Method Of Producing Microsprings Having Nanowire Tip Structures

Abstract

A stress-engineered microspring is formed generally in the plane of a substrate. A nanowire (or equivalently, a nanotube) is formed at the tip thereof, also in the plane of the substrate. Once formed, the length of the nanowire may be defined, for example photolithographically. A sacrificial layer underlying the microspring may then be removed, allowing the engineered stresses in the microspring to cause the structure to bend out of plane, elevating the nanowire off the substrate and out of plane. Use of the nanowire as a contact is thereby provided. The nanowire may be clamped at the tip of the microspring for added robustness. The nanowire may be coated during the formation process to provide additional functionality of the final device.

1 . A method of manufacturing a microspring having an in situ grown tip, comprising the steps of:
 depositing over a substrate a sacrificial release layer;   depositing over said sacrificial release layer a stress-engineered layer in a first plane;   patterning said stress-engineered layer to define a microspring body substantially in said first plane, said microspring body including an anchor portion and a tip portion;   defining a catalyst location at least at said tip portion of said microspring body for initiating growth of a nanowire;   growing said nanowire from said catalyst location located at said tip portion of said microspring body;   forming a clamping structure over and around at least a point of connection between said tip portion of said microspring body and said nanowire; and   removing a portion of said sacrificial release layer located under at least said tip portion of said microspring body such that stress within said stress-engineered layer causes said tip portion, with said nanowire to curve out of said first plane, while said anchor portion remains attached over said substrate.   
     
     
         2 . The method of  claim 1 , wherein said nanowire is grown substantially out of and not parallel to said first plane, further comprising the step of bending said nanowire into said first plane prior to the step of forming a clamping structure over and around at least a point of connection between said tip portion of said microspring body and said nanowire. 
     
     
         3 . The method of  claim 1 , further comprising the steps of:
 forming a mask structure over and encasing said microspring body and a first portion of said nanowire; and   etching so as to remove a second portion of said nanowire not encased within said mask structure; and   removing said mask structure.   
     
     
         4 . The method of  claim 1 , wherein said step of defining a catalyst location comprises:
 applying over said microspring body a suspension containing nanodots; and   evaporating said suspension such that said nanodots remain on at least said first and second sidewalls.   
     
     
         5 . The method of  claim 1 , wherein said step of defining a catalyst location comprises depositing then patterning a layer containing nanodots which may serve as catalyst locations.