Low damage photoresist strip method for low-k dielectrics

Abstract

Improved methods for stripping photoresist and removing etch-related residues from dielectric materials are provided. In one aspect of the invention, methods involve removing material from a dielectric layer using a hydrogen-based etch process employing a weak oxidizing agent and fluorine-containing compound. Substrate temperature is maintained at a level of about 160° C. or less, e.g., less than about 90° C.

What is claimed is:  
     
         1 . A method of removing material from a work piece after an etch process, the method comprising:
 forming a first plasma from a gas comprising hydrogen and a fluorine-containing compound;   exposing the work piece to the first plasma;   forming a second plasma from a gas comprising hydrogen; and   exposing the work piece to the second plasma,   wherein the work piece temperature is maintained at a temperature below about 200° C. during exposure to the first plasma, wherein at least some of the material is removed from the dielectric layer by exposure to the first and second plasmas and the removed material comprises one or more of photoresist and residue from the etch process.   
     
     
         2 . The method of  claim 1 , wherein the material comprises photoresist including a bulk portion and a skin covering the bulk portion. 
     
     
         3 . The method of  claim 2 , wherein exposure to the first plasma removes the skin. 
     
     
         4 . The method of  claim 1 , wherein the gas from which the first plasma is formed further comprises an oxidizing agent selected from carbon dioxide, carbon monoxide, nitrous oxide, nitric oxide and nitrogen dioxide and water. 
     
     
         5 . The method of  claim 1 , wherein the fluorine-containing compound is comprises at least one of nitrogen trifluoride (NF 3 ), sulfur hexafluoride (SF 6 ), hexafluoroethane (C 2 F 6 ), tetrafluoromethane (CF 4 ), trifluoromethane (CHF 3 ), difluoromethane (CH 2 F 2 ), octofluoropropane (C 3 F 8 ), octofluorocyclobutane (C 4 F 8 ), octofluoro[1-]butane (C 4 F 8 ), octofluoro[2-]butane (C 4 F 8 ), octofluoroisobutylene (C 4 F 8 ), and fluorine (F 2 ). 
     
     
         6 . The method of  claim 1 , wherein the second plasma is generated from a fluorine-free process gas chemistry. 
     
     
         7 . The method of  claim 1 , wherein the work piece temperature is maintained at a temperature below about 160° C. during exposure to the first plasma. 
     
     
         8 . The method of  claim 1 , wherein the work piece temperature is maintained at a temperature below about 120° C. during exposure to the first plasma. 
     
     
         9 . The method of  claim 1 , wherein the work piece temperature is raised to a second temperature during exposure to the second plasma, the second temperature greater than the workpiece temperature during exposure to the first plasma. 
     
     
         10 . The method of  claim 9 , wherein the second temperature is no more than about 285° C. 
     
     
         11 . The method of  claim 1 , wherein the same workpiece temperature is maintained during exposure to the first and second plasmas. 
     
     
         12 . The method of  claim 1  wherein the work piece has not undergone a previous oxygen-based plasma photoresist stripping operation. 
     
     
         13 . The method of  claim 1 , wherein the material is removed from a dielectric layer. 
     
     
         14 . The method of  claim 1 , wherein the material is removed from an oxide. 
     
     
         15 . The method of  claim 1 , wherein the material is removed from a carbon-doped oxide. 
     
     
         16 . A method of removing material from a dielectric layer on a work piece as part of a partially fabricated integrated circuit after an etch process, the method comprising:
 forming a first plasma from a gas comprising hydrogen, a fluorine-containing compound, and an oxidizing agent selected from carbon dioxide, carbon monoxide, nitrous oxide, nitric oxide and nitrogen dioxide and water;   exposing the work piece to the first plasma to thereby remove one or more of etch-related residue and photoresist from the dielectric layer, wherein the work piece temperature is maintained at a temperature below about 200° C. during the exposure to the first plasma.   
     
     
         17 . The method of  claim 16 , wherein the work piece temperature is maintained at a temperature below about 120° C. during the exposure to the first plasma. 
     
     
         18 . The method of  claim 16 , wherein the volume percentage of the oxidizing agent is between about 0.1% and 10% in the gas and the volume percentage of the fluorine-containing compound in the gas is no more than 10%. 
     
     
         19 . The method of  claim 16 , wherein the volume percentage of the fluorine-containing compound in the gas is no more than 1%. 
     
     
         20 . 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 for forming a first plasma from a gas comprising hydrogen, a weak oxidizing agent and a fluorine-containing compound; exposing the work piece to the first plasma; forming a second plasma from a gas comprising hydrogen and a weak oxidizing agent; exposing the work piece to the second plasma, and maintaining the work piece at a temperature below about 200° C. during the exposure operations.