Precise control of doping profile and crystal quality improvement of SiGe HBTs using continuous epitaxial growth technology

A continuous-epitaxial-growth technique, using a cold-wall rapid thermal UHV/CVD system, for Si/SiGe multi-layers containing different doping types has been developed. Extremely high phosphorous-doping in the silicon layer grown by LPCVD with Si2H6 can be achieved without high-temperature activation annealing, and good crystallinity of the Si layer results in very low resistivity. High-temperature surface cleaning prior to the epitaxial growth can be omitted, since contamination occurring during wafer transfer was minimized by using a UHV transfer chamber. Good crystallinity of the HBT structure after the whole fabrication process was confirmed by reciprocal lattice space mapping of high-resolution X-ray diffraction. These results indicate that the developed continuous-epitaxial-growth technique gives a major advantage in maintaining crystal quality of Si/SiGe multi-layers for future ultra-high-speed devices