Patent ID: 8860154

Claim:
A CMOS compatible silicon differential condenser microphone, comprising: a silicon substrate, wherein a CMOS circuitry is accommodated thereon; a first rigid conductive perforated backplate formed on the silicon substrate, wherein the outskirts of the first backplate are supported on the silicon substrate with an insulating layer inserted therebetween; a second rigid perforated backplate formed above the first backplate, including CMOS passivation layers and a metal layer sandwiched between the CMOS passivation layers as an electrode plate of the second plate; a compliant diaphragm formed with a CMOS compatible layer and provided between the first backplate and the second backplate; a first air gap separating the first backplate and the diaphragm and a second air gap separating the diaphragm and the second backplate, wherein both air gaps are bounded with a spacer provided between the first backplate and the second backplate; a back hole formed to be open in the silicon substrate underneath the first backplate so as to allow sound pass through, wherein the diaphragm and the first backplate form a first variable condenser, the diaphragm and the second backplate form a second variable condenser, and the first variable condenser and the second variable condenser form differential condensers.