Field‐induced segregation effects during secondary‐ion mass spectrometry depth profiling of Cu and Na implanted in silicon

Segregation effects during secondary‐ion mass spectrometry (SIMS) depth profiling of Cu and Na implanted in n‐ and p‐type Si are investigated under different oxygen bombardment conditions. The segregation effects are studied also with SIMS using Cs bombardment. These experiments revealed that Cu and Na segregate under primary beam conditions by which a SiO2 layer forms and positive primary ions are used. In agreement with the thermodynamics of the Si‐Cu‐O and Si‐Na‐O systems, the Na segregates at the oxide side of the SiO2/Si interface whereas Cu segregates at the silicon side of the interface. When primary O− ions are used the electric field is inverted and the segregation of Na disappears and is minimized in case of Cu. This dependence on the charge state of the primary ions demonstrates the overriding importance of the field‐induced effect of this phenomenon.