Comparison of secondary ion mass spectrometry profiling of sub-100 nm ultrashallow junctions using NO⁺₂ and O⁺₂ sputtering

Abstract

Secondary ion mass spectrometry (SIMS) with low energy sputtering is used to characterize ultrashallow dopant profiles. Molecular ion sputtering species help reduce the mixing depth of the sputtering process and the broadening of the measured dopant distributions. The depth resolution of NO+2 and O+2 primary beams at 2 keV net acceleration and 55° incidence angle to the sample are compared by the measurement of low energy ion implanted dopant distributions. The sputtering conditions result in a 380 eV/sputtering particle (normal to the sample surface) for NO+2, and a 570 eV/sputtering particle for O+2. Measurements of 1 and 2 keV BF2, as well as 5 keV As implants show trailing edge slopes of 2.6 nm/dec for the 1 keV BF2, and 5.5 nm/dec for arsenic. The pre-equilibrium region at the near-surface of the sample is shown to be similar for NO2 and O2, indicating that chemical segregation effects of the nitrogen in the sample are not detrimental to the profile accuracy. © 1998 American Vacuum Society.