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The CAMECA IMS 7f SIMS offers unparalleled depth profiling capabilities with high depth resolution and high dynamic range. A high efficiency optical gate is used to eliminate crater edge effects, and the high mass resolution ensures true elemental analysis by eliminating the numerous interfering ions (31P/30SiH, 56Fe/28Si2?). The superior qualities of the instrument are further enhanced by the Checkerboard optional add-on to the PC-Windows 'Analysis' and 'WinCurve' software for achieving dramatic improvements in depth resolution by optimizing the size and position of the gate.
In SIMS, when performing depth profiling, one goal is to achieve the best dynamic range for the recorded profiles. The dynamic range can be improved if the maximum intensity is increased, which requires to enlarge the analyzed area (restricted area inside the crater bottom from which the signals are collected). However, a major drawback to enlarging the analyzed area is the growing contribution of the crater edge effects, which may limit the background level, thus reducing the dynamic range.
The optimization of the analyzed area (neither too small nor too big) is a delicate issue, as SIMS is a destructive technique: once the analysis is performed, it is no longer possible to re-measure on the same analysis spot. This is a real challenge for patterned sample analysis, where only specific (limited) sample locations can be investigated. And even if the size of the sample allows to repeat the analysis, having to perform different runs has a direct cost in terms of instrument throughput.
In standard depth profiling, the analyzed area is fixed in the analysis recipe by defining the gating size, which may be optical (by a mechanical aperture), electronical (blanking of the secondary ions coming from an area outside the gate), or a combination of both. Ions coming from the crater bottom inside the area defined by the gating are collected and recorded, whereas the others are rejected.
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