Roles of Impurities and Implantation Depth on He+- Cavity Shape in Silicon

Abstract

AbstractSilicon samples were implanted with He+ ions at energies varying from 10keV to 1.55MeV using doses ranging from 1.45×1016 cm-2 to 5×1016cm-2 to obtain similar He concentration at each projection range (Rp). In few samples, gold, platinum, nickel or silver was introduced prior to He+ implantation by diffusion at temperatures ranging from 870°C to 1050°C. All samples were annealed in the 400°C–1050°C temperature range to determine the equilibrium stage of the growth of the cavity. The cavity characteristics (distribution, shape and size) were studied by cross section transmission electron microscopy (XTEM). Their morphology demonstrates the validity of the chemisorption hypothesis when they grow in silicon intentionally contaminated by metal. A consequence of the surface proximity on the cavity characteristics was verified and allows stepping forward two regimes of cavity growth: one, very fast, taking place in a He-free environment and another one, slower, occurring in a He-rich atmosphere.