Foundry-compatible through silicon via process for integrated micro-speaker and microphone

A Micro-Electric Mechanical System (MEMS) audio device comprising:

• a first wafer characterized by a first surface comprising a first cavity and a second surface comprising at least a first vent hole formed through the first wafer and coupled to the first cavity, wherein the second surface comprises a first plurality of electrical contacts;
• a second wafer disposed upon the first surface of the first wafer, wherein the second wafer is characterized by a flexible material layer, wherein a portion of the flexible material layer is disposed above the first cavity of the first wafer;
• a third wafer disposed upon the second wafer, wherein the third wafer is characterized by a first surface having a first plurality of physical contacts coupled to the second wafer, wherein the third wafer is characterized by a first cavity, and wherein the first cavity of the third wafer is disposed above the portion of the flexible material layer;
• a wiring wafer disposed below the second surface of the first wafer, wherein wiring wafer comprises at least a first vent hole, wherein the first vent hole of the wiring wafer is coupled to the first cavity of the first wafer, wherein the wiring wafer comprises a first plurality of electrical contacts, and wherein the first plurality of electrical contacts of the wiring wafer are coupled to the first plurality of electrical contacts of the first wafer;
• and
• wherein the first portion of the flexible material forms a diaphragm for the MEMS audio device.

A vertically integrated Micro-Electro Mechanical Systems (MEMS) assembly comprising:

• a MEMS wafer or a combination of wafers, comprising a substrate having a first cavity and a MEMS layer, wherein the MEMS layer comprises a frame, a micro speaker diaphragm, and a flexible element, wherein the substrate is coupled to the frame, wherein the micro speaker diaphragm is coupled to the frame via the flexible element, wherein the flexible element enables the micro speaker diaphragm to move out of a plane of the MEMS layer within the cavity, and wherein the substrate comprises at least one electrode associated with the micro speaker diaphragm;
• a wafer disposed above the MEMS wafer and coupled to the frame, wherein the wafer comprises another cavity, wherein the other cavity is disposed above the micro speaker diaphragm;
• a CMOS wafer disposed below the MEMS wafer and coupled to the frame, wherein the CMOS wafer comprises at least one active element, wherein the one active element is coupled to the one electrode, and wherein the one active element is configured to provide an electric signal to the one electrode;
• wherein the micro speaker diaphragm is configured to move out of the plane of the MEMS layer in response to the electrical signal.