Chitosan as a green resist for photolithography.


Résumé du projet

Today, micro and nanofabrication processes are employed for the manufacturing of innovative products in advanced industrial domains (120 micromarkets) such as communications, health, energy... Lithography is one of the key step in micro/nanofabrication. It allows materials patterning. Thus, several techniques, such as photolithography, electron beam (EB) lithography, focused ion beam (FIB) lithography or nano imprint lithography, are employed to generate user-defined patterned surfaces using polymeric resist material. Lithographic resists are generally composed of a polymer, a solvent, and additives. After exposure and development, they form a temporary mask that protects selected areas of the underlying substrate allowing the micro/nanopatterning by etching or local deposition of matter of the substrates for the fabrication of the devices.

Resists are currently based on organic polymers and additives that are synthesized and processed using organic chemicals and solvents. Most chemicals and solvents (i.e. TMAH, Hydrogen cyanide, Methyl-isobutyl ketone…) are classified as hazardous or ecotoxic leading to health, safety and environmental issues. These issues lead to environmental, safety and waste management related costs. Furthermore, the European and US regulation (REACh and US pollution act) have increased the pressure on industrials for suppressing hazardous chemicals. Therefore, concerns have emerged for anticipating future regulations as well as reducing the related environmental, safety and waste management costs. Finally, taking into account the time span for developing a reliable resist, a breakthrough greener alternative solution needs to be initiated now in order to anticipate the oil rarefaction.

Lithogreen ANR project (ANR-19-CE43-0009) aims at the replacement of current (Deep) UV photolithography synthetic resists for micro/nanofabrication by eco-friendly resist. We believe that water soluble polysaccharides issued from biomass can be advantageously employed as resist allowing for whole photolithography/etching processes free of organic solvent and hazardous compound additives.

Polysaccharides are good candidates because they are biocompatible, water soluble and eco-friendly. Among the various polysaccharides we have decided to focus on chitosan (issued from chitin the second most abundant biopolymer), alginate and hyaluronic acid because they can make films with controlled properties and they have a good adherence to substrates.

Among the three selected polysaccharides, chitosan is envisioned as the best candidate for microelectronic application and pre-industrialisation studies as we have a 5 year experience with this bioresist. Furthermore, it can easily be produced free of metallic cations which make it more suitable for microelectronic fabrication lines.

To reach these goals, lithogreen project gather 5 complementary academic partners with expertise in polysaccharides chemistry, photochemistry, physico-chemical characterisation, surface analysis, advanced lithography, nanofabrication and evaluation of process compatibility with industrial production.