Atomic layer deposition of tungsten nitride films using sequential surface reactions

Tungsten nitride films were deposited with atomic layer control using sequential surface reactions. The tungsten nitride film growth was accomplished by separating the binary reaction 2WF(6) + NH3 --> W2N + 3HF + 9/2F(2) into two half-reactions. Successive application of the WF6 and NH3 half-reactions in an ABAB... sequence produced tungsten nitride deposition at substrate temperatures between 600 and 800 K. Transmission Fourier transform infrared (FTIR) spectroscopy monitored the coverage of WFx* and NHy* surface species on high surface area particles during the WF6 and NH3 half-reactions. The FTIR spectroscopic results demonstrated that the WF6 and NH3 half-reactions were complete and self-limiting at temperatures greater than or equal to 600 K. In situ spectroscopic ellipsometry monitored the film growth on Si(100) substrates vs. temperature and reactant exposure. A tungsten nitride deposition rate of 2.55 Angstrom/AB cycle was measured at 600-800 K for WF6 and NH3 reactant exposures greater than or equal to 3000 L and 10,000 L, respectively. X-ray photoelectron spectroscopy depth-profiling experiments determined that the films had a W2N stoichiometry with low C and O impurity concentrations. X-ray diffraction investigations revealed that the tungsten nitride films were microcrystalline. Atomic force microscopy measurements of the deposited films observed remarkably flat surfaces indicating smooth film growth. These smooth tungsten nitride films deposited with atomic layer control should be useful as diffusion barriers for Cu on contact and via holes. (C) 2000 The Electrochemical Society. S0013-4651(99)05-028-4 All rights reserved.