We investigated the electrical characteristics and the junction depth of ultra-shallow junctions formed by using the plasma-doping method. Compared with ultra-low energy boron-ion implantation at 500 eV, the junctions formed with the plasma-doping process exhibited shallow junction depths and low sheet resistances. The junction depths of the plasma-doped samples were 150 Å and 330 Å after annealing for 10 s at 900 °C and 950 °C, respectively. For the same junction depth, the sheet resistance of the B2H6 plasma-doped sample was an order of magnitude less than that of the 500-eV B-ion implanted sample. Cross-sectional transmission electron microscopy and deep level transient spectroscopy showed that the defects formed by the B2H6 plasma-doping process could be removed by annealing at 950 °C for 10 s. The scaling of metal-oxide-semiconductor field-effect-transistor (MOSFET) device channel lengths for high-speed application requires the scaling down of the junction depth to suppress the short-channel effect. Based on the national technology roadmap for semiconductors, the junction depth of a lightly doped drain (LDD) region should be scaled down to 30∼40 nm for next-generation 0.1-μm MOSFET devices . Compared with n+/p junction, it is difficult to form an ultra-shallow p+/n junction due to boron channeling and to transient-enhanced diffusion related to extra interstitials generated during the implantation [2,3]. Due to the low beam current and the low throughput, it is difficult to use a conventional ion implantation system at very low energies. Consequently, the plasma ion implantation method is considered as a good candidate for achieving ultra-shallow junction profiles because of its ultra-low energy, high throughput, and room temperature operation . If plasma doping at an energy level of 100 eV is used, the locations of defects generated by plasma implantation are very close to the Si surface. It is known that the Si surface is an efficient sink for the removal of point defects. Therefore, we expect the transient-enhanced diffusion for a plasma doping process to be almost negligible. In this study, we investigated the characteristics of an ultra-shallow junction formed by plasma ion implantation as an alternative to the ion-implantation process.
ASJC Scopus subject areas
- Physics and Astronomy(all)