Properties of direct current magnetron reactively sputtered TaN

Tantalum nitride has been investigated for use as a diffusion barrier between aluminum alloy interconnect and shallow source-drain junctions in a 1-μ-complementary metal–oxide semiconductor technology. TaN films were reactively sputtered in a batch sputtering system equipped with dc magnetron cathodes, rf substrate bias, and independently controlled Ar and N2 sources. Film properties and their dependence on deposition parameters are discussed, and these properties are compared with those of titanium nitride films deposited using the same technique. Stoichiometric TaN films have resistivities of ∼220 μΩ cm. AlSi/TaN/Si contacts to shallow N+/P and P+/N junctions can withstand 575 °C 30 min heat treatments with no increase in junction leakage. The films can be etched in chlorine plasma chemistries typically used to etch aluminum alloys, and the aluminum etch has selectivity of ∼4:1 to TaN. This selectivity helps to protect inadvertently exposed Si junctions from damage during metal etch.