RBS characterization of the iridium diffusion in silicon

In this work, the Ir diffusion in Si has been studied in the high concentra tion regime. Si (1 0 0) samples were preamorphized by Si implantation and i mplanted with Ir with a peak concentration of 8 x 10(21) cm(-3), below the minimum necessary to the formation of a continuous layer of iridium silicid e. The amorphized region of the substrate was regrown by solid phase epitax y at 550 degrees C. This procedure eliminates the effect of the end of rang e region of the Ir implant on the diffusion process. After regrowth, the sa mples were annealed at temperatures in the 800-1000 degrees C range for dif ferent times. The Ir concentration profiles and the crystal quality were de termined from random and aligned RES spectra. Annealing at high temperature s causes a snowplow effect of Ir toward the surface of the sample, with a s egregation coefficient close to 1. An Ir diffusion mechanism through the de fect-free region of the Si substrate is also clearly identified, and a cons tant value of the diffusion coefficient D is derived for each temperature. The values of D follow an Arrhenius behavior with an activation energy E-a = 3.3 +/- 0.2 eV. This value agrees with the typical ones found in vacancy assisted diffusion mechanisms reported for other species. Comparison of the se results with the previously reported activation energy E-a = 1.3 eV for Ir diffusion from the vapour phase at low concentrations shows that the dif fusion mechanism is dependent on the concentration level. The values of D a t high concentrations are 6 to 7 orders of magnitude lower than the ones re ported for low concentrations. (C) 2000 Elsevier Science B.V. All rights re served.