Effect of low-temperature preannealing on laser-annealed p+/n ultrashallow junctions

The effect of low-temperature preannealing on ultrashallow p(+)/n junctions was examined. An ultrashallow junction was formed by means of B2H6 plasma doping at an energy of 500 V. The junction was activated by low-temperature (300-500 degreesC) annealing, followed by laser annealing. Compared with control samples which were not preannealed, low-temperature preannealing significantly improves junction characteristics, resulting in a reduction in junction depth and a lower leakage current density. A cross-sectional transmission-electron-microscopy analysis confirmed the lower defect density, which explains the lower leakage current. By optimizing the process conditions, excellent electrical characteristics of the p(+)/n junction, i.e., a junction depth of 28 nm and a sheet resistance of 250 Omega/sq, can be obtained. (C) 2002 American Institute of Physics.