Abstract
Constant-voltage time-dependent dielectric breakdown (TDDB) measurements are performed on recently manufactured commercial 1.2 kV 4H-SiC power metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs) from three vendors. Abrupt changes of the electric field acceleration parameters ( γ) are observed at oxide electric fields ( E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> ) around 8.5 MV/cm to 9 MV/cm for all commercial MOSFETs. Gate leakage currents and threshold voltage shifts are also monitored under different oxide fields ( E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> = 8 MV/cm and 10 MV/cm). The results suggest the failure mode under high oxide electric field is modified by impact ionization or Anode Hole Injection (AHI) induced hole trapping. This observation agrees with previously published oxide reliability studies on SiC MOSFETs and suggests that constant-voltage TDDB measurements need to be carefully performed under low oxide fields to avoid lifetime overestimation caused by hole trapping. The extrapolated t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63%</sub> lifetimes (times to 63% failures) from TDDB measurements performed at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> <; 8.5 MV/cm are longer than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> hours at 150°C for all vendors. The predicted lifetimes at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> = 4 MV/cm demonstrate more than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> times increases than the oxide lifetimes reported a decade ago, showing promising progress in SiC technology.
Highlights
S ILICON carbide (SiC) power metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs) are replacing Silicon (Si) insulated-gate bipolar transistors (IGBTs) in applications such as electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) [1]–[3] because of the superior material properties of SiC compared to Si for power electronics designs [4], [5]
Monitored on separated devices that are independent of the time-dependent dielectric breakdown (TDDB) measurements to study the different failure mechanisms under different oxide electric fields
The extrapolated t63% under typical use conditions (Eox = 4 MV/cm and 150°C) from TDDB measurements at Eox < 8.5 MV/cm are longer than 108 hours for all vendors!
Summary
S ILICON carbide (SiC) power metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs) are replacing Silicon (Si) insulated-gate bipolar transistors (IGBTs) in applications such as electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) [1]–[3] because of the superior material properties of SiC compared to Si for power electronics designs [4], [5]. The mentioned TDDB studies cannot fully reflect the oxide reliability of the currently available commercial SiC power MOSFETs for the following reasons. Currently available commercial SiC power MOSFETs typically have active areas that are orders of magnitudes larger than the reported small area SiC MOS capacitors and SiC DMOSFETs. More area-dependent extrinsic defects, which control the early failures of the MOS devices [29], can be included in the oxide with larger active areas at a given defect density. Constant-voltage TDDB needs to be performed under lower oxide electric fields to avoid overestimating the lifetime predictions. Direct TDDB measurements on SiC power MOSFETs at lower oxide electric fields are needed to evaluate the gate oxide reliability of these commercial products accurately. The gate leakage currents and threshold voltage shifts are monitored under different gate voltage stresses to investigate the underlying failure mechanisms at different oxide fields
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