Pd migration in tetragonal-Ni(1-x)Pd(x)Si/Si (001) using density functional theory.

Area of Science:

• Materials Science
• Computational Materials Science
• Surface Science

Background:

• Understanding palladium (Pd) segregation at interfaces is crucial for optimizing silicide formation in microelectronics.
• The tetragonal-Ni(1-x)Pd(x)Si/Si (001) structure is a key material system for studying interface phenomena.
• Previous studies have not fully elucidated the atomic mechanisms governing Pd segregation during silicidation.

Purpose of the Study:

• To investigate the mechanism of palladium (Pd) segregation at the tetragonal-Ni(1-x)Pd(x)Si/Si (001) interface.
• To determine the energetic feasibility of Pd migration through Ni vacancy sites at the interface.
• To provide insights into the role of density functional theory (DFT) in understanding interface segregation.

Main Methods:

• Utilized density functional theory (DFT) calculations to model Pd migration within the tetragonal-Ni(1-x)Pd(x)Si/Si (001) structure.
• Focused on a Ni-terminated interface model for the NiSi layer.
• Calculated the energy barrier for Pd migration from bulk Ni sites to interface Ni sites.

Main Results:

• Identified two distinct Ni sites at the interface, with sites farther from the Si substrate being more favorable for Pd substitution.
• Observed the formation of Ni vacancies at interface Ni sites.
• Calculated a high energy barrier of 4.56 eV for Pd migration from a bulk Ni site to an interface Ni site.

Conclusions:

• The calculated high energy barrier suggests that direct Pd migration through Ni vacancy sites is not the primary mechanism for interface segregation during silicidation.
• The findings indicate that alternative segregation pathways must be considered to explain observed Pd enrichment at the interface.
• DFT provides a powerful tool for dissecting atomic migration mechanisms at material interfaces.