microroughness

**Microroughness** is the **surface height variation at spatial wavelengths below ~1 µm (typically 0.01-10 µm)** — characterizing the atomic-scale and near-atomic-scale surface texture that affects interface quality, gate oxide reliability, and carrier mobility in semiconductor devices. **Microroughness Measurement** - **AFM**: Atomic Force Microscopy — the primary tool for measuring microroughness at nanometer resolution. - **Rq (RMS)**: Root Mean Square roughness — $R_q = sqrt{frac{1}{N}sum_i (z_i - ar{z})^2}$ — the standard metric. - **Ra**: Average roughness — $R_a = frac{1}{N}sum_i |z_i - ar{z}|$ — less sensitive to outliers. - **Scan Size**: Measured in 1×1 µm² or 10×10 µm² areas — roughness values depend on scan size. **Why It Matters** - **Gate Oxide**: Surface roughness at the Si/SiO₂ interface degrades gate oxide reliability and increases leakage. - **Carrier Mobility**: Interface roughness scattering reduces carrier mobility — critical for advanced transistors. - **Bonding**: Wafer bonding (for 3D integration) requires sub-nm roughness — rough surfaces don't bond. **Microroughness** is **the atomic-scale terrain** — surface texture at the smallest scales that affects device performance, oxide quality, and wafer bonding.