Depth profiling of micrometer‐order area by mesa‐structure fabrication

Fabricating mesa structures with photolithography in samples for analysis is a promising method for microarea analysis in SIMS depth profiling because undesired ions originating from the surroundings of the analysis area are eliminated. We investigated the depth profiles of B implants in Si by varying the primary ion energy, beam size, mesa size, raster area and gate area ratio. When a 50 µm × 50 µm mesa was rastered over a 60 µm × 60 µm area with a 15‐keV Cs + beam, a dynamic range for B of 3 × 10 5 and a detection limit of 3.2 × 10 15 atoms/cm 3 were obtained. As for a smaller mesa of 9 µm × 9 µm, the depth profiles of BSi − taken over a 30 µm × 30 µm raster area with a 5 keV beam were quite comparable to those over 13 × 13 and 11 µm × 11 µm raster areas with a 15 keV beam. The major advantages of using a mesa fabrication method are minimization of the raster area and maximization of the gate area ratio without deterioration of profile quality, which is quite favorable for microarea analysis. A very small mesa of 4 µm × 4 µm was also successfully analyzed, and a dynamic range of 4 × 10 3 was obtained. Copyright © 2010 John Wiley & Sons, Ltd.