Etching method

Abstract

An etching method is described, including a first etching step that uses a first etching gas including a first fluorinated hydrocarbon compound, and a second etching step that uses a second etching gas including a second fluorinated hydrocarbon compound. The hydrogen content in the first fluorinated hydrocarbon compound is lower than that in the second fluorinated hydrocarbon compound, such that the after-etching-inspection (AEI) critical dimension is smaller than the after-development-inspection (ADI) critical dimension.

1 . An etching method, comprising: 
 providing a semiconductor substrate, on which a dielectric layer, an anti-reflection coating (ARC) and a patterned photoresist layer are formed sequentially;    conducting a first etching step, which uses the patterned photoresist layer as a mask and uses a first etching gas including a first fluorinated hydrocarbon compound, to remove at least the ARC exposed by the patterned photoresist layer;    conducting a second etching step, which uses the patterned photoresist layer as a mask and uses a second etching gas including a second fluorinated hydrocarbon compound, to remove a portion of the dielectric layer; and    removing the patterned photoresist layer,    wherein a first hydrogen content in the first fluorinated hydrocarbon compound is lower than a second hydrogen content in the second fluorinated hydrocarbon compound.    
   
   
       2 . The etching method of  claim 1 , wherein the first fluorinated hydrocarbon compound comprises tetrafluoromethane (CF 4 ).  
   
   
       3 . The etching method of  claim 2 , wherein the first etching gas further comprises a mixed gas of octafluorobutene (C 4 F 8 ) and hexafluorobutyne (C 4 F 6 ).  
   
   
       4 . The etching method of  claim 3 , wherein the first etching gas further comprises CO or O 2 .  
   
   
       5 . The etching method of  claim 1 , wherein the second etching step comprises a main etching step and an over-etching step.  
   
   
       6 . The etching method of  claim 5 , wherein the second fluorinated hydrocarbon compound used in the main etching step comprises CHF 3  and CH 2 F 2 .  
   
   
       7 . The etching method of  claim 6 , wherein the second etching gas used in the main etching step further comprises CH 3 F.  
   
   
       8 . The etching method of  claim 7 , wherein the second etching gas used in the main etching step further comprises argon (Ar) or O 2 .  
   
   
       9 . The etching method of  claim 5 , wherein the second fluorinated hydrocarbon compound used in the over-etching step comprises hexafluorobutyne (C 4 F 6 ), octafluoropentyne (C 5 F 8 ) or octafluorobutene (C 4 F 8 ).  
   
   
       10 . The etching method of  claim 9 , wherein the second etching gas used in the over-etching step further comprises O 2  or Ar.  
   
   
       11 . The etching method of  claim 1 , wherein the first and the second etching steps are conducted at different temperatures.  
   
   
       12 . The etching method of  claim 11 , wherein the temperature of the first etching step is lower than the temperature of the second etching step.  
   
   
       13 . The etching method of  claim 12 , wherein the temperature of the first etching step is lower than the temperature of the second etching step by about 5-20° C.  
   
   
       14 . The etching method of  claim 11 , wherein the temperature of the first etching step is about 0-30° C.  
   
   
       15 . The etching method of  claim 11 , wherein the temperature of the second etching step is about 30-50° C.  
   
   
       16 . The etching method of  claim 11 , wherein the first and the second etching steps are conducted in different etching chambers.  
   
   
       17 . The etching method of  claim 1 , wherein in the first etching step, a polymer spacer is formed on a sidewall of the patterned photoresist layer.