Understanding cominatorial atomic layer deposition and chemical vapor deposition.

Abstract

The transformation of molecular precursor to solid film begins with an understanding of molecular structure, proceeds through delivery of the molecule to the surface and ends with the decomposition of precursor on the surface to form a deposit. An understanding of the physical and chemical processes leading from molecule to film enables the utilization of chemical precursors in effective deposition processes. Single crystal X-ray crystallography was used to study the structure of [NO]0.5[NO2]0.5[Zr(NO3)5] and [NO]0.5[NO2]0.5[Hf(NO3)5]. Infrared spectroscopy was employed to identify the nature of the cation in the crystal structure, and characteristic absorptions of both nitronium and nitrosonium cations were observed. Fluidized bed reactor technology has been used to study the sublimation behavior of solid-state chemicals. Fluidization behavior, precursor mass transfer rates and delivery uniformity for aluminum trichloride were studied and the results reported. Mixed metal oxide nanolaminate films of hafnium oxide and zirconium oxide interspersed with layers of silicon oxide have been deposited on silicon substrates by a combinatorial atomic layer deposition (ALD) technique. Exposure of repeated cycles of co-dosed alkoxide precursors Hf[OC(CH3)3]4 and Zr[OC(CH3)3]4 with counter-reactant pulses of Si[OC(CH3)3]3(OH) formed films of uniform thickness (±5%) and uniform silicon oxide concentration (85% per total metals basis). The hafnium and zirconium concentrations exhibited smooth gradation across the film from 18% - 82% (per Hf and Zr metals basis). Self-limiting deposition rates of 1.5 nm / cycle were measured, and a linear relationship of film thickness to number of deposition cycles was observed, both consistent with a true ALD process. Rutherford backscattering spectrometry, ellipsometry and X-ray reflectivity results were used to map the composition and determine the film microstructure. Single precursor depositions have been performed and compared to computational models created using CFD-ACE in order to further the understanding of the interaction of fluid dynamics and chemistry in the combinatorial chemical vapor deposition process. The physical and chemical processes contributing to film growth in combinatorial chemical vapor deposition were evaluated.