Abstract
We developed a low-pressure chemical vapor deposition (LPCVD) TaNx system and deposited TaNx films as diffusion barriers. The fulms were grown with the pressure 0.4 torr at the temperature of 400~450℃ using tantalum pentabromine (TaBr5), ammonia (NH3) as co-reactants, and argon (Ar) as the carry gas of TaBr5. The physical properties of the TaNx films with thickness <20nm were studied and compare these properties with the films that the thickness was more than 30 nm. The TaNx films were observed by scanning electron microscopy (SEM) to find out the incubation time. Four point probe and α-step were used to measure the resistivity. The depth profiles were analyzed by using Auger electron spectrometry (AES) and secondary ion mass spectrometry (SIMS) in order to understand the films composition. And we used glazing angle x-ray diffraction (XRD) to realize the crystalline structure. The MOS (Cu/TaN/SiO2/Si) capacitors were then annealed in nitrogen ambient at the temperature from 350-500℃ for 30 minutes for the thermal stability study. The films with the thickness more than 30 nm had the Ta3N5 poly-crystalline structures, the constant N/Ta ratio depth profile, and the resistivity is about 560 μΩ-cm. The films with the thickness less than 20 nm showed the amorphous structures. Auger showed the decreased N/Ta ratio near the barrier/SiO2 interface. Both of them could reach 400 ℃ thermal stability at least.