Emissions & Abatement
Semiconductor fabs use hundreds of chemicals and process gases — many of which are toxic, corrosive, or potent greenhouse gases. Managing emissions is not just an environmental compliance requirement, but a core part of fab safety, sustainability, and community acceptance. Abatement systems and cleaner chemistries are increasingly critical as fabs scale in both size and complexity.
Major Emission Sources
- Process Gases: Perfluorocarbons (PFCs), NF3, SF6, and others used in etching and cleaning can remain in the atmosphere for thousands of years.
- Volatile Organic Compounds (VOCs): Emitted from photoresists, solvents, and coatings used in lithography.
- Acidic & Basic Exhaust: From wet etching and cleaning processes (e.g., HCl, HF, NH3 vapors).
- Particulates & Metals: Generated during deposition, etching, and CMP processes.
- Combustion Emissions: From backup generators, thermal oxidizers, and boilers.
General Greenhouse Gases
These emissions are not unique to semiconductor fabs but result from the enormous electricity and thermal energy demands of fabrication:
- Carbon Dioxide (CO2): The largest by volume. Generated indirectly via grid electricity and directly from backup boilers or generators.
- Methane (CH4): Mostly indirect, associated with upstream natural gas extraction and transmission losses for electricity/heat supply.
- Nitrous Oxide (N2O): Minor source in fabs, primarily tied to combustion, though occasionally present in plasma processes.
Because fabs often consume hundreds of megawatts of continuous power, their Scope 2 CO2 footprint is immense, linking fab emissions closely to the carbon intensity of regional electricity grids.
High-GWP Process Gases
These gases are unique to semiconductor processing and, molecule-for-molecule, far more climate-damaging than CO2:
- Perfluorocarbons (PFCs): CF4, C2F6, C3F8 — used in plasma etching and chamber cleaning; GWPs > 7,000.
- Nitrogen Trifluoride (NF3): Widely used in chamber cleaning; GWP ~17,000.
- Sulfur Hexafluoride (SF6): Used in etching; GWP ~23,500.
- Hydrofluorocarbons (HFCs): CHF3, CH2F2 — used in etching and deposition; GWPs range 1,000–12,000.
Emissions in Fabs: Sources, Impact & Abatement
| Gas | Category | Main Source in Fabs | Global Warming Potential (GWP) | Typical Abatement Method |
|---|---|---|---|---|
| CO2 | General GHG | Grid electricity, boilers, backup generators | 1 (baseline) | Energy efficiency, renewable PPAs, onsite microgrids |
| CH4 (Methane) | General GHG | Upstream natural gas leakage (indirect) | ~28–34 | Switch to renewables, reduce reliance on fossil fuels |
| N2O | General GHG | Combustion, some plasma processes | ~265 | Optimized combustion, catalytic reduction |
| CF4 (Carbon Tetrafluoride) | Process Gas (PFC) | Plasma etching, chamber cleaning | ~7,390 | Point-of-use plasma scrubbers, gas recapture |
| C2F6 (Hexafluoroethane) | Process Gas (PFC) | Etching, cleaning | ~12,200 | Thermal oxidizers, alternative chemistries |
| NF3 (Nitrogen Trifluoride) | Process Gas | CVD chamber cleaning | ~17,200 | High-efficiency abatement, gas recapture |
| SF6 (Sulfur Hexafluoride) | Process Gas | Etching (especially MEMS) | ~23,500 | Plasma scrubbers, gas substitution |
| CHF3 (Fluoroform) | Process Gas (HFC) | Etching, deposition | ~1,240 | Point-of-use abatement, chemical substitution |
| CH2F2 (Difluoromethane) | Process Gas (HFC) | Etching, cleaning | ~675 | Catalytic abatement, reduced gas flow |
Abatement Methods
- Point-of-Use Abatement: Thermal oxidizers and plasma scrubbers destroy PFCs, NF3, SF6 before release.
- Wet Scrubbers: Neutralize acidic and basic gases with chemical solutions.
- Adsorption Systems: Activated carbon filters to capture VOCs and organics.
- Alternative Chemistries: Substituting NF3 cleaning with lower-GWP (global warming potential) gases like fluoronitriles.
- Energy Decarbonization: Transition to renewable PPAs, onsite solar + BESS microgrids to cut CO2 emissions.
- Efficiency & Recycling: Gas recapture systems for NF3 and PFCs; process optimization to reduce gas use intensity.
Strategic Considerations
- Regulatory Compliance: Fabs must meet strict EPA, EU REACH, and local environmental regulations for air emissions.
- Carbon Footprint: Scope 1 emissions (direct gases) are a growing focus for ESG reporting in semiconductor companies.
- Innovation Drivers: Industry is investing in low-GWP alternatives and abatement efficiency improvements.
- Community Trust: Transparent emission reporting is critical for public acceptance of new fab projects.
Case Examples
- Intel: Reports >90% abatement efficiency for high-GWP gases using point-of-use systems.
- TSMC: Introduced fluoronitrile gases in etching as NF3 alternatives to cut GHG impact.
- Samsung: Developed closed-loop argon recycling systems, reducing both emissions and cost.