Helium implant depth dependence on thermal growth of nanocavities in silicon

Silicon samples were implanted with both 50 keV and 1.55 MeV /sup 3/He ions and annealed at different temperatures. The thermal growth of cavities was performed using transmission electron microscopy (TEM) measurements. Results show a significant difference in the formation and growth of cavities. Implantation of 50 keV ions to a total dose of 2.83/spl times/10/sup 16/ He/cm/sup 2/ results in the unexpected formation of platelets when the annealing temperature is 400/spl deg/C, while a sample implanted with 1.55 MeV ions at an equivalent helium concentration (5/spl times/10/sup 16/ He/cm/sup 2/) gives rise to spherical cavities after the same thermal treatment.