Shallow P+-Junction Technology for 0.25 μm CMOS

A preamorphisation technology for fabrication of shallow p⁺-junctions for 0.25 μm CMOS was studied. Silicon and germanium ions were used for preamorphisation. A low energy BF2⁺ implantation was used for the formation of the p⁺-region. The physical (SIMS,XTEM) and electrical characterisation of shallow p⁺-junctions will be presented. Large p⁺-diodes and 0.25 μm PMOS transistors were fabricated. The best results were obtained for Ge preamorphised material. Low leakage current p⁺-junctions with depth of 0.15 μm were obtained. However, the preamorphisation technology is complex, has a small process window for shallow p⁺-junctions and the benefits over a conventional approach are not significant. Excellent results were obtained for shallow p⁺ junctions (0.18 μm) fabricated with conventional BF2⁺ implants with reduced implantation energy and thermal budget.