Electroless copper(EL-Cu) deposition is used as alternative method for seed layer formation in Cu multilevel metallization. This paper describes the study of various activation methods for EL-Cu deposition. The activation methods include the Cu flash layer deposited by PVD technology, Cu nuclei formed by contact displacement from wet solution, Pd layer deposited by PVD technology and Pd nuclei precipitated from wet solution with Pd ions. The microstructure of the EL-Cu is dependent on the activation method. EL-Cu seed layer with excellent step coverage and high (111) texture was obtained if deposited on PVD Cu flash layer. EL-Cu seed layers deposited on nuclei formed by contact displacement and Pd layer deposited by PVD technology were found to have very poor adhesion to the underlying barrier layer. EL Cu seed layer with good adhesion and conformal step coverage was achieved with Pd nuclei precipitated from wet solution with Pd ions.
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