IN-SITU MASS-SPECTRAL AND IR STUDIES OF THE ROLE OF AUXILIARY REAGENTS IN THE ENHANCEMENT OF COPPER GROWTH IN THE CHEMICAL-VAPOR-DEPOSITIONOF CU(II) BETA-DIKETONATE PRECURSORS

In spite of significant scientific and technical advances, the incorpo ration of chemical vapor deposition (CVD) of copper into emerging micr oelectronics manufacturing technologies remains inhibited by key proce ssing and reliability issues. The most critical of these issues at pre sent centers on the need to achieve industrially acceptable growth rat es in the planarized and void-free copper CVD filling of aggressive vi as and trenches (such as 0.25 mu m structures with aspect ratio 4 and above). In this respect, recent studies have shown that the use of aux iliary reagents such as water and alcohols can lead to an enhancement of copper growth rates for both Cu(I) and Cu(II) beta-diketonate precu rsors. However, the mechanisms that control this enhancement remain un clear. Accordingly, in situ quadrupole mass spectroscopy and Fourier t ransform IR studies were performed in the present investigation, under real CVD processing conditions, to examine the role of selected solve nts (2-propanol, ethanol, methanol and 2-butanol) in enhancing the Cu growth rate in the plasma-assisted CVD of Cu from Cu-II (hfac)(2). (hf ac = 1,1,1,5,5,5-hexafluoroacetylacetonate). The results of these stud ies showed that these solvents contribute atomic hydrogen which assist s in the Cu-II (hfac)(2) reduction process and lead to a higher probab ility of interaction-precursor reduction and therefore higher copper g rowth rates. In addition, the ability of these solvents to release ato mic hydrogen was investigated through experimental measurements of the IR absorbances of the O-H stretching bond in the parent solvent and t he C=O stretching bond in the ketone or aldehyde byproducts of the con version reaction. By examining the ratios of absorbances for the C=O a nd O-H bands for the various solvents, the concentrations of ketone or aldehyde resulting from the conversion of the various alcohols were c alculated and used to determine that 2-propanol can release hydrogen m ore efficiently than ethanol or 2-butanol. This ability was attributed to the hydrogen-primary carbon (C-H) bond in these solvents, which is significantly weaker in 2-propanol than in ethanol or 2-butanol. This study thus confirms the present authors' earlier findings concerning the appropriateness of 2-propanol for use as a solvent in the delivery of the solid Cu-II(hfac)(2) in liquid form, since not only can it rea dily decouple from the precursor in the gas phase but it can also help enhance copper growth rates.