Etch rate dynamics during plasma etching

📉 Etch rate dynamics during plasma etching – why fixed etch times aren't enough.

Here’s some new insight from our latest in-situ measurements during the plasma etching of an AlGaAs layer stack. The graph below shows the reflectance evolution at three wavelengths (488 nm, 633 nm, and 950 nm) during the etch process. These Fabry-Perot oscillations (FPOs) are a rich source of real-time information.

🔍 Key takeaway: By analyzing the FPOs, we can extract the etch rate evolution throughout the process – and the result is of paramount importance for ensuring quality during etching. The etch rate varies by more than a factor of two over time. This clearly demonstrates that process control based on fixed etch times is not reliable.

✅ Instead, optical in-situ reflectance monitoring provides the accuracy and adaptability needed. And with multi-wavelength analysis, we gain a powerful advantage:
- Etch rate changes affect all wavelengths similarly
- Temperature effects impact wavelengths differently
This distinction enables precise, nm-level process control.

LayTec’s TRIton^® in-situ metrology system is designed exactly for this: delivering real-time, multi-wavelength reflectance monitoring for accurate and adaptive etch process control.

🤝 These results are part of a collaboration between LayTec and the Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH) within the framework of the HOTSTACK research project, funded by the Investitionsbank Berlin (IBB).