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

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We investigated the impact of the mechanical uniaxial strain on the inversion channel mobility of lateral n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) on 4H-SiC(0001). We used custom-designed bend-holders to apply a tensile and compressive stress to the chip after MOSFET fabrication. The behavior of mobility with the two different channel directions and was investigated on the bend directions and with the tensile and compressive stress. We found that the inversion channel mobility effectively increases with the uniaxial compressive stress of the perpendicular configuration which is the drain current flow perpendicular to the bend direction. From the temperature dependence of mobility, we deduced that the enhancement of mobility is attributed to the reduction of the effective mass in 4H-SiC by introduced stress.

Section: Electrical Characteristic With Uniaxial Stressmentioning

confidence: 99%

Mobility enhancement by mechanical uniaxial stress on 4H-SiC (0001) lateral metal-oxide-semiconductor field-effect-transistor

Takeuchi

Kutsuki

Kagoshima

et al. 2020

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“…In SiC-MOSFETs, μ eff can be divided into three components based on the scattering factors, namely the Coulomb scattering mobility (μ C ), optical phonon scattering mobility (μ opt ), and surface roughness scattering mobility (μ SR ). [29][30][31] These scattering mobility values were calculated from the temperature dependence of μ eff versus the effective field (E eff ). 23) 3.…”

Section: Experimental Methodsmentioning

confidence: 99%

Enhancement of channel mobility in 4H-SiC trench MOSFET by inducing stress at SiO₂/SiC gate interface

Kagoshima¹,

Takeuchi²,

Kutsuki³

et al. 2022

To investigate the impact of stress at the SiO2/SiC gate interface on the channel mobility of 4H-SiC trench MOSFETs, we fabricated trench MOSFETs with two variations of stress in channel region by changing the deposition temperature of polycrystalline silicon used for gate electrodes. The results found that effective mobility was enhanced by several dozen MPa of tensile stress induced by the polycrystalline silicon. Based on the temperature dependence of mobility, all scattering mobilities were enhanced. It was supposed that the electron effective mass decreased because of tensile stress induced at the channel region.

“…For further investigation, μ eff was analyzed on the basis of the proposed mobility model including optical phonon scattering mobility (μ OP ). 27) The optical phonon scattering has been taken into account for the bulk mobility of SiC, and reported to have great impact on the total mobility. 28) Therefore, instead of acoustic phonon scattering mobility in conventional mobility models, [29][30][31][32][33] μ OP was applied to the improved mobility model with Coulomb scattering mobility (μ C ) 32) and surface roughness scattering mobility (μ SR ) 32) as follows:…”

Section: Experimental Methodsmentioning

confidence: 99%

“…where N T is the total number of trapped charges, which include fixed and interface-trapped charges, T is the absolute temperature, N S is the surface inversion carrier concentration, E eff is the effective field, 27,30) N(ω OP ) is the phonon occupation factor, ħω OP is the optical phonon energy, k is Boltzmann's constant, ε SiC is the permittivity of SiC, N dpl is the surface concentration of the depletion charge, η is taken to be 1=2 for the electron mobility, and Γ C , N scr , ζ C , δ, and C are empirical parameters. The empirical parameters were the same among the conditions considered.…”

Section: Experimental Methodsmentioning

confidence: 99%

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

Kutsuki

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.