ToF-SIMS Depth Profiling of Metal, Metal Oxide, and Alloy Multilayers in Atmospheres of H 2 , C 2 H 2 , CO, and O 2 .

The influence of the flooding gas during ToF-SIMS depth profiling was studied to reduce the matrix effect and improve the quality of the depth profiles. The profiles were measured on three multilayered samples prepared by PVD. They were composed of metal, metal oxide, and alloy layers. Dual-beam depth profiling was performed with 1 keV Cs + and 1 keV O 2 + sputter beams and analyzed with a Bi + primary beam. The novelty of this work was the application of H 2 , C 2 H 2 , CO, and O 2 atmospheres during SIMS depth profiling. Negative cluster secondary ions, formed from sputtered metals/metal oxides and the flooding gases, were analyzed. A systematic comparison and evaluation of the ToF-SIMS depth profiles were performed regarding the matrix effect, ionization probability, chemical sensitivity, sputtering rate, and depth resolution. We found that depth profiling in the C 2 H 2 , CO, and O 2 atmospheres has some advantages over UHV depth profiling, but it still lacks some of the information needed for an unambiguous determination of multilayered structures. The ToF-SIMS depth profiles were significantly improved during H 2 flooding in terms of matrix-effect reduction. The structures of all the samples were clearly resolved while measuring the intensity of the M n H m - , M n O m - , M n O m H - , and M n - cluster secondary ions. A further decrease in the matrix effect was obtained by normalization of the measured signals. The use of H 2 is proposed for the depth profiling of metal/metal oxide multilayers and alloys.