Process to open carbon based hardmask overlying a dielectric layer

Abstract

A method of opening a carbon-based hardmask layer composed of amorphous carbon containing preferably at least 60% carbon and between 10 and 40% hydrogen. The hardmask is opened by plasma etching using an etching gas composed of H 2 , N 2 , and CO. The etching is preferably performed in a plasma etch reactor having an HF biased pedestal electrode and a capacitively VHF biased showerhead.

1 . A method of etching a carbon-based layer formed over a substrate and comprising at least 40 at % carbon, the method comprising exposing the carbon-based layer to a plasma of an etching gas having active components consisting essentially of hydrogen, nitrogen, and carbon monoxide. 
   
   
       2 . The method of  claim 1 , wherein the carbon-based layer comprises at least 60 at % carbon. 
   
   
       3 . The method of  claim 2 , wherein the carbon-based layer comprises between 10 and 40 at % hydrogen. 
   
   
       4 . The method of  claim 1 , wherein the actives components of the etching gas consist of hydrogen, nitrogen, and carbon monoxide. 
   
   
       5 . The method of  claim 1 , wherein a flow of the hydrogen is between 50% and 300% of a flow of the nitrogen. 
   
   
       6 . The method of  claim 1 , further comprising optically patterning a photoresist layer formed over the carbon-based layer. 
   
   
       7 . The method of  claim 6 , further comprising etching a dielectric layer underlying the carbon-based layer using the etched carbon-based layer as a hardmask. 
   
   
       8 . The method of  claim 1 , further comprising placing the substrate into a plasma etch chamber and maintaining a pressure of the chamber at more than 50 milliTorr during the etching. 
   
   
       9 . The method of  claim 8 , wherein the pressure of the chamber is no more than 20 milliTorr during the etching. 
   
   
       10 . A method of etching a carbon-based layer overlying a dielectric layer and comprising at least 40 at % carbon, the method comprising exposing the carbon-based layer to a plasma of an etching gas having active components comprising hydrogen, nitrogen, and carbon monoxide and including no effective amount of fluorine. 
   
   
       11 . The method of  claim 10 , wherein the carbon-based layer comprises at least 60 at % carbon. 
   
   
       12 . The method of  claim 11 , wherein the carbon-based layer comprises between 10 and 40 at % hydrogen. 
   
   
       13 . The method of  claim 10 , wherein the active components of the etching gas consist essentially of hydrogen, nitrogen, and carbon monoxide. 
   
   
       14 . The method of  claim 13 , wherein the active components of the etching gas consist of hydrogen, nitrogen, and carbon monoxide 
   
   
       15 . The method of  claim 10 , wherein a flow of the hydrogen is between 50% and 300% of a flow of the nitrogen. 
   
   
       16 . The method of  claim 1 , further comprising optically patterning a photoresist layer formed over the carbon-based layer. 
   
   
       17 . The method of  claim 16 , further comprising etching the dielectric layer using the etched carbon-based layer as a hardmask. 
   
   
       18 . The method of  claim 17 , wherein the dielectric layer comprises an oxide and wherein the step of etching the dielectric layer includes a fluorine-based etch. 
   
   
       19 . The method of  claim 10 , further comprising placing the substrate into a plasma etch chamber and maintaining a pressure of the chamber at more than 50 milliTorr during the etching. 
   
   
       20 . The method of  claim 19 , wherein the pressure of the chamber is no more than 20 milliTorr during the etching.