Thermal Stability of TaSi x N y Films Deposited by Reactive Sputtering on SiO2

The thermal stability of TaSi x N y /SiO 2 /p-type Si metal-insulator-semiconductor structure has been evaluated by measuring equivalent oxide thickness (EOT) from capacitance-voltage curves and gate leakage current as a function of annealing temperatures. TaSi x N y films were deposited using reactive sputtering from a TaSi 2 target, varying the nitrogen/argon flow ratio. A reaction between Ta 53 Si 47 and SiO 2 was observed after a 1000°C anneal, resulting in the increase of interfacial roughness and oxide thickness in the TaSi x N y /SiO 2 /p-Si structures. Cross-sectional transmission electron microscopy shows no indication of an interfacial reaction or crystallization in Ta 22 Si 29 N 49 on SiO 2 up to 1000°C as manifested by the negligible change in EOT and the stable leakage currents density (2.0 x 10 -6 A/cm 2 at V g = -1 V). The presence of Si-N bonds is attributed to cause the amorphous nature of the high N-containing TaSi x N y films. This may retard the formation of an interface layer and improve the chemical-thermal stability of the gate electrode/dielectric interface and oxygen diffusion barrier properties under high-temperature annealing.

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