Yasufumi Matsumura

Fabrication of Copper Damascene Patterns on Polyimide Using Direct Metallization on Trench Templates Generated by Imprint Lithography

Facile imprint and wet chemical processes were used to fabricate copper damascene patterns on polyimide substrate. Poly(amic acid) substrate with trench structures as template has been successfully prepared by imprint lithography using a poly(dimethylsiloxane) mold. The doped Ni(2+) ions into a template through ion-exchange reaction were reduced by an aqueous NaBH(4) solution, resulting in the formation of a nickel thin layer along the surface structure of the template. The resulting nickel films can act as catalyst for subsequent electrodeposition of copper. After electrodeposition, a polishing process was carried out for removing excess deposited copper films, followed by imidization of the substrate. The resulting damascene structured copper films exhibited fine and good adhesion with the polyimide substrate, and they could be utilized for good application in the fields of minute copper circuit patterns on insulating substrates.

Direct metallization of nickel on polymeric template patterns for fabrication of copper circuits on glass substrates

We demonstrate a chemical route to depositing nickel granular layer patterns using ion-doped precursor templates, which can be used as adhesive interlayers for fabrication of copper circuit patterns on glass substrates. The poly(amic acid) templates were first dispensed from solution onto the glass surface using a fine-precision dispenser, followed by Ni2+ ion doping through selective ion exchange reaction. The reduction treatment using aqueous NaBH4 solution allowed the formation of a nickel granular layer on the poly(amic acid) surface, which could catalyze subsequent electrodeposition of copper. The resulting copper/nickel/polyimide-layered structure showed good adhesion with the glass substrate. This work can benefit the understanding of the growth process of metallic thin films via the direct metallization process and provide important experimental data for developing novel fabrication processes for copper circuit patterns on glass substrates.

Broadband absorption enhancement of thin SOI photodiode with high-density gold nanoparticles

We demonstrated the quantum efficiency (QE) of silicon-on-insulator (SOI) photodiode was enhanced in visible wavelength region by using gold (Au) nanoparticles. The photons plasmonically scattered by Au nanoparticles couples with the waveguide mode in SOI, and are absorbed efficiently. Optimum size and density of Au nanoparticles have been investigated by 3-D FDTD simulations for sensitivity improvement. The highest enhancement factor of the absorption efficiency in 100-nm-thick SOI is obtained by periodically attaching Au nanoparticles of about 140 nm in diameter and 1.7 × 109 particles/cm2 in density. Two-fold enhancement in QE was experimentally achieved in visible by the SOI photodiode with randomly arranged Au nanoparticles of the size and density close to the optimized values.

Metal (Au, Pt) Nanoparticle–Latex Nanocomposites as Probes for Immunochromatographic Test Strips with Enhanced Sensitivity

The development of a sensitive and rapid diagnostic test for early detection of infectious viruses is urgently required to defend against pandemic and infectious diseases including seasonal influenza. In this study, we developed noble metal (Au, Pt) nanoparticle-latex nanocomposite particles for use as probes for immunochromatographic test (ICT) strips. The nanocomposite particles were conjugated with monoclonal antibody (mAb) to detect an influenza A (H1N1) antigen. For comparison, Au nanoparticles conjugated with mAb were also prepared. The lowest detectable concentrations of the influenza A antigen were found to be 6.25 × 10-3 and 2.5 × 10-2 HAU/mL for Au nanoparticle-latex and Pt nanoparticle-latex nanocomposite particles, respectively, whereas it was 4.0 × 10-1 HAU/mL for Au nanoparticles. These results clearly demonstrated that the nanocomposite probes were more sensitive than conventional nanoparticle-based probes for ICT. To expand the versatility of the nanocomposite probes, the surfaces of the probes were functionalized with biotinylated proteins to enable modification of their surfaces with desired biotinylated antibodies through biotin-avidin binding.

Sensitivity Enhancement of SOI Photodiode with Randomly Arranged Au Nanoparticles

We demonstrated the quantum efficiency (QE) of silicon-on-insulator (SOI) photodiode was enhanced in visible frequency region by using Au nanoparticles. Two-fold enhancement in the QE was achieved in visible by the optimized particle size and density.