Boron Delta-Doping in Si : B Stacks By RP-CVD Epitaxy

Low resistivity materials are required for advanced MOS or equivalent technologies. High boron in-situ doped Si epitaxy is known to create defects that increase the resistivity. Boron delta-doping (Si:B epitaxy alternating with boron saturation layers) is a potential solution to overcome this limitation. Using the delta-doping process at 750 °C in a Reduced Pressure Chemical Vapor Deposition reactor, a resistivity two times lower than that without delta-doping (8.9x10 -4 Ω.cm and 1.86x10 -3 Ω.cm respectively) was achieved. SIMS characterization measured a total boron concentration of 3.3x10 21 at.cm -3 . However, the delta-doping processes , as a function of the soaking volume (product of B 2 H 6 flow and saturation time), resulted in low crystal quality and highly stressed layers. Moreover, thin layers were observed by TEM likely due to the formation of the SiB x phase at each saturation layer. For an equivalent soaking volume, a better crystal quality was obtained with a high B 2 H 6 flow and short saturation time.