spin rinse dryer (srd)

Spin rinse dryers (SRDs) spin wafers at high speed while rinsing with DI water and drying with heated nitrogen. **Process sequence**: Rinse phase with DI water spray, then spin-off at high RPM, followed by hot nitrogen purge for final drying. **Principle**: Centrifugal force throws water off wafer surface. N2 purge prevents watermarks and helps evaporate remaining moisture. **RPM**: Rinse at moderate speed, dry spin at 2000-4000+ RPM depending on wafer size. **Clean environment**: Enclosed chamber with HEPA-filtered environment. Prevents particle recontamination. **Batch vs single-wafer**: Batch SRD processes cassette of wafers. Single-wafer tools for tighter control. **Water quality**: UPW required to prevent residue. Final rinse purity critical. **Nitrogen**: Heated, filtered N2 (80-100 C typical) accelerates drying, prevents watermarks. **Watermark concerns**: Water droplet evaporation can leave residues. N2 assist and Marangoni techniques address this. **Process flow**: Follows wet bench processing. Critical final step before next dry process.