Cu배선을 위한 Ta-Si-N barrier에 관한 연구

초록

Cu is widely studied as an interconnection material which will substitute Al interconnection owing to its lower electrical resistivity and higher electromigration-resistance. However, a barrier metal is necessary in Cu interconnection because of the thermal instability of Cu like diffusion of Cu into the Si substrate through the SiO2 layer. The best barrier material against Cu reported until now is TaSixNy. TaSixNy was reported to fail at 950℃, but, there aremany things to be confirmed and newly investigated concerning the barrier properties of TaSixNy. In this study TaSixNy films were deposited on (100)Si wafers using a reactive sputtering technique and their thermal stability which is indispensable for a barrier metal against Cu was investigated using sheet resistance measurement, X-ray diffraction, and Auger electron spectroscopy depth profiling. The optimum N2/Ar gas flow ratio for the sputtering process with which the TaSixNy film of the highest thermal stability is depositied was found to be 15% TaSixNy failed at 900℃, while Ta and TaN failed at 600℃ and 800℃, respectively. The failure mechanism of the TaSixNy is as follows : Cu atoms move to the TaSixNy interface through the TaSixNy film and react with Si in the Si substrate. Conesquently Cu3Si forms at the TaSixNy interface.