On the influence of crater edges and neutral beam component on impurity profiles from raster scanning SIMS

Abstract

A mathematical evaluation is presented for the beam raster scanning mode of depth profiling with SIMS, combined with electronic gating of the detection system. A computer program was developed in which a former treatment of the influence of the crater edges is extended to arbitrary impurity profiles and which also accounts for neutral particles in the primary beam. It is shown that these neutrals have a dramatic effect on the obtained dynamic range and that the commonly used background subtraction technique does not necessarily lead to the correct profile. The simulation including neutrals shows good agreement with an experimentally measured profile. Finally, the influence of the crater edges and the choice of an appropriate structure for measuring depth resolution and outdiffusion are discussed.

Quantitative Depth Profiling of Argon in Tungsten Films by Secondary Ion Mass Spectrometry

“…The reason for this phenomenon would be the crater edge and sidewall effects due to a poorly focused primary beam and a small-area analysis. 5,7,19 Depth resolution Figure 5 shows examples of the Ar depth profiles in W, obtained by monitoring Ar + with O2 + primary-ion (JO 2 = 0.32 mA/cm 2 ) and monitoring ArCs + with Cs + primary-ion (JCs = 0.32 mA/cm 2 ). The erosion rates of O2 + and Cs + primary-ion beam measurements were 0.4 nm/s and 1.5 nm/s, respectively.…”

A new approach to express ToF SIMS depth profiling

“…By forming a flat crater bottom, one can reduce instrumental broadening of the profile tails, caused by the sidewalls contribution to the signal . For dynamic SIMS systems with quadruple and magnetic sector mass analyzers, the use of raster sputtering ion beams is of principle importance, because it helps form an electronic gate for collecting secondary ions only from the flat center of the crater in order to reduce instrumental broadening. The characteristic requirement here is that the size of the sputter raster should be at least three to five times larger than the beam diameter .…”

“…For dynamic SIMS systems with quadruple and magnetic sector mass analyzers, the use of raster sputtering ion beams is of principle importance, because it helps form an electronic gate for collecting secondary ions only from the flat center of the crater in order to reduce instrumental broadening. The characteristic requirement here is that the size of the sputter raster should be at least three to five times larger than the beam diameter . Using of low‐energy sputter ions and raster scanning largely degrade the sputtering rate, which makes a complete analysis of structures with thick layers an extremely time‐consuming procedure.…”

Quantification of cesium surface contamination on silicon resulting from SIMS analysis

“…5 While controlled Cs incorporation is useful, inadvertent Cs exposure can result in unintended changes in the apparent surface concentration of an element for samples previously analyzed using Cs. 8 One possible source of Cs neutrals is charge exchange of Cs primary ions in collisions with residual gas atoms. In addition to altering secondary ion yields, the Cs contamination may over time result in changes to the Si surface that cause movement of elements (e.g., phosphorus) to the sample surface or other deleterious effects.…”