The high-dose BF2+ implantation, which is employed for forming resistors and lowering the extrinsic base resistance in the SiGe heterojunction bipolar transistor (HBT) integrated circuit (IC) fabrication process, is shown to have strong effects on the Ti-silicidation behaviour of the polycrystalline Si/Si0.87Ge0.13/Si stack layer. As the dose of BF2+ increases from 4 x 10(14) to 4.4 x 10(15) cm(-2), the growth and C49-to-C54 transformation of the silicide/germanosilicide layer and protrusions are highly enhanced, which is consistent with previous observations on the defect-assisted nucleation of silicide grains. However, the final sheet resistance increases with increasing dose of BF2+. Such an inconsistency between the amount of C54 phase and the sheet resistance is probably due to the formation of numerous surface voids on the silicide layer from the fluorine-containing gaseous complexes. As the number of germanosilicide protrusions increases with increasing dose of BF2+, the contact resistance also increases because the protrusions are readily etched away during contact opening and leave behind cavities within the Si/Si0.87Ge0.13/Si layer. To achieve lower values of extrinsic base and contact resistances in SiGe HBT ICs, it is desirable to replace the BF2+ with B+ as well as thicken the Si cap layer on the contact region using the selective growth process of Si. (C) 2003 American Vacuum Society.