Ultrashallow and Low-Leakage p+n Junction Formation by Plasma Immersion Ion Implantation (PIII) and Low-Temperature Post-Implantation Annealing

Abstract

p+n junctions are fabricated by the combination of BF3 plasma immersion ion implantation (PIII) and low-temperature post-implantation annealing. Ultrashallow junctions and very low leakage currents (∼10-11 A at -1 V in 1 mm2 junctions) have been obtained. Despite the fact that the activation of the PIII layer is not sufficient, the I–V characteristics obtained are comparable to those of junctions formed by conventional ion implantation. By a combination of Si+ preamorphization and BF3 PIII aimed to improve the dopant activation, a maximum surface concentration of activated boron higher than 1020 cm-3 is obtained in 550°C annealing for p+n junctions with 5 nm depth. The leakage currents, however, are increased by the Si+ implantation in low-temperature post-implantation annealing.