Page 7 - Power Electronics News - December 2020

SEMICONDUCTORS Semiconductors

GENERATION 3 PREPARED THE telecom rectifiers, datacenter PFC and DC-DC
WAY conversion, as well as in renewable energy and

SiC FET Gen 3 technology, become a key enabler energy storage applications.
in many high-growth markets such as EVs, charg-
ers, IT infrastructure, circuit protection and alter- The 750V rating of the parts in UnitedSiC’s first
native energy. With the increase in SiC manufac- Gen 4 series is pitched to give a significant oper-
turing capabilities, these devices started to catch ating margin improvement compared with alter-
up with more traditional materials like Silicon as native 650V SiC MOSFETs in these applications,
this new technology became more readily availa- but with improved performance Figures of Merit
ble and affordable. (FOMs). Despite the higher voltage rating, better

FOMs than competing SiC MOSFETs are achieved
High power systems particularly showcased the with advanced techniques in wafer thinning and
advantages of SiC FETS with high-end superjunc- maximization of cell density, reducing RDS(ON)
tion designs transitioning to 650V SiC with 1200V per unit area. This crucial FOM combines meas-
and 1700V SiC parts effectively displacing IGBTs ures of static losses and die per wafer for econ-
Breakthrough and even the best of Si-superjunction MOSFETs. omy along with small size for low device capac-
itances, yielding fast switching and low dynamic

Performance of Gen 4 Gen 3 also saw the lowest-in-class R DS(ON) , when losses. Despite the reduced die size, current
UnitedSiC released devices with R
ratings remain high due to the low on-resistance
<7mohm
DS(ON)
at 650V and 9mohm at 1200V.
achieved, high thermal conductivity of SiC and
SiC FETs thermal performance of the advanced silver-sin-
tered die-attach.
MARKET DEMANDS PROPEL
By Anup Bhalla, VP of Engineering at UnitedSiC FURTHER IMPROVEMENTS
The power conversion market has insatiable HOW GEN 4 SIC FETS MEASURE
The third generation of SiC FETs enabled improved power conversion efficiency in demand for higher power density and efficiency, UP
many upcoming and existing application areas. Newly released Gen 4 devices offer from lower static and dynamic losses along with Specific on-resistance R DS(ON) A is compared in
further performance gains with initial 750V-rated parts targeted for use at 400/500V more thermal and electrical design margin. This Figure 1 between the UnitedSiC 750V, Gen 4

bus voltages. is all without compromising reliability or cost, in SiC FET, type UJ4C0750018K3S/4S and other-
an ever-wider range of hard and soft switched wise-comparable 650V rated SiC MOSFET com-
Silicon-based semiconductor switches have formance issues, SiC switches remained incon- applications. SiC FETs have become an ideal petitors. Significant improvements in the FOM
dominated the landscape of power conversion for venient to use, with SiC JFETS being normally-on solution to the demands, but at the same time, are clear at low and high temperatures for the
decades, with IGBTs and Si MOSFETs providing devices and SiC MOSFETs requiring very particular as wafer size and yield has increased, the devic- SiC JFET used here.

mature, robust solutions. The paradigm shift- gate drive for maximum performance. es have also become cost-effective in the larger
ed however when wide bandgap (WBG) devices market of 400V/500V bus applications seen in There are other figures of merit to compare as
started to become commercially available in 2008 UnitedSiC however pioneered a different imple- the battery charging, solar inverter and EV invert- well, such as R DS(ON) E OSS which is particularly
with Silicon Carbide (SiC) JFETs and then SiC mentation of a SiC switch, combining a SiC JFET er markets. important in hard-switching applications where
MOSFETs in 2011. The new technology promised with a low voltage Si MOSFET as a ‘cascode’ in a output capacitance C OSS is discharged rapidly from
higher efficiency and faster switching, with the single package, to form what they have dubbed a In response, new 750V ‘Gen 4’ SiC FETs with a high voltage, resulting in high transient ener-
consequent benefits of energy savings and better ‘SiC FET’, combining the speed and efficiency of breakthrough performance levels have reached gy dissipation E OSS . In fabrication, device output
power density. However, while manufacturers have WBG technology with the easy gate drive of an Si the market and are set to accelerate adoption of capacitance can be reduced but normally at the
successfully worked to overcome yield and per- MOSFET. SiC FETs in automotive and industrial charging, expense of on-resistance, so the FOM is a use-

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