Table 3.

Environmental impact of conventional lithographic routes is directly compared to emerging BCP and polymer brush lithography.

Sustainability Issue	Conventional Lithography		Bottom-Up BCP and Polymer Brush Nanofabrication Routes
	Process	Impact	Process	Impact
Carbon emissions	NGL tools such as EUV require high source power [214].	High power requirements increased strain on resources.	Predicted lower power requirements due to high-power optical set ups not being necessary and reduced number of processing steps [4,18].	Predicted reduced power consumption costs and energy resource strain.
Organohalogens	Use of PFCs for etching and to clean CVD chambers [157,179,215].	Enhances greenhouse effect [158,215].	Versatility of bottom-up lithography may allow for exclusion of PFCs from initial stages of lithography but may still be required during etching processes.	When scaling to industrial-scale green fabrication route can be selected. Predicted impact requires further investigation.
Wastewater	Accumulation of various wastes from conventional lithographic processes in wastewater is of concern [192,218,220].	Contamination of water systems, environmental toxicity and eutrophication [221,222,234]	BCP and polymer brush impact on wastewater is point of further research.	Unknown on an industrial scale. LCA studies may help predict impact.
Photoresists, photostrippers, BCP and polymer brush wastes	Wastes from photoresist and photostripper are of concern [34,180,228,230,231]. Photoresists after exposure to light decomposes into harmful chemicals [149]. This step is not required for bottom-up lithography.	Persistent, bio accumulative, toxic and bio accumulative and thus of substantial environmental concern [219,229,230].	BCP and polymer brushes are removed via processes such as reactive ion etch or UV ozone [125,226]. Potential use of biopolymers may avoid harmful by products of etching processes.	Reduced etch steps have been reported for DSA [232]. Further research is required to evaluate environmental impact.
Acids, bases and solvent waste	Wet etching processing uses various acids, bases and solvents of environmental concern for example Sulfuric acid [157,223,234,225].	Health risks and environmental toxicity [212,213,223,224,234].	Acid, base, and solvent use depends on polymer and metals used in BCP and polymer brush lithography.	Unknown environmental impact on industrial scale. Capability of using green fabrication routes [104,179]
Trace elements and heavy metals	Trace elements such as Gallium and Indium have reported toxicity as high as metals and are deposited during lithography [183].	Hazardous for both humans and wildlife [233,234,235].	Metal use is required for lithographic patterning in the electronics industry.	Research required to determined more efficient and less wasteful than conventional lithography.