Microphone with Irregular Diaphragm

Abstract

A microphone is formed to have a diaphragm that is configured to improve signal to noise ratio. To that end, the microphone has a backplate having a hole therethrough, and a diaphragm movably coupled with the backplate. The diaphragm has a bottom surface (facing the backplate) with a convex portion aligned with the hole in the backplate.

What is claimed is: 
     
         1 . A method of forming a MEMS device, the method comprising:
 providing a backplate having a hole;   depositing a filler material within the hole to form an uneven top surface;   forming a diaphragm above the uneven top surface so that the diaphragm has a protruding portion on a bottom surface, the diaphragm being formed to be coupled with the backplate; and   forming a space between the diaphragm and the backplate, the diaphragm bottom surface facing the backplate, the protruding portion being substantially aligned with the hole in the backplate.   
     
     
         2 . The method as defined by  claim 1  wherein the diaphragm has a top surface that opposes the bottom surface, the protruding portion of the diaphragm forming a depression in the top surface. 
     
     
         3 . The method as defined by  claim 1  wherein the backplate has a plurality of holes therethrough, the diaphragm having a plurality of protruding portions that each share a vertical plane with one of the plurality of holes. 
     
     
         4 . The method as defined by  claim 1  wherein coupling comprises forming an insulator layer between the backplate and the diaphragm. 
     
     
         5 . The method as defined by  claim 1  wherein forming a diaphragm and forming a space comprises using micromachining techniques. 
     
     
         6 . The method as defined by  claim 1  wherein forming a diaphragm comprises:
 adding a spacer layer to the uneven top surface of filler material; 
 adding diaphragm material to a surface of the spacer layer; and 
 removing at least a portion of the filler material. 
 
     
     
         7 . The method as defined by  claim 1  wherein the backplate is formed from an SOI wafer. 
     
     
         8 . The method as defined by  claim 1  wherein at least a portion of the filler material is between the backplate and the diaphragm. 
     
     
         9 . The method as defined by  claim 1  wherein the diaphragm has a bottom surface shape that is substantially the same as the surface shape of the uneven top surface of the filler material. 
     
     
         10 . The method as defined by  claim 1  wherein the protruding portion on the bottom of the diaphragm extends toward and does not extend into the hole in the backplate when at rest. 
     
     
         11 . The method as defined by  claim 1  wherein the diaphragm comprises a plurality of dimples, at least one of the dimples forming the protruding portion. 
     
     
         12 . The method as defined by  claim 1  further comprising forming a backside cavity under the backplate, the backplate being between the backside cavity and the diaphragm. 
     
     
         13 . A method of forming a MEMS device, the method comprising:
 forming a hole in a backplate;   depositing a filler material within the hole to form an uneven top surface;   forming a diaphragm above the uneven top surface so that the diaphragm has a protruding portion on a bottom surface, the diaphragm being formed to be coupled with the backplate; and   forming a space between the diaphragm and the backplate, the diaphragm bottom surface facing the backplate, the protruding portion being substantially aligned with the hole in the backplate.   
     
     
         14 . The method as defined by  claim 13  wherein the diaphragm has a top surface that opposes the bottom surface, the protruding portion of the diaphragm forming a depression in the top surface. 
     
     
         15 . The method as defined by  claim 13  wherein the backplate has a plurality of holes therethrough, the diaphragm having a plurality of protruding portions that each share a vertical plane with one of the plurality of holes. 
     
     
         16 . The method as defined by  claim 13  wherein coupling comprises forming an insulator layer between the backplate and the diaphragm. 
     
     
         17 . The method as defined by  claim 13  wherein forming a diaphragm comprises forming a diaphragm on the uneven top surface so that the diaphragm has a protruding portion on a bottom surface. 
     
     
         18 . The method as defined by  claim 13  wherein the diaphragm comprises a plurality of dimples, at least one of the dimples forming the protruding portion. 
     
     
         19 . The method as defined by  claim 13  further comprising forming a backside cavity under the backplate, the backplate being between the backside cavity and the diaphragm. 
     
     
         20 . The method as defined by  claim 13  wherein at least a portion of the filler material is between the backplate and the diaphragm.