Plasma immersion ion implantation of SiF4 and BF3 for sub-100 nm P+/N junction fabrication

Abstract

Sub-100 nm P+/N junctions were fabricated using plasma immersion ion implantation (PIII). With this technique, the silicon wafer was immersed in SiF4/BF3 plasma and biased with a negative voltage. The positively charged ions in the plasma sheath were accelerated by the electric field and implanted into the wafer. The dose rate of PIII can be much higher than that of conventional ion implanter. Whereas the dopant activation behavior is similar. For extremely shallow P+/N junction formation, sample preamorphization and short cycle rapid thermal annealing (RTA) are required. With SiF4 PIII preamorphization followed by BF3 PIII doping and RTA at 1060 °C for 1 s, 80 nm P+/N junctions were successfully obtained. Test diodes fabricated with this technique show good characteristics.