photoresist

Photoresist is a light-sensitive polymer that changes solubility when exposed to light, enabling pattern transfer in lithography. **Types**: **Positive resist**: Exposed areas become soluble, removed in developer. **Negative resist**: Exposed areas become insoluble, unexposed removed. **Chemistry**: Photoactive compound (PAC), polymer matrix, solvent. **DUV resists**: Chemically amplified - photoacid generator creates acid, acid catalyzes change during PEB. **Mechanism**: Light exposure triggers chemical reaction changing dissolution rate in developer. **Application**: Spin-coated onto wafer as liquid, dried to form thin film. **Thickness**: Typically 50nm-500nm depending on application. Thinner for high resolution. **Sensitivity**: Energy required for exposure. Balance sensitivity vs resolution vs line edge roughness. **Shelf life**: Limited lifetime. Stored in controlled conditions. **Vendors**: JSR, TOK, Shin-Etsu, DuPont, Merck. **EUV resist**: Specific formulations for 13.5nm EUV exposure. Ongoing development challenge. **Cost**: High-performance resists expensive. Significant consumables cost.