Dry-etch for selective oxidation removal

Abstract

Methods of selectively etching tungsten oxide relative to tungsten, silicon oxide, silicon nitride and/or titanium nitride are described. The methods include a remote plasma etch formed from a fluorine-containing precursor and/or hydrogen (H 2 ). Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the tungsten oxide. The plasmas effluents react with exposed surfaces and selectively remove tungsten oxide while very slowly removing other exposed materials. In some embodiments, the tungsten oxide selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region. The ion suppression element reduces or substantially eliminates the number of ionically-charged species that reach the substrate.

What is claimed is: 
     
         1 . A method of etching a substrate in a substrate processing region of a substrate processing chamber, wherein the substrate has exposed tungsten oxide, the method comprising:
 flowing a fluorine-containing precursor and hydrogen (H 2 ) into a remote plasma region fluidly coupled with the substrate processing region while forming a plasma in the plasma region to produce plasma effluents;   flowing the plasma effluents through a showerhead separating the remote plasma region from the substrate processing region; and   contacting the exposed tungsten oxide with the plasma effluents to etch the tungsten oxide from the substrate.   
     
     
         2 . The method of  claim 1  wherein the operation of etching the tungsten oxide comprises etching tungsten oxide faster than silicon by a ratio of about 20:1 or more, faster than silicon oxide by a ratio of about 15:1 or more or faster than titanium nitride by a ratio of about 20:1 or more. 
     
     
         3 . The method of  claim 1  wherein flowing the fluorine-containing precursor comprises flowing the fluorine-containing precursor at between about 25 sccm and about 400 sccm into the remote plasma region while etching the tungsten oxide. 
     
     
         4 . The method of  claim 1  wherein flowing the hydrogen (H 2 ) into the remote plasma region comprises flowing the hydrogen (H 2 ) at between about 1 sccm and about 25 sccm. 
     
     
         5 . The method of  claim 1  wherein the exposed tungsten oxide comprises about 20% or more tungsten and about 60% or more oxygen. 
     
     
         6 . The method of  claim 1  wherein a temperature of the substrate is greater than or about 30° C. and less than or about 200° C. during the etching operation. 
     
     
         7 . The method of  claim 1  wherein flowing a fluorine-containing precursor and hydrogen (H 2 ) results in an atomic flow ratio (F:H) of about 5:1 or more entering the substrate processing region. 
     
     
         8 . The method of  claim 1  wherein a pressure within the substrate processing region is between about 0.1 Torr and about 50 Torr. 
     
     
         9 . The method of  claim 1  wherein forming a plasma in the plasma region to produce plasma effluents comprises applying RF power between about 10 watts and about 200 watts to the plasma region. 
     
     
         10 . The method of  claim 1  wherein the operation of etching the tungsten oxide comprises etching tungsten oxide faster than tungsten by a ratio of about 10:1 or more. 
     
     
         11 . The method of  claim 1  wherein the operation of etching the tungsten oxide comprises etching tungsten oxide faster than silicon by a ratio of about 20:1 or more, faster than silicon oxide by a ratio of about 15:1 or more or faster than titanium nitride by a ratio of about 20:1 or more. 
     
     
         12 . A method of etching a substrate in a substrate processing region of a substrate processing chamber, wherein the substrate has exposed tungsten oxide, the method comprising:
 flowing hydrogen (H 2 ) into a remote plasma region fluidly coupled with the substrate processing region while forming a plasma in the plasma region to produce plasma effluents;   flowing the plasma effluents through a showerhead separating the remote plasma region from the substrate processing region; and   contacting the exposed tungsten oxide with the plasma effluents to etch the tungsten oxide from the substrate.   
     
     
         13 . The method of  claim 12  wherein the operation of etching the tungsten oxide comprises etching tungsten oxide faster than silicon by a ratio of about 20:1 or more, faster than silicon oxide by a ratio of about 15:1 or more or faster than titanium nitride by a ratio of about 20:1 or more. 
     
     
         14 . The method of  claim 12  wherein flowing the hydrogen (H 2 ) comprises flowing the hydrogen (H 2 ) at between about 100 sccm and about 2 slm into the remote plasma region while etching the tungsten oxide. 
     
     
         15 . The method of  claim 12  further comprising flowing a fluorine-containing precursor into the remote plasma region at a flow rate of about 20 sccm or less while etching the tungsten oxide. 
     
     
         16 . The method of  claim 15  wherein flowing hydrogen (H 2 ) and the fluorine-containing precursor results in an atomic flow ratio (H:F) of about 20:1 or more entering the substrate processing region. 
     
     
         17 . The method of  claim 12  wherein a temperature of the substrate is greater than or about 30° C. and less than or about 400° C. during the etching operation. 
     
     
         18 . The method of  claim 12  wherein a pressure within the substrate processing region is between about 0.1 Torr and about 50 Torr. 
     
     
         19 . The method of  claim 12  wherein forming a plasma in the plasma region to produce plasma effluents comprises applying RF power between about 100 watts and about 3000 watts to the plasma region. 
     
     
         20 . The method of  claim 12  wherein the operation of etching the tungsten oxide comprises etching tungsten oxide faster than tungsten by a ratio of about 10:1 or more.