Cross — Calibration of SIMS Instruments for Analysis of Metals and Semiconductors

It is known from previous round robin experiments [1] that relative sensitivity factors, obtained on identical samples by different SIMS instruments, frequently disagreee by a factor of up to 50 and that element concentrations, derived from the raw peak height data by some quantification algorithm, still disagree by a factor of ~5. Two methods, both based on the relative sensitivity factor (RSF) quantification scheme, have been suggested to obtain inter-laboratory standardization of quantitative SIMS analyses: (a) “Standard — Transfer”; for every element/matrix system to be analyzed, a well characterized external standard sample is distributed to each laboratory. Previous to analysis of the unknown, RSFs are determined from the appropriate standard and used for the quantification of the unknown. The method rests on the availability of identical standards in each laboratory and not on the agreement in raw ion intensity data. Each laboratory has to determine its own RSFs previous to each individual analysis. the accuracy is of the order of 20% [2], determined mainly by the accuracy of the standard composition. (b) “Cross-Calibration”; here, the aim is to tune different instruments to give identical RSFs from identical samples. If this can be realized, RSFs can be transferred between instruments and laboratories so that the workload of determining RSFs can be split between laboratories. Standard samples still are required for each unknown/matrix system,but essentially only in that laboratory determining the particular RSF. The accuracy of the method is determined by the quality of the standard and of the instrument tuning.