Application of cluster-plus-glue-atom model to barrierless Cu–Ni–Ti and Cu–Ni–Ta films

Abstract

Thin film reaction of transition metals with germanium J. Vac. Sci. Technol. A 24, 474 (2006); 10.1116/1.2191861 Correlation between outward diffusion of additives and oxidation of Cu ( 3.9 at. % Ti ) and Cu ( 2.3 at. % Ta ) thin films J. Appl. Phys. 99, 036104 (2006); 10.1063/1.2170410 Glass-forming ability and crystallization behavior of Ti-Cu-Ni-Sn-M (M=Zr, Mo, and Ta) metallic glassesTo improve the thermal stability of copper and avoid its diffusion into surrounding dielectrics or interfacial reactions with them, the authors applied the cluster-plus-glue-atom model to investigate barrierless Cu-Ni-M (M ¼ Ti or Ta) seed layers. The dissolution of the third element (Ti or Ta) in the Cu lattice with the aid of Ni significantly improved the thermal stability of the Cu seed layer. The appropriate M/Ni (M ¼ Ti or Ta) ratio was selected to obtain a low resistivity: the resistivity was as low as 2.5 lX cm for the (Ti 1.5/13.5 Ni 12/13.5 ) 0.3 Cu 99.7 film and 2.8 lX cm for the (Ta 1.1/13.1 Ni 12/13.1 ) 0.4 Cu 99.6 film after annealing at 500 C for 1 h. After annealing at 500 C for 40 h, the two films remained stable without forming a Cu 3 Si compound. The authors confirmed that the range of applications of the cluster-plus-glue-atom model could be extended. Therefore, a third element M with negative enthalpies of mixing with both Cu and Ni could be selected, under the premise that the mixing enthalpy of M-Ni is more negative than that of M-Cu.

Microstructure evolution and strengthening mechanism of Cux[Ni3Mo] alloys

“…The above changes confirm that the insoluble elements dissolve in copper alloys in the solid-solution state, which has a positive effect on the stability. Similar results have been reported for a copper alloy film [28][29][30].…”

“…The above changes confirm that the insoluble elements dissolve in copper alloys in the solid-solution state, which has a positive effect on the stability. Similar results have been reported for a copper alloy film [28–30].

Figure 9 Conductivity, hardness and melting point as Cu content for Cu x [Ni 3 Mo] ( x = 1, 2, 3, 4, 5, 7, 9 and 12) alloys after solution treatment (1238 K/6 h) and aging (923 K/4 h).

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Enhanced thermal stability of Cu alloy films by strong interaction between Ni and Zr (or Fe)

“…This model is described in detail in the literature [16]. Under the guidance of this model, we successfully introduced the insoluble barrier elements Mo [17], Nb [16], Ta and Ti [18] into the Cu lattice, and prepared a series of Cu-Ni-M films with high stability and low resistivity. However, because of the exclusion of radioactive elements, toxic elements and difficult smelted elements, etc, the choice of the third element M is very limited.…”