Time: Thursday May 30, 2019 4:00pm-5:00pm
Presenter: Charles H. Winter (Department of Chemistry, Wayne State University, Detroit, Michigan)
Continued size reduction of very large scale integrated circuits is leading to increasing resistivities in copper and tungsten features, since there is less room for the conductive metals and the thicknesses of the TaN/Ta and TiN/Ti liners cannot be decreased without loss of barrier properties. Recent reports have demonstrated that very thin, amorphous CoTix (x = 18-83 at%) alloy layers can serve as Cu diffusion barriers to replace Ta/TaN. Moreover, Co/CoTix can replace W/TiN/Ti contact plug and barrier materials. The CoTix layers were deposited by co-sputtering of Co and Ti, however, sputtering is a line-of-sight technique that cannot deliver conformal, uniform thickness coatings in the high aspect ratio features. Accordingly, CoTix alloy films will need to be deposited by ALD to meet future manufacturing demands. Our initial goal was to deposit Co metal films by ALD using a cobalt precursor with hydrazine or an alkyl hydrazine as a co-reactant. CoNx films decompose to Co metal at ~280 °C, so we require Co precursors that have thermal stabilities of >280 °C. The synthesis and precursor properties of a range of Co(II) complexes will be presented. Among these precursors, Co(hfac)2 (hfac = 1,1,1,5,5,5-hexafluoro-pentane-2,4-dionate) and Co(thd)2 (thd = 2,2,6,6-tetramethyl-heptane-3,5-dionate) are volatile and exhibit decomposition temperatures above 300 °C. ALD growth studies of Co metal films using Co(hfac)2 and Co(thd)2 will be presented, with 1,1-dimethylhydrazine as the co-reactant. Self-limited growth was demonstrated in Co(thd)2 and 1,1-dimethylhydrazine at 280 °C and an ALD window was observed from about 275 to 290 °C. The growth rate was about 0.20 Å/cycle in the ALD window. Characterization of these films will be presented. We will also describe the synthesis and characterization of the Ti(III) complex Ti(iPr2DAD)3 (iPr2DAD = 1,4-diisopropyl-1,3-diazadienyl). Remarkably, Ti(iPr2DAD)3 decomposes thermally to Ti metal at about 250 °C. Plans for the growth of CoTix films will be described.
This meeting is only available to the JUMP research community, such as Principal Investigators, Postdoc researchers, Students, and Industry/Government liaisons.