Yukinori Ochiai

ULTRAHIGH RESOLUTION OF CALIXARENE NEGATIVE RESIST IN ELECTRON BEAM LITHOGRAPHY

A nonpolymer material, calixarene derivative (hexaacetate p‐methnylcalix[6]arene) was tested as a high‐resolution negative resist under an electron beam lithography process. It showed under 10‐mm resolution with little side roughness and high durability to halide plasma etching. A sub‐10‐nm Ge quantum wire was perfectly etched off without defects. Such a performance is suitable for nanoscale device processes.

Focused ion beam applications to solid state devices

The current state of focused ion beam (FIB) applications in relation to solid state devices is reviewed, and recent use of FIB technology for lithography, etching, deposition, and doping are described. Etching and deposition have become essential processes for failure analysis and for mask repair in silicon ULSL production. Furthermore, the FIB doping technique has been used to fabricate quantum effect devices.

Patterns in the bulk growth of carbon nanotubes

Abstract The growth of nanotubes in carbon arc plasma is described in detail. The structure and organization of the nanotube deposits observed by SEM and AFM reveal a fractal-like pattern of growth. One of the key units of growth appears to be the micro-bundle composed of neatly packed and aligned nanotubes. The micro-bundle together with the field and current might explain the high formation yield of nanotubes.

Free-space-wiring fabrication in nano-space by focused-ion-beam chemical vapor deposition

Focused-ion-beam chemical vapor deposition (FIB-CVD) is an excellent technology for forming three-dimensional nanostructures. Various diamond-like-carbon (DLC) free-space-wirings have been demonstrated by FIB-CVD using a computer-controlled pattern generator, which is a commercially available pattern generator for electron-beam (EB) lithography. The material composition and crystal structure of DLC free-space-wiring were studied by transmission-electron microscopy and energy-dispersive x-ray spectroscopy. As a result, it became clear that DLC free-space-wiring is amorphous carbon containing a Ga core in the wire. Furthermore, the electrical resistivity measurement of DLC free-space-wiring was carried out by two terminal electrodes. Au electrodes were fabricated by EB lithography and a lift-off process. The electrical resistivity was about 100 Ω cm at room temperature.

Effects of thermal annealing on porous silicon photoluminescence dynamics

Photoluminescence (PL) spectra and decay dynamics were studied for the spontaneously oxidized porous Si with subsequent various thermal annealing procedures. The PL decay was highly nonexponential and well described by the stretched‐exponential function. The PL lifetime was shorter for the higher PL photon energy, but at the same photon energy it decreased by an order of magnitude by the thermal annealing in N2 gas, in parallel with the large PL intensity decrease. This PL quenching upon the annealing is presumably ascribable to both the structural changes and dangling bond formations in porous Si, as suggested by ESR measurements and the annealing experiments in H2 gas.

Observation and characteristics of mechanical vibration in three-dimensional nanostructures and pillars grown by focused ion beam chemical vapor deposition

The Young’s modulus of diamond-like carbon (DLC) pillars was measured by means of mechanical vibration using scanning electron microscopy. The DLC pillars were grown using Ga+ focused ion beam-induced chemical vapor deposition with a precursor of phenanthrene vapor. The Young’s modulus of the DLC pillars was around 100 GPa at vapor pressure of 5×10−5 Pa and it had a quality (Q) value of resonance exceeding 1200. There seemed to be a balance between the DLC growth rate and surface bombardment by the ions, and this played an important role in the stiffness of the pillars. Some of the DLC pillars showed a very large Young’s modulus over 600 GPa at low gas pressure conditions.

Room temperature replication in spin on glass by nanoimprint technology

A compact nanoimprint lithography (NIL) system using the driving power of a stepping motor has been developed. Compared to a conventional NIL system with a hydraulic press, there are some additional features of the NIL system such as compactness and low cost. We propose the use of spin on glass (SOG) instead of PMMA to avoid thermal expansion and demonstrate SOG patterns with 200 nm linewidths at room temperature replications using the NIL system. The SOG patterns were transferred to gold metal using liftoff and to a silicon substrate by reactive ion etching.

Room-temperature nanoimprint and nanotransfer printing using hydrogen silsequioxane

Room-temperature nanoimprint lithography (RT-NIL) technology has been developed to overcome critical dimensions and pattern placement errors caused by thermal expansion in the conventional nanoimprint lithography (NIL) process. We propose RT-NIL using hydrogen silsequioxane (HSQ) instead of the poly(methylmethacrylate) used in conventional NIL. We demonstrate HSQ-replicated patterns with a 90 nm diameter hole and 50 nm linewidth for room-temperature replications. Furthermore, we have developed new nanotransfer printing technology utilizing the adhesion characteristics of HSQ. We also demonstrate the transfer of photoresist and Au patterns from a mold to a substrate.

Nanomanipulator and actuator fabrication on glass capillary by focused-ion-beam-chemical vapor deposition

Three-dimensional (3D) nanostructures on a glass capillary have a number of useful applications such as manipulators, actuators, and sensors in the various microstructures. We observed a phenomenon that two diamondlike-carbon pillars on a tip of glass capillary fabricated by 30 keV Ga+ focused-ion-beam-chemical vapor deposition (FIB-CVD) with a precursor of phenanthrene vapor was able to work as a manipulator during FIB irradiation. It became clear that it was caused by electronic charge repulsion between two pillars, which accumulated electric charge by FIB irradiation. By applying this moving mechanism, we have developed a 3D nanomanipulator and actuator on a tip of glass capillary by FIB-CVD. Furthermore, in situ observations of movement for a 3D nanomanipulator and actuator have been demonstrated by applying voltage onto a Au-coated glass capillary.

Development of three-dimensional pattern-generating system for focused-ion-beam chemical-vapor deposition

We studied the fabrication of free-designed three-dimensional (3D) structures by using focused-ion-beam chemical-vapor deposition. The 3D structures are fabricated by scanning 30 keV Ga+ ion-beam-assisted deposition in a 1×10−4 Pa phenanthrene atmosphere. The scanning pattern and blanking signal of the ion beam are generated by a 3D computer-aided-designed model using a computer pattern-generating system. This 3D pattern-generating system is able to fabricate overhang and hollow structures by setting suitable parameters (for example, plot pitch, dwell time, time interval of irradiations, and priorities of scanning). In this article, we demonstrate the performance of a 3D pattern-generating system by fabricating a 1:100 000 000 scale model of the Enterprise spaceship, a microring, a moth’s eyelike structure, and a morpho butterflylike structure with 200 nm spacing.