In silico design of a thermal atomic layer etch process of cobalt

Suresh Kondati Natarajan*, Michael Nolan, Patrick Theofanis, Charles Mokhtarzadeh, Scott B. Clendenning

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Thermal atomic layer etch (ALE), facilitating the removal of up to one monolayer of material per cycle, is growing in importance for thin-film processing. The number of available ALE processes is much smaller than for atomic layer deposition, its complementary growth process. Quantum chemical simulations are a key approach in the development of new thermal ALE processes, however, methodologies and workflows need to be developed. In this regard, the present paper reports a simulation-based approach toward the development of new thermal ALE processes using metallic cobalt as a test case. We demonstrate a predictive process discovery approach for ALE in which target volatile etch products and the corresponding gas phase reactants are chosen from the literature, an overall ALE cycle for each combination of reactant is investigated for thermochemical favorability, and the detailed mechanisms of the individual reaction steps in the proposed ALE processes are studied using density functional theory. From these results, we derive a temperature-pressure process window for each combination of reactants at typical reactant and product pressures allowing the selection of an ALE process window. For Co ALE, we investigated propene, butyne, silane, and trimethyl silane as a first pulse reactant and CO as the second pulse reactant. We propose propene and CO as the best combination of reactants for Co ALE. Propene adsorbs with sufficient strength to the target Co atom at temperatures below the CO decomposition temperature of 440 K, which results in the lowest energy etch species. This approach is equally relevant for the ALE process design of elemental, binary, and ternary materials.

Original languageEnglish
Article number022603
Number of pages12
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Volume39
Issue number2
DOIs
Publication statusPublished - 1 Mar 2021
MoE publication typeA1 Journal article-refereed

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