Interactions of copper with oxidized TaSiN

Abstract

Tantalum rich TaSiN exposed to the ambient results in a homogenous surface composition of a silicon rich Ta x Si y O z mixture. The interaction of sputter deposited copper with oxidized TaSiN (O/TaSiN) is investigated using X-ray photoelectron spectroscopy (XPS). Copper is found to wet (grow conformally on) O/TaSiN at 300 K. For copper coverages of less 0.4 ML (based on the Cu to O atomic ratio), copper is present as Cu(I). At higher coverages, Cu(0) is observed. A change in slope of the copper coverage curve is coincident with the change in copper oxidation state. The data indicate that copper is initially deposited in a conformal ionic layer followed by Cu(0) formation in subsequent depositions. The data also show that although the O/TaSiN surface contains significant amounts of silicon and oxygen, the ability of copper to wet O/TaSiN is superior to that of SiO 2. Post-deposition annealing experiments performed indicate that although diffusion does not occur for temperatures less than 900 K, copper “de-wetting” occurs for temperatures above 500 K.