D-SIMS:Precision Surface Analysis for Quality Assurance

Dynamic Secondary Ion Mass Spectrometry (D-SIMS) involves bombarding the sample with gas ions, causing the ejection of surface atoms, molecules, or ions. The ejected secondary ions are then received by a mass analyzer, and their mass-to-charge ratio (m/z) is analyzed to obtain a secondary ion mass spectrum. Because the ion source in D-SIMS is a high-density ion beam (atomic dose > $10^{12}$ ions/cm²), it exerts a significant sputtering effect on the sample, making it a destructive analytical technique. Additionally, D-SIMS typically requires good electrical conductivity of the sample and is mainly used for longitudinal concentration profiling of inorganic samples and trace impurity identification, such as in geological research, isotope quantification analysis, and deep analysis of semiconductor doping.

Figure 1: Schematic Diagram of D-SIMS

Compared to other typical surface analysis techniques such as SEM-EDS (approximately 1%), Auger (approximately 0.1%), and XPS (approximately 0.1%), D-SIMS not only has an extremely low detection limit (ppm to ppb range) but also exhibits high sensitivity (in the order of ng/g) and image resolution. Additionally, it can achieve qualitative analysis for almost all elements, including hydrogen.

Products Quality Issues Addressed by D-SIMS

(1) Qualitative detection of tiny foreign substances on the product surface (≥10μm), especially when conventional composition testing methods fail.

(2) Measurement of the thickness and composition of multi-layer films or single-layer films (thickness ≥1nm).

(3) Analysis of ultra-trace substance composition on the surface to determine the presence of foreign contamination, with detection limits reaching ppb levels.

(4) Testing the distribution of elements at ultra-low concentrations from the surface to the interior in doping processes.

(5) Elemental content surface distribution maps, isotope abundance analysis, layer-by-layer peeling, achieving longitudinal analysis of each component (AES, XPS can only analyze the newly generated surface vertically)...

Requirements for D-SIMS Samples

(1) The surface of solid samples is preferably flat and smooth; powder samples must be pressed into soft metal foils (such as copper) or pressed into small pieces.

(2) The maximum size of the sample is 1×1×0.5cm; if the sample size is too large, it needs to be cut, and the sample surface must be flat.

(3) Avoid contact of hands and sampling tools with the tested positions. After removing the sample, vacuum packaging should be used to prevent external contamination from affecting the analysis results.