The Decomposition of tBAA on the Silicon Surface
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The Decomposition of tBAA on the Silicon Surface Che-Chen Chang,* Ing-Jye Huang Department of Chemistry, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei, Taiwan 10617, R. O. C. ABSTRACT Among the copper precursors used, cupric β-diketonate complexes exhibit a high sublimation rate and a low pyrolysis temperature. This work explored the possibility of using a nonfluorinated t-butylacetato complex of Cu(II) as the precursor. Secondary ion mass spectrometry and temperature-program desorption studies on the adsorption and decomposition of the ligand, tert-butyl acetoacetate (tBAA), of this precursor on Si(100) showed that at low doses, all tBAA molecules dissociated readily upon adsorption on the surface at substrate temperatures as low as –160 . For dissociation through tBAA bonding via the ester oxygen to the surface, the bond scission occurring at the tBu-O bond resulted in the formation of surface tert-butyl fragments, which in turn underwent a β-hydride elimination reaction to yield isobutene and surface hydride. In addition, the bond scission occurring at the tBuO-CO bond produced surface tert-butoxy specie, of which the hydrogen atom in the β position can be transferred to the oxygen atom of the butoxy group to yield isobutene and surface hydroxyl species. Its implication in the quality of the copper film generated is discussed.
INTRODUCTION The diverse and perplexing range of chemistries exhibited in chemical vapor deposition used for electronic materials growth and processing has attracted much attention in the microelectronic industry. At the center of the effort, however, lies a poor understanding of the interaction between a semiconductor substrate and hydrocarbon. The composition and the purity of the metal film deposited by chemical vapor deposition depend in part on the properties of the hydrocarbon chelated to the metal atom in the precursor molecules. It is essential that the precursor used is able to incorporate the desired chemical elements into the substrate and leave out the undesirable contaminants. The interaction and the reactivity of the precursor complex, including its ligands, on the substrate determine the fate of these elements and contaminants. As copper is more and more popularly used to replace aluminum as the metal of choice in an attempt to reduce the problems related to the conductivity and the electromigration resistance of the contact material, new classes of complexes have emerged as potential CVD precursors of copper. Among the various classes of copper precursors developed, the ones containing β-diketonate hydrocarbons [1-4] appear to be quite promising. Studies reported in the literature [5,6] about the reactivity of bis(tert-butylacetoacetate)copper(II) on the solid surface have shown that thermal deposition of this copper precursors led to incorporation of less carbon and oxygen impurities into the copper film during film formation than those containing other ligands. In this paper, the chemical reaction of β-diketonate on a single-crystal silicon surface was exami
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