On the Resistivity of TiSi2: The Implication for Low-Temperature Applications

Abstract

The electrical resistivity of TiSi2 formed on polysilicon implanted with phosphorus and arsenic and on n+ and p+ diffusions implanted with arsenic and boron was measured in the 4.2-300 K temperature range. It is found that in all cases, the resistivity is reduced by a factor of 3-4 when TiSi2 is cooled from room to liquid-nitrogen temperature. Sheet resistance as low as 1 Ω/sq. at liquid-nitrogen temperature can be easily achieved for self-aligned thin TiSi2 layers over polysilicon and diffusion regions, which is very attractive for low-temperature CMOS applications. The residual resistivity ratio, which is a measure of the electron mean free path, decreases with growing surface concentration of dopants, regardless of doping species. The analysis of thickness effects in terms of surface scattering and of grain boundary resistivity models, suggests that degradation of sheet resistance RS with increased implantation dose is due only partly to the difficulty in forming thick enough TiSi2 at high doses, and that dopant impurities segregated at the grain boundaries can account for the observed increase. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.