ZrO2 film growth by chemical vapor deposition using zirconium tetra-tert-butoxide

ZrO2 films were grown by chemical vapor deposition at T > 573 K with the precursor zirconium tetra-tert-butoxide (ZTB) Zr(OC(CH,),), The ZrO2 films were deposited on a Si(100) surface and film thicknesses were measured after growth at various temperatures using ellipsometry. ZrO2 film growth was negligible at T < 573 K, increased rapidly with temperature between T = 623-723 K, and then decreased at T > 773 K. Maximum ZrO2 growth rates of similar to 76 Angstrom/min were observed at 723 K with a ZTB pressure of 0.05 Torr. This ZrO2 growth rate is consistent with a reactive sticking coefficient of gamma = 6.8 x 10(-5). Auger depth-profile analysis measured low carbon levels of < 3%. Mass spectrometric investigations observed isobutylene (2-methyl propene) as the dominant reaction product. The isobutylene appeared with a magnitude that correlated with the temperature-dependent ZrO2 growth rates. This correlation indicates that ZTB decomposes to deposit ZrO2 by a beta-hydride elimination mechanism. Auger depth-profile analysis revealed higher carbon levels of greater than or equal to 10% where the ZrO2 growth rate decreased at T > 773 K. ZrO2 deposition may be partially poisoned by carbon at these higher temperatures. Fourier transform infrared (FTIR) studies examined the stability of hydroxyl (ZrOH*) and butoxide (ZrOC(CH3)(3)*) species on ZrO2. Both hydroxyl and butoxide species decreased roughy linearly with temperature from 300-800 K. The comparison between butoxide stability and ZrO2 growth rate argues that the butoxide species decomposition via beta-hydride elimination is the rate-limiting step for ZrO2 film growth. (C) 1999 Elsevier Science S.A. All rights reserved.