Seals for semiconductor manufacturing involve critical choices related to the material used. And this is not surprising, given the high stakes of semiconductor fabrication, where a single contamination event or seal failure can compromise an entire wafer batch, costing hundreds of thousands of dollars in yield loss.
While seals are small and often overlooked in semiconductor manufacturing, they are exposed to some of the most aggressive conditions imaginable in any industrial environment. However, selecting the right material means not only a reliable seal but also improved equipment uptime, yield, and process integrity.
The Hostile Environment of Semiconductor Manufacturing
There are several factors that contribute to the extremely hostile environment that semiconductor manufacturing seals must be able to withstand. Seals in semiconductor equipment are regularly exposed to acids, bases, solvents, amine-based strippers, and chlorinated gases, depending on the process step.
There is also exposure to plasma: fluorine and oxygen plasmas, commonly used in dry etch and resist stripping, are among the most chemically reactive environments currently known. In addition, plasma exposure will rapidly degrade traditional elastomers that lack full fluorination.
Another challenge lies in extreme temperatures and vacuum pressures. Processes such as CVD (Chemical Vapor Deposition) and LPCVD nitride deposition both demand good thermal stability under sustained high temperatures. Also, many chambers operate under vacuum conditions where outgassing becomes a critical failure mode for the seal material used.
There are also UHP (Ultra-high purity) requirements. In short, any ionic contamination, particulate generation, or elevated TOC (Total Organic Carbon) introduced by a seal can corrupt the process chemistry or inadvertently dope the wafer. This has serious repercussions for semiconductor manufacturing processes and quality.
Seals for Semiconductors: Application-Specific Demands
No single material or seal geometry will work for every process step, so requirements vary significantly by application.
CVD and LPCVD demand thermal stability and vacuum-compatible materials with minimal outgassing. On the other hand, dry and wet etch processes will require a material that is plasma-resistant and compatible with fluorine-based gases and corrosive media.
CMP is especially interesting as it presents a dual challenge: exposure to an abrasive slurry and high-pH chemistry. This necessitates seals with strong abrasion and chemical resistance. Also consider track and lithography equipment that prioritizes solvent resistance, as photoresist developers and solvents readily degrade standard elastomers. Finally, resist stripping adds yet another layer of complexity, requiring seals that can withstand aggressive strip chemistries and sustained ozone exposure.
| Process | Primary Sealing Challenge | Key Material Requirements |
|---|---|---|
| CVD / LPCVD | High-temperature vacuum operation | Thermal stability, vacuum compatibility, minimal outgassing |
| Dry & Wet Etch | Highly aggressive etch chemistries | Plasma resistance, compatibility with fluorine-based gases, and acid/base media |
| CMP | Abrasive, alkaline slurry exposure | Abrasion resistance, high-pH chemical resistance |
| Track & Lithography | Photoresist solvent and developer exposure | Broad solvent resistance, dimensional stability |
| Resist Stripping | Ozone and aggressive strip chemistry exposure | Exceptional chemical resistance, ozone resistance |
Material Solutions: Engineering Polymers With Superior Performance
The primary candidate materials for semiconductor manufacturing sealing solutions are polymers selected for their ability to meet the overlapping requirements just described. The engineering polymers discussed are well-adapted to the challenges related to semiconductor manufacturing environments.
FFKM (Perfluoroelastomer)
FFKM is considered the top choice for O-rings in semiconductor manufacturing. It is able to deliver the sealing force and resilience of rubber, but with the chemical compatibility of PTFE. It offers a wide operating temperature, approximately -15°F to 620°F. In addition, there are various grades available for UHP applications that have been optimized for minimal extractable ion content, low metallic contamination, and enhanced O₂/F₂ plasma resistance. FFKM is suitable for static and limited dynamic applications across CVD, CMP, etch, lithography, and stripping processes.
PTFE (Polytetrafluoroethylene)
PTFE is known for its extremely low coefficient of friction, self-lubrication, exceptional chemical compatibility, and high purity. It also performs extremely well in high-temperature, corrosive environments that degrade other material options. Note that PTFE is often the material of choice for highly effective spring-energized seals and reliable encapsulated O-ring jackets.
