Novel investigation of influencing factors for corrosive interface degradation in wire bond contacts

Wire bonding is still the dominating technology for realizing the first level contact of semiconductors. In the last decades miniaturization and increasing connection density resulted in new challenges in terms of reliability and long term stability. But now additionally the movement towards harsher application environments leads to new problems in automotive applications (also e-mobility) as well as in power applications for regenerative energy systems (solar, offshore, geothermal etc.). For example higher temperatures occur in the manufacturing process due to lead free soldering, in automotive applications close to the engine or in the exhaust area and in tracking systems of solar panels. Furthermore aggressive media like oily or salty atmosphere and moisture are a strain on the contact stability. Corrosion effects in especially Au/Al and Al/Cu wire bond interfaces are the interaction result of temperature, moisture, aggressive media and different electrical or electrochemical potentials. The paper presents the first step in a substantial investigation with the goal to get profound knowledge about the influencing factors for corrosive interface degradation in wire bond contacts. We tried to reproduce the corrosion mechanisms with different halides (e.g. iodine, fluorine, bromine) which are known as corrosion initiator. The halides concentrations were varied as well as the thermal aging conditions (e.g. high temperature storage, damp heat test, thermo cycling, biased high temperature storage). The interface morphology and micro structure of the samples were analysed after focused ion beam preparation (FIB) using scanning electron microscopy (SEM) and transmissions electron microscopy (TEM) including energy dispersive spectroscopy (EDS).