Ultra-shallow n+p junction formed by PH3 and AsH3 plasma immersion ion implantation

Ultra-shallow 28–88 nm n+p junctions formed by PH3 and AsH3 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 nAcm−2 and 2.4 nAcm−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 PH3 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 °C for 20 s has reverse results to that annealed at 900 °C for 6 s. For AsH3 PIII samples, it is observed that two-step annealing is more effective to activate the dopant and a lower reverse current density resulted.