Chemical Reaction Kinetics and Growth Rate of (Ba, Sr) TiO[sub 3] Films Prepared by Liquid Source Chemical Vapor Deposition

Abstract

A new liquid source chemical vapor deposition process is introduced for preparing (Ba, Sr)TiO 3 (BST) thin films from Ba(DPM) 2 (tetraglyme), Sr(DPM) 2 (tetraglyme), and Ti(DPM) 2 (i-OC 3 H 7 ) 2 (DPM ϭ dipivaloylmethanato) dissolved in butylacetate. The film deposition mechanism as well as the BST film growth rate are determined by studying the film formation and the associated chemical reaction kinetics as a function of temperature and gas flow rates. It is demonstrated that in the formation of BST films, the three precursors, TiO 2 , BaTiO 3 , and SrTiO 3 , react and produce deposits or intermediates independently. The deposition rate of BST films is the summation of the respective growth rates of the BaO, SrO, and TiO 2 films. The gas-phase decomposition reactions of the precursors, rather than their surface reactions on the substrate, dominate the BST film growth rate. The kinetics of the three overall chemical reactions to produce the oxide films of Ba, Sr, and Ti are determined by comparing the experimental film deposition rates and the numerical results. The suggested chemical reaction kinetics and the reaction rate constants are expected to be important in the design of metallorganic chemical vapor deposition reactors for BST films.

Thermal Decomposition of Ti(O–iPr)2(dpm)2 in the Gas Phase

“…For example, BST is a candidate dielectric material for the fabrication of capacitors in modern dynamic random access memory (DRAM). [1][2][3][4] In spite of difficulties encountered in process control, metalorganic chemical vapor deposition (MOCVD) is considered to be one of promising methods for use in producing films because of its excellent step coverage and high deposition rates. Although considerable progress has been made in the preparation of BST thin films using MOCVD, the selection of metalorganic compounds continues to be the key problem in the design of the process.…”

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The thermal decomposition of gaseous Ti(O-iPr) 2 (dpm) 2 dpm = bis(2,2,6,5heptadionate)], diluted with either argon or air, was investigated using infrared (IR) and mass spectrometry. The activation energies associated with the dissociation of individual bonds constituting the compound were estimated based on IR data obtained when the compound was heated at different rates.

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