Capacitive microphone sensor design and fabrication method for achieving higher signal to noise ratio

A method of fabricating a capacitive micro-electromechanical transducer, the method comprising:

• etching at least a portion of a top surface of a first substrate to form a first cavity;
• depositing a first silicon dioxide layer on the top surface of the first substrate;
• depositing a polysilicon layer on the top surface of the first substrate within the first cavity;
• etching a second cavity into a bottom surface of a second substrate;
• bonding the second substrate with the first substrate, thereby fluidically connecting the first cavity and the second cavity;
• depositing a second silicon dioxide layer on a bottom surface of the second substrate;
• etching a bottom surface of the first substrate to form a bottom cavity that merges with the first cavity;
• and
• etching away the first silicon dioxide layer from a bottom side of the first silicon dioxide layer, thereby releasing the polysilicon layer such that the polysilicon layer vibrates in response to receipt of sound pressure waves.

A capacitive micro-electromechanical transducer, comprising:

• a first substrate having an exterior surface, an interior surface, and a first cavity with a first opening at the exterior surface of the first substrate and a second opening at least proximate the interior surface of the first substrate;
• a second substrate including at least one layer and having an exterior surface, an interior surface, and a second cavity with an opening at least proximate the interior surface of the first substrate and a cavity bottom surface, the interior surface of the second substrate secured to the interior surface of the first substrate;
• and
• a diaphragm that is electrically conductive, the diaphragm including an anchor that secures the diaphragm to the first substrate, wherein the anchor is positioned within the first cavity, the diaphragm including a flat top boarder positioned within the second cavity, wherein at least a portion of the flat top boarder is moveable along an oscillation axis from the second cavity to the first cavity.

A capacitive micro-electromechanical transducer, comprising:

• a first substrate having an exterior surface, an interior surface, and a first cavity with a first opening at the exterior surface of the first substrate and a second opening at least proximate the interior surface of the first substrate;
• a second substrate including at least one layer and having an exterior surface, an interior surface, and a second cavity with an opening at least proximate the interior surface of the first substrate and a cavity bottom surface, the interior surface of the second substrate secured to the interior surface of the first substrate, the cavity bottom surface forming a plurality of stepped regions, and the second substrate including a plurality of holes that extend from the cavity bottom surface through the exterior surface of the second substrate, wherein a relative density of the plurality of holes or a relative size of the plurality of holes increases as the cavity bottom surface is laterally or radially traversed from a perimeter thereof to a center thereof;
• and
• a diaphragm that is electrically conductive, the diaphragm including an anchor that secures the diaphragm to the first substrate, and a flat top boarder, wherein at least a portion of the flat top boarder is moveable along an oscillation axis from one of the first cavity and the second cavity to the other of the first cavity and the second cavity.