Initial growth and properties of atomic layer deposited TiN films studied by in situ spectroscopic ellipsometry

Abstract

Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindho-ven, The Netherlands Received 13 May 2005, revised 7 September 2005, accepted 25 October 2005 Published online 29 November 2005 PACS 07.60.Fs, 68.55.–a, 73.61.At, 78.66.Bz Spectroscopic ellipsometry is used to study the initial growth of thin TiN films that are deposited by plasma-assisted atomic layer deposition (PA-ALD) in which the thickness is perfectly controlled by the number of PA-ALD cycles. After every PA-ALD cycle, ellipsometry data is obtained in the energy range 0.75–5.0 eV making a detailed study of the initial nucleation and the evolution of the film parameters as a function of the thickness possible. Both the Drude–Lorentz oscillator parameterization as well as the di-rect numerical inversion method are utilized to extract the film thickness and dielectric function from the ellipsometry data. From the Drude term, metallic properties of the TiN film, such as resistivity and mean free path, are calculated and it is shown that these properties vary with film thickness. A detailed study of the film nucleation on chemical and thermal oxide substrates showed that the difference in surface hy-droxyl density results in a different nucleation behavior. An immediate nucleation on chemical oxide and a distinct nucleation delay on the thermal oxides were observed.