Effects of implementation of decaborane ions in silicon
Committee for the Interdisciplinary Program in Materials Science and Engineering
Doctor of Philosophy
Materials Science and Engineering
Chin, Ken K.
Hirvonen, J. K.
Gossman, Hans-Joachim L.
The next generations of Si microelectronic devices will require ultra shallow p-type junctions formed by implantation of B ions with energies below 1 keV, at which available beam currents are severely limited by space charge effects. To solve this problem, decaborane (B10H14) cluster ion implantation has been suggested as an attractive alternative to conventional B implants, because one decaborane ion implants ten B atoms simultaneously and each of the B atoms only carries approximately 1/11 of the total ion energy. Thus the same implantation depth and dose as with monomer B ions can be obtained using decaborane ions but with 10 times less charge and ten times higher energy. In this dissertation research, various effects of implantation of decaborane cluster ions in silicon were studied, using an experimental ion implanter in the Ion Beam and Thin Film Research Laboratory at NJIT.
Secondary Ion Mass Spectrometry (SIMS) depth profiles of boron and hydrogen in decaborane-implanted samples were measured before and after thermal activation annealing and compared to that in the control samples. Shallow p-type junction could be achieved with decaborane implantation. The co-implanted hydrogen diffused out almost entirely after annealing and hence is expected to have a negligible effect on the device performance.
Transient enhanced diffusion (TED) of B atoms in Si implanted with mass analyzed decaborane ions of three energies were measured and compared to that of B atoms in Si implanted with B+ ions of equivalent B energy and dose. The resultsdemonstrated that implantation of B with decaborane cluster ions led to essentially the same amount of TED of B in Si as that in Si implanted with atomic B+ ions of the equivalent energy and dose.
The sputtering yields of Si with B in the form of decaborane clusters were measured and compared to those for boron monomer ions, estimated using an empirical formula. The surface morphology of amorphous Si, crystalline Si and Ta film irradiated with energetic decaborane ions and argon ions were studied using Atomic Force Microscopy (AFM). Results of surface roughness and Power Spectral Density (PSD) analysis show that decaborane cluster ions smooth rather than roughen these surfaces.
Molecular Dynamics (MD) simulations have been performed to compare impact effects on Si target by B monomers and B10 clusters at the same energy per B atom. B depth profiles were found to be similar for B atoms implanted with B10 clusters and with B monomers. The crater formation, a unique feature of cluster impacts, was also observed on the Si surface impacted by a B10 cluster. The calculated sputtering yield of Si (the number of ejected Si atoms per incident B) was much larger with B10 clusters than with B monomers and also larger than the experimental values.
The results of this research confirm that decaborane implantation is a viable alternative to low energy B implantation for ultra shallow p-type junction formation. These results also contribute to the knowledge base of the technology of ultra shallow B doping in CMOS devices and will help to better understand cluster-solid interactions in general.
njit-etd2003-078 (184 pages ~ 14,384 KB pdf)
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Created June 10, 2004