Offering chemical stability, thermal resistance, and the ability to repel water and contaminants, per- and polyfluoroalkyl substances (PFAS) have long been implemented in modern industrial processes. This includes semiconductor manufacturing, where these man-made compounds have been widely used in etch processes, coatings, and surface treatments.
Their chemical resilience has led to PFAS being labelled “forever chemicals,” as they do not readily break down in the environment. Mounting evidence of the damage and potential health risks associated with their persistence and bioaccumulation has made eliminating PFAS a global priority for semiconductor manufacturing and other industries.
Improving sustainability while advancing technical performance requires equipment and materials providers to rethink established process chemistries and toolsets. This opens the door to innovation in etch technologies and advanced coatings used in semiconductor manufacturing.
PFAS compounds have historically played a critical role in plasma etching, particularly in processes that rely on fluorinated gases such as sulphur hexafluoride (SF₆) and fluorocarbon (CxFy) compounds. These materials enable highly controlled, anisotropic etching—essential for defining nanoscale features in silicon and other materials—and are used in surface coatings to impart water and chemical resistance in demanding environments.
Because their environmental persistence has triggered increasing regulatory scrutiny, especially in Europe, where broad restrictions on PFAS use are under consideration, chipmaking processes that depend on PFAS will need viable alternatives that maintain performance without introducing new risks to yield, throughput, or device reliability. Additional global pressure is being driven by regulation, corporate sustainability commitments, and supply chain pressures.
Emerging Alternatives: Gas-Phase Etching
A highly promising development in PFAS-free processing is the evolution of gas-phase metal-assisted chemical etching (Gas-MacEtch). Unlike conventional plasma-based approaches that rely on fluorinated gases, Gas-MacEtch enables silicon etching without PFAS, SF₆, or CxFy chemistries.
This approach offers several notable advantages:
- PFAS-free processing, eliminating reliance on fluorinated gases
- Room-temperature operation, reducing energy consumption compared with cryogenic methods
- High-aspect-ratio etching, supporting increasingly complex device architectures
- Smooth sidewalls without scalloping, improving electrical and optical performance
- Plasma-free processing, minimizing surface damage
These characteristics position Gas-MacEtch as a compelling addition to the semiconductor manufacturing toolbox, particularly for applications requiring precision and low defectivity. From a sustainability perspective, the benefits are significant. Compared with traditional deep reactive-ion etching (DRIE), which relies heavily on PFAS-based chemistries, Gas-MacEtch offers a more environmentally friendly alternative while maintaining competitive process performance.
However, like many emerging technologies, Gas-MacEtch is still maturing and far from industrialization. Practical challenges remain around catalyst deposition prior to and integrity during Gas-MacEtch implementation, as well as eventual removal at the end. Also, Gas-MacEtch uses two parallel processes that must run in sync: silicon dioxide (SiO2) oxidation at the interface of the metal catalyst and silicon; and synchronous vapour hydrogen fluoride (vHF) etching of the SiO2.
Currently, Gas-MacEtch adoption is limited to niche applications such as X-ray gratings and non-linear optics. The technology holds huge potential for integrated optics (together with thermal atomic layer etching [ALE] for further sidewall roughness reduction) and quantum applications where field roughness leads to losses that result in decreased performance.
Advanced Coatings in a PFAS-Free Future
Beyond etch processes, coatings represent another critical area where PFAS alternatives are gaining traction. Self-assembled monolayer (SAM) coatings, in particular, are emerging as a viable path toward PFAS-free surface treatments.
SAM coatings can be engineered to provide hydrophobic or hydrophilic properties, support biocompatibility, and enhance microfluidic performance. These are key requirements for applications in MEMS, nanoelectromechanical systems (NEMS), and micro-opto-electromechanical systems (MOEMS), and in medical/diagnostic applications such as implantable electronics and lab-on-a-chip devices.
As materials science advances, PFAS-free coatings are becoming increasingly viable for a growing range of applications, from consumer electronics to biomedical devices. PFAS-free SAM coatings offer a clear sustainability advantage by eliminating fluorinated materials altogether. That said, in some cases, PFAS-based SAMs still demonstrate slightly more superior performance, stability, and ease of integration into complex film stacks (see table). PFAS-free alternatives are closing the gap, but process engineers must carefully balance sustainability goals with technical requirements.
Table 1. Comparative benefits of PFAS-based and PFAS-free SAM coatings
| PFAS SAM | Non-PFAS SAM | |
|---|---|---|
| Sustainability | – | + |
| Deposition Rate | + (CVD regime) – (ALD regime) |
+ (CVD regime) – (ALD regime) |
| Performance | + | + |
| Reliability | + | + |
| Process Complexity | + | +/- |
| Integration Complexity | + | – |
Abbreviations: ALD, atomic layer deposition; CVD, chemical vapour deposition.
The Role of Equipment Innovation
Transitioning to PFAS-free processes is not simply a matter of swapping chemistries; it requires new process capabilities, tool architectures, and integration strategies. This is where equipment providers play a critical role.
