Miniature condenser microphone and fabrication method therefor

A directional acoustic transducer comprising:

• a supporting substrate;
• at least two electrodes formed in said substrate;
• at least two movable diaphragms, each diaphragm being positioned over a corresponding electrode and including an indentation to maintain a fixed distance between said diaphragm and said diaphragm's corresponding electrode when a bias voltage is applied between said diaphragm and the corresponding electrode, each said electrode including a plurality of holes to allow air in a gap between the electrode and its corresponding diaphragm to escape, thereby reducing acoustical damping therein;
• a plurality of suspension structures formed on the substrate and attached to the diaphragms to support the diaphragms, the suspension structures supporting each diaphragm having a restoring force equal to or greater than surface contact forces between said diaphragm supported by said suspension structures and the supporting substrate, whereby an electrostatic force associated with the bias voltage overcomes the restoring force of said suspension structures, causing the corresponding diaphragm to be pulled towards the supporting substrate;
• and
• a support beam formed in the supporting substrate for providing a flexible mechanical coupling between said movable diaphragms, whereby the response of each diaphragm to incoming sound pressure waves not in phase with one another will be determined by the mechanical interaction between the diaphragms provided by the mechanical coupling beam.

A directional acoustic transducer comprising:

• supporting means;
• a plurality of means fixedly formed on the supporting means for conducting an electrical field;
• a plurality of means positioned over the fixed conducting means for conducting the electrical field and sensing acoustical pressure;
• each said sensing means including means for maintaining a selected distance between said sensing means and a corresponding said fixed conducting means when the electrical field is applied between the sensing means and the fixed conducting means;
• a plurality of means formed on the supporting means and attached to the sensing means to suspend and support the sensing means whereby intrinsic mechanical stress in said sensing means and imposed stress from said supporting means are eliminated, each of said suspension and support means having a restoring force equal to or greater than surface contact forces between corresponding sensing means and supporting means;
• means to provide electrical connections to said sensing means and fixed conducting means;
• and
• means for providing a flexible mechanical coupling between said plurality of sensing means, whereby the response of each sensing means to incoming sound pressure waves not in phase is determined by the mechanical interaction between the plurality of sensing means and the mechanical coupling means, and
• whereby an electrostatic force associated with the electric field overcomes the restoring force of each suspension means, causing the corresponding sensing means to be pulled towards the supporting means;
• and each said fixed conducting means includes means to allow air in a gap between each fixed conducting means and corresponding sensing means to escape, thereby reducing acoustical damping therein.