Tailored electroplated copper layers for 300 mm power devices
High Tech Campus Villach
9524 Villach, Austria
Abstract: The formation of Cu layers with certain properties such as low internal stress, high hardness, a lowered coefficient of thermal expansion and a less self-anneal behaviour were the main objectives of this work. Detailed studies were performed to investigate the effect of the plating bath composition and the applied deposition parameters on the obtained Cu layer as well as to elucidate the mechanical and electrical properties of the so deposited layers. Additives addition and process parameters were tailored iteratively with the objective to reduce the grain size of the copper crystallites and therefore the internal stress, the layer resistivity, and to increase the hardness. The role played by the deposition parameters on the formed Cu layer properties were thereby systematically examined as mentioned before. This allowed connecting each of the electroplating parameters that were investigated with the respective Cu layers properties. The highlight was the successful up-scaling for a 12” wafer where a homogeneous copper layer could be deposited together with a small crystallite size before annealing (up to 5 nm) and after annealing (14 nm), which is a certain improvement compared to commercial electrolytes.