Thermal ALD of metallic copper on cobalt for advanced interconnects
ALD is a potential process for the deposition of various thin films such as diffusion barriers, liner materials and seed layers, which are required for state-of-the-art interconnects. This layer stack consists currently of TaN, Ta and Cu deposited by PVD. Given that cobalt is a possible replacement for the present liner Ta we have investigated the ALD of copper on in vacuo prepared cobalt substrates. A further possible application for thin Cu films on Co is the formation of Co/Cu multilayers for magnetic sensors. For this [(nBu3P)2Cu(acac)] was applied as precursor together with H2 as coreactant at 125 °C. In vacuo X-ray photoelectron spectroscopy (XPS) revealed that the contamination of deposited film are oxygen (9.8 mol%) but no carbon or phosphorus are detectable. Besides, the investigation of the sample composition XPS allows the determination of the oxidation state of the deposited material with mainly metallic Cu. Furthermore, the layer growth is substrate enhanced with an initial GPC of 0.025 Å/cycles compared to a GPC of 0.008 Å/cycles after the nucleation phase.