Techniques and apparatus for anisotropic metal etching

Abstract

In one embodiment, a method for etching a copper layer disposed on a substrate includes directing reactive ions to the substrate when a mask that defines an exposed area and protected area is disposed on the copper layer, wherein an altered layer is generated in the exposed area comprising a chemically reactive material; and exposing the copper layer to a molecular species that is effective to react with the chemically reactive material so as to remove the altered layer.

What is claimed is: 
     
         1 . A processing apparatus, comprising:
 a plasma chamber configured to generate a plasma comprising reactive ions;   an extraction plate having an extraction aperture to direct the reactive ions to a substrate over trajectories that form a non-zero angle with respect to a perpendicular to a substrate plane;   an extraction voltage supply to impart an ion energy to the reactive ions sufficient to implant into a metal layer disposed on the substrate to form an altered layer comprising a chemically reactive material; and   a molecular source to provide a molecular species to the substrate that is effective to react with the chemically reactive material so as remove the altered layer from the metal layer.   
     
     
         2 . The processing apparatus of  claim 1 , wherein the plasma chamber and molecular source comprise separate chambers. 
     
     
         3 . The processing apparatus of  claim 1 ,
 wherein the extraction plate is configured to modify a shape of a plasma sheath boundary proximate the extraction aperture, and wherein at least some of the reactive ions are directed to the substrate over trajectories that form a non-zero angle with respect to a perpendicular to a substrate plane.   
     
     
         4 . The processing apparatus of  claim 1 , wherein the reactive ions comprise oxygen. 
     
     
         5 . The processing apparatus of  claim 4 , wherein metal layer is copper and the molecular species comprises an acetylacetonate. 
     
     
         6 . The processing apparatus of  claim 1 , wherein the reactive ions comprise hydrogen. 
     
     
         7 . The processing apparatus of  claim 6  wherein the molecular species comprise arsine, trimethylarsine, phosphine, or trimethylphosphine.