Study on SiN_x passivated Cu/Ta/SiO₂/Si multilayer structure

Silicon nitride (SiN_x) thin film layers were deposited on Cu/Ta/SiO₂/Si multilayer structures by Plasma Enhanced Chemical Vapor Deposition at the temperature 285°C. The influence of post deposition thermal annealing treatments on the micro-structural, compositional and thermal stability study of SiN_x/Cu/Ta/SiO₂/Si multilayer structure was studied and compared with unpassivated, Cu/Ta/SiO₂/Si multilayer structure. It was found that after SiN_x passivation, the formation of Cu₂O and Ta₂O₅ was significantly reduced and the structure becomes more stable than unpassivated one. The reaction between Cu, Ta and O was not found in this SiN_x/Cu/Ta/SiO₂/Si multiplayer structure but the out diffusion of Ta to the Cu surface was unable to be suppressed. The Ta barrier was observed to fail at temperatures above 750°C due to the formation of Ta_xN_y, at the interface of SiN_x/Cu.