Optimization of secondary ion mass spectrometry ultra-shallow boron profiles using an oblique incidence O2+ beam

The features of ultra-shallow junctions indicated by 2001 International Roadmaps require challenging characteristics for secondary ion mass spectrometry (SIMS) instruments: an ultra high depth resolution, minimization of transient width before the steady state and the ability to manage high concentration quantification in the near surface region. In this article a new magnetic sector SIMS, the Cameca Sc-Ultra, has been evaluated in order to profile boron ultra shallow junctions. In this apparatus the use of normal incidence oxygen bombardment is precluded and the primary column allows for a 60° nominal incidence angle. Several approaches varying analytical parameters as energy, incidence angle and oxygen flooding have been tested on boron delta layers samples. In this way a quantitative comparison of different analytical methodologies is possible and the better analytical approach is pointed out. Moreover, an in situ laser depth profile measurement tool has been tested and the advantages and limitation are shown. The minimum impact energy used is 0.5 keV, but the instrument performance can be further improved by using lower impact energy (300 eV), a rotating stage to minimize surface roughness, and a primary column with a nominal angle of 30°. SIMS depth profiles on technological samples have been also carried out and shown