CHEMICAL DRY-ETCHING MECHANISMS OF GAAS SURFACE BY HCL AND CL-2

Dry etching mechanisms of thermal and photochemical reactions with Cl- 2 and HCl on GaAs(100) Ga-rich c(8x2) surfaces were investigated, usin g x-ray and ultraviolet photoelectron spectroscopy. At a substrate tem perature of -100 degrees C, the etchant gases are chemisorbed on the G aAs surface. Cl-2 deposition on GaAs produces about five times more Cl -containing species than HCl deposition. The GaAs surface is disrupted with Cl-2 when the substrate temperature is increased to 250 degrees C after the saturated deposition of Cl-2 at -100 degrees C. A similar etching procedure with HCl farms an ordered surface of GaAs with As at oms on the top layer. After desorption of the etchant gases, the photo irradiation effect at room temperature was investigated by pulsed lase r irradiation with excimer (193 and 248 nm) and YAG (266, 355, and 532 nm) lasers at an intensity of 2-10 mj/cm(2). Only the 193 nm irradiat ion removes Cl-containing species from the surface. With cw laser irra diation at 488 nm (60 mW/cm(2)), photochemical reactions take place on the GaAs substrate on which Cl-2 has been deposited. (C) 1996 America n Vacuum Society.