Effect of Different Ni Contents on Thermal Stability of Cu(Ni) Alloy Film

Abstract

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 SiO 2 /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/SiO 2 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)/SiO 2 / Si interconnect structure materials.

Effect of Carbon-Doped Cu(Ni) Alloy Film for Barrierless Copper Interconnect

“…Notably, the XRD patterns of the barrierless Cu(Ni) and Cu(NiC) alloys annealed at 650 • C did not display any diffraction peaks that corresponded to the copper silicide. Previous research has reported that the interaction between a pure copper film and silicon typically takes place at a temperature of 200 • C, leading to the formation of copper silicide with a notable increase in electrical resistance [1,24]. However, the XRD results of the Cu(Ni) and Cu(NiC) films annealed at 650 • C revealed diffraction peaks only attributed to the existence of Cu.…”

“…It is known that Cu and Ni are miscible due to their similar crystal structures, slight differences in atomic radius, and electronegativity [23]. Our previous research has demonstrated that Cu(Ni) alloy has excellent barrier properties [24]. Doped Ni occupies the fast diffusion channel, thereby improving the thermal stability of barrierless Cu films.…”

Self-Formed Diffusion Layer in Cu(Re) Alloy Film for Barrierless Copper Metallization

“…The self-formed barrier layer offers low electrical resistivity, resistance to Cu diffusion, resistance to electromigration and compatibility with conformal deposition techniques [16][17][18][19][20][21]. A self-formed barrier scheme is achieved by doping with diffusion barrier elements as well as their nitrides and carbides, such as Ti, Zr, Mn and WN [22][23][24][25][26][27][28]. All these doped elements have low-concentration solutes in Cu, which are supposed to segregate at the interface as a diffusion layer during annealing [16,29].…”