DEPOSITION AND CHARACTERIZATION OF Ti-Si-N FILMS BY SPUTTERING

Abstract

Magnetron sputtering combined with pulsed do power supply is a powerful tool for the deposition of compound thin films This thesis involves the deposition of superhard nanocomposite coatings of TiN/Si3N4 using magnetron sputtering system. The coatings were deposited on silicon substrates using separate Ti and Si target in Ar/N2 gas mixture under high vacuum conditions. Co-sputtering of single element targets allows an easy adjustment of stoichiometry of deposited films, and ion assisted provides good control of energetic ion bombardment during film growth. An increase in surface mobility provided by this bombardment can enhance the segregation of nanocrystalline TiN in the a-SiNX matrix, leading to improved mechanical properties. The effects of the silicon addition, negative substrate bias on the texture development of the films were studied systematically by varying the bias voltage in range -20 V to -200V. The accompanying changes in the microstructure and growth morphology of the phases in these films were investigated in detail using X-ray diffraction, Atomic force microscopy and Nano-indentation technique. Pure TiN films deposited without silicon exhibits strong (111) preferred orientation, while with addition to Si, the orientation of the films changes from (111) to (200). Meanwhile the surface morphology of these films changed from a pronounced columnar microstructure to dense and fine grain structure. The effect of negative substrate bias voltage applied during deposition also resulted in similar change of orientation and leads to increase in hardness of films from 21 to 40 Gpa.