Development of a HBr-Based ICP-RIE Process for Smooth and Anisotropic Etching of III–V Semiconductors

Abstract

This thesis presents the development of a dry etching recipe using hydrogen bromide (HBr) for the fabrication of InP/InGaAs-based heterostructures. The recipe aims to replace a methane-based process to avoid chamber contamination while maintaining a highly directional etch profiles and smooth surfaces. HBr in particular was selected as an alternative etching chemistry due to its potential to achieve desired result, while also offering reduced plasma-induced damage compared to conventional processes. Though systematic research and optimization of process parameters such as, pressure, temperature, ICPpower, RF-power, and flowrate, a recipe was developed that produces sidewall-angles up to 88.9 degrees and smooth surfaces. A hard mask material combination of Ni and Cr was found to be optimal which yields a selectivity up to 22:1, and a Si carrier should be used to add a passivation mechanism to the etching recipe. The developed recipe has successfully been applied to Fermi-level managed barrier diodes (FMBD), resonant-tunnelling diodes (RTD), and heterostructure barrier varactors (HBV), demonstrating consistent etch-performance across different InP/InGaAs-layer stacks. Electrical measurements confirmed functionality of devices fabricated using the new process, validating the suitability as a replacement for the methane-based dry etch process recipe.