Resolution in sputter depth profiling assessed by AlAs/GaAs superlattices

Abstract

AlAs/GaAs superlattices are proposed as a potential reference material for sputter depth profiling since, at present, AlxGa1−xAs/GaAs superlattices are grown in a defect-free single crystalline state with atomically flat and abrupt interfaces by metalorganic chemical vapor deposition. It is anticipated that such superlattices should have wide applicability for the assessment of resolution in sputter depth profiling. A preliminary round-robin test was performed by the International Organization for Standardization (ISO)/Technical Committee (TC) 201 on Depth Profiling in Japan. It is clear that in all the Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) data obtained on these superlattices, the depth resolution is a constant unrelated to the sputtered depth. In the x-ray photoelectron spectroscopy data, which have a larger analyzed area, the depth resolution deteriorates with the sputtered depth, confirming that the depth resolution is affected by the analyzed area owing to the crater edge effects. Furthermore, in the SIMS data the resolution of the leading and trailing edges depends strongly on primary reactive ion species (O+2, Cs+). This is in contrast to AES data using inert gaseous ions (e.g., Ar+). Consequently, the present round-robin test demonstrated preparatorily that these superlattices are useful for work in order to understand why different techniques and sputtering conditions result in different determinations of resolution.