Patent ID: 6027951
Filing Date: 2000-02-22
Classification: B82Y,G01Q,Y10S

Abstract:
A process of fabricating high aspect ratio probes, comprising:covering a top surface of a substrate of single crystal silicon with successive first oxide, nitride and second oxide layers to form a dielectric stack;producing on said stack an island pattern of resist material defining the location of a probe to be fabricated in the substrate;transferring said island pattern to said dielectric stack to thereby produce an oxide, nitride, oxide dielectric island;etching said silicon substrate utilizing said second oxide dielectric layer as an etch mask to produce a silicon cone beneath and centered on said dielectric island, said cone having an etch profile defining an apex under said island and a wall tapering downwardly and outwardly to a cone base, level with an etched horizontal top surface of said substrate surrounding said base;thermally growing a third oxide layer on the wall of said cone and on said top surface of said substrate;removing said third oxide layer from said top surface surrounding said cone base and leaving said third oxide layer on said wall;etching said top surface around said base to remove substrate silicon to thereby form a post below and vertically aligned with said cone, said post being integral to said cone and having a vertical dimension greater than its horizontal dimension;thermally oxidizing said post and said cone to reduce the dimensions thereof, thereby producing a silicon needle having a sharpened tip beneath said dielectric island and to produce a conformal electrically insulating layer on said needle;covering said insulating and said dielectric island layer with a gate metal layer;depositing a masking layer on said gate metal layer;etching said metal from said island and to a depth along said needle to form a gate aperture surrounding said sharpened tip; andremoving said conformal insulating layer from the sharpened tip to provide a gap between said gate aperture and said tip to thereby produce a high aspect ratio gated probe.