Effects of Electroless Ni/Sn Bump Formation using Hydrogen-Plasma Reflow on the Electrical Characteristics of MOSFETs

Fine size Ni/Sn bumps were formed by electroless Ni/Sn plating and hydrogen plasma reflow, and then electrical characteristics of nMOSFETs and pMOSFETs were evaluated on the bumped chips. After the hydrogen plasma reflow, threshold voltages and carrier mobilities were not changed from those of the nMOSFETs and pMOSFETs as fabricated, before Ni/Sn plating. Also, gate leak currents were not increased by the plasma reflow for both the nMOSFETs and pMOSFETs. Off leak currents of the nMOSFETs were slightly decreased after the plasma reflow. In contrast, off leak currents of the pMOSFETs were slightly increased up to several tens of pA after the plasma reflow. However, the changes of the off leak currents by the plasma reflow were very small for both the nMOSFETs and pMOSFETs. Electrical damages induced by the plasma reflow were negligible for both the nMOSFETs and pMOSFETs.