Zr–Ti–Ni thin film metallic glass as a diffusion barrier between copper and silicon

In this study, the performance of Zr–Ti–Ni thin film metallic glass (TFMG) as a diffusion barrier between silicon and copper layers is reported. Three 5 nm TFMGs, deposited with or without nitrogen atmosphere, were prepared by magnetron sputtering sandwiched between Si substrate and 100 nm Cu. Rapid thermal annealing was conducted for 30 min at various temperatures between 500 and 800 °C to promote inter-diffusion of Cu and Si. Under transmission electron microscopy, there were no observable Cu–Si intermetallic compounds in the nitrogen-purged TFMG barrier annealed below 800 °C. The failure behaviors of TFMG characterized by the sheet resistance measurement and X-ray diffraction were in agreement. Compared to the sample without nitrogen purging, nitrogen atoms in TFMG were found to increase the failure temperature from 700 to 800 °C by retarding crystallization of TFMG and diffusion of copper. The failure mechanism of the barrier was also investigated in this work. Copper is confined at the interface between Cu and barrier layers and reacts with Ti to form new protective layer until full crystallization of TFMG. In conclusion, nitrogen purging could promote the performance of Zr-based TFMG as a diffusion barrier while preserving its amorphicity.