Ultra-high Performance, Low Power Dissipation SiC Power MOSFET

Kyoto, Japan - ROHM CO., LTD., has recently completed the development of a low power dissipation MOSFET using SiC (silicon carbide), a material whose characteristics make it more promising than silicon for use in high power devices. The newly developed SiC MOSFET can withstand voltages up to 900V and features an ON-resistance of 3.1mΩ/cm² - currently the lowest in the industry.
Low-power-dissipation MOSFETs can be used in power supply units and home electronic products to reduce space as well as increase operating efficiency. Or they can be applied to energy-saving vehicles (such as hybrid cars) to improve mileage. Samples are tentatively scheduled for release by the end of the year, while mass production dates are still pending.

Power dissipation during conversion poses a significant problem in the power electronics field. SiC features greater thermal conductivity, electric field breakdown strength, and current density than Si, resulting in significantly lower power dissipation.
Conventional SiC power MOSFETs possess high channel resistance. As a result, the ON-resistance becomes higher than the theoretical value. In response to this, ROHM has utilized ultra-fine processing methods and newly developed original technology regarding high-mobility gate insulators to achieve an ON-resistance of 3.1 mΩ/cm², which is 80 and 6 times smaller than Si-DMOS and Si coolMOS/IGBT devices in the same voltage resistance class, respectively. And although the current crop of SiC products features a voltage resistance of 600 to 900V, ROHM believes its ultra-fine processing technology will make it possible to attain a voltage resistance of up to approximately 1500V without changing the ON-resistance.

ROHM has succeeded in decreasing the ON-resistance to 1/2 or less per unit area through utilization of novel technology. This has made it possible to reduce the required chip area by up to 2/3rds the original value, allowing SiC power components to be used in a wide variety of applications, such as household appliances, in-vehicle devices, and power transmission equipment, contributing to energy savings on a global scale.

· Technology Features

1. An original process is used to form the Gate insulator to achieve a channel mobility that is three to four times as fast as conventional models, resulting in lower ON-resistance,
2. ROHM has utilized the most advanced ultra-fine processing technology to increase the number of integrated MOSFET cells per unit area to 2.5 times that of conventional products for lower power dissipation than ever before.
3. Minute cell and girdling structures were developed in order to achieve highly stable voltage resistance.

· Applications

SiC power devices are suitable for power supplies and inverters that convert or control power. For example, they can be used to convert power to drive electric motors in energy-saving vehicles such as hybrid cars in order to reduce carbon dioxide emissions. In addition, their low power dissipation capability makes it possible to develop a wide variety of environmentally friendly products that contribute to energy savings on a worldwide scale.

· Background

Conventional Si-based power MOSFETs are problematic in that they cannot simultaneously satisfy four key characteristics required of switching components: high voltage resistance, low ON-resistance, high-speed switching, and high heat dissipation. However, the unique physical properties of SiC make it possible to develop products possessing characteristics that greatly exceed the performance of conventional Si power devices. ROHM's SiC MOSFETs not only satisfy all of the aforementioned requirements, but also feature high-temperature operation, contribute to increased miniaturization, and are resistant to radiation.

· Glossary

• Silicon Carbide (SiC)
  A compound semiconductor that features characteristics superior to silicon: wide band gap (3 times as great), high electric field breakdown strength (10 times as large), and large thermal conductivity (3 times higher). These properties make silicon carbide better suited than silicon for power device applications.
• DMOS FET
  An acronym for Double-Diffused Metal-Oxide Semiconductor Field Effect Transistor. The structure of the DMOS FET makes high current operation and high voltage resistance possible.
  This name is mainly used for Si-based products, since double-diffusion technology is not applicable to SiC. In this case the acronym DIMOS FET (Double-Implantation Metal-Oxide Semiconductor Field Effect Transistor) is used instead.
• IGBT
  
An acronym for Insulated Gate Bipolar Transistor.
IGBT is a power transistor that uses both electron holes and electrons for current flow, resulting in low ON-resistance. It combines the simple Gate drive characteristics of MOSFETs with the high current and low saturation voltage capabilities of bipolar transistors by combining an isolated Gate FET for the control input and a bipolar power transistor as a switch in a single device., High-speed switching operation, however, has been problematic due to the time required for the accumulation of electron holes.