Date of Award




Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Physics

Content Description

1 online resource (x, 70 pages) : illustrations (some color)

Dissertation/Thesis Chair

T. S. Kuan

Committee Members

T. S. Kuan, Luke Henderson, John C. Kimball, William A. Lanford, Caroline A. MacDonald


agglomeration, Cu, Cu alloy, nucleation, Ta, wetting, Copper, Thin films, Metallic films, Nucleation, Wetting, Agglomeration

Subject Categories

Materials Science and Engineering | Physics


One of the key challenges in fabricating narrower and higher aspect ratio interconnects using damascene technology has been achieving an ultra-thin (~2 nm) and continuous Cu seed coverage on trench sidewalls. The thin seed is prone to agglomeration because of poor Cu wetting on the Ta liner. Using in-situ conductance measurements, the effect of lowering the substrate temperature during Cu seed deposition has been studied on tantalum (Ta) and ruthenium (Ru) liner surfaces. On a Ta surface, it was found that lowering the deposition temperature to -65°C increases the nucleation rate of the Cu thin film, and reduces the minimum coalescing thickness for Cu on Ta liner from ~4.5 nm (at room temperature) to ~2 nm. On a Ru surface, Cu coalesces at < 1 nm at room temperature, and no further reduction in initial coalescing thickness was found at low temperature. For the Cu seed deposited at -65°C on a Ta liner on trench sidewalls, extensive thermal stress-induced grain growth was observed during warming up to room temperature. No grain growth was observed in the seed layer deposited at low temperatures on a Ru liner.