Surface and Reactor Effects on Selective Copper Deposition from Cu(hfac)tmvs
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SURFACE AND REACTOR EFFECTS ON SELECTIVE COPPER DEPOSITION FROM Cu(hfac)tmvs John A. T. Norman, David A. Roberts, Arthur K. Hochberg Schumacher, 1969 Palomar Oaks Way, Carlsbad, CA 92002 ABSTRACT The selectivity of OMCVD copper films grown at 160'C/500 mTorr from the volatile liquid precursor Cu(hfac)tmvs was evaluated for various commercial 6" wafers patterned with either TiN/Si0 2 or TiN/Si 3N4. By processing wafers "as received", only thermal grown Si0 2 consistently resisted metallization, allowing copper films up to 1.5/A thick to be grown on TiN. For SiO 2 films containing H 20, especially from PECVD, only blanket deposition was observed. However, by a utilizing simple thermal predeposition dehydration some of these SiO 2 films were conditioned to give selective deposition. INTRODUCTION The effort to develop a manufacturable selective copper CVD process for 0.25 micron interconnects and beyond is intensifying to meet the needs of advanced memory and logic devices. Selective deposition onto metallic diffusion barriers versus dielectric insulators promises to greatly reduce production time. Key to developing such a process is understanding both the chemical interactions of the precusor with metallic or insulating surfaces and its gas phase chemistry in terms of which reactor conditions promote selective metallization. Numerous volatile copper compounds have been reported to yield either blanket or selective metal films' by OMCVD. The Cu(hfac)L series of copper complexes where L = alkene2 , alkyne3 , trialkylphosphine4 and (hfac) = hexafluoroacetylacetonato are especially noteworthy, conformally metallizing surfaces with high purity copper at low temperatures via a thermal disproportionation mechanism as shown in equation 1. 2 Cu(hfac)L --
Cu°
+ Cu(hfac) 2 + 2L
Metallization is favored on conducting metallic substrates, presumably because a key step in the disproportionation mechanism requires an electron transfer between copper centers. This pattern of selectivity is ideal for current IC device manufacture where metallic diffusion barriers will be needed to encapsulate the copper interconnects5 . To be most useful, the selectivity of metallization should be such that there is no deposition on the dielectric during the process of growing a copper film onto a conducting diffusion barrier substrate. Much of the recent work in this area has focused upon the more subtle aspects of the gas phase and surface chemistries7 of Cu(hfac)tmvs6 ; a volatile liquid OMCVD copper precursor which can metallize by the disproportionation mechanism described above. For instance, it has been found that overheating the precursor vapors prior to their introduction into the CVD processing chamber can yield blanket deposition. This is due to the generation of highly reactive; coordinately unsaturated, 14 electron Cu(hfac) Mat. Res. Soc. Symp. Proc. Vol. 282. ©1993 Materials Research Society
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species that are capable of very low temperature metallization of SiO 27. Recent studies have also focussed upon the chemistry of precurso
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