Reactor scale simulations of ALD and ALE: ideal and non-ideal self-limited processes in a cylindrical and a 300 mm wafer cross-flow reactor

TL;DR

This paper introduces a versatile simulation tool for modeling self-limited processes like ALD and ALE in reactors of various geometries, comparing ideal and non-ideal kinetics and their effects on process uniformity.

Contribution

The work presents a new simulation approach that accurately models complex reactor geometries and non-ideal surface kinetics, enhancing understanding of process variability and in-situ diagnostics.

Findings

Simulation results align with analytic models for cylindrical reactors.

Axial diffusion influences growth profiles, softening ideal kinetics.

Non-ideal processes cause measurable thickness variability across wafers.

Abstract

We have developed a simulation tool to model self-limited processes such as atomic layer deposition and atomic layer etching inside reactors of arbitrary geometry. In this work, we have applied this model to two standard types of cross-flow reactors: a cylindrical reactor and a model 300 mm wafer reactor, and explored both ideal and non-ideal self-limited kinetics. For the cylindrical tube reactor the full simulation results agree well with analytic expressions obtained using a simple plug flow model, though the presence of axial diffusion tends to soften growth profiles with respect to the plug flow case. Our simulations also allowed us to model the output of in-situ techniques such as quartz crystal microbalance and mass spectrometry, providing a way of discriminating between ideal and non-ideal surface kinetics using in-situ measurements. We extended the simulations to consider two non-ideal self-limited processes: soft-saturating processes characterized by a slow reaction pathway, and processes where surface byproducts can compete with the precursor for the same pool of adsorption sites, allowing us to quantify their impact in the thickness variability across 300 mm wafer substrates.