Date of Award

May 2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Chris Yuan

Committee Members

Jorg Woehl, Junhong Chen, Benjamin Church, Woo Chang, Emmanuel Wornyoh

Keywords

Atomic Layer Deposition, Experimental Characterization, Numerical Modeling, Sustainability, Throughput Improvement

Abstract

Atomic layer deposition (ALD) is an approved nano-scale thin films fabrication technique with remarkable uniformity and conformity in surface geometry. This dissertation presents numerical and experimental studies to investigate the transient physical and chemical ALD process in order to improve its sustainability performance in terms of throughput, wastes and emissions.

To be specific, in this dissertation, the transient process of ALD is studied extensively through both numerical and experimental approaches to find the influential factors on the two main critical sustainability issues: low throughput and negative environmental impacts. Different numerical schemes are developed and studied for ALD process simulations. In particular, the gas fluid dynamics of the carrier gas flow is studied numerically by introducing and comparing two Lattice Boltzmann Method (LBM) models. To account for the surface deposition process, the strong-coupled physical and chemical process of ALD is recovered numerically by Finite Volume Method (FVM). The 3D transient reactive thermal-fluid dynamic model adopts surface reaction kinetics and mechanisms based on the atomic-level calculations to study the surface deposition process.

Experimental investigations are carried out to characterize the growth rate under different deposition conditions. The experimental observations are correlated with the simulations for better understanding the transient physical and chemical ALD process. The experimentally-validated numerical model is further applied for in-depth investigation of two types of batch and spatial ALD process for throughput improvement. A multi-wafer batch ALD with vertical and horizontal wafer arrangements is studied to investigate the influences of wafer layout on the deposition process with both experimental and numerical approaches. An in-line spatial ALD is also studied numerically to investigate three geometric and process factors, gap size, temperature, and pressure on the precursor intermixing and chemical deposition process. Spatial ALD is shown significantly effective in improving the throughput of ALD thin film depositions.

To study the adverse environmental impacts of ALD nano-manufacturing technology on Al2O3 nano-scale thin films, numerical simulations with detailed ALD surface reaction mechanisms developed based on Density Functional Theory (DFT) are performed to investigate the effects of four process parameters on ALD film deposition rate, process emissions and wastes. The influential factors on process emissions and wastes are studied and identified.

Available for download on Friday, June 02, 2017

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