Dresden 2011 – scientific programme

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MI: Fachverband Mikrosonden

MI 4: Poster: Microanalysis and Microscopy

MI 4.3: Poster

Monday, March 14, 2011, 17:30–19:30, P5

Intermetallic phase formation in the system aluminium–gold studied by EBSD — •Stefan Scheibe, Benjamin März, Andreas Graff, and Matthias Petzold — Fraunhofer Institut für Werkstoffmechanik Halle IWMH, Halle, Deutschland

In the system aluminium–gold 5 stable intermetallic phases (Al₁₁Au₆, AlAu, AlAu₂, Al₃Au₈, AlAu₄) exist. The combination of aluminium and gold is often used for wire bond interconnects in microelectronic devices. Intermetallic Al–Au phases are formed at the Al–Au bond interface of these interconnects and affect their reliability. To understand the possible failure mechanisms it is important to know which phases are involved and where they are located.

In the study, two different sample types were used. To investigate phase formation in systems with excess of gold, Au wires were bonded on Al substrates. In contrast, Al wires were bonded on Au substrates to observe phase formation under excess of aluminium. After annealing at 150^∘C for different times, phase evolution was studied by EBSD. A metallographic preparation in combination with argon ion beam etching was developed to meet the requirements of the EBSD analysis. Pseudosymmetry, the similarity of diffraction patterns for different phases and the susceptibility to corrosion were specific challenges in this investigation. A precise phase differentiation with high spatial resolution was possible in most of the investigated cases. These results allow a better understanding of the Al–Au bonding mechanism as a function of the interface microstructure.