EPMA sputter depth profiling of an InGaAs-InP heterostructure

The chemical microanalysis of semiconductor heterostructures by electron pr obe x-ray microanalysis (EPMA) is presented. The great advantage of EPMA is the sensitive detection and accurate quantification of partial mass covera ge down to about 0.01 mu g/cm(2). To improve depth resolution of EPMA the s urface was sputtered by inert gas ions and x-ray intensities were measured with increasing sputter depth. These intensity-sputter profiles represent a convolution of the structure of the material by the excitation characteris tics of the incident electrons. They were interpreted and evaluated with re spect to the chemical composition and thickness of each layer. For this pur pose a Monte-Carlo-Simulation program package was developed, which can calc ulate realistic x-ray intensities versus sputter depth for a given material . Additionally, it can reconstruct the structure of the material assuming a laterally homogeneous multilayered system with sharp interfaces and consta nt composition inside each layer. The results of the reconstruction could b e quantified with an accuracy of less than 5% rel.. In spite of the large i nformation depth of x-rays a depth resolution of about 1-3 nm could be dete rmined.