Silicon surface cleaning by low dose argon-ion bombardment for low-temperature (750 °C) epitaxial deposition. II. Epitaxial quality

Abstract

Argon-ion bombardment has been optimized as a method to clean silicon substrates prior to epitaxial deposition at low temperatures (750 °C) and very low pressures (<1×10-2 Torr). Structural characterization of subsequently deposited films has been performed to establish the relations between cleaning conditions and film properties. When cleaning conditions are insufficient, a residue of native oxide remains at the interface and disrupts the transfer of crystalline structure from the substrate to the epitaxial layer. When cleaning conditions are excessive, the substrate is damaged and the initial stages of film nucleation and growth are disrupted. Using an elevated substrate temperature of 750 °C, a window in ion energy and dose has been found in which native oxide is removed without net damage being produced in the substrate. Under these conditions, epitaxial films of excellent structural quality may be deposited, as evidence by transmission electron microscopy and defect etching.