Impact of Al Doping Concentration at Channel Region on Mobility and Threshold Voltage Instability in 4H-SiC Trench N-MOSFETs

Kagoshima

Onishi

et al. 2020

Self Cite

We propose an experimental method for evaluating channel mobility that eliminates the parasitic series resistance in trench metal-oxidesemiconductor field-effect transistors (MOSFETs). It is found that the parasitic resistance increases with increasing temperature, which is mainly caused by optical phonon scattering in the drift layer of trench MOSFETs. The measurement method in which the current path is from the surface drain electrode to the source electrode underestimates the effective mobility because of the voltage drop caused by the drift layer resistance at the bottom of the trench gate. The proposed measurement method avoids this underestimation.

Section: Resultsmentioning

confidence: 69%

Section: Experimental Methodsmentioning

confidence: 99%

An extraction method of channel resistance for analysis of carrier scattering mechanism in SiC trench MOSFETs

Kagoshima

Onishi

et al. 2020

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“…μ eff was directly evaluated from the I D -V G characteristics measured at each temperature, by the following twostep process. [19][20][21] The first step was the definition of V th . By means of the ideal V th and ideal I D -V G characteristics in the subthreshold region, 21) the inversion current where the surface potential is equal to 2ψ B was obtained.…”

Section: Resultsmentioning

confidence: 99%

Impact of optical phonon scattering on inversion channel mobility in 4H-SiC trenched MOSFETs

Kawaji

Watanabe

et al. 2017

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Temperature characteristics of the channel mobility were investigated for 4H-SiC trenched MOSFETs in the range from 30 to 200 °C. The conventional model of channel mobility limited by carrier scattering is based on Si-MOSFETs and shows a greatly different channel mobility from the experimental value, especially at high temperatures. On the other hand, our improved mobility model taking into account optical phonon scattering yielded results in excellent agreement with experimental results. Moreover, the major factors limiting the channel mobility were found to be Coulomb scattering in a low effective field (<0.7 MV/cm) and optical phonon scattering in a high effective field.

“…The interface state density (D it ), V th and μ eff were calculated directly from the measured I D -V G charactesistics. 25,26) D it was calculated from the subthreshold swing of the measured I D -V G curves. The calculated D it locates at the energy level in the range of 0.1 to 0.2 eV from the conduction band edge of SiC.…”

Section: Experimental Methodsmentioning

confidence: 99%

Effect of surface roughness of trench sidewalls on electrical properties in 4H-SiC trench MOSFETs

Murakami

Watanabe

et al. 2018

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The effects of the surface roughness of trench sidewalls on electrical properties have been investigated in 4H-SiC trench MOSFETs. The surface roughness of trench sidewalls was well controlled and evaluated by atomic force microscopy. The effective channel mobility at each measurement temperature was analyzed on the basis of the mobility model including optical phonon scattering. The results revealed that surface roughness scattering had a small contribution to channel mobility, and at the arithmetic average roughness in the range of 0.4-1.4 nm, there was no correlation between the experimental surface roughness and the surface roughness scattering mobility. On the other hand, the characteristics of the gate leakage current and constant current stress time-dependent dielectric breakdown tests demonstrated that surface morphology had great impact on the long-term reliability of gate oxides.