Thermal Stability of Cu-Sn Metal-Metal Interconnects
Cu-Sn is currently being investigated as an alternative to Pb-Sn solders. It is especially interesting for small scale solder bumps and fine pitches. With the appropriate bonding conditions, the preferred phase of Cu-Sn (Cu3Sn) can be formed at the interface of two bond pads. This phase should be thermodynamically stable (for up to 350°C) and withstand multiple reflow cycles encountered during the assembly process of a multilayer interconnect stack. This paper investigates the thermal stability and reliability of Cu-Sn bonded die with different Sn thicknesses and bonding pressures. The samples are isothermally aged at 125°C ± 10°C and also subjected to thermal cycling from 125°C to -55°C. The samples are analyzed before and after experiments to track any changes in inter-metallic growth, grain-structure, die cracking, package cracking, and bond lifting with analytical tools including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Electron Back Scattered Diffraction (EBSD).
Jemima Fernandez, Megan Frary, and Amy Moll. "Thermal Stability of Cu-Sn Metal-Metal Interconnects" 2008 TMS Annual Meeting. New Orleans, LA. Mar. 2008.
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