SIMS Theory: Uses for SIMS

Today, SIMS is widely used for analysis of trace elements in solid materials, especially semiconductors and thin films. The SIMS ion source is one of only a few to produce ions from solid samples without prior vaporization. The SIMS primary ion beam can be focused to less than 1 um in diameter. Controlling where the primary ion beam strikes the sample surface provides for microanalysis, the measurement of the lateral distribution of elements on a microscopic scale. During SIMS analysis, the sample surface is slowly sputtered away. Continuous analysis while sputtering produces information as a function of depth, called a depth profile. When the sputtering rate is extremely slow, the entire analysis can be performed while consuming less than a tenth of an atomic monolayer. This slow sputtering mode is called static SIMS in contrast to dynamic SIMS used for depth profiles. Shallow sputtering minimizes the damage done to organic substances present on the sample surface. The resulting ion fragmentation patterns contain information useful for identifying molecular species. Only dynamic SIMS will be treated in this surface analysis computer aided instruction package because only dynamic SIMS yields quantitative information.

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