Resist planarization for trench first dual damascene

Resist planarization is applied to trench first dual damascene process in order to enhance focus margin for via lithography after hard mask etch. As a planarization process, resist CMP is better than conventional resist etch back, However, hard mask (HM) erosion by resist CMP causes serious problem of lessened thickness of Cu. To solve it, the combination of CMP and etch back (C+E) is adopted. This method realizes enhancement of the focus margin and prevention from the hard mask erosion at the same time.