ULSI Copper Interconnection Electromigration Reliability Research And Process Optimization

With the increasing of integration density and the scaling down of device feature size, RC (Resistance and Capacitance) delay introduced by the interconnect is more and more big. In order to reduce RC delay, the industry uses copper interconnects instead of the traditional aluminum interconnects and uses low-k materials to replace the traditional silicon dioxide. Compared with aluminum, copper has lower resistivity and higher reliability, but copper damascene process is more complex and results in some new reliability issues. In this thesis, we study the electromigration reliability in VLSI copper interconnect.Studying the basic principles of electromigration, we found directions to improve electromigration reliability.We focused on copper interconnects relevant process such as trenches and vias etch, barrier and seed deposition, ECP, CMP and found some optimization conditions to improve the electromigration reliability.We use SEM and TEM to check defect sampale cross sections. Comparative analysis with package level reliability tests was employed to obtain the median time to failure (MTTF) and the failure time Weibull distribution for a sample at different current densities and different temperatures. According to the Weibull distribution and the acceleration model, we can calculate the lifetime under normal conditions.