Ion beam sputtering - the effect of incident ion energy on atomic mixing in subsurface layers

Abstract

Secondary ion mass spectrometric methods were used to study the effect of incident ion energy on atomic mixing in subsurface layers. A Ta₂O₅ film containing a 50 A ^3lP-rich layer 230 A below the surface was depth profiled for phosphorus using normal incidence 160 primary particles of various energies (1.75 to 18.5 keV). A pronounced energy effect was observed in the widths of 31^P profiles generated by >4 keV ¹⁶O. For 18.5 keV ¹⁶O, the observed profile contained two distinct components-the 31^P-rich layer and the 31^P recoil distribution. This later condition, prevails when the peak of the incident ion damage distribution occurs at a depth which equal or exceeds the distance from the surface to the 31^P-rich layer. The desirable primary ion beam energy for characterizing the true elemental distribution is dictated by the shape and location of the layer to be profited. In most instances, a low energy beam is preferred.