| Summary: | 碩士 === 國立清華大學 === 電子工程研究所 === 90 === TaSix nano-cluster thin films with a various composition of Ta and Si are fabricated in Ar gas with Ta + 1/2 Si or Ta5Si3 targets by radio frequency reactive sputtering deposition. The resistivity, chemical composition, crystalline microstructure, diffraction pattern, and resistivity-temperature are investigated by four probe point, Auger, XRD, TEM, and current-voltage measurements. The thermal stability of diffusion barrier are studied using high frequency capacitance-voltage curve. According to those measurements, we try to understand the property is of TaSix nano-cluster thin film and find the optimum condition of diffusion barrier.
TaSix film with large Si/Ta composition ratio has higher resistivity and shows better diffusion barrier performance. The resistivity of TaSix film with Si/Ta ratio 1.043 is 444 mW-cm. The C-V curve of MOS capacitor Cu/TaSix/SiO2/Si remains thermally stability after annealing at temperature 600℃ for 30 mins. For the TaSix film with Si/Ta ratio 0.525, the C-V curve of MOS capacitor Cu/TaSix/SiO2/Si remains thermally stability after annealing at temperature 550℃ for 30 mins. It’s resistivity is 283 mW-cm, the thickness only 140 Å.
According to XRD and TEM pictures, as deposited TaSix nano-cluster thin films is amorphous. And TEM pictures had also shown the size of nano-cluster is smaller than 5nm. Their resistivity of the film is decreasing as the temperature rises. These current-voltage behavior can be explained by the Schottky emission of electrons between clusters Ta-Si-Ta and conduction of electron transport between clusters Ta-Ta or Si-Si. We believe the TaSix thin film is good candidate of diffusion barrier for the future ULSI processes.
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