New Approaches for Characterization of Advanced Annealing Techniques for Ultra-Shallow Junction Formation

Low thermal budget annealing approaches, such as millisecond annealing or solid-phase epitaxy (SPE), can electrically activate ultra-shallow junctions (USJ) without excessive diffusion, but they must also remove implant damage to minimize junction leakage. This paper presents results from annealing low-energy B implants into both crystalline and pre-amorphized silicon. Some wafers also received As implants for halo-style doping, and some halo-implanted wafers were pre-annealed at 1050 deg C before B-doping. The final anneal was either SPE at 650 deg C, spike annealing at 1050 deg C, or millisecond annealing with flash-assisted RTPTM (fRTPTM) at temperatures between 1250 deg C and 1350 deg C. Electrical activation was assessed by sheet resistance (Rs) measurements with conventional four-point probing (4PP) as well as Hg-probe 4PP and a non-contact method. Residual damage was characterized by photoluminescence, thermal wave studies, optical reflectance and non-contact junction leakage current measurements. Damage from the heavy ions used for the halo and pre-amorphization implants dominates the annealing behaviour. Halo doping is the critical factor in determining junction leakage current. High temperature fRTP is shown to minimize residual damage.