Optimization of wet thermal oxidation for 940 nm VCSELs using simplified and full epitaxial structures wafers

Abstract

This study presents the optimization of the wet thermal oxidation process for 940 nm vertical cavity surface emitting lasers (VCSELs) using both simplified and full epitaxial (epi) structure wafers. Through design of experiments (DOE), key process parameters were systematically investigated. A simplified epi structure wafer was used to develop an oxidation window, which was then applied to full epi structure wafers for validation. Infrared (IR) microscopy and wafer-level mapping confirmed consistent aperture formation, with an average diameter of 10.09 µm and within-wafer uniformity below 10%. Furthermore, analysis across multiple wafer lots and epi batches revealed significant cross-batch oxidation rate variation, highlighting the importance of batch-specific calibration using pilot wafers. The proposed strategy improves aperture control, enhances process reproducibility, and supports stable mass production of high-performance VCSELs.