Enhanced depth-resolution analysis with medium energy ion scattering (MEIS) for shallow junction profiling

A rapid shrinkage in the minimum feature size of Integrated circuits (ICs) requires analysis with an enhanced depth-resolution for dopants in shallow source-drain regions. Rutherford backscattering Spectroscopy (RBS) with medium energy ion scattering (MEIS) for such analysis should meet the requirement of a depth-resolution of less than 5 nn at a depth of 50 nm in the next 5 years. A toroidal electrostatic analyzer (TEA) with an energy resolution of 4×10^-3 has been used to detect scattering ions. Limitation of energy resolution due to Bohr straggling of probe ions at a shallow implanted depth has been taken into account. Arsenic ions were implanted in SiO₂/Si at energy of 5 keV with a dose of 2×10¹⁵ /cm². An ultra shallow profile with a projected range of 30 nm with a FWHM (full width at half maximum) of 4.7±0.4 nm was non-destructively measured