4th INTERNATIONAL WORKSHOP ON ELECTRODEPOSITED NANOSTRUCTURES 16-18 March 2006, Dresden, Germany	ABSTRACTS

INCORPORATION OF Cl AND S INTO ELECTRODEPOSITED Cu LAYERS M. Stangl, C. Hanzelmann, J. Acker, M. Uhlemann, K. Wetzig IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany Copper represents the material of choice for the fabrication of interconnect structures in integrated circuits because of its low resistivity and superior electromigration resistance [1]. However, in the sub-micrometer range electroplating of Cu is still a challenge regarding the improvement of material and microstructure properties. Particularly, the reduce of incorporated impurities represents a very important necessity concerning the improvement of grain boundary motion and grain growth in as-deposited Cu layers [3]. These impurities stem from additives in the electrolyte, which are required to achieve homogeneous plating and gap filling. In order to circumvent the incorporation, the basic mechanisms need to be understood more precisely. With the current state of knowledge, different species of additives are capable to adsorb at the cathodic surface and compete for adsorption sites during deposition. As one example, ethylen oxide ligands (e.g. PEG) and chloride are supposed to form complexes with Cu+ or Cu2+ ions which are enriched in a layer of approximately 100 µm thickness nearby the electrode surface in steady state [2,5]. Our studies aimed at the determination of adsorption kinetics by a quartz crystal micro balance device. This technique was applied for the most common additives PEG, SPS, and Cl as well as a commercial additive mixture. Consistently with the more or less fast surface adsorption, cyclic voltammetry investigations revealed a significant inhibition of deposition rate during the first cycle. Subsequent cycles did not show any inhibition confirming the assumption of a negligible adsorption during the deposition. Remarkably, secondary ion mass spectrometry (SIMS) analyses of galvanostatic deposited Cu layers proved an incorporation of Cl and S in the first electroplated Cu volume. The incorporation occurs at every new start of electroplating after an interruption of 30 s in minimum. This time is in correlation with the time for a complete surface covering by adsorbed additives [4]. Consequently, a shorter interruption or a pulsed deposition lead to a reduced Cl and S incorporation. The chlorine ion in the electrolyte and S containing additives were revealed as sources for incorporation. Possibly, the current start-up peak leads to the formation of CuCl and CuxS which are integrated into the growing film and influence the film properties. [1] P.C. Andricacos, C. Uzoh, J.O. Dukovic, J. Horkans, H. Deligianni, Electrochimical Microfabrication 42 (5) (1998) 567-574. [2] L. Bonou, M. Eyraud, R. Denoyel, Y. Massiani, Electrochim. Acta 47 (2002) 4139-4148. [3] S.H. Brongersma, G. Beyer, K. Maex, Future Fab Intl. 18 (2005). [4] T.P. Moffat, D. Wheeler, W.H. Huber, D. Jossell, Electrochem. Solid-State Lett. 4 (4) (2001) C26-C29. [5] T.P. Moffat, D. Wheeler, D. Jossell, J. Electrochem. Soc. 151 (4) (2004) C262-C271.

 
 
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