PEEK (Polyether Ether Ketone)
Like PTFE, PEEK offers good wear resistance and moderate friction properties. It also offers low outgassing, good plasma resistance, and excellent dimensional stability at elevated service temperatures (which can prove crucial). Because of these properties, PEEK is a strong candidate for labyrinth seals and spring-energized seal lips in dynamic semiconductor applications.
Supporting Materials: PI, PCTFE, and PAI (Torlon)
There are some additional supporting materials, namely:
- Polyimide (PI): known for its low outgassing, excellent cryogenic performance, and high purity
- PCTFE: offers improved strength and hardness over PTFE while retaining excellent chemical inertness
- PAI (Torlon): ideal where high pressure, cryogenic temperatures, and corrosive media are all part of the operating environment; known for excellent wear resistance and self-lubrication
Choosing the Right Material
| Process | Recommended Materials | Rationale |
| CVD / LPCVD | FFKM, PEEK, PI (Polyimide) | High thermal stability, low outgassing, vacuum-compatible; FFKM grades available for water vapor and ammonia processes |
| Dry & Wet Etch | FFKM, PTFE, PCTFE | Superior plasma resistance and broad chemical inertness, including fluorine-based gas compatibility; minimal particle generation |
| CMP (Chemical Mechanical Polishing) | FFKM, PAI (Torlon), PEEK | Abrasion-resistant with strong resistance to high-pH slurry chemistry; PAI offers excellent wear resistance and self-lubrication |
| Track & Lithography | FFKM, PTFE, PCTFE | Broad solvent resistance; chemically inert to photoresist solvents and developers that attack standard elastomers |
| Resist Stripping | FFKM, PTFE | Outstanding ozone resistance and broad chemical compatibility; FFKM specifically rated for ozone and aggressive strip process chemistry |
Material selection for semiconductor sealing applications must be matched carefully to the demands of each individual process. For CVD and LPCVD, FFKM, PEEK, and polyimide (PI) are the leading candidates, as all three offer the thermal stability and low outgassing required for sustained high-temperature vacuum operation. Specialized FFKM grades are also available that are formulated specifically for processes involving water vapor and ammonia.
In dry and wet etch environments, FFKM, PTFE, and PCTFE are the materials of choice, owing to their broad chemical inertness and resistance to fluorine-based plasmas and corrosive etch chemistries. Minimal particle generation is a critical secondary requirement in these applications, and all three materials perform well in this regard. For CMP, the combination of abrasive slurry and high-pH chemistry narrows the field to FFKM, PAI (Torlon), and PEEK, with PAI offering a particular advantage due to its exceptional wear resistance and self-lubricating properties.
Track and lithography equipment demands seals that can withstand the photoresist solvents and developers that rapidly degrade conventional elastomers, making FFKM, PTFE, and PCTFE the preferred options given their broad solvent resistance and dimensional stability. Resist stripping represents perhaps the most chemically aggressive environment of all, with ozone exposure compounding an already demanding chemical profile. Here, FFKM and PTFE are the primary recommendations, with select FFKM grades formulated specifically for ozone-intensive strip process chemistry.
Conclusion
In semiconductor manufacturing applications, the seal material selection has an incredible impact on process reliability, contamination control, and total cost of ownership. And there is no universal, one-size-fits-all solution to choosing a seal material. Engineers must look for the optimal combination of material properties to be matched to each process step’s specific chemical, thermal, and purity demands and there are engineering polymers available that are ideal for different applications.
Advanced EMC is your partner when it comes to semiconductor sealing solutions. With over 100 years of combined experience, Advanced EMC has access to UHP-grade FFKM along with a full range of engineered polymer seal type. The Advanced EMC Sealing Solutions Team is ready to identify and supply the right sealing solution for any semiconductor application, whether standard or custom-designed. Contact Advanced EMC today for a consultation or to request a quote.
