How to select an FFKM O-ring for a semiconductor process
Short answer: pick an FFKM O-ring in this order. First the process step and its service temperature, then whether the seal sees chemical (radical) or physical (ion) plasma, then whether the chemistry is a dry process gas or a wet or sub-fab fluid, and only then the seal location and the AS568 size. Each of the three FFKM families used in semiconductor equipment, Kalrez, Chemraz and Perlast, publishes grade data for exactly these questions, and this page collects it in one place.
Every number below is copied from the DuPont, Greene Tweed or Precision Polymer Engineering document listed under Sources. Where a manufacturer states a figure as typical, it is labelled typical. MST is a distributor, not the manufacturer of any of these compounds.
Step 1: name the exposure before you name the grade
- Process step and the highest service temperature at the seal, for example HDPCVD at 250 to 300 °C or dielectric etch at 100 to 180 °C.
- Plasma character: fluorine and oxygen radicals (chemical attack) versus ion bombardment (physical erosion). DuPont ranks its grades along this axis.
- Process chemistry: for example NF3, CF4, O2, O3, NH3, TEOS or water vapor in dry processes, or acids, solvents and ultrapure water in wet processes.
- Seal location: door, gate valve, pendulum valve, chamber lid, window, gas inlet, exhaust valve or a heat-traced sub-fab foreline. DuPont lists these as typical Kalrez applications.
- Static or dynamic duty, and whether the ring sits behind a quartz window in the path of UV or plasma radiation.
Step 2: the process and its temperature set the shortlist
DuPont's plasma-process selector guide ties each semiconductor process to a service temperature, the chemistries it uses and the Kalrez grades it suggests. Use it as the first filter: a grade whose published maximum service temperature is below the process temperature is out.
| Process | Service temperature | Chemistries listed | Suggested Kalrez |
|---|---|---|---|
| HDPCVD | 250 to 300 °C | TMS, DEMS, TEOS, SiH4, NH3, SiF4, O2, N2O, C4F8, NF3 | 9100 / 9500 |
| PECVD / PEALD | 275 to 310 °C | Same list as HDPCVD | 9600 |
| PECVD curing | 150 to 200 °C | O3 with UV | 8705 (quartz window), 9500 (all other seal locations) |
| SACVD / FCVD | 280 to 300 °C | TEP, TEBO, TEOS, O3, NF3, NH3 | 9500 / 9600 |
| Conductor (poly / metal) etch | 150 to 225 °C | CF4, CHF3, HBr, BCl3, CCl4, Cl2, NF3 | 9100 / 9300 |
| Dielectric (oxide) etch | 100 to 180 °C | CF4, C3F8, CHF3, SF6, O2, H2 | 9300 |
| Ash / strip | 180 to 250 °C | O2, CF4, CHF3, NH3, water vapor, H2, forming gas | 9300 / 8002 |
Source: DuPont Kalrez Semicon Product Selector Guide, Plasma Processes. Kalrez is a DuPont trademark.
Step 3: chemical plasma or physical plasma
DuPont describes its semiconductor grades by what attacks the seal. Kalrez 9600 targets PECVD and ALD seals where fluorine and oxygen radicals dominate and ultra-low outgassing matters. Kalrez 9500 targets deposition with ozone, ammonia and water vapor (SACVD, FCVD, PECVD curing) and chemical plasma. Kalrez 9300 is designed for dielectric etch, where a balance of physical and chemical plasma attack is present. Kalrez 9100 is aimed at PECVD, ALD, HDPCVD and conductor etch with low erosion and ultra-low particle generation. Kalrez 8002 is an unfilled grade for ash and strip and for static or low-stress door seals. Kalrez 8705 is designed for seal locations in the direct path of UV or plasma radiation, such as quartz windows and tubes, and for low sticking.
