Capacitive micromachined ultrasonic transducer and method of manufacturing the same

A method of producing a capacitive micromachined ultrasonic transducer, the method comprising the steps of:

• providing a device layer of undoped silicon with an outer surface that is exposed;
• etching the outer surface of the device layer to form post holes extending partially into the device layer;
• forming a first oxide growth layer on the device layer so as to fill the post holes and cover the outer surface of the device layer;
• forming a second oxide growth layer;
• removing portions of the first oxide growth layer and the second oxide growth layer to form anchors extending beyond the outer surface of the device layer and posts partially buried within the post holes and extending beyond the outer surface of the device layer;
• bonding the anchors to a first electrode forming a cavity defined by the first electrode, the device layer, and the anchors, the posts positioned within the cavity;
• and
• depositing an upper electrode on a surface of the device layer opposite from the outer surface of the device layer;
• wherein the device layer is a membrane of the capacitive micromachined ultrasonic transducer with the posts positioned within the cavity and partially buried within the membrane and extending towards the first electrode.