Atomic layer etching and smoothing of refractory metals and other high surface binding energy materials

Abstract

Etching a refractory metal or other high surface binding energy material on a substrate can maintain or increase the smoothness of the metal/high EO surface, in some cases produce extreme smoothing. A substrate having an exposed refractory metal/high EO surface is provided. The refractory metal/high EO surface is exposed to a modification gas to modify the surface and form a modified refractory metal/high EO surface. The modified refractory metal/high EO surface is exposed to an energetic particle to preferentially remove the modified refractory metal/high EO surface relative to an underlying unmodified refractory metal/high EO surface such that the exposed refractory metal/high EO surface after removing the modified refractory metal/high EO surface is as smooth or smoother than the substrate surface before exposing the substrate surface to the modification gas.

What is claimed: 
     
         1 . A method of etching a refractory metal or other high surface binding energy (high E O ) material on a substrate, the method comprising:
 providing a substrate comprising an exposed refractory metal/high E O  surface;   exposing the refractory metal/high E O  surface to a modification gas to modify the surface and form a modified refractory metal/high E O  surface; and   exposing the modified refractory metal/high E O  surface to an energetic particle to preferentially remove the modified refractory metal/high E O  surface relative to an underlying unmodified refractory metal/high E O  surface;   wherein the exposed refractory metal/high E O  surface after removing the modified refractory metal/high E O  surface is as smooth or smoother than the substrate surface before exposing the substrate surface to the modification gas.   
     
     
         2 . The method of  claim 1 , wherein the smoothness of the refractory metal/high E O  surface is maintained. 
     
     
         3 . The method of  claim 1 , wherein the smoothness of the refractory metal/high E O  surface is increased. 
     
     
         4 . The method of  claim 3 , wherein the smoothness of the refractory metal/high E O  surface is increased by more than 10% RMS, more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, 75% or more, more than 80%, or more than 90% RMS, on the order of an order of magnitude increase in smoothness. 
     
     
         5 . The method of  claim 1 , wherein the refractory metal/high E O  surface is a refractory metal selected from the group consisting of Nb, Mo, Ta, W, Re, Ru, Rh, Os, Ir, Ti, V, Cr, Zr and Hf. 
     
     
         6 . The method of  claim 5 , wherein the refractory metal is selected from the group consisting of Mo, Ta and Ru. 
     
     
         7 . The method of  claim 6 , wherein the refractory metal is Ru. 
     
     
         8 . The method of  claim 6 , wherein the refractory metal is Ta. 
     
     
         9 . The method of  claim 6 , wherein the refractory metal is Mo. 
     
     
         10 . The method of  claim 1 , wherein the modification gas comprises O 2  or other oxygen-containing gas. 
     
     
         11 . The method of  claim 1 , wherein the modification gas comprises Cl 2  or other chlorine-containing gas. 
     
     
         12 . The method of  claim 1 , wherein the modification gas comprises a mixture of O 2  or other oxygen-containing gas, and Cl 2  or other chlorine-containing gas. 
     
     
         13 . The method of  claim 7 , wherein the modification gas comprises O 2  or other oxygen-containing gas. 
     
     
         14 . The method of  claim 9 , wherein the modification gas comprises a mixture of O 2  or other oxygen-containing gas, and Cl 2  or other chlorine-containing gas. 
     
     
         15 . The method of  claim 9 , wherein the modification gas comprises a mixture of about 10-20% O 2  and about 90-80% Cl 2 . 
     
     
         16 . The method of  claim 1 , wherein the energetic particle is an inert ion plasma. 
     
     
         17 . The method of  claim 16 , wherein the plasma is an Ar plasma. 
     
     
         18 . The method of  claim 12 , wherein the modification gas mixture is selective to refractory metal. 
     
     
         19 . The method of  claim 1 , wherein the refractory metal/high E O  is a material selected from the group consisting of oxides such as Al 2 O 3 , In 2 O 3 , MgO, SnO, Ta 2 O 5 , TiO 2  and ZrO 2 ; carbides such as BC, SiC and WC; nitrides such as BN, TaN, TiN; sulfides such as ZnS and MoS 2 ; and superconductors such as YBCO. 
     
     
         20 . The method of  claim 1 , wherein the substrate surface is smoothened for non-semiconductor processing applications. 
     
     
         21 . An apparatus for processing a substrate, the apparatus comprising:
 a process chamber comprising a showerhead and a substrate support for holding the substrate having a material,   a plasma generator, and   a controller having at least one processor and a memory,   wherein the at least one processor and the memory are communicatively connected with one another,   the at least one processor is at least operatively connected with flow-control hardware, and   the memory stores machine-readable instructions for etching a refractory metal/high E O  on a substrate, the instructions comprising:
 providing a substrate comprising an exposed refractory metal/high E O  surface; 
 exposing the refractory metal/high E O  surface to a modification gas to modify the surface and form a modified refractory metal/high E O  surface; and 
 exposing the modified refractory metal surface to an energetic particle to preferentially remove the modified refractory metal/high E O  surface relative to an underlying unmodified refractory metal/high E O  surface; 
 wherein the exposed refractory metal/high E O  surface after removing the modified refractory metal/high E O  surface is as smooth or smoother than the substrate surface before exposing the substrate surface to the modification gas.