Search for adsorption geometry of precursor on surface using genetic algorithm: MoO 2 Cl 2 on SiO 2 surface
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ORIGINAL ARTICLE
Search for adsorption geometry of precursor on surface using genetic algorithm: MoO2Cl2 on SiO2 surface Jason Kim1 · Jun‑Young Jo2 · In‑Gyu Choi2 · Yeong‑Cheol Kim2 Received: 13 May 2020 / Revised: 17 August 2020 / Accepted: 20 August 2020 © The Korean Ceramic Society 2020
Abstract We searched for appropriate adsorption geometries of a M oO2Cl2 precursor on a -H terminated β-SiO2 surface using genetic algorithm (GA). The adsorption geometries were configured by translating and rotating the precursor located near the surface. Six parameters decided the translation and rotation of the precursor along and around X, Y, and Z axes, and the six parameters were optimized by using the GA to search for energetically favorable adsorption geometries. For accurate and fast convergence of the GA, a dataset of adsorption geometry and the adsorption energy pairs was collected by grid search. Using this dataset, the hyper-parameters for the GA were optimized to search for the energetically favorable adsorption geometries. The GA found more energetically favorable adsorption geometries than the grid search with less computation time. The GA would be applicable to finding appropriate adsorption geometries of other types of precursors and surfaces. Keywords Atomic layer deposition · Precursor adsorption · Surface reaction · Genetic algorithm · Density functional theory
1 Introduction As semiconductor device technology nodes decrease down below 10 nm, atomic layer deposition (ALD) becomes more critical than ever before because of its superior film thickness controllability and uniformity [1]. These advantages of ALD are mainly attributed to its self-limiting surface reaction [2]. Thermal ALD is still preferred to plasma enhanced ALD (PEALD) because of its less harmful effect to device quality and better conformality to high aspect ratio features [3, 4]. Precursor molecules for ALD should be inert enough not to react with each other, volatile enough to be easily delivered into reactor, and adsorptive enough to react with surface without being desorbed [5]. Inertness improves the storage period of precursors, and depends on the bond strength * Yeong‑Cheol Kim [email protected] 1
Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
School of Energy Materials and Chemical Engineering, Korea University of Technology and Education (KoreaTech), Cheonan, Chungnam, Republic of Korea
2
between atoms composing precursors and adsorption among precursors; strong bond strength and weak adsorption can improve inertness. Volatility of precursors depends on inertness, molecule weight, size, etc. Reactivity on surface, not in air, on the other hand, should be high for ALD. Strong adsorption of precursor with surface can weaken some bond strength between atoms and, therefore, increase the reactivity on surface. Adsorption energy should also be higher than reaction energy barrier for surface reaction; if adsorption energy is less than rea
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