Smooth titanium nitride films having low resistivity

Abstract

The resistivity of titanium nitride films is reduced, by about 40% (to less than about 60 .mu.Ohm-cm), for example; and, the film surface roughness is reduced, by about 45% (to less than 6 .ANG.) by using a combination of particular process conditions during deposition of the film. In particular, titanium atoms produced by impact of inert gas ions upon a titanium target travel through a high density, inductively coupled rf plasma, an ion metal plasma (IMP), in which the titanium atoms are at least partially ionized. The ionized titanium ions are contacted with ionized nitrogen atoms also present in the processing chamber. The resultant gas phase composition is contacted with the surface of a semiconductor substrate on which a titanium nitride barrier layer is to be deposited. By controlling the gas phase deposition mixture composition, the quantity of the deposition mixture contacting the substrate surface over a given time period, and the pressure in the process vessel, the resistivity and surface roughness of the titanium nitride layer is adjusted. The resistivity of the titanium nitride barrier layer is principally determined by the crystal orientation of the titanium nitride. The more nearly the crystal orientation approaches 100% of the {200} orientation (the lower the percentage of {111} orientation), the lower the film resistivity. Crystal orientation is obtained by increasing the ionized content of the deposition mixture and by slowing the rate of deposition of the titanium nitride film (barrier layer). The surface roughness of the titanium nitride layer is reduced principally by reducing the pressure in the process vessel, which affects the film formation dynamics. An increase in ionized content of the deposition mixture helps reduce surface roughness until an inflection point is reached, after which surface roughness increases with increased ionized content.