Direct chemical in-depth profile analysis and thickness quantification of nanometer multilayers using pulsed-rf-GD-TOFMS

作者：Valledor R; Pisonero J; Bordel N^*; Martin J I; Quiros C; Tempez A; Sanz Medel A

来源：Analytical and Bioanalytical Chemistry, 2010, 396(8): 2881-2887.

DOI：10.1007/s00216-009-3382-8

• Glow discharge
• Mass spectrometry
• Depth profile analysis
• Nanometer layers
• Useful yield

Nanometer depth resolution is investigated using an innovative pulsed-radiofrequency glow discharge time-of-flight mass spectrometer (pulsed-rf-GD-TOFMS). A series of ultra-thin (in nanometers approximately) Al/Nb bilayers, deposited on Si wafers by dc-magnetron sputtering, is analyzed. An Al layer is first deposited on the Si substrate with controlled and different values of the layer thickness, t(Al). Samples with t(Al) = 50, 20, 5, 2, and 1 nm have been prepared. Then, a Nb layer is deposited on top of the Al one, with a thickness t(Nb) = 50 nm that is kept constant along the whole series. Qualitative depth profiles of those layered sandwich-type samples are determined using our pulsed-rf-GD-TOFMS set-up, which demonstrated to be able to detect and measure ultra-thin layers (even of 1 nm). Moreover, Gaussian fitting of the internal Al layer depth profile is used here to obtain a calibration curve, allowing thickness estimation of such nanometer layers. In addition, the useful yield (estimation of the number of detected ions per sputtered atom) of the employed pulsed-rf-GD-TOFMS system is evaluated for Al at the selected operating conditions, which are optimized for the in-depth profile analysis with high depth resolution.

• 出版日期2010-4