Semiconductor Critical Chemicals
While elements provide the atomic building blocks of chips, semiconductor fabrication depends just as heavily on critical chemicals. These include acids, bases, solvents, photoresists, and CMP slurries used in cleaning, etching, lithography, and polishing. Their extreme purity requirements, hazardous properties, and regulatory exposure make them both essential and high-risk in the semiconductor supply chain.
Note on Terminology
In the semiconductor industry, the term “process chemicals” is often used broadly to cover both liquid-phase chemistries (acids, bases, solvents) and gaseous compounds used in deposition or etching. On SemiconductorX, we define Critical Chemicals as wet chemistries and solvents, while Process Gases are covered separately. Examples such as silane (SiH4), WF6, and PH3 may appear on both regulatory chemical lists and gas usage lists, depending on context.
Chemical Categories
- Acids & Bases: Hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric acid (H2SO4), ammonia (NH3), potassium hydroxide (KOH) — used for etching, wafer cleaning, and surface treatments.
- Solvents: Isopropyl alcohol (IPA), acetone, N-methyl-2-pyrrolidone (NMP) — used in photoresist stripping, cleaning, and rinse processes.
- Photoresists & Developers: Light-sensitive resins (often PFAS-based) and alkaline developers (e.g., tetramethylammonium hydroxide, TMAH) for photolithography.
- CMP Slurries: Colloidal silica or ceria-based abrasives used for planarization of wafer surfaces.
- Encapsulants & Adhesives: Epoxies and resins used in back-end packaging and die bonding.
Chemical Mapping
| Chemical | Category | Primary Use | Strategic Risk |
|---|---|---|---|
| Hydrofluoric Acid (HF) | Acid | Oxide etching, wafer cleaning | Highly toxic; few producers; critical to front-end steps |
| Sulfuric Acid (H2SO4) | Acid | Photoresist stripping, wafer cleaning | Hazardous handling; global availability but purity is key |
| Ammonia (NH3) | Base | Cleaning, doping atmospheres, nitridation | Produced at scale but requires high purity; energy-intensive |
| Isopropyl Alcohol (IPA) | Solvent | Rinsing, cleaning, drying wafers | Global production; pandemic highlighted fragility of supply |
| NMP (N-methyl-2-pyrrolidone) | Solvent | Photoresist stripping, cleaning | Toxic; increasingly regulated in EU/US |
| Photoresists | Polymer / Chemical Mixture | Pattern transfer during photolithography | PFAS-based; subject to environmental restrictions |
| TMAH (Tetramethylammonium Hydroxide) | Base / Developer | Developing exposed photoresist patterns | Highly toxic; safety incidents common in fabs |
| CMP Slurries | Abrasive Suspensions | Planarization of wafer surfaces | Specialty producers; key to scaling advanced nodes |
Most Strategic Chemicals Today
- Hydrofluoric Acid (HF): Indispensable for etching oxides, yet one of the most hazardous and irreplaceable chemicals in chipmaking.
- Photoresists: PFAS-based materials enabling EUV lithography; under scrutiny for environmental phase-outs.
- TMAH: Critical photoresist developer, but poses serious occupational safety risks.
- CMP Slurries: Bottleneck in advanced-node fabs where precise planarization is mandatory.
- Isopropyl Alcohol (IPA): High-purity IPA demand spikes during fab expansions; pandemic disruptions revealed fragility.
FAQs
- Why are chemicals so important in fabs? – Nearly every wafer step requires cleaning, etching, coating, or polishing, all of which rely on specialized chemicals.
- Which chemicals are most at risk? – HF, photoresists, and TMAH due to toxicity, limited suppliers, and regulatory pressure.
- Are there substitutes for HF or PFAS resists? – Research is underway, but no scalable alternatives yet match their performance in advanced nodes.
- Do chemicals impact environmental policy? – Yes, PFAS bans, greenhouse gas regulations, and hazardous waste disposal rules increasingly shape fab operations.
