SURFACE RECESSION AND OXIDATION OF SILICON DURING BOMBARDMENT BY LOW-ENERGY OXYGEN IONS

Vertical expansion of a silicon surface bombarded by 10 keV O+ ions is demonstrated using surface stylus profilometry. The surface expands gradually as the incorporated oxygen concentration increases, and a maximum is obtained when the bombardment dose reaches the critical one for formation of a continuous surface layer of SiO2. Through a combination of crater depth measurements and chemical etching the surface recession and the incorporation of oxygen are monitored as a function of bombardment dose. Comparison is made with calculations based on a model where simultaneous sputter erosion and surface swelling are taken into account. The surface swelling is assumed to be proportional to the retained oxygen dose. Experimentally determined sputtering yields are utilized in the calculations, and good agreement is shown with the measured data.