Patent ID: 8828773

Claim:
A method of forming a microphone, the method comprising: forming a backplate by etching trenches into a layer of an silicon-on-insulator wafer, wherein the trenches have walls; lining the trenches by adding sacrificial wet etch removable material to the walls of the trenches and along at least a top portion of the silicon-on-insulator wafer; adding sacrificial polysilicon to the lined trenches and to the sacrificial wet etch removable material on the top portion of the silicon-on-insulator wafer; adding more sacrificial wet etch removable material to encapsulate the sacrificial polysilicon material; forming a flexible diaphragm on at least a portion of the wet etch removable sacrificial material; adding a wet etch resistant material, a portion of the wet etch resistant material being positioned between the diaphragm and the backplate to support the diaphragm; removing the sacrificial polysilicon; removing the sacrificial wet etch removable material before removing any of the wet etch resistant material added by the act of adding wet etch resistant material; and removing the added wet etch resistant material after removing at least part of the wet etch removable sacrificial material.