This paper investigates the purge flow rate in a reactor scale simulation of an Atomic Layer Deposition (ALD) process. A three-dimensional numerical analysis approach was implemented in the ALD process to fabricate thin films of aluminium oxide (Al2O3). Despite the abundance of literature on the specific use of, and increase in deposited material through the process of ALD, limited studies exist on the physical and chemical processes that occur during the growth of ALD. Previous literature has indicated that purging has presented a major challenge in the effective deposition rate of the ALD process. The precise purge flow rate has also been greatly contended. The importance of the purge sequence within the ALD process cannot be overemphasized. The term purge sequence refers to the essential property that defines the ALD advanced nano-fabrication technique in producing ultra-thin film. Therefore, this study focused on the purge flow rate effects of the ALD process. The reactants employed in the simulation process were trimethyl-aluminium (TMA) and ozone (O3) as the metal and oxidant precursors, respectively, and inert argon as the purge gas. Numerical simulations were carried out at a stable operating pressure of 1 torr, with a substrate temperature of 200°C, and three purge flow rates of 20, 10 and 5 sccm, respectively. An extended ozone exposure is crucial to in providing an adequately oxidized substrate. It is discovered that the 5 sccm flow rate shows, superior mass fractions, unity surface coverage and a time extensive surface deposition rate. The 20 sccm, 10 sccm and 5 sccm purge flow rate growth obtained a 0.58, 0.92, and 1.6 Å/cycle, respectively. The findings revealed close similarities to experimental behaviours and recorded growth.