Observation of void formation patterns in SnAg films undergoing electromigration and simulation using random walk...

Area of Science:

• Materials Science
• Physics
• Electrical Engineering

Background:

• Electromigration (EM) is a significant reliability concern in miniaturized electronic devices.
• Existing EM models primarily focus on Sn-Ag solders within solder joint structures, leaving thin film behavior less explored.
• Understanding EM in thin films is critical for advancing microelectronic reliability.

Purpose of the Study:

• To evaluate the predictive capability of existing EM models for void nucleation and evolution in Sn-Ag thin films.
• To introduce and validate a novel random walk (RW) method for simulating coupled current, thermal, and atomic migration phenomena.
• To investigate the impact of film imperfections on EM behavior.

Main Methods:

• Experimental testing of a Sn-3.5Ag (wt.%) thin metallic film under a current density of 7.77 × 10⁴ A/cm² at 15°C.
• Development and application of a computer simulation using an original random walk (RW) method.
• Coupled simulation of current distribution, thermal distribution, and atomic migration, accounting for void formation.

Main Results:

• The RW method demonstrated successful application in predicting void nucleation and evolution due to atomic migration.
• Simulations showed good agreement with experimental results, validating the RW approach for EM studies.
• Deviations between simulation and experimental results were observed, attributed to imperfections within the thin film.

Conclusions:

• The random walk method is a viable and effective tool for modeling electromigration phenomena in metallic thin films.
• The study highlights the importance of considering material imperfections for accurate EM prediction.
• Further research can refine RW models to better incorporate the effects of microstructural defects on electromigration.