Selective etch chemistry for gate electrode materials

Abstract

A chemical solution including an aqueous solution, an oxidizing agent, and a pH stabilizer selected from quaternary ammonium salts and quaternary ammonium alkali can be employed to remove metallic materials in cavities for forming a semiconductor device. For example, metallic materials in gate cavities for forming a replacement gate structure can be removed by the chemical solution of the present disclosure with, or without, selectivity among multiple metallic materials such as work function materials. The chemical solution of the present disclosure provides different selectivity among metallic materials than known etchants in the art.

What is claimed is: 
     
         1 . A chemical composition for a stock solution for generating an etch solution for removal of a metallic material, the chemical composition comprising:
 at least one sequestering agent at a concentration in a range from 200 p.p.m. to 20,000 p.p.m. in weight percentage;   a pH stabilizer including at least one quaternary ammonium salt or at least one quaternary ammonium alkali; and   an aqueous solution.   
     
     
         2 . The chemical composition of  claim 1 , wherein said sequestering agent is selected from amines and amino acids. 
     
     
         3 . The chemical composition of  claim 1 , wherein said sequestering agent is at least one of 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CDTA), ethyenediaminetetraacetic acid (EDTA) and diethylenetriaaminopentaacetic acid (DTPA). 
     
     
         4 . The chemical composition of  claim 1 , wherein the pH stabilizer is selected from the group consisting of at least one quaternary ammonium salt and at least one quaternary ammonium alkali. 
     
     
         5 . The chemical composition of  claim 4 , wherein the pH stabilizer is selected from the group consisting of tetraethylammonium hydroxide, trimethyl-phenyl-ammonium hydroxide, dimethyl-dipropyl-ammonium hydroxide and tetrapropyl ammonium hydroxide. 
     
     
         6 . The chemical composition of  claim 5 , wherein the pH stabilizer is tetraethylammonium hydroxide. 
     
     
         7 . The chemical composition of  claim 1 , wherein the aqueous solution comprises de-ionized water. 
     
     
         8 . The chemical composition of  claim 1 , wherein the composition comprises hydrogen peroxide (H 2 O 2 ), benzotriazole, tetraethylammonium hydroxide, and de-ionized water, and wherein the composition has a pH in the range of about 7 to about 9. 
     
     
         9 . A chemical composition for a stock solution for generating an etch solution for removal of a metallic material, the chemical composition comprising:
 at least one metal protectant at a concentration in a range from 10,000 p.p.m. to 400,000 p.p.m. in weight percentage;   at least one sequestering agent at a concentration in a range from 200 p.p.m. to 20,000 p.p.m. in weight percentage;   a pH stabilizer including at least one quaternary ammonium salt or at least one quaternary ammonium alkali; and   an aqueous solution.   
     
     
         10 . The chemical composition of  claim 9 , wherein said sequestering agent is selected from amines and amino acids. 
     
     
         11 . The chemical composition of  claim 9 , wherein said sequestering agent is at least one of 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CDTA), ethyenediaminetetraacetic acid (EDTA) and diethylenetriaaminopentaacetic acid (DTPA). 
     
     
         12 . The chemical composition of  claim 9 , wherein said metal protectant comprises at least one of benzotriazole, 1,2,3 triazole, 1,3,4 triazole, 1,2,4 triazole, imidazole, methyl-thiol-triazole, thiol-triazole, and triazole acid. 
     
     
         13 . The chemical composition of  claim 9 , wherein the pH stabilizer is selected from the group consisting of at least one quaternary ammonium salt and at least one quaternary ammonium alkali. 
     
     
         14 . The chemical composition of  claim 13 , wherein the pH stabilizer is selected from the group consisting of tetraethylammonium hydroxide, trimethyl-phenyl-ammonium hydroxide, dimethyl-dipropyl-ammonium hydroxide and tetrapropyl ammonium hydroxide. 
     
     
         15 . The chemical composition of  claim 14 , wherein the pH stabilizer is tetraethylammonium hydroxide. 
     
     
         16 . The chemical composition of  claim 9 , wherein the aqueous solution comprises de-ionized water. 
     
     
         17 . The chemical composition of  claim 9 , wherein the composition comprises hydrogen peroxide (H 2 O 2 ), benzotriazole, tetraethylammonium hydroxide, and de-ionized water, and wherein the composition has a pH in the range of about 7 to about 9.