Greene Tweed and Precision Polymer Engineering use the same logic in their own naming: Chemraz XPE is published for O2 plasma and CF4 plasma resistance and for ozone and fluorine plasmas; Chemraz G20 for fluorine plasma, NF3 clean, forelines and pendulum valves; Perlast G65HP is described as radical-plasma resistant and Perlast G7HA as high-temperature and plasma resistant.
| Grade | Colour | Hardness (Shore A) | Max service temperature | Compression set, 70 h at 204 °C (ASTM D395B) |
|---|---|---|---|---|
| 9600 | Olive-green | 70 | 315 °C | 15% |
| 9500 | Tan | 76 | 310 °C | 20% |
| 9300 | Brown | 77 | 300 °C | 25% |
| 9100 | Amber | 70 | 300 °C | 18% |
| 8002 | Clear | 69 | 275 °C | 12% |
| 8705 | Black | 77 | 327 °C | 24% |
DuPont labels these as typical properties, not specification values. Lower compression set means the ring keeps more of its sealing force after heat soak.
Chemraz grades and their published service range
Greene Tweed publishes one overview that spans dry-process and wet-process Chemraz grades. The overview separates dry-process grades from wet-process grades, and one wet grade (551) is positioned for standardising on a single material.
| Grade | Service temperature | Published use |
|---|---|---|
| 657 | −18 to 280 °C, excursions to 300 °C | Dry process, many seal types |
| E38 | −20 to 260 °C | Bonded gate and chamber seals |
| XPE | Up to 280 °C | O2 plasma and CF4 plasma resistance; ozone and fluorine plasmas |
| 629 | −20 to 260 °C | H2, O2 and fluorine environments |
| G20 | −14 to 293 °C | Fluorine plasma, NF3 clean, forelines, remote plasma unit valves, pendulum valves |
| 513 | −30 to 220 °C | Universal dry-process grade: door, window and lid seals, KF fittings |
| XRZ | Up to 300 °C | Fluorine-plasma deposition, gate and isolator valves |
| XCD | Up to 300 °C | High-temperature chamber seals near wafer heaters, low sticking |
| 663 | −40 to 180 °C | Low-temperature seals, ESC, vacuum |
| 520 | −30 to 220 °C | Dry process with higher sealing loads |
| 550 | −30 to 220 °C | General purpose |
| 592 | −28 to 218 °C | Inert mineral filler for plasma-attack resistance |
| 551 | −12 to 316 °C | Wet and aqueous processes; single-material standardisation |
| 570 | −30 to 220 °C | Wet processes: acids, solvents, ultrapure water |
| 555 | −12 to 316 °C | Sub-fab: acids, caustics, aldehydes, esters, ethers, aromatics, hot water and steam, amines, methanol, ketones, MTBE |
Source: Greene Tweed Chemraz FFKM overview. Chemraz is a Greene Tweed trademark.
Perlast grades by temperature and purpose
Precision Polymer Engineering lists its Perlast FFKM grades by hardness and temperature range. Several pair a high ceiling with a specific job: G77X for the highest temperature (−15 to +350 °C), G7HA for high temperature with plasma resistance, G65HP for radical plasma, G67P for high purity, G70CR for plasma resistance combined with a low-temperature limit of −42 °C, and G90LT and G75LT for low-temperature service down to −46 °C.
| Grade | Hardness | Temperature range | Positioning |
|---|---|---|---|
| G77X | 77 | −15 to +350 °C | Highest-temperature grade |
| G7HA (Helios) | 66 | −15 to +310 °C | High temperature and plasma resistant |
| G65HP | 65 | −15 to +260 °C | Radical plasma resistant |
| G67P | 65 | −15 to +275 °C | High purity |
| G70CR | 62 | −42 to +260 °C | Plasma resistant, low temperature |
| G90LT | 88 | −46 to +275 °C | Low temperature |
| G75LT | 75 | −46 to +250 °C | Low temperature |
| G74S | 74 | −15 to +260 °C | FDA, USP VI and 3A compliant |
Source: Precision Polymer Engineering, high-temperature elastomers page. Perlast is a Precision Polymer Engineering trademark. PPE also lists compression set and thermal degradation among the failure modes of seals in high-temperature service.
