Migration and interaction properties of ion beam generated point defects in c-Si

摘要

We have analyzed the room temperature migration properties of ion beam generated self-interstitials and vacancies in crystalline Si using deep level transient spectroscopy and in situ leakage current measurements. Silicon p~+ -n junctions, formed by B diffusion in n-type epitaxial Si wafers, were implanted at room temperature with 2.5 MeV He ions to fluences in the range 1 X10~9-1 X 10~12 cm~-2. Diodes were reverse biased and leakage current was measured both during and immediately after ion implantation. At the beam turn-off, leakage current decreases by about a factor of 2 in times as long as few days. Ex situ deep level transient spectroscopy measurements show that the main contribution to leakage current is given by vacancy-type defects, i.e. phosphorous-vacancy and divacancy complexes. Hence, the leakage reduction at thebeam turn off has been associated to the recombination of vacancy clusters by residual free interstitials. Assuming a diffusion limited recombination process, a value of 1.5 X 10~15 cm~2/s has been determined for the interstitial diffusivity. When the dose rate of the beam is increased, a faster transient, lasting up to 1000 s, is revealed by the in situ measurements and it has been tentatively associated with the annihilation of residual free vacancies by migration to interstital sinks or by trapping at impurity atoms (O,C). direct c 1999 Elsevier Science B.V. All rights reserved.