First trench-type silicon carbide MOSFET cuts on-resistance

May 22, 2015 // By Graham Prophet
Rohm Semiconductor has recently announced the development and mass production of a silicon carbide (SiC) MOSFET that it claims as the first suc transistor to use a trench structure. Compared to existing planar-type SiC MOSFETs, ON resistance is reduced by 50% in the same chip size, making it possible to significantly decrease power loss.

The very high stability of silicon carbide makes it difficult to form deep structures within its crystal lattice; Rohm says it has overcome these limitations to produce a device that combines very low loss with high-speed switching performance. Rohm adds that the company is developing full SiC modules that integrate both SiC MOSFETs and SBDs.

The company notes that with the trench structure, a MOSFET gate is formed on the sidewall of a groove created on the chip surface. Unlike planar-type MOSFETs, JFET resistance does not exist, making greater miniaturisation possible. This is expected to result in ON resistance close to the theoretical limits of performance of the SiC material.

Features of the device include;

1. Trench structure to achieve lower ON resistance;

Although adopting a trench construction in SiC MOSFETs has been attracting increased attention due to its effectiveness in reducing ON resistance, there is a need to establish a structure for mitigating the electric field generated in the trench gate portion in order to guarantee long-term reliability. Rohm says it has overcome this limitation and can successfully mass-produce the first trench-type SiC MOSFETs with improved switching performance (approx. 35% lower input capacitance) and ON resistance reduced by 50% over planar-type SiC MOSFETs. The lineup is being expanded to include 3 models for each rated voltage: 650V and 1200V, with rated currents of 118A (650V) and 95A (1200V).

2. Full SiC power module development

ROHM has also developed a full SiC power module that incorporates these latest trench-type SiC MOSFETs in a 2-in-1 circuit with integrated SiC SBDs. The 1200V/180A module features the same rated current as Si IGBT modules while reducing switching loss by approximately 42% vs. planar-type SiC MOSFETs.

ROHM Semiconductor; www.rohm.com/eu