Y. Kimiya

Publications (2)0.94 Total impact

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

  A Ikeda, Y. Kimiya, Y. Fukunaga, H. Ogi, R Hattori, H. Kuriyaki, Y Ohno, Y. Kuroki
  [show abstract] [hide abstract]
  ABSTRACT: 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.
  Electronics Packaging Technology Conference, 2007. EPTC 2007. 9th; 01/2008
• Article: Uniformity of an Electroless Plated Ni on a Pad Connected to Different Size Pads or a Pn Junction for Under Bump Metallurgy in a Flip-Chip Assembly

  A. Ikeda, T. Saeki, A. Sakamoto, Y. Sugimoto, Y. Kimiya, Y. Fukunaga, R. Hattori, H. Kuriyaki, Y. Kuroki
  [show abstract] [hide abstract]
  ABSTRACT: We investigated electroless Ni uniformity on Al metal pads connected to different size pads or a pn junction for under bump metallurgy in flip-chip assemblies. In an electrically isolated pad, Ni thickness decreased as the pad size decreased. Because of nonlinear diffusion of Pb²⁺ stabilizer in the plating solution, fewer electrons were supplied to the smaller pad than to the larger pad by an anodic oxidation reaction on the pad surface. In pads smaller than 50 mum square, the Ni thickness increased when connected to a 100 mum square pad. This increase might be caused by electrons flowing from the 100 mum square pad to the smaller pad to produce an equipotential for the connected pads. In addition, the Ni thickness was increased by electrical connection to an n-type Si in the presence of fluorescent light illumination for a pn junction area larger than 100 mum². For a pad connected to a p-type Si, however, Ni thickness decreased in comparison to that of an electrically-isolated pad, regardless of the light illumination or pn junction area. The change of Ni height on pads connected to the pn junction is attributable to photoelectrons injected into the n-type Si, or to electron-hole recombination in the p-type Si. These results indicate that the pads should be of the same size within a chip for better Ni uniformity. Moreover, blocking light during Ni electroless plating can eliminate Ni thickness differences due to an n-type Si connection.
  IEEE Transactions on Components and Packaging Technologies 10/2007; · 0.94 Impact Factor