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World's First Non-latchup IGBT

Outside-the-box thinking leads to a solution for the latchup problem during development of the insulated gate bipolar transistor (IGBT).

World's First Non-latchup IGBT

The power semiconductor device is a key component in all fields of power conversion. Toshiba started the development of a high-power gate turn-off (GTO) thyristor in the early 1970s, and discovered that the obstacle preventing its practical application was current concentration, or current hogging, in the turn-off state. The company therefore decided to develop a new device to solve this problem.

In 1977, Toshiba put a 1.3 kV-600 A GTO thyristor on the market, and in 1979 delivered Japan's first variable-voltage variable-frequency (VVVF) inverter using GTO thyristors to the Osaka Municipal Transportation Bureau, for use in electric railways. GTOs are commonly used not only in electric railways, but also in variable-speed control for industrial AC motors and large power-inverter power supplies. In the late 1970s, Toshiba began to develop a direct-light-triggered high-power thyristor, and in 1981 launched on the market a device using a high-output LED as a light source.

In the early 1980s, following the invention of the giant transistor and the GTO thyristor, inverter technology progressed to the extent that inverter-equipped home air conditioners were able to be commercialized. High performance, reliability, low noise, and compactness were essential in switching devices for power conversion equipment such as elevator motors and electric railways, and particularly for equipment that required switching at frequencies higher than the audio frequency range. Metaloxide- semiconductor field-effect transistors (MOSFETs) were used as high-speed switching devices at the time. However, they were limited in terms of current and voltage, and were therefore only used in lower voltage equipment (up to AC 200 V).

Almost all of the world's semiconductor manufacturers were competing in the development of new devices, and in 1982 a new insulated gate bipolar transistor (IGBT) was announced by General Electric (GE). This consisted of a vertical N-channel MOS structure applying drain layer conductive modulation, achieved by adding a P layer to the drain side. However, GE's IGBT structure inherently contained a parasitic thyristor action that could cause the device to switch on after latchup. This made it impossible to cut off a high current, and so the IGBT could not be put to practical use.

At the time, the Toshiba Research & Development Center (currently the Corporate Research & Development Center) had started research on GE's IGBT structure based on the expectation that the device structure might have the potential to replace the bipolar giant transistor. Comparing data using a two-dimensional device simulator, the researchers discovered that a simple stripe pattern mask prevented unexpected latchup rather than the mesh pattern mask that was generally used in MOS devices at the time.Shortly after that, the researchers came up with another idea. They decided to design the MOS saturation current so as to be lower than the current at which device latchup occurred. As a result, they demonstrated that a non-latchup structured IGBT was capable of cutting off high currents, leading to the practical use of this device in the market and mass-production.

In 1984, Toshiba developed a fracture-resistant non-latchup IGBT by designing a new structure, and presented it at the International Electron Device Meeting (IEDM) that year. The following year, in 1985, the company announced the commercialization of its IGBT. The device, a world first, received the I-R 100 Award and the Okochi Memorial Technology Prize and was also honored as “Cornerstone of Electro-Technology” by the Institute of Electrical Engineers of Japan in 2010.

Awarded the

Awarded the "3rd Cornerstone of Electro-Technology” by the Institute of Electrical Engineers of Japan (2010

Okochi Memorial Technology Prize Medal (1990)

Okochi Memorial Technology Prize Medal (1990)

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