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

Abstract

Semiconductor devices with enclosed cavities and methods for fabricating semiconductor devices with enclosed cavities are provided. In an embodiment, a method for fabricating a semiconductor device with a cavity includes providing a substrate terminating at an uppermost surface and forming a sacrificial structure over the uppermost substrate of the substrate. The method includes 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. The method also includes depositing a permeable layer over the sacrificial structure, the device structure and the substrate. Further, the method includes 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.

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 over the uppermost substrate of 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.   
     
     
         2 . The method of  claim 1  wherein:
 forming the sacrificial structure over the uppermost substrate of 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. 
 
     
     
         3 . 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. 
     
     
         4 . The method of  claim 1  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. 
 
     
     
         5 . The method of  claim 1  wherein:
 depositing the permeable layer over the sacrificial structure comprises depositing a permeable material having a bottom surface in contact with the sacrificial structure and with the substrate and having a top surface; and 
 etching the sacrificial structure through the permeable layer to form the cavity bounded by the substrate and the permeable layer 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. 
 
     
     
         6 . The method of  claim 1  wherein:
 depositing the permeable layer over the sacrificial structure comprises depositing a permeable material having a bottom surface in contact with the sacrificial structure and with the substrate and having a top surface; and 
 the permeable material is unetched before etching the sacrificial structure through the permeable layer to form the cavity bounded by the substrate and the permeable layer. 
 
     
     
         7 . The method of  claim 1  wherein forming the sacrificial structure over the uppermost substrate of the substrate comprises:
 depositing a sacrificial layer over an upper surface of the substrate, wherein the upper surface of the substrate defines a plane; and 
 etching the sacrificial layer to form the sacrificial structure, wherein the sacrificial structure extends in a longitudinal direction parallel to the plane. 
 
     
     
         8 . The method of  claim 1  wherein:
 forming the sacrificial structure over the uppermost surface of the substrate comprises forming the sacrificial structure with a bottom surface in contact with the substrate, and with a top surface and side surfaces; and 
 depositing the permeable layer over the sacrificial structure and the substrate comprises depositing the permeable layer on the top surface and on the side surfaces. 
 
     
     
         9 . The method of  claim 8  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 top surface and side surfaces of the sacrificial structure. 
     
     
         10 . 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. 
     
     
         11 . The method of  claim 1  further comprising depositing a capping layer over the permeable layer. 
     
     
         12 . The method of  claim 1  wherein forming the device structure overlying the lower portion of the sacrificial structure, overlying the uppermost surface of the substrate, and underlying the upper portion of the sacrificial structure comprises forming a lower portion of the device structure over the uppermost surface of the substrate and forming an upper portion of the device structure on the lower portion of the device structure and on the lower portion of the sacrificial structure. 
     
     
         13 . The method of  claim 12  further comprising planarizing the lower portion of the sacrificial structure to the lower portion of the device structure. 
     
     
         14 . A method for forming a hidden cavity and device structure therein, the method comprising:
 forming a lower portion of the device structure over an upper surface of a semiconductor substrate;   forming a lower portion of a sacrificial structure on the upper surface of the semiconductor substrate;   forming an upper portion of the device structure on the lower portion of the device structure and on the lower portion of the sacrificial structure;   forming an upper portion of the sacrificial structure over the device structure and lower portion of the sacrificial structure;   encapsulating the sacrificial structure with a permeable layer; and   etching the sacrificial structure through the permeable layer to form the hidden cavity and the device structure encapsulated by the substrate and the permeable layer.   
     
     
         15 . The method of  claim 14  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. 
     
     
         16 . The method of  claim 14  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 
 
 encapsulating the sacrificial structure with the permeable layer comprises depositing a permeable material onto the top surface and side surfaces. 
 
     
     
         17 . The method of  claim 16  wherein etching the sacrificial structure through the permeable layer to form the hidden cavity encapsulated by the semiconductor substrate and the permeable layer comprises permeating an etchant through the permeable layer and into contact with the top surface and side surfaces. 
     
     
         18 . The method of  claim 14  wherein:
 forming the lower portion of the device structure over the upper surface of the semiconductor substrate comprises forming the lower portion of the device structure with a first side surface and a second side surface opposite the first side surface; and 
 forming the lower portion of the sacrificial structure on the upper surface of the semiconductor substrate comprises forming the lower portion of the sacrificial structure in direct contact with the first side surface and the second side surface of the lower portion of the device structure. 
 
     
     
         19 . The method of  claim 18  further comprising planarizing the lower portion of the sacrificial structure to the lower portion of the device structure. 
     
     
         20 . A semiconductor device comprising:
 a substrate including a topside;   a permeable layer located over the substrate and including an underside, wherein the underside of the permeable layer and the topside of the substrate bound a cavity; and   a capping layer located on the permeable layer.