Electrical resistivity of Cu films deposited by ion beam deposition: Effects of grain size, impurities, and morphological defect

Cu films deposited by ion beam deposition with or without a negative substrate bias voltage were found to have different states of dependence of electrical resistivity on film thickness. We have attempted to evaluate the effects of the film thickness, average grain size, impurities, and morphological defect on the resistivity increase of Cu films in addition to the surface scattering of the Fuch-Sondheimer model and the grain boundary scattering of the Mayadas-Shatzkes model. When the theoretical model was fit to the experimental data, the Cu films deposited at a substrate bias voltage of -50 V showed that the electrical resistivity was in good agreement with the theoretical curve under the condition that the film thickness was 2.3 times larger than the average grain size and when p=0 and R=0.24. For the Cu films deposited without a substrate bias voltage, however, there was a slight deviation between the theoretical curve and the measured resistivity below a 100 nm thickness, even at the condition of the film thickness that was six times larger than the average grain size, which is considered to result from the effect of solute impurities in the Cu films. Therefore it was found that the impurity effect on the electrical resistivity could not be neglected. It was also confirmed that the morphological defect, such as a columnar structure with noticeable gaps in the Cu films deposited without the substrate bias voltage, caused a great increase in resistivity even above the 100 nm thickness. (C) 2006 American Institute of Physics.