Abstract
With the recent increase in the scaling down of devices, there has been an immense increase in the need for nanotechnology. Nanoscale devices should have their layers of materials as thin and uniform as possible. Hence, the application of the atomic layer deposition (ALD) to emerging nano-devices has attracted a great deal of attention. This is because of its natural benefits of producing uniform, conformal, pinhole-free and ultra-thin films when compared to various deposition methods for thin-film production. With the ALD process being inherently atomic in character, this leads to the coordinated deposition of thin films at the atomic scale, it forms controlled nanometer-scale thickness layers with exquisite conformality. In this dissertation, the ALD process of varying purge flow rates was numerically investigated with the motive of achieving an improved deposition process while developing an appropriate recipe for the ALD process. To simulate the ALD process in a reactor scale, a numerical model was implemented, and three-dimensional ALD processes of Aluminium Oxide (Al2O3) in a typical Gemstar 6 ALD reactor were carried out. In this process, the deposition of Al2O3 was demonstrated using gaseous precursors of trimethylaluminium (TMA) and ozone (O3) respectively, with argon as the purge gas. The flow process is similar to that of a typical cross-flow ALD type of reactor. The Entrance of the reactant species into the reactor was presumed to be at 150oC, while a temperature of 200oC was used for the substrate, reactor walls, and the outlet. This study has an ALD sequence of purge-pulse-purge-pulse-purge which makes up the comprehensive ALD cycle. The ALD process in the reactor is analyzed by the numerical simulation, this is by the implementation of computational fluid dynamics (CFD) via ANSYS FLUENT and CHEMKINPRO software packages. The coupled-algorithm method was applied for the transient process to resolve the pressure and velocity constituents of mass, momentum, energy and species transport. The second-order upwind and first-order implicit methods were made use of, to spatially and temporarily discretize the governing equations of the system, with the application of linearization in the transport equation of the source terms. The varying purge flow rates on the distinct ALD processes are investigated. The simulation outcomes demonstrated the effects of the ALD process with contrasting purge flow rates of 5, 10 and 20 sccm, and investigation of the mass fraction, surface coverage, deposition rate and growth rate were carried out via these purge flow rates. It has been discovered that the 5 sccm purge flow...
M.Ing. (Mechanical Engineering)