Memsstar is helping to enable next-generation etch and coating processes through advanced platform development. By supporting technologies such as Gas-MacEtch and SAM deposition within integrated toolsets, the company is helping to bridge the gap between laboratory innovation and industrial adoption.
A key challenge in PFAS-free processing is process complexity. Gas-MacEtch, for instance, involves synchronized reactions—such as silicon oxidation and vapour-phase etching—that must be precisely controlled. Similarly, SAM coatings require careful management of deposition conditions and surface chemistry.
Addressing these challenges requires:
- Integrated process modules that maintain environmental control and minimize contamination
- Advanced monitoring capabilities, such as in-situ diagnostics, to ensure process consistency
- Best-known method (BKM) development, enabling reproducible, production-ready recipes
By focusing on these areas, equipment manufacturers are helping fabs to adopt PFAS-free processes without compromising yield or reliability.
Adoption Pathways
For semiconductor manufacturers, transitioning to PFAS-free processes is often tied to next-generation product development. Rather than retrofitting existing production lines, new process technologies are typically introduced alongside new device architectures, allowing them to mature in parallel.
In some cases, such as SAM coatings, there is potential to transition within existing process flows, though this may require equipment upgrades or modifications. Early adoption often involves joint development programs (JDPs) between fabs, equipment suppliers, and research institutions. These collaborations are essential for refining process understanding, optimizing performance, and accelerating commercialization.
As the technology matures, broader adoption is expected, driven by both sustainability requirements and the need for advanced capabilities in areas such as integrated optics, quantum devices, and AI-driven chip architectures.
Looking Ahead: Sustainability Driving Innovation
The move away from PFAS is more than a regulatory response; it represents a fundamental shift in how the semiconductor industry approaches process development. Sustainability is becoming a core design parameter, alongside performance, cost, and scalability.
For memsstar, this shift presents an opportunity to lead in enabling the next generation of semiconductor manufacturing. By advancing PFAS-free processes and supporting their integration into production environments, equipment providers are helping shape a more sustainable—and ultimately more resilient—industry. Technologies like Gas-MacEtch and PFAS-free SAM coatings illustrate how environmental goals can align with technical innovation, enabling new levels of precision and functionality while reducing ecological impact.
FAQs
1. What PFAS-free alternatives exist for release etching in MEMS manufacturing?
Gas-phase compounds such as vapour hydrogen fluoride (vHF) and xenon difluoride (XeF₂) provide PFAS-free MEMS release etching, eliminating the need for PFAS-based surfactants used in some wet chemistries. memsstar’s ORBIS™ systems with XERIC™ Vapour Release Etching and SVRT™ (Sacrificial Vapour Release Technology) process modules deliver controlled, selective vHF and XeF₂ release at production scale. Dry release processing removes all sacrificial material quickly, without leaving deposits or residues and with undamaged surfaces — reducing stiction risk and integrating cleanly with downstream surface treatments.
2. How can PFAS-based anti-stiction coatings be replaced with a PFAS-free alternative?
Self-assembled monolayer (SAM) coatings are emerging as a viable PFAS-free option for surface treatments in MEMS and semiconductor devices. memsstar’s AURIX™ SAM Coatings and MEMS process expertise extend beyond anti-stiction coatings to comprise hydrophobic anti-stiction precursors, anti-wear coatings, hydrophilic anti-fouling treatments, microfluidics, bio-inert implantable devices, and bio-active coatings. Applied via memsstar’s SPDT™ (Surface Preparation and Depletion Treatment) process module, AURIX SAMs deliver durable surface energy control without fluorinated materials. Self-assembled monolayers are produced in a two-stage process that combines plasma activation with surface deposition — all precision-controlled and monitored using innovative, patented systems.
3. What is Gas-MacEtch, and how does it support PFAS-free semiconductor processing?
Gas-phase metal-assisted chemical etching (Gas-MacEtch) is a promising PFAS-free technology that enables silicon etching without SF₆ or fluorocarbon chemistries. It offers room-temperature operation, high-aspect-ratio etching, and smooth sidewalls without scalloping, making it suitable for increasingly complex device architectures. While Gas-MacEtch is still maturing toward full industrialisation, as Europe’s premier process and equipment supplier of etch and deposition solutions for semiconductor, MEMS, and related technology manufacturing processes, memsstar supports gas-phase workflows through its technology expertise, including reactive ion etch (RIE), plasma-enabled chemical vapour deposition (PECVD), physical vapour deposition (PVD), vapour phase, and thermal integration steps to help qualify PFAS-free etch stacks.
4. How does memsstar help manufacturers transition to PFAS-free processes without disrupting production?
memsstar helps manufacturers transition to PFAS-free semiconductor and MEMS fabrication through its collaboration on the Gas-MacEtch process, which enables PFAS-free wafer restructuring via lower-temperature etching. The company’s ORBIS systems are engineered to integrate these new dry MEMS processes seamlessly into existing production lines. Moreover, as a leading remanufacturer of Applied Materials, Lam Research, and Novellus tools for semiconductor manufacturing processes, memsstar enables fabs to easily integrate PFAS-free steps such as XERIC™ vapour release etching and AURIX™ SAM coatings into existing lines — supporting regulatory compliance while maintaining throughput and yield.
