Mems device

A method of fabricating a micro-electrical-mechanical system (MEMS) microphone on a substrate, the method comprising:

• depositing first and second electrodes;
• and
• depositing a membrane so that it is mechanically coupled to the first electrode;
• and further comprising:
• applying a sacrificial layer between the first and second electrodes;
• and
• removing the sacrificial layer so as to form a MEMS structure with an air gap between the first and second electrodes, in which the membrane and the first electrode are able to move relative to the second electrode in response to pressure differences generated by sound waves,
• wherein the sacrificial layer is an organic sacrificial layer.

A method of fabricating a micro-electrical-mechanical system (MEMS) microphone on a substrate, the method comprising:

• depositing first and second electrodes:
• depositing a membrane so that it is mechanically coupled to the first electrode;
• and
• depositing a back plate so that it is mechanically coupled to the second electrode;
• wherein the back plate is deposited with an increased tensional stress.

A method of fabricating a micro-electrical-mechanical system (MEMS) microphone on a substrate, the method comprising:

• depositing first and second electrodes;
• depositing a silicon nitride membrane so that it is mechanically coupled to the first electrode;
• and
• depositing a silicon nitride back plate so that it is mechanically coupled to the second electrode;
• and further comprising:
• applying a polyimide sacrificial layer between the first and second electrodes;
• and
• removing the polyimide sacrificial layer so as to form a MEMS structure with an air gap between the first and second electrodes, in which the membrane and the first electrode are able to move relative to the second electrode in response to pressure differences generated by sound waves.

A method of fabricating a micro-electrical-mechanical system (MEMS) microphone array on a substrate, the method comprising:

• depositing a plurality of respective first and second electrodes;
• and depositing a plurality of membranes such that each membrane is mechanically coupled to the respective first electrode;
• and further comprising:
• applying a respective sacrificial layer between the each pair of first and second electrodes;
• and
• removing the sacrificial layers so as to form a plurality of MEMS structures with respective air gaps between the pairs of first and second electrodes, in which each of the membranes and the first electrodes coupled thereto are able to move relative to the second electrode in response to pressure differences generated by sound waves.

A micro-electrical-mechanical system (MEMS) microphone array, comprising a plurality of MEMS microphones formed on a single substrate, each MEMS microphone comprising:

• first and second electrodes;
• a membrane, mechanically coupled to the first electrode;
• and
• an air gap between the first and second electrodes, such that the membrane and the first electrode coupled thereto is able to move relative to the second electrode in response to pressure differences generated by sound waves, and
• the microphone array further comprising signal processing circuitry such that the array provides a directionally selective microphone.