Arsenic Redistribution during Rapid Thermal Chemical Vapor Deposition of TiSi₂ on Si

This paper studies the redistribution behavior of implanted arsenic during selective rapid thermal chemical vapor deposition of titanium disilicide (TiSi₂). The arsenic implant doses ranged from 3 × 10¹⁴ cm² to 5 × 10¹⁵ cm². The TiSi₂ films were deposited either directly on arsenic-implanted silicon substrates or on epitaxial silicon buffer layers selectively deposited with varying thicknesses before TiSi₂ depositions. SiH₄ and TiCl₄ were used as precursors for TiSi₂ depositions and Si₂H₆ and Cl₂ for selective silicon epitaxial growth. Experimental data revealed that the majority of the implanted arsenic was lost from the silicon substrate into the deposited TiSi₂ films when epitaxial silicon buffer layers were not employed. With the inclusion of the buffer layer, the arsenic loss could be reduced significantly. The loss of arsenic observed could not be explained by considering substrate consumption alone. In both cases, arsenic exhibited strongly enhanced out-diffusion from the silicon substrate into the TiSi₂ film. The injection of vacancies during the TiSi₂ depositions has been proposed as the reason for this enhanced out-diffusion. Monte Carlo simulations have been performed to verify the proposed model.