Effect of Different Ni Contents on Thermal Stability of Cu(Ni) Alloy Film
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https://doi.org/10.1007/s11664-020-08340-2 Ó 2020 The Minerals, Metals & Materials Society
Effect of Different Ni Contents on Thermal Stability of Cu(Ni) Alloy Film XU LI,1 BIN CHENG,1 ISAAC ASEMPAH,2 QUAN SHI,1 AN-QIONG LONG,1 YI-LIN ZHU,1 QI WANG,1 YUAN-LIANG LI,1 LEI WANG ,1,3,4 and LEI JIN3,5 1.—National Demonstration Center for Experimental Materials Science and Engineering Education, Jiangsu University of Science and Technology, Zhenjiang 212003, People’s Republic of China. 2.—Department of Mechanical Engineering, Accra Technical University, P.O. Box 561, Accra, Ghana. 3.—Stomatology Department, Nanjing General Hospital, Nanjing University, Medical School, Nanjing 210002, People’s Republic of China. 4.—e-mail: [email protected]. 5.—e-mail: [email protected]
The effect of doping different contents of Ni on the thermal stability of Cu(Ni) alloy films has been investigated. Cu(Ni) films with different Ni contents were deposited on SiO2/Si substrates by magnetron sputtering, then annealed in vacuum at 350°C to 650°C for 0.5 h. X-ray diffraction analysis and resistance measurements revealed that high-resistance copper silicide was formed after annealing at 450°C for the Cu(Ni, 1.66 at.%) and Cu(Ni, 9.16 at.%) samples. However, no copper silicide was observed for Cu(Ni, 3.59 at.%) even after annealing at 650°C. Transmission electron microscopy provided evidence for a 25-nm self-formed barrier layer at the Cu/SiO2 interface with Cu(Ni, 3.59 at.%). The failure to form a diffusion barrier for the Cu(Ni, 1.66 at.%) sample resulted from its low Ni doping concentration, which was insufficient to produce such a self-formed layer during annealing. The barrier failure was caused by grain refinement due to the increased Ni content, providing diffusion channels for atom diffusion. The results clearly suggest that addition of an appropriate amount of Ni can improve the thermal stability of Cu(Ni)/SiO2/ Si interconnect structure materials. Key words: Cu interconnection, Cu(Ni) alloy film, thermal stability, self-formed barrier
INTRODUCTION With the development of interconnections in integrated circuits (ICs), Cu has replaced Al as an emerging interconnection material because of its low resistivity and good resistance to electrical migration.1–6 However, Cu can react easily with Si to produce copper silicide with high resistivity at high temperature, leading to circuit damage and affecting the service life of electrical equipment.7–12
(Received December 4, 2019; accepted July 16, 2020)
To overcome this problem, it is now common to add a diffusion barrier between copper and silicon to prevent this reaction.8,13–15 Nonetheless, as the feature size of ICs shrinks and with increasing demands for interconnect materials with low resistivity, traditional diffusion barriers cannot meet current requirements.16–19 Therefore, barrierless Cu metallization methods have been introduced by doping Cu with diffusion-inhibiting elements.20–22 This ‘‘barrierless structure’’ not only prevents diffusion of Cu into the Si substrate but also
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