Ultra low silicon loss high dose implant strip

Abstract

Improved methods for stripping photoresist and removing ion implant related residues from a work piece surface are provided. According to various embodiments, plasma is generated using elemental hydrogen, a fluorine-containing gas and a protectant gas. The plasma-activated gases reacts with the high-dose implant resist, removing both the crust and bulk resist layers, while simultaneously protecting exposed portions of the work piece surface. The work piece surface is substantially residue free with low silicon loss.

1 . A method of removing material from a work piece surface in a reaction chamber, the method comprising:
 forming a first plasma from a process gas mixture comprising molecular hydrogen, a non-carbon-containing fluorine-containing gas and a fluorocarbon protectant compound, wherein said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound are provided in a first volumetric flow ratio;   exposing the work piece surface to the first plasma to thereby remove a first portion of material from the work piece surface;   changing the volumetric flow ratio of said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound to form a second plasma; and   exposing the work piece surface to the second plasma to thereby remove a second portion of material from the work piece surface.   
     
     
         2 . The method of  claim 1 , wherein the fluorocarbon protectant compound is one of CF 4 , C 2 F 6 , CHF 3 , CH 2 F 2 , C 3 F 8 . 
     
     
         3 . The method of  claim 2  wherein the fluorocarbon protectant compound is CF 4 . 
     
     
         4 . The method of  claim 1  wherein the non-carbon-containing fluorine-containing gas is one of NF 3 , F 2 , HF or SF 6 . 
     
     
         5 . The method of  claim 1  wherein the non-carbon-containing fluorine-containing gas is NF 3 . 
     
     
         6 . The method of  claim 1 , wherein the material removed from the work piece surface comprises a high-dose implanted resist. 
     
     
         7 . The method of  claim 1 , wherein the first volumetric flow ratio of said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound is between about 1:20-1:5 and changing the volumetric flow ratio comprises changing the ratio to between about 1:4-1:2. 
     
     
         8 . The method of  claim 1 , wherein the first volumetric flow ratio of the non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound is between about 1:20-1:5. 
     
     
         9 . The method of  claim 1 , wherein changing the volumetric flow ratio of said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound to form a second plasma comprises shutting off a flow of the fluorocarbon protectant compound. 
     
     
         10 . The method of  claim 1  wherein the process gas mixture further comprises carbon dioxide. 
     
     
         11 . The method of  claim 1 , wherein the work piece is substantially residue free of the high-dose implanted resist after removal and wherein less than about 2 angstroms silicon is lost from a silicon surface of the work piece. 
     
     
         12 . The method of  claim 1 , wherein the work piece is substantially residue free of the high-dose implanted resist after removal and wherein less than about 1 angstrom silicon is lost from a silicon surface of the work piece. 
     
     
         13 . A method of removing material from a work piece surface in a reaction chamber, the method comprising:
 forming a first plasma from a process gas mixture comprising molecular hydrogen, non-carbon-containing fluorine-containing gas and a fluorocarbon protectant compound, and   exposing the work piece surface to the first plasma to thereby remove a first portion of material from the work piece surface and simultaneously form a protective layer on a silicon-containing surface of the workpiece.   
     
     
         14 . The method of  claim 13 , wherein the fluorocarbon protectant compound is one of CF 4 , C 2 F 6 , CHF 3 , CH 2 F 2 , C 3 F 8 . 
     
     
         15 . The method of  claim 13 , wherein the non-carbon-containing fluorine-containing gas is one of NF3, F 2 , HF or SF 6 . 
     
     
         16 . The method of  claim 13 , wherein the fluorocarbon protectant compound is CF 4  and the non-carbon-containing fluorine-containing gas is NF 3 . 
     
     
         17 . The method of  claim 13 , wherein the process gas mixture further comprises carbon dioxide. 
     
     
         18 . The method of  claim 13 , wherein the work piece is substantially residue free of the high-dose implanted resist after removal and wherein less than about 2 angstroms silicon is lost from a silicon surface of the work piece. 
     
     
         19 . The method of  claim 13 , wherein the work piece is substantially residue free of the high-dose implanted resist after removal and wherein less than about 1 angstrom silicon is lost from a silicon surface of the work piece. 
     
     
         20 . A method of removing high-dose implanted resist from a work piece surface in a reaction chamber, the method comprising:
 removing a first portion of the material comprising:
 introducing a first gas comprising molecular hydrogen, a weak oxidizing agent, a non-carbon-containing fluorine containing gas and a fluorocarbon protectant gas into a plasma source; 
 generating a first plasma from the first gas introduced into the plasma source; and 
 exposing the workpiece to a first plasma to remove a first portion of the material; 
   and removing a second portion of the material comprising:
 introducing a second gas comprising molecular hydrogen, a weak oxidizing agent, a non-carbon-containing fluorine containing gas and essentially no fluorocarbon protectant gas into a plasma source; 
 generating a second plasma from the second gas introduced into the plasma source; and 
 exposing the workpiece to second plasma to remove a second portion of the material. 
   
     
     
         21 . An apparatus for removing material from a work piece surface comprising:
 a reaction chamber comprising
 a plasma source, 
 a showerhead positioned downstream of the plasma source, and 
 a work piece support downstream of the showerhead, said work piece support comprising a pedestal and temperature-controlling mechanism to control a temperature of a work piece supported on the work piece support; and, 
 a controller for executing a set of instructions, said set of instruction comprising instructions to form a first plasma from a process gas mixture comprising molecular hydrogen, non-carbon-containing fluorine-containing gas and a fluorocarbon protectant compound, wherein said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound are provided in a first volumetric flow ratio; 
 expose the work piece surface to the first plasma to thereby remove a first portion of material from the work piece surface; 
 change the volumetric flow ratio of said non-carbon-containing fluorine-containing gas and said fluorocarbon protectant compound to form a second plasma; and 
 expose the work piece surface to the second plasma to thereby remove a second portion of material from the work piece surface.