Low Energy Fluoroboron Ion Beam Interaction with Silicon Single Crystals

Abstract

Fluoroboron (BF₂⁺) ion implantation into silicon is frequently used for fabrication of shallow junctions. For scaling down of the junction dimensions, one of the efficient approaches is to lower the implantation energy. This work reports fluoroboron ion interactions with (100) oriented silicon at 10 to 500 eV ion energy. Ion bombardment was carried out using a mass-separated BF₂⁺ ion beam in an ultrahigh vacuum low energy ion beam system. The temperature of the silicon crystal during bombardment was kept either at room temperature or 500/dgC. The reactions (both etching and incorporation) were characterized by x-ray photoemission spectroscopy (XPS), Rutherford backscattering (RBS) and Raman scattering. The results show that BF₂⁺ ions dissociated on the silicon surface at an energy as low as 10 eV and most of fluorine segregated to the surface and desorbed. Both the physical and chemical etching rate of the beam were energy dependent but much lower than the accumulation rate. For beam fluences higher than 1 X 10¹⁸/cm², continuous amorphous boron films were deposited on silicon.