GOALI: Physically Based Models of Atomic Layer Deposition for High-Throughput Reactor Design

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With new energy, electronics, and consumer product applications, and the emergence of highthroughput reactor designs, Atomic Layer Deposition (ALD) is set to become a major thin-film manufacturing tool. Deposited using an alternating sequence of exposures to gas-phase precursors that would otherwise spontaneously react, ALD allows for the controlled deposition of a wide range of ultra-thin films at relatively low temperatures and potentially perfect conformality. Despite the upsurge in ALD process and equipment development, research on modeling deposition mechanisms and reaction kinetics in particular, continues to lag efforts devoted to new precursor chemistries and reactor designs. Because ALD is by its essential nature a completely dynamic process with no equivalent to steady-state deposition, the objective and primary intellectual merit of this proposal is to develop physically based models describing both ALD reaction rates and the changes occurring on the growth surface using transition-state (absolute rate) theory concepts. To achieve this objective, we identify three distinct subprojects to be pursued in this proposal: 1. Transition state rate model development for both reference and industrially relevant ALD reactions, combined with efficient numerical techniques to compute limit cycle solutions corresponding to continuous ALD reactor operation enabling optimization of the cyclic process.2. Development of micro- and nano-scale precursor transport models in the form of ballistic transport simulations coupled to the new surface reaction models, and spatial discretization techniques to simulate the time-evolution of the growth surface position.3. Validation of the reaction kinetics and ballistic transport models using reactors of the proposal industrial partner and dissemination of the rate modeling methods to the ALD community. The basic surface science research, numerical techniques, and reactor process research necessary to address the research goals described will potentially have a broad impact by contributing fundamentally to thin-film process engineering. Likewise, the physically based modeling methods developed are intended to be distributed to the ALD research and development community, further accelerating the range of applications of this manufacturing technology. The proposed research program will offer a unique educational opportunity for the engineering graduate students involved, giving them exposure to the scientists and engineers developing the next generation of ALD processes at Cambridge NanoTech. Furthermore, with support of this proposal, the PI will continue to develop hands-on demonstrations of the products of thin film engineering which will be used for middle- and high-school level outreach programs.