Study of pre-equilibrium sputter rates for ultrashallow depth profiling with secondary ion mass spectrometry

Sputter rates for sub-keV primary beam energies are investigated with atomi c force microscopy measurements of crater step heights. Using a 800 eV O-2( +) sputtering beam at an incidence angle of 50 degrees with oxygen flooding , the surface swells as the implanted oxygen forms an altered layer. After a fluence of 1E17 O/cm(2), the sputter rate reaches equilibrium. Characteri stic parameters such as the depth scale offset, z(d)(0), and the apparent i nitial silicon surface z(Si)(0), are extracted from the data (0.6 and -1.3 nm, respectively), and the magnitude of the profile shift is discussed in t erms of the final profile accuracy. (C) 2000 American Vacuum Society. [S073 4-211X(00)00801-0].