Smart Polymers for Future Damascene Applications: Combining Bottom-up and Levelling Capabilities

Classical additive concepts for the metallization of trenches and vias (Damascene applications) make use of a combination of polymeric suppressors (polyaklylene glycols, PAGs) and their specific antagonists (SPS). Their interplay is intended to regulate the desired bottom-up fill process. Typically, a leveler additive is added to the plating bath as a third additive component which is meant to avoid undesired overplating after the successful superfill.

In this contribution we discuss so-called hybrid polymers which comprise electrochemical characteristics of the PAG suppressors and classical leveler additives. Feature fill experiments demonstrate that bottom-up fill and leveling can indeed be achieved by using one single hybrid polymer component when combined with the SPS. Prototypical model additives showing these hybrid characteristics are polymerizates of epichlorohydrin and imidazole (Imep). Antagonistic Imep/SPS interactions required for the bottom-up fill are observed in particular at low (nominal) current densities whereas synergistic Imep/SPS interactions needed for leveling are dominant higher (nominal) current densities.

Copper films electrodeposited in the presence of an intact Imep leveler ensemble are essentially contamination-free. To probe the contamination level depth profiling experiments with sub-nm depth resolution were carried using a new femto-second laser ablation set-up coupled with a reflectron TOF mass spectrometer. This approach allows a true quantification of the contaminants which actually accumulate at the grain boundaries of the electrodeposited copper films.