ALD is mainly deployed in high-volume manufacturing in two industrial segments - semiconductor manufacturing and photovoltaics and specifically silicon-based solar cells. Other applications exist but do not yet use anywhere near the amount of processing equipment or plants or electrical energy, gases, chemicals, cooling, ventilation, and clean water. This is why it is important to understand the environmental footprint of ALD in those two industries as a whole and also the contribution from ALD. Here is a good paper breaking down the issues in a systematic way and coming up with some conclusions - three main routes to lower the environmental footprint of ALD.
Assessing the Environmental Impact of Atomic Layer Deposition (ALD) Processes and Pathways to Lower It
Matthieu Weber*, Nils Boysen, Octavio Graniel, Abderrahime Sekkat, Christian Dussarrat, Paulo Wiff, Anjana Devi, and David Muñoz-Rojas
ACS Mater. Au 2023, XXXX, XXX, XXX-XXX
Publication Date:April 27, 2023
https://doi.org/10.1021/acsmaterialsau.3c00002Due to concerns on resources depletion, climate change, and overall pollution, the quest toward more sustainable processes is becoming crucial. Atomic layer deposition (ALD) is a versatile technology, allowing for the precise coating of challenging substrates with a nanometer control over thickness. Due to its unique ability to nanoengineer interfaces and surfaces, ALD is widely used in many applications. Although the ALD technique offers the potential to tackle environmental challenges, in particular, considerations regarding the sustainability of renewable energy devices urge for greater efficiency and lower carbon footprint. Indeed, the process itself has currently a consequential impact on the environment, which should ideally be reduced as the technique is implemented in a wider range of products and applications. This paper reviews the studies carried out on the assessment of the environmental impact of ALD and summarizes the main results reported in the literature. Next, the principles of green chemistry are discussed, considering the specificities of the ALD process. This work also suggests future pathways to reduce the ALD environmental impact; in particular, the optimization of the reactor and processing parameters, the use of high throughput processes such as spatial ALD (SALD), and the chemical design of greener precursors are proposed as efficient routes to improve ALD sustainability.
Based on the literature review and the green principles applied to ALD depicted in this work, three main routes toward ALD processes with lower environmental impact could be deduced and should be applied where possible:
- The thorough optimization of the processing parameters and the reactor design and its infrastructure would drastically lower the undesired wastes and emissions. Computational simulations, machine learning, and artificial intelligence can, for example, be applied to optimize ALD processes faster than ever, as the saturation times can be precisely predicted using these innovative tools.
- High throughput processes such as SALD applied at atmospheric pressure could lead to depositions that are orders of magnitude faster and lower the overall energy budget and related emissions.
- The chemical design of greener precursors would have the largest impact as it could reduce the overall environmental impact: from the raw material extracted and the (limited) number of greener chemistry synthetic steps resulting in the precursor molecules to the thermal budget related to the deposition temperature, and to the emissions of less polluting byproducts.
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