Evaluation of AES depth profiles of thin-film systems by application of novel graphically interactive factor analysis software

Factor analysis has proved to be a powerful tool for the full expolitation of the chemical information included in the peak shapes and peak positions of spectra measured during AES depth profiling. Owing to its ability to extract the number of independent chemical components, their spectra and depth distributions, it is increasingly used in routine analysis. However, one has to be aware of the crucial role of the analyst in selecting the physically relevant result from the indefinite number of mathematical solutions. For this reason, he must be put in a position to define the matrix rotation and to check the resulting factors in a fast, flexible and transparent way. Therefore, factor analysis software offering a graphically interactive user interface has been devleoped. During the necessary rotations in factor space both the depth distributions and the corresponding spectra are displayed simultaneously, so that the analyst can judge the physical relevance of the solution and can quickly respond with the necessary adjustments. To demonstrate the capabilities of the software in the evaluation of AES depth profile data, a TiN/Ti/SiO2 layer sequence form microelectronics technology was chosen. As an important result, additional layers are recognized at the interfaces. This example demonstrates the advantages of factor analysis and emphasizes the necessity of the analyst's knowledge on both AES spectra and hte investigated material systems. In addition, it shows the importance of a fast, direct, transparent and interactive interface between the analyst and the mathematical tool of factor analysis.