single-wafer wet processing

Single-wafer wet processing cleans, rinses, and dries one wafer at a time for tighter process control and uniformity. **Advantages**: Better uniformity (each wafer same fresh chemistry), tighter process control, no cross-contamination between wafers, flexible recipes. **Disadvantages**: Lower throughput, higher cost per wafer, more equipment needed for same capacity. **Process**: Wafer spins while chemicals spray onto surface. Fresh chemistry for each wafer. Followed by rinse and spin dry. **Process modules**: Chemical dispense, rinse, and dry all in one chamber. **Applications**: Critical cleans at advanced nodes, post-etch residue removal, pre-gate clean, any process where batch variation is unacceptable. **Trends**: Increasingly dominant for leading-edge processes. Sub-20nm nodes largely single-wafer. **Chemistry control**: Precise volume, timing, temperature for each wafer. Recipe optimization per wafer. **Megasonic integration**: Can combine single-wafer spin with megasonic for enhanced particle removal. **Cycle time**: 1-3 minutes per wafer typical. Parallel processing needed for throughput. **Equipment**: Tokyo Electron, Lam, Screen, SEMES.