Traditional in-situ reflectometry sensing at blue (405 nm), red (630 nm) and NIR (950 nm) wavelengths cannot resolve variations in InAlGaN surface roughness or layer thickness with the precision necessary for effective in situ process control. LayTec has developed in situ reflectance metrology at 280 nm to address this need.

We report successful application of in situ UV reflect-ometry and curvature, distinguishing between various phases of strain relaxation and surface relaxation during non-pseudomorphic growth of Al_0.5Ga_0.5N on AlN/sapphire. Results were validated by XRD, TEM and AFM. Results illuminate the influence of reduced TDD on relaxation effects during growth of UVA and UVB LED structures.

10A.3 Final.2025

Abstract
VCSEL layer structures are among the most complicated ones in compound semiconductor device production. Re-establishing growth conditions for a new epi campaign after chamber maintenance can be challenging and time consuming. This work is about how to tackle this challenge by applying in-situ optical metrology during growth and processing of GaAs-based VCSEL devices as well as post-growth ex-situ wafer mapping. We demonstrate how to efficiently combine in-situ and ex-situ white light reflectance (WLR) measurements and modelling in order to increase the target wavelength accuracy.
Fitting the in-situ reflectance transient or the ex-situ WLR is used to generate a target reflectance trace for the subsequent plasma etching of the VCSEL mesa enabling automated end pointing.