Microphone with Irregular Diaphragm
A microphone is formed to have a diaphragm that is configured to improve signal to noise ratio. To that end, the microphone has a backplate having a hole therethrough, and a diaphragm movably coupled with the backplate. The diaphragm has a bottom surface (facing the backplate) with a convex portion aligned with the hole in the backplate.
1 . A method of forming a MEMS device, the method comprising:
providing a backplate having a hole;
depositing a filler material within the hole to form an uneven top surface;
forming a diaphragm above the uneven top surface so that the diaphragm has a protruding portion on a bottom surface, the diaphragm being formed to be coupled with the backplate; and
forming a space between the diaphragm and the backplate, the diaphragm bottom surface facing the backplate, the protruding portion being substantially aligned with the hole in the backplate.
2 . The method as defined by claim 1 wherein the diaphragm has a top surface that opposes the bottom surface, the protruding portion of the diaphragm forming a depression in the top surface.
3 . The method as defined by claim 1 wherein the backplate has a plurality of holes therethrough, the diaphragm having a plurality of protruding portions that each share a vertical plane with one of the plurality of holes.
4 . The method as defined by claim 1 wherein coupling comprises forming an insulator layer between the backplate and the diaphragm.
5 . The method as defined by claim 1 wherein forming a diaphragm and forming a space comprises using micromachining techniques.
6 . The method as defined by claim 1 wherein forming a diaphragm comprises:
adding a spacer layer to the uneven top surface of filler material;
adding diaphragm material to a surface of the spacer layer; and
removing at least a portion of the filler material.
7 . The method as defined by claim 1 wherein the backplate is formed from an SOI wafer.
8 . The method as defined by claim 1 wherein at least a portion of the filler material is between the backplate and the diaphragm.
9 . The method as defined by claim 1 wherein the diaphragm has a bottom surface shape that is substantially the same as the surface shape of the uneven top surface of the filler material.
10 . The method as defined by claim 1 wherein the protruding portion on the bottom of the diaphragm extends toward and does not extend into the hole in the backplate when at rest.
11 . The method as defined by claim 1 wherein the diaphragm comprises a plurality of dimples, at least one of the dimples forming the protruding portion.
12 . The method as defined by claim 1 further comprising forming a backside cavity under the backplate, the backplate being between the backside cavity and the diaphragm.
13 . A method of forming a MEMS device, the method comprising:
forming a hole in a backplate;
depositing a filler material within the hole to form an uneven top surface;
forming a diaphragm above the uneven top surface so that the diaphragm has a protruding portion on a bottom surface, the diaphragm being formed to be coupled with the backplate; and
forming a space between the diaphragm and the backplate, the diaphragm bottom surface facing the backplate, the protruding portion being substantially aligned with the hole in the backplate.
14 . The method as defined by claim 13 wherein the diaphragm has a top surface that opposes the bottom surface, the protruding portion of the diaphragm forming a depression in the top surface.
15 . The method as defined by claim 13 wherein the backplate has a plurality of holes therethrough, the diaphragm having a plurality of protruding portions that each share a vertical plane with one of the plurality of holes.
16 . The method as defined by claim 13 wherein coupling comprises forming an insulator layer between the backplate and the diaphragm.
17 . The method as defined by claim 13 wherein forming a diaphragm comprises forming a diaphragm on the uneven top surface so that the diaphragm has a protruding portion on a bottom surface.
18 . The method as defined by claim 13 wherein the diaphragm comprises a plurality of dimples, at least one of the dimples forming the protruding portion.
19 . The method as defined by claim 13 further comprising forming a backside cavity under the backplate, the backplate being between the backside cavity and the diaphragm.
20 . The method as defined by claim 13 wherein at least a portion of the filler material is between the backplate and the diaphragm.