DRY ASHING METHOD FOR ASHING TiN LAYER WITHOUT ISOTROPIC ETCHING

PROBLEM TO BE SOLVED: To remove a residue without excessive etching of the base layer of a via by ashing a residue generating during formation of the via by using a plasma containing an oxygen, a gas containing halogen and plasma water vapor. SOLUTION: A residue generated during the formation of via such as a resist 18a around the via and a polymer 22 on the inner wall of the via is removed through an reactive etching ashing process by using a plasma containing an oxygen, a fluorine gas (preferably NF3) and water vapor and N2H2 if necessary. The ashing process preferably uses a via provided with a titanium nitride base layer. Since the residue becomes soluble in a deionized (DI) water through the ashing process, a water can be cleaned through a rinsing process after the ashing process. The water vapor suppresses the etching of the titanium nitride layer during the ashing process.