Silicon Microphone

• US 20080185669A1
• Filed: 10/18/2005
• Published: 08/07/2008
• Est. Priority Date: 10/18/2004
• Status: Abandoned Application

• Current Assignee: Sensfab Pte., Ltd. (Mems Technology Berhad)
• Original Assignee: Sensfab Pte., Ltd. (Mems Technology Berhad)
• Inventors: Patmon, Bryan Keith, Sooriakumar, Kathirgamasundaram, Kok, Kitt-Wai, Ong, Kok Meng
• Application Number:
  US11/665,528
• Publication Number:
  US 20080185669A1
• Time in Patent Office: Days
• US Class Current: 257/416
• CPC Class Codes: H04R 19/005 using semiconductor materials

Abstract

A silicon microphone includes a diaphragm that is able to flex over an aperture, an area allowing electrical connection to the diaphragm, a backplate parallel to and spaced apart from the diaphragm and extending over the aperture, the backplate being fixed, the backplate and diaphragm forming the parallel plates of a capacitor, the backplate and diaphragm being attached to and insulated from each other around at least a portion the boundary of the aperture, and a backplate support attached to the backplate around the boundary of the aperture, the backplate support not forming an electrical connection with the backplate.

Claims

1. A silicon microphone including

a diaphragm that is able to flex over an aperture,

an area allowing electrical connection to the diaphragm,

a backplate parallel to and spaced apart from the diaphragm and extending over the aperture, the backplate being fixed,

the backplate and diaphragm forming the parallel plates of a capacitor,

the backplate and diaphragm being attached to and insulated from each other around at least a portion of the boundary of the aperture, and

a backplate support attached to the backplate around the boundary of the aperture, the backplate support not forming an electrical connection with the backplate.

2. A silicon microphone as claimed in claim 1 wherein the backplate support is formed from an insulator.

3. A silicon microphone as claimed in claim 1 or claim 2 wherein the silicon microphone includes a layer of insulating material between the backplate and the backplate support.

4. A method of manufacturing a silicon microphone including the steps of:

providing a first wafer including a layer of heavily doped silicon, a layer of silicon and an intermediate layer of oxide between the two silicon layers and having a first major surface on one surface of the layer of heavily doped silicon and a second major surface on the layer of silicon,

providing a second wafer of heavily doped silicon having a first major surface and a second major surface,

forming a layer of oxide on at least the first major surface of the first wafer,

forming a layer of oxide on at least the first major surface of the second wafer,

etching a cavity through the oxide layer on the first major surface of the first wafer and into the layer of heavily doped silicon,

bonding the first major surface of the first wafer to the first major surface of the second wafer,

thinning the first wafer at its second major surface,

patterning and etching acoustic holes in the second major surface of the second wafer,

etching the intermediate layer of oxide from the first wafer,

forming a metal layer on the second major surface of the first wafer, and

forming at least one electrode on the heavily doped silicon of the first wafer and at least one electrode on the second wafer.

5. A method of manufacturing a silicon microphone as claimed in claim 4 wherein the step of bonding a backplate support to the second major surface of the second wafer occurs at any stage after the acoustic holes have been formed in the second wafer.

6. A method of manufacturing a silicon microphone as claimed in claim 4 or claim 5 wherein the step of bonding a backplate support to the second major surface of the second wafer includes the step of bonding an insulator including an aperture to the second major surface of the second wafer and bonding the backplate support to the insulator.