vapor phase cleaning

Vapor phase cleaning uses heated chemical vapors instead of liquid immersion for surface cleaning and oxide removal. **Principle**: Reactive gas or vapor contacts wafer surface in controlled chamber. No liquid immersion required. **Common chemistries**: HF vapor (oxide removal), IPA vapor (drying), ozone (oxidation), anhydrous HF + alcohol. **Advantages**: Lower chemical consumption, reduced waste, no watermark issues, more uniform processing, single-wafer compatible. **HF vapor process**: HF vapor selectively etches oxide. Water vapor may be co-delivered to control etch. Used for contact etch, native oxide removal. **Selectivity**: Can achieve very high selectivity (oxide vs silicon, oxide vs nitride) with proper vapor chemistry. **Equipment**: Specialized vapor delivery chambers, temperature control, exhaust handling. **Drying applications**: IPA vapor used in Marangoni drying to prevent watermarks. **Challenges**: Uniformity across wafer, process control, particulate contamination in vapor phase. **Trend**: Increasing use for advanced nodes where liquid processing uniformity is challenging.