In-situ monitoring of the growth of nanostructured aluminum thin film

Abstract

Metal thin film functional properties depend strongly on its nanostructure, which can be manipulated by varying nucleation and growth conditions. Hence, in order to control the nanostructure of aluminum thin films fabricated by RF magnetron sputtering, we made use of in-situ monitoring of electrical and optical properties of the growing layer as well as plasma characterization by mass and optical emission spectroscopy. The electrical conductivity and I-V characteristics were measured. The optical constants were obtained from optical monitoring based on spectral ellipsometry. The relevant models (based on one or two Lorentz oscillators and B-spline functions) were suggested to evaluate the data obtained from the monitoring techniques. The results of the in-situ monitoring were correlated with scanning electron microscope analyses. We demonstrated the monitoring was able to distinguish the growth mode in real-time. We could estimate the percolation threshold of the growing layer and control layer nanostructure. The nanostructure was effectively manipulated by RF power variation. Optical functions exhibiting plasmonic behavior in the UV range and a strong nonlinear character of I-V curves were obtained for an ultrathin Al film deposited at a lower growth rate.