First stages of the formation of copper electrodeposits and copper sputtered deposits on amorphous carbon and polycrystalline silver substrates

Abstract

The first stages of the development of copper deposits on amorphous carbon and polycrystalline silver substrates are compared when the deposits are produced by electrodeposition under galvanostatic conditions and by high rate magnetron-enhanced sputtering. It is shown that the first stages of the formation of the metallic deposits are influenced by the deposition rate, the substrate-to-deposit interaction and by the deposition technique. These factors have a particular influence on the growth mode and on the nucleation stage of the deposit. When an island growth mode is observed, an increase of the deposition rate induces thinner covering films because the island density is higher and the islands are smaller for a given quantity of deposited matter. In electrodeposition, an island growth mode is observed on the two types of substrate, but for equivalent experimental conditions the superficial cluster density is higher on silver than on carbon substrates. Dissolution of some copper clusters occurs a short time after the onset of electrolysis. This can be explained by local changes of the supersaturation due to a current microdistribution at the cathode surface. In magnetron-enhanced sputtering, an island growth mode is observed on amorphous carbon substrates, while a layer-by-layer growth mode is detected on polycrystalline silver substrates. On silver substrates two different growth modes are thus observed depending on the deposition technique. In contrast, on carbon substrates, where an island growth mode is observed in both cases, the copper cluster superficial density is a factor 106 to 108 higher in sputtering than in electrodeposition for the same deposition rate. This paper shows that these differences can only be explained by physical and chemical mechanisms specific to each deposition technique taking place during the condensation process.