Titanium nitride films for barrier applications produced by rapid thermal CVD and subsequent in-situ annealing

TiN films with a thickness of typically 50 nm were deposited by rapid thermal chemical vapour deposition (RTCVD) using a TiCl4/NH3 process. The deposition temperature was varied between 300 degrees C and 600 degrees C. The aim was to develop a low-temperature CVD process with low film contamination for diffusion barriers. We achieved this by an in-situ annealing step immediately after deposition. A step coverage of nearly 100% and an excellent yield concerning barrier failures could be reached. The composition of the films was characterized by Rutherford backscattering spectroscopy, the structure by X-ray diffraction. The chlorine and oxygen contents highly depend on the chemical reactivity of the annealing gas. Deposition at 450 degrees C and subsequent annealing in ammonia at 450 degrees C leads to a very low chlorine content (<1.5 at.%) and a low specific resistivity of 250 mu Omega cm Apparently the chlorine can be mobilized during annealing and desorbed effectively from the surface by using an appropriate annealing gas. The chlorine uptake and loss can be traced by the lattice parameter as an indicator. At deposition temperatures higher than 350 degrees C, the films show a columnar growth with a [100] texture. Below 350 degrees C, chlorine-rich fine-grained polycrystalline TiN is deposited and can be purified by annealing. The crystallinity is not changed essentially by the anneal step. Its main action is to remove defects remaining after low-temperature deposition. With its low fabrication temperature and good film properties, this process can be used for barrier applications in multilayer metallization.