Determining the oxygen detection limit with magnetic sector dynamic secondary ion mass spectrometry (SIMS)

Dynamic SIMS is often used in evaluating the concentration of impurities in solids because of its high sensitivity and depth profiling capabilities with good depth resolution and high throughput. Continuous ion beam sputtering with a high-density primary beam provides high sensitivity and reduced background contribution from residual gases within the analytical chamber. Numerical simulations along with the data acquired in the real depth profiling experiment show a good agreement of the simple model, assuming that the surface uptake of the oxygen under Cs bombardment depends on the Cs surface retention concentration. In cases where high depth resolution is desired, requiring a low primary ion beam energy, a background subtraction option will help provide better detection limits. It is proposed to perform the background subtraction based on the difference between the continuous and interleaving sputtering modes of dynamic SIMS. The experiments performed on different instruments using different sputtering rate conditions (and different impact energies) show the power function dependence of oxygen detection limit on the reversed sputter rate variation or sputtering beam density. The proposed detection limit dependence curve can be used for analytical specifications benchmarking in most magnetic sector SIMS instruments.