enRESEARCH of NANOMECHATRONICS LABORATORY

RESEARCH

NANOMECHANICS, MICROMECHANICS, EXOTHERMIC THIN FILM FOR WAFER BONDING, NANOPARTICLES FOR NEW FUNCTIONS

RESEARCH

1．NANOMECHANICS

A unique self-made tensile testing system using MEMS technology allows the strength of nanomaterials to be measured directly in a field-emission scanning electron microscope (SEM). MEMS devices with electrostatic actuators and capacitance sensors are designed and fabricated, and an experimental system with unique modifications inside the SEM allows tensile testing of nanowire-shaped specimens while observing them in situ. Materials whose strength has been evaluated include carbon nanotubes, silicon nanowires, insulating nanofilms and carbide nanorods. In the study of silicon nanowires, the effects of FIB processing damage and vacuum annealing effects on mechanical properties have been experimentally evaluated. Recently, Young's modulus and tensile strength of single-walled carbon nanotubes with diameters of 1-3 nm have been measured and experimental correlations between nanotube structure and mechanical properties have been successfully obtained.

　MEMS devices for nanotensile testing in SEM (self-made)

Nano tensile test system in SEM

Pick up of single-walled carbon nanotubes

Stress-strain diagram of single-walled carbon nanotubes

Fracture analysis of single-walled carbon nanotube bundles

Si nanowire tensile specimen (20 nm width)

2．MICROMECHANICS

We have developed various original experimental techniques for thin films and micro-rods.For example, we have thin-film evaluation techniques such as uniaxial and in-plane biaxial tensile testing apparatus, Poisson's ratio evaluation apparatus and SEM tensile testing apparatus, as well as our own experimental apparatus such as strength measurement apparatus for micro-rods with joints, combined tensile, bending and torsion testing apparatus for micro-torsion bars and impact testing equipment for MEMS structures.We have experience in measuring mechanical properties (Young's modulus, Poisson's ratio, fracture strength, bonding strength, creep, stress relaxation, fatigue, etc.) of silicon-based film materials, various metal films and polymer films.Recently, we have also conducted research using our original material testing apparatus as a stress application device for MEMS and semiconductor ICs, as well as fatigue testing of thin films using MEMS resonance devices.The strength of the Ikutsu Laboratory lies in its ability to design and develop original mechanical loading devices for the evaluation of micromaterials.

Thin-film tensile test system in SEM (self-made)　

Tensile-bending-torsion combined mechanical testing of MEMS elements.

In-plane orthogonal biaxial tensile testing system for thin film materials.

Four-point bending test of micro specimens with joints.

Stress strain diagram of a nanosilver sintered film

Fatigue testing of Al alloy thin films in the SEM.

3．Exothermic Thin Films for Wafer Bonding

Multilayer films with nano-thickness layers of different metals are produced using a proprietary multi-source DC/RF sputtering system.When multilayers fabricated from a combination of light and transition metals (e.g. aluminium and nickel) are subjected to external microstimulation, an exothermic reaction is generated due to alloying.As these exothermic materials can be heated instantaneously and locally, they have a variety of potential applications, such as a heat source for solder joints.Recently, we have developed heat-generating multilayers that are ultra-sensitive to external stimuli and heat-generating materials made of biocompatible materials that respond to a simple poke with tweezers, with the aim of applying them to semiconductor devices and the medical field.

The self-propagating exothermic reaction of aluminium/nickel multilayers

Cross-sectional structure of aluminium/nickel heat-generating multilayer film (bilayer 300 nm)

Instantaneous bonding of silicon wafers

Cross-sectional view of the instantaneous joint

Two silicon chips with 0.1 second instantaneous bonding

Thermal shock testing of aluminium/nickel instantaneously heated nanosilver sintered bodies

4．Nanoparticles for New Functions

We conduct mechanics research that is both academically and visually interesting, using the new functions that emerge when materials are nanoparticulated and the physical phenomena that arise when nanoparticles are aligned, with free ideas.Examples include the development of nanoparticles with a heat-generating function by creating a repeating structure consisting of a combination of biocompatible materials (e.g. titanium and silicon oxide) within a single nanoparticle, the development of new sensor materials that express strain distribution by colour, by arranging self-made silica nanoparticles in a face-centred cubic structure to produce structural colour, and the development of new sensor materials that express strain distribution by colour.We are also developing a new sensor material that expresses strain distribution by colour, and modulating mechanical and electrical properties by creating single-crystal silicon nanodots in a silicon oxide film with an idea that differs from existing concepts.

Porous silica nanoparticles (self-made)　

Exothermic reaction of titanium/silica nanoparticles (diameter about 100 nm)

Exothermic reaction of aluminium/nickel microparticles (approx. 500 µm diameter)

Single-crystal silicon nanodots (diameter: about 10 nm) fabricated by electron irradiation

Structural colour films with silica nanoparticle arrays.

Angle dependence of structural colour from silica nanoparticle arrays

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