Kinetics and Mechanisms of Tin Chemical Vapour Deposition in Ti-CI-H-N System

Abstract

The effects of deposition parameters (temperature, total gas jlowrate, N2/H2 ratio, TiCl4 and HCI concentration) on the deposition rate of TiN were studied in a hot wall reactor. The conditions under which the deposition process is controlled by chemical equilibrium growth, mass transport limited growth, and surface limited growth processes were determined. Mechanisms of TiN chemical vapour deposition (CVD) in the regime of surface control are proposed. When the input partial pressure of hydrogen is 0·666 bar, that of nitrogen < 0·291 bar (i.e. N2/H2 ratio < 0·5), and that of TiCl4 0·145 bar, the rate limiting process is proposed to be the activated adsorption of nitrogen atoms; when N2/H2 = 0·5, the apparent activation energy for CVD of TiN was found to be 120·4 ± 24·2 kJ mol-l and the reactions on the substrate surface TiCl2(a)+H(a) ⇌ TiCI*+HCI(a) TiCI*+H(a) → Ti.HCI(a) Ti.HCI(a)+N(a) → TiN(s)+HCI(a) determine the rate of deposition. Equations for the TiN deposition rate under various conditions have been derived. HCI was proved to be a retarder, but loss of TiN by HCI etching was negligible. An equation for TiN deposition rate in the presence of added HCI was also derived. The equations were found to be in agreement with the experimental data.