Electroplating of copper-Tin alloys

Copper -Tin alloy was electroplated from an acidic Cu-EP bath with the addition of a complexing agent and a Tin source. About 4 atomic % of Sn was co-deposited on wafers. The concentration of Sn was found to be dependent on the deposition current. Annealing the CuSn film drove the tin atoms into the underlying layer. Good gap fill was exhibited on 0.15 micron features. XRD results indicate a strong Cu (111) preferred orientation normal to the surface, with small but measurable Cu(200), Cu(220) and Cu(311) intensity. Low comb leakage was measured. The resistance of the lines was found to increase with the tin content.