A method to determine the interface position and layer thickness in SIMS depth profiling of multilayer films

The measurement of layer thickness by compositional secondary ion mass spectrometry (SIMS) depth profiling is investigated for Si/Ge multilayer films using an oxygen ion beam. The original SIMS depth profiles were converted into compositional depth profiles by the relative sensitivity factors of Si and Ge derived from a Si_52.4Ge_47.6 alloy reference film. The locations of the interfaces in the Si/Ge multilayer films could be well determined by 50 at% definition where the relative composition of the constituent layer elements drops or rises to 50 at%. The layer thicknesses of Si and Ge of a test Si/Ge multilayer film were determined by the sputtering rates of Si and Ge determined from a reference Si/Ge multilayer film. Although the difference between the measured and the actual thicknesses is increased as the ion energy is increased, the layer thicknesses determined at low ion energies were very close to the actual values.