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

Abstract

It is demonstrated that the NH 3 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. NH 3 ashing process was the most effective way of removing etching residues as compared to the other processes such as O 2 and He/H 2 gas chemistries. However, NH 3 ashing after to CF 4 resulted in NH 4F formation by the reaction of NH 3 with F in the etching residue in porous silica low- k films. NH 4F could be removed by a carboxylic acid solution. Although the dielectric constant increased by NH 3 ashing and the wet cleaning, IPA rinse and TMCTS treatment could recover it to the initial value.