Ternary iron-cobalt silicide fabricated by ion beam synthesis

Abstract

Ternary silicide layers were fabricated by the implantation of iron and cobalt into (100) silicon wafers. Two sets of samples with different iron to cobalt ratios were prepared, with cobalt being implanted first followed by iron in the first set, and the implantation order being reversed for the second set. In all cases a total Fe + Co dose of 5 × 10 17 cm −2 was used. The structural properties of the synthesised layers were assessed by Rutherford backscattering spectrometry (RBS) and cross-sectional transmission electron microscopy (XTEM). Our results indicate that for the samples where cobalt was implanted first epitaxial layers are formed after implantation. However, when iron was implanted first the layers are non-crystalline. For the samples with iron implanted frrst no significant improvement in crystal quality was observed with increasing anneal temperature. However, for those samples where cobalt was implanted first we observed a strong dependence of the crystal quality on the annealing temperature. For the samples with cobalt doses ≥ 2.5 × 10 17 cm −2, where cobalt was implanted first, segregation of iron and cobalt within the synthesised layer is observed.