Smooth side wall
This shows an example of vertical mesa etching on a ø3 inch VCSEL (Vertical Cavity Surface Emitting Lasers) wafer. The etching rate was 320 nm / min and the selectivity to the SiN mask was 25:1. By observing the clear DBR (Distributed Bragg Reflector) contrast, it is known that the etched side wall is very smooth.