Surface exfoliation and defect structures in Si induced by 160keV He and 110keV H ion implantation

Cz n-type Si(100) wafers were implanted at room temperature with 160keV He ions at a fluence of 5×1016/cm2 and 110keV H ions at a fluence of 1×1016/cm2, singly or in combination. Surface phenomena and defect microstructures have been studied by various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). Surface exfoliation and flaking phenomena were only observed on silicon by successive implantation of He and H ions after subsequent annealing at temperatures above 400°C. The surface phenomena show strong dependence on the thermal budget. At annealing temperatures ranging from 500 to 700°C, craters with size of about 10μm were produced throughout the silicon surface. As increasing temperature to 800°C, most of the implanted layer was sheared, leaving structures like islands on the surface. AFM observations have demonstrated that the implanted layer is mainly transfered at the depth around 960nm, which is quite consistent with the range of the ions. XTEM observations have revealed that the additional low fluence H ion implantation could significantly influence thermal growth of He-cavities, which gives rise to a monolayer of cavities surrounded by a large amount of dislocations and strain. The surface exfoliation effects have been tentatively interpreted in combination of AFM and XTEM results.