Method of fabricating an electrostatic ultrasonic transducer
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsMatthew Isaac Haller, Butrus Thomas Khuri-Yakub
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Abstract
A method of fabrication wherein a nitride layer is spaced from a conductive substrate by an insulating layer and etching removes at least portions of an insulating layer to leave a nitride membrane spaced from the substrate. The surface of the conductive layer where the insulating layer is removed is chemically roughened and the etchant is removed by freeze-drying and sublimation to eliminate sticking of the nitride layer to the substrate surface during fabrication.
Claims1
The method of fabricating an electrostatic ultrasonic transducer array including a plurality of ultrasonic transducers each having spaced electrodes comprising the steps of:
- providing a substrate of conductive silicon material;
- forming a layer of silicon nitride on said substrate;
- selectively etching the silicon nitride layer to form a support structure which exposes therebetween a shaped area of the surface of the substrate;
- growing a silicon oxide layer on the exposed surface of the substrate between said support structure;
- growing a membrane layer of low stress silicon nitride directly over such silicon oxide layer and silicon nitride support structure;
- forming a metal layer on the surface of said silicon nitride layer;
- forming openings in said metal layer and said silicon nitride membrane layer to expose the silicon oxide between the silicon nitride support structure;
- and
- etching away all of the silicon oxide to leave a silicon nitride membrane at shaped area supported above the substrate by the silicon nitride support structure.
Dependencies are inferred from the claim text.