Ultra-shallow n~+p junction formed by PH_3 and AsH_3 plasma immersion ion implantation

摘要

Ultra-shallow 28-88 nm n~+p junctions formed by PH_3 and AsH_3 plasma immersion ion implantation (PIII) have been studied. The reverse leakage current density and intrinsic bulk leakage current density of the diodes are found to be as low as 4.2 nA cm~(-2) and 2.4 nA cm~(-2), respectively. The influences of pre-annealing condition and the carrier gas on the junction depth and the sheet resistance are also studied. It is found that the increase of H or He content in the PH_3 PIII can slow down the phosphorus diffusion and shallower junction can been obtained. Annealing conditions have pronounced effect on the sheet resistance. It was found that sample annealed at 850 ℃ for 20 s has reverse results to that annealed at 900 ℃ for 6 s. For AsH_3 PIII samples, it is observed that two-step annealing is more effective to activate the dopant and a lower reverse current density resulted.