Shown on this slide is a cross-section of ST’s MP34DT01 top-port digital MEMS microphone. In these top-port MEMS microphones, the acoustic sensor and the CMOS interface IC are attached to the package lid. A hole in the lid (the acoustic port) allows the sound waves to reach the sensor. Wire bonds connect the interface IC to the sensor and bond pads on the package. The substrate is soldered to the lid and sealed, creating an enclosed cavity. The difference in pressure created by the sound waves causes the membrane to move, creating the change in capacitance which is converted into a digital output by the CMOS interface IC.