Study of Cu Micro-via by TOF-SIMS and STEM

The micro-via is a sandwiched structure with Cu electrolyte plating/electroless Cu plating/Cu electrolyte plating Pad, and the quality of the electroless Cu layer significantly affects the reliability of micro-via. In this work, we investigated the elemental ingredient of micro-vias which were prepared by a traditional electroless Cu plating method and a newly developed electroless Cu plating method by time of flight secondary ion mass spectrometry (TOF-SIMS) and scanning transmission electron microscopy (STEM). It is found that the concentration of hydrogen, oxygen and several elements exist in the electroless Cu layer prepared by traditional method compared to the new one. These can be a potential risk of nanovoids formation in the electroless Cu layer and decrease the reliability of HDI substrate.