One wrong O-ring material choice leads to gas leaks, particle contamination, and equipment downtime. Material selection mistakes happen more often than expected.
OHI Tech supplies Viton, Kalrez, and Chemraz O-rings across semiconductor fabs and has directly observed what goes wrong and when. Here are the criteria.
Bottom Line: Viton in High-Temperature Plasma Processes Is Dangerous
Viton degrades rapidly above its 200°C limit. Using Viton in ICP etch or ALD (200–350°C) processes causes premature O-ring failure and gas leakage.
These environments require Kalrez 6375 grade or higher. The price difference is significant, but compared to one equipment downtime event, Kalrez is far more economical.
Viton vs Kalrez vs Chemraz Comparison
| Parameter | Viton (FKM) | Kalrez (FFKM) | Chemraz (FFKM) |
|---|---|---|---|
| Heat resistance | -20~200°C | -20~327°C | -20~316°C |
| Chemical resistance | Hydrocarbons, acids, oils | Nearly all chemicals | Nearly all chemicals |
| Plasma resistance | Medium | Very high | Very high |
| Compression set | Medium | Low | Lower than Kalrez in select grades |
| Price | Low | Very high | High (slightly below Kalrez) |
| Primary use | PVD, low-temp CVD | ICP, ALD, corrosive gases | High-temp, high-pressure sealing |
O-Ring Material Selection by Process
| Process | Temperature | Key Gases | Recommended Material |
|---|---|---|---|
| Plasma etch (CCP) | 80–150°C | Cl₂, HBr, CF₄ | Kalrez, Chemraz |
| Plasma etch (ICP) | 150–250°C | SF₆, NF₃ | Kalrez 6375+ |
| PECVD | 200–400°C | SiH₄, NH₃ | Kalrez 6221 |
| Ion implant | RT–100°C | BF₃, AsH₃ | Kalrez |
| Sputtering (PVD) | 100–200°C | Ar, N₂ | Viton or Kalrez |
| ALD | 200–350°C | TMA, H₂O | Kalrez 6375+ |
The 3 Most Common O-Ring Selection Mistakes
Mistake 1: Viton in ICP etch chambers Above 250°C, Viton degrades and fragments contaminate the chamber. Replace with Kalrez 6375+.
Mistake 2: Checking only inner diameter (ID) O-ring dimensions require all three: ID (inner diameter), OD (outer diameter), CS (cross-section diameter). Wrong CS means insufficient sealing force.
Mistake 3: Skipping preventive replacement Skipping O-ring replacement at PM intervals allows degraded O-rings to generate particles. Even if they look intact, preventive replacement is the rule.
O-Ring Management Tips
- Storage: 18–25°C cool dark place, away from UV, ozone, and heat sources
- Compression: keep below 25% (over-compression = shortened life)
- PM replacement: quarterly as standard (every 2 months for high-temp processes)
- Always confirm 3 dimensions: ID × OD × CS
FAQ
Q1. Kalrez or Chemraz — which should I choose? Kalrez is the standard for most semiconductor processes. For high-temperature, high-pressure applications where compression set is critical, certain Chemraz grades may outperform. Share your process conditions and we will recommend the optimal grade.
Q2. How do I identify the material of O-rings currently in use? Check the surface marking or part number. If unmarked, send a sample and OHI Tech will analyze the material and recommend alternatives.
Q3. Are small-quantity and rush orders available? Yes — single-piece orders and rush supply are both possible. Share the dimensions (ID × OD × CS) and material grade and we will confirm stock immediately. Contact: jino.kim@ohitech.co.kr