porosimetry

**Porosimetry** is a **metrology technique for characterizing the pore structure of materials** — measuring pore size distribution, total porosity, specific surface area, and pore connectivity, critical for porous low-k dielectrics in advanced semiconductor interconnects. **Key Porosimetry Methods** - **Ellipsometric Porosimetry (EP)**: Measures refractive index changes during controlled solvent adsorption/desorption. - **Positron Annihilation**: Positronium lifetime maps pore sizes at the sub-nm to nm scale. - **Small-Angle X-Ray Scattering (SAXS)**: Scattering from pore-matrix contrast reveals pore statistics. - **Adsorption Isotherms**: Gas/vapor uptake vs. pressure gives BET surface area and BJH pore distribution. **Why It Matters** - **Low-k Dielectrics**: Porosity is engineered into low-k films to reduce $k$ — porosimetry verifies the pore structure. - **Pore Sealing**: Barrier integrity depends on pores being sealed before metal deposition. - **Mechanical Impact**: Porosity reduces Young's modulus — porosimetry data feeds mechanical reliability models. **Porosimetry** is **measuring the void space** — characterizing the invisible pore network that gives low-k dielectrics their electrical properties.