Rohm (headquartered in Kyoto, Japan), a world-famous semiconductor manufacturer, has developed the “1200V 4th generation SiC MOSFET * 1”, which is very suitable for the power supply of vehicle powertrain system and industrial equipment including host inverter.

For power semiconductors, when the on resistance is reduced, the short-circuit withstand time will be shortened. There is a trade-off between the two. Therefore, it is always a challenge to consider the short-circuit withstand time when reducing the on resistance of SiC MOSFET.

By further improving Rohm’s unique double groove structure * 3, the new product improves the trade-off relationship between the two. Compared with the previous products, the on resistance per unit area is successfully reduced by about 40% without sacrificing the short-circuit withstand time.

Moreover, the switching loss is reduced by about 50% compared with the previous products by greatly reducing the parasitic capacitance ﹥ 4 (a subject in the switching process).

Therefore, using the 4th generation SiC MOSFET with low on resistance and high-speed switching performance will greatly reduce the volume and power consumption of vehicle mounted inverters and various switching power supplies. Samples of this product have been provided in the form of bare chip since June 2020. It is planned to provide samples in the form of discrete package in the future.

In recent years, the further popularization of a new generation of electric vehicles (xev) has promoted the development of more efficient, smaller and lighter electric systems. In particular, the miniaturization and high efficiency of the host inverter system, which plays a key role in the drive, has become one of the important issues, which requires further improvement of power components.

In addition, in the field of electric vehicles (EV), in order to extend the range, the capacity of on-board batteries is increasing. At the same time, it is required to shorten the charging time, and the battery voltage is also higher and higher (800V). In order to solve these problems, high voltage and low loss SiC power components are expected.

In this context, Rohm started the mass production of SiC MOSFET in the world in 2010. Rohm began to strengthen its product lineup in line with the reliability standard of automotive electronic products aec-q101 very early, and has a high market share in the field of on board charger (OBC). This time, the launch of the 4th generation SiC MOSFET, which achieves a better trade-off between on resistance and short-circuit withstand time, will accelerate its application in the market dominated by host inverter in addition to the existing market.

In the future, Rohm will continue to expand the product lineup of SiC power components, and will continue to contribute to the next generation of automotive technology innovation by combining the advantages of peripheral components such as control IC and modular technology that give full play to the performance of components. In addition, Rohm will continue to provide customers with diversified solutions, including cutting application development time and online simulation tools to help prevent and evaluate problems.

1. By improving the groove structure, the industry can achieve extremely low on resistance

Rohm achieved the first successful mass production of ﹥ 5sic MOSFET with trench structure in 2015 by adopting unique structure. Since then, efforts have been made to further improve the performance of the components, but in terms of reducing the low on resistance, how to take into account the short-circuit withstand time with contradictory trade-offs has always been a challenge.

This time, by further improving the unique double groove structure of Rohm, the on resistance is reduced by about 40% compared with the previous products without sacrificing the short-circuit withstand time.

2. Lower switching loss can be achieved by reducing parasitic capacitance

Generally, the parasitic capacitance of MOSFETs increases with the decrease of on resistance and the increase of current, so it is difficult to give full play to the original high-speed switching characteristics of SiC.

This time, by reducing the gate drain capacitance (CGD), the switching loss is reduced by about 50% compared with the previous products.

1) MOSFET (abbreviation of metal oxide semiconductor field effect transformer)

Metal oxide semiconductor field effect transistor is the most commonly used structure in FET. Used as switching element.

2) short circuit withstand time

The time required to reach the extent of damage when the MOSFET is short circuited. Usually, when a short circuit occurs, it will flow a large current beyond the design value, and cause thermal runaway due to abnormal heating, and finally lead to damage. The improvement of short-circuit withstand ability involves a trade-off with performance including on resistance.

3) double groove structure

Rohm unique groove structure. It has long been concerned that trench structure can effectively reduce the on resistance of SiC MOSFETs. However, it is necessary to mitigate the electric field generated by the gate trench to ensure the long-term reliability of components.

Rohm has successfully overcome this problem by adopting the unique dual trench structure which can alleviate the problem of electric field concentration. In 2015, Rohm achieved the first mass production of trench SiC MOSFET in the world.

* 4) parasitic capacitance

Parasitic capacitance caused by the internal physical structure of electronic components. For MOSFET, there are gate source capacitance (CGS), gate drain capacitance (CGD) and drain source capacitance (CDS). The gate source capacitance and gate drain capacitance depend on the capacitance of the gate oxide film. The drain source capacitance is the junction capacitance of the parasitic diode.

5) groove structure

Trench means groove. It is a structure of forming grooves on the chip surface and forming MOSFET gate on its side wall. There is no JFET resistance in the structure of planar MOSFET, and it is easier to realize micro refinement than the planar structure. It is expected to achieve on resistance close to the original properties of SiC materials.

The characteristics of the term are as follows

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