Thermal Decomposition of Ti(O-iPr)[sub 2](dpm)[sub 2] on a Silicon Surface Analyzed by TPD and XPS

Abstract

The thermal decomposition of titanium diisopropoxide dipivaloylmethanato ͓Ti͑O-iPr͒ 2 ͑dpm͒ 2 : dpm = bis͑2,2,6,6-tetramethyl-3,5-heptanedionato, C 11 H 19 O 2 ͔ on a silicon surface was studied using temperature-programmed desorption ͑TPD͒ and X-ray photoelectron spectroscopy ͑XPS͒, and the results were compared with those obtained for a platinum surface. Isopropoxy ligands, which had been dissociated from the Ti precursor and became adsorbed to the silicon surface in the precursor-dosage process, were decomposed to propylene and acetone on the surface at about 450 K. Other isopropoxy ligands, which remained bound to the Ti precursor, were decomposed at 530-620 K to produce either propylene and acetone or isopropanol. The dpm ligand was decomposed to propylene at 700 K, which was a determinant of the overall rates of Ti-precursor decomposition. Ti͑O-iPr͒ 2 ͑dpm͒ 2 was decomposed at higher temperatures by about 50 K on the silicon than on platinum, and the major decomposition product was titanium silicate, TiSiO x , on silicon while it was titanium oxide, TiO x , on platinum. These different results were obtained because silicon is not as active as platinum for the dissociative adsorption of dihydrogen, which promotes the dissociation of the ligands. The exposure of the silicon surface to O 2 prior to the Ti-precursor dosage lowered the temperatures required for the decomposition of the dpm ligand because oxygen, which was chemisorbed on the surface, promoted the dissociation of C-O bonds in the ligand.The quality of thin films fabricated by metallorganic chemical vapor deposition ͑MOCVD͒ or atomic layer deposition ͑ALD͒ is strongly dependent on the properties of the metal precursors used in the process, although it is also affected by the processing conditions used, such as temperature, equipment geometry, and oxidants. [1][2][3] Ti ␤-diketonates, which exhibit a high chemical and thermal stability, are considered to be likely candidate compounds for use in MOCVD and ALD for producing titanium dioxide ͑TiO 2 ͒ and other mixed metal oxides such as strontium titanate ͑STO͒ and barium strontium titanate ͑BST͒. However, the lack of information concerning the decomposition characteristics of Ti compounds hampers their full exploitation in film-deposition processes.Ryu et al. recently reported on the sequence in the dissociation of chemical bonds constituting titanium diisopropoxide dipivaloylmethanato ͓Ti͑O-iPr͒ 2 ͑dpm͒ 2 : dpm = bis͑2,2,6,6-tetramethyl-3,5-heptanedionato, C 11 H 19 O 2 ͔ in the solid phase. 4 Heo et al. obtained the sequence of activation energies for the dissociation, in the gas phase, of Ti-O and Ti-N bonds contained in the Ti compounds of different molecular structures and indicated that the growth of a TiO 2 film from the compounds was closely related to the activation energies for the dissociation of Ti-O and Ti-N bonds contained in the compounds. 5,6 However, these studies were limited to decomposition in the solid and gas phases and did not consider interactions between the compounds and the ...

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…It is worth noting that a recent set of TPD and XPS studies of titanium diisopropoxide dipivaloylmethanato [Ti(Oi-Pr)2(dpm) 2 : dpm = bis(2,2,6,6,-tetramethyl-3,5-heptanedionato] explored the thermal decomposition of this organometallic compound on a clean Si(100) surface [484]. Also of interest may be the recent approach in functionalization of Si(100) [485] and Si(111) [486] substrates by so-called click chemistry to move into the 3rd dimension.…”

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