Noboru Takano

Nanomachining of Silicon Surface Using Atomic Force Microscope With Diamond Tip

This paper investigates nanomachining of single-crystal silicon using an atomic force microscope with a diamond-tip cantilever. To enable nanomachining of silicon, a nanomachining cantilever with a pyramidal diamond tip was developed using a combination of photolithography and hot-filament chemical vapor deposition. Nanomachining experiments on silicon using the cantilever are demonstrated under various machining parameters. The silicon surface can be removed with a rate of several tens to hundreds of nanometers in ductile mode, and the cantilever shows superior wear resistance. The experiments demonstrate successful nanomachining of single-crystal silicon.

Rapid nanopatterning of a Zr-based metallic glass surface utilizing focused ion beam induced selective etching

A simple and rapid method is proposed for nanoscale patterning on a metallic glass surface using focused ion beam irradiation followed by wet etching. It was found that the etch rate of a metallic glass surface irradiated with Ga+ ions could be drastically changed, and rapid patterning was possible with this method. Cross-sectional transmission electron microscopy observation reveals that the metallic glass substrate maintains an amorphous phase following irradiation. Etching enhancement was not observed for irradiation with Ar+ ions. The results indicate that enhancement of etching results from the presence of implanted Ga+ ions rather than a change in crystallography.

Sub-micrometer-scale patterning on Zr-based metallic glass using focused ion beam irradiation and chemical etching

This report describes a method of sub-micrometer-scale rapid patterning on a Zr-based metallic glass surface using a combination of focused ion beam irradiation and wet chemical etching. We found that a Zr-based metallic glass surface irradiated with Ga+ ions could be selectively etched; a concave structure with a width and depth of several tens to hundreds of nanometers rapidly formed in the irradiated area. Moreover, we determined that the etching was enhanced by the presence of Ga+ ions rather than a change in the crystal structure, and the structure could be fabricated while the substrate remained amorphous. The shape of the structure was principally a function of the dose and the etch time.

Nanomachining Zr-based metallic glass surfaces using an atomic force microscope

This study investigated the nanomachining of metallic glass surfaces using an Atomic Force Microscope (AFM). To reveal the nanomachining characteristics of metallic glass, machining experiments were conducted under various machining parameters. The metallic glass was machined to fabricate an 8-nm-deep by 120-nm-wide groove pattern. It was found that metallic glass is a more challenging material to machine than single-crystal silicon. The tool life is significantly shorter, although it can be improved somewhat by machining in water. Observation of the machining residue revealed that continuous and shear cutting chips were generated that differed from those generated by machining amorphous silicon.

Nanoscale fabrication in aqueous KOH solution using tribo-nanolithography

A simple process to fabricate a three-dimensional structure on silicon surface was developed by using tribo-nanolithography (TNL) in an aqueous KOH solution. An inclined rectangular structure can be fabricated by a process where a thin amorphous layer, having corrosion resistance against KOH, rapidly forms on the substrate at the diamond tip sample junction along the scanning pass of the tip, while simultaneously, the area not covered with the amorphous layer is being etched in KOH. An inclination of structure can be controlled by the scanning velocity. The scanning pitch is related to the corrosion resistance of the amorphous layer, rather than the change of inclination. We fabricated a structure having multiple inclinations based on these results, which indicates the possibility of using the TNL for three-dimensional nanofabrication.

Diamond Tip Cantilever for Micro/Nano Machining Based on AFM

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip allows the formation of damaged layer on silicon substrate by a simple scratching process. A thin damaged layer forms in the substrate along scanning path of the tip. The damaged layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the fabrication processes of the micro cantilever and diamond tip as a tool for TNL. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.

Nanopatterning on Nano-Polycrystalline Diamond and Cubic Boron Nitride Using Focused Ion Beam and Heat Treatment to Fabricate Textured Cutting Tools

Texturing on the surface of cutting tools is an effective method to improve the friction and resultant machining performances of the tool. In this study, to fabricate nanotextures on various tools used for precision cutting, a patterning method on nanopolycrystalline diamond and cubic boron nitride tools was investigated using focused ion beam (FIB) irradiation and heat treatment. Patterning was possible using this method, and the patterning characteristics were different from those of single-crystal diamond. This method was more suitable for cutting tools compared with direct FIB machining because of its high efficiency and significantly low affected layer.

Etching characteristics of a silicon surface induced by focused ion beam irradiation

The etching resistance characteristics of a Focused Ion Beam (FIB) irradiated silicon surface against KOH are investigated in this study. An FIB irradiated silicon surface can withstand etching in KOH solution, whereas the non-irradiated area is etched and consequently, a protruding nanostructure can be fabricated on the irradiated area. Height dependence of the nanostructure on the FIB irradiating conditions is investigated in order to control the shape of the nanostructure for application to three-dimensional nanofabrication. As a consequence, it was found that the height of the nanostructure can be controlled by FIB irradiating conditions such as dose and acceleration voltage. The mechanism is investigated by a selective etching method using HF solution. The results of a simulation indicate that the amorphous layer induced by ion irradiation is strongly related to this phenomenon. In addition, surface roughness and line width dependence was investigated, and these results indicate the potential use of this method as a novel three-dimensional nanofabrication process.

3D Micro-Fabrication using Combination Technique of Nano-scale Processing and Chemical Etching : 5th Report, Dependence of Mask on Processing Conditions

This study is intended to fabricate 3D microstructures on single crystal silicon by tribo-nanolithography (TNL) and wet chemical etching. In previous report, it could be known that height of microstructure fabricated by the TNL and subsequent wet chemical etching can be controlled by adjusting the TNL conditions such as normal load, pitch of processing line and number of processing. This paper reports an etch result by HF solution in order to evaluate the mechanism of height change with the TNL conditions. As a result, it is found that amorphous layer formed by the TNL can be selectively etched in HF solution though non-processed area withstands etching. The mechanism of change of masking effect is evaluated by utilizing this phenomenon. As a result, it can be known that change of masking effect by normal load is resulted from change of thickness of the amorphous layer. On the other hand, those by pitch of processing line and number of processing are resulted from conversion ratio of single crystal to amorphous structure.