Miniature acoustic detector based on electron surface tunneling

An electron surface tunneling acoustic detector comprising:

• a support substrate,
• a rigid perforated suspension plate supported by the substrate,
• a tunneling tip formed on the suspension plate,
• a conductive pressure sensitive membrane mounted on the substrate over the tunneling tip,
• a plurality of control electrodes formed on the suspension plate, and
• a control circuit for applying an electrical potential to between the membrane and the control electrodes to control movement of the membrane and thereby maintain the membrane in a steady state position with respect to the tunneling tip, whereby adjustments to the electrical potential by the control circuit is a measure of sound pressure incident upon the membrane.

A method of fabricating an electron surface tunneling acoustic detector comprising the steps of:

• forming on a silicon substrate a handle substrate layer, a buried silicon dioxide layer, and a device layer,
• etching a plurality of cavities in the device layer, and subsequently filling and planarizing the cavities with a sacrificial material,
• forming a plurality of electrodes and a tunneling tip on the device layer,
• depositing and planarizing on top of the tunneling tip and plurality of electrodes a layer of sacrificial material,
• removing the layer of sacrificial material in a plurality of anchor areas in which a membrane will be attached to the support substrate,
• forming on top of the remaining sacrificial layer and anchor areas the membrane,
• etching the support substrate from its back to form a cavity, and
• etching all sacrificial layers to form the tunneling acoustic detector.