The drift of Cu ions into methyl-doped silicon oxide film was investigated by using bias temperature stressing/capacitance–voltage, current–voltage at high temperatures and time-dependent dielectric breakdown tests. Standard and control metal–insulator–semiconductor capacitor test samples with sandwich dielectric layer structures were used. Bias temperature stressing in N2 ambient at an electric field magnitude of up to 1.5MV/cm and with temperatures between 175 and 275C was used to accelerate the Cu ion drift. By studying flat band voltage shift in capacitance–voltage tests, leakage current magnitude in current–voltage tests and time to fail in time-dependent dielectric breakdown tests, it was demonstrated that Cu ions readily drift into methyl-doped silicon oxide under electric fields at elevated temperatures. Results obtained by using different techniques agreed well with each other. The activation energy of Cu drift was determined to be 0.76eV in N2 ambient. The film was found to have poorer resistance to Cu drift than did SiO2 which was deposited by using plasma-enhanced chemical vapor deposition. Therefore, good Cu drift barrier layers were required for reliable ULSI interconnects using this low-k material. A thin layer of plasma-enhanced chemical vapor deposited SiC was proved to be a good Cu drift barrier layer.

Copper Drift in Methyl-Doped Silicon Oxide Film. H.Cui, I.B.Bhat, S.P.Murarka, H.Lu, W.J.Hsia, W.Catabay: Journal of Vacuum Science & Technology B, 2002, 20[5], 1987-93