Room Temperature Recrystallization of Electroplated Copper Thin Films: Methods and Mechanisms

The room temperature recrystallization of electroplated Cu films is clearly related to the influence of organic and inorganic additives in the plating bath; however, the underlying mechanisms are still not well understood. In this paper we present preliminary results on (1) a radial variation in recrystallization rate that suggests a nonuniformity during plating related to the additives; (2) a volume influence on the recrystallization rate of Cu plated over wide trenches; and (3) the recrystallization of a thick (1 micron) sputtered Cu film at room temperature driven by recrystallization of the overlaying EP Cu film. It is notable that we observe high levels of C, N, and O in the sputtered Cu layer after recrystallization, indicating a high mobility of the additive-derived inclusions in the film. The concentration profiles of Cl and S are significantly different, decreasing rapidly close to the interface between the two Cu layers.