| A new method for creating heavily-doped, ultra-shallow junctions in boron-implanted silicon will be presented. This method uses nonmelt laser annealing (NLA) to supply energy to the surface region of the silicon at a ramp rate greater than 1010°C/sec. This study concentrates on high-dose, non-amorphizing boron implants. Boron implants into silicon at energies of 500 eV to 5 KeV at doses of 1e15–2e15 ions/cm2 are used. Samples are analyzed using the following techniques: four-point probe (FPP), Hall effect, secondary ion mass spectroscopy (SIMS), and transmission electron microscopy (TEM). The results from FPP and SIMS show increasing the number of laser shots decreases the sheet resistance without increasing the junction depth. Hall effect measurements show NLA can also increase the mobility. Also, NLA affects defect nucleation. Following NLA numerous small defects are nucleated resulting in a dramatic change in the defect population. This decrease in defect size and increase in population are shown to increase the scattering in the layer which decreases the mobility. Using NLA, heavily-doped 20 nm p-type layers with sheet resistances around 600 Ohms/sq are created. Also, NLA results in nearly 100% activation of the boron in the sample and reduces the dose loss during post-processing.; To help understand the changes in defect populations and mobility measurements introduced by the NLA, experiments as well as modeling efforts are made. A mobility model implemented in FLOOPS (Florida's Object Oriented Process Simulator) with terms to account for these defects is presented. With this mobility model the sheet resistance of the implanted layer as well as the mobility can be determined. Also, the temperature distribution in the silicon during the NLA and the cool-down will be implemented in FLOOPS. This temperature distribution along with the current process simulation models allows the calculation of the defect population following the NLA to be determined, thus allowing more accurate modeling during post anneals. |
