Semiconductor cleanrooms (ISO Class 1–5) demand ultra-pure, static-controlled cleaning to protect 3nm–7nm wafers, EUV scanners, and deposition chambers from sub-micron contaminants. Pre-wet cleanroom wipes—pre-impregnated with high-purity solvents (99.9% IPA, deionized water) or anti-static agents—deliver consistent, residue-free cleaning critical for reducing wafer defects. Below is a step-by-step guide tailored to semiconductor cleanroom workflows.
1. Pre-Use Preparation: Ensure Wipe Compatibility & Cleanroom Compliance
Semiconductor cleanrooms have strict standards—start by verifying wipe suitability and preparing the environment:
- Wipe Selection Criteria:
- ISO Class Matching: Choose wipes certified to the cleanroom’s ISO class (e.g., ISO Class 1 wipes for EUV tool cleaning, ISO Class 5 for general wafer handling areas). Verify via manufacturer test reports (particle count ≤1 particle ≥0.1μm per wipe).
- Solvent Compatibility: Select pre-wet wipes based on the target surface:
- Wafer Chucks/Reticles: Deionized water-based pre-wet wipes (avoids metal ion contamination from IPA).
- CVD/PVD Chambers: 99.9% electronic-grade IPA pre-wet wipes (dissolves sputtered metal residues).
- ESD-Sensitive Surfaces: Anti-static pre-wet wipes (surface resistance ≤10⁹ Ω) for sensor modules or control boards.
- Environment Prep:
- Don cleanroom PPE (lint-free gown, gloves, face mask) and ground yourself via an ESD wrist strap.
- Retrieve wipes from sealed, cleanroom-grade packaging inside a laminar flow hood to avoid airborne particle contamination.
2. Step-by-Step Cleaning Process: Tailored to Semiconductor Surfaces
Different semiconductor surfaces require specific techniques to avoid damage and ensure purity:
A. Wafer & Reticle Cleaning
- Action:
- Hold the pre-wet wipe by its edges (use plastic-tipped tweezers for reticles) to avoid direct contact.
- Wipe wafers in slow, radial strokes (from center to edge) to prevent particle accumulation at the edge. For reticles, use gentle linear strokes parallel to the pattern to avoid scratching the photomask.
- Use one wipe per wafer/reticle—never reuse wipes (risk of cross-contamination).
- Key Note: Use deionized water pre-wet wipes for bare wafers; avoid IPA (can leave ionic residues that affect doping).
B. EUV Scanner & Optical Component Cleaning
- Action:
- Use lens-safe pre-wet wipes (70% IPA + microfiber) for EUV mirrors/lenses—99% IPA degrades anti-reflective coatings.
- Dab, don’t wipe: Press the wipe lightly against the optical surface for 1–2 seconds to lift dust/residue, then lift straight up. Circular motions cause coating scratches.
- Follow with a dry, ultra-low-lint pre-wet wipe to blot excess solvent—prevents streaks that distort laser alignment.
C. CVD/PVD Chamber Cleaning
- Action:
- Use high-density, solvent-resistant pre-wet wipes (99.9% IPA + polyester) to clean chamber walls and targets.
- Wipe in overlapping linear strokes (top-to-bottom) to remove sputtered metal residues. For vacuum ports, fold the wipe into a narrow strip to reach inside without fiber shedding.
- Dispose of used wipes immediately in sealed, cleanroom-approved waste bags to prevent solvent vapor buildup.
3. Post-Clean Validation: Ensure Purity & Compliance
Semiconductor manufacturing requires traceable, verifiable cleaning—validate results to meet quality standards:
- Particle Counting: Use a portable particle counter to measure surface particles post-clean (≤1 particle ≥0.1μm/ft² for ISO Class 1 areas).
- Residue Testing: For critical surfaces (e.g., reticles), perform FTIR (Fourier Transform Infrared) spectroscopy to confirm no solvent or fiber residues.
- Documentation: Log wipe lot number, cleaning date/time, surface cleaned, operator ID, and validation results in the cleanroom’s electronic record system (compliant with SEMI S2 standards).
4. Critical Best Practices for Semiconductor Cleanrooms
- Avoid Over-Saturation: Pre-wet wipes should be “damp, not dripping”—excess solvent can pool in chamber crevices or leave residues on wafers.
- Limit Wipe Exposure: Open only one wipe package at a time; exposed wipes absorb airborne particles within 2–3 minutes.
- Storage Controls: Keep unused pre-wet wipes in temperature (20–22°C) and humidity (35–45%) controlled cabinets—extremes degrade solvent purity or cause wipe drying.