MOCVD Kinetics of Precursors for Ferroeletric SBT film
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MOCVD kinetics of precursors for ferroeletric SBT film A. Baeri, G.G. Condorelli, I.L. Fragalà Dipartimento di Scienze Chimiche, Università di Catania, - 95125 Catania, Italy ABSTRACT The metal organic chemical vapour deposition kinetics of Sr(hfa)2(tet) (H-hfa =1,1,1,5,5,5-hexafluoroacetylacetone and tet= tetraglyme) and Bi(C6H5)3 single precursors have been studied upon varying operational deposition parameters, namely temperature and precursor partial pressure. These precursors are of interest for the MOCVD of SBT ferroeletric thin films. Depending upon experimental conditions, deposition processes occur either in the reaction rate limited regime or in the mass transport regime. Kinetics controlled by reaction rates (T deposition< 673 K) gives insights on the process mechanisms. The activation energies of the Sr and Bi deposition processes have been determined from the Arrhenius plots. SrBi2Ta2O9 films were grown on industrial Pt/Ti/SiO2/Si substrates and perovskite phase films were obtained after annealing in O2 environment at 1073K. INTRODUCTION SBT ferroeletric films have been extensively investigated for Fe-RAM application due to their endurance resistance[1]. SBT films have been prepared by several techniques such as sol-gel[2], metalorganic deposition (MOD) [3], pulsed laser ablation[4] and metalorganic chemical vapor deposition (MOCVD)[5]. This last technique is best suited for semiconductor industry because of the superior step coverage compared to other deposition techniques. The phenomenological aspects of MOCVD fabrication of SBT film using various Bi and Sr sources as well as their electrical properties have been reported in many papers. However, if careful control of the properties of films grown for industrial application is to be achieved, it is important to understand factors affecting film growth. In this context, the kinetics and deposition mechanisms of single precursors play a critical role as far as industrial scaling-up is concerned. Little has been reported on the kinetics of the deposition of SBT precursors. Some kinetic investigations have been reported during multicomponent SBT deposition using the Bi(CH3)3Sr(Ta(O C2H5) system [6] and the Sr(tmhd)2-Bi(C6H5)3-Ta(OC2H5)5 (Htmhd=2,2’,6,6’tetramethylheptan-3,5-dione) system [7] This paper reports on deposition kinetics of single component films using Sr(hfa)2(tet) (H-hfa =1,1,1,5,5,5-hexafluoroacetylacetone and tet= tetraglyme) or Bi(C6H5)3 precursors. Kinetic results obtained from single component deposition have been applied to SBT fabrication using Sr(hfa)2(tet), Bi(C6H5)3 and Ta(OC2H5)5 precursors in O2. EXPERIMENTAL Experiments were performed in reduced-pressure, horizontal cold wall reactors for single and multi component depositions. Single component MOCVD system consists of a gashandling facility, a stainless steel evaporator, a reactor tube and a vacuum system. The quartz reactor inner diameter was 2.4 cm and the total length was 40 cm. Temperatures of the evaporator, connecting lines and reaction zones were controlled by EUROTHERMS
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