New approach in the monitoring and characterization of titanium nitride thin films
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New approach in the monitoring and characterization of titanium nitride thin films S. Logothetidis Department of Physics, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece
E. I. Meletis Mechanical Engineering Department, Materials Science and Engineering Program, Louisiana State University, Baton Rouge, Louisiana 70803
G. Kourouklis Physics Division, School of Technology, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece (Received 22 October 1996; accepted 1 October 1998)
In situ and ex situ spectroscopic ellipsometry (SE), Raman spectroscopy (RS), x-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) have been used to study the stoichiometry and characterize TiNx thin films deposited by magnetron sputtering at various stoichiometries. In situ SE can provide parameters, such as the plasma energy, that can be utilized for monitoring of the film stoichiometry. Besides plasma energy, optical phonon position in RS was also found to be a sensitive probe of TiNx stoichiometry as detected by RS, XPS, and ex situ SE. Under these conditions, AES faces difficulties for reliable film characterization, and the complementary use of other techniques is required for determining the exact film stoichiometry.
I. INTRODUCTION
II. EXPERIMENTAL
Titanium nitride (TiNx ) thin films ([N]y[Ti] close to 1) with the NaCl crystalline structure, termed as d –TiN, are known to exhibit a unique combination of high hardness, excellent wear, and corrosion resistance1 and are widely used as coatings for cutting tools and wear parts.2 Moreover, TiNx has lately gained much interest in different areas of Si device technology, as a diffusion barrier in metallization schemes, rectifying and ohmic contacts,3 as well as Schottky barrier contacts.4 Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) have been used in the past for the characterization of this type of films.1,5,6 However, the above and other analytical techniques used for compositional analysis may suffer from inherent difficulties since they usually require the exposure of the TiNx films to air, leading to absorption and reaction with oxygen, or even worse, are destructive. Optical nondestructive access to a surface in vacuum is important for real-time information, control, and characterization during film development. Techniques such as spectroscopic ellipsometry (SE) and Raman spectroscopy (RS) are already used to monitor deposition rates and composition of films during deposition and can be used in a complementary manner with other post-deposition techniques. Here we present a new approach to study the stoichiometry and characterize TiNx thin films by using either in situ or ex situ optical nondestructive techniques in combination with XPS and AES.
The TiNx thin films were deposited on (001) Si wafers by dc reactive magnetron sputtering from a Ti target (99.999% purity).7 The Si substrates were cleaned by standard surface cleaning procedures before entering
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