Copper Interconnect Development At RIT

Aluminum is the current metal of choice for metallization in the IC industry. However, serious electromigration problems, and inferior thermal stability limit its performance and reliability. Copper is an attractive alternative having higher electrical conductivity and improved electromigration performance compared to Aluminum. However, Cu is a fast diffuser in Si, Si02, and interlevel dielectrics (ILD). To eliminate this issue, a layer of diffusion barrier (DB) material which is conducting, chemically passive with Copper, has good adhesion properties with Cu and ltD and has high thermal stability is required. Damascene process for Cu was utilized to pattern the wafers in this study. Ta, TaN, Ti and TiN were used as barrier layers. The DB were deposited using pulsed DC sputtering (Ta and Ti) and reactive sputtering (TaN and TiN). A seed layer of Cu was deposited in the same sputtering tool. The wafers were electroplated with Cu and polished using CMP. They were then analyzed using SEM and a high-resolution optical microscope. No electrical tests were conducted at this stage due to lack of multilevel masks