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Cu metallization by electrochemical deposition has been implemented in ULSI circuit fabrication for forming interconnects since 1998 . As wafer size increases from 8- to 12-inch,and the Cu seed layer decreases in thickness for every technology node,ohmic resistance of Cu seed layer increases significantly,leading to severe non-uniform deposition of copper film due to a phenomenon called "terminal effect" . A deposited Cu film that has within-film non-uniformity (WFNU,defined as the thickness standard deviation divided by the thickness mean) exceeding 2.5% fails to meet the requirement for subsequent CMP process . In this report,impact on WFNU from chamber geometryfactors and process parameters was quantitatively evaluated by simulating the growth process of Cu film. WFNU less than 1.0% was achieved for 3000A Cu film deposited on 350A Cu seed through optimization of chamber design and the deposition process.