Yuji Kang

Room-Temperature Nanoimprinting Using Liquid-Phase Hydrogen Silsesquioxane with Hard Poly(dimethylsiloxane) Mold

A new room-temperature imprinting method was developed using liquid-phase hydrogen silsesquioxane (HSQ) with a hard poly(dimethylsiloxane) (h-PDMS) mold. The simultaneous imprinting of arbitrary patterns including both submicron and greater than 100 µm patterns on a 4-in. wafer were replicated at room-temperature and a low pressure with high throughput, because the solvent in HSQ gradually evaporated through the pores of the h-PDMS mold. A bilayer structure was successfully fabricated using as HSQ pattern as an etching mask without removing the residual layer.

Room temperature nanoimprinting using spin-coated hydrogen silsesquioxane with high boiling point solvent

The authors have previously used two methods for nanoimprinting hydrogen silsesquioxane (HSQ) patterns. In the casting method, the HSQ pattern was replicated at a low imprinting pressure of less than 1 MPa, however, the imprinting produced an uneven residue. On the contrary, in the spin-coating method, an evenly distributed HSQ film was produced. However, the HSQ pattern required a high imprinting pressure of about 40 MPa. To achieve imprinting at a low pressure with the spin-coating method, we propose a new room temperature nanoimprinting method using spin-coated HSQ and a poly(dimethylsiloxane) mold. The authors used high boiling point solvent, with a boiling point of greater than 200 °C, in place of the previously used solvent that had a boiling point of 96 °C. This method produced an evenly coated film in the liquid-phase.

Mechanical characteristics of imprinted nanostructures fabricated with a poly(dimethylsiloxane) mold

Nanoscale imprinted pillars were fabricated with three resin systems and characterized by measuring the spring constant using a scanning probe microscopy cantilever manipulated with a three-axis actuator. The functional dependence of the spring constant on the height and diameter of the pillar was then used to determine the Young’s modulus. Nanoindentation was used to determine the Young’s modulus of the base film. Before high temperature annealing, the Young’s modulus of the imprinted pillar was nearly the same as that of film. After the annealing, the Young’s modulus of the imprinted pillar was lower than that of the film.

Mechanical Characteristics of Nanosprings Fabricated by Focused-Ion-Beam Chemical Vapor Deposition Using Ferrocene Source Gas

The mechanical characteristics of iron-containing nanosprings (Fe-containing nanosprings) fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) using a ferrocene (C10H10Fe) source gas were investigated. The shear and Youngs moduli were 34 and 92 GPa, respectively. We also evaluated the annealing effect of Fe-containing nanosprings and observed a droplet containing Fe and Ga on the nanospring after annealing at 600 °C. The spring constant rapidly decreased after annealing at 600 °C. By scanning electron microscopy energy–dispersive X-ray spectroscopy (SEM–EDX) and transmission electron microscopy energy–dispersive X-ray spectroscopy (TEM–EDX) line analysis, it was confirmed that the decrease in the spring constant was due to Ga removal.

Structural Changes in Diamond-Like Carbon Films Fabricated by Ga Focused-Ion-Beam-Assisted Deposition Caused by Annealing

The desorption processes of H and Ga from diamond-like carbon (DLC) film synthesized by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated by elementary analysis and local structure analysis after heat treatment under various conditions. The elementary composition of FIB-CVD DLC film was determined using a combination of Rutherford backscattering spectra and elastic recoil detection analysis spectra. Local structure analysis was performed by the measurement of near-edge X-ray absorption fine structure using synchrotron radiation. Desorption of H from FIB-CVD DLC film by heat treatment was found to comprise two types of process. One is the local graphitization along paths, where residual Ga atoms move by annealing. In this process, Ga acts as a catalyst for the graphitization of DLC. The other process is derived from the graphitization of the whole DLC film by heat, regardless of Ga. In this process, the sp2 content increases considerably.

