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The use of a very small backing cavity is possible, thereby obviating the need for creating a backside hole.
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This invention consists of a differential microphone having a perimeter slit formed around the microphone diaphragm that replaces the backside hole previously required in conventional silicon, micromachined microphones. In typical micromachined microphones, it is necessary to incorporate a significant volume of air behind the microphone diaphragm in order to prevent the back volume air from impeding the motion of the diaphragm. The air behind the diaphragm acts as a linear spring whose stiffness is inversely proportional to the nominal volume of air. In order to make this air volume as large as possible, and hence reduce the effective stiffness, a through-hole is normally cut from the backside of the silicon chip. However, the invention enables the creation of the microphone that does not require this backside hole. ADVANTAGES: The use of a very small backing cavity is possible, thereby obviating the need for creating a backside hole. Lower cost since no secondary machining operation for creating backside holes is necessary INTELLECTUAL PROPERTY: US 7,992,283, 8,214,999, 8,276,254, PCT/US2007/01915, South Korea 2008-7021002