Semiconductor manufacturing Without eternaty chemicals: Polymer membranes developed for semiconductor manufacturing

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Eternity chemicals, also known as Perfluoroalkyl and Polyfluoroalkyl Substances (short PFAS), are not only used in frying pans, but also in semiconductor manufacturing. However, these chemicals, which promise non-stick properties, are suspected of being harmful to health. That's why researchers from the Fraunhofer Institute IAP have developed a polymer membrane for semiconductor manufacturing – without PFAS.

So-called eternity chemicals, per- and polyfluoroalkyl substances or PFAS for short, have some practical effects: they prevent materials from sticking to one another. However, PFAS are at least environmentally harmful because they cannot be degraded due to their stability. For this reason, they enter humans via the food chain, who also surround themselves with PFAS. These eternity chemicals are likely harmful to health; at the least, exposure can increase the risk of cancer.

The European Chemicals Agency (ECHA) is therefore aiming to ban the production, use, placing on the market and import of PFAS into the European Economic Area. In June, committees for risk assessment and socio-economic analysis will meet to discuss and refine the proposal to ban PFAS.

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The semiconductor industry views the efforts for a ban critically, as PFAS-containing materials are used in etching, cleaning, and filter processes. PFAS has so far been considered irreplaceable for such applications. However, that does not necessarily mean that alternatives could not be designed.

It would certainly be better if ways and means could be found to preserve the advantages of PFAS and to avoid the disadvantages. The researchers led by Dr. Murat Tutus, engineer at the Fraunhofer IAP and head of the "Membranes and Functional Films" department, have taken on this task.

They have developed a sustainable alternative to the polymer membranes used in semiconductor manufacturing. Specifically, for a semiconductor industry supplier, they have developed a PFAS-free membrane made of conventional, specifically stabilized polymers that can replace PFAS membranes.

PAN instead of PFAS.

The membrane made of polyacrylonitrile (PAN) impresses with its high chemical and mechanical stability as well as a small pore diameter of about seven nanometers. These properties enable the effective separation of particulate contamination and the filtration and recycling of operating fluids such as acids and solvents.

In addition, the membrane can be adapted to customer requirements in terms of permeability, which facilitates integration into existing plants for the production of the next generation of chips. A modification with a component patented by Fraunhofer IAM also makes it possible to stabilize the membrane for harsh process conditions.

"During chip production, countless process steps such as sawing, cleaning, and planarizing are carried out to apply the structures to the wafers. All these operations produce particulate contamination, which must be separated at each process, otherwise it would damage the production of the nanometer-sized structures," says Dr. Murat Tutus.

Dr. Tutus and his team see great potential for their development, especially in the pharmaceutical and chemical industry where aggressive solvents are used. During the production of the membrane, sustainable, REACH-compliant solvents are used and the entire production process is carried out sustainably at low temperatures. The membrane is produced using non-solvent induced phase separation (NIPS), which allows the morphology and pressure stability of the membrane to be adjusted. (sb)