Professor, New Industry Creation Hatchery Center, Tohoku University
Creating next generation industry based on ‘NEMS technology’
— Combining micromachining with nanomachining —
A slender catheter equipped with a sensor at its tip is inserted through a blood vessel to measure the pH of blood. Development of this semiconductor ion sensor for medical use by Prof. Esashi opened up a new world of micromachining research in Japan.
In the mid 70s, Prof. Esashi was a graduate student at Tohoku University when he developed a semiconductor ion sensor (ISFET) for medical use, using MOS transistors that were used for electric calculators. He was working with Prof. Jun-ichi Nishizawa who was a leader of Japanese semiconductor researches at that time. Later, he developed miniaturized technology for pressure and acceleration sensors and advanced technology in packaging that was important for devices applicable to practical uses. Prof. Esashi also developed original micromachining equipment and has been leading a way in pioneering research in the micromachining field. Micromachining is the technology based on silicon microfabrication technology and a combination of various technologies such as electronics, mechanics, optics, and material science. This technology has been utilized for the production of various microelectromechanical systems (MEMS) that are key components for information/communication systems, electric appliances for automobile/home, and medical/biological devices. Currently, Prof. Esashi is making efforts to combine micromachining with nanomachining because “The combination of micromachining and nanomachining will enable us to construct sensors and systems with higher performance and better quality than the existing MEMS.“ He aims at developing MEMS into NEMS (nanoelectromechanical systems) by applying nanomachining.
One of his remarkable achievements is the electron beam source for a lithography system that enables the fabrication of high performance VLSIs: it allows direct and maskless patterning narrower than 100 nm. It consists of deposited carbon nanotubes with nanomachining at the tips of a silicon needle array that has been prepared with micromachining. Another one is the next generation high-density data storage device with multi-nanoprobes. The device consists of 32 x 32 arrayed probes with nano heater tips each. A recording media is heated by the tips and data is written onto the medium at a density of as high as 1 Tb / inch2. The stored data are read out by using the conductivity difference of a single digit between the heated portions and unheated portions.
Prof. Esashi’s research theme, researches toward practical use, is based on the Tohoku University’s traditional philosophy, “Jitsugaku“ or practical science. He suggests “the small volume production of multiple kinds of high-value-added products using high technologies“ to utilize our own technological skills and know-how for national industrial recovery. He also suggests that joint industry-university research based on “open collaboration“ to make our industries more internationally competitive. Nanomachining can be applied in various fields.
Prof. Esashi always makes his standpoint clear by saying; “Providing industry with ‘NEMS technologies’ information that industry needs is the role of university researchers.“ Indeed, there are many visitors from private companies to share information with him. “Our job is to open up a new field into which no one has been. Therefore, our efforts could go wrong. What is important here is to find out what went wrong. Learning from failure will lead you to further research.“ adds Prof. Esashi.
