Draft:Direct Atomic Layer Processing

Direct Atomic layer processing(DALP), is a subset technique of Atomic Layer Deposition and Atomic Layer Etching, using exactly the same chemical processes. More specifically it is a subset of Spatial Atomic Layer deposition, where DALP is using micro-nozzles to have a fully constrained system in XYZ, essentially allowing for deposition with a micro-spot as seen on figure 1.

Fig1. a) DALP Microfluidic nozzle concept: Schematic view of the nozzle in frontal view (top) and in cross-section (lower panel). b) Demonstration of direct pattern generated by a DALP deposition. Top is a thickness map by Low Energy Ion Spectroscopy, bottom is a Pt concentration map (log scale) by the same technique. From ref. [1]

Introduction

DALP has via the development of micro-nozzles and appropriate driving gas systems achieved direct processing, essentially allowing ALD and ALE to be used in an additive manufacturing mode. This work via the spatial ALD route, where the precursor and reactant combination of ALD/ALE is separated in space via gas dynamics as seen on figure 1. Currently DALP is being developed by the company ATLANT 3D Nanosystems and an FAU university group Chemistry of Thin Film Materials. See examples of micronozzles and machines to drive them on figures 2 to X.

First ever working DALP machine

First ever working DALP nozzle clamped in its print head

The first industrial prototype of a DALP machine, constructed under the public funded H2020 EU project ATOPLOT

The Mesomorph machine, at SUPSI university, constructed under a public H2020 EU project of the same name. The right most possition is occupied by a DALP module.

The second industrial prototype of a DALP machine

A simplified model can be made to explain the basic nature of the DALP process, which consist of a circular precursor zone, with a concentration gradient from 0 to 1 in the center. This is surrounded by a reactant zone, with a concentration gradient from sides to the middle. Between these 2 zones there is a distance D with 0 concentration of either.
Such a model is what a substrate sees in terms of chemical concentration, and this is achieved by the gas dynamics from the micro nozzle shown in Figure 1.
If we wish to add layers of reality to the model, we would start by adjusting the shape from a perfect circle, to some less ideal shape.

We can represent the nature of ALD, with a few set rules to explain how the deposition/etching is created.
Rule 1: P , the precursors, sticks and saturates on the substrate, and remains until it is reacted by R, the reactant
Rule 2: R does not stick to the surface
Rule 3: The reaction is only possible one way. P+surface>P*>P*+R>F , with F being the film that is created or etched, and also
represents a new surface upon which P can stick again.

Fig2. a) Simple model of DALP deposition, showing a precursor zone in the middle, surrounded by a reactant zone with a distance of D b) "depositing" a line with the simplified model between point A and B, showing what happens in 2 passes. Most importantly, the demonstration naturally provides that the line will have edges where the deposition has N/2 passes and a middle where there are N passes