Tetrakis(dimethylamido)hafnium Adsorption and Reaction on Hydrogen Terminated Si(100) Surfaces

• Published in: Journal of physical chemistry. C 2010-08, Vol.114 (33), p.14061-14075
• Main Authors: Li, Kejing, Li, Shenggang, Li, Ning, Dixon, David A, Klein, Tonya M
• Format: Article
• Language: English
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp101363r

The adsorption and reaction of tetrakis(dimethylamido)hafnium (TDMAH) on hydrogen terminated Si(100) were studied by using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission IR, and quadrupole mass spectrometry (Q-MS). Surface and gas phase reactions were investigated at temperatures between 25 and 300 °C. Density functional theory (DFT) calculations benchmarked by coupled cluster calculations on small models were performed for gas phase decomposition via intramolecular insertion and β-hydride elimination as well as the adsorption and reaction of TDMAH onto a hydrogen terminated Si(100) surface. N−Si and CH2−Si bonds due to reactions on the Si windows were observed in transmission IR, while N−Ge and CH2−Ge bonds on a Ge internal reflectance element (IRE) were observed by ATR-FTIR at 25 and 100 °C. Also observed were the formation of Hf−H bonds and three-member-ring species on the Si surface; the former was confirmed by a control D2O exchange reaction experiment. Both transmission IR and Q-MS indicated the presence of decomposition products dimethylamine (DMA) and N-methyl methyleneimine (MMI). The calculated bond dissociation energies (BDE) at the CCSD(T)/CBS level roughly follow the order of Hf−O > Hf−N > N−H, C−H, Si−N > Si−H, Si−C > N−C, Hf−H > Hf−Si, and the BDEs of the same chemical bond can vary substantially in different molecules. The interface is predicted by DFT calculations to involve Hf−Si, Hf−N−Si, and/or HfNC-Si bonds. TDMAH decomposition products, such as MMI, can form a C−Si or N−Si bond with the silicon surface. The combined experimental and theoretical results suggest that insertion and β-hydride elimination reactions can occur during bidentate chemisorption on the H−Si(100) surface by forming N−Si bonds.