Temperature behavior of specific contact resistance and resistivity on nitrogen implanted 6H-SiC with titanium silicide ohmic contacts Available to Purchase

The electrical characteristics of $TiSix$ contacts to nitrogen implanted 6H-SiC are investigated using linear transmission line method structures at temperatures up to 673 K. Nitrogen is implanted into a p-type $(NA≈1×1016 cm−3)$ 6H-SiC epilayer at $500 °C$ and activated at $1700 °C$⁠, resulting in an activated donor concentration of $ND=5×1019 cm−3$ to a depth of 300 nm with a reduced electrically active surface concentration of about $ND≈5×1018 cm−3.$ Sputtered titanium silicide is used as contact metallization. Five different contact formation temperatures $TA$ ranging from 900 to $1150 °C$ are applied to the samples in order to investigate the specific contact resistance $ρc.$ Whereas an anneal of at least $950 °C$ is necessary to achieve an ohmic contact behavior, samples annealed at $1150 °C$ show specific contact resistance of $7×10−6 Ω cm2$ at room temperature, which decreases monotonically to $4×10−6 Ω cm2$ at 673 K. The sheet resistance $Rs$ (resistivity $ρs$⁠) of the $n+$-implanted layer is 521 Ω/□ $(15.6×10−3 Ω cm)$ at 303 K. Up to 573 K, $Rs$ declines to 354 Ω/□ $(10.6×10−3 Ω cm)$ as the incomplete ionization of the nitrogen dopants dominates the temperature behavior. Above 573 K, the reduction of the electron mobility via phonon scattering dominates, and $Rs$ increases to 363 Ω/□ $(10.9×10−3 Ω cm)$ at 673 K. From the resistivity as a function of temperature, the low field mobility $μ0$ is 149 cm²/V s at 300 K, and the temperature exponent α=1.62 of the power law dependence can be deduced.