Wet processes and sub-fab lines are a different question
A dry-process grade is chosen against plasma and gas chemistry. A wet-process or sub-fab seal sees liquids and hot vapors: Greene Tweed positions Chemraz 570 for acids, solvents and ultrapure water, and Chemraz 555 for the broader sub-fab list of acids, caustics, aldehydes, esters, ethers, aromatics, hot water and steam, amines, methanol, ketones and MTBE. DuPont lists seals for heat-traced sub-fab foreline and exhaust lines among typical Kalrez applications. Treat the fluid list and its temperature as the primary input for these seals instead of the plasma data above.
Step 4: size and ordering
Once the compound is chosen, the ring is specified by its AS568 dash number, which fixes inside diameter and cross-section. MST quotes FFKM O-rings by request, so the quote is where the grade, the manufacturer and the supply channel are written down against your size. Typical request lines are the AS568-128 FFKM O-ring (37.77 mm inside diameter, 2.62 mm cross-section), the AS568-214 and AS568-222 FFKM O-rings for 3.53 mm cross-section seals, and the AS568-325 for 5.33 mm cross-section seals.
The dimensions of each dash number, and why rings with the same inside diameter are not interchangeable, are in the AS568-128 dimensions guide listed below.
Frequently asked questions
What temperature can an FFKM O-ring handle in a semiconductor tool?
It depends on the grade. Published maximum service temperatures include Kalrez 9600 at 315 °C, Kalrez 9500 at 310 °C, Chemraz 657 at 280 °C with excursions to 300 °C, Chemraz G20 at 293 °C and Perlast G77X at +350 °C. Low-temperature grades such as Chemraz 663 (−40 to 180 °C) and Perlast G90LT (−46 to +275 °C) trade ceiling for cold flexibility.
When is FFKM needed instead of FKM?
Parker lists a general service range of about −26 to +205 °C for FKM. Processes above that range, or with fluorine, oxygen or NF3 plasma and aggressive wet chemistry, are the usual reasons to move to FFKM. The FFKM versus FKM guide compares the two in detail.
Which Kalrez grade does DuPont suggest for PECVD or PEALD?
DuPont suggests Kalrez 9600 for PECVD and PEALD (275 to 310 °C). For HDPCVD it suggests 9100 or 9500, and for dielectric etch it suggests 9300.
Which FFKM grades are published for wet chemistry?
Greene Tweed positions Chemraz 570 for acids, solvents and ultrapure water, and Chemraz 555 for a long sub-fab list that includes caustics, aldehydes, hot water and steam, amines and ketones. Chemraz 551 is positioned for wet and aqueous processes and single-material standardisation.
Is a Kalrez grade interchangeable with a Chemraz or Perlast grade?
No grade is a drop-in replacement for another. The three manufacturers formulate and test differently, and each publishes its own temperature range and chemistry list, so this page lists data by manufacturer and does not claim equivalence.
How do I request an FFKM O-ring quote from MST?
Send the AS568 dash number, the process step, the seal location, the maximum temperature and the chemistry through the quote form. MST is a distributor and technical sourcing partner, and the quote states the manufacturer, grade and supply channel.
Request a quote
Send the AS568 size, process step, seal location, temperature and chemistry. MST, as distributor and technical sourcing partner, replies with the candidate grades, manufacturer and supply channel. Kalrez is a trademark of DuPont, Chemraz of Greene Tweed and Perlast of Precision Polymer Engineering; all trademarks belong to their owners.
Request a quoteRelated pages
Sources
- DuPont Kalrez Semicon Product Selector Guide, Plasma Processes (KZE-A40111-00-A0422, June 2022)
- Greene Tweed Chemraz FFKM overview
- Precision Polymer Engineering, high-temperature elastomers (Perlast)
- Parker O-Ring Handbook ORD 5700
Values are taken from the manufacturer documents above, checked 2026-10-27. Request a quote for current price and availability. MST is a distributor; products are made by the manufacturers named.