Optimization of TiN thin film growth with in situ monitoring: the effect of bias voltage and nitrogen flow rate

Abstract

TiN x thin films were deposited by d.c. reactive magnetron sputtering over a wide range of stoichiometry. The stoichiometry, structure and composition were monitored by in situ spectroscopic ellipsometry (SE). The effect of the substrate bias voltage ( V b) and nitrogen flow rate ( Φ N) on the above film properties was studied. Due to the bias voltage, nitrogen is extracted from the film surface and, for ¦ V b¦>120 V, substantial Ti resputtering takes place. By varying the nitrogen flow, Ti y N x phases stable at low percentages of nitrogen are deposited, while the transition to f.c.c. TiN x is always observed at Φ N=1.9 sccm. X-Ray diffraction was used to identify the phases. Finally, the results of the fitting and simulation of the SE measurements using the effective medium approximation are presented to demonstrate the suitability of SE for the in situ characterization of complex Ti y N x film structures offering special properties.