Thermal cycle reliability of stacked via structures with copper metallization and an organic low-k dielectric

The reliability of a stacked via chain stressed under various thermal cycle conditions is described. The chain consists of Cu Dual Damascene metallization with SiLK (trademark of Dow Chemical) as the organic low-k dielectric. Failure analysis indicates that cracks form in the Cu vias during thermal cycle stress. Due to the presence of two failure modes, the thermal cycle statistical behavior is described by a bimodal lognormal failure distribution. The thermal cycle lifetime exhibits a strong dependence on the temperature range and a rather weak dependence on the maximum temperature in the cycle. Evidence of a threshold temperature range below which thermal cycle fails should not occur as well as a correlation between the test structure yield and reliability are also reported.