Fachbereich 11 - Physik
Institut für Materialphysik
Diffusion and Defects in Elementary and Compound Semiconductors

Iridium diffusion in silicon

Diffusion plays an important role in the fabrication of semiconductor-based electronic devices. Moreover, diffusion studies provide basic knowledge about the lattice defects involved in atomic transport such as vacancies and self-interstitials.Diffusion of Ir into Si was investigated by annealing of front-side deposited floating-zone Si wafers at temperatures between 1000 and 1200 °C. Concentrations-depth profiles were measured by means of neutron activation analysis in conjunction with mechanical sectioning. The observed deep penetrations and anomalous profile shapes point to a diffusion process involving both highly mobile interstitial Ir_i as diffusion vehicle and immobile substitutional Ir_s as dominating species. The experimental findings are best reproduced by making allowance for Ir_i -Ir_s exchanges that simultaneously take place via Si self-interstitials (kick-out mechanism) and Si vacancies (dissociative mechanism). As a unique feature it is found that the Si:Ir system is subject to a gradual transition from a Ir_i-controlled diffusion mode at higher temperatures to a self-interstitial-controlled diffusion mode at lower temperatures. The special properties of Ir in Si are used in further diffusion experiments at lower temperatures to obtain information about grown-in and equilibrium vacancy concentrations in Si.

Beteiligte Wissenschaftler:

Dipl. Phys. Sh. Obeidi, L. Lerner, PD Dr. N.A. Stolwijk (project leader)

Veröffentlichungen:

Obeidi, S., N. A. Stolwijk: Diffusion and solubility of iridium in silicon, Defect and Diffusion Forum 194-199 (2001) 635

S. Obeidi and N.A. Stolwijk: Diffusion of iridium in silicon: Changeover from a foreign-atom-limited to a native-defect-controlled transport mode, Phys. Rev. B64 (2001) 113201