Microspring with conductive coating deposited on tip after release

Abstract

Efficient methods are disclosed for fabricating spring structures in which a passive, conductive coating is deposited onto the spring structure after release. A release layer is deposited on a substrate and then a spring metal layer is formed thereon. A first mask is then used to etch the spring metal layer to form a spring metal finger. A second (release) mask is then deposited that defines a release window used to remove a portion of the release layer and release a free end of the spring metal finger. The second mask is also used as a mask during the subsequent directional deposition of a conductive coating material on the cantilevered tip of the finger. The second mask is then stripped, and the residual coating deposited thereon is lifted off. The resulting spring structure includes conductive coating on the upper surface and front edge of the finger tip.

1 . A spring structure comprising: 
 a substrate;    a release material portion located over the substrate;    a spring metal finger having an anchor portion attached to the release material portion such that the release material portion is located between the anchor portion and the substrate, the spring metal finger also having a free portion extending over the substrate; and    a conductive coating deposited on a front edge of the free portion of the spring metal finger.    
     
     
         2 . The spring structure according to  claim 1 , wherein the conductive coating comprises at least one refractory noble metal.  
     
     
         3 . The spring structure according to  claim 1 , 
 wherein the spring metal finger comprises at least one of Molybdenum (Mo), Chromium (Cr), and Nickel-Zirconium (NiZr), and    wherein the conductive coating comprises at least one of Rh, Ir, Re, Pt, and Pd.    
     
     
         4 . The spring structure according to  claim 1 , wherein the release material portion is electrically conductive.  
     
     
         5 . The spring structure according to  claim 4 , wherein the release material portion comprises at least one metal selected from the group consisting of Ti, Cu, Al, Ni, Zr, and Co.  
     
     
         6 . The spring structure according to  claim 4 , wherein the release material portion comprises heavily doped silicon.  
     
     
         7 . The spring structure according to  claim 4 , further comprising a conductor formed on the substrate, wherein the spring metal finger is electrically connected to the conductor via the release material portion.  
     
     
         8 . The spring structure according to  claim 1 , wherein the conductive coating includes a second portion formed on the anchor portion of the spring metal finger.