Chemical vapor deposition of tantalum nitride films using pentakis(diethylamido)tantalum and ammonia

Tantalum nitride (TaN) films were deposited by using pentakis(diethylamido)tantalum and ammonia. The activation energies of the surface reaction were obtained with the NH3 flow rate. In addition, the resistivity, composition, crystal structure, and microstructure were systematically studied with the NH3 flow rate from 0 to 25 seem. The resistivity of the as-deposited film was decreased as the NH3 flow rate was increased, but it was increased at the NH3 flow rate of 25 seem. The minimum value of resistivity is about 7000 mu Ohm-cm at the NH3 flow rate of 20 seem. The carbon content in the film was decreased down to 1 at.% as the NH3 flow rate was increased up to 25 seem by Auger electron spectroscopy. Rutherford backscattering spectrometry showed that the N/Ta ratio is about 1.75, which is not considerably changed with the NH3 flow rate. In spite of this high nitrogen content in the film it was revealed that the fee TaN was formed by x-ray diffractometry and transmission electron microscopy. The etch-pits test showed that 50-nm-thick TaN films deposited at the NH. flow rate of 0 and 25 seem prevented the diffusion of Cu into the Si substrate at the annealing condition of 500 degrees C and 550 degrees C for 1 hour, respectively The step coverage was estimated as over 80 % at the NH3 flow rate of 0 seem and below 10 % with the addition of NH3 in 0.5 mu m x 1.5 mu m contacts by cross-section scanning electron microscopy.