Low temperature inorganic chemical vapor deposition of Ti-Si-N diffusion barrier liners for gigascale copper interconnect applications

A new low temperature inorganic thermal chemical vapor deposition process has been developed for the growth of titanium–silicon–nitride (Ti–Si–N) liners for diffusion barrier applications in ultralarge scale integration copper interconnect schemes. This process employs the thermal reaction of tetraiodotitanium (TiI4), tetraiodosilane (SiI4), and ammonia (NH3) as, respectively, the individual Ti, Si, and N sources. Ti–Si–N films were successfully grown over a broad range of deposition conditions, including wafer temperature, process pressure, and TiI4, SiI4, and NH3 flows ranging, respectively, from 350 to 430 °C, 0.1–1 Torr, and 2.5–8.0, 2.5–12.5, and 100–250 sccm. Film stoichiometry was tightly tailored through independent control of the Ti, Si, and N source flows. Film properties were characterized by x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, and four-point resistivity probe. Resulting findings indicated that the texture and resistivity of the Ti–Si–N system were dependent on composition. In particular, films with a Ti33Si15N51 stoichiometry exhibited a nanocrystalline TiN phase within an amorphous SiN matrix, highly dense morphology, resistivity of ~800 µ cm for 25 nm thick films, and step coverage of ~50% in 130 nm wide, 10:1 aspect ratio trenches. Oxygen and iodine contaminant levels were below, respectively, 3 and 1.4 at. % each. Preliminary copper diffusion-barrier studies indicated that barrier failure for 25 nm thick Ti34Si23N43 films did not occur until after annealing for 30 min at 700 °C