MOCVD Processes for Electronic Materials Adopting Bi(C 6 H 5 ) 3 Precursor
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MOCVD Processes for Electronic Materials Adopting Bi(C6H5)3 Precursor C. Bedoya1, G. G. Condorelli1, G. Anastasi1, J. Lisoni2, D. Wouters2 and I.L. Fragalà1 * Dipartimento di Scienze Chimiche, Università di Catania, Catania, Italy 2 IMEC, Leuven, Belgium 1
ABSTRACT MOCVD of Bi2O3 has been investigated using Bi(C6H5)3 precursor. The decomposition products obtained at various deposition temperatures were determined using in situ FT-IR analysis. Benzene was the main product formed in the heterogeneous decomposition of Bi(C6H5)3 at temperature lower than 450°C, while above 450°C typical products of the combustion of aromatic ring were observed. The effect of oxygen on the film composition and its role in the decomposition process was evaluated by XPS depth profiles. Moreover, preliminary studies on the initial step of the film deposition suggested that Bi2O3 nucleation rate depends upon precursor partial pressure. INTRODUCTION Bi2O3-based layered-perovskites are promising materials for superconducting electronics and for the new non-volatile ferroelectric memories (NVFeRAM) [1-9]. Among ferroelectric oxides, SrBi2Ta2O9 (SBT) [1,2] and Bi(LaxTi1-x)4O12 (BLT) [3,4] are very attractive materials due to their superior endurance resistance and good remnant polarization. High level integration required by commercially competitive 1T1C stacked ferroelectric cells is entirely suited with MOCVD due to the better conformality of deposition and the higher throughput with respect to other available deposition techniques [10-11]. β-diketonates or alkoxides have been proposed as Bi sources to obtain smooth and homogeneous morphologies. These sources, however, require MOCVD reactors equipped with liquid delivery systems (LDS) due to their low thermal stabilities precluding efficient sublimation/evaporation processes [12]. Moreover, they are highly moisture-sensitive, thus requiring particular care for storage and manipulations. By contrast, Bi(C6H5)3 is more versatile and represents the most used, thermally stable precursor. It can be efficiently used in both classical and LDS equipped MOCVD reactors without problems for storage and manipulations [13,14]. In this paper we report on a study on the MOCVD of Bi2O3 on technological substrates adopting Bi(C6H5)3 as precursor. In particular, an accurate evaluation of the decomposition products has been obtained by the analysis of in situ FT-IR spectra. The effect of the reacting gas on film composition and purity has been evaluated by XPS depth profiles. Moreover, the study of the dependence of the Bi2O3 growth upon the deposition time was performed to obtain information on the nucleation process. EXPERIMENTAL DETAILS Bismuth tri-phenyl was purchased from Merck (99+%). In situ FTIR measurements were performed in a MOCVD hot wall reactor interfaced with a 4600/FT/IR 430 Jasco spectrometer. A detailed description of the experimental apparatus has been reported elsewhere.[15] Depositions were performed in a reduced pressure, horizontal cold wall MOCVD reactor consisting of contiguous
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