| AVS 54th International Symposium | |
| Thin Film | Thursday Sessions |
| Session TF-ThM |
| Session: | Thin Films for Electronic Applications |
| Presenter: | J. Shin, University of Texas at Austin |
| Authors: | J. Shin, University of Texas at Austin H. Kim, University of Texas at Austin L.B. Henderson, University of Texas at Austin G.S. Hwang, University of Texas at Austin J.G. Ekerdt, University of Texas at Austin |
| Correspondent: | Click to Email |
For advanced VLSI devices, Cu metallization has replaced Al due to its low resistivity and high intrinsic electromigration resistance. It is well known that Cu requires liner materials that function as a diffusion barrier, a seed layer for electroplating, and an adhesion promoting layer. Ru has been considered as a promising liner material for Cu metallization, however it has been reported that Ru itself is not an effective Cu diffusion barrier due to its microstructure, which is polycrystalline and features a columnar structure. Therefore, controlling the microstructure of Ru films is crucial in obtaining the required liner properties. Here we report ultra thin Ru alloy films having amorphized microstructure by incorporating P into the films. The metal (Ru) - metalloid (P) amorphous films were grown at 300°C by co-dosing triruthenium dodecarbonyl (Ru3(CO)12) and trimethylphosphine (P(CH3)3) into a cold wall chemical vapor deposition system having base pressure of 5x10-8 Torr. X-ray photoelectron spectroscopy (XPS) was employed to analyze the film composition and chemical states of the elements in the films, and grazing angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for microstructure analysis. Amorphous films were formed when more than ~ 15 at% of P was incorporated, and the amorphous microstructure remained stable after 3 hrs of annealing at 400°C. Electrical resistivity was measured with a four point probe, and a 15 nm thick amorphous Ru-P film showed a resistivity of ~ 200 Ωcm. Strong adhesion between Ru-P and Cu films was observed in annealing experiments, which revealed adhesion strength in the order of Ru-P alloy > Ta > TaN. More conformal films were grown on trench features by introducing P(CH3)3 as a result of the improved film step coverage due to the inhibited reaction and lowered sticking coefficient of Ru3(CO)12 by the adsorption of the P(CH3)3 molecules on the Ru surface. The barrier capability of the Ru-P films against Cu diffusion evaluated by bias temperature stress (BTS) technique will be discussed. First principles density functional theory calculations and ab-initio molecular dynamic simulation results will also be presented to elucidate the interaction between Ru and P, short range order of amorphous structure, and the causes for P stabilizing the Ru based metal - metalloid amorphous films.