Ultrashallow junction formation for next generation MOS technology

POON CHYIU HYIA, DEBORA

Publication

Ultrashallow junction formation for next generation MOS technology

POON CHYIU HYIA, DEBORA

Abstract

A defect-free, highly activated and ultrashallow boron junction can be achieved by multiple-pulse laser annealing of preamorphized silicon, using laser fluence sufficient to melt amorphous but not crystalline silicon. By analyzing sheet resistance measurements, the optimum number of pulses required to fully remove the damage for each preamorphization condition can be predicted. Hall measurements performed display unexpected n-behaviour for laser annealed p-layers above certain temperatures due to junction leakage. By monitoring the transition temperature from expected p-type to unexpected n-type, junction integrity can be estimated. Upon post-laser annealing, surface defects that are not removed would induce uphill diffusion, resulting in dose loss and shallower junctions. However, with subsequent pulses and surface defect removal, transient enhanced diffusion due to end-of-range defects dominates, deepening junction. Phosphorus diffusion behaviour in germanium is studied and severe dose loss observed is attributed to implantation damage. Rapid n-diffusion in germanium is suggested to be due to surface melting when amorphization lowers the melting temperature.