Tip Sheet #1

WASTE ORIGINS: Semiconductor Production Processes (Crystal Preparation, Wafer Fabrication, Final Layering, and Cleaning Assembly)
WASTE TYPES: Spent Process Baths, Sludges, Rinse Waters, and Aqueous Metals

WASTE REDUCTION AND RECYCLING OPTIONS:

• Process or equipment modification examples:
• Installing a system (e.g., the CALFRAN process) to reduce pressure of vaporization at cooler temperatures, recycle water by condensing the vapors in another container, and concentrate and precipitate solutes. Waste Savings/Reduction: reduce volume and quantity of aqueous waste solutions by recovering pure water.
• Reducing chrome waste generation by:
  • Treating on-site with caustics and sodium bisulfite to reduce chrome VI liquid to chrome III sludge.
  • Repairing water leaks in process rinse tank to reduce chrome waste.
    Capital Investment: $30,000 for the rain cover, pipe repairs, and on-site treatment system. Waste Savings/Reduction: Savings: $15,000/year in disposal costs, and reduce 95 percent of chrome wastes from 6,000 gallons to two or three drums generated per quarter.
• Raw material substitution examples:
  • Replacing chlorinated solvent baths with a non-hazardous product to reduce, and later eliminate chlorinated solvent use.
• Recycling examples:
  • Converting an open-top still into a closed loop system to recycle Freon 113.
    Costs: $20,000. Waste Savings/Reduction: $57,000/year in disposal and feedstock costs, and reduce waste volume by 85 percent.
  • Using an "Athens" system to reprocess sulfuric acid generated during wafer fabrication operations. The acid is heated to boil off water and other impurities, purified through distillation, and pumped back into wet stations to continue wafer processing. Annual savings/Reductions: $2.9 million from not purchasing sulfuric acid and 28 percent reduction in sulfuric acid generated in 1993.

Sources