Back in 1980, technological competition in the semiconductor manufacturing industry was hotting up. It was in that year that Tokuyama launched a new research program at the Fujisawa laboratory, a brand-new research facility that had just been established close to Tokyo. The laboratory’s mission was to develop a revolutionary new ceramic material that would become a core new business for Tokuyama.

Current Company Director and General Manager of the R&D Division, Nobuyuki Kuramoto, was involved in the research in those days. As Kuramoto himself says, “We were unsure which materials should be chosen, so we started by making various nitrides and carbides through reducing oxides with carbon.”

Kuramoto had investigated pressure-less sintering of Si-Al-O-N ceramics for two years beginning in 1977, at the National Institute for Research in Inorganic Materials of the Science and Technology Agency. As Kuramoto says, “Fine ceramics sintered at high temperatures can be converted into ceramics that have a variety of useful properties.” It was such properties that inspired the researchers and drove them forward in their quest.

At a very early stage in the research, Kuramoto and his colleagues even had to develop new methods to evaluate chemical and physical properties of the new materials that would be created. The researchers faced great challenges in developing these new technologies, but it was these initial efforts that built a sturdy foundation to move to the next stage of development.

One day, in the laboratory, the breakthrough they had been waiting for happened. The researchers hot-pressed AlN powder made from alumina. While AlN ceramics are usually black, this hot-pressing had resulted in a ceramic that looked different to usual. When sliced thinly and held up to the light, Kuramoto could see his fingers moving through the ceramic.

“Sinter highly pure and sharply distributed AIN powder … and get a translucent ceramic body!”

“Thermal conductivity and all other properties are ideal…almost identical to those of a single crystal!”

This discovery happened near the end of 1981, a happy day for Kuramoto and his colleague Taniguchi, now General Manager of Tsukuba Research Laboratory.

After the initial discovery, research focused on developing translucent AlN ceramics and raw material powder for them. A year of experimentation resulted in the completion of a translucent AlN ceramic. The researchers reduced and nitrided alumina with carbon to synthesize very pure AlN powder, which is sintered to produce a new pure and dense ceramic through the pressure-less sintering method that is commonly used in industrial mass production.

Research showed that the AlN ceramic had almost the same thermal conductivity as aluminum metal. Furthermore, it had high mechanical strength and a thermal expansion coefficient close to that of silicon.

“With this material, we can solve the thermal management pressure caused by high power IC chips!”

The amazing properties of the new ceramic material represented a great leap forward in the development of highly thermal conductive and insulated AlN substrates.

Tokuyama applied for a material patent for this very pure aluminum nitrate powder (Note 1) and the ceramic. This was the first example in the world of making a translucent substrate from a homogenous nitride through a pressure-less sintering process. In 1984, Tokuyama publicly announced the technology for its AlN Powder (Note 2), AlN Granules (Note 2) and translucent AlN ceramics called Shapal (Note 3), receiving worldwide attention. Given the advances in semiconductor technology and their increasing power, heat management of silicon die chips was becoming an ever more serious issue. The AlN ceramic, which is insulative and also capable of absorbing a great deal of heat, met industry needs, providing a perfect solution to a problematic issue.

At the time the invention was announced to the world, industrial-use and commercialized AlN products were not available. Tokuyama decided to be the first to manufacture commercial volumes of AlN based on the inventions resulting from corporate research. Tokuyama is now producing not only AlN powders, but also substrates and thin-film or thick-film metallized ceramics products which have been widely and successfully accepted industry-wide.

AlN is used in products as follows: cooling materials for large-sized computers and supercomputers.
AlN is now widely used as an industrial material. Examples of use include as an insulation substrate for overseas and domestic locomotives, including the ICE train of Germany. AlN is also used in laser diode submounts used in DVDs and control module substrates in hybrid and other vehicles. Tokuyama has also licensed the patent to a large U.S. chemical manufacturer.

In 1998, these achievements were recognized and the Prime Minister’s Prize (Note 4) was awarded for the invention of advanced-function AlN ceramics (Patent No. 1579756).

Many new applications for AlN continue to be developed, taking advantage of its superior properties of high thermal conductivity and high electrical insulation. The advantages of AlN ceramics continue to spread through the market, replacing alumina or beryllia and metal components that were once used as heat dissipation substrates. There are great expectations that AlN products will be developed for use in areas in which their properties can be usefully and profitably applied, including plasma resistance and high wave frequency performance. AlN will continue to be widely used as a material that meets the needs of cutting edge technologies, in IT, the automotive sector, optical communications, and semiconductors.