A CFD-Based Digital Twin Framework for Transient MoCl5 Transport in an Experimental Atomic Layer Deposition Process

Published

March 23, 2026

Author(s)

Abdulrahman Alghamdi, Feiyang Ou, Berc Kalanyan, James Maslar, Panagiotis Christofides

Abstract

A physics-based digital twin framework is developed for transient molybdenum pentachloride (MoCl5) transport in an optically-accessible, experimental atomic layer deposition (ALD) reactor at the National Institute of Standards and Technology (NIST). The framework is anchored to high-speed absorption-imaging measurements reported by NIST and is implemented using a three-dimensional, time-resolved computational fluid dynamics (CFD) model that resolves momentum, heat, and species transport during pulsed precursor delivery. Experimentally measured, time-dependent absorbance data are used to inform the inlet precursor waveform, enabling direct comparison of normalized transport behavior between simulation and experiment in the absence of calibrated absolute concentrations. The digital twin of the reactor gas delivery system is validated against multiple experimental observables, including inlet velocity, precursor buildup and decay dynamics, residence time, spatial plume structure, and wafer chuck-level transport behavior, for representative operating conditions. The model reproduces the dominant temporal and spatial trends observed experimentally, including plume symmetry, transport delays, and purge dynamics, while maintaining physically consistent flow scaling near the wafer surface. Image-based comparisons further confirm that the modeling framework captures the transient evolution and symmetry of MoCl5 plumes under both low- and high-flow conditions. Beyond validation, a parametric study is conducted in which flow rate, chamber pressure, and injection duration are varied using a unified model configuration, including evaluation of an intermediate 300 SCCM condition to assess consistency between baseline cases. The results demonstrate that the model responds smoothly and predictably across the operating space, with wafer chuck-level velocity governed primarily by mass flow rate and precursor exposure transitioning from transport-limited to injection-duration–limited behavior for long pulses. Together, these results establish the present modeling framework as an experiment-informed, reusable digital twin suitable for rapid evaluation of ALD operating conditions and future extension to reaction-coupled modeling and process optimization.

Citation

Digital Chemical Engineering

Pub Type

Journals

Keywords

ALD, atomic layer deposition, chemical vapor deposition, CVD, molybdenum pentachloride, computational fluid dynamics simulations, CFD, reactor scale modeling, Semiconductor Manufacturing

Citation

Alghamdi, A. , Ou, F. , Kalanyan, B. , Maslar, J. and Christofides, P. (2026), A CFD-Based Digital Twin Framework for Transient MoCl5 Transport in an Experimental Atomic Layer Deposition Process, Digital Chemical Engineering (Accessed June 3, 2026)

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