Study of ultra-shallow p(+)n junctions formed by excimer laser annealing

Abstract

Excellent ultra-shallow p(+)n junctions have been formed by thermally treating the BF(2)(+)-implanted Si samples by excimer laser annealing (ELA) at 300-400 rnJ cm(-2) with post low-temperature long-time furnace annealing (FA) at 600 degrees C. A junction with a leakage current density lower than 20 nA cm(-2) and a sheet resistance smaller than 200 Omega square(-1) can be well achieved. No considerable dopant diffusion is observed by using this low-thermal-budget annealing process. However, by simply using the ELA treatment at 300-400 mJ cm(-2), the resultant junction shows a leakage current density as high as 10(4) nA cm(-2) and a peripheral leakage current density of 10(3) nA cm(-1). The large junction leakage is primarily due to the leakage current generated within the junction region near the local-oxidation-of-silicon (LOCOS) edge, and which is substantially caused by the ELA treatment. The large peripheral junction leakage current density can be significantly reduced to be about 0.2 nA cm(-1) after a post low-temperature FA treatment at 600 degrees C. As a result, the scheme that employs ELA treatment with post low-temperature FA treatment would be efficient for forming excellent ultra-shallow p(+)n junctions at low thermal budget. (C) 2010 Elsevier BM. All rights reserved.