Effects of beam energy purity on junction depths in submicron devices

As CMOS device dimensions continue to scale down, source-drain junction depths are reduced accordingly. Shallow p+ junction formation will require the use of very low energy (1-3 keV) source/drain implants at doses ⩾1×10¹⁵/cm² for forming final p+ source/drain junctions <0.1 μm. Deceleration of boron ions after mass analysis has been proposed as a method to provide adequate beam currents in this energy range without extensive redesign of the source chamber and beamline. Charge exchange reactions that occur after the mass analysis magnet but prior to the deceleration electrode can result in contamination of the final beam with a fractional component of ions possessing the original extraction energy. This has the potential to seriously impact the off-state leakage current of advanced PMOS devices. The pressure dependent nature of charge exchange reactions suggests that device performance will show significant variations in a typical manufacturing environment