Method of manufacturing single-wafer tunneling sensor

A method for sensing rotation rate, comprising:

• (a) providing a tunneling sensor having an unitary structure including:
• a substrate,
• a conductive cantilever electrode extending from the substrate and capable of deflection in response to a Coriolis force induced by rotation,
• a conductive tunneling electrode on the substrate, and
• a lateral control electrode;
• (b) applying a bias voltage across the cantilever and tunneling electrodes so that a tunneling current flows between the cantilever and tunneling electrodes in response to the applied bias voltage, the cantilever and tunneling electrodes forming part of a circuit that produces an output signal such that the Coriolis force which urges the cantilever electrode to deflect relative to the tunneling electrode modulates the output signal;
• (c) applying a modulating voltage to the lateral control electrode to induce a lateral vibration at a known maximum velocity in the cantilever electrode;
• (d) determining the magnitude of the Coriolis force from the modulated output signal, and
• (e) determining the rotational rate from the magnitude of the Coriolis force.

A method for fabricating a tunneling tip sensor for sensing a z-axis force, comprising:

• providing a single semiconductor wafer having a surface that lies in an xy-plane;
• forming an oxide isolation layer on the wafer's surface;
• forming a metal layer on the isolation layer;
• patterning a negative resist over the metal layer to expose a portion of the metal layer;
• ion milling the exposed portion of the metal layer to a reduced thickness and, as part of said ion milling, eroding the negative resist to form a tunneling tip on the metal layer;
• removing the negative resist;
• patterning a positive resist over the metal layer that covers the tunneling tip and exposes selected portions of the metal layer;
• etching the exposed portions of the metal layer down to the isolation layer to define a tunneling tip electrode that is integrally formed with said tip and a cantilever pad that adheres to the isolation layer;
• and
• photolithographically extending the cantilever pad to form a cantilever electrode that extends over the tunneling tip electrode to define a tunneling tip sensor having a unitary structure on the semiconductor wafer, said cantilever and tunneling tip electrodes forming a part of a circuit in which a tunneling current flows between the cantilever and tunneling electrodes in response to an applied bias voltage across the two electrodes and in which a force applied along a z-axis perpendicular to the xy-plane urges said cantilever electrode to deflect relative to said tunneling electrode and to modulate an output signal.