Tomohiro Ohta

Cu Wettability and Diffusion Barrier Property of Ru Thin Film for Cu Metallization

The main issue of Cu metallization is the electromigration of Cu through the interface between Cu and the barrier or capping layer. To improve electromigration resistance at the Cu and barrier metal interface, insertion of a glue layer which enhances the adhesion of Cu onto the under layer may be effective. The wettability of Cu on Ru and Ta glue layers was evaluated as the index of Cu adhesion strength onto glue layers. The wetting angle of Cu (43°) on a Ru substrate was three times lower than that of Cu (123°) on a Ta substrate after annealing. Lower wetting angle of Cu on a Ru substrate indicates a good adhesion property between Cu and Ru and may imply a high electromigration resistance. The better Cu wettability of Ru compared to Ta can be explained by the concept of lattice misfit. A Ru(002) plane has lower lattice misfit, which suggests lower interface energy, and enhanced the adhesion of Cu onto Ru. However, the Ru film showed poor Cu diffusion barrier properties, which suggests Ru should be used as a glue layer in combination with another barrier layer.

Formal boundary spanning by industry liaison offices and the changing pattern of university–industry cooperative research: the case of the University of Tokyo

Although university–industry (U–I) collaborations promise numerous benefits, both parties need to overcome high cultural and organisational barriers in order to materialise potentials. A variety of boundary spanning structures have developed in the USA and other countries, and this paper examines the roles and effects of industry liaison offices (ILOs) in Japan based on the case study of the Division of University Corporate Relations (DUCR) at the University of Tokyo. In Japan, because of governmental regulations, traditional U–I cooperative research has been formed within faculty members’ interpersonal networks with corporate researchers. Thus, the cooperative research projects were small in size and limited to bring actual commercial benefits. This paper suggests that formal boundary spanning by ILOs could facilitate the formation of ‘inter-organisational’ alliances between university and industry, and the alliances could generate larger, interdisciplinary, explorative cooperative research, overcoming the limitations of traditional cooperative research projects initiated in informal and interpersonal approaches.

Material Consideration on Ta, Mo, Ru, and Os as Glue Layer for Ultra Large Scale Integration Cu Interconnects

The electromigration resistance of ultra-large scale integration (ULSI) Cu interconnects can be improved by inserting an adhesion promoter between Cu and the diffusion barrier. A metallurgical survey was accomplished to select the element having a good Cu adhesion property. For adoption as an interconnect material, it should have a low resistivity and should not react with Cu to avoid increasing the resistance of Cu interconnects. Ru, Os, Mo, W, and Ta satisfied the above conditions. The Cu adhesion property of these elements was estimated by the lattice misfit concept. The Cu adhesion property was experimentally examined and compared hcp elements (Ru and Os), which have a good matching interface with fcc Cu, with the bcc elements (Mo and Ta). Ru and Os, which had lower lattice misfit values, showed a better adhesion property than the bcc elements having higher lattice misfit values. Among these elements, Ru had the best Cu adhesion property and thus it can be an optimum glue layer element for Cu interconnects.

New opportunities in chemical applications of X-ray absorption fine structure

Abstract The surface X-ray absorption fine structure (XAFS) method has been extensively applied for the study of molecular adsorbates on metal substrates. It provides useful information about local geometrical and electronic structures around the X-ray absorbing atom. Three typical applications are described: (1) surface structures of SO 2 adsorbed on Ni(100) and Pd(100); (2) surface chemical reaction of SO 2 on the Cu(100) surface; (3) local structures of alkanethiols on Cu(111). Some future prospects for the use of the third generation light source are also addressed.

One-dimensional band-like electronic states on Ni(755) surfaces studied by angle-resolved ultraviolet photoelectron spectroscopy using synchrotron radiation

Abstract New electronic states localized at step edges on Ni(755) surfaces are found by angle-resolved ultraviolet photoelectron spectroscopy. Characteristics of those state are examined and compared with the previous results of Ni(7911) surfaces. One-dimensional band states are found at the step edges on the Ni(755) surface.

Photoelectron diffraction study of the Si(001)c(4×4)–C surface

Abstract X-ray photoelectron diffraction (XPD) and synchrotron radiation photoelectron diffraction (SRPD) have been applied to a Si(001) c (4×4)–C surface in order to determine the site of carbon atoms on the surface. The c (4×4)–C surface, which typically appears during the incubation time of carbonization of Si, was prepared by exposing a single-domain Si(001)2×1 surface at 680°C to C 2 H 4 of 1×10 −6 mbar for 600 s. XPD revealed that, except for carbon atoms on the topmost layer, carbon atoms occupy the substitutional sites of Si up to the fourth layer and form a Si 1− x C x ( x ≠0.5) alloy layer. SRPD with a resolution of the chemical-shift C 1s components revealed that the carbon atoms present on the topmost layer occupy random sites and thus are not essential elements of the c (4×4) periodicity.

Photo-stimulated desorption of hydrogen ions from water chemisorbed and condensed on Si(100) surfaces by synchrotron radiation

Abstract Photo-stimulated ion desorption of water chemisorbed and condensed on Si(100) surfaces in the photon energy range from 10 to 50 eV has been studied. Only H + desorption was detected on the chemisorbed monolayer of water. Two thresholds of H + desorption were observed at 20 and about 25 eV. In PSD of water condensed on the substrate, H + and H + 2 were found. The thresholds of H + desorption were resolved at 24 and 28 eV. Molecular hydrogen cations are found at photon energies above 27.5 eV.