Investigation of Cu growth phenomena on Ru substrate during electroless deposition using hydrazine as a reducing agent

Cu growth phenomena during electroless deposition (ELD) on Ru substrate were investigated in this study. Different to the formaldehyde based Cu ELD bath, the use of hydrazine based Cu ELD bath facilitated the observation of Cu growth phenomena during ELD. The whole surface-catalyzed ELD occurred on Ru, and electrochemical quartz crystal microbalance as well as linear sweep voltammetry studies revealed that Cu covered Ru surface within a few seconds of ELD. Measurement of sheet resistance change confirmed that Cu nucleation on Ru was continuous with forming a film. During the period, Cu film growth was monitored by an atomic force microscope imaging, indicating that Cu was deposited on Ru preferentially, rather than on the deposited Cu at the initial stage of the deposition. The whole surface-catalyzed ELD achieved 55 nm gap-filling, and this showed the possibility of the practical adoption of ELD as a method for metallization in ultralarge-scale integration.