Microstructure and Grain Orientation Evolution in SnPb/SnAgCu Interconnects Under Electrical Current Stressing at...

Area of Science:

• Materials Science
• Solid-State Physics
• Physical Chemistry

Background:

• Electromigration is a critical degradation mechanism in microelectronic interconnects.
• Understanding electromigration at cryogenic temperatures is essential for advanced electronics.
• Joule heating effects can mask intrinsic electromigration phenomena.

Purpose of the Study:

• To characterize electromigration at the Cu/solder interface without Joule heating.
• To investigate the impact of cryogenic temperatures (-196 °C) on electromigration.
• To elucidate the mechanisms behind abnormal diffusion and intermetallic compound growth.

Main Methods:

• Scanning Electron Microscopy (SEM) for microstructural analysis.
• Electron Backscatter Diffraction (EBSD) for crystallographic orientation.
• Controlled electrical stressing at ultra-low temperatures.

Main Results:

• Rapid (Cu_x,Ni_1-x)₆Sn₅ intermetallic compound growth observed at the cathode due to current crowding.
• Abnormal isotropic diffusion and parallel distribution of lead (Pb) at -196 °C.
• Pb atoms accumulated at high-energy grain boundaries via face-centered cubic lattice diffusion.

Conclusions:

• Cryogenic temperatures combined with electrical stressing induce crystallographic transformations affecting diffusion.
• Isotropic diffusion of Pb in face-centered cubic lattices leads to long-range accumulation.
• Findings provide insights into cryogenic electromigration and abnormal lattice behavior.