UV irradiation effect on sol-gel indium tin oxide nanopatterns replicated by room-temperature nanoimprint

The authors report the first room-temperature nanoimprint lithography (RT-NIL) process using sol-gel indium tin oxide (ITO) as a replicated material. The spin-coated ITO film has to be annealed over 600°C to obtain a low resistivity. The spin-coated ITO film can be delineated by RT-NIL, but the patterns disappear after annealing at 200°C. To overcome the above problem, they examined UV irradiation effects on a spin-coated ITO film. As a result, they found that the ITO patterns imprinted by RT-NIL stayed the same after being annealed at 600°C for 1h due to 254nm UV irradiation before annealing.

Characteristics of Antisticking Layer Formed by CHF3 Plasma Irradiation for Nanoimprint Molds

Nanoimprint lithography (NIL) is very useful for mass-producing nanostructure devices at a low cost and a high throughput. To avoid the adhesion of replication materials, NIL molds are usually coated with an antisticking fluorinated self-assembled monolayer. In this study, we used a fluorinated plasma chemical vapor deposition film as the antisticking layer. First, we formed a CHF3 plasma chemical vapor deposition (CVD) film on SiO2/Si and quartz molds and carried out thermal and UV nanoimprint using these molds. However, the film was removed from these molds. We found that the proposed method can solve this problem. We irradiated plasma using a gas mixture of CHF3 and O2 as the source gas onto SiO2/Si and quartz molds. As imprinting results, the patterns were successfully imprinted onto the resins without the removal of the plasma CVD film. In addition, we were able to carry out 100 times of repeated nanoimprinting using the plasma-CVD-film-coated SiO2/Si mold.

Nanoimprint replication of nonplanar nanostructure fabricated by focused-ion-beam chemical vapor deposition

Nanoimprint lithography (NIL) is a very useful technique for replicating planar nanostructures at low cost with high throughput, but an expansion from planar to nonplanar will probably be required to enhance the functional capabilities of nanodevices. On the other hand, focused-ion-beam chemical vapor deposition (FIB-CVD) is a promising technology for fabricating nonplanar nanostructures. In this study, the authors demonstrated a new nonplanar replication method using a combination of FIB-CVD and NIL to achieve nonplanar replication with submicrometer feature sizes. Furthermore, they replicated nonplanar nanostructures by using step and repeat NIL.

Density measurement of pillar structure fabricated via nanoimprinting using a poly(dimethylsiloxane) mold

The authors report density measurements of a pillar structure that was fabricated via nanoimprinting using a poly(dimethylsiloxane) mold. The imprinted pillars were fabricated using two types of resin, SU-8 and hydrogen silsesquioxane, and were characterized by measuring the spring constant using a scanning probe microscopy cantilever, which was manipulated with a three-axis actuator. The spring constant determined Youngs modulus of the imprinted pillars. The authors measured the resonant frequency using the alternating current electrostatic force. Using the results for Youngs modulus and the resonant frequency, they determined the density of the pillar structure fabricated via nanoimprinting.The authors report density measurements of a pillar structure that was fabricated via nanoimprinting using a poly(dimethylsiloxane) mold. The imprinted pillars were fabricated using two types of resin, SU-8 and hydrogen silsesquioxane, and were characterized by measuring the spring constant using a scanning probe microscopy cantilever, which was manipulated with a three-axis actuator. The spring constant determined Youngs modulus of the imprinted pillars. The authors measured the resonant frequency using the alternating current electrostatic force. Using the results for Youngs modulus and the resonant frequency, they determined the density of the pillar structure fabricated via nanoimprinting.

Thermal Durability of Diamond Like Carbon Films Containing Tungsten Fabricated by Focused-Ion-Beam Chemical Vapor Deposition

Diamond like carbon film containing tungsten (W-DLC) was fabricated by focused-ion-beam chemical-vapor deposition (FIB-CVD), and its thermal durability was investigated using near the carbon K-edge X-ray absorption fine structure (C-K NEXAFS) spectroscopy and a combination of Rutherford backscattering and elastic recoil detection analysis, in comparison with those of commercial DLC and W-DLC films. The concentration of W in the films did not decrease when the annealing temperature was increased, while the concentration of H did. The sp2/(sp2+sp3) ratio of carbon atoms in the films increased with annealing temperature. The W-DLC film fabricated by FIB-CVD unchanged after annealing for 32 h at 873 K in vacuum. Its thermal durability was comparable to that of commercially available films.