Reactive ion etching-induced damage studies and application to self-aligned InP/InGaAs heterojunction bipolar transistor technology

Abstract

A self-aligned InP/InGaAs heterojunction bipolar transistor (HBT) technology which makes use of a combination of CH4/H2/Ar reactive ion etching (RIE) and wet chemical etching to reduce the base-emitter separation is described. Surface damage and contamination induced by the CH4/H2/Ar discharge can, if not properly removed, degrade the current gain or lead to device failure. Surface analysis techniques, such as electron spectroscopy for chemical analysis and secondary ion mass spectrometry have been used to examine dry-etched surfaces. Submicron I-bar structures with varying InP air-bridge channel widths were defined by electron beam lithography and used for the analysis of vertical sidewall damage. Based on these studies, a RIE process has been defined and incorporated in the development of a self-aligned HBT technology. By eliminating the damaged regions and creating an overhang in the emitter layer using wet chemical etching, damage-free self-aligned HBTs with excellent characteristics were fabricated and their properties are reported.