photolithography

Semiconductors play an essential role in modern society by enabling ground-breaking technological advances. The manufacture of high-volume and advanced semiconductors requires the use of fluorinated chemicals known as PFAS. Representing the voice of SEMI members, I explained the important role of these substances and their “essential use” in the semiconductor manufacturing supply chain at a Chemical Watch conference for industry and European Union decision-makers on 3rd of December 2020.In order to achieve the European Green Deal’s zero pollution ambition for a toxic-free environment, the European Commission announced in its recently published Chemicals Strategy for Sustainability its intention to restrict the use of the most harmful chemicals, except in cases where they are deemed essential for society. Per- and polyfluoroalkyl substances – known as PFAS – are the first group of chemicals facing regulatory scrutiny on this basis. This begs the question: What chemicals should be characterized as essential for society and what uses will they encompass? The key and enabling role of semiconductors in modern lifeSemiconductors are essential and ubiquitous in our lives. They are integral to enabling modern society to function – driving advancements in mobile communication technologies for the smartphones and computers that help us work more efficiently and connect us with our loved ones. These benefits have never been more evident than in 2020 with billions of people finding themselves working and studying remotely and safely from home.At the same time, technologies relying on semiconductors have been vital in the effort to combat COVID-19 – in ventilators, medical imaging devices and digital healthcare solutions. In addition, semiconductors will also enable the next leap in society to Industry 4.0 and as essential building blocks in connected and electric vehicles, artificial intelligence (AI) and quantum computing.The Commissioner for Internal Market, Thierry Breton, has highlighted the strategic importance of semiconductors in achieving European digital sovereignty (for instance, in his speech at Hannover Messe Digital Days), and the EU’s New Industrial Strategy[1] also points to the importance of semiconductors and microelectronic systems. What must also be appreciated are the cost and complexity of producing these valuable technologies. Setting up a cutting-edge fabrication plant with the hundreds of pieces of semiconductor manufacturing equipment typically required can cost around €15 billion.[2] A single semiconductor manufacturing tool typically consists of millions of articles, and a typical fab may house several hundred pieces of equipment. Furthermore, according to SEMI estimates, the fabrication of semiconductor wafers requires approximately 500 highly specialized process chemicals. In many cases, these processes, equipment and facilities rely on the unique properties offered by PFAS.“SEMI has worked diligently to highlight the strategic importance of semiconductors in achieving European digital sovereignty, and we are pleased that the critical role of microelectronics has been fully recognized by the EU and Member States. Fluorinated chemicals are essential for semiconductor manufacturing. "These specific chemicals are necessary due to their unique properties, and no alternatives are currently available that can adequately provide the functional properties required in semiconductor manufacturing. The essential use concept, therefore, must enable technological innovation, must apply across the entire supply chain, and must enable EU’s critical infrastructure and strategic objectives.” What are PFAS, and why and where are they used in semiconductor manufacturing?PFAS are a broad and highly diverse group of substances with unique properties and characteristics. The Organisation for Economic Co-operation and Development (OECD) has compiled a list of approximately 4,700 substances,[3] a handful of which are used in the semiconductor manufacturing industry. These very specific chemicals are necessary due to their unique and unparalleled properties that enable them to be used in the demanding conditions of semiconductor manufacturing.Semiconductor chemicalsAt the very core of semiconductor manufacturing is the photolithography process, where microscopic geometric patterns are transferred onto a film or substrate. Photolithography specialty formulations containing fluorinated compounds are used in various steps of this process to ensure quality and reduce the probability of defects. PFAS must be used due to their low surface tension and compatibility with other chemicals. PFAS are typically no longer present in the finished product. However, there are applications where PFAS are present in the final semiconductor device, particularly in imaging semiconductors used in cameras, displays and some medical devices, amongst others. Semiconductor manufacturing equipmentPFAS are also essential to semiconductor manufacturing equipment and factory infrastructure. The exceptional combination of their heat and chemical resistance and their chemical inertness allows fluoropolymers to be used both in equipment components (tubing, gaskets, containers, filters, etc.) and lubrication (such as various oils and greases). These same properties are also needed to ensure the functioning of the surrounding infrastructure. Finally, some fluorinated gases, which are already regulated by specific legislation,[4] are used as refrigerants and to clean the facilities.These are a handful of examples of how PFAS are used in semiconductor manufacturing. Today, there is no other way to undertake these processes or to build semiconductor manufacturing equipment without PFAS. No alternatives are currently available that can adequately provide the functional properties required. Even if alternative chemicals and technologies were discovered today, due to the extremely complex qualification process throughout the value chain, it would take another 15 years to deploy them in high-volume manufacturing. Therefore, continued access to PFAS is a prerequisite for high-volume and advanced semiconductors. Lack of continued access to PFAS could lead to an inability to produce and supply the EU with semiconductor manufacturing technology.How should we think about essential uses?Regulators have started to think about what uses of PFAS are essential and in which cases their use should be allowed. In developing this concept, there are a few aspects to keep in mind.Essential use must enable, not hinder, technological innovationFirst and foremost, the essential uses concept should enable continued technological innovation instead of acting as a hindrance. Semiconductors and manufacturing technology are constantly evolving and becoming more diverse to help meet increasing societal demands. What we see as innovative today may be commonplace in the future, while future innovations may be unimaginable today. We must therefore be careful not to accidentally limit our future potential for innovation.Essential use must apply across the entire supply chainSecondly, classifying a use as essential should apply throughout the entire supply chain. We must, for example, avoid defining semiconductors as essential while classifying the semiconductor manufacturing equipment and chemicals used to produce semiconductors as not essential. In the semiconductor manufacturing supply chain, where one manufacturer can have up to 16,000 suppliers, this risk is evident.