Solvent Recovery

Solvent recovery recycles and reuses solvents from semiconductor cleaning and lithography processes, reducing chemical costs and waste generation. Primary solvents: (1) IPA (isopropyl alcohol)—wafer drying, cleaning; (2) PGMEA—photoresist solvent, edge bead remover; (3) Acetone—resist stripping, cleaning; (4) NMP (N-methyl-2-pyrrolidone)—resist stripping; (5) Cyclohexanone—developer solvent. Recovery methods: (1) Distillation—heat to separate solvents by boiling point, most common method; (2) Fractional distillation—multi-stage for mixed solvent separation; (3) Vacuum distillation—lower temperatures for heat-sensitive solvents; (4) Membrane separation—pervaporation for solvent-water mixtures; (5) Activated carbon adsorption—for dilute solvent recovery from exhaust air. Recovery process: collect spent solvent → test purity → distill → quality check → return to process or blend with fresh. Purity requirements: recovered solvent must meet semiconductor-grade specifications (metals <1 ppb, particles, moisture). On-site vs. off-site: large fabs may operate on-site recovery systems; smaller fabs contract solvent recycling services. Recovery rates: 70-90% typical for distillation depending on contamination level. Economics: cost savings from reduced virgin solvent purchase plus reduced hazardous waste disposal. Environmental: reduces volatile organic compound (VOC) emissions and waste generation. Integration: dedicated piping for spent vs. recovered solvent, quality monitoring. Part of comprehensive sustainability strategy in modern semiconductor manufacturing.