Nanometer-thick copper films grown by thermal atomic layer deposition

• Resistance of nanometer-thick Cu film was sensitive to deposition temperature.
• Optimal temperature deposition was determined to obtain low-resistivity.
• Critical thickness at which Cu films exhibit continuous growth was determined.
• Resistivity reduced with annealing at 300–350 °C.

Because of the superior properties of copper, it has been of great interest as a conducting material to replace aluminum in device manufacturing. In this study, we investigated the influence of substrate temperature, film thickness, and rapid thermal annealing (RTA) on the deposition of Cu films of thickness less than 10 nm. Compared to thicker films, the electrical properties of nanometer-thick films were found to be very sensitive to the deposition temperature. Further, we determined the optimal deposition temperature to obtain low-resistivity nanometer-thick Cu films. The Cu films were deposited with island-type growth, and the interconnection between grains plays a major role in the resistivity of the films. We also determined the critical thickness at which Cu films exhibit continuous growth as 8 nm. After RTA, the film color darkened, electron scattering became weak, and the resistivity reduced more than 20% with annealing at 300–350 °C, because of the growth of Cu grains. The results of this study indicate that thermal ALD can be used in conjunction with RTA to produce low-resistivity Cu thin films, the thickness, uniformity, and conformality of which can be easily controlled.