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 spring contact, comprising:
 a substrate;   a stress-engineered member having an anchor portion and a free portion, the anchor portion fixed to the substrate and substantially extending in a first plane, the free portion not fixed to the substrate and extending out of and not parallel with the first plane;   a nanowire formed on the free portion and extending out of and not parallel with the first plane;   wherein the stress-engineered member as-formed is provided with an inherent stress gradient in a direction substantially perpendicular to the first plane, said nanowire initially formed on and in electrical communication with the free portion, and the free portion released from the substrate such that the inherent stress gradient in the stress-engineered member biases the free portion away from the substrate carrying with it the nanowire.   
     
     
         2 . The spring contact of  claim 1  wherein said stress-engineered member is formed to have a sidewall extending substantially perpendicular to said first plane, and said nanowire is formed on said sidewall. 
     
     
         3 . The spring contact of  claim 2 , wherein said stress-engineered member comprises a stress engineered layer over a single-crystal silicon layer such that said sidewall presents the <111> plane of said single crystal silicon in the region in which said nanowire is formed on said sidewall. 
     
     
         4 . The spring contact of  claim 1 , wherein said nanowire has a tip which, following release of the free portion of said stress-engineered member, extends above said substrate by a distance greater than the greatest distance said free portion extends above said substrate. 
     
     
         5 . The spring contact of  claim 1 , wherein each of the stress-engineered member and the nanowire have a primary long axis, and further wherein each said primary long axis is generally parallel to the other. 
     
     
         6 . The spring contact of  claim 1 , further comprising a clamping structure formed over and around at least the point of connection between the stress-engineered member and the nanowire. 
     
     
         7 . The spring contact of  claim 6 , wherein said nanowire originally extends out of and not parallel with said first plane, and further wherein said nanowire is bent and clamped by said clamping structure into said first plane prior to release of said free portion. 
     
     
         8 . The spring contact of  claim 1 , wherein at least a tip portion of said nanowire has a coating applied thereto. 
     
     
         9 . The spring contact of  claim 1 , wherein at least a tip portion of said nanowire is doped. 
     
     
         10 . The spring contact of  claim 1 , further comprising a plurality of nanodots applied as a coating over said microspring body, and wherein said nanodots form catalyst sites from which said nanowire forms. 
     
     
         11 . The spring contact of  claim 10 , wherein said nanowire originally extends out of and not parallel with said first plane, and further wherein said nanowire is bent and clamped by a clamping structure into said first plane prior to release of said free portion.