Atomic layer deposition of tungsten nitride films using sequential surfacereactions

Tungsten nitride films were deposited with atomic layer control using seque ntial 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-reactio ns in an ABAB... sequence produced tungsten nitride deposition at substrate temperatures between 600 and 800 K. Transmission Fourier transform infrare d (FTIR) spectroscopy monitored the coverage of WFx* and NHy* surface speci es on high surface area particles during the WF6 and NH3 half-reactions. Th e FTIR spectroscopic results demonstrated that the WF6 and NH3 half-reactio ns 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 d eposition 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, re spectively. X-ray photoelectron spectroscopy depth-profiling experiments de termined that the films had a W2N stoichiometry with low C and O impurity c oncentrations. X-ray diffraction investigations revealed that the tungsten nitride films were microcrystalline. Atomic force microscopy measurements o f the deposited films observed remarkably flat surfaces indicating smooth f ilm growth. These smooth tungsten nitride films deposited with atomic layer control should be useful as diffusion barriers for Cu on contact and via h oles. (C) 2000 The Electrochemical Society. S0013-4651(99)05-028-4 All righ ts reserved.