a bottom surface in contact with the sacrificial structure and with the substrate; and

etching the sacrificial structure through the permeable layer to form the cavity, wherein the cavity has an outer surface completely bounded by the substrate, the device structure, and the permeable layer.

2. The method of claim 1 wherein etching the sacrificial structure through the permeable layer to form the cavity results in encapsulating the cavity with the substrate, the device structure, and the permeable layer upon formation.

3. The method of claim 2 further comprising:

depositing a capping layer over the permeable layer; and

etching an opening through the capping layer and through the permeable layer to open the cavity at a selected location.

4. The method of claim 1 wherein:

the permeable material has a top surface; and

etching the sacrificial structure through the permeable layer to form the cavity comprises contacting the top surface of the permeable material with an etchant and permeating the etchant through the permeable material into contact with the sacrificial structure and into contact with the substrate.

5. The method of claim 1 wherein the permeable material is unetched before etching the sacrificial structure through the permeable layer to form the cavity.

6. The method of claim 1 wherein etching the sacrificial structure through the permeable layer to form the cavity comprises permeating an etchant through the permeable layer and into contact with the sacrificial structure.

7. The method of claim 1 further comprising depositing a capping layer over the permeable layer.

8. The method of claim 1 wherein at least a portion of the device structure is housed within the cavity after etching the sacrificial structure through the permeable layer.

9. A method for forming a hidden cavity and a device structure therein, the method comprising:

etching a trench into a semiconductor substrate;

depositing a sacrificial material in the trench and outside of the trench over the semiconductor substrate;

removing portions of the sacrificial material outside of the trench to form a lower portion of a sacrificial structure in the trench and on the semiconductor substrate;

after removing the portions of the sacrificial material to form the lower portion of the sacrificial structure, forming the device structure over the semiconductor substrate and the lower portion of the sacrificial structure;

after forming the device structure, forming an upper portion of the sacrificial structure over the device structure and lower portion of the sacrificial structure;

after forming the upper portion of the sacrificial structure, covering the sacrificial structure with a permeable layer; and

etching the sacrificial structure through the permeable layer to form the hidden cavity encapsulated by the semiconductor substrate, the device structure, and the permeable layer.

10. The method of claim 9 further comprising depositing a capping material over the permeable layer to form a capping layer, wherein the permeable layer is impermeable to the capping material and separates the capping layer from the hidden cavity.

11. The method of claim 9 wherein:

forming the upper portion of the sacrificial structure comprises:

depositing a sacrificial material on the semiconductor substrate, wherein the sacrificial material has a top surface; and

etching the sacrificial material to define the sacrificial structure with side surfaces; and

covering the sacrificial structure with the permeable layer comprises depositing a permeable material onto the top surface and side surfaces.

12. The method of claim 11 wherein etching the sacrificial structure through the permeable layer to form the hidden cavity comprises permeating an etchant through the permeable layer and into contact with the top surface and side surfaces.

13. The method of claim 9 depositing the sacrificial material in the trench and outside of the trench over the semiconductor substrate comprises filling the trench with a sacrificial material.

14. The method of claim 13 further comprising depositing a capping layer over the permeable layer, wherein the capping layer has a continuous planar bottom surface extending over the semiconductor substrate and the hidden cavity.

15. The method of claim 1 wherein forming the sacrificial structure in and/or over a substrate comprises:

depositing a sacrificial material in and/or over the substrate; and

etching the sacrificial material to form the sacrificial structure in and/or over the substrate.

16. The method of claim 1 wherein forming the sacrificial structure in and/or over a substrate comprises:

etching the substrate to form a trench, wherein the trench is bounded by a trench bottom surface formed by the substrate and trench side surfaces formed by the substrate;

depositing a sacrificial material in and/or over the substrate, wherein the sacrificial material fills the trench; and

removing the sacrificial material outside the trench to form a lower portion of the sacrificial structure in the trench;

wherein etching the sacrificial structure through the permeable layer forms the cavity completely bounded by the trench bottom surface, the trench side surfaces, the device structure, and the permeable layer.

17. The method of claim 1 wherein forming the sacrificial structure in and/or over the substrate comprises forming at least a portion of the sacrificial structure in a trench formed in the substrate, wherein the trench is bounded by a trench bottom surface formed by the substrate and trench side surfaces formed by the substrate; and wherein etching the sacrificial structure through the permeable layer forms the cavity completely bounded by the trench bottom surface, the trench side surfaces, the device structure, and the permeable layer.

18. A method for fabricating a semiconductor device with a cavity, the method comprising:

providing a substrate terminating at an uppermost surface;

forming a sacrificial structure in and/or over the substrate, wherein the sacrificial structure has side surfaces in contact with the substrate;

forming a device structure overlying a lower portion of the sacrificial structure, overlying the uppermost surface of the substrate, and underlying an upper portion of the sacrificial structure;

depositing a permeable layer over the sacrificial structure, the device structure and the substrate; and

etching the sacrificial structure through the permeable layer to form the cavity, wherein the cavity has an outer surface completely bounded by the substrate, the device structure, and the permeable layer.

19. The method of claim 18 wherein:

forming the sacrificial structure in and/or over the substrate comprises forming the sacrificial structure with a top surface; and

depositing the permeable layer over the sacrificial structure and the substrate comprises depositing the permeable layer on the top surface.

20. The method of claim 18 wherein:

forming the sacrificial structure in and/or over the substrate comprises forming the sacrificial structure with a bottom surface in contact with the substrate and with a top surface; and

depositing the permeable layer over the sacrificial structure and the substrate comprises depositing the permeable layer on the top surface.