resputtering

Resputtering is the deliberate removal and redistribution of deposited material by energetic ion bombardment, used to improve step coverage and film quality in PVD processes. **Mechanism**: Substrate bias attracts Ar+ ions (or metal ions in IPVD) that sputter already-deposited material from feature bottoms, redistributing it onto sidewalls. **Net effect**: Material moves from bottom and field areas to sidewalls, improving overall conformality. **Barrier application**: In TaN/Ta barrier deposition, resputtering redistributes barrier material from thick bottom coverage to thin sidewalls, achieving more uniform barrier thickness. **Control**: Wafer bias power controls resputter rate. Must balance deposition and resputtering to avoid excessive material removal. **Etch-back mode**: High bias can create net etch (removing more than depositing). Used for cleaning or overhang removal. **Overhang reduction**: Resputtering can remove excess material accumulated at feature top (overhang), preventing premature closure during subsequent fill. **Corner rounding**: Ion bombardment rounds sharp corners at feature openings, improving subsequent deposition coverage. **Damage risk**: Excessive ion bombardment can damage underlying films or interfaces. Must optimize bias carefully. **Process integration**: Resputtering step often integrated into IPVD deposition recipe as a separate process step with different power/gas settings. **Self-sputtering**: In IPVD, ionized metal atoms can also resputter deposited film when biased.