Highly selective spacer etch process with reduced sidewall spacer slimming

Abstract

A method for performing a spacer etch process is described. The method includes conformally applying a spacer material over a gate structure on a substrate, and performing a spacer etch process sequence to partially remove the spacer material from a capping region of the gate structure and a substrate region on the substrate adjacent a base of the gate structure, while retaining a spacer sidewall positioned along a sidewall of the gate structure. The spacer etch process sequence may include oxidizing an exposed surface of the spacer material to form a spacer oxidation layer, performing a first etching process to anisotropically remove the spacer oxidation layer from the spacer material at the substrate region on the substrate and the spacer material at the capping region of the gate structure, and performing a second etching process to selectively remove the spacer material from the substrate region on the substrate and the capping region of the gate structure to leave behind the spacer sidewall on the sidewall of the gate structure.

What is claimed is: 
     
         1 . A method for performing a spacer etch, comprising:
 providing a substrate having a spacer material conformally applied over a gate structure;   exposing an exposed surface of said spacer material to an oxygen-containing environment to elevate an oxygen content in said spacer material; and   performing a spacer etch process sequence to partially and selectively remove said spacer material from a capping region of said gate structure and a substrate region on said substrate adjacent a base of said gate structure, while retaining a spacer sidewall positioned along a sidewall of said gate structure.   
     
     
         2 . The method of  claim 1 , wherein said spacer material comprises silicon nitride, silicon carbide, or silicon carbonitride. 
     
     
         3 . The method of  claim 2 , wherein said spacer material conformally applied over said gate structure has a thickness less than or equal to about 10 nanometers (nm). 
     
     
         4 . The method of  claim 1 , wherein said oxygen-containing environment contains an oxygen-containing plasma. 
     
     
         5 . The method of  claim 4 , wherein said oxygen-containing environment contains O, O 2 , O 3 , CO, CO 2 , NO, N 2 O, or NO 2 , or any combination of two or more thereof. 
     
     
         6 . The method of  claim 1  wherein performing said spacer etch process sequence comprises:
 performing a first etching process to anisotropically remove said spacer oxidation layer from said spacer material at said substrate region on said substrate and said spacer material at said capping region of said gate structure, while substantially retaining said spacer oxidation layer on said spacer material along said sidewall of said gate structure, and 
 performing a second etching process to selectively remove said spacer material from said substrate region on said substrate and said capping region of said gate structure to leave behind said spacer sidewall on said sidewall of said gate structure. 
 
     
     
         7 . The method of  claim 6 , wherein said performing said first etching process comprises forming plasma from a first etching process composition containing a halomethane gas and a noble gas. 
     
     
         8 . The method of  claim 7 , wherein said performing said first etching process comprises:
 introducing said first etching process composition containing CF 4  and Ar to a plasma processing system,   setting a pressure in said plasma processing system at or less than about 50 mTorr,   forming a first etching plasma from said first etching process composition, and   exposing said substrate to said first etching plasma.   
     
     
         9 . The method of  claim 8 , wherein said performing said first etching process further comprises:
 forming said first etching plasma by coupling electromagnetic (EM) radiation from a radial line slot antenna to said first etching process composition, and   applying an electrical bias to said substrate by coupling radio frequency (RF) power to a substrate holder upon which said substrate rests.   
     
     
         10 . The method of  claim 9 , wherein said forming said first etching plasma comprises coupling electromagnetic (EM) energy at a microwave frequency in a desired EM wave mode to said first etching plasma by generating a surface wave on a plasma surface of an EM wave launcher adjacent said first etching plasma, said EM wave launcher comprises a slot antenna having a plurality of slots formed there through configured to couple said EM energy from a first region above said slot antenna to a second region below said slot antenna. 
     
     
         11 . The method of  claim 6 , wherein said performing said second etching process comprises forming plasma from a second etching process composition containing a halomethane gas, an oxygen-containing gas, and a noble gas. 
     
     
         12 . The method of  claim 11 , wherein said performing said second etching process comprises:
 introducing said second etching process composition containing CH 3 F, O 2 , and Ar to a plasma processing system,   setting a pressure in said plasma processing system at or greater than about 50 mTorr,   forming a second etching plasma from said second etching process composition, and   exposing said substrate to said second etching plasma.   
     
     
         13 . The method of  claim 12 , wherein said performing said second etching process further comprises:
 forming said second etching plasma by coupling EM radiation from a radial line slot antenna (RLSA) to said second etching process composition, and   applying an electrical bias to said substrate by coupling RF power to a substrate holder upon which said substrate rests.   
     
     
         14 . The method of  claim 13 , wherein said forming said second etching plasma comprises coupling electromagnetic (EM) energy at a microwave frequency in a desired EM wave mode to said second etching plasma by generating a surface wave on a plasma surface of an EM wave launcher adjacent said first etching plasma, said EM wave launcher comprises a slot antenna having a plurality of slots formed there through configured to couple said EM energy from a first region above said slot antenna to a second region below said slot antenna. 
     
     
         15 . The method of  claim 1 , further comprising:
 selecting process conditions for said spacer etch process sequence to achieve a substrate recess at said substrate region on said substrate adjacent said base of said gate structure having a value of 1.5 nm or less.   
     
     
         16 . The method of  claim 1 , further comprising:
 selecting process conditions for said spacer etch process sequence to achieve a substrate recess at said substrate region on said substrate adjacent said base of said gate structure having a value of 1 nm or less.   
     
     
         17 . The method of  claim 1 , further comprising:
 selecting process conditions for said spacer etch process sequence to achieve a top recess at said top of said sidewall space on said gate structure having a value of 5 nm or less; and/or   selecting process conditions for said spacer etch process sequence to achieve a CD reduction of said sidewall spacer having a value of 2 nm or less; and/or   selecting process conditions for said spacer etch process sequence to achieve substantially no footing at said base of said gate structure.   
     
     
         18 . The method of  claim 1 , wherein the exposing said exposed surface of said spacer material to an oxygen-containing environment and performing said spacer etch process sequence is performed more than once. 
     
     
         19 . The method of  claim 12 , wherein the plasma processing system comprises one of an electrode through which radio frequency (RF) power is coupled to the plasma, a stationary or an upper electrode through which power can be coupled by an impedance generator, an upper electrode through which power can be coupled to an impedance generator with the upper electrode coupled to a direct current (DC) supply, an inductive coil to which RF power is coupled via an RF generator through an optional impedance network, or an electrode through which RF power and a surface wave plasma (SWP) source are coupled to the plasma. 
     
     
         20 . The method of  claim 1 , wherein the spacer material is applied over the gate structure using a chemical vapor deposition (CVD), a plasma enhanced chemical vapor deposition (PECVD), an atomic layer deposition (ALD), a plasma enhanced atomic layer deposition (PEALD), or a physical vapor deposition (PVD) process; and/or the oxygen-generating environment is an in situ or an ex situ environment.