Dr Ha Pham

The heat-processing of next-generation wide-band gap semiconductors is expected to require temperatures higher than 1500 K and rapid heat-up rates of more than than 100 K/s.

Of the various methods available for this high-temperature treatment of semiconductors, high-frequency induction heating is one of the most promising candidates.

However, induction heating has a shortcoming related to temperature uniformity and heat distribution due to deviations in the magnetic flux density of the induction heating coils.

Many researchers have attempted to solve this problem by using multiple working coils and high-frequency power supplies, but, in 20 years of trying, no one has succeeded.

As a part of a cooperative research project, Tokyo Tech and Mitsui Engineering and Ship Builder Co. Ltd. have developed a new zone-control induction heating (ZCIH) system.

Between 2007 and 2012 at Tokyo Tech, Dr Ha Pham contributed to the project as the inventor of current phase synchronisation technology and three-dimensional resistance matrix theory. He developed the theory, built prototypes and conducted experimental validation.

The ZCIH system consists of six sets of working coils and inverter circuits, and is controlled with newly developed current phase synchronisation technology and Pham’s theory.

The new ZCIH system enabled stable operation and flexible heat distribution in experiments conducted by the researchers, yielding flat temperature profiles. This heat distribution control method is applicable not only to semiconductor processing but for the development of a wide range of other materials.

The successful project enabled rapid thermal processing and high efficiency, including high-accuracy uniform temperature control.

This allows a high-accuracy, reproducible process applicable to a production line of small batches of many different parts.

Ultimately, the innovation will lead to cost savings for the manufacturing industry.