AVS 56th International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF2-MoM

Paper TF2-MoM10
Interconnect Reliability Improvement by Selective CVD of Co Capping Layer on SAM Treated Copper/Low-k Surface

Monday, November 9, 2009, 11:20 am, Room B4

Session: Metals and Nitrides (ALD/CVD)
Presenter: H.B. Bhandari, Harvard University
Authors: H.B. Bhandari, Harvard University
H. Park, Harvard University
R.G. Gordon, Harvard University
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Electromigration in copper interconnects is a surface phenomenon and therefore becomes a dominant reliability concern as the Cu line widths are narrowed to accommodate the continuing scaling of interconnect structures. Reliability can be improved by applying a layer of cobalt metal on the top surface of Cu lines, thereby improving its adhesion to an overlying etch-stop layer such as silicon nitride. Thus selective deposition of Co metal on ultra narrow Cu lines integrated in low-k dielectric is of critical importance in preserving the electrical performance of future integrated circuits. Here we propose a chemical vapor deposition process for applying Co thin films selectively on Cu surfaces. XPS showed complete coverage by Co films less than 2 nm thick on Cu substrates. The selectivity of the Co deposition was confirmed by Cu line to line leakage measurements on long interdigitated comb structures. Further enhancement of Co selectivity was achieved by employing self-assembled monolayers (SAMs) to passivate low-k surfaces. XPS and TEM characterizations indicate that low-k surfaces treated with (heptadecafluoro-1,1,2,2,-tetrahydrodecyl)trimethoxysilane or (heptadecafluoro-1,1,2,2,-tetrahydrodecyl)dimethyl(dimethylamino)silane inhibited Co nucleation on insulators. Clean Cu surfaces were unmodified by the SAM treatment. The selective passivation was investigated using both solution- and vapor-based SAMs to obtain complete blocking of Co deposition on low-k surfaces.