in-situ ellipsometry

**In-Situ Ellipsometry** is the **real-time application of ellipsometry during a thin-film deposition or processing step** — monitoring film thickness, growth rate, composition, and optical properties as the process occurs, enabling real-time process control. **How Does In-Situ Ellipsometry Work?** - **Optical Ports**: Polarized light enters and exits the deposition chamber through strain-free windows. - **Real-Time**: Measure $Psi$ and $Delta$ continuously (1-100 Hz acquisition rate). - **Dynamic Analysis**: Track the trajectory in the $Psi$-$Delta$ plane to determine growth rate and mode. - **Endpoint**: Use real-time thickness to trigger process endpoint (e.g., stop etching at target thickness). **Why It Matters** - **Growth Monitoring**: Observe film nucleation, coalescence, and steady-state growth in real time. - **ALD Monitoring**: Detect each ALD half-cycle and measure per-cycle growth rate. - **Process Control**: Real-time feedback enables closed-loop control of film thickness and composition. **In-Situ Ellipsometry** is **watching the film grow** — measuring optical properties in real time during deposition for ultimate process insight and control.