Thin Film Analysis

Analysis of the elemental composition and thickness of a Fe-Ni film using ESPRIT and STRATAGem

Monte Carlo Simulation for 15 kV Electron Energy
Monte Carlo simulation, illustrating
penetration depth of electrons into
the sample at 15 kV acceleration

Quantitative analysis of a bulk sample requires that the composition of the sample is homogeneous over the analyzed volume. For inhomogenous samples the calculation of the matrix effects is not correct and this can lead to wrong
results in the element concentrations. For samples containing a layer structure a different quantitative evaluation has to be applied. This can be provided with the standard-based analysis in ESPRIT in combination with the STRATAGem software.

Therefore, the quantitative analysis of a Fe-Ni film on a Si substrate was performed using ESPRIT and STRATAGem. The sample analyzed was provided by the German Federal Institute for Materials Research and Testing (BAM) and the Korean Research Institute of Standards and Science (KRISS). It consists of a 200 nm thick Fe-Ni film that has been sputtered on a Si wafer. The elemental composition of the Fe-Ni alloy was certified by ICP-MS to be Fe (50.02 ±1.23 at.%) and Ni (49.98 ±1.23 at.%).

Spectra of the sample were obtained at different acceleration voltages to realize different penetration depths and k ratios for the elements, which are required for layer thickness calculation. In this case 12, 15, 20, 25 and 30 kV were used. The K ratios were determined by the ESPRIT software and input to STRATAGem. Results are obtained through fit procedures, involving K ratios, layer thickness, layer composition and substrate composition.

This procedure generates reliable results for many different types of layers with different compositions and thicknesses ranging from nm to several µm, including multi-layer structures. In this example it could be determined that the layer is approximately 185 nm thick and consists of 50.3% Fe and 49.7% Ni, which is in good agreement with the given values.

Download the corresponding application note #11 (PDF)