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

Area of Science:

• Materials Science
• Microelectronics Engineering
• Surface Science

Background:

• Silicon-based microelectronics rely on metal silicide contacts for efficient operation.
• Forming platinum silicide (Pt₂Si) via non-thermal methods, such as electronic excitation, offers potential advantages over traditional thermal processes.
• Investigating novel methods for silicide formation is crucial for advancing microelectronic device fabrication.

Purpose of the Study:

• To investigate the formation of platinum silicide (Pt₂Si) induced by electron irradiation in platinum/amorphous silicon oxide composite films.
• To understand the mechanism of Pt₂Si formation under electronic excitation at different temperatures (298 K and 90 K).
• To determine the influence of film architecture and interfacial area on the efficiency of Pt₂Si formation.

Main Methods:

• Transmission electron microscopy (TEM) for structural analysis.
• Electron diffraction for phase identification.
• 75 keV electron irradiation of composite films (Pt/a-SiO₂ bilayers and a-SiO₂/Pt/a-SiO₂ sandwiches).
• Elemental analysis (e.g., EDX) to study compositional changes.

Main Results:

• Pt₂Si formation was observed in both bilayer and sandwiched films upon 75 keV electron irradiation at 298 K and 90 K.
• The reaction is attributed to the dissociation of amorphous silicon oxide (a-SiO₂) triggered by electronic excitation.
• Complete consumption of Pt in Pt₂Si formation was observed in sandwiched films at 298 K, indicating interfacial area is critical.
• Significant morphological changes in Pt islands occurred even at 90 K, driven by athermal processes associated with silicide formation.
• Elemental analysis revealed a faster decrease in Si concentration than O concentration near Pt, suggesting Si depletion zones.

Conclusions:

• Electron irradiation provides a viable route for forming Pt₂Si at low temperatures, distinct from thermal methods.
• The extent of the interfacial area significantly impacts the efficiency and completeness of Pt₂Si formation.
• Athermal processes, not thermal effects, govern the morphological evolution and particle coalescence during electron-induced silicide formation.
• The formation of Pt₂Si is accompanied by the creation of silicon depletion zones within the amorphous silicon oxide matrix.