Kenichi Kanzaki

Low-Acceleration-Voltage Electron Irradiation Damage in Single-Walled Carbon Nanotubes

Low-acceleration-voltage electron irradiation effects on single-walled carbon nanotubes were studied by resonant Raman spectroscopy. The irradiation at acceleration voltages of 0.5 to 25 kV was found to extinguish the characteristic optical property of the nanotubes and reduce their tolerance against annealing in air, indicating that the nanotubes are inevitably damaged by ordinary scanning electron microscope observation. The acceleration voltage of around 1 kV caused the most extensive damage. Less defective SWNTs were found to have a higher tolerance against the irradiation damage.

Let effects of ion beam irradiation on poly(di-n-hexylsilane)

Abstract Thin films of poly(di-n-hexylsilane) were irradiated with 2–20 MeV H + , He + and He 2+ ion beams. The beams caused heterogeneous reactions of crosslinking and main chain scission in the films. The relative efficiency of the crosslinking was drastically changed in comparison with that of main chain scission. The anomalous change in the molecular weight distribution was analyzed with increasing irradiation flux, and the ion beam induced reaction radius; the track radius was determined for the radiation sources by the function of molecular weight dispersion. The values obtained ranged from 5.9 ± 1.5 nm for 2 MeV He + to 1.0 ± 0.5 nm for and 20 MeV H + ion beam irradiation.

Positive-Negative Inversion of Silicon Based Resist Materials: Poly(di-n-hexylsilane) for Ion Beam Irradiation

The present paper describes radiation induced solubility changes and emission spectra of poly(di-n-hexylsilane) and their temperature dependence on. Poly(di-n-hexylsilane) has a clear phase transition temperature at around 312 K with change of the silicon skeleton structure. Radiation induced reactions differed greatly above and below this temperature, showing large emission spectral changes. High LET (linear energy transfer; energy deposition rate of incident particles per 100 A ion beams induced main chain crosslinking in the polymer. PDHS behaved as a negative-type resist material below 312 K, although it had been previously confirmed that PDHS had shown positive-type resist properties for UV light, electron beams, X-rays, low LET proton beams at any temperature range and for higher LET He ion beams at a temperature above 312 K.

Graphene Layer Formation on Polycrystalline Nickel Grown by Chemical Vapor Deposition

We studied the structure of graphene layers grown by chemical vapor deposition on polycrystalline nickel. The conditions of the polycrystalline nickel catalyst (size of fine crystals and surface roughness) were controlled by cyclic heating and cooling, and its effect on the graphene layer formation was evaluated. By increasing the average size of the nickel fine crystals and thereby increasing of the surface roughness, nonuniformity of the graphene sheet numbers tends to increase. A marked change in graphene sheet number tends to occur at discontinuities in the polycrystalline nickel surfaces. From the structural analysis, the graphene layer is found to be made up of single or multiple crystal graphene thin films with different crystallographic directions. The size of each thin film is independent of and not restricted by the size of the nickel fine crystals, and a certain thin film passes over the discontinuities.

Resist Thinning Effect on Nanometer-Scale Line-Edge Roughness.

The thickness dependence of the roughness of ultrathin ( 100 nm) electron-beam resist (ZEP520) was investigated using an atomic force microscope (AFM). The roughness (linewidth fluctuations of line patterns) increased with decreasing resist thickness, especially below 30 nm. On the other hand, polymer aggregates, which are well observed in conventional resists, existed in compressed form even in this ultrathin film. In addition, the dissolution rate of the resist tended to be faster with thickness reduction. Both the existence of polymer aggregates and the fast dissolution of the entire resist polymer possibly caused the larger roughness in the ultrathin resist films.

Nonhomogeneous Pattern Formation in the Dissolution Processes of Novolak-Diazonaphthoquinone Resists

The development mechanisms of irradiated novolak-diazonaphthoquinone resists have been studied on the basis of the atomic force microscopy (AFM) data of resist surface images. The characteristic surfaces with large holes or island structures, that is, nonhomogeneous surfaces, have been observed at the exposure doses near the beginning of the film thickness reduction. The changes in the size of holes and island structures roughly correspond to the changes of cluster size estimated by percolation theory. From the dissolution pattern changes which depend on exposure dose, it is considered that an adequate exposure dose is indispensable for high-precision patterns and such an exposure dose determines the sensitivity of positive-type resists.

T-top forming simulation using percolation theory

In KrF or ArF resist processing, a chemically amplified resist is widely used for ultralarge scale integrated device fabrication. Decomposition (positive resist) or cross linking (negative resist) is amplified by an acid catalytic reaction during post-exposure baking (PEB). T-top forming becomes a serious problem in these resists. In resist simulation, to take these characteristics into account, percolation theory is introduced. The acid and product distributions during PEB are iteratively calculated. Thus, we can conclude that the acid and product distribution in resist films are time dependent. Moreover, a resist simulator that can take into account macroscopic feature changes from microscopic molecular structural change is necessary. From resist surface observation and slow positron annihilation measurements, free volume generation is confirmed. A new resist process model, including prebake, PEB, and development for chemically amplified resists is established by the cluster model. CPU time is 1 min eac...

Atomic Force Microscopy Study on the Dissolution Processes of Chemically Amplified Resists for KrF Excimer Laser Lithography

The surface images of chemically amplified KrF excimer laser resists after development were measured by atomic force microscopy (AFM). From the AFM images at various exposure doses, the dissolution behavior of the polyvinylphenol-based KrF resists differed from that of novolak-diazonaphthoquinone (DNQ) resists. An explanation for the different dissolution behavior has been proposed by considering the difference in the mechanisms of formation of soluble sites between chemically amplified resists and novolak-DNQ resists (non-chemically amplified resists). In addition, AFM topographic images of the resists dissolving layer by layer were observed clearly in the resist spin-coated on a Si wafer. The step heights of the layered structure observed by AFM are in good agreement with the computed value of the distance between two adjacent nodes of standing waves formed by KrF excimer laser exposure. The layered dissolution may be applied to the processing of thin polymer films.