MEMS acoustic transducer with combfingered electrodes and corresponding manufacturing process

A MEMS acoustic transducer, comprising:

• a substrate of semiconductor material having a back surface and a front surface opposite with respect to a vertical direction;
• a first cavity in the substrate, the first cavity extending from the back surface to the front surface;
• a membrane at the front surface and suspended over the first cavity, a perimeter of the membrane being anchored to the substrate;
• and
• a combfingered electrode arrangement including a plurality of mobile electrodes coupled to the membrane and a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes for forming a sensing capacitor, a deformation of the membrane as a result of incident acoustic pressure waves being configured to cause a capacitive variation of the sensing capacitor,
• wherein the combfingered electrode arrangement lies vertically with respect to the membrane and extends parallel to the membrane, and
• wherein the perimeter of the membrane is anchored to the substrate along its entire perimeter by a membrane anchorage element, wherein the membrane has at least one through opening that places the first cavity in fluidic communication with a second cavity arranged on an opposing side of the membrane.

A MEMS acoustic transducer, comprising:

• a substrate of semiconductor material having a back surface and a front surface opposite with respect to a vertical direction;
• a first cavity in the substrate, the first cavity extending from the back surface to the front surface;
• a membrane at the front surface and suspended over the first cavity, a perimeter of the membrane being anchored to the substrate;
• and
• a combfingered electrode arrangement including a plurality of mobile electrodes coupled to the membrane and a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes for forming a sensing capacitor, a deformation of the membrane as a result of incident acoustic pressure waves being configured to cause a capacitive variation of the sensing capacitor,
• wherein the combfingered electrode arrangement is arranged vertically with respect to the membrane and extends parallel to the membrane,
• wherein each of the plurality of mobile electrodes has a coupling portion directly coupled to the membrane and a main portion supported by the coupling portion in cantilever fashion above the membrane, and
• wherein the plurality of fixed electrodes are arranged in cantilever fashion over the membrane facing, and parallel to, the plurality of mobile electrodes, in a resting condition.

A MEMS acoustic transducer, comprising:

• a substrate of semiconductor material having a back surface and a front surface opposite with respect to a vertical direction;
• a first cavity in the substrate, the first cavity extending from the back surface to the front surface;
• a membrane at the front surface and suspended over the first cavity, a perimeter of the membrane being anchored to the substrate;
• and
• a combfingered electrode arrangement including a plurality of mobile electrodes coupled to a central portion of the membrane and a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes for forming a sensing capacitor, a deformation of the membrane as a result of incident acoustic pressure waves being configured to cause a capacitive variation of the sensing capacitor,
• wherein the combfingered electrode arrangement is arranged vertically with respect to the membrane and extends parallel to the membrane, and
• wherein the deformation of the membrane is designed to cause a first displacement of vertical translation of the plurality of mobile electrodes with respect to the plurality of fixed electrodes.

A MEMS acoustic transducer, comprising:

• a substrate of semiconductor material having a back surface and a front surface opposite with respect to a vertical direction;
• a first cavity in the substrate, the first cavity extending from the back surface to the front surface;
• a membrane at the front surface and suspended over the first cavity, a perimeter of the membrane being anchored to the substrate;
• a combfingered electrode arrangement including a plurality of mobile electrodes coupled to the membrane and a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes for forming a sensing capacitor, a deformation of the membrane as a result of incident acoustic pressure waves being configured to cause a capacitive variation of the sensing capacitor, wherein the combfingered electrode arrangement lies vertically with respect to the membrane and extends parallel to the membrane, wherein the plurality of mobile electrodes and the plurality of fixed electrodes are arranged radially with respect to a center of the membrane;
• a suspension structure including a wall portion that is coupled to the front surface of the substrate and extends vertically with respect to the substrate;
• and
• a cover portion that closes the wall portion at a top and is arranged above the membrane.

An electronic apparatus comprising:

• a control unit;
• and
• a MEMS acoustic transducer coupled to the control unit, the MEMS acoustic transducer including:
• a substrate of semiconductor material;
• a cavity in the substrate;
• a membrane suspended at the cavity, the membrane being configured to deform in response to acoustic pressure;
• a plurality of mobile electrodes coupled to a central portion of the membrane and configured to move in response to the membrane being deformed;
• and
• a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes, thereby forming a sensing capacitor.

A process for manufacturing a MEMS acoustic transducer, the process comprising:

• forming a membrane at a first surface of a substrate, wherein the membrane is suspended by a cavity;
• and
• forming a combfingered electrode arrangement including a plurality of mobile electrodes coupled to the membrane and a plurality of fixed electrodes coupled to the substrate and facing the plurality of mobile electrodes for forming a sensing capacitor, wherein the plurality of mobile electrodes and the plurality of fixed electrodes are arranged to face a surface of the membrane in a direction in which the membrane is configured to deform as a result of incident acoustic pressure waves thereby causing a capacitive variation of the sensing capacitor,
• wherein forming the combfingered electrode arrangement comprises forming the combfingered electrode arrangement to include the plurality of mobile electrodes coupled to a central portion of the membrane.