Athermal Solid Phase Reaction in Pt/SiOx Thin Films Induced by Electron Irradiation

Microelectronics based on Si requires metal silicide contacts. The ability to form platinum silicide (Pt2Si) by electronic excitation instead of thermal processes would benefit the field. We studied the effects of electron irradiation on Pt2Si formation in composite films-composed of Pt and amorphous silicon oxides (a-SiOx)-by transmission electron microscopy and electron diffraction. Pt2Si formed in Pt/a-SiOx bilayer and a-SiOx/Pt/a-SiOx sandwiched films by 75 keV electron irradiation, at 298 and 90 K. The reaction is attributable to dissociation of SiOx triggered by electronic excitation. In a-SiOx/Pt/a-SiOx sandwiched films, reflections of pure Pt were not present after irradiation, i.e., Pt was completely consumed in the reaction to form Pt2Si at 298 K. However, in Pt/a-SiOx bilayer films, unreacted Pt remained under the same irradiation conditions. Thus, it can be said that the extent of the interfacial area is the predominant factor in Pt2Si formation. The morphology of Pt islands extensively changed during Pt2Si formation even at 90 K. Coalescence and growth of metallic particles (Pt and Pt-Si) are not due to thermal effects during electron irradiation but to athermal processes accompanied by silicide formation. To maintain the reaction interface between metallic particles and the dissociation product (i.e., Si atoms) by electronic excitation, a considerable concomitant morphology change occurs. Elemental analysis indicates that the decrease in Si concentration near Pt is faster than the decrease in O concentration, suggesting formation of a Si depletion zone in the amorphous silicon oxide matrix associated with formation of Pt2Si.

Automated summary

The study successfully formed Pt2Si in Pt/a-SiOx bilayer and a-SiOx/Pt/a-SiOx sandwiched films by electron irradiation, indicating that the extent of the interfacial area plays a key role in Pt2Si formation. The morphology of Pt islands extensively changed during Pt2Si formation process.