MICROSTRUCTURE AND BARRIER PROPERTIES OF REACTIVELY SPUTTERED TI-W NITRIDE

The materials properties of Ti-W, sputter deposited in pure Ar, and Ti-W-N deposited in Ar-N2 mixtures containing up to 50% N2 have been reported. Films with N contents between 0 and 45 at.% have been produced. The W/Ti ratio in the nitrided alloy has been varied from that corresponding to pure W, to that of pure Ti. The metastable ternary phase diagram Ti-W-N was composed from data presented in this paper and literature data. For low N contents (up to about 20 at.%) the film consists of a metastable solid solution of N in bcc Ti-W. For high N contents (from about 35 to 45 at.%). We observed the film to consist of an fcc ternary Ti-W nitride. The barrier performance was evaluated in an Al-Cu metallization to TiSi2/Si contacts by Auger electron spectroscopy and junction leakage measurements. In clean sputtering environments, we need to create the ternary nitride to form a reliable barrier. Adding some N to "stuff" the grain boundaries of the bcc phase, or contaminating the Ti-W surface by an exposure to atmosphere, was found to be less effective in producing a reliable barrier.