Preparation And Characterization Of Cu-Ni-Sn And Cu-Ni-Nb Films On Barrierless Si

As the feature size of interconnects continue to shrink, more attention has been paid to Cu seed layer by the method of alloying with elements, which could both inhibit the diffusion of Cu/Si and improve the properties of thin films. This method of Cu alloying is expected to solve some practical problems of Cu interconnects.The stable solid solution cluster model for Cu-Ni-alloy established by C. Dong and J. Zhang dissociates a structure into a cluster part and a glue atom part. The cluster refers to the nearest neighbor coordination polyhedron and is composed of elements with negative enthalpies of mixing, while the glue atoms refer to those atoms that situate outside the clusters in the structure and usually have weaker enthalpies of mixing with the cluster elements. A structure satisfying ideally the nearest neighbor configuration as demanded by the enthalpies of mixing between the constituent elements should naturally possess a high thermal stability.This study reports the thermal stability of NiSn-doped and NiNb-doped Cu films prepared by magnetron sputtering onto the barrierless Si(100) substrates, were enhanced, and exhibits higher thermal stability with a better electrical property than the Cu films doped only one element. And adding less Ni-Sn or Ni-Nb elements can keep the native resistivity of Cu films much better. Cu-Ni-Sn film systems showed:the film (Sn1.1/13.1Ni12/13.1)0.23Cu99.77had a resistivity of2.73μΩcm after annealing at500℃for1h. Sn exists evenly in Cu films by the way of (Ni12Sn) clusters, and reduces the reactivity of Cu and Si, improving thermal stability of the film. Those extra Sn precipitate out and react with Cu generating CuSn compounds, this kind of the nanometer level compounds can also play block diffusion effect in the grain boundary. Increasing interface amorphous layer can also block the diffusion of Cu/Si and restrain Cu/Si compound reactions.Cu-Ni-Nb film systems:The film (Nb1.2/13.2Ni12/13.2)0.32Cu99.68exhibited minimal resistivity of2.73μΩ·cm at500℃for1hour. thermal stabilities of this ternary solid solution Cu films were mainly due to the combined effects of the pinning effect of (Ni12Nb1) clusters and excess undissolved element Nb in the defects. stable (Ni12Nb1)clusters acted the pinning effect of grain interiors by solid-solution state, to reduce the reactivity of Cu and Si; But the precipitated Nb mainly blocked fast diffusion channels (grain boundaries, interface and defects, etc.), and inhibited grain growth to a certain extent。 The preparation of High stability Cu-Ni-Sn and Cu-Ni-Nb films provides tangible evidences for the application of Stable Solid Solution Cluster Model in the scheme of Cu alloy thin film, and has significant importance to developing new Cu interconnects...