Ion bombardment effects in plasma-assisted etching of silicon

Effects of low energy ion bombardment on silicon surfaces were investigated using ion beam techniques coupled with surface characterization methods. Those processes important to plasma-assisted etching of silicon such as crystalline damage formation, incorporation of energetic ions and adsorbed gas atoms, and sputtering were emphasized. The employed surface characterization techniques included Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. The amount of crystalline damage decreased with increasing ion mass and increased with increasing ion energy and dose. Damage produced by 1 keV argon and neon ions was confined to within 100 A of the surface. Hydrogen ion bombardment produced crystalline damage extending at least 400 A into the bulk, however. Exposure of the silicon surface to a flux of Cl2 molecules during 1 keV Ar+ bombardment at normal incidence lead to the incorporation of 1-2 monolayers of chlorine and a three-fold increase in the silicon removal rate. Crystalline damage, implanted carbon and fluorine atoms and deposition of a fluorocarbon overlayer were all detected after bombardment of silicon with a CHF3 ion beam