1. Wipe Selection: Match to Cleanroom Task & ESD Sensitivity
- For Wafer/Optic Cleaning:
Choose ultra-low-lint anti-static microfiber wipes (0.1μm fiber diameter) pre-wet with 99.9% electronic-grade IPA. Microfiber traps sub-micron particles (down to 0.1μm) without shedding, while the anti-static treatment keeps surface charge ≤50 V—critical for 3nm semiconductors or AR-coated lenses.
- For Chamber/Equipment Maintenance:
Opt for conductive anti-static polyester wipes (10³–10⁶ Ω) for high-ESD-risk tasks (e.g., CVD/PVD chamber cleaning). Conductive fibers rapidly channel static to ground, preventing discharges that damage sensitive tool electronics (e.g., sensor modules).
- For Dry Dust Removal:
Use dry anti-static cellulose-polyester blend wipes—the blend’s low-outgassing property avoids contaminating cleanroom air, and anti-static additives prevent dust from reattaching to surfaces (e.g., reticle pods).
- Tip: Verify wipe certification (e.g., ISO 14644-1 Class 3, ANSI/ESD S20.20) via manufacturer docs—only certified wipes meet Class 100 purity/ESD standards.
2. Wipe Handling: Minimize Particle Generation & ESD Risks
- Open Wipes in Mini-Environments:
Retrieve wipes from sealed, Class 100-compatible packaging inside a laminar flow hood or glove box. Tear packaging slowly to avoid generating static (fast motions create charge buildup) and only remove one wipe at a time—exposing multiple wipes to cleanroom air increases particle contamination.
- Hold Wipes by Edges Only:
Grip anti-static wipes by their outer edges (not the cleaning surface) to avoid transferring skin oils or fibers. For small wipes (e.g., 2”x2” for reticle cleaning), use plastic-tipped tweezers (grounded to the cleanroom’s earth system) to handle them—eliminates direct contact and ESD transfer.
- Fold for Multi-Use Coverage:
Fold wipes into a 4-layer pad to create multiple “clean zones.” Use one layer per surface (e.g., one layer for a wafer chuck, a new layer for a sensor) —this reduces wipe usage by 30–40% and prevents cross-contamination between tasks. Avoid refolding soiled layers inward (traps particles).
3. Cleaning Techniques: Tailored to Class 100 Surfaces
- Wafer Chucks/Reticles:
Wipe in slow, linear strokes (parallel to wafer/reticle edges) to avoid pushing particles into precision grooves. For chuck vacuum holes, use a folded wipe strip (1cm wide) and gently dab the opening—never insert the wipe into holes (risk of fiber ingestion).
- Optical Tools (EUV Lenses, Laser Mirrors):
Dab, don’t rub: Press the anti-static wipe lightly against the optical surface for 1–2 seconds to lift residue, then lift straight up. Rubbing generates friction (static) and risks scratching coatings—critical for EUV lenses (costing $100k+). Follow with a dry anti-static wipe to blot excess solvent.
- Equipment Interfaces (USB Ports, Sensor Connectors):
Use mini anti-static wipes wrapped around a non-metallic probe to clean narrow interfaces. Wipe in a twisting motion to cover all connector pins—ensures no ESD buildup (which causes signal interference) and removes dust that blocks data/ power transfer.
4. Post-Use Practices: Maintain Cleanroom Integrity
- Dispose of Wipes Immediately:
Place used anti-static wipes in sealed, Class 100-approved waste bags (labeled “ESD-Safe Waste”) immediately after use. Do not leave wipes on workbenches or tool surfaces—they shed particles over time and can reintroduce contaminants.
- Validate Post-Clean Conditions:
After cleaning, use a portable particle counter to verify surface particle counts (≤1 particle ≥0.1μm per ft²) and an ESD field meter to check surface charge (≤50 V). Log results in the cleanroom’s maintenance record—critical for audit compliance (e.g., SEMI S2).
- Store Wipes Properly:
Keep unused anti-static wipes in temperature- and humidity-controlled cabinets (20–24°C, 30–50% RH). Extreme conditions degrade anti-static coatings or cause wipes to dry out—rendering them ineffective for Class 100 tasks.