Diffusion Barriers and Self-encapsulation

Abstract

As feature sizes in multilevel metallization continue to shrink, the thermal stability of metallization and barrier layers become more critical for device reliability. The application of silver in multilevel metallization schemes require thermal stability when in contact with other metal layers and dielectrics. Therefore, developing a suitable diffusion barrier to retard the diffusion of Ag into adjacent materials and to prevent agglomeration is indispensable for the Ag metallization scheme. There have been extensive efforts to investigate qualified diffusion barrier layers interposed between Ag and SiO₂ [1]. The stability of silver thin films on various underlying layers at elevated temperatures has also been investigated [1]. Several authors have investigated the behavior of Ag on SiO₂/Si substrates [2],[3]. The addition of a thin Au layer between the Ag and Si was found to improve the stability of the interface by forming an intermixed region, resulting in a lowering of the interfacial energy of the Ag/Si system [3].