High-resolution sputter depth profiling with a low pressure hf plasma

An arrangement for sputter-depth profiling by means of a low pressure hf plasma is described. Extremely plane bombarding craters are obtained when the bombarding voltage, the plasma parameters and the geometry of the target assembly are fitted appropriately. A quantitative relation for plane crater conditions is established, and verified by a comparison with crater profiles created in Ta₂O₅ layers by the bombardment with Ar⁺ ions of 100–600 eV. Under optimum conditions the flatness of the crater bottoms being investigated by optical interferometry was in the order of 10Å. The method has been applied for depth profiling of 3500Å thick Ta₂O₅ layers by Sputtered Neutral Mass Spectrometry (SNMS).