The Effect of Thermal History On Interconnect Reliability

Abstract

AbstractThe reliability of interconnects is strongly affected by their thermal history, including the deposition temperature, the temperature at which patterned films are passivated, and the temperature and cooling rates of the final packaging processes. The thermal history affects the stress, the grain structure, and the distribution of alloy additions, such as Cu. All of these affect the reliability of interconnects, especially as it is limited by electromigration. The postpatterning thermal history is especially important. For example, it is post-patterning annealing which leads to the evolution of electromigration resistant bamboo-microstructures. In Al-Cu alloy interconnects, pre- and post-patterning anneals can also affect the distribution of Cu in solution and in precipitates. This too can affect interconnect reliability. Experiments and modeling concerned with these effects of thermal history will be reviewed and discussed.