Invited Paper TF-TuM3
Process Design and Development of ALD for Co(W) Alloy Films as Single Layered Barrier and Liner Material in Future Cu ULSI Interconnects

Tuesday, October 29, 2013, 8:40 am, Room 104 A

The aggressive scaling of ULSI devices requires ultra-narrow Cu interconnect features which have width of 20nm or less and aspect ratio of over 5. Cu diffusion barrier metal (DBM) and adhesion promoting liner layer (APL) should be made on the side wall of these features to protect Low-k layers from Cu diffusion and enhance the electro-migration life time of Cu lines. As the feature dimension is decreasing, the APL/DBM layers should be less than 3 nm in thickness which may result in poor diffusion barrier performance. We have proposed that Co(W) alloy may be a good alternative to the conventional Ta/TaN as APL/DBM. Co(W) alloy can have a lower resistivity and better barrier property compared to TaN. It can also enhance the adhesion of Cu, better than Ta. Thus Co(W) alloy can work as a single-layered APL/DBM for the future ULSIs.

We have developed novel ALD process using hot-wire assisted technique. Metallocene precursors were effectively reduced by using NH₂ radical generated by hot-wire from NH₃. Conventional ALD process using amidindate precursors was also developed to form Co(W) alloy thin film. The microstructure of the deposited Co(W) alloy films were intensively examined using TEM and the Cu diffusion barrier properties were correlated with the structure. As a summary, the developed ALD process could successfully deposit Co(W) alloy thin film with low resistivity and good barrier properties. The adhesion strength of Cu onto Co(W) alloy will be also discussed.