Defects and voids in He+-implanted Si studied by slow-positron annihilation and transmission electron microscopy
The distribution and annealing behavior of defects in crystalline silicon caused by 7×1016 /cm2 He+ implantation were investigated by slow-positron annihilation technique, transmission electron microscopy, Rutherford backscattering, and channeling spectroscopy. It was found that small vacancy clusters were induced in the surface region and big clusters (microbubbles) formed around the projected range in which the crystal was heavily damaged by the implantation. The small vacancy clusters in the near-surface region start to disappear at 300 °C and can be removed at temperatures up to 700 °C by dissociation and diffusing to the damaged region. This results in the growth of voids. The severely damaged region around the projected range begins to anneal out at temperatures higher than 600 °C, and He is released, leaving voids embedded inside the crystalline silicon.