Silicide Formation by Pulsed Excimer Laser Annealing

Abstract

AbstractSilicide formation may occur at the interface of metal and a-Si films upon annealing with a pulsed excimer laser (XeCl 308 nm; 30 ns). During laser-induced melting, the melt front reaches the Si/metal interface, where liquid phase kinetics allow reaction to occur to form a silicide, despite the <100 ns time-scale. It is thought that silicide reaction would occur if TM, metal ≍ TM, a-Si (1480 ± 50K). The a-Si/metal film stacks that have been investigated include a-Si/Al/Cr, a-Si/Ti, and a-Si/W on thermally oxidized Si. Samples were laser-annealed at varying energy densities in order to determine the onset of melt, and the fluence at which Si/metal interface reaction and film ablation occurs. Rutherford backscattering (RBS), optical inspection, cross-sectional scanning transmission electron microscopy (STEM), as well as parallel and serial electron energy loss spectroscopy (EELS) were used to analyze the films. For the a-Si/Al/Cr and a-Si/W films, no reaction is observed at the Si/metal interface. With a-Si/Ti, intermixing of Si and Ti at the interface is observed, as indicated by RBS and parallel EELS analysis. Laser annealing at higher fluences and further characterization is needed to determine if this mechanism does allow for silicide reaction to take place.