Optimization of BF2+ implanted and rapidly annealed junctions in silicon

The electrical properties and defect characteristics of shallow junctions fabricated by using BF2+‐ion implantation and followed by either furnace or rapid thermal annealing (RTA) have been investigated. The RTA temperature‐time cycle was optimized in terms of leakage current, junction depth, and sheet resistivity of junctions. Specifically, shallow p+ junctions (∼180 nm) with low leakage current (∼2 nA/cm2 at −5 V) were obtained with 49‐keV, 2×1015‐cm−2 BF2+ implantation and RTA at 1050 °C for 15 s. The effects of a Si+ preamorphizing implant and pre‐ or post‐RTA low‐temperature furnace anneal were also studied. p+/n diodes fabricated with a preamorphizing implantation exhibit about 3 orders of magnitude higher leakage current than the diodes without preimplantation. The excessive leakage current of the preamorphized junctions arises from a band of post‐annealing defects located in the depletion region of the n well (from ∼220 to 420 nm). Samples without the Si+ implant have very shallow and narrow defec...