Preamorphization Techniques for Shallow Junctions in SI
Due to dopant channeling during ion implantation into crystalline silicon, shallow junctions are difficult to achieve. The scope of this study was to investigate the preamorphization technique as a tool to prevent channeling during transistor fabrication. Implantation of heavy ions such as Si+ and Ge+ offers the possibility of amorphizing a desired region in a highly controllable way. The preamorphization experiments were carried out using these species of atoms. In both cases boron channeling was found to be completely suppressed. In the case of Si+ preamorphization transistors show significant leakage currents due to a high density of residual stacking faults and dislocation loops inside the active region. In the case of Ge+ preamorphization complete recrystallization of the amorphized layer was obtained. No stacking faults or dislocation loops could be observed by TEM analysis after a two-step low temperature annealing process. A slight improvement of the peak value of the transit frequency was obtained for the preamorphized transistors.
KeywordsTransmission Electron Microscopy Analysis Rapid Thermal Annealing Dislocation Loop Amorphized Layer Bipolar Transistor
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- Crowder, B.L., Ziegler, J.F., and Cole, G.W. (1973) ‘The Influence of the amorphous phase on boron atom distributions in ion implanted silicon’, in Ion Implantation in Semiconductors and Other Materials, Plenum, New York, pp. 257 – 266Google Scholar
- Seidel, T. E., Knoell, R., Poli, G., Schwartz, B., Stevie, F.A., Chu, P. (1985) ‘Rapid thermal annealing of dopants implanted into preamorphized silicon’, J. Appl. Phys. 58, 683 –687Google Scholar
- Tsai, M.Y. and Streetman, B.G. (1979) ‘Recrystallization of implanted amorphous silicon layers. I. Electrical properties of silicon implanted with BF2 or Si + + B +’, J. Appl. P hys. 50, 183 – 187Google Scholar
- Ozturk, M. C., Wortman, J.J., Osburn, C. M., Ajmera, A. Rozgonyi, A., Frey, E., Chu, W.-K., and Lee, C. (1988) ‘Optimization of the Germanium Preamorphization Conditions for Shallow-Junction Formation’, IEEE Trans. on Electr. Dev. 35, 659 – 668Google Scholar
- Ozturk, M.C., Wortman, J.J., Chu, W.-K., Rozgonyi, G.A., and Griffis, D. (1987) ‘BF2 ionimplantation through surface oxides and the behaviour of the fluorine with rapid thermal annealing’, Mat. Left. 5, 311 – 314Google Scholar
- Cho, K., Allen, W.R., Finstad, T.G., Chu, W.-K., Liu, J., Wortman, J.J. (1985) ‘Channeling effect for low energy ion implantation in Si’, Nucl. Instrum. Meth. (B) 7, 265 – 272Google Scholar
- Ehinger, K., Kabza, H., Weng, J., Miura-Mattausch, M. Maier, I., Schaber, H., and Bieger, J. (1988) ‘Shallow doping profiles for high-speed bipolar transistors’, J. Physique 9, C4, 109–112Google Scholar
- Imschweiler, J., Hefner, H. A., and Seibt, M., to be publishedGoogle Scholar