Evolution Of Defects Induced By High Energy He Implantation In Gold-Diffused Silicon

Abstract

Silicon samples were gold-diffused at different temperatures, implanted with He ions at 1.6 MeV and then annealed at 1050°C for 2 hours. The implantation induced-defect structure and their distribution in the depth of the sample, studied by conventional and high resolution cross section electron microscopy (HRXTEM) depend on the gold level introduced in the wafer prior to the gettering process. A high concentration of gold in silicon seems to influence the defect configuration in the cavity zone. Indeed, gold chemisorbed at cavities can homogenize the surface energy of their planes in different orientations, and can increase the cavity critical diameter beyond they become facetted. Secondary ion mass spectroscopy (SIMS) profiles exhibit a shouldered shape and a width closely related to the presence of the defects (observed by XTEM) which are very efficient sinks both for gold and copper atoms. Unfortunately, the electrical improvement of the material (checked by minority carriers diffusion length measurements MCDL) is not achieved by this gettering process, probably due to the high metal impurity concentrations remaining out of the gettering zone, to the presence of AuCu complexes and η-Cu 3 Si precipitates identified by deep level transient spectroscopy (DLTS) measurements and HRXTEM observations respectively.