ELSEVIER Surface and Coatings Technology 76-77 (1995) 142-148 SURIICE &CIIIlINIiS I8HKOJDGY Effect of substrate bias on sputter-deposited TiC x , Ti'N, and TiCxN y thin films A.A.Adjaottor a, E.I. Meletis a, S. Logothetidis b, I. Alexandrou b, S. Kokkou b a Louisiana State University, Mechanical Engineering Department, Materials Science and Engineering Program, Baton Rouge, LA 70803, USA b Aristotle University of Thessaloniki, Department of Physics, Thessaloniki, GR 540 06, Greece Abstract Carbides and nitrides of transition metals such as Ti attract significant interest since they find a wide field of applications ranging from high-temperature structural materials to contact layers in solar cells. In the present study we report on the influence of the bias voltage on the development of TiC x, TrN, and TiCxNy films (600-3000 A thick) developed by magnetron sputtering. The TiC x films were deposited by r.f. magnetron sputtering from TiC targets, while the TiNy and TiCxNyfilms were deposited by d.c. and r.f reactive sputtering from Ti and TiC targets, respectively. The bias voltage was varied from 0 to 200 V for all three types of film. In-situ spectroscopic ellipsometry (SE) was used in the energy region 1.5-5.5 eV to monitor film characteristics. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and microhardness measurements were taken to characterize the composition, stoichiometry, structure, quality and integrity of the films as a function of the bias voltage. For the present deposition conditions, the substrate bias voltage was found to have a significant effect on the stoichiometry and structure of all three types of films. The results show that for TiNy films the substrate bias can promote stoichiometry and structure refinement through resputtering effects. For TiC x and TiCxNyfilms, substrate bias can influence stoichi- ometry and structure by increasing reaction probabilities (of carbon and nitrogen, respectively) in the plasma through ionization and plasma activation effects. Mechanistic aspects of the film development process are discussed in view of the in-situ SE results and the post deposition AES, XPS, XRD and microhardness evaluation. Keywords: Sputter deposition; Titanium nitride; Titanium carbide; Titanium carbonitride; Spectroscopic ellipsometry 1. Introduction Carbides and nitrides of transition metals such as Ti exhibit a unique combination of properties and find a wide range of high-technology applications. The latter are spanning from cutting tools and high-temperature structural materials to diffusion layers in semiconductor devices and contact layers in solar cells [1-4]. Carbide and nitride films can be deposited by a variety of chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques. Usually the CVD methods are limited owing to the high temperatures involved during processing. Among the PVD methods, sputtering is one of the most commonly used. However, during sputter deposition it is difficult to maintain the appro- priate processing parameters in order to obtain films of desirable nature (stoichiometry, structure, etc.). Thus, there is a great need for new in-situ techniques that would be able to control sputtering parameters since film stoichiometry, structure and morphology may be of vast importance in particular applications. Recently, 0257-8972/95/$09.50 © 1995 Elsevier Science SA All rights reserved SSDI 0257 -8972 (95) 02594-4 in-situ and real-time information was obtained during thin film deposition using the optical technique of spec- troscopic ellipsometry (SE), indicating the capability of this technique in in-situ monitoring and controlling film quality [5]. In the present study we report on the influence of the substrate bias voltage on the development of TiC x , TfN, and TiCxN y films by magnetron sputter deposition. Film characteristics were monitored in-situ by SE and com- pared with post deposition Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. Mechanistic aspects of the film development process with sputtering are discussed in view of the experimental measurements. 2. Experimental 2.1. Film development TiC x, TrN, and TiCxN y films deposited to thicknesses of approximately 600 and 3000A onto Si (001) sub-