Ultra-shallow, super-doped and box-like junctions realized by laser-induced doping

Laser-induced boron doping of silicon, in a special configuration where the precursor gas (BCl3) is injected and chemisorbed on the Si surface prior to each laser pulse, is shown to be a very attractive technique capable to meet the International Technology Roadmap for Semiconductors (ITRS) requirements for the future CMOS technologies. The laser-processed samples have been characterized by the four-point probe method, X-ray diffraction (XRD), atomic force microscopy (AFM) and finally by secondary ion mass spectrometry (SIMS). Junction depths as shallow as 20 nm, with boron concentrations above the solubility limit, sheet resistances as low as 20 Ω/sq, box-like and very abrupt profiles have been obtained. We show that optical diagnostics, based on the transient reflectivity at 675 nm, allow an in situ control of the evolution of the dopant concentration and of the doped layer thickness during the laser doping process.