In this paper the influence of CuSO4, HCHO and NaOH concentrations on the alkaline chemical plating of Ca is discussed and an applicable plating solution for the fabrication of copper interconnect tfor ULSI is then derived. The application of acid-alkaline combined chemical plating of Ca to ULSI interconnect is studied. At first the acid chemical plating of Cu is employed to fabricate the copper seed layer on TiN barrier, and then the alkaline chemical plating of Cu is followed to achieve Cu films. Through the study, we find that the morphology and crystallography orthe seed layer has an important effect on the as-deposited Cu films.