Search

Abstract: Boron out-diffusion in epitaxially grown n-Si/p+-Si1-xGex/n-Si heterojunction bipolar transistors is significantly enhanced during 850C, 10 s rapid thermal annealing following arsenic emitter contact implantation. In this paper, we introduce three techniques which dramatically reduce boron out-diffusion during implant activation. Limiting the post-implant processing to 600C for 2 min results in minimal diffusion giving acceptable device performance. A second technique involves pulsed laser annealing of the As implant, which removes residual defects and eliminates enhanced diffusion during subsequent thermal processing. Finally, we show that high bulk concentrations of oxygen in the Si1-xGex (∼1020 cm-3) dramatically reduce the implant-damage-enhanced boron diffusion. In addition to the depth profiles, electrical measurements performed on heterojunction bipolar transistors, incorporating these fabrication techniques, show ideal collector current characteristics and confirm the absence of deleterious boron out-diffusion effects.