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

Abstract

TIN films with a thickness of typically 50 nm were deposited by rapid thermal chemical vapour deposition (RTCVD) using a TiCl 4 NH 3 process. The deposition temperature was varied between 300 °C and 600 °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 °C and subsequent annealing in ammonia at 450 °C leads to a very low chlorine content (<1.5 at.%) and a low specific resistivity of 250 μΩ 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 °C, the films show a columnar growth with a 〈100〉 texture. Below 350 °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.