What cleanroom class is required for semiconductor manufacturing?

ISO Standards for Semiconductor Cleanrooms

• ISO Class 3–5 (very stringent)
• Used in photolithography, etching, and wafer patterning, where particles as small as 0.1 microns can cause defects.
• For example, Intel, TSMC, and Samsung fabs often operate at ISO Class 4 or better in critical areas.
• ISO Class 6–7
• Used in less particle-sensitive zones, such as wafer cleaning, coating, and non-critical assembly.
• These areas still maintain strict controls but allow slightly higher particle counts.
• ISO Class 8–9
• Applied in support and gowning areas where operators prepare before entering higher-grade zones.

GMP and Federal Standards

Before ISO 14644, cleanrooms in semiconductor fabs often followed the older US Federal Standard 209E:

• Class 1 and Class 10 (≈ ISO Class 3–4) were used in wafer fabrication lines.
• Class 100 or Class 1000 (≈ ISO Class 5–6) were applied in secondary processing steps.

Even though FS 209E was retired in 2001, the terminology (Class 10, Class 100, etc.) is still widely used in the semiconductor industry.

Practical Example

• Photolithography area: ISO Class 3–4 (Class 1–10 FS209E)
• Wafer cleaning & etching: ISO Class 4–5
• Assembly & packaging: ISO Class 6–7
• Gowning area: ISO Class 8

This tiered system balances cost vs. contamination control, since maintaining an ISO Class 3 environment across an entire fab would be prohibitively expensive.

Conclusion

In summary, semiconductor manufacturing requires ISO Class 3–5 cleanrooms in the most critical stages, with supporting processes running at ISO Class 6–7. This ensures ultra-low contamination levels, allowing manufacturers to produce chips with billions of transistors on nanometer scales.