A TEM cross-section of a 9.5 nm wide Ru interconnect line is shown in Fig. 4. Good filling with no apparent pinholes or seams was observed. The absence of a seam in the structure is surprising for a conformal filling method such as ALD and can be ascribed to a recrystallization process at the thermal budget of the processing route (420°C). This is consistent with the large grain size observed in the TEM cross-section along the line in Fig. 5, further confirming the absence of significant voids in the structure.