INVESTIGATIONS ON MICROSTRUCTURE, COMPOSITION AND PROPERTIES OF PECVD TINX-COATINGS

Nearly stoichiometric TiNx-coatings have been deposited on different substrates using a gaseous reaction mixture of TiCl4, N-2, H-2 and Ar in a pulsed d.c. plasma discharge. The influence of substrate temperature: plasma power density, argon partial pressure and type of substrate on chlorine content, texture and microstructure of the coatings has been investigated keeping constant the other parameters of the plasma enhanced chemical vapor deposition (PECVD) process. Microstructure has been characterized by scanning electron microscopy (SEM) fractographs of the coatings and by determination of texture. The chlorine content quantitatively determined from energy-dispersive X-ray spectra (EDX) using a chlorine containing mineral as standard decreases on an increase of substrate temperature or plasma power density. Texture changes from <200> to <111> and random and microstructure changes from columnar growth to granular for decreasing substrate temperature as well as decreasing plasma power density. Argon partial pressure does not affect the microstructure but the texture. The properties of the coatings are independent of type of substrate for higher plasma power densities. Oxygen present at the surface of the substrate stimulates the development of a texture at low plasma power densities.