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.