Plasma for patterning advanced gate stacks

Abstract

A plasma composition and its use in a method for the dry etching of a stack of at least one material chemically too reactive towards the use of a Cl-based plasma are provided. Small amounts of nitrogen (5% up to 10%) can be added to a BCl 3 comprising plasma and used in an anisotropical dry etching method whereby a passivation film is deposited onto the vertical sidewalls of stack etched for protecting the vertical sidewalls from lateral attack such that straight profiles can be obtained.

1 . A dry-etch plasma composition for preserving a vertical profile of a structure comprising a stack of layers, wherein a removable water-soluble film is deposited onto the sidewalls of the stack from the plasma composition during dry-etch patterning of the stack, such that lateral attack of the patterned stack is avoided.  
     
     
         2 . The plasma composition of  claim 1 , wherein the plasma comprises a boron-halogen compound and nitrogen.  
     
     
         3 . The plasma composition of  claim 2 , further comprising an inert compound.  
     
     
         4 . The plasma composition of  claim 2 , wherein a ratio of the boron-halogen compound to nitrogen is from 19:1 to 9:1.  
     
     
         5 . The plasma composition of  claim 2 , wherein the boron-halogen compound is BCl 3 .  
     
     
         6 . The plasma composition of  claim 1 , wherein the stack of layers is a metal gate-comprising stack.  
     
     
         7 . The plasma composition of  claim 6 , wherein the metal gate-comprising stack comprises TaN or TaN/TiN.  
     
     
         8 . The plasma composition of  claim 6 , wherein at least one layer of the stack of layers is a germanium-comprising layer.  
     
     
         9 . The plasma composition of  claim 8 , wherein the germanium layer is situated upon a layer to be patterned by the plasma composition.  
     
     
         10 . The plasma composition of  claim 1 , wherein the substrate bias is different from zero.  
     
     
         11 . The plasma composition of  claim 1 , wherein the plasma power is from 100 W to 1200 W.  
     
     
         12 . The plasma composition of  claim 11 , wherein the plasma power is about 450 W.  
     
     
         13 . The plasma composition of  claim 1 , wherein the pressure in the plasma chamber is from 0.666 Pa to 10.665 Pa.  
     
     
         14 . The plasma composition of  claim 1 , wherein the pressure in the plasma chamber is 0.666 Pa.  
     
     
         15 . The plasma composition of  claim 1 , wherein a temperature of the plasma during patterning is below 100° C.  
     
     
         16 . The plasma composition of  claim 1 , wherein a temperature of the plasma during patterning is about 60° C.  
     
     
         17 . The plasma composition of  claim 1 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein from 5% to 10% of the total plasma composition is nitrogen.  
     
     
         18 . The plasma composition of  claim 1 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein less than 10% of the total plasma composition is nitrogen.  
     
     
         19 . The plasma composition of  claim 1 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein less than 8% of the total plasma composition is nitrogen.  
     
     
         20 . The plasma composition of  claim 1 , wherein the plasma is a BCl 3  plasma wherein 5% of the total plasma composition is nitrogen.  
     
     
         21 . An anisotropical dry etching method for patterning a stack of layers to create a vertical structure, the method comprising the steps of: 
 patterning a stack of layers to create a vertical structure by dry etching using a plasma composition comprising a boron-halogen compound and nitrogen, wherein a protective and water-soluble film is deposited from the plasma onto vertical sidewalls of the structure during dry etching, such that a vertical profile of the structure is preserved and lateral attack is avoided during dry etching; and    removing the film from the structure.    
     
     
         22 . The method of  claim 21 , wherein the film is removed by a wet removal process using water.  
     
     
         23 . The method of  claim 21 , wherein a ratio of boron-halogen compound to nitrogen is from 19:1 to 9:1.  
     
     
         24 . The method of  claim 21 , wherein the boron-halogen compound is BCl 3 .  
     
     
         25 . The method of  claim 21 , wherein the plasma further comprises an inert compound.  
     
     
         26 . The method of  claim 21 , wherein the stack of layers is a metal gate-comprising stack.  
     
     
         27 . The method of  claim 26 , wherein the metal gate-comprising stack comprises TaN or TaN/TiN.  
     
     
         28 . The method of  claim 26 , wherein at least one layer of the stack of layers comprises germanium.  
     
     
         29 . The method of  claim 28  wherein the germanium-comprising layer is situated upon a layer to be patterned by the plasma composition.  
     
     
         30 . The method of  claim 21 , wherein a substrate bias during patterning is different from zero.  
     
     
         31 . The method of  claim 21 , wherein a plasma power during patterning is from 100 W to 1200 W.  
     
     
         32 . The method of  claim 21 , wherein a plasma power during patterning is about 450 W.  
     
     
         33 . The method of  claim 21 , wherein a pressure in the plasma chamber during patterning is from 0.666 Pa to 10.665 Pa.  
     
     
         34 . The method of  claim 21 , wherein a pressure in the plasma chamber during patterning is 0.666 Pa.  
     
     
         35 . The method of  claim 21 , wherein the temperature of the plasma during patterning is below 100° C.  
     
     
         36 . The method of  claim 21 , wherein the temperature of the plasma during patterning is about 60° C.  
     
     
         37 . The method of  claim 21 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein from 5% to 10% of the total plasma composition is nitrogen.  
     
     
         38 . The method of  claim 21 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein less than 10% of the total plasma composition is nitrogen.  
     
     
         39 . The method of a  claim 21 , wherein the plasma consists of a boron-halogen compound and nitrogen, and wherein less than 8% of the total plasma composition is nitrogen.  
     
     
         40 . The method of  claim 21 , wherein the plasma is a BCl 3  plasma wherein 5% of the total plasma composition is nitrogen.