TCAD modeling and experimental investigation of indium for advanced CMOS technology

Indium is a key element in the formation of well, channel, and HALO profiles, especially for very deep sub-μm technologies with gate length below 150nm. Indium (¹¹⁵In⁺) has the advantage of being a large atom and having a small projected range. Hence ion implanted indium produces steeper profiles than boron, providing that the retrograde doping is maintained after the subsequent annealing steps. Therefore, knowledge of the diffusion behavior of indium is extremely important. In this work, Indium diffusion and dose loss are studied both experimentally and by TCAD simulation. N-type silicon wafers were capped with a 50Å thick SiO₂ layer, followed by In⁺ implantation on an Applied Materials Quantum LEAP™ ion implanter at a range of energies from 50keV to 150keV, and at different doses from 1E13 ions/cm² to 1E14 ions/cm². The wafers were then annealed under different annealing conditions reflecting typical well and HALO anneal steps, and for calibration purposes. Calibration of the process simulation was done for indium implantation and diffusion, allowing us to describe Indium implantation and diffusion in general, and quantitatively for special effects such as double peak formation and dose loss. It is shown that the double peak, which appears for an Indium dose higher than 4E13/cm² and energies higher than 50keV for selected anneal conditions, is strongly related to amorphization and defect distribution after implantation. The dose loss is diffusion limited and therefore controlled by the diffusion coefficients in the region close to the silicon surface.