Low energy implantation of boron with decaborane ions.

摘要

The goal of this dissertation was to determine the feasibility of a novel approach to forming ultra shallow p-type junctions (tens of nm) needed for future generations of Si MOS devices. In the new approach, B dopant atoms are implanted by cluster ions obtained by ionization of decaborane (B ₁₀H₁₄) vapor.; An experimental ion implanter with an electron impact ion source and magnetic mass separation was built at the Ion Beam and Thin Film Research Laboratory at NJIT. Beams of B₁₀H_x+ ions with currents of a few microamperes and energies of 1 to 12 keV were obtained and used for implantation experiments. Profiles of B and H atoms implanted in Si were measured by Secondary Ion Mass Spectroscopy (SIMS) before and after rapid thermal annealing (RTA). From the profiles, the junction depth of 57 nm (at 1018 cm−3 B concentration) was obtained with 12 keV decaborane ions followed by RTA. The dose of B atoms that can be implanted at low energy into Si is limited by sputtering as the ion beam sputters both the matrix and the implanted atoms. As the number of sputtered B atoms increases with the implanted dose and approaches the number of the implanted atoms, equilibrium of B in Si is established. This effect was investigated by comparison of the B dose calculated from the ion beam integration with B content in the sample measured by Nuclear Reaction Analysis (NRA). Maximum (equilibrium) doses of 1.35 × 1016 B cm −2 and 2.67 × 1016 B cm−2 were obtained at the beam energies of 5 and 12 keV, respectively.; The problem of forming shallow p-type junctions in Si is related not only to implantation depth, but also to transient enhanced diffusion (TED). TED in Si implanted with B₁₀H_x+ was measured on boron doping superlattice (B-DSL) marker layers. It was found that TED, following decaborane implantation, is the same as with monomer B+ ion implantation of equivalent energy and that it decreases with the decreasing ion energy. (Abstract shortened by UMI.)