MEMS acoustic transducer with silicon nitride backplate and silicon sacrificial layer
AssigneeRobert Bosch GmbH
InventorsAndo Feyh, Andrew Graham
Life of this patent
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Abstract
A microelectromechanical system (MEMS) microphone has a substrate including a backside trench, and a flexible membrane deposited on the substrate extending over the backside trench. The flexible membrane includes a first electrode. A silicon spacer layer is deposited on a perimeter portion of the flexible membrane. The spacer layer defines an acoustic chamber above the membrane and the backside trench. A silicon rich silicon nitride (SiN) backplate layer is deposited on top of the silicon spacer layer extending over the acoustic chamber. The backplate defines a plurality of opening into the acoustic chamber and includes a metallization that serves as a second electrode.
Claims19
A microelectromechanical system (MEMS) device comprising:
- a substrate including a backside trench;
- a flexible membrane deposited on the substrate extending over the backside trench, the flexible membrane including a first electrode;
- a silicon spacer layer deposited on a perimeter portion of the flexible membrane, the spacer layer defining an acoustic chamber positioned above the membrane and the backside trench;
- and
- a silicon rich silicon nitride (SiN) backplate layer deposited on top of the silicon spacer layer extending over the acoustic chamber, the backplate defining a plurality of opening into the acoustic chamber and including a second electrode.
A method of fabricating a MEMS device, the method comprising:
- depositing a conductive layer onto a thermally oxidized substrate configured to serve as a movable electrode for a MEMS microphone;
- depositing an oxide layer on an upper surface of the conductive layer;
- depositing a sacrificial silicon layer on the oxide layer;
- forming plug structures in the sacrificial silicon layer that define a horizontal extent of an air gap for the MEMS device and are configured to serve as etch stops;
- depositing a silicon rich silicon nitride (SiN) layer onto the sacrificial silicon layer to serve as a backplate;
- depositing a conductive layer adjacent to the SiN backplate layer to serve as fixed electrode for the MEMS microphone;
- and
- etching the sacrificial silicon layer using the oxide layer and the plug structures as etch stops to form an acoustic chamber between the conductive layer and the backplate.
Dependencies are inferred from the claim text.