SHIMODA Laboratory
<Major Research Areas>Magnetic materials, electronic devices, micro-liquid processes

Direct Formation of
Electronic Devices
Using Functional Solution

Research activity

　　Technologies in the field of highly developed electronic devices seem to have almost reached their maximum level of advancement. It seems, however, that insufficient attention has been given to viewpoints related to efficient use of production energy and materials, and the usability of production facilities. Let us consider efficiency in the use of materials, taking as an example the production of films using vacuum systems such as CVD and PVD. The ratio of the material that deposits on the substrate after this process is less than 10% of the amount of source material. Since the accumulated material is then scraped off using the photolithographic method, the final amount becomes less than 1% of the initial amount, which means 99% of the expensive high-tech material is wasted. Likewise, production energy should also be improved. The electronic device industry is currently at a very low level with respect to efficiency in its use of energy and material. A fundamental improvement in efficiency is urgently required from an environmental point of view.

　　The micro-liquid process used for manufacturing electronic devices from functional solutions is attracting a great deal of attention as a way to solve this problem of production efficiency. This process is defined as: (1) a method using functional solutions as the source material, and (2) a method of manufacturing electronic devices without any material losses.. The process is also called the inkjet printing method. This method has enabled a decrease in production energy and has improved efficiency in the use of material; it is expected to fundamentally change the method of manufacturing display devices.

　　Figure 1 shows the film formation method using the microliquid process. This method consists of the following four processes: (1) production of functional liquid, (2) generation of micro droplets, (3) patterning of the liquid, and (4) formation of solid film by drying. Functional liquid is a precursor solution that can be reformed into semiconductors, insulators or metal films. Micro droplets are formed by means of the inkjet method or the LSMCD method (Figure 2). Micro droplets create fine selforganizing patterning on substrates by using their surface energy. They have a relatively large surface area in relation to their volume, a feature that causes rapid drying of the surface and movement of solute toward the surface. If this phenomenon can be thoroughly investigated and controlled, it will be possible to form films with specific desirable profiles.

　　We analyze the fundamentals of the micro-liquid process, such as micro-liquid patterning and film formation, in order to systematize the process. We also investigate the characteristics of organic devices through research into new organic devices and organic transistor circuits using the micro-liquid process.

Equipment

LSMCD (Liquid Source Misted Chemical Deposition), ink-jet drawing device

The main research achievements in the past five years

1. T. Miyasako, B. Nguyen Quoc Trinh , M. Onoue , T. Kaneda , P. Trong Tue , E. Tokumitsu , T. Shimoda, "Totally solution-processed ferroelectric-gate thin-film transistor", APPLIED PHYSICS LETTERS 97, 173509(2010).
2. J. Li, H. Kameda, B. Nguyen Quoc Trinh, T. Miyasako, P. Trong Tue, E. Tokumitsu, T. Mitani and T. Shimoda, "A low-temperature crystallization path for device-quality ferroelectric film", APPLIED PHYSICS LETTERS 97, 102905 (2010).
3. T. Masuda, Y. Matsuki, and T. Shimoda , Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents, J. Colloid Interf. Sci., 340, 298-305 (2009).
4. T. Shimoda, Y. Matsuki, M. Furusawa, T. Aoki, I. Yudasaka, H. Tanaka, H. Iwasawa, D. Wang, M. Miyasaka, and Y. Takeuchi, Solution-processed silicon films and transistors, Nature, 440, 783-786 (2006).
5. Nikkei BP Technology Award (Information Division)(2006). 　Technology for Global Environment Award provided by Nihon Keizai Shimbun Inc.(2006).