dry cleaning (plasma)

Dry cleaning uses plasma-based processes to remove organic contamination and residues without wet chemicals. **Mechanism**: Plasma generates reactive species (oxygen radicals, ions) that react with organics, converting them to volatile products (CO2, H2O). **Common plasmas**: O2 plasma (ashing), H2 plasma (native oxide removal), N2/H2 (gentle clean), Ar (sputtering). **Applications**: Photoresist ashing and stripping, post-etch residue removal, surface preparation, descum. **Advantages**: No wet chemical waste, environmentally friendly, can reach small features, vacuum compatible. **Photoresist ashing**: O2 plasma converts photoresist to CO2 and H2O. High throughput. May damage some materials. **Residue removal**: Post-etch polymer removal, sidewall clean. Critical for high aspect ratio features. **Downstream plasma**: Remote plasma generation reduces damage to sensitive devices. **Damage concerns**: Plasma can damage gate oxides, introduce charging. Careful recipe required for sensitive structures. **Integration**: Often used in combination with wet cleans for complete contamination removal. **Equipment**: Plasma asher (barrel or downstream), RIE-style tools for more control.