infrared ellipsometry

**Infrared Ellipsometry** is the **application of spectroscopic ellipsometry in the infrared wavelength range (2-50 μm)** — measuring vibrational absorption, free carrier concentration, and phonon properties that are invisible to visible-wavelength ellipsometry. **What Does IR Ellipsometry Measure?** - **Vibrational Bonds**: Si-O, Si-N, C-H, and other molecular vibrations are in the IR range. - **Free Carriers**: Drude absorption from free carriers allows measurement of carrier concentration and mobility. - **Phonons**: Lattice vibrations (reststrahlen bands) characterize crystal quality and composition. - **Dielectric Function**: Full complex dielectric function $epsilon(omega)$ in the IR. **Why It Matters** - **Chemical Bonding**: Identifies bonding environment in SiO$_2$, SiNx, low-k dielectrics, and organic films. - **Doping**: Measures free carrier concentration through Drude absorption (non-contact, non-destructive alternative to Hall). - **Low-k Dielectrics**: Characterizes porosity and bonding in porous low-k films through IR absorption. **IR Ellipsometry** is **ellipsometry in the vibrational world** — using infrared light to probe chemical bonds and free carriers that visible light cannot see.