Time-Dependent Dielectric Breakdown of Commercial 1.2 kV 4H-SiC Power MOSFETs

Abstract

Constant-voltage time-dependent dielectric breakdown (TDDB) measurements are performed on recently manufactured commercial 1.2 kV 4H-SiC power metal-oxidesemiconductor (MOS) field-effect transistors (MOSFETs) from three vendors. Abrupt changes of the electric field acceleration parameters (γ) are observed at oxide electric fields (Eox) 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 (Eox = 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 63% lifetimes (times to 63% failures) from TDDB measurements performed at Eox < 8.5 MV/cm are longer than 10 8 hours at 150°C for all vendors. The predicted lifetimes at Eox = 4 MV/cm demonstrate more than 10 5 times increases than the oxide lifetimes reported a decade ago, showing promising progress in SiC technology.Index Terms-Electron and hole trapping, impact ionization, gate oxide reliability, lifetime, silicon carbide (SiC) power MOS-FETs, time-dependent dielectric breakdown (TDDB).

Effect of 20 MeV Electron Radiation on Long Term Reliability of SiC Power MOSFETs

“…The difference in characteristic lifetimes between V GS = 33 V and V GS = 38.3 V configuration is four orders of magnitude. Similar, strong electric field dependence has been observed for both Si and SiC based technologies [21], [22], [30]. The increasing injected electron energy with increasing electric field in the oxide during the stress will result in faster accumulation of trapped charge which will eventually lead to oxide breakdown [30].…”

“…However, regarding the effect of the electron radiation on the long term reliability and the lifetime of the device, it should be kept in mind that V GS during CVS should be low enough in order to be able to conclude on possible lifetime reduction. As discussed in [21] and [22], the lifetime extrapolation should be performed with gate voltages for which the electric field in the oxide is below the impact ionization current threshold. Such threshold value for the E ox is suggested to range from 8.5 MV/cm to 9 MV/cm [21], [22], [28].…”

“…Even though the intrinsic reliability of the gate SiO 2 has improved over the years, the material defects as well as the radiation impact have a significant effect on the oxide reliability [4]- [6], [20], [21]. The lifetime of the devices at their normal operating voltage conditions is commonly predicted through accelerated timedependent dielectric breakdown (TDDB) measurements and extrapolation [21], [22].…”

Effects of JFET Region Design and Gate Oxide Thickness on the Static and Dynamic Performance of 650 V SiC Planar Power MOSFETs

“…Although BV does not change with variation, a smaller improves the gate oxide reliability of the MOSFETs by better shielding the gate oxide on the top of the JFET region from high oxide fields under the blocking condition [ 14 , 16 ]. These high oxide fields may cause high gate leakage currents, degrade the gate oxide, and reduce the oxide lifetime [ 13 , 17 ], and can lead to failures during High-Temperature Reverse Bias (HTRB) testing.…”

The Road to a Robust and Affordable SiC Power MOSFET Technology

“…One can also perform these experiments at a much higher temperature such as 300 • C to reduce the measurement time. A detailed explanation of TDDB studies is provided elsewhere [23,24].…”