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

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 degrees C. Density functional theory (DFT) calculations benchmarked by coupled cluster calculations on small models were performed for gas phase decomposition via intramolecular insertion and beta-hydricle 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 degrees 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 and/or HfNC-Si bonds. TDMAH decomposition products, such as M M I, can form a C-Si or N-Si bond with the silicon surface. The combined experimental and theoretical results suggest that insertion and beta-hydride elimination reactions can occur during bidentate chemisorption on the H-Si(100) surface by forming N-Si bonds.