Abstract

We present an investigation of the initial stages of Fe layer growth by thermal decomposition of Fe(CO)₅ on Si(100) substrates. Scanning tunneling microscopy has been employed to study the evolution of film morphology. Specifically, this investigation has determined the scaling behavior of average cluster density and cluster size distributions for growth over a range of substrate temperatures (100 - 215°C) and coverages. In general, clusters are found to nucleate on Si terraces showing no preference for dissociation of precursor molecules at Si steps. (See Fig. 1) Fig. 2 shows a plot of average island number / area (and areal coverage) vs. exposure for samples dosed with 1x10^-8 Torr of Fe(CO)₅ at several different temperatures. Fig. 3 shows the corresponding island size distributions for growth at 165°C. By comparing the morphology of submonolayer films measured by STM to that predicted by a rate equation analysis and kinetic Monte Carlo calculations, we have monitored the relative roles of various kinetic processes on changing layer morphology. The nucleation model that will be presented accounts for various processes occuring during CVD growth including formation of nuclei on the Si starting surface and decomposition of the precursor molecule on pre-existing clusters (either by diffusing to a cluster or by direct impingement from the gas phase) and therefore should accurately predict the evolution of layer morphology for other systems. We have also begun to investigate the influence of surface chemistry on nucleation. Preliminary work involving passivating the Si surface prior to CVD growth will be presented.

© 1995 Optical Society of America