High Dopant Activation of Boron in SiGe with two-step Implantation and Microwave Annealing

Abstract

In this study, two-step, low energy (2 keV + 1 keV) ion implantation and low-temperature microwave annealing (MWA) were employed to recover and activate boron implanted SiGe wafers. The boron was introduced by a combination of in situ doping during epi-growth (3.2 × 1020 cm−3) and a two-step ion implantation process (3 × 1015 cm−2 and 2 × 1015 cm−2). The activation of boron, which is close to the solid solubility limit in SiGe, was investigated following MWA or rapid thermal annealing. The thermal process was found to have the dominant effect on activation, but the SiGe composition also had an effect. For Ge content between 20% and 40%, Si 0.65 Ge 0.35 is an optimum alloy. Following implantation and annealing, boron distribution, sheet resistance, and mobility were checked to infer the activation level and defect evolution. A pre-amorphization implant using Ge ions has the best performance, and can effectively enhance the boron activation while preventing diffusion, when followed by MWA.