CHEMICAL-ANALYSIS OF A CL-2 BCL3/IBR3 CHEMICALLY ASSISTED ION-BEAM ETCHING PROCESS FOR GAAS AND INP LASER-MIRROR FABRICATION UNDER CRYO-PUMPED ULTRAHIGH-VACUUM CONDITIONS/

We have investigated the compatibility of Cl-2/BCl3/IBr3 etch gas mixt ures with a cryo-pumped ultrahigh vacuum chemically assisted ion-beam etching system. The machine was designed for the fabrication of ultrah igh-quality laser facets in monolithically integrated GaAs- and InP-ba sed optoelectronic integrated circuits. The chemical composition of et ch byproducts deposited in the vacuum chambers and the pumping system has been examined in particular detail. After 70 h of process time, sa mples of such deposits were scraped from the chamber walls and the var ious stages of the cryo-pump and roughing pump; these samples were ana lyzed using energy-dispersive x-ray measurements. Automated overnight regeneration of the cryopump, the use of integrated external bakeout h eaters, and the implementation of a cryo-pumped load-lock chamber allo w the deposition of reactive Cl-containing residues to be confined to surfaces and components which can be cleaned or replaced during routin ely scheduled yearly maintenance. (C) 1995 American Vacuum Society.