Chemical reactions determining the step-coverage quality in plasma-assisted chemical vapor deposition of titanium

Abstract

Chemical reactions in plasma-assisted chemical vapor deposition of Ti from TiCl 4, which determine the step-coverage quality at contact holes in ultra-large-scale integrated circuits, have been studied by macrocavity analysis and ab initio molecular orbital calculations. Our results suggest that the sticking probability of the main intermediate species for the Ti deposition is high on the TiSi 2 surface due to the Si atoms supplied from the Si substrate to the surface, so the main intermediate of Ti is consumed efficiently in the deposition of Ti. On the other hand, desorption of Ti intermediate on the Ti surface occurs during growth. Thus, some of the intermediate species of Ti, which is adsorbed on the surface, does not contribute to the Ti deposition and the deposition rate falls. As the substrate temperature increases, the reaction rate of Cl with H on the Ti surface increases and the deposition rate on the Ti surface increases. Thus, the difference in the deposition rates on these surfaces becomes smaller, causing the step-coverage quality to deteriorate at higher temperatures. Therefore, the deposition rate on a TiSi 2 surface is higher than that on a Ti surface in a particular deposition temperature region (550°C⩽ T⩽600°C), and good step coverage quality can be obtained.