Atmospheric Pressure Chemical Vapor Deposition of Titanium Nitride

Titanium nitride (TiN) is a technologically important material due to its chemical inertness, high melting point, hardness, and electrical and optical properties. The low resistivity and chemical inertness make TiN the material of choice for diffusion barriers in microelectronic applications. Thin films (<800A) of TiN were grown by Atmospheric Pressure Chemical Vapor Deposition (APCVD) from tetrakis(dimethylamido) titanium (TDMAT) or tetrakis(diethylamido) titanium (TDEAT) with and without ammonia. Depositions were conducted under cold wall reactor and laminar flow conditions in a belt furnace at low temperatures (190^circ C-420^circC). Films were characterized by four point probe, Rutherford Backscattering, Forward Recoil, and X-Ray Photoelectron Spectroscopies. Films grown from TDMAT and TDEAT in the absence of ammonia were substoichiometric (N/Ti < 0.76), highly resistive (rho > 2.2 times 10^4 muOmega-cm), and contained carbon (C/Ti = 0.15-0.45), oxygen (O/Ti = 0.7-1.3), and hydrogen. TDMAT was more reactive than TDEAT, depositing films at lower temperatures and lower ammonia concentrations. TiN deposition rates ranged from 10A/min (280^ circ, TDEAT) to 190A/min (420^ circC, TDMAT) in the absence of ammonia. Film stoichiometries improved dramatically with the addition of ammonia (NH_3/TDMAT >=q 1; NH_3/TDEAT >=q 4). N/Ti ranged from 0.9-1.1, increasing with the ammonia concentration. Oxygen and carbon concentrations fell to 0.5 and <0.1 respectively, relative to the titanium content. Nitrogen, oxygen, and carbon concentrations were insensitive to temperature when ammonia was coreacted with the metal precursor. Hydrogen concentration continued to fall with increasing ammonia partial pressure. Film growth rates (220-300 A/min) were only weakly dependent on temperature or ammonia concentration, except for TDMAT at 420^circC. Ammonia reduced the film growth rate at these conditions. Lowest resistivities were obtained at 370^circ under high ammonia concentrations (NH_3 /TDMAT = 26, rho = 1500 muOmega-cm; NH_3/TDEAT = 110, rho = 660 mu Omega-cm). Though less reactive, TDEAT had a higher conversion rate of titanium atoms (gas phase)/titanium atoms (deposited film) of 35% than TDMAT (10%), probably due to excessive dust formation from TDMAT. Preliminary conformality measurements suggest that TDEAT films have better step coverage than films from TDMAT.