Time of flight elastic recoil detection analysis with toroidal electrostatic analyzer for ultra shallow dopant profiling

Abstract

A time of flight (TOF) elastic recoil detection analysis (ERDA) with a toroidal electrostatic analyzer (TEA) using 100 keV Ar+ probe was developed for B profiling in a Si substrate with low energy ion implantation for shrunk semiconductor devices. In the original ERDA, Bohr energy straggling at a stopping foil affects an energy resolution. Thus, in this study, a flight time from the sample to the TEA detector was used for a mass separation in ERDA without the stopping foil. A beam incident angle normal to the sample and a recoil scattering angle were 75° and 50°, respectively. The samples were Si substrates with and without B+ implantation at 2 keV with a dose of 1.5 × 1016/cm2. A boron depth profile was calculated from the difference of the ERDA spectra with TEA for the Si samples with and without B+ implantation. The recoiled B+ and Si+ signals were well separated in the TOF‐ERDA spectra for B+ implanted Si with TEA applied voltages of 0.45 to 1.13 kV. The TOF‐ERDA spectra with TEA applied voltages of 0.45 to 3.44 kV were converted to the ERDA spectra for B+ and Si+. The B segregation at the surface was observed in both B depth profile calculated from the decrease in the Si yield by ERDA and the ERDA spectrum for B+ converted from the TOF‐ERDA spectra. Copyright © 2012 John Wiley & Sons, Ltd.