Fabrication of submicron-sized features in InP/InGaAsP/AlGaInAs quantum well heterostructures by optimized inductively coupled plasma etching with Cl2/Ar/N2 chemistry

Abstract

Inductively coupled plasma dry etching for the fabrication of fine-pitch patterns in a wide range of InP-based materials has been developed. The effect of plasma chemistry (the N2 content in the total Cl2/Ar/N2 gas mixture) on the degree of undercut in the sidewall profile and surface morphology has been studied. Optimization of the etch process conditions produces strong passivation effects on the sidewalls, together with a highly anisotropic process, while still maintaining a good etch rate (560–730 nm/min). Single-step etching using hydrogen silsesquioxane as a resist/hard-mask resulted in high aspect ratio features being obtained (up to 30:1). Low plasma excitation power (inductively coupled plasma machine operating power of 400 W) and moderate ion energy (rf power of 120 W) were utilized to minimize etch-induced damage and provide low scattering losses. Low-loss (<0.3 dB/mm) optical ridge waveguides and high reflectivity and high-wavelength selectivity (Δλ=2 nm) results with 236 nm period sidewall gratings were demonstrated experimentally.