Removal of etching/ashing residues and ashing/wet-clean damage in porous silica low-k films

It is demonstrated that the NH3 ashing followed by wet cleaning in carboxylic acid solution, IPA rinse and the TMCTS (1,3,5,7-tetramethylcyclotetrasiloxane) vapor anneal is an effective process for the removal of etching/ashing residues from porous silica low-k films. NH3 ashing process was the most effective way of removing etching residues as compared to the other processes such as O2 and He/H2 gas chemistries. However, NH3 ashing after to CF4 resulted in NH4F formation by the reaction of NH3 with F in the etching residue in porous silica low-k films. NH4F could be removed by a carboxylic acid solution. Although the dielectric constant increased by NH3 ashing and the wet cleaning, IPA rinse and TMCTS treatment could recover it to the initial value.