Standards prepared by drop-on-demand dispenser for SIMS

Quantitative determination of metal impurities becomes increasingly crucial for the semiconductor industry as integrated circuit critical dimensions continue to shrink. Time-of-flight secondary ion mass spectrometry (TOF SIMS) has been widely used for this purpose. Proper standards are necessary to ensure measurement accuracy and precision. Ion implanted samples with known dose conventionally serve as SIMS standards because of high precision and good uniformity. However, due to the matrix effect, implanted standards may not always be available for different matrixes. In this paper, the authors proposed to prepare SIMS standard samples using the drop-on-demand technique. A series of droplet arrays were dispensed on silicon wafers from solutions of Fe, Ni, and Cu with concentrations ranging from 2 to 1000 ppm. The dose determined by TOF SIMS linearly correlated with the calculated dose of the droplets. The linearity of these metals was better than 0.99, which demonstrated that the drop-on-demand technique can be a promising technique to prepare SIMS standards.