Acceleration sensor

Abstract

Various acceleration sensors are disclosed. In some cases, an inertial mass may be formed during back-end-of-line (BEOL). In other cases, a membrane may have a bent, undulated or winded shape. In yet other embodiments, an inertial mass may span two or more pressure sensing structures.

What is claimed is: 
     
         1 . An acceleration sensor, comprising:
 a pressure sensing structure formed in a wafer, and   an inertial mass provided on the pressure sensing structure, the inertial mass comprising a back-end-of-line structure.   
     
     
         2 . The acceleration sensor of  claim 1 , wherein the pressure sensing structure comprises a membrane. 
     
     
         3 . The acceleration sensor of  claim 2 , wherein the membrane, in a membrane portion free of the inertial mass, has at least one of a winded shape, an undulating shape or a bent shape. 
     
     
         4 . The acceleration sensor of  claim 2 , wherein the membrane has an area between 5 μm·5 μm and 30 μm·30 μm. 
     
     
         5 . The acceleration sensor of  claim 1 , wherein the inertial mass comprises at least one metal layer. 
     
     
         6 . The acceleration sensor of  claim 1 , wherein the inertial mass comprises at least one dielectric layer. 
     
     
         7 . The acceleration sensor of  claim 1 , wherein the inertial mass is capped with a metal layer. 
     
     
         8 . The acceleration sensor of  claim 1 , further comprising a further pressure sensing structure formed in the wafer adjacent to the pressure sensing structure, wherein the inertial mass spans the pressure sensing structure and the further pressure sensing structure. 
     
     
         9 . The acceleration sensor of  claim 8 , wherein the further pressure sensing structure comprises a membrane. 
     
     
         10 . An acceleration sensor, comprising:
 a membrane formed on a wafer, and   an inertial mass covering part of the membrane,   wherein a portion of the membrane outside an area covered by the inertial mass has at least one of a winded, undulated or bent shape.   
     
     
         11 . The acceleration sensor of  claim 10 , wherein the inertial mass comprises a back-end-of-line structure. 
     
     
         12 . The acceleration sensor of  claim 10 , further comprising elements formed on the wafer under the portion of the membrane to cause the at least one of a winded, undulated or bent shape. 
     
     
         13 . The acceleration sensor of  claim 12 , wherein the elements are front-end-of-line structures. 
     
     
         14 . The acceleration sensor of  claim 12 , wherein the elements are made of polycrystalline silicon. 
     
     
         15 . An acceleration sensor, comprising:
 a first pressure sensing structure formed in a wafer,   a second pressure sensing structure adjacent to the first pressure sensing structure, and   an inertial mass on and spanning the first pressure sensing structure and the second pressure sensing structure.   
     
     
         16 . The acceleration sensor of  claim 15 , wherein the inertial mass is a back-end-of-line inertial mass. 
     
     
         17 . The pressure sensor of  claim 15 , wherein the first pressure sensing structure comprises a first membrane, and wherein the second pressure sensing structure comprises a second membrane. 
     
     
         18 . The pressure sensor of  claim 15 , wherein the first pressure sensing structure is operable independent from the second pressure sensing structure. 
     
     
         19 . The acceleration sensor of  claim 15 , further comprising at least one further pressure sensing structure, the at least one further pressure sensing structure being located adjacent to at least one of the first or second pressure sensing structure, the inertial mass also on and spanning the at least one further pressure sensing structure.