Control of implant-damage-enhanced boron diffusion in epitaxially grown n-Si/p-Si1-xGex/n-Si heterojunction bipolar transistors |
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Authors: | T Ghani J L Hoyt A M McCarthy J F Gibbons |
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Affiliation: | (1) Solid State Electronics Laboratory, Stanford University, 94305 Stanford, CA;(2) Lawrence Livermore National Laboratory, 94551 Livermore, CA |
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Abstract: | Boron out-diffusion in epitaxially grown n-Si/p+-Si1-xGex/n-Si heterojunction bipolar transistors is significantly enhanced during 850°C, 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 600°C 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. |
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Keywords: | Boron diffusion in Si heterojunction bipolar transistor (HBT) implant damage enhanced diffusion pulsed laser annealing SiGe |
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