[5]Essential use must enable critical infrastructures and the EU’s strategic objectivesFinally, we should keep Europe’s societal priorities in mind. The EU needs to be able to maintain and protect its critical infrastructures. Similarly, we should not lose sight of the EU’s strategic objectives of a green and digital Europe.Semiconductors, in conjunction with their corresponding manufacturing equipment and chemicals, are essential technologies in everyday life and the backbone of the EU’s strategic value chains. Manufacturing semiconductors is a very expensive and complex process that would not be possible without the unique properties of PFAS, making them essential to achieving the EU’s strategic objectives today – whether the European Green Deal or digital autonomy – and in the future. Therefore, we must ensure that essential uses will enable the continued use of PFAS in semiconductor manufacturing.The SEMI presentation delivered at the Chemical Watch event can be accessed here.Emir Demircan is director of Public Policy and Advocacy at SEMI Europe.[1] “The EU will also support the development of key enabling technologies that are strategically important for Europe’s industrial future. These include robotics, microelectronics, high-performance computing and data cloud infrastructure, blockchain, quantum technologies, photonics [etc.]”[2] Emerging technologies in electronic components and systems (ECS) Opportunities Ahead – A study by DECISION, 2018 for the European Commission[3] Available here[4] Regulation (EU) No 517/2014, “F-Gas Regulation”[5] SIA Nathan Associates, 2016, https://www.semiconductors.org/wp-content/uploads/2018/06/SIA-Beyond-Borders-Report-FINAL-June-7.pdf

On behalf of its global membership, SEMI is actively addressing a variety of environment, health and safety (EHS) dossiers impacting the semiconductor manufacturing supply chain. Together with its dedicated working groups (WGs), SEMI educates regulators globally on semiconductor manufacturing technology and advocates a balanced policy framework supporting innovation, growth and sustainability.Perfluorooctanoic acid and related compounds and salts (collectively known as PFOA) have been on the radar of the SEMI PFOA WG and EHS Advocacy Program for several years. PFOA is reported to cause severe and irreversible adverse effects to the environment and human health. PFOA is very stable and will last for years in the environment, and so it is considered a Persistent Organic Pollutant (POP). As such, PFOA is in scope of the Stockholm Convention and meetings to consider revisions to the Convention take place regularly. During these consultative meetings, Parties to the Convention are invited to provide observations and propose amendments. SEMI participated in the ninth meeting of the Conference of Parties (COP) in Geneva in late April and early May to provide the position of the semiconductor manufacturing industry.Among the many substances used to manufacture equipment components, fluoropolymers and fluoroelastomers (together known as fluoromaterials) have been produced sometimes with PFOA as a processing aid. To reduce hazardous effects to the environment and human health and to meet regulatory obligations, many (but not all) fluoromaterial manufacturers worldwide have been eliminating PFOA from their processes. Over the past several years, the WG has been studying equipment components – as well as related supply chains – that might contain fluoromaterials made with PFOA. The WG has learned that if PFOA is present in fluoromaterials, it is only as an unintentional contaminant or impurity. The WG has also confirmed that PFOA serves no intended purpose or performance function in the fluoromaterial-containing components that might be present in semiconductor manufacturing equipment. Although more testing is needed, the WG also believes PFOA that might be present in fluoromaterials does not move freely out of the material into the surrounding environment. In this light, the WG reviewed a draft of exemption recommendations from the Persistent Organic Pollutants Review Committee (POPRC) to the full Stockholm Convention. The exemptions in the draft recommendations addressed new and legacy equipment, fabrication plant-related infrastructure and related refurbishment parts for the manufacture of semiconductors and related electronic devices, and it imposed a commitment to remove any ‘PFOA residue’ from equipment components in five years (10 years for legacy equipment and refurbishment parts). Additionally, there was also an exemption in the draft for PFOA related to photo-lithography and etch processes, which the WG fully supported to maintain, as the presence of PFOA in process chemicals is fairly well understood, but viable substitutes have not yet been found for some applications.The outcome of the WG review was a concern because the equipment-focused exemptions introduced the concept of a ‘PFOA residue,’ and the Stockholm Convention already contains an exemption for ‘Unintentional Trace Contaminants’ (UTCs). The WG concluded that the existing UTC exemption was already sufficient. Additionally, although the WG does have spot information that PFAO can be present in fluoromaterial components, there is no comprehensive data about PFOA presence throughout the deep and complex equipment component supply chain, particularly regarding older parts in storage.Additionally, the WG has seen that very low levels of PFOA can be unintentionally created by some fluoromaterial post-processing steps such as processes intended to control PTFE polymer chain length in fluoro-lubricants that unintentionally create small quantities PFOA (note that PFOA is roughly a very short PTFE chain with a ‘carboxyl’ ending). Also, the WG has learned that PFOA can, in some cases, be accidentally created from fluoropolymers, adding to doubts as to whether ‘PFOA free’ can be determined or achieved. Therefore, the commitment contained in the draft exemption to have all ‘PFOA residues’ removed in five or 10 years was not based on a well-defined action timeline.Therefore, the WG in its discussions with governments around the world, prior to and during the Stockholm Convention COP meetings, requested the removal of specific exemptions related to equipment used in semiconductor manufacturing. The WG also requested that the specific exemption related to photolithography or etch processes be maintained. SEMI appreciates that its recommendations were accepted by the COP. This will help avoid country-specific regulations based on the Convention that are not fit-for-purpose. SEMI and its WG will continue to study PFOA and its elimination from the semiconductor manufacturing supply chain, and educate regulators globally on semiconductor manufacturing technology, underpinning sustainability, innovation and growth in a balanced manner.