Silicon microphone with suspended diaphragm and system with the same
A silicon microphone with a suspended diaphragm and a system with the same are provided, the microphone comprises: a silicon substrate provided with a back hole therein; a compliant diaphragm disposed above the back hole of the silicon substrate and separated from the silicon substrate; a perforated backplate disposed above the diaphragm with an air gap sandwiched in between; and a precisely defined support mechanism, disposed between the diaphragm and the backplate with one end thereof fixed to the edge of the diaphragm and the other end thereof fixed to the backplate, wherein the diaphragm and the backplate are used to form electrode plates of a variable condenser. The microphone with a suspended diaphragm can improve the repeatability and reproducibility in performance and can reduce the diaphragm stress induced by the substrate.
1. A silicon microphone with a suspended diaphragm, comprising:
a silicon substrate provided with a back hole therein;
a compliant diaphragm disposed above the back hole of the silicon substrate and separated from the silicon substrate;
a perforated backplate disposed above the diaphragm with an air gap sandwiched in between;
a spacer forming a boundary of the air gap; and
a support mechanism, circumferentially positioned on the edge of the diaphragm and disposed between the diaphragm and the backplate with one end thereof physically connected and fixed to the edge of the diaphragm and the other end thereof physically connected and fixed to the backplate to allow a vibrating area of the diaphragm to be solely constrained by the support mechanism,
wherein the back hole is formed with a lateral dimension error of about 20 μm, and the support mechanism is defined with a lateral dimension error of less than 1 μm,
wherein the diaphragm and the backplate are used to form electrode plates of a variable condenser.
2. A silicon microphone with a suspended diaphragm of claim 1 , wherein the support mechanism includes a plurality of separate supports.
3. A silicon microphone with a suspended diaphragm of claim 1 , wherein the support mechanism includes a ring-shaped support.
4. A silicon microphone with a suspended diaphragm of claim 1 , wherein the support mechanism is made of stacked layers of one or more materials selected from a group consisting of metals, semiconductors and insulators.
5. A silicon microphone with a suspended diaphragm of claim 1 , further comprising an interconnection column provided in the support mechanism for electrically wiring out the diaphragm.
6. A silicon microphone with a suspended diaphragm of claim 1 , further comprising dimples protruding from the lower surface of the perforated backplate opposite to the diaphragm.
7. A silicon microphone with a suspended diaphragm of claim 1 , wherein, said compliant diaphragm is formed with a part of a silicon device layer or a polysilicon layer stacked on the silicon substrate with an oxide layer sandwiched in between.
8. A silicon microphone with a suspended diaphragm of claim 1 , wherein, said perforated backplate is formed with CMOS passivation layers with a metal layer imbedded therein which serves as an electrode plate of the backplate.
9. A silicon microphone with a suspended diaphragm of claim 1 , wherein said perforated backplate is formed with a polysilicon layer or a SiGe layer.
10. A microphone system, comprising the silicon microphone with a suspended diaphragm of claim 1 and a CMOS circuitry integrated on a single chip.